RU2461980C2 - Interface management in wireless communication system using subframe-based time reuse - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: method, apparatus and communication medium determine interfering subframe gating sequences. The transmission gating in a home access point is adjusted by determining a first gating sequence from a first unplanned access point. A second gating sequence is selected based on the first gating sequence, wherein the first and second gating sequences are non-interfering. Signals are transmitted according to the second gating sequence from a second unplanned access point to an associated access terminal.

EFFECT: interference which occurs during wireless communication can be managed by subframe-based time reuse.

28 cl, 23 dwg

Description

This application claims the priority of the jointly owned provisional patent application US No. 60/990541, filed November 27, 2007, attorney case number 080324P1; US Provisional Patent Application No. 60/990547, filed November 27, 2007, Attorney Case Number 080325P1; US Provisional Patent Application No. 60/990459 filed November 27, 2007, Attorney Case Number 080301P1; US Provisional Patent Application No. 60/990513, filed November 27, 2007, Attorney Case Number 080330P1; US Provisional Patent Application No. 60/990564, filed November 27, 2007, Attorney Case Number 080323P1; and U.S. Provisional Patent Application No. 60/990570, filed November 27, 2007, Attorney Case Number 080331P1, the disclosure of each of which is hereby incorporated by reference.

State of the art

FIELD OF THE INVENTION

This application, in General, relates to wireless communications, and more specifically, but not only to improve communication performance.

Introduction

Wireless communication systems are widely deployed in order to provide various types of communication (eg, voice, data, multimedia services, etc.) to multiple users. As the demand for high-speed multimedia and data transfer services is growing rapidly, the challenge is to implement efficient and fault-tolerant communication systems with increased productivity.

To complement the base stations of a traditional mobile telephone network, base stations with a small coverage can be deployed (for example, installed at the user's home) to provide more fault-tolerant internal wireless coverage for mobile modules. Such base stations with little coverage are commonly known as access point base stations, proprietary B nodes, or femtocells. As a rule, such base stations with a small coverage are connected to the Internet and the mobile operator’s network via a DSL router or cable modem.

Since the radio frequency (RF) coverage of base stations with a small coverage may not be optimized by the mobile operator, and the deployment of such base stations may be arbitrarily organized, RF interference problems may arise. In addition, soft handoff may not be supported for base stations with little coverage. Finally, the mobile station may not be allowed to communicate with an access point that has the best RF signal due to the requirement of limited association (i.e., a closed subscriber group). Thus, there is a need for improved interference management for wireless networks.

SUMMARY OF THE INVENTION

This disclosure relates to interference management through time reuse based on subframes. By determining the interfering gating sequences of the subframes, the transmission gating at the native access point can be controlled. In one exemplary embodiment, the communication method includes determining a first gate sequence from a first unplanned access point. The second gating sequence is selected based on the first gating sequence, wherein the first and second gating sequences are non-interfering. The method further transmits signals according to a second gating sequence from a second unplanned access point to an associated access terminal.

In another exemplary embodiment, the communication device includes an interference controller configured to determine a first gate sequence from the first unplanned access point and select a second gate sequence based on the first gate sequence, wherein the first and second gate sequences are non-interfering. The device further includes a communication controller configured to transmit signals according to the second gate sequence from the second unplanned access point to the associated access terminal.

Brief Description of the Drawings

These and other exemplary aspects of the disclosure are described in the detailed description and the attached claims, which are given below, and in the accompanying drawings, in which:

FIG. 1 is a simplified block diagram of several exemplary aspects of a communication system;

FIG. 2 is a simplified block diagram illustrating several exemplary aspects of components in an exemplary communication system;

FIG. 3 is a flowchart of a method of several exemplary aspects of operations that may be performed in order to control interference;

FIG. 4 is a simplified diagram of a wireless communication system;

FIG. 5A is a simplified diagram of a wireless communication system including femto nodes;

FIG. 5B is a simplified diagram of a specific arrangement of femto nodes and access terminals illustrating non-optimal geometries;

FIG. 6 is a simplified diagram illustrating coverage areas for wireless communications;

FIG. 7 is a flowchart of a method of several exemplary aspects of operations that can be performed in order to control interference using beamforming and controlling the zero position of a beamform;

FIG. 8 is a flowchart of a method of several exemplary aspects of operations that may be performed in order to control interference using optimized reduced power levels for the overhead channel;

FIG. 9 is a flowchart of a method of several exemplary aspects of operations that may be performed in order to control interference using optimized reduced power levels for an overhead channel;

FIG. 10 is a flowchart of a method for several aspects of operations that may be performed in order to control interference using a frequency selective transmission to resolve intentional interference and non-optimal geometries;

FIG. 11A-11B are flowcharts of a method for several aspects of operations that can be performed in order to control interference using an adaptive noise figure and controlling path loss;

FIG. 12 is a flowchart of a method of several aspects of operations that can be performed in order to control interference using sub-frame time reuse technologies;

FIG. 13 is a time quantum diagram illustrating a time division for femto nodes that can be performed in order to control interference using hybrid time reuse technologies;

FIG. 14 is a flowchart of a method of several aspects of operations that can be performed in order to control interference using hybrid time reuse;

FIG. 15 is a simplified block diagram of several exemplary aspects of communication components; and

FIG. 16-21 are simplified block diagrams of several exemplary aspects of devices configured to control interference, as discussed herein.

In accordance with established practice, various features illustrated in the drawings may not be presented to scale. Accordingly, the sizes of the various elements can be arbitrarily increased or decreased for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not illustrate all the components of a given device (eg, device) or method. Finally, like reference numbers may be used to refer to like features throughout the detailed description and drawings.

Detailed description

Various aspects of the disclosure are described below. It should be obvious that the disclosed solutions can be implemented in many forms and that all the specific structures, functions, or both, disclosed in this document are simply representative. Based on the disclosed solutions, those skilled in the art should take into account that the presented aspects can be implemented independently of any other aspects and that two or more of these aspects can be combined in various ways. For example, a device may be implemented or the method may be practiced using any number of aspects set forth herein. In addition, such a device can be implemented or the method can be used in practice using a different structure, functionality or structure and functionality, in addition to or different from one or more aspects set forth herein. In addition, the aspect may contain at least one element of the claims.

In some aspects, the disclosed solutions may be used in a network that includes macro coverage (for example, a large area cellular network such as a 3G network, typically referred to as a macro cellular network) and small scale coverage (for example, the network environment in an apartment or houses). As the access terminal (AT) moves in this network, the access terminal can be served at specific locations through access nodes (AN) that provide macro coverage, while the access terminal can be served at other locations through access nodes that provide small-scale coverage. . In some aspects, small scale coverage nodes can be used to provide incremental throughput, indoor coverage, and various services (for example, for more reliable user experience). As explained in this document, a site that provides coverage in a relatively large area may be referred to as a macro site. A node that provides coverage in a relatively small area (for example, in an apartment) may be referred to as a femto node. A node that provides coverage for an area that is smaller than the macroregion and larger than the femtoregion may be referred to as a pico node (for example, when providing coverage inside an office building).

A cell associated with a macro node, a femto node, or a pico node may be referred to as a macro cell, a femto cell, or a pico cell, respectively. In some implementations, each cell may be further associated (eg, divided) with one or more sectors.

In various applications, other terms may be used to refer to a macro node, a femto node, or a pico node. For example, a macro node may be configured or referred to as an access node, base station, access point, e-node B, macro cell, etc. In addition, the femto node can be configured or referred to as own node B, own e-node B, access point, base station, femtocell, etc.

FIG. 1 illustrates exemplary aspects of a communication system 100 in which distributed nodes (eg, access points 102, 104, and 106) provide wireless connectivity to other nodes (eg, access terminals 108, 110, and 112) that can be installed or which can move throughout the associated geographic area. In some aspects, access points 102, 104, and 106 may communicate with one or more network nodes (eg, a centralized network controller, such as network node 114) to facilitate connectivity to a wide area network.

An access point, such as access point 104, can be limited, whereby only certain access terminals (eg, access terminal 110) are allowed to access the access point, or the access point can be limited in some other way. In this case, the limited access point and / or its associated access terminals (for example, access terminal 110) may interfere with other nodes in the system 100, such as, for example, an unlimited access point (for example, macro access point 102), its associated access terminals (e.g., access terminal 108), another limited access point (e.g., access point 106) or its associated access terminals (e.g., access terminal 112). For example, the closest access point to a given access terminal may not be the serving access point for this access terminal. Therefore, transmissions through this access terminal may interfere with reception at the access terminal. As explained in this document, frequency reuse, frequency selective transmission, interference suppression, and an intelligent antenna (e.g., beamforming and zero position control), as well as other technologies, can be used to reduce interference.

Exemplary system operations, such as system 100, are explained in more detail in connection with the flowchart of FIG. 2. For convenience, the operation of FIG. 2 (or any other operations explained or discussed herein) may be described as being performed by specific components (for example, components of a system 100 and / or components of a system 300, as shown in FIG. 3). It should be appreciated, however, that these operations can be performed by other types of components and can be performed using a different number of components. You should also take into account that one or more of the operations described in this document may not be used in this implementation.

For purposes of illustration, various aspects of the disclosure are described in the context of a network node, an access point, and an access terminal that communicate with each other. It should be appreciated, however, that the disclosed solutions may be applicable to other types of devices or devices that are referred to using other terms.

FIG. 3 illustrates several exemplary components that may be included in a network node 114 (eg, a radio network controller), an access point 104, and an access terminal 110 in accordance with the disclosed solutions. It will be appreciated that the components illustrated for a given one of these nodes may also be included in other nodes in the system 100.

Network node 114, access point 104, and access terminal 110 include transceivers 302, 304, and 306, respectively, for exchanging data with each other and with other nodes. The transceiver 302 includes a transmitter 308 for sending signals and a receiver 310 for receiving signals. The transceiver 304 includes a transmitter 312 for transmitting signals and a receiver 314 for receiving signals. The transceiver 306 includes a transmitter 316 for transmitting signals and a receiver 318 for receiving signals.

In a typical implementation, the access point 104 communicates with the access terminal 110 via one or more wireless links, and the access point 104 communicates with the network node 114 via a backhaul. It should be appreciated that wireless or non-wireless communication links may be used between these nodes or others in various implementations. Therefore, transceivers 302, 304, and 306 may include wireless and non-wireless communication components.

Network node 114, access point 104, and access terminal 110 also include various other components that may be used in connection with interference management, as discussed herein. For example, network node 114, access point 104, and access terminal 110 may include interference controllers 320, 322, and 324, respectively, to reduce interference and to provide other related functionality discussed herein. Interference controller 320, 322, and 324 may include one or more components for performing specific types of interference control. Network node 114, access point 104, and access terminal 110 may include communication controllers 326, 328, and 330, respectively, for controlling communication with other nodes and for providing other related functionality discussed herein. Network node 114, access point 104, and access terminal 110 may include synchronization controllers 332, 334, and 336, respectively, for controlling communications with other nodes and for providing other related functionality discussed herein. Other components illustrated in FIG. 3 are explained in the following disclosure.

For purposes of illustration, interference controllers 320 and 322 are illustrated as including several controller components. In practice, however, this implementation may not use all of these components. Here, the hybrid automatic retransmission request (HARQ) controller component 338 or 340 may provide functionality regarding HARQ interlace operations, as discussed herein. The profile controller component 342 or 344 may provide functionality regarding the transmit power profile or reception attenuation operations, as discussed herein. The time quantum controller component 346 or 348 may provide functionality regarding operations of a portion of the time quantum, as discussed herein. Component 350 or 352 of the antenna controller may provide functionality regarding the operation of an intelligent antenna (e.g., forming a radiation pattern and / or controlling the zero position of the radiation pattern), as discussed herein. Reception noise controller component 354 or 356 may provide functionality regarding adaptive noise figure and loss path control operations, as discussed herein. Transmit power controller component 358 or 360 may provide functionality regarding transmit power operations, as discussed herein. The reuse time controller component 362 or 364 may provide functionality regarding time reuse operations, as discussed herein.

FIG. 2 illustrates how a network node 114, an access point 104, and an access terminal 110 can communicate with each other to provide interference control (eg, interference mitigation). In some aspects, these operations may be used in the uplink and / or downlink to reduce interference. In general, one or more of the techniques described in FIG. 2 can be used in more specific implementations, which are described in connection with FIG. 7-14 below. Therefore, for purposes of clarity, descriptions of more specific implementations may not describe these technologies in detail repeatedly.

As represented by step 202, the network node 114 (e.g., the interference controller 320) may optionally set one or more interference control parameters for the access point 104 and / or the access terminal 110. Such parameters can take various forms. For example, in some implementations, the network node 114 may specify types of interference control information. Examples of such parameters are described in more detail below in connection with FIG. 7-14.

In some aspects, setting the interference parameters may include determining how to allocate one or more resources. For example, the operations of step 402 may include specifying how the allocated resource (e.g., frequency spectrum, etc.) can be divided to reuse fractional frequencies. In addition, setting the parameters for the repeated use of fractional frequencies can include determining how much of the allocated resource (for example, how many HARQ interlaces, etc.) can be used through any of a set of access points (for example, limited access points) . Setting parameters for the repeated use of fractional frequencies can also include determining how much of a resource can be used through a set of access points (for example, limited access points).

In some aspects, the network node 114 may set a parameter based on received information that indicates whether or not interference may occur in the uplink or downlink and, if so, the extent of such interference. Such information can be received from various nodes in the system (for example, access points and / or access terminals) and in various ways (for example, via a transit connection, over the air interface, etc.).

For example, in some cases, one or more access points (eg, access point 104) may monitor the uplink and / or downlink and send an interference indicator detected in the uplink and / or downlink to the network node 114 (for example, on a repeated basis or upon request). As an example of the first case, the access point 104 can calculate the signals, the intensity of the signals that it receives from nearby access terminals that are not associated (for example, are not served by) with the access point 104 (for example, access terminals 108 and 112), and report them to the network node 114.

In some cases, each of the access points in the system can form a load indicator when it is subjected to a relatively high load. Such an indicator may take the form of, for example, a 1xEV-DO busy bit, relative transmission grant channel (RGCH) in 3GPP, or some other suitable form. In a traditional scenario, the access point may send this information to the associated access terminal via a downlink. However, such information can also be sent to network node 114 (for example, through a transit connection).

In some cases, one or more access terminals (eg, access terminal 110) may monitor downlink signals and provide information based on this monitoring. Access terminal 110 may send such information to access point 104 (for example, which can redirect information to network node 114) or to network node 114 (via access point 104). Other access terminals in the system may send information to network node 114 in a similar manner.

In some cases, the access terminal 110 may generate measurement reports (e.g., on a repeated basis). In some aspects, such a measurement report may indicate from which access points the access terminal 110 receives signals, a received signal strength indicator associated with signals from each access point (e.g., Ec / Io), path loss to each of the points access or some other suitable type of information. In some cases, the measurement report may include information regarding all load indicators that the access terminal 110 receives via the downlink.

Network node 114 may then use the information from one or more measurement reports to determine whether or not access point 104 and / or access terminal 110 is relatively close to another node (eg, to another access point or access terminal) . In addition, the network node 114 may use this information to determine whether or not any of these nodes interferes with any other of these nodes. For example, the network node 114 may determine the intensity of the received signal at the node based on the transmit power of the node that transmits the signals and the path loss between these nodes.

In some cases, the access terminal 110 may generate information that is indicative of a signal-to-noise ratio (e.g., a signal-to-interference-and-noise ratio, SINR) in a downlink. Such information may include, for example, a channel quality indicator (CQI), a data rate control indicator (DRC), or some other appropriate information. In some cases, this information may be sent to access point 104, and access point 104 may redirect this information to network node 114 for use in interference control operations. In some aspects, the network node 114 may use such information to determine whether or not there is interference in the downlink, or to determine whether the interference in the downlink is increasing or decreasing.

As described in more detail below, in some cases, interference-related information can be used to determine how to reduce interference. As one example, CQI or other suitable information may be received based on HARQ interlaces, whereby it can be determined which HARQ interlaces are associated with the least interference. A similar technology can be used for other fractional frequency reuse technologies.

It should be appreciated that the network node 114 may set parameters in various other ways. For example, in some cases, the network node 114 may optionally select one or more parameters.

As represented by step 204, the network node 114 (for example, communication controller 326) sends the specified interference control parameters to the access point 104. As explained below, in some cases, the access point 104 uses these parameters, and in some cases, the access point 104 redirects these parameters to the access terminal 110.

In some cases, the network node 114 may control the interference in the system by setting the interference control parameters to be used by two or more nodes (eg, access points and / or access terminals) in the system. For example, in the case of the fractional frequency reuse scheme, the network node 114 may send various (e.g., mutually exclusive) interference control parameters to neighboring access points (e.g., access points that are close enough to potentially interfere with each other) . As a specific example, network node 114 may assign a first HARQ interlace to access point 104 and assign a second HARQ interlace to access point 106. Thus, communication in one limited access point may practically not interfere with communication in another limited access point.

As represented by step 206, the access point 104 (e.g., the interference controller 322) determines the interference control parameters that it can use or which it can send to the access terminal 110. In cases where the network node 114 sets the interference control parameters for the access point 104, this determination operation may simply include receiving the specified parameters and / or retrieving the specified parameters (for example, from a storage device).

In some cases, the access point 104 determines the interference control parameters on its own. These parameters may be similar to the parameters explained above in connection with step 202. In addition, in some cases, these parameters can be determined in the same way as explained above in step 202. For example, the access point 104 may receive information (for example, reports on measurements, CQI, DRC) from access terminal 110. In addition, access point 104 may monitor the uplink and / or downlink to determine interference on that link. Access point 104 may also optionally select a parameter.

In some cases, the access point 104 may interact with one or more other access points to determine an interference control parameter. For example, in some cases, the access point 104 may exchange data with the access point 106 to determine which parameters are used by the access point 106 (and thereby select different parameters), or to coordinate the use of different (for example, mutually exclusive) parameters. In some cases, the access point 104 may determine whether or not it can interfere with another node (for example, based on CQI feedback, which indicates that another node is using a resource), and if so, set the interference control parameters so, to reduce such potential interference.

As represented by step 208, the access point 104 (eg, communication controller 328) may send interference control parameters or other related information to the access terminal 110. In some cases, this information may relate to power control (for example, indicates uplink transmit power).

As represented by steps 210 and 212, the access point 104 may thereby transmit to the access terminal 110 in the downlink, or the access terminal 110 may transmit to the access point 104 in the uplink. Here, the access point 104 may use its interference control parameters to transmit in the downlink and / or receive in the uplink. Similarly, access terminal 110 may take into account these interference control parameters for downlink reception or uplink transmission.

In some implementations, an access terminal 110 (eg, an interference controller 306) may set one or more interference control parameters. Such a parameter may be used by the access terminal 110 and / or sent (for example, via the communication controller 330) to the access point 104 (for example, for use during uplink operation).

FIG. 4 illustrates a wireless communication system 400 configured to support a certain number of users in which ideas in this document may be implemented. System 400 provides communication for several cells 402, such as, for example, macro cells 402A-402G, with each cell being served by a corresponding access node 404 (e.g., access nodes 404A-404G). As shown in FIG. 4, access terminals 406 (e.g., access terminals 406A-406L) may be dispersed at various locations throughout the system over time. Each access terminal 406 can communicate with one or more access nodes 404 in a downlink (DL) (also known as a forward link (FL)) and / or an uplink (UL) (also known as a reverse link (RL )) at the moment, depending, for example, on whether or not access terminal 406 is active and whether or not it is in soft handoff mode. Wireless communication system 400 may provide services for a large geographic area. For example, 402A-402G macro cells can cover several neighborhoods in an environment.

As indicated, a node or localized access point that provides coverage in a relatively small area (for example, in an apartment) may be referred to as a femto node. FIG. 5A illustrates an example communications system 500 in which one or more femto nodes are deployed within a network environment. In particular, the system 500 includes several femto nodes 510 (for example, femto nodes 510A and 510B) installed in a relatively small-scale network environment (for example, in one or more user apartments 530). Each femto node 510 can be connected to a global network 540 (for example, the Internet) and a core network 550 of a mobile operator via a DSL router, cable modem, wireless line, or other means of connection (not shown). As explained below, each femto node 510 can be configured to serve associated access terminals 520 (e.g., access terminal 520A) and, optionally, unassociated (extraneous) access terminals 520 (e.g., access terminal 520F). In other words, access to the femto nodes 510 can be limited, whereby a given access terminal 520 can be serviced by a set of said own femto nodes 510, but cannot be served by unspecified external (extraneous) femto nodes 510 (for example, by means of a neighboring femto node 510).

FIG. 5B illustrates a more detailed view of the non-optimal geometries of several femto nodes and access terminals within a network environment. In particular, the femto node 510A and the femto node 510B, respectively, are deployed in neighboring user apartment 530A and user apartment 530B. Access terminals 520A-520C are allowed to associate and exchange data with the femto node 510A, but not with the femto node 510B. Similarly, the access terminal 520D and the access terminal 520E are allowed to associate and communicate with the femto node 510B, but not with the femto node 510A. Access terminal 520F and access terminal 520G are not allowed to associate or exchange data with either the femto node 510A or the femto node 510B. Access terminal 520F and access terminal 520G may be associated with a macro cell access node 560 (FIG. 5A) or another femto node in another apartment (not shown).

In unplanned deployments of a femto node 510 with limited associations (i.e., the access point may not be allowed to associate with the “closest” femto node providing the most preferred signal quality), intentional interference and non-optimal geometries may be common. Solutions to resolve these non-optimal geometries are further explained below.

FIG. 6 illustrates an example of a coverage map 600 when multiple tracking areas 602 (or routing areas or location areas) are defined, each of which includes several macro coverage areas 604. Here, coverage areas associated with tracking areas 602A, 602B and 602C are delineated by wide lines, and macrocoating areas 604 are represented by hexagons. Tracking areas 602 also include femto coverage zones 606. In this example, each of the femto coverage zones 606 (e.g., the femto coating zone 1606C) is illustrated within the macro coverage zone 604 (e.g., the macro coating zone 604B). It should be noted, however, that the femto coating area 606 may not be entirely within the macro coverage area 604. In practice, a large number of femto coverage zones 606 can be defined using this tracking area 602 or macro coverage zone 604. In addition, one or more peak coverage areas (not shown) may be defined within a given tracking area 602 or macro coverage area 604.

Referring again to FIG. 5A-5B, the owner of the femto node 510 may subscribe to a mobile service, such as, for example, a 3G mobile service offered through a core network 550 of a mobile operator. In addition, access terminal 520 may be capable of operating both in macro-environments and in small-scale network environments (e.g., residential). In other words, depending on the current location of the access terminal 520, the access terminal 520 may be served by the access node 560 of the macrocellular mobile network 550 or by any of a set of femto nodes 510 (for example, femto nodes 510A and 510B, which are permanently located inside the corresponding apartment 530 of the user ) For example, when a subscriber is away from home, he is served through a standard access macro node (e.g., node 560), and when a subscriber is at home, he is served through a femto node (e.g., node 510A). Here, it should be appreciated that the femto node 520 may be backward compatible with existing access terminals 520.

Femtocell 510 may be deployed at a single frequency or, alternatively, at multiple frequencies. Depending on the specific configuration, one frequency or one or more of several frequencies may overlap with one or more frequencies used by the macro node (for example, node 560).

In some aspects, the access terminal 520 may be configured to connect to a preferred femto node (eg, a native femto node of an associated access terminal 520) whenever this connectivity is possible. For example, each time the access terminal 520 is in the user's apartment 530, it may be desirable for the access terminal 520 to communicate only with its own femto node 510.

In some aspects, if the access terminal 520 operates on a macrocellular network 550 but is not permanently located in its most preferred network (e.g., specified in the preferred roaming list), the access terminal 520 may continue to search for the most preferred network (e.g., its own femto node 510) by re-selecting the best system (BSR), which can include periodically scanning available systems to determine whether or not optimal systems are currently available, and last riding activities in order to be associated with such preferred systems. When recording a discovery, access terminal 520 may limit the search to a specific frequency band and channel. For example, a search for the most preferred system may be repeated periodically. Upon detection of the preferred femto node 510, the access terminal 520 selects the femto node 510 to wait for a call within its coverage area.

Femtocell may be limited in some aspects. For example, a given femto node can provide only certain services to certain access terminals. In deployments with so-called limited (or closed) association, this access terminal can only be serviced by a macrocellular mobile network and a given set of femto nodes (for example, femto nodes 510, which are constantly located in the corresponding apartment 530 of the user). In some implementations, a node may be limited so as not to provide at least one node with at least one of the following: signaling, data access, registration, paging, or service.

In some aspects, a restricted or external (extraneous) femto node (which may also be referred to as a private node B of a closed subscriber group) is a femto node that provides services to a limited initialized set of access terminals. This kit can be expanded temporarily or continuously as needed. In some aspects, a closed subscriber group (CSG) may be defined as a set of access nodes (eg, femto nodes) that share a common access control list of access terminals. A channel in which all femto nodes (or all restricted femto nodes) in a region operate may be referred to as a femto channel.

Various relationships can thus exist between a given femto node and a given access terminal. For example, from the point of view of an access terminal, an open femto node may be referred to as a femto node without limited association. A restricted femtocell may be referred to as a femtocell, which is limited in some way (for example, restricted for association and / or registration). An own femtocell may be referred to as a femtocell for which the access terminal is authorized to access and operate. The invited femtocell may be referred to as a femtocell for which the access terminal is temporarily authorized to access and operate. A limited or external (extraneous) femtocell can be referred to as a femtocell for which the access terminal is not authorized to access and operate, with the possible exception of emergency situations (for example, emergency calls).

From the point of view of a restricted or external femto node, an associated or own access terminal may be referred to as an access terminal that is authorized to access the restricted femto node. The invited access terminal may be referred to as an access terminal with temporary access to a limited femto node. An unassociated (rogue) access terminal may be referred to as an access terminal that does not have permission to access a limited femto node, except possibly in emergency situations, such as emergency calls (for example, an access terminal that does not have credentials or permission to register with limited femto node).

For convenience, the disclosure in this document describes various functionality in the context of a femto node. It should be noted, however, that the pico node can provide identical or similar functionality for a larger coverage area. For example, a pico node may be limited, a private pico node may be defined for a given access terminal, etc.

A multiple access wireless communication system may simultaneously support communication for multiple wireless access terminals. As mentioned above, each terminal can exchange data from one or more base stations by transmitting on the downlink (forward link) and uplink (reverse link). A downlink refers to a communication link from base stations to terminals, and an uplink refers to a communication link from terminals to base stations. This communication line can be established through a system with one input and one output, a system with many inputs and many outputs (MIMO), or some other type of system.

The MIMO system uses several (N _T ) transmit antennas and several (N _R ) receive antennas for data transmission. A MIMO channel formed by N _T transmit and N _R receive antennas can be decomposed into N _S independent channels, which are also referred to as spatial channels, where N _S <min {N _T , N _R }. Each of the N _S independent channels corresponds to a dimension. A MIMO system can provide increased performance (for example, higher throughput and / or greater reliability) if additional dimensions are created using multiple transmit and receive antennas.

A MIMO system can support time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, forward and reverse link transmissions are in the same frequency domain, so the reversibility principle provides an opportunity to estimate a downlink channel (forward link) from an uplink channel (reverse link). This allows the access point to benefit from the downlink transmission pattern when multiple antennas are available at the access point.

As indicated, in unplanned deployments of base stations with limited association (i.e., the mobile station is not allowed to associate with the “closest” base station with which it has the strongest link), intentional interference and non-optimal geometries may be common. In one exemplary embodiment described in detail in connection with FIG. 5B, the femto node 510A and the femto node 510B are deployed in neighboring apartments. Access terminals 520A-520C are allowed to associate and exchange data with the femto node 510A, but not with the femto node 510B. Similarly, access terminals 520D-520E are allowed to associate and exchange data with the femto node 510B, but not with the femto node 510A. Access terminals 520F-520G are not allowed to associate or exchange data with femto nodes 510A-510B. Access terminals 520F-520G may be associated with a macro cell access node 560 (FIG. 5A) or another femto node in another apartment (not shown). Accordingly, such non-optimal geometries with respect to authorized access femto nodes and neighboring access terminals may occur under various conditions of mutual interference or suppression in the uplink and downlink.

Uplink interference

As an example, let L _A3 (dB) and L _A5 (dB) be the path loss between the femto node 510A and the access terminal 520C and the access terminal 520D, respectively. In particular, L _A3 can far exceed L _A5 . Thus, when the access terminal 520D transmits to the own femto node 510B, it causes excessive interference (or suppression) in the femto node 510A, effectively blocking the reception of the access terminals 520A-C in the femto node 510A. In case of interference in the uplink, even if the access terminal 520C transmits at a maximum Tx power P _3max , the received C / I for the access terminal in the femto node 510A may differ as follows:

C / I (AT 520C in the femto node 510A) = P _3max -L _A3 - (P ₅ -L _A5 ) (dB)

In some exemplary embodiments, depending on the transmit power P ₅ C / I of the access terminal 520C, the femto node 510A may be a very large negative value due to the large value of L _A3 . This configuration geometry is referred to as very non-optimal uplink geometry.

Downlink interference

Similarly, in one exemplary embodiment, L _B5 can far exceed L _A3 . This implies that when the femto node 510A transmits to the access terminal 520A, it can cause excessive interference (or suppression) in the access terminal 520D, effectively blocking the reception of the femto node 510B in the access terminal 520D. In this case, the downlink interference received by the C / I for the femto node 510B in the access terminal 520D can be calculated as follows:

C / I (femtocell B in AT 5) = P _B -L _B5 - (P _A -L _A3 ) (dB)

On the other hand, the C / I of the femto node 510B in the access terminal 520D can be a very large negative value due to the large value of L _B5 . This configuration geometry is referred to as very negative downlink geometry.

An additional practical consideration includes the resolution of non-optimal geometries without the need for modifications to the operation of deployed (existing) access terminals. Therefore, it is desirable in the present exemplary embodiment to allow the reduction of interference from non-optimal geometries through modification processes in the femto node instead of the need for modifications in access terminals. Accordingly, non-optimal geometries in the uplink and downlink are preferably resolved according to the exemplary embodiment disclosed below.

Referring now to FIG. 7 and again referring to FIG. 5A-5B, operations are described in more detail regarding the use of beam control and zero position control to resolve intentional interference and non-optimal geometries. The present exemplary embodiment uses methods and devices to prevent interference and non-optimal geometries using radiation pattern control and radiation pattern control in unplanned deployments of restricted base stations.

In an exemplary scenario for the deployment of femto nodes, the nearest signals (required or interference) may have a Ricean distribution in nature, which includes a strong directional component and uniform attenuation over the frequency band (due to a small spread of delays and several reflected paths in indoor environments). In particular, for cases of interference, sectorization may provide the desired method for counteracting the strong interference component with Rays distribution.

As represented by step 702, the femto node 510 continuously listens (i.e., receives according to various receiver configurations described herein) for transmissions from access terminals 520. As represented by request 704, the femto node 510 determines whether or not an access test message (eg, transmission) is sent via the access terminal to the femto node 510. If the detected access terminal test message is sent to a specific femto node 510, then as represented by step 706 , interference mitigation is not required since the access terminal is an “associated” access terminal with a “native” femto node.

As represented by query 708, the femto node 510 further compares the characteristic (eg, power level) of the access test message to determine whether or not the characteristic has a sufficient threshold level to cause interference in its own femto node. When the test access message does not exceed the interference threshold, then, as represented by step 706, interference mitigation is not required, since the characteristic of the access test message through the “native” femto node 510 leads to acceptable interference.

As represented by step 710, when the native femto node 510 receives a strong enough (i.e., above the threshold interference value) access test message or other strong uplink transmission from an unassociated access terminal 520, the native femto node 510 applies antennas with beamforming ( i.e., directional transmission and reception) in order to control signals or the absence of signals (e.g., zeros) towards a downstream access terminal 520 communication and uplink.

By way of example, beamforming (i.e., beamforming control) can be performed using a sectorized or directional (e.g., switched beam) antenna configuration described herein to form a transmitted signal beam and / or zero or beam received signal and / or zero. In particular, interference cancellation can be provided for a received radio frequency (RF) signal, thereby reducing problems such as overloading the high frequency path and reducing the sensitivity to interference of the analog-to-digital converter of the receiving device that result from intentional interfering femto nodes. In addition, sectorized or directional antenna configurations allow the downlink and uplink to support an identical directional component for use in both directions of the communication line.

As represented by step 712, the transmission of pilot and overhead signals in the downlink, as well as the transmission of traffic channels, if any, are transmitted according to beamforming so that the minimum energy is directed towards a nearby unassociated access terminal. Controlling the transmitted signal from the unassociated access terminal reduces the non-optimal geometry in the unassociated access terminal.

As represented by step 714, the directional zero is controlled toward a nearby unassociated access terminal 520 using an antenna configuration (e.g., sectorized antennas or zero position control with adaptive phased array antennas) described herein. Therefore, when the associated access terminal 520 attempts to communicate with its own femto node 510, the test access message of the associated access terminal, as well as the transmission of other traffic (e.g., speech / data) are not intentionally interfered with by strong transmissions from nearby unassociated access terminals having non-optimal geometry.

As an example, if the access point uses two separate antennas, the AP can track the characteristics of the AT access test message for both antennas. If it is determined that strong uplink transmission from an unassociated access terminal in one of the antennas is performed, the AP may disable the transmit (beam control) function and disable the receive (zero beam control) function for that antenna.

As presented in the request 716, periodically (for example, once per second) the femto node 510 excludes zero sectorization in the receiving direction to determine, as presented in step 702, whether the strong unwanted unassociated access terminal 520 has moved or not. If, as presented in request 704, the strong interfering signal has disappeared, the femto node 510 can eliminate sectorization zero and continue to operate in the omnidirectional transmission and reception mode, as presented in step 706. If the strong interfering signal is still present or has shifted and exceeds the threshold value, as represented by block 708, the femto node 510 may adjust the sectorization zero position control for transmission and reception, as shown in block 710, in the direction of the undesired unassociated access terminal 520.

The above example with reference to FIG. 5B illustrates a femto node 510A controlling the receive and transmit sectorization zero towards an unassociated access terminal 520D as long as an unassociated access terminal 520D is present and supports an active call with the femto node 510B. When the unassociated access terminal 520D is idle, the femto node 510A should return to the omnidirectional transmission and reception mode.

During periods when the femtocell controls sectorization zero in a particular direction, if there are any associated access terminals 520 in that direction, they are prone to interruptions. Accordingly, in an exemplary embodiment, the femto node 510 controls sectorization zeros (i) as long as the strong unwanted unassociated access terminal 520 is active, and (ii) only if the unwanted transmission from the unassociated access terminal 520 exceeds a high threshold signal strength at the receiver, as defined in request 408, which means that test access messages from the required associated access terminals should not be decoded in the femto node 510. With reference to fi g. 5B, it should be noted that the femto node 510B need not necessarily control the sectorization zero towards the unassociated access terminal 520A, since the signal from the unassociated access terminal 520A is not very strong. If the femto node 510B controls this sectorization zero towards the unassociated access terminal 520A, the sectorization zero should cause interruptions in the desired associated access terminal 520E.

As a general case of the described method, if the AP cannot determine the direction of interference from an unassociated access terminal (for example, the very strong intentional interference that saturates the receiving device of the AP), it can try different directions to control the radiation pattern and control the zero position of the radiation pattern, to maximize the quality of the received signal from the associated AT.

Referring now to FIG. 8 and again referring to FIG. 5A-5B, operations are described in more detail regarding the use of optimization in transmission power over service channels to resolve intentional interference and non-optimal geometries. The present exemplary embodiment uses methods and devices to prevent deliberate interference and non-optimal geometries using optimized overhead transmission power levels in unplanned base station deployments.

In general, the overhead transmission power amplification and the total femto node transmit power are selected based on the desired femto node range. To allow access terminals to detect a femto node at a location where the access terminal is intentionally interrupted by a neighboring femto node that restricts association, overhead channels (for example, common control channels such as pilot, synchronization, and broadcast / paging channels) can be multiplexed time division channels. Various numbers of timelines and methods for time division multiplexing are considered. In addition, overhead channels can only be switched on periodically, for example, at a time quantum index of the associated access terminals, so that the associated access terminals can receive paging messages. In an additional configuration, the femto node may not transmit a signal at all.

However, during an active voice call or data transfer, there may not be periods of inactivity that allow a neighboring femto node to multiplex time-division channels of intentional interference in service channels resulting from non-optimal geometries. Accordingly, an exemplary embodiment describes a method for optimizing transmission power for overhead signals (e.g., pilot, synchronization, and broadcast / paging channels) when there is an active call in the femto node and time division multiplexing of overhead channels is impractical.

For example, in 1xRTT and WCDMA networks, the gain settings of service channels (for example, pilot signal channels, search calls, synchronization) are adjusted for a specific performance based on limitations in geometry and coverage. In addition, femto node deployments show some significant differences compared to macro cell access node deployments. Various differences include:

1. Due to the limited coverage size, the maximum values of losses in the transmission path are much lower in areas (for example, cells) served by femtocells, compared with areas (for example, cells) served by macrocell access nodes (for example, maximum losses in the transmission path of 80 dB compared to 140 dB in macrocell deployment);

2. The number of simultaneously active access terminals is less in cells served by femto nodes than in cells served by macrocell access nodes (for example, 1-2 users compared to 20-40 users);

3. As explained above, due to the requirements of limited association for the femto node, non-optimal geometries may be characteristic of the deployment of femto nodes as opposed to the deployment of macrocell access nodes.

These differences can lead to completely different optimal power values for service channels for femto nodes 510. Since a femto node 510 generally has few (or no at all) active access terminals 520, it should be desirable to maintain service channels at a minimum power value to minimize interference for neighboring cells served by femtocells 510 and cells served by macrocell access nodes 560 (i.e., under the condition of an intra-channel mode of operation). As an example, one exemplary embodiment is aimed at optimizing the pilot channel, however, the analysis can also be applied to other overhead channels.

In an exemplary embodiment, the optimal traffic to pilot ratio (T2P) value is determined for the case of a single voice call, as well as the default pilot strength setting, Ecp _DEFAULT . When downlink power control (forward link) results in a modified traffic to pilot ratio, the pilot power is adjusted to maintain the lowest total transmit power and interference caused by the adjacent femto node.

As an example, the access terminal 520A at the boundary of the own femto node 510A and the neighboring femto node 510B shows equal losses in the transmission path to both femto nodes 510, and the neighboring femto node 520B transmits at full power, thereby creating interference, Ior_max. In the present example, provided that the native femto node 510A transmits the pilot channel at a gain level, Ecp, the signal-to-noise ratio of the pilot channel (SNR) can be written as follows: Ecp / Ior_max. According to the present exemplary embodiment, it is desirable to find the optimal Ecp setting that results in the smallest total transmitted power from the own femto node 510A.

As represented by step 802, the gain of the pilot channel Ecp is initialized to Ecp _DEFAULT . Thus, the default value Ecp (Ecp _DEFAULT ) can be determined on the basis of reasonable values of the difference between the load and the losses in the transmission path expected in femto networks.

As presented at block 804, a traffic call (e.g., a voice call) is established between the own femtocell 510A and the access terminal 520A with the power used in the traffic channel designated as Ect. In one exemplary embodiment, the Ect value is determined by downlink power control (forward link), as represented by request 806. Downlink power control (forward link, FL) is used to maintain the required quality of service ( for example, packet error rate, PER). Downlink power control (forward link, FL) may indicate a decrease in Ect, as represented by block 808, an increase in Ect, as represented by block 810, or no change in Ect.

As presented in request 812, packet error rate determination (PER) is used to identify adequate signal quality. In general, if Ecp is very low, then the quality of the channel estimate is degraded, resulting in a very large Ect. As Ecp increases, the channel estimate should improve, and the required Ect should decrease. Nevertheless, if Ecp is very large, then the quality of the channel estimate exceeds the required value, which does not lead to a further decrease in Ect. Accordingly, when the PER is insufficient, the downlink (forward link, FL) power control adjusts the Ect.

Since interference with other femto nodes should be minimized, it should be desirable to have an optimal Ecp value that minimizes (Ect + Ecp). As represented by block 814, Ecp _OPTIMAL is determined where

at another optimal Ecp value, it was found that minimizes the total transmit power, where

(The function f (.) Can be defined through offline simulations or tests).

Then, as represented by step 816, the optimal value of Ect is determined as follows:

As represented by step 818, the T2P _OPTIMAL is determined as follows:

In another exemplary embodiment, simulations can be performed to find Ecp _OPTIMAL and Ect _OPTIMAL for typical channel types expected in femtocell cells using, for example, uniform attenuation models with a Rayleigh or Rais distribution with a low Doppler frequency that can tracked by power control. These optimal values depend, in one exemplary embodiment, on the specific difference in the losses in the transmission path of the access terminal to the neighboring femtocell and the interference power received from the neighboring femtocell (for example, if the mobile terminal has losses in the transmission path to the neighboring femtocell 3 dB less compared with the own femtocell, the optimal values of Ecp and Ect should be increased by 3 dB).

On the other hand, in an alternative exemplary embodiment, if a neighboring femtocell transmits halfway from Ior_max, then the optimal Ecp and Ect values should be reduced by 3 dB. However, we also note that it is not very practical to change Ecp values very often, since it determines the boundaries of the femto cell handoff. Thus, as indicated, the default value Ecp (Ecp _DEFAULT ) can be determined on the basis of reasonable values of the difference in load and losses in the transmission path expected in femto networks.

Referring now to FIG. 9, in order to maintain an optimal mode of operation for cases with a higher than expected difference in load and loss in the transmission path, in one exemplary embodiment, the following algorithm may be performed for each of the plurality of calls made between the femto node and several associated access terminals.

As represented by step 902, the gain of the Ecp pilot channel is initialized to Ecp _DEFAULT to analyze each voice call. Thus, the default value Ecp (Ecp _DEFAULT ) can be determined on the basis of reasonable values of the difference between the load and the losses in the transmission path expected in femto networks.

As presented at 904, the process is repeated for each call setup between the own femtocell 510A and the associated access terminals 520 with the power used in the traffic channel designated as Ect. In one exemplary embodiment, the value of Ect is determined by controlling downlink power (forward link, FL), as represented by request 906. Downlink power control (forward link, FL) is used to maintain the required quality of service (for example, packet error rate, PER). Downlink power control (forward link, FL) may indicate a decrease in Ect, as represented by step 908, an increase in Ect, as represented by step 910, or no change in Ect.

As presented in Request 912, packet error rate determination (PER) is used to identify adequate signal quality. Accordingly, when the PER is insufficient, the downlink (forward link, FL) power control adjusts the Ect.

As represented by step 918, T2 _PFILTERED (e.g., Ect _FILTERED / Ecp _FILTERED ) is monitored during a call. The purpose of T2P filtering is to exclude small-scale fluctuations from the T2P calculation. For example, a moving average filter can be used to filter Ect and Ecp values to calculate Ect _FILTERED and Ecp _FILTERED , respectively.

As presented in query 920, a determination is made with respect to the value of T2 _PFILTERED . If T2P _FILTERED > T2P _OPTIMAL + Δ ₁ , then, as presented in step 922, Ecp rises to the following value:

As presented in query 924, a determination is made regarding the value of T2 _PFILTERED . If T2P _FILTERED <T2P _OPTIMAL -Δ ₂ , then, as presented in step 926, Ecp decreases to the following value:

T2P _OPTIMAL depends on the specific traffic configuration (speed, encoding, etc.). For example, if two users make voice calls with vocoders of the same speed, they should have the same T2P _OPTIMAL . However, if there is another user performing the data transfer (for example, data transmission according to 1xRTT at 153 Kbps), this should be required by another T2P _OPTIMAL . When T2P _{OPTIMAL is} defined for a given user (based on his type of traffic), then the algorithm automatically adjusts Ecp. The above algorithm is specified for a single user. If there are several users, then the algorithm can lead to different Ecp values for each user. However, service channels are common to all users, and there can only be one Ecp setting. Thus, the algorithm can be generalized to the case of multiple users. As an example, the “optimal” Ecp _i for each user (i = 1, ..., N) in the system can be detected as described above, and then the actual Ecp can be defined as max (Ecp ₁ , ..., Ecp _N ). Another option may be to find the optimal Ecp so that the total power transmitted as overhead information and traffic to all users is minimized. This means modifying the calculation of step 814 as follows:

for 1-N users in a femtocell. The purpose of T2P filtering is to exclude small-scale fluctuations from the T2P calculation. For example, a moving average filter can be used to filter Ect and Ecp values to calculate Ect _FILTERED and Ecp _FILTERED , respectively.

The optimal T2P can be obtained through simulations, and after T2P is determined, the power control adjustment Ect (which is part of the standard 3G operation mode) can be determined. Then Ecp is adjusted to achieve / maintain optimal T2P. In particular, two algorithms can be performed together: 1) the power control algorithm that controls Ect, and 2) the Ecp regulation described in this document.

In the above algorithm, Δ ₁ and Δ ₂ are the hysteresis parameters used to prevent rapid fluctuations in Ecp. In addition, in order to prevent sudden changes in Ecp, the equations above can be modified, in one exemplary embodiment, so as to enable slower execution of Ecp correction. Finally, other overhead channels (e.g., paging, synchronization) can be adjusted based on the power level of the pilot signals (i.e. their relative power level relative to the power level of the pilot signals can be kept constant).

Accordingly, exemplary embodiments are described to reduce transmission power for overhead signals (eg, pilot, synchronization, and broadcast / paging channels) when there is an active call in the femto node by determining the optimal overhead power level. An exemplary embodiment is disclosed as an example using a pilot channel as an example channel, however, analysis can also be applied to other overhead channels.

Referring now to FIG. 10 and again referring to FIG. 5A-5B, operations regarding the use of frequency selective transmission to resolve intentional interference and non-optimal geometries are described in more detail. As indicated, due to the unplanned deployment of the femto nodes, the receive SINR for the associated access terminal may become very low due to interference from the transmission of the neighboring femto node. This interference degrades the performance of the control channel and the traffic channel for the access terminal and may lead to interruptions or degraded services. The exemplary embodiment disclosed herein allows operations to improve the performance of an access terminal in a high interference area without having to modify existing access terminals.

In general, an exemplary embodiment introduces intentional frequency selectivity into downlink transmissions by orthogonalizing the transmission waveform for neighboring femto nodes to minimize interference. As an example, each femto node 510 selects the formation of the transmitted pulses by reading the channel from the available waveforms, for example, from three waveforms of the channel with 3 taps for each set of coefficients from this row, for example, a 3x3 DFT matrix. In this case, for a given access point, the transmitted waveform must be filtered using FIR with three taps (in addition to the usual filtering of the modulating frequency band) with the pulse characteristics of the filter selected from one of the following three waveforms:

where exp (jx) = cos (x) + j sin (x).

An alternative is two impulse responses with a factor of DFT 2x2 (N = 2). A transmission filter option is stored for a certain period, after which the femto node 510 can make a selection again based on the channel read.

FIG. 10 describes a method for controlling interference in selecting a transmission waveform of a wireless communication system. As represented by step 1002, a set of N transmit waveforms is allocated to the femto nodes 510 for use in downlink transmissions. In one exemplary embodiment, the channel waveforms may be formed from channel filter coefficients with N taps, each set of coefficients being extracted from a particular row in the NxN DFT matrix.

As represented by step 1004, the femto node 510 selects the default waveform after initialization (e.g., power-up) according to a predetermined selection process (e.g., randomization randomly assigned via the network, etc.). The default waveform comes from a set of N transmit waveforms (in the downlink). The default waveform is initially assigned as the preferred transmit waveform, TxWave _PREFERED .

As represented by request 1006, the femto node 510 transmits on the downlink using the preferred waveform of the transmission when the call is initiated. A call is established with an associated access terminal 520 and includes channel quality indicators (for example, channel quality indicator — CQI, data rate control — DRC) determined by access terminal 520 and routed to the femto node 510 on the uplink.

As represented by query 1008, the femto node initiates a waveform testing cycle for the T_test_waveform time period until all possible waveforms have been tested. As represented by block 1010, the femto node 510 communicates with the associated access terminal 520 using the current waveform. The associated access terminal receives downlink transmissions and generates a channel quality indicator in response to signal quality. The channel quality indicator is redirected in the uplink (reverse link) to the femto node 510.

As represented by block 1012, the femto node monitors the uplink to determine channel quality using the current waveform based on the received channel quality indicator. Femtocell 510 can either generate a table of waveforms and corresponding channel quality indicators, or compare the current channel quality indicator with all previous channel quality indicators and save the indicator relative to the preferred waveform.

As represented by block 1014, the waveform testing is increased to the next extracted waveform for further evaluation. An exemplary waveform selection process is performed iteratively until possible waveforms have participated in the downlink transmission and the corresponding channel quality indicator has not been received in the uplink. As represented by step 1016, the preferred waveform based on determining the channel quality is then selected as the preferred transmission waveform that provides better channel quality in the presence of interference from non-optimal geometries associated with deployments of other unplanned deployments of base stations.

As represented by block 1018, the preferred waveform may be periodically updated based on various factors including a particular time period, call termination, channel degradation threshold value, or other channel characteristics known to those skilled in the art. After determining the update, processing returns to evaluate the channel quality of the various possible transmission waveforms.

The present exemplary embodiment controls interference from a strong interference energy from neighbors due to the orthogonality of the Fourier sequence in the dominant signal energy during convolution by creating intrinsic noise through ISI and thereby limiting performance with good geometry. Additional amplifications can be achieved using the MMSE corrector due to the different frequency coloring of the impulse characteristics for the desired signals and interference signals. This mechanism is valid in the configuration of a femto node when the delay spread is significantly less than one symbol interval of a noise-like sequence.

Referring now to FIG. 11A-11B and again referring to FIG. 5A-5B, operations are described in more detail regarding the use of adaptive noise figure and loss path control to resolve intentional interference and non-optimal geometries. The present exemplary embodiment uses methods and devices to prevent intentional interference and to resolve intentional interference and non-optimal geometries using adaptive noise factors and loss path controls.

In general, femto nodes are connected to the Internet 540 and the base network 550 of a mobile operator via a broadband connection (for example, a DSL router or cable modem). Since the RF coverage of the femto nodes 510 is not manually optimized by the mobile operator's core network 550, and the deployment is generally randomly organized, serious RF interference problems can arise if appropriate mitigation methods are not used.

In a macrocellular network, access terminals 520 and macrocell access nodes 560 are configured to operate in a specific dynamic range. In the cells formed by the femto nodes 510, the own femto node 510 and the associated access terminal 520 can be arbitrarily spatially adjacent, thereby creating very high signal levels outside the sensitivity range of the respective receiving devices. In the downlink (forward link, FL), such a configuration can saturate the receiver of the associated access terminal and create degraded demodulation performance. On the reverse link, this configuration can create a very high noise increase (RoT), which is also known to create instability in the own femto node 510. Thus, the maximum and minimum values of the transmit power levels and noise figure of the receiving device must be adjusted accordingly for own femto nodes 510. This case is illustrated in FIG. 5B with respect to the own femto node 510A and the associated access terminal 520A.

Femto nodes 510B can cause interference both in the uplink (UL) (reverse link, RL) and in the downlink (DL) (forward link, FL) of cells served by macrocell access nodes 560. For example, a femto node 510B installed, for example, near the window of an apartment 530B, can cause significant downlink (DL) interference to outdoor access terminals 520F (i.e., an unassociated access terminal) that are not served by the femto node 510B. In addition, in the uplink (UL), associated access terminals 520 that are served by a particular native femto node 510 can cause significant interference to macro cell access nodes 560.

In the uplink (UL), unassociated access terminals 520F that are served by macrocell access nodes 560 can cause significant interference to the native femto node 510A.

As indicated, femto nodes 510 can also cause significant interference with each other due to unplanned deployment. For example, in nearby apartments 530, the femto node 510 installed near the wall separating the two apartments 530 can cause significant interference to the neighboring femto node 510 in the adjacent apartment 530. In this case, the strongest signal (in terms of the RF signal intensity) from the femto node 510 to the access terminal 520 may not necessarily be the own femto node of the associated access terminal due to the limited association requirement described above. Such a scenario is illustrated in FIG. 5B, when in the downlink (DL), the femto node 510A can cause significant interference (eg, low SINR) for the access terminal 520D. In addition, in the uplink (UL), an unassociated access terminal 520D can cause significant interference (e.g., high RoT) to an external (rogue) femto node 510A.

For example, in the uplink of wireless CDMA networks, system stability and load are usually determined by the ratio of total power to thermal noise (RoT), also known as noise increase, in a femto node. The ratio of total power to thermal noise (RoT) indicates the ratio between the total power received from all sources in the femto node and thermal noise:

Where

Ior: total received power received in the femto node from all wireless devices for which the femto node is in the active set.

Ioc: total received power received in the femto node from all wireless devices for which the femto node is not in the active set.

No: thermal noise dispersion including the femto node noise figure (NF).

For stable uplink (UL) system operation, RoT must be controlled. Typically, RoT is controlled to be approximately 5 dB or higher. High RoT values can lead to significant performance degradation. For example, in FIG. 5B for two neighboring cells generated by the femto nodes 510A and 510B, the high RoT caused by the access terminal 520D in the femto node 510A results in poor performance for the associated access terminal 520C. One particular interference scenario occurs when the neighboring access terminal 520D has packet uplink (UL) traffic and exhibits excessively high power levels (e.g., in the immediate vicinity) in the femto node 510A. Accordingly, during high-speed transmission of data packets on the uplink (UL) from the access terminal 520D, the RoT in the femto node 510A exceeds 20 dB. In addition, the uplink (UL) power control mechanism in CDMA systems (e.g., CDMA2000, WCDMA, 1xEV-DO) is a circuit to withstand this type of interference scenario. However, due to excessive variation in RoT, it may take time for the mechanism through the femto node 510A to control the power of the associated access terminal 520C so as to overcome the interference caused by the unassociated access terminal 520D. Meanwhile, the signal-to-noise ratio (SIR) of the associated access terminal 520C falls below the required levels, resulting in successive uplink (UL) packet transmission errors from the associated access terminal 520C to its own femto node 510A.

In order to minimize the sudden decrease in SIR in the described scenario, one alternative may be to increase the size of the uplink (UL) power control step when transmitting from the own femto node 510A to the associated access terminal 520C. However, upper limits are usually provided for the power control step size, imposed according to communication standards, since other quality degradations in the system occur when the system operates at a very high power control step. Thus, it is desirable to control the RoT level in the femto node 510.

To prevent abrupt transitions to RoT due to a sudden increase in interference caused by unassociated access terminals (e.g., interference generated by an unassociated access terminal 520D at the femto node 510A), the noise figure NF may increase, or the received signal may be attenuated by adding some loss component in the transmission path (PL) in the uplink (UL). However, such an operation is performed in a femto node exposed to a high level of interference. For example, in the scenario shown in FIG. 5B, if both the femto node 510A and the femto node 510B increase the noise figure NF or attenuation by the same amount, the result is large transmission power levels in the uplink (UL) for both the access terminal 520C and the access terminal 520D. As a result, the problem of the occurrence of high RoT in the 510A femto node is not resolved.

According to an exemplary embodiment, a femto node exhibiting high RoT, a femto node 510A in the present scenario, increases its noise figure NF or attenuation level, while femto nodes not showing a high RoT, a femto node 510B in this scenario, keep their noise factors NF constant until until they are exposed to high levels of out-of-band interference. Thus, a method is provided for adjusting the noise figure NF or attenuation when there is a high level of out-of-station interference in a particular femto node. According to an exemplary embodiment for controlling interference in a wireless communication system, RoT in a given time quantum n can be expressed as follows:

and

where Ec _i is the total received energy i for each user.

With an initial reference to FIG. 11A-11B, FIG. 11A-11B describe a method for controlling interference in a wireless communication system using adaptive noise figure and path loss control to adaptively control path loss for RoT control. It should be noted that the control coefficient can be applied either to attenuation in the uplink (UL), or to the noise figure NF of the femto node.

As represented by query 1104, the operations described herein may be performed periodically, for example, after the start of the next time slot n. As an example, in each time quantum n, the femto node 510 may perform the following method to provide interference control to a communication system. As represented by block 1104, various signals are measured and levels are calculated. In particular, as represented by step 1106, the thermal noise figure: No (n) is measured in the femto node 510. The thermal noise coefficient No (n) is a dispersion of thermal noise, including the femto node noise figure (NF).

As represented by step 1108, the intensity of the total received signal Io (n) is measured. The intensity of the total received signal Io (n) is the total received power received in the femto node from all wireless devices for which the femto node is in the active set, and from all wireless devices for which the femto node is not in the active set. As represented by block 1112, the intra-cell interference level Ior (associated access terminal), which is the total received power received at the femto node from all wireless devices for which the femto node is in the active set, is calculated. The calculated level of intra-cell interference can be expressed as follows:

As represented by step 1110, the ratio of the symbol energy of the noise-like sequence for the received pilot signal Ecp (n) to the interference and noise Nt (n) is measured from all wireless devices for which the femto node is in the active set.

As represented by step 1114, the Ioc extracellular interference level (for an unassociated access terminal) is calculated, which is the total received power received at the femto node from all wireless devices for which the femto node is not in the active set. The calculated level of out-of-band interference can be expressed as follows:

As represented by step 1116, the ratio of the received out-of-band interference level to the thermal noise coefficient No (n) and the ratio of the maximum filtered symbol energy of the noise-like sequence for the received pilot signal Ecp (n) to the interference plus noise Nt (n) for the intra-cell access terminals are calculated. As represented by step 1118, the signal-to-noise ratio of the access terminal, measured as the ratio of the symbol energy of the noise-like sequence for the received pilot signal Ecp (n) to the interference and noise Nt (n) for all intra-cell access terminals, is filtered, as an example, according to filtering with infinite impulse response (IIR) in the dB domain. The maximum filtered value for access terminals for which the femto node is in the active set can be expressed as follows:

As represented by block 1120, the signal-to-noise ratio of the received out-of-channel interference level Ioc and thermal noise coefficient No (n) are calculated. The signal-to-noise ratio is also further filtered, as an example, according to filtering with a finite impulse response (FIR) in the dB domain. The calculated extracellular (for an unassociated access terminal) signal-to-noise ratio can be expressed as follows:

As represented by block 1122, the excessive received out-of-band interference is determined outside the allowed (target) value at which the communication system can operate reliably, and the maximum excessive ratio of the symbol energy of the noise-like sequence for the received pilot to interference and noise for the intra-cell access terminals. As represented by step 1124, the excess value for the ratio of the symbol energy of the noise-like sequence for the received pilot signal to interference and noise can be expressed as follows:

where the above permitted threshold value EcpNt_target has units of dB.

As represented by block 1126, the excess level of received out-of-band interference Ioc_excess can be expressed as follows:

where the above allowed threshold value Ioc_target has units of dB.

As presented in step 1128, the amount of additional path loss (PL_adjust) to be applied is calculated. As presented at step 1130, options for controlling losses in the transmission path are determined. Regulation options can be expressed as follows:

With respect to determining the values of the control options, the value of the options may be based on various characteristics or rules. As an example, various points can be expressed as follows:

(1) PL_cand ₁ and PL_cand ₂ are configured to quickly adjust PL based on high Ecp / Nt or Ioc values exceeding the high threshold value.

(2) If Ecp / Nt and Ioc are below the allowed limits, PL_cand _{3 is} configured to slowly decrease (decrease) PL so that it should not be excessively high.

(3) If there is only one active user in a cell, there may be no reason to directly restrict Ioc, since RoT control mechanisms can already control the RoT level. Thus, in the case where there is only one active user in the system, Ioc_target can be assigned a very large value.

As presented in step 1132, the corresponding path loss (PL_adjust) can be applied according to the upper and lower restrictions of the PL path loss control, expressed as follows:

As presented in step 1134, attenuation (or noise figure) in the uplink (UL) is increased by PL_adjust (n). It should be noted that in an actual implementation, hardware constraints may require quantization of PL_adjust (n) to the nearest possible setting.

Referring now to FIG. 12 and again referring to FIG. 5A-5B, operations related to using re-use of time based on subframes to resolve intentional interference and non-optimal geometries are described in more detail. The present exemplary embodiment uses methods and devices to prevent intentional interference and resolve intentional interference and non-optimal geometries using sub-frame time reuse.

In one exemplary embodiment, if the radio interface permits time division multiplexing, transmissions can be scheduled so as to exclude time periods with non-optimal geometries. Thus, the femto node 510B can communicate with the associated access terminal 520D during the period when the femto node 510A is in silent mode. Similarly, the associated access terminal 520C may communicate with the femto node 510A during the period when the unassociated access terminal 520D is scheduled by the femto node 510A so as to be in silent mode. Such methods of synchronization and scheduling approaches are used in systems that enable time-division scheduling, such as 1xEVDO. As an example, since 1xEVDO control channels are time division multiplexed, adjacent femto nodes 510 can be arranged to use the time reuse of these control channels.

However, as explained below, this is not suitable for radio interface technologies that do not allow scheduling and time division multiplexing, for example, technologies that use CDM control channels, including, for example, 1xRTT, WCDMA and HSPA. Details of a sub-frame time reuse scheme are described in detail in the embodiments below.

In one exemplary embodiment, sub-frame-based time reuse is applicable to technologies in which hybrid time reuse cannot be applied. In many cellular technologies, such as cdma2000 and WCDMA, the base station transmits continuous pilot channels and other CDM control channels (e.g., synchronization, paging and broadcast, etc.) that access terminals use for a variety of purposes, in including initial scanning and detection, inactive tracking and channel estimation. This continuous transmission of pilot and service channels from femto nodes can lead to the above-described intentional interference in the downlink, even when there is no active traffic in the deliberate jammer.

In one exemplary embodiment, the first step is to resolve interruptions when the desired pilot and service channels (e.g., synchronization and paging) of the femto node 510 cannot be received at the access terminal 520. As an example, a cdma2000 frame is divided into sixteen power control groups (PCGs). To enable the detection of a pilot signal, a portion of the transmission of the pilot and service channels is locked.

With reference to FIG. 5B, the femto node 510A transmitting to the associated access terminals 520A-C transmits such gated frames (i.e., no FL traffic is transmitted during the blocking periods). In the unassociated access terminal 520D, the carrier-to-interference power ratio, C / I, for transmissions from the femto node 510B dramatically improves during the period when the femto node 510A is locked, allowing detection of pilot and synchronization channels from the femto node 510B in the access terminal 520D, despite very non-optimal geometry in access terminal 520D.

In one exemplary embodiment, these lock-unlock periods are scheduled as non-overlapping. Thus, the femto node 510A and the femto node 510B can use non-overlapping subframes (or power control groups). In one exemplary embodiment, by locking (i.e., not transmitting FL traffic) parts 1/2, 2/3, or 3/4 of the subframes, for example, a reusable time division configuration of 2, 3, or 4 can be created . If the pilot and service channels have sufficient redundancy for detecting pilot signals, as well as for decoding service channels, this should have an effect of 3-6 dB, for example, on the budget of the communication line of pilot and service channels. However, this can be easily compensated by increasing the transmission power of the femto node 510, since in the deployment of the femto node 510, the layouts are not limited by the transmission power.

In addition to the pilot and service channels, this gating method can also be applied to transmissions of voice and data channels. In one exemplary embodiment, the femto node 510 locks a portion of each frame transmission. If, for example, the part (for example, 1/2) that is turned off is less than the channel coding rate used for this transmission, for example, when transmitting voice packets on the cdma2000 forward link, a specific standard format (RC3) uses a convolution code with a speed of 1 / 4, the access terminal 520 must be able to decode the packet, even when half the packet transmission is locked. In order to exclude the obligatory knowledge of these geometries and the scheduling of these non-overlapping locking periods, the following method is disclosed in order to prevent deliberate interference and to resolve deliberate interference and non-optimal geometries using sub-frame time reuse.

With an initial reference to FIG. 12, FIG. 12 describes an exemplary embodiment for managing interference in a wireless communication system using sub-frame time reuse. As represented by step 1202, the gate sequences (or configurations) are identified by locking each gate sequence, for example, either eleven of sixteen power control groups (PCGs) to receive 5/16 reuse, or eight of sixteen PCGs to receive multiple use in 2.

The gating sequence may be selected so as to minimize cross-correlation between pairs of gating sequences from potentially interfering femto nodes 510. As represented by step 1204, each femto node 510 selects one of the gating sequences. Although the femto node 510 may attempt to select a gating sequence that is non-overlapping with neighboring femto nodes, a common selection does not necessarily result in an non-overlapping arrangement. However, an exemplary embodiment provides such a mechanism that a non-overlapping gating sequence can be identified and selected.

As represented by step 1206, the access terminal 520 establishes an active connection with the femto node 510. In response to the establishment of the connection, the access terminal 520 provides “fast” downlink (forward link) power control per subframe, enabling the femto node 510l select the desired non-overlapping gating sequence.

In particular, and as presented in step 1208, the femto node 510B transmits a sequence of frames, for example, on a data channel / voice channel to access terminal 520D when all power control groups (PCGs) are unlocked. As represented by step 1210, since the potentially interfering neighboring femto node 530A is already participating in communication with access terminals 520A-C using gating technologies of subframes, access terminal 520D should observe interference with a subset of subframes in response to gated transmissions by interfering neighboring femto node 510A. In addition, the access terminal 520D must also observe another subset of subframes in which interference from a neighboring femto node 520A is not observed when the neighboring femto node 510A is locked during this subset of subframes.

During subframes in which the femto node 510A is unlocked, the access terminal 520D should observe, for example, low Eb / No. As represented by block 1212, downlink (forward link) power control feedback from access terminal 520D indicates that the femto node 510B should increase transmission power for specific subframes. Similarly, during subframes when the femto node 510A is locked, the access terminal 520D should observe a high Eb / No, and downlink power control (forward link) feedback from the access terminal 520D indicates that the femto node 510B should lower the transmit power for specific subframes.

As represented by block 1214, the subframe-based downlink power control (forward link) feedback provided by the femto node 510B access terminal 520D indicates which subframes from transmitted by the interfering neighboring femto node 510A are unlocked and which locked up. Accordingly, this indicator enables the femto node 510B to select a gating sequence (configuration) that is non-overlapping (complementary) with a gating sequence (configuration) selected and used by interfering with the neighboring femto node 510A. An exemplary embodiment finds application for a gating sequence (configuration) selected by interfering an adjacent femto node 510A.

Depending on the implementation technology, other considerations may additionally determine the types of gating sequences (configurations) that are best suited for this gating technology of subframes. In addition, since existing access terminals are not aware of performing gating in a downlink (forward link), other considerations may apply to include the selection of gating sequences (configurations) that insert shortened deactivation periods between shortened activation periods. This consideration may reduce the impact on downlink channel estimation methods (forward link) and channel quality feedback estimates used by an existing access terminal. Thus, for example, in the case where eight of the sixteen subframes are locked, there may be good reasons for choosing alternating subframes to be locked and unlocked.

In another exemplary embodiment, the selection of gating sequences may apply various considerations for deployment in which neighboring femto nodes 510 are not synchronized. Such considerations may exist, for example, when the WCDMA femto nodes 510 are not synchronized. In one exemplary embodiment of unsynchronized femto nodes 510, instead of alternating unlocked / locked subframes, it may be advantageous to have all or most of the locked subframes adjacent, like all or most of the unlocked subframes. For example, in the case of a WCDMA system with fifteen subframes for 10 ms or thirty subframes for 20 ms, an advantageous way for each femto node 510 may be to lock nine adjacent of these fifteen subframes and unlock six adjacent subframes. Alternatively, when using a 20 ms frame, the femto node 510 may lock sixteen adjacent subframes and unlock fourteen adjacent subframes of thirty subframes.

In alternative exemplary embodiments, other methods for resolving this case and improving downlink C / I include femto nodes 510 configured to block pilot and service channel transmissions when there are no associated access terminals and include pilot and overhead channels periodically and / or at very low power only during periods when it is expected that the associated access terminals 520 should scan the femto node 510.

Referring now to FIG. 13-14 and again referring to FIG. 5A-5B, operations regarding the use of hybrid time reuse in order to resolve intentional interference and non-optimal geometries are described in more detail. The present exemplary embodiment uses methods and devices to prevent intentional interference and to resolve intentional interference and non-optimal geometries using hybrid time reuse technologies.

In an exemplary embodiment, if the radio interface permits time division multiplexing (eg, 1xEV-DO), then transmissions can be scheduled so as to exclude time periods with non-optimal geometries. Thus, the femto node 510B can communicate with the associated access terminal 520D during the period when the femto node 510A does not transmit. Similarly, the associated access terminal 520C may communicate with the femto node 510A during the period when the access terminal 520D is scheduled by the femto node 510B so as not to transmit.

In an exemplary embodiment of the hybrid time reuse method, DL downlink transmission is divided into three separate groups in time:

1. Transmission period of the synchronous control channel (SCC)

2. Transmission period with limited HARQ rotation

3. Transmission period with unlimited HARQ interlace

FIG. 13 illustrates an exemplary downlink (DL) timeline including three different time periods during each cycle period of a synchronous control channel (SCC) of 256 time slices. In one exemplary embodiment, based on the time sharing of resources during “unlimited HARQ interlace”, three different predetermined femto channels are provided. As described in more detail later, it is required that neighboring femto nodes 510 select different femto channels so that they are not interfered with by other neighboring femto nodes 510 (i.e., each femto node selects a primary femto channel different from the neighboring femto node 510). If there is no interference from a neighboring femto node, several femto channels (besides the main femto channel) can be used through one femto node 510. The details of one exemplary embodiment of the hybrid time reuse operation are described below.

With an initial reference to FIG. 14, FIG. 14 describes a method for managing interference in a wireless communication system using hybrid time reuse, in accordance with an exemplary embodiment. As represented by step 1402, upon initial power-up or other synchronization of the femto node 510, the femto node 510 temporarily synchronizes with the macrocell network (e.g., macrocell access node 560). As represented by block 1404, during temporal synchronization with the macro cell access node 560, the femto node 510 measures the off-synchronization channel (SCC) offsets (MSCCOs) used by the macro cell access node 560 and neighboring femto nodes 510. Based on the measurement, the femto node 510 identifies the preferred HARQ the least interference interlace, as represented by step 1406. The preferred time quantum offset (PSO) is specified from the identified preferred HARQ interlace.

As presented in step 1408, the primary femto channel is selected. As an example, an exemplary selection process may adhere to the following algorithm:

if mod (PSO-MSCCO, 4) = 1, then femtochannel 1 is selected as the main femtochannel;

if mod (PSO-MSCCO, 4) = 2, then femtochannel 2 is selected as the main femtochannel;

if mod (PSO-MSCCO, 4) = 3, then femtochannel 3 is selected as the main femtochannel,

where Chn1 (channel 1), Chn2 (channel 2) and Chn3 (channel 3) are described in FIG. 13.

After femtochannels are determined, femtocells 510 can transmit traffic in a downlink (forward link). Transmissions via femto nodes 510 are set in time so as to reduce interference for transmissions in the macro cell and other transmissions in the femto node. A femto node transmission protocol for various transmission periods in a macro cell, an SCC transmission period, a transmission period with limited HARQ interlace, and a transmission period with unlimited HARQ interlace is described below.

As presented at block 1410 and with reference to FIG. 13, an SCC transmission period 1302 is set at the beginning of each SCC cycle 1304 (e.g., 256 time slices) to provide SCC bias transmission (e.g., the first 32 time slices of each SCC loop). In one exemplary embodiment, two sub-periods 1306, 1308 are defined based on HARQ interlacing: a preferred and non-preferred time quantum offset.

In HARQ interlacing with a preferred time quantum offset (PSO), the femto node 510 transmits SCC information. This provides reliable control channel information and allows associated access terminals 520 to enter and exit femto node 510. During HARQ interlaces with non-preferred time-quantum offsets, femto nodes 510 do not transmit downlink traffic (forward link) (DTX FL transmission ), so that minimal interference is caused for SCC transmission of neighboring macro cells and neighboring femto nodes. At these time-quantum offsets, a portion of the downlink (DL) power is used for pilot channels and MAC channels, so that these channels can operate successfully.

As presented at block 1412 and with reference to FIG. 13, during a transmission period with limited HARQ interlace, the femto node 510 is allowed to transmit downlink (forward link) traffic in the PSO HARQ interlace, and delay-sensitive traffic is given absolute priority over traffic according to the maximum efficiency principle. With reference to FIG. 13, the transmission period with limited HARQ interlace allows transmission for each femto node in such a way that delay-sensitive traffic (such as VoIP, etc.) does not contain excessive delay. In one example, during a transmission period with limited HARQ interlace, if the requested DRC is zero, then a single-user packet type of 38.4 kbit / s can be used. If the DRC is zero or erased, then compatible packet types, such as a 38.4 kbps single-user packet (SUP) or 256/512/1024 bit multi-user packet (MUP), can be used (similar to DRC erasure conversion) .

In one exemplary embodiment, downlink (forward link) traffic may also be transmitted in the MSCCO HARQ interlace. In one embodiment, neighboring femto nodes 510 can also use this interlace (i.e., without interference protection). During HARQ interlaces of other time quantum offsets, the femto nodes do not transmit downlink (forward link) traffic (time reuse), however, part of the downlink (forward link) power can be allocated to pilot channels and MAC channels for successful operation of these channels.

As presented in step 1414 and with reference to FIG. 13, during a transmission period with unlimited HARQ interlace, the femto node 510 is allowed to transmit downlink (forward link) traffic in all four of these HARQ interlaces. At the beginning of the period, the downlink transmit power (forward link) can slowly increase linearly so as to allow the predictive parameter of the access terminal speed to increase linearly. In one exemplary embodiment, in order to further increase the linear increase in DRC values, a DRC length of 1 time slot should be used. Due to the conservative nature of the change in the predictor parameter, if a zero DRC is requested by the mobile device at the beginning of the transmission period with unlimited HARQ interlacing, the femto node 510 can transmit compatible packet types (multi-user packet or single-user packet of 38.4 kbit / s). In addition, the femto node downlink (forward link) scheduler can track previously requested DRC values and store DRC values from recent transmission periods and HARQ early completion statistics to select which data rates can be decoded by access terminal 520.

The disclosed solutions may be included in a node (for example, a device) using various components for exchanging data with at least one other node. FIG. 15 illustrates several exemplary components that can be used to facilitate communication between nodes. In particular, FIG. 15 illustrates a wireless device 1510 (e.g., an access point) and a wireless device 1550 (e.g., an access terminal) of a MIMO system 1500. At device 1510, traffic data for a certain number of data streams is provided from a data source 1512 to a transmit processor 1514 (TX ) data.

In some aspects, each data stream is transmitted through a respective transmit antenna. TX data processor 1514 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide encoded data.

The encoded data for each data stream can be multiplexed with pilot data using OFDM technologies. The pilot data is typically a known data pattern that is processed in a known manner and can be used in a receiver system in order to evaluate channel response. The multiplexed pilot and encoded data for each data stream is then modulated (i.e., mapped to symbols) based on a particular modulation scheme (e.g., BPSK, QSPK, M-PSK or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions executed by processor 1530. Memory device 1532 may store program code, data, and other information used by processor 1530 or other components of device 1510.

Modulation symbols for all data streams are then provided to the TX MIMO processor 1520, which can further process modulation symbols (for example, for OFDM). The TX MIMO processor 1520 then provides N _T modulation symbol streams to N _T transceivers (XCVR) 1522A-1522T. In various embodiments, TX MIMO processor 1520 applies beamforming weights to the symbols of the data streams and to the antenna from which the symbol is transmitted.

Each transceiver 1522 receives and processes a corresponding symbol stream to provide one or more analog signals, and further leads to the desired parameters (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for MIMO transmissions. N _T modulated signals from transceivers 1522A-1522T are then transmitted from N _T antennas 1524A-1524T, respectively.

At device 1550, the transmitted modulated signals are received by N _R antennas 1552A-1552R, and the received signal from each antenna 1552 is provided to a respective Transceiver (XCVR) 1554A-1554R. Each transceiver 1554 leads to the required parameters (for example, filters, amplifies, and downconverts) the corresponding received signal, digitizes the signal brought to the required parameters to provide samples, and further processes the samples to provide the corresponding “received” stream characters.

A receive (RX) data processor 1560 then receives and processes N _R received symbol streams from N _R transceivers 1554 based on a particular receiver processing technology to provide N _T “detected” symbol streams. The RX data processor 1560 then demodulates, interleaves, and decodes each detected symbol stream to recover traffic data for the data stream. The processing by the RX data processor 1560 is complementary to the processing performed by the TX MIMO processor 1520 and TX data processor 1514 in the device 1510.

The processor 1570 periodically determines which precoding matrix to use (described below). The processor 1570 formulates a reverse link message comprising a matrix index portion and a rank value portion. A storage device 1572 may store program code, data, and other information used by processor 1570 or other components of device 1550.

The reverse link message may comprise various types of information related to the communication link and / or the received data stream. The reverse link message is then processed by a TX data processor 1538, which also receives traffic data for a specific number of data streams from a data source 1536, modulated by a modulator 1580, adjusted to the desired parameters by transmitters 1554A-1554R, and transmitted back to the device 1510.

At device 1510, modulated signals from device 1550 are received via antennas 1524, adjusted to desired parameters via transceivers 1522, demodulated by demodulator (DEMOD) 1540, and processed by RX data processor 1542 to extract a reverse link message transmitted by devices 1550. The processor 1530 then determines which precoding matrix to use to determine the weighting factors of the radiation pattern, and then ops extracted message.

FIG. 15 also illustrates that communication components may include one or more components that perform interference control operations, as discussed herein. For example, Interference Control (INTER) component 1590 may interact with processor 1530 and / or other components of device 1510 to send / receive signals to / from another device (e.g., device 1550), as discussed herein. Similarly, the interference control component 1592 may interact with the processor 1570 and / or other components of the device 1550 to send / receive signals to / from another device (e.g., device 1510). It will be appreciated that for each device 1510 and 1550, the functionality of two or more of the described components may be provided through one component. For example, one processing component may provide the functionality of an interference control component 1590 and a processor 1530, and one processing component may provide the functionality of an interference control component 1592 and a processor 1570.

The disclosed solutions may be included in various types of communication systems and / or system components. In some aspects, the disclosed solutions may be used in a multiple access system capable of supporting communication with multiple users by sharing available system resources (for example, by indicating one or more of bandwidth, transmit power, encoding, interleaving, etc.) . For example, the disclosed solutions can be applied to any or a combination of the following technologies: code division multiple access (CDMA) systems, multi-carrier CDMA systems (MCCDMA), wideband CDMA systems (W-CDMA), high-speed packet access systems (HSPA, HSPA +) , time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, single carrier FDMA systems (SC-FDMA), orthogonal frequency division multiple access (OFDMA) systems or other multiple technology about access. A wireless communication system using the ideas in this document may be configured to implement one or more standards, such as IS-95, cdma2000, IS-856, W-CDMA, TDSCDMA and other standards. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, or some other technology. UTRA includes W-CDMA and the Low Noise Sequence Character (LCR) standard. Additionally, cdma2000 technology covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement such radio technology as Enhanced UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA and GSM are part of the Universal Mobile Telecommunications System (UMTS). The ideas in this document can be implemented in a 3GPP (LTE) long-term development standard system, UMB system for mobile devices (UMB), and other types of systems. LTE is a version of UMTS that uses EUTRA. Although certain aspects of disclosure can be described using 3GPP terminology, it should be understood that the ideas in this document can be applied to 3GPP technology (Re199, Re15, Re16, Re17), as well as to 3GPP2 technology (1xRTT, 1xEV-DO RelO, RevA, RevB) and other technologies.

The disclosed solutions may be included (for example, implemented within or implemented by) in a variety of devices (for example, nodes). In some aspects, a node (eg, a wireless node) implemented in accordance with the teachings herein may comprise an access point or access terminal.

For example, an access terminal may comprise, be implemented as, or known as a subscriber unit, subscriber station, subscriber module, mobile station, mobile device, mobile node, remote station, remote terminal, user terminal, user agent, user device, or some other term. In some implementations, the access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) telephone, a Wireless Subscriber Access Station (WLL), a personal digital device (PDA), a handheld wireless device, or some other suitable processing device connected to a wireless modem. Accordingly, one or more of the aspects discussed herein may be included in a telephone (e.g., a cell phone or smartphone), a computer (e.g., a travel computer), a portable communications device, a portable computing device (e.g., a personal digital device), a household device (for example, a music or video device or satellite radio device), a global positioning system device or any other suitable device that is capable of exchanging yes GOVERNMENTAL through a wireless transmission medium.

An access point may comprise, be implemented as or known as a Node B, an e-Node B, a radio network controller (RNC), a base station (BS), a radio base station (RBS), a base station controller (BSC), a base transceiver station ( BTS), Transceiver Function (TF), Radio Transceiver, Radio Router, Basic Service Set (BSS), Advanced Service Set (ESS), or some other similar term.

In some aspects, a node (eg, an access point) may comprise an access node for a communication system. Such an access device may provide, for example, connectivity to a network (e.g., a wide area network, such as the Internet or a cellular network) via a wired or wireless connection to a network. Accordingly, an access node may provide an opportunity to another node (for example, an access terminal) to access a network or some other functionality. In addition, it should be borne in mind that one or both of the nodes can be portable or, in some cases, relatively non-portable.

In addition, it should be borne in mind that the wireless node can allow the transmission and / or reception of information in a non-wireless manner (for example, via a wired connection). Thus, the receiving device and the transmitting device, as explained herein, may include appropriate components of a communication interface (for example, components of an electrical or optical interface) to exchange data via a non-wireless transmission medium.

A wireless node may communicate via one or more wireless links that are based or otherwise support any suitable wireless technology. For example, in some aspects, a wireless node may be associated with a network. In some aspects, the network may comprise a local area network or a wide area network. A wireless device may support or otherwise use one or more of a variety of technologies, protocols, or wireless standards, such as those described herein (e.g., CDMA, TDMA, OFDM, OFDMA, WiMAX, Wi-Fi, etc.) . Similarly, a wireless node may support or otherwise use one or more of a plurality of respective modulation or multiplexing schemes. The wireless node may thereby include appropriate components (e.g., radio interfaces) to establish and exchange data through one or more wireless communication lines using the above or other wireless communication technologies. For example, a wireless node may comprise a wireless transceiver with associated components of a transmitter and receiver, which may include various components (eg, signal conditioners and signal processors) that facilitate communication over a wireless transmission medium.

The components described herein can be implemented in a variety of ways. In FIG. 16-21, devices 1600, 1700, 1800, 1900, 2000, and 2100 are represented as a series of interconnected function blocks. In some aspects, the functionality of these units may be implemented as a processing system including one or more processor components. In some aspects, the functionality of these units may be implemented using, for example, at least a portion of one or more integrated circuits (eg, ASICs). As explained herein, an integrated circuit may include a processor, software, other related components, or some combination of the above. The functionality of these blocks can also be implemented in some other way, as discussed in this document.

Devices 1600, 1700, 1800, 1900, 2000, and 2100 may include one or more modules that may perform one or more of the functions described above with respect to the various drawings. In some aspects, one or more components of the interference controller 320 or the interference controller 322 may provide functionality regarding, for example, interference reception / direction means 1602, interference comparison / determination / update means 1606, overhead channel power means 1702, transmission signal waveform means 1802 , channel quality means 1806, interference determination means 1902, transmission path loss means 1906, gating sequence means 2002, reusable configuration means 2102 and synchronization means 2106 tation / bias / time distribution. In some aspects, the communication controller 326 or the communication controller 328 may provide functionality relating, for example, to transceiver (receive / transmit) means 1604, 1704, 1804, 1904, 2004, and 2104.

It should be understood that any reference to an element in this document using such a designation as "first", "second", etc., in general, does not limit the number or order of these elements. Instead, these designations may be used herein as a convenient way of distinguishing between two or more elements or instances of an element. Thus, references to the first and second elements do not mean that only two elements can be used in this case or that the first element must precede the second element in some way. In addition, unless stated otherwise, a set of elements may contain one or more elements.

Specialists in the art should understand that information and signals can be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols and symbols of a noise-like sequence, which can be given as an example throughout the description above, can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles or any combination of the above.

Those skilled in the art will further appreciate that any of the various illustrative logic blocks, modules, processors, tools, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware (to for example, a digital implementation, an analog implementation, or a combination of them, which can be designed using source coding or some other technology), various forms of program or design code, with holding instructions (which, for convenience, may be referred to herein as "software" or "software module"), or a combination thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are described above generally in terms of functionality. This functionality is implemented as hardware or software, depends on the specific application and design restrictions imposed on the system as a whole. Highly qualified specialists can implement the described functionality in various ways for each specific application, but such implementation decisions should not be interpreted as being a departure from the scope of the present disclosure.

Various illustrative logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented within or implemented by an integrated circuit (IC), access terminal, or access point. An IC may include a general purpose processor, a digital signal processor (DSP), a custom integrated circuit (ASIC), a user programmable gate array (FPGA) or other programmable logic device, a discrete logic element or transistor logic, discrete hardware components, electrical components, optical components , mechanical components, or any combination of the above, configured to perform the functions described herein, and may lead to codes or instructions that are constantly posted on the IC, outside the IC, or both. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors together with a DSP core, or any other similar configuration.

It should be understood that the specific order or hierarchy of steps in the disclosed processes is an example of a typical approach. Based on design preferences, it should be understood that the specific order or hierarchy of stages in the processes can be changed, while remaining within the scope of this disclosure. The method points in the attached claims represent elements of the various steps in an exemplary order and are not intended to be limited to the particular order or hierarchy presented.

The functions described may be implemented in hardware, software, firmware, or any combination of the above. If implemented in software, the functions may be stored or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and a communication medium that includes any transmission medium that facilitates moving a computer program from one place to another. Storage media can be any available media that can be accessed through a computer. By way of example, but not limitation, these computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage device, magnetic disk storage device or other magnetic storage device, or any other medium that can be used in order to transfer or save the required program code in the form of instructions or data structures, and which can be accessed by computer. Also, any connection is correctly called a computer-readable medium. For example, if software is transferred from a Web site, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair cable, digital subscriber line (DSL), or wireless technologies such as infrared, radio transmission, and microwave media, then coaxial cable, fiber optic cable, twisted pair cable, DSL, or wireless technologies such as infrared, radio transmission, and microwave media are included in the definition of media. A disc and a disc, as used herein, include a compact disc (CD), a laser disc, an optical disc, a digital versatile disc (DVD), a floppy disk and a Blu-ray disc, and discs (disk ) typically reproduce data magnetically, while discs typically reproduce data optically with lasers. Combinations of the above should also be included in the number of computer-readable media. Thus, it should be appreciated that computer-readable media can be implemented in any suitable computer program product.

The foregoing description of the disclosed aspects is provided to enable any person skilled in the art to create or use the present disclosure. Various modifications in these aspects should be apparent to those skilled in the art, and the general principles described herein can be applied to other aspects without departing from the scope of the disclosure. Thus, the present disclosure does not intend to be limited by the aspects shown in this document, but should satisfy the widest scope consistent with the principles and new features disclosed in this document.

Claims (28)

1. A communication method comprising the steps of:
determining a first gating sequence from a first unplanned access point;
selecting a second gating sequence based on the first gating sequence, wherein the first and second gating sequences are not interfering; and
transmitting signals according to a second gating sequence from a second unplanned access point to an associated access terminal,
wherein the determination of the first gating sequence comprises steps in which:
transmitting a signal in all subframes of the active connection to the associated access terminal; and
receive downlink power control feedback from the associated access terminal indicating signal interference in those of all subframes that correspond to the first gating sequence. 2. The method of claim 1, further comprising establishing an active connection from the second unplanned access point to the associated access terminal. 3. The method according to claim 1, in which the selection of the second gate sequence comprises the steps of:
identify a complementary sequence for the first gating sequence; and
a second gating sequence is selected from at least a portion of the complementary sequence. 4. The method according to claim 1, in which the selection of the second gating sequence further comprises selecting a second gating sequence so as to minimize cross-correlation with the first gating sequence. 5. The method according to claim 1, in which the selection of the second gate sequence further comprises selecting a second sequence so as to include shortened on-periods and shortened off periods. 6. The method according to claim 5, in which the selection of the second gate sequence further comprises selecting a second sequence so as to include alternating periods of on and off. 7. The method according to claim 1, in which the selection of the second gate sequence further comprises selecting a second sequence so as to include at least one of adjacent enabled subframes or adjacent disabled subframes. 8. A communication device comprising:
an interference controller configured to determine a first gate sequence from the first unplanned access point and select a second gate sequence based on the first gate sequence, wherein the first and second gate sequences are not interfering; and
a communication controller configured to transmit signals according to a second gating sequence from a second unplanned access point to an associated access terminal,
wherein the communication controller is further configured to transmit a signal in all subframes of the active connection to the associated access terminal and receive downlink power control feedback from the associated access terminal indicating signal interference in those of all subframes that correspond to the first gating sequence. 9. The device of claim 8, in which the communication controller is further configured to establish an active connection from the second unplanned access point to the associated access terminal. 10. The device of claim 8, in which the interference controller is additionally configured to identify a complementary sequence for the first gating sequence and selecting a second gating sequence from at least part of the complementary sequence. 11. The device according to claim 8, in which the interference controller is further configured to select a second gate sequence so as to minimize cross-correlation with the first gate sequence. 12. The device of claim 8, in which the interference controller is additionally configured to select a second sequence so as to include reduced on-time periods and shortened off periods. 13. The device according to item 12, in which the interference controller is additionally configured to select a second sequence so as to include alternating periods of on and off. 14. The device of claim 8, in which the interference controller is further configured to select a second sequence to include at least one of adjacent enabled subframes or adjacent disabled subframes. 15. A communication device comprising:
means for determining the first gating sequence from the first unplanned access point;
means for selecting a second gating sequence based on the first gating sequence, wherein the first and second gating sequences are not interfering; and
means for transmitting signals according to a second gating sequence from a second unplanned access point to an associated access terminal,
moreover, the means for determining the first gate sequence further comprises:
signal transmission means in all subframes of the active connection to the associated access terminal; and
means for receiving downlink power control feedback from an associated access terminal indicating signal interference in those of all subframes that correspond to the first gating sequence. 16. The device according to clause 15, further comprising means for establishing an active connection from the second unplanned access point to the associated access terminal. 17. The device according to clause 15, in which the means of selecting the second gate sequence comprises:
complementary sequence identification means for the first gating sequence; and
means for selecting a second gating sequence from at least a portion of the complementary sequence. 18. The device according to clause 15, in which the means for selecting the second gating sequence further comprises means for selecting the second gating sequence so as to minimize cross-correlation with the first gating sequence. 19. The device according to clause 15, in which the means for selecting the second gate sequence further comprises means for selecting the second sequence so as to include shortened on-periods and shortened off periods. 20. The device according to claim 19, in which the means for selecting the second gate sequence further comprises means for selecting the second sequence so as to include alternating periods of on and off. 21. The device according to clause 15, in which the means for selecting the second gate sequence further comprises means for selecting the second sequence so as to include at least one of adjacent included subframes or adjacent disabled subframes. 22. Machine-readable medium containing stored on it computer-executable instructions, and the instructions contain codes to prompt the computer
determine the first gating sequence from the first unplanned access point;
select a second gate sequence based on the first gate sequence, wherein the first and second gate sequences are not interfering; and
transmit signals according to the second gating sequence from the second unplanned access point to the associated access terminal,
while the codes that prompt the computer to determine the first gating sequence, additionally contain codes that prompt the computer:
transmit a signal in all subframes of the active connection to the associated access terminal; and
receive downlink power control feedback from the associated access terminal indicating signal interference in those of all subframes that correspond to the first gating sequence. 23. The computer-readable medium of claim 22, further comprising codes prompting the computer to establish an active connection from the second unplanned access point to the associated access terminal. 24. The computer-readable medium of claim 22, wherein the codes prompting the computer to select a second gate sequence comprise codes that prompt the computer:
identify a complementary sequence for the first gating sequence; and
select a second gating sequence from at least a portion of the complementary sequence. 25. The computer-readable medium of claim 22, wherein the codes prompting the computer to select a second gate sequence further comprise codes prompting the computer to select a second gate sequence so as to minimize cross-correlation with the first gate sequence. 26. The computer-readable medium of claim 22, wherein the codes prompting the computer to select the second gate sequence further comprise codes prompting the computer to select the second sequence to include shortened on-times and shortened-off periods. 27. The computer-readable medium of claim 26, wherein the codes prompting the computer to select the second gate sequence further comprise codes prompting the computer to select the second sequence to include alternating on and off periods. 28. The computer-readable medium of claim 22, wherein the codes prompting the computer to select the second gate sequence further comprise codes prompting the computer to select the second sequence to include at least one of adjacent connected subframes or adjacent disabled subframes.

Images