HK1229081A1 - System and method for performance optimization in and through a distributed antenna system - Google Patents

Description

System and method for performance optimization in and by distributed antenna systems

Cross reference to related applications

This application claims priority from U.S. provisional patent application No. 61/939,650 entitled "System and method Performance Optimization In and Through a Distributed antenna System" filed on 13.2.2014, which is hereby incorporated by reference In its entirety for all purposes.

Disclosure of Invention

Embodiments of the present invention relate to communication networks. More particularly, embodiments of the present invention provide methods and systems related to the preparation and operation of Distributed Antenna Systems (DAS). Merely by way of example, the present invention applies to distributed antenna systems. Another example of the invention may include a system of distributed and configurable radios connected via a router to a donor feeding a base station. The methods and systems described herein are applicable to a variety of communication systems, including systems that utilize a variety of communication standards.

According to an embodiment of the present invention, a method for operating a Distributed Antenna System (DAS) is provided. The method comprises the following steps: a set of Digital Remote Units (DRUs) is provided that is operable to transmit and receive wireless radio signals. Each DRU in the set of DRUs is associated with a geographic area. The method further comprises the following steps: a Digital Access Unit (DAU) is provided that is operable to communicate with the set of DRUs via optical signals. The DAU is coupled to at least a sector of a Base Transceiver Station (BTS). The method further comprises the following steps: uplink signals at one or more DRUs in the set of DRUs are received and train activity in a geographic area associated with the set of DRUs is monitored. The method comprises the following steps: increasing a gain factor associated with one DRU of the set of DRUs in response to determining an increase in monitored train activity in a geographic area associated with the one DRU of the set of DRUs; reducing a gain factor associated with another DRU in the set of DRUs in response to determining a decrease in monitored train activity in a geographic area associated with the another DRU in the set of DRUs; and transmitting the scaled uplink signal associated with the one DRU of the set of DRUs and the another DRU of the set of DRUs to the DAU.

In accordance with another embodiment of the present invention, a system for operating a Distributed Antenna System (DAS) is provided. The system comprises: a plurality of Digital Remote Units (DRUs), each DRU configured to receive wireless radio uplink signals and transmit wireless radio downlink signals; and a plurality of interconnected Digital Access Units (DAUs), each DAU configured to communicate with at least one of the plurality of DRUs via optical signals, and each DAU coupled to at least one sector of the base station. The system further comprises: a plurality of detectors, each detector configured to measure uplink power at one of the plurality of DRUs; and a processor coupled to the plurality of detectors and configured to change a gain factor for each of the wireless radio uplink signals in response to the measured uplink power.

According to certain embodiments of the present invention, methods for operating a Distributed Antenna System (DAS) are provided. The method comprises the following steps: providing a plurality of Digital Remote Units (DRUs), each DRU configured to transmit and receive wireless radio signals; and providing a plurality of interconnected Digital Access Units (DAUs), each DAU configured to communicate with at least one of the plurality of DRUs via optical signals, and each DAU coupled to at least one sector of the base station. The method further comprises the following steps: providing a plurality of sensors operable to detect activity at each of the plurality of DRUs and turning off DRU downlink signals at one of the plurality of DRUs in response to an output from one of the plurality of sensors. The method further comprises the following steps: switching on a DRU downlink signal at another DRU of the plurality of DRUs in response to an output from another sensor of the plurality of sensors.

Embodiments of the present invention relate to dynamic configuration of Digital Remote Unit (DRU) parameters of a DAS network such that DRU parameters can be modified regardless of the fixed physical architecture. An example of a Digital Remote Unit (DRU) is a configurable radio with integrated routing capability located at a remote location from a base station (BTS) or baseband unit (BBU). An example of a Digital Access Unit (DAU) is a configurable radio co-located with a base station or baseband unit with integrated routing capabilities. This goal can be accomplished, for example, by using a plurality of Digital Remote Units (DRUs) based on a Distributed Antenna System (DAS). Each DAS may receive resources (e.g., radio frequency carriers, long term evolution resource blocks, code division multiple access codes, or time division multiple access slots) from a central base station that includes multiple sectors and allocate the resources to multiple Digital Remote Units (DRUs). Each DRU may act as an antenna, receiving and transmitting signals, thereby providing network coverage to a local geographical area surrounding the physical DRU. The DAS may be physically coupled to the base station and a plurality of DRUs, for example, by fiber optic links. Thus, resources provided by one base station may be allocated to multiple DRUs, providing coverage for a larger geographic area.

The DAS may be coupled (e.g., by another fiber link) to one or more other BTSs. Thus, the DAS can also: (1) allocating a portion of resources associated with another base station (which may be referred to as a sector) to a DRU physically coupled to the DAS; and/or (2) allocate resources from sectors physically coupled to a DAS to serve DRUs physically coupled to another DAS. This may enable the system to dynamically allocate resources from multiple sectors to the network of DRUs (e.g., in response to geographic and temporal patterns of device usage), thereby increasing the efficiency of the system and meeting desired capacity and throughput targets and/or wireless subscriber needs.

DAS network performance may be optimized for environments with intermittent activity, such as intermittent activity along a train track. Train activity at each DRU can be synchronized with multiple DRU parameters to improve performance and reduce operating expenses. Although some embodiments of the present invention are shown in the context of train applications, the present invention is not limited to this particular transportation system and other transportation systems including highways, rivers, etc. are included within the scope of the present invention. Thus, while a train is one example of a system that may be used with embodiments of the present invention, other vehicles, including cars, trucks, boats, planes, etc., may benefit from embodiments of the present invention. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

According to an embodiment of the present invention, a system for optimizing performance in a distributed antenna system is provided. The system comprises: a plurality of Digital Remote Units (DRUs) configured to transmit and receive wireless radio signals; and a plurality of interconnected Digital Access Units (DAUs), each DAU configured to communicate with at least one of the plurality of DRUs via optical signals, and each DAU coupled to at least one sector. The system further comprises: a plurality of detectors for measuring uplink power at each of a plurality of DRUs; and is operable to switch off or switch on DRU uplink signals from one or more of the plurality of DRUs based on the uplink power detected by the plurality of detectors.

Each of the plurality of detectors may be implemented digitally using signal processing or as a discrete analog device. Each of the plurality of DAUs may be configured to communicate with at least one of the DRUs by transmitting and receiving signals over at least one of optical fiber, ethernet cable, microwave line-of-sight link, wireless link, or satellite link. The DRU may be connected to a plurality of DAUs in a loop form.

According to another embodiment of the present invention, a system for optimizing performance in a distributed antenna system is provided. The system comprises: a plurality of Digital Remote Units (DRUs) configured to transmit and receive wireless radio signals; and a plurality of interconnected Digital Access Units (DAUs), each DAU configured to communicate with at least one of the DRUs via optical signals, and each DAU coupled to at least one sector. The system further comprises: a plurality of sensors operable to detect activity at each of a plurality of DRUs; and an algorithm for turning off and on DRU downlink and DRU uplink signals associated with each DRU of the plurality of DRUs based at least in part on the outputs of the plurality of sensors.

In an embodiment, each of the plurality of DAUs is configured to communicate with at least one of the plurality of DRUs by transmitting and receiving signals over at least one of optical fiber, ethernet cable, microwave line-of-sight link, wireless link, or satellite link. Each DAU of the plurality of DAUs may be co-located with at least one sector. Each of the plurality of DAUs can be connected to a plurality of DRUs, wherein, for example, at least some of the plurality of DRUs are connected in a daisy chain configuration or the plurality of DRUs are connected to at least one of the plurality of DAUs in a star configuration.

According to a particular embodiment of the present invention, a non-transitory computer-readable storage medium is provided that includes a plurality of computer-readable instructions tangibly embodied on the computer-readable storage medium, which when executed by one or more data processors provide routing of wireless network signals. The plurality of instructions includes: instructions that cause the data processor to decode the digital signal; and instructions that cause the data processor to identify a Digital Remote Unit (DRU) based on the decoded signal. The plurality of instructions further comprises: instructions that cause the data processor to convert the digital signal to a radio frequency signal; instructions that cause a data processor to dynamically determine an allocation pairing a DRU with one or more base transceiver station sectors, wherein the allocation is determined at least in part by dynamic geographic differences in network usage; and instructions that cause the data processor to transmit the digital signal to one or more of the assigned sectors.

Many benefits are achieved by the present invention over conventional techniques. For example, embodiments of the present invention enable a network to respond efficiently to a geographically varying mobile subscriber base. For example, focusing on a user in a train traversing the network of DRUs along a train track, some DRU resources may be allocated for serving the train only during periods when the user is actually at the location or is predicted to be at the location. Thus, the network operator need not waste DRU resources to provide coverage during these times in other segments of the track, nor does it degrade system performance by adding noise from inactive DRUs. Instead, DRU resources can be flexibly managed and controlled, thereby improving the efficiency, usage, overall performance, and economic significance of the network. Furthermore, due to this foreseeable efficiency, specialized applications and enhancements may be achieved, such as flexible simulcast, automatic traffic load balancing, network and radio resource optimization, network calibration, autonomous/assisted commissioning, carrier pooling, automatic frequency selection, radio frequency carrier placement, traffic monitoring, traffic marking, traffic shaping, traffic allocation, traffic management, etc. Embodiments may also be implemented to serve multiple operators, multiple standards, multi-mode radios (independent of modulation), and multiple frequency bands per operator to increase the efficiency and traffic capacity of an operator's wireless network.

These and other embodiments of the present invention, as well as many of its advantages and features, are described in more detail in conjunction with the following text and accompanying drawings.

Drawings

Fig. 1 is a high-level schematic diagram illustrating a wireless network system providing coverage over a geographic area in accordance with an embodiment of the present invention;

FIG. 2 is a high-level schematic diagram illustrating a wireless network system including interconnected DAUs, wherein the network provides coverage over a geographic area, according to an embodiment of the present invention;

fig. 3 is a high-level schematic diagram illustrating a wireless network system including interconnected DAUs and a plurality of base station hotels, wherein the network provides coverage over a geographic area, in accordance with an embodiment of the present invention;

FIG. 4 is a high level schematic diagram illustrating a Distributed Antenna System (DAS) covering a portion of a train track according to an embodiment of the present invention;

fig. 5 is a high level flow chart illustrating a method of detecting train activity and controlling DRU uplink signals according to an embodiment of the present invention;

fig. 6 is a high level flow chart illustrating a method of detecting train activity and enabling and disabling a DRU downlink transmitter in accordance with an embodiment of the present invention;

fig. 7 is a high-level schematic diagram illustrating a DAU according to an embodiment of the present invention;

fig. 8 is a high level schematic diagram illustrating a DRU according to an embodiment of the present invention;

FIG. 9 is a high-level schematic diagram illustrating a computer system according to an embodiment of the present invention.

Detailed Description

Wireless and mobile network operators face the following continuing challenges: networks are established that efficiently manage high data traffic growth rates and keep traffic distribution changing. To ensure customer satisfaction, network operators attempt to provide the following networks: the network is available and functional in most locations where customers of a network operator would like to be able to use their devices. This is a difficult task because it is difficult to determine how to geographically allocate resources given the unpredictability of where users will want to be and how to use their devices.

Allocating network resources is complicated by the mobility and unpredictability of the users. For example, configuring a network to efficiently allocate wireless network resources to users on a train may present challenges (e.g., with respect to available wireless capacity and data throughput) as the train travels along a track.

It is the responsibility of the network operator to establish wireless (e.g., cellular mobile communications system) coverage across one or more large geographic areas. As described in more detail below, dividing a geographic area into multiple cells enables a network operator to reuse resources (e.g., frequency spectrum) across geographically separated cells.

Fig. 1 is a diagram illustrating a wireless network system 100 that may provide coverage for a geographic area in accordance with an embodiment of the present invention. The geographical area in fig. 1 is along a train track 120. Although embodiments have been described with reference to examples of train tracks, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. System 100 may include a Distributed Antenna System (DAS) that may efficiently use base station resources. One or more base stations 105, also referred to as Base Transceiver Stations (BTSs), may be located at a central location and/or at base station hotels. One or more base stations 105 may include multiple independent outputs or radio resources, referred to as sectors 110. Each sector 110 may be responsible for providing wireless resources (e.g., radio frequency carrier signals, long term evolution resource blocks, code division multiple access codes, time division multiple access slots, etc.). The resources may include one or more resources that enable the wireless user mobile device to efficiently and wirelessly send and receive communications over the network. Thus, resources may include one or more resources, such as those listed above, that enable signals to be encoded or decoded in a manner to prevent signals from interfering with or being interfered by other wireless signals.

Each sector may be coupled to a Digital Access Unit (DAU) 115, and the DAU115 may connect the sector 110 (and thus the base station 105) with Digital Remote Units (DRUs) installed along the train track 120. Coupling may mean physical coupling. For example, DAU115 can be connected to sector 110 and/or DRU1 via a cable, link, fiber, radio frequency cable, optical fiber, ethernet cable, microwave link with or without line of sight (line of sight), wireless link, satellite link, or the like. In some examples, DAU115 is connected to sector 110 via a radio frequency cable. In some examples, the DAU115 is connected to one or more DRUs via fiber optic or ethernet cables. The associated sectors 110 and DAUs 115 may be located close to each other or at the same location. The DAU115 may convert one or more signals, such as optical signals, radio frequency signals, digital signals, and the like. The DAU115 can include a multi-directional signal transformer such that, for example, radio frequency signals can be transformed into optical signals and optical signals into radio frequency signals, or signals can be transformed between a signal type associated with a sector and a signal type associated with a DRU. In one embodiment, the DAU115 converts downlink radio frequency signals of the sector into optical signals and/or converts uplink optical signals of the DRU into radio frequency signals. As explained in more detail below, the DAU115 can also or alternatively control the routing of data and/or signals between sectors and DRUs. DAU115 can generate, collect, and/or store traffic statistics (e.g., number of communications, calls, network accesses, and/or communication sessions), traffic volume, quality of service data, etc., between sector 110 and one or more DRUs.

Each DAU115 may be coupled to a plurality of Digital Remote Units (DRUs). The plurality of DRUs may be coupled to 115 by, for example, a daisy chain or loop (indirectly coupling the DAU to one or more DRUs) and/or a star configuration (directly coupling the DAU to the plurality of DRUs). Fig. 1 illustrates an example of a daisy chain configuration, where a DAU is directly coupled to a first DRU (e.g., a direct connection from DAU1 to DRU 1), indirectly coupled to a second DRU (e.g., an indirect connection from DAU1 to DRU 2 through DRU 1), indirectly coupled to a third DRU (e.g., an indirect connection from DAU1 to DRU 3 through DRU1 and DRU 2), and so on. Fig. 1 also shows an example of a star configuration, where the DAU is directly coupled to multiple DRUs (e.g., direct connections from DAU1 to DRU1 and from DAU1 to DRU 15).

Each of the DRUs may provide coverage and capacity within a geographic area physically surrounding the DRU. DRUs can be strategically located to effectively provide combined coverage across a large geographic area. For example, DRUs 1 may be located, for example, along train tracks, and/or coverage areas associated with adjacent DRUs may have little overlap. The network may include a plurality of independent cells spanning the full coverage area.

As shown in fig. 1, DRUs 8-14 are daisy-chained to each other, and DRU 8 is coupled to DAU1 (115) via optical fiber. Due to the daisy-chain architecture of this embodiment, uplink signals communicated by DRUs 14 are transmitted along the daisy-chain toward DRUs 8 as trains move along the track from the cell associated with DRUs 14 toward the cell associated with DRUs 8. In some implementations, as the uplink signals move along the daisy chain toward the DRUs 8, the noise associated with the uplink signals from each DRU in the daisy chain adds up as the uplink signals from the individual DRUs are combined. Thus, for the uplink signal received at DRU 14, noise from each of the intermediate DRUs (DRUs 13-DRU 8) is combined to the original signal, thereby reducing the signal-to-noise ratio as the uplink signal moves along the daisy chain.

As described herein, to improve the signal-to-noise ratio of the uplink signal, the importance of DRUs not in active communication with the train is reduced in various embodiments. As an example, the amplitude/power of noise and signals associated with DRUs not in active communication with a train may be reduced if the communication level with the train is low and increased for DRUs in the vicinity of the train. For example, with respect to fig. 4 below, additional description is provided relating to reducing noise signals by controlling uplink signals. In addition to controlling uplink signals, the DRUs may be controlled to reduce power associated with downlink signals broadcast by DRUs not in active communication with the train. Accordingly, power budget and operation expenses can be reduced by controlling uplink traffic and downlink traffic in areas where train traffic is not present. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

In a conventional DAS network, a first group of remote units in a first geographic region may be connected to a first BTS or a first sector of a BTS, and a second group of remote units in a second geographic region may be connected to a second BTS or a second sector of a BTS. In an environment where people communicate while a train is moving, a call for a user is handed over from a first BTS to a second BTS when the train moves from a first geographical area to a second geographical area. Heavy messaging traffic at the handoff point can result in dropped calls, reduced data rates, etc., if the number of users is large. Embodiments of the present invention provide methods and systems for ameliorating these problems associated with conventional systems.

Referring to fig. 1, the benefits provided by the illustrated DAS network with along-track located DRUs associated with a single sector of a BTS (e.g., DRUs 1-7 may connect to sector 1 (110)) are: as the train moves along the track from cell 1 to cell 7, no handover is required, thereby reducing the number of dropped calls and interruptions in data service. The digital DAS system shown in fig. 1 provides DRUs that are positioned in a substantially linear fashion along an orbit, in contrast to a closed cell structure in which cells are packed together in a hexagonal pattern covering a substantially hexagonal/circular coverage area.

It should be noted that while in some embodiments a single train moving along a track is discussed, it should be understood that multiple trains may be simultaneously traveling along the track and that the discussion relating to a single train may be extended to multiple trains as appropriate for a particular application.

Each cell may be assigned to a sector 210. Fig. 2 shows, for example, the following embodiments: in this embodiment, sector 1 provides resources to cells 15-21, sector 2 provides resources to cells 1-7, and sector 3 provides resources to cells 8-14. The associated sector may provide resources, e.g., radio frequency carriers, resource blocks, etc., to each DRU. In one embodiment, each sector in the plurality of sectors 210 is associated with a set of "channels" or frequency ranges. The set of channels associated with each sector 210 can be different from the set of channels associated with other sectors 2 and 3 in base station 205. The network may be configured such that neighboring cells are associated with different channels (e.g., by being associated with different sectors 210), as shown in fig. 2. This may enable reuse of the channel between multiple cells without risk of interference.

In the embodiment shown in fig. 1, each sector 110 is connected to an associated subset of all DRUs in the network. Thus, for example, the resources (e.g., allocated channels) of sector 1 cannot be used by DRUs located in cell 8 without physically changing the network hardware (e.g., by rerouting the optical fibers). The embodiment shown in fig. 2 avoids this limitation. In particular, DRUs may be dynamically assigned to sectors 210 based on the interconnection between DAUs 215. Thus, for example, DRUs 8 to 14 in cells 8 to 14 may be initially all allocated to sector 3 (fig. 2). DRU 7 can then be assigned to sector 3 and DRU 14 can be assigned to sector 1. In such an instance, the signal to DRU 7 may pass through DAU 2 and DAU 3 starting from sector 2. Similarly, signals may start from DRU 14 through DAU 3 and DAU1 to sector 1. In this manner, a sector may be indirectly connected with a larger subset of DRUs in the network or with all DRUs in the network. Communication between the DAUs may be controlled in part by one or more servers 225, as explained in more detail below.

DAU 210 may be physically and/or virtually connected. For example, in one embodiment, the DAU 210 is connected via a cable or fiber (e.g., fiber optic, ethernet cable, microwave link with or without a line of sight, wireless link, or satellite link). In one embodiment, the plurality of DAUs 210 are connected to a wireless network that enables information to be communicated from one DAU 210 to another DAU 210 and/or enables information to be communicated from/to the plurality of DAUs 210.

As shown in fig. 3, a multi-operator system or a system with multiple base stations of one operator or a combination of both may include multiple base stations (or multiple base station hotels) 305. A neutral host solution is defined when multiple operators coexist relying on the same infrastructure and the system is hosted by either the operator or a third party. Different base stations 305 may be associated with the same, overlapping, non-overlapping, or different frequency bands. The base stations 305 may be interconnected, for example, to serve a geographic area. The interconnection may include indirect connections (e.g., each base station is connected to a DAU, which are directly connected to each other) or direct connections (e.g., cables) extending between the base stations. A larger number of base stations may improve the ability to increase the capacity of a given cell. The base stations 305 may represent independent wireless network operators and/or multiple standards (WCDMA, LTE, etc.) and/or they may represent the provision of additional radio frequency carriers as well as additional baseband capacity. In some embodiments, the base station signals are combined before they are connected to the DAU, which may be the case for neutral host applications. In one example, as shown in fig. 3, sectors from BTS 1 are directly coupled to the same DAU and/or DRU as the DAU and/or DRU to which the sectors of BTS N are directly coupled. In some other instances, one or more sectors from different BTSs may be directly coupled to a DAU that is not shared by sectors of one or more other DAUs.

Fig. 4 is a diagram illustrating a Distributed Antenna System (DAS) covering a portion of a train track according to an embodiment of the present invention. As shown in fig. 4, the high level diagram illustrates a wireless network system including DRUs linked in a daisy-chain fashion, wherein the uplink signals from each DRU are scaled and summed and the network provides coverage over a geographic area. In this example, DRUs 15 to 21 covering cells 15 to 21 are allocated to sector 1. Signals from DRUs 15 to DRU 21 are routed to DAU1 based on network hardware and architecture. The DAU1 combines uplink signals from the DRUs 15 to 21 or receives signals that are combined in turn at each DRU. In this embodiment, DAU1 associates a gain factor { α, β … } for each of the individual DRUs {15, 16.. 21} assigned to DAU 1. The gain factor is used to scale the uplink signal. The following equations illustrate how the uplink signals from DRUs k through DRU N (e.g., 15 through 21) are combined to provide a scaled uplink signal that is transmitted to DAU 1.

The gain factor may be adjusted from 0 to 1 to provide separate control of the signals transmitted on the uplink using each DRU. In some implementations, the sum of the scaled uplink signals from the DRUs is referred to as the scaled uplink signal, which is received at the DAU. In addition to uplink control, downlink control is provided in some embodiments. As an example, when a train moves from cell 15 towards cell 21, initially cell 15 is at full power (i.e. α = 1) and cell 21 is off (= 0). The cells between cell 15 and cell 21 are at a level between 0 and 1. As the train moves towards the cell 21, the gain factor is adjusted by decreasing alpha and increasing so that the gain associated with the DRU matches the location of the moving train.

Trains contain a high density of mobile users. Different DRUs are active as the group of mobile users moves along the track. However, the uplink signal presented to BTS 405 includes the addition of all DRUs connected to DAU 1. When all gain coefficients are set to 1, the DRU will still contribute to the overall noise floor even if it is not experiencing activity. The DAS system in fig. 4 may change the gain factor so that the uplink channel from the DRU is turned up or down (or, turned on or off) according to the train activity at the corresponding location of the DRU. Inactive DRUs may be switched off to reduce the noise contribution associated with those inactive DRUs. As discussed above, in addition to control of the uplink channel, control of the downlink channel may also be implemented to reduce power consumption by DRUs not in active communication with the train and to reduce the ultimate operating overhead.

Fig. 5 is a simplified flowchart illustrating a method of controlling DRU uplink gain according to an embodiment of the present invention. In this embodiment, a performance optimization algorithm for DAS networks on the train trackside is provided. In a function block 505, DRUs are assigned to respective DAUs. As an example, DRUs connected to DAUs using optical fibers may be assigned to the DAUs to which they are connected. The DAU is connected to a sector in a Base Transceiver Station (BTS). The function block 510 assigns a subset of DRUs to a portion of the train track. The assignment relates the geographical location of the cells associated with the DRUs to their location along the orbit. The network of DRUs, DAUs and BTSs is configured and the allocations are stored in memory (515).

Routing downlink signals from BTS sectors to assigned DAUs and then to DRsU (520). DRU uplink signals received at the DRUs are routed to DAUs allocated for a subset of DRUs allocated to the DAU. In block 525, the uplink signals from the DRUs are scaled by gain factors and then combined and fed to the sector of that particular BTS. As described above, inactive DRUs may contribute noise to the uplink signal, thereby reducing overall system performance. The function block 530 monitors what is referred to as a DRU_kIs active at each respective DRU. Although embodiments have been described with reference to the train activity monitor example, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention.

The train activity monitor may be a sensor (e.g., an external monitor) that detects movement of the train along the track, or it may be a measure of cellular signal strength or cellular data activity in the geographic area. The monitor may be implemented using signal processing within the DRU, for example, based on uplink signal strength. The external monitor may be an optical detector, a vibration detector, a radar detector, or the like. In some embodiments, train scheduling is utilized to provide input to the system, effectively providing monitoring input. In other embodiments, communications from the train (e.g., the broadcast GPS location) may be used as a monitor input instead of or in conjunction with other monitors. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

The train activity monitor will become active as the train passes through DRU cells that provide coverage to the geographical area. This would be an indication as to: the DRU will temporarily experience a large number of mobile users when the train enters the geographical area associated with the DRU. In some embodiments, a threshold value will be set for the train activity monitor. Although embodiments have been described with reference to threshold trigger examples, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention.

If the train activity monitor indicates that activity is increasing (or, alternatively, exceeding a threshold setting), the gain factor corresponding to the DRU will be transitioned towards 1 (540). This will effectively connect the DRU with the designated BTS sector via the DAU. If the train activity monitor indicates that activity is decreasing (or, alternatively, falls below a threshold), the DRU uplink gain coefficient corresponding to that DRU will be transitioned towards 0 (550). This will reduce the noise contribution from those DRUs that do not have active mobile users passing through their cell.

A closed loop is shown in flow chart 500 whereby the train activity monitor is continuously or periodically analyzed or compared to a threshold and the gain factor is adjusted accordingly. In some embodiments, the closed loop returns to block 530 after decision point 535 and gain adjustment in block 540 or block 550.

The train activity monitor/sensor is thus configured to provide data used by the system to control the operation of the DRU as described herein. As shown by the operations discussed with respect to fig. 5, some embodiments increase/decrease the gain factor in small steps or continuously to vary the gain between a value of 0 and a value of 1. As an example, the gain may be gradually adjusted up as the train approaches the DRU, reaching peak 1 as the train approaches the DRU, and then gradually adjusted down as the train leaves the region of the DRU. Thus, some embodiments utilize the following ratios: the ratio increases/decreases the gain in response to an increase/decrease in train activity. In other embodiments, the train activity is compared to a threshold. If the threshold is exceeded, the DRU uplink gain is set to 1. If the activity does not exceed the threshold, the DRU uplink gain is set to 0. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Fig. 6 is a flow chart of one embodiment of a performance optimization algorithm for DAS networks on a train trackside. The flow diagram 600 has similar functionality as the flow diagram 500, except that DRU transmitters and/or receivers will be controlled (e.g., turned off and on) according to the train activity monitor. The main purpose of switching off DRU transmitters and/or receivers is to reduce operating overhead and reduce interference to macro-BTS in neighboring cells. In some embodiments, the DRU downlink path is not shut down, but instead is reduced in power based on monitored train activity. In these embodiments, train activity is monitored periodically or on other time bases. If the train activity is increasing, the power associated with the downlink transmitter is increased toward the maximum power (similar to block 640). If train activity is decreasing, then the power associated with the downlink transmitter is decreased toward 0 (similar to block 650). Thus, blocks 540 and 550 shown in FIG. 5 may be substituted for blocks 640 and 650 in FIG. 6. Likewise, blocks 640 and 650 shown in FIG. 6 may be substituted for blocks 540 and 550 in FIG. 5 discussed above.

Fig. 7 illustrates components of a DAU700 according to an embodiment of the present invention. DAU700 may include a router (i.e., local router 705). DAU700 may include one or more ports 715 and 720. Ports 715 and 720 may, for example, enable the DAU to connect with the internet and/or a host unit or server 725. The server 725 may configure, at least in part, the routing of DAUs and/or control signals between the various local router ports. The server 725 may, for example, be controlled, at least in part, by the remote operation controls 730 (e.g., setting reallocation conditions, identifying allocations, storing allocations, entering network configurations, receiving/collecting/analyzing network usage, etc.).

DAU700 may include one or more physical nodes 710, and physical nodes 710 may be coupled to local router 705 through one or more first end ports 735. Each physical node 710 may include one, two, or more ports, such as a first end port, where each of the ports may enable signals (e.g., radio frequency signals and/or signals from/to a sector) to be received by DAU700 or transmitted from DAU 700. In some embodiments, each of the plurality of physical nodes 710 includes a downlink port 712 and an uplink port 713. In some embodiments, physical node 710 may also include additional uplink ports, e.g., to handle diversity connections. The output ports (e.g., downlink port 712 and uplink port 713) may be coupled to one or more ports (e.g., radio frequency ports) of the base station. Thus, DAU700 may be physically coupled to a base station.

The local router 705 may include one or more second ports 740, and the second ports 740 may couple the DAU700 to one or more DRUs or DAUs via, for example, fiber optics, ethernet cables, line-of-sight or non-line-of-sight microwave connections, and the like. The second end port 740 may include a LAN port or a peer port. The second port 740 may be configured to send and/or receive signals, such as digital signals and/or optical signals. In one embodiment, at least one second port 740 couples DAU700 to another DAU, and at least one second port 740 couples DAU700 to DRUs. The local router not only encodes signals for transmission over the optical link, but also decodes optical signals from the optical link. The physical node performs the following functions: converting the radio frequency signal to baseband or converting the baseband signal to radio frequency. The DAU may monitor traffic on various ports and route this information to a server or store the information locally.

Fig. 8 illustrates components of a DRU 800 according to an embodiment of the present invention. DRU 800 may include a router (i.e., remote router 805). The DRU may include a network port 810, and the network port 810 may enable the DRU 800 to couple to a (e.g., wireless) network (via an ethernet switch). The DRU 800 can then connect with the computer 820 via a network. Accordingly, a remote connection with the DRU 800 can be established.

The remote router 805 may be configured by a server, such as server 130, server 725, a server connected to one or more DAUs, and/or any other server. The network port 810 may serve as a wireless access point for connection to the internet. An internet connection may be established, for example, at the DAU, and internet traffic may be part of the data transfer between the DRU physical node and the DAU physical node.

DRU 800 may include one or more physical nodes 825. Each physical node 825 can include one, two, or more ports, such as first end port 830, wherein each of the ports can enable signals (e.g., radio frequency signals and/or signals from mobile devices) to be received by DRU 800 or transmitted from DRU 800. In some implementations, each of the plurality of physical nodes 825 includes one or more ports configured to transmit/receive signals (e.g., radio frequency signals) from/to DRU 800. The ports may include, for example, a downlink port 827 and an uplink port 828. In some embodiments, there are additional uplink ports for handling diverse connections. The physical node ports (e.g., downlink output port 827 and uplink output port 828) may be connected to one or more antennas (e.g., radio frequency antennas) so that signals may be received from and/or transmitted to, for example, a mobile wireless device.

The remote router 805 may include one or more second ports 835, which second ports 835 may couple the DRU 800 to one or more DAUs or DRUs. The second end port 835 may comprise a LAN port or a peer port, which may couple (e.g., physically) the DRU 800 to one or more DAUs or DRUs via fiber optics, ethernet cables, line-of-sight or non-line-of-sight microwave connections.

It should be understood that the specific steps shown in fig. 5 and 6 provide a particular method according to embodiments of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in fig. 5 and 6 may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. In addition, additional steps may be added or removed depending on the particular application. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

The methods shown in fig. 5 and 6 or described elsewhere may be performed by various devices or components. For example, some of the processing may be performed separately or in part by one or more DAUs. Some of the processing may be performed separately or in part, for example, by a remote computer coupled to one or more DAUs. Some of the processing may be performed by one or more DRUs. In some implementations, the processes shown or described may be performed by multiple devices or components (e.g., by multiple DAUs, by one DAU and a remote server, by one or more DRUs and DAUs, etc.).

The above-described embodiments may be implemented using, for example, distributed base stations, distributed antenna systems, distributed repeaters, remote radio units, mobile devices and wireless terminals, portable wireless devices, and/or other wireless communication systems such as microwave and satellite communications. Many variations are possible. For example, embodiments comprising a single base station may be applied in systems comprising a plurality of interconnected base stations. Embodiments may be modified to replace a daisy chain configuration with a star configuration or to replace a star configuration with a daisy chain configuration or to extend a daisy chain configuration into a loop. Embodiments showing a single server (e.g., connected to multiple DAUs) may be modified to include multiple servers (e.g., each connected to a different DAU or to all DAUs).

Fig. 9 is a high-level schematic diagram illustrating a computer system 900 including instructions for performing any one or more of the methods described above. One or more of the above-described components (e.g., DAU115, DRU1, server 130, server 725, computer 920, etc.) may comprise a portion or all of computer system 900. The system 900 may likewise perform all or a portion of one or more of the methods described above. Fig. 9 is intended only to provide a broad illustration of the various components, any or all of which may be suitably utilized. Thus, fig. 9 broadly illustrates how individual system elements may be implemented in a relatively separated or relatively more integrated manner.

Computer system 900 is shown including hardware elements that can be electrically coupled (or otherwise suitably in communication) via bus 905. The hardware elements may include: one or more processors 910, including but not limited to one or more general-purpose processors and/or one or more special-purpose processors (e.g., digital signal processing chips and/or graphics acceleration processors, etc.); one or more input devices 915, which may include, but are not limited to, a mouse and/or a keyboard, etc.; and one or more output devices 920, which can include, but are not limited to, a display device and/or a printer, etc.

Computer system 900 may also include (and/or be in communication with) one or more storage devices 925, storage devices 925 may include, but are not limited to, local and/or network accessible memory, and/or may include, but is not limited to, disk drives, arrays of disk drives, optical storage devices, solid state storage devices such as random access memory ("RAM") and/or read only memory ("ROM"), which may be programmable and/or flash updateable, etc. Such storage devices may be configured to implement any suitable data storage, including but not limited to various file systems and/or database structures, and the like.

Computer system 900 may also include a communication subsystem 930 that may include, but is not limited to, modems, network cards (wireless or wired), optical communication devices, infrared communication devices, wireless communication devices, and/or chipsets (e.g., bluetooth devices, WiFi (802.11) devices, WiMax (802.16) devices, zigbee (802.15) devices, cellular communication facilities, etc.). The communication subsystem 930 may permit data to be exchanged using a network (e.g., the network described below, to name one example), other computer systems, and/or any other devices described herein. In many embodiments, the computer system 900 will also include a working memory 935, which working memory 935 may include a RAM device or a ROM device as described above.

Computer system 900 may also include software elements, shown as being currently located within working memory 935, including an operating system 940, device drivers, executable libraries, and/or other code, such as one or more application programs 945, which application programs 945 may include computer programs provided by various embodiments and/or may be designed to implement methods and/or configure systems provided by other embodiments described herein. Merely by way of example, one or more processes described with respect to the methods discussed above may be implemented as code and/or instructions executable by a computer (and/or a processor within a computer); in one aspect, such code and/or instructions may then be used to configure a general purpose computer (or other apparatus) and/or adapt a general purpose computer (or other apparatus) to perform one or more operations in accordance with the described methods.

A set of these instructions and/or code may be stored on a computer-readable storage medium, such as storage device 925 described above. In some cases, the storage medium may be incorporated in a computer system, such as system 900. In other embodiments, the storage medium may be separate from the computer system (e.g., a removable medium such as an optical disk) and/or may be provided in the form of an installation package such that the storage medium can be used to program, configure and/or adapt a general purpose computer with the instructions/code stored thereon. These instructions may take the form of executable code that is executable by computer system 900, and/or may take the form of source code and/or installable code, which when compiled and/or installed on computer system 900 (e.g., using any of a variety of commonly used compilers, installation programs, compression/decompression tools, etc.) then takes the form of executable code.

It will be apparent to those skilled in the art that substantial modifications may be made in accordance with specific requirements. For example, customized hardware might also be used and/or particular elements might be implemented in hardware, software (including portable software, such as applets, etc.), or both. In addition, connections to other computing devices, such as network input/output devices, may be employed.

As described above, in one aspect, some embodiments may employ a computer system (e.g., computer system 900) to perform a method in accordance with various embodiments of the present invention. According to a series of embodiments, some or all of the procedures of such a method may be performed by computer system 900 in response to processor 910 executing one or more sequences of one or more instructions (which may be incorporated in operating system 940 and/or other code, such as application programs 945) contained in working memory 935. Such instructions may be read into the working memory 935 from another computer-readable medium, such as one or more of the storage devices 925. By way of example only, execution of the sequences of instructions contained in the working memory 935 may cause the processor 910 to perform one or more processes of the methods described herein.

The terms "machine-readable medium" and "computer-readable medium" as used herein refer to any medium that participates in providing data that causes a machine to operation in a specific fashion. Computer-readable media and storage media do not refer to transitory propagating signals. In an implementation implemented using computer system 900, various computer-readable media may be involved in providing instructions/code to processor 910 for execution and/or may be used to store such instructions/code. In many implementations, the computer-readable medium is a physical and/or tangible storage medium. Such a medium may take the form of a non-volatile medium or a volatile medium. Non-volatile media includes, for example, optical and/or magnetic disks, such as storage device 925. Volatile media include, but are not limited to, dynamic memory, such as working memory 935.

Common forms of physical and/or tangible computer-readable media include: such as a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM, a FLASH-EPROM, any other memory chip or cartridge, etc.

Cloud-based computing is another example of an implementation of computer system 900.

Embodiments described herein may be implemented in an operating environment including software installed on any programmable device, in hardware, or in a combination of software and hardware. Although embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Although embodiments of the present invention have been discussed with respect to digital DAS networks, the present invention is not limited to digital implementations and embodiments of the present invention are applicable to analog DAS networks. In these analog implementations, the following analog remote devices are utilized: which receives the wireless signals in the uplink path and transmits analog signals to the analog host unit. In some analog implementations, the analog remote devices may be connected to the analog host unit using a star configuration in which the host unit is connected to each analog remote device separately using a suitable connection (e.g., an analog connection over a fiber). One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

It is also to be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.

Claims (19)

1. A method for operating a Distributed Antenna System (DAS), the method comprising:

providing a set of Digital Remote Units (DRUs) operable to transmit and receive wireless radio signals, wherein each DRU of the set of DRUs is associated with a geographic area;

providing a Digital Access Unit (DAU) operable to communicate with the set of DRUs via optical signals, wherein the DAU is coupled to at least a sector of a Base Transceiver Station (BTS);

receiving uplink signals at one or more DRUs of the set of DRUs;

monitoring train activity in the geographic area associated with the set of DRUs;

increasing a gain factor associated with one of the set of DRUs in response to determining an increase in monitored train activity in the geographic area associated with the one of the set of DRUs;

reducing a gain factor associated with another DRU of the set of DRUs in response to determining a decrease in monitored train activity in the geographic area associated with the another DRU of the set of DRUs; and

transmitting, to the DAU, a scaled uplink signal associated with the one DRU of the set of DRUs and the other DRU of the set of DRUs.

2. The method of claim 1, wherein the set of DRUs are located along a train track in a daisy-chain configuration.

3. The method of claim 1, wherein providing a DAU comprises providing a plurality of DAUs, wherein each of the plurality of DAUs are interconnected.

4. The method of claim 1, wherein monitoring train activity comprises receiving input from an external monitor.

5. The method of claim 1, wherein monitoring train activity comprises measuring radio activity in the geographic area.

6. The method of claim 1, wherein the scaled uplink signal uses a zero gain coefficient for one or more DRUs of the set of DRUs.

7. A system for operating a Distributed Antenna System (DAS), the system comprising:

a plurality of Digital Remote Units (DRUs), each DRU configured to receive wireless radio uplink signals and transmit wireless radio downlink signals;

a plurality of interconnected Digital Access Units (DAUs), each DAU configured to communicate with at least one of the plurality of DRUs via optical signals, and each DAU coupled to at least one sector of a base station;

a plurality of detectors, each detector configured to measure uplink power at one of the plurality of DRUs; and

a processor coupled to the plurality of detectors and configured to change a gain factor for each of the wireless radio uplink signals in response to the measured uplink power.

8. The system of claim 7, wherein each detector of the plurality of detectors is implemented digitally using signal processing.

9. The system of claim 7, wherein each detector of the plurality of detectors comprises a discrete analog device.

10. The system of claim 7, wherein each of the plurality of interconnected DAUs is configured to communicate with the at least one of the plurality of DRUs by transmitting and receiving signals over at least one of optical fiber, ethernet cable, microwave line-of-sight link, wireless link, or satellite link.

11. The system of claim 7, wherein the plurality of DRUs are connected to each other in a daisy chain configuration and are each positioned in a substantially linear manner along the train track.

12. The system of claim 7, wherein one of the plurality of interconnected DAUs includes the processor.

13. The system of claim 7, wherein the processor is provided in a server coupled to the plurality of interconnected DAUs.

14. A method for operating a Distributed Antenna System (DAS), the method comprising:

providing a plurality of Digital Remote Units (DRUs), each DRU configured to transmit and receive wireless radio signals;

providing a plurality of interconnected Digital Access Units (DAUs), each DAU configured to communicate with at least one of the plurality of DRUs via optical signals, and each DAU coupled to at least one sector of a base station;

providing a plurality of sensors operable to detect activity at each of the plurality of DRUs;

turning off a DRU downlink signal at one of the plurality of DRUs in response to an output from one of the plurality of sensors; and

switching on a DRU downlink signal at another of the plurality of DRUs in response to an output from another of the plurality of sensors.

15. The method of claim 14, wherein each of the plurality of DAUs is configured to communicate with the at least one of the plurality of DRUs by transmitting and receiving signals over at least one of optical fiber, ethernet cable, microwave line-of-sight link, wireless link, or satellite link.

16. The method of claim 14, wherein the plurality of interconnected DAUs comprises a first DAU connected to a first sector of the base station and a second DAU connected to a second sector of the base station.

17. The method of claim 14, wherein each sensor of said plurality of sensors is provided by a signal processing processor in each DRU of said plurality of DRUs.

18. The method of claim 14, wherein the plurality of DRUs are connected in a daisy chain configuration.

19. The method of claim 14, wherein the plurality of DRUs includes a first group of two or more DRUs and a second group of two or more DRUs, the first and second groups coupled to at least one of the plurality of DAUs in a star configuration.