HK1181952B - Flexible medium access control (mac) method for ad hoc wireless networks - Google Patents

Description

Flexible Medium Access Control (MAC) method for ad hoc wireless networks

The patent application of the invention is a divisional application of an invention patent application with the international application number of PCT/US2006/060262, the international application date of 26.10.2006 and the application number of 200680040437.1 entering the Chinese national stage, and is named as a flexible Media Access Control (MAC) method for a self-organizing wireless network.

Priority requirements according to 35U.S.C. § 119

The present application claims priority from U.S. provisional application S/n.60/730,631, entitled "weighted fair sharing of wireless channels using resource utilization masks" (handed over edfas airen offtake away channel transmission method, green channel utilization tlzatzone), filed 26.2005, and U.S. provisional application S/n.60/730,727, entitled "interference management using resource utilization masks transmitted at constant power spectral density" (fed forward channel transmission method), filed 26.2005, both of which are incorporated herein by reference.

Technical Field

The following description relates generally to wireless communications, and more particularly to reducing interference and improving throughput and channel quality in a wireless communication environment.

Background

Wireless communication systems have become a prevalent means by which a large percentage of people worldwide have come to communicate. Wireless communication devices have become smaller and more powerful in order to meet customer needs and to improve portability and convenience. The increase in processing power of mobile devices, such as cellular telephones, has led to an increase in demand for wireless network transmission systems. These systems are typically not as easily updated as the cellular devices that communicate over them. As mobile device capabilities evolve, it is difficult to maintain older wireless network systems in a manner that facilitates fully exploiting new and improved wireless device capabilities.

A typical wireless communication network (e.g., employing frequency, time, and code division techniques) includes one or more base stations that provide a coverage area and one or more mobile (e.g., wireless) terminals that can transmit and receive data within the coverage area. A typical base station can simultaneously transmit multiple data streams for broadcast, multicast, and/or unicast services, wherein a data stream is a stream of data that is of independent reception interest to a mobile terminal. A mobile terminal within the coverage area of that base station can intentionally receive one, more than one, or all of the data streams carried by the composite stream. Likewise, a mobile terminal may transmit data to the base station or another mobile terminal. Such communication between a base station and a mobile terminal or between several mobile terminals may be degraded by channel variations and/or interference power variations. Accordingly, there is a need in the art for systems and/or methods that facilitate reducing interference and improving throughput in a wireless communication environment.

Disclosure of Invention

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

According to various aspects, the subject innovation relates to systems and/or methods that provide unified techniques for wide and local area wireless communication networks in order to facilitate achieving benefits associated with both cellular and Wi-Fi technologies while mitigating deficiencies associated therewith. For example, cellular networks may be arranged according to planned deployments, which may increase efficiency when designing or building networks, whereas Wi-Fi networks are typically deployed in a more convenient ad hoc manner. Wi-Fi networks may also help provide symmetric Media Access Control (MAC) channels for access points and access terminals, as well as backhaul support with in-band wireless capabilities not provided by cellular systems.

The unified techniques described herein help provide symmetric MAC and backhaul support with in-band wireless capability. Furthermore, the present invention facilitates the deployment of networks in a flexible manner. The method described in the present invention allows performance to be adjusted according to the deployment, thereby providing better efficiency if the deployment is planned or semi-planned, and sufficient robustness if the network is unplanned. That is, the aspects described herein allow for networks to be deployed using planned deployments (e.g., in a cellular deployment scenario), ad hoc deployments (e.g., such as may be used for Wi-Fi network deployments), or a combination of both. Further, other aspects relate to supporting nodes with different transmit power levels and achieving inter-cell fairness in terms of resource allocation, which aspects are not sufficiently supported by Wi-Fi or cellular systems.

For example, according to some aspects, weighted fair sharing of wireless channels may be facilitated by joint scheduling of transmissions by both a transmitter and a receiver using Resource Utilization Messages (RUMs), whereby the transmitter requests a set of resources based on knowledge of availability of its neighbors, while the receiver grants a subset of the request channels based on knowledge of availability of its neighbors. The transmitter learns of availability based on listening to its nearby receivers, and the receiver learns of potential interference by listening to its nearby transmitters. According to related aspects, the RUM may be weighted to indicate not only that the node is disadvantaged (e.g., due to a receiver of the data transmission experiencing interference upon reception) and that a collision avoidance transmission mode is desired, but also the degree of disadvantage of the node. The RUM-receiving node may utilize the fact that it has received a RUM, as well as its weight, to determine an appropriate response. This advertisement of weights allows collision avoidance to be performed in a fair manner, as an example. This invention describes such a technique.

According to other aspects, a RUM Rejection Threshold (RRT) may be used to facilitate determining whether to respond to a received RUM. For example, metrics may be calculated using various parameters and/or information included in the received RUM, and the metrics may be compared to the RRT to determine whether the RUM of the sending node is responsible for responding. According to related aspects, a RUM-sending node may indicate its degree of disadvantage by indicating the number of channels to which the RUM applies, such that the number of channels (which may be resources, frequency subcarriers, and/or time slots, in general) indicates the degree of disadvantage. If the level of disadvantage decreases in response to a RUM, the number of channels for which RUMs are transmitted may be reduced for subsequent RUM transmissions. If the level of disadvantage is not reduced, the number of channels available for the RUM may be increased for subsequent RUM transmissions.

A RUM may be transmitted at a constant Power Spectral Density (PSD), and a receiving node may estimate the Radio Frequency (RF) channel gain between itself and the RUM transmitting node using the received power spectral density and/or received power of the RUM to determine whether it will cause interference at the transmitting node (e.g., above a predetermined acceptable threshold level) if it transmits. Thus, there may be situations where a RUM receiving node is able to decode a RUM from a RUM sending node but determines that it will not cause interference. When a RUM reception determines that it should obey the RUM, it may do so by choosing to backoff from the resource completely or by choosing to use a transmit power reduced enough to cause its estimated potential interference level to fall below the predetermined acceptable threshold level. Thus, "hard" interference avoidance (full back-off) and "soft" interference avoidance (power control) are simultaneously supported in a unified manner. According to related aspects, a RUM may be used by a receiving node to determine a channel gain between the receiving node and a RUM-transmitting node in order to determine whether to transmit based on estimated interference caused at the transmitting node.

According to an aspect, a method of wireless communication may comprise: generating a Resource Utilization Message (RUM) at a first node, the RUM indicating that a first predetermined threshold has been met or exceeded; weighting the RUM with a value indicating the extent to which a second predetermined threshold has been reached or exceeded; and transmitting the weighted RUM to one or more second nodes.

Another aspect relates to an apparatus that facilitates wireless communication, the apparatus comprising: a generation module that generates a Resource Utilization Message (RUM) at a first node, the RUM indicating that a first predetermined threshold has been met or exceeded; a weighting module to weight the RUM with a value indicating a degree to which a second predetermined threshold has been reached or exceeded; and a transmitting module to transmit the weighted RUM to one or more second nodes.

Another aspect relates to an apparatus for wireless communication, the apparatus comprising: means for generating a Resource Utilization Message (RUM) at a first node, the RUM indicating that a first predetermined threshold has been met or exceeded; means for weighting the RUM with a value indicating a degree to which a second predetermined threshold has been reached or exceeded; and means for transmitting the weighted RUM to one or more second nodes.

Yet another aspect relates to a machine-readable medium comprising instructions for wireless communication, wherein the instructions upon execution cause a machine to: generating a Resource Utilization Message (RUM) at a first node, the RUM indicating that a first predetermined threshold has been met or exceeded; weighting the RUM with a value indicating the extent to which a second predetermined threshold has been reached or exceeded; and transmitting the weighted RUM to one or more second nodes.

Another aspect relates to a processor that facilitates wireless communications, the processor configured to: generating a Resource Utilization Message (RUM) at a first node, the RUM indicating that a first predetermined threshold has been met or exceeded; weighting the RUM with a value indicating the extent to which a second predetermined threshold has been reached or exceeded; and transmitting the weighted RUM to one or more second nodes.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative aspects of the one or more aspects. These aspects are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed and the described aspects are intended to include all such aspects and their equivalents.

Drawings

Fig. 1 illustrates a wireless communication system with multiple base stations and multiple terminals, such as may be utilized in conjunction with one or more aspects.

Fig. 2 is an illustration of a methodology for performing weighted fair sharing of a wireless channel using a resource utilization mask/message (RUM) in accordance with one or more aspects described herein.

Fig. 3 illustrates a sequence of request grant events that can facilitate resource allocation in accordance with one or more aspects described herein.

Fig. 4 is an illustration of several topologies that facilitate an understanding of a request grant scheme in accordance with various aspects.

Fig. 5 illustrates a methodology for managing interference by employing Resource Utilization Messages (RUMs) transmitted at constant Power Spectral Density (PSD), in accordance with one or more aspects presented herein.

Fig. 6 is an illustration of a methodology for generating txrums and requests that facilitate providing flexible Medium Access Control (MAC) in a wireless network for ad hoc deployment, in accordance with one or more aspects.

Fig. 7 is an illustration of a methodology for generating a grant of a request to send, in accordance with one or more aspects.

Fig. 8 is an illustration of a methodology for achieving fairness among contending nodes by adjusting a number of subcarriers used to transmit RUMs as a function of a level of disadvantage associated with a given node, in accordance with one or more aspects.

Fig. 9 is an illustration of an RxRUM transmission with constant Power Spectral Density (PSD) between two nodes, in accordance with one or more aspects.

Fig. 10 is an illustration of a methodology for employing a constant PSD for RUM transmission to facilitate estimating an amount of interference that a first node will cause at a second node, in accordance with one or more aspects.

Fig. 11 illustrates a methodology for responding to interference control packets in a planned and/or ad hoc wireless communication environment, in accordance with various aspects.

Fig. 12 is a diagram of a method for generating an RxRUM, in accordance with the above-described aspects.

Fig. 13 is an illustration of a methodology for responding to one or more received rxrums, in accordance with one or more aspects.

Fig. 14 is an illustration of a wireless network environment that can be employed in conjunction with the various systems and methods described herein.

Fig. 15 is an illustration of an apparatus that facilitates wireless data communication in accordance with various aspects.

Fig. 16 is an illustration of an apparatus that facilitates wireless communication using a Resource Utilization Message (RUM), in accordance with one or more aspects.

Fig. 17 is an illustration of an apparatus that facilitates generating a Resource Utilization Message (RUM) and weighting the RUM to indicate a level of disadvantage, in accordance with various aspects.

Fig. 18 is an illustration of an apparatus that facilitates comparing relative conditions at nodes in a wireless communication environment to determine which nodes are least favorable, in accordance with one or more aspects.

Detailed Description

Various aspects are now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident, however, that such aspect(s) may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more aspects.

As used in this application, the terms "component," "system," and the like are intended to refer to a computer-related entity, either hardware, software in execution, firmware, middle ware, microcode, and/or any combination thereof. For example, a component may be, but is not limited to being, a process running on a processor, an object, an executable, a thread of execution, a program, and/or a computer. One or more components may reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. Also, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the internet with other systems by way of the signal). Additionally, components of systems described herein may be rearranged and/or complimented by additional components in order to facilitate achieving the various aspects, goals, advantages, etc., described with regard thereto, and are not limited to the precise configurations set forth in a given figure, as will be appreciated by one skilled in the art.

Moreover, various aspects are described herein in connection with a subscriber station. A subscriber station can also be called a system, a subscriber unit, mobile station, mobile, remote station, remote terminal, access terminal, user agent, user equipment, or user device. A subscriber station may be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device having wireless connection capability, or other processing device connected to a wireless modem.

Moreover, various aspects or features described herein may be implemented as a method, apparatus, or article of manufacture using standard programming and/or engineering techniques. The term "article of manufacture" as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier, or media. For example, computer-readable media include, but are not limited to, magnetic storage devices (e.g., hard disk, floppy disk, magnetic strip …), optical disks (e.g., Compact Disk (CD), Digital Versatile Disk (DVD) …), smart cards, and flash memory devices (e.g., card, stick, key drive …). In addition, various storage media described herein can represent one or more devices and/or other machine-readable media for storing information. The term "machine-readable medium" can include, but is not limited to: wireless channels and various other media capable of storing, containing, and/or carrying instruction(s) and/or data. It should be understood that the word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects and designs.

It should be understood that a "node," as used herein, may be an access terminal or access point, and each node may be a receiving node as well as a transmitting node. For example, each node may include at least one receive antenna and associated receive chain, and at least one transmit antenna and associated transmit chain. Further, each node may include one or more processors to execute software code to implement any or all of the methods and/or protocols described herein and memory to store data and/or computer readable instructions associated with the various methods and/or protocols described herein.

Referring now to fig. 1, a wireless network communication system 100 is illustrated in accordance with various aspects presented herein. System 100 may include multiple nodes, such as one or more base stations 102 (e.g., cellular, Wi-Fi, or ad hoc, etc.) in one or more sectors, that receive, transmit, and relay wireless communication signals between each other and/or one or more other nodes, such as access terminal 104. Each base station 102 can comprise a transmitter chain and a receiver chain, each of which can in turn comprise a plurality of components associated with signal transmission and reception (e.g., processors, modulators, multiplexers, demodulators, demultiplexers, antennas, etc.), as will be appreciated by one skilled in the art. The access terminal 104 may be, for example, a cellular phone, a smart phone, a laptop, a handheld communication device, a handheld computing device, a satellite radio, a global positioning system, a PDA, and/or any other device suitable for communicating over a wireless network.

The following discussion is provided to facilitate an understanding of various systems and/or methods described herein. According to various aspects, node weights may be assigned (e.g., to a transmitting and/or receiving node), where each node weight is a function of the number of streams supported by the node. "flow," as used herein, refers to a transmission into or out of a node. The total weight of the node may be determined by accumulating the weights of all the flows through the node. For example, a Constant Bit Rate (CBR) stream may have a predetermined weight, a data stream may have a weight proportional to its type (e.g., HTTP, FTP, etc.), and so on. In addition, each node may be assigned a predetermined static weight that may be added to the flow weight of each node to provide additional priority to each node. The node weights may also be dynamic and reflect the current status of the flows carried by the node. For example, the weight may correspond to the worst throughput of the flow being carried (received) at the node. In essence, the weight represents the degree of disadvantage that the node is experiencing and is used for fair channel access among a set of interfering nodes contending for a common resource.

The request message, grant message, and data transmissions may be power controlled, however, the node may still experience excessive interference resulting in an unacceptable signal-to-interference-and-noise ratio (SINR) level for the node. To mitigate the undesirable low SINR, a Resource Utilization Message (RUM), which may be receiver-side (RxRUM) and/or transmitter-side (TxRUM), may be utilized. A receiver may broadcast an RxRUM when the interference level on its desired channel exceeds a predetermined threshold level. The RxRUM may contain a list of grant channels on which the receiver desires reduced interference, as well as node weight information. In addition, rxrums may be transmitted at a constant Power Spectral Density (PSD) or constant power. A node decoding the RxRUM (e.g., a transmitter contending with a receiver transmitting the RxRUM) may respond to the RxRUM. For example, each node listening to the RxRUM may calculate its corresponding channel gain from the receiver (e.g., by measuring the received PSD and exploiting knowledge of the constant PSD at which the RxRUM was sent) and may reduce its corresponding transmit power level to mitigate interference. The RxRUM receiver may even choose to backoff completely from the indicated channel on that RxRUM. To ensure that interference avoidance occurs in a fair manner, i.e., to ensure that all nodes get a fair share of the transmit opportunities, weights may be included in the RxRUM. The weight of a given node may be used to compute a fair share of the resources to be allocated to that node. According to an example, a threshold for transmitting and/or reflecting the RUM may be determined based on a behavior of the system. For example, in a pure collision avoidance type system, a RUM may be sent for each transmission, and any node that hears the RUM may respond by not sending on the associated channel.

An additional dimension of collision avoidance may be achieved if the RUM includes a channel bit mask that indicates which channels the RUM applies to, which may be useful if the receiver needs to arrange a small amount of data on a portion of the channel and does not want the transmitter to completely backoff from the entire channel. This aspect provides finer granularity in the collision avoidance mechanism, which is important for bursty traffic.

A transmitter may broadcast a TxRUM when it is unable to request sufficient resources (e.g., in the case that the transmitter listens for one or more rxrums that force it to back off on most channels). The TxRUM may be broadcast prior to actual transmission to inform neighboring receivers of impending interference. The TxRUM may inform all receivers within its listening range: based on each RxRUM that the transmitter has heard, the transmitter believes it has the most appropriate claims for bandwidth. The TxRUM may carry information about the weight of the transmitter node, which may be used by each neighboring node to calculate its respective share of resources. Additionally, the TxRUM may be transmitted at a PSD or transmit power that is proportional to the power level at which the data is transmitted. It should be appreciated that the TxRUM need not be transmitted at a constant (e.g., high) PSD, since only potentially affected nodes need to know the transmitter conditions.

Rxrums carry weight information intended to convey to all transmitters within "listening" range (e.g., whether they are transmitting data to the receiver or not), the degree to which the receiver is demanding on bandwidth due to interference from other transmissions. The weight may represent a degree of disadvantage and be greater when the receiver is more disadvantageous and smaller when the disadvantage is somewhat less. As an example, if throughput is used to measure the degree of disadvantage, one possible relationship may be expressed as:

wherein R is_targetRepresenting the required throughput, R_actualIs the actual throughput currently achieved, and q (x) represents the quantized value of x. When there is a single stream at the receiver, R_targetMay represent the minimum throughput required for the flow, and R_actualMay represent the average throughput that the flow has achieved. Note that weighting higher values, which indicate a deeper penalty level, is a convention. In a similar manner, a less disadvantageous contract may be represented by a higher value of weight, as long as the weight resolution logic is appropriately modified. For example, the weight may be calculated using the ratio of the actual throughput to the target throughput (the inverse of the example shown above).

When there is a potential difference of R at the receiver_targetMultiple streams of values, then the receiver may choose to set the weights based on the least favorable stream. For example:

where j is the stream index at the receiver. Other options such as basing the weights on the sum of the stream throughputs may also be performed. Note that the functional form used for the weights in the above description is purely for illustration. The weights may be calculated in a variety of different ways and using different measures other than throughput. According to related aspects, a receiver may determine whether it has outstanding data from a sender (e.g., a transmitter). This is the case if it has received a request or if it has received a previous request that was not granted. In this case, the receiver may be at R_actualLower than R_targetThe RxRUM is transmitted.

The TxRUM may carry a single bit of information that conveys whether it is present. The transmitter may set the TxRUM by performing a predetermined sequence of actions. For example, a transmitter may collect the rxrums it has recently heard, including rxrums from its own receiver in the case that it has already sent an RxRUM. If the transmitter has not received any rxrums, it may send a request to its receiver without sending a TxRUM. If the only RxRUM is from its own receiver, the transmitter may send a request and TxRUM.

Alternatively, if the transmitter has received several rxrums, including rxrums from its own receiver, the transmitter may order the rxrums based on their respective RxRUM weights. The transmitter may send a TxRUM and a request if its own receiver has the highest weight. However, if the transmitter's own receiver is not the highest weight, the transmitter need not send a request or TxRUM. In the case where the transmitter's own receiver is one of several rxrums, all at the highest weight, then the transmitter may send the TxRUM and request with a probability of 1/(all rxrums at the highest weight). According to another aspect, the transmitter may not send a request if the receiver has received an RxRUM that does not include one from its own receiver. Note that the entire sequence of RxRUM processing described above may even be applied in the absence of a TxRUM. In this case, logic is used by the transmitter node to determine whether to send a request to its receiver and, if so, for which channels.

Based on the request and/or TxRUM that the receiver hears, the receiver may decide to grant a given request. The receiver need not send a grant when the transmitter has not made a request. If the receiver has listened to the TxRUM, but none of them came from its serving transmitter, then the receiver does not send a grant. The receiver may decide to grant if it only listens to txrums from its serving transmitter. There may be two results if the receiver has listened to txrums from its own transmitter and from transmitters that are not served by it. For example, if the running average of the transmission rate is at least R_targetThen the receiver is not granted (e.g., it forcesIts transmitter is stationary). Otherwise the receiver grants with a probability defined as 1.0/(sum of txrums listened to). If the transmitter has been granted, the transmitter transmits a data frame that can be received by the receiver. Upon successful transmission, both the transmitter and receiver update the average rate for the connection.

According to other aspects, the scheduling actions may be programmed to achieve equal grade of service (EGOS) or other schemes for managing fairness and quality of service among multiple transmitters and/or streams to a receiver. The scheduler may use the rate it knows is received by its partner node to decide which nodes to schedule. However, the scheduler may comply with interference rules imposed by the medium access channel operating thereon. Specifically, the scheduler may obey the RUMs it listens to from its neighbors. For example, on the forward link, a scheduler on an Access Point (AP) may send requests to all Access Terminals (ATs) that have traffic for them unless they are blocked by an RxRUM. The AP may receive grants back from one or more of these ATs. If the AT is replaced by a competing TxRUM, it may not send a grant. The AP may then schedule the AT with the highest priority according to the scheduling algorithm and may transmit.

On the reverse link, each AT having traffic to send may request from the AP. If the AT is blocked by an RxRUM, it will not send a request. The AP schedules the AT with the highest priority according to the scheduling algorithm while observing any txrums heard in the previous time slot. The AP then sends a grant to the AP. Upon receiving the grant, the AT transmits.

Fig. 2 is an illustration of a methodology 200 that performs weighted fair sharing of wireless channels using resource utilization masks/messages (RUMs), in accordance with one or more aspects described herein. At 202, a determination is made regarding a number of channels over which a node (e.g., access point, access terminal, etc.) will prefer to transmit. Such a determination may be based on, for example, the requirements associated with a given amount of data to be transmitted, the interference experienced at the node, or any other suitable parameter (e.g., latency, data rate, spectral efficiency, etc.). At 204, one or more channels may be selected to achieve a desired number of channels. Channel selection may be performed preferably on available channels. For example, a channel known to be available in a previous transmission time period may be selected before a channel occupied in the previous transmission time period. At 206, a request for these selected channels may be sent. The request may include a bit mask of a preferred channel over which the transmitter (e.g., transmitting node, etc.) wants to send data, and may be sent from the transmitter to a receiver (e.g., receiving node, handset, smartphone, wireless communication device, access point, etc.). The request may be a request for a first plurality of channels that are not blocked in the most recent time slot, and may be a request for a second plurality of channels in the case that the first plurality of channels is insufficient for data transmission. The request message sent at 206 may additionally be power controlled to ensure a desired level of reliability at the receiver.

According to other aspects, the determination of the number of channels desired for a given transmission may be a function of the weights associated with that node, a function of the weights associated with other nodes requesting channels, a function of the number of channels available for transmission, or any combination of the preceding factors. For example, the weight may be a function of the number of streams passing through the node, a function of the level of interference experienced at the node, etc. According to other features, the channel selection can include partitioning channels into one or more sets, and can be based in part on a received Resource Utilization Message (RUM) indicating that one or more channels of a set of channels are unavailable. The RUM may be evaluated to determine whether a given channel is available (e.g., not identified by the RUM). For example, a determination may be made that a given channel is available in the case that the channel is not listed in the RUM. Another example is that a channel is considered available even if a RUM for that channel is received, but the advertised weight for that channel is lower than the weight advertised in the RUM sent by the node's receiver.

Fig. 3 illustrates a sequence of request-grant events that can facilitate resource allocation in accordance with one or more aspects described herein. A first sequence of events 302 is depicted that includes a request sent from a transmitter to a receiver. Upon receiving the request, the receiver may send a grant message to the transmitter granting permission to all or a subset of the channels requested by the transmitter. The transmitter may then transmit data over some or all of the granted channels.

In a related aspect, the sequence of events 304 can include a request sent from a transmitter to a receiver. The request may include a list of channels on which the transmitter wishes to send data to the receiver. The receiver may then send a grant message to the transmitter indicating that all or a subset of the desired channels have been granted. The transmitter may then send pilot information to the receiver, which upon receipt may send rate information back to the transmitter to help mitigate the undesirably low SINR. Upon receiving the rate information, the transmitter may transmit data on the granted channel and at the specified transmission rate.

According to a related aspect, a transmitter may broadcast a TxRUM when the transmitter is unable to request sufficient resources (e.g., in the event that the transmitter listens for one or more rxrums that occupy most of the transmitter's available channels). Such txrums may carry information about the weights of the transmitter node, which may be used by each neighboring node to calculate its respective share of resources. Additionally, the TxRUM may be transmitted at a PSD proportional to the power level at which the data is transmitted. It should be appreciated that the TxRUM need not be transmitted at a constant (e.g., high) PSD, as only potentially affected nodes need to know the transmitter conditions.

The sequence of events 302 and 304 may be performed in view of a number of constraints that may be enforced during a communication event. For example, the transmitter may request any channels that have not been blocked by an RxRUM in the previous time slot. The requested channels may be arranged in order of preference for successful channels in the most recent transmission period. Without enough channels, the transmitter may request other channels to get their fair share by sending txrums to announce contention for the other channels. In view of the rxrums that have been listened to, the fair share of the channel may then be determined based on the number and weights of the contending neighbors (e.g., nodes).

The grant from the receiver may be a subset of the channels listed in the request. The receiver may be given authority to avoid channels exhibiting high interference levels in recent transmissions. Without enough grant channels, the receiver may increase the channel (e.g., up to the fair share of the transmitter) by sending one or more rxrums. In view of the listened (e.g., received) txrums, the fair share of the transmitter over the channel can be determined by, for example, evaluating the number and weights of neighboring nodes.

When transmitting, the transmitter may transmit data on all or a subset of the channels granted in the grant message. The transmitter may reduce transmit power on some or all of the channels once it listens to the RxRUM. In the case where the transmitter listens for a grant and multiple rxrums on the same channel, the transmitter may transmit with a reciprocal probability. For example, if for a single channel, one grant and three rxrums are listened to, the transmitter may transmit at a probability of 1/3, etc. (e.g., the probability that the transmitter will use the channel is 1/3).

According to other aspects, excess bandwidth may be allocated according to a sharing scheme that is not limited by the above constraints. For example, weight-based scheduling as described above may facilitate weighted fair sharing of resources. However, in situations where there is excess bandwidth, there is no need to constrain resource allocation (e.g., above a minimum fair share). For example, a scenario may be considered in which two nodes with full buffers and each having a weight of 100 (e.g., corresponding to a 100kbps flow rate) are sharing a channel. In this case, the two nodes may share the channel equally. Each of these two nodes may be permitted, for example, 300kbps, if they experience varying channel quality. However, it may be desirable to give only 1200kbps to node 2 in order to raise the share to 500 kbps. That is, in this case, it may be desirable to share any excess bandwidth in some unfair manner in order to achieve greater sector throughput. The weighting mechanism can be extended in a simple manner to facilitate unfair sharing. For example, each node may have a notion of its assigned rate, in addition to the weight, which information may be associated with the service purchased by the AT. A node may continually update its average rate (at some suitable interval) and send RUMs when its average throughput is lower than the allocated rate to ensure that the node will not contend for excess resources beyond its allocated rate, which may then be allocated in other sharing schemes.

Fig. 4 is an illustration of several topologies that facilitate an understanding of a request-grant scheme in accordance with various aspects. The first topology 402 has three links (A-B, C-D, E-F) in close proximity, where each node A-F can listen for RUMs from all other nodes. The second topology 404 has three links in a chain, and the middle link (C-D) interferes with two outer links (a-B and E-F) that do not interfere with each other. A RUM may be modeled according to this example such that the range of the RUM is two nodes. The third topology 406 includes three links (C-D, E-F, and G-H) on the right hand side that interfere with each other and can listen to each other's RUMs. The single link on the left (A-B) only interferes with the link (C-D).

According to examples, the performance of three systems is described below in table 1 for the above topology. In the "all information" case, the availability of rxrums with bitmasks and weights, and txrums with bitmasks and weights, is assumed. In the "partial information" case, RxRUM with bitmask and weight and TxRUM with weight but no bitmask are assumed. Finally, in the "RxRUM alone" case, the TxRUM is not transmitted.

TABLE 1

As can be seen from table 1, the partial information proposal enables a fair share of weights with less delay in convergence. The number of convergence indicates the number of cycles it takes for the scheme to converge to a stable allocation of available channels. Each node may then continue to utilize these same channels.

Fig. 5 is an illustration of a methodology 500 for managing interference by employing a Resource Utilization Message (RUM) transmitted at a constant Power Spectral Density (PSD), in accordance with one or more aspects presented herein. The request message, grant message, and transmission may be power controlled, however, the node may still experience excessive interference resulting in an unacceptable signal to interference and noise ratio (SINR) level for the node. To mitigate the undesirably low SINR, a Resource Utilization Message (RUM), which may be receiver-side (RxRUM) and/or transmitter-side (TxRUM), may be utilized. A receiver may broadcast an RxRUM when the interference level on its desired channel exceeds a predetermined threshold level. The RxRUM may contain a list of channels on which the receiver desires reduced interference, as well as node weight information. In addition, rxrums may be transmitted at a constant Power Spectral Density (PSD). A node "listening" to the RxRUM (e.g., a transmitter contending with the receiver transmitting the RxRUM) may respond to the RxRUM by stopping its transmission, or by reducing the transmit power.

For example, in an ad hoc deployment of wireless nodes, the carrier-to-interference ratio (C/I) on some nodes may be undesirably low, which may prevent successful transmissions. It should be appreciated that the interference level used to calculate C/I may include noise, such that C/I may be similarly expressed as C/(I + N), where N is noise. In this case, the receiver may manage the interference by requesting other nodes in the vicinity, either to reduce their respective transmit powers, or to backoff completely from the indicated channel. At 502, an indication of channels (e.g., in a multi-channel system) exhibiting a C/I below a first predetermined threshold may be generated. At 504, a message may be sent including information indicating which channels exhibit inadequate C/I. For example, a first node (e.g., receiver) may broadcast a RUM along with a bitmask that includes information indicating channels with undesirably low C/is. The RUM may additionally be sent with a constant PSD known to all nodes in the network. In this way, nodes with varying power levels may broadcast at the same PSD.

At 506, the message (e.g., RUM) may be received by other nodes. At 508, upon receiving the RUM, a second node (e.g., a transmitter) may utilize a PSD associated with the RUM to calculate a Radio Frequency (RF) distance (e.g., channel gain) between itself and the first node. The reaction of a given node to the RUM may vary depending on the RF range. For example, a comparison of the RF distance to a second predetermined threshold may be performed at 510. If the RF distance is below the second predetermined threshold (e.g., the first node and the second node are close to each other), then at 512, the second node may cease any further transmissions on the channel indicated in the RUM to mitigate interference. Alternatively, if the second node and the first node are sufficiently far from each other (e.g., the RF distance between them when compared at 510 is equal to or greater than the second predetermined threshold), then at 514, the second node may utilize the RF distance information to predict the magnitude of interference that would be caused at the first node and attributed to the second node if the second node continued to transmit on the channel indicated in the RUM. At 516, the predicted interference level may be compared to a third predetermined threshold level.

For example, the third predetermined threshold may be a fixed fraction of a target Interference Over Thermal (IOT) level that is a ratio of interference noise to thermal noise power measured over the common bandwidth (e.g., approximately 25% of the target IOT of 6dB, or some other threshold level). At 520, if the predicted interference is below the threshold level, the second node may continue to transmit on the channel indicated in the RUM. If, however, the predicted interference is determined to be equal to or greater than a third predetermined threshold level, then at 518 the second node may reduce its transmit power level until the predicted interference is below the third threshold level. In this manner, a single message, or RUM, may be used to indicate interference on multiple channels. By powering down the interfering nodes, the affected nodes (e.g., receivers, access terminals, access points, etc.) may successfully receive bits on a subset of the plurality of channels, and the nodes that have lowered their transmit power levels may also be allowed to continue their respective transmissions.

Referring to fig. 6 and 7, flexible medium access control can be facilitated by allowing a receiver to communicate with one or more transmitters in a manner that not only favors a collision avoidance mode of transmission, but also measures how adverse it is with respect to other receivers. In third generation cellular MACs, the need for cross-cell interference avoidance can be mitigated by employing a planned deployment scheme. Cellular MACs generally achieve high spatial efficiency (bits/unit area), but planned deployments are expensive and time consuming, and may not be suitable for hotspot deployments. In contrast, WLAN systems such as those based on the 802.11 family of standards place few restrictions on deployment, but achieve the cost and time savings associated with deploying WLAN systems compared to cellular systems at the expense of building enhanced interference robustness into the MAC. For example, the 802.11 family uses Carrier Sense Multiple Access (CSMA) based MAC. CSMA is fundamentally a "listen before transmit" method in which a node contending for transmission must first "listen" to the medium, determine that it is idle, and then follow a back-off protocol before transmitting. Carrier sense MAC can result in poor utilization, limited fairness control, and susceptibility to hidden and exposed nodes. To overcome the drawbacks associated with planning deployment of both cellular and Wi-Fi/WLAN systems, aspects described with reference to fig. 6 and 7 may employ synchronized control channel transmissions (e.g., transmit requests, grants, pilots, etc.), efficient use of RUMs (e.g., a receiver may transmit an RxRUM when a receiver wishes to interfere with a transmitter backoff, a transmitter may transmit a TxRUM to make its target receiver and a receiver with which it interferes aware of its intent to transmit, etc.), and improved control channel reliability through reuse (e.g., so that multiple MUMs may be decoded simultaneously at the receiver), and so forth.

According to some features, rxrums may be weighted with coefficients indicating how unfavorable the receiver is when serving its transmitter. The interfering transmitter may then use both the fact that it listened to the RxRUM and the value of the weight associated with that RxRUM to determine the next action. According to an example, when a receiver receives a single stream, the receiver can be at

RxRUM is sent in time, where RST (RUM send threshold) is the throughput target for the stream, R_actualIs the actual achieved throughput calculated as a short-term moving average (e.g., by a single pole HR filter, etc.), and T is the threshold against which the ratio is compared. If the receiver is unable to schedule its transmitter at a particular time slot, the rate of that time slot may be assumed to be 0. Otherwise the rate achieved in the time slot is the sample that can be fed to the averaging filter. The threshold T may be set to unit 1 so that the weight is generated and sent whenever the actual throughput falls below the target throughput.

A transmitter may "listen" for an RxRUM if it can decode the RxRUM message. The RxRUM message may optionally be ignored by the transmitter if it estimates that it will cause interference below a RUM Rejection Threshold (RRT) at the RxRUM transmitter. In the instant MAC design, Rx/TxRUM, request and quasi-grant are sent on a control channel with a very low reuse factor (e.g., 1/4 or less) to ensure that the interference impact on the control channel is low. A transmitter may analyze the set of rxrums it has heard, and if the RxRUM heard from its target receiver is the highest weight RxRUM, the transmitter may send a request with a TxRUM indicating to all receivers (e.g., including its own receivers) that can hear the transmitter that it has won the contention and is authorized to use the channel. Other conditions for transmitting a TxRUM, processing of multiple rxrums of equal weight, processing of multiple TxRUM requests, etc., are described below with more specific reference to fig. 6 and 7. Setting the RxRUM weights and corresponding actions at the transmitter allows for deterministic contention resolution, thereby allowing improved utilization of the shared medium and weighted fair sharing through the setting of the RST. In addition to setting the RST, which controls the probability that an RxRUM is sent out, the setting of the RRT can help control the degree to which the system operates in a collision avoidance mode.

With respect to RST, RST may be employed such that a collision avoidance protocol or a simultaneous transmission protocol may be invoked based on an analysis of which protocol enables higher system throughput configured for a particular user, from a system efficiency standpoint. From a peak rate perspective or a delay zero tolerance service, the user may be allowed to burst data at a higher rate than is achievable using simultaneous transmission at the expense of system efficiency. In addition, certain types of fixed rate traffic channels (e.g., control channels) may be required to achieve a particular throughput and RST may be set accordingly. In addition, some nodes may have higher traffic requirements due to aggregation of large traffic volumes. This is especially true when wireless backhaul is used in a tree architecture and a receiver is scheduling nodes near the tree root.

One method of determining the fixed RST is to set the RST based on the forward link edge spectral efficiency achieved in the planned cellular system. Cell-edge spectral efficiency indicates the throughput that an edge user can achieve in a cellular system when a BTS sends to a given user and the neighbors are always on. This is to ensure that the throughput in the case of simultaneous transmission is not worse than the cell-edge throughput in a planned cellular system, which can be used to trigger a transition to collision avoidance mode to improve throughput (e.g., due to the throughput achievable using the simultaneous transmission mode). According to other features, the RST can be different for different users (e.g., a user can subscribe to different levels of service associated with different RST, etc.).

Fig. 6 is an illustration of a methodology 600 for generating txrums and requests that facilitate providing flexible Medium Access Control (MAC) in a wireless network for ad hoc deployment, in accordance with one or more aspects. The TxRUM may inform all receivers within listening range: a transmitter believes to be the most bandwidth-demanding on the basis of each RxRUM that it has heard. The TxRUM carries a single bit of information indicating its presence, and the transmitter may set the TxRUM bit in the following manner.

At 602, the transmitter may determine whether it has heard (e.g., within a predetermined monitoring period, etc.) one or more rxrums (e.g., a may hear rxrums from B, C and D, where B is its receiver, assuming a is communicating with B and interfering with C and D), including an RxRUM from its own receiver if it has sent one RxRUM (i.e., if B has sent one in the operational example). As described herein, a "node" may be an access terminal or an access point and may include both a receiver and a transmitter. The use of terms such as "transmitter" and "receiver" in this description should therefore be construed as "when a node functions as a transmitter" and "when a node functions as a receiver", respectively. If the transmitter has not received any rxrums, then it sends a request to its receiver without sending a TxRUM at 604. If the transmitter has received at least one RxRUM, then at 606 a determination may be made as to whether an RxRUM has been received from the transmitter's own receiver (e.g., a receiver at the transmitter node). If not, at 608, a decision may be made to refrain from sending the TxRUM and associated request.

If the determination at 606 is positive, then at 610, a further determination may be made as to whether the RxRUM received from the transmitter's own receiver is the only RxRUM that has been heard. If so, the transmitter may send the TxRUM to be transmitted and a request at 612. If the transmitter has received multiple rxrums, including rxrums from its own receiver, then at 614, the transmitter may order the rxrums based on associated weights. At 616, a determination may be made as to whether the RxRUM received from the transmitter's own receiver has the highest weight (e.g., the greatest level of disadvantage) of all received rxrums. If so, the transmitter may send both the TxRUM to be transmitted and the request at 618. If the determination at 616 is negative, the transmitter may refrain from transmitting the TxRUM and the request at 620. In the case where the transmitter receives an RxRUM from its own receiver as well as one or more other rxrums, all with equal weights, the transmitter may send the TxRUM and request with a probability of 1/N, where N is the number of rxrums with the highest weight. In an aspect, the logic of FIG. 6 may be applied without any TxRUM, but only with requests. That is, an RxRUM controls whether a node can send a request for a particular resource.

As used herein, "penalties" may be determined for a given node as a function of, for example, the ratio of the target value to the actual value. For example, when the penalty is measured as a function of throughput, spectral efficiency, data rate, or some other parameter for which a higher value is desired, then the actual value will be relatively lower than the target value when the node is at a penalty. In this case, the weighted value indicating the level of disadvantage of the node may be a function of the ratio of the target value to the actual value. Where unfavorable based parameters are desired to be low (e.g., latency), the inverse of the ratio of the target value to the actual value may be utilized to generate the weight. As used herein, a node described as having a "better" condition relative to another node may be understood as having a lesser level of disadvantage (e.g., a node having a better condition has less interference, less latency, higher data rate, higher throughput, higher spectral efficiency, etc. than another node with which it is compared).

According to an example, transmitter a and transmitter C can simultaneously transmit to receiver B and receiver D, respectively (e.g., according to a synchronous medium access control scheme in which the transmitter transmits at specified times and the receiver transmits at other specified times). Receiver B may determine and/or have a predetermined amount of interference being experienced and may send an RxRUM to transmitters such as transmitter a and transmitter C. Since receiver D transmits at the same time as receiver B, receiver D does not need to listen to the RxRUM. This example is further that upon listening for an RxRUM from receiver B, transmitter C may evaluate the condition of receiver B as indicated in the RxRUM and may compare its own condition (possibly an RxRUM advertisement known to C or sent by D) with the condition of receiver B. On the basis of this comparison, the transmitter C may take several actions.

For example, based on a determination that transmitter C is experiencing less interference than receiver B, transmitter C may back off by refraining from sending a request to transmit. Additionally or alternatively, transmitter C may evaluate or determine how much interference it causes at receiver B (e.g., in the case where rxrums from the receiver are transmitted at the same, or constant, power spectral density). This determination may include estimating the channel gain to receiver B, selecting a transmit power level, and determining whether the level of interference that a transmission from transmitter C at the selected transmit power level will cause at receiver B exceeds a predetermined acceptable threshold interference level. Based on this determination, transmitter C may select to transmit at a power level equal to or less than the previous transmit power level.

In the event that the conditions of transmitter C (e.g., unfavorable levels with respect to lack of resources, interference, etc.) are substantially the same as the conditions of receiver B, transmitter C may evaluate and/or process the weights associated with the rxrums it has heard. For example, if transmitter C has heard 4 RUMs with weights 3, 5, and 5, then the rxrums heard from receiver B carry a weight of 5 (e.g., have a weight equal to the most heavy of all rxrums heard by transmitter C), then C will send the request with probability 1/3.

Fig. 7 illustrates a methodology 700 for generating a grant of a request to send, in accordance with one or more aspects. At 702, the receiver may evaluate the TxRUM and requests it has recently listened to or received (e.g., during a predetermined monitoring period, etc.). If a request has not been received, the receiver may refrain from sending the grant message at 704. If at least one request and TxRUM have been received, at 706, a determination may be made as to whether the received TxRUM is from a transmitter served by the receiver. If not, the receiver may refrain from transmitting the grant at 708. If so, at 710, the receiver may determine whether all of the received txrums are from transmitters serviced by the receiver.

If the determination at 710 is positive, a grant may be generated and sent to one or more requesting transmitters at 712. If the determination at 710 is negative and the receiver has received a TxRUM from its own transmitter plus a TxRUM from a transmitter that the receiver is not serving, then at 714, a running average for the transmission rate may be greater than or equal to R_targetA determination is made. If the running average of the transmission rate is greater than or equal to R_targetThen, at 716, the receiver may refrain from granting the requested resources. If not, at 718, the receiver may send a grant with a probability of 1/N, where N is the number of TxRUMs received. On the other hand, a TxRUM may include the same weights as in an RxRUM and when multiple txrums are heard, at least one from one of its transmitters and one from another, then grants are based on whether the TxRUM with the highest weight was sent by one of its transmitters. In the case where txrums with the highest weights (including one TxRUM from one of their transmitters) are flat, grants can be sent with a probability of m/N, where N is the number of txrums with the highest weights heard and m is the number of transmitters from the receiver.

According to related aspects, a receiver may periodically and/or continuously assess whether it has outstanding data from a sender. This is the case if the receiver has received a current request or if it has received a previously unapproved request. In either case, the receiver may send out an RxRUM as long as the average transmission rate is below R_targetAnd (4) finishing. In addition, based on the grant of the transmitter request, the transmitter may transmit a data frame that may be received by the receiver. If there is outstanding data for the transmitter-receiver pair, both the transmitter and the receiver can update the average rate information for the connection.

Fig. 8 is an illustration of a methodology 800 for achieving fairness among contending nodes by adjusting a number of channels for which RUMs are transmitted according to a level of disadvantage associated with a given node, in accordance with one or more aspects. As described above with respect to the previous figures, rxrums are issued to indicate that the receiver is experiencing poor communication conditions and wishes to reduce the interference it encounters. The RxRUM includes a weight that quantifies the degree of disadvantage that the node is experiencing. According to an aspect, the weight may be set equal to RST/average throughput. Here, RST is the average throughput expected by the node. When a transmitting node listens to multiple rxrums, it may use the corresponding weights to resolve contention among them. The RxRUM with the highest weight may decide to transmit if it originates from the transmitter's own receiver. If not, the transmitter may inhibit transmission.

The TxRUM is issued by the transmitter to announce an impending transmission and has two uses. First, the TxRUM lets the receiver know that its RxRUM won the local contention, so it can schedule a transmission. Second, the TxRUM informs other neighboring receivers of the impending interference. When the system supports multiple channels, the RUM may carry a bitmask in addition to the weight. The bit mask indicates the channel for which the RUM is applicable.

An RxRUM allows a node to clear its immediate neighbors of interference, since the node receiving the RxRUM may be caused to refrain from transmitting. While the weights allow for fair contention (e.g., with the most disadvantaged node winning), having a multi-channel MAC may provide another degree of freedom. The number of channels for which a node may send an RxRUM may be based on its degree of disadvantage to cause a node with a very bad history to catch up faster. When these rxrums succeed and the node improves its condition in response to the transmission rate received by the node, the node may reduce the number of channels for which rxrums are transmitted. If the RUM was not initially successful and throughput did not improve due to more severe congestion, the node may increase the number of channels for which RUMs are sent. In a very congested situation, the node may become very disadvantaged and may send rxrums for all channels, thereby degrading to a single carrier situation.

According to the method, at 802, a level of disadvantage of a node may be determined and a RUM may be generated to indicate the level of disadvantage to other nodes within listening range. For example, the adverse level may be determined as a function of the level of service received at the node that may be affected by various parameters such as latency, IOT, C/I, throughput, data rate, spectral efficiency, and the like. At 804, the number of channels for which RUMs are sent may be selected, which may be commensurate with the level of disadvantage (e.g., the more disadvantageous, the greater the number of channels). The RUM may be sent for the channel at 806. The quality of service (QoS) of the node may be measured and the disadvantages may be re-assessed at 808 to determine whether the condition of the node has improved. Based on the measured QoS, at 810, the number of channels for which subsequent RUMs are sent may be adjusted. For example, if the QoS of the node does not improve or deteriorate, the number of channels for which subsequent RUMs are transmitted may be increased at 810 to improve the level of service received at the node. If the QoS of the node has improved, then at 810, the number of channels for which subsequent RUMs are sent may be reduced to conserve resources. The method may return to 806 for further iterations of RUM transmission, service evaluation, and channel number adjustment. The decision as to whether to increase or decrease the number of channels over which the RUM is sent may also be a function of the QoS metric being used by the node. For example, increasing the number of channels for which RUMs are sent (based on a level of disadvantage of still or degradation) may be meaningful for throughput/data rate type measurements, but may not be the case for latency measurements.

According to related aspects, node-based and/or traffic-based priorities may be incorporated by allowing nodes with higher priorities to recruit a greater number of channels than lower priority nodes. For example, a disadvantaged video caller may receive 8 channels at a time, while a similarly disadvantaged voice caller only receives two carriers. The maximum number of channels available to a node may also be limited. The upper limit may be determined by the type of traffic being carried (e.g., smaller voice packets typically do not require more channels), the power classification of the node (e.g., a weaker transmitter may not spread its power over too much bandwidth), the distance from the receiver, and the resulting receive PSD. In this way, the method 800 may further reduce interference and improve resource savings. Other aspects provide for employing a bit mask to indicate the number of channels allocated to the node. For example, a 6-bit mask may be used to indicate that a RUM may be sent for up to 6 channels. The node may additionally request that the interfering node refrain from transmitting on all or a subset of the allocated subcarriers.

Fig. 9 is an illustration of RxRUM transmission at constant Power Spectral Density (PSD) between two nodes in accordance with one or more aspects. When a node experiences more severe interference, it may benefit from limiting the interference caused by other nodes, thereby allowing better spatial reuse and improved fairness. In the 802.11 family of protocols, request-to-send (RTS) and clear-to-send (CTS) packets are used to achieve fairness. The node that hears the RTS stops sending and allows the requesting node to successfully send the packet. However, this mechanism often results in a large number of nodes being unnecessarily shut down. Further, a node may send RTS and CTS at full power over the entire bandwidth. The RTS and CTS ranges for different nodes may differ if some nodes have higher power than others. Thus, a low power node that may be strongly interfered by a high power node may not be able to turn off the high power node through RTS/CTS because the high power node will be out of range of the low power node. In this case, the high power node is a permanent "hidden" node to the low power node. Even if the low power node sends an RTS or CTS to one of its transmitters or receivers, it will not be able to turn off the high power node. Thus, 802.11MAC requires all nodes to have equal power. This introduces a limit on performance, especially from a coverage point of view.

The mechanism of fig. 9 facilitates broadcasting of RUMs from receivers at nodes that are experiencing undesirably low SINR for one or more channels. The RUM may be sent at a constant known PSD, regardless of the transmit power capability of the node, and a receiving node may observe the received PSD and calculate the channel gain between itself and the RUM-transmitting node. Once the channel gain is known, the receiving node may determine the amount of interference it may cause at the RUM-transmitting node (e.g., based in part on its own transmit power), and may decide whether to temporarily refrain from transmitting.

In the case where nodes in the network have different transmit powers, the nodes that listen to the RUM may decide whether to turn off based on their respective known transmit powers and the calculated channel gain. Thus, the low power transmitter need not be unnecessarily turned off, as it will not cause significant interference. In this way, only the nodes causing interference may be turned off, thereby mitigating the drawbacks of the conventional RTS-CTS mechanism described above.

For example, a first node (node a) may receive an RxRUM from a second node (node B) on channel h. The RxRUM may be transmitted at a power level pRxRUM, and X may be estimated in a manner such that the received signal value X is equal to the sum of channel h times the transmit power pRxRUM plus noise. Node a may then perform a channel estimation protocol to estimate h by dividing the received signal value X by pRxRUM. If the weight of node B is higher than the weight of node A, node A can pass

I_A=h_est*p_A

By multiplying the channel estimate by the desired transmit power (p)_A) To further estimate the interference that node a transmissions may cause to node B, where I_AIs the interference caused by node a at node B.

According to an example, considering a system where the maximum transmit power M is determined to be 2 watts and the minimum transmit bandwidth is 5MHz, the maximum PSD is 2 watts/5 MHz, or 0.4W/MHz. It is assumed that the minimum transmit power in the system is 200 mW. The RUM is designed to have a range equal to the maximum PSD range allowed in the system. The power spectral density for the 200mW transmitter and the data rate for the RUM are then selected to be equal to these ranges. It should be appreciated that the above examples are presented for illustrative purposes, and that the systems and/or methods described herein are not limited to the specific values presented above, but may also utilize any suitable values.

Fig. 10 is an illustration of a methodology 1000 for utilizing a constant PSD for RUM transmission to facilitate estimating an amount of interference that a first node will cause at a second node, in accordance with one or more aspects. At 1002, a first node may receive an RxRUM at a known PSD from a second node. At 1004, the first node may calculate a channel gain between itself and the second node based on the known PSD. At 1006, the first node may estimate an amount of interference that the first node may cause at the second node using the transmit PSD associated with its own transmission based at least in part on the channel gain calculated at 1004. At 1008, the interference estimate may be compared to a predetermined threshold to determine whether the first node should transmit or refrain from transmitting. If the estimate is greater than the predetermined threshold, then the first node may refrain from transmitting (which may include any of transmitting data or transmitting a request) at 1012. If the estimate is less than the predetermined threshold, then the first node may transmit at 1010 because it does not substantially interfere with the second node. It should be appreciated that an RxRUM transmitted by the second node may be heard by multiple receiving nodes within a given proximity of the second node, each of which may perform method 1000 to evaluate whether it should transmit.

According to another example, the second node may transmit at, for example, 200 milliwatts, and the first node may transmit at 2 watts. In this case, the second node may have a transmission radius r, and the first node may have a transmission radius 10 r. Thus, the first node may be placed 10 times further away from the second node than the second node normally transmits or receives, but may still interfere with the second node due to its higher transmit power. In this case, the second node may boost its transmit PSD during RxRUM transmission to ensure that the first node receives the RxRUM. For example, the second node may transmit the RxRUM with a maximum allowed PSD that may be predetermined for a given network. The first node may then perform method 1000 and determine whether to transmit as described above.

Fig. 11 illustrates a methodology 1100 for responding to interference control packets in a planned and/or ad hoc wireless communication environment, in accordance with various aspects. At 1102, an RxRUM from a first node may be received at a second node. At 1104, a metric value may be generated based at least in part on a predetermined value associated with the RUM. For example, when a RUM is received at 1102, a receiving node (e.g., a second node) may know or may determine a RUM _ Rx _ PSD, a RUM _ Tx _ PSD (a known constant for the system), and a Data _ Tx _ PSD (a PSD at which the RUM receiving node wishes to transmit Data) by estimating the RUM received power. The RUM _ Tx _ PSD and RUM _ Rx _ PSD are also quantized in dBM/Hz, where the former is constant for all nodes and the latter depends on the channel gain. Similarly, the Data _ Tx _ PSD is measured in dBM/Hz and may depend on the power level associated with the node. The metric generated at 1104 may be expressed as:

metric = Data _ Tx _ PSD + (RUM _ Rx _ PSD-RUM _ Tx _ PSD)

Which represents an estimate of the possible interference caused by the RUM-transmitting node (e.g., for txrums) or the RUM-receiving node (e.g., for rxrums) at other nodes.

At 1006, the metric value may be compared to a predetermined RUM Rejection Threshold (RRT) defined in dBM/Hz. If the metric is greater than or equal to the RRT, then the second node may respond to the RUM at 1108. If the metric is less than the RRT, then at 1110, the second node may refrain from responding to the node (e.g., because it does not substantially interfere with the first node). The response to the RUM at 1108 removes noise associated with an interference over thermal noise (IOT) ratio, where the IOT, measured in decibels, is greater than the thermal noise N, measured in dBM/Hz, over a predetermined value Ω₀(e.g., such that the metric ≧ Ω + N₀). To ensure that all significant potential interferers are silenced, RRT may be set to RRT = Ω + N₀. It should be noted that the task of determining whether the RRT threshold will be reached is undertaken by the RxRUM-receiving node only if the advertised weight on the RUM indicates that the RUM transmitter indicates a greater degree of disadvantage than the RUM receiver.

Fig. 12 is a diagram of a method 1200 for generating an RxRUM, in accordance with the above-described aspects. At 1202, a RUM may be generated at a first node, where the RUM includes information indicating that the first predetermined threshold has been met or exceeded. The first predetermined threshold may represent, for example, an Interference Over Thermal (IOT) level, a data rate, a carrier-to-interference ratio (C/I), a throughput level, a spectral efficiency level, a latency level, or any other suitable metric according to which services at the first node may be measured. At 1204, the RUM may be weighted to indicate a degree to which a second predetermined threshold has been exceeded. According to some aspects, the weight value may be a quantized value.

The second predetermined threshold may represent, for example, an interference over thermal noise (IOT) level, a data rate, a carrier-to-interference ratio (C/I), a throughput level, a spectral efficiency level, a latency level, or any other suitable metric according to which a level of service at the first node may be measured. Although the first and second predetermined thresholds may be substantially equal, this is not required. In addition, the first and second predetermined thresholds may be associated with different parameters (e.g., IOT and C/I, respectively; latency and data rate, respectively; or any other permutation of the parameters). At 1206, the weighted RUM may be sent to one or more other nodes.

Fig. 13 is an illustration of a methodology 1300 for responding to one or more received rxrums, in accordance with one or more aspects. At 1302, an RxRUM may be received at a first node from a second (or more) node. The RxRUM may include information related to a condition of the second node (e.g., a level of disadvantage, as described above), which may be used by the first node to determine the condition of the second node at 1304. At 1306, the condition of the second node may be compared to the condition of the first node. At 1308, the comparison may allow a determination to be made whether to transmit data.

For example, if the comparison indicates that the first node is better than the second node, the first node may refrain from sending data (e.g., backoff and allow the less favorable second node to communicate more efficiently). Additionally or alternatively, if the condition of the first node is better than the second node, the first node may determine the level of interference that the first node may cause at the second node as described above with respect to fig. 10. Such a determination may include, for example, utilizing a known constant power or known constant power spectral density at which the second node transmits the RxRUM, estimating a channel gain between the first node and the second node, selecting a transmit power level for a transmission from the first node to the second node, estimating a level of interference that the transmission at the selected power level will cause at the second node, and determining whether the estimated interference level exceeds a predetermined acceptable interference threshold level.

In the event that the comparison indicates that the condition of the first node is worse than the condition of the second node, the first node may choose to ignore the RUM. According to another aspect, where the first node and the second node have substantially the same conditions, a weight handling mechanism may be employed as described above with respect to FIG. 6. According to other aspects, information contained in the RUM may be used to generate a metric value that may be compared to a RUM Rejection Threshold (RRT) to determine whether to respond to the RUM as described with respect to fig. 11. According to other aspects, based on the determination to transmit data at 1308, the transmitting can include transmitting communication data on a first channel, transmitting a request to transmit message on the first channel, and/or transmitting a request to transmit message on a second channel requesting that data be transmitted on the first channel.

In another aspect, additional information may be included with the request to help the scheduler know the results of RxRUM processing at the node. For example, suppose a sends data to B and C sends data to D. Assume that both B and D send RxRUMs, but B uses a higher (or less favorable) weight than D. A will send a request to B (because it processed the received RxRUM and concluded that its receiver, i.e., B, is the least favorable) and include a "best" bit indicating that it won contention and should be scheduled quickly (because it may not continue to win in the future). Instead, C will process the RUM and conclude that it cannot request. However, it may let D know that even though it cannot currently be scheduled, it has data to send and D should insist on sending an RxRUM. For example, if D does not listen to any requests, it may erroneously conclude that none of its receivers has any data to send and may stop sending rxrums. To prevent this, C sends a "request" with an indication that it is "blocked" by other rxrums. This will serve to indicate to D that C is not currently scheduled but that RxRUM remains being sent in hopes that C will win contention at some point.

Fig. 14 illustrates an exemplary wireless communication system 1400. The wireless communication system 1400 depicts one base station and one terminal for sake of brevity. However, it is to be appreciated that the system can include more than one base station and/or more than one terminal, wherein other base stations and/or terminals can be substantially similar or different for the exemplary base station and/or terminal described below. In addition, it is to be appreciated that the base station and/or the terminal can employ the methodologies (fig. 2, 5-8, and 10-13) and/or systems (fig. 1, 3, 4, 9, and 15-18) described herein to facilitate communications therebetween. For example, a node (e.g., a base station and/or terminal) in system 1400 can store and execute instructions for performing any of the above-described methods (e.g., generating a RUM, responding to a RUM, determining that a node is unfavorable, selecting a number of subcarriers for RUM transmission, etc.), as well as data associated with performing these actions and any other suitable actions to implement the various protocols described herein.

Referring now to fig. 14, on the downlink at access point 1405, a Transmit (TX) data processor 1410 receives, formats, codes, interleaves, and modulates (or symbol maps) traffic data and provides modulation symbols ("data symbols"). A symbol modulator 1415 receives and processes the data symbols and pilot symbols and provides a stream of symbols. A symbol modulator 1420 multiplexes data and pilot symbols and provides them to a transmitter unit (TMTR) 1420. Each transmit symbol may be a data symbol, a pilot symbol, or a signal value of 0. The pilot symbols may be sent continuously in each symbol period. The pilot symbols may be Frequency Division Multiplexed (FDM), Orthogonal Frequency Division Multiplexed (OFDM), Time Division Multiplexed (TDM), Frequency Division Multiplexed (FDM), or Code Division Multiplexed (CDM).

TMTR1420 receives and converts the stream of symbols into one or more analog signals and further conditions (e.g., amplifies, filters, and frequency upconverts) the analog signals to generate a downlink signal suitable for transmission over the wireless channel. The downlink signal is then transmitted through an antenna 1425 to the terminals. At terminal 1430, an antenna 1435 receives the downlink signal and provides a received signal to a receiver unit (RCVR) 1440. Receiver unit 1440 conditions (e.g., filters, amplifies, and frequency downconverts) the received signal and digitizes the conditioned signal to obtain samples. A symbol demodulator 1445 demodulates and provides received pilot symbols to a processor 1450 for channel estimation. Symbol demodulator 1445 also receives a frequency response estimate for the downlink from processor 1450, performs data demodulation on the received data symbols to obtain data symbol estimates (which are estimates of the transmitted data symbols), and provides the data symbol estimates to an RX data processor 1455, which demodulates (i.e., symbol demaps), deinterleaves, and decodes the data symbols to recover the transmitted traffic data. The processing by symbol demodulator 1445 and RX data processor 1445 is complementary to the processing by symbol modulator 1415 and TX data processor 1410, respectively, at access point 1405.

On the uplink, a TX data processor 1460 processes traffic data and provides data symbols. A symbol modulator 1465 receives and multiplexes the data symbols with pilot symbols, performs modulation, and provides a stream of symbols. A transmitter unit 1470 then receives and processes the stream of symbols to generate an uplink signal, which may be transmitted by the antenna 1435 to the access point 1405.

At access point 1405, the uplink signal from terminal 1430 is received by the antenna 1425 and processed by a receiver unit 1475 to obtain samples. A symbol demodulator 1480 then processes the samples and provides received pilot symbols and data symbol estimates for the uplink. An RX data processor 1485 processes the data symbol estimates to recover the traffic data transmitted by terminal 1430. A processor 1490 performs channel estimation for each active terminal transmitting on the uplink. Multiple antennas may transmit pilot concurrently on the uplink on their respective assigned sets of pilot subbands, where the pilot subband sets may be interlaced.

Processors 1490 and 1450 direct (e.g., control, coordinate, manage, etc.) operation at access point 1405 and terminal 1430, respectively. Respective processors 1490 and 1450 can be associated with memory units (not shown) that store program codes and data. Processors 1490 and 1450 can also perform computations to derive frequency and impulse response estimates for the uplink and downlink, respectively.

For a multiple-access system (e.g., FDMA, OFDMA, CDMA, TDMA, etc.), multiple terminals may transmit concurrently on the uplink. For such a system, the pilot subbands may be shared among different terminals. The channel estimation techniques may be used in cases where the pilot subbands for each terminal span the entire operating band (possibly except for the band edges). Such a pilot subband structure may be desirable to achieve frequency diversity for each terminal. The techniques described herein may be implemented by various means. For example, these techniques may be implemented in hardware, software, or a combination thereof. For a hardware implementation, the processing units for channel estimation may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. With respect to software, implementation can be through means (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory unit and executed by the processors 1490 and 1450.

For a software implementation, the techniques described herein may be implemented with modules/means (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. In the case where the memory unit may be communicatively coupled to the processor via various means as is known in the art, the memory unit may be implemented within the processor or external to the processor.

Turning now to fig. 15-18 and the various modules described in connection therewith, it should be appreciated that the means for transmitting may comprise, for example, a transmitter, and/or may be implemented in a processor. Similarly, the means for receiving may comprise a receiver and/or may be implemented in a processor. Additionally, modules for comparing, determining, calculating, and/or performing other analytical actions may include a processor executing instructions for performing various and corresponding actions.

Fig. 15 is an illustration of an apparatus 1500 that facilitates wireless data communication in accordance with various aspects. Apparatus 1500 is represented as a series of interrelated functional blocks, which can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). For example, apparatus 1500 may provide modules for performing acts such as those described above with respect to various figures. Apparatus 1500 includes a module 1502 for determining a number of channels needed for transmission. The determination may be performed as a function of a weight associated with a node in which the apparatus is employed, a weight associated with one or more other nodes, a number of channels available for transmission, and/or the like. In addition, each weight may be a function of the number of flows supported by the node associated with the weight. Additionally or alternatively, a given weight may be a function of the interference experienced by the node.

Apparatus 1500 additionally comprises a selecting module 1504 that selects a channel for which the node can send a request. The selection module 1504 additionally may evaluate received Resource Utilization Messages (RUMs) to determine which channels are available and which are not. For example, each RUM may include information associated with unavailable channels, and the selection module 1504 may determine that a given channel that is not indicated by the RUM is available. The sending module 1506 may send a request for at least one channel selected by the selecting module 1504. It should be appreciated that apparatus 1500 can be employed in an access point, an access terminal, etc., and can include any suitable functionality to implement the various methods described herein.

Fig. 16 is an illustration of an apparatus 1600 that facilitates wireless communication using a Resource Utilization Message (RUM), in accordance with one or more aspects. Apparatus 1600 is represented as a series of interrelated functional blocks, which can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). For example, apparatus 1600 may provide modules for performing acts such as those described above with respect to various figures. The apparatus 1600 includes a determination module 1602 that determines a level of disadvantage for a node, and a RUM generation module 1604 that generates a RUM if the determination module 1602 determines that the level of service received at the node is at or below a predetermined threshold level. A selection module 1606 may select one or more resources for which to send RUMs, and a RUM generation module 1604 may then indicate these channels in the RUMs. A transmitting module 1608 may then transmit the RUM.

Resource selection module 1606 may adjust the number of selected resources for which subsequent RUMs are subsequently sent based on determination module 1602 determining that the level of received service has improved in response to a previous RUM. For example, in this case, selection module 1606 may decrease the number of resources indicated in the subsequent RUM in response to an improved level of received service at the node, and may increase the number of selected resources in response to a decreased or static level of received service. According to other aspects, determining module 1602 may determine the level of service received at the node based on one or more of interference over thermal noise ratio, latency, data rate achieved at the node, spectral efficiency, throughput, carrier-to-interference ratio, or any other suitable parameter of service received at the node. It should be appreciated that apparatus 1600 may be employed in an access point, access terminal, etc., and may include any suitable functionality to implement the various methods described herein.

Fig. 17 is an illustration of an apparatus 1700 that facilitates generating a Resource Utilization Message (RUM) and weighting the RUM to indicate a level of disadvantage, in accordance with various aspects. Apparatus 1700 is represented as a series of interrelated functional blocks, which can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). For example, apparatus 1700 may provide modules for performing acts such as those described above with respect to various figures. The apparatus 1700 includes a RUM generation module 1702 that may generate a RUM indicating that a first predetermined threshold has been exceeded. The first predetermined threshold may be associated with and/or representative of a threshold level of interference over thermal noise ratio (IOT), a data rate, a carrier-to-interference ratio (C/I), a throughput level, a spectral efficiency level, a latency level, etc.

Apparatus 1700 may additionally comprise a RUM weighting module 1704 that may weight the RUM with a value indicative of a degree to which a second predetermined threshold has been exceeded, which may comprise determining a ratio of an actual value of a parameter (e.g., interference over thermal noise ratio (IOT), data rate, carrier-to-interference ratio (C/I), throughput level, spectral efficiency level, latency level, etc.) achieved at the node to a target or desired value. In addition, the weighting value may be a quantized value. It should be appreciated that apparatus 1700 can be employed in an access point, access terminal, etc., and can include any suitable functionality to implement the various methods described herein.

Fig. 18 is an illustration of an apparatus 1800 that facilitates comparing relative conditions at nodes in a wireless communication environment to determine which nodes are most adverse, in accordance with one or more aspects. Apparatus 1800 is represented as a series of interrelated functional blocks, which can represent functions implemented by a processor, software, or combination thereof (e.g., firmware). For example, apparatus 1800 may provide modules for performing acts such as those described above with respect to various figures. Apparatus 1800 may be employed in a first node and comprise a RUM reception module 1802 that receives a RUM from at least one second node. Apparatus 1800 may additionally comprise a determination module 1804 that determines a condition of the second node based on information associated with the RUM received from the second node, and a comparison module 1806 that compares the condition of the first node to the determined condition of the second node. The determining module 1804 may then further determine whether to transmit data on the first channel based on the comparison.

According to various other aspects, the determination of whether to send may be based on whether the condition of the first node is better than, substantially equal to, or worse than the condition of the second node. Additionally, the determining module 1804 may transmit a data signal on a first channel, a request to send message on a first channel, or a request to send message on a second channel. In the latter case, the request-to-send message sent on the second channel may include a request to send data on the first channel. It is to be appreciated that apparatus 1800 can be employed in an access point, access terminal, etc., and can include any suitable functionality to implement the various methods described herein.

What has been described above includes examples of one or more aspects. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned aspects, but one of ordinary skill in the art may recognize that many further combinations and permutations of various aspects are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in a claim.

Claims (39)

1. A method of achieving fairness among contending nodes based on a level of disadvantage associated with a first node, comprising:

generating a resource utilization message, RUM, at the first node, wherein the RUM specifies one or more resources that the first node is requesting to reduce interference from at least one second node and specifies a weight of the first node indicating a degree of disadvantage of the first node;

selecting a number of channels for which to send the RUM based on the degree of disadvantage; and

transmitting the RUM from the first node to the at least one second node.

2. The method of claim 1, wherein the one or more resources comprise at least one channel.

3. The method of claim 1, wherein the one or more resources comprise one or more subcarriers.

4. The method of claim 1, wherein the one or more resources comprise one or more time slots.

5. The method of claim 1, wherein the degree of disadvantage is a function of at least one of the group consisting of: a throughput of the first node, a latency experienced by the first node, a data rate of the first node, and a spectral efficiency of the first node.

6. The method of claim 1, wherein the RUM further specifies a target interference level at the first node.

7. The method of claim 1, wherein the RUM further specifies a target reduction in interference level related to a current interference level experienced by the first node.

8. The method of claim 1, wherein the second node is an access terminal.

9. The method of claim 1, wherein the second node is an access point.

10. The method of claim 9, wherein the RUM further specifies a weight of a third node.

11. The method of claim 10, wherein the weight is associated with a degree of disadvantage of the third node.

12. The method of claim 11, wherein the degree of disadvantage is a function of at least one of the group consisting of: a throughput of the third node, a latency experienced by the third node, a data rate of the third node, and a spectral efficiency of the third node.

13. The method of claim 9, wherein the RUM further specifies a target interference level at the third node.

14. The method of claim 9, wherein the RUM further specifies a target reduction in interference level related to a current interference level experienced at the third node.

15. The method of claim 1, wherein the weight is based on an actual performance level achieved at the first node and a target performance level for the first node.

16. The method of claim 1, wherein the weight is based on an actual throughput achieved at the first node and a target throughput for the first node.

17. The method of claim 1, wherein the weight is based on a ratio of a target performance level of the first node and an actual performance level achieved at the first node.

18. The method of claim 1, wherein the weight is based on a ratio of a target throughput at the first node and an actual throughput achieved at the first node.

19. An apparatus for achieving fairness among contending nodes based on a level of disadvantage associated with a first node, comprising:

a processor configured to generate a resource utilization message, RUM, at the first node, wherein the RUM specifies one or more resources that the apparatus is requesting to reduce interference from at least one node and specifies a weight of the apparatus indicating a degree of disadvantage of the apparatus;

selecting a number of channels for which to send the RUM based on the degree of disadvantage; and

a transmitter configured to transmit the RUM from the first node to the at least one node.

20. The apparatus of claim 19, wherein the one or more resources comprise at least one channel.

21. The apparatus of claim 19, wherein the one or more resources comprise one or more subcarriers.

22. The apparatus of claim 19, wherein the one or more resources comprise one or more time slots.

23. The apparatus of claim 19, wherein the degree of disadvantage is a function of at least one of the group consisting of: a throughput of the apparatus, a latency experienced by the apparatus, a data rate of the apparatus, and a spectral efficiency of the apparatus.

24. The apparatus of claim 19, wherein the RUM further specifies a target interference level at the apparatus.

25. The apparatus of claim 19, wherein the RUM further specifies a target reduction in interference level related to a current interference level experienced by the apparatus.

26. The apparatus of claim 19, wherein the node is an access terminal.

27. The apparatus of claim 19, wherein the node is an access point.

28. The apparatus of claim 27, wherein the RUM further specifies a weight of a second node.

29. The apparatus of claim 28, wherein the weight is associated with a degree of disadvantage of the second node.

30. The apparatus of claim 29, wherein the degree of disadvantage is a function of at least one of the group consisting of: a throughput of the second node, a latency experienced by the second node, a data rate of the second node, and a spectral efficiency of the second node.

31. The apparatus of claim 28, wherein the RUM further specifies a target interference level at the second node.

32. The apparatus of claim 28, wherein the RUM further specifies a target reduction in interference level related to a current interference level experienced at the second node.

33. The apparatus of claim 19, wherein the weight is based on an actual performance level achieved at the first node and a target performance level for the first node.

34. The apparatus of claim 19, wherein the weight is based on an actual throughput achieved at the first node and a target throughput for the first node.

35. The apparatus of claim 19, wherein the weight is based on a ratio of a target performance level of the first node and an actual performance level achieved at the first node.

36. The apparatus of claim 19, wherein the weight is based on a ratio of a target throughput at the first node and an actual throughput achieved at the first node.

37. An apparatus for achieving fairness among contending nodes based on a level of disadvantage associated with a first node, comprising:

means for generating, at the first node, a resource utilization message, RUM, wherein the RUM specifies one or more resources that the first node is requesting to reduce interference from at least one second node and specifies a weight of the first node indicating a level of disadvantage of the first node;

means for selecting a number of channels for which to send the RUM based on the degree of disadvantage; and

means for transmitting the RUM from the first node to the at least one second node.

38. An access point for achieving fairness among contending nodes based on a level of disadvantage associated with a first node, comprising:

a processor configured to generate a resource utilization message, RUM, at the first node, wherein the RUM specifies one or more resources that the access point is requesting to reduce interference from at least one node and specifies a weight for the access point that indicates a level of disadvantage for the access point and selects a number of channels for which to transmit the RUM based on the level of disadvantage;

an antenna; and

a transmitter configured to transmit the RUM from the first node to the at least one node.

39. An access terminal that achieves fairness among contending nodes based on a level of disadvantage associated with a first node, comprising:

a processor configured to generate a resource utilization message, RUM, at the first node, wherein the RUM specifies one or more resources that the access terminal is requesting to reduce interference from at least one node and specifies a weight for the access terminal indicating a level of disadvantage for the access terminal and selects a number of channels for which to transmit the RUM based on the level of disadvantage;

an antenna; and

a transmitter configured to transmit the RUM from the first node to the at least one node.