Mitigating interference in a communication network

Aspects relate to mitigating interference in a communication network that does not employ a centralized scheduler. A transmission sent on a subset of resources is evaluated to determine a number of communication pairs that have selected that subset of resources on which to transmit. If there are a large number of communication pairs transmitting on that subset, the transmission is ignored by a receiving device. The number of degrees of freedom that contain energy on the subset is evaluated to determine if an expected number of degrees of freedom that should have energy is met or exceeded. If the expected threshold number is met or exceed, the transmission is decoded by the receiving device, else the transmission is not decoded.

BACKGROUND

The following description relates generally to wireless communications and more particularly to mitigating interference in a communication network that does not utilize a centralized scheduler.

Wireless communication systems are widely deployed to provide various types of communication. For example, voice, data, video, and so forth can be provided through wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources. For instance, a system may use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.

Wireless communication networks are commonly utilized to communicate information regardless of where a user is located (inside or outside a structure) and whether a user is stationary or moving (e.g., in a vehicle, walking). Generally, wireless communication networks are established through a mobile device communicating with a base station or access point. The access point covers a geographic range or cell and, as the mobile device is operated, the mobile device can be moved in and out of these geographic cells.

A network can also be constructed utilizing solely peer-to-peer devices without utilizing access points or the network can include both access points (infrastructure mode) and peer-to-peer devices. These types of networks are sometimes referred to as ad hoc networks. Ad hoc networks can be self-configuring whereby when a mobile device (or access point) receives communication from another mobile device, the other mobile device is added to the network. As mobile devices leave the area, they are dynamically removed from the network. Thus, the topography of the network can be constantly changing.

At times, some signals might experience interference, which might be strong interference, from other signals. This interference can be caused by the random deployment that exists in ad hoc networks. For example, in a peer-to-peer ad hoc network, there is no central authority (e.g., base station) that transmits broadcast signals. Thus, synchronization is performed in an informal manner by the devices within the peer-to-peer network. Therefore, a problem that can result in peer-to-peer ad hoc networks is interference since the number of interfering transmitters using the same wireless resource and their interference levels are not known.

SUMMARY

In accordance with one or more aspects and corresponding disclosure thereof, various aspects are described in connection with using a certain wireless resource to convey a certain number of bits with the additional constrain that the number of interferers using the same wireless resource and their interference levels are not known.

According to an aspect is a method performed by a receiver device for mitigating interference in a communication network. Method includes selecting a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier and monitoring the selected subset to receive a signal from a transmitter device. The identifier is determined by at least one of transmitter device or receiver device. A degree of freedom corresponds to a communication resource unit of the communication network.

Another aspect relates to a wireless communications apparatus that includes a memory and a processor. The memory retains instructions related to choosing a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier and monitoring the selected subset to receive a signal. A degree of freedom corresponds to a communication resource unit of a communication network. The identifier is determined by at least one of a transmitter device, or a receiver device, or combinations thereof. The processor is coupled to the memory and is configured to execute the instructions retained in the memory.

A further aspect relates to a wireless communications apparatus that mitigates interference in a communication network. The communication apparatus includes means for choosing a subset from a plurality of disjoint subsets of degrees of freedom as a function of a chosen identifier. A degree of freedom corresponds to a communication resource unit of the communication network and the communication resource unit is separated into the plurality of disjoint subsets of degrees of freedom. The communication apparatus also includes means for reviewing the selected subset in order to receive a signal from a peer node.

Still another aspect relates to a computer program product that comprises a computer-readable medium. Included in the computer-readable medium is a first set of codes for causing a computer to select a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier. The identifier is determined by at least one of a transmitter device, a receiver device, or both the transmitter device and the receiver device. A degree of freedom corresponds to a communication resource unit of the communication network. Also included in computer-readable medium is a second set of codes for causing the computer to evaluate the selected subset to receive a signal.

Yet another aspect relates to at least one processor configured to mitigate interference in a communication network that does not have a centralized scheduler. Processor includes a first module for selecting a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier. The selected subset comprises a plurality of resource blocks. Processor also includes a second module for selecting at least one degree of freedom within each of the plurality of resource blocks and a third module for monitoring the selected subset to receive a signal. Also included in processor is a fourth module for estimating a number of interfering transmitters as a function of energy of the received signal in the degrees of freedom of each selected subset. Further, processor includes a fifth module for selectively decoding a message from the received signal in the selected degrees of freedom based on a comparison of the estimated number of interfering transmitters with an interference threshold.

A further aspect relates to a method for operating a transmitter device for mitigating interference in a communication network. Method includes selecting a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier and transmitting a signal to the receiver device using the selected subset. The identifier is determined by at least one of the transmitter device, a receiver device, or combinations thereof. A degree of freedom corresponds to a communication resource unit of the communication network.

Another aspect relates to a wireless communications apparatus that includes a memory and a processor. The memory retains instructions related to choosing a subset from a plurality of disjoint subsets of degrees of freedom as a function of a chosen identifier and transmitting a signal to a receiver device using the selected subset. A degree of freedom corresponds to a communication resource unit of a communication network. The processor is coupled to the memory and is configured to execute the instructions retained in the memory.

Yet another aspect relates to a wireless communications apparatus that mitigates interference in a communication network. The communication apparatus includes means for choosing a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier. Communication apparatus also includes means for conveying a signal using the selected subset. A degree of freedom corresponds to a communication resource unit of the communication network.

Still another aspect relates to a computer program product comprising a computer-readable medium. Included in computer-readable medium is a first set of codes for causing a computer to select a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier. The identifier is determined by one or more of a transmitter device, a receiver device, or combinations thereof. A degree of freedom corresponds to a communication resource unit of a communication network. The communication resource is divided into the plurality of disjoint subsets of degrees of freedom and the plurality of disjoint subsets are fixed. Also included in computer-readable medium is a second set of codes for causing the computer to transmit a signal to the receiver device using the selected subset.

A further aspect relates to at least one processor configured to mitigate interference in a communication network that does not have a centralized scheduler. Processor includes a first module for selecting a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier. The identifier is determined by at least one of the transmitter device or a receiver device. A degree of freedom corresponds to a communication resource unit of the communication network. Processor also includes a second module for transmitting a signal to the receiver device using the selected subset. The transmitted signal is a paging signal and the identifier is a paging identifier of the receiver device.

DETAILED DESCRIPTION

Furthermore, various aspects are described herein in connection with a mobile device. A mobile device can also be called, and may contain some or all of the functionality of a system, subscriber unit, subscriber station, mobile station, mobile, wireless terminal, node, device, remote station, remote terminal, access terminal, user terminal, terminal, wireless communication device, wireless communication apparatus, user agent, user device, or user equipment (UE), and the like. A mobile device can be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a smart phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a laptop, a handheld communication device, a handheld computing device, a satellite radio, a wireless modem card and/or another processing device for communicating over a wireless system. Moreover, various aspects are described herein in connection with a base station. A base station may be utilized for communicating with wireless terminal(s) and can also be called, and may contain some or all of the functionality of, an access point, node, Node B, e-NodeB, e-NB, or some other network entity.

FIG. 1illustrates a schematic representation of a set of resources100available for communication within a communication network. Horizontal axis102represents time and vertical axis104represents frequency. A vertical column, of which a few are labeled at106, represents resources (e.g., tones) in a given symbol period. Each small box, such as box108, represents a tone-symbol, which is a single tone over a single transmission symbol period. A degree of freedom in an OFDM symbol is a tone-symbol108, representing a basic unit of the wireless resource. In accordance with some aspects, set of resources100can have N degrees of freedom, where N is an integer.

For purposes of explanation, assume a wireless resource with N degrees of freedom. This resource is being shared by an unknown number of communication pairs. Each communication pair wants to communicate a number of bits. Further, there is no central coordinator to allocate resources among these communication pairs. A simple solution would involve dividing the N degrees of freedom into distinct subsets and each communication pair randomly chooses one of the subsets and transmits on that entire subset. This is similar to a random access scheme and can have potential failure in the case of a collision (e.g., two or more communication pairs chose the same subset on which to communicate). The disclosed aspects overcome the situation of interference and the situation where a dominant interferer (e.g., interfering transmitter) causes a communication failure (e.g., interference).

The set of N degrees of freedom can be divided into M disjoint subsets, for example, with K=N/M, where K is the number of degrees of freedom in each subset. In an aspect, the partition of the total N degrees of freedom into the M disjoint subsets is fixed and divided in a pre-determined manner.

For purposes of explanation, the following will discuss a wireless resource comprising 28 tones, along the vertical axis, and 56 symbols, along the horizontal axis. The 28 tones can be divided into 14 tone subsets, each tone subset consisting of two adjacent tones, as illustrated along the left side of vertical axis104as 1, 2, . . . 14. Then, M=14, and each disjoint subset of degrees of freedom contains a plurality of resource blocks. For example, there is horizontal partitioning where the 56 symbols are divided into 28 different symbol subsets, each symbol subset contains two adjacent symbols, as illustrated along the top horizontal axis102as 1, 2, 3, 4, . . . 28. In this example, a resource block includes two adjacent tones over two adjacent symbols. In an aspect, the partition of a subset into a plurality of resource blocks is fixed and performed in a pre-determined manner.

Further aspects will now be described with reference also toFIG. 2, which illustrates a system200for transmitting information in a manner that mitigates interference, according to an aspect. A communication apparatus202can be included in system200, which can be a communication network that includes a multitude of communication apparatuses that communicate with each other as communication pairs (e.g., a first communication apparatus is paired with a second communication apparatus). In accordance with some aspects, communication network does not include a centralized scheduler.

Communication apparatus202is shown to be transmitting data through a channel204. Although depicted as transmitting data, communication apparatus202can also receive data through the channel204(e.g., communication apparatus202can transmit and receive data at substantially the same time, communication apparatus202can transmit and receive data at different times, or combinations thereof).

Communication apparatus202, sometimes referred to herein as transmitting device or Device A, can be paired with another apparatus206, sometimes referred to herein as receiving device or Device B. Included in communication apparatus202is a subset selector208that is configured to select one of the M disjoint subsets on which to transmit (and transmits on that entire subset). Thus, subset selector208can choose one from the M disjoint subsets (1through14) along the vertical axis104(ofFIG. 1). The subset selection can be based on an identifier determined by transmitting device202, receiving device206, or both transmitting device202and receiving device206. For example if transmitting device202is to send a paging signal to receiving device206, the identifier can be a paging identifier of receiving device206. Thus, even if receiving device206does not know the identity of transmitting device202, receiving device206can still monitor the correct subset for a possible paging signal (e.g., receiving device206knows which subset to monitor based on receiving device's identifier).

Each M disjoint subset includes a multitude of resource blocks. Each resource block includes a plurality of degrees of freedom. For example, inFIG. 1, each resource block includes four degrees of freedom. The resource block illustrated on the right bottom corner ofFIG. 1includes four degrees of freedom labeled110,112,114, and116. Each degree of freedom corresponds to a communication resource unit of the communication network.

Also included in communication apparatus202is a resource selector210that is configured to select at least one of the K degrees of freedom in each resource block within the chosen M subset. For example, resource selector210can select various degrees of freedom, as illustrated by the black boxes inFIG. 1(e.g., box118), wherein there is one black box (chosen degree of freedom) in each resource block along the chosen subset. In accordance with some aspects, resource selector210can choose the degrees of freedom based on an identifier.

Also included in apparatus202is a transmitter212that is configured to transmit information on the selected resources. In accordance with some aspects, transmitter212can use some of the selected resources to transmit a pilot and use the remaining selected resources to transmit phase and/or amplitude modulated signals to convey certain message information (e.g., a paging message).

When transmitting device202transmits a signal to intended receiving device206, the signal is transmitted over the chosen degrees of freedom in the resource blocks in the chosen subset (e.g., the black boxes inFIG. 1). When another transmitting device (not shown) is transmitting, that device might select the same subset and further select one degree of freedom in each resource block. In a given resource block the two (or more) transmitting devices might select the same or different degrees of freedom. When at least two transmitting devices selected the same degree of freedom, the signals collide.

A memory214can be operatively coupled to communication apparatus202. Memory214can be external to communication apparatus202or can reside within communication apparatus202. Memory214can store information related to selecting one of M disjoint subsets, choosing a degree of freedom within each block of the selected subset, and transmit a signal on the chosen degrees of freedom. Further, memory214can store other suitable information related to signals transmitted and received in a communication network. A processor216can be operatively connected to communication apparatus202(and/or memory214) to facilitate analysis of transmitting information in a communication network. Processor216can be a processor dedicated to analyzing and/or generating information received by communication apparatus202, a processor that controls one or more components of system200, and/or a processor that both analyzes and generates information transmitted by communication apparatus200and controls one or more components of system200.

As discussed above, there can be multiple communication pairs in a communication network. For example,FIG. 3illustrates a schematic representation300of signaling and interference within a communication network. Illustrated are four devices, Device A302, Device B304, Device C306, and Device D308. Device A302is attempting to send a signal310to Device B304. The signal can be a paging signal that indicates Device A302intends to establish a connection with Device B304. At substantially the same time, Device C is attempting to send a signal312to Device D308. These two signals310and312might interfere with each other such that Device B304receives signal310as well as interfering signal314from Device C306. Thus, Device C306is an interfering transmitter as far as Device B304is concerned. In a similar manner, Device D308might receive signal312and an interfering signal316from Device A302. Thus, at times, Device A302can be an interfering transmitter as far as Device D308is concerned.

However, in some communication networks, such as the illustrated network300, there is no centralized authority to schedule the resources between Device A302and Device C306. Thus, there is no controller to mitigate cross interference, illustrated at314and316. Further, without a centralized authority, there is no entity that authorizes the transmissions of Devices A302and C306. For purposes of this detailed description, the behavior of Devices A302and B304is similar to the behavior of Devices C306and D308. Further, it should be understood that a communication network can have any number of devices and only four devices are illustrated for purposes of simplicity.

As discussed above, there can be multiple communication pairs. A transmitting device (e.g., apparatus202ofFIG. 2, Node A302, and/or Node C306) selects one of the M disjoint subsets on which to transmit and within that selected subset selects at least one degree of freedom in each resource block, based on an identifier of the receiving device (e.g., apparatus206ofFIG. 2, Node B304, and/or Node D308). The receiving devices (e.g., Device B304and Device D308) know the M subset on which they should receive information, based on their respective IDs, for example. If the resources for Devices B304and D308happen to map to different subsets, the signals will not interfere. However, in the situation where Devices A302and C306choose the same subset, interface can occur. For example, consider the case where Devices A302and C306happen to choose the same subset and the same degree of freedom in at least one resource block within that subset, illustrated by block118(ofFIG. 1). In this situation, a collision will occur since information for both devices has been sent on the same resource. It should be noted that the selection of resources is determined time interval by time interval, thus, on a subsequent time interval, there might not be a collision (e.g., devices A302and C306choose a different resource in a subsequent signaling time interval).

FIG. 4illustrates a system400that receives information in a manner that mitigates interference, according to an aspect. Included in system400is a communication apparatus402that is shown to be receiving data through a channel404. Although depicted as receiving data, communication apparatus402can also transmit data through the channel404(e.g., communication apparatus402can transmit and receive data at substantially the same time, communication apparatus402can transmit and receive data at different times, or combinations thereof).

Communication apparatus402, also referred to as receiving device, is aware of the degrees of freedom on which information is expected to be received (e.g., transmitting device selected a subset based on an identifier determined by transmitting device406, receiving device402, or combinations thereof, as discussed with reference to previous figures). A simple strategy to receive and decode the information would be for communication apparatus402to review the expected degrees of freedom and attempt to decode the information on those degrees of freedom. However, this simple strategy does not take into account potential collisions and further does not provide for mitigation of interference.

Thus, communication apparatus402should determine if there is interference (e.g., two or more transmitting devices have chosen the same subset and the same degree of freedom in at least one resource block). If it is determined there is a collision, that tone is considered unreliable and apparatus402will not attempt to decode that tone.

Apparatus402includes a subset determiner408that is configured to select a subset from a plurality of disjoint subsets of degrees of freedom. The subset can be selected as a function of an identifier, which can be determined by receiving device402, transmitting device406, or both receiving device402and transmitting device406. The degrees of freedom correspond to a communication resource unit of the communication network. Also included is an observation module410that is configured to monitor the selected subset in order to receive a signal from transmitting device406. If there is energy on the selected subset, the energy indicates that there might be a signal intended for receiving device402. In accordance with some aspects, the received signal is an OFDM signal and a degree of freedom is a tone in an OFDM symbol.

The subset selected by subset determiner408can include a multitude of resource blocks. Each resource block can include a number of degrees of freedom. Thus, in accordance with some aspects, apparatus402includes a degree of freedom selector412that chooses at least one degree of freedom within each of the plurality of resource blocks as a function of the identifier. An energy evaluator414can be configured to estimate the number of interfering transmitters as a function of the energy of the received signal in the degrees of freedom of the selected subset. An interference evaluator416can be configured to determine if the estimated number of interfering transmitters exceeds a certain interference threshold. If the interference threshold is exceeded, a decoder418can discard the received signal. If interference evaluator416determines that the number of interfering transmitters does not exceed the interference threshold, decoder418can decode the message from the received signal in the selected degrees of freedom.

In accordance with some aspects, energy evaluator414can be configured to review the number of degrees of freedom in a particular resource block in a chosen subset and estimate the number of degrees of freedom with energy in that resource block. This provides an indication of the total number of transmitters using that resource, including the desired transmitter as well as interfering transmitters. For example, if a block has two degrees of freedom with energy, it indicates that at least two transmitters are utilizing the same subset. In accordance with some aspects, the number of degrees of freedom with energy is estimated when the energy of the received signal exceeds a threshold level of energy.

For example, in the example ofFIG. 1, if only apparatus402is receiving a message (e.g., no other devices are using that resource), there should be only 28 tones with energy in the entire subset. However, if another transmitting device is transmitting on the same subset, there will be more than 28 tones with energy. Based on the total number of tones that have energy, apparatus402can determine the potential number of interfering transmitters that have selected the same subset.

The determination of the number of interferers can be performed on a block by block analysis. The first resource block, containing four degrees of freedom can be reviewed and if two tones have energy, it indicates that there are two or more transmitters. If a subsequent block has only one tone with energy, it indicates that there is a collision (e.g., multiple transmitters are sending a signal the same tone). If there is a collision, the information in that block is considered not reliable and can be ignored. If it is determined that the number of communication pairs is more than a threshold number of transmitters (e.g., three transmitters), decoding might not be attempted for the entire subset.

In accordance with some aspects, the energy of the received signal might exceed an energy threshold. In this case, energy evaluator414can estimate a first number of degrees of freedom among the set of selected degrees of freedom. For example, if a signal were indeed sent to apparatus402, then apparatus402would expect signal energy in the selected degrees of freedom in the resource blocks of the subset (e.g., the black boxes inFIG. 1). Based on this estimate, interference evaluator416can determine if the first number is below a first energy threshold, indicating that not a sufficient number of degrees of freedom are estimated to have energy. When the estimate is below the first energy threshold, apparatus402may conclude there is no intended signal and, therefore, decoder418discards the received signal.

Further, energy evaluator414can estimate a second number of degrees of freedom in a resource block in which the energy of the received signal exceeds a second energy threshold. Interference evaluator416can determine whether the signal received in the selected degree of freedom is reliable. For example, apparatus402estimates that two transmitters have selected the same subset to send the signals (as discussed above). Then, if apparatus402estimates only one degree of freedom in a resource block has energy (e.g., the signal energy exceeds an energy threshold), then apparatus402may conclude that the two transmitters have selected the same degree of freedom to send the signals. As a result, the received signal on the selected degree of freedom is considered not reliable. However, if apparatus402estimates two degrees of freedom in a resource block have energy, then apparatus402may conclude that the two transmitters have selected different degrees of freedom to send the signals. As a result, the received signal on the selected degree of freedom is considered reliable. The estimated second number is to estimate whether the received signal on the selected degree of freedom in a resource block is reliable or is not reliable. If not reliable, decoder418can discard the received signal in the selected degree of freedom. If the signal is reliable, it is decoded by decoder418.

Interference evaluator416can determine the reliability of the signal as a function of the estimated second number and the estimated number of interfering transmitters. In accordance with some aspects, if the estimated second number is greater than the estimated number of interfering transmitters, the signal received in the selected degree of freedom is determined to be reliable.

Thus, each transmitting device406(or element202ofFIG. 2), based on an identifier known to its intended receiver402(or element206ofFIG. 2) chooses one out the M disjoint subsets on which to transmit. Further, among K degrees of freedom in that subset, transmitting device406selects a certain subset (e.g., of size K/4) on which to transmit. In the example ofFIG. 1, the K degrees of freedom is divided into a number of resource blocks, each having four degrees of freedom. Transmitting device406selects one degree of freedom in each resource block to be the selected degrees of freedom. The selected degrees of freedom is size K/4. Transmitting device406transmits the information on this subset of resources.

Receiving device402(or element206ofFIG. 2), based on the identifier transmitter would have used to communicate, wants to determine if any information was transmitted to receiving device. Further, receiving device402would like to decode that information. Receiving device402determines if there was a transmission to it by reviewing the number of degrees of freedom in the particular subset (of size K) and determines the number of degrees of freedom with energy. If the number is significant (e.g., more than three), receiving device402does not attempt decoding. In the example ofFIG. 1, if there is one transmitting device406, then the number of degrees of freedom with energy is expected to be 28. If it is estimated that the number of degrees of freedom with energy in the subset exceeds a certain number (e.g., 36), then receiving device402may conclude that there are two transmitting devices. If the number of degrees of freedom with energy in the subset exceeds another number (e.g., 42), then receiving device406may conclude there are three transmitting devices. Receiving device402evaluates the energy in the selected K/4 degrees of freedom that it was supposed to receive on (in the particular subset that it is expecting to receive in). Receiving device402declares that a transmission was received. The threshold above can in turn depend on the estimated number of communication pairs using that resource. If there was a transmission, receiving device402decodes the transmission.

In accordance with some aspects, receiving device402will in general use the K/4 degrees of freedom that it is expected to receive on for decoding. However, receiving device420would also like to mitigate the interference in case there is more than one communication pair using the same subset. In this situation, there can be further structure on how the subset of size K/4 is picked by receiving device402.

Continuing the above example, each transmitting device406, based on an identifier that is known to its intended receiving device402, chooses one out of the M disjoint subsets on which to transmit. Each subset is divided into K/4 further subsets of size four each. Transmitting device406chooses one among these four degrees of freedom on which to transmit. Thus, transmitting device406selects a total of K/4 degrees of freedom on which to transmit and transmits the information on this subset of resources.

Receiving device402, based on the identifier that transmitting device406would have used to communicate, wants to determine if any information was transmitted to it and, further, would like to decode that information. Therefore, receiving device402determines if there was a transmission to it by reviewing the number of degrees of freedom in that particular subset (of size K) and ascertains the number of degrees of freedom with energy. This is given as an indication of the total number of communication pairs using that resource. Receiving device402will not attempt decoding if this number is signification (e.g., more than three communication pairs).

Next, receiving device402looks at the energy K/4 degrees of freedom that it was supposed to receive on (in the particular subset that it is expecting to receive in). Receiving device402confirms that the number of degrees of freedom with energy is above a certain threshold (e.g., 0.9*K/4). If confirmed, receiving device402declares that a transmission was received.

The threshold can in turn depend on the estimated number of communication pairs using that resource. If there was a transmission, receiving device402will decode the transmission. Based on the number of communication pairs estimated to be using that resource (as discussed above), receiving device402makes a decision for each of the K/4 degrees of freedom whether it has been interfered with. For example, the estimate indicated one more communication pair using the same resource. Then, if among the smaller subset of size four, two degrees of freedom carry energy, there has not been a collision (e.g., each communication pair selected a different degree of freedom). However, if only one of the four degrees of freedom has energy, there has been a collision (e.g., both communication pairs selected the same degree of freedom). In the case of a collision, receiving device402may wish to discard that degree of freedom, depending on the power level of the interference relative to its own power level. Receiving device402thus determines the clean degrees of freedom and utilizes those degrees of freedom to decode the information.

Apparatus402can include memory420operatively coupled to apparatus402. Memory420can be external to apparatus402or can reside within apparatus402. Memory420can store information related to selecting a subset from a plurality of disjoint subsets of degrees of freedom and monitoring the selected subset to receive a signal from a transmitter device. Alternatively or additionally, memory420can store information related to selecting at least one degree of freedom in a resource block included in the selected subset, estimating a number of interfering transmitters, and selectively decoding a message from the received signal. Further, memory420can store other suitable information related to signals transmitted and received in a communication network. A processor422can be operatively connected to apparatus402(and/or memory420) to facilitate analysis of information related to mitigating interference in a communication network. Processor422can be a processor dedicated to analyzing and/or generating information received by apparatus402, a processor that controls one or more components of system400, and/or a processor that both analyzes and generates information received by apparatus402and controls one or more components of system400. Memory420can store protocols associated with mitigating interference, taking action to control communication between apparatus402and other devices such that system400can employ stored protocols and/or algorithms to achieve improved communications in a wireless network as described herein.

In view of the exemplary systems shown and described above, methodologies that may be implemented in accordance with the disclosed subject matter, will be better appreciated with reference to the following flow charts. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the number or order of blocks, as some blocks may occur in different orders and/or at substantially the same time with other blocks from what is depicted and described herein. Moreover, not all illustrated blocks may be required to implement the methodologies described herein. It is to be appreciated that the functionality associated with the blocks may be implemented by software, hardware, a combination thereof or any other suitable means (e.g. device, system, process, component). Additionally, it should be further appreciated that the methodologies disclosed hereinafter and throughout this specification are capable of being stored on an article of manufacture to facilitate transporting and transferring such methodologies to various devices. Those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram.

FIG. 5illustrates a method500for operating a transmitter device for mitigating interference in a communication network, according to an aspect. At502, a subset is selected from a plurality of disjoint subsets of degrees of freedom. The subset can be selected as a function of an identifier, which can be determined by a transmitter device, a receiver device, or both transmitter device and receiver device. A degree of freedom corresponds to a communication resource unit of the communication network. According to some aspects, the communication resource is divided into a plurality of disjoint subsets of degrees of freedom and the disjoint subsets are fixed.

A signal is transmitted, at504, to receiver device using the selected subset. In accordance with some aspects, the transmitted signal is an OFDM signal and a degree of freedom is a tone in an OFDM symbol. According to other aspects, the transmitted signal is a paging signal and the identifier is a paging identifier of the receiver device.

FIG. 6illustrates a method600for mitigating interference when transmitting signals in a communication network, according to an aspect. Method600starts, at602, when a subset is selected from a plurality of disjoint subsets of degrees of freedom. The selected subset includes a plurality of resource blocks. Each resource block includes a number of degrees of freedom. At604, at least one degree of freedom in each of the plurality of resources blocks is chosen. The degrees of freedom can be chosen as a function of the identifier. At606, a signal is transmitted in the selected degrees of freedom. According to some aspects, the signal is transmitted using at least one of phase and amplitude modulation schemes in the selected degrees of freedom. In these aspects, a pilot is transmitted in at least one of the selected degrees of freedom.

In accordance with various aspects, the number of degrees of freedom within a resource block is fixed and is the same for all resource blocks. The number of selected degrees of freedom within each resource block can be less than half the number of degrees of freedom within a resource block. According to some aspects, the number of degrees of freedom within a resource block is at least four and one degree of freedom is selected within each resource block. According to various aspects, the selected degrees of freedom are non-overlapping in time.

FIG. 7illustrates a method700performed by a receiver device for mitigating interference in a communication network, according to an aspect. At702, a subset from a plurality of disjoint subsets of degrees of freedom is chosen. The subset can be chosen as a function of an identifier that is determined by receiver device, a transmitter device, or both receiver device and transmitter device. The degree of freedom can correspond to a communication resource unit of communication network. At704, the selected subset is monitored in order to receive a signal from transmitter device. The received signal can be an OFDM signal and a degree of freedom is a tone in the OFDM symbol. In accordance with some aspects, the communication resource of the communication network is divided into a plurality of disjoint subsets of degrees of freedom and the plurality of disjoint subsets are fixed.

FIG. 8illustrates a method800for mitigating interference when receiving signals in a communication network, according to an aspect. At802, a subset is selected from a plurality of disjoint subsets of degrees of freedom. The selected subset includes a plurality of resource blocks. Each resource block includes a number of degrees of freedom.

At804, at least one degree of freedom within each of the plurality of resource blocks is selected. The selection can be a function of the identifier. A number of interfering transmitters is estimated, at806. The estimation can be a function of the energy of the received signal in the degrees of freedom of the selected subset. The interfering transmitters are transmitting interfering signals in the selected subset.

A determination is made, at808, whether the number of interfering transmitters exceeds a threshold. If the threshold is exceeded (“YES”), at810, the received signal is discarded. If it is determined that the number of interfering transmitters does not exceed the threshold (“NO”), at812, the message from the received signal in the selected degrees of freedom is decoded.

FIG. 9illustrates a method900for operating a receiving device for mitigating interferences in a communication network. At902, a subset is selected from a plurality of disjoint subsets. The subset can include a plurality of resource blocks, wherein each resource block includes a number of degrees of freedom. At904, one or more degrees of freedom within each of the plurality of resource blocks is selected. The section can be made based on an identifier. At906, the number of interfering transmitters is estimated. If the number of interfering transmitters exceeds an interference threshold, a message from the received signal in the selected degrees of freedom can be decoded.

Method900continues, at908, where a first number of degrees of freedom among the set of selected degrees of freedom in which the energy of the received signal exceeds a first energy threshold is estimated. At910, a determination is made whether the estimated first number is below the first energy threshold. If the estimated first number is below the first energy threshold (“YES”), at912, the received signal is discarded. If the estimated first number is above the first energy threshold (“NO”), at914, the received signal can be decoded.

Alternatively or additionally, at916, a second number of degrees of freedom in a resource block in which the energy of the received signal exceeds a second energy threshold is estimated. At918, a determination is made whether the signal received in the selected degree of freedom in the resource block is reliable. The reliability determination can be made as a function of the estimated second number and the estimated number of interfering transmitters. In accordance with some aspects, the signal received in the selected degree of freedom in the resource block is reliable if the estimated second number is greater than the estimated number of interfering transmitters. If the determination, at918, is that the received signal is not reliable (“NO”), at912, the received signal is discarded. If the determination is that the received signal is reliable (“YES”), at914, the received signal can be decoded.

According to some aspects, if there is only one page being sent (e.g., the estimated number of interfering transmitters is one), the energy threshold (e.g., the number of tones that should have energy) is 24 tones out of 28 tones (in a system that utilizes 28 tones). If there are two pages being sent (e.g., the estimated number of interfering transmitters is two), then the threshold is that 26 out of 28 tones should have energy (the energy threshold is 26). If it is estimated that there are three interfering transmitters, then all the tones (e.g., 28 tones) should have energy. Increasing the number of tones that have energy (energy threshold) in proportion to the number of interfering transmitters utilizing the resource can mitigate the probability of false alarms.

With reference toFIG. 10, illustrated is a system1000that mitigates interference in a communication network without a centralized scheduler, according to an aspect. System1000can reside at least partially within a mobile device, which can be a transmitting device, according to an aspect. It is to be appreciated that system1000is represented as including functional blocks, which may be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware).

System1000includes a logical grouping1002of electrical components that can act separately or in conjunction. Logical grouping1002can include an electrical component1004for selecting a subset from a plurality of disjoint subsets of degrees of freedom as a function of an identifier. The identifier can be determined by transmitting device and/or a receiving device. A degree of freedom corresponds to a communication resource unit of a communication network. Logical grouping1002also includes an electrical component1006for conveying a signal to the receiver device using the selected subset.

In accordance with some aspects, the selected subset includes a multitude of resource blocks. Each resource block can include a number of degrees of freedom. In accordance with these aspects, logical grouping1002can also include an electrical1008for selecting at least one degree of freedom within each of the multitude of resource blocks as a function of the identifier. The signal is transmitted in the selected degrees of freedom.

According to some aspects, the signal is transmitted using at least one of phase and amplitude modulation schemes in the selected degrees of freedom. Electrical component1006for transmitting a signal can transmit a pilot in at least one of the selected degrees of freedom.

Additionally, system1000can include a memory1010that retains instructions for executing functions associated with electrical components1004,1006, and1008, or other components. While shown as being external to memory1010, it is to be understood that one or more of electrical components1004,1006, and1008can exist within memory1010.

With reference toFIG. 11, illustrated is a system1100that mitigates interference in a communication network, according to an aspect. System1100can reside at least partially within a mobile device, which can be a receiving device. It is to be appreciated that system1100is represented as including functional blocks, which may be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware).

System1100includes a logical grouping1102of electrical components that can act separately or in conjunction. Logical grouping1102can include an electrical component1104for selecting a subset from a plurality of disjoint subsets of degrees of freedom. The selection can be a function of an identifier that is determined by receiving device, transmitting device, or both receiving device and transmitting device. A degree of freedom corresponds to a communication resource unit of the communication network. Logical grouping1102also includes an electrical component1106for monitoring the selected subset in order to receive a signal from the transmitting device.

In accordance with some aspects, the selected subset includes a plurality of resource blocks. Each resource block includes a number of degrees of freedom. Logical grouping1102can include an electrical component1108for selecting at least one degree of freedom within each of the plurality of resource blocks as a function of the identifier. Also included in logical grouping1102can be an electrical component1110for estimating the number of interfering transmitters as a function of the energy of the received signal in the degrees of freedom of the selected subset. The interfering transmitters are transmitting interfering signals in the selected subset. An electrical component1112for determining if the number of interfering transmitters exceeds an interference threshold is included in logical grouping1102. If the interference threshold is not exceeded, an electrical component1114for decoding decodes the message from the received signal in the selected degrees of freedom. If the interference threshold is exceeded, the received signal is discarded.

Alternatively or additionally, logical grouping1102can include an electrical component1116for calculating a number of degrees of freedom in the received signal that include energy and an electrical component1118for evaluating energy levels as a function of the energy calculation. For example, electrical component1116can calculate a first number of degrees of freedom among the set of the selected degrees of freedom in which the energy of the received signal exceeds a first energy threshold and electrical component1118can determine if the first number is below a first energy threshold. If the number is below the first energy threshold, the received signal can be discard.

In accordance with some aspects, electrical component1116can estimate a second number of degrees of freedom in a resource block in which the energy of the received signal exceeds a second energy threshold. An electrical component1120for determining reliability can decide if the signal received in the selected degree of freedom in the resource block is reliable as a function of the estimated second number and the number of interferes estimated by electrical component1110. If the signal is not reliable, the received signal in the selected degree of freedom can be discarded. Electrical component1120can determine the signal is reliable if the estimated second number is greater than the estimated number of interfering transmitters.

Additionally, system1100can include a memory1122that retains instructions for executing functions associated with electrical components1104,1106,1108,1110,1112,1114,1116,1118, and1120, or other components. While shown as being external to memory1122, it is to be understood that one or more of electrical components1104,1106,1108,1110,1112,1114,1116,1118, and1120can exist within memory1122.

FIG. 12illustrates an example wireless terminal (e.g., mobile device, transmitting device, receiving device, and so forth)1200, which can be used as any one of the wireless terminals (e.g., mobile devices, transmitting device, receiving device, and so on) described herein. According to various aspects, wireless terminal1200implements interference mitigation in a communication network. Wireless terminal1200includes a receiver1202that includes a decoder1204, a transmitter1206that includes an encoder1208, a processor1210, and a memory1212which are coupled together by a bus1214over which the various elements1202,1206,1210,1212can interchange data and information. An antenna1216used for receiving signals from a transmitting device is coupled to receiver1202. An antenna1218used for transmitting signals (e.g., to a receiving device, to a peer node) is coupled to transmitter1206. Processor1210(e.g., a CPU) controls operation of wireless terminal1200and implements methods by executing routines1220and using data/information1222in memory1212.

Data/information1222includes user data1224, user information1226, and tone subset allocation sequence information1228. User data1224can include data, intended for a peer node, which will be routed to encoder1208for encoding prior to transmission by transmitter1206, and data received from a peer node, which has been processed by decoder1204in receiver1202. User information1226includes uplink channel information1230and downlink channel information1232. Uplink channel information1230includes information identifying uplink channels segments that have been assigned for wireless terminal1200to use when transmitting information. Uplink channels can include uplink traffic channels, dedicated uplink control channels (e.g., request channels, power control channels and timing control channels). Each uplink channel includes one or more logic tones, each logical tone following an uplink tone hopping sequence. The uplink hopping sequences are different between each sector type of a cell and between adjacent cells. Downlink channel information1232includes information identifying downlink channel segments that have been assigned to wireless terminal1200for use when receiving data/information. Downlink channels may include downlink traffic channels and assignment channels, each downlink channel including one or more logical tone, each logical tone following a downlink hopping sequence, which is synchronized between each sector of the cell.

User information1226also includes terminal ID information1234, which is an assigned identification, base station ID information1236, which identifies the specific base station that wireless terminal1200might have established communications with, and sector ID info1238, which identifies the specific sector of the cell where wireless terminal1200is presently located. Base station ID1236provides a cell slope value and sector ID info1238provides a sector index type; the cell slope value and sector index type may be used to derive tone hopping sequences. Mode information1240, also included in user information1226, identifies whether the wireless terminal1200is in sleep mode, hold mode, on mode, and so forth.

Tone subset allocation sequence information1228includes downlink strip-symbol time information1242and downlink tone information1244. Downlink strip-symbol time information1242includes frame synchronization structure information, such as the superslot, beaconslot, and ultraslot structure information and information specifying whether a given symbol period is a strip-symbol period, and if so, the index of the strip-symbol period and whether the strip-symbol is a resetting point to truncate the tone subset allocation sequence used by the base station. Downlink tone info1244includes information including a carrier frequency assigned to the base station, the number and frequency of tones, and the set of tone subsets to be allocated to the strip-symbol periods, and other cell and sector specific values such as slope, slope index and sector type.

Routines1220include communications routines1246and wireless terminal control routines1248. Communications routines1246control the various communications protocols used by wireless terminal1200. For example, communications routines1246can enable communicating through a wide area network and/or a local area peer-to-peer network (e.g., directly with disparate wireless terminal(s)). By way of further example, communications routines1246can enable receiving a broadcast signal. Wireless terminal control routines1248control basic wireless terminal1200functionality including the control of the receiver1202and transmitter1206.

Routines1220can also include interference mitigation routines1250. When transmitting information, interference mitigation routines1250can include selecting a subset from a multitude of disjoint subsets of degrees of freedom and transmitting a signal using the selected subset. When receiving information, interference mitigation routines1250can include selecting a subset from a multitude of disjoint subsets of degrees of freedom and monitoring the selected subset in order to receive a signal. Further, interference mitigation routines1250for receiving information can include estimating a number of interfering transmitters (or simultaneous communication pairs), determining that the number of interferers are small, estimating a first number of degrees of freedom with energy within a selected set of degrees of freedom in which a desired signal is expected, and ascertaining there are enough number of degrees of freedom carrying the desired signal. In accordance with some aspects, the receiving interference mitigation routines1250includes, in each resource block, estimating a second number of degrees of freedom with energy to determine whether a collision occurs in that resource block, determining a desired signal is not collided and declaring the desired signal in that resource block is clean and can be used for decoding.

Referring now toFIG. 13, illustrated is a wireless communication system1300in accordance with various aspects. System1300comprises a base station1302that can include multiple antenna groups. For example, one antenna group can include antennas1304and1306, another group can comprise antennas1308and1310, and an additional group can include antennas1312and1314. Two antennas are illustrated for each antenna group; however, more or fewer antennas can be utilized for each group. Base station1302can additionally include 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, and so forth), as will be appreciated by one skilled in the art. Additionally, base station1302can be a home base station, a Femto base station, and/or the like.

Base station1302can communicate with one or more devices such as device1316; however, it is to be appreciated that base station1302can communicate with substantially any number of devices similar to device1316. As depicted, device1316is in communication with antennas1304and1306, where antennas1304and1306transmit information to device1316over a forward link1318and receive information from device1316over a reverse link1320. In a frequency division duplex (FDD) system, forward link1318can utilize a different frequency band than that used by reverse link1320, for example. Further, in a time division duplex (TDD) system, forward link1318and reverse link1320can utilize a common frequency band.

In addition, devices1322and1324can be communicating with one another, such as in a peer-to-peer configuration. Moreover, device1322is in communication with device1324using links1326and1328. In a peer-to-peer ad hoc network, devices within range of each other, such as devices1322and1324, communicate directly with each other without a base station1302and/or a wired infrastructure to relay their communication. Additionally, peer devices or nodes can relay traffic. The devices within the network communicating in a peer-to-peer manner can function similar to base stations and relay traffic or communications to other devices, functioning similar to base stations, until the traffic reaches its ultimate destination. The devices can also transmit control channels, which carry information that can be utilized to manage the data transmission between peer nodes.

A communication network can include any number of devices or nodes that are in wireless (or wired) communication. Each node can be within range of one or more other nodes and can communicate with the other nodes or through utilization of the other nodes, such as in a multi-hop topography (e.g., communications can hop from node to node until reaching a final destination). For example, a sender node may wish to communicate with a receiver node. To enable packet transfer between sender node and receiver node, one or more intermediate nodes can be utilized. It should be understood that any node can be a sender node and/or a receiver node and can perform functions of either sending and/or receiving information at substantially the same time (e.g., can broadcast or communicate information at about the same time as receiving information) or at different times.

FIG. 14illustrates an exemplary wireless communication system1400, according to various aspects. Wireless communication system1400depicts one base station and one terminal for sake of brevity. However, it is to be appreciated that system1400can include more than one base station or access point and/or more than one terminal or user device, wherein additional base stations and/or terminals can be substantially similar or different from the exemplary base station and terminal described below. In addition, it is to be appreciated that the base station and/or the terminal can employ the systems and/or methods described herein to facilitate wireless communication there between.

Referring now toFIG. 14, on a downlink, at access point1405, a transmit (TX) data processor1410receives, formats, codes, interleaves, and modulates (or symbol maps) traffic data and provides modulation symbols (“data symbols”). A symbol modulator1415receives and processes the data symbols and pilot symbols and provides a stream of symbols. Symbol modulator1415multiplexes data and pilot symbols and obtains a set of N transmit symbols. Each transmit symbol may be a data symbol, a pilot symbol, or a signal value of zero. The pilot symbols may be sent continuously in each symbol period. The pilot symbols can be frequency division multiplexed (FDM), orthogonal frequency division multiplexed (OFDM), time division multiplexed (TDM), frequency division multiplexed (FDM), or code division multiplexed (CDM).

A transmitter unit (TMTR)1420receives 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 antenna1425to the terminals. At terminal1430, an antenna1435receives the downlink signal and provides a received signal to a receiver unit (RCVR)1440. Receiver unit1440conditions (e.g., filters, amplifies, and frequency downconverts) the received signal and digitizes the conditioned signal to obtain samples. A symbol demodulator1445obtains N received symbols and provides received pilot symbols to a processor1450for channel estimation. Symbol demodulator1445further receives a frequency response estimate for the downlink from processor1450, 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 processor1455, which demodulates (symbol demaps), deinterleaves, and decodes the data symbol estimates to recover the transmitted traffic data. The processing by symbol demodulator1445and RX data processor1455is complementary to the processing by symbol modulator1415and TX data processor1410, respectively, at access point1405.

On the uplink, a TX data processor1460processes traffic data and provides data symbols. A symbol modulator1465receives and multiplexes the data symbols with pilot symbols, performs modulation, and provides a stream of symbols. A transmitter unit1470then receives and processes the stream of symbols to generate an uplink signal, which is transmitted by the antenna1435to the access point1405.

At access point1405, the uplink signal from terminal1430is received by the antenna1425and processed by a receiver unit1475to obtain samples. A symbol demodulator1480then processes the samples and provides received pilot symbols and data symbol estimates for the uplink. An RX data processor1485processes the data symbol estimates to recover the traffic data transmitted by terminal1430. A processor1490performs channel estimation for each active terminal transmitting on the uplink.

Processors1490and1450direct (e.g., control, coordinate, manage, and so on) operation at access point1405and terminal1430, respectively. Respective processors1490and1450can be associated with memory units (not shown) that store program codes and data. Processors1490and1450can 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, and the like), multiple terminals can 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 would be desirable to obtain 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 used 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 software, implementation can be through modules (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 processors1490and1450.

For a software implementation, the techniques described herein may be implemented with modules (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. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor through various means as is known in the art. Further, at least one processor may include one or more modules operable to perform the functions described herein.

Single carrier frequency division multiple access (SC-FDMA), which utilizes single carrier modulation and frequency domain equalization is a technique that can be utilized with the disclosed aspects. SC-FDMA has similar performance and essentially a similar overall complexity as those of OFDMA system. SC-FDMA signal has lower peak-to-average power ratio (PAPR) because of its inherent single carrier structure. SC-FDMA can be utilized in uplink communications where lower PAPR can benefit a mobile terminal in terms of transmit power efficiency.

While the foregoing disclosure discusses illustrative aspects and/or aspects, it should be noted that various changes and modifications could be made herein without departing from the scope of the described aspects and/or aspects as defined by the appended claims. Accordingly, the described aspects are intended to embrace all such alterations, modifications and variations that fall within scope of the appended claims. Furthermore, although elements of the described aspects and/or aspects may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any aspect and/or aspect may be utilized with all or a portion of any other aspect and/or aspect, unless stated otherwise.

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. Furthermore, the term “or” as used in either the detailed description or the claims is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from the context, the phrase “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form.