Multi-channel management and load balancing

Certain aspects of the present disclosure provide a protocol to allow for load balancing between multiple frequency channels in a wireless communications system.

TECHNICAL FIELD

The present disclosure generally relates to wireless communications and, more specifically, to multi-channel wireless communications.

BACKGROUND

In order to address the issue of increasing bandwidth requirements demanded for wireless communication systems, different schemes are being developed to allow multiple user terminals to communicate with a single base station utilizing the same shared single channel or multiple channels.

A multiple-input multiple-output (MIMO) wireless system employs a number (NT) of transmit antennas and a number (NR) of receive antennas for data transmission. A MIMO channel formed by the NTtransmit and NRreceive antennas may be decomposed into NSspatial streams, where, for all practical purposes, NSmin {NT,NR}. The NSspatial streams may be used to transmit NSindependent data streams to achieve greater overall throughput.

In wireless networks with a single Access Point (AP) and multiple stations (STAs), concurrent transmissions may occur on multiple channels toward different stations, both in the uplink and downlink direction. However, each STA may be capable of transmitting or receiving in only one channel at a time, while the AP is typically capable of transmitting or receiving concurrently on multiple channels. One challenge in such systems is to allocate STAs to operate (transmit and/or receive) on different channels in a manner that achieves acceptable performance, in terms of load balancing and/or some other consideration, such as Quality of Service (QoS) targets.

SUMMARY

Certain aspects provide a method of wireless communications. The method generally includes communicating with a plurality of wireless apparatuses concurrently via a plurality of frequency channels and transmitting a request for at least one of the wireless apparatuses to switch from communicating via a first one of the frequency channels to communicating via a second one of the frequency channels.

Certain aspects provide a method of wireless communications. The method generally includes communicating with an access point via a first of a plurality of frequency channels, receiving a request, from the access point, to switch from the first to a second of the plurality of frequency channels, and communicating with the access point via the second frequency channel.

Certain aspects provide a method of wireless communications. The method generally includes communicating with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, transmitting, on at least a first one of the frequency channels, a message containing information regarding traffic loading of one or more of the frequency channels, receiving, from a first one or more of the stations, a request to switch from the first frequency channel to a second frequency channel, and receiving data from the first station via the second frequency channel.

Certain aspects provide a method of wireless communications. The method generally includes communicating with an apparatus via a first of a plurality of frequency channels, receiving, from the apparatus on the first frequency channel, a message containing information regarding traffic loading of one or more of the frequency channels, transmitting, to the apparatus, a request to switch from the first frequency channel to a second frequency channel, and transmitting data via the second frequency channel.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes a device configured to communicate with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, and a transmitter configured to transmit a request for at least one of the wireless apparatuses to switch from communicating via a first one of the frequency channels to communicating via a second one of the frequency channels.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes a device configured to communicate with an apparatus via a first of a plurality of frequency channels, a receiver configured to receive a request, from the access point, to switch from the first to a second of the plurality of frequency channels, and a device configured to communicate with the access point via the second frequency channel.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes a device configured to communicate with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, a transmitter configured to transmit, on at least a first one of the frequency channels, a message containing information regarding traffic loading of one or more of the frequency channels, a receiver configured to receive, from a first one or more of the wireless apparatuses, a request to switch from the first frequency channel to a second frequency channel, and a receiver configured to receive data from the first wireless apparatus via the second frequency channel.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes a device configured to communicate with another apparatus via a first of a plurality of frequency channels, a receiver configured to receive, from the other apparatus on the first frequency channel, a message containing information regarding traffic loading of one or more of the frequency channels, a transmitter configured to transmit, to the other apparatus, a request to switch from the first frequency channel to a second frequency channel, and a transmitter configured to transmit data via the second frequency channel.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes means for communicating with a plurality of wireless apparatuses concurrently via a plurality of frequency channels and means for transmitting a request for at least one of the wireless apparatuses to switch from communicating via a first one of the frequency channels to communicating via a second one of the frequency channels.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes means for communicating with another apparatus via a first of a plurality of frequency channels, means for receiving a request, from the other apparatus, to switch from the first to a second of the plurality of frequency channels, and means for communicating with the access point via the second frequency channel.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes means for communicating with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, means for transmitting, on at least a first one of the frequency channels, a message containing information regarding traffic loading of one or more of the frequency channels, means for receiving, from a first one or more of the stations, a request to switch from the first frequency channel to a second frequency channel, and means for receiving data from the first station via the second frequency channel.

Certain aspects provide an apparatus for wireless communications. The apparatus generally includes means for communicating with another apparatus via a first of a plurality of frequency channels, means for receiving, from the other apparatus on the first frequency channel, a message containing information regarding traffic loading of one or more of the frequency channels, means for transmitting, to the other apparatus, a request to switch from the first frequency channel to a second frequency channel, and means for transmitting data via the second frequency channel.

Certain aspects provide a computer-program product for wireless communications. The computer-program product includes a computer-readable medium encoded with instructions executable to communicate with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, and transmit a request for at least one of the wireless apparatuses to switch from communicating via a first one of the frequency channels to communicating via a second one of the frequency channels.

Certain aspects provide a computer-program product for wireless communications. The computer-program product includes a computer-readable medium encoded with instructions executable to communicate with an apparatus via a first of a plurality of frequency channels, receive a request, from the apparatus, to switch from the first to a second of the plurality of frequency channels, and communicate with the apparatus via the second frequency channel.

Certain aspects provide a computer-program product for wireless communications. The computer-program product includes a computer-readable medium encoded with instructions executable to communicate with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, transmit, on at least a first one of the frequency channels, a message containing information regarding traffic loading of one or more of the frequency channels, receive, from a first one or more of the wireless apparatuses, a request to switch from the first frequency channel to a second frequency channel, and receive data from the first wireless apparatus via the second frequency channel.

Certain aspects provide a computer-program product for wireless communications. The computer-program product includes a computer-readable medium encoded with instructions executable to communicate with an apparatus via a first of a plurality of frequency channels, receive, from the apparatus on the first frequency channel, a message containing information regarding traffic loading of one or more of the frequency channels, transmit, to the apparatus, a request to switch from the first frequency channel to a second frequency channel, and transmit data via the second frequency channel.

Certain aspects provide a wireless node. The wireless node generally includes at least one antenna, a device configured to communicate, via the at least one antenna, with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, and a transmitter configured to transmit via the at least one antenna a request for at least one of the wireless apparatuses to switch from communicating via a first one of the frequency channels to communicating via a second one of the frequency channels.

Certain aspects provide a wireless node. The wireless node generally includes at least one antenna, a device configured to communicate with an apparatus via a first of a plurality of frequency channels, a receiver configured to receive via the at least one antenna a request, from the apparatus, to switch from the first to a second of the plurality of frequency channels, and a device configured to communicate with the access point via the second frequency channel.

Certain aspects provide a wireless node. The wireless node generally includes at least one antenna, a device configured to communicate with a plurality of wireless apparatuses concurrently via a plurality of frequency channels, a transmitter configured to transmit via the at least one antenna, on at least a first one of the frequency channels, a message containing information regarding traffic loading of one or more of the frequency channels, a receiver configured to receive via the at least one antenna, from a first one or more of the wireless apparatuses, a request to switch from the first frequency channel to a second frequency channel, and a receiver configured to receive data from the first wireless apparatus via the second frequency channel.

Certain aspects provide a wireless node. The wireless node generally includes at least one antenna, a device configured to communicate with an apparatus via a first of a plurality of frequency channels, a receiver configured to receive via the at least one antenna, from the wireless node on the first frequency channel, a message containing information regarding traffic loading of one or more of the frequency channels, a transmitter configured to transmit via the at least one antenna, to the wireless node, a request to switch from the first frequency channel to a second frequency channel, and a transmitter configured to transmit data via the second frequency channel.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Also as used herein, the term “legacy stations” generally refers to wireless network nodes that support 802.11n or earlier versions of the IEEE 802.11 standard.

The multi-antenna transmission techniques described herein may be used in combination with various wireless technologies such as Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiplexing (OFDM), Time Division Multiple Access (TDMA), Spatial Division Multiple Access (SDMA), and so on. Multiple user terminals can concurrently transmit/receive data via different (1) orthogonal code channels for CDMA, (2) time slots for TDMA, or (3) sub-bands for OFDM. A CDMA system may implement IS-2000, IS-95, IS-856, Wideband-CDMA (W-CDMA), or some other standards. An OFDM system may implement IEEE 802.11 or some other standards. A TDMA system may implement GSM or some other standards. These various standards are known in the art.

AN EXAMPLE MIMO SYSTEM

FIG. 1illustrates a multiple-access MIMO system100with access points and user terminals. For simplicity, only one access point110is shown inFIG. 1. An access point (AP) is generally a fixed station that communicates with the user terminals and may also be referred to as a base station or some other terminology. A user terminal may be fixed or mobile and may also be referred to as a mobile station, a station (STA), a client, a wireless device or some other terminology. A user terminal may be a wireless device, such as a cellular phone, a personal digital assistant (PDA), a handheld device, a wireless modem, a laptop computer, a personal computer, etc.

Access point110may communicate with one or more user terminals120at any given moment on the downlink and uplink. The downlink (i.e., forward link) is the communication link from the access point to the user terminals, and the uplink (i.e., reverse link) is the communication link from the user terminals to the access point. A user terminal may also communicate peer-to-peer with another user terminal. A system controller130couples to and provides coordination and control for the access points.

As used herein, the term wireless node may generally refer to an access point, user terminal, or any type of wireless device capable of performing operations described herein.

System100employs multiple transmit and multiple receive antennas for data transmission on the downlink and uplink. Access point110is equipped with a number Napof antennas and represents the multiple-input (MI) for downlink transmissions and the multiple-output (MO) for uplink transmissions. A set Nuof selected user terminals120collectively represents the multiple-output for downlink transmissions and the multiple-input for uplink transmissions. In certain cases, it may be desirable to have Nap≧Nu≧1 if the data symbol streams for the Nuuser terminals are not multiplexed in code, frequency or time by some means. Numay be greater than Napif the data symbol streams can be multiplexed using different code channels with CDMA, disjoint sets of sub-bands with OFDM, and so on. Each selected user terminal transmits user-specific data to and/or receives user-specific data from the access point. In general, each selected user terminal may be equipped with one or multiple antennas (i.e., Nut≧1). The Nuselected user terminals can have the same or different number of antennas.

MIMO system100may be a time division duplex (TDD) system or a frequency division duplex (FDD) system. For a TDD system, the downlink and uplink share the same frequency band. For an FDD system, the downlink and uplink use different frequency bands. MIMO system100may also utilize a single carrier or multiple carriers for transmission. Each user terminal may be equipped with a single antenna (e.g., in order to keep costs down) or multiple antennas (e.g., where the additional cost can be supported).

On the uplink, at each user terminal120selected for uplink transmission, a TX data processor288receives traffic data from a data source286and control data from a controller280. TX data processor288processes (e.g., encodes, interleaves, and modulates) the traffic data {dup,m} for the user terminal based on the coding and modulation schemes associated with the rate selected for the user terminal and provides a data symbol stream {sup,m}. A TX spatial processor290performs spatial processing on the data symbol stream {sup,m} and provides Nut,mtransmit symbol streams for the Nut,mantennas. Each transmitter unit (TMTR)254receives and processes (e.g., converts to analog, amplifies, filters, and frequency upconverts) a respective transmit symbol stream to generate an uplink signal. Nut,mtransmitter units254provide Nut,muplink signals for transmission from Nut,mantennas252to the access point110.

A number Nupof user terminals may be scheduled for simultaneous transmission on the uplink. Each of these user terminals performs spatial processing on its data symbol stream and transmits its set of transmit symbol streams on the uplink to the access point.

At access point110, Napantennas224athrough224apreceive the uplink signals from all Nupuser terminals transmitting on the uplink. Each antenna224provides a received signal to a respective receiver unit (RCVR)222. Each receiver unit222performs processing complementary to that performed by transmitter unit254and provides a received symbol stream. An RX spatial processor240performs receiver spatial processing on the Napreceived symbol streams from Napreceiver units222and provides Nuprecovered uplink data symbol streams. The receiver spatial processing is performed in accordance with the channel correlation matrix inversion (CCMI), minimum mean square error (MMSE), successive interference cancellation (SIC) or some other technique. Each recovered uplink data symbol stream {sup,m} is an estimate of a data symbol stream {sup,m} transmitted by a respective user terminal. An RX data processor242processes (e.g., demodulates, deinterleaves, and decodes) each recovered uplink data symbol stream {sup,m} in accordance with the rate used for that stream to obtain decoded data. The decoded data for each user terminal may be provided to a data sink244for storage and/or a controller230for further processing.

On the downlink, at access point110, a TX data processor210receives traffic data from a data source208for Ndnuser terminals scheduled for downlink transmission, control data from a controller230and possibly other data from a scheduler234. The various types of data may be sent on different transport channels. TX data processor210processes (e.g., encodes, interleaves, and modulates) the traffic data for each user terminal based on the rate selected for that user terminal. TX data processor210provides Ndndownlink data symbol streams for the Ndnuser terminals. A TX spatial processor220performs spatial processing on the Ndndownlink data symbol streams, and provides Naptransmit symbol streams for the Napantennas. Each transmitter unit (TMTR)222receives and processes a respective transmit symbol stream to generate a downlink signal. Naptransmitter units222provide Napdownlink signals for transmission from Napantennas224to the user terminals.

At each user terminal120, Nut,mantennas252receive the Napdownlink signals from access point110. Each receiver unit (RCVR)254processes a received signal from an associated antenna252and provides a received symbol stream. An RX spatial processor260performs receiver spatial processing on Nut,mreceived symbol streams from Nut,mreceiver units254and provides a recovered downlink data symbol stream {sdn,m} for the user terminal. The receiver spatial processing is performed in accordance with the CCMI, MMSE or some other technique. An RX data processor270processes (e.g., demodulates, deinterleaves and decodes) the recovered downlink data symbol stream to obtain decoded data for the user terminal.

At each user terminal120, Nut,mantennas252receive the Napdownlink signals from access point110. Each receiver unit (RCVR)254processes a received signal from an associated antenna252and provides a received symbol stream. An RX spatial processor260performs receiver spatial processing on Nut,mreceived symbol streams from Nut,mreceiver units254and provides a recovered downlink data symbol stream {sdn,m} for the user terminal. The receiver spatial processing is performed in accordance with the CCMI, MMSE or some other technique. An RX data processor270processes (e.g., demodulates, deinterleaves, and decodes) the recovered downlink data symbol stream to obtain decoded data for the user terminal.

FIG. 3illustrates various components that may be utilized in a wireless device302that may be employed within the system100. The wireless device302is an example of a device that may be configured to implement the various methods described herein. The wireless device302may be an access point110or a user terminal120.

The wireless device302may include a processor304which controls operation of the wireless device302. The processor304may also be referred to as a central processing unit (CPU). Memory306, which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processor304. A portion of the memory306may also include non-volatile random access memory (NVRAM). The processor304typically performs logical and arithmetic operations based on program instructions stored within the memory306. The instructions in the memory306may be executable to implement the methods described herein.

The wireless device302may also include a housing308that may include a transmitter310and a receiver312to allow transmission and reception of data between the wireless device302and a remote location. The transmitter310and receiver312may be combined into a transceiver314. A plurality of transmit antennas316may be attached to the housing308and electrically coupled to the transceiver314. The wireless device302may also include (not shown) multiple transmitters, multiple receivers, and multiple transceivers.

The wireless device302may also include a signal detector318that may be used in an effort to detect and quantify the level of signals received by the transceiver314. The signal detector318may detect such signals as total energy, energy per subcarrier per symbol, power spectral density and other signals. The wireless device302may also include a digital signal processor (DSP)320for use in processing signals.

The various components of the wireless device302may be coupled together by a bus system322, which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus.

Those skilled in the art will recognize the techniques described herein may be generally applied in systems utilizing any type of multiple access schemes, such as SDMA, OFDMA, CDMA, SDMA and combinations thereof.

MULTI-CHANNEL MANAGEMENT AND LOAD BALANCING

According to certain aspects, in a system utilizing multiple wireless communications channels for exchanging data between an access point (AP) and multiple stations (STAs), techniques are provided for allocating stations to transmit on different channels. The techniques presented herein include, for example, an “AP managed” scheme, in which the AP can decide where (on what channels) to allocate the STAs for downlink transmissions. The techniques presented herein also include, for example, a “STA managed” switching scheme, in which STAs can autonomously switch across different channels to send uplink data to an AP. Various algorithms are provided that may be applied to the case of “STA managed” techniques. Such algorithms allow for load balancing across channels

As used herein, the phrase “simultaneous and asynchronous communication capability” generally refers to the capability of the AP to transmit data on one or more channels, while also asynchronously receiving data on a disjoint set of channels. Access terminals (ATs) or stations (STAs), on the other hand, may be restricted, such that they are not capable of simultaneously receiving data on any channel while transmitting data on one or more channels.

FIG. 4illustrates example operations400, in accordance with certain aspects of the present disclosure. The operations400may be performed, for example, by an AP capable of simultaneous and asynchronous communication in a multi-channel wireless communications system.

The operations begin, at402, by simultaneously and asynchronously communicating with a plurality of STAs via a plurality of channels and, at404, receiving data from at least one of the STAs, wherein the data was transmitted via at least one of the channels.

FIG. 5illustrates example operations, in accordance with certain aspects of the present disclosure. The operations500may be performed, for example, by a STA in a multi-channel wireless communications system, communicating with an AP performing the operations400shown inFIG. 4.

The operations500begin, at502, by transmitting data to an AP via at least one channel of a set of channels being supported by the AP for simultaneous communication via a plurality of STAs. At504, the STA receives data from the AP via said at least one channel, wherein the reception does not occur during the transmission.

FIG. 6illustrates example operations600, in accordance with certain aspects of the present disclosure. The operations600may be performed, for example, by an AP in an “AP managed’ allocation scheme in an effort to balance the transmission load between the AP and a set of STAs on a plurality of channels.

The operations begin, at602, by communicating with a plurality of stations via a plurality of frequency channels. At604, the AP transmits a request for at least one of the stations to switch from communicating via a first one of the frequency channels to communicating via a second one of the frequency channels. The AP may decide which stations to request to switch and to which channels based on a number of factors, such as class (switching speed), traffic for a given station, and/or load on the channels. The AP may maintain such statistics to assist in switching decisions.

FIG. 7illustrates example operations700, in accordance with certain aspects of the present disclosure. The operations700may be performed, for example, by a STA in a multi-channel wireless communications system, communicating with an AP performing the operations600shown inFIG. 6.

The operations700begin, at702, by communicating with an AP via a first of a plurality of frequency channels. At704, the STA receives a request from the AP to switch from the first frequency channel to a second frequency channel of the plurality of frequency channels. At706, the STA communicates with the AP via the second frequency channel.

FIG. 8illustrates example transmissions between an access point and multiple stations in an AP managed allocation scheme, in accordance with certain aspects of the present disclosure. The illustrated example assumes a first station (STA1) is communicating with the AP initially using a first frequency channel (virtual channel VC1). The AP sends a channel switch request message (CSRM)802requesting STA1switch to a second frequency channel VC2. According to certain aspects, the AP may also transmit a clear-to-send to Self (CTS-to self) message804on VC2, in order to reserve VC2and help facilitate the channel switch. This is possible, since the AP may know the appropriate Network Allocation Vector (NAV) setting, while the STA may not. If VC2is reserved, then the AP may directly access the medium, otherwise, the AP may have to perform an EDCA access.

According the certain aspects, the CSRM802may be a broadcast message, identifying multiple stations and to which channels they should switch, thus allowing multiple STAs to be switched at the same time. Each of the STAs (e.g., station STA1) receiving the CSRM may acknowledge the CSRM with corresponding request to send multiple access (RTS-MA) messages808during an ACK interval806.

Once on the new channel, the stations may wait for a transmission from the AP, such as an RTS812. STA1may respond with a CTS814, after which the AP may send a data transmission816to STA1. STA1may acknowledge receipt of the data transmission816with an ACK818.

FIG. 9illustrates example operations900, in accordance with certain aspects of the present disclosure. The operations900may be performed, for example, by an AP in a “STA managed’ switching scheme in an effort to balance the transmission load between the AP and a set of STAs on a plurality of channels.

The operations900begin, at902, by communicating with a plurality of stations via a plurality of frequency channels. At904, the AP transmits, on at least one of the frequency channels, a message containing information regarding traffic loading of one or more of the frequency channels. At906, the AP receives, from a first one or more of the stations, a request to switch from the first frequency channel to a second frequency channel. At908, the AP receives data from the first station via the second frequency channel.

FIG. 10illustrates example operations1000, in accordance with certain aspects of the present disclosure. The operations1000may be performed, for example, by a STA in a multi-channel wireless communications system, communicating with an AP performing the operations900shown inFIG. 9.

The operations1000begin, at1002, by communicating with an AP via a first of a plurality of frequency channels. At1004, the STA receives, from the AP on the first frequency channel, a message containing information regarding traffic loading of one or more of the frequency channels. At1006, the STA may transmit, to the AP, a request to switch from the first frequency channel to a second frequency channel. At1008, the STA transmits data to the AP via the second frequency channel.

The message containing information regarding traffic loading of one or more of the frequency channels may be any suitable message format and may contain various information regarding traffic loading, such as a loading parameter, available bandwidth, number of stations on a particular channel, and the like. An STA receiving this information may, thus, make an intelligent decision regarding which channel to switch to based on this information. For example, a STA may examine the information and learn that it is currently communicating on a frequency channel that is much more heavily loaded than one or more other frequency channels. Thus, the STA may send a request to switch to one of the less loaded other frequency channels.

FIG. 11illustrates example transmissions between an access point and multiple stations in a STA managed switching scheme, in accordance with certain aspects of the present disclosure. Again, the illustrated example assumes STA1is communicating with the AP initially using a first frequency channel (virtual channel) VC1.

In this example, the AP sends an M-NAV message1102, which may contain information about other channels, such as the current loading or traffic conditions. The STA may decide, based on the information about the other channels, that it would be beneficial to switch to VC2. As will be described in greater detail below, different criteria may be considered and different algorithms may be designed to decide to which channel to switch.

The AP may apply some type of algorithm to determine when and/or where (on what channels) to transmit the M-NAV, and may consider parameters, such as class (switching speed), traffic and/or load. According to certain aspects, the AP may send the M-NAV periodically and/or may send the M-NAV on multiple channels.

In order to switch to VC2, the STA may send a request message to the AP, for example, in the form of an RTS1106sent on VC2. The AP may respond with a CTS1108, after which the STA may send an uplink data transmission1110to the AP. The AP may acknowledge receipt of the data transmission1110with an ACK1112.

According to certain aspects, if STA1does not receive the CTS1108and/or does not receive the ACK1112from the AP, STA1may switch back to VC1or to another channel. Thus, the STA managed scheme may help avoid channel ambiguities between the AP and STA.

FIGS. 12A and 12Billustrate example state diagrams from the AP perspective and, the STA's guess on the AP perspective. The states represent the STA1channel location kept at the AP.

As illustrated in the state diagram1200A ofFIG. 12A, from the AP perspective, after the STA sends the RTS on VC2, there may be some ambiguity as to whether the STA has successfully switched to VC2. If the STA sends data and the AP sends an ACK, the AP may update the STA1channel location to VC2. However, if no data is received after the CTS NAV expires, the AP may consider the STA1channel location to be VC1.

As illustrated in the state diagram1200B ofFIG. 12B, from the STA perspective, after the STA receives the CTS on VC2, there may be some ambiguity as to whether the STA has successfully switched to VC2. If the AP acknowledges data sent to the AP on VC2, the STA may assume the AP has updated its STA1channel location to VC2. However, if no ACK is received and the NAV on VC1has expired, the STA may assume the AP has returned/maintained the STA1channel location to be VC1.

In the STA managed scheme, various algorithms may be used to decide whether to switch and, possibly, to which channel to switch. One such algorithm, is generally referred to herein as a “NAV aware” algorithm considers NAV expiration timer versus medium access time. Generally, the algorithm may decide there is no need to switch if the estimated medium access time involved in switching to another channel is greater than the NAV expiration time for the current channel. The algorithm may be described logically as follows:

Another switching algorithm is generally referred to herein as a “LOAD aware” switching algorithm. As the name implies, this algorithm considers the loading of other channels when deciding whether to switch and to what channel to switch. This algorithm may be described logically as follows:

The term access_delay in the logical expression above may be defined as backoffTimer.remaining*avg_busy_time*Ptx, where Ptx represents the probability that a packet transmission starts in a given time slot and may be estimated based on measurements kept at the AP. For example, the average arrival rate per STA may be computed, counting the number of packets sent by each station, and the channel location of each STA is known by the AP. By estimating the medium access delay on a channel, this algorithm may allow for load and may be relatively independence of packet length statistics. Further, with the Q and D factors, this algorithm may amortize switching time.

FIGS. 13A-B,14A-B, and15A-B illustrate and compare example performance results, in accordance with certain aspects of the present disclosure. Simulations results for an example configuration of 2 channels and 3 stations, with fixed packet length, increasing arrival intensity.

FIGS. 13A and 13Billustrate a static allocation, meaning no dynamic switching of a station between channels. The example assumes a static allocation with STA1and STA3on VC1and STA2on VC2. As illustrated inFIG. 13A, since the load is not balanced, as the per-Station load increases, the achievable throughput for STA1and STA3levels off. As illustrated inFIG. 13B, as the per-Station load increases, the average delay for STA1and STA3increases rapidly, while the average delay for STA2on VC2increases only gradually.

FIGS. 14A and 14Billustrate the “NAV aware” switching algorithm. As illustrated, assuming a switching time of 100 us and a maximum packet duration of 1000 us, this algorithm is able to achieve relatively efficient load balancing. As illustrated, the throughput attainable on STA1and STA3is increased at higher per-STA load, relative to the static switching illustrated inFIGS. 13A and 13B, while the average delay does not increase significantly until much higher per-STA loads. As switching time is increased relative to maximum packet duration, the NAV aware switching will approach the static case.

FIGS. 15A and 15Bcompare performance results of the NAV aware switching algorithm to the Load aware switching algorithm. As illustrated, assuming a switching time of 1000 us and a maximum packet duration of 500 us, the NAV aware algorithm suffers, while the Load aware algorithm achieves lower average delays and fewer collisions. This result may be because the Load aware algorithm allows for load balancing independently of the packet length statistic, which may help by effectively amortizing switching overhead.

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrate circuit (ASIC), or processor. Generally, where there are operations illustrated in Figures, those operations may have corresponding counterpart means-plus-function components with similar numbering. For example, example operations400,500,600,700,900and1000illustrated inFIGS. 4,5,6,7,9and10, respectively, correspond to circuit blocks400A,500A,600A,700A,900A and1000A illustrated inFIGS. 4A,5A,6A,7A,9A and10A, respectively.

As used herein, the term device may refer to hardware, software, firmware or combination thereof. According to certain aspects, a device may be implemented as a transmitter, receiver, logic to control a transmitter and/or receiver, or a combination thereof.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, and c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.

The techniques provided herein may be utilized in a variety of applications. For certain aspects, the techniques presented herein may be incorporated in an access point, a mobile handset, a personal digital assistant (PDA) or other type of wireless devices with processing logic and elements to perform the techniques provided herein.