Patent ID: 12200681

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

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.

Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, or objectives. Rather, aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof.

An Example Wireless Communication System

The techniques described herein may be used for various broadband wireless communication systems, including communication systems that are based on an orthogonal multiplexing scheme. Examples of such communication systems include Spatial Division Multiple Access (SDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems, and so forth. An SDMA system may utilize sufficiently different directions to simultaneously transmit data belonging to multiple user terminals. A TDMA system may allow multiple user terminals to share the same frequency channel by dividing the transmission signal into different time slots, each time slot being assigned to different user terminal. An OFDMA system utilizes orthogonal frequency division multiplexing (OFDM), which is a modulation technique that partitions the overall system bandwidth into multiple orthogonal sub-carriers. These sub-carriers may also be called tones, bins, etc. With OFDM, each sub-carrier may be independently modulated with data. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on sub-carriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent sub-carriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent sub-carriers. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDMA.

The teachings herein may be incorporated into (e.g., implemented within or performed by) a variety of wired or wireless apparatuses (e.g., nodes). In some aspects, a wireless node implemented in accordance with the teachings herein may comprise an access point or an access terminal.

An access point (“AP”) may comprise, be implemented as, or known as a Node B, a Radio Network Controller (“RNC”), an evolved Node B (eNB), a Base Station Controller (“BSC”), a Base Transceiver Station (“BTS”), a Base Station (“BS”), a Transceiver Function (“TF”), a Radio Router, a Radio Transceiver, a Basic Service Set (“BSS”), an Extended Service Set (“ESS”), a Radio Base Station (“RBS”), or some other terminology.

An access terminal (“AT”) may comprise, be implemented as, or known as a subscriber station, a subscriber unit, a mobile station (MS), a remote station, a remote terminal, a user terminal (UT), a user agent, a user device, user equipment (UE), a user station, or some other terminology. In some implementations, an access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (“SIP”) phone, a wireless local loop (“WLL”) station, a personal digital assistant (“PDA”), a handheld device having wireless connection capability, a Station (“STA”), or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or smart phone), a computer (e.g., a laptop), a tablet, a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a global positioning system (GPS) device, or any other suitable device that is configured to communicate via a wireless or wired medium. In some aspects, the node is a wireless node. Such wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link.

FIG.1illustrates a multiple-access multiple-input multiple-output (MIMO) system100with access points and user terminals in which aspects of the present disclosure may be practiced. For example, one or more user terminals120may signal capabilities (e.g., to access point110) using the techniques provided herein.

For simplicity, only one access point110is shown inFIG.1. An access point 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 wireless node, a wireless node, or some other terminology. 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.

While portions of the following disclosure will describe user terminals120capable of communicating via Spatial Division Multiple Access (SDMA), for certain aspects, the user terminals120may also include some user terminals that do not support SDMA. Thus, for such aspects, an AP110may be configured to communicate with both SDMA and non-SDMA user terminals. This approach may conveniently allow older versions of user terminals (“legacy” stations) to remain deployed in an enterprise, extending their useful lifetime, while allowing newer SDMA user terminals to be introduced as deemed appropriate.

The access point110and user terminals120employ multiple transmit and multiple receive antennas for data transmission on the downlink and uplink. For downlink MIMO transmissions, Napantennas of the access point110represent the multiple-input (MI) portion of MIMO, while a set of K user terminals represent the multiple-output (MO) portion of MIMO. Conversely, for uplink MIMO transmissions, the set of K user terminals represent the MI portion, while the Napantennas of the access point110represent the MO portion. For pure SDMA, it is desired to have Nap≥K≥1 if the data symbol streams for the K user terminals are not multiplexed in code, frequency or time by some means. K may be greater than Napif the data symbol streams can be multiplexed using TDMA technique, different code channels with CDMA, disjoint sets of subbands 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 K selected user terminals can have the same or different number of antennas.

The 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). The system100may also be a TDMA system if the user terminals120share the same frequency channel by dividing transmission/reception into different time slots, each time slot being assigned to different user terminal120.

FIG.2illustrates a block diagram of access point110and two user terminals120mand120xin MIMO system100that may be examples of the access point110and user terminals120described above with reference toFIG.1and capable of performing the techniques described herein. The various processors shown inFIG.2may be configured to perform (or direct a device to perform) various methods described herein.

The access point110is equipped with Napantennas224athrough224ap. User terminal120mis equipped with Nut,mantennas252mathrough252mu, and user terminal120xis equipped with Nut,xantennas252xathrough252xu. The access point110is a transmitting entity for the downlink and a receiving entity for the uplink. Each user terminal120is a transmitting entity for the uplink and a receiving entity for the downlink. As used herein, a “transmitting entity” is an independently operated apparatus or device capable of transmitting data via a wireless channel, and a “receiving entity” is an independently operated apparatus or device capable of receiving data via a wireless channel. In the following description, the subscript “dn” denotes the downlink, the subscript “up” denotes the uplink. For SDMA transmissions, Nupuser terminals simultaneously transmit on the uplink, while Ndnuser terminals are simultaneously transmitted to on the downlink by the access point110. Nupmay or may not be equal to Ndn, and Nupand Ndnmay be static values or can change for each scheduling interval. The beam-steering or some other spatial processing technique may be used at the access point and user terminal.

On the uplink, at each user terminal120selected for uplink transmission, a transmit (TX) data processor288receives traffic data from a data source286and control data from a controller280. The controller280may be coupled with a memory282. TX data processor288processes (e.g., encodes, interleaves, and modulates) the traffic data 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. A TX spatial processor290performs spatial processing on the data symbol stream 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 point.

Nupuser 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), soft interference cancellation (SIC), or some other technique. Each recovered uplink data symbol stream is an estimate of a data symbol stream transmitted by a respective user terminal. An RX data processor242processes (e.g., demodulates, deinterleaves, and decodes) each recovered uplink data symbol stream 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. The controller230may be coupled with a memory232.

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 controller230, and 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 (such as a precoding or beamforming, as described in the present disclosure) on the Ndndownlink data symbol streams, and provides Naptransmit symbol streams for the Napantennas. Each transmitter unit222receives and processes a respective transmit symbol stream to generate a downlink signal. Naptransmitter units222providing Napdownlink signals for transmission from Napantennas224to the user terminals.

At each user terminal120, Nut,mantennas252receive the Napdownlink signals from access point110. Each receiver unit254processes 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 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. The decoded data for each user terminal may be provided to a data sink272for storage and/or a controller280for further processing.

At each user terminal120, a channel estimator278estimates the downlink channel response and provides downlink channel estimates, which may include channel gain estimates, SNR estimates, noise variance and so on. Similarly, at access point110, a channel estimator228estimates the uplink channel response and provides uplink channel estimates. Controller280for each user terminal typically derives the spatial filter matrix for the user terminal based on the downlink channel response matrix Hdn,mfor that user terminal. Controller230derives the spatial filter matrix for the access point based on the effective uplink channel response matrix Hup,eff. Controller280for each user terminal may send feedback information (e.g., the downlink and/or uplink eigenvectors, eigenvalues, SNR estimates, and so on) to the access point. Controllers230and280also control the operation of various processing units at access point110and user terminal120, respectively.

In a Wi-Fi network, wireless devices such as APs and STAs may perform a clear channel assessment (CCA) to determine whether a transmission channel is busy or idle for purposes of determining whether data may be transmitted to another wireless device. A CCA has two components: carriers sense (CS) and energy detection. Carrier sense refers to an ability of a wireless device (e.g., AP or STA) to detect and decode incoming Wi-Fi preambles having information that enables the receiver to acquire a wireless signal from and synchronize with the transmitter, from other wireless devices. For example, a first AP may broadcast a Wi-Fi signal preamble, and the Wi-Fi signal preamble may be detected by a second AP or a STA. Similarly, a third AP may broadcast a Wi-Fi signal preamble, and the Wi-Fi signal preamble may be detected by the second AP. When the second AP detects one or more of the Wi-Fi signal preambles, the second AP may determine that the transmission channel is busy and may not transmit data. The CCA may remain busy for the length of a transmission frame associated with the Wi-Fi preambles.

The second component of CCA is energy detection, which refers to the ability of a wireless device to detect an energy level present on a transmission channel. The energy level may be based on different interference sources, Wi-Fi transmissions, a noise floor, and/or ambient energy. Wi-Fi transmissions may include unidentifiable Wi-Fi transmissions that have been corrupted or are so weak that the transmission can no longer be decoded. Unlike carrier sense, in which the exact length of time for which a transmission channel is busy may be known, energy detection uses periodic sampling of a transmission channel to determine if the energy exists. Additionally, energy detection may require at least one threshold used to determine whether the reported energy level is adequate to report the transmission channel as busy or idle. This energy level may be referred to as the ED level/ED threshold level or the CCA sensitivity level. For example, if an ED level is above a threshold, a wireless device may defer to other devices by refraining from transmitting.

In one aspect of communicating over a medium, a device may reduce transmit power, which may lead to loss of coverage or throughput. Another possibility is to increase the CCA threshold (e.g., an energy detection level threshold), but doing so may create issues with coexistence. As such, a need exists to enable medium coexistence without excessively diminishing throughput or creating coexistence problems.

FIG.3illustrates an exemplary method300for communicating over a medium. Referring toFIG.3, a first AP302and a first STA306may be associated with a first BSS (BSS1). A second AP304and a second STA308may be associated with a second BSS (BSS2). The first AP302may be within CCA range of the second AP304. In various aspects, the first AP302and/or the second AP304may monitor the shared transmission medium to determine one or more parameters. In one aspect, the second AP304may send, on a channel, a first transmission312to the second STA308. In an aspect, the second STA308may measure the received signal strength indicator (RSSI) of the first transmission312, and provide the RSSI measurement in a first feedback message314to the second AP304.

Referring toFIG.3, the first transmission312from the second AP304may cause interference to the first AP302associated with the first BSS. In one configuration, upon detecting the first transmission312(e.g., a preamble is detected or energy detection level is above a threshold), the first AP302may refrain from the transmitting because the medium is busy. In one configuration, the first AP302may detect interference based on detecting the first transmission312, such as by detecting energy associated with the first transmission312.

In an aspect, in a first mode, the first AP302may transmit a number of data frames in which each transmission is separated by a fixed time interval. In this first mode, each data frame may be transmitted concurrently with another data frame transmitted by the second AP304. In a second mode, one or more of the APs302,304may transmit data frames at different times. For example, the first AP302may transmit a data frame at the end of a random time interval following a fixed time interval. The second AP304may transmit a data frame at the end of a different random time interval following a fixed time interval.

In an aspect, althoughFIG.3depicts the network entity310as a separate entity within a network managing a medium, the network entity310may also be a component within the first AP302and/or the second AP304. The network entity310may communicate with the first AP302and/or the second AP304(e.g., over communication link318).

FIGS.4A and4Billustrate diagrams400,450of an AP operating in a first mode and a second mode. Referring toFIG.4A, both the first AP302and the second AP304may have data for transmission. After an interframe space (IFS) such as a point coordination function (PCF) interframe space (PIFS) or a distributed coordination function (DCF) interframe space (DIFS), the first and second APs302,304may perform CCA. Based on the CCA, the second AP304may determine that the medium is available and may transmit Packet B1 (e.g., the first transmission312) after performing CCA. The first AP302may perform CCA as well and detect the packet transmission (Packet B1). In one configuration, the first AP302may determine that the medium or channel is busy and may not transmit. In another configuration, based on a first channel information message316and/or a third channel information message322, the network entity310may instruct the first AP302to operate in the first mode (via the first control message326) and may instruct the second AP304to operate in the first mode (e.g., via a second control message328) to increase usage of a medium. In the first mode, first AP302may wait for the transmission of Packet B1 to finish. After a fixed interval (e.g., an IFS), during which the first and second APs302,304detect the absence of traffic (e.g., no traffic is detected after Packet B1 was transmitted), the first AP302may transmit Packet A1 (e.g., the second transmission320) concurrently as the second AP304transmits packet B2. After another fixed interval (e.g., PIFS or DIFS), the first AP302may transmit Packet A2 concurrently with the second AP304's transmission of the Packet B3. After another fixed interval, the first AP302may transmit Packet A3 concurrently with the second AP304's transmission of the Packet B4. And finally, the first AP302may transmit Packet A4 concurrently with the second AP304's transmission of Packet B5. In an aspect, the APs may perform CCA during each of the fixed intervals.

In another aspect, one or more of the APs302,304may follow a backoff procedure (e.g., a standard backoff procedure may be defined in one or more 802.11 specifications). Such a backoff procedure may use a certain an arbitration IFS (AIFS) and/or SLOT time parameters for the backoff countdown. If the medium is idle, according to CCA, for the AIFS time, one or more of the APs302,304may decrement a backoff counter by 1, and then the one or more of the APs302,304may further decrement the backoff counter by 1 for each consecutive SLOT time during which the medium keeps continuously idle. In an aspect, the AIFS may be equal to a short IFS (SIFS)+(1SLOT)=PIFS; however, the AIFS may be larger.

Once the medium is accessed, the second AP304may transmit a sequence of at least one physical layer convergence procedure (PLCP) protocol data unit (PPDU) (e.g., PPDUs B1, B2, . . . , BN). Each of the PPDUs of the sequence may be separated by a same AIFS time. In some aspects, the AIFS is to be equal to the PIFS (e.g., based on certain conditions).

The first AP302may detect at least one of the PPDUs (e.g., B1), and the first AP302may halt backoff by the first AP302, thereby deferring transmission by the first AP302. Once the at least one PPDU (e.g., B1) ends, the first AP302may sense the medium for the AIFS time, and the first AP302may decrement the backoff counter by 1. If the backoff counter reaches 0, the first AP302may transmit a packet A1 (e.g., of a sequence of at least one PPDU). In some aspects, the first AP302may transmit the packet A1 contemporaneously (e.g., simultaneously) with the packet B2 of the at least one PPDU. Once the packet A1 is completed, the first AP302may perform channel sensing for the PIFS time and, if the channel is idle, the first AP302may transmit a packet A2. Similarly, once B2 is completed, the second AP304may perform channel sensing for the PIFS time and, if the channel is idle, the second AP304may transmit a packet B3. In some aspects, the first and/or second AP302,304may refrain from additional SLOT time sensing, e.g., until the duration of the transmission sequence (e.g., of PPDUs) exceeds a transmit opportunity (TXOP) value.

While the first and second APs302,304are in the first mode, the APs may concurrently transmit a sequence of packets. That is, the packets transmitted by the first AP302may be time synchronized with packets transmitted by the second AP304. In an aspect, the packets may be of the same length and may be of relatively short lengths. In another aspect, the packets from the first AP302and the second AP304may be of different lengths but less than a threshold length. In another aspect, the packet length may be signaled by the network entity310. As shown inFIG.4A, the start of the packet transmissions, regardless of packet length, may be at approximately the same time. In another aspect, before transmitting the sequence of packets, each of the APs may first transmit a clear-to-send (CTS) packet indicating that each AP intends to utilize the shared medium for data transmission. The CTS packet may include a special address or indication that indicates other APs not to defer. In another aspect, each of the APs may conclude the sequence of packets with a CTS until the end of the maximum time interval.

As such, in the first mode, the APs may transmit a sequence of relatively short data frames all separated by an IFS (e.g., a PIFS). In an aspect, the IFS or the fixed interval may be specified by the network entity310and communicated to the first and second APs302,304. The first AP302, which was deferring initially in the second mode, after entering the first mode, will wait until the end of the packet (e.g., Packet B1) and then collide on all of the following frames. As noted, even if the packet sizes are not the same length, synchronization may be preserved because one AP may wait for the other AP. In the sequence of packet transmissions in the first mode, the contention window for each AP may be set to 0 or some other common value between the APs. For example, the fixed time interval may be a DIFS or PIFS and the APs may transmit following a contention window in which the value is set to 0. In another aspect, instead of DIFS or PIFS, the APs may delay transmission for a SIFS.

In an aspect, the first and second APs302,304may remain in the first mode and transmit a number of relatively short packets (or data frames) for a maximum time interval (e.g., 200 ms). Subsequently, after the maximum time interval, the first and second APs302,304may terminate the transmission. In an aspect, the first and second APs302,304may autonomously revert to the second mode without having received further signaling from the network entity310. In another aspect, the first and the second APs302,304may remain in the first mode until otherwise instructed by the network entity310.

FIG.4Billustrates the diagram450in which the first and second APs302,304are operating in the second mode. In this mode, the first and second APs302,304do not transmit over one another. In this mode, after an IFS after a transmission, both APs may perform CCA. The second AP304may perform CCA and determine that the medium is available and transmit Packet B1. The first AP302may perform CCA and detect Packet B1 and determine that the medium is busy. After Packet B1 is transmitted and after an IFS, the first AP302may wait for a random backoff time (shown as Random Backoff1 inFIG.4B) and perform CCA again. If the medium is available, then the first AP302may transmit Packet A1. Subsequently, after an IFS after Packet A1 is transmitted, the second AP304may wait a random backoff time (shown as Random Backoff2 inFIG.4B) and then perform CCA. If the medium is available, then the second AP304may transmit Packet B2. Unlike inFIG.4A, the transmission times of the first and second APs302,304are not aligned and each AP will defer when the other AP is transmitting.

FIGS.5A and5Billustrate diagrams500,550related to sequence robustness. Even assuming fine time synchronization, one AP, e.g., the first AP302, may start its schedule transmission sequence with a delay. In a first option, as shown inFIG.5A, each of the APs may wait an IFS (e.g., DIFS) and perform CCA. The first AP302, however, may start its transmission sequence with a delay. The network entity310may instruct the first AP302to stop transmitting if a transmission would exceed a maximum time interval. For example, the first AP302may stop transmitting after Packet A3 and not transmit Packet A4. The second option may be preferred and may also be beneficial for a block acknowledgment procedure.

FIGS.6A and6Billustrates diagrams600,650for acknowledging transmissions in a synchronized sequence. For example, referring toFIG.6A, assuming the second option is utilized, the first and second APs302,304may schedule block acknowledgment requests (BARs) and block acknowledgments (BAs). In an aspect, the BAR may be scheduled following a maximum time interval. In another aspect, the APs may initiate transmission of a BAR when absence of traffic is detected following the data transmission. In an aspect, the BAR and the BA may be hard scheduled. That is, the BAR and the BA may be transmitted after the medium is seen as idle for more than PIFS.

Referring toFIG.6B, if the late AP (or the first AP302) is allowed to transmit, then BARs and BA could not be hard scheduled. In this aspect, the APs may use a deterministic backoff with AIFS. The deterministic backoff may have a large AIFS to give the late AP time to finish transmitting the late packet. In an aspect, the sequence inFIG.6Bmay be implemented using a cascade, even if the APs are within range of a transmission.

In an aspect, forFIGS.6A and6B, the network entity310may signal the first and the second APs302,304to set an acknowledgment policy to BAR for all frames. As such, frames may not be acknowledged unless a BAR is included with the frame or separately transmitted after the frame, for example. In another aspect, the APs may transmit a BAR to the STAs during an assigned slot time.

FIG.7is a diagram700illustrating an exemplary method for communicating over a medium. Referring toFIG.7, in an aspect, communication may occur over a medium when APs are loosely synchronized and are within CCA range. InFIG.7, APs may be instructed to deterministically collide by using IFS (e.g., PIFS) bursting. Referring toFIG.7, a downlink controlled access interval may include a data interval for data transmission and a BA interval for BAR and BA transmission. During the data interval, and after an IFS, an AP may transmit a CTS frame. An IFS after the CTS frame is transmitted, the AP may transmit a sequence of packets to its associated STAs. Each packet in the sequence of packets may be separated by a fixed time interval (e.g., PIFS). In another aspect, as shown in the previous FIGs., the AP may transmit the entire packet sequence during the data interval before a BAR or BA is transmitted during the BA interval. After transmitting the packet sequence, the AP may transmit another CTS frame.

FIG.8shows an example functional block diagram of a wireless device802configured to communicate over a medium. The wireless device802is an example of a device that may be configured to implement the various methods described herein. For example, the wireless device802may be the AP110and/or the UT120.

The wireless device802may include a processor804which controls operation of the wireless device802. The processor804may also be referred to as a central processing unit (CPU). Memory806, which may include both read-only memory (ROM) and random access memory (RAM), may provide instructions and data to the processor804. A portion of the memory806may also include non-volatile random access memory (NVRAM). The processor804typically performs logical and arithmetic operations based on program instructions stored within the memory806. The instructions in the memory806may be executable (by the processor804, for example) to implement the methods described herein.

The wireless device802may also include a housing808, and the wireless device802may include a transmitter810and a receiver812to allow transmission and reception of data between the wireless device802and a remote device. The transmitter810and receiver812may be combined into a transceiver814. A single transmit antenna or a plurality of transmit antennas816may be attached to the housing808and electrically coupled to the transceiver814. The wireless device802may also include multiple transmitters, multiple receivers, and multiple transceivers.

The wireless device802may also include a signal detector818that may be used in an effort to detect and quantify the level of signals received by the transceiver814or the receiver812. The signal detector818may detect such signals as total energy, energy per subcarrier per symbol, power spectral density and other signals. The wireless device802may also include a digital signal processor (DSP)820for use in processing signals. The DSP820may be configured to generate a packet for transmission. In some aspects, the packet may comprise a PPDU.

The various components of the wireless device802may be coupled together by a bus system822, which may include a power bus, a control signal bus, and a status signal bus in addition to a data bus. The wireless device802may include a medium component824. The medium component824, which may include one or more interfaces such as a bus interface (e.g., of a processor), may be configured to perform various operations. The medium component824may be configured to a first interface configured to obtain a signal from a wireless node. The medium component824may be configured to: select operation in a first mode or a second mode in the response to the signal; detect an absence of traffic on the shared medium during a fixed time interval; and initiate the data transmission at the end of the fixed time interval if operating in the first mode or initiate the data transmission at the end of a random time interval following the fixed time interval if operating in the second mode. The medium component824may be further configured to initiate the data transmission in the first mode by generating a plurality of data frames separated by the fixed time interval, and further configured to output the plurality of data frames for transmission. The medium component824may be further configured terminate the data transmission if a time period associated with the data transmission exceeds a maximum time interval, the time period being after the initiation of the data transmission. The medium component824may be further configured to generate a block acknowledgement request, and schedule transmission of the block acknowledgement request following the maximum time interval, and output the block acknowledgement request for the scheduled transmission. The medium component824may be further configured to initiate transmission of a block acknowledgement if another absence of traffic is detected on the shared medium following an end of the data transmission. The medium component824may be further configured to monitor the shared medium to determine one or more parameters and provide the one or more parameters to a remote wireless node. In an aspect, the one or more parameters comprise at least one of received signal strength from a wireless node in communication with the apparatus or detected interference associated with the shared medium.

FIG.9is a flowchart900of a method for communicating over a medium. The first method may be performed using an apparatus (e.g., the AP110, the UT120, the wireless device802, or the medium component824, for example). Although the method is described below with respect to the elements of wireless device802ofFIG.8, other components may be used to implement one or more of the steps described herein.

At operation902, the apparatus may be configured to monitor the shared transmission medium to determine one or more parameters and provide the one or more parameters to a remote apparatus. The apparatus may monitor the shared transmission the shared transmission medium by determining if signals are transmitted on the shared transmission medium and by receiving signals on the shared transmission medium. The apparatus may determine the one or more parameters by measuring the RSSI of the received signals or by measuring an energy detection level on the transmission medium (e.g., interference) and by storing the measurements. In another aspect, the apparatus may determine the one or more parameters by receiving one or more parameters, such as by receiving an RSSI from another wireless node (e.g., STA). For example, the first AP302and/or the second AP304may monitor the shared transmission medium to determine one or more parameters, and the first AP302and/or the second AP304may provide the determine one or more parameters to the network entity310.

At operation904, the apparatus may obtain a signal from a remote wireless node. For example, the signal may include an instruction configured to cause the apparatus to select between different transmission modes. In an aspect, the remote wireless node may be a network server. In the context ofFIG.3, the first AP302may receive the control message326from the network entity310, and/or the second AP304may receive the control message328from the network entity310.

At906, the apparatus may select operation in a first mode or a second mode in response to the signal. For example, the apparatus may switch between a first mode by setting a mode status indicator to a first value or a second value corresponding to the selected mode. For example, the first AP302may select operation in the first mode or the second mode in response to the control message326, and/or the second AP304may select operation in the first mode or the second mode in response to the control message328.

At operation908, the apparatus may detect an absence of traffic on the shared transmission medium during a fixed time interval. For example, the apparatus may sense the shared transmission medium by determining if any signals are present in the medium (e.g., signals above a signal strength) and, if not, whether the signals are absent or below a signal strength for greater than a time duration. For example, the first AP302and/or the second AP304may detect an absence of traffic on the shared transmission medium.

At operation910, the apparatus may initiate the data transmission at the end of the fixed time interval if operating in the first mode or initiate the data transmission at the end of a random time interval following the fixed time interval if operating in the second mode. For example, the apparatus may begin a timer having a duration of the fixed time interval. Upon expiration of the timer, the apparatus may initiate a data transmission if operating in the first mode. If operating in the second mode, the apparatus may additionally wait for a randomly selected time interval to elapse and then initiate the data transmission. For example, the first AP302and/or the second AP304may initiate a data transmission at the end of a fixed time interval if operating in the first mode. In the first mode, one or more data frames transmitted by the first AP302may be synchronized (e.g., concurrent) with one or more data frames transmitted by the second AP304. In the second mode, the first AP302or the second AP304may initiate a data transmission at the end of a random time interval following the fixed time interval.

In an aspect, the apparatus may perform operation912and/or operation914in order to initiate the data transmission at the end of the fixed time interval if operating in the first mode or initiate the data transmission at the end of a random time interval following the fixed time interval if operating in the second mode. At operation912, the apparatus may generate a plurality of data frames separated by a fixed time interval. For example, the first AP302may generate one or more of Packet A1 through A4, and/or the second AP304may generate one or more of Packet B2-B5.

At operation914, the apparatus may output the plurality of data frames for transmission. For example, the first AP302may output the one or more of Packet A1 through A4, and/or the second AP304may output the one or more of Packet B2-B5.

At operation916, the apparatus may terminate the data transmission if time period associated with the data transmission exceeds a maximum time interval. For example, the first AP302may terminate the data transmission if time period associated with the data transmission exceeds a maximum time interval, and/or the second AP304may terminate the data transmission if time period associated with the data transmission exceeds a maximum time interval.

At operation918, the apparatus may generate a block acknowledgement request. For example, the first AP302may generate a block acknowledgement request, and/or the second AP304may generate a block acknowledgement request.

At operation920, the apparatus may schedule transmission of a block acknowledgment request following the maximum time interval. For example, the apparatus may detect the shared transmission medium as idle, and the apparatus may hard schedule the block acknowledgement request following the maximum time interval. For example, the first AP302may schedule the block acknowledgement request following the maximum time interval, and/or the second AP304may schedule the block acknowledgement request following the maximum time interval.

At operation922, the apparatus may output the block acknowledgement request for the scheduled transmission. For example, the apparatus may initiate, according to the scheduled transmission, transmission of the block acknowledgment when an absence of traffic is detected following the data transmission. For example, the first AP302may output the block acknowledgement request for the scheduled transmission, and/or the second AP304may output the block acknowledgement request for the scheduled transmission.

At operation924, the apparatus may initiate transmission of a block acknowledgement if another absence of traffic is detected on the shared medium following an end of the data transmission. For example, the apparatus may detect another absence of traffic on the shared medium, and may initiate transmission of the block acknowledgement based on the detection of the other absence of traffic. For example, the first AP302and/or the second AP304may initiate transmission of a block acknowledgement if another absence of traffic is detected on the shared medium following an end of the data transmission.

FIG.10illustrates exemplary means1000capable of performing the operations set forth inFIG.9. The exemplary means may include means for monitoring the shared transmission medium to determine one or more parameters and providing the one or more parameters to a remote apparatus1002. Means1002may include a bus interface (e.g., of a processor), antennas224, antennas252, receiver units222, receiver units254, RX spatial processor240, RX spatial processors260, RX data processor242, RX data processors270, transmitter units222, transmitter units254, TX spatial processor220, TX spatial processors290, TX data processor210, TX data processors288controller230, controllers280, antennas816, transmitter810, receiver812, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for obtaining a signal from a remote wireless node1004. Means1004may include a bus interface (e.g., of a processor), antennas224, antennas252, receiver units222, receiver units254, RX spatial processor240, RX spatial processors260, RX data processor242, RX data processors270, controller230, controllers280, antennas816, receiver812, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for selecting operation in a first mode or a second mode in the response to the signal1006. Means1006may include controller230, controllers280, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for detecting an absence of traffic on the shared medium during a fixed time interval1008. Means1008may include a bus interface (e.g., of a processor), antennas224, antennas252, receiver units222, receiver units254, RX spatial processor240, RX spatial processors260, RX data processor242, RX data processors270, controller230, controllers280, antennas816, receiver812, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for initiating the data transmission at the end of the fixed time interval if operating in the first mode or initiating the data transmission at the end of a random time interval following the fixed time interval if operating in the second mode1010. In an aspect, means1010may be configured to generate a plurality of data frames separated by a fixed time interval. In an aspect, means1010may be configured to output the plurality of data frames for transmission. Means1010may include a bus interface (e.g., of a processor), antennas224, antennas252, transmitter units222, transmitter units254, TX spatial processor220, TX spatial processors290, TX data processor210, TX data processors288, controller230, controllers280, antennas816, transmitter810, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for terminating the data transmission if time period associated with the data transmission exceeds a maximum time interval1012. Means1012may include a controller230, controllers280, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for means for generating a block acknowledgement request1014. Means1014may include controller230, controllers280, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for scheduling transmission of the block acknowledgement request following the maximum time interval1016. Means1016may include controller230, controllers280, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for outputting the block acknowledgement request for the scheduled transmission1018. Means1018may include a bus interface (e.g., of a processor), antennas224, antennas252, transmitter units222, transmitter units254, TX spatial processor220, TX spatial processors290, TX data processor210, TX data processors288, controller230, controllers280, antennas816, transmitter810, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

The exemplary means may include means for initiating transmission of a block acknowledgement if another absence of traffic is detected on the shared medium following an end of the data transmission1020. Means1020may include a bus interface (e.g., of a processor), antennas224, antennas252, transmitter units222, transmitter units254, TX spatial processor220, TX spatial processors290, TX data processor210, TX data processors288, controller230, controllers280, antennas816, transmitter810, digital signal processor820, and/or processor804shown inFIG.2andFIG.8.

In the exemplary means1000, one or more means may be at least partially the same means. For example, means1004may include a first interface for obtaining the signal and means1010may include a second interface for outputting the plurality of data frames. Potentially, the first interface and the second interface may be the same interface.

The various operations of methods described above may be performed by any suitable means capable of performing the operations. 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 integrated circuit (ASIC), or processor. Generally, any operations illustrated in the Figures may be performed by corresponding functional means capable of performing the operations.

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like.

As used herein, the term receiver may refer to an RF receiver (e.g., of an RF front end) or an interface (e.g., of a processor) for receiving structures processed by an RF front end (e.g., via a bus). Similarly, the term transmitter may refer to an RF transmitter of an RF front end or an interface (e.g., of a processor) for outputting structures to an RF front end for transmission (e.g., via a bus).

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, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, and also a-a, b-b, and c-c.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array signal (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the present disclosure may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in any form of storage medium that is known in the art. Some examples of storage media that may be used include random access memory (RAM), read only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM and so forth. A software module may comprise a single instruction, or many instructions, and may be distributed over several different code segments, among different programs, and across multiple storage media. A storage medium may be coupled to a processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

The functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in hardware, an example hardware configuration may comprise a processing system in a wireless node. The processing system may be implemented with a bus architecture. The bus may include any number of interconnecting buses and bridges depending on the specific application of the processing system and the overall design constraints. The bus may link together various circuits including a processor, machine-readable media, and a bus interface. The bus interface may be used to connect a network adapter, among other things, to the processing system via the bus. The network adapter may be used to implement the signal processing functions of the PHY layer. In the case of a user terminal120(seeFIG.1), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus. The bus may also link various other circuits such as timing sources, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further.

The processor may be responsible for managing the bus and general processing, including the execution of software stored on the machine-readable media. The processor may be implemented with one or more general-purpose and/or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Machine-readable media may include, by way of example, RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media may be embodied in a computer-program product. The computer-program product may comprise packaging materials.

In a hardware implementation, the machine-readable media may be part of the processing system separate from the processor. However, as those skilled in the art will readily appreciate, the machine-readable media, or any portion thereof, may be external to the processing system. By way of example, the machine-readable media may include a transmission line, a carrier wave modulated by data, and/or a computer product separate from the wireless node, all which may be accessed by the processor through the bus interface. Alternatively, or in addition, the machine-readable media, or any portion thereof, may be integrated into the processor, such as the case may be with cache and/or general register files.

The processing system may be configured as a general-purpose processing system with one or more microprocessors providing the processor functionality and external memory providing at least a portion of the machine-readable media, all linked together with other supporting circuitry through an external bus architecture. Alternatively, the processing system may be implemented with an ASIC (Application Specific Integrated Circuit) with the processor, the bus interface, the user interface in the case of an access terminal), supporting circuitry, and at least a portion of the machine-readable media integrated into a single chip, or with one or more FPGAs (Field Programmable Gate Arrays), PLDs (Programmable Logic Devices), controllers, state machines, gated logic, discrete hardware components, or any other suitable circuitry, or any combination of circuits that can perform the various functionality described throughout this disclosure. Those skilled in the art will recognize how best to implement the described functionality for the processing system depending on the particular application and the overall design constraints imposed on the overall system.

The machine-readable media may comprise a number of software modules. The software modules include instructions that, when executed by the processor, cause the processing system to perform various functions. The software modules may include a transmission module and a receiving module. Each software module may reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module may be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor may load some of the instructions into cache to increase access speed. One or more cache lines may then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

If implemented in software, the functions may be stored or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium may be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media may comprise non-transitory computer-readable media (e.g., tangible media). In addition, for other aspects computer-readable media may comprise transitory computer-readable media (e.g., a signal). Combinations of the above should also be included within the scope of computer-readable media.

Thus, certain aspects may comprise a computer program product for performing the operations presented herein. For example, such a computer program product may comprise a computer-readable medium having instructions stored (and/or encoded) thereon, the instructions being executable by one or more processors to perform the operations described herein. For certain aspects, the computer program product may include packaging material.

Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.