HK1188529B - Access point, station and method for transmission management of wireless medium - Google Patents

Abstract

The present invention provides an access point (AP), a station (STA) and a method for transmission management of a wireless medium, the method comprising: receiving and decoding a Multiple Receiver Aggregate Multi- Poll/Power Save Aggregation Descriptor (MMP/PSAD) frame that includes scheduled Uplink Transmission Time (ULT) information for a plurality of stations STAs; extracting timing information relating to one of the plurality of STAs from the MMP/PSAD frame; and the STA transmitting during the scheduled ULT for the one of the plurality of STAs.

Description

Method, access point and station for transmission management of a wireless medium

The present application is a divisional application of chinese patent application having an application date of 20/9/2006, an application number of 200680034793.2, entitled "method and apparatus for transmission management in a wireless communication system".

Technical Field

The present invention relates to data transmission in a wireless communication system. In particular, the present invention relates to a method and apparatus for transmission management for multi-point polling and power saving in a wireless communication system.

Background

In the implementation of the proposed IEEE802.11 standard, in particular the IEEE802.11n standard, Higher Throughput (HT) Wireless Local Area Network (WLAN) devices are allowed. One way to achieve higher throughput is by using signal sets in both the Medium Access Control (MAC) layer and the Physical (PHY) layer. When the aggregate signal is sent to a single receiver address, it is called Single Receiver Aggregate (SRA). When an aggregate signal is transmitted to multiple receivers, it is called a Multiple Receiver Aggregate (MRA).

The MRA may be transmitted in a multi-receiver aggregate multipoint polling (MMP) sequence or a Power Save Aggregate Descriptor (PSAD). The above set helps to improve the performance of the system and provide a power saving means in case of MMP/PSAD.

One or more MAC Service Data Units (MSDUs) sent to the same receiver may be aggregated in a single aggregate MSDU (a-MSDU). This aggregation of multiple frames improves the efficiency of the MAC layer, especially when there are multiple small MSDUs, such as transmission control protocol acknowledgements (tcp acks). Overhead related to channel access, such as Physical Layer Convergence Protocol (PLCP) preamble, MAC header, and IFS interval, may be amortized into two or more MSDUs. Additionally, the STA may only use the MSDU set when the STA knows that the receiver supports the MSDU set. In some cases, the receiver may be forced to support MSDU aggregation.

Fig. 1 shows an example of an a-MSDU frame 10. The A-MSDU frame 10 includes a plurality of subframe header fields 11 and a plurality of MSDU fields 12 (labeled MSDU)₁…MSUD_n). Each subframe header field 11 includes an MSDU length field 13, a source address (SourceAddr) field 14, and a destination address (DestAddr) field 15. Typically, the subframe header field 11 separates MSDUs to help the receiver indicate whether the frame was sent to the receiver. Typically, the MSDU length field 13 includes a length, the source address field 14 includes an address of a transmitter, and the destination address field 15 includes an address of a receiver. Typically, two or more MSDUs are grouped together to form an A-MSDU 10.

Another type of aggregation may be formed by concatenating multiple MAC Protocol Data Units (MPDUs) together. Fig. 2 shows an example of an aggregate MPDU (a-MPDU) frame 20. The a-MPDU frame 20 includes a plurality of MPDU delimiter fields 21 and a plurality of MPDU fields 22 (labeled MPDU)₁…MPDU_n). Each MPDU delimiter field 21 also includes a reserved field 31, MSDU length field 24, Cyclic Redundancy Check (CRC) field 25 and unique pattern field 26. The a-MPDU frame 20 is typically transmitted in a single aggregate PLCP service data unit (a-PSDU). In addition, except in MPDU_nIn the case of (1), if necessary, a padded octet (octet) is appendedExpressed) such that each MPDU field 22 has four octets in length.

One purpose of the MPDU delimiter field 21 is to fragment the MPDUs 22 in the set. For example, the structure of the aggregation may generally be restored when one or more MPDU delimiters are received in error. Also, the single MPDU delimiter field 21 has the same Block Error Rate (BER) as the surrounding MPDUs 22 and can therefore be discarded in transmission.

One benefit of using a-MPDU frames 20 is that unlike a-MSDUs, a-MPDU frames 20 can be aggregated to multiple receivers. That is, a multi-receiver assembly (MRA) may include MPDUs addressed to multiple receivers. Further, the MRA may be transmitted in one of two contexts, distinguished by whether it is transmitted in the MMP/PSAD sequence. If multiple responses are required, the multiple responses are scheduled by the transmission of an MMP or PSAD frame.

Fig. 3 shows a typical multi-receiver aggregate multipoint poll (MMP) frame 30. The MMP frame 30 includes a frame control field 31, a duration field 32, a Receiver Address (RA) field 33, a Transmitter Address (TA) field 34, a number of receivers (N) field 35, a receiver information (info) field 36, and a Frame Check Sequence (FCS) field 37. The RA field 33 is typically a broadcasted group address. The TA field 34 is typically the address of the wireless transmit/receive unit (WTRU) that sent the MRA set. The number of receivers (N) field 35 includes the number of receivers whose MPDUs are included in the MRA set.

In addition, the receiver information field 36 includes a plurality of subfields, such as an Association Identifier (AID) field 61, a Transmission Identifier (TID) field 62, a new PPDU flag field 63, a reserved field 64, a receive (Rx) offset field 65, an Rx duration field 66, a transmit (Tx) offset field 67, and a Tx duration field 68. The AID field 61 identifies the Station (STA) addressed by the frame. The TID field 62 defines the TID transmitted by the STA. The new PPDU flag field 63 indicates that the Downlink (DL) start of the STA is at the beginning of the PPDU. The Rx offset field 65 defines the start of the first symbol containing DL data for the STA. The Rx duration field 66 defines the length of the downlink. The Tx offset field 67 defines the time at which transmissions by the STA may begin, while the Tx duration field 68 defines the duration limit of the transmissions.

Fig. 4 shows a typical power saving set descriptor (PSAD) frame 40. The PSAD frame 40 includes a frame control field 41, a duration field 42, an RA field 43, a TA field 44, a Basic Service Set Identifier (BSSID) field 45, a PSAD Parameter (PARAM) field 46, a number of receivers field 47, and an FCS field 48. The PSADPARAM field 46 further includes a reserved field 71, a more PSAD indicator 72, and an end of descriptor field 73. The number of receivers field 47 includes a plurality of individual station information fields, which further include a reserved field 81, a sta id field 82, a downlink transmission (DLT) start offset field 83, a DLT duration field 84, an uplink transmission (ULT) start offset field 85, and a ULT duration field 86.

The MMP/PSAD frame may be transmitted in non-aggregate or may also be aggregated with downlink MPDUs. Since the MMP/PSAD frame format defines the receive and transmit duration of each STA, STAs are enabled to enter sleep mode when neither receiving nor transmitting, thereby saving power. Meanwhile, since MMP sequences are protected using a Network Allocation Vector (NAV) and Extended PHY Protection (EPP), MMP provides a mechanism for scheduling multiple transmission opportunities (TXOPs).

Fig. 5A shows an MMP/PSAD downlink frame exchange sequence 50 and fig. 5B shows an MMP/PSAD uplink frame exchange sequence 55. In PSAD, the time periods of downlink transmission (DLT) and uplink transmission (ULT) are described by PSAD frame 40. Which time period is planned to be used to transmit frames from/to the PSAD transmitter to one of the PSAD receivers is also described by the PSAD frame 40.

In particular, fig. 5A and 5B show the start offsets from DLT1 to DLTn, and ULT1 to ULTn. Similarly, in MMP, offsets from downlink transmission RX1 to RXn series and uplink transmission TX1 to TXn series are shown.

Aggregation at the PHY level layer is also possible for a physical layer (PHY) protocol data unit (PPDU). Such a set may be referred to as a set PPDU (A-PPDU). The A-PPDU comprises one or more pairs of PLCP headers and PPDU or PHY service data unit PSDU. To form an a-PPDU, two or more PPDUs (or PSDUs) are grouped together, separated by a high throughput signal (HT-SIG) field.

FIG. 6 shows a typical aggregate PPDU (A-PPDU) 60. The A-PPDU60 includes a legacy preamble (L-preamble) 91, a high throughput preamble (HT-preamble) 92, a plurality of PSDU fields 93 (PSDUs)₁…PSDU_n) And a plurality of HT-Signal (HT-SIG) fields 94 (HT-SIG)₁…HT-SIG_n). The HT-SIG field 94 may also include a length field 95, an MCS field 96, an advanced decoding field 97, a sounding packet 98, a number HT-legacy training field (HT-LTF) 99, a short GI field 101, an 20/40 field 102, a Cyclic Redundancy Check (CRC) field 103, and a suffix field 104.

As shown in FIG. 6, the A-PPDU60 generated is a combination of all PPDUs (or PSUDs) in the A-PPDU along with HT-SIG94 of the PSDU93 of each element. Since each PSDU93 shown in fig. 6 is partitioned by HT-SIG94 defining different physical layer parameters, the a-PPDU includes multiple rate PSDUs.

However, one drawback in existing systems is that when the MMP/PSAD is transmitted by the AP, it is possible that one or more STAs associated with the MMP/PSAD may not receive correctly or decode the MMP/PSAD frame incorrectly. In these cases, STAs that fail to correctly receive or decode MMP/PSAD frames will miss their scheduled uplink transmission time, severely wasting WLAN transmission time.

It would therefore be advantageous if there were a method and apparatus that could be used as a mechanism to recover the structure of the a-PPDU90 in the event that one or more of the HT-SIG94 or PSDU93 were received in error due to poor channel conditions. Further, it would be advantageous to have a method and apparatus in which an AP recovers any unutilized ULT that can send multiple MMP/PSAD frames and can schedule multicast and broadcast transmissions in the MMP/PSAD frames.

Disclosure of Invention

A method for transmission management of a wireless medium in a wireless communication system including at least one Access Point (AP) and a plurality of Stations (STAs), the method comprising the AP equipping the plurality of STAs with a multi-receiver aggregate multi-poll/power save set descriptor (MMP/PSAD) frame with modulated uplink transmission time (ULT) information. The AP then sends the MMP/PSAD frame to multiple STAs. Upon successful reception and decoding of the MMP/PSAD frame, the STA transmits during the STA's scheduled ULT.

Drawings

The foregoing summary, as well as the following detailed description of preferred embodiments according to the present invention, will be better understood when read in conjunction with the appended drawings, wherein:

FIG. 1 shows an example of an A-MSDU frame;

FIG. 2 shows an example of an aggregate MPDU (A-MPDU) frame;

FIG. 3 illustrates a typical multiple receiver aggregate multipoint poll (MMP) frame;

FIG. 4 illustrates a typical power saving set descriptor (PSAD) frame;

FIG. 5A shows an MMP/PSAD downlink frame exchange sequence;

FIG. 5B shows an MMP/PSAD uplink frame exchange sequence;

FIG. 6 shows a typical aggregate PPDU (A-PPDU);

fig. 7 illustrates a wireless communication system configured in accordance with the present invention;

fig. 8 is a functional block diagram of an AP and STA configured to perform a method of transmission management according to the present invention;

fig. 9 is a flow chart for managing transmission time in the wireless communication system shown in fig. 7 according to an embodiment of the present invention;

fig. 10 is an exemplary signal diagram of downlink and uplink exchange in the wireless communication system shown in fig. 7 according to an embodiment of the present invention;

fig. 11 is an exemplary signal diagram of downlink and uplink exchanges in a wireless communication system 100 in which a particular STA fails to successfully receive and decode downlink and uplink scheduling information of the STA;

FIG. 12 is a flow diagram of a method of restoring media according to an embodiment of the invention;

fig. 13 is an exemplary signal diagram of downlink and uplink exchanges in a wireless communication system illustrating a broadcast or multicast MMP/PSAD transmitted during a broadcast of the downlink phase; and

fig. 14 is an exemplary signal diagram of downlink and uplink exchanges in a wireless communication system, illustrating a broadcast or multicast MMP/PSAD transmitted between the downlink and uplink.

Detailed Description

In the following, a Station (STA) includes, but is not limited to, a wireless transmit/receive unit (WTRU), a User Equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, or any other device capable of operating in a wireless environment. When referred to hereafter, an Access Point (AP) includes but is not limited to a base station, a node B, a site controller, an access point, or any other interfacing device in a wireless environment.

Fig. 7 illustrates a wireless communication system 100 configured in accordance with the present invention. The wireless communication system 100 may be a Wireless Local Area Network (WLAN) in a preferred embodiment and includes an AP110 and a plurality of STAs 120 (labeled STA1, STA2, and STA 3) capable of wireless communication with the AP 110. The AP110 is in the preferred embodiment connected to a network 130, the network 130 being, for example, the internet, a Public Switched Telephone Network (PSTN), etc. In this way, STA120 may access network 130 through AP 110. Although only three STAs 120 are shown in the wireless communication system 100, it should be noted that any number of STAs 120 may be present in the wireless communication system 100 and communicate with the AP 110.

Fig. 8 is a functional block diagram of an AP110 in communication with STAs 120 configured to perform a transmission management method in the wireless system 100.

In addition to the components typically included in a typical AP, the AP110 includes a processor 115 configured to manage transmissions in the wireless communication network 100, a receiver 116 in communication with the processor 115, a transmitter 117 in communication with the processor 115, and an antenna 118 in communication with the receiver 116 and the transmitter 117 to facilitate wireless transmission and reception. Additionally, in a preferred embodiment, the processor 115 may be in communication with a network 130.

In addition to the components typically included in a typical STA, the STA120 includes a processor 125 configured to manage transmissions in the wireless communication system 100, a receiver 126 in communication with the processor 125, a transmitter 127 in communication with the processor 125, and an antenna 128 in communication with the receiver 126 and the transmitter 127 to facilitate wireless transmission and reception.

Fig. 9 is a flow chart 900 for managing transmission times in the wireless communication system 100 in accordance with an embodiment of the present invention. In step 910, the AP110 configures an MMP/PSAD frame to signal to the STA120 the transmission time of the STA120 in the UL phase. In particular, the MMP/PSAD frame schedules downlink and uplink frame exchanges for a subsequent duration specified in the duration field of the MMP/PSAD. For example, the AP110 may implement the scheduling by arranging the order of the PSAD descriptor fields (or MMP receiver information fields) according to an increased value of the Rx/DLT start offset or according to the transmission order when the Rx/DLT start offset is equal. The above scheduling is particularly useful when the AP110 transmits a-PPDU containing multiple PPDUs to the multi-receiver STA 120. In addition, the AP110 constructs the TA field (34, 44) using its own identifier, e.g., its MAC address, and constructs the RA field using the address of the target receiver. In one embodiment, the RA field may be constructed using the MAC address of the STA120 to which the MMP/PSAD frame is to be sent.

The AP110 then sends an MMP/PSAD frame to the STA120 (step 920). Each particular STA120 then receives the MMP/PSAD frame (step 930). If a particular STA120 successfully receives and decodes the MMP/PSAD frame (step 940), the STA120 extracts the STA's transmission time from the MMP/PSAD frame (step 950). If the STA120 cannot successfully receive and decode the MMP/PSAD frame (step 940), the AP110 recovers the medium (step 970), which will be described in detail below.

In one example, the STA120 extracts the time information of the individual PPDUs forming the a-PPDU set. The STA120 receiving the MMP/PSAD frame can derive HT-SIG time information of the STA120 from the offset field and duration field defined in the MMP/PSAD frame. In particular, the Rx (or DLT) start offset and duration fields are used for the purpose of extracting HT-SIG time information of the A-PPDU, thereby improving the reliability of the A-PPDU aggregation scheme. This also simplifies the implementation of the receiver.

For purposes of illustration, it may be assumed that one set of MMP/PSAD exchanges is the A-PPDU set. For STAs 120 in the MMP/PSAD frame identified as having downlink data in the MMP/PSAD exchange, the MMP/PSADRx offset and Rx duration fields of the previous station may be used to determine the start time of the STA's HT-SIG field. However, this sharing of Rx offset information only occurs if two stations have the same Rx offset. Otherwise, the Rx offset of the particular STA120 is used. Thus, by adding the Rx offset and Rx duration of the previous station, the particular STA120 may determine when the PPDUHT-SIG of that STA120 begins.

Alternatively, the particular STA120 may use multiple previous fields of the MMP/PSAD frame instead of only one previous field, e.g., only previous station information. Such a change is useful, for example, when the Rx duration field is defined not to relate to the usual Rx offset but to the actual duration of the data PPDU. In this case, the particular STA120 may need to perform a full addition of all previous Rx duration fields.

In another alternative, a field or bit is added to the MMP/PSAD descriptor field or MMP receiver information field. The field or bit distinguishes whether the time information relates to an MPDU of the a-MPDU set or to the start of a PPDU of the a-PPDU set. For example, the added field may be used to indicate that a particular STA120 should receive and decode HT-SIG on this Rx offset, preamble training field, or MPDU delimiter field.

If there is no MMP/PSAD in the transmitted a-PPDU, it should be protected using Network Allocation Vector (NAV) setting or spoofing (spoofing) because the irregular error probability and error propagation will interfere with power savings, medium access, and NAV of other STAs 120 in the system. For example, the a-PPDU from AP110 may provide NAV and/or EPP protection by clearing a send (CTS) -to-self (self) transmission first. The a-PPDU from the non-ap sta120 may provide NAV and EPP protection through an RTS/CTS exchange.

Once the STA120 extracts its time information (step 950), the STA120 transmits within the transmission time of the STA120 in the UL phase (step 960).

Fig. 10 shows an exemplary signal diagram for downlink and uplink exchanges for the wireless communication system 100 in accordance with the method 900 described above. AP110 transmits MMP/PSAD frames including downlink and uplink scheduling information for STA1, STA2, and STA 3. In the downlink phase, AP110 transmits downlink information for STA1, STA2, and STA3, labeled D1, D2, and D3. If each STA120 successfully receives and decodes the MMP/PSAD frame, each STA120 (STA 1, STA2, and STA 3) receives respective downlink information during respective scheduled times, D1, D2, and D3, respectively. In the uplink phase, STA1 transmits at the scheduled uplink time of STA1 (U1), STA2 transmits at the scheduled uplink time of STA2 (U2), and STA3 transmits at the scheduled uplink time of STA3 (U3). In this way, each STA120 knows when it needs to start up to receive downlink data associated with it, or transmit during its scheduled uplink time. Thus, each STA120 may power down during the time period it knows not to be scheduled to transmit or receive, thereby saving it energy.

Since the scheduling of the uplink and downlink frame exchanges is scheduled in the MMP/PSAD frame, STAs 120 that did not successfully receive and decode the MMP/PSAD frame (step 940) will not know their timing and may miss their opportunity to transmit on the UL. Since there is no mechanism for preventing or recovering from such a situation occurring, the time of the medium may be wasted. To prevent such a situation from occurring, the AP110 should resume the medium (step 970).

Fig. 11 is an exemplary signal diagram 101' of a downlink and uplink exchange in a wireless communication system 100 in which a particular STA120 (in this example STA 2) has not successfully received and decoded its downlink and uplink scheduling information in step 940. Thus, STA2 does not transmit during its scheduled uplink time (U2').

Fig. 12 shows a flow diagram of a method 970 of restoring a medium according to one embodiment of the invention. In step 980, the AP110 monitors the medium to detect whether a particular STA120 transmits within its scheduled UL time. The AP110 may use the time information in the MMP/PSAD frame to determine when the medium should be monitored (step 980), or the AP110 may continue to monitor the medium.

If AP110 monitors that STA120 is not engaged in uplink transmissions by STA120 at its scheduled time, AP110 may reclaim the medium (step 990).

Referring again to fig. 11, the AP110 monitors the uplink phase and detects that STA1 transmits uplink data for STA1 during its scheduled uplink window (U1). The AP110 will then detect STA2, e.g., no transmission in STA 2's scheduled uplink transmission window (U2'). After waiting for the idle period, the AP110 will reclaim the medium (step 990).

In a preferred embodiment, the idle period is a predetermined period that the AP110 will wait to give the STA120 sufficient opportunity to begin transmitting during the STA 120's uplink time before the AP110 regains the medium. For example, the idle time period may be equal to the point control function interframe space (PIFS) time period. If the AP110 is not transmitting, the AP110 monitors the medium during the MMP/PSAD exchange period (step 980), or the AP110 may monitor the medium only during the time periods during which each STA120 is transmitting in the uplink, since the AP110 may know the time periods during which each STA120 is transmitting in the uplink.

Alternatively, the AP110 may monitor the medium for frame errors or collisions that occur in the uplink phase and make decisions about reclaiming the medium based on those observations. In addition, the AP110 may decide to cancel MMP/PSAD in order to transmit or schedule data traffic with higher priority than what the AP110 has already described. For example, the AP110 may wish to improve quality of service (QoS) requirements for particular traffic or to schedule control traffic.

At any rate, once the AP110 has decided to reclaim the medium in step 990, there are several ways the AP110 can achieve this.

One way the AP110 can reclaim the medium is by rescheduling DLT or ULT transmissions (step 991). In the preferred embodiment, the AP110 achieves this by transmitting a frame that indicates to all or selected STAs 120 that these STAs 120 should ignore the previously transmitted MMP/PSAD frame (step 992). The frame may have a variety of formats.

For example, the frame transmitted in step 992 may be a newly defined frame for resetting or canceling a preferred MMP schedule, or any control, management, or data frame that may be configured to instruct the STA120 to reset a preferred MMP/PSAD schedule.

However, in a preferred embodiment, the AP110 forwards another MMP/PSAD frame. The MMP/PSAD frame may be an initial MMP/PSAD frame but includes a field specifying that previous scheduling information should be ignored by all or selected STAs 120. Alternatively, the MMP/PSAD frame may be the same as the previously transmitted MMP/PSAD frame, but with defined rules specifying that if STA120 receives an MMP/PSAD frame, then STA120 will ignore any scheduling information received from any prioritized MMP/PSAD frame.

The NAV duration of the new MMP/PSAD, or any frame used to cancel or reset the prioritized MMP/PSAD schedule, may be used to reset or update the NAV at the receiving STA 120. Another frame, such as a CFEND frame, may likewise be used to reset the NAV duration of the STA 120. Alternatively, the wireless communication system 100 may be configured such that the duration of the most recent MMP/PSAD frame replaces any locally stored NAV duration at the STA 120.

Another way the AP110 can reclaim the medium is by sending a poll frame to STAs 120 that did not transmit during the scheduled transmission time (step 993). The polling frame may include a contention free Poll (CF-Poll), a QoS Poll, another MMP/PSAD frame, and the like. Alternatively, the AP110 may transmit the polling frame to STAs 120 other than the scheduled STAs for uplink transmission. The STA120 receiving the polling frame will then begin transmitting in response to the polling frame (step 994). If the STA120 has data to transmit, the STA120 will transmit the data. Otherwise, the STA120 will send an acknowledgement frame, QoS null frame (QoSNull), data null frame (DataNull), or another frame to indicate that the STA120 does not have any data to send.

Another way in which the AP110 may reclaim the medium is by sending downlink data, and in the preferred embodiment a Reverse Direction Grant (RDG) signal, as shown in step 995. For example, the AP110 may transmit downlink data to any STAs 120 that the AP110 desires, or the AP110 may transmit any control or management frames during this period. Upon receiving the downlink data and the RDG signal, the receiving STA transmits its own uplink data for its duration (step 996). Even if the AP110 does not have any downlink data to transmit, the AP110 may continue to transmit data null frames, QoS null frames, etc. to indicate that the non-transmitting STA should begin transmitting for its particular duration.

For example, referring back to fig. 11, if AP110 detects that the medium is idle for too long in the uplink transmission (U1) time of STA1, AP110 sends downlink data and RDG to STA 2. Upon receiving the downlink data and RDG, the STA2 transmits data for STA2 in STA2 for a particular duration (U2').

If STA120 has no data to transmit in the uplink, the STA120 should transmit a response frame to the AP110, such as a Qos null frame, a data null frame, etc., to indicate to the AP110 that the STA has no data to transmit during its allocated uplink time. The AP110 may therefore reclaim the medium and take some other remedial action to avoid wasting the medium, such as polling another STA120 to begin its transmission.

Another way the AP110 can reclaim the medium is by sending redundant MMP/PSAD frames (step 997). This redundant MMP/PSAD frame may repeat some or all of the ULT information during the time period when the STA120 misses the transmission window during the uplink phase. This is particularly useful if more than one STA120 does not successfully receive or decode the MMP/PSAD frame. If the AP110 detects that a certain event occurred in the wireless communication system 100 during a previous MMP/PSAD exchange sequence, or because the AP110 has specific knowledge of ULT information or the number of STAs 120, the AP110 may also decide to utilize redundant MMP/PSAD frames, which makes it more appropriate to transmit redundant MMP/PSAD.

For example, the AP110 may have detected in a previous MMP/PSAD frame exchange that certain STAs 120 did not transmit their information in their scheduled uplink time. In this case, the AP110 may determine that redundant MMP/PSAD frames will be sent in the next MMP/PSAD exchange to increase the probability that all STAs 120 will properly receive their scheduled ULTs.

Additionally, the AP110 may know that there are a large number of STAs 120 in the wireless communication system 100 and thus increase the probability that any particular STA120 will fail to receive that STA's ULT information in the first MMP/PSAD. Similarly, the AP110 may know about the ULT schedule for most STAs 120 in the wireless communication system 100, meaning that if one STA120 fails to receive the first MMP/PSAD, a significant amount of wasted bandwidth may occur if that STA is unable to transmit in its scheduled ULT. In these cases, sending redundant MMP/PSAD frames increases the probability that all STAs 120 in the system utilize their scheduled ULTs, reducing wasted bandwidth. Importantly, the AP110 can utilize the duration of individual ULTs, the total duration of all ULTs, and the number of STAs 120 with ULTs in comparison to a predetermined threshold to decide whether redundant MMP/PSAD frames should be transmitted.

Referring again to fig. 11, assume that not only does STA2 not successfully receive and decode the MMP/PSAD frame, STA3 is likewise unsuccessful. In this case, STA2 and STA3 would miss their scheduled transmission times absent remedial measures by AP 110. Thus, if AP110 detects too long an idle period following the uplink transmission of STA1 (U1), AP110 sends redundant MMP/PSAD frames. In this way, STA3 receives redundant MMP/PSAD frames and transmits data for STA3 in a scheduled uplink window (U3) of STA3, thereby limiting further waste of medium.

In yet another alternative embodiment of the present invention, the AP110 may schedule broadcast or multicast frames utilizing MMP/PSAD frames. To perform this, AP110 must reconfigure the existing PSAD frame 40 of the MMP/PSAD frame, since the current format specifies STA ID field 82 as the association ID of STA 120. Therefore, in order to support the transmission of broadcast or multicast frames in the MMP/PSAD sequence, the existing PSAD frames 40 should be reconfigured.

One way to reconfigure the PSAD frame 40 is to include a bit or field in the MMP/PSAD frame. In a preferred embodiment, this bit or field is contained in the station information field. For example, a bit may be included in the reserved field 81 of the station information field, specifying that the broadcasted frame is to be transmitted with the specified DLT parameters, and that the STA should remain awake during this period. Alternatively, for a specific value of the STA id field 82, for example, all "1's" may be used to indicate that a broadcasted frame is to be transmitted and that the STA should remain awake during this period. That is, the STAID field 82 should set all bits to "1".

Fig. 13 is an exemplary signal diagram for downlink and uplink exchanges for the wireless communication system 100 in which a broadcast or multicast MMP/PSAD is transmitted during the broadcast phase of the downlink phase. In this example, the AP110 sends the first MMP/PSAD before the downlink phase, which indicates some or all STAs 120 that should listen during the broadcast interval that occurs at the end of the downlink phase. At the end of the downlink phase, the AP110 may send a frame, and preferably an additional MMP/PSAD frame to confirm the ULT scheduling. In this manner, STAs 120 will receive their ULT schedule twice and are therefore less likely to miss their uplink transmission times.

Alternatively, AP110 may insert a second MMP/PSAD frame at the first MMP/PSAD frame exchange sequence by including a unicast MMP/PSAD entry in the first MMP/PSAD frame, the unicast MMP/PSAD entry describing the Tx start offset and Tx duration at which the second MMP/PSAD frame is to be transmitted. As an example, the entry may include any MAC address of any STA120 as a virtual receiver address. The entry may also include inaccurate Tx start offset and Tx duration information. At the end of the downlink phase, the AP110 may send frames and preferably additional MMP/PSAD frames to confirm the ULT scheduling. In this manner, only STAs 120 that did not successfully receive and decode the first MMP/PSAD frame will remain awake or awakened to receive and decode the second MMP/PSAD frame, while those stations that successfully received and decoded the first MMP/PSAD frame will not need to wake up to receive and decode the second MMP/PSAD frame. This is because those STAs 120 that successfully receive and decode the first MMP/PSAD frame know that the second MMP/PSAD frame is not intended for them. Alternatively, no information about the second MMP/PSAD frame can be transmitted in the first MMP/PSAD frame.

Fig. 14 is an exemplary signal diagram 141 for downlink and uplink exchanges for the wireless communication system 100 in which a broadcast or multicast MMP/PSAD is transmitted between a downlink phase and an uplink phase. In this example, the AP110 inserts a second MMP/PSAD frame in the first MMP/PSAD frame, but the AP110 does not include any entry in the first MMP/PSAD frame to describe the second MMP/PSAD frame. The AP110 then transmits a second MMP/PSAD frame to verify the ULT scheduling in the interval between the downlink phase and the uplink phase, as shown in fig. 14. In this case, only STAs 120 that did not successfully receive and decode the first MMP/PSAD frame wake up to receive the second MMP/PSAD frame, since those STAs 120 that did successfully receive and decode the first MMP/PSAD frame will not wake up until they need to wake up based on their successful decoding of the first MMP/PSAD frame.

Importantly, however, it should be noted that AP110 should account for the effects of the inserted or nested MMP/PSAD frames during the ULT offset and duration calculations of AP 110. Otherwise, the AP110 will not be able to keep in synchronization with the offsets, and the STAs 120 think they need to follow the offsets.

Such nested or redundant MMP/PSAD frames may or may not contain the same information as the first MMP/PSAD frame. In a preferred embodiment, however, the MMP/PSAD frame may contain ULT information for STA120, and typically contains information consistent with the first MMP/PSAD frame. That is, the second MMP/PSAD frame should contain the same scheduling information as contained in the first MMP/PSAD frame.

Although in the foregoing embodiments, the AP110 is described as monitoring the medium for determining whether to reclaim the medium, the STA120 may also monitor the medium for further improving system performance. Generally, the STA120 receiving the ULT scheduling information of the STA120 in the MMP/PSAD frame does not perform sensing of the medium. They simply blindly start their transmissions with their scheduled ULT. However, in some instances it may be desirable to have these STAs 120 monitor the medium instead of or in addition to the AP 110. In one embodiment, the STA120 may monitor the medium for any idle period. If the STA120 detects that the idle period continues to exceed the predetermined threshold, the STA then transmits its uplink transmission for the remaining ULT duration, thereby avoiding collisions with other STAs while maximizing the use of the medium.

Although fig. 1 depicts only one AP110, it may equally be used for several APs present in a wireless communication system. In this case, some STAs in the wireless communication system may associate with one AP and other STAs may associate with other APs, which may present some difficulties. In one scenario, one of the APs (AP 1) may be associated with an Overlapping Basic Service Set (OBSS) or a co-channel BSS with another AP (AP 2). If AP1 were to send a MMP/PSAD frame, STAs associated with AP2 could ignore the MMP/PSAD frame after receiving it because they did not see any indication in the RA field that the frame was intended for them and entered sleep. If the AP2 then transmits traffic during this time, the intended STA will not be able to receive this information because it is already in a sleep state during the transmission.

Thus, a STA120 receiving a MMP/PSAD frame may be configured to read the TA field in the frame to determine whether the MMP/PSAD frame was transmitted from an AP associated with the STA. If the STA determines that the AP address in the TA field is the address of the AP associated with the STA, the STA may decode downlink transmissions and perform uplink transmissions according to the contents of the MMP/PSAD frame and enter sleep mode at other times. Conversely, if the STA determines that the AP that sent the MMP/PSAD frame is not the AP with which the STA is associated, the STA ignores the frame, but continues to remain awake to receive any transmissions that may have been sent from the AP with which the STA is associated. Additionally, however, the STA may wish to read the duration ID value in the MMP/PSAD frame and update the NAV duration of the STA, even if the frame is not transmitted from an associated AP. In this way, the STA will know when the medium is in use and can avoid transmitting during these times.

In another alternative embodiment of the invention, the MMP/PSAD frame may be used to poll certain types of packets, such as Block Acknowledgement (BA) response frames. In this case, the AP110 may indicate to a particular STA120 that the particular STA120 transmits their BA response frame in their scheduled ULT using one or more flags in the MMP/PSAD frame. The flag may also indicate to the STAs 120 whether the STAs 120 transmit only BA response frames during their scheduled ULT, or whether the STAs 120 transmit BA response frames along with other frames that the STA is transmitting. This replacement facilitates the addition of new schemas to existing schemas of BAs.

Currently, existing BA modes include immediate block ACK and delayed block ACK. In immediate block ACK mode, the STA responds to a BA request (BAR) immediately following the SIFS delay. In the delayed block ACK mode, the STA decides on its own when to transmit a BA frame.

This alternative embodiment includes polling for delayed BAs as opposed to BAs sent by STAs at any time. For example, the AP110 may send a BAR to the STA120 to indicate to the STA120 that the STA120 should prepare a BA packet or BA frame, and to instruct the STA120 to only send the packet when it receives another poll message from the AP 110. The polling message may be in the form of MMP or another packet sent by AP 110. This provides AP110 with the ability to determine when STAs 120 for association transmit their BA frames, rather than having STAs decide themselves when to transmit BA frames.

The above-described features may be implemented in a wireless transmit/receive unit (WTRU), a base station, and/or a peer node device. The above method may be applied to the physical layer and/or the data link layer. Applicable forms of the specific implementation include Application Specific Integrated Circuits (ASICs), middleware, and software. The invention can be applied to OFDM/MIMO systems and IEEE802.11 compliant systems.

In addition, the features of embodiments of the present invention may be implemented in various ways, such as in an application running on a WTRU, AP, or STA, for example. These features may be incorporated into an Integrated Circuit (IC) or be configured in a circuit comprising a plurality of interconnected components. Further, these features may be performed by a software application running on the IC or a software application running on the processor.

Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone (without the other features and elements of the preferred embodiments) or in various combinations with or without other features and elements of the present invention.

Examples

1. A method for transmission management for a wireless communication system including at least one Access Point (AP) and a plurality of Stations (STAs).

2. The method of embodiment 1, further comprising: the AP configures a multi-receiver aggregate multi-poll/power save set descriptor (MMP/PSAD) frame with scheduled uplink transmission time (ULT) information for the plurality of STAs.

3. The method of any preceding embodiment, further comprising: the AP sends MMP/PSAD frames to multiple STAs.

4. The method of any preceding embodiment, further comprising: a STA that successfully receives and decodes the MMP/PSAD frame transmits during its scheduled ULT.

5. The method of any preceding embodiment, wherein the MMP/PSAD frame includes a duration field specifying a duration for the ULT and a downlink transmission time (DLT).

6. The method of any preceding embodiment, wherein the AP arranges the order of the PSAD descriptor fields included in the MMP/PSAD frame according to an incremented value included in a receiver (Rx) DLT start offset field of the MMP/PSAD frame.

7. The method of any preceding embodiment, wherein the AP arranges the order of MMP receiver information fields included in the MMP/PSAD frame according to an incremented value included in a receiver (Rx) DLT start offset field of the MMP/PSAD frame.

8. A method as in any preceding embodiment, wherein the MMP/PSAD frame comprises a Transmitter Address (TA) field and a plurality of receiver fields.

9. A method as in any preceding embodiment, wherein an AP fills a TA field with its own identifier and a plurality of receiver fields with identifiers identifying intended recipient STAs.

10. A method as in any preceding embodiment, wherein the AP identifier comprises a Media Access Control (MAC) address of the AP.

11. A method as in any preceding embodiment, wherein the STA identifier comprises a MAC address of the STA.

12. The method of any preceding embodiment, further comprising: STAs that successfully receive and decode the MMP/PSAD frame extract the time information from the MMP/PSAD frame.

13. A method as in any preceding embodiment wherein a transmitting STA derives its high throughput signal (HT-SIG) timing from an offset field and duration field specified in the MMP/PSAD frame.

14. The method of any preceding embodiment, wherein the offset field comprises an Rx or DLT start offset field.

15. The method of any preceding embodiment, wherein the MMP/PSAD frame comprises an aggregate physical layer protocol data unit (a-PPDU).

16. A method as in any preceding embodiment wherein a transmitting STA reads the Rx offset and Rx duration fields of STAs scheduled for prioritized immediate transmission to determine the start of the STA's own HT-STG field.

17. A method as in any preceding embodiment wherein a transmitting STA adds the Rx offset and Rx duration values contained in the Rx offset and Rx duration fields of a STA that is transmitting immediately prior to determining the STA's own start time.

18. A method as in any preceding embodiment wherein a transmitting STA adds values contained in the Rx duration fields of all priority transmitting STAs to determine its own start time.

19. The method of any preceding embodiment, further comprising: a field is added in the MMP/PSAD descriptor field.

20. The method of embodiment 19 wherein the added field indicates that the time information of the particular STA is related to the beginning of a Mac Pdu (MPDU) in the a-MPDU set.

21. The method of embodiment 19 wherein the added field indicates that the time information of the particular STA is related to the start of a PPDU in the set of a-PPDUs.

22. The method of any preceding embodiment, further comprising: a field is added in the MMP receiver information field.

23. The method of embodiment 22 wherein the added field indicates that the time information of the particular STA is related to the beginning of a Mac Pdu (MPDU) in the a-MPDU set.

24. The method of embodiment 22 wherein the added field indicates that the time information of the particular STA is related to the start of a PPDU in the set of a-PPDUs.

25. A method as in any preceding embodiment wherein STAs that successfully receive and decode MMP/PSAD frames enter sleep mode during periods when STAs are not required to transmit or receive data in the wireless communication system.

26. The method of any preceding embodiment, further comprising: the AP recovers the wireless communication system transmission medium.

27. The method of any preceding embodiment, further comprising: the AP monitors the wireless communication system transmission medium.

28. A method as in any preceding embodiment wherein an AP continuously monitors a wireless communication system transmission medium.

29. A method as in any preceding embodiment wherein an AP monitors a wireless communication system transmission medium for a specified period of time.

30. A method as in any preceding embodiment wherein the AP determines a time period for monitoring the wireless communication system transmission medium based on time information contained in the MMP/PSAD frame.

31. A method as in any preceding embodiment wherein an AP detects that a particular STA is not transmitting during its scheduled ULT.

32. The method of any preceding embodiment, further comprising: the AP reclaims the wireless communication system transmission medium.

33. The method of any preceding embodiment, further comprising: the AP waits a predetermined period of time after detecting that a particular STA is not transmitting during the STA's scheduled ULT before reclaiming the wireless communication system transmission medium.

34. The method as in embodiment 33 wherein the predetermined period of time is a predetermined idle period of time.

35. The method as in any one of embodiments 33-34 wherein the predetermined idle period comprises a point control function interframe space (PIFS) period in the wireless communication system.

36. A method as in any preceding embodiment wherein reclaiming of the wireless communication system transmission medium comprises the AP rescheduling the ULT and DLT.

37. A method as in any preceding embodiment wherein the AP transmits an additional frame to at least one STA to indicate that the at least one STA should ignore a previously transmitted MMP/PSAD frame.

38. A method as in any preceding embodiment wherein an AP sends additional frames to all STAs in a wireless communication system.

39. The method as in embodiments 1-37 wherein the AP transmits additional frames to selected STAs in the wireless communication system.

40. The method of any preceding embodiment, wherein the additional frame comprises a control frame.

41. A method as in any preceding embodiment, wherein the additional frame comprises a data frame.

42. The method of any preceding embodiment, wherein the additional frame comprises a management frame.

43. A method as in any preceding embodiment wherein the additional frame is an additional MMP/PSAD frame.

44. The method of any preceding embodiment, wherein the additional MMP/PSAD frame includes a field indicating to at least one STA to ignore previous scheduling information.

45. A method as claimed in any preceding embodiment, wherein the additional MMP/PSAD frame is substantially identical to the previous MMP/PSAD frame.

46. The method of any preceding embodiment, further comprising: the Network Allocation Vector (NAV) duration is updated at least one STA.

47. The method of any preceding embodiment, wherein the updating of the NAV duration comprises sending a contention-free END (CF-END) frame to the at least one STA.

48. A method as in any preceding embodiment wherein the reclaiming of the wireless communication transmission medium comprises sending a polling frame to a particular STA.

49. The method of any preceding embodiment, wherein polling frames comprise one of the group consisting of contention free polling (CF-Poll), quality of service (QoS) polling, and MMP/PSAD frames.

50. A method as in any preceding embodiment wherein a particular STA is an STA that does not transmit during its scheduled ULT.

51. The method of any preceding embodiment, wherein the particular STA is an STA other than the STA that did not transmit during the STA's scheduled ULT.

52. The method of any preceding embodiment, further comprising: the particular STA transmits in response to the polling frame.

53. A method as in any preceding embodiment wherein a particular STA sends data in response to the polling frame.

54. The method of any preceding embodiment, wherein a particular STA sends an acknowledgement frame, QoS null frame, or data null frame in response to the polling frame.

55. The method of any preceding embodiment, wherein the reclaiming of the wireless communication transmission medium comprises the AP sending downlink data and a Reverse Direction Grant (RDG) signal to at least one STA.

56. The method of any preceding embodiment, further comprising: the AP transmits a management frame to at least one STA.

57. The method of any preceding embodiment, further comprising: the AP transmits a control frame to at least one STA.

58. A method as in any preceding embodiment wherein an AP transmits downlink data to STAs other than STAs that did not transmit during their scheduled ULT.

59. A method as in any preceding embodiment wherein an AP transmits downlink data to STAs that are not transmitting during their scheduled ULT.

60. A method as in any preceding embodiment wherein an AP sends a data null frame or a QoS null frame.

61. The method of any preceding embodiment, further comprising: the STA transmits uplink data in response to reception of the RDG.

62. The method of any preceding embodiment, further comprising: the STA transmits a data null frame or a QoS null frame in response to receipt of the RDG.

63. The method of any preceding embodiment, further comprising: the AP polls another STA to start transmitting.

64. A method as in any preceding embodiment wherein retraction of the wireless communication system transmission medium comprises sending redundant MMP/PSAD frames.

65. A method according to any preceding embodiment, wherein a redundant MMP/PSAD frame includes all ULT information included in a previous MMP/PSAD frame.

66. A method as in any preceding embodiment wherein the AP sends redundant MMP/PSAD frames during the downlink phase.

67. A method as in any preceding embodiment, wherein the AP sends redundant MMP/PSAD frames between the downlink phase and the uplink phase.

68. The method of any preceding embodiment, further comprising: the AP reclaims the medium in response to detecting a transmission collision in the uplink phase.

69. The method of any preceding embodiment, further comprising: the AP reclaims the medium in response to detecting a frame error in the uplink phase.

70. The method of any preceding embodiment, further comprising: the AP sends redundant MMP/PSAD frames based on prior knowledge of conditions in the wireless communication system.

71. In a wireless communication system including at least one Access Point (AP) and a plurality of Stations (STAs), a method for transmission management of a wireless medium, the method comprising: the AP configures a multi-receiver aggregate multipoint poll/power save aggregate descriptor (MMP/PSAD) frame to include information about the broadcast frame in an MMP/PSAD exchange sequence.

72. The method of embodiment 71, further comprising: the AP sends the MMP/PSAD frame to a plurality of STAs.

73. The method as in any one of embodiments 71-72, further comprising: STAs that successfully receive and decode the MMP/PSAD frame operate according to the information contained in the broadcast frame.

74. The method of any of embodiments 71-73, further comprising: the AP transmits the broadcast frame.

75. The method as in any one of embodiments 71-74 wherein the AP includes an additional field in a station info field of the MMP/PSAD frame.

76. The method as in any one of embodiments 71-75 wherein the AP includes a bit in a reserved field of the station information field.

77. A method as in any of embodiments 71-76 wherein a bit specifies that a broadcast frame is to be transmitted with a specified downlink time parameter, the bit also specifying that the STA should not enter sleep mode for this duration.

78. A method as in any of embodiments 71-77 wherein a bit specifies that all STAs in the wireless communication system should not enter sleep mode for the duration of time.

79. A method as in any of embodiments 71-77 wherein a bit specifies that a selected STA in a wireless communication system should not enter a sleep mode for the duration.

80. The method as in any one of embodiments 71-79 wherein the broadcast frame is an MMP/PSAD frame.

81. The method as in any one of embodiments 71-80 wherein the AP sends a broadcast frame at the end of the downlink phase.

82. The method as in any one of embodiments 71-81 wherein the AP includes unicast MMP/PSAD entries in the MMP/PSAD frame.

83. The method as in embodiment 82 wherein the entry indicates a transmit (Tx) start offset and a Tx duration when the broadcast frame is to be transmitted.

84. The method as in any one of embodiments 71-83 wherein the entry comprises a virtual receiver address.

85. The method as in any one of embodiments 71-84 wherein the entries further comprise inaccurate Tx start offset and Tx duration entries.

86. The method as in any one of embodiments 71-85 wherein STAs that successfully receive and decode MMP/PSAD frames enter sleep mode during broadcast frames.

87. The method as in any one of embodiments 71-86 wherein the AP sends a broadcast frame between an uplink phase and a downlink phase.

88. The method of any of embodiments 71-87 wherein the broadcast frame is substantially the same MMP/PSAD frame as a previously sent MMP/PSAD frame.

89. The method of any preceding embodiment, further comprising: the STA monitors the wireless communication system transmission medium for a predetermined idle period.

90. The method of embodiment 89, further comprising: if the STA detects that an idle period in a transmission medium of the wireless communication system exceeds a predetermined idle period, the STA transmits its own uplink information.

91. A method for transmission management of a wireless medium in a wireless communication system including a plurality of Access Points (APs) and a plurality of Stations (STAs), each STA associated with a particular AP.

92. The method of embodiment 91, further comprising: the first AP configures a multi-receiver aggregate multi-poll/power save set descriptor (MMP/PSAD) frame with scheduled uplink transmission time (ULT) information for STAs associated with the first AP.

93. The method as in any one of embodiments 91-92 further comprising: the first AP sends MMP/PSAD frames to the plurality of STAs.

94. The method as in any one of embodiments 91-93, further comprising: the STA receives the MMP/PSAD frame and determines whether the MMP/PSAD frame is intended for the STA.

95. The method as in any one of embodiments 91-94 wherein a Transmitter Address (TA) field in the MMP/PSAD frame comprises an address of the first AP.

96. A method as in any of embodiments 91-95 wherein a STA reads a TA field in a MMP/PSAD frame to determine whether an AP that sent the MMP/PSAD frame is an AP associated with the STA.

97. A method as in any of embodiments 91-96 wherein a STA that receives a MMP/PSAD frame determines that the AP that sent the MMP/PSAD frame is not an AP associated with the STA.

98. The method as in any one of embodiments 91-97 wherein the STA enters a sleep mode.

99. The method as in any one of embodiments 91-97 wherein the STA does not enter sleep mode.

100. The method as in any one of embodiments 91-99 wherein the STA reads the value in the duration ID field.

101. A method as in any of embodiments 91-96 wherein a STA that receives a MMP/PSAD frame determines that the AP that sent the MMP/PSAD is the AP with which the STA is associated.

102. The method of embodiment 101 wherein the STA decodes downlink and uplink transmission information contained in the MMP/PSAD frame.

103. The method as in any one of embodiments 101-102 wherein the STA enters the sleep mode in a time period not scheduled for downlink or uplink.

104. The method of any preceding embodiment, further comprising: the AP configures a multi-receiver aggregate multi-poll/power save aggregate descriptor (MMP/PSAD) frame for polling a Block Acknowledgement (BA) response frame and having scheduled uplink transmission time (ULT) information.

105. A method as in any preceding embodiment, wherein a STA that successfully receives and decodes a MMP/PSAD frame transmits its BA response frame during its scheduled uplink transmission time.

106. A method as in any preceding embodiment, wherein a STA that successfully receives and decodes a MMP/PSAD frame only transmits the STA's BA response frame during the STA's scheduled uplink transmission time.

107. The method of any preceding embodiment, further comprising: the AP transmits an additional polling message to the STA to transmit a BA response frame of the STA.

108. The method of embodiment 107 wherein the additional polling message is an MMP frame.

109. The method of any preceding embodiment, further comprising: a wireless communication system transmission medium is monitored.

110. The method of any preceding embodiment, further comprising: the wireless communication system transmission medium is reclaimed when a predetermined event is detected.

111. The method as in any one of embodiments 109-110 wherein the predetermined event comprises detection of a frame error in an uplink phase.

112. The method as in any one of embodiments 109-111 wherein the predetermined event comprises detection of a collision between transmitted data in an uplink phase.

113. The method as in any one of embodiments 109-112 wherein the predetermined event comprises detection of new higher priority traffic.

114. An Access Point (AP) configured to perform the method of any of the preceding embodiments.

115. The AP of embodiment 114, further comprising a receiver.

116. The AP as in any one of embodiments 114 and 115, further comprising a transmitter.

117. The AP as in any one of embodiments 114 and 116 further comprising a processor in communication with the receiver and the transmitter.

118. The AP as in any one of embodiments 114 and 117, wherein the processor is configured to: configuring a multi-receiver aggregate multi-poll/power save set descriptor (MMP/PSAD) frame with scheduled uplink transmission time (ULT) information for a plurality of STAs.

119. The AP as in any one of embodiments 114 and 118, wherein the processor is configured to: sending the MMP/PSAD frame to a plurality of STAs.

120. The AP as in any one of embodiments 114-119, wherein the processor is configured to: a wireless communication system transmission medium is monitored to detect whether a STA transmits during its scheduled uplink transmission time.

121. The AP as in any one of embodiments 114-120, wherein the processor is configured to reclaim the wireless communication system transmission medium.

122. A Station (STA) configured to perform the method of any of embodiments 1-113.

123. The STA of embodiment 122, further comprising a receiver.

124. The STA as in any embodiments 122-123 further comprising a transmitter.

125. The STA as in any one of embodiments 122-124 further comprising a processor in communication with the receiver and transmitter.

126. The STA as in any embodiments 122-125, wherein the processor is configured to: a multi-receiver aggregate multi-poll/power save set descriptor (MMP/PSAD) frame with scheduled uplink transmission time (ULT) information is received.

127. The STA as in any embodiments 122-126, wherein the processor is configured to: the scheduled ULT of the STA is determined.

128. The STA as in any embodiments 122-127, wherein the processor is configured to: transmitted during the ULT scheduled by the STA.

129. The STA as in any embodiments 122-128, wherein the processor is configured to: the wireless communication system transmission medium is monitored for idle periods exceeding a predetermined threshold.

130. The STA as in any embodiments 122-129, wherein the processor is configured to: the uplink data is transmitted after detecting an idle period exceeding a predetermined threshold.

131. A wireless transmit/receive unit (WTRU) configured to perform the method of any of embodiments 1-113.

132. The WTRU as in embodiment 131 further comprising a receiver.

133. The WTRU as in any one of embodiments 131-132 further comprising a transmitter.

134. The WTRU as in any one of embodiments 131-133 further comprising a processor in communication with the receiver and the transmitter.

135. The WTRU as in any one of embodiments 131-134 wherein the processor is configured to: configuring a multi-receiver aggregate multipoint poll/power save set descriptor (MMP/PSAD) frame with scheduled uplink transmission time (ULT) information for other WTRUs.

136. The WTRU as in any one of embodiments 131 through 135 wherein the processor is configured to: sending the MMP/PSAD frame to other WTRUs.

137. The WTRU as in any one of embodiments 131-136 wherein the processor is configured to: reclaiming the wireless communication system transmission medium.

138. The WTRU as in any one of embodiments 131-137 wherein the processor is configured to: receiving the MMP/PSAD with scheduled uplink transmission time (ULT) information.

139. The WTRU as in any one of embodiments 131-138 wherein the processor is configured to: transmitting during a scheduled ULT of the WTRU.

140. The WTRU as in any one of embodiments 131-139 wherein the processor is configured to: the wireless communication system transmission medium is monitored for idle periods exceeding a predetermined threshold.

141. The WTRU as in any one of embodiments 131 through 140 wherein the processor is configured to: the uplink data is transmitted after detecting an idle period exceeding a predetermined threshold.

Claims (23)

1. A method for transmission management of a wireless medium, the method comprising:

receiving and decoding a multi-receiver aggregate multipoint poll/power save aggregate descriptor (MMP/PSAD) frame including uplink transmission time (ULT) information scheduled for a plurality of station STAs;

extracting time information related to one of the plurality of STAs from the MMP/PSAD frame; and

the STA transmitting during a ULT scheduled for one of the plurality of STAs.

2. The method of claim 1, wherein the MMP/PSAD frame includes a duration field specifying a duration of the ULT and downlink transmission time, DLT.

3. The method of claim 2, wherein the order of the PSAD descriptor fields included in the MMP/PSAD frame is arranged according to an incremental value contained in a receiver RxDLT start offset field of the MMP/PSAD frame.

4. The method of claim 2, wherein the order of MMP receiver information fields included in the MMP/PSAD frame is arranged according to an incremental value contained in a receiver RxDLT start offset field of the MMP/PSAD frame.

5. The method of claim 1, wherein the MMP/PSAD frame comprises a transmitter address, TA, field and a plurality of receiver fields.

6. The method of claim 5, wherein the TA field is populated with an identifier of a transmitting Access Point (AP) and the plurality of receiver fields are populated with identifiers of intended recipient STAs among the plurality of STAs.

7. The method of claim 6, wherein the identifier of the transmitting AP comprises a Media Access Control (MAC) address of the AP.

8. The method of claim 6, wherein the identifier of the intended recipient STA comprises a MAC address of the intended recipient STA.

9. The method of claim 1 wherein a transmitting STA derives high throughput signal HT-SIG timing for the transmitting STA from an offset field and a duration field specified in the MMP/PSAD frame.

10. The method of claim 9, wherein the offset field comprises an Rx or DLT start offset field.

11. The method of claim 10, wherein the MMP/PSAD frame comprises an aggregate physical layer protocol data unit, a-PPDU.

12. The method of claim 11, wherein the transmitting STA reads an Rx start offset field and an Rx duration field of an STA scheduled for transmission immediately prior to the transmitting STA to determine the start of an HT-SIG field of the transmitting STA.

13. The method of claim 11, wherein the transmitting STA adds an Rx offset value and an Rx duration value contained in an Rx start offset and Rx duration field of an STA transmitting immediately prior to the transmitting STA to determine a start time of the transmitting STA.

14. The method of claim 11, wherein the transmitting STA adds values contained in Rx duration fields of all priority transmitting STAs to determine a start time of the transmitting STA.

15. The method of claim 1, wherein the MMP/PSAD descriptor field includes a field indicating that the time information for a STA is related to the start of a mac pdu in a-MPDU set.

16. The method of claim 1, wherein the MMP/PSAD descriptor field includes a field indicating that the time information of a STA is related to a start of a PPDU in a set of a-PPDUs.

17. The method of claim 1, wherein the MMP receiver information field comprises a field indicating that the time information for a STA is related to a start of a mac pdu in a-MPDU set.

18. The method of claim 1, wherein the MMP receiver information field includes a field indicating that the time information of a STA is related to a start of a PPDU in a-PPDU set.

19. The method of claim 1, wherein one of the plurality of STAs enters a sleep mode during a time period in which it does not need to transmit or receive data in a wireless communication system.

20. An access point, AP, comprising:

a receiver;

a transmitter; and

a processor in communication with the receiver and the transmitter, the processor configured to configure a multi-receiver aggregate multipoint poll/power save set descriptor (MMP/PSAD) frame with scheduled uplink transmission time (ULT) information for a plurality of Station (STAs), transmit the MMP/PSAD frame to the plurality of STAs, and monitor a wireless medium to detect whether one of the plurality of STAs transmits during the STAs' scheduled uplink transmission time.

21. The AP of claim 20, wherein the processor is further configured to recover the wireless medium.

22. A station, STA, comprising:

a receiver;

a transmitter; and

a processor in communication with the receiver and the transmitter, the processor configured to receive a multi-receiver aggregate multi-poll/power save set descriptor (MMP/PSAD) frame with scheduled uplink transmission time (ULT) information, determine a scheduled ULT for the STA, transmit during the scheduled ULT of the STA, and monitor a wireless medium for idle periods exceeding a predefined threshold.

23. The STA of claim 22, wherein the processor is further configured to transmit uplink data after detecting an idle period that exceeds the predefined threshold.