Method and apparatus for determining and managing congestion in a wireless communications system

The present invention relates to the field of wireless communication. More specifically, the present invention provides a means for determining and managing congestion (communication line congestion) using a carrier sense multiple access (CSMA / CA) mechanism. For wireless local area network (WLAN) systems that further enhance network management by providing novel medium access control (MAC) measurements in wireless communications.

Wireless communication systems are well known in the art. Generally, such systems include communication stations that send and receive wireless communication signals between each other. Depending on the system type, a communication station is typically one of two types: a base station or a radio transmit / receive unit (WTRU), including a mobile unit (mobile).

As used herein, the term base station refers to a base station, node B, site controller, access point, or other interface in a wireless environment that provides the WTRU with wireless access to the network to which the base station is associated. Devices are included, but not limited to the above.

As used herein, the term WTRU includes user equipment, mobile stations, fixed or mobile subscriber units, pagers, or any other type of device that can operate in a wireless environment. However, it is not limited to the above. WTRUs include personal communication devices such as telephones, video telephones, and Internet-enabled telephones with network connectivity. In addition, WTRUs include personal computing devices such as PDAs and notebook computers with wireless modems with similar network capabilities. A WTRU that is portable or otherwise mobile is called a mobile unit. Generally, the base station is also WTRU.

Usually, a network of base stations is provided so that each base station can perform wireless communication at the same time as a properly configured WTRU group. Some WTRUs are configured to communicate wirelessly with each other directly, that is, without being relayed over a base station in the network. This is commonly referred to as peer-to-peer wireless communication. When a WTRU is configured to communicate with another group of WTRUs, the WTRU itself is configured as a base station and can function as a base station. The WTRU has both network capability and peer-to-peer communication capability and can be configured to be used in multiple networks.

One type of wireless system, called a wireless local area network (WLAN), is configured to communicate wirelessly with a group of WTRUs equipped with a WLAN modem that can also perform peer-to-peer communication with a group of WTRUs with similar provisions. Is possible. Currently, WLAN modems are incorporated into many traditional communication and computing devices by manufacturers. For example, a cellular phone (mobile phone), a personal digital assistant (personal digital assistant), and a laptop computer (notebook computer) are built with one or more WLAN modems.

A typical local area network environment, typically with one or more WLAN base stations, called an access point (AP), is built according to a set of IEEE 802.11 standards. The exemplary 802.11 Local Area Network (LAN) shown in Figure 1 is based on an architecture in which the system is divided into cells. Each cell contains a basic service set (BSS) that contains at least one AP for communicating with one or more WTRUs, commonly referred to as stations (STAs) in the context of 802.11 systems. Communication between the AP and STA is based on the IEEE 802.11 standard, which defines the wireless interface between the wireless STA and the wired network.

A wireless LAN (WLAN) can be formed by a single BSS with a single AP, with a portal (entrance) to the distribution system (DS). However, an installation usually consists of several cells, and APs are connected via a backbone called DS.

A mobile ad hoc network (MANET) is also shown in Figure 1. MANET is a self-configuring network of mobile routers (and related hosts) connected by wireless links, and the coupling of routers forms an arbitrary topology (connection form). Routers are free to move randomly and organize themselves arbitrarily, so the radio topology of a network can change rapidly and unpredictably. Such networks may operate stand-alone (a proprietary method that is not connected to the network) or may be connected to the larger Internet.

WLANs connected to each other, including various cells, their respective APs, and DSs, are considered a single IEEE 802.11 network and are referred to as the Extended Services Set (ESS). IEEE 802.11 networks typically use carrier sense multiple access (CSMA / CA) protocols to wirelessly exchange information between nodes (ie, STAs) in a WLAN network. In the above framework, the STAs wishing to transmit are naturally competing for access to the wireless medium. Competing mechanisms include waiting for a medium to remain idle for a period of time (according to a set of rules specified by the standard) before sending a data packet. The time it takes for a node to access a channel and send packets for that node increases as the number of stations and data traffic (data access volume) increases. Congestion in such systems can occur when the time it takes to gain access to a medium becomes unacceptable because too many stations are competing for the same medium. ..

Due to the nature of the CSMA / CA protocol and given that most transmissions are best effort, it is extremely difficult to determine when a system is classified as experiencing congestion. .. Determining congestion in such a complex system is a simple task, as one selected metric (metric) may indicate congestion while another metric may not. Absent.

Some metrics that can be used to indicate congestion include collision rate and channel uptime, i.e., how long the medium is in use. However, these metrics, when measured individually, do not necessarily give a true picture of congestion. For example, the channel uptime metric does not give an accurate picture of the congestion situation. There is only one station on a channel, and it is possible that it is transmitting at all times. In that case, the channel uptime metric is high. The system may appear unable to support further traffic from other stations. However, if a new station accesses the channel, the station may still experience good throughput, thanks to the CSMA / CA mechanism. That is because the channel is then evenly shared between the two stations. The system is competing for the same channel at a given point in time, with serious delays due to longer times and more conflicts, where each station has to wait for access to the medium. If there are several stations that you are experiencing, you are actually congested.

In another aspect, limited network management capabilities currently exist, especially in systems that comply with the IEEE 802.11 and IEEE 802.11k standards. We have recognized that in the context of network management, there are some limitations to the usefulness of the channel load information currently in use. There is also a need for improved methods to achieve better network management, given the limitations of using channel load measurements. The present invention provides enhanced network management associated with the IEEE 802.11 and IEEE 802.11k standards in the context of channel load information.

<p> The present invention provides a method for determining and advertising congestion in a wireless local area network (WLAN) system. The present invention also provides a method for managing congestion when it is detected. One aspect of the invention applies to wireless systems using CSMA / CA. Preferably, several metrics are used to determine congestion, including: That is, the average time of the backoff procedure, the deferral rate within the basic service set (in the BBS), the delay rate outside the BSS, the number of related stations, the average WTRU channel uptime, and the average buffer medium access control (MAC) occupancy. The rate. The steps taken to mitigate congestion are preferably to sort the set of WTRUs in descending order of wasted time spent trying to send packets with / without acknowledgments, and to mitigate congestion. It involves detaching each WTRU one by one until it is done.</p><p> The invention also provides an improved method of network management, preferably through the use of two new MAC measurements, especially in the context of the IEEE 802.11 standard and the IEEE 802.11k standard. More specifically, the two new measurements include the STA uplink traffic load measurement and the access point (AP) service load measurement.</p>

<p> The present invention includes the consideration of a Management Information Base (MIB) display of transmit queue sizes, which provides new measurements of STA transmit load for unserved queued traffic requests. The present invention further includes consideration of the MIB display of the AP service load, which provides new measurements of the AP service load used to assist the STA in making handoff decisions. Implementation of the above features is possible as software or in any other convenient form. The above aspects of the invention are generally applicable to Layer 1 and Layer 2 applied to IEEE 802.11k compliant systems in the context of, for example, Orthogonal Frequency Division Multiple Access (OFDM) and Code Division Multiple Access 2000 (CDMA2000) systems. Is. However, the present invention also has general applicability to other scenarios.</p><p> The present invention is advantageously carried out in various forms of selectively constructed WTRUs.</p><p> A more detailed understanding of the present invention can be obtained from the following description of preferred embodiments which are given by way of example and should be understood in connection with the accompanying drawings.</p>

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

One aspect of the invention introduces two different approaches for measuring load metrics for channel congestion: That is, first, a basic services set (BSS) -based load metric that is primarily based on the load of individual APs. Second, a channel-based load metric, which is a metric that shows the load shared among the various APs.

BSS-based load metrics are metrics that determine high load conditions and high channel congestion. Two preferred BSS-based load metrics are the intra-BSS delay rate metric and the packet error rate metric.

The deferral rate (DR) is that the AP has one or more packets to send (ie, the AP's queue is not empty), but the AP's receiver is carrier-locked (ie). That is, it is a measure that represents the percentage of time (clear channel assessment (CCA) indicates in-use conditions). That is, the DR represents the amount of time the AP spends deferring transmissions to other WLAN nodes.

Intra-BSS delay rate means that the AP has one or more packets to send, but the receiver of the AP originates from an intra-BSS packet (ie, one of the WTRUs associated with the BSS). Represents the percentage of time the carrier is locked. That is, the intra-BSS DR is spent by the AP deferring its own transmission because one of the WTRUs associated with the AP dominates the medium (ie, is sending the packet). Represents the amount of time.

The deferral rate within the BSS indicates the level of current load the system is receiving and was spent deferring the transmission if it needed to be transmitted to another node within the same BSS. By measuring the time. A low BSS deferral metric indicates a low load on that BSS. A high BSS delay rate indicates that there are many nodes transmitting at the same time, and therefore a considerable load.

In the case where there are only two nodes in the system with a significant amount of data to send, the delay rate can be high and will show congestion when used alone. However, this is not considered a congestion situation as there are only two nodes in the system. To address these situations, the present invention uses packet error rate (PER) in addition to the delay rate metric.

Packet error rate (PER) is the ratio of the number of failed transmissions (ie, packet transmissions for which an ACK was not received) to the total number of packets transmitted. The PER metric is a good indication of collision rates in a system when modest data transmission rates are used. The greater the number of nodes in the system, the higher the probability of collision. Using both the intra-BSS delay rate metric and the PER metric together provides a better view of the AP load than using either metric individually.

In the present invention, as shown in FIG. 2, in step S1 and step S3, the intra-BSS delay rate metric and the PER metric are measured, respectively, and then in step S2 and step S4, respectively, a predefined period (eg, eg). , 30 seconds). The average of both metrics is used in steps S5 and S6 to signal that congestion has occurred. More specifically, over a given period (eg, 30 seconds), the intra-BSS delay rate (DR) metric exceeds the first predefined threshold as determined in step S5, and the PER metric is stepped. If the determination in S6 exceeds the second predefined threshold, this is an indication of congestion.

Whether congestion is detected based on the criteria described above or other techniques for determining congestion are used, the present invention provides the following actions. That is, first, in step S7, the AP sorts all WTRUs in the basic service set (BSS) in order of the amount of time spent trying to retransmit. The wasted time is preferably the wasted time algorithm ALG described below._{wt wt}It is calculated according to. More specifically, a set or list of WTRUs with unacknowledged packets is created. For each unacknowledged packet to the WTRU, the sum of all wasted time spent trying to send and retransmit the packet (ie, penalty for each packet retransmitted to packet size / packet transmission rate) The value obtained by adding) is recorded. The penalty reflects the increased delay associated with retransmissions, that is, the backoff (transmission delay after a collision on the network) time due to the doubling of the congestion frame (CW). The penalty represents the additional delay incurred from the time the packet is ready to be transmitted to the time the packet is actually transmitted over the medium. Therefore, the above retransmission time metric is very large for stations that waste time retransmitting packets after a collision. The retransmission time metric is normalized over the selected time period.

An exemplary formula for determining the wasted time for WTRU is given by: That is,

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However, wated_time_WTRU= Total wasted time spent trying to send unacknowledged packets to WTRU and resend them j = jth packet i = i-th transmission of j-th packet #_pkts_j= # Of the jth packet transmission, eg 1, 2, 3, ... Pkt_size_ij= Bit size of the i-th transmission of the jth packet Pkt_tx_rate_ij= Transmission rate in bps of the i-th transmission of the jth packet RTx_{i&gt; 1}=2^i-2However, if i&gt; 1, otherwise 0, Penalty = CW_min^*Slot time, eg CW_min= 32 and slot time = 20 microseconds Note: CW is 2xCW after the first transmission_min#_pkts_jNote that is consistent with the number of unacknowledged transmissions of a given packet. If the packet is finally successfully sent, #_pkts_jExactly matches the number of retransmissions. If the packet is dropped (ie never sent successfully), #_pkts_jMatches (number of retransmissions + 1).

wated_txtime_STAAn example of is given below. That is, Suppose the AP has 20 packets to send to a particular STA. During multiple transmissions, the AP monitors and records, for example, whether the packet was successfully acknowledged and the number of packet retransmissions, as follows: GGGGGBBB BBB GGGGG GGGGGG BBB GGGG However, = Increase in rate = Decrease in rate G = Acknowledgment, i.e., "good" frame B = No acknowledgment, i.e. "bad" frame The first B is the 6th packet, and there were 6 transmissions of that 6th packet, i.e. BBB BBB. #_pkts₆= 6 Pkt_size_i6= 12000 bits Pkt_tx_rate_i6= {11.0, 11.0, 11.0, 5.5, 5.5, 5.5} Mbps RTx_{i&gt; 1}^*Penalty = {0.0, 640.0, 1280.0, 2560.0, 5120.0, 10240.0} μs The 7th B is the 17th packet, and there were 3 transmissions of the 17th packet, that is, BBB . #_pkts₁₇= 3 Pkt_size_i17= 8000 bits Pkt_tx_rate_i17= {11.0, 11.0, 11.0} Mbps RTx_{i&gt; 1}^*Penalty = {0.0, 640.0, 1280.0} μs Therefore, wasted_txtime_STA= (12000 / 11e6) + (12000 / 11e6 + 640.0) + (12000 / 11e6 + 1280.0) + (12000 / 5.5e6 + 2560.0) + (12000 / 5.5e6 + 5120.0) + (12000 / 5.5e6 + 10240.0) + (8000 / 11e6) + (8000 / 11e6 + 640.0) + (8000 / 11e6 + 1280.0) = 33.76ms

Preferably, the WTRUs are sorted from maximum time to minimum time in steps S7-S4. The program then proceeds to step S8. In step S8 (Figure 2), each STA from the sorted list is detached from the largest time first until the congestion is alleviated.

The present invention also allows the use of other metrics, including: That is, the BSS-based load metric, the number of associated WTRUs, and the access point (AP) receive all ACKs (acknowledgements) (eg, fragmentation) associated with the packet in medium access control (MAC). Time and average buffer MAC occupancy (based on buffer size).

The present invention further provides a method of taking into account the load of neighboring AP groups when assessing the need for a system to perform either load shedding (ie, decoupling) or load balancing. For example, as shown in FIG. 3, if the load on each AP in the neighboring AP group, which is collected in steps S9 and S10 and compared to the neighboring AP group in steps S11 and S12, is also high, the user may be in another location. Load shedding is delayed (step S14) because it is unlikely to be serviced at, i.e., because L1, L2, and L3 are all high (step S13). Load shedding is done in step S16 if L1 or L2 has a lower load than the advertised load (regular delivery of the latest information needed for network management) (step S15B). If the L3 load is less than L1 and L2, the AP can accept the WTRU, as shown in steps S15A and S17.

Since the access point (AP) advertises the load to multiple stations (WTRU group) of the AP, for example, comparing the load of the AP to the neighboring AP group, that is, AP (x) and AP (y). Can be done. When the AP load is high compared to the estimated load of the AP's neighboring AP group, the AP advertises the high load in response to the determination in step S15A (FIG. 3). If the AP load is low compared to the estimated load in the vicinity of the AP, the AP advertises the low load in response to the determination in step S15B.

Another method of the invention is to use metrics to measure media (eg, channel) loads. The metric allows the WTRU to select the least loaded AP. A BSS with an intra-BSS channel load can simply be left to the neighboring BSS, so the intra-BSS channel load is not valid, as is the case when the AP load is low but the medium load is high. In the case, the media load metric is used. In that case, the advertised load shall represent the medium load. In that case, the AP advertises only low loads if it can support the new WTRU.

The metric that gives an indication of the media load is the average time (Avg D) required to perform the backoff procedure determined in the manner shown in Figure 4 for downlink transmission at the AP. More specifically, this metric is measured in steps S18-S23, which advertises AvgD to the WTRUs in step S24 and initiates a CSMA / CA access conflict when the packet is ready to be sent. ), Represents the medium access delay incurred by the packet before it begins transmitting over the medium.

The size of the conflict slot affects the time required to perform the backoff procedure. The competition slot size is increased whenever the acknowledgment is not received from the receiving node. This aspect includes cases where collisions occur between nodes of the same BSS or between nodes of different BSS. During the countdown of the backoff procedure, the countdown is suspended whenever it senses that the medium is in use, which increases the time of the backoff procedure. This further aspect includes cases where the medium is heavily loaded due to the WTRU group of the proprietary BSS and / or the WTRU group of the neighboring BSS group. This metric alone provides a good indication of the congestion perceived by that node in the BSS. You can also consider simply using the time the medium is in use (channel uptime) as a metric. However, in an embodiment where only one WTRU is associated with the access point (AP) and is sending or receiving large amounts of data, the channel uptime metric does not give a good indication of congestion. Channel uptime actually shows high congestion when the system only supports one user. A second user (WTRU) added to the AP can be easily supported. In the single user example, the new proposed Avg.D metric (ie, the average time to perform the backoff procedure) correctly indicates low congestion.

The AvgD metric is a preferred measure because the short time required for the backoff procedure indicates a lightly loaded medium when the long time indicates a heavily loaded medium. As an example, consider the current IEEE 802.11b standard. The minimum value of the competition frame (CW) is 32 x 20 microseconds = 640 microseconds, and the maximum value is 1023 x 20 microseconds = 20.5 milliseconds. However, the time required to perform the backoff can be greater than the maximum size of the CW provided by the pause in the countdown due to sensing the medium in use. This increase in time gives an indication of the load due to the activity of the medium.

Reasons for using MAC load measurements in the context of the present invention include: That is, The MAC layer has a lot of information that is not currently available via the Management Information Base (MIB) or through measurements in the IEEE 802.11 and IEEE 802.11k standards. New information items provided by the present invention that are useful for higher layers can be provided within 802.11k, but are not currently available. -IEEE802.11e has identified channel uptime (CU) as a useful load information item.

The present invention also recognizes the need for WTRU uplink load information and AP service load information. Some of the limitations of CU information include: That is, -Load information is useful for handoff determination in WTRU and AP. Potential target AP CU information is useful for WTRU when evaluating handoff options. CU is the sum of the uplink-capable load (from all WTRUs to APs) and the downlink-capable load (from APs to all WTRUs), also known as channel uptime. The traffic load, however, consists of two parts: a supported traffic load and an unenabled (queued) traffic load. The CU does not currently provide dynamic unenabled queued traffic load information.

The network has no current way to access unserved uplink traffic requests (queued traffic load).

Benefits of WTRU Uplink Traffic Load Measurements (UTLM) in network management include: That is, A high channel load indicates a serviced traffic that is close to the maximum value. This is optimal channel management when unsupported traffic demands are low. · If unsupported traffic demands are high, this is not optimal. · Unsupported uplink traffic requests are extremely helpful in allowing APs to better split frame-time uplink and downlink segments. APs need to manage channels for maximum traffic uptime and minimum traffic block. Queued uplink traffic in the WTRU group indicates transmission delays and potential channel blocks. The amount of data queued in the MAC transmit buffer provides a good measure of the queued uplink load.

The present invention provides a new MAC Management Information Base (MAC MIB) element for outbound traffic load, namely, Outgoing Queue Size (TQS). The send queue size (TQS) is defined as follows: That is, the new MIB information includes the following three items. That is, the total transmit queue size (total TQS), which is the sum of the non-conflicting transmit queue size (CFTQS) and the conflicting transmit queue size (CFTQS).

TQS contains the current MAC queue size in bytes. TQS can be included in the MAC MIB802.11 Counters table. The Dot11Counters table is a defined data structure in the standard. The TQS information can be implemented by a counter, as shown in FIG. 5, where the WTRU initializes the TQS counter to 0 at system startup in step S25. The WTRU receives the frame in step S26 and queues the frame in the MAC layer in step S27. In step S28, the WTRU increments the TQS counter by the number of bytes in the queued frame. Alternatively, the cumulative total can be incremented by replacing the PC (current count) with PC + 1, for example, as the count is stored in memory and each byte of the frame is queued. There are software technologies that can be used.

When the session is started, the WTRU sends a frame using the physical (PHY) layer in step S29, and if it is operating in unacknowledged mode, or after the PHY transmission, the AP sends the frame to the frame. When the acknowledgment is made, the TQS counter is decremented by the number of bytes transmitted in step S30. The WTRU transmits the TQS count to the neighboring AP group in step S31. TQS is a new MIB element. All MIB elements are sent to the neighbor as needed via a MIB query that is executed to retrieve the element from the neighboring MIB.

The Conflict Send Queue Size (CTQS) is implemented, for example, as shown in FIG. 6, and the WTRU initializes the CTQS counter to 0 at system startup in step S32. The WTRU MAC layer receives a conflicting frame in step S33 and puts that frame into the MAC layer's conflicting queue in step S34. In step S35, the CTQS counter is incremented by the number of bytes in the received frame.

The WTRU uses the PHY layer to send a frame (for example, to an AP) in step S36 if it is operating in a no-acknowledgement mode, or if the frame is acknowledged after the PHY transmission. Transmit and decrement the CTQS counter by the number of bytes transmitted in step S37, in no acknowledgment mode, or if the frame is acknowledged after the PHY layer transmission. At step S38, the WTRU transmits the CTQS count to the neighboring AP group.

Conflict-free send queue size (CFTQS) is implemented by providing a CFTQS counter, as shown in Figure 7, where WTRU initializes the CFTQS counter to 0 at system startup in step S39.

In step S40, the WTRU MAC layer receives the non-conflict frame and in step S41 puts the frame into the non-conflict queue (CFQ). In step S42, the WTRU increments the CFTQS by the number of bytes in the queued frame.

In step S43, the WTRU uses the PHY layer to send a non-conflicting frame, and in step S44, when the frame is acknowledged in non-acknowledgement mode or after the PHY layer transmission. , Decrease the CFTQS counter by the number of bytes transmitted in the frame. At step S45, the WTRU transfers the count to the neighboring AP group.

FIG. 8 shows one way for APs to utilize MAC MIB information, where APs, for example, in steps S46, S47, and S48, respectively, eg, WTRU (x), WTRU (y), and Receive MAC MIB information from WTRU (z), including one or more TSQ counts, CTQS counts, and CFTQS counts. This data, which represents unsupported traffic, is combined with supported traffic data, such as channel load with both uplink and downlink loads, evaluated by the AP in step S49, and in step S50, eg, traffic. Manage channels with supported and unsupported load data by tailoring traffic to maximize uptime and minimize traffic blocks. APs can adjust the uplink and downlink segments of a frame based on unsupported uplink traffic data to optimize channel uptime.

Considerations for providing AP service load measurements in the context of the present invention include: That is, The WTRU group can consider multiple APs as the target AP group for handoffs. If the two APs have similar channel loads and acceptable signal quality, the WTRU needs the ability to determine which is the better AP. Channel uptime can be optimized by allowing APs to advertise information about their ability to serve existing WTRU sets and further WTRUs. .. This information is similar to the downlink traffic queue measurements for APs, modified by AP-specific information about expected capacity.

The following addresses the AP service load. That is, A new MAC MIB information item is provided to assist WTRU in WTRU handoff determination.

255 values from "currently not serving any WTRU" to "cannot handle new services at all" with a defined center point indicating that the supported load is optimal Quantitative representation of the scale (eg, represented by 8 binary bits). For example: That is, 0 == Not serving any WTRU (idle AP or WTRU is not an AP) 1 to 254 == Scalar display of AP service load 255 == Cannot accept new services at all The exact specifications of this MIB item are processing-dependent and do not have to be strictly specified, and the detailed definition for obtaining maximum uptime can be tailored to the characteristics of a particular network.

The new AP service load can be included in the MAC dot11Counters table, or elsewhere in the MIB.

A WTRU with multiple APs that can be selected as the target AP is shown in steps S51, S52, and S53, respectively, in addition to channel load and acceptable signal quality considerations, as shown in FIG. , AP (x), AP (y), and AP (z) can receive load advertisements, and in step S54, the received APs regularly advertise (update the latest information required for network management). The load (SL scalar) that has been delivered (to be delivered) can be evaluated, so that the determination can be made based on the comparison of the advertised load by the received AP, and in step S55, the AP is determined. select.

AP service load (SL) is a scalar value, such as signal quality and expected capacity based on enabled and unsupported traffic, as well as statistical data. It can be based on other data. AP SL scalars can be created as shown in step S50A of FIG. 8 and advertised to neighboring WTRU groups as shown in step S50B.

The methods described above are preferably performed in a selectively constructed WTRU group. For example, a WTRU can be configured to assist channel management in a wireless network by providing memory devices, processors, and transmitters. The memory device is preferably configured to provide a queue of data frames for the WTRU's Medium Access Control (MAC) layer. The processor is preferably configured to calculate queue size data representing unqueued traffic requests in each WTRU. The transmitter is preferably configured to transmit the queue size data to the access point (AP) of the wireless network so that the receiving AP can utilize the queue size data to help channel management. In particular, the processor initializes the queued data size count to zero at system startup, and when a frame is queued by the WTRU Medium Access Control (MAC) layer, only the number of bytes in the frame. It is configured to increment the counter. Preferably, the processor is configured to decrement the count by the number of bytes in the frame when the frame is transmitted by the WTRU's physical (PHY) layer in unacknowledged mode. Alternatively, the processor decrements the count by the number of bytes in the frame when the frame is transmitted by the WTRU's physical (PHY) layer when the frame is acknowledged after the PHY transmission. It can be configured as follows.

Within such a WTRU, the memory is preferably configured with a Conflict Queue and a Conflict-Free Queue at the Media Access Control (MAC) Layer, and the processor is queued to unqueued traffic for the Conflict Queue. Conflict Send Queue Size (CTQS) data representing requests, conflict-free Send Queue Size (QFTQS) data representing unconstrained queued traffic requests for non-conflict queues, and all of the Media Access Control (MAC) layers It is configured to calculate total transmit queue size (TQS) data that represents unqueued traffic requests for the transmit data queue of.

Also, such a WTRU is preferably a receiver configured to receive from the AP group a service load indicator created by the AP group based on the queue size data received from the WTRU group, and received. It also includes a controller configured to select APs for wireless communication based on load indicators.

An access point (AP) configured to provide channel management over a wireless network to both the access point (AP) group and the wireless transmit / receive unit (WTRU) that can wirelessly communicate with the AP group over the wireless channel. ) Can be provided. The receiver is configured to receive unsupported traffic request data received from a group of WTRUs located within the radio service range of the AP. The AP preferably has a processor configured to calculate a service load indicator based on unsupported traffic request data received from the WTRU group. WTRUs within the AP radio service range include transmitters configured to advertise service load indicators, and WTRUs located within the AP radio service range of the AP use the advertised service load indicators. , Can be useful in selecting the AP of the other party to perform wireless communication. In such APs, the receiver is preferably configured to receive advertised service load indicators from other AP groups, and the processor is preferably advertised, received from other AP groups. It is configured to use the service load index to help determine the operational isolation of the associated WTRU group from communication with the AP.

In another embodiment, the radio transmit / receive unit (WTRU) is configured to manage congestion in the radio communication system defined by the basic service set (BSS). The WTRU has a processor configured to calculate the delay factor (DR) within the basic service set (BSS) and average the DR over a given time interval. Preferably, the processor is also configured to calculate the packet error rate (PER) and average the PER over the time intervals. The memory is configured to store a comparison value that reflects the wasted time spent trying to send data for each WTRU in the WTRUs that are operationally associated with the WTRUs in the BSS. If the average DR and the average PER are greater than a given threshold, work from the WTRU, starting with the WTRU with the stored comparison values, which reflects the maximum time spent trying to send the data. Above, a transceiver (radiotelephone) configured to separate the associated WTRUs is included.

Within such a WTRU, the processor is preferably configured to average the DR and PER over a time interval of as much as 30 seconds, and the transceiver will transmit data for each WTRU operationally associated with the WTRU. It is configured to periodically receive comparison values that reflect the wasted time spent as, and update the memory with those comparison values.

Within such a WTRU, the processor also measures the time it takes for a WTRU to receive a successful acknowledgment (ACK) or a negative acknowledgment (NACK) in response to a transmitted data packet. However, it can also be configured to calculate the comparative wasted time value by summing the measured times during the beacon period and normalizing the total by the beacon period. In that case, the transceiver is preferably configured to periodically send up-to-date comparisons that reflect the wasted time spent trying to send data to other WTRU groups.

The access point AP also provides the WTRU with components that are selectively configured for the wireless transmitter / receiver (WTRU) to select the access point AP of the other party with which it communicates wirelessly in the wireless communication system. It can be configured to assist. Preferably, the receiver is configured to receive advertised load indicators for other AP groups. Processors configured to compare the AP's communication load with received advertised load indicators from other AP groups and calculate the AP's tuned load based on the above comparisons are included. The transmitter is configured to advertise the tuned AP load to the WTRU group. Preferably, the processor is configured to periodically perform the above-mentioned comparison operation and the above-mentioned calculated operation in order for the transmitter to update the load advertised to the WTRU group.

Within such an AP, the transmitter advertises a low load when the processor determines that the AP's communication load is low compared to the advertised load of the other AP groups, and the AP's communication load is high. If the processor determines that the load is higher than the advertised load of other AP groups, it can be configured to advertise the high load. The processor also measures the delay from the time the data packet is ready to be transmitted until the time the packet is actually transmitted to the WTRU, averages the delay over a given period of time, and averages that delay. It is also possible to calculate the communication load of the AP by indicating the load using.

In another embodiment, the base station is configured to disconnect the WTRU group from its operational association with the base station when a congestion condition is detected in the wireless network. For each associated WTRU, the base station calculates the wasted time (Tw) spent trying to send / retransmit unacknowledged packets and is given the wasted time Tw for each associated WTRU. Has a processor configured to normalize over a period of time. A list of associated WTRUs and memory configured to store the normalized wasted time of each of those WTRUs is provided. The transceiver is configured to decouple the WTRU group based on each normalized wasted time of the WTRU to alleviate the congestion, with the WTRU having the highest Tw being decoupled first. Preferably, the processor adds a penalty to the Tw that represents the increased delay associated with retransmission, such as by being configured to calculate the wasted transmission time (Tw) of the WTRU group according to the equations described above. It is configured as follows.

IEEE802.11e supports several access categories (access types), such as voice traffic, video traffic, best effort traffic, and background traffic. In one embodiment, the invention preferably utilizes the AP service load for each access category. The BSS load element contains information about the current station population, traffic level, and service level within the BSS. FIG. 10 shows an example of an element information field according to the present invention.

The Length field shall be set to the number of octets (8 bits) in the subsequent field. The station count field is interpreted as an unsigned integer that indicates the total number of STAs currently associated with that BSS. The station count field is purely an example, if dot11QoSOptionImplemented, dot11QBSSLoadImplemented, and dot11RadioMeasurementEnabled are all true, then it shall not be present in the beacon frame or probe response frame.

The channel utilization field is defined as the percentage of time the AP perceives that the medium is in use, as indicated by the physical or virtual carrier sensing mechanism. This percentage is ((Channel total uptime / (dot11ChannelUtilizationBeaconIntervals)^*dot11BeaconPeriod^*1024))^*Expressed as a moving average of 255), the channel total uptime is defined as the number of microseconds in which the carrier sensing mechanism indicates a channel in-use indication, and dot11ChannelUtilizationBeaconIntervals is the continuous beacon interval for which the average should be calculated. Represents a number. The channel utilization field shall not be present in the beacon frame or probe response frame if dot11QoSOptionImplemented, dot11QBSSLoadImplemented, and dot11RadioMeasurementEnabled are all true.

AP service load shall be a scalar representation of the relative level of service load in the AP. A low value shall indicate more available service capacity than a higher value. A value of 0 shall indicate that the AP is not currently servicing any STA. Values from 0 to 254 are the average medium access for DCF transmit packets measured from the time the DCF packet is ready to be transmitted (ie, start CSMA / CA access) to the actual start of packet transmission. It is assumed that the display is represented by a logarithmic scale of delay. A value of 1 shall represent a delay of 50 microseconds, whereas a value of 253 shall represent a delay of 5.5 ms, or any delay greater than 5.5 ms. A value of 254 shall indicate that additional AP service capacity is not available. A value of 255 shall indicate that the AP service load is not available. The AP shall use the DCF access mechanism to measure and average the media access delay for all transmitted packets over a predetermined grace period, such as a 30 second measurement window. The accuracy for average media access delay shall be within +/- 200 microseconds when averaged over at least 200 packets.

The access category (AC) service load factor is BSS only in the quality of service (QoS) enhanced AP (QAP) group. It can be provided in Load. The AC service load is a scalar representation of the average access delay (AAD) in QAP for services in the directed access category. A low value shall indicate a shorter access delay than a higher value. A value of 0 shall indicate that the QAP is not currently providing the services of the indicated AC. Values from 0 to 254 are measured from the time the EDCF packet is ready to be sent (ie, the CSMA / CA access is initiated) to the actual packet transmission start time, and are for the transmit packet transmit packet of the indicated AC. It is assumed that the display is represented by a logarithmic scale of the average medium access delay. A value of 1 represents a delay of 50 microseconds, whereas a value of 253 represents a delay of 5.5 ms, or any delay greater than 5.5 ms. A value of 254 shall indicate that the service at the indicated AC is currently blocked or suspended. A value of 255 shall indicate that the AC service load is not available.

The QAP shall measure and average the media access delay for all transmitted packets of the indicated AC using the EDCF access mechanism over a predetermined grace period, such as a continuous 30 second measurement window. The accuracy of the average media access delay shall be within +/- 200 microseconds when averaged over at least 200 packets. The AC service load is preferably shown in FIG. 11 as a sub-element of the first octet containing the AC display (ACI) and the second octet containing the measured value of AAD for the indicated AC. Formatted as per. Note that the octets shown in FIGS. 10 and 11 are given merely as illustrations and any other octet can be utilized. Table 1 shows examples of ACI coding.

<tables num="1"><img file="JP4804470B2_D0002.tif" /></tables>

Next, referring to FIG. 12, a communication station 100 configured according to the present invention is illustrated. Note that the communication station 100 can be an access point (AP), a WTRU, or any other type of device that can operate in a wireless environment. The communication station 100 preferably includes a receiver 102 configured to receive unsupported traffic request data from a group of WTRUs located within the radio service range 108 of the communication station 100. The communication station 100 also includes a processor 104. Processor 104 is preferably coupled to receiver 102 and configured to calculate BSS load elements for each of the plurality of access categories. The communication station 100 also includes a transmitter 106. The transmitter 106 is preferably configured to advertise the BSS load element within the service range 108 of the communication station 100. In that case, the BSS load element is received by other communication station groups (eg, access point group and / or WTRU group) within the service range 108 of the communication station 100, and gives those stations information related to BSS. It is possible to provide.

(Embodiment 1) Network uptime by both access points (APs) and WTRUs (wireless transmit / receive units) capable of wirelessly communicating with each other over a wireless channel, including creating a service load indicator by the first AP for each access category. A method for providing channel management in wireless networks to optimize.

(Embodiment 2) The method of Embodiment 1 further comprising advertising the service load index to the WTRU group within the service range of the first AP.

(Embodiment 3) The method of any of the above embodiments, further comprising selecting an AP by WTRU based on the service load index above.

(Embodiment 4) The method of any of the above embodiments, wherein the service load index is a display of the average access delay in the first AP.

(Embodiment 5) The method of embodiment 4, wherein the average access delay is measured within a predetermined validity period.

(Embodiment 6) The method of embodiment 5, wherein the period is 30 seconds.

(Embodiment 7) The method of any of the above embodiments, wherein the access category includes voice traffic, video traffic, best effort traffic, and / or background traffic.

(Embodiment 8) The method of any of the above embodiments, further comprising receiving an advertised service load indicator from a second AP.

(Embodiment 9) The method of embodiment 8 further comprising using the advertised service load index in determining the isolation of the WTRU group by the second AP.

(Embodiment 10) The second AP is an embodiment in which the WTRU group is separated from the second AP when the service load index from the first AP is lower than the service load index measured by the second AP. The method of any of the embodiments 8-9.

(Embodiment 11) An access point (AP) configured to provide channel management according to the method of any of the above embodiments.

(Embodiment 12) An AP of Embodiment 11 comprising a processor configured to calculate a service load indicator for each access category.

(Embodiment 13) The AP of any of the above embodiments, including a transmitter configured to advertise a service load indicator to a group of WTRUs within the AP radio service range.

(Embodiment 14) The AP of any of the above embodiments, wherein the WTRU group located within the AP radio service range of the AP helps to select the AP of the other party to perform wireless communication by using the advertised service load index. ..

(Embodiment 15) The AP of any of the above embodiments, including a receiver configured to receive advertised service load indicators from other AP groups.

(Embodiment 16) An AP of any of the above embodiments, wherein the processor is configured to use an advertised service load indicator received from another group of APs to help make a decision regarding the isolation of the WTRU group from the AP.

(Embodiment 17) A wireless transmit / receive unit (WTRU) configured to provide channel management in a wireless network according to the method of any of the above embodiments.

(Embodiment 18) WTRU of Embodiment 17 including a receiver for receiving a service load indicator for each access category from the AP.

(Embodiment 19) The WTRU of any of embodiments 17-18, comprising a processor configured to utilize a service load indicator when selecting the AP of the other party to perform wireless communication.

(Embodiment 20) Optimize network uptime by a set of stations that can wirelessly communicate with each other on a wireless channel, including a first station that provides a basic service set (BSS) load element for each of multiple access categories. , A method for providing channel management in wireless networks.

(Embodiment 21) The method of Embodiment 20, further comprising advertising the BSS load element to other communication stations within the service range of the first communication station.

(Embodiment 22) The method of any of embodiments 20-21, further comprising at least one communication station that selects another communication station to communicate with based on the BSS load element.

(Embodiment 23) The method of any of embodiments 20-22, wherein the BSS load element comprises an element identification field.

(Embodiment 24) The BSS load element includes a communication station field, an AP field, or a WTRU service load field, and the communication station field, the AP field, or the WTRU service load field is the relative level of the service load in the first communication station. The method of any of embodiments 20 to 23, which is a scalar display of.

(Embodiment 25) The method of any of embodiments 20-24, comprising a length field, wherein the BSS load element is set to a value for the total number of octets contained in all fields of the BSS load element.

(Embodiment 26) One of embodiments 20-25, wherein the BSS load element further includes a station count field, which is an unsigned integer indicating the total number of communication stations associated with the current BSS. Form method.

(Embodiment 27) The method of any of embodiments 20-26, wherein the first communication station is a quality of service (QoS) enhanced communication station (QCS) or a quality of service (QoS) enhanced AP (QAP).

(Embodiment 28) Access formatted as four subfields, one for each of the above BSS load elements to provide a scalar display of average access delay (AAD) in QCS or QAP for services in one access category in the access category. The method of embodiment 27, further comprising a Category (AC) service load field.

(Embodiment 29) The method of embodiment 28, wherein the AC service load field is included in the BSS load element only if the QoS-Option-Implemented parameter is true.

(Embodiment 30) From Embodiment 28, the above four subfields include an AAD (AADBE) field for best effort, an AAD (AADBG) field for background, an AAD (AADVI) field for video, and / or an AAD (AADVO) field for audio. The method of any of 29 embodiments.

(Embodiment 31) The method of any of embodiments 28-30, wherein a low AAD value indicates a shorter access delay than a higher AAD value.

(Embodiment 32) If the QCS or QAP does not provide services for the directed access category, the AAD value for the first subfield of the four subfields will be the AAD value of the right subfield adjacent to the first subfield. The method of any of embodiments 28-31, further comprising setting the AAD value.

(Embodiment 33) The method of any of the above embodiments, further comprising measuring and / or averaging media access delay (MAD) values for all transmitted packets in the indicated access category.

(Embodiment 34) The MAD values are measured and / or averaged using the EDCF access mechanism over a continuous grace period, and the averaged MAD has a predetermined accuracy range and is the minimum number of transmit packet delay measurements. The method of embodiment 33, based on values.

(Embodiment 35) The method of embodiment 34, wherein the grace time is a 30 second measurement frame, the predetermined accuracy range is 200 microseconds, and / or the MAD average is based on a transmit packet delay measurement of at least 200.

(Embodiment 36) The EDCF packet is actually from the time when the AAD value within the predetermined value range in one of the above four subfields is ready to send the EDCF packet for the packet sent in the indicated access category. The method of any of embodiments 28-35, which is a logarithmic representation of the average MAD measured before being transmitted to.

(Embodiment 37) The method of embodiment 36, wherein the range of the above values is from 0 to 254.

(Embodiment 38) A given AAD value in any of the four subfields above indicates that QCS or QAP is not servicing either the directed access category or any of the higher priority access categories. Shown, the method of any of embodiments 28-37.

(Embodiment 39) The method of embodiment 39, wherein the predetermined AAD value is 0.

(Embodiment 40) The method of any of embodiments 28-39, wherein the other predetermined AAD value represents a variety of average MAD times.

(Embodiment 41) The method of any of embodiments 28-40, wherein the AAD value of 1 represents an average MAD of 50 microseconds.

(Embodiment 42) The method of any of embodiments 28-41, wherein the AAD value of 253 represents an average MAD of 5.5 microseconds or greater.

(Embodiment 43) The method of any of embodiments 28-42, wherein the AAD value of 254 indicates that the services in the directed access category are currently blocked.

(Embodiment 44) The method of any of embodiments 28-42, wherein an AAD value of 255 indicates that the AC service load is not available.

(Embodiment 45) The method of any of the above embodiments, wherein the BSS load element further includes a channel utilization field.

(Embodiment 46) The method of embodiment 45, wherein the channel utilization field defines a percentage of the time that the first communication station perceives that the transmitting medium is in use, as indicated by the carrier sensing mechanism.

(Embodiment 47) The method of embodiment 46, wherein the percentage of time is a moving average.

(Embodiment 48) The method of embodiment 47, wherein the moving average is determined using at least one parameter selected from the group consisting of channel total uptime parameters, channel uptime beacon interval parameters, and / or beacon duration parameters.

(Embodiment 49) The moving average is defined as the product of the channel total operating time parameter and 255 divided by the product of the channel operating time beacon interval parameter and the beacon period and 1024, according to any of embodiments 47-48. Method.

(Embodiment 50) The method of any of embodiments 48-49, wherein the channel full operating time parameter is defined as the number of microseconds in which the carrier sensing mechanism indicates a channel in-use indication.

(Embodiment 51) The method of any of embodiments 48-50, wherein the channel uptime beacon interval parameter is defined as the number of consecutive beacon intervals for which an average can be calculated.

(Embodiment 52) The channel utilization field is one of embodiments 48-51, which is included in the BSS load element if at least one of the QoS-Option-Implemented and PBSS-Load-Implemented parameters is false. The method of the embodiment.

(Embodiment 53) A method of measuring media access delay (MAD) timing for a single access to a communications station, including measuring the first point in time when a data packet is ready to be sent.

(Embodiment 54) The method of embodiment 53, wherein the first time point is when the carrier sense multiple access (CSMA / CA) protocol is initiated.

(Embodiment 55) The method of any of embodiments 53-54, comprising measuring a second time point at which a transmission request has been made to the physical (PHY) layer transmission process.

(Embodiment 56) The method of any of embodiments 53-55, comprising measuring a third time point at which the acknowledgment is made to the transmission request.

(Embodiment 57) Packet Transmission-A method of any of embodiments 53-56, comprising calculating the acknowledgment timing as the difference between a second time point and a third time point.

(Embodiment 58) The method of any of embodiments 53-57, comprising calculating the total access timing as the difference between a third time point and a first time point.

(Embodiment 58) The method of any of embodiments 53-58, comprising calculating the MAD timing by subtracting the packet transmission-acknowledgement timing from the total access timing.

(Embodiment 59) The method of any of embodiments 53-59, wherein the transmission request is preceded by a Request-to-Send / Clear-to-Send (RTS / CTS) handshake.

(Embodiment 60) How to measure MAD timing for data packet retransmissions. (Embodiment 61) The method of embodiment 60, which comprises measuring the first time point at which a data packet enters a medium access control (MAC) queue.

(Embodiment 62) The method of any of embodiments 60-61, comprising measuring a second time point when the data packet is at the beginning of a MAC queue.

(Embodiment 63) The method of any of embodiments 60-62, comprising calculating the MAC queuing delay as the difference between a second time point and a first time point.

(Embodiment 64) The method of any of embodiments 60-63, comprising determining the first retransmission timing as the difference between the first transmission start time and the first transmission end time.

(Embodiment 65) The first transmission start time indicates the start of the first transmission of the data packet, and the first transmission end time indicates the start of the first transmission without receiving a transmission acknowledgment. The method of embodiment 64, which indicates the end.

(Embodiment 66) The method of any of embodiments 60-64, comprising determining the second retransmission timing as the difference between the second transmission start time and the second transmission end time.

(Embodiment 67) The second transmission start time described above starts after the postponement / backoff period to indicate the start of the second transmission of the data packet, and the second transmission end time described above receives a transmission confirmation response. The method of embodiment 66, indicating the end of the second transmission above, without the need for.

(Embodiment 68) The method of any of embodiments 60-67, comprising determining the Nth retransmission timing as the difference between the Nth transmission start time and the Nth transmission end time.

(Embodiment 69) The Nth transmission start time starts after the postponement / backoff period to indicate the start of the Nth transmission of the data packet, and the Nth transmission end time indicates the reception of the transmission confirmation response. The method of embodiment 68 shown.

(Embodiment 70) Any of embodiments 60-69, comprising calculating the total retransmission timing as the sum of the first retransmission timing, the second retransmission timing, and the Nth retransmission timing. the method of.

(Embodiment 71) The method of any of embodiments 60-70, comprising determining a completion time that indicates when the acknowledgment is received.

(Embodiment 72) Embodiments 60-71 include calculating the MAD timing for a data packet from the difference between the completion time and the first time point, subtracting the MAC queuing delay, subtracting the total retransmission timing, and dividing the whole by N. The method of any of the embodiments.

(Embodiment 73) One of embodiments 20-52, wherein the first communication station is an access point (AP) and features of the BSS load element are configured to be used in and / or by the AP. Form method.

(Embodiment 74) The method of any of embodiments 20-53, wherein any of the other communication stations is an AP.

(Embodiment 75) The method of any of embodiments 20-54, wherein the first communication station is the WTRU and the features of the BSS load element are configured to be used by the WTRU.

(Embodiment 76) Any of the other communication stations, within the WTRU and / or by the WTRU, the method of any of embodiments 20-55.

(Embodiment 77) The method of any of embodiments 53-72, wherein the communication station is an AP.

(Embodiment 78) The method of any of embodiments 53-72, wherein the communication station is WTRU.

(Embodiment 79) A communications station configured to provide channel management according to any of the methods 20-52 and 73-76.

(Embodiment 80) The communication station of embodiment 79 including a receiver configured to receive unsupported traffic request data from a group of other communication stations located within the radio service range of the communication station.

(Embodiment 81) The communication station of any of embodiments 79-80, comprising a processor configured to compute the BSS load element for each of the plurality of access categories.

(Embodiment 82) The communication station of any of embodiments 79-81, comprising a transmitter configured to advertise the BSS load element to other communication stations within the service scope of the communication station.

(Embodiment 83) The communication station of any of embodiments 79-82, wherein the receiver is configured to receive an advertised BSS load element from another group of communication stations.

(Embodiment 84) Any of embodiments 79-83, wherein the processor is further configured to utilize a BSS load element received from another group of communication stations to assist the group of communication stations in making a disconnect decision. Communication station of the embodiment.

(Embodiment 85) The communication station of any of embodiments 79 to 84, wherein the communication station is an AP.

(Embodiment 86) Communication according to any of embodiments 79 to 84, wherein the communication station is WTRU.

(Embodiment 87) A communication station according to any one of embodiments 79 to 86, wherein any communication station in the other communication station group is an AP.

(Embodiment 88) Any communication station in the other communication station group is a communication station according to any one of embodiments 79 to 87, which is a WTRU.

(Embodiment 89) A communication station configured to calculate media access delay according to any of the methods and / or features of embodiments 53-72 and 77-78.

(Embodiment 90) The communication station of embodiment 89, wherein the communication station is an AP.

(Embodiment 91) The communication station of embodiment 89, wherein the communication station is WTRU.

(Embodiment 92) Communication of any of embodiments 90-91, comprising a processor configured to calculate media access delay according to any of the methods and / or features of embodiments 53-72 and 77-78. Station.

(Embodiment 93) A method of calculating the average MAD timing evaluated over a given validity period, including defining a validity period.

(Embodiment 94) The total packet transmission time is calculated by summing the packet transmission time and the time spent waiting for and / or receiving an acknowledgment of a certain amount of packet transmission during the above period. 93.

(Embodiment 95) The method of any of embodiments 93-94, wherein the packet transmission comprises a packet retransmission.

(Embodiment 96) The method of any of embodiments 93-95, comprising determining the total empty send queue time for a plurality of access categories.

(Embodiment 97) The method of any of embodiments 96, wherein the total empty send queue time includes the period during which the send queue for the access category remains empty.

(Embodiment 98) The method of any of embodiments 93-96, comprising subtracting the total packet transmission time, the total empty transmission queue time, and / or the total transmission queue deferral time from the validity period to result in a total difference.

(Embodiment 99) The method of any of embodiments 93-97, comprising dividing the total difference by the amount of packet transmission to obtain the average MAD timing.

(Embodiment 100) The method of any of embodiments 93-99, comprising determining the total send queue deferral time for a plurality of access categories, wherein the send queue deferral time is such that the access category is each of those categories. A method that includes a period of time when a transmission is transferred to a higher priority queue.

(Embodiment 101) The method of Embodiment 100 comprising subtracting the total transmit queue postponement time from the total difference and then dividing the total difference by the amount of packet transmission to obtain the average MAD timing.

(Embodiment 102) A communication station configured to measure MAD timing according to any of the methods and / or features of embodiments 93-101.

(Embodiment 103) Communication station of embodiment 102 including a processor.

(Embodiment 104) The communication station according to any one of embodiments 102 to 103, wherein the communication station is an AP.

(Embodiment 105) The communication station according to any one of embodiments 102 to 103, wherein the communication station is WTRU.

(Embodiment 106) A communications station configured to perform any of the methods and / or features described in any of the above embodiments and / or comprising any of the features described in any of the above embodiments. ..

(Embodiment 107) The communication station of embodiment 106, wherein the communication station is an AP.

(Embodiment 108) The communication station of embodiment 106, wherein the communication station is WTRU.

Although the present invention has been illustrated and described in particular in relation to preferred embodiments, various modifications of embodiments and details have been made in those embodiments without departing from the scope of the invention described above. Those skilled in the art will understand that it is okay.

<figref num="1">It is a schematic diagram which shows the conventional IEEE 802.11 WLAN which has a corresponding component.</figref><figref num="2">2 to 9 are flow charts showing various techniques of the present invention for determining and managing congestion in a wireless communication system. More specifically, FIG. 2 is a flow diagram showing a method for determining congestion using the delay rate (DR) metric and the packet error rate (PER) metric.</figref><figref num="2A">It is a flow chart which shows the method for disconnecting a WTRU based on measuring the time wasted trying to send / retransmit a packet without an acknowledgment.</figref><figref num="3">It is a flow chart which shows the method for managing the load cutoff by comparing the load of a node with the advertised load of a group of neighboring nodes.</figref><figref num="4">It is a flow chart which shows the method for showing the load advertised to WTRU group based on the average delay from the arrival of a packet at the head of a queue to the transmission of a packet.</figref><figref num="5">It is a flow chart which shows the method for showing a transmission queue size (TQS) to a group of neighboring nodes.</figref><figref num="6">It is a flow chart which shows the method for showing the transmission queue size (CFTQS) without a conflict to a group of neighboring nodes.</figref><figref num="7">It is a flow chart which shows the method for showing the contention transmission queue size (CTQS) to a group of neighboring nodes.</figref><figref num="8">The method used by a node to manage channels based on an assessment of the supported and unsupported traffic loads from the WTRUs and to provide a service load scalar for advertising to the WTRUs. It is a flow chart which shows.</figref><figref num="9">FIG. 6 is a flow diagram showing the method used by the WTRU group to select nodes based on the load scalar provided by the neighboring node group.</figref><figref num="10">It is a figure which shows the BSS load element format by this invention.</figref><figref num="11">It is a figure which shows the access category service load element format by this invention.</figref><figref num="12">It is a figure which shows the communication station configured according to this invention.</figref>