Wireless communication method and apparatus for dynamically adapting packet transmission rates

TECHNICAL FIELD The present invention relates to data transmission in a wireless communication system. More particularly, the present invention relates to dynamically adapting the packet transmission rate in response to changing attenuation conditions.

BACKGROUND Wireless communication systems such as wireless local area networks (WLANs) are well known in the technical field. Generally, the system includes transceivers (that is, communication stations (STAs)), which can transmit and receive wireless communication signals between each other. Depending on the system type, the transceiver can be in the form of an access point (AP), a wireless transmit/receive unit (WTRU), a node, or the like.

FIG. 1 shows a conventional wireless communication system 10 in which an access point 12 can provide communication services to a plurality of wireless transmitting/receiving units 14. The access point 12 can communicate with the network 18 via an optional access controller (AC) 16, thereby providing additional network services to the wireless transmission/reception unit 14, such as access to the Internet or a public service telephone network (PSTN). Alternatively, the access point 12 may communicate directly with the network 18 without going through the optional access controller 16.

In theory, all connections in the system 10 can operate at the highest achievable transmission rate to maximize performance and overall system capacity. However, due to the relatively high signal-to-noise ratio (SNRs) required at the receiver, it is not always possible to achieve receivable quality at higher data rates.

Depending on the signal-to-noise ratio perceived by the transceiver receiving the packet, this creates a favorable situation for adjusting the transmission rate of the packet. However, the system 10 does not provide a mechanism to transfer the received signal power, signal-to-noise ratio or packet error rate (PER) type of perceived channel quality to the packet source. Therefore, the determination basis for adjusting the transmission rate of the access point 12 and the wireless transmission/reception unit 14 in the system 10 is limited to the local transmission condition.

SUMMARY OF THE INVENTION The present invention relates to a first transceiver (such as a wireless transmitting/receiving unit, access point, node, or the like) receiving a signal from a second transceiver, which is used by the first transceiver to adjust the signal to be transmitted. Method and device for packet transmission rate to the second transceiver. In one embodiment, transmission packet error rate (TxPER) processing is used to adjust the packet transmission rate. In another embodiment, the relative signal strength indicator (RSSI) is used as the basic processing system,

200680005801.0 Firstly, the relative signal strength indicator of the packet received by the first transceiver from the second transceiver is used to adjust the packet transmission rate. In another embodiment, the transmission quality indicator is measured at the second transceiver and transmitted to the first transceiver, which can drive the new packet transmission rate based on the quality indicator. Optionally, the second transceiver can determine a better packet transmission rate and transmit it to the first transceiver, so it can adjust its packet transmission rate.

Although two different processing methods for determining the packet transmission rate (that is, transmission packet error rate processing and relative signal strength indicator based processing are disclosed here, these processings can be used individually, in conjunction with each other, or in conjunction with other processing.

According to the present invention, the transceiver can select a better data transmission rate from among several available rates based on the measurement at the transceiver. These measurements are the received signal strength (RX power) of the packet received at the transceiver, and the packet error rate of the signal transmitted by the transceiver, which can be determined by assuming that the packet does not correspond to an acknowledgement (ACK) each time. It is inferred by errors when received from another transceiver. The transceiver can quickly establish the best available data transmission rate while still maintaining acceptable quality of service (QoS). Thereafter, the transceiver can adapt its transmission rate in response to changing attenuation conditions.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention can be understood in more detail from the following descriptions of preferred embodiments and the accompanying drawings, in which: Figure 1 shows a conventional wireless communication system; Figure 2 is a block diagram of a wireless transmitting/receiving unit configured according to the present invention; Figure 3 It is a flow chart of all rate adaptation processing implemented according to the present invention; Fig. 4 is a basic processing flow chart of transmission packet error rate for all rate adaptation processing of Fig. 3; Fig. 5 is a relative signal strength pointer training for all rate adaptation processing of Fig. 3 Processing flowchart; FIG. 6 is a flowchart of another embodiment of the relative signal strength pointer training process of the full rate adaptation process of FIG. 3; and FIG. 7 is an alternative relative signal strength pointer training process example of the full rate adaptation process of FIG. 3.

List of Abbreviations

<td>ACK</td><td>confirm</td>

<td>ΑΡ</td><td>Access point</td>

<td>BS</td><td>Base station</td>

200680005801.0 No.

<td>CS</td><td>Client station</td>

<td>CTS</td><td>Clean up and send</td>

<td>MAC</td><td>Media access control</td>

<td>NF</td><td>Noise index</td>

<td>PER</td><td>Packet error rate</td>

<td>Pwr</td><td>power</td>

<td>QoS</td><td>service quality</td>

<td>RSSI</td><td>Relative signal strength indicator</td>

<td>RTS</td><td>Request to send</td>

<td>Rx</td><td>receive</td>

<td>SNR</td><td>Signal-to-noise ratio</td>

<td>STA</td><td>station</td>

<td>STA Tx</td><td>Transfer station</td>

<td>STA Rx</td><td>Receiving station</td>

<td>Tx</td><td>Send</td>

<td>TxPwr</td><td>Transmission power</td>

<td>WLAN</td><td>Wireless local area network</td>

Table 1 Specific implementation manners Hereafter, the access point terminology used includes but not limited to base station, node B, address controller, wireless router or can provide wireless transmitting/receiving unit to wirelessly connect to the network connected to the access point Any other interfacing devices in the wireless environment accessed.

Hereafter, the term used for wireless transmission/reception unit includes, but is not limited to, client station, user equipment, station, mobile station, fixed or mobile subscriber unit, pager, or any other type of user that can operate in a wireless environment Device. The wireless transmitting/receiving unit includes personal communication devices, such as telephones, video phones, and Internet backup phones with network connections. In addition, the wireless transmitting/receiving unit includes portable personal computing devices, such as personal digital assistants (PDAs) and notebook computers with wireless modems similar to network functions. A portable or positionable wireless transmitting/receiving unit is called a mobile unit.

Since then, the wireless connection used is defined as the wireless communication between a pair of nodes that can send and receive packets with each other. Each wireless connection system contains a pair of nodes, in which the roles of the transmitter and receiver of the packet are handed back and forth in time.

200680005801.0 is changed between the nodes. For example, a wireless communication system operating in an architecture mode in which two wireless transmitting/receiving units communicate with a single access point includes two wireless connections. Rate control processing should reside in each transmitting node, and its purpose is to determine the optimal rate at which each packet is transmitted for each active wireless connection.

Preferably, the implementation of the transmitter and receiver functions described herein can be incorporated on a single integrated circuit such as an application-specific integrated circuit. However, the circuit can also be easily implemented using multiple discrete components and/or discrete integrated circuits.

The specific transmitter and receiver configurations described herein are only provided as an illustration and not limitation. Those skilled in the art will understand other variations and modifications consistent with the present invention.

The present invention is to prompt the transceiver (that is, the wireless transmitting/receiving unit, the access point, the node) to be engaged with one or more wireless connections to dynamically adapt its transmission rate according to the propagation conditions of each wireless channel over time. In order to do so, the present invention relies on two processes to determine a better transmission rate depending on the availability and effectiveness of a particular measurement. In the first processing, the transmission packet error rate, which is referred to as the transmission packet error rate as the basic processing, is used to determine the optimal transmission rate. Alternatively, the optimal transmission rate is determined based on the relative signal strength indicator or its transmission power, and other received packet metrics related to the transmission packet error rate of the transmitted packet. The relative signal strength indicator is related to the transmission packet error rate in a process referred to herein as the relative signal strength indicator training process. Although the relative signal strength indicator is used in the description of the preferred embodiment of the relative signal strength indicator training process, alternative embodiments may also use other metrics such as signal-to-noise ratio.

FIG. 2 is an example of a block diagram of a wireless transmitting/receiving unit 100 configured in accordance with the present invention. The same configuration example disclosed here for the wireless transmission/reception unit 100 can also be incorporated into the access point. The wireless transmitting/receiving unit 100 includes at least one antenna 102, a transmitter 104, a receiver 106, a processor 108, A transmission rate database 110 and a memory 112. The transmitter is configured to transmit the output signal 114 via the antenna 102 at a transmission rate selected from a plurality of available transmission rates stored in the transmission rate database 110. The receiver 106 is configured to receive the input signal 116 from the antenna 102. The processor 108 is coupled to the transmitter 104, the receiver 106, the transmission rate database 110 and the memory 112. The processor 108 selects the transmission rate from the transmission rate database 110 and changes the current transmission rate of the transmitter 104 to the selected rate. This selection may be based on the evaluation of the output signal 114, the evaluation of the output signal 114 and the input signal 116, or it may be based on the rate command received at the receiver 106. The memory 112 is used to store data for the input signal 116 and/or the output signal 114, and/or for the rate command received at the receiver 106. The processor 108 is configured to process the data stored in the memory 112 and store the processed data result in the memory 112 for further access to select and change the transmission rate of the transmitter 104.

The wireless transmitting/receiving unit 100 further includes a plurality of packet transmission counters, including a total successful packet transmission

200680005801.0 The first transmission counter 120, an individual packet transmission error counter 122, a total failed packet transmission counter 124, a relative signal strength indicator level total packet transmission counter 126, and a relative signal strength indicator level packet transmission error counter 128. The functions of the packet transmission counters 120, 122, 124, 126, and 128 can be implemented on an individual basis or as a maintenance group through one or more databases, processors, software, or the like. For example, multiple sets of packet transmission counters 120, 122, 124, 126, and 128 and related measurement systems can be maintained to individually control each station, access point, and wireless transmission/reception of the wireless transmission/reception unit 100 communicating on a specific communication link. The packet transmission rate associated with the receiving unit or the like.

It is advantageous to define a number of terms listed in Table 2 below before explaining the processing performed by the present invention. Although the processing of the present invention will be described in these, it should be understood that these terms do not need to be used; on the contrary, the terms are only used to illustrate the convenience of the processing characteristics. In one implementation, the parameters can be stored in the memory and updated as needed, or can be maintained and updated in any suitable way.

<td>parameter</td><td>Description</td><td>example</td>

<td>Maximum duration</td><td>The maximum duration during which the measurement or command system of the node to which the packet is transmitted from the transmitter is valid. The maximum duration parameter should preferably represent the consistency time of the channel. The received packet can be of any type (such as DATA, ACK, RTS, CTS or similar)</td><td>100ms</td>

<td>Allowable rate</td><td>A list of the supported rates of the transmitters sorted in ascending order. The allowable rate can be represented by a vector stored in the memory, where each position of the vector corresponds to a specific rate.</td><td>[6, 9, 12, 18, 24, 36,4&amp; 54] Mbps of IEEE 802. 11a</td>

<td>Preset rate</td><td>When rate control is activated, the rate that should be used by the transmitter. This can be represented by the start pointer of the allowable rate vector.</td><td>8 (indicating that the default rate is the 8th highest supported rate, such as 54Mbps in the 802.11a system)</td>

<td>Current rate</td><td>The rate used by the transmitter to transmit the next packet. This can be represented by the current pointer of the allowable rate vector.</td><td>5 (indicating that the next packet will be transmitted at the fifth highest supported rate, such as 24Mbps in the 802.11a system)</td>

<td>Maximum rate pointer</td><td>The number of different transmission rates supported by the machine</td><td>8</td>

200680005801.0 No.

<td>Rate down trigger</td><td>A predetermined pattern or plan that adjusts the transmission rate in response to continuous transmission errors. For retransmission attempts, it indicates whether the transmission rate should be reduced, and if so, by how much rate level it should be reduced. The pattern should be stored as a vector. For example, in the IEEE 802.11a system, [0, 0, 1, 1, 2, 2, 1, 0] means the wireless transmission/reception unit operating at 54 Mbps until the transmission rate is reduced by one level to 48 Mbps. Repeated transmission (that is, after three errors) does not reduce its transmission rate. If an error occurs, the rate is reduced by one level to 36 Mbps in the fourth retransmission, and then reduced by two levels in the fifth (to 18 Mbps) and sixth retransmission (to 9 Mbps), and then reduced by one. Level (to 6 Mbps, the lowest supported rate).</td><td>[0,0, 1, 1,2, 2, 1,0]</td>

<td>Rate increase ratio</td><td>Maximum allowable ratio of failure to successful packet transmission</td><td>0. 10</td>

<td>Packets required for rate increase</td><td>The maximum number of packets that must be transmitted since the last rate change to allow the transmission rate to increase</td><td>10</td>

<td>Good packet count</td><td>The number of successful packets sent to a specific wireless transmitting/receiving unit. This count is reinitialized to zero after the rate change is implemented.</td><td></td>

<td>Bad packet count</td><td>The number of failed packets sent to a specific wireless transmitting/receiving unit. This count is reinitialized to zero after the rate change is implemented.</td><td></td>

<td>Retry count</td><td>The number of failed delivery attempts for a given packet. When the packet is successfully transmitted, this count is re-initialized to zero.</td><td></td>

Table 2 FIG. 3 is a flowchart of all rate adaptation processing 300 implemented according to the present invention. The transmission rate is determined by using the transmission packet error rate implemented by the processor 108 in the wireless transmitting/receiving unit 100 of FIG. 2 as the basic processing or the relative signal strength indicator. The decision of which processing to use is based on whether the relative signal strength indicator is previously trained, and whether a specific relative signal strength indicator level can obtain a valid relative signal strength indicator measurement as the basis. If so, the relative signal strength indicator-based processing system is used to determine the transmission rate. Otherwise, the transmission packet error rate is used by the basic processing system. In either case, the packet is then transmitted at a determined rate of the process, and the success or failure of the packet transmission is used to dynamically train the relative signal strength indicator as a basis for processing and adjusting the transmission rate.

200680005801.0 The first effective relative signal strength indicator measurement is defined as the relative signal strength indicator measurement of the packet received from the node to which the transmitter last transmitted the packet within a predetermined duration (designated as the maximum duration here). The maximum duration is the channel consistency time. The received packet can be of any type, such as DATA, ACK, RTS, CTS or similar.

As shown in Figure 3, when the first station (that is, the wireless transmitting/receiving unit 100) prepares to transmit packets to the second station for the first time by setting the packet transmission rate of the first station to the preset rate, all rate adaptation processing 300 activation (step 305) ο When the first station has a packet to transmit to the second station (step 310), determine whether there is any effective relative signal strength for any packet received from the second station during the last maximum duration Pointer measurement (step 315) ο If no packet is received during the duration or no such measurement can be used for any received packet, the transmission packet error rate basic processing is implemented to determine the packet transmission rate of the first station ( Step 320), which will be described in detail later.

However, if the effective relative signal strength pointer measurement is determined to be available in step 315, then the relative signal strength pointer level that can be measured with the effective relative signal strength pointer is determined (step 325). In step 325, if the effective relative signal strength indicator measurement system is determined to exist at more than one relative signal strength indicator level, then the representative relative signal strength indicator level system is determined. The representative relative signal strength indicator level can be based on the last relative signal strength indicator value, or it can be static (such as an average value), based on several relative signal strength indicator values, or based on the relative signal strength indicator value combined with other values basis. In step 330, it is determined whether the relative signal strength indicator processing has been trained to the relative signal strength indicator level within the last maximum duration. If yes, the packet transmission rate of the first station is set to the relative signal strength indicator level better rate as determined by the relative signal strength indicator training process (step 335), the packet is transmitted (step 340) and The relative signal strength pointer training process is implemented (step 345). When the first station has another packet to transmit to the second station, the process 300 returns to step 310. For example, the transmission packet error rate will be explained as follows after the basic processing is explained. The success or failure of the transmitted packet is used to dynamically update the relative signal strength indicator training processing 345 to indicate the better transmission rate.

In step 330, if it is determined that the relative signal strength indicator processing is not trained at the relative signal strength indicator level during the last maximum duration, the transmission packet error rate basic processing is implemented to determine the packet transmission rate of the first station (step 320) ο The packet is then transmitted (step 340), and the relative signal strength indicator training process is implemented (step 345) Figure 4 is a flow chart of the basic processing 320 of the transmission packet error rate of the all rate adaptation processing 300 of Figure 3 . Generally, according to the basic processing 320 of the transmission packet error rate, the transmitter 104 in the wireless transmitting/receiving unit 100 of FIG. 2 can adjust its packet transmission by reflecting the transmission events experienced when transmitting to a receiving node.

200680005801.0 The first rate.

If the transmitter 104 of the wireless transmitting/receiving unit 100 of FIG. 2 experiences continuous packet transmission errors, its packet transmission rate is reduced according to a predetermined plan or mode designated here as a Rate Down Trigger. The rate downward trigger may be a vector stored in the memory 112 in the wireless transmitting/receiving unit 100 of FIG. 2. After each successive packet transmission error, the rate downward trigger can indicate whether the packet transmission rate should be reduced before the next packet retransmission attempt, and if so, by how much. If so, the instructed rate reduction is then implemented. The packet transmission rate is reduced in this way until the packet is successfully transmitted, or until the packet transmission rate is reduced to a predetermined minimum packet transmission rate.

For example, if the wireless transmitting/receiving unit 100 is configured for use in an IEEE 802.11a system, the supported packet transmission rate (that is, the supported packet transmission rate level) classified in ascending order is 6, 9, 12 , 18, 24, 36, 48 and 54Mbps. In this example, the rate downward trigger vector of [0, 0, 1, 1, 2, 2, 1, 0] instructs the wireless transmitting/receiving unit 100 until after the third retransmission attempt (that is, the third transmission error of the specific packet). After that, the packet transmission rate will be reduced. At this point, the packet transmission rate will be reduced by one step. Therefore, if the wireless transmitting/receiving unit 100 operates at 54 Mbps after the third transmission error, the transmission rate will be reduced by one step to 48 Mbps, and the packet will be retransmitted. If the transmission error still occurs, the fourth retransmission, the rate is then reduced by one step to 36 Mbps, and then the fifth (to 18 Mbps) and the sixth retransmission (to 9 Mbps) are reduced by two steps, and then reduced One step (to 6 Mbps, the lowest supported rate).

On the other hand, if the transmitter 104 of the wireless transmission/reception unit 100 experiences a consistent continuous packet transmission error, the transmission rate of the transmitter 104 is increased based on the transmission packet error rate for the basic processing 320. In this example, for the sufficient number of packets transmitted to the receiving node, when the transmission packet error rate experienced by the transmitter 104 drops below a certain threshold, the transmission rate is increased to the next support step.

As shown in FIG. 4, if an acknowledgment (ACK) is received (step 405), the total successful packet transmission counter 120 in the wireless transmission/reception unit 100 is increased, and the individual packet transmission error in the wireless transmission/reception unit 100 The counter 122 is reset to zero (step 430). As explained below, these counters 120, 122 are used to determine whether the transmission rate should be increased.

If the confirmation is not received in step 405, the total failed packet transmission counter 124 in the wireless transmitting/receiving unit 100 is increased, and the individual packet transmission error counter 122 is also increased (step 410). The rate-down trigger vector is checked to determine whether the packet transmission rate should be reduced for individual packet transmission error counts, and if so, how many steps are involved (step 415). If the rate downward trigger indicates that the packet transmission rate should not be reduced, the same packet is prepared for retransmission. However, if the rate-down trigger in step 415 indicates that the packet transmission rate should be reduced by one or more steps, then the packet transmission rate is reduced by the number of steps indicated by the rate-down trigger, and always succeeds

200680005801.0 The first packet transmission counter 120 and the total failed packet transmission counter 124 are reset to zero (step 420). The same packet is then prepared to be retransmitted at the packet transmission rate indicated by the rate down trigger (step 425). The transmission packet error rate basic process 320 may be repeated during the communication session until the packet transmission rate is equal to the minimum supported transmission rate or until an acknowledgment (ACK) is received.

The requirement to experience continuous error events before triggering a decrease in transmission rate is an error event that leads to a tendency to differentiate between bad signal conditions and packet collisions. It also contributes to reducing the response time at a faster rate than the criterion that considers the average number of packet error events, and provides an additional transmission rate reduction when the rate reduction has been implemented without producing more reliable communication.

When an acknowledgment (ACK) is determined to be received in response to the transmitted packet in step 405, the total successful packet transmission counter 120 is incremented, and the individual packet transmission error counter 122 is reset to zero (step 430). Next, decide whether the increase in transmission rate can be expected. Generally, when the transmission rate increases, the proportion of packets that cause transmission errors also increases. The preferred transmission rate is the highest supported rate that can be used while still achieving acceptable service quality. For example, the quality of service can be expressed as the transmission packet error rate or the ratio of transmission errors to successful transmissions. If the transmitter experiences a lower transmission error to successful transmission ratio than necessary to maintain acceptable service quality, the transmission rate increase can be expected.

Transmission packet error rate basic processing 320 can determine whether the increase in transmission rate can be achieved by the first summation of the total successful packet transmission count and total failed packet transmission count (that is, the total number of packet transmissions is found since the start of transmission or since the last packet transmission rate is changed) Come as expected. This sum is compared with the threshold value (indicated here as the packets required for the rate increase) (step 435). The number of packets required for the rate increase indicates the minimum number of packets that must be transmitted after the change in the transmission rate of the last packet generated by the rate increase is allowed. If the sum is not greater than or equal to the packets required for the rate increase, no packet transmission rate adjustment is allowed and the packet transmission rate is not increased.

If the sum of the total successful packet transmission count and the total failed packet transmission count is greater than or equal to the packets required for the rate increase (step 435), the process 320 may determine whether the rate increase is guaranteed. The rate increase is to ensure whether the proportion of transmission failures is less than that is allowed to maintain the predictable service quality. For example, the transmission failure ratio can be indicated by determining the transmission failure to successful transmission ratio or in any other suitable way. The increase in the packet transmission rate is determined by whether the ratio of the guaranteed total successful packet transmission count to the total failed packet transmission count is less than that required to maintain acceptable service quality. The ratio required to maintain acceptable service quality is a threshold (designated here as the rate increase ratio). If the ratio of the total failed packet transmission count to the total successful packet transmission count is determined in step 440 to be not less than the rate increase ratio, the packet transmission rate increase is not guaranteed, and the packet transmission rate is not adjusted.

However, if the ratio of the total failed packet transmission count to the total successful packet transmission count is determined in step 440 to be less than the rate increase ratio, the packet transmission rate increase is increased to the next highest step (that is, the second highest support packet transmission rate

200680005801.0 first rate), if one is available, the total successful packet transmission counter 120 and the total failed packet transmission counter 124 are reset to zero (step 445). During the communication session, the process 25 may be repeated until the maximum supported transmission rate is reached or an acknowledgement (ACK) is not received.

When the communication is carried out between the first station (where the present invention is implemented) and the second station, the relative signal strength indicator processing is dynamically trained at the first station. When the relative signal strength pointer processing is trained, the relative signal strength pointer processing preferably determines the preferred transmission rate of the first station. The relative signal strength indicator is the basic rate adaptation process that adapts the packet transmission rate of the packet from the first station to the second station by reflecting the variation of the received packet power from the second station at the first station. In the embodiment, the received power is reflected in the measured relative signal strength indicator of the received packet; however, the signal-to-noise ratio or other metrics related to the received power may also be used.

The relative signal strength indicator based processing can dynamically correlate the packet transmission error rate of the packet transmitted by the first station to the second station with the relative signal strength indicator of the packet received at the first station from the second station. This dynamic correlation is referred to as training relative signal strength indicator based processing in this system. The correlation is made for each supported transmission rate used by the first station. It helps to divide the level of the expected range of received signal power. For example, if the expected range of received signal power is -97dBm to -64dBm, the range can be easily divided into levels separated by 3dBm; for example, for a total of 12 separate power levels, -97dBm to -94dBm, -94dBm to -91dBm, --67dBm to -64dBm. Any received power less than -97dBm can be combined together as an additional power level, and any received power greater than -64dBm can be combined together as another power level. It should be understood that the range is from -97 to -64, the range is divided into levels separated by 3 dBm, and the 12th separation level is only used as an example and is not limited. The transmission packet error rate and the relative signal strength indicator of the received packet are determined by collecting the measurement and information of the first station for each packet transmitted from the first station to the second station and from the second station to the first station. The collected information about each packet transmitted from the first station to the second station includes the transmission rate at which the packet was transmitted and whether the transmission was successful (ACK (acknowledgment) was received) or caused a transmission error (ACK (acknowledge) was not received). Received). From this information, the transmission packet error rate is calculated at each transmission rate used.

The collected information about each packet transmitted from the second station to the first station includes the signal strength measurement of each received packet (such as the relative signal strength indicator) and the received information of the packet. The relative signal strength indicator measurement system is considered valid only for a specified maximum duration. For relative signal strength pointer training, it should be noted that all packet types can be used (ie DATA, ACK, RTS, CTS or similar). If more than one packet is received from the second station within the maximum duration, the processing can use the relative signal strength indicator from the last received packet or calculate a statistical value (such as an average) based on a number of packets. Since it takes a short time between the packet being transmitted and the ACK (acknowledgement) being received, the relative signal strength of the ACK (acknowledgement) frame of the transmitted packet in the case of confirming a successful transmission

200680005801.0 The first-degree pointer measurement system is particularly relevant. Therefore, in the first embodiment, only the relative signal strength indicator of the ACK (acknowledgement) signal is used.

In this embodiment, the relative signal strength indicator training process is related to the relative signal strength indicator of each ACK (acknowledgement) received at the transmission rate of the confirmed transmission packet. If an ACK (acknowledgement) is received, its relative signal strength indicator is measured and its relative signal strength indicator level is determined, then the packet transmission belongs to the relative signal strength indicator level at the used transmission rate. If no ACK (acknowledgement) is received, the transmission error is assumed. In this example, if the relative signal strength pointer processing is not used to select the transmission rate, the error does not belong to any specific relative signal strength pointer level. However, if the relative signal strength indicator processing is used to select the transmission rate, the relative signal strength indicator level used to select the transmission rate is identified, and the error is attributed to the relative signal strength indicator level and transmission rate . Calculating the total number of transmitted packets and transmission errors is maintained at each relative signal strength indicator level of each transmission rate. The transmission error rate of each relative signal strength indicator level and transmission rate is calculated for the relative signal strength indicator level and transmission rate by dividing the number of transmission errors by the number of packet transmissions.

FIG. 5 is a flowchart of the relative signal strength pointer training process 345 of the overall rate adaptation process 300 of FIG. 3. Since it is determined whether the relative signal strength pointer training process is used to determine the packet transmission rate first, the relative signal strength pointer training process is started after the packet is transmitted (step 505). If not, it is determined whether the ACK (acknowledgement) is received Respond to the transmitter packet (step 510). If it is determined in step 510 that no ACK (acknowledgement) is received, the transmission error cannot be attributed to the specific relative signal strength indicator level, and the relative signal strength indicator training process 345 is terminated. If it is determined in step 510 that an ACK (acknowledgement) is received in response to the transmitted packet, the relative signal strength indicator measurement of the ACK (acknowledgement) is retrieved from the memory 112 in the wireless transmitting/receiving unit 100, and the relative signal strength indicator level It is determined by the processor 108, and the relative signal strength indicator level total packet transmission counter 126 is incremented for the relative signal strength indicator level (step 515) ο If it is determined in step 505 that the relative signal strength indicator training process is used first To determine the packet transmission rate, the relative signal strength indicator level used by the relative signal strength indicator training process to determine the transmission rate is identified (step 520). Then it is determined whether the ACK (confirmation) is received for the transmitted packet (step 525). If in step In step 525, it is determined that the ACK (acknowledgement) is not received, and the relative signal strength indicator level total packet transmission counter 126 and the relative signal strength indicator level packet transmission error counter are incremented for the relative signal strength indicator level (step 530). If it is determined in step 525 that ACK (acknowledgement) is received, the relative signal strength indicator measurement of ACK (acknowledgement) is retrieved from the memory 112 in the wireless transmission/reception unit 100, and the relative signal strength indicator level of ACK (acknowledgement) is As determined by the processor 108, the relative signal strength indicator level total packet transmission counter 126 is increased for the relative signal strength indicator level of the ACK (acknowledgement) (step 535).

This information is used to calculate the transmission at each relative signal strength indicator level for each transmission rate used

200680005801.0 The first packet error rate (step 540) ο This information can be collected in the following table 3, which shows the statistical value of the transmission packet error rate versus the relative signal strength indicator for each transmission rate used by the station to transmit the packet example.

<td rowspan="2">Transmission power (dBm) (relative signal strength indicator level)</td><td colspan="4">Transmission packet error rate at different transmission rates</td>

<td>Rate 1 (such as 1Mbps)</td><td>Rate 2 (such as 2Mbps)</td><td></td><td>Rate N (such as 54Mbps)</td>

<td>-8 to one 97</td><td>1. 00</td><td>1. 00</td><td>···</td><td>1. 00</td>

<td>-97 to -94</td><td>0. 64</td><td>0. 92</td><td></td><td>1. 00</td>

<td>-94 to -91</td><td>0. 22</td><td>0. 47</td><td></td><td>1. 00</td>

<td>-91 to -88</td><td>0. 07</td><td>0. 18</td><td></td><td>1. 00</td>

<td>-88 to -85</td><td>0. 01</td><td>0. 08</td><td></td><td>0. 95</td>

<td>…</td><td>…</td><td>・・・</td><td></td><td>・・・</td>

<td>-70 to -67</td><td>0. 00</td><td>0. 00</td><td></td><td>0. 15</td>

<td>-67 to -64</td><td>0. 00</td><td>0. 00</td><td></td><td>0. 03</td>

<td>-64 to 8</td><td>0. 00</td><td>0. 00</td><td>…</td><td>0. 00</td>

Table 3 As shown in FIG. 5, the given relative signal strength indicator level and transmission rate are updated after each new packet is transmitted (step 540). If the packet is received in error when it is first transmitted and retransmitted, the second transmission is regarded as a unique packet transmission. In the event of a successful transmission, the database is updated using the relative signal strength indicator measurement of the ACK (acknowledgement) frame alone or in combination with the relative signal strength indicator used to determine the transmission rate. If multiple effective relative signal strength pointer measurements are available, the latest or statistical value (such as the average of two or more recent measurements) can be used to determine the relative signal strength pointer level. However, it may be advantageous to use the relative signal strength indicator measurement of the last received ACK (acknowledgement) because it is temporarily close to the transmitted packet.

The relative signal strength indicator is based on processing and is also used as the input expected target to be transmitted packet error rate or the maximum allowable packet error rate. The error rate of the target transmitted packet is the same for all transmission rates, or it is different for different rates. For example, in Table 3, the maximum allowable packet error rate is set to 0.10 for all rates. Therefore, the preferred transmission rate at any relative signal strength indicator level is the highest transmission rate at that level with a transmission packet error rate not greater than 0.10. For the effective transmission packet error rate, there must be a sufficient number of measurements to establish the packet error rate.

The received error rate of the relative signal strength indicator used to establish the effective transmission packet should be a configurable number. example

200680005801.0 For example, in order to establish a transmission packet error rate no greater than 0.10, at least 10 packets must be received. Alternatively, the transmission packet error rate is preferably regarded as stable only after the number of received better packets is equal to the reverse expected multiple of the transmission packet error rate. For example, if the expected multiple is two and the target transmission packet error rate value of the specific relative signal strength indicator level and transmission rate is 0.10, then in order to make the transmission packet error rate value stable, at least 2x(l/10)= 20 packets must be received at the relative signal strength indicator level and transmission rate.

In Table 3, the bold font values indicate the preferred transmission rate for each relative signal strength indicator level. For example, at the relative signal strength indicator level of -88dBm to -85dBm, rate 1 (1Mbps, with a transmission packet error rate of 0.01) and rate 2 (2Mbps, with a transmission packet error rate of 0.08) have both lower than 0.10 The maximum allowable value of the transmission packet error rate. If the second highest rate (no icon) has a packet error rate higher than the maximum allowable (such as 0.15), then the preferred transmission rate is rate 2, which is the highest rate with a packet error rate less than the maximum allowable packet error rate. The relative signal strength indicator is very low (for example, any one less than -91 dBm in Table 3), so the rate is not supported. The transmission packet error rate statistical value is lower than the maximum allowable packet error rate. For example, the relative signal strength indicator is the basic processing application. Preferably, a flag is used to indicate that no supported rate produces an acceptable transmission packet error rate. In this example, the packet should not be transmitted because the transmitted packet may generate errors compared to the target or the maximum allowable packet error rate indicated. Alternatively, the preferred transmission rate can be set at the lowest supported rate before transmitting the packet. This information can be summarized in the table below, Table 4o

<td>Transmission power (dBm) (relative signal strength indicator level)</td><td>Better rate</td>

<td>-8 to one 97</td><td>Non-flag</td>

<td>-97 to -94</td><td>Non-flag</td>

<td>-94 to -91</td><td>Non-flag</td>

<td>-91 to -88</td><td>Rate 1</td>

<td>-88 to -85</td><td>Rate 2</td>

<td>…</td><td>·・・</td>

<td>-67 to -64</td><td>Rate N</td>

<td>-64 to °°</td><td>Rate N</td>

Table 4 As shown in FIG. 5, the transmission packet error rate is calculated for the relative signal strength indicator level and the transmission rate, and the better transmission rate for the relative signal strength indicator level is also determined as above (step 540). After obtaining the statistical value of the transmission rate versus the relative signal strength indicator level and being determined to be stable for the specific relative signal strength indicator level, the relative signal strength indicator based processing is then used to adjust the transmission rate of the transmitter. Otherwise, the transmission packet error rate

200680005801.0 The first basic processing is implemented to determine the transmission rate.

6 is a flowchart of the alternative relative signal strength pointer training process 345' of the full rate adaptation process 300. In this example, it is generally assumed that the transmitter power and channel conditions are substantially constant for the time interval substantially equal to the maximum duration.

After the packet is transmitted, it is determined whether an ACK (acknowledgement) is received for the transmitted packet (step 605). If yes, the relative signal strength indicator measurement system of the ACK (acknowledgement) signal is retrieved from the memory 112 in the wireless transmission/reception unit 100, the relative signal strength indicator level is determined, and the relative signal strength indicator level transmission count system Is added (step 610). The transmission packet error rate is then updated for the relative signal strength indicator level to determine whether the transmission packet error rate is stable against the relative signal strength indicator level. If so, the better packet transmission rate for the relative signal strength indicator level is Is updated (step 615) ο If it is determined in step 605 that the transmitted packet does not receive ACK (acknowledgement), then it is determined whether any packet received from the second station within the last maximum duration can obtain relative signal strength indicator measurement (step 620). If not, the transmission error cannot be attributed to the specific relative signal strength indicator level, and processing 345 is terminated. However, if it is determined in step 620 that one or more relative signal strength indicator measurements are available, then the relative signal strength indicator level of the measurement is determined. If more than one relative signal strength indicator level is found in step 625, the representative relative signal strength indicator level is determined, and the relative signal strength indicator level is the total packet transmission counter 126 and the relative signal strength indicator level packet transmission The error counter 128 is based on the relative signal strength indicator level system Is increased. The transmission packet error rate of the relative signal strength indicator level is then updated, and it is determined whether the transmission packet error rate is stable to the relative signal strength indicator level. If so, the preferred packet transmission rate of the relative signal strength indicator level is updated (step 615). It should be noted that the relative signal strength indicator training processes 345 and 345' are ongoing processes. The transmission packet error rate is based on Figures 5 or 6 to follow the incoming packet transmitted per packet, or instead of the relative signal strength indicator bit after each N packet transmission, even after the relative signal strength indicator level is regarded as "trained" The quasi place is updated. The old statistical value can preferably be deleted from the memory 112 after the significant time interval has elapsed, or be used by maintaining only the last measured optimal number (such as 100) in the memory. Alternatively, the relative signal strength indicator statistics stored in the memory 112 can be periodically flushed, whereby the relative signal strength indicator training processes 345 and 345 are restarted from zero.

According to the embodiment of the present invention shown in FIG. 7, the first station transmitting to the second station adjusts its transmission rate in response to the rate command received from the second station. This embodiment involves measuring at the second station, determining the preferred rate, generating a rate command, transmitting the rate command to the first station, and implementing the preferred rate at the first station. Optionally, the measurement itself can be transmitted to the first station, which can determine the better transmission rate. The measurement system used to determine the better rate can include links

200680005801.0 The first quality indicator and/or other measurements, such as the relative signal strength indicator or signal-to-noise ratio of the signal received from the second station from the first station. The rate command from the second station to the first station is preferably placed in the packet media access control header sent by the second station to the first station, but it can also be sent via other devices, such as frame rewards. Or one or more dedicated packets.

This implementation assumes that the second station has stored the sensitivity (such as signal-to-noise ratio) required to achieve the expected service quality (such as packet error rate) in memory for each allowed transmission rate. The method of obtaining this information through the second station may include pre-configuration, training, or the like, and is beyond the scope of this invention.

For each packet received by the second station from the first station (including packets addressed to nodes other than the second station), the second station measures and stores the signal-to-noise ratio of the packet and the time it was received in the memory . Thereafter, whenever the second station needs to send a packet to the first station, it needs to check its memory to see if it has received any packets from the first station within the last maximum duration. If so, the second station generates a statistical value from the signal-to-noise ratio measurement (such as the average signal-to-noise ratio of the packet received during the maximum duration, or the latest effective signal-to-noise ratio or the like), and compares it with the one stored in Compare the sensitivity numbers in the memory. The preferred rate is the highest rate at which the statistical value of the generated signal-to-noise ratio is better than the signal-to-noise ratio required to achieve the expected service quality. The second station then encodes the expected rate as a rate command transmitted to the first station.

If the second station has not received the packet from the first station during the maximum duration, the second station can set the better transmission rate to the preset rate; or the last rate for successfully receiving the packet; or it is marked on it Send to the last speed command of the first station. Alternatively, it can send an indication that the second station does not provide the transmission rate that the first station should use, so it is left to the first station to determine its transmission rate. The second station encodes the expected rate or signal as a rate command and transmits it to the first station. The first station then stores the last speed command and the time it was received in the memory, and implements it when it is transmitted to the second station.

FIG. 7 is a flow chart of the rate adaptation process 700 in which the transmission rate command is generated in the second station and transmitted to the first station. When the first station has a packet to transmit to the second station (step 705), it can check its memory 112 to see if it has received the effective rate command from the second station within the last maximum duration (step 710). , The first station can set its transmission rate according to the last rate command received. If the effective rate command is not available, the first station can determine its own transmission rate as described above (step 720). The packet is then transmitted (step 725).

Although the features and components of the present invention are described in the preferred embodiment in specific combinations, each feature and component does not require other features and components of the preferred embodiment, or various features and components with or without other features and components of the present invention Used alone in combination.

200680005801.0