CN101036061A - System and method for battery conservation in wireless stations - Google Patents

Abstract

Described are a system and method for battery conservation in a wireless station. Initially, a wireless station switches, according to a predetermined time schedule, from a first communications mode into a second communications mode. The station is capable of at least one of receiving and transmitting data packets only when the station is in the second communications mode. The first mode is a power conservation mode. When the station is in the second mode, a wireless access point obtains a priority access to a radio channel. Then, the access point reserves the radio channel for wireless communications between the access point and the station. Wireless communications are conducted between the access point and the station over the radio channel. Upon a termination condition, the station switches into the first mode.

Description

Be used for saving the system and method for battery in air station

Priority request

The application requires in right of priority submission on August 5th, 2004, that be entitled as the U.S. Provisional Patent Application sequence number 60/599,142 of " Automatic Power-Save Deliveryin 802.11e Networks (the automatic economize on electricity in the 802.11e network transmits) ".This is regarded as the part of the disclosure of appended application in whole disclosures of preceding application, and is included in this by reference clearly.

Background

Many air station (" STA ") (for example, cellular phone, PDA, scanner, laptop computer, Hand held PC etc.) can be wirelessly connected to such as computer networks such as the Internet, LAN (Local Area Network), enterprise network.Therefore, these STA also can realize its function without any need for wired connection.Usually use battery to come to STA power supply described here, because they can provide absolute freedom of movement to its user.Perhaps, can use the power supply adaptor electrical outlets to power as STA.Yet this method need use flexible cord that the STA bolt is tied to fixing power supply, and this has reduced mobility and practicality.Therefore, keeping movability and reduction power consumption is user and institute of the manufacturer first concern of STA.

STA is the known communication protocol of general using (for example, IEEE 802.11 standards) with the access point that is connected to network (" AP ") radio communication the time.Owing to recognize that power consumption and battery life are extremely important to user and the manufacturer of STA, so 802.11 standards comprise power-save mechanism.According to these mechanism, the packet that will send to STA when STA is in park mode (that is energy-saving mode) is cushioned at the AP place.In case wake up from park mode, AP just sends to STA with the packet of buffering.Therefore, STA does not need to be in permanent awakening mode (that is consume battery power) and can receive packet yet.

For (for example, VoIP, video flowing etc.) expection has been developed the 802.11e standard and supported these application to the real-time application that service quality (" QoS ") requires is arranged.Qos requirement has been reacted STA and consistent packet has been transmitted the ability of guaranteeing that provides to a certain degree with AP.802.11e standard also transmits (" APSD ") by economizing on electricity automatically power-save mechanism is provided.Use APSD, two class sections service time are possible: non-scheduling (unscheduled) and scheduling (scheduled).The non-scheduled services time period is only the QoS-enhanced wireless platform (" QSTA ") that uses enhanced distributed channel to insert (" EDCA ") access channel to be defined.The scheduled services time period is the QSTA definition that the channel that uses the control of EDCA or Hybrid Coordination Function (" HCF ") is inserted (" HCCA ").Yet according to the 802.11e standard and for scheduling and non-scheduling section two kinds of service times, QSTA is in awakening mode for a long time because its must contention to access as the radio channel of the medium of wireless transmission.Though the APSD of 802.11e standard is intended to reduce power consumption, requires AP and QSTA contention may have spinoffs such as the battery power consumption of increasing, thereby cause delay jitter and/or increase system overhead the access of channel.

Summary of the invention

According to a kind of system and method that is used for saving battery of the present invention in air station.At first, air station switches to the second communication pattern according to predetermined time schedule from first communication pattern.This only just can carry out in packet reception and the transmission at least one when it is in the second communication pattern.First pattern is an energy-saving mode.When platform was in second pattern, WAP obtained the preferential access to radio channel.Then, access point keeps this radio channel and is used for radio communication between access point and this platform.Between access point and this platform, carry out radio communication by this radio channel.One satisfies end condition, and this promptly switches to first pattern.

In a further exemplary embodiment, when air station had first packet that is addressed to WAP, this switched to the second communication pattern from first communication pattern.This only just can carry out in packet reception and the transmission at least one when it is in the second communication pattern.First pattern is an energy-saving mode.When but this has the radio channel time spent, this sends to access point by using this radio channel with first packet.Access point receives this first packet.Access point will confirm that bag sends to this.Confirm bag indication access point receive this first packet and following both one of, promptly (1) exists and there is not second packet that is addressed to this in (2).If satisfy following both one of, promptly (1) confirms the bag indication to have second packet and (2) this is addressed to another packet of access point in addition that then access point obtains the preferential access to radio channel.Then, access point keeps this radio channel and is used for radio communication between access point and this platform.Between access point and this platform, carry out radio communication by this radio channel.In case satisfy end condition, this promptly switches to first pattern.

The accompanying drawing summary

Fig. 1 shows an exemplary embodiment according to wireless network of the present invention;

Fig. 2 shows conventional scheduling machine-processed the schematically showing of transmissions (" APSD ") of economizing on electricity automatically;

Fig. 3 shows schematically showing according to an exemplary embodiment of enhanced scheduled APSD mechanism of the present invention;

Fig. 4 shows an exemplary embodiment according to a kind of enhanced scheduled APSD method of the present invention;

Fig. 5 shows schematically showing of conventional unschelduled APSD mechanism;

Fig. 6 shows schematically showing according to an exemplary embodiment of enhancement mode unschelduled APSD mechanism of the present invention;

Fig. 7 shows schematically showing of another conventional unschelduled APSD mechanism;

Fig. 8 shows schematically showing according to another exemplary embodiment of enhancement mode unschelduled APSD mechanism of the present invention;

Fig. 9 shows the exemplary embodiment according to enhancement mode unschelduled APSD method of the present invention.

Specify

By can further understanding the present invention with reference to following explanation and accompanying drawing, identical element is represented with same numeral in the accompanying drawing.Embodiments of the invention (for example relate to STA, cellular phone, PDA, bar code scanner, laptop computer, Hand held PC etc.) with the improvement in the power-save mechanism, relate in particular that (for example, employed automatic economize on electricity transmits (" APSD ") mechanism in 802.11e) in 802.11 standards.Improvement described here can reduce the battery power consumption of STA, reduces the shake of scheduled services and the agreement overhead of the application-specific (for example, VoIP, video flowing etc.) that minimizing has predetermined characteristic.

Fig. 1 shows an exemplary embodiment according to system 5 of the present invention.System 5 can comprise the access point (" AP ") 15 that is connected to communication network 10.Communication network 10 can be connected to server 12.AP 15 can with any a plurality of air station that can use the switched wireless framework (for example, cellular phone, laptop computer, Hand held PC, printer, earphone etc.) radio communication.The present invention will be described with reference to AP 15, an air station (" STA ") 20 and another STA 25.As the person skilled in the art to be understood, system 5 can comprise a plurality of AP and STA arbitrarily.

AP 15 and STA 20,25 can be according to coming work such as conventional wireless communication agreements such as IEEE 802.11 standards.In a preferred embodiment, 802.11 standards are to realize the 802.11e standard of service quality (" QoS ") in 802.11 networks (that is WLAN (wireless local area network) (" WLAN ")).As understood by those skilled in the art, QoS revises 802.11 access rules by the data that allow to have higher-priority to the preferential access of the radio channel of network 10 uses.Therefore, can authorize high priority data (for example, VoIP, stream video etc.) and have precedence over low priority data (for example, Email, webpage etc.) access channel.

According to the present invention, STA 20 can have STA 20 economize on electricitys therein (promptly, do not send/receive data) first communication pattern (that is " dormancy " pattern) and it may be or is being ready for sending or is receiving the second communication pattern (that is, " waking " pattern up) of data therein.STA 20 switches between park mode and awakening mode according to regard to scheduling and the agreement of non-scheduled services time period.When STA 20 was in the awakening mode, it can receive packet and send packet to AP 15 and/or another STA 25 from AP 15 and/or another STA 25.Yet, in the time of in park mode, originally be under the situation in the awakening mode and will be cushioned at AP 15 from the packet that AP 15 sends to STA 20 at STA 20.Therefore, when service time, section began, STA 20 switchings entered awakening mode and receive those bags that are cushioned.Yet conventional 802.11 access rules require STA 20 to remain on the bag that just can transmit and receive data in the awakening mode for a long time, and this causes the system communication amount to increase and reduced the efficient of STA 20 used batteries.

In order to save battery, the 802.11e standard definition conventional automatic economize on electricity transmit (" APSD ") mechanism, if wherein another STA 25 sends packet by channel, AP 15 must wait for to STA 20 and send packets so.Therefore, AP 15 must wait for the time (for example, " keeping out of the way (backoff) ") of random quantity and could send packet to STA 20 up to channel idle.Waiting time and then cause STA 20 to be in for a long time in the awakening mode, increased its power consumption thus and increased system overhead (for example, channel traffic) potentially.

Fig. 2 shows the conventional scheduling APSD mechanism 200 of using enhanced distributed channel to insert (" EDCA ") pattern.As known in the art, the 802.11e standard definition new coordination function, i.e. the Hybrid Coordination Function (" HCF ") that in QoS enhancement mode Basic Service Set (" QBSS "), uses.HCF has two kinds of mode of operations, and the channel of EDCA pattern and HCF control inserts (" HCCA ") pattern.The EDCA pattern is the channel access function based on contention in the contention-free period operation.Contention-free period is the part (or all) of the time between the beacon that sends of AP.In contention-free period, air station (for example, STA and AP) use channel access mechanism (for example, the carrier sense multiple access avoided of EDCA pattern, decentralized coordinating function (" DCF "), point coordination function (" PCF "), band conflict inserts (" CSMA/CA ")) to come contention channel to insert.

When contention-free period was not All Time between the beacon, the remainder of the time between the beacon was no contention-free period.In no contention-free period, STA is by telegon (for example, some telegon, the hybrid coordinator) poll at access point place.When polled, STA can communicate by letter with AP and not need contention channel to insert.Therefore, the EDCA pattern can be moved (for example, between identical beacon period) simultaneously with the HCCA pattern.As known in the art, EDCA pattern and HCCA pattern strengthen and have expanded original cut-in method---the function of DCF and PCF.

As shown in Figure 2, in contention-free period, conventional scheduling APSD mechanism 200 is used AP 205, STA 210 and another STA 215.Though will the present invention will be described with regard to the running in the contention-free period (for example, use EDCA pattern), it should be appreciated by those skilled in the art that each side of the present invention may be used on not having the running (for example, use HCCA pattern) in the contention-free period.

As understood by those skilled in the art, AP 205 and STA 210 can be QoS enhancement mode, and are called as QAP 205 and QSTA 210 after this.Another STA 215 also can be a QoS enhancement mode.Though put up with the composition of mechanism 200 is described according to the QoS of 802.11e standard, but it should be appreciated by those skilled in the art that the network that the present invention also can be other version (for example, 802.11a, 802.11b, 802.11g etc.) that uses 802.11 standards uses.

According to the scheduling APSD mechanism 200 of routine, service time, section started in service start time (" SST ") 220.In the scheduling APSD of routine mechanism 200, SST 220 is based on the predetermined agreement between QAP 205 and the QSTA 210.SST 220 expression QSTA 210 should switch to awakening mode 230 from park mode 225.SST 220 can for example occur on 30 milliseconds the interval.As understood by those skilled in the art, QSTA 210 can enter awakening mode 230 by preset time before SST 220 or SST 220.

Yet, as shown in Figure 2, at SST 220, because another QSTA 215 or any other STA are just sending packet 235 on this channel, so this channel busy.Because this channel busy, so QAP 205 will wait for up to channel idle.As understood by those skilled in the art, if SST 220 channels idle (that is, not sending on it), then QAP 205 need not to wait for and can send.Yet after detecting channel busy, QAP 205 begins to keep out of the way 240, and the timer among the QAP 205 is from the random value countdown therebetween.In countdown, QAP 205 constantly evaluates channel again, and at one's leisure, the timer that successively decreases of each the idle time slot on QAP 205 respective channels.As shown in Figure 2, keeping out of the way duration of 240 may make before random value is decremented to zero another QSTA 215 or any other STA can send second packet 245 on channel because the timer of another QSTA 215 or any STA keep out of the way 240 finish before arrival zero.When QAP 205 when execution keeps out of the way 240, QSTA 210 remains in the awakening mode 230.If channel is very busy, then QSTA 210 may remain in the awakening mode 230 for a long time, and consume battery power all the time.

As long as it is busy that channel keeps, QAP 205 just may experience other to be kept out of the way, and all increases this random value thereby keep out of the way at every turn.When channel idle, QAP 205 sends to QSTA 210 with the packet 250 of buffering.The packet 250 that it will be apparent to one skilled in the art that buffering can comprise the packet of one or more bufferings and the packet that should arrive in the section in service time.

As understood by those skilled in the art, QSTA 210 can wait for after receiving packet 250 that short inter-frame space (" SIFS ") back sends affirmation (" ACK ") 260 to QAP 205.If QSTA 210 have packet 265 will to QAP 205 send and channel busy once more, then QSTA 210 must carry out one and keeps out of the way 270 before sending packet 265.

After QSTA 210 sends to QAP 205 with packet 265, the ACK 275 that QSTA 210 waits for from QAP 205.Be similar to the performed response of QSTA 210 from the response of QAP 205.After QAP 205 sent ACK 275, QAP 205 may not have other packet to send to QSTA 210, and perhaps QAP205 may plan to stop this of section service time.In either case, QAP 205 sends empty packet 190 with indication section service time end (" EOSP ") to QSTA 210.Empty packet 290 can comprise the EOSP designator, and it can be the bit value in the control field (for example, QoS control field) in the sky packet 290 (for example, QoS packet).If channel busy when QAP 205 attempts to send empty packet 290, then QAP 205 can carry out second and keeps out of the way 285.QSTA 210 usefulness ACK 295 respond empty packet 290.After receiving the EOSP designator and ACK 295 sent to QAP 205, QSTA 210 returns park mode 225.

In the embodiment of the APSD of routine shown in Figure 2 mechanism 200 and since QAP 205 and QSTA 210 want that access channel must carry out keep out of the way 240,270,285, so QSTA 210 is in the awakening mode 230 for a long time.230 li sizable parts of awakening mode, QSTA 210 is waiting for that transmission or wait from QAP 205 send to QAP 205.Therefore, QSTA 210 consumes increasing energy in to be sent/reception packets such as less efficiently.In addition, the transmission in order to the empty packet 290 that stops the period of service may increase system overhead and reduce bandwidth availability ratio.

As shown in Figure 3, the invention provides a kind of enhanced scheduled APSD mechanism 300.Enhanced scheduled APSD mechanism 300 can be in contention-free period be used by the assembly of system shown in Figure 15.That is, enhancement mode APSD mechanism 300 can be used by QAP 305, QSTA 310 and/or other QSTA 315.Correspondingly, the present invention can be such as supporting 802.11 agreements (for example, 802.11a, 802.11b, 802.11g, 802.11e), other be multimedia application (for example, VoIP) and/or lower powered Asset Tag use (for example, lower powered 802.11 RFID labels) and provide on the wireless network of the agreement that QoS and/or economize on electricity support and realize.As the person skilled in the art to be understood, the present invention can be used by the scheduling APSD in the unschelduled APSD in the EDCA pattern and EDCA and/or the HCCA pattern.

In an exemplary embodiment of enhanced scheduled APSD mechanism 300, QAP 305 and QSTA 310 agree to start section service time according to predetermined time schedule (for example, at SST 330).Before SST 330 or its, QSTA 310 switches to awakening mode 325 from park mode 320.As shown in Figure 3, because another QSTA 315 is just sending packet 335 on channel, so this channel busy.As the person skilled in the art to be understood, any activity on the transmission of packet 335 or the channel is not the prerequisite of enhanced scheduled APSD mechanism 300 work.That is, can use enhanced scheduled APSD mechanism 300 no matter channel is whether busy.

According to the present invention, QAP 305 can be by the preferential access of using point coordination function (" PCF ") interFrameGap (" PIFS ") 340 to obtain channel.QAP 305 can use PIFS 340 to obtain before other any QSTA access to channel, because any keep out of the way all more performed than any QSTA duration of PIFS 340 lacks.That is, PIFS 340 allows QAP 305 to have precedence over other QSTA on this channel.It is preferential that use PIFS 340 provides, and QAP 305 can be unique equipment that can send on this channel.Therefore, QAP 305 sends to QSTA 310 with the packet 345 of buffering.As mentioned above, the packet 345 of buffering can comprise the packet of a plurality of bufferings and/or will send to the packet of QSTA 310.

QSTA 310 can use SIFS 350 to obtain access to channel before sending packets and/or ACK to QAP 305.SIFS 350 can allow QSTA 310 access channel before other any QSTA, because the duration of SIFS 350 all lacked than any other stand-by period (for example, keeping out of the way).Described as above scheduling APSD mechanism 200 about routine, QSTA 310 must carry out before transmission and keep out of the way the access that could obtain channel, prolong the time that is in awakening mode 325 thus.

According to the present invention, QAP 305 can keep channel and only be used for communication between itself and QSTA 310.QAP305 for example uses, and send opportunity (" TXOP ") distribution keeps channel.TXOP keeps for QAP 305 and/or a certain amount of time of QSTA 310 communication usefulness or the transmission of certain number of times.As the person skilled in the art to be understood, QAP 305 can be when the beginning (for example, SST 330) of the period of service and/or is shown at the ACK from QSTA 310 that QSTA 310 is waiting under the situation of packet to be sent and use TXOP.If QSTA 310 is waiting packet to be sent, then as discussed below, one satisfies end condition, and it will return park mode 320.In another embodiment, as shown in Figure 3, can be with packet and ACK binding 255.That is, packet can be born on ACK, and this can reduce the time that is in awakening mode 325 and reduce system overhead.It will be apparent to one skilled in the art that about every kind of packet of the present invention-ACK combination and can be born.

End condition can be that indication section service time will finish or finish and QSTA 310 should switch the incident and/or the condition of park mode 320.End condition can have a plurality of exemplary embodiments.In first exemplary embodiment, end condition can be about section will finish service time predetermined agreement between QSTA 310 and the QAP 305.The duration that should predetermined agreement can reflect section service time for example (for example, 50ms) expires.In a further exemplary embodiment, end condition can be to receive the ACK (for example, ACK 360) with sky data field.That is, " more multidata " field in the frame of ACK 360 can comprise the bit value (for example, 0) that indication air station (for example, QAP 305) does not have other packet to send.Therefore, in case receive ACK 360, QSTA 310 can send its any packet that has and/or switch to park mode 320.In another exemplary embodiment, end condition can be that the EOSP designator is set as this bit value (for example, packet EOSP=1).As understood by those skilled in the art, the EOSP designator can be included in packet or the empty packet.In a further exemplary embodiment, end condition can be represented the transmission (for example, the agreement of regulation) of pre-determined number.For example, QAP 305 can send to QSTA 310 with first packet, and QSTA 310 can send to QAP 305 with second packet.After this exchange, QSTA 310 switches to park mode 320.The transmission that it should be appreciated by those skilled in the art that this pre-determined number comprises the transmission from the arbitrary number of times of QAP 305 and/or QSTA 310.

The another exemplary embodiment of end condition is that the data in packet are when having special significance.For example, the user can use the transaction (for example, detecting stock) of application-specific.In case transaction stops, this application can generate " closing the transaction " packet.In case receive " closing the transaction " packet, QSTA 310 promptly switches to park mode 320.In another embodiment, for the web browse application, QSTA 310 can receive with indicate this QSTA should switch to park mode 320 "＜/body＜/html " packet that finishes.In this exemplary embodiment, if for example QAP 305 has formed private communication protocol with QSTA 310, then this packet can be generated by QAP 305, and perhaps another QSTA that is being communicated with by QSTA 310 generates to QSTA 310.

As shown in the exemplary embodiment of enhanced scheduled APSD mechanism 300, in response to packet and ACK 355 from QSTA 310, QAP 305 can send the ACK 360 that comprises frame control field.As mentioned above, frame control field comprises " more multidata " field.Therefore, ACK 360 can comprise in " more multidata " field whether expression QAP 305 also has (for example, end condition) other packet will send to the bit value of QSTA 310.By this way, the empty packet that need not to receive band EOSP designator as long as QSTA 310 receives ACK 360 just can return park mode 320.As above described about the exemplary embodiment of end condition, if for example based on preset time and/or after sending the packet of pre-determined number (for example, the agreement of regulation) stop section service time, then QAP 305 can not send empty packet.(for example, VoIP), QSTA 310 can know that each, section QAP 305 sent the packet of predetermined numbers service time to agreement according to the rules.After receiving the packet of predetermined number, QSTA 310 need not to receive empty packet can return park mode 320.Under the situation that need not the sky packet, service time, section just was kept to two packets (Fig. 3) from 3 packets (Fig. 2).The minimizing of packet can be optimized power consumption, bandwidth availability ratio and reduce shake (that is, because bad synchronous caused signal/pattern distortion).

Fig. 4 shows according to a kind of enhanced scheduled APSD illustrative methods 400 of the present invention, and is described with reference to the composition of Fig. 3 below.In step 405, QSTA 310 wakes up according to predetermined time schedule (for example, before the SST 330 that reaches an agreement or at that time).

In step 410, QAP 305 obtains channel and inserts.As mentioned above, QAP 305 can be as described above by using PIFS 340 for example to obtain preferential access to channel.By this way, may not request QAP 305 to carry out before obtaining the channel access keeps out of the way.By obtaining preferential access, QAP 305 can begin the transmission to QSTA 310.Therefore, in a preferred embodiment, section service time (for example) at the beginning at SST 330, QAP 305 just will obtain that channel inserts and send bag to QSTA 310.

In step 415, QAP 305 sends bag to QSTA 310.If QAP 305 has the packet 345 of buffering, then the packet 345 of this buffering is sent to QSTA 310.If QAP 305 does not have the packet 345 of buffering, then QAP 305 can will send empty packet to QSTA 310.It will be apparent to one skilled in the art that QSTA 310 receives the sky packet and can indicate to QSTA 310: QAP 305 is without any the buffered data packet that will issue QSTA310.Utilize TXOP, shown in step 428, QAP 305 sends to QSTA310 with other bag.

In step 420, determine whether QAP 310 has other packet and will send to QSTA 310.If QAP 310 places do not have other packet, then this method enters step 430.If QAP 305 has other packet will issue QSTA 310, then shown in step 425, QAP 305 can authorize self TXOP.As understood by those skilled in the art, TXOP can keep the transmission that channel is used for QAP 305.Therefore, TXOP can have the duration that the number with for example other packet changes.

In step 430, determine whether QSTA 310 has packet and will send.If QSTA 310 does not have packet, then this method enters step 445.If QSTA 310 has packet, then shown in step 435, QAP 305 can authorize QSTA 310 TXOP.As mentioned above, the TXOP that authorizes QSTA 310 can have the duration that changes with for example number of QSTA 310 place's packets.As understood by those skilled in the art, can notify QAP 305:QSTA 310 that packet is arranged by the indication among the ACK that is sent to QAP 305 in response to the bag that sends in the step 415.For example, after receiving bag, can indicate (for example, by the bit value in the field of ACK) QSTA 310 whether packet is arranged from the ACK of QSTA310 from QAP 305.Therefore, QAP 305 can authorize QSTA 310 TXOP according to the ACK from QSTA 310.

In step 440, QSTA 310 sends to QAP 305 with packet.In one exemplary embodiment, divide the transmission of sending of opening as ACK with packet with QSTA 310 transmissions.In a further exemplary embodiment, packet is born in ACK and is gone up and send with binding form 355.Whether in this embodiment, ACK and/or packet can comprise QSTA 310 has other packet will send to the indication of QAP 310.Therefore, the TXOP that authorizes QSTA 310 can be the result who sends ACK and/or packet to QAP 305.As the person skilled in the art to be understood, QAP 305 and QSTA 310 step 415 and 440 that sends bag separately can allow in proceeding method 400 that all packets all are transmitted before next corresponding steps therein.

In step 445, determine whether to reach end condition.The exemplary embodiment of end condition has been discussed above.Therefore, for example when end condition was the transmission of pre-determined number, QAP 305 may send first packet in step 415, and QSTA 310 may send second packet in step 440.In this example, the transmission of pre-determined number can be each to once send (for example, on the contrary QAP 305 to QSTA 310 and).Send second packet (and receive ACK 360 from QAP 305) afterwards at QSTA 310, shown in step 450, the QSTA 310 changeable park modes 320 that enter.As the person skilled in the art to be understood, method 400 can comprise any one in these exemplary embodiments of end condition.

Fig. 5 shows conventional unschelduled APSD mechanism 400.As understood by those skilled in the art, Chang Gui unschelduled APSD mechanism 400 starts when QSTA 410 has packet 420 to send to QAP 405.Therefore, QAP 405 and QSTA 410 just serve the start time to be in agreement as in scheduling APSD.

As shown in Figure 5, according to the unschelduled APSD mechanism 500 of routine, service time, section was when QSTA 510 switches to awakening mode 540, because it has packet 520 will send to QAP 505.Yet another QSTA 515 is just sending packet 525 on channel when the period of service begins.Thus, QSTA 510 must carry out and keep out of the way 530.Keeping out of the way during 530, this another QSTA 515, other QSTA or QAP 505 may send packet 555 on channel.

Keeping out of the way 530 and channel after the free time, QSTA 510 sends packets 520 to QAP 505.In case receive packet 520, QAP 505 promptly waits for SIFS 560 and sends ACK 565 to QSTA 510.If QAP 505 to be ready sending to QSTA 510 packet 570 of buffering, then QAP 505 must carry out under the situation of channel busy and keep out of the way 535.It will be apparent to one skilled in the art that each trial that under the situation of channel busy QAP 505 and QSTA 510 can be packet sends (and repeating transmission) and carries out and keep out of the way.As mentioned above, keep out of the way in a large number and can prolong section service time, and prolong QSTA 510 thus and be in time in the awakening mode 540.One receives the packet 570 of buffering, and QSTA 510 promptly sends ACK 575 to QAP 505.

After the packet 570 that sends buffering, QAP 505 may want to finish this of section service time.Yet according to the unschelduled APSD mechanism of routine, QAP 505 must send the packet 550 (or empty packet) of being with the EOSP designator should section termination service time with notice QSTA 510.Therefore, QAP 505 must regain channel and insert, and this may comprise that carrying out another time keeps out of the way 580.Behind QAP 505 access channel again, packet 550 is sent to QSTA 510.EOSP designator in the packet 550 is indicated this section end service time, and QSTA 510 should switch to park mode 545 after sending ACK 585 to QAP 505.

Fig. 6 shows an exemplary embodiment according to enhancement mode unschelduled APSD mechanism 600 of the present invention.Service time, section had packet 635 will send to QAP 605 and when park mode 620 switches to awakening mode 625 at QSTA 610.Yet, as shown in Figure 6, when QSTA 610 enters awakening mode 625, because another QSTA 615 (or QAP 605) is just sending packet 630 on channel, so this channel busy.Therefore, QSTA 610 carried out before sending packet 635 to QAP 605 and keeps out of the way 640.As understood by those skilled in the art, if when QSTA 610 enters awakening mode 625 channel idle, QSTA 610 can need not to carry out and keeps out of the way 640 so.

When channel idle, QSTA 610 sends to QAP 605 with packet 635.In case receive packet 635, QAP 605 promptly waits for SIFS 645 and sends ACK 650 thereafter.QAP 605 uses PIFS 655 to obtain the preferential access of channel then.As shown in Figure 6, QAP 605 has the data of buffering will send to QSTA 610.As mentioned above, after using PIFS 655 to obtain channels to insert, QAP 605 can authorize self TXOP in order to keep the communication that channel is used for QAP 605.By this way, QAP 605 sends to QSTA 610 with the packet 660 of buffering, and each buffered data packet 660 corresponding ACK 665 of receiving of reception and QSTA 610.As the person skilled in the art to be understood, QAP 605 can authorize QSTA 610 TXOP, because packet 635 can indicate QSTA 610 to have other packet 635 will send to QAP 605.The TXOP that authorizes QSTA 610 can keep channel before or after QAP 610 sends the packet that cushions.

After receiving ACK 665, QAP 605 can wait for SIFS 670 before sending another packet 675.If this another packet 675 is last packet that will issue QSTA 610, then QAP 605 can comprise EOSP designator (for example, end condition) with it.Therefore, after this another packet 675 that receives band EOSP designator, QSTA 610 sends ACK 680 and switches and enters park mode 620.

Fig. 7 shows another conventional unschelduled APSD mechanism 700 that QAP 705 does not wherein have the packet of buffering.QSTA 710 switches to awakening mode 725 and is keeping out of the way 730 (for example, because another QSTA 715 is sending packet 735) back access channel from park mode 720.Execution keep out of the way 730 and detect channel idle after, QSTA 710 sends packets 740.In case receive packet 740, QAP 705 promptly waits for SIFS 745 and sends ACK 750 to QSTA 710.In Fig. 7, QAP 705 is without any the buffered data packet that will issue QSTA 710, and uses empty packet 755 that this situation is conveyed to QSTA 710.Yet if channel busy, QAP 705 must carry out before sending empty packet 755 and keep out of the way 760.QAP 705 can be provided with the EOSP designator and should be terminated to indicate this section service time in empty packet 755.In case receive sky packet 755, QSTA 710 promptly sends ACK 765 and switches back park mode 720.

As shown in Figure 8, significantly having reduced QSTA 810 according to another exemplary embodiment of enhancement mode unschelduled APSD mechanism 800 of the present invention remains on the time of awakening mode 825 and has reduced in the conventional unschelduled APSD mechanism 700 because the system overhead of using empty packet 715 to be introduced.In enhanced mechanism 800, service time, section began when QSTA 810 has packet 840 to send to QAP 805, and QSTA 810 switches to awakening mode 825 from park mode 820.QSTA 810 attempts to send packet 840 to QAP 805, but channel busy (for example, another QSTA 815 is sending packet 835).Execution keep out of the way 830 and detect channel idle after, QSTA 810 sends to QAP 805 with packet 840.As shown in Figure 8, QAP805 does not have to issue the buffered data packet of QSTA 810.If QSTA 810 indications (for example, by the bit value in the frame field) it have other packet will send to QAP 805, then QAP 805 can authorize QSTA 810TXOP, is that QSTA 810 keeps channel thus.

If packet 840 is the unique transmissions (for example, the only packet in QSTA 810 places) from QSTA 810, then QAP 805 can wait for SIFS 845 and send ACK 850 to QSTA 810.As above described with reference to the exemplary embodiment of end condition, ACK 850 (and packet 840) can comprise frame control field, and frame control field can comprise " more multidata " field.According to one example embodiment, " more multidata " field can be set as the value (for example, 0) that expression QAP 805 (or QSTA 810) does not have packet (or not having other packet) to send.Thus, in case receive ACK 850, QSTA 810 can switch to park mode 820 from awakening mode 825.Therefore, in an example embodiment, for example, EOSP designator and empty packet can replace with the value in " more multidata " field of ACK 850.It will be apparent to one skilled in the art that any one of exemplary embodiment that can use above-mentioned end condition with it.

Fig. 9 shows according to a kind of enhancement mode unschelduled APSD illustrative methods 900 of the present invention, and is described with reference to the composition of enhancement mode unschelduled APSD mechanism 600 shown in Figure 6 below.In step 905, service time, section began when QAP 605 enters awakening mode 625 because of there being packet 635 to send at QSTA 610.In step 910, QSTA 610 access channels.As mentioned above, if channel busy, then QSTA 610 must carry out and keep out of the way 640 and wait for and could send up to channel idle.In step 915, QSTA 610 sends packet 635 to QAP605.

In step 920, determine whether QAP 605 has buffered data packet 660 will send to QSTA 610.If QAP 605 does not have buffered data packet 660, then this method enters step 940.If QAP 605 has buffered data packet 660, then QAP 605 can use PIFS 655 to obtain the preferential access of channel, shown in step 925.In step 930, QAP 605 authorizes self TXOP, and in step 935, QAP 605 sends buffered data packet 660 to QSTA 610.When QAP 605 had kept channel, it can send another packet 675 to QSTA 610.

In step 940, determine whether QSTA 610 has other packet to send.If QSTA 610 does not have other packet, then this method enters step 955.If QSTA 610 has other packet to send, then shown in step 945, QAP 605 can authorize QSTA 610 TXOP.As mentioned above, packet 635 and/or ACK 665 can comprise other packet to QAP 605 indication QSTA 610 and will send.In step 950, QSTA 610 sends other these packets.

In step 955, reach end condition.As understood by those skilled in the art, QAP 605 and QSTA610 can send packet back and forth up to reaching end condition.As said, end condition can be any one or its combination in the above-mentioned exemplary embodiment.After reaching end condition, shown in step 960, QSTA610 switches to park mode 620 from awakening mode 625.As understood by those skilled in the art, before switching to park mode 620, QSTA 610 can send ACK 680 to QAP 605.

Describe the present invention with reference to QAP, QSTA and end condition.Correspondingly, can carry out various modifications and changes and can not deviate from the most wide in range spirit of the present invention and the scope of setting forth as claims these embodiment.Correspondingly, illustrate with accompanying drawing and should on illustrative rather than restrictive meaning, understand.

Claims (19)

1. one kind is used for method of wireless communication, and described method comprises:

(a) according to predetermined time schedule, air station is switched to the second communication pattern from first communication pattern, described only just can be carried out at least one in receiving and sending of packet when it is in described second pattern, and described first pattern is an energy-saving mode;

(b) when being in described second pattern for described, obtain preferential access to radio channel by WAP;

(c) afterwards, keep described radio channel by described access point and be used for radio communication between described access point and described in step (b);

(d) carry out radio communication by described radio channel between described access point and described; And

(e) in a single day satisfy end condition, just switch to described first pattern described.

2. the method for claim 1, it is characterized in that described end condition is one of the following: (a) the band section service time empty packet, (c) that finish packet, (b) band EOSP designator of (EOSP) designator expires with affirmation bag, (d) schedule time of empty data field and (e) transmission of the packet of predetermined number between described and the described access point.

3. the method for claim 1 is characterized in that, obtains the preferential access to described radio channel when described access point utilizes PIFS.

4. the method for claim 1 is characterized in that, described reservation step comprises following substep:

Authorize a send opportunity to one of described access point and described.

5. method as claimed in claim 4 is characterized in that described send opportunity comprises a time period, and one of described during this period access point and described send one group of packet by described radio channel.

6. method as claimed in claim 5 is characterized in that, the described time period is determined according to the number of packet in described one group of packet.

7. method as claimed in claim 5 is characterized in that, the described time period is represented in the duration field of the packet that is sent by described access point.

8. the method for claim 1 is characterized in that, described step (a) is carried out between contention-free period to (e).

9. one kind is used for method of wireless communication, and described method comprises:

(a) when air station has first packet that is addressed to WAP, switch to the second communication pattern with described from first communication pattern, described only just can be carried out at least one in receiving and sending of packet when it is in described second pattern, described first pattern is an energy-saving mode;

(b) but arranged when described the radio channel time spent, by described by using described radio channel to send described first packet to described access point;

(c) receive described first packet by described access point;

(c) send to confirm bag by described access point to described, described affirmation bag indicates described access point to receive one of described first packet and the following: (1) exists second packet that is addressed to described and (2) not to exist to be addressed to described second packet;

(d) if the indication of (1) described affirmation bag exists described second packet and (2) described that a establishment in other packet that is addressed to described access point is arranged, then carry out following substep:

(i) by the preferential access of described access point acquisition to described radio channel;

(ii) afterwards, keep described radio channel by described access point and be used for radio communication between described access point and described at substep (i); And

(iii) carry out radio communication between described access point and described by described radio channel; And

(e) in a single day satisfy end condition, just switch to described first pattern described.

10. method as claimed in claim 9 is characterized in that, when there was not described second packet in the indication of described affirmation bag, described affirmation bag comprised the sky data field.

11. method as claimed in claim 10, it is characterized in that described end condition is one of the following: (a) packet, (b) of band end-of-segment indicator service time expire with affirmation bag, (c) schedule time of empty data field and (d) transmission of the packet of predetermined number between described and the described access point.

12. method as claimed in claim 9 is characterized in that, the preferential access of described radio channel is obtained when described access point utilizes PIFS.

13. method as claimed in claim 9 is characterized in that, described reservation substep comprises following substep:

Authorize a send opportunity for one to (1) described access point and (2) in described.

14. method as claimed in claim 13 is characterized in that, described send opportunity comprises a time period, and one of described during this period access point and described send one group of packet by described radio channel.

15. method as claimed in claim 14 is characterized in that, the described time period is determined according to the number of packet in described one group of packet.

16. method as claimed in claim 14 is characterized in that, the described time period is represented in the duration field of the packet that is sent by described access point.

17. method as claimed in claim 9 is characterized in that, described step (a) is carried out between contention-free period to (e).

18. a system, described system comprises:

Air station; And

With described WAP of communicating by letter;

Wherein, described switches to the second communication pattern according to predetermined time schedule from first communication pattern, and described only just can be carried out at least one in receiving and sending of packet when it is in described second pattern, and described first pattern is an energy-saving mode,

When being in described second pattern for described, described access point obtains the preferential access to radio channel,

Described access point keeps described radio channel and is used for radio communication between described access point and described,

Described radio communication is carried out between described access point and described by described radio channel, and

In case satisfy end condition, described promptly switches to described first pattern.

19. a system comprises:

Air station; And

With described WAP of communicating by letter,

Wherein, described air station switches to the second communication pattern from first communication pattern when it has first packet that is addressed to described access point, described only just can be carried out at least one in receiving and sending of packet when it is in described second pattern, described first pattern is an energy-saving mode

But arranged when described the radio channel time spent, described is used described radio channel to send described first packet to described access point,

Described access point receives described first data and sends the affirmation bag to described, described affirmation bag indicates described access point to receive one of described first packet and the following, promptly (1) exists second packet be addressed to described and (2) not to exist to be addressed to described second packet

If satisfy one of the following, i.e. (1) described affirmation bag indication exists described second packet and (2) described that other packet that is addressed to described access point is arranged, then (i) described access point obtains the preferential access of described radio channel and (ii) keeps described radio channel to be used for the radio communication between described access point and described and to carry out radio communication by described radio channel between described access point and described, and

In case satisfy end condition, described promptly switches to described first pattern.

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