Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W52/00—Power management, e.g. Transmission Power Control [TPC] or power classes
  • H04W52/04—Transmission power control [TPC]
  • H04W52/30—Transmission power control [TPC] using constraints in the total amount of available transmission power
  • H04W52/36—Transmission power control [TPC] using constraints in the total amount of available transmission power with a discrete range or set of values, e.g. step size, ramping or offsets
  • H04W52/367—Power values between minimum and maximum limits, e.g. dynamic range
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W84/00—Network topologies
  • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
  • H04W84/10—Small scale networks; Flat hierarchical networks
  • H04W84/12—WLAN [Wireless Local Area Networks]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W92/00—Interfaces specially adapted for wireless communication networks
  • H04W92/16—Interfaces between hierarchically similar devices
  • H04W92/18—Interfaces between hierarchically similar devices between terminal devices

Definitions

• the present invention is directed, in general, to wireless local area networks and, more specifically, to using transmit power control in conjunction with hybrid coordination function operation within wireless local area networks.
• WLANs Wireless local area networks
• IEEE Institute of Electrical and Electronic Engineers 802.11- 1999 standard, often referred to as “wireless fidelity” or “WiFi”.
• WiFi wireless fidelity
• the IEEE 802.11 Working Group's Medium Access Control (MAC) Enhancements task group (Task Group E) is working to incorporate quality of service (QoS) into wireless local area networks for high quality delivery of video, voice and multimedia (see IEEE 802.1 le QoS draft D2.0a, November 2001), while the IEEE 802.11 Task Group H (TGh) is developing a standard for incorporation of dynamic frequency selection and transmit power control into IEEE 802.1 la implementations (see “DFS and TPC Joint Proposal for 802.1 lh", IEEE 802.11-01/I69r2). Energy consumption has become an important issue in IEEE 802.11 wireless networks since mobile terminal battery life is limited.
• QoS quality of service
• TGh IEEE 802.11 Task Group H
• TPC transmit power control
• PHY physical
• TPC mechanism in an IEEE 802.1 le network operating under the hybrid coordination function (HCF) would be desirable, particularly since direct communication between quality-of-service (QoS) stations (QSTAs) without external control is permitted ⁇ that is, one QSTA can transmit to another without first transmitting to the access point/hybrid coordinator (AP/HC). Presumptively individual stations (STAs) would control transmit power during each contention-free period (CFP) and contention-free burst under the HCF operation. Under one proposed implementation for the HCF, however, the hybrid coordinator (HC) must "hear" all frames in the CFB/CFP.
• the HC sensing the medium as idle for a distributed coordination function (DCF) inter-frame spacing (DIFS) period, will reclaim the channel and attempt to transmit.
• DCF distributed coordination function
• DIFS inter-frame spacing
• the HC needs to receive certain frames (e.g., to update queue sizes) for correct operation of the QoS-supporting basic service set (QBSS) network. Therefore every QSTA in a QBSS network should transmit every frame at a high enough power so that the HC can hear the frame, which considerably reduces the benefits of TPC.
• the transmit power may not be as low as possible. There is, therefore, a need in the art for improving the adaptation of transmit power control to hybrid coordination function operation under quality-of-service supporting basic service set networks.
• a primary object of the present invention to provide, for use in a quality-of-service supporting basic service set (QBSS) network, a granted TxOP holder which transmits the first frame of a QBSS network.
• QBSS quality-of-service supporting basic service set
• QSTA-to-QSTA communication at a power level sufficient to ensure correct reception by the destination and at least detection by the HC, and then, with exceptions, transmits subsequent frames at a power level merely sufficient to ensure correct reception by the destination, regardless of reception or detection by the HC.
• Subsequent frames that must be received by the HC such as those changing the TC queue size or requesting extension of the current TxOP, are transmitted at a power sufficient to ensure reception by the HC as well as the destination, as are the last frame(s).
• the HC is constrained from reclaiming the channel unconditionally merely because of failure to detect activity, and recovery is limited to the TxOP holder.
• Figs. 1 A-1B depict quality-of-service supporting basic service set (QBSS) wireless communications networks under one set of proposed rules (IEEE 802.1 le/D 1.0) for hybrid coordination function (HCF) operation;
• QBSS quality-of-service supporting basic service set
• HCF hybrid coordination function
• Figs. 2A-2D depict the structure and power level operation of a quality-of- service supporting basic service set (QBSS) wireless communications network implementing transmit power control and hybrid coordination function (HCF) operation according to one embodiment of the present invention
• QBSS quality-of- service supporting basic service set
• HCF hybrid coordination function
• Fig. 3 is a high level flowchart for a process of transmit power control during station-to-station communications under hybrid coordination function operation according to one embodiment of the present invention.
• Fig. 4 is a high level flowchart for a process of transmit power control during station-to-station communications under hybrid coordination function operation according to one embodiment of the present invention.
• Figs. 1 A through 3, discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any suitably arranged device.
• Figs. 1 A and IB depict quality-of-service supporting basic service set (QBSS) wireless communications networks under currently proposed rules for hybrid coordination function (HCF) operation.
• QBSS quality-of-service supporting basic service set
• HCF hybrid coordination function
• a transmission opportunity (TxOP) holder such as QSTAj needs to transmit frames at a sufficient power level to be received by the intended recipient QSTA 2 and at least heard (and preferably received) by the HC.
• the ideal case for TPC in QSTA-to-QSTA communication would be to set the transmit power level at QSTAj to the minimum level required to ensure reception of the transmitted frame at QSTA 2 (i.e., to ensure that QSTA 2 lies within the transmission range 101).
• the transmit power level that is sufficient to ensure reception of the transmitted frame at QSTA 2 may be insufficient to ensure that the transmission will be "heard" by the HC (i.e., that the HC lies within the CCA busy range 102).
• the transmit power level at QSTA ⁇ must be set to the minimum level required to ensure that HC lies within the CCA busy range 103, even though the resulting transmission range 104 is greater than necessary to ensure reception by QSTA 2 .
• the transmit power in QSTA-to-QSTA communications may not be as low as possible, resulting in inefficient use of power resources.
• Figs. 2A through 2D depict the structure and power level operation of a quality-of-service supporting basic service set (QBSS) wireless communications network implementing transmit power control and hybrid coordination function (HCF) operation according to one embodiment of the present invention.
• Figs. 2 A through 2C depict positions of QSTAs and HC and relative transmission and CCA busy ranges, while Fig. 2D depicts transmission power over time for a granted TxOP.
• QBSS quality-of-service supporting basic service set
• HCF hybrid coordination function
• the transmit power controller for the granted TxOP holder (QSTA t in the example shown) transmits at a sufficiently high power so that the intended recipient (QSTA in the example) may correctly receive the frame 201 and the HC at least hears the frame.
• the power level PI must be sufficient to cover the CCA busy range 103 and transmission range 104 as shown in Fig. 2A.
• the TxOP holder QSTAi uses the best power and data rate combination with this constraint, but the HC needs to hear the first frame to determine whether the polled QSTA received the QoS CF-polling frame correctly. Notably, if the HC is at least as close to the TxOP holder QSTAj as the intended recipient QSTA 2 , the power level PI for the first frame need only be sufficient to ensure correct reception by the intended recipient QSTA 2 .
• Subsequent frames 202 for QSTA-to-QSTA communication during the TxOP may be transmitted at a power level P2 (and data rate) selected by QSTAi solely to ensure correct reception of the frames 202 by the intended recipient (or destination) QSTA 2 , without regard to whether the frames 202 are received or even heard by the HC. That is, the transmission power need only be sufficiently high to ensure that QSTA 2 lies within the transmission range 200 as shown in Fig. 2B.
• one or more selected frames 203 may optionally be transmitted by QSTA1 at a higher power level P3 (and selected data rate) sufficient to ensure that BOTH the destination QSTA within the QSTA-to-QSTA communication (QSTA 2 ) AND the HC correctly receive the frame(s) 203.
• the granted TxOP holder QSTA ! desires to update the traffic category (TC) queue size, update the granted TxOP (i.e., request a new duration) or request a new TxOP
• the transmit power controller for QSTAi transmits at the higher power level P3, corresponding to the transmission range 204 in Fig. 2C.
• Subsequent frames 205 within the TxOP are again transmitted at the lower power level P2 by QSTA L
• Such power levels for the last frame(s) are desirable to save bandwidth, particularly when the TxOP holder QSTAj finishes earlier than the end of the originally granted TxOP.
• the HC may NOT, however, unconditionally reclaim the channel after merely sensing the medium idle for DIFS or PIFS.
• the TxOP holder is responsible for recovery from the absence of an expected reception.
• the recovery may be performed by: retransmitting the frame; sending a frame to another QSTA; or sending a QoS Null Data frame to the HC with the NF bit equal to 0 (in this manner, the TxOP ends and the HC can reclaim the channel). All other QSTAs, including the HC, shall not initiate channel recovery since they cannot reliably determine if the medium in the QBSS is in use or not.
• Fig. 3 is a high level flowchart for a process of transmit power control during station-to-station communications under hybrid coordination function operation according to one embodiment of the present invention.
• the process 300 which is performed by the TxOP holder, begins with a TxOP being granted for QSTA-to-QSTA communication (step 301).
• the HC is precluded from reclaiming the channel except under pre-defined conditions excluding inactivity (unconditionally), and recovery is limited to the TxOP holder (step 302).
• the first frame from the TxOP holder is transmitted at a power level (and data rate) sufficient to ensure correct reception by the intended recipient (or recipients for multi-casts) and being at least detection by the HC (step 303).
• the next frame transmitted by the TxOP holder is transmitted at a power level (and data rate) that is merely sufficient to ensure correct reception by intended recipient(s)
• step 304 regardless of reception or even detection by the HC.
• the above description relates solely to the TxOP holder selectively adapting power.
• the recipients need to respond with protocol frames, such as QoS CF-ACK.
• protocol frames such as QoS CF-ACK.
• the same rules for selectively transmitting a lower power levels apply to the other station(s) within a QSTA-to-QSTA communication.
• Fig. 4 is a high level flowchart for a process of transmit power control during station-to-station communications under hybrid coordination function operation according to one embodiment of the present invention. Since the QoS CF-ACK may be employed to update the TC queue status, adherence by the other stations involved in the station-to-station communication to the transmit control rules defined above is equally important.
• the process 400 implemented within the other stations to the station-to-station communication, begins the necessity for transmission of a protocol frame by a non-TxOP holder involved in a station-to-station communication arising (step 401). A determination is made, on a frame-by- frame basis, of whether the next frame to be transmitted must be heard by the HC as well as the intended recipients (step 402).
• the frame is transmitted at a power level sufficient for correct reception by the HC and the intended recipients (step 403); otherwise, the frame is transmitted at a power level merely sufficient to ensure correct reception by the intended recipients (step 404), without regard to whether the frame is received or detected by the HC.
• a determination is then made regarding whether the last required frame has been transmitted (step 405), with the process becoming idle (step 406) in that event.
• the present invention improves the performance of transmit power control under hybrid coordination function operation.
• the hybrid coordination controller need only detect the first frame after the contention free polling, after which the transmission opportunity holder may transmit at the lowest power and highest data rate possible for correct reception by the destination enhanced station, without consideration of whether the hybrid coordination controller is detecting the frames, which can be of substantial benefit in direct enhanced station to enhanced station communications. Transmit power control is thus employed in an efficient manner while maintaining correct operation of a quality-of-service supporting basic service set network.
• machine usable mediums include: nonvolatile, hard-coded type mediums such as read only memories (ROMs) or erasable, electrically programmable read only memories (EEPROMs), recordable type mediums such as floppy disks, hard disk drives and compact disc read only memories (CD-ROMs) or digital versatile discs (DVDs), and transmission type mediums such as digital and analog communication links.
• ROMs read only memories
• EEPROMs electrically programmable read only memories
• CD-ROMs compact disc read only memories
• DVDs digital versatile discs

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Small-Scale Networks (AREA)
• Transceivers (AREA)

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• 2002
  • 2002-04-10 US US10/119,577 patent/US7245592B2/en not_active Expired - Lifetime
  • 2002-06-28 AT AT02738561T patent/ATE324727T1/de not_active IP Right Cessation
  • 2002-06-28 JP JP2003513190A patent/JP2004535139A/ja not_active Withdrawn
  • 2002-06-28 DE DE60210975T patent/DE60210975T2/de not_active Expired - Lifetime
  • 2002-06-28 ES ES02738561T patent/ES2261684T3/es not_active Expired - Lifetime
  • 2002-06-28 WO PCT/IB2002/002584 patent/WO2003007551A1/en not_active Ceased
  • 2002-06-28 KR KR10-2003-7003462A patent/KR20030029953A/ko not_active Abandoned
  • 2002-06-28 CN CNA028137264A patent/CN1526219A/zh active Pending
  • 2002-06-28 EP EP02738561A patent/EP1407579B1/en not_active Expired - Lifetime

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