as) United States
`a2) Patent Application Publication 0) Pub. No.: US 2005/0025080 Al
`(43) Pub. Date: Feb. 3, 2005
`
`Liu
`
`US 20050025080A1
`
`(54) POWER SAVING VIA PHYSICAL LAYER
`ADDRESS FILTERING IN WLANS
`
`(76)
`
`Inventor: Yonghe Liu, Dallas, TX (US)
`
`Correspondence Address:
`TEXAS INSTRUMENTS INCORPORATED
`PO BOX 655474, M/S 3999
`DALLAS, TX 75265
`
`(21) Appl. No.:
`
`10/630,437
`
`(22)
`
`Filed:
`
`Jul. 30, 2003
`
`Publication Classification
`
`(SL) Ute C0 eee ceeccccsssssssssneescceceennnnseeseeseee HO4L 12/28
`(52) US. C1. eee ecsesesessseecnsceneeeneeseess 370/311; 370/389
`
`(57)
`
`ABSTRACT
`
`A system and method is described for saving power in a
`wireless network, using a physical layer address filtering
`protocol based on a partial address subset of the complete
`
`destination MAC address. The system comprises a PHY
`layer filtering protocol for generating the partial address and
`writing the partial address into a PHY layer header portion
`(e.g., PLCP header) of a sending station, or reading the
`partial address from the PHY layer header portion upon
`transmission of each frame. A receiving station receives and
`decodes these PHY layer headerportion bits, in accordance
`with the protocol, and compares whether the subset of bits
`match that of the stations’ own partial address. If a station
`finds a match, the station then continues further decoding the
`frame at PHY layer and send the complete frame to the MAC
`layer for further processing. The stations that do not have a
`match will not activate their MAC layer components. Thus,
`the stations of the network will avoid wasting power decod-
`ing a significant portion of the complete frame of other
`stations of the wireless local area networks and unnecessary
`MAC layer processing. When group addressed, control/
`management frames or other such frames are detected at the
`sending station, the addressfiltering protocol may be “dis-
`abled” using a partial address containing a predetermined
`value (e.g., all zeros).
`
`700 m™.
`
`705 ~
`
`AP
`
`710
`
`PARTIAL ADDRESS
`
`
`MobN HY
`
`' PHY LAYER ADDRESS|
`|FILTERING PROTOCOL|
`
`
`
`
`
` 710
`
`PARTIAL ADDRESS
`
`
`Mob~ LY
`
`' PHY LAYER ADDRESS|
`
`
`|FILTERING PROTOCOL|
`
`PARTIAL ADDRESS
`
`
`
`710b ~
`
`| BHY LAYER ADDRESS|
`
`
`|FILTERING PROTOCOL|
`
`
`Page | of 20
`
`Samsung Exhibit 1039
`
`Page 1 of 20
`
`Samsung Exhibit 1039
`
`

`

`Patent Application Publication Feb. 3, 2005 Sheet 1 of 10
`
`US 2005/0025080 Al
`
`1 y,
`
`BSS
`
`
`
`
`
`4
`
`AP
`
`2
`
`STATION
`¢
`
`STATION
`A
`
`2
`
`STATION
`B
`
`2
`
`20
`
`FIG. 1
`PRIOR ART
`
`DATA PACKET
`
` TT 1
`
`PRIOR ART
`
`Page 2 of 20
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`Page 2 of 20
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 2 of 10
`
`US 2005/0025080 Al
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`100 oN
`
`Page 3 of 20
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`Page 3 of 20
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 3 of 10
`
`US 2005/0025080 Al
`
`400 ~%
`
`Basic Frame Format
`
`405
`
`410
`
`415
`
`420
`
`425
`
`
`
`
`PREAMBLE|WEADER|HEADER DATA (CRC)
`
`
`
`PHY
`
`MAC
`
`
`
`FSC
`
`
`
`
`
`
`
`Frame_|Duration/
`Sequence|Addr|Frame ECS
`Control
`ID
`Control
`4
`Body
`
`MAC Frame
`(PHY Payload)
`
`
`
`
`
`FIG. 4
`
`430 ~
`
`MAC Frame Format
`
`450
`
`460
`
`455
`
`431
`
`435
`
`4
`
`445
`
`40
`
`
`
`
`
`
`
`
`
`
`MAC Header
`
`FIG. 5
`
`Page 4 of 20
`
`420
`
`425
`
`
`
`
`Page 4 of 20
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 4 of 10
`
`US 2005/0025080 Al
`
`IEEE 802.11b PHY Frame Format
`
`
`Reserved|Reserved Reserved|Reserved|Reserved|Length
`extension
`clocksbit|selection
`
`0=not
`bit
`bit
`
`
`
`1=locked |0 =CCK
`
`
`1=PBCC
`
`621
`
`622
`
`623
`
`625
`
`626
`
`
`
`
`
`
`
`
`
`
`
`SYNC
`128 bits
`
`SIGNAL
`8 bits
`
`SERVICE
`8 bits
`
`LENGTH
`16 bits
`
`CRC
`16 bits
`
`PLCP PREAMBLE|PLCP HEADER
`144 bits
`48 bits
`
`613
`
`610 *
`
`FIG. 6
`
`Page 5 of 20
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`Page 5 of 20
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 5 of 10
`
`US 2005/0025080 Al
`
`700 ~
`
`705 ~
`
`AP
`
`710
`
`PARTIAL ADDRESS
`
`
`
`8
`710b ~
`
`| PHY LAYER ADDRESS|
`
`
`|FILTERING PROTOCOL|
`
`
`
`
`710
`
`PARTIAL ADDRESS
`
`
`710b ~
`
`PHY LAYER ADDRESS|
`[FILTERING PROTOCOL|
`
`
`
`
`
`PARTIAL ADDRESS
`
`
`
`
`| PHY LAYER ADDRESS|
`|FILTERING PROTOCOL|
`
`
`FIG. 7
`
`Page 6 of 20
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 6 of 10
`
`US 2005/0025080 Al
`
`802
`
`x 800
`
`(Optional)
`
` 3-bit Partial Address 3BitDestinationPartialAddr.
`
` ca eee i ei eee Ce Ce
`
` 805
`
`MAC LAYER
`
`3-bit Address Encoder
`
`Page 7 of 20
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`Page 7 of 20
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 7 of 10
`
`US 2005/0025080 Al
`
`902
`
`MAC LAYER
`
`3-bit Address Encoder
`(Optional)
`942
`
`y- 900
`
`
`| Filtering Protocol
`
`
`910
`| PHYLayr |
`
`#4|of4
`
`
`
`3-bit Partial Address 905
`
`Page 8 of 20
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`Page 8 of 20
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 8 of 10
`
`US 2005/0025080 Al
`
`zs 1000
`
`BEGIN PHY LAYER FILTERING
`PS METHOD, T, ACTION
`
`1005
`
`
`
`
`GROUP ADDRESSED OR
`CONTROL/MANAGEMENT
`FRAMES
`
`1020
`
`CALCULATE DESTINATION
`PARTIAL ADDRESS
`
`
`
`
`
`
`NORMAL
`
`DATA FRAME ?
`
`
`
`
`
`PASS PARTIAL ADDRESS TO
`PHY LAYER
`
`1060
`
`
`PUT PARTIAL ADDRESS
`
`(N-BITS) IN PLCP HEADER
`
`END PHY LAYER FILTERING PS
`METHOD, T, ACTION
`
`FIG. 10
`
`Page 9 of 20
`
`
`
`
`PUT ALL ZEROES IN
`
`N-BIT PARTIAL ADDRESS 1050
` 1070
`
`Page 9 of 20
`
`

`

`Patent Application Publication Feb. 3, 2005 Sheet 9 of 10
`
`US 2005/0025080 Al
`
`= 1100
`
`BEGIN PHY LAYER FILTERING
`PS METHOD, R, ACTION
`
`1105
`
`1110
`
`STORE OWN PARTIAL ADDRESS
`HAVING N BITS IN PHY LAYER
`
`R, FRAME IN PHY LAYER
`
`1115
`
`1120
`
`
`
`
`DECODE PLCP HEADER OF
`RECEIVED FRAME
`
`
`AND CHECK THEN BITS
`
`
` PARTIAL ADDR.
`
`MATCH OWN?
`
`
`
`
`PARTIAL ADDR.
`SEND FRAME TO MAC FOR
`ALL ZEROES?
`COMPLETE ADDRESS DECODE
`
`
`
`
`1130
`
`
`
`STOP DECODING
`AFTER PHY HEADER
`
`REJECT FRAME, NOT OWN
`ADDRESS, DO NOT ACTIVATE
`MAC MODULE HIGH DATA RATE
`
`
`
`
`END PHY LAYERFILTERING PS\_4440
`METHOD, R, ACTION
`
`FIG. 11
`
`Page 10 of 20
`
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`

`

`Patent Application Publication Feb. 3, 2005 Sheet 10 of 10
`
`US 2005/0025080 Al
`
`= 1200
`
`1210
`
`MAC
`
`Adtinoes coorkoro
`
`
`
`
`1240
`
`4220
`
`Encoded
`Partial
`Address
`
`FIG. 12
`
`Partial
`Vendor
`ID No.
`
`Partial
`Address
`
`Page 11 of 20
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`US 2005/0025080 Al
`
`Feb. 3, 2005
`
`POWERSAVING VIA PHYSICAL LAYER
`ADDRESS FILTERING IN WLANS
`
`FIELD OF INVENTION
`
`[0001] The present invention relates generally to wireless
`networks and more particularly to systems and methods for
`saving powerin wireless local area networks.
`BACKGROUND OF THE INVENTION
`
`peer-to-peer level sharing a given cell coverage area. This
`mode was designed such that only the clients within trans-
`mission range of each other can communicate. If a client in
`an ad-hoc network wishes to communicate outside of the
`range, one of the clients (members) must operate as a
`gateway and perform routing.
`
`[0008] FIG. 1 illustrates the basic service set BSS 1
`operating in the infrastructure mode, wherein a wireless
`network is formed between one or more stations (STA) 2
`[0002] The Institute of Electrical and Electronics Engi-
`communicating with an access point (AP) 4 such as a
`neers (IEEE) has producedaseries of standards referred to
`communications tower. The access point acts as an Ethernet
`as 802.X, which encompasses LANs (Local Area Net-
`bridge and forwards the communications onto the network
`works), MANs (Metropolitan Area Networks) and PANs
`(e.g., either wired or wireless network). Several such BSS
`(Personal Area Networks) such as Bluetooth. The IEEE 802
`networks communicating together over the infrastructure
`is confined to standardizing processes and procedures that
`between APs further form an Extended Service Set (ESS), or
`take place in the bottom twolayers of the OSI (Open System
`a Distribution System (DS).
`Interconnection) reference model—the media access control
`(MAC)sublayer of the link layer and the physical layer.
`
`is currently used to
`[0003] The original standard that
`establish a wireless local area network (WLAN)is the IEEE
`802.11 standard. The IEEE 802.11 standard was published
`first in 1997 and it was designed to provide data rates up to
`2 Mbps(such as a DSL connection) at 2.4 Ghz. The standard
`includes specifications for Media Access Control (MAC)
`and physical layer operation. The physical layer standard
`was designed to use either frequency hopping spread spec-
`trum (FHSS)or direct sequence spread spectrum (DSSS). In
`1999, 802.11a and 802.11b provided enhancements at the
`physical layer with higher data rate support up to 54 Mbps
`in the 5 GHz band and 11 Mbps in the 2.4 GHz band,
`respectively.
`
`[0004] The newly developed 802.11e standard is working
`to enhance the current 802.11 MACto expand support for
`applications with high QoS (Quality Of Service) require-
`ments. Wireless networks fit both business and home envi-
`ronments, that both require the support of multimedia, and
`the 802.11 e standard provides the solution for this need. In
`both wired and wireless networks, data transmission is
`susceptible to interruptions caused when packets are present
`or lost during the transmission process. These interruptions
`can cause problemsfor data to be streamed in a contiguous
`fashion. The 802.11e has created a QoS baseline document
`that proposes methods for handling time-sensitive traffic.
`
`In the WLAN topology, each wireless network
`[0005]
`requires a radio transceiver and antenna. Components on the
`wireless network are either stations (STAs) or access points
`(APs). Typically, a station STA is mobile or portable, and the
`access point AP may be a permanentstructure analogous to
`a base station tower used in cellular phone networksor to a
`hub used in a wired network. A basic service set (BSS) is
`formed when two or more stations have recognized each
`other and established a network. An extended service set
`(ESS) is formed when BSSs (each one comprising an AP)
`are connected together.
`
`[0006] Astandard WLAN according to 802.11 operates in
`one of two modes—ad-hoc (peer-to-peer) or infrastructure
`mode. The ad-hoc mode is defined as Independent BSS
`(IBSS), and the infrastructure mode as a BSS. WLANs may
`also be classified as distributed (ad-hoc), or as centralized
`systems (infra-structure based system).
`
`In ad-hoc mode (IBSS), each client communicates
`[0007]
`directly with the other clients within the network on a
`
`Page 12 of 20
`
`[0009] Before stations and access points can exchange
`data, they must establish a relationship, or an association.
`Only if an association is established can the STA and AP
`exchange data. The association process involvesthreestates:
`
`[0010] Unauthenticated and unassociated
`
`{0011] Authenticated and unassociated
`
`[0012] Authenticated and associated
`
`In the transition between the states, the communi-
`[0013]
`cating parties exchange messages called management
`frames. The APs are designed to transmit a beacon manage-
`ment frame at fixed intervals. To associate with an access
`
`point and join the BSS, a station listens for beacon messages
`to identify the access points within the range. After the
`station receives a beacon frame (message) it selects the BSS
`to join. The network names,or service set identifiers (SSID)
`contained in the beacon frame, permit the user to choose the
`SSIDthe user wishes to join. A station can also send a probe
`request frame to find the associated access point with the
`desired SSID. After the station identifies the access point,
`they perform an authentication by exchanging several man-
`agement frames.
`
`[0014] As illustrated in prior art FIG. 2, a wireless trans-
`ceiver 20, according to the OSI (Open System Interconnec-
`tion) reference model, comprises in part, a series of protocol
`layers 23 having a physical layer PHY 24, a data link layer
`26, and a NETWORKlayer 28. The data link layer 26
`further comprises a medium access control MAC 26a sub-
`layer and a logical link control LLC 266 sublayer. The OSI
`reference model describes networkingas a series of protocol
`layers with a specific set of functions allocated to each layer.
`Each layer offers specific services to higher layers while
`shielding these layers from the details of how the services
`are implemented. A well-defined interface between each pair
`of adjacent layers defines the services offered by the lower
`layer to the higher one and how thoseservices are accessed.
`
`layer PHY 24 is involved in the
`{0015] The physical
`reception and transmission of the unstructured raw bit
`stream over a physical medium. It describes the electrical/
`optical, mechanical, and functional interfaces to the physical
`medium. The PHY 24 layer carries the signals for all the
`higher layers. The MAC 26a sublayer of the data link layer
`26, manages access to the network media, checks frame
`errors, and manages address recognition of received frames.
`
`Page 12 of 20
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`US 2005/0025080 Al
`
`Feb. 3, 2005
`
`[0016] The LLC 26b sublayer establishes and terminates
`logical
`links, controls
`frame flow,
`sequences
`frames,
`acknowledges frames, and retransmits unacknowledged
`frames. The LLC 266 sublayer uses frame acknowledge-
`mentand retransmission to provide virtually error-free trans-
`mission over the link to the layers above. The NETWORK
`layer 28 controls the operation of the subnet. It determines
`the physical path the data should take, based on network
`conditions, priority of service, and other factors, including
`routing,traffic control, frame fragmentation and reassembly,
`logical-to-physical address mapping, and usage accounting.
`
`[0017] Wireless transceiver 20 also illustrates a packet of
`data 30 which may be transmitted or received via the
`NETWORKlayer 28 and other higher level layers of the
`transceiver 20.
`
`[0018] Wireless Local Area Networks (WLANs)are gain-
`ing increasing popularity today by establishing anywhere
`and anytime connections. According to recent predictions,
`the market of WLAN adapters will reach 35 million units in
`2005. However, a larger market for WLAN liesin the mobile
`device world such as cellular phones and PDAs, whose
`market is projected to reach 500 million units in 2005.
`
`[0019] As more WLAN chips are embedded into battery
`powered mobile devices, power consumption inevitably
`becomesa bottleneck to its wide deployment. The average
`power consumption for a typical WLAN adaptor, employing
`the power saving technique specified in the IEEE 802.11
`standard,
`is significantly higher than a normal cellular
`phone. This further implies that a cellular phone with current
`battery capacity will be drained in substantially less time if
`a WLAN chip is embedded.
`
`in circuit design have
`advancements
`[0020] Recent
`reduced the power consumption of WLAN chips dramati-
`cally in sleep mode. For example, the power consumption in
`deep sleep state is only 2 mw in the Texas Instruments
`TNETW1100Bseries chips. Howeverthis reduction alone is
`not able to alleviate the problem to the same degree in
`current wireless LANs, as the power reduction in the deep
`sleep mode cannot be fully utilized.
`
`[0021] The impeding force is the broadcast based wireless
`MACprotocol. To receive a frame addressed to itself, a
`station has to continuously monitor the wireless channel and
`decode every frame for the MAC address to be checked
`against its own. Compared with the stations transmission or
`reception of data,
`this contending procedure commonly
`dominates the activity of a wireless station and prevents the
`station from sleeping. Consequently, power consumption
`during contention is a major contribution to battery drain.
`
`[0022] Recent research proposes exploiting the low power
`consumption available during sleep mode. Allowing a sta-
`tion to wake up only periodically, often at several beacon
`intervals,
`this approach requires the AP to buffer power
`saving traffic and deliver it according to the station’s pre-
`negotiated listening interval.
`
`[0023] Although such an approach reduces the power
`consumption significantly,
`it does not fully address the
`problem. For example, all portable devices can benefit from
`power savings. With the increasing amount of power saving
`traffic, a station waking up at a certain beacon will likely
`face fierce competition retrieving or receiving data from the
`AP, and once again, waste significant power during conten-
`
`tion. Further, power saving traffic may be associated with
`additional QoS and non-QoS constraints. For example, a
`voice traffic stream has a stringent delay requirement, but
`relatively low and periodic bandwidth consumption. How-
`ever, the delay requirement will preclude the station from
`entering sleep mode according to the protocol given above,
`as frequently a beacon interval is about 100 ms. In addition,
`the situation is exacerbated by the increasing set of QoS
`applications incorporating WiFi networks. Further, power-
`ing on and off different modules in WLAN devices may
`incur additional power consumption and delays, if power
`savings techniques are not carefully applied.
`
`[0024] Accordingly, there is a need for an improved pro-
`tocol to address the problems associated with QoS as well as
`non-QoStraffic flows and minimizing total power consump-
`tion across all the power saving stations, while ensuring
`scalability during increased power saving traffic on a wire-
`less local area network.
`
`SUMMARYOF THE INVENTION
`
`[0025] The following presents a simplified summary in
`order to provide a basic understanding of one or more
`aspects of the invention. This summaryis not an extensive
`overview of the invention, and is neither intended to identify
`key orcritical elements of the invention, nor to delineate the
`scope thereof. Rather, the primary purpose of the summary
`is to present some concepts of the invention in a simplified
`form as a prelude to the more detailed description that is
`presentedlater.
`
`[0026] The present invention relates to a new system and
`method implemented in the physical (PHY) layer, using a
`PHY layer address filtering protocol based on a partial
`address subset of the complete destination MAC address.
`Suchfiltering saves power in wireless local area networks,
`as identified in the IEEE 802.11x (e.g., a, b, g,e).
`
`[0027] The power saving system utilizing the PHY layer
`addressfiltering protocol comprises a WLAN having two or
`morestations, each comprising a partial address in the PHY
`layer for holding a portion or subset of the destination MAC
`address, and a PHY layer address filtering protocol for
`generating the partial address and writing the partial address
`into the PHY header (e.g., a physical layer convergence
`procedure (PLCP) header) upon transmission of each frame
`from a sending station, or reading the partial address from
`the PHY layer header portion (e.g., the PLCP header) of a
`receiving station. The receiving station receives and decodes
`the partial address bits at the PHY layer, in accordance with
`the protocol of the present invention, and compares whether
`the subset of bits match that of the stations’ own partial
`address.If a station finds a match in the partial address, the
`station then continues further decoding the remainingpart of
`the frame at the physical layer and passes the complete
`frame to the MAC layer for further address checking and
`processing. Thus, a number of the stations on the network
`will avoid wasting power decoding a significant portion of
`the complete frame and unnecessary MAClayer processing.
`
`In accordance with one aspect of the invention, by
`[0028]
`doing physical address filtering, irrelevant frames can be
`filtered out before activating the MAC module, the high data
`rate path, and even from decoding all the data for many
`stations that are not the intended data recipient. This may
`provide a significant reduction of power consumption in a
`WLAN.
`
`Page 13 of 20
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`

`US 2005/0025080 Al
`
`Feb. 3, 2005
`
`In accordance with another aspect of the present
`[0029]
`invention, when group addressed, control/management
`frames or other such frames which mayneedto be broadcast
`to all the stations are detected at the sending station, the
`addressfiltering protocol may be “disabled”in the receiving
`station using a partial address containing a predetermined
`value such as all zeros.
`
`(including the PLCP
`[0030] The PHY frame format
`header) and the MAC frame format is fully detailed in the
`IEEE 802.11x specifications, therefore need only be sum-
`marized herein asto their utility as may be used in associa-
`tion with the present invention. For example, bits b4-b6 are
`currently reserved in the service field of the PLCP header of
`the IEEE 802.11b specification. These three unusedbits, or
`any numberof other such unused or newly defined bits could
`be utilized, in accordance with one aspect of the invention,
`for the partial address of a destination MAC address of a
`station. If these three bits, for example, mirror the last three
`bits of the MACaddress,statistically only about one of each
`eight stations on the network would match the partial
`address and require further decoding at the MAC layer.
`
`In another aspect of the present invention,the last
`[0031]
`several (e.g., three, four) bits of the MAC address may be
`exclusive OR’d (XOR) with the first several (e.g., three,
`four) bits to obtain an alternate subset of the MAC address
`for better distinction. IEEE, the administrator of IEEE MAC
`address space, assigns MAC address blocks with the same
`first 24 bits to companies. Using both the first several bits
`and last several bits facilitate differentiating the block
`address in conjunction with the individual address assign-
`ment within the block.
`
`mined that the received partial address matches that of the
`station, or contains all zeros, the decoding continues and the
`complete frame is sent to the MACfor further processing,
`otherwise, decoding of the frame may be stopped at the PHY
`layer and the process does not continue into the MAClayer.
`The frame is therefore rejected at this point as it has been
`determinedthat the data frameis not intended for the present
`station, thus the MAC module or MAChigh datarate for that
`station is not triggered, and power consumption may be
`significantly reduced by avoiding further decoding at the
`physical
`layer and unnecessary processing of the MAC
`layer.
`
`To the accomplishmentof the foregoing and related
`[0035]
`ends, the following description and annexed drawings set
`forth in detail certain illustrative aspects and implementa-
`tions of the invention. These are indicative of but a few of
`
`the various ways in which the principles of the invention
`may be employed. Other aspects, advantages and novel
`features of the invention will become apparent from the
`following detailed description of the invention when con-
`sidered in conjunction with the drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0036] FIG. 1 is a prior art diagram illustrating a basic
`service set BSS of a wireless network operating in the
`infrastructure mode;
`
`[0037] FIG. 2 is a prior art diagram of a wireless trans-
`ceiver, according to the OSI reference model illustrating a
`series of protocol layers and a data packet to be transmitted
`or received;
`
`[0032] Still another aspect of the invention provides a
`method of saving power in a wireless network comprising
`two or morestations, a partial address for holding a portion
`or subset of the destination MAC address, and a PHY layer
`address filtering protocol for generating the partial address
`and writing the partial address into a PLCP header from a
`sendingstation, or reading the partial address from the PLCP
`header of a receiving station. The method may be accom-
`[0040] FIG.5isa diagram illustrating an exemplary MAC
`plished in two areas of the network: a sending station area
`frame format and exemplary fields used according to IEEE
`and a receiving station area.
`802.11b including the fields which comprise the MAC
`header area;
`
`[0038] FIG. 3 is a simplified diagram of an exemplary
`data packet exchange between a station and an access point
`during an uplink or a downlink;
`
`[0039] FIG. 4 isa diagram illustrating an exemplary basic
`PHYframe format and exemplary fields used according to
`IEEE 802.11b including the fields which comprise the MAC
`Frame or PHY payload area;
`
`In the sending station, the method comprises, in
`[0033]
`one aspect of the invention, generating a partial address
`associated with the destination MAC address, passing the
`partial address to the PHY layer, determining whether a
`normal data frameis to be transmitted, and if so, writing the
`partial address information into the PHY header (e.g., PLCP
`header) for filtering to take place. Otherwise, if specific
`types of frames are to be transmitted to all stations, such as
`group addressed or control/management frames, then “dis-
`abling”thefiltering is performed by writing all zeros into the
`bits assigned for the partial address bits. The method may
`then continue in accordance with other protocols for sending
`and receiving data.
`
`In the receiving stations, in another aspect of the
`[0034]
`present invention, the method comprises storing the stations
`ownpartial address in the PHY layer, receiving a transmitted
`frame into the PHY layer, decoding the PHY header (PLCP
`header) and checking the partial address bits. The receiving
`station then compares the received frame partial address
`with that of the stations’ own stored address, or determines
`whether the partial address containsall zeros. If it is deter-
`
`Page 14 of 20
`
`[0041] FIG. 6 is a diagram illustrating an exemplary PHY
`frame format according to 802.11b further illustrating the
`fields of the PLCP header,
`the service field, and several
`reserved bits that may be utilized for the partial address bits
`in association with the protocol of the present invention;
`
`FIG.7 is a simplified block diagram of an exem-
`[0042]
`plary WLAN powersavings system operating in the infra-
`structure mode, utilizing a partial address and PHY layer
`addressfiltering protocol in accordance with various aspects
`of the present invention;
`
`FIGS.8-9 are simplified functional block diagrams
`[0043]
`of a station utilizing the exemplary PHY layer address
`filtering protocol and the partial address of the power saving
`WLAN system of FIG.7 illustrating an exemplary sending
`and receiving station, respectively;
`
`[0044] FIGS. 10-11 are flow charts illustrating a method
`of saving power in an exemplary sending and receiving
`station, respectively, of a wireless network using the PHY
`
`Page 14 of 20
`
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`

`US 2005/0025080 Al
`
`Feb. 3, 2005
`
`layer addressfiltering protocol in accordance with the power
`saving system of FIG.7, and various aspects of the present
`invention; and
`
`[0045] FIG. 12 is a diagram illustrating an exemplary
`encoding of the partial address by exclusive XOR-ing a
`vendor ID numberandthe partial address as used in the PHY
`layer addressfiltering protocol in accordance with an aspect
`of the present invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`[0046] The present invention will now be described with
`reference to the attached drawings, wherein like reference
`numerals are used to refer to like elements throughout. The
`invention relates to a PHY layer addressfiltering protocol as
`a power savings mechanism in a wireless network in which
`a subset of the destination MACaddressis represented as a
`partial address having several bits utilized in association
`with a portion of the PHY header (the PLCP header)at the
`PHYlayer.
`
`[0047] Current wireless LANs based on IEEE 802.11
`employ a broadcast based access mechanism.
`In other
`words, a station will have to receive all the frames on the
`wireless channel and decode the MAC header to see if a
`frame is addressedto itself. Therefore, a significant amount
`of power may be consumed decoding irrelevant data
`intended for other stations. It is the intent of this invention
`
`to present a method for performing physical layer frame
`filtering. Such a method has the following merits on power
`saving.
`
`1) It can prevent most of the irrelevant data from
`[0048]
`reaching the MAClayer and hence reduce power consump-
`tion by allowing many stations to maintain their MAC
`module in a sleep modeoroff-state.
`
`2) The 802.11 b/g physical layer header is trans-
`[0049]
`mitted at a relatively lower data rate than physical layer
`payload, therefore the high data rate path does not need to
`be activated for irrelevant data for many stations.
`
`3) The physical layer can discontinue decoding
`[0050]
`operations in further layers immediately after decoding the
`physical header and hence save power.
`
`[0051] Physical Layer Filtering
`
`Ifthe destination MACaddress were presentin the
`[0052]
`PHY header (PLCPheader) at the physical layer, the physi-
`cal layer could perform a complete address check and hence
`reject frames not addressed to the current station. However,
`the relatively long MACaddress,usually 6 bytes, is extrava-
`gant for the limited resources available at the physical layer
`and would not comply with the communications standard.
`By contrast the design of the present invention simply uses
`a few bits of the MAC address at
`the physical layer to
`perform partial address filtering while still maintaining a
`large percentage of the power savings advantage which will
`be referred to herein, as “gain”. These bits can be accom-
`modated, for example, by either currently reserved bits, or
`by newly created bits at the PHY layer.
`
`[0053] Setting the Partial Address
`
`[0054] The present invention utilizes part of the MAC
`destination address for the purpose of partial addressfilter-
`
`ing. For example, if three bits are available, we can use the
`last three bits of the destination MAC address to represent
`the partial address. Or, for example, one can use the last
`three bits, and XOR these bits with the first three bits. Any
`portion of the MACdestination address may be employed,
`whether or not encoded, and any such variation is contem-
`plated by the present invention.
`
`[0055] The 802.11 MAC protocol employsa virtualcarrier
`sensing mechanism to reduce collision on the shared wire-
`less channel. This mechanism is executed at each station by
`setting the NAV, for which the duration field in the MAC
`header needsto be accessed. Because physicallayerfiltering
`may prevent the MAC from accessing the duration field of
`the MACframe, this problem can be avoided by disabling
`the filtering protocol
`for certain types of frames,
`for
`example, RTS/CTS/ACK/POLLframes and other such con-
`trol or management frames. Moreover, if a large number of
`bits are available, the Duration field may be put in the header
`along with the partial address, insuring that the NAV is also
`accommodated and set correctly. Note, data frames that are
`not among the RTS/CTS/ACK/POLLframesand other such
`control or management frames, will be termed “normal”
`frames herein.
`
`[0056] Group addressed frames mayalso not be filtered
`out, as all stations may needto receive such data. For those
`frames that are intended to not befiltered out, all zeros (or
`other predetermined value) are simply written into the
`partial address field, which is the same as the default case.
`
`[0057] Gain
`
`If N bits are employed as the partial address,
`[0058]
`roughly only “4% of the normal data frames need to be
`decoded on the wireless channel, providing that all
`the
`stations in the network employ this technique. In other
`words, the power for decoding roughly (1-’4")of the total
`numberof frames on the network may be saved. Notice that
`this gain quickly saturates as N increases, hence the first
`several bits of the partial address protocol concept provides
`the greatest benefit and thereafter becomesincreasingly less
`useful. For example, assume a three bit partial address.
`Then, the portion of normal data frames that need to be
`decoded on the wireless channel would be: (with N=3)
`YNIg
`
`and the portion of the power saved would be
`
`[0059]
`roughly:
`(1-¥#®)=(1-4)=%
`[0060] An increase in the partial address bits used from
`three to four bits results in the following. The portion of
`normal data frames that need to be decoded on the wireless
`channel would be: (with N=4)
`YNaVeo,
`
`and the portion of the power saved would be
`
`[0061]
`roughly:
`(1-*®)=(1-Me)=!e.
`[0062] This illustrates that the gain, or the change in the
`power savings is about “6 of the total power savings.It
`will be noted, however, as these bits only form a partial
`address and not a complete address, an early address deter-
`mination is greatly enhanced statistically, but not fully
`assured until a final address match is determined in the
`MAC.
`
`Page 15 of 20
`
`Page 15 of 20
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`

`US 2005/0025080 Al
`
`Feb. 3, 2005
`
`[0063] Sender Side Action
`
`[0064] To use physical layer filtering, a sender (the send-
`ing STA) writes the partial address of the destination MAC
`address of the destination STA into, for example, the PLCP
`header. This partial address information may be generated at
`the MAC module and passed to the physical module via a
`writable register upon each frame transmission.
`
`the sender will
`1) For normal data frames,
`[0065]
`simply write the partial address into the PLCP
`header.
`
`2) For group addressed (broadcast or multi-
`[0066]
`cast) frames, the sender will write all zeros (or some
`predetermined value) for the partial address into the
`PLCPheader.
`
`3) For management frames (RTS, CTS, ACK,
`[0067]
`POLL,etc.), the sender will write all zeros (or