APL 1003
`IPR of U.S. Pat. No. 6,128,290
`
`0001
`
`

`
`U.S. Patent
`
`Aug. 31, 1993
`
`Sheet 1 of 9
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`5,241,542
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`0002
`0002
`
`

`
`U.S. Patent
`
`Aug. 31, 1993
`
`Sheet 2 of 9
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`5,241,542
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`
`U.S. Patent
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`Aug. 31, 1993
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`Sheet 4 of 9
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`5,241,542
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`0005
`0005
`
`

`
`U.S. Patent
`
`Aug. 31, 1993
`
`Sheet 5 of 9
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`5,241,542
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`80
`
`RECEIVE HEADER AH
`I-‘DR PERIDD A
`
`32.
`
`9
`
`FIG. 8A
`
`
`
`
`
`INCLUDED IN THE
`AM I
`LIST HF RECEIVING
`MEIBILE UNITS
`
`NU
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`RLIST={
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`
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`F-—MY PEISITIUN IN _RIIIST:
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`SL.EEP__DURATIElN-"— E S}
`i=0
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`SLEEFLDURATIDN-I—TA
`
`
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`
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`‘MAKEUP AFTER SLEEF’_DURATIlJN
`SLEITS HAVE ELAPSED:
`RECEIVE PACKETS FEIR
`
`THE NEXT 8; SLDTS
`
`0006
`0006
`
`

`
`U.S. Patent
`
`Aug. 31, 1993
`
`Sheet 6 of 9
`
`5,241,542
`
`95
`
`FIG. 8B
`
`96
`
`
`
`TURN RECEIVER EJFFJ
`ENTER SLEEP MIJDEJ
`WAKE UP AFTER
`SLEEP_.DURATIEIN
`SLEITS HAVE ELAPSEIJ
`
`
`
`RECEIVE HEADER BH FUR PERIEID B
`TURN RECEIVER UFF FEIR DURATIEIN TB
`
`98
`
`100
`
`
`
`
`AM I
`
`IN
`
`THE LIST DF MDBILE
`ND
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`UNITS ALLUVED TD TRANSMIT IN THIS
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`FRAME ? Tl_IST={VLV2;-u.Vn}
`
`
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`
` a---wr PEISITIUN IN_ 711.137;
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`SLEEP_DURATIE|N -e-; 2* +j
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`
`102
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`SL.EEP_IJURATIUN-— TB
`
`106
`.
`
`TURN TRANSMITTER DFFJ
`ENTER SLEEP MEIDE
`
`108
`
`wm<|-: UP AFTER
`SLEEP_DURATIDN
`31.073 HAVE ELAPSED
`
`
`
` 110
`
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`TURN TRANSMITTER UN)
`TRANSMIT FDR ‘ti SLUTSI
`S1_EEP_DURATIl3N-—-TB —_2+ 3
`J =4
`
`
`
`0007
`0007
`
`

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`U.S. Patent
`
`Aug. 31, 1993
`
`Sheet 7 of9
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`5,241,542
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`111
`
`FIG. 8C
`
`
`
`
`
`ENTER SLEEP MUDE FUR TRANSMITTER
`FUR SLEEP__DURATIEIN
`WAKE UP RECEIVER AFTER
`PERIUD B HAS ELAPSED
`
`112
`
`RECEIVE HEADER CH FUR PERIUD C
`AND TURN RECEIVER UFF
`
`114
`
`116
`
`
`
`
`DE I HAVE ANY
`PACKET TD TRANSMIT IN RANDOM
`ACCESS MEIDE (PERIUD c > 7
`
`
`
`
`NU
`
`118
`(FIG.8D)
`
`
`
`
`
`
`132
`(Fmsm
`
`YES
`
`FULLUW SLUTTED PRUTUCUL AND SCHEDULE
`TRANSMISSIUN IN SLUT T INTU THE FUTURE
`SLEEP__DURATIUN---T-1
`
`120
`
`TURN TRANSMITTER UFFJ
`ENTER SLEEP MUDEt
`
`122
`
`
`
`WAKE UP TRANSMITTER SLEEP_DURATIUN
`HAS ELAPSED AND TRANSMIT AT SLUT T
`8: THEN GU TU SLEEP (TRANSMITTER)
`
`
`
` 184
`
`WAKE UP RECEIVER AND RECEIVE
`ACK/NAK MESSAGE AT SLUT
`T + A(A= DELAY FUR GENERATING
`THE ACK/NAK MESSAGE) &
`
`GU TU SLEEP RECEIVER
`
`135
`
`128
`
`0008
`0008
`
`

`
`U.S. Patent
`
`Aug. 31, 1993
`
`Sheet 8 of 9
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`5,241,542
`
`FIG. 8D
`
`198
`
`130
`
`138
`
`YES
`
`(FIG.8C)
`
`ANY MDRE PACKET
`
`
`
`
`
`TD TRANSMIT IN RANDEIM
`
`
`ACCESS MEIDE 7
`
`118
`
`(F'IG.8C)
`
`NE!
`
`SLEEP_DURATIE|N ""' REMAINING
`
`134
`
`TIME IN PERIEID C
`
`TURN TRANSMITTER AND RECEIVER DFFJ
`ENTER SLEEP MDDE
`
`136
`
`WAKE UP AFTER
`SLEEPJJURATIUN
`HAS ELAPSED
`
`133
`
`CHANGE CARRIER FREQUENCY
`(IN A FREQUENCY HDPPING SYSTEM)
`
`140
`
`80
`
`(FIG.8A)
`
`0009
`0009
`
`

`
`U.S. Patent
`
`Aug. 31, 1993
`
`Sheet 9 of 9
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`5,241,542
`
`PREIXIM- mm RADIU
`
`
`
`
`
`TIMEUUT
`VAKEUP
`
`154
`
`158
`
`SET
`TIMER
`AND
`
`SLEEP
`
`158
`
`TRANSHIT
`
`160
`
`SLEEP
`
`V/AKEUP
`
`166
`
`155
`
`RADIIJ
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`
`MEMDRY
`
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`
`0010
`0010
`
`

`
`1
`
`BATTERY EFFICIENT OPERATION OF
`SCHEDULED ACCESS PROTOCOL
`
`5,241,542
`
`2
`FIG. 2 is a block diagram of the system shown in
`FIG. 1 illustrating the basic components of a mobile
`station and a base station;
`FIG. 3 is a block diagram of the radio system used in
`the implementation of a preferred embodiment of the
`invention;
`FIG. 4 is a diagram of the frame structure of a multi-
`access protocol for describing the battery efficient oper-
`ation of a wireless link adapter according to the inven-
`non;
`FIG. 5 is a diagram of a Receiving Users Index mes-
`sage as a bit-vector 64 bits long;
`FIG. 6 is a diagram of receiver allocations for the
`multiaccess protocol;
`FIG. ‘I is a diagram of transmitter allocations for the
`multiaccess protocol;
`FIG. 8A-SD, when taken together as shown in FIG.
`8, are block diagram representations of how the battery
`efficient operation of the wireless link adapter is con-
`trolled by the multiaccess protocol, as implemented
`according to the invention;
`FIG. 9 is a block diagram of how a controller in the
`wireless link adapter sets a time to accomplish the im-
`plementation set forth in FIGS. BA—BD.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The invention is described relative to operation in a
`wireless radio communications link. It is to be appreci-
`ated that the invention is also applicable to other wire-
`less communication links such as infrared links as well
`as microwave links. FIG. 1 depicts mobile stations 10,
`12, 14, and 16 that communicate via wireless links.
`Gateways, referred to as base stations, are augmented
`according to the invention to provide certain radio
`system management functions which coordinate the
`mobile stations‘ access to the common radio channel.
`Communications between mobile stations is supported
`via relay through the base stations 26 and 28.
`As shown in more detail in FIG. 2, a base station 26
`or 28, which may be conventional microcomputer. has
`a LAN adapter 30 inserted in a bus slot and connected
`to LAN cabling 32. A server 18, typically also a con-
`ventional microcomputer and including one or more
`direct access storage devices (DASDs) such as hard
`disks (not shown). also has a LAN adapter 34 inserted in
`a bus slot and connected to LAN cabling 32. The LAN
`adapters 30 and 34 and the LAN cabling 32 together
`with LAN software constitute the LAN 2.4. The LAN
`24 is of conventional design and does not form pan of
`the invention. The base station 26 or 28 also has an RF
`transceiver adapter 36 implemented as a printed circuit
`card which is inserted in a bus slot of the base station.
`The transceiver adapter 36 includes a spread spectrum
`transceiver of conventional design. The transceiver
`adapter 36 has an antenna 38 by which a radio link 40 is
`established with one or more remote or mobile stations,
`Ill, 12, 14, or 16. The mobile station may itself be a hand
`held or laptop computer such as an IBM PS/2 Model
`L4-0 SX laptop computer as described in Technical
`Reference Manual. Order Number: S/SF-2270, Part
`No. 15172270, which may be ordered from an IBM
`Authorized Dealer.
`IBM and PS/2 are registered Trademarks of Interna-
`tional Business Machines Corporation. The laptop com-
`puter
`like the base station,
`is provided with an
`antenna 42 and a
`transceiver
`adapter 44,
`also
`implemented as
`a printed circuit card which is
`inserted
`in
`a bus
`slot of
`the
`computer. The
`
`FIELD OF THE INVENTION
`
`The invention is in the field of wireless communica-
`tions, and in particular is directed to power conserva-
`tion due to wireless communication. Specifically, the
`invention is directed to battery efficient operation of
`wireless link adapters of mobile computers as controlled
`by multiaccess protocols used in wireless communica-
`tion.
`
`BACKGROUND OF THE INVENTION
`
`In order to obtain true portability in micro-computers
`and workstations, battery powered operation is essen-
`tial. Moreover, given the capacity versus size limita-
`tions of known batteries, it is essential to minimize total
`power consumption in order to extend the operating life
`of the batteries.
`
`It is relatively easy to reduce battery consumption by
`an initial 60 to 70 percent in the computer portion of a
`mobile station. This initial savings can be accomplished
`by simply turning selected pieces of hardware in the
`computer portion off when they are not being used. The
`last 30 to 40 percent savings in the computer portion
`becomes increasingly more difficult to achieve, while
`simultaneously becoming increasingly more valuable in
`terms of extending battery life. This is due to the inverse
`relationship between battery life and battery load. Ac-
`cordingly, savings that would seem trivial in off-line
`applications, might be momentous in a battery powered
`environment.
`
`While the above is directed to the computer portion,
`to date no work has been done relative to the wireless
`link adapter portion of the mobile station.
`There has been recent work directed to the design of
`multiaccess protocols for portable mobile computer
`users. as well as movable boundary protocols for sup-
`porting integrated voice/data users in mobile indoor
`radio networks. The schemes proposed to date do not
`take into explicit account the effective conservation of
`battery power used by the multiaccess scheme relative
`to the wireless link adapter.
`Since portable laptop computers run on battery
`power, the implementation of a multiaccess protocol
`described in this invention attempts to minimize the
`consumption of battery power in a wireless link adapter
`to the minimum amount required. as a function of the
`protocol.
`According to this invention. several techniques are
`disclosed for minimizing the battery power wasted at
`the wireless link adapters of mobile units. as controlled
`by a multiaccess protocol for wireless communication.
`
`DISCLOSURE OF THE INVENTION
`
`Method and apparatus is described for the battery
`efficient operation of wireless link adapters of mobile
`computers as controlled by scheduled multiaccess pro-
`tocols for wireless communication.
`
`10
`
`IS
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`55
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`65
`
`FIG. 1 is a pictorial diagram showing an indoor digi-
`tal data communication system of the type in which the
`invention is implemented;
`
`0011
`0011
`
`

`
`5,241,542
`
`3
`transceiver adapter 44, like transceiver adapter 36. in-
`cludes a spread spectrum transceiver of similar design.
`The base station and the mobile stations are further
`provided with software. generally indicated by refer-
`ence numerals 46 and 48, respectively, which support
`their respective transceiver adapters.
`FIG. 3 shows the radio system common to both the
`mobile stations and the base stations of FIG. 1. The
`radio system includes a transceiver adapter 36 or 44
`connected to a computer 50 via a computer’s bus inter-
`face 52. The transceiver adapter 36 section is itself di-
`vided into an RF transceiver 54, which may be com-
`mercially available spread spectrum transceiver. and a
`dedicated microprocessor system 56 which controls the
`transceiver via an interface 58. The microprocessor
`system 56 further includes a system interface 60 which
`interfaces the transceiver adapter 36 section to the com-
`puter section 50. The microprocessor system includes a
`dedicated microprocessor 62 containing high-resolution
`time interval determination hardware or "timers” typi-
`cal of real-time microprocessor systems.
`Microprocessor 62 is connected by a memory bus 64
`to program storage 66 and data storage 68 as well as to
`interfaces 60 and 58 providing attachment to bus inter-
`face 52 and RF transceiver 54, respectively. Program
`storage 66 is typically read only memory (ROM), while
`data storage 68 is static or dynamic random access
`memory (SRAM or DRAM). Packets received or to be
`sent are held in data storage 68 and communicated to or
`from the RF transceiver 54 via interface 58 under con-
`trol of serial channels and a direct memory access
`(DMA) controller (not shown) which is part of the
`microprocessor 62. The function of these serial channels
`is to encapsulate data and control information in an
`HDLC {high-level data link control} packet structure
`and provide the packet in serial form to the RF trans-
`ceiver 54. For more information on the I-IDLC packet
`structure. see. for example. Mischa Schwartz, Telecom-
`munication Networks: Protocols. Modeling and Analy-
`sis. Addison-Wesley (1988).
`When a packet
`is received through the RF trans-
`ceiver 54, the serial channels check the packet destina-
`tion address, check for errors, and deserialize the packet
`to data storage 68. The serial channels must have the
`capability to recognize a specific adaptor address as
`well as a broadcast address. Specific microprocessors
`with appropriate serial channel and timer facilities in-
`clude the Motorola 68302 and the National Semicon-
`ductor I-IPC46400E microprocessors.
`The computer 50 runs an operating system 70 which
`supports one or more user application programs 72. The
`operating system 70 may include a communications
`manager 74. or the communications manager 74 may
`itself be an application program installed on the com-
`puter. In either case, the communications manager 1'4
`controls a device driver 76 via the operating system '70.
`The device driver 76. in turn, communicates with the
`transceiver adapter 36 or 4-4 via bus interface 52.
`In general.
`the main idea for minimizing battery
`power consumed by wireless link adapters at the mobile
`units is as follows. The transmitter and receiver units at
`the communication adapter(s) of a portable terminal
`expend some power that depend on their states (OFF
`state/ON state/ACTIVE ON). The ratio of transmit-
`to-receive power depends also on the type of wireless
`link adapter used (radio or infrared). Scheduled access
`multiaccess protocols can be implemented to effectively
`conserve battery power by suitable control of the state
`
`4
`of transmitter and receiver units at the portable units
`(i.e., by scheduling when they should be turned ON or
`OFF). A desirable solution is one in which the transmit-
`ter (or receiver) consumes power only when it is ac-
`tively transmitting a message (or actively receiving a
`message). Traditional multiaccess protocols do not have
`the above desirable characteristics because:
`
`10
`
`IS
`
`20
`
`25
`
`35
`
`45
`
`55
`
`65
`
`A receiver may consume power while waiting to
`receive a packet. Some examples are as follows:
`A mobile station may be waiting to hear a polling
`message from the base station station before it can
`transmit a packet.
`Outbound messages are broadcast from the base sta-
`tion. Mobiles keep their receiver ON in order to
`receive packets that may be addressed to them.
`Battery power is wasted in receiving packets that
`are addressed to others.
`A transmitter may consume power while waiting to
`transmit a packet.
`In the scheme described here, a scheduled multiac-
`cess protocol is used in which time is divided into fixed-
`length frames, and frames are divided into slots as
`shown in FIG. 4. It is to be appreciated that different
`frame divisions and header lengths and content may be
`utilized in the practice of the invention. and the scheme
`set forth here is merely exemplary.
`The beginning of the frame is a header G of fixed
`length FH. The frame is divided into multiple subframes
`as described below.
`Period A for broadcast of packets from base station to
`mobile units (outbound traffic), with a header All
`for period A.
`Period B for the contention-free transfer of all traffic
`from mobile units to base station (inbound traffic).
`with a header B}! for period B.
`Period C for the transfer of all bursty data traffic in a
`contention mode from mobile units to base station
`(inbound traffic}, with a header CI-I.
`Referring to FIG. 1, in conjunction with FIG. 4. in
`interval A the base station 26 or 28 controls the trans-
`missions outbound to the mobile units 14. The corre-
`sponding header (AH) control information for this in-
`terval is broadcast reliably by the base station. and is
`assumed to be received correctly by relevant mobile
`stations. The header includes:
`
`, UH}, that will be
`.
`.
`A list of mobile users (Ur. U3. .
`receiving data from the base station in the current
`frame and the order in which they will receive
`packets.
`.
`.
`Bandwidth allocated to users in this frame (S1, S2.
`.
`. S.,). where S.-, is the number of packets that will
`be directed to User U; from the base station in the
`current frame.
`In the description that follows, a transmitter or re-
`ceiver is considered ON or awake when it is in a normal
`running mode. A transmitter or receiver is considered
`OFF or asleep when it is in an idle or standby mode.
`The following is a general description of the method
`of battery efficient control of a wireless link adapter as
`controlled by a scheduled multiaccess protocol for
`wireless communication as shown in FIG. 4. a more
`detailed description is set
`forth relative to FIGS.
`BA-8D. On correct reception of the above broadcast
`information as shown in FIG. 4, a mobile unit that is not
`included in Header AH can turn its receiver OFF for a
`time duration TA (total number of slots allocated to
`interval A). The adapter of each receiving mobile unit
`can compute exactly when it should be ready to receive
`
`0012
`0012
`
`

`
`5,241,542
`
`5
`packets from the base station (add up the slots allocated
`to all receiving units that precede it). Each receiving
`mobile unit goes to sleep after scheduling to wake itself
`up at its designated time for receiving data. After re-
`ceiving its packets, the mobile unit goes to sleep for the
`remainder of period A. At the end of the A interval, all
`mobile units turn their receiver ON and receive Header
`BI-I corresponding to the B interval.
`Header BH contains an ordered list of users that will
`be allowed to transmit to the base station in the current
`frame.
`
`, V") that are
`.
`.
`.
`A list of mobile stations (V 1. V3,
`allowed to transmit packets to the base station in
`the current frame and the order in which they
`should transmit.
`Bandwidth allocated to mobile stations in this frame
`(t1, t3,
`.
`.
`.
`, t,,), where t; is the number of packets
`that the mobile station Vgcan transmit in the cur-
`rent frame.
`
`6
`messages at the correct time and then go to sleep. It is
`likely that battery power savings resulting from effi-
`cient operation of interval C may be significantly less
`compared to those realized in the contention-free inter-
`vals A and B.
`
`Next a brief outline of a scheme for implementing
`battery efficient execution of a simple version of the
`Scheduled Access Protocol for wireless communication
`is described. The implementation is based on the con-
`cept of broadcasting shon user activity (in transmit and
`receive modes) indexing messages in the header sections
`of a frame. For purpose of description, assume that in
`each frame a mobile unit is allocated at least one slot for
`receiving traffic and at least one slot for transmitting
`traffic.
`'
`In Period A. before the base station broadcasts mes-
`sages to receivers, it includes a Receiving Users Index
`in the Header AH section of the frame. The Receiving
`Users Index is a coded description of mobile users that
`will receive data in the current frame. That is, it is a
`designation of which mobile users are to communicate
`with the base station during this frame. All the mobiles
`listen to this designation or indexing message and all
`Receive-Inactive users (i.e., users who do not have a
`message coming in from the base station in the current
`frame) can simply turn their receiver power OFF until
`the beginning of Header BH for Period B. At that time
`all the mobiles turn their receivers ON and listen to
`Transmitting Users Index in the Header BI-I section of
`the frame. The receivers are turned OFF until the be-
`ginning of Header CH for Period C. The Transmitting
`Users Index is a coded designation or description of
`mobile users that can transmit data in the current frame.
`Transmit-Inactive users (i.e., users who do not have a
`slot designated or allocated to them for transmission)
`can simply continue to keep their transmitters powered
`OFF until the beginning of Header CI-I for Period C.
`Significant power savings can be achieved due to the
`following two observations:
`Most users are very likely to be inactive (both Trans-
`rnit-Inactive and Receive-Inactive) most of the
`time for most applications. This is primarily due to
`the bursty nature of data communication traffic.
`The designation or indexing messages in the header
`sections (AH and BH) represent a small fraction of
`the whole frame length.
`A method of implementation of the multiaccess pro-
`tocol is described below. Here, assume that there are N
`users in the system, say, N=6-4. Then the users can be
`indexed from 1 to 64 by the base station in each user's
`initial registration period. The registration is needed to
`associate each mobile unit in the network with the in-
`tended base station.
`
`In the initial portion of the header section AH, the
`base station sends out the Receiving Users designation
`or Index message portion of the header as a bit-vector.
`64 bits long as shown in FIG. 5.
`The content of each bit location signals the receiver
`activity of the user designated or indexed by the bit
`location. For example. reading left to right, a “1" in the
`4‘th. B‘th, 9'th, etc. bit location can be used to signal that
`the -i‘th, 8’th. 9‘th, etc. mobile unit is designated to
`receive one message in the current frame period. ‘'0'’ in
`the l‘st, 2’nd, 3’rd, etc. bit location signals that the 1'th,
`2‘r1d, 3'rd. etc. mobile unit is inactive (is not designated
`to receive any data) and can turn its receiver power
`OFF until the beginning of Header BH.
`
`l0
`
`I5
`
`20
`
`25
`
`35
`
`Using the information regarding the number of pack-
`ets that each user can transmit. each mobile unit can
`compute exactly when it should begin its transmission.
`Once each mobile station computes its exact time for
`transmission, it can schedule to wake up its transmitter
`at its designated time and then go to sleep (i.e., shut both
`it s transmitter and receiver OFF). At its designated
`time. the transmitter at a mobile station can turn ON
`and transmit for a fixed period of time whose duration
`depends on the number of slots allocated to it.
`It is pointed out that explicit polling messages are not 30
`used to address users individually. The advantage of
`avoiding explicit polling on a peruser basis is the follow-
`ing. Each polling message spacing incurs a fixed over-
`head time per station that is polled. The overhead is
`independent of whether the station has anything to
`transmit or not. The polling overhead is the sum of the
`following components:
`Time to transmit a polling message.
`Effective propagation time for the polling message
`(this includes the delay due electromagnetic radia-
`tion plus the radio turnaround time from receive-
`to-transmit mode at the mobile unit that responds
`to a poll message and radio turnaround time at the
`base station itself) could significantly impair perfor-
`mance in radio-based networks.
`The execution of scheduled access in the manner
`described here has the following advantages over ex-
`plicit polling schemes. They are summarized below:
`Effective elimination of the polling overhead for all
`inbound traffic from mobile users.
`More importantly. the mobile stations economize the
`use of battery power by utilizing the control infor-
`mation contained in the AH (Outbound) and EH
`(Inbound) headers and scheduling their transmit-
`ters/receivers to be turned ON just in time and
`turned OFF at the earliest opportunity.
`In interval C (Random Access or Contention Mode),
`only those mobile units that do not wish to transmit go
`to sleep (by turning both their transmitter and receiver
`OFF) till the end of the current frame. The inbound
`traffic from remaining mobile units may include: regis-
`tration requests (that enable mobile stations to request
`the services of the base station), bandwidth reservation
`requests for use in interval B, single packet messages
`etc. A mobile unit executing a random access protocol
`wakes up its transmitter at its designated time and trans-
`mits and then goes to sleep. The receiver at the mobile
`unit can wake itself up to receive acknowledgement
`
`45
`
`50
`
`S5
`
`65
`
`0013
`0013
`
`

`
`5,241,542
`
`7
`Optimization of transmit power is done in an analo-
`gous manner. In the initial portion of the Header BH.
`the base station sends out another 64 bit-vector repre-
`senting the Transmitting Users designation or Index.
`Mobile user i turns its transmitter ON only if the i"" bit
`in the bit-vector is I.
`The methods described above are simple and effec-
`tive in reducing power consumption in any frame based
`Scheduled Access Protocol scheme for sharing wireless
`communications channels (radio and infrared) among
`portable mobile users. The techniques for battery effi-
`cient operation of the protocol rely on implementation
`of timers that do not consume significant battery power
`when compared with transmitter,
`receiver, micro-
`processor or logic in the wireless adapter cards. A de-
`tailed description of an exemplary wireless link adapter
`is set forth shortly relative to FIG. 9. The adapter de-
`scribed, utilizes the components described below. The
`following data taken from manufacturer's manuals indi-
`cate that timers can be implemented with relatively low
`power consumption. The example is representative of
`what can be saved in a realistic system. As an example.
`a HPC microcontroller 464-ODE consumes 385 mW in
`Normal running mode and 55 mW in Idle mode (i.e.
`with internal timer and oscillator running}. The Proxim
`transceiver (RDA-100/2) consumes 325 mW in Trans-
`mitter ON mode. 400 mW in Receiver ON mode and 1
`mW in Standby mode. When the timer is used to put the
`transmitter and receiver into sleep mode, the HPC mi-
`crocontroller can be put into Idle mode (55 mW) and
`the Proxim radio can be put in Standby mode (1 mW).
`Thus the minimum power consumed is 56 mW in sleep
`mode. When the transmitter is ON.
`the power con-
`sumed is the sum of HPC running in normal mode (385
`mW) and the transmitter in ON mode (325 mW}. Simi-
`larly. when the receiver is ON. the power consumed is
`the sum of HPC running in normal mode (385 mW) and
`the receiver in ON mode (400 mw).
`Suppose fI is the fraction of the time a user is actively
`transmitting (i.e.. user is allocated (TA+TB) f, slots in
`Period B) packets to the base station. Suppose f,, is the
`fraction of the time the user is actively receiving pack-
`ets addressed to him (i.e., user is allocated (TA+TB) f,
`slots in Period A). The power consumed using the cur-
`rent invention is:
`
`I0
`
`[5
`
`20
`
`25
`
`30
`
`35
`
`45
`
`8
`to transmit information to the base station. It is seen that
`there are 14 slots allocated, 4 in time period R1 for the
`first unit, 3 in time period R2 for the second unit and 7
`in time period R3 for the third unit.
`Refer now to FIGS. SA-SD which constitute a flow
`chart of a program operable in controller 152 of the
`wireless link adapter of FIG. 9 for controlling the bat-
`tery efficient operation of a wireless link adapter as
`controlled by the multiacoess protocol as illustrated in
`FIGS. 4, 6 and 7. In the following description. it is to be
`appreciated that any reference to a transmitter or re-
`ceiver, is to the transmitter or receiver of the wireless
`link adapter.
`In FIG. BA at input 80 the header AH (FIG. 4) is
`received for period A atbloclt 82. At decision block 84
`a determination is made by a given mobile unit, such as
`unit 10 (FIG. 1) if it is designated in the RLIST of
`receiving mobile units (FIG. 5). If the determination
`NO is indicated. at block 86 the adapter of the given
`mobile station 10 mts the variable sleep duration (indi-
`cates how long it can sleep) to TA. At block 86, the
`receiver is turned off for the duration TA (FIG. 4) of
`the broadcast of the base station such as base station 26
`to the given mobile station 10. resulting in a conserva-
`tion of power at the mobile station ll] for the period TA:
`If the determination at block 84 is YES that the given
`mobile station 10 is designated in the RLIST. a determi-
`nation is made at block 83 what the position of the given
`mobile station is in the RLIST. User ui must wait until
`all preceding users (U1, U2, .
`.
`.
`, U“ have received
`their packets. The length of the wait equals the sum of
`receiver slot allocations as computed at block 88. The
`receiver of the mobile station II] is turned OFF at block
`90, and turned back ON at block 92 when the time slots
`allocated in the RLIST for the mobile station ll] is
`reached. After receiving the packets addressed to it,
`mobile station 10 at block 94 computes the remaining
`time in period A that it should sleep.
`The sleep duration as computed in blocks 86 and 94 is
`provided at point 95 to block 96 of FIG. 8B. The re-
`ceiver for the mobile station is once again turned off as
`indicated at block 96 after its allotted time slots have
`passed. Since the receiver for the mobile station 10 is on
`only during allotted time slots. once again battery con-
`servation duiing the receive mode has been achieved.
`During the transmission cycle for mobile unit to base
`station transmission. the header BH (FIGS. 4.6 and 7)
`for period B is received by the given mobile station 10
`at block 98. as previously explained, and the receiver is
`turned off for entire duration of period B. A determina-
`tion is then made at decision block 100 whether or not
`the given mobile station is designated to transmit in this
`frame. If the determination is NO. the adapter of the
`given mobile station 10 sets variable sleep-duration
`(indicates how long the transmitter is off) to TB, as
`indicated at block 102. The transmitter of the mobile
`station 10 is turned off at block 102 (FIG. 8C) for the
`duration TB of the period B (FIG. 4), resulting in a
`conservation of power at the mobile station 10 for the
`period TB. Ifthe determination at block 100 is YES that
`the given mobile station II] is designated in the TLIST
`a determination is made at block 104 what the position
`of the given mobile station is in the TLIST. User Vi
`must wait until all preceding users V1, V2, . . .
`, V5.1 have
`transmitted their packets in their allocated slots. The
`length of the wait equals the sum of transmitter slot
`allocations as computed in block 104. The transmitter of
`
`(385+325}f,+(385+-1-O0}f,+(S5+l)
`{I —f;—f,J='.-'1Df;+?3Sf,+5{!i I --I,--f,) m\‘»\-'
`
`The power consumed without the techniques of this
`invention is:
`
`S0
`
`4-00(1-_.fil+325fi+335=(T35—‘l5_,(.-) rnw
`
`If f.-=0. l, f,=0.l power consumption with this inven-
`tion is 194.3 mW. Otherwise the power consumed
`would have been 7715 mW. Significant power savings
`can be realized with this invention. especially as f.-—>O,
`fp-O.
`FIG. 6 is a diagram of receiver allocation of the mul-
`tiaccess protocol. If there are 64 mobile units as shown
`in FIG. 5, four (4) of these units are designated to re-
`ceive information from the base station. It is seen that
`there are 15 slots allocated, 3 in time period 81 for the
`first unit, 5 in time period S2 for the second unit, 3 in
`time period 53 for the third unit, and 4 in time period 55
`for the fourth unit.
`FIG. 7 is a diagram of transmitter allocations for the
`rnultiaccess protocol. Three mobile units are designated
`
`55
`
`65
`
`0014
`0014
`
`

`
`9
`the mobile station 10 is turned off at block 106, and
`turned back on at block 108 when the time slots allo-
`
`cated in the TLIST for the given mobile station It} is
`reached.'After transmitting its packets, mobile station
`10 computes at block 110 the remaining length of period
`B.
`
`The sleep duration as computed in blocks 102 and 110
`is provided at point 111 to block 112 of FIG. 8C. The
`transmitter for the given mobile station 10 is once again
`turned off as indicated at block 112 after its allotted time
`slots have passed. Since the transmitter for the mobile
`station 10 is on only during its allotted time slots, once
`again battery conservation during the transmit mode
`has been achieved.
`During the contention cycles for mobile stations rela-
`tive to transmission to the base station station,
`the
`header CH for period TC (FIGS. 4,6 and 7) is received
`by the given mobile station 10 at block 114 and the
`receiver is turned off for the duration of pet-ion C. A
`determination is made at decision block 116 whether or
`not the given mobile station 10 has any packets to trans-
`mit in the random access mode (period C). If the answer
`is NO as indicated at point 118 proceed to block 134 of
`FIG. SD. The function of the block 134 is explained
`shortly. If the determination at block