PCT
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`(51) International Patent Classification 6 :
`WO 99/23844
`H04Q 7/22
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`(11) International Publication Number:
`
`A2
`
`(43) International Publication Date:
`
`14 May 1999 (14.05.99)
`
`(81) Designated States: AL, AM, AT, AU, AZ, BA, BB, BG, BR,
`BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, Fl, GB, GE,
`GH, GM, HR, HU, ID, IL, IS, JP, KE, KG, KP, KR, KZ,
`LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW,
`MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ,
`TM, TR, TT, UA, UG, UZ, VN, YU, ZW, ARIPO patent
`(GH, GM, KE, LS, MW, SD, SZ, UG, ZW), Eurasian patent
`(AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European patent
`(AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT,
`LU, MC, NL, PT, SE), OAPI patent (BF, BJ, CF, CG, CI,
`CM, GA, GN, GW, ML, MR, NE, SN, TD, TG).
`
`Published
`Without international search report and to be republished
`upon receipt of that report.
`
`(21) International Application Number:
`
`PCT/US98/23428
`
`(22) International Filing Date:
`
`3 November 1998 (03.11.98)
`
`(30) Priority Data:
`08/963,386
`
`3 November 1997 (03.11.97)
`
`us
`
`(71) Applicant: QUALCOMM INCORPORATED [US/US]; 6455
`Lusk Boulevard, San Diego, Ca 92121 (US).
`
`(72) Inventors: PADOVANI, Roberto; 13593 Penfield Point, San
`Diego, CA 92130 (US). SINDHUSHAYANA, Nagab(cid:173)
`hushana, T.; 10635 Dabney Drive #63, San Diego, CA
`92126 (US). WHEATLEY, Charles, E., III; 2208 Camino
`Del Barco, Del Mar, CA 92014 (US). BENDER, Paul, E.;
`2879 Angell Avenue, San Diego, CA 92122 (US). BLACK,
`Peter, J.; Apartment 258, 8558 Villa La Jolla Drive, La Jolla,
`CA 92037 (US). GROB, Matthew; 2757 Bordeaux Avenue,
`La Jolla, CA 92037 (US). HINDERLING, Jurg, K.; 4655
`Serenata Place, San Diego, CA 92130 (US).
`
`(74) Agents: OGROD, Gregory, D. et al.; Qualcomm Incorporated,
`6455 Lusk Boulevard, San Diego, CA 92121 (US).
`
`(54) Title: METHOD AND APPARATUS FOR HIGH RATE PACKET DATA TRANSMISSION
`
`30
`
`PSTN
`
`' '.
`: ---- ................... J: ............................. -_____ J
`
`(57) Abstract
`
`In a data communication system capable of variable rate transmission, high rate packet data transmission improves utilization of the
`forward link and decreases the transmission delay. Data transmission on the forward link is time multiplexed and the base station transmits
`at the highest data rate supported by the forward link at each time slot to one mobile station. The data rate is determined by the largest
`C/1 measurement of the forward link signals as measured at the mobile station. Upon determination of a data packet received in error,
`the mobile station transmits a NACK message back to the base station. The NACK message results in retransmission of the data packet
`received in error. The data packets can be transmitted out of sequence by the use of sequence number to identify each data unit within the
`data packets.
`
`IPR2018-1556
`HTC EX1009, Page 1
`
`

`

`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
`
`AL
`AM
`AT
`AU
`AZ
`BA
`BB
`BE
`BF
`BG
`BJ
`BR
`BY
`CA
`CF
`CG
`CH
`CI
`CM
`CN
`cu
`CZ
`DE
`DK
`EE
`
`Albania
`Armenia
`Austria
`Australia
`Azerbaijan
`Bosnia and Herzegovina
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Ci\te d'Ivoire
`Cameroon
`China
`Cuba
`Czech Republic
`Germany
`Denmark
`Estonia
`
`ES
`FI
`FR
`GA
`GB
`GE
`GH
`GN
`GR
`HU
`IE
`IL
`IS
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`LC
`LI
`LK
`LR
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People's
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`LS
`LT
`LU
`LV
`MC
`MD
`MG
`MK
`
`ML
`MN
`MR
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`
`Lesotho
`Lithuania
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`The former Yugoslav
`Republic of Macedonia
`Mali
`Mongolia
`Mauritania
`Malawi
`Mexico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`
`SI
`SK
`SN
`sz
`TD
`TG
`TJ
`TM
`TR
`TT
`UA
`UG
`us
`uz
`VN
`YU
`zw
`
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`Turkmenistan
`Turkey
`Trinidad and Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`Viet Nam
`Yugoslavia
`Zimbabwe
`
`IPR2018-1556
`HTC EX1009, Page 2
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`1
`
`METHOD AND APPARATUS FOR HIGH RATE PACKET DATA
`TRANSMISSION
`
`BACKGROUND OF THE INVENTION
`
`5
`
`10
`
`I. Field of the Invention
`
`to data communication. More
`relates
`invention
`The present
`particularly, the present invention relates to a novel and improved method
`and apparatus for high rate packet data transmission.
`
`II. Description of the Related Art
`
`15
`
`20
`
`30
`
`A modern day communication system is required to support a variety
`of applications. One such communication system is a code division
`multiple access (CDMA) system which conforms to the "TIA/EIA/IS-95
`Mobile Station-Base Station Compatibility Standard
`for Dual-Mode
`Wideband Spread Spectrum Cellular System", hereinafter referred to as the
`IS-95
`standard.
`The CDMA system allows
`for voice
`and data
`communications between users over a terrestrial link. The use of CDMA
`techniques in a multiple access communication system is disclosed in U.S.
`Patent No. 4,901,307, entitled "SPREAD SPECTRUM MULTIPLE ACCESS
`COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL
`25 REPEATERS", and U.S. Patent No. 5,103,459, entitled "SYSTEM AND
`METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR
`TELEPHONE SYSTEM", both assigned to the assignee of the present
`invention and incorporated by reference herein.
`In this specification, base station refers to the hardware with which
`the mobile stations communicate. Cell refers to the hardware or the
`geographic coverage area, depending on the context in which the term is
`used. A sector is a partition of a cell. Because a sector of a CDMA system has
`the attributes of a cell, the teachings described in terms of cells are readily
`extended to sectors.
`In the CDMA system, communications between users are conducted
`through one or more base stations. A first user on one mobile station
`communicates to a second user on a second mobile station by transmitting
`data on the reverse link to a base station. The base station receives the data
`and can route the data to another base station. The data is transmitted on
`the forward link of the same base station, or a second base station, to the
`
`35
`
`40
`
`IPR2018-1556
`HTC EX1009, Page 3
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`2
`
`5
`
`15
`
`20
`
`second mobile station. The forward link refers to transmission from the
`base station to a mobile station and the reverse link refers to transmission
`from the mobile station to a base station. In IS-95 systems, the forward link
`and the reverse link are allocated separate frequencies.
`The mobile station communicates with at least one base station
`during a communication.
`CDMA mobile
`stations are capable of
`communicating with multiple base stations simultaneously during soft
`handoff. Soft handoff is the process of establishing a link with a new base
`station before breaking the link with the previous base station. Soft handoff
`10 minimizes the probability of dropped calls. The method and system for
`providing a communication with a mobile station through more than one
`base station during the soft handoff process are disclosed in U.S. Patent No.
`5,267,261, entitled "MOBILE ASSISTED SOFT HANDOFF IN A CDMA
`CELLULAR TELEPHONE SYSTEM," assigned to the assignee of the present
`invention and incorporated by reference herein. Softer handoff is the
`process whereby the communication occurs over multiple sectors which are
`serviced by the same base station. The process of softer handoff is described
`in detail in copending U.S. Patent Application Serial No. 08/763,498, entitled
`"METHOD AND APPARATUS FOR PERFORMING HANDOFF BETWEEN
`SECTORS OF A COMMON BASE STATION", filed December 11, 1996,
`assigned to the assignee of the present invention and incorporated by
`reference herein
`Given the growing demand for wireless data applications, the need
`for very efficient wireless data communication systems has become
`increasingly significant. The IS-95 standard is capable of transmitting traffic
`data and voice data over the forward and reverse links. A method for
`transmitting traffic data in code channel frames of fixed size is described in
`detail in U.S. Patent No. 5,504,773, entitled "METHOD AND APPARATUS
`FOR THE FORMATTING OF DATA FOR TRANSMISSION", assigned to
`the assignee of the present invention and incorporated by reference herein.
`In accordance with the IS-95 standard, the traffic data or voice data is
`partitioned into code channel frames which are 20 msec wide with data rates
`as high as 14.4 Kbps.
`A significant difference between voice services and data services is the
`fact that the former imposes stringent and fixed delay requirements.
`Typically, the overall one-way delay of speech frames must be less than
`100 msec. In contrast, the data delay can become a variable parameter used
`to optimize the efficiency of the data communication system. Specifically,
`more efficient error correcting coding techniques which require significantly
`
`25
`
`30
`
`35
`
`IPR2018-1556
`HTC EX1009, Page 4
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`3
`
`10
`
`15
`
`20
`
`larger delays than those that can be tolerated by voice services can be
`utilized. An exemplary efficient coding scheme for data is disclosed in U.S.
`Patent Application Serial No. 08/743,688, entitled "SOFT DECISION
`OUTPUT DECODER FOR DECODING CONVOLUTIONALLY ENCODED
`5 CODEWORDS", filed November 6, 1996, assigned to the assignee of the
`present invention and incorporated by reference herein.
`Another significant difference between voice services and data
`services is that the former requires a fixed and common grade of service
`(GOS) for all users. Typically, for digital systems providing voice services,
`this translates into a fixed and equal transmission rate for all users and a
`maximum tolerable value for the error rates of the speech frames.
`In
`contrast, for data services, the GOS can be different from user to user and
`can be a parameter optimized to increase the overall efficiency of the data
`communication system. The GOS of a data communication system is
`typically defined as the
`total delay
`incurred
`in
`the
`transfer of a
`predetermined amount of data, hereinafter referred to as a data packet.
`Yet another significant difference between voice services and data
`services is that the former requires a reliable communication link which, in
`the exemplary CDMA communication system, is provided by soft handoff.
`Soft handoff results in redundant transmissions from two or more base
`stations to improve reliability. However, this additional reliability is not
`required for data transmission because the data packets received in error can
`be retransmitted. For data services, the transmit power used to support soft
`handoff can be more efficiently used for transmitting additional data.
`The parameters which measure the quality and effectiveness of a data
`communication system are the transmission delay required to transfer a
`data packet and the average throughput rate of the system. Transmission
`delay does not have the same impact in data communication as it does for
`voice communication, but it is an important metric for measuring the
`quality of the data communication system. The average throughput rate is a
`measure of the efficiency of the data transmission capability of the
`communication system.
`It is well known that in cellular systems the signal-to-noise-and(cid:173)
`interference ratio C/1 of any given user is a function of the location of the
`user within the coverage area. In order to maintain a given level of service,
`TDMA and FDMA systems resort to frequency reuse techniques, i.e. not all
`frequency channels and/ or time slots are used in each base station.
`In a
`CDMA system, the same frequency allocation is reused in every cell of the
`system, thereby improving the overall efficiency. The C/1 that any given
`
`25
`
`30
`
`35
`
`IPR2018-1556
`HTC EX1009, Page 5
`
`

`

`WO 99/23844
`
`PCT /US98/23428
`
`4
`
`5
`
`15
`
`user's mobile station achieves determines the information rate that can be
`supported for this particular link from the base station to the user's mobile
`station. Given the specific modulation and error correction method used
`for the transmission, which the present invention seek to optimize for data
`transmissions, a given level of performance is achieved at a corresponding
`level of C/I. For idealized cellular system with hexagonal cell layouts and
`utilizing a common frequency in every cell, the distribution of C/I achieved
`within the idealized cells can be calculated.
`The C/I achieved by any given user is a function of the path loss,
`10 which for terrestrial cellular systems increases as r3 to r5, where r is the
`distance to the radiating source. Furthermore, the path loss is subject to
`random variations due to man-made or natural obstructions within the
`path of the radio wave. These random variations are typically modeled as a
`lognormal shadowing random process with a standard deviation of 8 dB.
`The resulting C/I distribution achieved for an ideal hexagonal cellular
`layout with omni-directional base station antennas, r4 propagation law, and
`shadowing process with 8 dB standard deviation is shown in Fig. 10.
`The obtained C/I distribution can only be achieved if, at any instant in
`time and at any location, the mobile station is served by the best base station
`20 which is defined as that achieving the largest C/I value, regardless of the
`physical distance to each base station. Because of the random nature of the
`path loss as described above, the signal with the largest C/I value can be one
`which is other than the minimum physical distance from the mobile
`station. In contrast, if a mobile station was to communicate only via the
`base station of minimum distance, the C/I can be substantially degraded. It
`is therefore beneficial for mobile stations to communicate to and from the
`best serving base station at all times, thereby achieving the optimum C/I
`value. It can also be observed that the range of values of the achieved C/I,
`in the above idealized model and as shown in FIG. 10, is such that the
`difference between the highest and lowest value can be as large as 10,000. In
`practical implementation the range is typically limited to approximately
`1:100 or 20 dB. It is therefore possible for a CDMA base station to serve
`mobile stations with information bit rates that can vary by as much as a
`factor of 100, since the following relationship holds:
`
`25
`
`30
`
`35
`
`(1)
`
`IPR2018-1556
`HTC EX1009, Page 6
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`5
`
`5
`
`where Rb represents the information rate to a particular mobile station, W
`is the total bandwidth occupied by the spread spectrum signal, and Eb/I0 is
`the energy per bit over interference density required to achieve a given level
`of performance. For instance, if the spread spectrum signal occupies a
`bandwidth W of 1.2288 MHz and reliable communication requires an
`average Eb/I0 equal to 3 dB, then a mobile station which achieves a C/I
`value of 3 dB to the best base station can communicate at a data rate as high
`as 1.2288 Mbps. On the other hand, if a mobile station is subject to
`substantial interference from adjacent base stations and can only achieve a
`10 C/I of -7 dB, reliable communication can not be supported at a rate greater
`than 122.88 Kbps. A communication system designed to optimize the
`average throughput will therefore attempts to serve each remote user from
`the best serving base station and at the highest data rate Rb which the
`remote user can reliably support. The data communication system of the
`present invention exploits the characteristic cited above and optimizes the
`data throughput from the CDMA base stations to the mobile stations.
`
`15
`
`20
`
`SUMMARY OF THE INVENTION
`
`30
`
`is a novel and improved method and
`The present invention
`apparatus for high rate packet data transmission in a CDMA system. The
`present invention improves the efficiency of a CDMA system by providing
`for means for transmitting data on the forward and reverse links. Each
`25 mobile station communicates with one or more base stations and monitors
`the control channels for the duration of the communication with the base
`stations. The control channels can be used by the base stations to transmit
`small amounts of data, paging messages addressed to a specific mobile
`station, and broadcast messages to all mobile stations. The paging message
`informs the mobile station that the base station has a large amount of data
`to transmit to the mobile station.
`It is an object of the present invention to improve utilization of the
`forward and reverse link capacity in the data communication system. Upon
`receipt of the paging messages from one or more base stations, the mobile
`station measures the signal-to-noise-and-interference ratio (C/I) of the
`forward link signals (e.g. the forward link pilot signals) at every time slots
`and selects the best base station using a set of parameters which can
`comprise the present and previous C/I measurements.
`In the exemplary
`embodiment, at every time slot, the mobile station transmits to the selected
`
`35
`
`IPR2018-1556
`HTC EX1009, Page 7
`
`

`

`WO 99/23844
`
`PCT /US98/23428
`
`6
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`base station on a dedicated data request (DRC) channel a request for
`transmission at the highest data rate which the measured C/I can reliably
`support. The selected base station transmits data, in data packets, at a data
`rate not exceeding the data rate received from the mobile station on the DRC
`channel. By transmitting from the best base station at every time slot,
`improved throughput and transmission delay are achieved.
`It is another object of the present invention to improve performance
`by transmitting from the selected base station at the peak transmit power for
`the duration of one or more time slots to a mobile station at the data rate
`requested by the mobile station. In the exemplary CDMA communication
`system, the base stations operate at a predetermined back-off (e.g. 3 dB) from
`the available transmit power to account for variations in usage. Thus, the
`average transmit power is half of the peak power. However, in the present
`invention, since high speed data transmissions are scheduled and power is
`typically not shared (e.g., among transmissions), it is not necessary to back(cid:173)
`off from the available peak transmit power.
`It is yet another object of the present invention to enhance efficiency
`by allowing the base stations to transmit data packets to each mobile station
`for a variable number of time slots. The ability to transmit from different
`base stations from time slot to time slot allows the data communication
`system of the present invention to quickly adopt to changes in the operating
`environment.
`In addition, the ability to transmit a data packet over non(cid:173)
`contiguous time slots is possible in the present invention because of the use
`of sequence number to identify the data units within a data packet.
`It is yet another object of the present invention to increase flexibility
`by forwarding the data packets addressed to a specific mobile station from a
`central controller to all base stations which are members of the active set of
`the mobile station. In the present invention, data transmission can occur
`from any base station in the active set of the mobile station at each time slot.
`Since each base station comprises a queue which contains the data to be
`transmitted to the mobile station, efficient forward link transmission can
`occur with minimal processing delay.
`to provide a
`It is yet another object of the present invention
`In the
`retransmission mechanism for data units received
`in error.
`exemplary embodiment, each data packet comprises a predetermined
`number of data units, with each data unit identified by a sequence number.
`Upon incorrect reception of one or more data units, the mobile station sends
`a negative acknowledgment (NACK) on the reverse link data channel
`indicating
`the
`sequence numbers of
`the missing data units
`for
`
`IPR2018-1556
`HTC EX1009, Page 8
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`7
`
`retransmission from the base station. The base station receives the NACK
`message and can retransmit the data units received in error.
`It is yet another object of the present invention for the mobile station
`to select the best base station candidates for communication based on the
`procedure described in U.S. Patent Application Serial No. 08/790,497,
`entitled "METHOD AND APPARATUS FOR PERFORMING SOFT
`HANDOFF IN A WIRELESS COMMUNICATION SYSTEM", filed January
`29, 1997, assigned to the assignee of the present invention and incorporated
`by reference herein. In the exemplary embodiment, the base station can be
`added to the active set of the mobile station if the received pilot signal is
`above a predetermined add threshold and dropped from the active set if the
`pilot signal is below a predetermined drop threshold.
`In the alternative
`embodiment, the base station can be added to the active set if the additional
`energy of the base station (e.g. as measured by the pilot signal) and the
`energy of the base stations already in the active set exceeds a predetermined
`threshold. Using this alternative embodiment, a base station which
`transmitted energy comprises an insubstantial amount of the total received
`energy at the mobile station is not added to the active set.
`It is yet another object of the present invention for the mobile stations
`to transmit the data rate requests on the DRC channel in a manner such that
`only the selected base station among the base stations in communication
`with the mobile station is able to distinguish the DRC messages, therefore
`assuring that the forward link transmission at any given time slot is from
`the selected base station. In the exemplary embodiment, each base station in
`communication with the mobile station is assigned a unique Walsh code.
`The mobile station covers the DRC message with
`the Walsh code
`corresponding to the selected base station. Other codes can be used to cover
`the DRC messages, although orthogonal codes are typically utilized and
`Walsh codes are preferred.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The features, objects, and advantages of the present invention will
`become more apparent from the detailed description set forth below when
`taken in conjunction with the drawings in which like reference characters
`identify correspondingly throughout and wherein:
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`IPR2018-1556
`HTC EX1009, Page 9
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`8
`
`FIG. 1 is a diagram of a data communication system of the present
`invention comprising a plurality of cells, a plurality of base stations and a
`plurality of mobile stations.
`FIG. 2 is an exemplary block diagram of the subsystems of the data
`communication system of the present invention;
`FIGS. 3A-3B are block diagrams of the exemplary forward link
`architecture of the present invention;
`FIG. 4A is a diagram of the exemplary forward link frame structure of
`the present invention;
`FIGS. 4B-4C are diagrams of the exemplary forward traffic channel
`and power control channel, respectively;
`FIG. 4D is a diagram of the punctured packet of the present invention;
`FIGS. 4E-4G are diagrams of the two exemplary data packet formats
`and the control channel capsule, respectively;
`FIG. 5 is an exemplary timing diagram showing the high rate packet
`transmission on the forward link;
`FIG. 6 is a block diagram of the exemplary reverse link architecture of
`the present invention;
`FIG. 7 A is a diagram of the exemplary reverse link frame structure of
`the present invention;
`FIGS. 7B is a diagram of the exemplary reverse link access channel;
`FIG. 8 is an exemplary timing diagram showing the high rate data
`transmission on the reverse link;
`FIG. 9 is an exemplary state diagram showing the transitions between
`the various operating states of the mobile station; and
`FIG. 10 is a diagram of the cumulative distribution function (CDF) of
`the C/I distribution in an ideal hexagonal cellular layout.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`the data
`the exemplary embodiment of
`In accordance with
`link data
`communication system of the present
`invention,
`forward
`transmission occurs from one base station to one mobile station (see FIG. 1)
`at or near the maximum data rate which can be supported by the forward
`link and the system. Reverse link data communication can occur from one
`mobile station to one or more base stations. The calculation of the
`maximum data rate for forward link transmission is described in detail
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`IPR2018-1556
`HTC EX1009, Page 10
`
`

`

`WO 99/23844
`
`PCT /US98/23428
`
`9
`
`below. Data is partitioned into data packets, with each data packet being
`transmitted over one or more time slots (or slots). At each time slot, the
`base station can direct data transmission to any mobile station which is in
`communication with the base station ..
`Initially, the mobile station establishes communication with a base
`station using a predetermined access procedure. In this connected state, the
`mobile station can receive data and control messages from the base station,
`and is able to transmit data and control messages to the base station. The
`mobile station then monitors the forward link for transmissions from the
`base stations in the active set of the mobile station. The active set contains a
`list of base stations in communication with the mobile station. Specifically,
`the mobile station measures the signal-to-noise-and-interference ratio (C/I)
`of the forward link pilot from the base stations in the active set, as received
`at the mobile station. If the received pilot signal is above a predetermined
`add threshold or below a predetermined drop threshold , the mobile station
`reports this to the base station. Subsequent messages from the base station
`direct the mobile station to add or delete the base station(s) to or from its
`active set, respectively. The various operating states of the mobile station is
`described below.
`If there is no data to send, the mobile station returns to an idle state
`and discontinues
`transmission of data rate information
`to the base
`station(s). While the mobile station is in the idle state, the mobile station
`monitors the control channel from one or more base stations in the active
`set for paging messages.
`If there is data to be transmitted to the mobile station, the data is sent
`by a central controller to all base stations in the active set and stored in a
`queue at each base station. A paging message is then sent by one or more
`base stations to the mobile station on the respective control channels. The
`base station may transmit all such paging messages at the same time across
`several base stations in order to ensure reception even when the mobile
`station is switching between base stations. The mobile station demodulates
`and decodes the signals on one or more control channels to receive the
`paging messages.
`Upon decoding the paging messages, and for each time slot until the
`data transmission is completed, the mobile station measures the C/I of the
`forward link signals from the base stations in the active set, as received at
`the mobile station. The C/I of the forward link signals can be obtained by
`measuring the respective pilot signals. The mobile station then selects the
`best base station based on a set of parameters. The set of parameters can
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`IPR2018-1556
`HTC EX1009, Page 11
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`10
`
`5
`
`10
`
`comprise the present and previous C/I measurements and the bit-error-rate
`or packet-error-rate. For example, the best base station can be selected based
`on the largest C/I measurement. The mobile station then identifies the best
`base station and transmits to the selected base station a data request message
`(hereinafter referred to as the DRC message) on the data request channel
`(hereinafter referred to as the DRC channel). The DRC message can contain
`the requested data rate or, alternatively, an indication of the quality of the
`forward link channel (e.g., the C/I measurement itself, the bit-error-rate, or
`the packet-error-rate). In the exemplary embodiment, the mobile station can
`direct the transmission of the DRC message to a specific base station by the
`use of a Walsh code which uniquely identifies the base station. The DRC
`message symbols are exclusively OR' ed (XOR) with the unique Walsh code.
`Since each base station in the active set of the mobile station is identified by
`a unique Walsh code, only the selected base station which performs the
`identical XOR operation as that performed by the mobile station, with the
`correct Walsh code, can correctly decode the DRC message. The base station
`uses the rate control information from each mobile station to efficiently
`transmit forward link data at the highest possible rate.
`At each time slot, the base station can select any of the paged mobile
`stations for data transmission. The base station then determines the data
`rate at which to transmit the data to the selected mobile station based on the
`most recent value of the DRC message received from the mobile station.
`Additionally, the base station uniquely identifies a transmission
`to a
`particular mobile station by using a spreading code which is unique to that
`25 mobile station.
`In the exemplary embodiment, this spreading code is the
`long pseudo noise (PN) code which is defined by IS-95 standard.
`The mobile station, for which the data packet is intended, receives the
`data transmission and decodes the data packet. Each data packet comprises a
`plurality of data units. In the exemplary embodiment, a data unit comprises
`eight information bits, although different data unit sizes can be defined and
`are within
`the scope of the. present
`invention.
`In
`the exemplary
`embodiment, each data unit is associated with a sequence number and the
`mobile stations are able
`to
`identify either missed or duplicative
`transmissions.
`In such events, the mobile stations communicate via the
`reverse link data channel the sequence numbers of the missing data units.
`The base station controllers, which receive the data messages from the
`mobile stations, then indicate to all base stations communicating with this
`particular mobile station which data units were not received by the mobile
`station. The base stations then schedule a retransmission of such data units.
`
`15
`
`20
`
`30
`
`35
`
`IPR2018-1556
`HTC EX1009, Page 12
`
`

`

`W099/23844
`
`PCT /US98/23428
`
`11
`
`5
`
`system can
`the data communication
`in
`Each mobile station
`communicate with multiple base stations on the reverse link.
`In the
`exemplary embodiment, the data communication system of the present
`invention supports soft handoff and softer handoff on the reverse link for
`several reasons. First, soft handoff does not consume additional capacity on
`the reverse link but rather allows the mobile stations to transmit data at the
`minimum power level such that at least one of the base stations can reliably
`decode the data. Second, reception of the reverse link signals by more base
`stations increases the reliability of the transmission and only requires
`additional hardware at the base stations.
`In the exemplary embodiment, the forward link capacity of the data
`transmission system of the present invention is determined by the rate
`requests of the mobile stations. Additional gains in the forward link
`capacity can be achieved by using directional antennas and/ or adaptive
`spatial filters. An exemplary method and apparatus for providing
`directional transmissions are disclosed in copending U.S. Patent Application
`No.
`08/575,049,
`entitled
`"METHOD AND APPARATUS
`FOR
`DETERMINING THE TRANSMISSION DATA RATE IN A MULTI-USER
`COMMUNICATION SYSTEM", filed December 20, 1995, and U.S. Patent
`20 Application Serial No. 08/925,521, entitled "METHOD AND APPARATUS
`FOR PROVIDING ORTHOGONAL SPOT BEAMS, SECTORS, AND
`PICOCELLS", f