(12) United States Patent
`Cheng et al.
`
`USOO641.1817B1
`(10) Patent No.:
`US 6,411,817 B1
`(45) Date of Patent:
`Jun. 25, 2002
`
`(54) METHOD AND SYSTEM FOR DYNAMIC
`DOWNLINK POWER CONTROLINA
`TIME-DIVISION, MULTIPLEX WIRELESS
`SYSTEM
`
`(*) Notice:
`
`(75) Inventors: Terry Sifong Cheng, Randolph; Joe
`Huang, Parsippany; Aparajita Misra,
`West Caldwell, all of NJ (US); Kevin
`John Murphy, Westminster, CO (US)
`(73) Assignee: Lucent Technologies Inc., Murray Hill,
`NJ (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 09/488,543
`(22) Filed:
`Jan. 21, 2000
`H04B 7/00; HO4O 7/20
`(51) Int. CI.7
`(55 U.S.C. .4551522; 455/67 1; 455/450;
`455/436; 370/331; 370/318
`(58) Field of Search ................................. 455/522, 422,
`455/450, 436, 437, 439, 13.4, 67.1, 67.4;
`370/331, 329, 318,321
`References Cited
`U.S. PATENT DOCUMENTS
`6,072,792 A * 6/2000 Mazur et al. ............... 370/345
`
`(56)
`
`6,144,861. A 11/2000 Sundelin et al. ............ 455/522
`6,154,450 A 11/2000 Wallentin ................... 370/311
`6,167,035 A * 12/2000 Veeravalli et al. .......... 370/331
`6,185,413 B1 * 2/2001 Mueller et al. ............. 455/405
`6,175,745 B1 * 6/2001 Bringby et al. ............. 455/522
`6,314.299 B1 * 11/2001 Schreib et al. .............. 455/465
`
`* cited by examiner
`
`Primary Examiner Edward F. Urban
`ASSistant Examiner Marceau Milord
`(57)
`ABSTRACT
`-
`-
`-
`A method for controlling downlink power in a time-division
`multiplex wireless system may provide different downlink
`transmit Signal powers to different time-division multiplex
`channels of a single carrier. A base Station receives a
`measured signal parameter data for a downlink transmit
`Signal of a time-division multiplex channel. The base Station
`determines an initial adjustment for the downlink transmit
`Signal power of the time division multiplex channel if the
`measured Signal parameter data differs from a target Signal
`parameter data. The base Station determines a revised adjust
`ment for the downlink transmit power of the time division
`multiplex channel based on the initial adjustment and at least
`one adjustment range as appropriate to achieve Synchroni
`Zation of the demodulation of the downlink transmit signal.
`
`21 Claims, 8 Drawing Sheets
`
`
`
`
`
`
`
`
`
`
`
`RECEIVE AMEASURED SIGNAL PARAMETER DATA (e.g. BIT-ERROR
`RAFE DATA FOR ADOWNLINK TRANSMIT SIGNAL OF A TIME-DIVISION
`MULTIPLEXCHANNEL THROUGH AMOBILE ASSISTED HAND-OFF (MAHO) REPORT
`
`CONVERT THE RECEIVE MEASURED SIGNAL PARAMETER DATA TO A
`CORRESPONDING OPERATIONAL SIGNAL-TO-INTERFERENCE RATIO (CII)
`IF APPROPRIATE
`
`COMPARE THE OPERATIONAL SIGNAL-TO-INTERFERENCE RATIO
`TO A TARGET SIGNAL-TO-INTERFERENCE RATIO
`
`DETERMINE AN INITIAL ADJUSTMENT FOR THE DOWNLINK TRANSMIT POWER
`OF THE TIME-DIVISION MULTIPLEXCHANNEL IF THE OPERATIONAL SIGNAL
`TO INTERFERENCE RATIO DIFFERS FROM A TARGET SIGNAL TO INTERFERENCE RATIO
`
`DETERMINE A FINAL ADJUSTMENT FOR THE DOWNLINK TRANSMIT POWER OF THE
`TIME-DIVISION MULTIPLEX CHANNEL BASED ON THE INITIAL ADJUSTMENT
`ANDAT LEAST ONE ADJUSTMENT RANGE
`
`ADJUST THE DOWNLINK TRANSMIT POWER OF THE TIME-DIVISION
`MULTIPLEXCHANNEL ACCORONG TO THE FINAL ADJUSTMENT
`
`SO
`
`S12
`
`S14
`
`S15
`
`S6
`
`S1
`
`Ericsson Exhibit 1005
`Page 1
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 1 of 8
`
`US 6,411,817 B1
`
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`Ericsson Exhibit 1005
`Page 2
`
`Ericsson Exhibit 1005
`Page 2
`
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 2 of 8
`
`US 6,411,817 B1
`
`
`
`
`
`
`
`
`
`FIG 2
`
`RECEIVE A MEASURED SIGNAL PARAMETER DATA (e.g. BIT-ERROR
`RATE DATA) FOR ADOWNLINK TRANSMIT SIGNAL OF A TIME-DIVISION
`MULTIPLEX CHANNEL THROUGH A MOBILE ASSISTED HAND-OFF (MAHO) REPORT
`
`CONVERT THE RECEIVED MEASURED SIGNAL PARAMETER DATA TO A
`CORRESPONDING OPERATIONAL SIGNAL-TO-INTERFERENCE RATIO (C|I).
`IF APPROPRIATE
`
`COMPARE THE OPERATIONAL SIGNAL-TO-INTERFERENCE RATIO
`TO A TARGET SIGNAL-TO-INTERFERENCE RATIO
`
`DETERMINE AN INITIAL ADJUSTMENT FOR THE DOWNLINK TRANSMIT POWER
`OF THE TIME-DIVISION MULTIPLEX CHANNEL IF THE OPERATIONAL SIGNAL
`TO INTERFERENCE RATIO DIFFERS FROM A TARGET SIGNAL TO INTERFERENCE RATIO
`
`DETERMINE A FINAL ADJUSTMENT FOR THE DOWNLINK TRANSMIT POWER OF THE
`TIME-DIVISION MULTIPLEX CHANNEL BASED ON THE INITIAL ADJUSTMENT
`AND AT LEAST ONE ADJUSTMENT RANGE
`
`ADJUST THE DOWNLINK TRANSMIT POWER OF THE TIME-DIVISION
`MULTIPLEX CHANNEL ACCORDING TO THE FINAL ADJUSTMENT
`
`SO
`
`S12
`
`S14
`
`S15
`
`S16
`
`S18
`
`Ericsson Exhibit 1005
`Page 3
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 3 of 8
`
`US 6,411,817 B1
`
`FIG. 3
`
`
`
`BIT PATTERN
`000
`
`BER INTERVAL (%)
`OOBER
`
`APPROXIMATE CII (dB)
`
`O11
`OO
`
`= 10
`=2.. O
`
`Ericsson Exhibit 1005
`Page 4
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 4 of 8
`
`US 6,411,817 B1
`
`FIG. 4
`DETERMINE THE INITIAL PROPOSED POWERS OF EACH TIME
`DIVISION MULTIPLEXCHANNEL ASSOCIATED WITH ACARRIER /S26
`BASED ON AT LEAST ONE TARGET SIGNAL
`TO-INTERFERENCE GOAL
`
`DETERMINE A MAXIMUM INITIAL PROPOSED POWER AMONG
`THE TIME-DIVISION MULTIPLEX CHANNELS ASSOCIATED
`WITH THE CARRIER
`
`
`
`ESTABLISH A REFERENCE RANGE WITH AN UPPER LIMIT SET
`EQUAL TO THE MAXIMUM INITIAL PROPOSED POWER AND A
`LOWER LIMIT HAVING ACERTAIN OFFSET
`FROM THE UPPER LIMIT
`
`IS A REMAINING CHANNEL OF THE CARRIER
`WITH A LOWER INITIAL PROPOSED POWER
`THAN THE MAXIMUM PROPOSED POWER
`WITHIN THE REFERENCE RANGE
`NO
`
`SET THE FINAL PROPOSED POWER FOR THE
`REMAINING CHANNEL EQUAL TO THE LOWER LIMIT
`
`SET THE FINAL PROPOSED POWER FOR THE REMAINING CHANNEL
`EQUAL TO THE INITIAL PROPOSED POWER FOR THE REMAINING
`CHANNEL WITHIN THE REFERENCE RANGE
`
`HAVE ALL OF THE CHANNELS OF THE CARRIER BEEN
`CONSIDERED FOR COMPLIANCE WITH
`THE ADJUSTMENT RANGE?
`YES
`
`END ADJUSTMENT TUNING CYCLE
`
`S4O
`
`S28
`
`S30
`
`S32
`YES
`
`S34
`
`S36
`
`S38
`NO
`
`Ericsson Exhibit 1005
`Page 5
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 5 of 8
`
`US 6,411,817 B1
`
`FIG. 5
`
`DETERMINE THE INITIAL PROPOSED POWERS OF EACH TIME DIVISION
`MULTIPLEX CHANNEL ASSOCIATED WITH A CARRIER BASED ON AT LEAST
`ONE TARGET SIGNAL-TO-INTERFERENCE GOAL
`
`S42
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`IS AN INITIAL PROPOSED POWER LARGER V NO
`THAN AN AUTHORIZED MAXIMUM POWER2
`
`LIMIT THE INITIAL PROPOSED POWER
`TO THE AUTHORIZED MAXIMUM POWER
`
`IS AN INITIAL PROPOSED POWER LOWER THAN AN
`AUTHORIZED MINIMUM POWER
`
`RAISE THE INITIAL PROPOSED POWER
`TO THE AUTHORIZED MINIMUM POWER
`
`RETAIN THE INITIAL PROPOSED POWER AS A FINAL POWER
`WITHIN AN AUTHORIZED ABSOLUTE RANGE
`
`HAVE ALL OF THE CHANNELS OF THE
`CARRIER BEEN CONSIDERED FOR
`COMPLIANCE WITH THE ABSOLUTE
`ADJUSTMENT RANGE?
`
`END ADJUSTMENT TUNING CYCLE
`
`S56
`
`Ericsson Exhibit 1005
`Page 6
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 6 of 8
`
`US 6,411,817 B1
`
`FIG EA
`
`DOWNLINK
`SIGNAL-TO
`INTERFERENCE
`RATIO
`
`
`
`DOWNLINK
`SIGNAL-TO
`INTERFERENCE
`RATIO
`
`
`
`DOWNLINK
`SIGNAL-TO
`INTERFERENCE
`RATIONK
`
`1ST FRAME
`
`2ND FRAME
`
`3RD FRAME
`
`FIG. 6B
`
`40 MSeC
`1ST FRAME
`
`40 MSeC
`2ND FRAME
`
`40 MSeC
`3RD FRAME
`
`FIG. SC
`
`40 mSeC
`1ST FRAME
`
`40 MSec
`2ND FRAME
`
`40 MSec
`3RD FRAME
`
`Ericsson Exhibit 1005
`Page 7
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 7 of 8
`
`US 6,411,817 B1
`
`FIG 7
`
`
`
`RECEIVE MEASURED RECEIVED SIGNAL STRENGTH INTENSITY WALUES
`FOR THE DOWNLINK SIGNAL
`
`DETERMINE WHETHER THE RECEIVED SIGNAL STRENGTH FALLS BELOW
`A MINIMUM THRESHOLD SIGNAL STRENGTH
`
`RESTRICT THE POWER WARIATION BETWEEN DIFFERENT TIME SLOTS
`WITHIN A FRAME THAT SERVE DIFFERENT MOBILE STATIONS IF THE
`RECEIVED SIGNAL STRENGTH FALLS BELOW THE MINIMUM THRESHHOLD SIGNAL
`STRENGTH, SO THAT A MOBILE STATION CAN MAINTAIN SYNCHRONIZATION
`
`S2O
`
`S22
`
`S24
`
`Ericsson Exhibit 1005
`Page 8
`
`

`

`U.S. Patent
`
`Jun. 25, 2002
`
`Sheet 8 of 8
`
`US 6,411,817 B1
`
`WNOIS
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`Ericsson Exhibit 1005
`Page 9
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`Ericsson Exhibit 1005
`Page 9
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`

`

`US 6,411,817 B1
`
`1
`METHOD AND SYSTEM FOR DYNAMIC
`DOWNLINK POWER CONTROLINA
`TIME-DIVISION, MULTIPLEX WIRELESS
`SYSTEM
`
`2
`FIG. 5 is a flow diagram of a method of determining an
`adjustment of a downlink transmit power based on compli
`ance with an absolute adjustment range in accordance with
`the invention.
`FIG. 6A and FIG. 6B illustrate the relative power levels
`of time-slots within frames for the power control method of
`FIG. 4.
`FIG. 6C illustrates the relative power levels of time-slots
`within frames for the power control method of FIG. 5.
`FIG. 7 is a flow diagram of a method of determining an
`adjustment of a downlink transmit power based on compli
`ance with a reference adjustment range in accordance with
`the invention.
`FIG. 8 is a block diagram of another embodiment of a
`wireleSS communications System in accordance with the
`invention.
`
`DETAILED DESCRIPTION OF A PREFERRED
`EMBODIMENT
`In accordance with one embodiment of the invention,
`FIG. 1 shows a time-division multiplex communication
`System. AS used herein, the term time-division multiplex
`System shall refer to a time-division, multiple-acceSS System,
`a global system for mobile communications (GSM) or
`another communication System which assigns different time
`Slots to mobile Stations to accommodate communication
`services to multiple mobile stations individually. The com
`munication System includes a mobile Switching center 12
`which is preferably coupled to a base station 16 and the
`public switched telephone network (PSTN) 10. The base
`Station 16 communicates over an electromagnetic carrier to
`a plurality of mobile stations including a first mobile Station
`24, a second mobile station 30 and a third mobile station36.
`Although, three mobile Stations are shown communicating
`over a single carrier, in an alternate embodiment Virtually
`any number of mobile Stations may operate over channels
`defined on a carrier.
`The base station 16 includes a transmitter 22. The trans
`mitter 22 may transmit a downlink Signal over a first
`time-division multiplex channel of the carrier to the first
`mobile station 24. The base station 16 may transmit a
`downlink transmit Signal over a Second time-division mul
`tiplex channel of the carrier to the second mobile station 30.
`The base station 16 transmitter 22 may transmit a downlink
`transmit signal over a third time-division multiplex channel
`of the carrier to the third mobile station 36.
`The first mobile station 24 receives the first time-division
`multiplex channel via the first transceiver 28. The second
`mobile station 30 receives the second time-division multi
`plex channel via the second transceiver 34 and the third
`mobile station 36 receives the third time-division multiplex
`channel via the third transceiver 40. The first signal param
`eter measurer 26 measures a signal parameter associated
`with the first time-division multiplex channel to determine
`whether the downlink Signal meets a target Signal parameter.
`A target Signal parameter represents a value of a received
`Signal parameter of a downlink Signal that provides a desired
`downlink performance or a desired signal quality level at a
`mobile Station. For example, the target Signal parameter may
`represent a particular signal-to-noise ratio of the downlink
`Signal to provide communications with a desired frame error
`rate (e.g., 1% maximum frame error rate). A mobile Station
`may be equipped to allow a technician to program a target
`Signal parameter. The Second Signal parameter measurer 32
`measures a Signal parameter of the Second time-division
`multiplex channel to determine if the Second time-division
`
`1O
`
`15
`
`FIELD OF INVENTION
`This invention relates to a method and system for
`dynamic downlink power control in a time-division multi
`plex wireleSS System.
`BACKGROUND
`Presently, many time-division multiple-access (TDMA)
`wireleSS Systems use no dynamic downlink power control
`based on the actual activity of mobile Stations. Instead, the
`downlink transmit power is typically Set at a fixed level high
`enough to provide an adequate downlink Signal to the
`mobile Station receiving the worst downlink Signal Strength
`on the carrier. For example, the mobile Station receiving the
`Worst downlink Signal Strength may be located furthest away
`from a base Station site transmitting to this mobile Station.
`Meanwhile, the base Station may provide one or more closer
`mobile Stations to the base Station site a Stronger Signal
`Strength than is really required to maintain reliable commu
`nications with the furthest mobile Station. Accordingly, the
`25
`difference between the power required by one or more closer
`mobile Stations and the actual power received by the closer
`mobile Stations is, in essence, wasted power that increases
`co-channel interference. Thus, a need exists for reducing
`interference and increasing wireleSS System capacity in a
`time-division multiplex System through an enhanced down
`link power control Scheme.
`SUMMARY OF THE INVENTION
`In accordance with one aspect of the invention, a method
`for controlling downlink power in a time-division multiplex
`wireleSS System may provide different downlink transmit
`Signal powers to different time-division multiplex channels
`of a single carrier. A base Station receives a measured signal
`parameter data for a downlink transmit Signal of a time
`division multiplex channel. The base Station determines an
`initial adjustment for the downlink transmit signal power of
`the time division multiplex channel if the measured signal
`parameter data differs from a target Signal parameter data.
`The base Station determines a revised adjustment for the
`downlink transmit power of the time division multiplex
`channel based on the initial adjustment and at least one
`adjustment range as appropriate to achieve Synchronization
`of the demodulation of the downlink transmit signal. The
`initial adjustment is based on dynamic measurements of
`Signal parameter data, whereas the revised adjustment may
`be based on the capabilities of the mobile station or other
`considerations.
`
`35
`
`40
`
`45
`
`50
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of one embodiment of a wireless
`communications System in accordance with the invention.
`FIG. 2 is a flow diagram of a method for dynamic
`downlink power control in accordance with FIG. 1.
`FIG. 3 is a chart of the conversion database that illustrates
`a possible relationship between bit-error rate and an approxi
`mate signal-to-interference ratio for adjusting downlink
`power in accordance with the method of FIG. 2.
`FIG. 4 is a flow diagram of a method of determining an
`adjustment of a downlink transmit power based on compli
`ance with a reference adjustment range in accordance with
`the invention.
`
`55
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`60
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`Ericsson Exhibit 1005
`Page 10
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`

`

`3
`multiplex channel meets a target Signal parameter associated
`with the second time-division multiplex channel. The third
`Signal parameter measurer 38 measures a signal parameter
`of the third time-division multiplex channel to determine
`whether the third channel meets a Signal parameter target
`asSociated with the Signal parameter target.
`The Signal parameter may represent a signal Strength
`measurement, a bit-error rate measurement, a frame-error
`rate measurement, a signal-to-interference measurement, a
`Signal-to-noise measurement, or another Suitable indicator
`of Signal quality. The target Signal parameters for the first
`time-division multiplex channel, the Second time-division
`multiplex channel and the third time-division multiplex
`channel may be identical or different depending upon a
`particular configuration chosen by a Service provider oper
`ating the wireleSS System.
`The first, second, and third mobile stations (24, 30, 36)
`may send adjustment data to the base station 16 for the first
`time-division channel, the Second time-division channel
`and/or the third time-division channel, respectively. The
`receiver 18 receives the adjustment data for the first time
`division channel, the Second time-division channel and the
`third time-division channel and downlink power controller
`20 may adjust the transmitter 22 so that the transmit power
`of the first time-division channel, the Second time-division
`channel, and the third time-division channel meet their
`respective target Signal parameters for a group of Successive
`time intervals. The mobile Station (e.g., 24) or the base
`Station 16 may determine, refine, or otherwise process the
`adjustment data to facilitate adjustment of the downlink
`transmit power of the base Station 16. Although the forego
`ing adjustment Scheme has been described with reference to
`three time-division channels per carrier, the adjustment
`Scheme may be implemented, in practice, with Virtually any
`number of time-division channels per carrier.
`In the wireless system of FIG. 1, the base station 16
`includes an integral controller (not shown) for assigning
`channels to the mobile stations (24, 30, 36) and communi
`cating with the mobile Switching center 12. However, if the
`system of FIG. 1 were a GSM system, it would include a
`base Station controller interconnected between the mobile
`Switching center 12 and the base Station 16 to perform
`control functions and channel assignments for the mobile
`stations (24, 30, 36).
`In accordance with the invention, FIG. 2 illustrates a
`method for adjusting the downlink transmit power of a
`time-division multiplex channel in accordance with the
`wireless system of FIG. 1. Starting in step S10, the base
`Station 16 receives adjustment data in the form of measured
`Signal parameter data (e.g., bit-error rate data) for a down
`link transmit Signal of a time-division multiplex channel.
`For example, the base Station 16 may receive the adjustment
`data in a mobile assisted hand-off (MAHO) report. The
`mobile-assisted hand-off report is generated by one of the
`mobile stations (24, 30, 36) communicating with the base
`Station 16. Although the measured Signal parameter data is
`typically Sent via a mobile assisted hand-off report, in an
`alternate embodiment the measured signal parameter data
`may be sent by any type of message data transmitted from
`a mobile station to the base station 16.
`In step S12, the base station 16 converts the signal
`parameter data to an appropriate format for comparison to
`the target Signal parameter data, which is Stored in a refer
`ence database accessible by the base station 16. For
`example, the base Station 16 converts the measured bit-error
`rate data to a corresponding operational Signal-to
`
`15
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`US 6,411,817 B1
`
`4
`interference ratio to facilitate comparison to a target signal
`to-interference ratio as the target Signal parameter. The base
`Station 16 may store a conversion database or a look-up table
`that relates values of measured signal parameter data asso
`ciated corresponding Signal-to-interference ratioS. The base
`Station 16 preferably includes a Storage device for Storing
`the reference database and the conversion database.
`In an alternate method, the base Station 16 may use a
`mathematical formula to derive a signal-to-interference ratio
`from a corresponding measured bit-error rate, in lieu of
`referencing the conversion database.
`In Step S14, the base Station 16 compares a measured or
`converted Signal parameter to the target Signal parameter.
`For example, the base Station 16 compares the operational
`Signal-to-interference ratio to a target Signal-to-interference
`ratio for the time-division multiplex channel. The opera
`tional signal-to-interference ratio is preferably derived from
`Signal parameter measurements on a channel-by-channel
`basis so that each of the mobile stations (24, 30, 36) on a
`carrier has a distinct operational Signal-to-interference ratio.
`The target Signal-to-interference ratio maybe the Same for all
`of the mobile Stations using a Single carrier. However, a
`Service provider may have the option of Selecting different
`levels of target signal-to-interference ratioS for each channel
`on the same carrier.
`In step S15, the base station 16 determines an initial
`adjustment for the downlink transmit power of a time
`division multiplex channel if the measured or converted
`Signal-to-interference ratio differs from a target Signal-to
`interference ratio. For example, if the operational Signal-to
`interference ratio differs from a target Signal-to-interference
`ratio, the difference between the operational Signal-to
`interference ratio and the target Signal-to-interference ratio
`for a particular time-division multiplex channel provides the
`initial adjustment or at least a basis for determining the
`initial adjustment.
`The target Signal-to-interference ratio may be set by a
`Service provider. On one hand, if the determined signal-to
`interference ratio is below the target Signal-to-interference
`ratio, the base Station increases the downlink transmit power
`to the mobile station. On the other hand, if the determined
`Signal-to-interference ratio is below the target Signal-to
`interference ratio, the base Station decreases the downlink
`transmit power to the mobile Station to reduce co-channel
`interference and/or increase the traffic capacity of the wire
`leSS System.
`In a preferred embodiment, the difference between the
`target Signal-to-interference ratio and the operational signal
`to-interference ratio is used as the initial adjustment for
`increases to the downlink transmit power of the time
`division multiplex channel. However, in the case of
`decreases to the downlink transmit power of the time
`division multiplex channel, the base Station 16 may use the
`difference (e.g., in decibels) between the operational Signal
`to-interference ratio and the target Signal-to-interference
`ratio divided by Some divisor as the initial adjustment.
`Accordingly, the initial adjustment downward of a downlink
`transmit power is preferably less than the difference between
`the operational Signal-to-interference ratio and the target
`Signal-to-interference ratio to protect the reliability of Voice
`or data information transmitted on the time-division multi
`plex channel. Although the initial adjustment is described in
`terms of decibel values related to the Signal-to-interference
`ratio, in alternate embodiments the initial adjustment may be
`accomplished with reference to other signal parameter, Such
`aS error rateS.
`
`Ericsson Exhibit 1005
`Page 11
`
`

`

`US 6,411,817 B1
`
`15
`
`25
`
`S
`Step S15 represents an initial adjustment for the downlink
`transmit power which is further defined in accordance with
`step S16. In step S16, the base station 16 determines a
`revised adjustment based on the initial adjustment for the
`downlink transmit power of the time-division multiplex
`channel. The revised adjustment is based both on the initial
`adjustment and at least one adjustment range.
`An adjustment range may include an absolute adjustment
`range, a reference adjustment range, or both. The actual
`decision to use one or more of the different adjustment
`ranges will depend, in Some cases, on the Synchronization
`capabilities of the mobile stations (24, 30, 36) using the
`wireleSS System at any given time. The reference adjustment
`range refers to a maximum allowable difference in downlink
`transmit power among the time-division multiplex channels
`carried over a single carrier. That is, the forward channels of
`a single carrier within a frame cannot differ by more than a
`certain power differential. For example, a first time-division
`multiplex channel, a Second time-division multiplex channel
`and third time-division multiplex channel within a frame
`may not differ by more than a 6 dB power differential to
`avoid loss of Synchronization of the mobile Stations.
`The reference range is preferably employed to compen
`Sate for technical limitations of the particular mobile Stations
`using the wireleSS System. A basic mobile Station is a mobile
`Station that is not modified in any particular way to be
`compatible with dynamic downlink power control. For
`example, a basic mobile Station may include pre-TIA/EIA
`(Telecommunication Industry/ASSociation/ Electronics
`Industry Association) IS-136 Revision A mobiles. An
`enhanced mobile Station is a mobile Station that features
`modifications for power control. For example, an enhanced
`mobile station may comprise a TIA/EIA IS-136 Revision A
`mobile Station. The reference range is preferably used for
`35
`basic mobile Stations, whereas the reference range is pref
`erably not used for enhanced mobile stations. However, if at
`least one basic mobile Station is on a common carrier, the
`other mobile stations and the basic mobile station on the
`Same carrier use the reference adjustment range.
`A pre-TIA/EIA IS-136 Revision A mobile station moni
`tors more than the time slots that are assigned to the
`time-division channel for the use of the pre-TIA/EIAIS-136
`Revision A mobile station. For example, if the first mobile
`station 24 is a pre-TIA/EIA IS-136 Revision A mobile
`station, the first mobile station 24 monitors the time slots
`asSociated with the Second time-division multiplex channel
`and the third time-division multiplex channel or any other
`channel on the common carrier. The first mobile station 24
`monitors the Second time-division multiplex channel and the
`third time-division multiplex channel as well as the first
`channel to properly Synchronize its demodulation circuitry
`to decode the downlink transmit Signal.
`However, in post-TIA/EIA IS-136 Revision A mobile
`Stations, the mobile Station is able to properly Synchronize
`by decoding only its time-division multiplex channel with
`out any reliance on monitoring the other time-division
`multiplex channels on the same carrier. Thus, no reference
`range or restriction in variation among different channels of
`a common carrier is required to maintain Synchronization for
`enhanced or post-TIA/EIA IS-136 Revision A mobile sta
`tions on different channels of the common carrier.
`The absolute range is distinct from the reference range.
`The absolute range primarily depends upon limitations of
`the base Station 16, limitations of governmental authorities
`Such as the Federal Communications Commission or the
`like. In one example, a governmental entity may license the
`
`6
`Service provider to use a maximum downlink power in a
`certain geographic region. The base Station 16 may not
`exceed the maximum downlink power without violating a
`regulation or law or interfering with other communications
`Services. Thus, an authorized maximum power of the abso
`lute range may be determined by the foregoing governmen
`tal considerations.
`In another example, the base Station 16 is not physically
`capable of exceeding a certain maximum power, which may
`be referred to as an authorized maximum power of the
`absolute adjustment range. Similarly, the base Station 16
`may not be capable of operating properly below a particular
`minimum downlink transmit power. Accordingly, the mini
`mum authorized power within the absolute reference range
`may also require consideration. A wireleSS Service provider
`may also wish to adjust the absolute range or the maximum
`authorized power to manipulate or define coverage areas of
`base Station sites within a wireleSS System, even if govern
`ment restrictions or physical limitations would not require
`Such an adjustment.
`The absolute reference range is considered regardless of
`whether the mobile Stations on the wireleSS communication
`System are basic mobile Stations or enhanced mobile Sta
`tions. If both the reference adjustment range and the absolute
`adjustment range are used for the time-division multiplex
`channels of a carrier, then compliance with the reference
`range is preferably executed prior to executing compliance
`with the absolute adjustment range.
`In a preferred embodiment, the initial adjustments are
`merely proposed adjustments and downlink transmit power
`is not transmitted at the initial adjustment value, unless it is
`first validated as a bona fide revised adjustment value by
`compliance with at least one reference range. Accordingly,
`the a adjustment occurs in Step S18 following determination
`of the revised adjustment in step S16. In step S18, the base
`station 16 adjusts the downlink transmit power of one of the
`time-division multiplex channels according to the revised
`adjustment determined in step S16.
`A carrier may serve a group of mobile Stations on Separate
`downlink channels. The carrier is transmitted in frames, with
`each frame potentially containing time-slots representing
`any channel within the group (e.g., 3 channels in TDMA) of
`downlink channels. Adjacent slots within a frame are usually
`asSociated with different time-division multiplex channels.
`Enhanced mobile Stations on a Single carrier are able to
`tolerate drastic power changes between adjacent time slots
`within a frame of a downlink Signal.
`In one illustrative embodiment, the base station 16 may
`adjust the power as frequently as once every 25 frames (e.g.,
`1 Second) before being updated with the next mobile assisted
`hand-off (MAHO) report. The MAHO report is readily
`available or modifiable for transmission of desired power
`adjustment data in many commercially available mobile
`Stations. However, in another embodiment, instead of using
`the MAHO report, the mobile station may transmit adjust
`ment data as a data message at an interval shorter than once
`every 25 frames.
`The mobile Station could transmit power adjustment data
`to the base station 16 to facilitate downlink transmit power
`adjustment as frequently as from one time slot to the next
`during a frame. For changes in power between Successive
`time slots, the base Station 16 preferably makes the power
`adjustment during the last two Symbols of a time slot Such
`that downlink transmit power is not necessarily uniform for
`an entire time slot. However, two consecutive slots for one
`time-division multiple channel or one mobile Station should
`
`40
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`45
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`50
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`55
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`60
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`65
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`Ericsson Exhibit 1005
`Page 12
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`7
`not change by more than allowed under the applicable
`standard. For example, for a TDMA system two consecutive
`Slots should not change by more than one dB under current
`Standards.
`In accordance with FIG. 3, a conversion database is
`shown that includes a bit-error rate interval and a corre
`sponding approximate operational Signal-to-interference
`ratio for the bit-error rate interval. The bit-error rate range
`may be identified by a bit pattern shown in the first column.
`The mobile station may transmit the bit pattern over a
`reverse channel during a mobile assisted hand-off report or
`otherwise. The conversion database provides correlation
`information between the bit-error rate and Signal-to
`interference radio. The conversion database is preferably
`Stored in a storage device and the base Station 16 for
`reference in step S12 of FIG. 2.
`FIG. 4 illustrates a reference adjustment step S16 in FIG.
`2 in more detail. Starting in step S26 of FIG. 4, the base
`Station 16 determines the initial proposed powers of each
`time-division multiplex channel associated with a carrier
`based on at least one target Signal-to-interference goal. The
`time-division multiplex channels associated with the carrier
`may have distinct target Signal-to-interference goals or an
`identical target Signal-to-interference goal. The initial
`adjustment powerS may be determined based on the differ
`ence between the operational Signal-to-interference ratio and
`the target Signal-to-interference ratio in accordance with Step
`S15. The initial proposed power represents a potential
`downlink transmit power for a particular time-division mul
`tiplex channel that would result from application of the
`initial adjustment power determined in step S15 of FIG. 2.
`After step S26 in step S28, the base station 16 determines
`a maximum initial proposed power among the time-division
`multiplex channel associated with the carrier. For example,
`if the carrier includes three time-division multiplex