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`US 20030123382Al
`
`(19) United States
`(12) Patent Application Publication
`Wang et al.
`
`(10) Pub. No.: US 2003/0123382 Al
`Jul. 3, 2003
`(43) Pub. Date:
`
`(54) ADAPTIVE SPREADING FACTOR BASED
`ON POWER CONTROL
`
`(22) Filed:
`
`Jan.2,2002
`
`(75)
`
`Inventors: Yan Wang, Placentia, CA (US); Roy
`Thomas Derryberry, Plano, TX (US)
`
`Correspondence Address:
`WARE FRESSOLA VAN DER SLUYS &
`ADOLPHSON,LLP
`BRADFORD GREEN BUILDING 5
`755 MAIN STREET, P 0 BOX 224
`MONROE, CT 06468 (US)
`
`(73) Assignee: Nokia Corporation
`
`(21) Appl. No.:
`
`10/040,891
`
`Publication Classification
`
`(51)
`Int. CI.7 ...................................................... H04J 11/00
`(52) U.S. Cl. ............................................ 370/208; 370/441
`
`(57)
`
`ABSTRACT
`
`Near-far effect fading is counteracted by changing the
`spreading factor used for uplink channel spreading. The
`determination that a radio uplink channel power fade exists
`can be made in either the radio access network or the mobile
`station.
`
`power
`
`10
`
`point to
`change SF
`
`SIR Threshold
`
`__)
`
`channel fading
`(without power control)
`
`received power at UTRAN
`(with power control)
`
`received power at UTRAN
`(decrease SF by 2)
`
`received power at UTRAN
`(decrease SF by 4)
`
`time
`
`Ericsson v. IV II LLC
`Ex. 1020 / Page 1 of 16
`
`

`

`'"""' 0 .....,
`~ .....
`'Jl =(cid:173)~
`8
`N c
`~~
`~ = :-
`.... 0 =
`O' -....
`~
`.... 0 =
`~ "Cl -....
`~ = .....
`~ .....
`""C
`
`~ .....
`
`I")
`
`N
`00
`~
`~
`'"""' N
`c
`@
`N c
`'Jl
`d
`
`'"""'
`>
`
`-..J
`
`(PRIOR ART)
`FIG. lA
`
`command
`
`power control
`
`time
`
`(2
`
`SIR Threshold
`
`~ .....
`
`I")
`
`(with power control)
`
`UT RAN
`
`received power at
`
`\_14
`
`(without power control)
`
`channel fading
`
`IO
`
`power
`
`Ex. 1020 / Page 2 of 16
`
`

`

`N
`00
`~
`~
`'"""' N
`~ c
`N c
`'Jl
`d
`
`'"""'
`>
`
`-..J
`0 .....,
`N
`~ .....
`'Jl =(cid:173)~
`8
`N c
`~~
`
`(without power control)
`
`channel fading
`
`(with power control)
`
`atUTRAN
`
`received power
`
`(PRIOR ART)
`FIG. lB
`
`16
`
`.... 0 =
`~ "Cl -....
`~ = .....
`
`~ .....
`O' =:
`~
`
`~ :-
`.... 0 =
`
`I")
`
`~ .....
`
`I")
`
`~
`""C
`
`time
`
`SIR Threshold
`
`command
`power control
`
`power
`
`Ex. 1020 / Page 3 of 16
`
`

`

`.... 0 =
`~ "Cl -....
`~ = .....
`
`~ .....
`
`I")
`
`~
`""C
`
`N
`00
`~
`~
`'"""' N
`~ c
`N c
`'Jl
`d
`
`'"""'
`>
`
`-..J
`0 .....,
`~
`
`~ .....
`'Jl =(cid:173)~
`8
`N c
`~~
`
`~ .....
`O' =:
`~
`
`~ :-
`.... 0 =
`
`I")
`
`FIG. 2A
`
`command
`
`power control
`
`time
`
`(decrease SF by 4)
`
`received power at UTRAN
`
`(decrease SF by 2)
`
`received power at UTRAN
`
`(with power control)
`
`received power at UTRAN
`
`t--24
`t--22
`l=14
`
`(2
`
`tl
`
`(without power control)
`
`channel fading
`
`change SF
`point to
`
`10
`
`power
`
`SIR Threshold fl
`
`Ex. 1020 / Page 4 of 16
`
`

`

`-..J
`0 .....,
`.i;;..
`~ .....
`'Jl =(cid:173)~
`8
`N c
`~~
`~ = :-
`.... 0 =
`O' -....
`~
`.... 0 =
`~ "Cl -....
`~ = .....
`~ .....
`""C
`
`~ .....
`
`I")
`
`(with power control)
`
`received power at UTRAN
`
`(increase SF by 2)
`
`received power at UTRAN
`
`(increase SF by 4)
`
`l ,__ r-e-c-ei-v-ed-p-ow-er_a_t_U_T_RA--N---.1
`
`~time
`
`l--20
`
`l--26
`l--28
`
`~ .....
`
`I")
`
`command
`
`power control
`
`18~
`
`power
`
`N
`00
`~
`~
`'"""' N
`~ c
`N c
`'Jl
`d
`
`'"""'
`>
`
`(without power control)
`
`channel fading
`
`16
`
`FIG. 2B
`
`change SF
`point to
`
`t1
`1
`
`I
`
`\
`
`fj
`
`SIR Threshold
`
`Ex. 1020 / Page 5 of 16
`
`

`

`.... 0 =
`~ "Cl -....
`= .....
`~ .....
`""C
`
`N
`00
`~
`~
`'"""' N
`~ c
`N c c
`'Jl
`d
`
`'"""'
`>
`
`-..J
`0 .....,
`Ul
`~ .....
`'Jl =-~
`
`N c c
`~ = :-
`
`~~
`
`~
`
`=
`.... 0
`.....
`O' =:
`~
`
`~
`I")
`
`~ .....
`
`I")
`
`~
`
`FIG. 4
`
`I
`
`(decided by U'fRA1\f)
`point to change SF
`
`I
`
`SF2
`
`I
`
`SF2 ( > SFl)
`
`I
`
`SFl
`
`I
`
`I
`
`UE
`
`UT'RA1\f li!.!.!.l.lil•l•l•l•l•l•lil.1.l.!.lil•l•lilil•lll•lil•lil•lll•lil•lil•lil•lil•lil•lll•lll•l
`
`FIG. 3
`
`I
`
`(decided by UE)
`point to change SF
`
`I
`
`SF2
`
`I
`
`SF2 ( > SFl)
`
`I
`
`SFl
`
`I
`
`I
`
`UE
`
`U'fRA1\f lil•l•l•l•lll•l•l•l•l•l•lll•l•l•l•lll•l•lllll•lll•lll•lll•lll•lll•lll•lll•lll•lll•lll•lll•I
`
`allow to I
`
`change SF
`
`Ex. 1020 / Page 6 of 16
`
`

`

`~
`
`""""
`N >
`QO
`~
`"""" N
`
`N
`rJ1
`Cj
`
`'-1
`0 ....,
`~
`~ ......
`==(cid:173) ~
`rJ1
`
`N §
`~ :-
`.... 0 =
`O"' -....
`~
`.... 0 =
`~ -....
`~ = ......
`~ ......
`"C
`
`~ ......
`I")
`
`~ ......
`I")
`
`~~
`
`L ...... .-. --._. ._. ...... -._. .._. ._. .._. ,._. .
`-so
`I
`
`L
`
`78
`
`DL Signal
`
`Mux
`
`76
`
`TPC
`
`TPC
`
`58
`
`quality meas.
`I Decode and I Signal
`
`1
`1 NODE BI RNC I UTRAN [ 50 UL
`r--------------
`
`52
`
`54
`
`loop
`Outer
`56
`
`Loop
`Inner
`
`-~~-~~~~~~ ...... -.-. ...... ~~.-.~--J
`I
`' 82 I
`r Demux ... , .. .__,, __
`I
`I
`I
`I
`I
`I
`I
`I
`
`86
`
`SF command
`
`TPC
`
`88
`
`...
`
`Decode
`
`,
`
`DL signal
`
`94
`
`Decision
`
`92
`
`\
`
`'4
`
`SF
`
`Change I command I SF
`
`SF
`
`FIG. 5
`
`84
`
`-------------------~
`
`I
`MOBILE STATION I
`
`Amp
`Power
`
`UL Signal
`
`Load
`
`96
`
`98
`
`,
`
`Ex. 1020 / Page 7 of 16
`
`

`

`Patent Application Publication
`
`Jul. 3, 2003 Sheet 7 of 7
`
`US 2003/0123382 Al
`
`62
`
`SIR target
`
`64
`
`Threshold
`Establishment
`
`Thresh
`
`Fading report
`
`68
`
`74
`
`-
`
`-
`
`---------------,
`I
`I
`
`100
`
`TPC
`
`Counter
`
`I - i04-
`: Threshold Thresh
`& window
`I
`I
`adaptation
`I
`I
`
`102
`
`91
`
`106
`
`Decider
`
`Load
`
`I 96
`I
`I
`SF command I
`.
`I 86
`I
`I
`I
`SFDECISIO~
`~-------------[----
`88
`FIG. 7
`
`SF command
`
`92
`
`Ex. 1020 / Page 8 of 16
`
`

`

`US 2003/0123382 Al
`
`Jul. 3, 2003
`
`1
`
`ADAPTIVE SPREADING FACTOR BASED ON
`POWER CONTROL
`
`BACKGROUND OF THE INVENTION
`
`[0001] 1. Technical Field
`
`[0002] The present invention relates to channel fading in
`a mobile telecommunications network and, more particu(cid:173)
`larly, efficient power control between a transmitter and a
`receiver of a radio signal undergoing fading.
`
`[0003] 2. Discussion of Related Art
`
`[0004] A base station or radio network controller will
`normally be in radio communication with several mobile
`stations within its coverage area. It is desirable for uplink
`signals from the mobile stations to the base station to be
`received with the same signal power. Because the mobile
`stations are at different distances from the base station they
`cannot transmit using fixed power levels since mobile sta(cid:173)
`tions close to the base station would have too strong a signal
`and mobile stations far away would be too weak. This is
`called the near-far effect and is solved by uplink power
`control. The faraway mobile station transmits with more
`power than the mobile station close to the base station so
`they are received with the same signal power.
`
`[0005] Usually, there are two types of power control used,
`i.e., open-loop and closed-loop. The open-loop method
`requires the mobile station to measure channel interference
`and adjust its own transmission power according to the
`measured interference without any interaction with the base
`station. This approach has certain problems, particularly
`where the uplink and the downlink are transmitted on
`different frequencies and fading on the different frequency
`carriers are not particularly well correlated.
`
`[0006] Fading exists because a single line-of-sight radio
`path may not exist from the mobile station to the base
`station. Consequently, the base station may observe the
`superposition of many copies of the same signal from the
`mobile station, each one with a different delay. These
`delayed signals are due to the reflection from objects such as
`trees, cars, buildings, etc. If the mobile station is moving, the
`copies of the signal can add constructively or destructively
`and the signal received at the base station appears to
`fluctuate, or fade wildly.
`
`[0007]
`In an uplink closed-loop power control approach,
`the quality of the uplink from the mobile station to the base
`station is measured in the base station. Power control
`commands formulated in the base station are adjusted
`accordingly and sent back to the mobile station so that it
`adjusts its transmission power correspondingly. This gives
`faster and better results than the above-mentioned open-loop
`approach, but it still cannot react to rapid fading as well as
`might be desired. Aknown way to address this problem is to
`make the closed-loop measurements and reporting very fast.
`However, the transmit power control (TPC) commands that
`are sent e.g., every time slot (667 microseconds) are still
`only commanding a small increment of change in power
`while the fading may be more extreme. In that case it takes
`a long time for the power control commands to elicit the
`desired response and by that time the fading may be chang(cid:173)
`ing in the opposite direction.
`
`DISCLOSURE OF INVENTION
`
`[0008] An object of the present invention is to provide an
`enhanced power control between a radio transmitter and
`receiver to counteract fast signal fading variations in the
`channel.
`
`[0009] According to a first aspect of the present invention,
`a method comprises the steps of determining that a radio
`uplink channel power fluctuation exists, and changing a
`spreading factor used for uplink channel spreading to coun(cid:173)
`teract said power fluctuation.
`
`[0010] Further according to the first aspect of the inven(cid:173)
`tion, the change in spreading factor is an increase due to the
`channel power fluctuation determined as comprising a
`decreasing power fluctuation.
`
`[0011] Further still according to the first aspect of the
`invention, the change in spreading factor is a decrease due
`to the channel power fluctuation determined as comprising
`an increasing power fluctuation.
`
`[0012] Still further according to the first aspect of the
`invention, the step of determining is carried out in a radio
`network and wherein the method further comprises the step
`of sending a spreading factor control signal from the net(cid:173)
`work to a mobile station followed by the mobile station
`carrying out the step of changing the spreading factor.
`
`[0013] Yet still further according to the first aspect of the
`invention, the step of changing is carried out by the mobile
`station only if the mobile station independently determines
`that the step of changing the spreading factor is permissible.
`
`[0014] Further in accord with the first aspect of the inven(cid:173)
`tion, the method farther comprises the step of sending a
`transmit power control (TPC) signal from the network to the
`mobile station and wherein the step of determining com(cid:173)
`prises the step of counting instances of the TPC signal at the
`network and carrying out the step of determining by deter(cid:173)
`mining at the network if a count of the instances exceeds a
`selected number.
`
`[0015] Yet further in accord with the first aspect of the
`invention, the selected number is adaptable.
`
`[0016] Further still in accord with the first aspect of the
`invention, the selected number is adaptable within a window
`comprising a selected plurality of TPC signal instances.
`
`[0017] Further according to the first aspect of the inven(cid:173)
`tion, the step of determining further comprises the step of
`determining a frame or block error rate of the radio uplink
`channel and wherein the step of changing the spreading
`factor is carried out only if the frame or block error rate
`meets a selected criterion.
`
`[0018] Further still according to the first aspect of the
`invention, the step of determining comprises the step of
`detecting in a radio network the radio uplink channel power
`fluctuation in the radio uplink channel from a mobile station
`to the network, and wherein the method further comprises
`the step of transmitting a transmit power control (TPC)
`signal from the network to the mobile station commanding
`a change in transmit power to counteract power fluctuation.
`
`[0019] Yet further still according to the first aspect of the
`invention, the step of determining comprises the step of
`counting instances of said TPC signal at the network or at
`
`Ex. 1020 / Page 9 of 16
`
`

`

`US 2003/0123382 Al
`
`Jul. 3, 2003
`
`2
`
`the mobile station and carrying out the step of determining
`by determining at the network or at the mobile station if a
`count of the instances exceeds a selected number followed
`by the mobile station carrying out the step of changing the
`transmit power in response to a command signal from the
`network or in response to the count at the mobile station
`exceeding the selected number.
`
`[0020] Yet still further according to the first aspect of the
`invention, the step of changing is carried out by the mobile
`station only if the mobile station independently determines
`that the step of changing the spreading factor is permissible.
`
`[0021] Yet further still according to the first aspect of the
`invention, step of counting, at the mobile station, instances
`of the TPC signal and wherein the step of determining
`comprises the step of determining at the mobile station if a
`count of the instances exceeds a selected number.
`
`[0022] Further in accord with the first aspect of the inven(cid:173)
`tion, the step of determining is carried out in a mobile
`station.
`
`[0023] Yet further in accord with the first aspect of the
`invention, the step of counting, at the mobile station,
`instances of a transmit power control (TPC) signal received
`from a radio network and the step of determining comprises
`the step of determining at the mobile station if a count of the
`instances exceeds a selected number.
`
`[0024] According to a second aspect of the invention, an
`apparatus comprises means for determining that a radio
`uplink channel power fluctuation exists, and means for
`changing a spreading factor used for uplink channel spread(cid:173)
`ing to counteract said power fluctuation.
`
`[0025] Further according to the second aspect of the
`invention, the change in spreading factor is an increase due
`to said channel power fluctuation determined as comprising
`a decreasing power fluctuation.
`
`[0026] Still further according to the second aspect of the
`invention, the change in spreading factor is a decrease due
`to the channel power fluctuation determined as comprising
`an increasing power fluctuation.
`
`[0027] Further still according to the second aspect of the
`invention, the means for determining is located in a radio
`network and wherein said apparatus further comprises
`means for sending a spreading factor control signal from the
`network to a mobile station to means for deciding a change
`in spreading factor.
`
`[0028] Yet further according to the second aspect of the
`invention, the change is carried out by the mobile station
`only if the means for deciding independently determines that
`the change in the spreading factor is permissible.
`
`[0029] Yet still further according to the second aspect of
`the invention, the apparatus further means for sending a
`transmit power control (TPC) signal from the network to the
`mobile station and wherein the means for determining
`comprises means for counting instances of the TPC signal at
`the network and means for deciding at the network if a count
`of the instances exceeds a selected number.
`
`[0030] Yet further still according to the second aspect of
`the invention, the selected number is adaptable.
`
`[0031] Further in accord with the second aspect of the
`invention, the selected number is adaptable within a window
`comprising a selected plurality of TPC signal instances.
`
`[0032] Further still in accord with the second aspect of the
`invention, the step of determining further comprises means
`for determining a frame or block error rate of the radio
`uplink channel and wherein the means for changing the
`spreading factor changes the spreading factor only if said
`frame or block error rate meets a selected criterion.
`
`[0033] Yet still further in accord with the second aspect of
`the invention, the means for determining comprises means
`for detecting in a radio network the radio uplink channel
`power fluctuation in the radio uplink channel from a mobile
`station to the network, and the apparatus further comprises
`means for transmitting a transmit power control (TPC)
`signal from the network to the mobile station commanding
`a change in transmit power to counteract the power fluctua(cid:173)
`tion.
`
`[0034] Yet further still in accord with the second aspect of
`the invention, the means for determining comprises means
`for counting instances of the TPC signal at the network or at
`the mobile station and means for determining at the network
`or at the mobile station if a count of the instances exceeds
`a selected number followed by the mobile station changing
`the transmit power in response to a command signal from the
`network or in response to the count at the mobile station
`exceeding the selected number.
`
`[0035] Further according to the second aspect of the
`invention, the means for determining further comprises
`means for determining a frame or block error rate of the
`radio uplink channel and wherein the means for changing
`the spreading factor changes the spreading factor only if the
`frame or block error rate meets a selected criterion.
`
`[0036] Yet further according to the second aspect of the
`invention, the means for changing is carried out by the
`mobile station only if the mobile station independently
`determines that the changing the spreading factor is permis(cid:173)
`sible.
`
`[0037] Further still according to the second aspect of the
`invention, the means for counting, at the mobile station,
`instances of TPC signal and wherein the means for deter(cid:173)
`mining comprises means for determining at the mobile
`station if a count of the instances exceeds a selected number.
`
`[0038] Still further according to the second aspect of the
`invention, the means for determining further comprises
`means for determining a frame or block error rate of the
`radio uplink channel and wherein the means for changing
`the spreading factor changes the spreading factor only if the
`frame or block error rate meets a selected criterion.
`
`[0039] Yet further still according to the second aspect of
`the invention, the means for determining is located in a
`mobile station.
`
`[0040] Yet still further according to the second aspect of
`the invention, the apparatus further comprises means for
`counting, at the mobile station, instances of a transmit power
`control (TPC) signal received from a radio network and the
`means for determining comprises means for determining at
`the mobile station if a count of the instances exceeds a
`selected number.
`
`Ex. 1020 / Page 10 of 16
`
`

`

`US 2003/0123382 Al
`
`Jul. 3, 2003
`
`3
`
`[0041] These and other objects, features and advantages of
`the present invention will become more apparent in light of
`the following detailed description of a best mode embodi(cid:173)
`ment thereof, as illustrated in the accompanying drawing.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0042] FIG. lA shows a prior art fading phenomenon with
`rapidly-increasing power received at the base station coun(cid:173)
`teracted by a series of transmit power commands from the
`base station to the mobile station to lower its transmitting
`power level in steps.
`[0043] FIG. lB is similar to FIG. lA, except showing the
`mobile station power sensed by the base station falling
`rapidly and the base station responding by sending a series
`of increase power commands.
`[0044] FIG. 2A shows an improvement to the solution
`shown in FIG. lA, wherein, according to the present inven(cid:173)
`tion, in response to a rapidly-increasing channel fade deter(cid:173)
`mined either at the base station or at the mobile station, the
`spreading factor used for uplink channel spreading by the
`mobile station is changed to dramatically counteract the
`power fluctuation.
`
`[0045] FIG. 2B improves over the prior art of FIG. lB by
`causing the spreading factor used for uplink channel spread(cid:173)
`ing to be dramatically increased in the presence of channel
`fading in a decreasing direction in order to counteract same.
`[0046] FIG. 3 shows a methodology according to a second
`embodiment of the present invention, wherein the mobile
`station determines that a power fade exists and takes steps to
`change the spreading factor on its own initiative by counting
`successive up or down transmit power commands received
`from the base station within a given time frame.
`[0047] FIG. 4 illustrates a third embodiment of the inven(cid:173)
`tion which is similar to the second embodiment, except that
`the TPC is counted at the base station and the count is used
`to formulate a spreading factor command for use in the
`mobile station in controlling its spreading factor used for the
`uplink channel spreading to counteract the power fluctua(cid:173)
`tion.
`[0048] FIG. 5 shows an uplink closed-loop power control
`modified to include components useful for carrying out the
`first, second and third embodiments of the present invention.
`
`[0049] FIG. 6 shows the decode and quality measurement
`block in the radio network controller of FIG. 5.
`[0050] FIG. 7 shows the spreading factor decision block
`of the mobile station of FIG. 5 in more detail.
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`base station receives the signal from the mobile station (MS)
`(called UE or user equipment in 3 GPP) at a low power level,
`the base station will send an "up" power control command
`on the downlink to the mobile station (user equipment). If
`the mobile station receives this command without error, it
`will "raise" its transmitted power by a small step. If the base
`station receives the MS signal at too high a level, the base
`station will send a "down" power control command. The
`mobile station will then reduce its transmitted power. Power
`control is described in general at pages 30-35 of "Introduc(cid:173)
`tion to 3G Mobile Communications" by Juha Korhonen,
`Artech House 2001. Power control is also described in
`Section 3.5 at pages 33-36 of "WCDMA for UMTS" by H.
`Halma and A Toskala, Revised Edition, Wiley 2001.
`According to Section 6.6 of the last-mentioned reference,
`the fast closed loop power control procedure operates on the
`basis of one command per slot, resulting in a 1,500 Hertz
`command rate with a basic step size of 1 dB.
`
`[0052] FIG. lA shows a rapidly increasing channel fading
`phenomenon indicated by a reference numeral 10 wherein a
`base station is receiving an uplink channel from a mobile
`station (again, called user equipment or UE in 3G) or MS
`with a received channel power level increasing rapidly
`above a signal interference ratio (SIR) threshold with
`increasing time. This threshold may be a target SIR, be a
`threshold level above a SIR target level, or the like. In any
`event, the network, e.g., the base station, which may be part
`of a universal terrestrial radio access network (UTRAN) for
`third generation (3G) mobile telecommunications, will
`detect the increasing channel fading 10 and will initiate
`power control with instructions issued in steps correspond(cid:173)
`ing to slots of a frame to gradually decrease its transmitted
`power. These power control commands are shown as a
`declining staircase signified by a reference numeral 12 in
`FIG. lA. These power control commands cause the mobile
`station to incrementally decrease its transmitted power with
`the effect shown by the received signal power 14 at the base
`station with this power control effectively reducing the
`increasing channel fading but only very gradually.
`
`[0053] Likewise, as shown in FIG. lB, if the channel
`fading is in the opposite direction as signified by a reference
`numeral 16, showing a given mobile station's power rapidly
`decreasing as detected at the base station below a SIR
`threshold, the base station will cause power control com(cid:173)
`mands 18 to be issued to command the mobile station to
`increase its transmitted output power in small steps. In
`carrying out these commands, the channel fading 16 is
`ameliorated as shown by reference numeral 20 showing
`received power at the base station with power control. As in
`FIG. lA, the fading effect is ameliorated but not as effec(cid:173)
`tively or as rapidly as might be desired.
`
`[0054] First Embodiment
`
`[0051] The capacity of a conventional CDMA system is
`maximized if the power transmitted from each mobile
`station is controlled so that at the base station the same
`power level is received from each mobile station. The power
`control is used to combat the near-far effect and thereby
`minimize the effect of interference on system capacity.
`However, due to fast signal fading variations in the channel
`and the use of a fixed and rather small power control step,
`the transmit signal power is not able to track quickly
`changing uplink channel variations. For the uplink, if the
`
`[0055] FIG. 2A is similar to FIG. lA in that an increasing
`fading channel 10 is shown without power control and with
`power control 14 according to power control commands 12.
`However, unlike FIG. lA, in addition to power control
`commands 12, another or a different control message is sent
`from the base station on the downlink to the mobile station
`to cause the mobile station to change its spreading factor in
`order to further reduce power and to do so more dramatically
`and more quickly. This can be done by signaling, for
`instance by way of the transmit format combination indica-
`
`Ex. 1020 / Page 11 of 16
`
`

`

`US 2003/0123382 Al
`
`Jul. 3, 2003
`
`4
`
`tor (TFCI) signal which is sent in every time slot. For
`example, at a certain point in time t1 the spreading factor can
`be decreased by two or, for another example, by four. The
`result of these two possible decreases of spreading factor are
`shown by reference numerals 22 and 24, respectively. As can
`be seen in FIG. 2A, the received power at the base station
`is quickly and dramatically reduced to near the SIR thresh(cid:173)
`old, especially by using a decrease of four. This improves
`favorably to the level received as the base station according
`to reference numeral 14 in FIG. lA where the received
`power still is very high even after numerous power control
`commands 12. This combination of power control com(cid:173)
`mands 12 and decreases in spreading factor can work to
`quickly and powerfully reduce the deleterious affects of
`channel fading, according to the present invention. Or, the
`adaptive spreading factor approach can be used by itself.
`[0056] Similarly, as shown in FIG. 2B for a rapidly
`decreasing channel fading condition, the base station not
`only sends power control commands 18 as in FIG. lB but
`also causes a TFCI command at time t1 to increase the
`spreading factor for example by two or by four. This causes
`for instance an increase in detected power from the mobile
`station at the base station indicated by reference numerals 26
`and 28, respectively. Either of these increase in SF improves
`over the prior art signified by reference numeral 20.
`[0057]
`In addition to or as an alternative to using a
`command signal from the network, e.g., from the base
`station or radio network controller to change its spreading
`factor, the mobile station may rely on other factors which it
`may evaluate together with or independently in order to
`make a decision or final decision as to whether to change the
`spreading factor. Such factors might include whether there
`would be enough codes available after a commanded
`decrease, whether there would be enough power available
`for a reasonable period after an increase in spreading factor.
`Such factors might also alternatively include the frame or
`block error rate. Using such statistics will make the algo(cid:173)
`rithm more robust and less susceptible to erroneous deci(cid:173)
`s10ns.
`[0058] Second Embodiment
`[0059] The second embodiment can be explained by
`FIGS. 2A and 2B as well, except that the change in
`spreading factor is decided and controlled at the mobile
`station. In this case, the mobile station receives the transmit
`power command (TPC) sent from the network, e.g., from the
`base station or UTRAN to the mobile station. If the mobile
`station receives several successive "up" transmit power
`commands sent by the base station, that may mean the signal
`currently transmitted by the mobile station is fading greatly.
`Consequently, the mobile station will decide that in fact
`fading is occurring and will increase the spreading factor at
`the next transmission interval such as shown occurring at
`time t1 in FIG. 2B. Subsequently, if the mobile station then
`receives several "down" power control commands from the
`base station, that may mean the channel condition has
`become "good" and the mobile station will decrease the
`spreading factor at the next transmission time interval (TTI).
`[0060] Both the first and second embodiments described
`above constitute adaptive power control schemes according
`to the present invention.
`[0061]
`It should be noted that the second embodiment is
`sensitive to TPC error. To cope with this problem a slide
`
`command window can be used. The slide command window
`is a window containing a selected number (W) of the last
`power commands. If in the slide command window there
`have been B1 (with B1 less than W) "up" power control
`commands received, the spreading factor is increased pro(cid:173)
`vided, that B1 is greater than B2 where B2 is the number of
`received "down" power control commands. In the reverse
`situation, if the received number of "down" power control
`commands equals B2 and the number of received "down"
`power control commands is greater than the received num(cid:173)
`ber of "up" power control commands B1 , the spreading
`factor is decreased. Otherwise, the current spreading factor
`is used to transmit the signal on the uplink. Adaptive
`window thresholds B1 and B2 can also be used as well as an
`adaptive size of the slide command window W. The adaptive
`thresholds and the adaptive size of the window can be freely
`chosen by the system designer who will have the flexibility
`to pick and choose depending on particular design choices/
`criteria.
`
`[0062]
`In this case where the decision is determined by the
`mobile station, after counting the number of up/down power
`control commands and deciding that a change in spreading
`factor is appropriate, the UTRAN or base station will be told
`by the mobile station that a change in spreading factor is
`desired. The UTRAN or base station may then decide
`whether to allow the mobile station to change its spreading
`factor or not at the next transmission time interval. Based on
`the information sent by the UTRAN or base station and the
`total received up/down power control command in a trans(cid:173)
`mission time interval, the mobile station will then decide
`whether to change the spreading factor or not. This is shown
`in FIG. 3.
`
`[0063] Third Embodiment
`
`[0064]
`Instead of having the network or base station make
`the decision based per se on the same data it uses to decide
`whether to send an up or down TPC, as in the first embodi(cid:173)
`ment, the present invention can be carried out by having the
`network, e.g., the base station instead use a decision-making
`criterion such as described above in connection with the
`second embodiment. In that case, the UTRAN or base
`station will e.g. count the number of up/down power control
`commands that the base station has sent to the mobile
`station. If the total number of up or down power control
`commands exceeds the threshold which may be fixed or
`adaptive, e.g., based on current system load, the network,
`e.g., the UTRAN or base station will send a command to ask
`the mobile station to change its spreading factor. This is
`shown in FIG. 4.
`
`[0065] For either the second or third embodiments for UE
`or network-based decision making, the spreading factor
`adjustment can also be made as a function of the frame or
`block error rate, as suggested above. Monitoring and using
`such a statistic either separately or in conjunction with a
`windowed or series version of the TPC commands will make
`the algorithm more robust and less susceptible to erroneous
`decisions. For instance, if used in conjunction with a count
`of the TPC signal, the spreading factor could be changed
`only if the frame or block error rate meets or fails to meet
`a selected criterion. If used alone, the spreading factor could
`be changed if the frame or block error rate meets or fails to
`meet a selected criterion.
`
`Ex. 1020 / Page 12 of 16
`
`

`

`US 2003/0123382 Al
`
`Jul. 3, 2003
`
`5
`
`[0066] Uplink Closed-Loop Power Control
`[0067] FIG. 5 shows an uplink closed-loop power control
`modified, according to the present invention, to include the
`ability to change the mobile station's spreading factor to
`countera