US007813753B2
`
`(12) United States Patent
`Santhanam
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 7,813,753 B2
`Oct. 12, 2010
`
`(54) POWER CONTROL IN COMMUNICATION
`SYSTEMS
`
`2006/0148485 A1
`2007/0153719 A1
`
`7/2006 Kangas et a1.
`7/2007 Gopal
`
`(75) Inventor: Arvind Vardarajan Santhanam, San
`Diego, CA (US)
`
`(73) Assignee: QUALCOMM Incorporated, San
`Diego, CA (Us)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1127 days.
`
`(21) Appl, NQ_; 11/363,670
`
`(22) Filed;
`
`(65)
`
`Feb 27 2006
`’
`Prior Publication Data
`
`US 2007/0201405 A1
`
`Aug, 30, 2007
`
`(51) Int CL
`(2006.01)
`H04B 7/00
`(52) U.S. Cl. ........................ .. 455/522; 455/69; 370/318
`(58) Field of Classi?cation Search ................. .. 455/69,
`455/522; 370/318
`See application ?le for complete search history.
`
`EP
`EP
`EP
`WO
`WO
`WO
`
`FOREIGN PATENT DOCUMENTS
`1024606
`8/2000
`1024606 A2 * 8/2000
`1538810
`8/2005
`WO9914869
`3/1999
`WO02054622
`7/2002
`03017621
`2/2003
`OTHER PUBLICATIONS
`
`Search
`
`International Search RepoItiPCT/US07/062913, International
`Search AuthorityiEuropean Patent Of?ce, Jul. 2, 2007.
`Written OpinioniPCT/US07/062913, International
`AuthorityiEuropean Patent Of?ce, Jul. 2, 2007.
`International Preliminary Report on PatentabilityiPCT/US06/
`021384, International Search AuthorityiEuropean Patent Of?ce,
`Jun. 11,2008.
`US Non-Final Of?ce Action issued in U.S. Appl. No. 11/364,148, on
`Jun. 11, 2009.
`US Non-Final Of?ce Action issued in U.S. Appl. No. 11/609,500, on
`May 21, 2009
`* Cited by examiner
`
`Primary ExamineriRaymond S Dean
`(74) Attorney’ Agent’ Or FirmiRaphael Freiwinh
`
`(56)
`
`References Cited
`
`(57)
`
`ABSTRACT
`
`U'S' PATENT DOCUMENTS
`6,118,997 A
`9/2000 Kim et a1‘
`6,445,925 B1
`9/2002 Kwon et a1,
`6,631,121 B1
`10/2003 Yoon
`7,082,472 B1
`7/ 2006 Peder et 31
`2002/0136929 A1
`9/2002 Oikawa et a1~
`2003/0027580 A1
`2/2003 Goodjohn et al.
`2003/0087645 A1
`5/2003 Kim et al.
`2003/0189948 A1 10/2003 Sashihara
`2003/0199252 A1 10/2003 Tiedemann et al.
`2006/0039281 A1
`2/2006 Benveniste
`
`Systems and methods for estimating transmit poWer in a
`communication system are disclosed. An estimate of a
`reverse channel condition is based on a received signal from
`an access point. A correction factor is determined based on at
`least one of the number of access points detected, a Rise-over
`Thermal (RoT) at the access point, a message error rate, and
`a message siZe. Then the correction factor is applied to the
`transmit poWer determination.
`
`25 Claims, 8 Drawing Sheets
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 001
`IPR2017-01508
`
`

`

`US. Patent
`
`0a. 12, 2010
`
`Sheet 1 of8
`
`US 7,813,753 B2
`
`Air Interface
`
`104
`
`MPT/
`BS
`
`Carrier
`
`A
`126
`
`Fig. 1
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 002
`IPR2017-01508
`
`

`

`US. Patent
`
`0a. 12, 2010
`
`Sheet 2 of8
`
`US 7,813,753 B2
`
`4 2 2
`
`226
`
`200
`
`206
`
`208
`
`210
`
`212
`
`Transceiver
`
`202
`
`e S a b a t a D a C O L
`
`214
`
`Fig. 2
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 003
`IPR2017-01508
`
`

`

`US. Patent
`
`0a. 12, 2010
`
`Sheet 3 of8
`
`US 7,813,753 B2
`
`340
`
`S
`
`330
`
`320
`
`Transmit
`power
`
`A
`
`310
`
`Finit ——
`
`000
`
`000
`
`.....
`
`->
`
`time
`
`S W
`
`312
`
`314 316
`
`Fig. 3
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 004
`IPR2017-01508
`
`

`

`US. Patent
`
`Oct. 12, 2010
`
`Sheet 4 0f 8
`
`US 7,813,753 B2
`
`Estimating a reverse
`channel condition based
`on a received signal from
`an access point
`
`__J Using Rise-over
`
`Thermal at Access
`W440
`Point
`
`l
`
`UsmgSAi/lzeéssage 0450
`
`420% Determining a correction
`factor
`
`<—
`
`l
`
`Using a Target
`—-—> Message Error @460
`Rate
`
`Applying the correction
`430%
`factor to the transmit
`power estimation
`
`>1 Pilot Signal
`ln Active Set
`
`470
`
`l
`
`Using
`demodulation of
`pilot signal of
`associated access
`point
`
`8
`
`472
`
`l
`
`Adding a
`predetermined gain
`
`8
`
`474
`
`l
`
`Using a calculated
`value based on
`sum of pilot signals
`and associated
`pilot signal
`
`8
`
`476
`
`Fig. 4
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 005
`IPR2017-01508
`
`

`

`US. Patent
`
`0a. 12, 2010
`
`Sheet 5 of8
`
`US 7,813,753 B2
`
`Message Error
`Rate (MER)
`
`0.400
`
`0.350
`
`0.300
`0.250
`
`0.200
`
`0.150
`
`0.100
`
`0.050
`
`/
`/ /I/
`
`////I//‘/././'?17
`
`‘
`
`0.000
`
`0
`
`f
`0.02
`
`I
`0.04
`
`1
`0.06
`
`r
`0.08
`
`1
`0.1
`
`0.12
`
`Frame Error Rate (FER)
`
`Fig. 5A
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 006
`IPR2017-01508
`
`

`

`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 007
`IPR2017-01508
`
`

`

`US. Patent
`
`0a. 12, 2010
`
`Sheet 7 of8
`
`US 7,813,753 B2
`
`600
`
`Fig. 6
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 008
`IPR2017-01508
`
`

`

`US. Patent
`
`0a. 12, 2010
`
`Sheet 8 of8
`
`US 7,813,753 B2
`
`f ' _ G?6iip— '
`Communication I
`
`
`
`. _ . _ . T. . __ . Server
`
`
`
`750
`
`732 \
`Group
`Communication
`Server
`
`Group
`Communication
`Sewer
`
`752
`
`PD SN
`
`PDSN
`
`Fig. 7
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 009
`IPR2017-01508
`
`

`

`US 7,813,753 B2
`
`1
`POWER CONTROL IN COMMUNICATION
`SYSTEMS
`
`BACKGROUND OF THE INVENTION
`
`1. Field
`The present invention generally relates to communication
`systems. More particularly, the invention relates to poWer
`control in communication systems that measure channel
`quality.
`2. Background
`Wireless communication systems have developed through
`various generations, including a ?rst-generation analog Wire
`less phone service (1 G), a second-generation (2G) digital
`Wireless phone service (including interim 2.5G and 2.75G
`networks) and a third-generation (3G) high speed data/Inter
`net-capable Wireless service. There are presently many dif
`ferent types of Wireless communication systems in use,
`including Cellular and Personal Communications Service
`(PCS) systems. Examples of knoWn cellular systems include
`the cellular Analog Advanced Mobile Phone System
`(AMPS), and digital cellular systems based on Code Division
`Multiple Access (CDMA), Time Division Multiple Access
`(TDMA), the Global System for Mobile access (GSM) varia
`tion of TDMA, and neWer hybrid digital communication sys
`tems using both TDMA and CDMA technologies.
`The method for providing CDMA mobile communications
`Was standardized in the United States by the Telecommuni
`cations Industry Association/Electronic Industries Associa
`tion in TIA/EIA/IS-95-A entitled “Mobile Station-Base Sta
`tion Compatibility Standard for Dual-Mode Wideband
`Spread Spectrum Cellular System,” referred to herein as
`IS-95. Combined AMPS & CDMA systems are described in
`TIA/EIA Standard IS-98. Other communications systems are
`described in the IMT-ZOOO/U M, or International Mobile Tele
`communications System 2000/Universal Mobile Telecom
`munications System, standards covering What are referred to
`as Wideband CDMA (WCDMA), CDMA2000 (such as
`CDMA2000 lxRTT, “1x”, and lxEV-DO standards,
`“lXEV”, for example) or TD-SCDMA.
`In Wireless communication systems mobile stations or
`access terminals receive signals from ?xed position base sta
`tions (also referred to as cell sites or cells) that support com
`munication links or service Within particular geographic
`regions adjacent to or surrounding the base stations. In order
`to aid in providing coverage, each cell is often sub-divided
`into multiple sectors, each corresponding to a smaller service
`area or geographic region. An array or series of base stations
`placed adjacent to each other form a communication system
`capable of servicing a number of system users, over a larger
`region.
`Typically, each mobile station monitors a control channel
`that can be used to exchange messages betWeen the mobile
`station and the base station. The control channel is used to
`transmit system/ overhead messages, Whereas tra?ic channels
`are typically used for substantive communication (e.g., voice
`and data) to and from the mobile station. For example, the
`control channel can be used to establish tra?ic channels,
`control poWer levels, and the like, as is knoWn in the art.
`Generally, there are tWo types of poWer control for the reverse
`link, open-loop and closed-loop poWer control. The open
`loop poWer control typically occurs prior to the mobile ter
`minal establishing contact With a base station. The closed
`loop control occurs after the mobile and the base station are in
`communication and the base station can measure the received
`poWer levels and feedback poWer level adjustments to the
`mobile terminal.
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`In the open loop condition, the reverse link poWer for an
`initial communication signal (e.g., access probe) from the
`mobile terminal to the base station can be determined by
`monitoring specialiZed signals from a base station or access
`point. For example, in CDMA systems a pilot signal can be
`use to estimate the channel condition and then determine a
`poWer estimate for transmitting back to the base station. The
`accuracy of the channel conditions and poWer estimation can
`greatly impact performance of the system, particularly in
`terms of latency of the system. For example, 1x and lxEV
`systems Will transmit an access probe at a ?rst poWer level
`based on a poWer control algorithm. If the ?rst access attempt
`does not succeed, then the probe is resent at increasingly
`higher poWer levels, until it is successful or the poWer level
`maximum is reached.
`The existing open-loop poWer control algorithm used to
`transmit access probes over the Access channel in
`CDMA2000 lx-A and lxEVDO netWorks tend to be prone to
`inaccuracies and can result in underestimation of transmit
`poWer for access probes. This leads to an increased loss rate of
`access probes over the access channel, particularly on the ?rst
`access attempt. Accordingly, errors in the determination of
`the poWer level for the ?rst transmission can lead to a high rate
`of unsuccessful ?rst access attempts, Which can cause
`increased system latency as the probes are resent. By limiting
`retransmissions of the access probes, the latency incurred by
`access probes can be reduced.
`
`SUMMARY OF THE EXEMPLARY
`EMBODIMENTS
`
`Exemplary embodiments of the present invention are
`directed to systems and methods for improved poWer control
`in a communication system.
`Accordingly, an embodiment of the invention can include a
`method for determining an access probe transmit poWer com
`prising: estimating a reverse channel condition based on a
`received signal from an access point; determining a correc
`tion factorbased on at least one of the number of access points
`detected, a Rise-over-Thermal (RoT) at the access point, a
`target message error rate, and a message siZe; and applying
`the correction factor to an open-loop access probe transmit
`poWer determination.
`Another embodiment of the invention can include an appa
`ratus comprising: logic con?gured to estimate a reverse chan
`nel condition based on a received signal from an access point;
`logic con?gured to determine a correction factor based on at
`least one of the number of access points detected, a Rise-over
`Thermal (RoT) at the access point, a target mes sage error rate,
`and a message siZe; and logic con?gured to apply the correc
`tion factor to an open-loop access probe transmit poWer deter
`mination.
`Another embodiment of the invention includes a system for
`determining an access probe transmit poWer comprising:
`means for estimating a reverse channel condition based on a
`received signal from an access point; means for determining
`a correction factor based on at least one of a number of access
`points detected, a Rise-over-Thermal (RoT) at the access
`point, a target message error rate, and a message siZe; and
`means for applying the correction factor to an open-loop
`access probe transmit poWer determination.
`Another embodiment of the invention can include a com
`puter-readable medium on Which is stored a computer pro
`gram for determining an access probe transmit poWer. The
`computer program comprising instructions Which, upon
`being executed, causes the computing device to perform a
`process of: estimating a reverse channel condition based on a
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 010
`IPR2017-01508
`
`

`

`US 7,813,753 B2
`
`3
`received signal from an access point; determining a correc
`tion factor based on at least one of a number of access points
`detected, a Rise-over-Thermal (RoT) at the access point, a
`target message error rate, and a message siZe; and applying
`the correction factor to an open-loop access probe transmit
`power determination.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A more complete appreciation of embodiments of the
`invention and many of the attendant advantages thereof will
`be readily obtained as the same becomes better understood by
`reference to the following detailed description when consid
`ered in connection with the accompanying drawings which
`are presented solely for illustration and not limitation of the
`invention, and in which:
`FIG. 1 is a diagram of a wireless network architecture that
`supports access terminals and access networks in accordance
`with at least one embodiment of the invention;
`FIG. 2 is an illustration of an access terminal in accordance
`with at least one embodiment of the invention;
`FIG. 3 is an illustration of an access probe sequence having
`several failed probe attempts;
`FIG. 4 is a ?owchart in illustrating methods in accordance
`with at least one embodiment of the invention;
`FIG. 5A is a graph illustrating the effect of message siZe on
`the message error rate for given frame error rates;
`FIG. 5B is a graph illustrating a relationship between frame
`error rate and given wireless system conditions;
`FIG. 6 is an illustration of a wireless network topology
`having a plurality of cells, base stations and mobile terminals;
`and
`FIG. 7 is an illustration of a group communication network
`in accordance with at least one embodiment of the invention.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Aspects of the invention are disclosed in the following
`description and related drawings directed to speci?c embodi
`ments of the invention. Alternate embodiments may be
`devised without departing from the scope of the invention.
`Additionally, well-known elements of the invention will not
`be described in detail or will be omitted so as not to obscure
`the relevant details of the invention.
`The word “exemplary” is used herein to mean “serving as
`an example, instance, or illustration.” Any embodiment
`described herein as “exemplary” is not necessarily to be con
`strued as preferred or advantageous over other embodiments.
`Likewise, the term “embodiments of the invention” does not
`require that all embodiments of the invention include the
`discussed feature, advantage or mode of operation.
`Further, many embodiments are described in terms of
`sequences of actions to be performed by, for example, ele
`ments of a computing device. It will be recogniZed that vari
`ous actions described herein can be performed by speci?c
`circuits (e.g., application speci?c integrated circuits
`(ASICs)), by program instructions being executed by one or
`more processors, or by a combination of both. Additionally,
`these sequence of actions described herein can be considered
`to be embodied entirely within any form of computer readable
`storage medium having stored therein a corresponding set of
`computer instructions that upon execution would cause an
`associated processor to perform the functionality described
`herein. Thus, the various aspects of the invention may be
`embodied in a number of different forms, all of which have
`been contemplated to be within the scope of the claimed
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`subject matter. In addition, for each of the embodiments
`described herein, the corresponding form of any such
`embodiments may be described herein as, for example, “logic
`con?gured to” perform the described action.
`A High Data Rate (HDR) subscriber station, referred to
`herein as an access terminal (AT), may be mobile or station
`ary, and may communicate with one or more HDR base
`stations, referred to herein as modern pool transceivers
`(MPTs) base station transceivers (BTS), base stations (BS) or
`more generally access points. An access terminal transmits
`and receives data packets through one or more modern pool
`transceivers to an HDR base station controller, referred to as
`a modem pool controller (MPC), base station controller
`(BSC) and/or mobile switching center (MSC). Modem pool
`transceivers and modem pool controllers are parts of a net
`work called an access network. An access network transports
`data packets between multiple access terminals. The access
`network may be further connected to additional networks
`outside the access network, such as a corporate intranet or the
`Internet, and may transport data packets between each access
`terminal and such outside networks. An access terminal that
`has established an active tra?ic channel connection with one
`or more modern pool transceivers is called an active access
`terminal, and is said to be in a traf?c state. An access terminal
`that is in the process of establishing an active tra?ic channel
`connection with one or more modern pool transceivers is said
`to be in a connection setup state. An access terminal may be
`any data device that communicates through a wireless chan
`nel or through a wired channel, for example using ?ber optic
`or coaxial cables. An access terminal may further be any of a
`number of types of devices including but not limited to PC
`card, compact ?ash, external or internal modem, or wireless
`or wireline phone. The communication link through which
`the access terminal sends signals to the modem pool trans
`ceiver is called a reverse link or tra?ic channel. The commu
`nication link through which a modem pool transceiver sends
`signals to an access terminal is called a forward link or traf?c
`channel. As used herein the term traf?c channel can refer to
`either a forward or reverse tra?ic channel.
`Additionally, although exemplary embodiments of the
`invention are described in terms of a wireless system and
`speci?c technologies such as CDMA 1x and lxEV system,
`those skilled in the art will appreciate that the invention is not
`limited to the illustrated systems. For example, embodiments
`of the invention can include any system that uses a signal from
`an access point to estimate channel parameter and uses that
`estimation to control power in the reverse link. Those skilled
`in the art will appreciate that signals transmitted over many
`mediums can be considered to have channel parameters. For
`example, signals over wireline systems, such as copper wire,
`coaxial cable, ?ber optic cables, and the like have channel
`parameters that can be affected by transmission/modulation
`frequency, modulation technique, noise sources, cross talk,
`medium characteristics, and the like.
`FIG. 1 illustrates a block diagram of one exemplary
`embodiment of a wireless system 100 in accordance with at
`least one embodiment of the invention. System 100 can con
`tain access terminals, such as cellular telephone 102, in com
`munication across an air interface 104 with an access network
`or radio access network (RAN) 120 that can connect the
`access terminal 102 to network equipment providing data
`connectivity between a packet switched data network (e. g., an
`intranet, the Internet, and/or carrier network 126) and the
`access terminals 102, 108, 110, 112. As shown here, the
`access terminal can be a cellular telephone 102, a personal
`digital assistant 108, a pager 110, which is shown here as a
`two-way text pager, or even a separate computer platform 112
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 011
`IPR2017-01508
`
`

`

`US 7,813,753 B2
`
`5
`that has a Wireless communication portal. Embodiments of
`the invention can thus be realized on any form of access
`terminal including a Wireless communication portal or having
`Wireless communication capabilities, including Without limi
`tation, Wireless modems, PCMCIA cards, personal comput
`ers, telephones, or any combination or sub-combination
`thereof. Further, as used herein, the terms “access terminal”,
`“Wireless device”, “client device”, “mobile terminal” and
`variations thereof may be used interchangeably. Further as
`used herein the terms “access point”, “modem pool trans
`ceiver (MPT)”, “base transceiver station (BTS)”, “base sta
`tion (BS)” and like variations thereof may be used inter
`changeably.
`Referring back to FIG. 1, the components of the Wireless
`netWork 100 and interrelation of the elements of the exem
`plary embodiments of the invention are not limited to the
`con?guration illustrated. System 100 is merely exemplary
`and can include any system that alloWs remote access termi
`nals, such as Wireless client computing devices 102, 108, 110,
`112 to communicate over-the-air betWeen and among each
`other and/or betWeen and among components connected via
`the air interface 104 and RAN 120, including, Without limi
`tation, carrier netWork 126, a core netWork, the Internet,
`and/ or other remote servers.
`The RAN 120 controls messages (typically sent as data
`packets) sent to a MPC/MSC 122. The carrier netWork 126
`may communicate With the MPC/MSC 122 by a netWork, the
`Internet and/or a public sWitched telephone netWork (PSTN).
`Alternatively, the MPC/MSC 122 may connect directly to the
`Internet or external netWork. Typically, the netWork or Inter
`net connection betWeen the carrier netWork 126 and the MPC/
`MSC 122 transfers data, and the PSTN transfers voice infor
`mation. The MPC/MSC 122 can be connected to multiple
`base stations (BS) or modern pool transceivers (MPT) 124. In
`a similar manner to the carrier netWork, the MPC/MSC 122 is
`typically connected to the MPT/BS 124 by a netWork, the
`Internet and/or PSTN for data transfer and/or voice informa
`tion. The MPT/BS 124 can broadcast data messages Wire
`lessly to the access terminals, such as cellular telephone 102.
`The MPT/BS 124, MPC/MSC 122 and other components
`may form the RAN 120, as is knoWn in the art. HoWever,
`alternate con?gurations may also be used and the invention is
`not limited to the con?guration illustrated.
`Referring to FIG. 2, the access terminal 200, (here a Wire
`less device), such as a cellular telephone, has a platform 202
`that can receive and execute softWare applications, data and/
`or commands transmitted from the RAN 120 that may ulti
`mately come from the carrier netWork 126, the Internet and/ or
`other remote servers and netWorks. The platform 202 can
`include a transceiver operably coupled to an application spe
`ci?c integrated circuit (“ASIC” 208), or other processor,
`microprocessor, logic circuit, or other data processing device.
`The ASIC 208 or other processor executes the application
`programming interface (“API”) 210 layer that interfaces With
`any resident programs in the memory 212 of the Wireless
`device. The memory 212 can be comprised of read-only or
`random-access memory (RAM and ROM), EEPROM, ?ash
`cards, or any memory common to computer platforms. The
`platform 202 also can include a local database 214 that can
`hold applications not actively used in memory 212. The local
`database 214 is typically a ?ash memory cell, but can be any
`secondary storage device as knoWn in the art, such as mag
`netic media, EEPROM, optical media, tape, soft or hard disk,
`or the like. The internal platform 202 components can also be
`operably coupled to external devices such as antenna 222,
`display 224, push-to-talk button 228 and keypad 226 among
`other components, as is knoWn in the art.
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`Accordingly, an embodiment of the invention can include
`an access terminal including the ability to perform the func
`tions described herein, related to access probe poWer control.
`As Will be appreciated by those skilled in the art, the various
`logic elements can be embodied in discrete elements, soft
`Ware modules executed on a processor or any combination of
`softWare and hardWare to achieve the functionality disclosed
`herein. For example, ASIC 208, memory 212, API 210 and
`local database 214 may all be used cooperatively to load, store
`and execute the various functions disclosed herein and thus
`the logic to perform these functions may be distributed over
`various elements. Alternatively, the functionality could be
`incorporated into one discrete component. Therefore, the fea
`tures of the access terminal in FIG. 2 are to be considered
`merely illustrative and the invention is not limited to the
`illustrated features or arrangement.
`As used herein “access terminal” includes, for example,
`one or more processing circuits executing resident con?gured
`logic, Where such computing devices include, for example,
`microprocessors, digital signal processors (DSPs), microcon
`trollers, or any suitable combination of hardWare, softWare
`and/or ?rmWare containing processors and logic con?gured
`to at least perform the operations described herein. Some
`examples of access terminals or Wireless devices Which may
`be used in accordance With embodiments of the present
`invention include cellular telephones or other Wireless com
`munication units, personal digital assistants (PDAs), paging
`devices, handheld navigation devices, handheld gaming
`devices, music or video content doWnload units, and other
`like Wireless communication devices.
`The Wireless communication betWeen the access terminal
`102 and the RAN 120 can be based on different technologies,
`such as code division multiple access (CDMA), time division
`multiple access (TDMA), frequency division multiple access
`(FDMA), the Global System for Mobile Communications
`(GSM), or other protocols that may be used in a Wireless
`communications netWork or a data communications netWork.
`The data communication is typically betWeen the client
`device 102, MPT/BS 124, and MPC/MSC 122. The MPC/
`MSC 122 can be connected to multiple data netWorks such as
`the carrier netWork 126, PSTN, the Internet, a virtual private
`netWork, and the like, thus alloWing the access terminal 102
`access to a broader communication netWork. As discussed in
`the foregoing and knoWn in the art, voice transmission and/or
`data can be transmitted to the access terminals from the RAN
`120.
`As discussed in the background, paging can be used to
`notify an access terminal (e.g., a Wireless device) that a com
`munication directed to that terminal is available. Typically,
`the access terminal monitors a non-tra?ic channel (e.g., con
`trol channel/access channel) to check for paging directed to
`the access terminal and to receive poWer control signals and/
`or pilot signals that can be used to determine an initial poWer
`level of an access probe. Further, as discussed in the forego
`ing, the access probe’s transmit poWer is determined by mea
`suring a received signal strength (e.g., pilot signal) from a
`base station and estimating the forWard link path loss. It is
`assumed that the path loss for the reverse link Will be similar,
`so the access terminal can use this information to determine
`the access probe transmit poWer. The ?rst transmission on the
`access channel may be in response to a page from the base
`station or to initiate a voice or data call. To avoid interfering
`With other access terminals, that initial poWer is set loW and
`then the poWer is increased on successive attempts until the
`base station acknoWledges the signal or a time out is reached.
`For example, a sequence of access probes 300 is illustrated
`in FIG. 3. The ?rst probe 310 is transmitted at an initial poWer
`
`HTC CORPORATION, ET AL. v. CELLULAR COMMUNICATIONS EQUIPMENT LLC
`CCE EX2004 (U.S. Patent No. 7,813,753) – 012
`IPR2017-01508
`
`

`

`US 7,813,753 B2
`
`7
`(Pl-nit) during a ?rst access channel slot 312. The probe waits
`for acknowledgement from the access point (e.g., base sta
`tion) or for an acknowledgement timeout 314 to occur. Then,
`a random backoff time 316 is determined before the next
`access probe 320 is sent. As illustrated the second access
`probe 320 and subsequent access probes 330 and 340, will be
`sent using increasingly higher transmit powers until an
`acknowledgement is received, a maximum power is reached
`or the access process timeout occurs.
`A conventional equation to estimate the initial transmit
`power in decibels (dB) in the open-loop case is de?ned in the
`lS-95 standard as:
`
`Pini,:—P,—Const+N OMiPW R+IN ITiPW R
`
`(1)
`
`where P, is the received power from the base station in dB,
`Const is a default constant (e.g., —73 dB for cellular and —76
`dB for PCS systems), NOM_PWR and INIT_PWR are
`adjustment factors in dB that can be set by the system opera
`tor. The NOM_PWR and INIT_PWR can be broadcast from
`the base station along with other data in an access parameter
`message. Additional details of the conventional access probe
`and initial power estimates are not provided as these are well
`known in the art and can be obtained from references such as
`Yang, “CDMA RF System Engineering”, Artech House, Inc.,
`1998, pages 85-88 and 141-145, which are incorporated
`herein in their entirety.
`However, the existing open-loop power control algorithms
`such as described above (Eq. 1) used to transmit access probes
`over the access channel in CDMA2000 lX-A and lxEVDO
`(e. g., lS-856 standard) networks are prone to inaccuracies and
`can result in underestimation of the transmit power for access
`probes. This underestimation can lead to an increased loss
`rate of access probes over the access channel, particularly on
`the ?rst access attempt. Existing open-loop power control
`algorithms often determine a transmit power that is lower
`because of: inaccuracies in estimating the path-loss between
`the access terminal and the access point/base transceiver sta
`tion (BTS), crude estimation of the Rise-over-Therrnal (RoT)
`at the BTS, and failure to take the siZe of the access message
`into account.
`Accordingly, embodiments of the invention can provide
`correction factors to improve the initial (open-loop) transmit
`power determination which can be generally described as
`follows:
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`P ’init:Pinit+Pcorr
`
`(2)
`
`corr
`
`where P'im-t is the corrected initial power determination in dB
`and P
`is a correction factor in dB that can include constants
`and other system compensating factors. Additionally, the cor
`rection factors discussed in the following can be used in
`combination with, or in place of, the conventional system
`parameters and/or power determination (Pl-nit).
`Embodiments of the present invention can overcome at
`least some of the problems associated with the existing open
`loop power control policy so that a target success rate on the
`?rst access attempt is achieved. Thus, embodiments of the
`invention can use a correction factor or term (e.g., P60”) to
`improve the initial transmit power determination and the tar
`get success rate on the ?rst access attempt.
`For example, the correction factor/term may include com
`pensation for the siZe of the access probe. The correction term
`may also be used to correct the estimated path-loss. The
`correction term may also take into account the actual Rise
`over-Thermal (RoT) at the access point (e.g., MPT, BTS).
`
`50
`
`55
`
`60
`
`65
`
`8
`Additionally, some or all of the proposed correction terms can
`be subject to lower and upper bounds, as dictated by the
`speci?c system parameters.
`Accordingly, embodiments of the invention can be used to
`improve over the existing open-loop algorithm so that the
`number of access probe retransmissions is reduced. Limiting
`these retransmissions can reduce the latency incurred by
`access probes substantially (e.g., 200~300 msec.), reduce
`power consumption and reduce the possibility of collisions.
`In one embodiment of the invention, the path-loss between
`the access terminal and the access point (e.g., BTS) can be
`determined with greater accuracy by only considering the
`demodulated energy of th