(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2008/0316959 A1
`(43) Pub. Date:
`Dec. 25, 2008
`Bach] et al.
`
`US 20080316959A1
`
`(54) METHOD OF TRANSMITTING SCHEDULING
`REQUESTS OVER UPLINK CHANNELS
`
`(76) Inventors:
`
`Rainer Bachl, Nuremberg (DE);
`Matthias Schneider, Nuremberg
`(DE); Jung A. Lee, PittstoWn, NJ
`(Us)
`
`Correspondence Address:
`MARK W. SINCELL
`Williams, Morgan & Amerson, P.C.
`Suite 1100, 10333 Richmond
`Houston, TX 77042 (US)
`
`(21) App1.No.:
`
`11/765,063
`
`(22) Filed:
`
`Jun. 19, 2007
`
`Publication Classi?cation
`
`(51) Int. Cl.
`H04Q 7/20
`
`(2006.01)
`
`(52) us. c1. ...................................................... .. 370/329
`(57)
`ABSTRACT
`
`In various embodiments of the present invention, methods are
`provided for transmitting scheduling requests over uplink
`channels. One embodiment includes determining Whether a
`?rst resource for transmission of a scheduling request over an
`unscheduled uplink control channel is allocated concurrently
`With a second resource for transmission of user data over a
`scheduled uplink shared channel. This embodiment also
`includes encoding the user data and bit(s) of control informa
`tion to form encoded information for transmission using the
`second resource. The additional bit(s) indicate Whether the
`mobile unit is transmitting the scheduling request. Another
`embodiment includes determining Whether a ?rst resource for
`transmission of a scheduling request over an unscheduled
`uplink control channel is allocated concurrently With a sec
`ond resource for transmission of other control information
`over the unscheduled uplink control channel. This embodi
`ment includes modulating the scheduling request and the
`other control information into one symbol for transmission
`using the ?rst resource.
`
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`US 2008/0316959 A1
`
`Dec. 25, 2008
`
`METHOD OF TRANSMITTING SCHEDULING
`REQUESTS OVER UPLINK CHANNELS
`
`BACKGROUND OF THE INVENTION
`
`[0001] 1. Field of the Invention
`[0002] This invention relates generally to communication
`systems, and, more particularly, to Wireless communication
`systems.
`[0003] 2. Description of the Related Art
`[0004] The coverage area of a Wireless communication sys
`tem is typically divided into a number of cells or sectors,
`Which may be grouped into one or more networks. Base
`stations provide Wireless connectivity to the cells or sectors
`Within the Wireless communication system. Alternatively,
`Wireless connectivity may be provided by access points, base
`station routers, access networks, and the like. Mobile units
`located in each cell may access the Wireless communications
`system by establishing a Wireless communication link, often
`referred to as an air interface, With the base station associated
`With the cell or sector. The mobile units may also be referred
`to using terms such as access terminal, user equipment, sub
`scriber station, and the like. The mobile units may include
`devices such as mobile telephones, personal data assistants,
`smart phones, Global Positioning System devices, Wireless
`netWork interface cards, desktop or laptop computers, and the
`like.
`[0005] The Wireless communication link typically includes
`one or more doWnlink (or forWard link) channels for trans
`mitting information from the base station to the mobile unit
`and one or more uplink (or reverse link) channels for trans
`mitting information from the mobile unit to the base station.
`The uplink and doWnlink channels include data channels for
`transmitting data traf?c, signaling or control channels to carry
`control information that is used to decode the data channels,
`paging channels for locating mobile units, broadcast channels
`for broadcasting information to multiple mobile units, multi
`cast channels for broadcasting information to a subset of
`mobile units that have subscribed to the multicast service, and
`the like. The channels may be shared by multiple mobile units
`or dedicated to one mobile unit at a time. Channels can be
`de?ned using different time slots (e.g., Time Division Mul
`tiple Access or TDMA), frequencies (e.g., Frequency Divi
`sion Multiple Access or FDMA), code sequences (e.g., Code
`Division Multiple Access or CDMA), orthogonal subcarrier
`frequencies or tones in a carrier frequency band (e.g.,
`Orthogonal Frequency Division Multiplexing or OFDM), or
`combinations thereof.
`[0006] Each base station typically provides Wireless con
`nectivity to more than one mobile unit. Consequently, air
`interface resources are shared betWeen the multiple mobile
`units. For example, mobile units may share one or more
`uplink channels to a base station. When a mobile unit has
`information to transmit over the uplink channel, such as a data
`burst, the mobile unit transmits a scheduling request to
`request access to the uplink channel. The mobile unit then
`Waits to transmit information over the uplink channel until
`after receiving an access grant from the base station. The
`access grant typically indicates the resources that have been
`allocated to the mobile unit to transmit the information, such
`as a timeslot, a channel code, a frequency or tone, and the like.
`The mobile unit relinquishes the channel once the data burst
`has been transmitted. Base stations that implement these so
`called schedule-on-demand or bandWidth-on-demand
`schemes can control access to the uplink channel to prevent
`
`collisions betWeen different mobile units attempting to trans
`mit over the same uplink channel. The base station may also
`schedule access to the air interface resources to take advan
`tage of ?uctuations in channel conditions.
`[0007] In next generation Wireless systems like the Univer
`sal Mobile Telecommunication System (UMTS) Long-Term
`Evolution, mobile units are required to transmit certain types
`of control messages in a portion of the uplink and doWnlink
`data that is transmitted in an unscheduled mode that is distinct
`from a scheduled mode that may be used to transmit other
`portions of the user and control data that are scheduled explic
`itly by the base station system. For example, systems like
`UMTS-LTE implement physically different channels for
`scheduled user and control data (e.g., the physical uplink
`shared channel or PUSCH) and unscheduled control data
`(e.g., the physical uplink control channel or PUCCH) that are
`transmitted in different frequency bands or sub-bands and
`may make use of different modulation and coding schemes.
`Time and frequency resources may be pre-allocated to both
`the scheduled and unscheduled channels. HoWever, due to
`constraints on the peak-to-average poWer of the transmitter,
`the UMTS-LTE standards specify that information cannot be
`transmitted concurrently on the scheduled and unscheduled
`channels by the same mobile unit. For example, When a
`mobile unit is scheduled to transmit data via the PUSCH in a
`speci?c timeslot, it may not send control data concurrently
`via the PUCCH. The mobile units can transmit via the sched
`uled PUSCH only When explicitly signaled by the scheduler
`from the base station system, but the mobile units can use the
`PUCCH at regular pre-allocated time intervals.
`[0008] Three types of control information are typically
`transmitted over unscheduled uplink data channels such as
`the PUCCH de?ned in UMTS-LTE. AcknoWledgement and/
`or Non-Acknowledgement (ACK/NAK) messages may be
`transmitted over the uplink in response to receiving doWnlink
`data from a base station. An ACK message is transmitted to
`acknoWledge successful reception of each doWnlink block of
`data is acknoWledged on correct reception and a NACK mes
`sage is sent if a failure is detected during the reception. The
`NACK messages may trigger a retransmission of the unsuc
`cessfully received data. Channel Quality Information (CQI)
`that indicates the quality of signals received on the doWnlink
`is transmitted over the uplink at predetermined periodic inter
`vals. Mobile units may also transmit scheduling requests over
`the uplink in order to request resources in the scheduled data
`channels such as the PUSCH. For example, a mobile unit may
`transmit a scheduling request When its transmit buffer is
`?lled.
`[0009] Timing of the uplink control data transmissions
`must be knoWn to both the base station and the mobile units.
`In conventional Wireless communication systems, the ACK/
`NACK messages are transmitted over the scheduled uplink
`channel a selected amount of time after the associated doWn
`link transmission. Both the mobile unit and the base station
`knoW the value of the delay betWeen reception of a doWnlink
`data block and transmission of the ACK/NACK over the
`uplink. The CQI is transmitted at regular intervals using a
`pre-allocated resource. For example, the CQI may be trans
`mitted in predetermined time slots using a predetermined
`group of subcarriers and code sequence. Thus, the base sta
`tion knoWs When the mobile unit Will be transmitting CQI
`over the uplink. Uplink channel resources are also pre-allo
`cated for transmission of scheduling requests, but the sched
`uling requests are only transmitted When the mobile unit is
`
`5
`
`

`

`US 2008/0316959 A1
`
`Dec. 25, 2008
`
`requesting uplink resources for data transmission. Thus, the
`base station cannot predict When the mobile unit Will actually
`transmit a scheduling request.
`[0010] The control data cannot be transmitted using the
`unscheduled uplink control channels When user data has been
`scheduled for transmission in the same timeslot over the
`scheduled data channels. The control information may there
`fore be concatenated to the user data that has been scheduled
`for transmission over the scheduled data channels. In this
`circumstance, the amount of data that actually has to be
`transmitted over the scheduled data channels is larger than the
`requested scheduling grant. The mobile unit can adapt its
`code rate (also called rate matching, puncturing, and repeti
`tion) to squeeZe the extra bits into the same physical resource
`allocation. The base station can decode the received transmis
`sion correctly as long as it can predict When the mobile unit
`Will adapt its code rate to transmit additional control infor
`mation. For example, the base station knoWs that CQI Will be
`transmitted in the pre-allocated time slot and that ACK/NAK
`messages Will be transmitted at a ?xed time after a doWnlink
`transmission. The base station can therefore predict When the
`scheduled data and unscheduled CQI or ACK/NACK mes
`sages Will collide, thereby forcing the mobile unit to modify
`its code rate to transmit the combined user data and control
`data using the scheduled physical resources. The base station
`can use this prediction to apply the correct decoding algo
`rithms to the received transmission Without additional infor
`mation.
`[0011] Scheduling requests are transmitted in pre-con?g
`ured resources knoWn to the base station and the mobile
`station, but they are only transmitted When the mobile station
`actually has some data to be transmitted on the uplink. The
`base station cannot predict When the scheduled data and
`unscheduled scheduling request Will collide. Consequently,
`the base station cannot predict When the mobile unit Will
`modify its code rate to transmit the combined user data and
`control data (i.e., the scheduling request) using the scheduled
`physical resources. Instead, the base station has to “blind
`decode” the message by applying all possible combinations
`of code rate parameters (such as puncturing or repetition
`parameters) and check Whether it has received valid data at
`each assumed code rate. Blind decoding is much more com
`plex than conventional decoding using a knoWn code rate.
`Thus, blind decoding consumes more time and requires more
`complex hardWare, ?rmware, and/ or softWare to implement.
`[0012] Different types of control data may also collide. For
`example, CQI and scheduling requests are transmitted in
`pre-allocated time-intervals on the unscheduled uplink chan
`nels. HoWever, the ACK/NAK messages are transmitted over
`the uplink a ?xed time after a transmission is received over the
`doWnlink. Thus, the ACK/NAK and the scheduling request
`may have to be transmitted over the unscheduled uplink chan
`nel in the same allocated time interval. The ACK/NAK and
`the scheduling request may be code-multiplexed onto the
`unscheduled uplink channels. HoWever, code-multiplexing
`the ACK/NAK and the scheduling request Would increase the
`peak-to-average poWer ratio, Which is undesirable.
`
`SUMMARY OF THE INVENTION
`
`[0013] The present invention is directed to addressing the
`effects of one or more of the problems set forth above. The
`folloWing presents a simpli?ed summary of the invention in
`order to provide a basic understanding of some aspects of the
`invention. This summary is not an exhaustive overvieW of the
`
`invention. It is not intended to identify key or critical elements
`of the invention or to delineate the scope of the invention. Its
`sole purpose is to present some concepts in a simpli?ed form
`as a prelude to the more detailed description that is discussed
`later.
`[0014] In various embodiments of the present invention,
`methods are provided for transmitting scheduling requests
`over uplink channels. One embodiment includes determining
`Whether a ?rst resource for transmission of a scheduling
`request over an unscheduled uplink control channel is allo
`cated concurrently With a second resource for transmission of
`user data over a scheduled uplink shared channel. This
`embodiment also includes encoding the user data and at least
`one bit of control information to form encoded information
`for transmission using the second resource. The additional
`bit(s) indicate Whether the mobile unit is transmitting the
`scheduling request. Another embodiment includes determin
`ing Whether a ?rst resource for transmission of a scheduling
`request over an unscheduled uplink control channel is allo
`cated concurrently With a second resource for transmission of
`other control information over the unscheduled uplink con
`trol channel. This embodiment includes modulating the
`scheduling request and the other control information into one
`symbol for transmission using the ?rst resource.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0015] The invention may be understood by reference to the
`folloWing description taken in conjunction With the accom
`panying draWings, in Which like reference numerals identify
`like elements, and in Which:
`[0016] FIG. 1 shoWs one exemplary embodiment of a Wire
`less communication system, in accordance With the present
`invention;
`[0017] FIG. 2 conceptually illustrates the timeslot structure
`of a scheduled uplink channel and an unscheduled uplink
`channel, in accordance With the present invention;
`[0018] FIG. 3 conceptually illustrates the timeslot structure
`of an unscheduled uplink channel, in accordance With the
`present invention; and
`[0019] FIG. 4 conceptually illustrates one exemplary
`embodiment of a decision tree hat may be used for the selec
`tion of transmission means of the scheduling request, in
`accordance With the present invention.
`[0020] While the invention is susceptible to various modi
`?cations and alternative forms, speci?c embodiments thereof
`have been shoWn by Way of example in the draWings and are
`herein described in detail. It should be understood, hoWever,
`that the description herein of speci?c embodiments is not
`intended to limit the invention to the particular forms dis
`closed, but on the contrary, the intention is to cover all modi
`?cations, equivalents, and alternatives falling Within the
`scope of the invention as de?ned by the appended claims.
`
`DETAILED DESCRIPTION OF SPECIFIC
`EMBODIMENTS
`
`[0021] Illustrative embodiments of the invention are
`describedbeloW. In the interest of clarity, not all features of an
`actual implementation are described in this speci?cation. It
`Will of course be appreciated that in the development of any
`such actual embodiment, numerous implementation-speci?c
`decisions should be made to achieve the developers’ speci?c
`goals, such as compliance With system-related and business
`related constraints, Which Will vary from one implementation
`
`6
`
`

`

`US 2008/0316959 A1
`
`Dec. 25, 2008
`
`to another. Moreover, it Will be appreciated that such a devel
`opment effort might be complex and time-consuming, but
`Would nevertheless be a routine undertaking for those of
`ordinary skill in the art having the bene?t of this disclosure.
`[0022] Portions of the present invention and corresponding
`detailed description are presented in terms of software, or
`algorithms and symbolic representations of operations on
`data bits Within a computer memory. These descriptions and
`representations are the ones by Which those of ordinary skill
`in the art effectively convey the substance of their Work to
`others of ordinary skill in the art. An algorithm, as the term is
`used here, and as it is used generally, is conceived to be a
`self-consistent sequence of steps leading to a desired result.
`The steps are those requiring physical manipulations of
`physical quantities. Usually, though not necessarily, these
`quantities take the form of optical, electrical, or magnetic
`signals capable of being stored, transferred, combined, com
`pared, and otherWise manipulated. It has proven convenient at
`times, principally for reasons of common usage, to refer to
`these signals as bits, values, elements, symbols, characters,
`terms, numbers, or the like.
`[0023] It should be borne in mind, hoWever, that all of these
`and similar terms are to be associated With the appropriate
`physical quantities and are merely convenient labels applied
`to these quantities. Unless speci?cally stated otherWise, or as
`is apparent from the discussion, terms such as “processing” or
`“computing” or “calculating” or “determining” or “display
`ing” or the like, refer to the action and processes of a computer
`system, or similar electronic computing device, that manipu
`lates and transforms data represented as physical, electronic
`quantities Within the computer system’s registers and memo
`ries into other data similarly represented as physical quanti
`ties Within the computer system memories or registers or
`other such information storage, transmission or display
`devices.
`[0024] Note also that the softWare implemented aspects of
`the invention are typically encoded on some form of program
`storage medium or implemented over some type of transmis
`sion medium. The program storage medium may be magnetic
`(e. g., a ?oppy disk or a hard drive) or optical (e. g., a compact
`disk read only memory, or “CD ROM”), and may be read only
`or random access. Similarly, the transmission medium may
`be tWisted Wire pairs, coaxial cable, optical ?ber, or some
`other suitable transmission medium knoWn to the art. The
`invention is not limited by these aspects of any given imple
`mentation.
`[0025] The present invention Will noW be described With
`reference to the attached ?gures. Various structures, systems
`and devices are schematically depicted in the draWings for
`purposes of explanation only and so as to not obscure the
`present invention With details that are Well knoWn to those
`skilled in the art. Nevertheless, the attached draWings are
`included to describe and explain illustrative examples of the
`present invention. The Words and phrases used herein should
`be understood and interpreted to have a meaning consistent
`With the understanding of those Words and phrases by those
`skilled in the relevant art. No special de?nition of a term or
`phrase, i.e., a de?nition that is different from the ordinary and
`customary meaning as understood by those skilled in the art,
`is intended to be implied by consistent usage of the term or
`phrase herein. To the extent that a term or phrase is intended
`to have a special meaning, i.e., a meaning other than that
`understood by skilled artisans, such a special de?nition Will
`be expressly set forth in the speci?cation in a de?nitional
`
`manner that directly and unequivocally provides the special
`de?nition for the term or phrase.
`[0026] FIG. 1 conceptually illustrates one exemplary
`embodiment of a Wireless communication system 100. In the
`illustrated embodiment, the Wireless communication system
`includes one or more base stations 105 for providing Wireless
`connectivity. Although a single base station 105 is depicted in
`FIG. 1, persons of ordinary skill in the art having bene?t of the
`present disclosure should appreciate that alternate embodi
`ments of the Wireless communication system 100 may
`include any number of base stations 105. Furthermore, other
`devices may alternatively be used to provide Wireless connec
`tivity. Exemplary devices for providing Wireless connectivity
`include access points, accessing serving netWorks, access
`netWorks, base station routers, and the like. In various
`embodiments, the functionality of the base stations 105 may
`be implemented in hardWare, ?rmWare, softWare, or any com
`bination thereof.
`[0027] The base station 105 may provide Wireless connec
`tivity to one or more mobile units 110. Although a single
`mobile unit 110 is depicted in FIG. 1, persons of ordinary skill
`in the art having bene?t of the present disclosure should
`appreciate that alternate embodiments of the Wireless com
`munication system 100 may include any number of mobile
`units 110. Mobility does not necessarily imply portability and
`exemplary mobile units 110 may include cellular telephones,
`personal data assistants, smart phones, pagers, text messaging
`devices, netWork interface cards, notebook computers, desk
`top computers, and the like. In various embodiments, the
`functionality of the mobile units 110 may be implemented in
`hardWare, ?rmWare, softWare, or any combination thereof.
`[0028] In the illustrated embodiment, a Wireless communi
`cation link has been established betWeen the base station 105
`and the mobile unit 110. The Wireless communication link
`includes a doWnlink 115 and an uplink 120. The doWnlink
`115 may include one or more data, control, paging, and/or
`broadcast channels (not shoWn in FIG. 1) and the uplink 120
`may include one or more scheduled uplink channels 125 and
`one or more unscheduled uplink channels 130. For example,
`a Wireless communication system 100 may implement sched
`uled channels 125 for transmitting scheduled user and control
`data (e.g., a physical uplink shared channel or PUSCH) and
`unscheduled channels 130 for transmitting unscheduled con
`trol data (e. g., the physical uplink control channel or
`PUCCH). The scheduled and unscheduled channels 125, 130
`may be transmitted in different frequency bands or sub-bands
`and may make use of different modulation and coding
`schemes. In one embodiment, the mobile unit 110 may not
`transmit information concurrently on the scheduled channels
`125 and the unscheduled channels 130.
`[0029] The mobile unit 110 may transmit scheduling
`requests to the base station 105 over the unscheduled uplink
`channel(s) 130. In one embodiment, uplink resources includ
`ing a portion of a timeslot are pre-allocated to the mobile unit
`110 for transmitting scheduling requests over the unsched
`uled uplink channel 130. HoWever, the mobile unit 110 may
`not be able to transmit a scheduling request during the pre
`allocated portion of the time slot if data and/or control infor
`mation is scheduled for transmission during the same time
`slot over one or more of the scheduled uplink channels 125.
`The mobile unit 1 1 0 may therefore add one or more additional
`bits to the data that is scheduled for transmission over the
`scheduled uplink channels 125 Whenever the resources allo
`cated for transmission of the scheduling requests over the
`
`7
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`

`US 2008/0316959 A1
`
`Dec. 25, 2008
`
`unscheduled uplink channel 130 overlap With the resources
`allocated for transmission of data over the scheduled uplink
`channels 125. In one embodiment, the mobile unit 110 uses
`one coding algorithm or coding rate to encode the data and/or
`control information for transmission over the scheduled
`uplink channels 125 and a different coding algorithm or cod
`ing rate to encode the data and/ or control information With the
`additional bit(s) indicative of the scheduling request. The
`mobile unit 110 may therefore transmit the data and/or con
`trol information With the additional scheduling request bit
`using the resources originally allocated for transmitting only
`the data and/or control information.
`[0030] FIG. 2 conceptually illustrates a scheduled uplink
`channel 200 and an unscheduled uplink channel 205. The
`channels 200, 205 are divided into a plurality of time slots that
`may be allocated for transmission of data and/ or control infor
`mation. User data is transmitted in time slot 210 of the sched
`uled uplink channel 200, as indicated by the dashed bold line,
`and so no information can be transmitted in the time slot 215
`of the unscheduled uplink channel 205, as indicated by the
`crosshatching. Control information is transmitted in time slot
`220 of the unscheduled uplink channel 200, as indicated by
`the dashed bold line, and so no information can be transmitted
`in the time slot 225 of the scheduled uplink channel 200, as
`indicated by the crosshatching.
`[0031] In the illustrated embodiment, the time slots 230,
`235 are allocated for transmitting data and control informa
`tion over the scheduled uplink channel 200 and the unsched
`uled uplink channel 205, respectively. Since a mobile unit is
`not permitted to transmit concurrently over the scheduled
`uplink channel 200 and the unscheduled uplink channel 205,
`the coding algorithm used for the data scheduled for trans
`mission in timeslot 230 is modi?ed so that the information
`scheduled for transmission in the timeslot 235 can be trans
`mitted With the data in the timeslot 230, as indicated by the
`bold line. No data or control information is transmitted in the
`timeslot 235, as indicated by the crosshatching.
`[0032] Referring back to FIG. 1, scheduling requests may
`also collide With other control information transmitted over
`the unscheduled uplink channel 13 0. For example, the mobile
`unit 110 may need to transmit a scheduling request over the
`unscheduled uplink channel 130 concurrently With transmit
`ting an acknowledgment or non-acknoWledgment message.
`The mobile unit 110 may therefore be able to transmit infor
`mation indicative of the scheduling request and the other
`control information using the resources allocated for trans
`mission of the other control information over the unscheduled
`uplink channel 130. For example, When the scheduling
`request collides With an acknowledgment or non-acknoWl
`edgment message, the mobile unit 110 may sWitch from the
`Binary Phase Shift Key (BPSK) modulation that is typically
`used to modulate the acknoWledgment or non-acknoWledg
`ment message to a higher order modulation scheme such as
`Quadrature Phase Shift Key (QPSK) modulation. Using the
`higher order modulation scheme increases the siZe of the
`constellation of symbol values so that information indicative
`of both the scheduling request and the acknoWledgement or
`non-acknoWledgment message can be transmitted using the
`resources allocated for transmission of the acknoWledgment
`or non-acknoWledgment message Without increasing the
`peak-to-average poWer ratio.
`[0033] FIG. 3 conceptually illustrates an unscheduled
`uplink channel 300. The channel 300 is divided into a plural
`ity of time slots that may be allocated for transmission of data
`
`and/or control information. In the illustrated embodiment, a
`scheduling request is transmitted in the timeslot 305, as indi
`cated by the horizontal hatching. The information indicative
`of the scheduling request is modulated into one symbol using
`BPSK modulation to indicate the possible symbol values of 0,
`Which indicates no scheduling requests, and 1, Which indi
`cates a scheduling request. An acknoWledgment or non-ac
`knoWledgment message may be transmitted in the timeslot
`310, as indicated by the vertical hatching. The information
`indicative of the acknoWledgment or non-acknoWledgment
`message is modulated into one symbol using BPSK modula
`tion to indicate the possible symbol values of 0 for a non
`acknoWledgment indicating unsuccessfully received doWn
`link information and 1 for an acknoWledgment of
`successfully received doWnlink information.
`[0034] In the illustrated embodiment, a scheduling request
`and an acknoWledgment or non-acknowledgment message
`are to be transmitted in the timeslot 315. The information
`indicative of the scheduling request and the acknoWledgment
`or non-acknoWledgment is therefore modulated into one
`symbol using a higher order modulation schemes such as
`QPSK modulation. Increasing the order of the modulation
`scheme from binary to quadrature doubles the siZe of the
`symbol constellation so that each symbol can represent values
`of the scheduling request and the acknoWledgment or non
`acknoWledgment message. For example, the symbol value 00
`may indicate no scheduling request and a non-acknoWledg
`ment indicating unsuccessfully received doWnlink informa
`tion. The symbol value 01 may indicate no scheduling request
`and an acknoWledgment indicating successfully received
`doWnlink information. The symbol value 10 may indicate a
`scheduling request and a non-acknoWledgment indicating
`unsuccessfully received doWnlink information. The symbol
`value 11 may indicate a scheduling request and an acknoWl
`edgment indicating successfully received doWnlink informa
`tion.
`[0035] FIG. 4 conceptually illustrates one exemplary
`embodiment of a decision tree 400 that may be used for
`transmitting scheduling requests over uplink channels. The
`embodiment of the decision tree 400 depicted in Figure
`numeral for may be implemented in the mobile unit. HoW
`ever, persons of ordinary skill in the art having bene?t of the
`present disclosure should appreciate that an analogous deci
`sion tree may also be implemented in an associated base
`station. Consequently, the base station and the mobile unit
`may operate in a coordinated fashion to transmit and receive
`scheduling requests over uplink channels because both the
`base station and the mobile unit have access to the informa
`tion required to navigate the relevant portions of the decision
`tree 400.
`[0036] In the illustrated embodiment, the decision tree 400
`begins When a mobile unit allocates (at 405) resources of an
`unscheduled uplink channel (such as PUCCH) for transmit
`ting a scheduling request (SR). If the mobile unit determines
`(at 410) that resources are allocated for a concurrent trans
`mission over a scheduled uplink channel, than one or more
`bits indicative of the scheduling request are added (at 413) to
`the scheduled uplink channel transmission. This bit or bits
`may also be added to the scheduled uplink channel data if no
`scheduling request is pending if the respective timeslot is
`pre-allocated for the transmission of scheduling requests,
`hoWever the bit may have a different value to indicate that no
`scheduling request is pending. The mobile unit may modify
`the coding algorithm so that the additional bits can be trans
`
`8
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`

`US 2008/0316959 A1
`
`Dec. 25, 2008
`
`mitted using the resources allocated for the original sched
`uled uplink transmission. If the mobile unit determines (at
`415) that no resources have been allocated for concurrent
`transmission over the scheduled uplink channel, then the
`mobile un