as) United States
`a2) Patent Application Publication 10) Pub. No.: US 2007/0064669 Al
`
`Classon etal.
`(43) Pub. Date:
`Mar. 22, 2007
`
`US 20070064669A1
`
`(54) METHOD AND APPARATUS FOR
`REDUCING ROUND TRIP LATENCY AND
`
`(21) Appl. No.:
`
`11/276,982
`
`OVERHEAD WITHIN A COMMUNICATION
`SYSTEM
`
`(22)
`
`Filed:
`
`Mar. 20, 2006
`
`(75)
`
`Inventors: Brian K. Classon, Palatine, IL (US);
`Kevin L. Baum, Rolling Meadows, IL
`(US); Amitava Ghosh, Buffalo Grove,
`IL (US); Robert T. Love, Barrington,
`IL (US); Vijay Nangia, Algonquin, IL
`Lt A. Stewart, Grayslake,
`Correspondence Address:
`MOTOROLA,INC.
`1303 EAST ALGONQUIN ROAD
`IL01/3RD
`SCHAUMBURG,IL 60196
`
`(73) Assignee: MOTOROLA,
`(US)
`
`INC., Schaumburg,
`
`IL
`
`Related U.S. Application Data
`
`(60) Provisional application No. 60/666,494, filed on Mar.
`30, 2005.
`
`.
`.
`oo
`Publication Classification
`
`Int. Cl.
`(51)
`(2006.01)
`HO4B 7/212
`(52) US. CM cceeeeseeneeee 370/347; 370/337; 709/236
`
`(57)
`
`ABSTRACT
`
`During operation radio framesare divided into a plurality of
`subframes. Data is transmitted over the radio frames within
`a plurality of subframes, and having a frame duration
`selected from two or more possible frame durations.
`
`701701
`702
`|_\ RADIO FRAME CONSTRUCTED FROM SHORT FRAMES
`
`
`
`CONTROL REGION"
`Pw
`al
`
`eee
`
`SYNCHRONISATION AND
`
`ae ~
`
`SHORTFFRAMES
`
`_ _—
`
`-1f&} RADIO FRAME n | RADIO FRAME ntl}
`
`
`RADIO FRAME (10ms)
`~~
`~~
`RADIO FRAME CONSTRUCTED FROM LONG FRAMES
`
`~
`
`see
`
`703
`
`LONG
`
`FRAME
`
`E=} CONTROL SYMBOL
`
`APPLE 1015
`
`1
`
`APPLE 1015
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 1 of 19
`
`US 2007/0064669 Al
`
`FIG. 1
`100
`
`oe
`
`DATA
`
`2
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 2 of 19
`
`US 2007/0064669 Al
`
`pl
`
`RADIO FRAME (10ms)
`
` a SUB-FRAWE
`500
`
`FIG. 3
`
`SYMBOLS
`
`SCHEDULABLE
`
`y
`
`
`SHORT FRAME MULTIPLEX
`Meee?Tt|||tT||ftttfee
`
`
`
`)ATH
`
`SSS
`NELLY|
`
`
`0.5ms
`SHORT FRAME
`ZACOMMON PILOT
`(0.5ms)
`FI CONTROL
`OODATA
`
`0.5ms
`
`0.5ms
`
`FIG... 4
`
`3
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 3 of 19
`
`US 2007/0064669 A1
`
`SCHEDULABLE
`UNIT
`eee
`
`LONG FRAME MULTIPLEX
`
`
` SS88g|neRXsgQQRSQ QV RQQgqQq1 SSS7Rg RSS7RSQQ9gqy
`
`
`
`
`
`RSS|eeeeere
`|__|
`SSS8g
`aD.
`
`0.5ms 0.5ms 0.5ms 0.5ms
`
`
`
`LONG
`(3ms)
`= CONTROL SYMBOL
`
`[| COMMON PILOT SYMBOL
`
`VYDATA SYMBOL
`
`FIG. 5
`
`PARAMETER
`
`RADIO FRAME DURATION (ms)|
`SUBFRAMES / RADIO FRAME
`SUBFRAME DURATION (ms
`UBFRAMES / LONG FRAME
`LONG FRAME DURATION (ms
`OVERHEED SUBFRAMES
`
`oo=Oo4
`
`uw
`
`oe
`
`<=
`
`==
`
`bo
`
`oOo
`
`nmLe=ao
`
`eo
`
`=>
`
`oa
`
`<x
`
`=oeSEe
`
`FIG.
`
`© EXEMPLARY LONG FRAME CONFIGURATIONS vs. SUBFRAME DURATION
`
`4
`
`
`
`
`
`
`
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 4 of 19
`
`US 2007/0064669 Al
`
`~~,
`
`
`
`aes
`
`
`71.) “RADIO. FRAME CONSTRUCTED FROM SHORT FRAMES
`
`SHORTFRAMES oo
`
`-1fE RADIO FRAME n =
`SYNCHRONISATION AND
`~~
`RADIO FRAME (10ms) a
`CONTROL REGION oa
`
`
`RADIO FRAME CONSTRUCTED FROM LONG FRAMES
`
`703
`
`LONG FRAME
`
`E=| CONTROL SYMBOL
`
`FIG. 7
`
`- eS 7?
`
`=
`
`ee
`
`. i RADIO FRAME n-t} | RADIO FRAME n ) RADIO FRAME ntl}
`a7
`RADIO FRAME (10ms)
`9 ~~_
`~~ RADIO FRAME CONSTRUCTED FROM LONG FRAMES ~~ _
` a
`
`TOOT
`
`SHORT FRAMES
`
`LONG FRAME
`
`
`STWTW)
`SUD
`SHORT FRAMES
`LONG FRAME
`
`RADIO FRAME CONSTRUCTED FROM LONG FRAMES
`
`OR
`
`E} CONTROL SYMBOL
`
`SHORT FRAMES
`
`[_]
`
`LONG FRAMES
`
`FIG. 8
`
`5
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 5 of 19
`
`US 2007/0064669 Al
`
`CYCLIC
`PREFIX
`901
`
`NORMAL SUB-FRAME
`10 OFDM SYMBOLS
`
`_-
`
`PAYLOAD
`
` 50DOiS2a—,,,,,.—_
`
`144
`
`50.0us
`FIG. 9
`
`CYCLIC
`PREFIX
`1001
`
`BROADCAST SUB-FRAME
`9 OFDM SYMBOLS
`
`~oeeo7 PAYLOAD
`
`Tips
`HAAS
`55.0648
`
`FIG. 10
`
`6
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 6 of 19
`
`US 2007/0064669 Al
`
`PARAMETER
`
`SUBFRAME CONFIGURATION
`
`RADIO FRAME DURATION (ms)] 10bio10|10|10|10|10|
`SUBFRAWES / RADIO FRAME|2017207420|1|8|6|6|6|16|
`
`SUBFRAME DURATION (ms)|0.5(70.57770.5 [0.55956/0.55556/0.55556] 0.625|0.625|0.625|0.66667| 0.66667 [0.66667
`SUBCARRIER SPACING (kHz spayefms|ms2s|ms|a5|ms|adms||
`SYMBOL DURATION {us)[55.5556 [77507/7)45.4545 [55.5556|50.5051|46.2963|56.8187[56.0833|48.0769 [756.5556] 91.2821|47.619
`
`USEFUL (us)|44.44 [444A] 44.44|4444|4444|44.44|44.44|4444|a4ne|44a|44nd|4444
`
`ns)atBZ ZAMNYbuZZe7317.64736574Wi76.8473.
`SYMBOLS PER SUBFRAME|9=[7107Aeaae
`
`TABLE 2 - EXEMPLARY SUBFRAME CONFIGURATIONS vs. THE NUMBER OF OFDM
`SYMBOLS PER SUBFRAME AND SUBFRAME DURATION.
`
`FIG. 11
`
`PARAMETER
`
`SUBFRAME CONFIGURATION
`
`SUBCARRIER SPACING (kHz
`
`
`40.00
`
`
`
`SYMBOL DURATION {us Lets 41,6667 48.0769|44.6429|41.6667
`
`
`
`
`
`USEFUL (us)|40.00 ,
`
`TABLE 3 - FURTHER EXEMPLARY SUBFRAME CONFIGURATIONS vs. THE NUMBER OF
`OFDM SYMBOLS PER SUBFRAME AND SUBFRAME DURATION
`
`7
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 7 of 19
`
`US 2007/0064669 Al
`
`NORMAL SUB-FRAME
`
`. a
`
`LONG FRAME
`
` ~
`
`~~ N
`
`eo
` RADIO FRAME n-1
`=
`RADIO FRAME n
`=
`RADIO FRAME n+l
`
`=_
`
`BROADCAST FRAME
`
`[| UNICAST FRAME
`F=| SYNCHRONIZATION AND CONTROL REGION
`
`FIG. 12
`
`8
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 8 of 19
`
`US 2007/0064669 Al
`
`NORMAL SUB-FRAME
`
`UB-FRAME
`
`x
`
`1 i"RADIOi a T0 ——
`eee
`=
`RADIO FRAME n
`=
`RADIO FRAME n+1
`RADIO FRAME n-1
`
`V/A BROADCAST FRAME
`[J UNICAST FRAME
`F=3 SYNCHRONIZATION AND CONTROL REGION
`
`FIG. 13
`
`Z
`
`:
`
`.
`
`50.0p8
`
`Z
`
`Z
`
`9
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 9 of 19
`
`US 2007/0064669 A1
`
`RADIO FRAME CONSTRUCTED FROM SHORT & LONG FRAMES
`
`»
`
`TATA
`AAARAAT
`AAARAAT
`AAR
`AAMAS
`AAR
`AANARAAT
`AURA
`
`ARTI RATAN
`AEN
`AURAL
`AAR
`ARRON
`AAT
`ANITA
`{ahaa
`
`LONG FRAME
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ATTEN VOARTTENTTNT
`AAAFAUNA
`WAARARTEL
`AATANTHAT
`AAACN
`AAA
`AAACN AATANT
`LAHAT
`
`
`
`
`
`PZASHORT FRAMES
`(_JLONG FRAME
`EBSSYNCHRONIZATION AND CONTROL REGION
`[_]suB-FRAME
`[JcELL SYNCHRONIZATION SYMBOL
`LOBAL SYNCHRONIZATION SYMBOL
`
`[J] COMMON PILOT
`IXY CONTROL
`FE) DATA
`PCH - PAGING CHANNEL INFORMATION
`- BROADCAST CONTROL CHANNEL INFO
`PAGING INDICATORS
`ACKNOWLEDGEMENT INDICATORS
`
`
`
`
`- OTHER INDICATORS (NOT SPECIFIED)
`- BROADCAST INDICATORS
`
`FIG. 14
`
`10
`
`10
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 10 of 19
`
`US 2007/0064669 Al
`
`RADIO FRAME i CONSTRUCTED FROM SHORT & LONG FRAMES
`SYNCHRONIZATION
`
`
`AND. CONTROL
`REGION (EVERY
`
`jth RADIO FRAME)
`ADSs
`
`
`
`
`
`ANATY
`TRAIAN
`RATATAT
`RAR
`
`
`
`SARA
`AAA,
`AWA
`SASNY
`
`
`AYA
`ARANAAT,
`AURA
`AAA
`SAMAR
`AAA,
`AURA
`ANAT
`AHURA
`AAWANARTARR,
`AAA
`ST TS
`AeMAMANMMARANY
`aKahAnANNT,
`AAA
`AHP
`AMRANNOY
`AMARA
`LAMANAAA,
`AHA
`ARNT
`Lary
`haan
`hunumndaamnn
`
`=
`
`
`
`RADIO FRAME i+1
`
`
`
`
` AfA
`
`DL
`
`f3|SYNCHRONIZATION AND CONTROL REGION
`(C]L0Nc FRANE©[_]SUB-FRAME
`[QJCELL SYNCHRONIZATION SYMBOL
`LOBAL SYNCHRONIZATION SYMBOL
`
`OMMON PILOT
`
`IXY CONTROL
`FFE] DATA
`FS] PCH - PAGING CHANNEL INFORMATION
`Fe] BCCH - BROADCAST CONTROL CHANNEL INFO
`
`(PI - PAGING INDICATORS
`[JAI - ACKNOWLEDGEMENT INDICATORS
`[il] o1 - OTHER INDICATORS (NOT SPECIFIED)
`[2] BI - BROADCAST INDICATORS
`
`
`FIG. 18
`
`
` [ZFISHORT FRAMES
`
`
`LONG FRAME
`
`lees
`
`
`
`11
`
`11
`
`

`

`
`
`CONTROL REGION
`
`Patent Application Publication Mar. 22,2007 Sheet 11 of 19
`
`US 2007/0064669 Al
`
`++ SUPER FRAME i-1|SUPER FRAME i|SUPER FRAME i+! |++- SYNCHRONIZATION AND
`
`
`
`RADIO FRANE:
`
`
`TO
`CONTROL REGION
`
` RADIO FRAME n-I
`RADIO FRAME n = RADIO FRAME 0
`
`
`~~~
`
`RADIOFRAME(10ms)
`
`oN
`a
`RADIO FRAME CONSTRUCTED FROM SHORT AND LONG FRAMES
`
`|-+-
`
`~~
`
`SHORT“FRANES
`
`LONG FRAME
`
`[FAJSHORT FRAMES
`[C_JLONG FRAWE
`EE\SYNCHRONIZATION AND CONTROL REGION
`[_]SUB-FRAME
`
` AI SUPER FRAME CONTROL REGION
`
`SUPER FRAME k
`
`FIG. 16
`
`12
`
`12
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 12 of 19
`
`US 2007/0064669 Al
`
`++ SUPER FRAME i-1|SUPER FRAME i|SUPER FRAME i+! |>-=
`
`
`
`RADIO FRAME:
`
`SYNCHRONIZATION AND
`CONTROL REGION
`7
`
`~~
` SHORT“FRAMES
`
`
`
`
`
`=| —RADIO FRAME n|_treesES RADIO FRAME 0 |+-
`
`CONTROL REGION
`
`LONG FRAME
`
`FIG. 17
`
`[Z7]SHORT FRAMES
`[[_]LONG FRAME
`EE\SYNCHRONIZATION AND CONTROL REGION
`[_]SUB-FRAME
`SUPER FRAME CONTROL REGION
`SUPER FRAME k
`
`
`
`
`13
`
`13
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 13 of 19
`
`US 2007/0064669 Al
`
`he
`SYNCHRONIZATION
`AND CONTROL
`
`RADIO FRAME CONSTRUCTED FROM SHORT & LONG FRAMES
`
`>!
`
`
`
`
`
`
`
`
`
`
`
`ea
`
`ee
`
`
`miRATTi
`Aaah
`AAA
`AMMANin
`anata
`vvnnannauadiauanniaans
`Ayia
`Lani,
`
`
`
`AMMAN
`AeA
`
`AANA
`ReanyPARRANNA
`AeA
`AePRORANNA
`Naat
`hymns
`oe ee
`p
`p
`
`REGION
`
`DL
`
`UL
`
`rene
`
`ARRAN
`
`FRAME
`OFFSET
`
`RACH
`
`6
`
`~
`~
`TTT
`SUA
`AUG
`ASAIN
`SQUARE
`Sasa
`SAAN
`SUNTAN
`
`LONG FRAME
`ARR RTT
`SAKATA
`
`AMAA MSTRAY
`AAAS
`AAAARAARAATRGY
`ARRAY
`AMARA
`{umf
`_
`
`6
`
`P
`
`ONE DOWNLINK AND UPLINK RADIO FRAME STRUCTURE
`
`FIG. 18
`
`EEJRAcH
`EZFISHORT FRAMES
`common PILOT
`[_JLONG FRAME
`EZJsYNCHRONIZATION AND CONTROL REGION [XY CONTROL
`[_]SUB-FRAME
`DATA
`rm]
`PA SUPER FRAME CONTROL REGION
`Fo] SUPER FRAME k
`
`14
`
`14
`
`

`

`le
`RADIO FRAME CONSTRUCTED FROM SHORT & LONG FRAMES
`>!
`
`SYNCHRONIZATION
`
`
`
` Q.5ms
`
`AND CONTROL
`
`REGION
`a
`KSGs
`
`
`
`
`
`
`
`AYA RARAY
`
` ANUSARA
`
`ANALG
` AGRAATA
`
`Nin NAAN
`
`ATAUAASV
`ANN ANA
`
`
`
`SHORT FRAMES
`
`LONG FRAME
`
`CELLCO
`
`
`Patent Application Publication Mar. 22,2007 Sheet 14 of 19
`
`US 2007/0064669 Al
`
`DL
`
`LONG RACH LONG FRAME
`EVERY 100ms OTHERWISE
`DATA LONG FRAME
`
`SHORT RACH
`
`
`
`SHORT RACH
`
`
`SUBFRAME
`
`ALTERNATIVE UPLINK FRAME STRUCTURE
`
`EEqRACH
`[ZZISHORT FRAMES
`ZZ COMMON PILOT
`[C_JLONG FRAWE
`EE\SYNCHRONIZATION AND CONTROL REGION [XY CONTROL
`[[1sub-FRANE
`Fy DATA
` | SUPER FRAME CONTROL REGION
`
`SUPER FRAME k
`
`FIG. 19
`
`15
`
`15
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 15 of 19
`
`US 2007/0064669 Al
`
`
`
`
`ai
`
`
`
`
`DL
`
`UL
`
`SHORT FRAMES
`
`LONG FRAME
`
`le
`RADIO FRAME CONSTRUCTED FROM SHORT & LONG FRAMES
`»
`
`
`SYNCHRONIZATION
`
`
`AND CONTROL
`.
`0.5ms
`0.5ms
`
`
`: CLE L
`=
`
`
`N
`
`ewanfnAUTEN ATUL
`
`
`wy cSANNA
`
` NANAANANEESUNERRERLE
`nN ANN
`AviATHLONE
`
`
`
`
`
`FRAME
`OFFSET ONG RACH LONG FRANE
`EVERY 100ms OTHERWISE
`DATA LONG FRAME
`
`
`
`
`
`SHORT RACH
` |RACH GUARD
`
`ALTERNATIVE UPLINK FRAME STRUCTURE SHORT RACH’|—SUBFRAME
`
`
`[ZAISHORT FRAMES
`EEARACH
`
`[C_JLONG FRAME
`EE\SYNCHRONIZATION AND CONTROL REGION [RY CONTROL
`(1sup-FRAME
`FF] DATA
`PA SUPER FRAME CONTROL REGION
`SUPER FRAME k
`
`
`FIG. 20
`
`16
`
`16
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 16 of 19
`
`US 2007/0064669 Al
`
`»!
`RADIO FRAME CONSTRUCTED FROM SHORT & LONG FRAMES
`
`
`
`le
`SYNCHRONIZATION
`AND CONTROL
`REGION
`
`OL
`
`
`
`UL
`FRAME
`
`OFFSET
`
`
`
`
`0.5ms
`
`SHORT RACH
`
`SUBFRAME
`RACH GUARD
`
`FIG. 21
`°
`
`EEgRACH
`[ZJSHORT FRAMES
`[J coMmMON PILOT
`(_JLone FRAME
`EEJSYNCHRONIZATION AND CONTROL REGION [RQ CONTROL
`[Jsub-FRAWE
`DATA
`SUPER FRAME CONTROL REGION
`e
`
`SUPER FRAME k
`
`
`- b
`
`17
`
`17
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 17 of 19
`
`US 2007/0064669 A1
`
`js
`
`=Qo==So
`
`—_—!—a.
`
`—oS
`
`co=>wn
`
`Qo
`
`—_—!
`
`Le)
`
`oSa—=Oo
`
`=!
`
`S&Sa=>rn
`
`=!
`
`[—_] UNALOCATED
`SUB-CARRIER(S)
`
`IYI
`
`SYNN
`
`ZGL
`
`ANAND
`
`
`
`FIG.
`
`22
`
`18
`
`18
`
`

`

`—So
`
`oS=aeo=Ij>sma
`
`co=>wa—_I
`
`oOaWYNWN
`
`—=Oo4=—==SooS
`
`[] UNALOCATED
`SUB-CARRIER(S)
`
`AQNINOINS
`
`FIG. 23
`
`19
`
`

`

`Patent Application Publication Mar. 22,2007 Sheet 19 of 19
`
`US 2007/0064669 A1
`
`Wa COMMON PILOT SYMBOL
`
`CONTROL SYMBOLS
`
`FREQUENCY DIVERSE
`RESOURCE ALLOCATION
`
`AQNANDIYS
`
`
`TIME
`
`FREQUENCY SELECTIVE
`RESOURCE ALLOCATION
`
`FIG. 24
`
`20
`
`20
`
`
`

`

`US 2007/0064669 Al
`
`Mar. 22, 2007
`
`METHOD AND APPARATUS FOR REDUCING
`ROUND TRIP LATENCY AND OVERHEAD
`WITHIN A COMMUNICATION SYSTEM
`
`RELATED APPLICATIONS
`
`[0001] This application claimspriority to U.S. Provisional
`Application Ser. No. 60/666,494 filed Mar. 30, 2005.
`
`FIELD OF THE INVENTION
`
`[0002] The present invention relates generally to commu-
`nication systemsand in particular, to a method and apparatus
`for reducing round-trip latency and overhead within a com-
`munication system.
`
`BACKGROUND OF THE INVENTION
`
`[0003] One of the key requirements for wireless broad-
`band system development, such as in the 3" generation
`partnership project (GPP) Long Term Evolution (LTE), is
`reducing latency in order to improve user experience. From
`a link layer perspective,
`the key contributing factor to
`latency is the round-trip delay between a packet transmis-
`sion and an acknowledgment of the packet reception. The
`round-trip delay is typically defined as a numberof frames,
`wherea frame is the time duration upon which scheduling is
`performed. The round-trip delay itself determines the overall
`automatic repeat request (ARQ) design, including design
`parameters such as the delay betweena first and subsequent
`transmission of packets, or the number of hybrid ARQ
`channels (instances). A reduction in latency with the focus
`on defining the optimum frame duration is therefore key in
`developing improved user experience in future communica-
`tion systems. Such systems include enhanced Evolved Uni-
`versal Terrestrial Radio Access (UTRA) and Evolved Uni-
`versal Terrestrial Radio Access Network (UTRAN) (also
`known as EUTRA and EUTRAN)within 3GPP, and evolu-
`tions of communication systems within other technical
`specification generating organizations (such ‘Phase 2’ within
`3GPP2, and evolutions of IEEE 802.11, 802.16, 802.20, and
`802.22).
`
`[0004] Unfortunately, no single frame duration is best for
`differenttraffic types requiring different quality of service
`(QoS) characteristics or offering differing packet sizes. This
`is especially true when the control channel and pilot over-
`head in a frame is considered. For example, if the absolute
`control channel overhead is constant per user per resource
`allocation and a single user is allocated per frame, a frame
`duration of 0.5 ms would be roughly four times less efficient
`than a frame duration of 2 ms. In addition, different frame
`durations could be preferred by different manufacturers or
`operators, making the developmentof an industry standard
`or compatible equipmentdifficult. Therefore, there is a need
`for an improved methodfor reducing both round-trip latency
`and overhead within a communication system.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0005] FIG. 1 is a block diagram of a communication
`system.
`
`[0006] FIG. 2 is a block diagram of circuitry used to
`perform uplink and downlink transmission.
`
`[0007] FIG. 3 is a block diagram of a radio frame.
`
`[0008]
`frames.
`
`[0009]
`frames.
`
`FIG. 4 shows a sequence of consecutive short
`
`FIG. 5 shows a sequence of consecutive long
`
`FIG. 6 showsa table for a 10 ms radio frame and
`[0010]
`subframes of approximately 0.5 ms, 0.55556 ms, 0.625 ms,
`and 0.67 ms.
`
`FIG. 7 shows examplesfor the third data column of
`[0011]
`Table 1, with 0.5 ms subframes and 6 subframes per long
`frame (3 ms).
`
`FIG. 8 shows two examples of radio frames based
`[0012]
`on a combination of 2 ms long frames and 0.5 ms short
`frames.
`
`[0013] FIG.9 showsa subframe comprised ofj=10 OFDM
`symbols each with a cyclic prefix 901 of 5.56 us which may
`be used for unicast transmission.
`
`FIG. 10 showsa ‘broadcast’ subframe comprised
`[0014]
`of j=9 symbols each with a cyclic prefix 1001 of 11.11 ps
`which maybe used for broadcast transmission.
`
`FIG. 11 shows a table having examples of three
`[0015]
`subframe types.
`
`FIG. 12 shows a long frame composedentirely of
`[0016]
`broadcast subframes or composed entirely of normal (uni-
`cast) subframes.
`
`FIG. 13 showsa short frame composed of either a
`[0017]
`normal or a broadcast subframe and one or more broadcast
`
`type short frames.
`
`FIG. 14 shows an example of the radio frame
`[0018]
`overhead.
`
`FIG. 15 showsan alternate Radio Framestructure
`[0019]
`of arbitrary size where the synchronization and control
`(S+C) region is not part of a radio frame butpart of a larger
`hierarchical
`frame structure composed of radio frames
`where the (S+C) region is sent with every j Radio Frames.
`
`FIG. 16 and FIG.17 illustrate a hierarchical frame
`[0020]
`structure where a Super frame is defined to be composed of
`n+1 radio frames.
`
`FIG. 18 shows the uplink subframes to be of the
`[0021]
`same configuration as the downlink subframes.
`
`FIG. 19 through FIG. 21 show 2 ms long frames
`[0022]
`composed of 0.5 ms subframesthat are of frame type long
`RACH, Data, or Composite.
`
`FIG. 22 through FIG. 24 show short frame fre-
`[0023]
`quencyselective (FS) and frequency diverse (FD) resource
`allocations respectively for several users.
`
`DETAILED DESCRIPTION OF THE DRAWINGS
`
`In order to address the above-mentioned need, a
`[0024]
`method and apparatus for reducing round-trip latency is
`provided herein. During operation radio frames are divided
`into a plurality of subframes. Data is transmitted over the
`radio frames within a plurality of subframes, and having a
`frame duration selected from two or more possible frame
`durations.
`
`[0025] The present invention encompasses a method for
`reducing round-trip latency within a communication system.
`
`21
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`US 2007/0064669 Al
`
`Mar. 22, 2007
`
`The method comprises the steps of receiving data to be
`transmitted over a radio frame, where the radio frame is
`comprised of a plurality of subframes. A frame duration is
`selected from two or more possible frame durations, where
`a frameis substantially equal to a multiple of subframes. The
`data is placed within the multiple subframes to produce
`multiple subframes of data, and the frame is transmitted
`having the multiple subframes of data over the radio frame.
`
`invention additionally comprises a
`[0026] The present
`method comprising the steps of receiving data to be trans-
`mitted to a first user over a radio frame, where the radio
`frame is comprised of a plurality of subframes. A frame
`duration is selected for the first user from two or more
`possible frame durations, where a frame is substantially
`equal to a multiple of subframes. The data for the first user
`is placed within the multiple subframes to produce multiple
`subframes of data and then transmitted to the first user
`having the multiple subframes of data over the radio frame.
`Second data is received to be transmitted to a second user
`over the radio frame. A second frame duration is selected for
`the second user from the two or more possible frame
`durations, where a second frame is substantially equal to
`multiple of subframes. The second data for the second user
`is placed within the multiple subframes to produce second
`multiple subframes of data, and the second frameis trans-
`mitted to the second user having the second multiple sub-
`frames of data over the radio frame.
`
`[0027] The present invention encompasses a method for
`transmitting data within a communication system. The
`method comprises the steps of receiving data to be trans-
`mitted over a radio frame, where the radio frame is com-
`prised of a plurality of subframes. A frame length is selected
`comprising multiple subframes and a subframe type is
`selected from one of two or more types of subframesfor the
`multiple of subframes. The data is placed within the multiple
`subframes to produce multiple subframes of data and the
`frame is transmitted having the multiple subframes of data
`and the subframe type over the radio frame.
`
`[0028] The present invention encompasses a method for
`transmitting data within a communication system. The
`method comprises the steps of receiving data to be trans-
`mitted over a radio frame, where the radio frame is com-
`prised of a plurality of subframes. A frame is selected
`wherein the frame is substantially equal to a multiple of
`subframes. The data is placed within the multiple subframes
`to produce multiple subframes of data and a common pilot
`is placed within each subframe of the multiple subframes.
`The frame having the multiple subframes of data is trans-
`mitted over the radio frame.
`
`[0029] The present invention encompasses a method for
`transmitting data within a communication system. The
`method comprises the steps of determining a system band-
`width from two or more system bandwidths and receiving
`data to be transmitted over a radio frame and the system
`bandwidth. The radio frame is comprised of a plurality of
`subframes, and a radio frame duration and a subframe
`duration is based on the system bandwidth. A frame is
`selected, where a frame is substantially equal to a multiple
`of subframes. The data is placed within the multiple sub-
`frames to produce multiple subframes of data and the frame
`is transmitted having the multiple subframes of data and the
`subframe type over the radio frame.
`
`[0030] A method for transmitting data within a commu-
`nication system. The method comprises the steps of deter-
`mining a carrier bandwidth and receiving data to be trans-
`mitted over a radio frame, where the radio frame is
`comprised of a plurality of subframes. A frame is selected,
`where the frame is substantially equal
`to a multiple of
`subframes and each subframe is comprised of resource
`elements, where a resource element comprises multiples of
`sub-carriers such that a carrier bandwidth is divided into a
`
`numberof resource elements. The data is placed within the
`multiple subframes to produce multiple subframes of data
`and the frame is transmitted having the multiple subframes
`of data and the subframe type over the radio frame.
`
`[0031] Turning nowto the drawings, wherein like numer-
`als designate like components, FIG. 1 is a block diagram of
`communication system 100. Communication system 100
`comprises a plurality of cells 105 (only one shown) each
`having a basetransceiver station (BTS,or base station) 104
`in communication with a plurality of remote, or mobile units
`101-103. In the preferred embodimentof the present inven-
`tion, communication system 100 utilizes a next generation
`Orthogonal Frequency Division Multiplexed (OFDM) or
`multicarrier based architecture, such as OFDM with or
`without cyclic prefix or guard interval (e.g., conventional
`OFDM with cyclic prefix or guard interval, OFDM with
`pulse shaping and no cyclic prefix or guard interval (OFDM/
`OQAMwith IOTA ([sotropic Orthogonal Transform Algo-
`rithm) prototype filter), or single carrier with or without
`cyclic prefix or guard interval (e.g., IFDMA, DFT-Spread-
`OFDM), or other. The data transmission may be a downlink
`transmission or an uplink transmission. The transmission
`scheme may include Adaptive Modulation and Coding
`(AMC). The architecture mayalso include the use of spread-
`ing techniques such as multi-carrier COMA (MC-CDMA),
`multi-carrier direct sequence CDMA (MC-DS-CDMA),
`Orthogonal Frequency and Code Division Multiplexing
`(OFCDM)with one or two dimensional spreading, or may
`be based on simpler time and/or frequency division multi-
`plexing/multiple access techniques, or a combination of
`these various techniques. However,
`in alternate embodi-
`ments communication system 100 may utilize other wide-
`band cellular communication system protocols such as, but
`not limited to, TDMA or direct sequence CDMA.
`
`In addition to OFDM, communication system 100
`[0032]
`utilizes Adaptive Modulation and Coding (AMC). With
`AMC, the modulation and coding format of a transmitted
`data stream for a particular receiver is changed to predomi-
`nantly match a current received signal quality (at
`the
`receiver) for the particular frame being transmitted. The
`modulation and coding scheme may change on a frame-by-
`frame basis in order to track the channel quality variations
`that occur in mobile communication systems. Thus, streams
`with high quality are typically assigned higher order modu-
`lations rates and/or higher channel coding rates with the
`modulation order and/or the code rate decreasing as quality
`decreases. For those receivers experiencing high quality,
`modulation schemes such as 16 QAM, 64 QAM or 256
`QAMare utilized, while for those experiencing low quality,
`modulation schemes such as BPSK or QPSKare utilized.
`
`[0033] Multiple coding rates may be available for each
`modulation scheme to provide finer AMC granularity,
`to
`enable a closer match between the quality and the transmit-
`ted signal characteristics (e.g., R='4, 2, and *%4 for QPSK;
`
`22
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`US 2007/0064669 Al
`
`Mar. 22, 2007
`
`R=% and R=% for 16 QAM,etc.). Note that AMC can be
`performed in the time dimension(e.g., updating the modu-
`lation/coding every N, OFDM symbol periods) or in the
`frequency dimension (e.g., updating the modulation/coding
`every N,, subcarriers) or a combination of both.
`
`[0034] The selected modulation and coding may only
`predominantly match the current received signal quality for
`reasons such as channel quality measurementdelay or errors
`or channel quality reporting delay. Such latency is typically
`caused by the round-trip delay between a packet transmis-
`sion and an acknowledgmentof the packet reception.
`
`In order to reduce latency, a Radio Frame (RAF)
`[0035]
`and subframeare defined such that the RAF is divided into
`
`a number(an integer number in the preferred embodiment)
`of subframes. Within a radio frame, frames are constructed
`from an integer number of subframes for data transmission,
`with two or more frame durations available (e.g., a first
`frame duration of one subframe, and a second frame dura-
`tion of three subframes).
`
`[0036] For example, a 1 0 ms core radio frame structure
`from UTRA maybe defined, with N,, subframes per radio
`frame (e.g., N.=20 T,,=0.5 ms subframes, where T,,=dura-
`tion of one subframe). For OFDM transmission, subframes
`comprise an integer number P of OFDM symbolintervals
`(e.g., P=10 for T,,=50 us symbols, where T,,=duration of
`one OFDM symbol), and one or more subframe types may
`be defined based on guard interval or cyclic prefix (e.g.,
`normal or broadcast).
`
`[0037] As one of ordinary skill in the art will recognize, a
`frame is associated with a scheduled data transmission. A
`
`frame may be defined as a resource that is ‘schedulable’, or
`a schedulable unit,
`in that
`it has an associated control
`structure—possibly uniquely associated—that controls the
`usage of the resource (i.e. allocation to users etc.). For
`example, when a user is to be scheduled on a frame, a
`resource allocation message corresponding to a frame will
`provide resources (e.g., for an OFDM system a numberof
`modulation symbols each of one subcarrier on one OFDM
`symbol) in the frame for transmission. Acknowledgements
`of data transmissions on a frame will be returned, and new
`data or a retransmission of data may be scheduled in a future
`frame. Becausenotall resources in a frame maybe allocated
`in a resource allocation (such as in an OFDM system), the
`resource allocation may not span the entire available band-
`width and/or time resources in a frame.
`
`[0038] The different frame durations may be used to
`reduce latency and overhead based on the type oftraffic
`served. For example, if a first transmission and a retrans-
`mission are required to reliably receive a voice over internet
`protocol (VoIP) data packet, and a retransmission can only
`occur after a one frame delay, allocating resources within a
`0.5 ms frame instead of a 2 ms frame reduces latency for
`reliable reception from 6 ms (transmission,
`idle frame,
`retransmission) to 1.5 ms. In another example, providing a
`resource allocation that will fit a user’s packet without
`fragmentation, such as a 1 ms frame instead of a 0.5 ms
`frame, can reduce overhead such as control and acknowl-
`edgement signaling for multiple fragments of a packet.
`
`aggregation of
`the
`reflecting
`names
`[0039] Other
`resources such as consecutive OFDM symbols may be used
`instead of subframe, frame, and radio frame. For example,
`
`the term ‘slot’ may be used for ‘subframe’, or ‘transmission
`time interval (TT])’ used for ‘frame’ or ‘frame duration’. In
`addition, a frame may be considered a user transmission
`specific quantity (such as a TT] associated with a user and
`a data flow), and frames therefore need not be synchronized
`or aligned between users or even transmissions from the
`same user (e.g., one subframe could contain parts of two
`data transmissions from a user, the first transmitted in a one
`subframe frame and the second transmitted in a four sub-
`
`frame frame). Of course, it may be advantageousto restrict
`either transmissions with a user or transmissions with mul-
`
`tiple users to have synchronized or aligned frames, such as
`when time is divided into a sequence of 0.5 ms or 2 ms
`frames and all resource allocations must be within these
`
`frames. As indicated above a radio frame can represent an
`aggregation of subframes or frames of different sizes or an
`aggregation of resources such as consecutive OFDM or
`DFT-SOFDM symbols exceeding the number of such sym-
`bols in a subframe where each symbol is composed of some
`numberof subcarriers depending on the carrier bandwidth.
`
`[0040] The radio framestructure may additionally be used
`to define common control channels for downlink (DL)
`transmissions (such as broadcast channels, paging channels,
`synchronization channels, and/or indication channels) in a
`manner which is time-division multiplexed into the sub-
`frame sequence, which may simplify processing or increase
`battery life at the user equipment (remote unit). Similarly for
`uplink (UL) transmissions, the radio frame structure may
`additionally be used to define contention channels (e.g.
`random access channel_(RACH)), control channels includ-
`ing pilot time multiplexed with the shared data channel.
`
`FIG. 2 is a block diagram ofcircuitry 200 for base
`[0041]
`station 104 or mobile station 101-103 to perform uplink and
`downlink transmission. As shown,circuitry 200 comprises
`logic circuitry 201,
`transmit circuitry 202, and receive
`circuitry 203. Logic circuitry 200 preferably comprises a
`microprocessor controller, such as, but not
`limited to a
`Freescale PowerPC microprocessor. Transmit and receive
`circuitry 202-203 are commoncircuitry knownin the art for
`communication utilizing a well known network protocols,
`and serve as meansfor transmitting and receiving messages.
`For example, transmitter 202 and receiver 203 are preferably
`well known transmitters and receivers that utilize a 3GPP
`
`network protocol. Other possible transmitters and receivers
`include, but are not limited to transceivers utilizing Blue-
`tooth, IEEE 802.16, or HyperLANprotocols.
`
`[0042] During operation, transmitter 203 and receiver 204
`transmit and receive frames of data and control information
`
`as discussed above. More particularly, data transmission
`takes place by receiving data to be transmitted over a radio
`frame. The radio frame (shown in FIG. 3) is comprised of a
`plurality of subframes 300 (only one labeled) wherein the
`duration of subframe 301 is substantially constant and the
`duration of the radio frame 300 is constant. For example
`only, a radio frame comprises m=20 subframes 300 of
`duration 0.5 ms consisting of j=10 symbols. During trans-
`mission, logic circuitry 201 selects a frame duration from
`two or more frame durations, where the frame duration is
`substantially the subframe duration multiplied by a number.
`Based on the frame duration, the number of subframes are
`grouped into the frame and data is placed within the sub-
`
`23
`
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`

`

`US 2007/0064669 Al
`
`Mar. 22, 2007
`
`frames. Transmission takes place by transmitter 202 trans-
`mitting the frame 300 having the numberof subframes over
`the radio frame.
`
`For simplicity and flexibility, it is preferred but not required
`that the radio frame overhead be an integer number of
`subframes.
`
`Asnoted previously, the data transmission may be
`[0043]
`a downlink transmission or an uplink transmission. The
`transmission scheme may be OFDM with or without cyclic
`prefix or guard interval (e.g., conventional OFDM with
`cyclic prefix or guard interval, OFDM with pulse shaping
`and no cyclic prefix or guard interval (OFDM/OQAM with
`IOTA (Isotropic Orthogonal Transform Algorithm) proto-
`typefilter), or single carrier with or without cyclic prefix or
`guard interval (e.g., IFDMA, DFT-Spread-OFDM), CDM,
`or other.
`
`Frame Durations
`
`[0044] There are two or more frame durations. If two
`frame durations are defined, they may be designated short
`and long, where the short frame duration comprises fewer
`subframes than the long frame duration. FIG. 4 shows a
`sequence of consecutive short frames 401 (short frame
`multiplex), and FIG. 5 shows a sequenceof consecutive long
`frames 501 (long frame multiplex). Time may be divided
`into a sequence of subframes, subframes grouped into
`frames of two or more durations, and frame duration may be
`different between consecutive frames. Subframes of a frame
`
`are of a subframetype, with typically two or more subframe
`types. Each short and long frame is a schedulable unit
`composedof ns (n) subframes. In the example of FIG. 4 and
`FIG. 5, a subframe is of duration 0.5 ms and 10 symbols,
`ns=1 for the short frame 401 while n=6 (3 ms) for the long
`frame 501, although other values may be used. A radio frame
`need not be defined, or, if defined, the frame(e.g., short or
`long frame) may span more than one radio frame. As an
`example, a common pilot or common reference symbol or
`common reference signal
`is
`time division multiplexed
`(TDM)onto the first symbol of each subframe, and control
`symbols are TDM onto the first symbols of each frame
`(other forms of multiplexing such as FDM, CDM, and
`combinations mayalso be used). Pilot symbols and resource
`allocation control configurations will be discussed in later
`sections—th