IEEE Broadband Wireless Access Working Group < Modifications to the Feedback Methodologies in UL Sounding

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1 Poject Title Date Submitted IEEE Boadband Wieless Access Woking Goup < Modifications to the Feedback Methodologies in UL Sounding Souce(s) Fed Vook, Jeff Zhuang, Tom Kauss, Fan Wang, Kishna Sayana Motoola Re: LB26 IEEE REV2/D2. Abstact Pupose Notice Release Patent Policy This contibution poposes modifications to the feedback mechanism contained in the UL sounding signaling. Review and adopt. This document does not epesent the ageed views of the IEEE Woking Goup o any of its subgoups. It epesents only the views of the paticipants listed in the Souce(s) field above. It is offeed as a basis fo discussion. It is not binding on the contibuto(s), who eseve(s) the ight to add, amend o withdaw mateial contained heein. The contibuto gants a fee, ievocable license to the IEEE to incopoate mateial contained in this contibution, and any modifications theeof, in the ceation of an IEEE Standads publication; to copyight in the IEEE s name any IEEE Standads publication even though it may include potions of this contibution; and at the IEEE s sole discetion to pemit othes to epoduce in whole o in pat the esulting IEEE Standads publication. The contibuto also acknowledges and accepts that this contibution may be made public by IEEE The contibuto is familia with the IEEE-SA Patent Policy and Pocedues: < and < Futhe infomation is located at < and < 1

2 Modifications to the Feedback Methodologies in UL Sounding Fed Vook, Jeff Zhuang, Tom Kauss, Fan Wang, Kishna Sayana Motoola Intoduction Diect feedback techniques such as diect o analog feedback of channel coefficients ae geneally effective techniques fo enabling closed loop tansmission techniques such as beamfoming and closed-loop MIMO. Howeve, the diect coefficient feedback methodology ("include additional feedback"==0b01) in the UL sounding signaling has modes that ae eithe vey inefficient o not well specified. An altenative diect feedback method is equied. This contibution poposes a simple modification to the UL Sounding Command IE that enables the diect feedback of the tansmit covaiance matix fom the MS to the BS. This functionality povides a bette altenative to the diect coefficient feedback methodology cuently included in the sounding signaling. Note that in the UL Sounding Command IE (Table 463), the "Include Additional Feedback" has a setting of 0b11 to mean "include feedback message"; howeve no coesponding feedback message o method is defined in the spec. This contibution can be viewed as filling in the missing functionality fo when the Include Additional Feedback is set to 0b11. Oveview of poposed modifications The poposed modifications ae staightfowad and do not beak backwad compatibility with any mobile stations that ae constucted to suppot UL Sounding as specified in [1] and pofiled in [2]. These modifications enable the MS to tansmit to the BS an analog copy of the downlink tansmit covaiance matix as estimated by the MS. The BS then can use the tansmit covaiance matix to pefom closed-loop tansmission on the downlink (e.g., beamfoming and MIMO+Beamfoming). Within each sounding band allocated to an MS, the MS constucts a modified UL sounding wavefom that consists of the usual UL sounding wavefom in which the usual sounding wavefom values have been punctued by the unique analog values of the covaiance matix enties. Covaiance matix feedback is defined fo cyclic shift sepaability. When this covaiance matix feedback methodology is used, the multi-antenna flag is not needed since only one MS tansmit antenna is used to send back the modified sounding wavefom. Hence, when covaiance matix feedback is used, the multi-antenna flag is used as a band elevance flag to indicate whethe the covaiance matix being sent back on a sounding band must be computed ove the subcaies coesponding to that sounding band (naowband covaiance matix) o whethe the covaiance matix must be computed ove all subcaies of the downlink signal bandwidth (boadband covaiance matix). Finally, when the band AMC bit-map allocation mode is used (athe than the nomal allocation mode) to indicate which AMC logical bands the MS must sound on, only one of the fou bands within a logical AMC band ae used by the MS to tansmit the modified sounding wavefom, and that sub-band is indicated with a sounding sub-band index that eplaces two peviously unused eseve bits. 2

3 Poposed Text Changes [Table 463 UL Sounding Command IE Fomat] [Additions in undelined blue. Deletions in stikethough ed.] Syntax Size (Bit) Notes UL_Sounding_Command_IE(){ Extended-2 UIUC 4 UL_Sounding_Command_IE() = 0x04 Length 8 vaiable Sounding_Type 1 0 = Type A 1 = Type B Send Sounding Repot Flag 1 - Sounding_Relevance_Flag 1 0 = Sounding elevance is the same fo all CIDs 1 = Sounding elevance is specified fo each CID if(sounding_relevance_flag == 0) { - - Sounding_Relevance 1 0 = All CIDs espond in the fame caying the instuction 1 = All CIDs espond in next fame Reseved 2 Shall be set to zeo. else { - - Reseved 3 Shall be set to zeo. Include additional feedback 2 0b00 = No additional feedback 0b01 = Include channel coefficients (see ) 0b10 = Include eceived pilot coefficients 0b11 = Include feedback message 0b11 = Include covaiance matix feedback (See ) if (Sounding_Type == 0) { - - Num_Sounding_symbols 3 Total numbe of sounding symbols being allocated, fom 1 (0b000) to 2 3 = 8 (0b111) eseved 1 Shall be set to zeo fo(i=0; i<num_sounding_symbols;i++){ - - 3

4 Sepaability Type 1 0: occupy all subcaies in the assigned bands 1: occupy decimated subcaies if (Sepaability type == 0) { - (using cyclic shift sepaability) Max Cyclic Shift Index P 3 0b000: P = 4 0b001: P = 8 0b010: P = 16 0b011: P = 32 0b100: P = 9 0b101: P = 18 0b110 0b111: Reseved Reseved 1 Shall be set to zeo. else { - (using decimation sepaability) Decimation Value D 3 Sound evey Dth subcaie within the sounding allocation. Decimation value D is 2 to the powe of (1 plus this value), hence 2,4,8, up to maximum of 128, and 0b111 means decimation of 5. Decimation offset andomization 1 0 = no andomization of decimation offset 1 = decimation offset pseudo-andomly detemined Sounding symbol index 3 Symbol index within the Sounding Zone, fom 1 (value 0b000) to 2 3 = 8 (value 0b111) Numbe of CIDs 7 Numbe of CIDs shaing this sounding allocation Reseved 1 Shall be set to zeo. fo (j = 0; j < Num. of CIDs; j++) { - - Shoted basic CID LSBs of the MS basic CID value Powe Assignment Method 2 0b00 = Equal powe 0b01 = Reseved 0b10 = Intefeence dependent; pe subcaie powe limit 0b11 = Intefeence dependent; total powe limit. Powe boost 1 0 = No powe boost 1 = Powe boost If (Include additional feedback == 0b11){ Covaiance matix feedback (Section ) else { Band Relevance Flag 1 0 = Covaiance matix being fed back on a sounding band coesponds to the entie DL signal bandwidth 1 = Covaiance matix being fed back on a sounding band coesponds to the subcaies of that sounding band. 4

5 Multi-Antenna Flag 1 0 = MS sounds fist antenna only 1 = MS sounds all antennas Allocation Mode 1 0: Nomal 1: Band AMC If (Allocation Mode == 1) { - - Band bit Map 12 See logical band defined in If (Include additional feedback == 0b11){ Covaiance matix feedback (Section ) Sounding Sub-band index within AMC logical subband 2 AMC logical sub-band has 72 subcaies. Sounding subband has 18 subcaies. This field futhe instucts the MS to sound on one of the fou sounding bands within AMC logical band in case of 1 in the coesponding AMC band bitmap else { Reseved 2 Shall be set to zeo. Else { - - Stating Fequency Band 7 Out of 96 bands at most (FFT size dependent) Numbe of fequency bands 7 Contiguous bands used fo sounding If (Sounding Relevance Flag == 1) { - - Sounding_Relevance 1 - else { - - Reseved 1 Shall be set to zeo if (Sepaability Type == 0) { Cyclic time shift index n 5 Specifies a fequency-domain phase amp to be multiplied to the Golay Sequence as shown in Equation 83. The value of n anges fom 0 to P-1. else { - - 5

6 Decimation Offset d 6 Relative stating offset position fo the fist sounding occupied subcaie in the sounding allocation If (Include additional feedback == 0b01) { - Use same symbol fo additional feedback 1 0 = The additional feedback is sent in the symbol( s) following the allocated sounding symbol. 1 = The additional feedback is sent in the same symbol as the allocated sounding symbol. Reseved 2 Shall be set to zeo else { Reseved 3 Shall be set to zeo. Peiodicity 3 0b000 = Single command, not peiodic, o te-minate peiodicity. Othewise, epeat sounding once pe fames, whee = 2 (n 1), whee n is the decimal equivalent of the peiodicity field. else { - - Pemutation 3 0b000 = PUSC pem 0b001 = FUSC pem 0b010 = Optional FUSC pem 0b011 = PUSC-ASCA 0b100 = TUSC1 0b101 = TUSC2 0b110 = AMC (2x3) 0b111 = Reseved DL_PemBase 6 - Num_Sounding_symbols 3 - fo (i = 0; i < Num_Sounding_symbols; i++){ - - Numbe of CIDs 7 - Reseved 1 Shall be set to zeo. fo (j = 0; j < Numbe of CIDs; j++) { 6

7 Shotened basic CID LSBs of the MS basic CID value If(Sounding_Relevance_Flag == 1){ - - Sounding_Relevance 1 0 = Respond in the fame caying the instuction 1 = Respond in next fame Reseved 3 Shall be set to zeo Subchannel offset 7 The lowest index subchannel used fo caying the bust, stating fom subchannel 0 Powe boost 1 0 = No powe boost 1 = Powe boost Numbe of subchannels 3 The numbe subchannels with subsequent indexes, used to cay the bust. Peiodicity 3 0b000 = Single command, not peiodic, o teminate peiodicity. Othewise, epeat sounding once pe fames, whee = 2 (n 1), whee n is the decimal equivalent of the peiodicity field. Powe Assignment Method 2 0b00 = Equal powe 0b01 = Reseved 0b10 = Intefeence dependent; pe subcaie powe limit 0b11 = Intefeence dependent; total powe limit Padding Vaiable Pad IE to octet bounday. Bits shall be set to 0 [Inset new Section ] Diect Feedback of Tansmit Covaiance Matix If the Include Additional Feedback field is set to 0b11, then the UL Sounding Command IE() enables the MS to pefom diect tansmission of the DL tansmit covaiance matix to the BS along with the UL sounding wavefom. This functionality povides the BS with the tansmit covaiance matix of the DL channel, which the BS can use to pefom closed loop tansmission on the DL (e.g., beamfoming o MIMO+Beamfoming in an STC zone with dedicated pilots ==1). When diect feedback of the tansmit covaiance matix is equested, the sounding command IE will indicate which sounding bands will be occupied by the MS in the elevant sounding symbol of the sounding zone. When the allocation mode is zeo, then the Stat fequency band and numbe of fequency bands indicates a 7

8 ange of contiguous sounding bands that the MS occupies as is done when no additional feedback is equested. Howeve, when the allocation mode is one (sounding band allocations accoding to the Band AMC bitmap), then fo each AMC logical band fo which the bitmap value is set to one, the MS will occupy only the sounding band indicated by the field Sounding Sub-band index within AMC logical subband athe than all fou bands that belong to that AMC logical subband. When using diect feedback of the tansmit covaiance matix, the sounding sepaability type must be set to cyclic shift sepaability. Futhemoe, since only one MS tansmit antenna is used fo feedback of the covaiance matix, the multi-antenna flag is not used and is eplaced with the band-elevance flag as descibed in moe detail below. The fequency domain signal to be tansmitted on an occupied sounding bands is constucted as follows: The MS is fist expected to measue the DL tansmit covaiance matix by fist estimating the multi-antenna downlink channel esponse acoss the signal bandwidth by using fo example the MIMO midamble (Section ) o by using the boadcast pilots tansmitted by the BS in an STC zone with boadcast pilots o by using any othe means of estimating the DL multi-tansmit antenna channel. Because the MIMO midamble and STC zones suppot only up to fou tansmit antennas, the diect feedback of the tansmit covaiance matix is suppoted only fo two and fou BS tansmit antennas. Let the matix H(k) be the M Mt estimate of the downlink channel matix at subcaie k, whee Mt is the numbe of downlink tansmit antennas used by the BS (eithe physical o othewise), and M is the numbe of eceive antennas used by the MS. The Mt Mt DL tansmit covaiance matix R fo a given set of subcaies S(k) is defined to be: R = H k S ( k ) H ( k) H( k) Duing each sounding band assigned to the MS, the MS is expected to tansmit an encoded fom of the tansmit covaiance matix, whee thee ae two possible types of tansmit covaiance matix to be tansmitted depending on the setting of the Band Relevance Flag. If the Band Relevance Flag is set to 0, then the set of subcaies S(k) ove which R is computed using the pevious equation is equal to all usable subcaies of the DL signal bandwidth. If the Band Relevance Flag is set to 1, then the set of subcaies ove which the MS must compute the R is equal to the subcaies contained in that sounding band. The methodology fo encoding the tansmit covaiance matix onto a sounding band is as follows. Fo two tansmit antennas at the BS, the covaiance matix R has the following stuctue: R = Fo fou tansmit antennas at the BS, the covaiance matix R has the following stuctue: R =

9 Once the covaiance matix R to be conveyed on that sounding band is calculated, a scaling facto must be computed. Fo fou BS tansmit antennas, the scale facto is β = ij i= 1 j= i 2 Fo two BS tansmit antennas, the scale facto is 1 β = ij i= 1 j= i 2 Figue NNN shows a sounding band fomat fo use when the BS has two and fou tansmit antennas. The sounding band fomat with diect covaiance matix feedback contains two types of fequency domain symbols: P n and R ij. The symbol P n is equal to the value of the sounding wavefom value fo the n th caie within the sounding band. The symbol R ij is the (i,j) th enty of the R matix scaled by one ove the squae oot of the scale facto β: 1 R ij = ij β As shown in Figue NNN, cetain sounding values that would have odinaily been tansmitted accoding to the settings within the UL Sounding Command IE ae eplaced with scaled analog values of the DL tansmit covaiance matix. 9

10 P 0 P 0 R 11 R 11 P 2 P 2 R 12 R 12 P 4 R 22 R 13 P 5 Legend: P 6 R 14 R ij = i-j th scaled Covaiance Matix enty 18 subcaie sounding band R 11 P 8 R 12 P 10 R 22 P subcaie sounding band P 7 R 22 R 23 P 10 R 24 P 12 P n = Sounding signal value fo the n th caie within the sounding band R 11 R 33 P 14 R 34 R 12 P 15 P 16 R 44 R 22 P 17 2 Tansmit Antennas at BS 4 Tansmit Antennas at BS Figue NNN 18 subcaie sounding band layout fo tansmitting diect covaiance matix feedback. Refeences [1] IEEE P /Co2/D4 Daft Coigendum to IEEE Std , May 22, 2007 [2] WiMAX Foum TM Mobile System Pofile Release 1.0 Appoved Specification (Revision 1.4.0: ). 10