Evaluation on Subcarrier Permutation Document Number: IEEE C802.16m-09/0318 Date Submitted: Source: HanGyu Cho, Seunghyun Kang, Sunam Kim, Jin Sam Kwak {hgcho, sh_kang, snkim86, LG Electronics Venue: IEEE C802.16m-08/053 “Call for Comments and Contributions on Project m Amendment Working Document ” Purpose: To provide details on subband partitioning to be approved by TGm and adopted in the Amendment Working Document Notice: This document does not represent the agreed views of the IEEE Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE Patent Policy : The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and. Further information located at and.

Motivation In the current IEEE m Amendment Working Document (IEEE m-08/050), the subband permutation rule in the section is TBD In the document C80216m-08_1508, there are many subcarrier permutation rules proposed by many companies This contribution reviews those rules and suggests a subcarrier permutation rule based on some simulation results.

Evaluation Criteria for subcarrier permutation System level simulation desirable to show the combined effect of diversity gain and interference-averaging (hit ratio) But, difficult to compare the different subcarrier permutation rules (performance gap is not remarkable) Based on our internal simulation results (which is not shown here), all the performances are almost the same (when considering full-loading. Partial loading will be considered later.) We don ’ t show SLS simulation results here Link level simulation To show only the diversity gain for distributed LRU We show LLS simulation results here Hit ratio To check the interference averaging effect of distributed LRU We show hit ratio results here

Proposals from companies Compare LGE, Intel, Samsung firstly NSN  will be added later (difficult to simulate due to virtual DRU concept) ITRI and ZTE proposed the same permutation equation with Intel, but with different permutation sequences. We used the subcarrier permutation rules shown in C80216m-08_1508 or its latest version. pair(s,m,l,t)= L DRU, FPi *f(m,s)+g(PermSeq(),s,m,l,t ), l = 0, 1,…, Nsym

Proposals from companies For comparison, we simulated two schemes for LGE LGE_proposed (cell-specific symbol shift) where LGE_compared (cell-common symbol shift) The only difference is

Proposals from companies Intel PermSeq is the sequence of length L DRU, FPi specified in Table Samsung PermSeq is the sequence of length LDRU,FPi and is determined by SEED = {(IDcell+1024*t)* } mod 2 20 and the permutation sequence generation algorithm specified in C80216m-08_1508

Simulation Environment: LLS MIMO mode SFBC Antenna configuration 2 Tx antennas with zero correlation (4 wavelengths) 2 Rx antennas Channel PedB 3Km/h System BW 5MHz 4,8,24 DRUs are equi-distantly chosen from the total 24 PRUs – Plot CDF of all SNRs measured at all DRUs like in C80216m- 08_1445r1 (Intel) Perfect channel estimation TX SNR per subcarrier per Antenna: 7dB

Simulation Results: LLS Case 1) 4 DRU CDF SNR (dB)

Simulation Results: LLS Case 2) 8 DRU CDF SNR (dB)

Simulation Results: LLS Case 3) 24 DRU CDF SNR (dB)

Simulation Results: LLS Same performance between LGE/Intel/Samsung 10% outage SNR in each CDF graph are the same (small difference within the simulation error) We don’t see large difference in terms of diversity (LLS) Hit ratio simulation is necessary LGEIntelSamsung 4 DRU (dB) DRU DRU No perm

Simulation Environment: Hit ratio Case 1) For choose(512,2)= cell pairs, For each cell pair, there are N DRU * N DRU sub-channel pairs, Hit Number: the number of same subcarrier-pairs for each sub-channel pair Average Hit Number: hit statistic over cell pairs % of total hits: (Average Hit Number) / ( N DRU * N DRU ) * 100% Case 2) For choose(N DRU, 2) cell pairs, For each cell pair, there are N DRU * N DRU sub-channel pairs, Hit Number: the number of same subcarrier-pairs for each sub-channel pair Average Hit Number: hit statistic over choose(N DRU, 2) cell pairs % of total hits: (Average Hit Number) / ( N DRU * N DRU ) * 100% BW10MHz #Cell ID512 Distributed LRU 48 subcarrier-pairs (excluding pilot subcarriers for 2Tx streams) N DRU varying

Simulation Results: Hit ratio For case 1, “ LGE_proposed ” reduces the larger hit ratios remarkably % of total hits adding from 24 hits to 48 hits Refer to the following excel file N DRU LGEIntelSamsung 414.6%31.3%23.7% 81.2%1.5%5.1% 120.2%1.0%2.6% 160.1%4.9%1.0% %0.2%0.6% %0.04%0.12%

Simulation Results: Hit ratio For case 2, Difficult to say which one is the best Refer to the following excel file

Conclusions In terms of LLS, there is no large difference between different proposals The diversity gain is almost the same among the proposals LGE ’ s proposal reduces larger hit ratio due to cell- specific symbol shift Good interference averaging effect

Proposed Text Discuss and adopt the subcarrier permutation formula proposed by LGE in IEEE C802.16m-08/1508r1