Performance Evaluation of MIMO midamble design for IEEE m IEEE Presentation Submission Template (Rev. 9) Document Number: IEEE C802.16m-09/1237 Date Submitted: Source: Jerry Pi, Jiann-An Tsai, Bruno Clerkx, David Samsung Electronics Venue: Re : m amendment working document Base Contribution: IEEE C802.16m-09/1237 Purpose: To discuss and adopt the proposed text in the revision of the m SDD 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 is located at and. 1

Background AWD, section – “MIMO midamble is used for PMI selection in closed loop MIMO. For OL MIMO, midamble can be used to calculate CQI. The midamble signal occupies the one OFDMA symbol in a DL sub-frame. For the type-1 subframe case, the remaining 5 consecutive symbols form a type-3 subframe. For the type-2 subframe case, the remaining 6 consecutive symbols form a type-1 subframe.” AWD text proposal for detailed MIMO midamble design is provided in C80216m-09_1236 This contribution provides performance evaluation of the MIMO midamble design as in C80216m-09_1236 2

Time domain interlacing Time domain interlacing enables collision avoidance of midamble among neighboring cells – Allow power boosting of midamble to improve channel estimation performance The subframe index for MIMO midamble is explicitly signaled The OFDM symbol index within the subframe is derived from the Cell_ID – MIMO midamble is transmitted on the first OFDM symbol of a subframe if the Cell_ID is even – MIMO midamble is transmitted on the last OFDM symbol of a subframe if the Cell_ID is odd 3

Frequency domain placement Cell-specific frequency domain shift applied – To further minimize collision of midamble among neighboring cells Terminology – i : antenna index, i = 1, …, N T – j : subcarrier index, j = 0, 1, …, 17 – k : Cell_ID – n : Frame index In frame n, midamble for antenna i is transmitted on subcarrier j in cell k – if and only if the following two conditions are met mod(j +  k/2 , 9)  0 mod(mod(j +  k/2 , 9) + 4  mod(n, 2) – 1, 8) = BRO(i – 1, 3) – BRO(x, 3) is the 3-bit bit-reversal value of x Subcarriers not used for midamble transmission are reserved as null subcarriers – The unused power can be allocated to midamble for power boosting – Null subcarriers can be used for interference estimation 4

Properties of the midamble Up to 16 time-domain interlaces to reduce midamble collision Midamble is transmitted once every frame in the same OFDM symbol Midamble for each antenna is regularly spaced in frequency (1 in every 9 subcarriers)  A single midamble channel estimator for all antennas in 2, 4, or 8 Tx cases Midamble in adjacent frames are staggered – Increase the frequency sampling rate to 16 frequency samples per subband per antenna – Improve channel estimation performance by 2-D MMSE channel estimation across frames Midamble among neighboring cells are shifted in frequency – Further minimize midamble collision – Particularly beneficial in TDD system with limited DL subframes for midamble transmission Enable channel estimation to benefit from power boosting – 2Tx : 6.5dB, 4Tx : 3.5dB, 8Tx : 0.5dB – Further midamble boosting possible if low PAPR sequences are designed 5

MIMO midamble for 2Tx systems 6

MIMO midamble for 4Tx systems 7

MIMO midamble for 8Tx systems 8

Performance Evaluation Comparison – Fixed subframe transmission vs. non-fixed subframe transmission – Symbol interlacing vs. Non Symbol interlacing Simulation configuration – System topology: 19 cells / 57 sectors wrap-around – MIMO configuration: (2, 4, or 8) Tx, 2Rx – System bandwidth: 10MHz – Subband size: 4 PRUs – CQI feedback: once per 5ms (all sub-bands) – Rank adaptation: ON – Receiver: LMMSE – Scheduling: Proportional Fair Metric: – System throughput – 5-percentile user throughput 9

10 SLS Results 8TX Midamble Relative Cell Edge Throughput (%) Relative Sector Throughput (%) Full loaded (Non Fixed subframe TX Only) % loaded (Non Fixed subframe TX Only) % loaded (Non Fixed subframe TX Only) % load (Symbol Interlacing Only) % loaded (Non Fixed subframe TX+ Symbol Interlacing)

11 SLS Results 4TX Midamble Relative Cell Edge Throughput (%) Relative Sector Throughput (%) Full loaded (Non Fixed subframe TX Only) % loaded (Non Fixed subframe TX Only) % loaded (Symbol Interlacing Only)

12 SLS Results 2TX Midamble Relative Cell Edge Throughput (%) Relative Sector Throughput (%) Full loaded (Non Fixed subframe TX Only) % loaded (Non Fixed subframe TX Only) % loaded (Symbol Interlacing Only)

Summary Both schemes of non-fixed subframe transmission and symbol interlacing provide significant system gain over fixed subframe/fixed symbol transmission As shown, gain is particularly significant for light- loaded system As observed, the improvement on cell edge throughput is substantial as compared to sector throughput Recommendation – TGm adopt the text proposal in C80216m-09_1236 into AWD 13