SFH PHY Structure for IEEE m Amendment Document Number: IEEE C802.16m-09/0977r2 Date Submitted: Source: Pei-Kai Liao Chih-Yuan Lin Yih-Shen Chen, Paul MediaTek Inc. Venue: Category: AWD comments / Area: Chapter (DL-CTRL) “Comments on AWD DL-CTRL” Base Contribution: This is base contribution. Purpose: Propose to be discussed and adopted by TGm for IEEE m Amendment. 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.

FR-1 + Interlaced Pilot Pattern + Frequency-domain Repetitions  FR-1+ interlaced pilot pattern + frequency-domain repetitions  Pilot power boosting, a = 5 dB  Claims: Common structure to both DL data channel and control channel so that same receiver design can be shared Using MMSE receiver can achieve system requirement under code rate 1/24 (1/4 TBCC + 6 repetitions) Capacity for SFH  160 bits, if 24 PRUs are considered (24*80*2/24)  133 bits, if 20 PRUs are considered (20*80*2/24)

Interlaced Pilot Patterns

MMSE Receiver  Received signal model:  MMSE receiver Signal Part Color Noise White Noise

Interference Model Assumption: 6 Cells  Interfered environment One serving BS Five interfering BSs  Two are first-tier and three are second-tier  Since FR = 1, BCH messages of three BS collide at cell-edge MS Serving BS interfering BS 1 interfering BS 2 interfering BS 3 interfering BS 4 interfering BS 5 Pilot pattern 1 Pilot pattern 2 Pilot pattern 3 Pilot pattern 1 Pilot pattern 2 Pilot pattern 3

Analysis of Interference Covariance Estimation (1/3)  Received signal model of data tones All are data tones  Interference covariance of data tones

Analysis of Interference Covariance Estimation (2/3)  Received signal model of pilot pattern 1 Some are data tones; some are pilot tones  Interference covariance of pilot pattern 1

Analysis of Interference Covariance Estimation (3/3)  The interference covariance of data tones is different from that of pilot tones due to pilot power boosting  Therefore, the interference covariance estimated by pilot tones can not be used for data tones  It can only measure 2 nd tier interferences, especially for cases with large pilot power boosting

Remarks  Pros: Common structure to both DL data channel and control channel so that same receiver design can be shared More data tones per PRU  Cons: Different data mappings among different cells Data-to-pilot collision induces large channel estimation error and more bit errors in data channel so it may take more frequency-domain repetitions to achieve system requirement Higher pilot power boosting results in higher PAPR in time domain and thus reduce the coverage of data tones Interference covariance estimated by pilot tones is different from that of data tones  It can only measure 2 nd tier interferences, especially for cases with large pilot power boosting  No optimal receiver for the transmission scheme of FR-1 + interlaced pilot pattern + frequency-domain repetitions  Requires more frequency-domain repetitions to compensate performance loss

MediaTek’s Proposal  FR-1 + interlaced pilot pattern + tone nulling + Frequency- domain repetitions  Pilot power boosting, a = 3 or 5 dB [TBD]  Claims: There is no data-to-pilot collision so that high accuracy of channel estimation can be achieved even under low SIR Lower pilot power boosting (ex. 3 dB) can be applied for reduced PAPR and thus increase the coverage of data tones 1/16 (1/2 CTC + 8 repetitions) can achieve similar performance as that of 1/24 using interlaced pilot pattern only Capacity for SFH  180 bits, if 24 PRUs are considered (24*60*2/16)  150 bits, if 20 PRUs are considered (20*60*2/16) Flexibility for system upgrading due to higher SFH capacity

Proposed SFH PHY Structure for One PRU

Proposed MMSE Receiver (1/2)  Received signal model  Proposed optimal MMSE Receiver Signal PartColor Noise White Noise Interference Part

Proposed MMSE Receiver (2/2)  Proposed suboptimal MMSE Receiver Only first-tier interferences are considered and other interferences are considered as white noise or neglected

Interference Model Assumption: 6 Cells  Interfered environment One serving BS Five interfering BSs  Two are first-tier and three are second-tier  Since FR = 1, BCH messages of three BS collide at cell-edge MS Serving BS interfering BS 1 interfering BS 2 interfering BS 3 interfering BS 4 interfering BS 5 Pilot pattern 1 Pilot pattern 2 Pilot pattern 3 Pilot pattern 1 Pilot pattern 2 Pilot pattern 3

Analysis of Interference Covariance Estimation (1/5)  Received signal model of data tones All are data tones  Interference covariance of data tones

Analysis of Interference Covariance Estimation (2/5)  Received signal model of pilot pattern 1 All are pilot tones of pilot pattern 1  Interference covariance of pilot pattern 1

Analysis of Interference Covariance Estimation (3/5)  Received signal model of pilot pattern 2 All are pilot tones of pilot pattern 2  Interference covariance of pilot pattern 2

Analysis of Interference Covariance Estimation (4/5)  Received signal model of pilot pattern 3 All are pilot tones of pilot pattern 3  Interference covariance of pilot pattern 3

Analysis of Interference Covariance Estimation (5/5)  The covariance matrix of each single pilot pattern is different from that of data tones  However, the sum of these covariance matrices can be used for covariance matrix calculation for data tones

Issues of Proposed Receiver Scheme  If PRBS sequence is applied to pilot tones, how does AMS know the PRBS sequences of the other two pilot patterns? SFH is decoded immediately after synchronization This information can be obtained from SA-Preamble by knowing cell ID if the PRBS sequence assignment depends cell ID Since three interlaced pilot patterns align with three segments of SA-Preamble, there is no problem for an AMS to obtain this information by SA-Preamble

Remarks  Pros: Same data mappings among all cells There is no data-to-pilot collision so that accurate channel estimation can be achieved and the bit errors in data channel can be reduced so it may take less repetitions to achieve system requirement Flexibility to system upgrade by reserving more SFH bits Lower pilot power boosting can be applied and thus increase the coverage of data tones Accurate interference covariance estimation can be obtained  There is an optimal receiver for the transmission scheme of FR-1 + interlaced pilot pattern + tone nulling + frequency-domain repetitions  Requires less frequency-domain repetitions to achieve the same performance  Cons: No common structure to both DL data channel and control channel so that the receiver design for SFH may be different from data channel Less data tones per PRU

Simulation Parameters  2x2 MIMO SFBC system with 512-size FFT  Modulation/coding: QPSK ½ + 6, 8 or 12 repetitions  Optimal whole-band MMSE-based combing  Channel model: VA 120  2D MMSE channel estimator PRU-based channel estimation  2-PRU CE window for interlaced pilot pattern  1-PRU CE window for interlaced pilot pattern + tone nulling  Pilot power boosting: 5 dB  Noise level: INR = 10 dB  Interference limited environment 3-cell case: interference ratio: 0.5:0.5  1 serving BS, two interferers 6-cell case: interference power ratio: 0.35 : 0.35 : 0.1 : 0.1 : 0.1  1 serving BS, five interferers

Interference Scenarios  Interfered environment 3-cell case  One serving BS  Two interfering BSs 6-cell case  One serving BS  Five interfering BSs  Since FR = 1, SFH messages of three BS collide at cell-edge MS  All pilot values are assumed to be 1 x power boosting level, no PRBS sequence applied

Receiver Scheme for Simulation  Sub-optimal MMSE-CNC Receiver Only first-tier interferences are considered and other interferences are considered as white noise or neglected Imperfect interference covariance estimation may result in performance loss

Simulation Results (1/2)  3-cell case: VA 120 channel model (INR = 10 dB) For interlaced only structure, 2-PRU CE window is used, but only 1-PRU CE window is used for interlaced nulltone structure

Simulation Results (2/2)  6-cell case: VA 120 channel model (INR = 10 dB) For interlaced only structure, 2-PRU CE window is used, but only 1-PRU CE window is used for interlaced nulltone structure Suboptimal receiver; perfect channel information Suboptimal receiver; imperfect channel information

Simulation Results (2/2)  6-cell case: VA 120 channel model (INR = 10 dB) For both structures, 3-PRU CE window is used and 3 binary random sequences to mask pilots of 3 second-tier BSs

Conclusion  MMSE receiver with wrong interference covariance estimation results in large performance loss Interference covariance can’t be estimated correctly using pilot tones if only interlaced pilot pattern is applied  Due to data-to-pilot collision, interlaced pilot pattern also has large performance loss in channel estimation, compared to MediaTek’s proposal  Due to pilot-to-data collision, there are also more bit errors caused by pilot interference  Same performance can be achieved by MediaTek’s proposal with less number of frequency-domain repetitions, compared to interlaced pilot pattern MediaTek’s proposal requires 1/16 code rate (1/2 CTC+8 repetitions) to provide capacity of 180 bits at most Interlaced pilot pattern requires 1/24 code rate (1/2 CTC+12 repetitions) to provide capacity of 160 bits at most  It requires 1/16 code rate only to achieve 1% PER below SIR = -3 dB  It is recommended to adopt MediaTek’s proposal for FR-1 SFH PHY structure design with code rate 1/16

Text Proposal (1/3) [Add the following text into the TGm AWD ] Start of the Text Superframe Header ………………………… The PHY structure of a PRU for resource allocation of the SFH is described in Figure X Section >. The SFH is transmitted within a predefined frequency partition called the SFH frequency partition. The SFH frequency partition consists of N PRU, SFH PRUs within a 5 MHz physical bandwidth. The PRUs in the SFH frequency partition uses the 2-stream pilot pattern defined in >. The PRUs in the SFH frequency partition are permuted to generate N PRU, SFH distributed LRUs.

Text Proposal (2/3) (a) Stream one

Text Proposal (3/3) (b) Stream Two Figure X — PHY Structure of a PRU in SFH End of the Text