P-SFH Code Rate
Document Number: IEEE C80216m-09/0959
Date Submitted: 2009-4-27
Source:
Debdeep Chatterjee, Yi Hsuan, Hujun Yin Email: {[email protected], [email protected], [email protected]}
Intel Corporation
Venue:
IEEE Session #61, Cairo, Egypt.
Re: AWD comments / Area: Chapter 15.3.6 (DL-CTRL), “Comments on AWD 15.3.6 DL-CTRL”
Base Contribution:
N/A
Purpose:
For TGm discussion and adoption of 802.16m AWD text.
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1
Super Frame Header (SFH) Performance Requirements
• SFH is to be deployed in reuse 1 mode
• Coverage requirements:
– 95% coverage at a PER of at most 1%
• For baseline cell size of 1.5km ISD:
– Need to achieve 1% PER at an SINR as low as -3.7dB
• For larger cell size of 5km cell-radius:
– Need to achieve 1% PER at an SINR as low as -6dB
2
Simulation Parameters
Total available bandwidth
5 MHz (512 subcarriers)
Carrier Frequency
2.5GHz
Number of OFDM symbols per subframe
5
Number of information bits
48
Number of total RU in one subframe
24
Number of Antennas
2 transmitter antennas, 2 receiver antennas [2Tx,2Rx]
MIMO mode
2x2 SFBC
Tone selection
Fully distributed (uniformly) over the entire band in units of tone-pairs (SFBC)
Modulation/Coding
QPSK, rate ¼ TBCC with different repetitions in the frequency domain
MIMO Receiver
MMSE
Traffic model
eITU-PedB 3 km/h
eITU-VehA 120 km/h
Channel estimation
2-D MMSE channel estimator with estimation window sizes of 1 and 3 PRUs
Scenarios
Noise-limited (NL): SIR = Inf
Interference-limited (IL): INR = 10dB
Number of Interferers
3
3
Pilot Patterns, Channel Estimation,
and Receiver Structures
• SFBC, two stream pilot pattern, as in SDD. Each antenna boosts its
pilot tone by 5dB.
• Interlaced pilot pattern used for scenarios with interference
• The MMSE receiver (Rx.) with colored noise consideration (MMSECNC) is used instead of the MMSE Rx. with white noise assumption
(MMSE-WNA)
• Since a separate 5MHz bandwidth is allocated to SFH, wideband
channel estimation over 3 PRUs is also considered to improve
channel estimation performance
4
The MMSE-CNC Receiver (1/2)
• MMSE receiver that estimates the noise + interference power from
the pilot tones and performs MMSE detection/equalization with
colored noise consideration
• Perfect knowledge of SINR at the receiver is not assumed. The
receiver estimates the noise power from the pilots
– Causes some degradation in the noise-limited performance, but
this is more realistic
• The MMSE equalization is performed using the estimated noise
covariance matrix (that may be colored in the presence of
interference), instead of the white noise assumption (for which the
noise covariance matrix is diagonal)
– Improves the BLER performance in interference-limited
scenarios
5
The MMSE-CNC Receiver (2/2)
•
Received symbol:
•
Noise covariance estimated from the pilots averaged over a particular PRU
(or over 3 PRUs when wideband channel estimation is supported):
•
For a particular data tone
is
•
Proceed with the standard MMSE detection/equalization with
covariance matrix for data tone
, the estimated noise covariance matrix
as the noise
6
Noise-Limited (NL): MMSE-WNA Rx, 1-PRU Ch. Est.
7
NL: MMSE-WNA Rx, 3-PRU Ch. Est.
8
NL: MMSE-CNC Rx, 1-PRU Ch. Est.
9
NL: MMSE-CNC Rx, 3-PRU Ch. Est.
10
Interference-Limited (IL) Model
• Interference-limited (IL):
– INR = 10dB
– Division of powers between the 3 interferers: 37.5%, 37.5%, and 25%
respectively (heuristic)
– This division of interference power implies:
Path loss for the 3 interferers w.r.t. the 1st interferer: 0dB, 0dB, -1.7dB
11
IL: Interlaced Pilots, MMSE-WNA Rx, 1-PRU Ch.Est.
12
IL: Interlaced Pilots, MMSE-WNA Rx, 3-PRU Ch.Est.
13
IL: Interlaced Pilots, MMSE-CNC Rx, 1-PRU Ch.Est.
14
IL: Interlaced Pilots, MMSE-CNC Rx, 3-PRU Ch.Est.
15
Summary and Conclusion
• In general, 3-PRU channel estimation (CE) provides 1~1.5dB gain over 1-PRU
CE
• For 3-PRU CE, the MMSE-CNC Rx results in approximately 0.3~0.4dB
degradation in BLER performance when compared to perfect SNR at the
receiver for NL scenarios (cf. slides 8, and 10)
• For 3-PRU CE, the MMSE-CNC Rx provides gains of about 1.75~2.25dB over
the MMSE-WNA Rx for IL scenarios (cf. slides 13 and 15)
• Using the MMSE-CNC Rx with 3-PRU CE, 6 repetitions (with QPSK and ¼
TBCC) would be sufficient to meet the requirements for SFH, with margins of
0.75dB and 1.0~1.5dB for NL and IL scenarios respectively  Effective code
rate = 1/24
• Capacity analysis:
–
# of data tones available per LRU = 80
–
# of SFH bits possible using MMSE-WNA Rx = (24 LRUs)*80 *2/48 = 80 [Need
12 repetitions + QPSK ¼ => 1.2dB margin for scenarios with interference]
–
# of SFH bits possible using MMSE-CNC Rx = (24 LRUs)*80 *2/24 = 160
16
Proposed AWD Text Change:
Replace the following sentence on page 51, line 62 of 15.3.6.3.1.1
“The encoded sequences shall be repeated NRep,P-SFH times.”
with
“The encoded sequences shall be repeated NRep,P-SFH times to effective
code rate of 1/24.”
17