Proposed Randomization for 16m
Document Number: S80216m-09/1415
Date Submitted: 2009-07-07
Source:
Changlong Xu, Tom Harel, Huaning Niu, Jong-Kae Fwu, Yang-Seok Choi, Hujun Yin
Intel Corporation
Venue:
IEEE Session #62, San Francisco, US.
Re:
Base Contribution:
N/A
Purpose:
To be discussed and adopted by TGm for the 802.16m amendment.
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1
Outline
• Data randomization and subcarrier randomization in 16e
• Data randomization in current AWD text
• Proposed randomization
• Summary
2
1. Data randomizer and subcarrier
randomizer in 16e
Subcarrier
randomizer
Data to
transmit in
PHY burst
Randomizer
(8.4.9.1)
FEC
(8.4.9.2)
Bit-interleaver
(8.4.9.3)
Repetition
(8.4.9.5)
Modulation
(8.4.9.4)
Mapping to
OFDMA
subchannels
Figure 1 Channel coding process for regular and repetition coding transmission
3
1.1 Data randomizer
LSB
MSB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
data out
data in
• Generator polynomial 1 + x14+x15
• Initial Vector [LSB] 0 1 1 0 1 1 1 0 0 0 1 0 1 0 1 [MSB] –Each FEC block
• Function Avoiding long runs of bit that are bad for modulator
Example, long runs of 1’s, coming from the data source or padding,
generate the peak amplitude of 64 QAM modulator consumes 3.7dB
higher power than the average.
4
1.2 Subcarrier Randomizer
LSB
1
MSB
2
3
4
5
6
7
8
9 10 11
wk
•
•
Generator polynomial 1 + x14+ x15
Initial Vector - Each sub-frame
– b0 .. b4 5 LSB of IDcell
– b5,b6 the segment number + 1
– b7..b10 0b1111 for downlink; four least significant bits of the Frame
number in the uplink.
•
Function
– Randomize the interference between different cells
– Avoid exact repetition of QAM symbol. Repetition within an OFDM
symbol causes high PAPR and repetitive interference.
5
2. Data randomization in current AWD text
Subcarrier
randomizer
Necessary
Burst
CRC
encoder
Data
Randomizer
Burst
partition
FEC
block
CRC
encoder
FEC
encoder
Bit selection
&
Repetition
Collection
Modulation
Figure 2 Channel coding procedure in current AWD text
Problem:
Data Randomize is same as that in 16e. Thus, subcarrier randomizer is necessary.
Solution:
1.
Adding subcarrier randomizer
2.
Proposed algorithm
6
3. Proposed randomization
Move randomizer to the position before the modulation
Burst
CRC
encoder
Data
Randomizer
Burst
partition
FEC
block
CRC
encoder
FEC
encoder
Bit selection
&
Repetition
Collection
Modulation
7
Parameters for proposed randomization
LSB
1
MSB
2
3
4
Data in
5
6
. . .
18 19 20 21 22 23
Data out
•
Generator polynomial 1 + x18+x23
•
Initial Vector
b13 … b22 IDcell
b12
1
b0 … b11 STID
Reset the seed for each burst
8
Summary
• Proposed a new randomizer instead of the original one in current
AWD
• Merit of the proposed randomizer
– Low complexity (one randomizer instead of the two randomizer in 16e)
– Good performance
• Randomize the interference between adjacent cell
• Avoid exact repetition of QAM symbol
• Avoiding long runs of bit
9
10