Supplementary Channel for Talk-around Direct Communications
Document Number:
IEEE S802.16n-11/0154
Date Submitted:
2011-09-20
Source:
Jihoon Choi, Young-Ho Jung
Korea Aerospace University
E-mail: jihoon@kau.ac.kr,
yhjung@kau.ac.kr
Sungcheol Chang, Seokki Kim, Eunkyung Kim, Miyoung Yun, Won-Ik Kim,
Sungkyung Kim, Hyun Lee, Chulsik Yoon, Kwangjae Lim
ETRI
E-mail: scchang@etri.re.kr
Re:
Call for comments on the 802.16n AWD
Base Contribution:
IEEE C802.16n-11/0154
Purpose:
To be discussed and adopted by 802.16 TGn
Notice:
This document does not represent the agreed views of the IEEE 802.16 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.
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Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.
Introduction
• Frame structure for TDC (talk-around direct communication)
– Sync-CH (synchronization channel)
– Ded-CH (dedicated channel)
– Sup-CH (supplementary channel).
Super frame
Super frame
CDMZ
• Sup-CH
Super frame
CDMZ
CDMZ
Slot 1
mRB
3-1
mRB
2-2
mRB
3-2
mRB
2-3
mRB
3-3
mRB
2-4
mRB
3-4
mRB
2-5
mRB
3-5
mRB
2-6
mRB
3-6
mRB
2-7
mRB
3-7
mRB
2-8
mRB
3-8
mRB
2-9
mRB
3-9
mRB
2-10
mRB
3-10
mRB
2-11
mRB
3-11
mRB
2-12
mRB
3-12
m-tile 1
m-tile 2
m-tile 3
m-tile 4
m-tile 5
m-tile 6
m-tile 7
m-tile 8
m-tile 9
m-tile 10
m-tile 11
m-tile 12
m-tile 13
m-tile 14
m-tile 15
m-tile 16
m-tile 17
m-tile 18
m-tile 19
m-tile 20
m-tile 21
m-tile 22
m-tile 23
m-tile 24
m-tile 25
m-tile 26
m-tile 27
m-tile 28
m-tile 29
m-tile 30
m-tile 31
m-tile 32
m-tile 33
m-tile 34
m-tile 35
m-tile 36
mRB
5-1
mRB
6-1
mRB
5-2
mRB
6-2
mRB
5-3
mRB
6-3
mRB
5-4
mRB
6-4
mRB
5-5
mRB
6-5
mRB
5-6
mRB
6-6
mRB
5-7
mRB
6-7
mRB
5-8
mRB
6-8
mRB
5-9
mRB
6-9
mRB
5-10
mRB
6-10
mRB
5-11
mRB
6-11
mRB
5-12
mRB
6-12
subframe
time
frequency
mRB
2-1
Slot 2
…
mRB (mini-resource block)
time
frequency
Sync-CH_message
Sync-CH_sequence
– Ranging channel
– CQI (channel quality indicator)
– Feedback channel
CDMZ
m-tile (mini-tile)
2
Sup-CH Structure
time
• Resource elements for Sup-CH
– One m-tile (mini-tile) is a (5 OFDM symbols)  (2 subcarriers) rectangular region.
– One Sup-SubCH (supplementary subchannel) is
composed of 4 distributed m-tiles (mini-tiles).
• Relationship between Ded-CH and Sup-CH
– One-to-one mapping between Ded-SubCH (dedicated
subchannel) and Sup-SubCH.
– Each slot supports up to 9 Sup-SubCHs (also supports
up to 9 Ded-SubCHs).
– Example
OFDM symbol
frequency
mini-tile
subcarrier
 5th Sup-SubCH is composed of m-tiles 5,14,23, and 32.
3
Ranging Channel Structure
• Ranging channel
– Estimation of time offset, frequency offset, SINR
(signal to interference plus noise ratio), etc.
– Periodically transmitted, where the starting slot
number and the period are determined during link
initialization.
• Sequence allocation for ranging channel
– The ranging sequence is defined by a binary
code
with length 8, given by
[S0 S1 S2 S3 S4 S5 S6 S7] = [1,-1, -1,1, -1,1, 1,-1]
– The same sequence is repeatedly transmitted for
5 OFDM symbols.
time
frequency
S0
S0
S0
S0
S0
S1
S1
S1
S1
S1
S2
S2
S2
S2
S2
S3
S3
S3
S3
S3
S4
S4
S4
S4
S4
S5
S5
S5
S5
S5
S6
S6
S6
S6
S6
S7
S7
S7
S7
S7
4
CQI Channel Structure
• CQI channel
time
– Used for feedback of measured channel quality
such as SINR or MCS level.
– One CQI channel payload carries up to 4-bit
information.
C0,0 C0,2 C0,4 C0,6 C0,8
frequency
C0,1 C0,3 C0,5 C0,7 C0,9
C1,0 C1,2 C1,4 C1,6 C1,8
• Mapping of information in the CQI channel
C1,1 C1,3 C1,5 C1,7 C1,9
CQI
payload
Sequence
generation
Modulation
(& repetition)
Symbol sequence to
subcarrier mapping
– Sequence generation
CQI
channel
symbol
C2,0 C2,2 C2,4 C2,6 C2,8
C2,1 C2,3 C2,5 C2,7 C2,9
 See the following slide.
– BPSK modulation
 0 mapped to +1 and 1 mapped to -1
C3,0 C3,2 C3,4 C3,6 C3,8
C3,1 C3,3 C3,5 C3,7 C3,9
– Symbol sequence to subcarrier mapping
 See the right figure.
5
CQI Sequence Generation
• Sequence mapping table for CQI channel
Index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Sequence
1111111111
0010110001
0100100110
1001101000
1011000100
0110001010
0000011101
1101010011
1100011000
0001010110
0111000001
1010001111
1000100011
0101101101
0011111010
1110110100
Usage
level 0
level 1
level 2
level 3
level 4
level 5
level 6
level 7
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
• Sequence permutation
Ci , j  s[ K i [ j ]], for i  0,1, 2,3, 0  j  9
where K0  {0,1, 2,3, 4,5, 6, 7,8,9}
K1  {2,3, 4, 6, 7,8,9, 0,1,5}
K2  {8,9, 2,3, 4,5,6,7,0,1}
K3  {5, 6, 7,8,9, 0,1, 2,3, 4}
6
CQI Transmission
• CQI channel
– Periodically transmitted, where the starting slot number and the period are
determined during link initialization.
– The ranging channel and the CQI channel should be assigned to separate time
slots by adjusting the starting slot number and the transmission period.
• CQI payload
– The AMS estimates the SINR using the Ded-CH preamble and the pilot symbols
included in the Ded-CH.
– The CQI index is determined using the estimated SINR.
• Property of CQI sequences
– Correlation between CQI sequences is minimized for non-coherent detection.
– CQI sequences are designed to have small correlation with the ranging
sequence.
 Using this property, an AMS without knowledge of CQI transmission slots can separate
the ranging channel and the CQI channel.
7
Feedback Channel Structure
• Feedback channel
– Uses the same sequences as the CQI channel.
– Includes the following control signals.
 ACK channel, NAK channels
 MCS Change Confirm: a response message to the MCS Change Command
 RCHG (resource change) indication: a response message to the RCHG Command
– Transmitted using the slots which are not used by the ranging channel and the
CQI channel.
• Sequence mapping
Index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Sequence
1111111111
0010110001
0100100110
1001101000
1011000100
0110001010
0000011101
1101010011
1100011000
0001010110
0111000001
1010001111
1000100011
0101101101
0011111010
1110110100
Usage
ACK
NAK for frame 0
NAK for frame 1
NAK for frame 2
NAK for frame 3
MCS Change Confirm
RCHG Indication
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
8
Simulation Results
9
S k0
Simulation Environments
•
Parameters
Parameter
Carrier frequency
Bandwidth
FFT size
CP size
Sampling rate
Number of transmit antennas
Number of receive antennas
Velocity of transmitter
Velocity of receiver
Moving direction of transmitter
Moving direction of receiver
Timing offset
Normalized frequency offset
Fading channel
Value
2.3 GHz
10 MHz
1024
128
11.2 MHz
1
1
30 km/h
30 km/h
/6
-/4
16 samples
0.02
Bad Urban Macro NLOS of 16m EMD
(modified for TDC)
• Estimation and detection
– Using the ranging channel, the time and frequency offsets were estimated in the
frequency domain.
– For the CQI and feedback channels, non-coherent detection was used.
10
Ranging Channel
•
Requirements
–
•
Performance
–
10
10
When SNR = 5 dB, the requirements can be satisfied by accumulating more than 30 ranging
channels.
4
10
3
MSE (Freq Offset)
MSE (Time Offset)
10
MSE (time offset) < 100, MSE (freq offset) < 4.4x10-5
2
1 ranging channel
3 ranging channels
5 ranging channels
10
1
0
5
10
SNR (dB)
15
20
-1
10
-2
10
-3
10
-4
10
-5
10
-6
-10
1 ranging channel
3 ranging channels
5 ranging channels
5 ranging channels (no offset)
-5
0
5
SNR (dB)
10
20
15
11
Sequences for CQI and Feedback Channels
• Sequences for 6-bit, 5-bit, 3-bit payload
Index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Sequence
1111111111
1010101111
1100111110
1001101110
1111001111
1010011111
1100001110
1001011110
1111110110
1010100110
1100110111
1001100111
1111000110
1010010110
1100000111
1001010111
1111111010
1010101010
1100111011
1001101011
1111001010
1010011010
1100001011
1001011011
1111110011
1010100011
1100110010
1001100010
1111000011
1010010011
1100000010
1001010010
Index
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
Sequence
1111111100
1010101100
1100111101
1001101101
1111001100
1010011100
1100001101
1001011101
1111110101
1010100101
1100110100
1001100100
1111000101
1010010101
1100000100
1001010100
1111111001
1010101001
1100111000
1001101000
1111001001
1010011001
1100001000
1001011000
1111110000
1010100000
1100110001
1001100001
1111000000
1010010000
1100000001
1001010001
Index
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Sequence
1111111111
1010111101
1100111110
1001111100
1111010101
1010010111
1100010100
1001010110
1111100110
1010100100
1100100111
1001100101
1111001100
1010001110
1100001101
1001001111
Index
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Sequence
1111111000
1010111010
1100111001
1001111011
1111010010
1010010000
1100010011
1001010001
1111100001
1010100011
1100100000
1001100010
1111001011
1010001001
1100001010
1001001000
Index
0
1
2
3
Sequence
1111111111
1010101010
1100110001
1001100100
Index
4
5
6
7
Sequence
1111000011
1010010110
1100001101
1001011000
12
Simulation Results – CQI and Feedback
10
0
10
-1
10
-2
10
-3
10
-4
-7
• Fading channel
0
10
-1
10
BLER
BLER
• AWGN
Sup-CH 6bits
Sup-CH 5bits
Sup-CH 4bits
Sup-CH 3bits
16m CQI 6bits
-6
-5
-4
-2
10
-3
10
Sup-CH 6bits
Sup-CH 5bits
Sup-CH 4bits
Sup-CH 3bits
16m CQI 6bits
-4
-3
-2
SNR (dB)
-1
0
1
10
-7
-6
-5
-4
-3
-2
-1
SNR (dB)
0
1
2
3
– Considering the power spectral density, the Sup-CH requires 1.25 dB gain to
achieve the same coverage as 802.16m PFBCH.
– The Sup-CH with 4-bit payload has slightly better coverage than 16m PFBCH.
13
Conclusion
• Ranging channel
– Only 8 subcarriers are used for the channel channel in TDC, while 72 subcarriers
are used for the ranging channel in 802.16m.
– The ranging period needs to be shortened.
 For example, when the ranging period is 100 ms, the adjustment of time and frequency
requires about 3 sec.
• CQI and feedback channel
– When the 4-bit payload is used, the CQI and feedback channels for TDC perform
comparable to 802.16m PFBCH.
• Note
– The performance can be improved by
 Using more transmit and receive antennas
 Employing more elegant estimation algorithms or detection schemes.
14