1. Considerations on Subframe MAP Design
IEEE Presentation Submission Template (Rev. 9)
Document Number:
IEEE S802.16m-08/493
Date Submitted:
Source:
Youngsoo Yuk
Kiseon Ryu
Ronny (Yong-Ho) Kim
LG Electronics
*<
Venue:
(Macau, China, May 2008)
Base Contribution:
IEEE C802.16m-08/493
Purpose:
Discussion
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2. Overall Downlink Control Structure
Superframe
Header
PBCH
SBCH
SCH
Superframe (20ms)
Subframe MAP
BSD
BSDI
Frame (5ms)
Data
for UL Grant
PBCH : Network-wide common (Type 2a)
SBCH : Sector-specific (Type 2b)
BSD : Remaining essential (Type 2c),Extended SCI (Type 3)
Note : The period of SCH is TBD (pending #55 meeting)

3. Design Considerations on Subframe MAP
Multiplexing Scheme
TDM vs. FDM vs. Hybrid TDM/FDM
Transmission Scheme
Separate Coding vs. Joint Coding
Rate Control vs. Power Control

4. Multiplexing Comparison
TDM
FDM
Advantages
Short feedback delay
MS power saving with microsleep
Simple separation of data & control region especially on MBS subframe
Low MS complexity with small required buffer size
High frequency diversity
Frequency selective allocation gain
High granularity of the ratio between the control channel and the data channel
Relatively low unused subcarriers.
Better MAP coverage by power sharing with the data channel
Drawbacks
Low granularity of the ratio between the control channel and the data channel
Coverage/throughput loss due to large unused subcarriers
Relative long feedback latency (upto 1ms)
Large required buffer size for MS
Cannot apply microsleep
Selectivity loss for localized subchannel comes from pre-allocated control RB
Hard to achieve frequency selective gain
Low MS Complexity
Power Saving
Relatively Low Latency
Simple Control/Planning
Localized/Diversity allocation
High granularity
Power balancing
Better Coverage

5. Problem of FDM Processing Delay Feedback Latency (a) TDM (b) FDM
MAP
Decoding
FFT
Demodulation
DeMUX, DeInterleaving,
HARQ Combining
Burst Decoding
(a) TDM
(b) FDM
DL:UL Ratio
Delay (TDM)
Delay (FDM)
Difference (ms)
5:3
1.6
2.6 1
4:4
1.85
4:4 (2 switching point)
2.78
0.93
6:2
2.47
3.29
0.82
FDD
1.23
0.62

6. Problem of FDM Required Buffer Size Microsleep/Power Saving
Configuration
TDM
(1 OFDMA symbol)
(2 OFDMA symbols)
FDM
(6OFDMA symbols)
Additional buffer size for FDM
4 symbol-buffering
5 symbol-buffering
9~10 symbol-buffering
5~6 symbols
10 MHz, 2 Rx Antennas
17 KB
21 KB
38 ~ 42 KB
21 ~ 25 KB
20 MHz, 2 Rx Antennas
34 KB
42 KB
76 ~ 84 KB
42 ~ 50KB
20 MHz, 4 Rx Antennas
67.5 KB
84.4 KB
152 ~ 169 KB
84.4 ~ 101 KB
MAP
FFT
Demodulation
Decoding
(a) TDM and Hybrid TDM/FDM
(b) FDM
Baseband
Power
Saving
Microsleep (RF)

7. Problem of TDM Resource Waste (Unused resource) Low granularity of TDM
Cannot share the resource with data (Power Trading)
Power Trading of FDM : Enhance MAP coverage
However, Large Power Trade  CQI mismatch, Interference
SubMAP
Flexible Allocation
Power Trade
1 RB
1 RB
SubMAP
SubMAP … …
1 RB
1 RB
1 RB
Unused
Unused
(a) TDM (Total SubMAP size < 1 symbol)
(b) TDM (Total SubMAP size > 1 symbol)
(c) FDM

8. Hybrid TDM/FDM Enhancing TDM advantages Supplementary FDM MAP
CAU concept
Diversity + Localized allocation for control channels
Additional TDM Granularity (1 CAU is 2~4 % of total resource)
Cell specific Rotation for Interference Mitigation for SFCH
Supplementary FDM MAP
Enhancing poor resource allocation by adopting FDM for UL control channels
FDM MAP is located at the diversity subchannel without reservation.
Allocation granularity is 1 RB (1.7% of one subframe)
Influence on MS complexity
No Buffering Problem
This problem is related only to DL MAP
Microsleep
UL grant is the response for UL request  MS can know if UL grant exists or not
Some UL grants can be located in TDM region  Possible to microsleep

9. Hybrid TDM/FDM TDM Allocation : CAU (Control Allocation Unit)
3 ~ 8 CAUs/subframe ( if 10MHz: 16CRUs/CAU ~ 6CRUs/CAU )
Remained CAU can be allocated to data or remained empty for interference mitigation
Each CAU can be localized or diversity
Different Rotation is applied to each cell …
Uplink Subframe MAP
(Supplementary)
Subframe MAP (Downlink /Uplink)
SFCH
Data Bursts
Subchannels
Time
1 OFDMA Symbol
(b) Logical Subchannel
(a) Physical CRUs
CRU
(18x1)
Diversity
Mapping
Localized
CAU 1
CAU 2
CAU 3
CAU 4
Permutation ……
Cell-specific Rotation (0,1,2,3)
Subframe MAPs

10. Hybrid TDM/FDM FDM Allocation First N diversity subchannel
The RB distribution is indicated by SFCH
No reservation only for Subframe MAP
Data
(Diversity Subchannel) …
Uplink Subframe MAP
(Supplementary)
Subframe MAP (Downlink /Uplink)
SFCH
Data Bursts
Subchannels
Time
1 OFDMA Symbol
(b) Logical Subchannel
(a) Physical RB
Localized RB
1 RB
Distributed RB
1 subchannel
Uplink
Subframe MAP
(Localized Subchannel)

11. Multiplexing Comparison
FDM
TDM
Hybrid TDM/FDM
Processing delay
Longer than TDM
Same as TDM
Microsleep
Impossible
Possible (2 symbols)
Partially Possible
(if no FDM UL MAPs)
Symbols to be buffered after FFT (Assuming 0.5TTI (3 symbols) for MAP decoding)
9~10 symbols
(Additional 21~101KB)
4~5 symbols
4 symbols
Frequency Selectivity Gain for MAP
Hard to apply
Possible
Possible with TDM
Flexible Resource Usage
(Power and Subcarrier)
Good
Poor
Slightly less than FDM
Allocation unit/ % ratio w.r.t. one subframe
1 RB/
2.08%
1 symbol/
16.67%
1 CAU and
1 subchannel (2~4%)
Effects on resource allocation of data channel
Some limitations on localized RB
No Limitation
Overhead for indicating MAP size (Assuming 16%~25% of control overhead)
3~4 bits
(8~12 RBs)
0~1 bit
(1~2 OFDMA symbols)
2~3 bits (4 CAUs ~
1 OFDMA symbol + 4 subchannel)

12. Transmission Scheme Separate Coding vs. Joint Coding  Separate Coding
Rate Control vs. Power Control
 Rate Control + Power Control (Limited variation)
Separate Coding
Joint Coding
Advantages
Band Selection Gain
Simple Coding/Decoding
Link Adaptation Gain (Power control, AMC)
High Coding Gain (CTC)
Relatively high diversity gain
Low Resource Indication Overhead
Drawbacks
High Resource Indication Overhead
Relatively lower diversity gain than JC
High Decoding Complexity
Hard to get link adaptation gain (PC, AMC)
Cannot adopt band selection gain
Variable MAP size
Rate Control (Variable MCS)
Power Control (Fixed MCS)
Advantages
Static interference (Easy to control)
Can utilize higher-order modulation
High Control Granularity
Easy to apply the blind decoding
Drawbacks
Low Control Granularity
Hard to blindly decoded
Hard to manage interference (Dynamic variation of interference)
Require feedback channel for control channel
Cannot utilize higher-order modulation

13. Text Proposal
Insert the following text in SDD Chapter 11.x (Physical Layer):
11.x DL Control Structure
11.x.5 Unicast Service Control Channels
11.x.5.2 Multiplexing Scheme for data and unicast service control
DL control channels and data are multiplexed in a subframe using a combination of TDM and FDM.
One OFDMA symbol is used for default configuration with one subframe. FDM multiplexing scheme is applied only for control channels related to uplink procedure if one OFDMA symbol is not enough to transmit all of the subframe control channels.

14. Text Proposal
Insert the following text in SDD Chapter 11.x (Physical Layer):
11.x.5.4 Transmission Scheme
Multiple unicast service control information elements are coded separately and a different MCS can be used for each control information element that is transmitted.
Control information common to scheduled users is multicast, and the modulation and coding scheme is informed by SFH.