Elimination of Repeated Information in Persistent Allocation Sub-burst IEs

1
Elimination of Repeated Information in Persistent
Allocation Sub-burst IEs

• Yair Bourlas, Nextwave
• Kamran Etemad, Intel
• Shantidev Mohanty, Intel
• Mo-Han Fong, Nortel
• Geunhwi Lim, Samsung Electronics
• Jianmin Lu, Huawei Technologies
• Sean McBeath, Huawei Technologies
• Changyoon Oh, Samsung Electronics
• Hua Xu, Motorola

2
MAP Overhead for VoIP

• VoIP allocations are typically of small size,
  e.g. AMR 12.2Kbps
• 44 bytes in active state and 18 bytes in inactive
  state
• Large number of VoIP allocations per frame, e.g.,
  40-50 per frame
• This leads to large number of Sub-Bursts IEs to
  specify the allocation information (when HARQ is
  used)
• Large number of Sub-Burst IEs incur high MAP
  overhead adversely affects VoIP capacity
• Observation Many VoIP allocations have similar
  MCS and/or size.
• This is because VoIP packet size is same when
  same CODEC is used by all the users and close to
  one another when different CODECs are used by
  different users.
• These same/similar length VoIP packet sizes
  result in similar allocation size in terms of
  number of slots (for more refer backup slide
  11)
• The size of Sub-Burst IEs can be reduced by
  exploiting
• Multiple allocations with the same MCS (used in
  802.16Rev2/D2 for DL Chase HARQ and DL IR HARQ
  for CC) (proposed for other HARQ modes in this
  contribution)
• Multiple allocations with the same allocation
  size (Proposed in this contribution)

3
Persistent Allocation Sub-Burst IE Optimization
in 802.16Rev2/D3

• IEEE 802.16Rev2/D3 uses Sub-Burst DIUC
  Indicator flag in Persistent sub-burst IEs
• to eliminate repetitive indication of MCS in the
  Sub-Burst IEs of N consecutive subbursts having
  same MCS (DIUC and Repetition Coding Indication)
• Only the Sub-Burst IE of the first one of these N
  subbursts specifies the MCS of allocation
• The remaining (N-1) Sub-Burst IEs do not specify
  the MCS of allocation
• A one-bit flag, Sub-Burst DIUC Indicator, is used
  in the Sub-Burst IE to indicate if the MCS of a
  subburst is same as that of the previous subburst
• This is referred to as MCS Optimization in this
  contribution
• IEEE 802.16Rev2/D3 Persistent Sub-burst IEs do
  not use similar optimization for other
  information fields such as Duration, Allocation
  Period, N_ACID, MAP NACK Channel Index.

4
Proposed Persistent Sub-Burst IE Optimization

• When N consecutive subbursts have same
  Duration/Allocation Period/N_ACID/MAP NACK
  Channel Index
• Only the Sub-Burst IE of the first subburst
  specifies the parameter
• The remaining (N-1) Sub-Burst IEs do not specify
  the parameter
• A one bit flag, Duration Indicator, and
  Allocation Period and Index Indicator is used
  in the Sub-Burst IE to indicate if the
  corresponding parameter of a subburst is same as
  the size of the previous sub-burst.

5
An Example Persistent Allocation in a Randomly
Chosen frame

• Persistent Chase Sub-burst IE
• IE Index MCS Duration Allocation
  Period N_ACID MAP NACK Channel Index
• 1 4 8 5
  6 10
• 2 4 8 5
  6 10
• 3 3 15 5
  6 10
• 4 3 15 5
  6 10
• 5 3 15 5
  6 10
• 6 3 15 5
  6 10
• 7 4 8 5
  6 10
• 8 4 8 5
  6 10
• 9 3 15 5
  6 10
• 10 3 15 5
  6 10
• 11 3 15 5
  6 10
• 12 3 15 5
  6 10
• 13 3 15 5
  6 10
• 14 3 15 5
  6 10
• 15 3 7 5
  6 10

Observation many VoIP allocations have same
Duration and/or Allocation Period, N_ACID, MAP
NACK Channel Index
6
What is done now for the Example Persistent
Allocation in a Randomly Chosen frame

• Persistent Chase Sub-burst IE
• IE Flag 1 MCS Duration Allocation
  N_ACID MAP NACK Index
  Period
  Chanel Index
• 1 1 4 8 5
  6 10
• 2 0 8 5
  6 10
  
• 3 1 3 15 5
  6 10
• 4 0 15 5
  6 10
• 5 0 15 5
  6 10
• 6 0 15 5
  6 10
• 7 1 4 8 5
  6 10
• 8 0 8 5
  6 10
• 9 1 3 15 5
  6 10
• 10 0 15 5
  6 10
• 11 0 15 5
  6 10
• 12 0 15 5
  6 10
• 13 0 15 5
  6 10
• 14 0 15 5
  6 10
• 15 0 7 5
  6 10

Observation many VoIP allocations have same
Duration and/or Allocation Period, N_ACID, MAP
NACK Channel Index
7
Proposed Optimization for Persistent Sub-Burst IE
in 802.16Rev2/D3 of the Example DL Allocation

• Persistent Chase Sub-burst IE
• IE Flag 1 MCS Flag 2 Duration
  Flag 3 Allocation N_ACID MAP NACK
  Index
  Period
  Chanel Index
• 1 1 4 1 8 1
  5 6
  10
• 2 0 0
  0
• 3 1 3 1
  15 0
• 4 0 0
  0
• 5 0 0
  0
  
• 6 0 0
  0
  
• 7 1 4 1 8
  0
  
• 8 0 0
  0
  
• 9 1 3 1 15
  0
  
• 10 0 0
  0
• 11 0 0
  0
• 12 0 0
  0
• 13 0 0
  0
• 14 0 0
  0
  
• 15 0 1
  7 0
  

Observation many VoIP allocations have same
Duration and/or Allocation Period, N_ACID, MAP
NACK Channel Index
8
Proposed Optimization for Persistent Sub-Burst IE
in 802.16Rev2/D3 of the Example DL Allocation

• Persistent Chase Sub-burst IE
• IE Index MCS Duration Allocation
  Period N_ACID MAP NACK Channel Index
• 1 4 8 5
  6 10
• 2 4 8 5
  6 10
• 3 3 15 5
  6 10
• 4 3 15 5
  6 10
• 5 3 15 5
  6 10
• 6 3 15 5
  6 10
• 7 4 8 5
  6 10
• 8 4 8 5
  6 10
• 9 3 15 5
  6 10
• 10 3 15 5
  6 10
• 11 3 15 5
  6 10
• 12 3 15 5
  6 10
• 13 3 15 5
  6 10
• 14 3 15 5
  6 10
• 15 3 7 5
  6 10

Observation many VoIP allocations have same
Duration and/or Allocation Period, N_ACID, MAP
NACK Channel Index
9
Number of DL Slots for a VoIP Packet
MCS Slots active (44 bytes) Slots silence (18 bytes)
10 64 QAM 3/4 STBC (rep. 1) 2 1
11 64 QAM 5/6 STBC (rep. 1) 2 1
12 QPSK ½ SM (rep. 1) 4 2
13 QPSK 3/4 (rep. 1) 3 1
14 16 QAM 1/2 SM (rep. 1) 2 1
15 16 QAM 3/4 SM (rep. 1) 2 1
16 64 QAM 1/2 SM (rep. 1) 2 1
17 64 QAM 2/3 SM (rep. 1) 1 1
18 64 QAM 3/4 SM (rep. 1) 1 1
19 64 QAM 5/6 SM (rep. 1) 1 1
MCS Slots active (44 bytes) Slots silence (18 bytes)
1 QPSK ½ STBC (rep. 6) 44 18
2 QPSK ½ STBC (rep. 4) 30 12
3 QPSK ½ STBC (rep. 2) 15 6
4 QPSK ½ STBC (rep. 1) 8 3
5 QPSK 3/4 STBC (rep. 1) 5 2
6 16 QAM 1/2 STBC (rep. 1) 4 2
7 16 QAM 3/4 STBC (rep. 1) 3 1
8 64 QAM 1/2 STBC (rep. 1) 3 1
9 64 QAM 2/3 STBC (rep. 1) 2 1
Multiple MCS options have similar allocation size
10
Summary

• The proposed technique is very simple to
  implement
• Up to 40 MAP reduction
• Robust against
• Variable voice codec
• Variable VoIP packet because of header
  compression, active/silence
• Applicable when different users use different
  codec
• Backbone delay variation
• Useful across all mobility (slow, medium, fast
  users)