Transcript IEEE C802.16m-09/2295

Multicast A-A-MAP Symbols Mapping Scheme in 802.16m systems
(15.3.6.2.2.2 )
Document Number: C80216m-09/2295
Date Submitted: 2009-11-06
Source:
Yu-Hao Chang, Yih-Shen Chen, Pei-Kai Liao
Chih-Yuan Lin, Paul Cheng
MediaTek
[email protected], [email protected]
Venue:
IEEE Session #64, Atlanta, USA.
Re:
Base Contribution:
N/A
Purpose:
To be discussed and adopted by TGm
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1
Background and Motivation (1/2)
• Different A-A-MAP-IEs encoded by the same modulation and
coding scheme are grouped together and form an A-A-MAP group
• AMS can perform blind decoding in the resource unit (RU) region
reserved for the corresponding group to find its A-A-MAP-IE
• The group size information is broadcasted so that the search
space of blind decoding is reduced
• Multicast A-A-MAP-IE, e.g., group resource allocation (GRA) and
composite persistent allocation (composite PA), may occupy more
resource than the individual A-A-MAP-IE in the same group
• The size of multicast A-A-MAP-IE is not fixed, but depends on the
information carried
2
Background and Motivation (2/2)
• Since AMS does not know the exact number of MLRUs used in its
multicast-A-AMAP-IE, it needs to check all possible MLRU sizes
with different shifts to find its A-A-MAP-IE
• This operation demands huge computational complexity for blind
decoding, especially when more than one multicast A-A-MAP-IE
are there in the same group
• The location and size information of multicast A-A-MAP-IE should
be effectively delivered to AMS to save the blind decoding
complexity
3
Summary of the proposed scheme
• The multicast A-A-MAP-IE is divided into two segments, namely,
segment 1 and segment 2 multicast A-A-MAP-IEs. Both of them
are individually encoded and mapped onto contiguous MLRUs
• The size of segment 2 is flexible and depends on the information
carried while that of segment 1 is fixed and is known to AMS
• Segment 2 symbol size in terms of MLRUs is also indicated in the
corresponding segment 1 symbol so that there is no size ambiguity
for segment 2 decoding after AMS decodes segment 1 symbol
successfully
• Note that, the partition between segment-1 and segment-2 is
logically
– if the required bit number can be filled into a single basic unit A-MAPIE, e.g., DL/UL basic A-A-MAP-IE, segment 1 and segment 2 can be
composed into a single GRA-A-MAP IE
– Otherwise, segment-1 and segment-2 are sent in separate but
contiguous MLRUs
4
The proposed multicast A-A-MAP-IE
mapping scheme
•
Separate the multicast A-A-MAP-IE into two segments, i.e.,
– multicast A-A-MAP-IE segment 1 (fixed size)
– multicast A-A-MAP-IE segment 2 (variable size)
• Multicast A-A-MAP-IE segment 1 and 2 are called segment 1 and 2, respectively, in
the following slides
•
•
•
Additional one-bit type field IE is inserted in segment 1 and segment 2 to
differentiate these two segments
The size of segment 2 symbol in terms of MLRUs is indicated in segment
1
The size of information bits in segment 1 is upper bounded by a fixed
number so that the data size after channel encoder is known
– For example, the number of information bits in segment 1 is bounded by 40
bits. This corresponds to one MLRU when 16-bit CRC and QPSK ½ are
applied
•
•
•
MCRC is independently generated and inserted in both segment 1 and
segment 2
Both segment 1 and segment 2 are separately encoded by the same MCS
after MCRC insertion
After channel coding, segment 1 and segment 2 symbols are mapped
onto contiguous MLRUs while segment 1 symbol occupies a lower MLRU
index than segment 2
5
Decoding of the proposed multicast
A-A-MAP mapping
• Since the size of segment 1 symbol is fixed and known
to AMS, AMS can first perform blind decoding for the
segment 1 symbol without size ambiguity
• After decoding segment symbol 1 successfully, AMS
learns how many MLRUs right after segment 1 symbol
are reserved for segment 2 symbol. Therefore, it can
decode the segment 2 symbol immediately without
further searching process
6
Information Element in segment 1
•
segment 1 can contain the following IEs
–
–
–
–
–
–
–
–
A-MAP IE type
Type field
segment 2 size
User bit map size
User bit map
Re-arrange Indicator
[Segment 2 indicator]
Optional fields:
•
•
•
•
•
•
•
•
•
•
•
•
•
Long TTI Length
Resource offset
ACK Channel Offset
N_deallocated_AMS
De-allocated AMS index
Re-arrange Bitmap if Re-arrange Indicator == 1
MIMO Bitmap if Group MIMO mode set == 0b01 or 0b11
PSI Bitmap if Group MIMO mode set == 0b11
Pairing Bitmap if Group MIMO mode set == 0b11
Resource assignment bitmap
Padding
The idea of having user bit map in segment 1 is to save the computational power
of inactive AMS for segment 2 symbol decoding in the corresponding multicast AA-MAP-IE
Note that, the optional fields exists when segment-1 and segment-2 information
are composed into a single A-A-MAP IE
7
Information Element in segment 2
• Segment 2 can contain the following IEs
–
–
–
–
–
–
A-MAP IE type
Type field
Long TTI Length
Resource offset
ACK Channel Offset
N_deallocated_AMS
• De-allocated AMS index
–
–
–
–
–
–
Re-arrange Bitmap if Re-arrange Indicator == 1
MIMO Bitmap if Group MIMO mode set == 0b01 or 0b11
PSI Bitmap if Group MIMO mode set == 0b11
Pairing Bitmap if Group MIMO mode set == 0b11
Resource assignment bitmap
Padding
8
Example of multicast A-A-MAP decoding
based on the proposed scheme
• AMS searches for the segment 1 of its multicast A-A-MAP-IE first
– There is no MLRU size ambiguity in segment 1 decoding
– Only location of segment 1 symbol is unknown
• Segment 1 symbol carries information necessary for segment 2
decoding. For example,
– MLRUs reserved for the corresponding segment 2 symbol
• Location of segment 2 is now known to AMS after segment 1
decoding
Seg. 1
Seg. 2
Multicast A-A-MAP-1
Seg. 1
Seg. 2
Multicast A-A-MAP-2
Individual A-A-MAP-IEs
MLRU Index
9
Example of Proposed GRA A-MAP IE
Syntax
Size
Description
A-MAP IE Type
4
Group Resource Allocation AMAP IE
Format type
1
0: Fixed part (segment-1)
1: extension part (segment-2)
If(Format type == 0)
{
GRA control
information
// information given in page 6
} else
{
GRA allocation
information
// information given in page 7
}
10
Text Proposal (1/2)
[ Recommended AWD Text Proposal 1 (Section 15.3.6.2.2.2, page 334, line 45) ]
The assignment A-MAP IE shall be transmitted with one MLRU or multiple concatenated MLRUs in the A-MAP
region. The number of logically contiguous MLRUs is determined based on the assignment A-MAP IE size and
channel coding rate, where channel coding rate is selected based on AMS’ link condition.
Assignment A-MAP IEs with less than 40 bits are zero-padded to 40 bits. Assignment A-MAP IEs with more than 40
bits are divided into two segmented IE, namely, segment 1 and segment 2. Additional 1-bit type field is inserted in
segment 1 and 2 to indicate the segment type and the size of segment 2 in terms of MLRU is also provided in segment
1 using a [5]-bit IE. The size of segment 1 is fixed and is bounded by 40 bits while the size of segment 2 is variable.
Segments of an A-A-MAP IE should be separately coded with the same MCS and occupy a number of logically
contiguous MLRUs. The process of assignment A-MAP IE segmentation is described in <<15.3.6.5.2.15>>.
Assignment A-MAP IEs are grouped together based on channel coding rate and A-MAP IE sizes. Assignment
A-MAP IEs in the same group are transmitted in the same frequency partition with the same channel coding rate and
contain the same A-MAP IE size. Each assignment A-MAP group contains several logically contiguous MLRUs. The
number of assignment A-MAP IEs in each assignment A-MAP group is signaled through non-user specific A-MAP in
the same AAI subframe.
11
Text Proposal (2/2)
[ Recommended AWD Text Proposal 2 (New Section 15.3.6.5.2.15, page 401, line
14) ]
15.3.6.5.2.15
If an assignment A-MAP IE is larger than 40 bits, the IE should be segmented into two parts and coded separately with
the same MCS in the following steps:
1. The first 34 bits of the original IE, including IE type, are allocated to segment 1 while the rest of bits are left to
segment 2.
2. An 1-bit type field and a [5]-bit segment 2 size indicator are added to segment 1 while 4-bit IE type and an 1-bit
type field are also inserted in segment 2
3. Some padded bits for segment 2 may be necessary to reach the MLRU boundary and the size information of
segment 2 is signaled in segment 1 using the size indicator mentioned in the previous step.
4. For each segment, a 16-bit CRC is generated and masked by the corresponding STID before being attached at
the end of each segment.
5. These two segments from the assignment A-MAP IE are coded with the same MCS and occupy a number of
logically contiguous MLRUs in sequence.
12