Proposal of Different CRC Masks for Concatenated Subband Assignment A-MAP IEs (16.3.6.5.2.4)

Document Number: IEEE C802.16m-10/0041

Date Submitted: 2010-3-5

Source: Yan-Xiu Zheng, Chang-Lan Tsai E-mail: zhengyanxiu@itri.org.tw Yu-Chuan Fang, Chung-Lien Ho tsaichangl@itri.org.tw ITRI

Venue:IEEE 802.16 Session#66 at Orlando, USA.

Base Contribution:

Purpose:Propose to be discussed and adopted by TGm for the use in Project 802.16m/D4

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Motivation

• When the subband allocation is made using two concatenated IEs, there shall exist a bit in subband A-A-MAP for indicating the IE to be concatenated with the previous or next IE for subband allocation.

• The same CRC mask is used for the two concatenated subband A-A-MAP IEs.

• There would be hesitation in searching concatenated subband A-A-MAP IEs.

Example 1

• IE1 and IE4 are single IEs with STID1 and STID4, respectively. The CRC masks are (0000|STID1) and (0000|STID4), respectively. The one bit indicator NumIEs is set to 0 representing a single IE.

• IE2 and IE3 are concatenated for subband allocation. They have the same STID and CRC mask which are STID2 and (0000|STID2), respectively. The one bit indicator NumIEs is set to 1 representing that the IE is concatenated with another IE with NumIEs equaling 1.

IE1 IE2 IE3 IE4

NumIEs = 0

(0000|STID1)

NumIEs = 1

(0000|STID2)

NumIEs = 1

(0000|STID2)

NumIEs = 0

(0000|STID3)

Example 1

• In the case that the two subband A-A-MAP IE2 and IE3 are decoded correctly and CRC check is success, since the indicator NumIEs == 1 in subband IE2, AMS check the next subband IE content to find the IE with NumIEs == 1 and combine these two IEs for subband allocation.

• In the case that the CRC check for IE2 is failure, IE2 is discarded. And if CRC check for IE2 is success, since the indicator NumIEs == 1, AMS has to seek another subband IE with NumIEs == 1. This wastes logic processing time.

Distinct CRC Masks on Concatenated IEs

• We propose to use distinct CRC mask for the second IE of the two concatenated subband A-A-MAP IEs.– CRC mask = (0010|STID)

• Using the previous example for explanation. Now CRC mask of the second subband IE is (0010|STID2).

IE1 IE2 IE3 IE4

NumIEs = 0

(0000|STID1)

NumIEs = 1

(0000|STID2)

NumIEs = 1

(0010|STID2)

NumIEs = 0

(0000|STID3)

CRC Check

• In the case that CRC check of subband IE2 is success using CRC mask (0000|STID2) and the indicator NumIEs == 1, the next subband IE is check by CRC mask (0010|STID2). If the CRC check of subband IE2 is success, then IE2 and IE3 are combined for subband allocation

• In the case that the CRC check for IE2 is failure using CRC mask (0000|STID2), IE2 is discarded. AMS continues using CRC mask (0000|STID2) to check IE3. Of course the check would be failure.

Flow Chart

Success

CRC mask(0000|STID)

Yes No

Yes No

IEk

IEk

Yes No

Discard IEk

Single IE

Discard IEk-1 and IEk

k = k + 1

Concatenate IEk-1 and IEk

CRC mask(0010|STID)

Subband A-A-MAP and NumIEs == 1

Success

k = k + 1

Text Modification[Modify Table 819 on page 461]

Masking Prefix

Description

0b0 CRC is masked by 1 bit masking prefix, 3 bit message type indicator, and 12 bit Masking CodeThe 3-bit type indicator shall be set/interpreted as follows.000: 12 bit Masking Code refers to an STID (i.e. CRC mask = 0000| Masking Code)010: 12 bit Masking Code refers to an STID used to mask the second IE if two assignment A-MAP IEs are concatenated for resource allocation (i.e. CRC mask = 0010| Masking Code)001: 12 bit Masking Code used to mask Broadcast Assignment A-MAP IE, BR-ACK A-MAP IE, and Group Resource Allocation A-MAP IE, which is described in Table 820 (i.e. CRC mask = 0001| Masking Code).

0b1 CRC is masked by 1 bit masking prefix, and 15 bit RAID (i.e. CRC mask = 1|RAID)