IEEE C802.16m-08/935r1
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
Remove MS in Group Assignment
Date
Submitted
2008-09-09
Source(s)
Allan Xu
Huawei Technologies Co., Ltd.
Re:
IEEE 802.16m-08/033: Call for Comments and Contributions on Project 802.16m System
Description Document (SDD) :
Voice:
E-mail:
+86-755-28970188
zhier81@huawei.com
*<http://standards.ieee.org/faqs/affiliationFAQ.html>
PHY group (SDD Cleanup)
Abstract
When MS terminates services, BS should remove this MS from corresponding group. Here we
propose a new mechanism for removing MS.
Purpose
Discuss and adopt
Notice
Release
Patent
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Remove MS in Group Assignment
Allan
Huawei Technologies Co., Ltd
1.
Background
In now SDD document, group assignment is supported. But MS can terminate services. So BS can remove
MS from one group. And when MS is removed, other MSs in this group shall move their positions in this group.
We consider BS can remove MS in group assignment messages, and the removed MS will find it is removed
from its group when it decodes the group assignment messages, and other MSs will move their positions in this
group to avoid hole. But how the stayed MS moves?
Usually we just move the stayed MS after the removed MS to the position of removed MS, and the back
MSs will be moved from first to last. We can name this way of moving as ordinal filling. But this is not so good.
If we consider BS may allocate feedback channel to the MS that shall be moved, and we move MS from first to
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IEEE C802.16m-08/935r1
last, then we need so many feedback channels. If we consider BS doesn’t allocate feedback channel to the MS
that shall be moved, then the probability of group assignment message loss is too large. So this solution is not
good. Following we will introduce a better solution for removing MS from one group.
2. Discussion
Here we propose a mechanism to remove MS from one group efficiently.
In group assignment message, every bit in the bitmap corresponds an MS or one resource. And we define
the order of bit in the bitmap is the order of corresponding MS in the group. When an MS is removed, the stayed
MS in this group will know which MS is removed when it decodes group assignment messages. Then the last
stayed MS will substitute the position of first removed MS, and the second last stayed MS will substitute the
position of second removed MS, and so on. We define the way of substitution as reversed filling.
Following is the comparison between ordinal filling and reversed filling. Assuming one group has 8 MSs,
so the bitmap has 8 bits. These 8 bits corresponds 8 MS orderly (MS1, MS2, MS3, MS4, MS5, MS6, MS7,
MS8). And at one time MS1 is removed then for ordinal filling 7 MSs will be moved, but for reversed filling
only one MS will be moved. The number of move MSs decreases, so the probability of group assignment
message loss decreases and if we allocate feedback channels for adjusting, the number of allocated feedback
channels decreases.
Following we give the figures of ordinal filling and reversed filling when MS1 is removed.
MS1 MS2 MS3 MS4 MS5 MS6 MS7 MS8
0
0
1
1
1
0
0
1
1
0
0
1
0
1
0
MS2 MS3 MS4 MS5 MS6 MS7 MS8
Figure 1: ordinal filling when MS1 is removed.
MS1 MS2 MS3 MS4 MS5 MS6 MS7 MS8
0
0
1
1
1
0
0
1
1
0
0
1
0
1
0
MS8 MS2 MS3 MS4 MS5 MS6 MS7
Figure 2: reversed filling when MS1 is removed.
Based on the discussion reversed filling mechanism is better than ordinal filling, so we propose reversed
filling in 16m system.
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IEEE C802.16m-08/935r1
3. Text Proposal
-------- Start of the text proposal --------------------------------------------------------------------------------------[Change third paragraph of Section 11.7.2.3.1.2 of IEEE 802.16m-08/003r4 as following:]
A group message is used to allocate resources and/or configure resources to one or multiple mobile stations
within a user group. Each group is associated with a set of resources. When some MSs are removed, reversed
filling is used, that is the last stayed MS will substitute the position of first removed MS, and the second last
stayed MS will substitute the position of second removed MS, and so on. VoIP is an example of the subclass of
services that use group messages.
------- End of proposed text ---------------------------------------------------------------------------------------------
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