Transcript Slides S802.16j-08/050

Maximum number of hops for centralized scheduling mode
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE 802.16j-08/050
Date Submitted: 2008-01-23
Source:
Yuefeng Zhou
NEC
Voice:
E-mail:
+44 20 87523460
[email protected]
IEEE 802.16 Session #53, Levi, Finland
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None
Purpose:
For the discussion of the Maximum number of hops for centralized scheduling mode
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1
Maximum number of hops for centralized scheduling mode
As defined in the standard draft, P802.16j/D2, the centralized
scheduling is the mode of operation applicable to multihop relay
where an MR-BS determines the bandwidth allocations and
generates the corresponding MAPs (or dictates the information used
by RSs to generate their MAPs) for all access and relay links in the
MR-cell.
When increasing the number of hops, the MR-BS will have very
heavy MAP overhead, since it has to generates the MAPs for each
hop.
Maximum number of hops for centralized scheduling mode
Figure 1 shows the estimated MAP and FCH overhead for legacy
one-hop 16e system, when normal map is used. (FFT size = 1024;
DL:UL = 32:15; Assume one burst for one connection; assume UL
and DL subframe has same number of connections; 3 segmentation
70
is used)
repetition rate = 4
repetition rate =2
FCH & MAP overhead (%)
60
Fig. 1.
FCH & MAP overhead
(percentage within DL
subframe) vs. Number of
connections (CIDs) used.
50
40
30
20
10
1
2
3
4
5
6
7
Number of connections
8
9
10
Maximum number of hops for centralized scheduling mode
From the estimated results in Fig. 1, when number of connections is
10, by using repetition rate of 4 and normal MAPs, the overhead of
FCH and MAPs will use about 70% of the whole DL subframe! In
16j with centralized scheduler mode, when number of hops is
bigger, the MR-BS will consume much bigger FCH&MAP
overhead. For example, when number of hops is 3, averagely, only
two connections could be supported by each RS and MR-BS to
make sure the MR-BS has enough resource to allocate all FCH and
MAPs. Obviously, it is not efficient to use centralized scheduling
mode when number of hops is big, e.g. > 2.