IEEE C802.16m-08/1376
1
Project
IEEE 802.16 Broadband Wireless Access Working Group <http://ieee802.org/16>
Title
MS Association Procedure Proposal for Relay Evaluation Methodology
Date
Submitted
2008-10-31
Source(s)
Eldad Zeira
eldad.zeira@interdigital.com
Ron Murias, Sana Sfar, Prabhakar Chitrapu
All authors are affiliated with InterDigital
Communications LLC
Re:
Change request for 802.16m EMD
Abstract
The contribution provides a definition and procedure for the MS association to a relay and BS.
Purpose
To be discussed and agreed by TGm
This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It
represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for
discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material
contained herein.
Notice
Release
The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution,
and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name
any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole
discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor
also acknowledges and accepts that this contribution may be made public by IEEE 802.16.
Patent Policy The contributor is familiar with the IEEE-SA Patent Policy and Procedures:
<http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and
<http://standards.ieee.org/guides/opman/sect6.html#6.3>.
Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and
<http://standards.ieee.org/board/pat>.
2
3
4
5
6
MS Association Procedure Proposal for Relay Evaluation Methodology
7
8
Eldad Zeira, Ron Murias, Sana Sfar, Prabhakar Chitrapu
9
InterDigital Communications LLC
10
1
IEEE C802.16m-08/1376
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
Introduction
MS association is an essential part of Relay evaluation methodology in that simulation results can be very dependent of
the association procedure. We think that it is important to establish a baseline procedure that can be used in most
simulations in order to make comparisons easier.
The association procedure should be flexible enough to allow for different relaying schemes without biasing the results.
Specifically, the following schemes should be accommodated:
- Basic 2-hop: this scheme is appropriate for coverage extension in low interference areas (coverage holes) e.g.
indoors. The largest benefits will be obtained for low latency low data rate services utilizing distributed
scheduling.
- Cooperative relaying: in this scheme a relay cooperates with the BS in downlink and potentially with the MS in
uplink in transmission of a previously received packet. This technique requires centralized scheduling and
therefore is the most appropriate for services which can tolerate longer latencies. It is also most appropriate for
high interference scenarios in areas where the BS-MS link is comparable to the RS-MS link (for downlink) or RSBS link (for uplink).
- As we have previously shown, multicast cooperative scheme can enhance the performance of cooperative relaying
without additional penalty in resources when the links are comparable.
In order to avoid biasing the association procedure against cooperative scheme, it seems reasonable that both RS-MS and
BS-MS links need to be taken into account in the selection of the relay. On the other hand one would want to avoid
unnecessary complication and excessive simulation run time that would be required if all cells and relays are considered
for MS association. In the procedure we propose MS initially selects (based on SINR) a best BS, a best RS that may not
belong to the best BS, with final choice based on effective relayed capacity as described below.
To compute the effective relayed capacity, we need to consider the possibility of connection through the relay as well as
direct connection to the BS, with the better option selected. All involved links are computed taking into account averaged
SINR that is derived taking into account the transmission power, transmission scheme, path loss, noise and interference
levels. Any resource reuse or cooperative scheme is taken into account implicitly through the effective SINR.
34
35
2
IEEE C802.16m-08/1376
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Text Proposal
14.6. MS Association
13 MS association is the procedure of selecting the BS or RS each MS within the desired
14 sectors will associate with. A default procedure should be is specified here. The specifics
15 of such a procedure are left for further study. One potential method is to assign MSs
16 according to the following procedure:
17 • Estimate of the received signal strength (SNR) for each MS in the deployment
18 delivered from each access station (BS and RS) of the deployment
19 • Associate the MS with the sector (BS or RS) delivering the maximum received
20 signal strength.
21 • Final association to the BS or RSs may be performed on the base of effective
22 throughput/spectral efficiency metrics, taking into account the relay link overhead
23 for transmission via relay. This final association models the process by which the
24 BS and RSs perform load-balancing within the sector. The definition of effective
25 throughput is for further study.
26
27 Other schemes for MS Association can be used as long as the details of the scheme
28 are described in sufficient detail in order to allow other members to duplicate the
29 simulation in order to verify the results.
The default MS Association procedure uses a two step association process:
Step-1:
1. Estimate SNR between MS and BS of cells of interest. This is the SNR of the direct BS-MS link
computed simply from transmission power, path loss, noise and interference (but without considering
the impact of the association on the interference level)
a. Mark sector A that provides highest SNR on MS-BS link
2. Estimate SNR between MS and RS of cells of interest (not limited to sector-A above). This is the SNR
of the RS-MS link computed as for BS-MS.
a. Mark sector B that provides highest SNR on RS-MS link
Step-2:
1. Effective capacity is calculated between each MS and the BS of both A and B. The effective capacity
takes relaying into account as detailed below.
a. The MS is assigned to the BS/RS with which it has the highest value of effective capacity.
Effective capacity calculations (downlink)
Direct communications:
Direct communication is defined as the BS-to-MS communication without relay and is calculated from the
SINR, averaged over whole the applicable system bandwidth:
C direct  C BS  MS  log 2 1  SINRBS  MS 
Where SINRBS-MS is the effective SINR obtained considering the transmission scheme, transmission power,
channel, path loss noise and interference level. The interference ignores the effect of the attachment of the
MS.
3
IEEE C802.16m-08/1376
1
2
3
4
5
6
7
8
9
10
11
Relayed communications:
Relayed communication is defined as the BS-to-MS communication through a relay, denoted as BS-RS-MS.
The communication consists of two phases.
Phase-1:
Phase 1 is defined as the phase where BS is communicating with RS. It may or may not communicate with the
MS simultaneously.
During this phase MS receiving capacity is C MS (1) . If the BS is communicating to MS then its receiving
capacity is, as above,
C MS (1)  C BS  MS  log 2 1  SINRBS  MS 
12
13
14
15
16
17
The effective SINRBS-MS for this case depends on the transmission scheme. In the case where same data is
transmitted to both RS and MS, it is the same as for direct transmission above. The procedure is however
general enough to allow multiplexing different information on same resources (as has been already proposed).
18
If BS is not communicating with MS (such as for 2-hop protocol) and nor any other node, than CMS (1)  0 .
19
20
The relay capacity in phase-1 is similarly CRS (1)  log 2 1  SINRBS  RS 
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
The effective SINR of the BS-RS link is also defined by the coding scheme thus enabling a variety of
cooperative protocols.
Phase 2:
Defined as the phase where the MS is receiving data from RS and possibly also the BS in cooperative
scheme. More than one RS can be used as well.
Receiving capacity at MS: CMS (2)
The exact CMS (2) will be given by the actual cooperation scheme used. For example, if a simple 2 hop,
C MS (2)  C RS  MS  log 2 (1  SINRRS  MS )
Effective relayed capacity
The effective relayed capacity is defined as the compounded throughput achieved at the MS after phase 1 and
phase 2 took place and does take into account the relay overhead. It can be computed as
Crelayed ( RS ) 
38
39
40
41
42
43
44
45
46
47
1
1
1 
1 
1  CMS (1)


CRS (1) CMS (2) 
CRS (1) 
Effective capacity
Defined as the maximum effective throughput between direct and relayed communications


eCapacity  max CDirect , max Crelayed ( RS )
Sector
RSSector
4