1. Presented by Hermes Y.H. Liu
Minimum-Cost QoS-Constrained Deployment and Routing Policies for Wireless Relay Networks of Maximal Ratio Combining Capacities
考慮服務品質限制之具最大比率合成能力
中繼站無線網路成本最小化建置與路由策略
Advisor: Lin Yeong-Sung, Ph.D.
Chu Kuo-Chung, Ph.D.
Presented by Hermes Y.H. Liu
2018/11/24
OPLab, IM, NTU

2. Agenda Introduction and Motivation Problem Description
Problem Formulation
2018/11/24
OPLab, IM, NTU

3. Introduction and Motivation
2018/11/24
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4. Introduction
Relay technology has been used widely in wireless communication, such as IEEE j, IEEE s, and seed concept in 3GPP
Advantages of relay:
1. radio range extension
2. overcome shadow fading
3. reduce infrastructure deployment costs
4. enhance capacity
5. reduce outage probability
2018/11/24
OPLab, IM, NTU

5. Relay
Figure: Left: tree topology in relay network; Right: mesh topology in mesh network
2018/11/24
OPLab, IM, NTU

6. Relay (contd.)
Relays are designed to improve the coverage of a BS and overcome the shadows caused by obstacles.
Figure: City scenario of relays deployment with one BS
2018/11/24
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7. Relay (contd.) three types of relay protocols:
1. Amplify-and-Forward : Relays act as analog repeaters by retransmitting an amplified version of their received signals. The noise is amplified as well.
2. Decode-and-Forward: Relays attempt to decode, regenerate and retransmit the same information from the original source, the propagating decoding errors may occur.
3. Decode-and-Reencode: Relays attempt to decode, reencode the received signals with codewords that are different from the received codewords. Again, there is the probability of error propagation.
2018/11/24
OPLab, IM, NTU

8. IEEE j
IEEE j is now a developing specification established by IEEE j task group
the enhancement of original /802.16e-2005
Compatible to the legacy standard
A relay station (RS) will be recognized as a base station (BS) by the mobile station (MSs) for the transparency reasons
2018/11/24
OPLab, IM, NTU

9. IEEE j (contd.)
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10. Diversity Techniques
Frequency diversity: transmitting or receiving the signal at different frequencies;
Time diversity: transmitting or receiving the signal at different times;
Space diversity: transmitting or receiving the signal at different locations;
Polarization diversity: transmitting or receiving the signal with different polarizations.
2018/11/24
OPLab, IM, NTU

11. Cooperative Diversity
Cooperative diversity is a relatively new class of spatial diversity techniques that is enabled by relaying
to improve the reliability of communications in terms of, for example, outage probability, or symbol-or bit-error probability, for a given transmission rate
2018/11/24
OPLab, IM, NTU

12. Diversity Signal-processing Techniques
selection diversity (SD)
equal gain combining (EGC)
maximal ratio combining (MRC)
2018/11/24
OPLab, IM, NTU

13. Maximal Ratio Combining (MRC)
Figure: Maximal ratio combining
2018/11/24
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14. Motivation
Figure: Left: single-stage concept; Right: multistage concept
2018/11/24
OPLab, IM, NTU

15. Motivation
Allow multiple source nodes jointly transmit one single information if the signal strength is not robust enough in the link between one source node to the destination
The routing policy is no longer a single path but with more complex multicast-tree algorithms
2018/11/24
OPLab, IM, NTU

16. Problem Description
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17. Problem Description Figure: Network separations with several BSs
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18. Problem Description (contd.)
Figure: DL transmission tree and one OD pair routing subtree
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19. Problem Description (contd.)
Figure: UL transmission tree and one OD pair routing subtree
2018/11/24
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20. Problem Description (contd.)
In this paper, we try to find a near optimal relays development policy to minimize the total development costs; meanwhile, to maintain both DL and UL spanning trees and using multicast-tree based routing algorithm to ensure the bit error probability (BEP) and data rate requirements of each mobile cluster must be satisfied.
2018/11/24
OPLab, IM, NTU

21. Problem Formulation
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22. Problem Formulation Assumption:
The relaying protocol in this model is Decode-and-Forward
Each mobile cluster (MC) must home to either a BS or relay(s)
The relays selected by one MC must associate with the same BS
The routing path of each OD pair in DL (UL) is a subtree of the DL (UL) spanning tree
The spatial diversity gains are represented by the aggregate SNRs with MRC techniques
The BEP of a transmission is measured by the receiving SNR value
The aggregate BEPs of the destination are the summation of BEPs of each node on the routing subtree
The numbers of links of each path adopted by each MC are assumed to be equal to ensure the MRC is achievable within limited delay
2018/11/24
OPLab, IM, NTU

23. Problem Formulation (contd.)
Objective:
To minimize the total cost of wireless relay network deployment
Subject to:
Relay selection constraints
Nodal capacity constraints
Cooperative relaying constraints in DL and UL
Routing constraints in DL and UL
Link capacity constraints in DL and UL
2018/11/24
OPLab, IM, NTU

24. Problem Formulation (contd.)
To determine:
Whether or not a location should be selected to build a relay
The DL and UL spanning trees
The cooperative relays of each MC
The subtree , which is on the spanning tree, selected by each MC
2018/11/24
OPLab, IM, NTU

25. Problem Formulation (contd.)
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26. Problem Formulation (contd.)
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27. Problem Formulation (contd.)
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28. Problem Formulation (contd.)
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29. Problem Formulation (contd.)
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30. Problem Formulation (contd.)
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31. Objective function:
(IP 1)
Subject to: (General Constraint)

33. (DL Constraint)

38. (UL Constraint)

43. Optimal Problem (LR):

57. Thanks for Your Listening
2018/11/24
OPLab, IM, NTU