8/13/2019 20121128 Xiaoxia Green

1/27

1

Optimal Power Allocation and AP Deployment in

Green Wireless Cooperative Communications

Xiaoxia Zhang

x79zhang@bbcr.uwaterloo.ca

Department of Electrical and Computer Engineering

University of Waterloo

mailto:x79zhang@bbcr.uwaterloo.camailto:x79zhang@bbcr.uwaterloo.ca

8/13/2019 20121128 Xiaoxia Green

2/27

2

Outline

Introduction

System Model

Power Allocation for a Single-User Link

AP Deployment

Conclusions and Future Work

8/13/2019 20121128 Xiaoxia Green

3/27

Global Emission of CO2 in 2011

- Increased by 3%

- Reaching an all-time high of 34 billion tonnes

Figure 1. Global Emission of CO2 in 2011

Introduction

3

8/13/2019 20121128 Xiaoxia Green

4/27

Eco-friendly renewable energy: solar, wind, tide, etc.

Occupied 16.7 % of global energy in 2011

Figure 2. Renewable Energy Share of Global Final Energy Consumption, 2011.

Sustainable Energy

4

8/13/2019 20121128 Xiaoxia Green

5/27

8/13/2019 20121128 Xiaoxia Green

6/27

Characteristics of Sustainable Energy

- Variable or intermittent in its capacity

- Highly dependent on the location and weather

Fulfillment of users QoS demand is challenging.

- Introduction of cooperative communication

- More efficient green wireless network

o Device deployment

o Resource allocation

Motivation

6

8/13/2019 20121128 Xiaoxia Green

7/27

In a WLAN network where green APs are

deployed, we would like to maximize the overall

throughput by jointly allocating transmitting powerand deploying the green APs, subject to the

harvested energy constraint.

Objective

7

8/13/2019 20121128 Xiaoxia Green

8/278

Outline

Introduction

System Model

Power Allocation for a Single-User Link

AP Deployment

Conclusions and Future Work

8/13/2019 20121128 Xiaoxia Green

9/279

System Model

A wireless local area network

(WLAN) where a green AP is

deployed.

Nodes could communicate with each

other in an ad hoc manner.

Transmission links are separated by

TDMA.

AP can cooperate with the source

nodes to transmit data to the

destination.

nlinks in total.Figure 4.A green wireless cooperative communication network.

8/13/2019 20121128 Xiaoxia Green

10/2710

System Model

During each transmission period, only one source-destination

pair (si,di) exists.

AP

The AP functions as a relay node.

- Two relaying protocols:

Amplify-and-Forward

Decode-and-Forward

Easy to implement Noise cannot be eliminated

Coding cost Noise free

need extra

resources

8/13/2019 20121128 Xiaoxia Green

11/2711

Information theoretic achievable rate

Achievable Rate for Single-User Relay

Channel

relaydecoding rate

destinationdecoding rate

AWGN channel with path loss

path loss exponent

constant and identical for all links

8/13/2019 20121128 Xiaoxia Green

12/2712

Achievable Rate for Single-User Relay

Channel

Noise variances received at the

relay and at the destination are

the same value.

Joint superposition

encoding/decoding to maximize

cooperation between source

and relay.

Generation of two codes.

+

relaydecoding rate

destination

decoding rate

8/13/2019 20121128 Xiaoxia Green

13/27

13

Problem Formulation

Objective: maximize overall throughput under instant available

power constraint.

Links are scheduled by TDMA

Power allocation on one link

does not affect other links

8/13/2019 20121128 Xiaoxia Green

14/27

14

Outline

Introduction

System Model

Power Allocation for a Single-User Link

AP Deployment

Conclusions and Future Work

8/13/2019 20121128 Xiaoxia Green

15/27

15

Objective: jointly determine , and to maximize

the achievable rate.

Power Allocation for a Single-User

Link

Note: optimum is achieved when

destination decoding rate = relay decoding rate

relaydecoding rate

destination

decoding rate

8/13/2019 20121128 Xiaoxia Green

16/27

16

Destination decoding rate is the bottleneck.

Increase and reduce to balance.

Coherent transmission.

Synchronous Case

relay

decoding rate

destination

decoding rate

Optimal power allocation is:

Largest achievable rate is:

8/13/2019 20121128 Xiaoxia Green

17/27

17

Relay decoding rate is the bottleneck.

Source will set and .

Independent transmission.

Asynchronous Case

Optimal power allocation is:

Largest achievable rate is:

relay

decoding rate

destination

decoding rate

8/13/2019 20121128 Xiaoxia Green

18/27

18

Outline

Introduction

System Model

Power Allocation for a Single-User Link

AP Deployment

Conclusions and Future Work

8/13/2019 20121128 Xiaoxia Green

19/27

19

Optimal power allocation and maximum rate depends on

the location of AP.

AP Deployment

Direct transmission without help of

relay can achieve highest rate.

Relay closer to the source

Synchronous case achieves higher rate

Relay closer to the destination

Asynchronous case achieves higher rate

8/13/2019 20121128 Xiaoxia Green

20/27

20

Two local maximum

Optimal AP Deployment for a Single Link

Let , the two possible relay positions to

maximize the throughput is the solutions to the following

two equations:

,

,

8/13/2019 20121128 Xiaoxia Green

21/27

21

Sustainable energy can only be exploited in some

specific locations due to the availability and neighboring

environment.

Several candidate AP locations are considered.

The optimal location can be decided based on the

overall throughput which is calculated by

Optimal AP Deployment

8/13/2019 20121128 Xiaoxia Green

22/27

22

Simulation Results

Figure 5. Rate comparison of three power allocation schemes when and .

Synchronous

Asynchronous

8/13/2019 20121128 Xiaoxia Green

23/27

23

Simulation Results

Figure 6.Achievable rate of a single user link with different AP locations.

8/13/2019 20121128 Xiaoxia Green

24/27

24

Simulation Results

Figure 7. The overall throughput by our proposed AP deployment metric and random deployment method.

100m100m area

30 candidate locations

8/13/2019 20121128 Xiaoxia Green

25/27

25

Outline

Introduction

System Model

Power Allocation for a Single-User Link

AP Deployment

Conclusions and Future Work

8/13/2019 20121128 Xiaoxia Green

26/27

8/13/2019 20121128 Xiaoxia Green

27/27