Outage Performance of Two-Hop OFDM Systems With Spatially Random Decode-and-Forward Relays

Shuping Dang,Gaojie Chen,Justin P Coon

doi:10.1109/access.2017.2773658

Abstract

In this paper, we analyze the outage performance of different multicarrier relay selection schemes for two-hop orthogonal frequency-division multiplexing (OFDM) systems in a Poisson field of relays. In particular, special emphasis is placed on decode-and-forward (DF) relay systems, equipped with bulk and per-subcarrier selection schemes, respectively. The exact expressions for outage probability are derived in integrals for general cases. In addition, asymptotic expressions for outage probability in the high signal-to-noise ratio (SNR) region in the finite circle relay distribution region are determined in closed forms for both relay selection schemes. Also, the outage probabilities for free space in the infinite relay distribution region are derived in closed forms. Meanwhile, a series of important properties related to cooperative systems in random networks are investigated, including diversity, outage probability ratio of two selection schemes and optimization of the number of subcarriers in terms of system throughput. All analysis is numerically verified by simulations. Finally, a framework for analyzing the outage performance of OFDM systems with spatially random relays is constructed, which can be easily modified to analyze other similar cases with different forwarding protocols, location distributions and/or channel conditions.

Highlights

Cooperative communications have become an important topic for research and industry in recent years [1]–[4]
We simulate the relation between the outage probability and the transmit power with spatially random relays distributed over a finite circle region
A series of important properties related to cooperative systems in random networks were investigated, including diversity, outage probability ratio of two selection schemes and the optimization of the number of subcarriers

Summary

Introduction

Cooperative communications have become an important topic for research and industry in recent years [1]–[4]. All of the above achievements regarding cooperative OFDM systems do not consider the location distribution of relays. The conventional network model employed in these previous OFDM-related works assumes the locations of all nodes to be deterministic and stationary, which form a stationary network topology. The dynamic nature of communication nodes is common and should be considered in order to provide a more general and meaningful analysis [12]. A more realistic way to model a communication network is to assume the location of a node to be a random variable. To perform the analysis effectively, Poisson point processes (PPPs) have been used to analyze the location distribution of communication nodes for a large number of applications in wireless communications [13]–[16]. Generalized analyses of DF and amplifyand-forward (AF) cooperative systems with spatially random

Results

Discussion

Conclusion