Performance comparison of cooperative relay links with different relay processing strategies: Nakagami/Gamma approximation approaches
Jia Shi
Chen Dong
Lie-Liang Yang
0
School of Electronics and Computer Science, University of Southampton
, Southampton, SO17 1BJ,
UK
In this article, we investigate and compare the error performance of two-hop communication links (THCLs) with multiple relays, when distributed and cooperative relay processing schemes are respectively employed. Our main objectives include finding some general and relatively simple ways for estimating error performance and demonstrating the trade-off of using cooperative relay processing. One distributed relay processing and two cooperative relay processing schemes are compared. In the two cooperative relay processing schemes, one assumes the ideal relay cooperation, in which relays exchange information without consuming energy, while the other one assumes energy consumption for relay cooperation. In this paper, the error performance of the THCLs employing the considered relay processing schemes is investigated, when the channels from source to relays, the channels for information exchange and that from relays to destination experience various types of fading modeled by the Nakagami-m distributions. In order to derive the formulas for the bit error rate (BER) of the THCLs employing binary phase-shift keying (BPSK) modulation and various relay processing schemes, we introduce the Nakagami and Gamma approximation for finding the distribution functions of various variables encountered. Our studies show that the proposed approximation approaches are highly effective, which are capable of accurately predicting the BER of the THCLs supported by the different relay processing schemes.
1 Introduction
It has been widely recognized that cooperative
communications will play important roles in the future
generations of wireless communication systems [1-4]. One
type of cooperative communication systems is the
relayassisted, where distributed mobile nodes, often referred to
as relays, are employed for attaining cooperative diversity,
in order to enhance the reliability of wireless
communications [5,6]. The relay-assisted wireless communication
systems have been investigated in the context of
various relay protocols, which include amplify-and-forward
(AF), decode-and-forward (DF), compress-and-forward
(CF) protocols, etc. [5-7].
Along with the relay-assisted wireless communications,
a lot of researches have addressed the bit error rate
(BER) or symbol error rate (SER) analysis, when
assuming communications over, such as, Rayleigh fading, Rician
fading and Nakagami-m fading channels [8-15]. In the
analyses, various cooperative relay scenarios have been
considered, which include the classic three-node relay
network [13,14], serial or parallel multihop cooperative relay
networks [9,12,15], etc. A lot of exact or approximate
closed-form formulas have been derived for evaluating the
BER/SER of considered scenarios. In [10], the exact
average SER formulas have been obtained for the cooperative
network, where a source sends messages to a destination
with the aid of multiple AF relays, when assuming
communications over flat Rayleigh fading channels. In [11],
the SER analysis has been done in the context of the
multihop cooperative relay networks over various types of
fading channels, when both the number of relays and the
number of hops may take arbitrary values.
In addition to BER/SER, the outage probability of
cooperative wireless systems has been investigated, for
example, in [16-19]. In more detail, the lower and asymptotic
bounds of outage probability have been derived in [16]
for dual-hop relay networks experiencing Rayleigh fading.
By contrast, in [17,19], the outage probability has been
derived, when assuming communication over
independent and non-identically distributed Nakagami-m fading
channels. Furthermore, considering capacity/throughput,
in [20-22], the authors have studied the capacity bound
and rate region of two-hop relay networks. In [21], a
traditional three-node relay system has been considered, and
the upper and lower bounds of ergodic capacity have
been derived, when various relay schemes are employed.
In [22], the capacity bounds have been analyzed in the
context of multinode ad hoc networks.
In the published references, such as [13,18,23,24], on
the relay communications employing cooperative relays,
a typical assumption used is ideal cooperation among
relays. Under this assumption, there is no energy
consumption for the information exchange required by
cooperation and, furthermore, other overheads required are
also often ignored.
Against this background, in [25], we studied and
compared various relay processing schemes in association
with the two-hop communication links (THCLs), where
multiple relays assisted one source to communicate with
a destination. We demonstrated that the studies under
ideal assumptions often result in misleading observations,
when practical scenarios were considered. Continuing the
work in [25], in this paper, we investigate further three
types (...truncated)