3586 Wang et al.: Error Rate of DAS with Dual-Channel Recption
1. Introduction
Multiple-antenna systems in cellular networks have garnered rising interest due to the fast
growing demand for higher data rates [1-2]. Unlike the traditional Co-Located Antenna
System (CAS) in which antennas are deployed around the Central Base Station (CBS), the
Remote Antenna Units (RAUs) in Distributed Antenna System (DAS) are geographically
deployed but connected to the CBS via optical backhaul [3]. This architecture forms a virtual
cooperative network which can acquire macro-diversity gain [4]. The average distance
between transmitters and recievers can be shortened, which leads to mitigating the path-loss
and saving the transmit power [5-6].
However, in the multicell DAS, the performance is constrained by the Co-Channel
Interference (CCI) produced from the adjacent cells [7]. The impact of the CCI on the system
performance is more serious for a cell edge User Equipment (UE) [8]. To this end, various
approaches to mitigate the CCI have been proposed. One effective method to alleviate the
negative impact of the CCI is to employ the antenna selection scheme [9]. The authors in [10]
and [11] presented a minimized bit-error rate (BER) based antenna selection scheme, and
investigated the spectral efficiency with frequency reuse. The antenna selection strategies
based on the RAUs cooperative transmission and the pilot signals in [12] and [13] were
utilized for the system performance analysis. Li et al. proposed antenna selection algorithms
based on the path-loss and energy efficiency for homogeneous and heterogeneous networks,
respectively [14]. An antenna selection transmission based on the maximized
Signal-to-Interference-plus-Noise Ratio (SINR) was adopted to study the ergodic capacity for
DAS in the multicell environment [15]. Most of the previous literatures treat the noise and the
CCI as Gaussian distributed with fixed variance. The performance evaluated from this
assumption can approximately depict the real performance if the number of the CCI is
sufficiently large. Nevertheless, these analytical results cannot precisely depict the
performance when the number of interfering signals decreases to a single digit. Although the
authors in [16] used non-central limit theory to investigate the error probability, the analytical
results derived from Gaussian and Q-function cannot match the accurate performance. In
addition, compared to Binary Phase Shift Keying (BPSK) signals, little work have been done
on the bandwidth efficient Quadrature Phase Shift Keying (QPSK) modulation signals in
multicell DAS [17]. It is noted by [18] that the Nakagami-m distribution can unify various
fading channels with different degrees of severity, and it is a suitable model to depict the
propagation of the desired signal and the CCI. Since signals experience multipath fading with
different severities in DAS, Nakagami-m fading channel is used in this study. As the in-phase
and the quadrature components of the signals are correlated over Nakagami-m fading channels
[19], it is essential to consider the dependency between the two components of the signals for
the precise performance analysis in the multicell environment.
In this paper, we study the exact error rate performance of the circularly DAS based on the
RAU selection transmission. This architecture has a flexible and open infrastructure, leading
to tractable performance analysis. The contributions of this paper are as follows. Unlike most
previous studies in which the noise and the CCI are assumed to be Gaussian distributed, we
treat the CCI as a random variable with non-constant variance. The dependency between the
in-phase and the quadrature components of the CCI is considered with dual-channel reception
over Nakagami-m fading channels. To reduce the CCI, we present two RAU selection
schemes based on the Best Channel Quality (BCQ) and the Maximized Path-Loss (MPL),