209 research outputs found
Cooperative Visible Light Communications With Full-Duplex Relaying
In this paper, we investigate cooperative visible light communication (VLC) system where an intermediate light source acts as a relay terminal. We assume that relay terminal operates in full-duplex mode. In contrast to radio frequency counterparts, full-duplex VLC
terminal is relatively easier to implement due to directive propagation characteristic of light. We first model VLC relay terminal taking into account loop interference channel based on ray tracing simulations. Then, we investigate error rate performance of the relay-assisted VLC system. Our performance evaluations demonstrate the superiority of full-duplex relaying over half-duplex counterpart especially for high modulation sizes
Dispensing with channel estimation: differentially modulated cooperative wireless communications
As a benefit of bypassing the potentially excessive complexity and yet inaccurate channel estimation, differentially encoded modulation in conjunction with low-complexity noncoherent detection constitutes a viable candidate for user-cooperative systems, where estimating all the links by the relays is unrealistic. In order to stimulate further research on differentially modulated cooperative systems, a number of fundamental challenges encountered in their practical implementations are addressed, including the time-variant-channel-induced performance erosion, flexible cooperative protocol designs, resource allocation as well as its high-spectral-efficiency transceiver design. Our investigations demonstrate the quantitative benefits of cooperative wireless networks both from a pure capacity perspective as well as from a practical system design perspective
BER Analysis of Full Duplex Relay assisted BPSK-SIM based VLC System for Indoor Applications
This paper contemplates a relay-assisted visible light communication (VLC)
system, where the light source (Table lamp) acts as a relay node and cooperates
with the main light source. Following the IEEE 802.15.7r1 VLC reference channel
model, we assume that there are two different light sources present in an
office room. The first one is the source terminal present on the ceiling and
another one is the desk lamp that serves as the relay station which works in
full-duplex method. Because of the loop interference channel, we model VLC
relay terminal using ray tracing simulations. We have analyzed bit error rate
(BER) performance of the relay-assisted VLC system using binary phase shift
keying-subcarrier intensity modulation (BPSK-SIM) technique. The proposed
method outperforms existing phase shift keying (PSK) and square M-quadrature
amplitude modulation (M-QAM) techniques. The proposed VLC system using BPSK-SIM
technique achieves a BER performance of for an SNR of 20 dB. The results of
proposed full duplex and half duplex relayed VLC system are evaluated using
equal power allocation (EPA) and optimum power allocations (OPA) techniques
over three different modulation schemes which are 2-PSK, square M-QAM,
BPSK-SIM
Linear Precoding Designs for Amplify-and-Forward Multiuser Two-Way Relay Systems
Two-way relaying can improve spectral efficiency in two-user cooperative
communications. It also has great potential in multiuser systems. A major
problem of designing a multiuser two-way relay system (MU-TWRS) is transceiver
or precoding design to suppress co-channel interference. This paper aims to
study linear precoding designs for a cellular MU-TWRS where a multi-antenna
base station (BS) conducts bi-directional communications with multiple mobile
stations (MSs) via a multi-antenna relay station (RS) with amplify-and-forward
relay strategy. The design goal is to optimize uplink performance, including
total mean-square error (Total-MSE) and sum rate, while maintaining individual
signal-to-interference-plus-noise ratio (SINR) requirement for downlink
signals. We show that the BS precoding design with the RS precoder fixed can be
converted to a standard second order cone programming (SOCP) and the optimal
solution is obtained efficiently. The RS precoding design with the BS precoder
fixed, on the other hand, is non-convex and we present an iterative algorithm
to find a local optimal solution. Then, the joint BS-RS precoding is obtained
by solving the BS precoding and the RS precoding alternately. Comprehensive
simulation is conducted to demonstrate the effectiveness of the proposed
precoding designs.Comment: 13 pages, 12 figures, Accepted by IEEE TW
A Tutorial on the Optimization of Amplify-and-Forward MIMO Relay Systems
The remarkable promise of multiple-input multiple-output (MIMO) wireless channels has motivated an intense research activity to characterize the theoretical and practical issues associated with the design of transmit (source) and receive (destination) processing matrices under different operating conditions. This activity was primarily focused on point-to-point (single-hop) communications but more recently there has been an extensive work on two-hop or multi-hop settings in which single or multiple relays are used to deliver the information from the source to the destination. The aim of this tutorial is to provide an up-to-date overview of the fundamental results and practical implementation issues of designing amplify-and-forward MIMO relay systems
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