Error Rate Analysis of GF(q) Network Coded Detect-and-Forward Wireless Relay Networks Using Equivalent Relay Channel Models

This paper investigates simple means of analyzing the error rate performance of a general q-ary Galois Field network coded detect-and-forward cooperative relay network with known relay error statistics at the destination. Equivalent relay channels are used in obtaining an approximate error rate of the relay network, from which the diversity order is found. Error rate analyses using equivalent relay channel models are shown to be closely matched with simulation results. Using the equivalent relay channels, low complexity receivers are developed whose performances are close to that of the optimal maximum likelihood receiver.Comment: 28 pages, 10 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Performance analysis of diversity techniques in wireless communication systems: Cooperative systems with CCI and MIMO-OFDM systems

This Dissertation analyzes the performance of ecient digital commu- nication systems, the performance analysis includes the bit error rate (BER) of dier- ent binary and M-ary modulation schemes, and the average channel capacity (ACC) under dierent adaptive transmission protocols, namely, the simultaneous power and rate adaptation protocol (OPRA), the optimal rate with xed power protocol (ORA), the channel inversion with xed rate protocol (CIFR), and the truncated channel in- version with xed transmit power protocol (CTIFR). In this dissertation, BER and ACC performance of interference-limited dual-hop decode-and-forward (DF) relay- ing cooperative systems with co-channel interference (CCI) at both the relay and destination nodes is analyzed in small-scale multipath Nakagami-m fading channels with arbitrary (integer as well as non-integer) values of m. This channel condition is assumed for both the desired signal as well as co-channel interfering signals. In addition, the practical case of unequal average fading powers between the two hops is assumed in the analysis. The analysis assumes an arbitrary number of indepen- dent and non-identically distributed (i.n.i.d.) interfering signals at both relay (R) and destination (D) nodes. Also, the work extended to the case when the receiver employs the maximum ratio combining (MRC) and the equal gain combining (EGC) schemes to exploit the diversity gain

Selection Combiner in Time-Varying Amplify Forward Cooperative Communication

This research presents the diversity combining schemes for Multiple Symbol Double Differential Sphere Detection (MSDDSD) in a time-varying amplify-and-forward wireless cooperative communication network. Four diversity combiners, including direct combiner, Maximal Ratio Combiner (MRC), semi MRC and Selection Combiner (SC) are demonstrated and explained in details. A comprehensive error probability and outage probability performance analysis are carried through the flat fading Rayleigh environment for semi MRC and SC. Specifically, error performance analysis is obtained using the PDF for SC detectors. Finally, power allocation expression based on error performance minimization approach is presented for the proposed SC performance optimization. It is observed that the performance analysis matches well with the simulation results. Furthermore, the proposed SC scheme offers better performance among the conventional MRC and direct combiner schemes in the presence of frequency offsets

Performance Analysis of AF Relaying With Selection Combining in Nakagami-m Fading

This paper investigates the performance analysis of a selection combining scheme, which utilizes a variable gain amplify and forward relay over a Nakagami-m fading channel. A selection combiner at a destination node chooses the better link between a relay channel and a direct channel. We derived exact closed-form expressions for moments of signal to noise ratio (SNR), ergodic capacity, and average symbol error probability. Simulation examples confirm that our exact formulas offer a more accurate analysis tool for selection combining than other prevailing approximations without extra complexity. The derived expressions serve as a useful tool for system design due to their validity for any SNR and arbitrary system parameters

Differential Coding for MIMO and Cooperative Communications

Multiple-input multiple-output (MIMO) wireless communication systems have been studied a lot in the last ten years. They have many promising features like array gain, diversity gain, spatial multiplexing gain, interference reduction, and improved capacity as compared to a single-input single-output (SISO) systems. However, the increasing demand of high data-rate in current wireless communications systems motivated us to investigate new rate-efficient channel coding techniques. In this dissertation, we study differential modulation for MIMO systems. Differential modulation is useful since it avoids the need of channel estimation by the receiver and saves valuable bandwidth with a slight symbol error-rate (SER) performance loss. The effect of channel correlation over differential MIMO system has not been studied in detail so far. It has been shown in the literature that a linear memoryless precoder can be used to improve the performance of coherent MIMO system over correlated channels. In this work, we implement precoded differential modulation for non-orthogonal and orthogonal space-time blocks codes (STBCs) over arbitrarily correlated channels. We design precoders based on pair-wise error probability (PEP) and approximate SER for differential MIMO system. The carrier offsets, which result because of the movement of the receiver or transmitter and/or scatterers, and mismatch between the transmit and receive oscillators, are a big challenge for the differential MIMO system. The carrier offsets make the flat fading channel behave as a time-varying channel. Hence, the channel does not remain constant over two consecutive STBC block transmission time-intervals, which is a basic assumption for differential systems and the differential systems break down. Double-differential coding is a key technique which could be used to avoid the need of both carrier offset and channel estimation. In this work, we propose a double-differential coding for full-rank and square orthogonal space-time block codes (OSTBC) with M-PSK constellation. A suboptimal decoder for the double-differentially encoded OSTBC is obtained. We also derive a simple PEP upper bound for the double-differential OSTBC. A precoder is also designed based on the PEP upper bound for the double-differential OSTBC to make it more robust against arbitrary MIMO channel correlations. Cooperative communication has several promising features to become a main technology in future wireless communications systems. It has been shown in the literature that the cooperative communication can avoid the difficulties of implementing actual antenna array and convert the SISO system into a virtual MIMO system. In this way, cooperation between the users allows them to exploit the diversity gain and other advantages of MIMO system at a SISO wireless network. A cooperative communication system is difficult to implement in practice because it generally requires that all cooperating nodes must have the perfect knowledge of the channel gains of all the links in the network. This is infeasible in a large wireless network like cellular system. If the users are moving and there is mismatch between the transmit and receive oscillators, the resulting carrier offset may further degrade the performance of a cooperative system. In practice, it is very difficult to estimate the carrier offset perfectly over SISO links. A very small residual offset error in the data may degrade the system performance substantially. Hence, to exploit the diversity in a cooperative system in the presence of carrier offsets is a big challenge. In this dissertation, we propose double-differential modulation for cooperative communication systems to avoid the need of the knowledge of carrier offset and channel gain at the cooperating nodes (relays) and the destination. We derive few useful SER/bit error rate (BER) expressions for double-differential cooperative communication systems using decode-and-forward and amplify-and-forward protocols. Based on these SER/BER expressions, power allocations are also proposed to further improve the performance of these systems. List of papers included in the dissertation This dissertation is based on the following five papers, referred to in the text by letters (A-E)

Performance Analysis of M-Ary PSK Modulation Schemes over Multiple Double Rayleigh Fading Channels with EGC in Cooperative Networks

paper presented at the 2010 IEEE International Conference on Communications Workshops, Cape Town.(c) 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. Paper also available from the publisher: http://dx.doi.org/10.1109/ICCW.2010.5503940This article studies the performance of M-ary phase shift keying (PSK) modulation schemes over mobile-to-mobile (M2M) fading channels with equal gain combining (EGC) in cooperative networks. The frequency-nonselective M2M fading channels are modeled assuming non-line-of-sight (NLOS) propagation conditions. Furthermore, a dual-hop amplify-and-forward relay type cooperative network is taken into consideration here. It is assumed that K diversity branches are present between the source mobile station and the destination mobile station via K mobile relays. The performance of M-ary PSK modulation schemes is analyzed by evaluating the average bit error probability (BEP). We have derived a simple analytical approximation for the average BEP of M-ary PSK modulation schemes over relay-based M2M fading channels with EGC. The validity and accuracy of the analytical approximation is confirmed by simulations. The presented results show that in a dual-hop relay system with EGC, there is a remarkable improvement in the diversity gain as the number of diversity branches K increases

Wireless Cooperative Networks

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