A Comparative Study of Relaying Schemes with Decode-and-Forward over Nakagami-m Fading Channels

Utilizing relaying techniques to improve performance of wireless systems is a promising avenue. However, it is crucial to understand what type of relaying schemes should be used for achieving different performance objectives under realistic fading conditions. In this paper, we present a general framework for modelling and evaluating the performance of relaying schemes based on the decode-and-forward (DF) protocol over independent and not necessarily identically distributed (INID) Nakagami-m fading channels. In particular, we present closed-form expressions for the statistics of the instantaneous output signal-to-noise ratio of four significant relaying schemes with DF; two based on repetitive transmission and the other two based on relay selection (RS). These expressions are then used to obtain closed-form expressions for the outage probability and the average symbol error probability for several modulations of all considered relaying schemes over INID Nakagami-m fading. Importantly, it is shown that when the channel state information for RS is perfect, RS-based transmission schemes always outperform repetitive ones. Furthermore, when the direct link between the source and the destination nodes is sufficiently strong, relaying may not result in any gains and in this case it should be switched-off.Comment: Submitted to Journal of Computer Systems, Networks, and Communication

Cognitive Multihop Wireless Sensor Networks over Nakagami-m Fading Channels

This work is supported by the National Science Foundation of China (NSFC) under Grant 61372114, by the National 973 Program of China under Grant 2012CB316005, by the Joint Funds of NSFC-Guangdong under Grant U1035001, and by Beijing Higher Education Young Elite Teacher Project (no. YETP0434)

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

Performance of Two-Hop DS-CDMA Systems Using Amplify-and-Forward Protocol over Different Fading Channels

This study analyses the performance of directsequence code division multiple access (DS-CDMA) based on two-hop amplify-and-forward protocol over Weibull symmetric fading channels as well as Rayleigh/Rician, Rician/Rayleigh asymmetric fading phenomenas. We investigate the bit-error rate (BER) of the considered system using multiple relays by considering the effect of Weibull fading parameter and Rician K factor on the system performance. Our simulation results demonstrate the positive impacts of the value of fading parameter, Rician K factor and increasing number of relay nodes on BER performance. It is also confirmed that the Rician K factor is more effective on the system performance over Rician/Rayleigh fading channels in comparison with Rayleigh/Rician fading environment

Multi-antenna aspects of wireless fixed relays

Abstract — Multiple antenna schemes can provide performance enhancement but the small size and cost constraints of wireless terminals preclude their use at these terminals. This paper investigates distributed fixed relays (infrastructure-based relaying) which are engaged in cooperation in a two-hop wireless network as a means of removing the burden of multiple antennas on wireless terminals. In contrast to mobile terminals, a small number of antennas can be deployed on infrastructure-based fixed relays. Hence, the paper investigates performance of the distributed cooperative multi-antenna fixed relays. Threshold maximal ratio combining and threshold selection combining of these multiple antenna signals are studied and analyzed. The following results are derived. For a given performance requirement, the multiple antennas at relays can significantly reduce the number of relays required in a network area, ultimately, reducing system deployment cost. In addition, threshold selection combining at the relays represents an excellent compromise between performance and system cost. Finally, the analysis performed in this paper uses the versatile Nakagami fading channel model. I