The high attenuation which increases as frequency increases in power line communication systems (PLC) makes achieving and sustaining high data rates over such channels a challenging task. In most communication systems, relays are normally deployed to overcome the effect of signal attenuation and to achieve reliable transmissions between users. Amplifyand-forward (AF) and decode-and-forward (DF) relays are often used. In contrast to the existing work on this topic which advocate utilizing relays either between PLC links or between wireless links, the authors of this paper focus on using AF relaying for in-home PLC and wireless systems where one PLC user wants to share data with one wireless user which has no access to the PLC network. We refer to this system as the Hybrid approach. A mathematical method is developed for this network to formulate the capacity of the system by exploiting the statistical properties of both PLC and wireless channels. Monte Carlo simulations are used throughout this paper to validate the analytical results. The impact of several system parameters is investigated in this paper. For the sake of comparison, we also provide the performance analysis and results for a PLC only network. The results showed that the performance of the hybrid system enhances as we increase the relay gain and deteriorates as the end-to-end distance increases. It is also found that the PLC only scheme may outperform the hybrid one if the relay gain is relatively small; however, the user mobility offered by the hybrid system remains the main advantage over the PLC only system. Index Terms-Power-line communications, amplify-andforward, decode-and-forward, wireless communications, signalto-noise ratio.
Abstract-This paper is concerned with the performance analysis of a dual-hop random access network where a single gateway is employed to connect a random number of independent users which are hidden from their destination(s). The gateway is an amplify and forward relay, and is the only mean to connect users to their destinations. We develop accurate mathematical models for the multiple access interference which take into account, in addition to the distribution of the number of active users and their random locations, the effects of fading and thermal noise at both the relay and destinations. A new unified mathematical method is developed, which leads to the derivation of new analytical expressions for the overall spectral-efficiency of the dual-hop random access network over Rayleigh and Nakagamim fading channels. The accuracy of the new mathematical results is confirmed by Monte Carlo simulation. The results of this paper can be used to estimate the aggregate throughput of a dual-hop system employing the slotted-Aloha type protocols.
Abstract-Cooperative diversity is a promising technique for use in wireless networks because it can provide diversity gain without the need to install multiple antennas at the source or destination. This paper is concerned with the performance analysis of a dual-hop random access network employed adaptive power technique (APT) relay in cooperative diversity networks. The network considered uses amplify-and-forward relaying, and is the only mean to connect source to its destination. This scheme is compared with such popular schemes as the orthogonal scheme, best relay selection, maximal ratio transmission (MRT) and the optimum combining scheme. A new unified mathematical method is developed, which leads to the derivation of new analytical expressions for the overall spectral-efficiency of the dual-hop random access network over Rayleigh fading channels. Numerical results show that the APT can benefit from an increase in the number of relays and reduction of the noise power at the relay and destination. The results also show that the performance of the APT is comparable to the other cooperative schemes, except the MRT. Furthermore, the new mathematical results obtained for APT have been confirmed by Monte Carlo simulation.
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