Advances in hybrid power line/wireless systems

Abstract

This dissertation investigates the hybrid power line/wireless system (HPWS), which consist of using power line and wireless media in parallel, to improve point-to-point data communication performance. In this context, the studied topics are: power allocation and subcarrier permutation in orthogonal frequency-division multiplexing schemes, as well as the application of orthogonal chirp-division multiplexing (OCDM) schemes into the HPWS. Throughout the dissertation, the simultaneous transmission of the same symbols through power line and wireless channels is considered so that maximal-ratio combining can be employed at the receiver. Regarding power allocation, the achievable data rate and average bit error probability are individually optimized under two and distinct transmission power constraints. Regardless of the power constraint, it is demonstrated that at most one medium must be used in the same subchannel index when the objective is to maximize the achievable data rate or to minimize the average bit error probability. Consequently, well-known solutions are adapted to provide power allocation algorithms that demand low computational costs. Numerical analyses validate the proposed algorithms, proving their optimality and superiority in relation to other algorithms of the literature. With respect to subcarrier permutation, its optimality is analyzed to either maximize the achievable data rate or minimize the average bit error probability, assuming the optimal or uniform power allocations. For all cases, it is shown that the subcarriers used in one medium must be sorted in ascending order of normalized signal-to-noise ratios (nSNRs) and then combined with the subcarriers used in the other medium sorted, in its turn, in descending order of nSNRs. Numerical results show that higher gains of this subcarrier permutation are obtained as frequency selectivity increases and that subcarrier permutation can be extremely useful for increasing the achievable data rate or decreasing the average bit error probability. Regarding the application of OCDM schemes into the HPWS, wide-sense stationary random processes in the discrete-Fresnel domain are studied so that the maximal-ratio combining technique can be derived. In addition, the optimal power allocation is analyzed. Numerical analyses then show that the OCDM-based HPWS may be a suitable choice if the aim is to minimize the bit error probability and the transmitter has partial (one bit of information) or no knowledge of the channel state. Finally, a pilot symbol that enables joint channel estimation and synchronization is derived for power line and wireless OCDM schemes. Numerical results based on measurements validate the proposed symbol