Hybrid Power Line/Wireless Systems: An Optimal Power Allocation Perspective

This paper investigates optimal power allocation in hybrid power line/wireless systems (HPWS). By adopting maximal-ratio combining (MRC) for the signals received from different channels, power allocation problems under sum power and sum power-channel constraints are formulated. These power constraints impose distinct bounds on the transmission power and, as a consequence, constitute different optimization problems. Therefore, two power allocation algorithms, which aim to maximize the achievable data rate in HPWS, are obtained. Furthermore, mathematical analyses show that data communication must employ only one medium per subchannel as the sum power constraint and frequency-selective channels are taken into account. Also, with high probability, the sum power-channel constraint results in the same conclusion with respect to the sole use of one medium per subchannel when the channels are frequency selective. In other words, MRC and selection-combining yield the same performance in terms of achievable data rate. Numerical analyses evaluate the proposed power allocation algorithms for exploiting the diversity between power line and wireless media by comparing them to alternative algorithms reported in the literature, especially when the total transmission power belongs to a practical range, and the attained results confirm their effectiveness and validate their usage in practical scenarios.