This paper introduces a multicarrier communication technique termed orthogonal chirp-frequency division multiplexing (OCFDM). It relies on a unitary transform named discrete modular chirp transform. The proposed OCFDM amalgamates characteristics from the orthogonal frequency division multiplexing (OFDM) and orthogonal chirp division multiplexing (OCDM), partitioning the frequency spectrum into distinct subbands and populating each of them with orthogonal chirps. By deriving the reconstructed signal at the receiver, the paper shows that the normalized signal-to-noise ratio exhibits changes across subbands, allowing the use of resource allocation, for instance, for power allocation or bit-loading. Moreover, it is shown that the OCFDM introduces an additional degree of freedom through its tile geometries, allowing it to be configured to perform in between OFDM and OCDM and, consequently, to offer novel and balanced trade-offs among symbol error rate, data rate, and robustness to interference. Numerical analyses illustrate those trade-offs and confirm the versatility and efficacy of the OCFDM.

This paper proposes the hybrid power line/wireless system (HPWS) based on the orthogonal chirp-division mul-tiplexing (OCDM) scheme. In this system, the same discrete- Fresnel domain symbols are transmitted through power line and wireless channels, enabling the application of combining techniques in the same domain and hence the signal-to-noise ratio increase at the receiver side. Furthermore, the optimal power allocation for maximizing the achievable data rate or minimizing the average bit error probability is discussed for OCDM-based HPWS. Finally, numerical analyses demonstrate that the OCDM- based HPWS is more appropriate for minimizing the average bit error probability if the transmitter is unaware of the channel state information.

This paper advances the studies regarding inter-ference caused by the cyclic prefix violation and the symbol timing offset in data communication schemes applied to power line communication systems. In this sense, it is shown that a few closed-form expressions can be used to characterize the orthogonal Stockwell division multiplexing (OSDM) scheme, as long it follows a couple of conditions. Moreover, the OSDM is compared to the Hermitian symmetric orthogonal frequency division multiplexing (HS-OFDM) scheme in terms of data rate and bit error probability (BEP) while contemplating narrowband power line channels corrupted by an additive colored Gaussian noise. The numerical results show that the OSDM performs better in terms of data rate than the HS-OFDM when interference affects the data communication system. In addition, the OSDM also surpasses the HS-OFDM in terms of BEP when the data communication system operates without interference or weak interference.

This article studies optimal subcarrier permutation in hybrid power line/wireless systems to either maximize the achievable data rate or minimize the average bit error probability (BEP). In order to better exploit the frequency selectivity of power line and wireless media, subcarrier permutation is optimized under uniform or optimal power allocation over an orthogonal frequency-division multiplexing scheme using maximal-ratio combining. Different from previous works, we demonstrate that the normalized signal-to-noise (nSNR) must be considered instead of the SNR and prove that it can be extended to cases where the minimization of the average BEP and optimal power allocation are considered. Moreover, we show that subcarrier permutation and power allocation problems can be assumed to be decoupled. Numerical results show that performance gains associated with subcarrier permutation become more relevant as the frequency selectivity of the nSNRs increases. In addition, the optimal subcarrier permutation is more effective for minimizing the average BEP than maximizing the achievable data rate and yields similar improvement under the usage of uniform and optimal power allocations.

This paper investigates power allocation for minimizing the average bit error probability (BEP) in hybrid communication systems, more specifically hybrid power line/wireless systems (HPWSs). In this regard, a brief discussion of HPWSs is presented in order to point out the complementary characteristics of power line and wireless media. By considering orthogonal frequency-division multiplexing and maximal-ratio combining, optimization problems associated with the minimization of the average BEP in hybrid communication systems are formulated under two distinct transmission power constraints, called sum power and sum power-channel constraints. For both constraints, it is demonstrated that at most one medium should be used for data transmission over subchannels with the same index in order to minimize the average BEP in hybrid communication systems. Based on this finding, power allocation algorithms are derived for this purpose in HPWSs. Numerical analyses are then used to validate the proposed algorithms by comparing them with interior-point-based power allocation algorithms. In addition, performance comparisons show the advantage of the proposals over alternative algorithms from the literature, including previous algorithms proposed for maximizing the achievable data rate.

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.

This paper outlines important characteristics of hybrid power line/wireless data communication system for smart grid (SG) and Internet of Things (IoT) applications. Moreover, we discuss the hybrid systems advantages in comparison to nonhybrid ones. These advantages are demonstrated not only in the technical point of view, but also in the infrastructural perspective. Also, we highlight a connection between the capillarity of IoT and the communication infrastructure provided by SG. Furthermore, we address the environmental influence on wireless and power line communications. Additionally, we present ergodic achievable data rate expressions for the hybrid power line/wireless channel (HPWC) and hybrid power line/wireless single-relay channel (HSRC) and provide performance analyses by considering four different cases, which are associated with the relative relay position in the single-relay channel model. Based on numerical results, we show that HPWC and HSRC offer a more reliable data transmission path when compared to power line or wireless system working alone.