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Proposed is a zero-inserting precoder and a two-stage linear equaliser, to shorten the guard interval in block-based single-carrier modulation. The first-stage equaliser consists of a linear single-tapper-subcarrier frequency-domain equaliser. The second-stage equaliser maximises the SINR, in the time-domain, based on the interference-plus-noise estimated from the zero-padded sub-intervals of the single-carrier modulation. This proposed scheme is applicable even without cyclic prefixing.

It has been known that communication systems are susceptible to strong impulsive noises. To combat this, convolutional coding has long served as a cost-effective tool in the context of moderately frequent occurrence of memoryless impulses with given statistics. Nevertheless, the impulsive noise statistics is hard to be accurately modeled and is generally not time-invariant, making the respective system design challenging. In this article, in the absence of full knowledge of the probability density function (PDF) of impulsive noises, we devise an efficient decoding scheme for single-carrier narrowband communication systems by incorporating a design parameter into the recently introduced joint erasure marking and This is the Pre-Published Version 2 Viterbi decoding algorithm, dubbed the metric erasure Viterbi algorithm (MEVA). The proposed scheme is equivalent to incorporating a well-designed clipping operation into the Viterbi algorithm, of which the clipping threshold has to be appropriately set. In contrast with existing publications that often resort to extensive simulations, we characterize the bit error probability performance associated with the clipping threshold by deriving its Chernoff bound. Simulation results reveal that with a judicious selection of the clipping threshold, the MEVA can be on par with its optimal maximum-likelihood decoding counterpart under fairly general circumstances.

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SUMMARYWe consider the multihop power line communication (PLC) networks of one source, two repeaters, and one destination. In the previous scheme, when the repeaters receive the retransmission data from the source, they use the traditional distributed space-time block code (DSTBC) with all decode-and-forward (DAF) elements to transmit the data, and they do not consider the incorrect decoding. The original contribution is that we propose a novel DSTBC scheme with embedded adaptive DAF/amplify-and-forward (AAF) elements for data retransmission in multihop PLC networks with existing opportunistic listening (OL) protocols. The new scheme has two types (instead of only one type as in the previous scheme), and, in the second type, the coding matrix for data retransmission can use either all DAF elements or hybrid AAF/DAF elements depending on the correctness of OL results. The advantage is to avoid a loss of diversity because of incorrectly received data at the relays. The effectiveness of the proposed scheme is shown in the simulation results. For the impulsive noise parameter δ = 0.8 and worst case background noise (narrowband interference and colored noise) at bit error rate 10 À3 , our proposed system has 1 dB gain over the previous scheme with the traditional DSTBC with all DAF elements.

SUMMARYWe propose that the throughput performance of the DS CDMA unslotted ALOHA system with two user classes is analyzed by the M/M/infinity queueing model without the death rate approximation. The previous scheme uses the M/D/infinity queueing model with the death rate approximation. The new analysis method is simpler than the previous one because four-dimensional summation is replaced by two-dimensional summation in the packet success probability calculation. The speed of new analysis program is 250 times faster than that of the previous one. In the numerical results, we consider the cases when the message arrival rates of the two classes are equal or not equal, and the access control is present or not. It shows that the proposed scheme has more accurate analyzed throughput than the previous one does.

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Power-line communications, conceived as an enabling technology for data networking alternative, is known to be susceptible to impulsive noises to attain assured transmission rate. To combat this obstacle, we design an efficient decoding scheme to incorporate erasures into the Viterbi algorithm. A unique feature of the decoding scheme is that it does not need the detailed knowledge of impulse statistics and only requires an estimate of impulse arrival probability. Surprisingly, our simulation results show that the proposed decoding scheme is on par with its optimal counterpart, where the exact impulse statistics is assumed to be known at receiver, in terms of bit error rate.