MAC Performance Analysis for Reliable Power-Line Communication Networks with ARQ Scheme.

We propose and analyze a scheme for wireless channels, which is a combination of a hybrid type I automatic repeat request (ARQ) scheme and a power ramping. In the hybrid type I ARQ scheme, the same redundancy bits for error correction is transmitted repeatedly when a negative acknowledgment (NAK) is obtained. In addition to the ARQ scheme, the power ramping is considered for more reliable downlink data transmission, in which the transmission power is gradually changed from a small level to large levels when the number of retransmission increases. This is done without any knowledge of the channels at the transmitter. Simulation results show that by applying the combined hybrid ARQ and power ramping scheme with properly selected parameters, it has a throughput advantage of 3-5%.

Various Automatic Repeat Request (ARQ) schemes have been used to combat errors that befall information transmitted in digital communication systems. Such schemes include simple ARQ, mixed mode ARQ and Hybrid ARQ (HARQ). In this study we introduce extended ARQ schemes and derive expressions for their throughput performance. We then compare their performance with mixed mode ARQ schemes where it is shown that extended ARQ schemes outperform the mixed mode ARQ schemes. We also show how the parameters for the schemes can be chosen to maximize performance.Keywords: ARQ, extended ARQ, HARQ, mixed mode ARQ, throughput

In an automatic repeat request (ARQ) scheme, a packet is retransmitted if it gets corrupted due to transmission errors caused by the channel. Here we describe a ready-to-implement ARQ scheme with packet combining. An analytical description of the scheme in random error channel shows excellent agreement with simulation results. An upper bound for type-II schemes is defined. For smaller packet sizes, throughput of the proposed scheme is sufficiently close to the upper bound till a very high bit error rate.

Sequential decoding is analyzed in conjunction with an efficient incremental redundancy automatic repeat request (ARQ) scheme using punctured convolutional coding. With the incremental redundancy ARQ scheme, whenever the decoding time of a given data packet exceeds some predetermined value T/sub max/, decoding of that data packet is stopped and incremental redundancy bits are provided by the transmitter, a few bits at a time, as needed. It is shown that the incremental redundancy ARQ scheme provides throughput improvement over the partial retransmission code combining ARQ scheme. The advantage of the incremental redundancy ARQ scheme is that the throughput increases as the starting coding rate increases over all ranges of signal-to-noise ratios. >

As one of the most promising networking technologies, power-line communication (PLC) networks have been gradually used not only in home networking systems but also in industrial IoT (Internet of things). Current studies of PLC medium access control (MAC) protocol (i.e., IEEE 1901) only focus on the single-hop environment; however, in practical industrial IoT and home access communication systems, PLC networks generally utilize a multi-hop architecture. In addition, due to the difference in the MAC standard between 802 series and 1901, existing analytical models of multi-hop IEEE 802.11 wireless networks are not suitable for multi-hop IEEE 1901 PLC networks. In this paper, we propose a theoretical model for performance analysis of multi-hop IEEE 1901 PLC networks, where the impacts of traffic rate (containing relay traffic), buffer size, deferral counter process of 1901, hidden terminal problem and multi-hop environment are comprehensively considered. The modeling process is divided into two parts. In the local modeling part, we construct a brand-new Markov chain model to investigate the carrier sense multiple access with collision avoidance process of IEEE 1901 protocol under the multi-hop environment. In the coupling queueing modeling part, we employ queueing theory to analyze the packet transmission procedure between successive hops. On the basis, we derive the closed-form expressions of throughput, medium access delay, packet blocking probability, end-to-end successful transmission delay and goodput. Through extensive simulations, we verify that our theoretical model can accurately estimate the MAC performance of IEEE 1901 PLC networks in the multi-hop environment.

This paper proposes a new automatic repeat request (ARQ) scheme for reliable broadcasting in distributed wireless LANs. Unlike traditional ARQ schemes for reliable broadcasting, the proposed scheme is highly efficient in its ARQ control information delivery and only introduces light control overhead in the network. Our simulation results show that as compared with traditional ARQ schemes, the proposed scheme improves the LAN throughput by from several tens to more than one hundred percent, depending on the number of nodes in the LAN.

An automatic repeat-request (ARQ) scheme with memory and soft error detectors has been recently proposed by Benelli. Its performance was studied mainly through computer simulation. In this paper, a generalized version of this ARQ scheme is examined. The selection of certain thresholds and weights to minimize the bit error rate in systems using a fixed number of packet repeats is considered. Finally, the evaluation of the average number of transmissions per packet in systems in which negatively acknowledged packets are retransmitted until successfully received is described.

An adaptive control procedure is proposed for the go-back-N and selective-repeat automatic repeat-request (ARQ) schemes. The procedure is to dynamically vary the number and length of continuously transmitted data blocks according to the bit error rate. The throughput of the adaptive ARQ schemes for a half-duplex transmission line is compared with the throughput of corresponding conventional schemes. Numerical results indicate that adaptive ARQ schemes are superior to conventional ARQ schemes when the bit error rate is not known or varies with time.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Although Power Line Communication (PLC) is not a new technology, its use to support data transmission over low voltage (LV) distribution networks is still the focus of ongoing research. This thesis focuses on the channel modelling and performance evaluation of narrowband (NB) PLC system. First, the channel modelling approaches of PLC are studied. Then, the proposed PLC channel modelling method based on the bottom-up approach for LV narrowband PLC in a frequency band between 9 kHz and 490 kHz is presented. This proposed model employs the transmission and scattering matrix methods to calculate the transfer function of a typical LV PLC network which comprises two common cable types (copper cables and aluminium conductor steel reinforced). Unlike the top-down approaches, this model is scalable as the network complexity increases and can better describe the network behaviour as a function of physical parameters.In addition, the noise characteristics and popular noise reduction techniques of PLC are studied. The major impairment to the PLC is the impulsive noise which is mainly generated by the switching transient in the network. Hence, a new technique is proposed to mitigate the impact of impulsive noise on data transmission over power lines. This proposed technique is an optimal Clipping/Blanking nonlinearity technique which is based on the minimum bit error rate (BER) search. Results obtained from the simulation of this technique demonstrate that performance has been enhanced in the NB-PLC system. The performance of the narrowband PLC system is also evaluated in both physical (PHY) and medium access control (MAC) layers. Since Orthogonal Frequency Division Multiplexing (OFDM) is a suitable modulation scheme for hostile environment of the power line, it is used to evaluate the PHY layer performance. As a result of the PHY layer performance analyses, it is found that the BER performance between neighbouring points in the typical LV PLC network is reasonable, but communication beyond one hop have to rely on upper layer protocols. In the MAC layer performance evaluation of the PLC system, the widely known random access MAC protocol that uses the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) will be utilised. The MAC performance evaluation of the PLC system demonstrates a significant packet loss in LV PLC network even with a light traffic condition due to the noisy channel. Furthermore, the goodput declines abruptly once the individual transmission rate is high enough to block the network. In addition, the simulation results show that the channel errors can be reduced by adjusting the MAC parameters to allow the re-transmissions mechanisms to recoup the lost packets.

In this paper1, we investigate different practical automatic repeat request (ARQ) retransmission protocols for twowaywireless relay networks based on network coding (NC). Theidea of NC is applied to increase the achievable throughput for the exchange of information between two terminals through one relay. Using NC, throughput efficiency is significantly improved due to the reduction of the number of retransmissions. Particularly, two improved NC-based ARQ schemes are designed based on go-back-N and selective-repeat (SR) protocols. The analysis of throughput efficiency is then carried out to find the best retransmission strategy for different scenarios. It is shown that the combination of improved NC-based SR ARQ scheme in the broadcast phase and the traditional SR ARQ scheme in themultiple access phase achieves the highest throughput efficiency compared to the other combinations of ARQ schemes. Finally, simulation results are provided to verify the theoretical analysis.

Exponential demand for broadband applications has elicited renewed interest in characterizing noise in power line communication (PLC) networks for optimal error performance analysis. PLC is economical and ubiquitous, however due to multipath phenomena and nonstationary impulsive noise, the PLC channel is very harsh to signal transmission. Recent studies reveal that PLC noise is cyclostationary and modelling its characteristic should exploit the spectral and temporal redundancy. In addition, preliminary research shows that PLC noise exhibits self-similarity and can be predicted by fractal theory. In modelling noise employing fractal theory, the Hausdorff dimension (D) needs to be approximated. D is related to Hurst parameter (H), which is a measure of self-similarity. Hence, it is important to estimate H for accurate noise prediction using fractal theory. H parameter estimators assume stationarity in time series data. Therefore, preprocessing is required for the case of PLC noise before estimating H to make it stationary as periodicity and nonstatioanrity affects the H estimators. In this study, we remove the periodicity hidden in the PLC noise obtained from measurement campaign within several university offices, workshops and laboratories. Then long-range dependence is estimated from this pre-processed noise data by employing three estimation algorithms: R/S (rescaled adjusted range) method, aggregated variance method and absolute values of aggregated series method. Results from the said estimation methods though not the same, show that the Hurst parameters obtained from various noise measurements are greater than 0.5, implying presence of self-similarity with long-term memory. Results from this study will find valuable applications in PLC noise modelling using fractal and chaos theory and in error performance analysis in both narrowband and broadband PLC systems.

Power line Communications (PLC) has gained a lot of interest for the last mile or access because the normal electric power line is utilized for transmission also communication signals. Considerable research effort has been extended on investigating the technologies about the physical (PHY) layer and the medium access control (MAC) layer. But the transmissions scheduling is still a key design problem, especially in multi-hop PLC networks. In this paper, a time slot reuse schedule (TSRS) is proposed, to scheduled access in the networks. It utilizes time slots assignment with special reuse for the nodes in the cell, to improve the channel efficiency. TSRS is an appealing concept for PLC networks, since there is always a manager controlling the network, and PLC networks are often master slave structure with tree topologies. For successfully preventing the potential collision between the nodes, the performance of networks is improved significantly, which is also corroborated by the simulation results.

Power line communication (PLC) technology has created a niche use in the Internet of Things (IoT) by offering flexible and reliable connection among power-driven IoT devices/sensors over existing wired networks. In IoT over PLC networks, massive real-time data generated by the ever-growing connected devices will eventually pose an overwhelming burden on the IoT cloud, which in turn severely degrades the network performance. To cope with these issues, edge computing (EC) has emerged as a complement to cloud computing, aiming at offloading a portion of computing in the cloud to the network edges closer to the IoT devices. However, confronting a practical scenario that some electrical devices cannot communicate with wireless and mobile networks directly, existing EC paradigms may not be directly applied to IoT over PLC networks. In this paper, we propose a novel EC-IoT over PLC paradigm to reduce the transmission latency while migrating a portion of computing from the cloud to the edges. First, we develop a distributed EC platform to serve terminal users (TUs) in different IoT systems with various IoT services. Second, we put forth a cache-enabled scheme to store the popular contents from the cloud and edge sensors to reduce redundant data transmissions between TUs and the cloud. Finally, our experimental results demonstrate that the proposed EC-IoT over PLC network can significantly reduce energy consumption and transmission latency.

Power Line Communications have been the subject of an important research work. At the same time, the growing demand for multimedia communications provides a good prospect for PLC as a promising transmission technique for the “last mile” access network. Orthogonal Frequency Division Multiplexing (OFDM) is a spectrally efficient multicarrier modulation technique for high speed data transmission over multipath fading channels. High Peak-to-Average Power Ratio (PAPR) is a major drawback of OFDM. The high PAR of the OFDM signal has to be considered when setting the range of the digital-to-analog converter (DAC) and dimensioning the line-driver. This paper introduced an improved PAPR reduction scheme using constant envelope modulation. Furthermore, by utilizing continuous phase modulation (CPM) in a CE-OFDM system, the PAPR can be effectively reduced to 0 dB. The paper describes a CE-OFDM based modem for Power Line Communications (PLC) over the low voltage distribution network. Relying on a preliminary characterization of a PLC network, a complete description of the modem is given.

Due to limited buffer space available at routers, the packets in the Internet gets lost or dropped, especially when the network is congested. Automatic repeat request (ARQ), is an error-control method that uses acknowledgments and timeouts to decide retransmission of messages to achieve reliable data transmission. However, the re-transmission of a lost packet further increases the congestion in the network, and hence the end-to-end delay of other coexisting flows. This paper aims at improving the performance of ARQ schemes by introducing a lightweight re-transmission mechanism called LW-ARQ based on the concept of caching of packets at intermediate routers that are indented to be dropped. To evaluate the performance of proposed LW-ARQ scheme, we chose to implement it over TCP protocol considering that TCP has become a de-facto transport layer protocol standard for the Internet. However, the proposed LW-ARQ scheme can be integrated with any protocol that uses either stop-and-wait or sliding window based ARQ scheme to handle packet losses. On analyzing the results obtained by performing simulations, we found that the proposed LW-ARQ scheme improves the average end-to-end delay performance of the TCP protocol.