The adverse propagation phenomena along medium-voltage broadband over power-line (MV-BPL) networks necessitate appropriate resource allocation to ensure that the available bandwidth is optimally exploited and the end devices served by a BPL cell are fairly treated. In this paper, a cross-layer resource allocation scheme is proposed aiming at optimally managing the tradeoff between spectrum utilization and fairness on a BPL cell basis. The proposed scheme has been verified in the framework of the transmission control protocol transmission over BPL networks. Various topologies of BPL cells have been studied with regard to aggregate cell throughput and fairness. The analysis and the simulations performed reveal that the performance of MV-BPL networks is drastically dependent on the grid topology and the users distribution over the BPL cells. In this framework, design considerations concerning the optimal design of wide-area BPL networks are discussed.

Modem satellite networks have emerged as able competitors in a rapidly growing communications market due to several unique inherent characteristics,such as their broadcasting ability and the easy deployment of large scale scalable infrastructure. In order to accommodate the increasing user demand for packet-based applications, satellite systems face the challenge of effective integration of all types of IP services in the unfavorable satellite environment. The Transmission Control Protocol (TCP) is used to transfer the majority of IP traffic over the Internet due to its reliable data delivery and congestion control mechanisms. However, TCP design is based on assumptions that are realistic for wired networks but do not apply to the satellite environment. Phenomena such as high loss rates, long propagation delays and network asymmetry, all commonly encountered in satellite systems, create an unfavorable setting for TCP based applications. This chapter provides an overview of how satellite networking affects TCP performance. It also presents the main performance enhancing techniques encountered in the literature.

In broadband fixed wireless access (BFWA) networks mainly operating above 20 GHz, a clear line-of-sight (LOS) path is necessary between the base stations (BS) and the subscribers (S). In this letter, a Markov-based method to estimate the packet loss rate (PLR) statistical characteristics over a dynamically, due to propagation, varying LOS BFWA channel is presented. The method is verified by means of information theoretic metrics and tested against simulation results.

In this Letter, the first-order Markovian assumption for the description of the dynamic behaviour of rain attenuation is validated by means of information theoretic metrics. An accurate first-order Markov model with parameters calculated by physical inputs is also presented. The proposed method is verified by a stochastic analysis of the first-order distribution and the autocorrelation function (ACF) of the model compared to experimental data.

The transmission control protocol (TCP) is widely used to provide reliable data transmission due to its congestion and flow control mechanisms that provide reliable error recovery in higher layers. In satellite links, various atmospheric phenomena may lead to high packet loss rate (PLR) degrading the TCP throughput. Modem satellite systems operate at frequencies above 10 GHz, where rainfall is the dominant fading mechanism leading to high bit error ratio and correlated packet losses. In this paper, a mathematical analysis is presented to accurately describe the statistical properties of the packet-error process in a dynamically varying satellite channel. The proposed method is extended to provide PLR estimations when block forward error correction (FEC) is employed. A new Markov-based method, based on the previous analysis and adapted to the rain-faded satellite channel, is also presented for the estimation of TCP SACK throughput and tested against simulation results. Based on the information provided by the packet-error model, a study between the TCP performance under various FEC schemes and a proposed adaptive FEC scheme has provided indications about the superiority of the proposed model. Copyright (c) 2007 John Wiley & Sons, Ltd.

The performance evaluation of communication protocols in broadband fixed wireless access (BFWA) networks needs the accurate description of the statistical properties of the packet error process. In BFWA networks mainly operating above 20 GHz, a clear line-of-sight (LOS) path is necessary between the base stations (BS) and the subscribers (S). Rain attenuation is the dominant fading mechanism at these frequencies. In this paper, a Markov- based method to estimate the packet loss rate (PLR) performance over a dynamically, due to propagation, varying LOS BFWA channel is presented and tested against simulation results. The proposed method is based on the first- order Markovian modeling of the rain attenuation process. The proposed method can serve as a performance evaluation tool of various modulation and coding schemes (MCS) and is also applicable even when adaptive fade mitigation techniques are employed in the BFWA network.