Issue editor: Piotr Zwierzykowski
This special issue collects extended versions of the selected papers from the 8th IEEE, IET International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP 2012) conference, 18-20 July, 2012, Poznan, Poland, as well as papers on Wire and Wireless Networks accepted from open call.
From the viewpoint of service operators the Total Cost of Ownership (TCO) for developing a communication service comprises from two parts; CAPital EXpenditure (CAPEX) and OPerational EXpenditure (OPEX). These two types of costs are interrelated and affect any service provider’s deployment strategy. In many traditional methods, selection of critical elements of a new service is performed in a heuristic manner aimed at reducing only the OPEX part of the TCO which is not necessarily optimal. Furthermore, exact cost modeling for such services is not always possible and contains some uncertainties. In the current work, after cost modeling of each video streaming element by capturing the effect of the model uncertainties, the TCO optimization problem for video streaming over IP networks is formulated as a stochastic optimization problem. The solution of the proposed optimization problem can cope with the cost modeling uncertainties and track the dynamism in the TCO and lead to a time-varying optimal solution. Numerical analysis results verify the developed method.
Andreas Papadakis, Theodore Zahariadis, George Mamais
Current computer networks are challenged by the overwhelming multiplication of available content and the increasing requirements of the content delivery applications. Content caching is already playing its role in content delivery solutions. In this paper we identify the parameters and conditions that affect the performance of content caching solutions and the improvement of the content delivery process. We evaluate caching solutions performing simulation under varying external conditions based on typical service provision considering user requests, content features and network conditions awareness. Based on the simulation results we then describe the mechanisms of a cache federation using various algorithms. We propose novel ways of multimedia data object identification and the exploitation of the network awareness, for further enhancing of the caching capabilities and related service provision.
Robin Seggelmann, Michael Tuxen, Erwin P. Rathgeb
Secure Shell (SSH) is a multi-channel security protocol running over the Transmission Control Protocol (TCP), which offers channels for several services over a secured connection, such as remote shells and connection forwarding. In this paper we introduce a method for using SSH over the Stream Control Transmission Protocol (SCTP), a transport protocol supporting multi-homing and multi-streaming. We examine benefits of this adaptation, which can be made available to generic
applications with SSH’s connection forwarding without further changes. The results also apply to other application protocols supporting a concept similar to channels.
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In this paper, we consider the two-way relay channel (TWRC) over which communication is performed using space-time block codes (STBC) with physical-layer network coding (PNC) protocol. The three-node two-way relaying (TWR) model consists of two end nodes (sources) simultaneously communicating with each other over a relay node where each node is equipped
with two antennas and uses Alamouti’s STBC to provide diversity. We consider non-reciprocal channels where fading channel coefficients are independent for opposite directions of the same link. We first derive closed form expressions for the outage probability of the STBC-TWR system and uncoded TWRC assuming equal transmit power at each node and decode-and-forward (DF)
strategy at the relay. We show that the STBC-TWR system significantly improves the uncoded TWRC outage performance. Then, to further improve the performance, we propose an optimal
power allocation in TWR scheme employing Alamouti’s STBC and PNC protocol. The optimal power allocation is obtained by maximizing the sum-rate under the total power constraint. We
show that the optimal power allocation considerably improve the outage performance as well as the sum-rate compared to the equal-power case.
Wilfried Gappmair, Otto Koudelka
Due to aggressive goals for future communication systems, direct-conversion receivers are an attractive option in terms of compactness and power dissipation. But the price to pay is an additional impairment introduced by IQ mismatch and DC offset, which might be compensated by appropriately designed DSP algorithms. In this context, recovery of carrier and imbalance parameters has been investigated in many publications available from the open literature. For the current paper, however, we first derive the Cramer-Rao lower bound (CRLB) as the theoretical limit of the jitter variance for joint estimation of carrier frequency/phase, IQ gain/phase imbalance, and DC offset; to this end, the correlation of the noise components – in numerous contributions tacitly neglected – is explicitly taken into account. In the sequel, by means of several simplification steps, we present an approximate closed-form solution for the recovery of carrier and imbalance parameters, whose jitter performance is verified to be close to the CRLB, underlining this way the efficiency of the proposed method.
Ioannis D. Moscholios, John S. Vardakas, Michael D. Logothetis, Anthony C. Boucouvalas
We consider a multirate access tree network accommodating K service-classes of Poisson traffic, and focus on the determination of derivatives of Call Blocking Probabilities (CBP) with respect to offered traffic-load of any service-class. Based on the derivatives, we further show how we can successfully approximate CBP for small variations of offered traffic-load.
Maciej Piechowiak, Piotr Prokopowicz
The paper presents a proposal of a new methodology that evaluates multicast routing algorithms in packet-switched networks with an application of fuzzy sets. Proposed multicriteria mechanism evaluate representative multicast routing algorithms: KPP, CSPT and MLRA (Multicast Routing Algorithm with Lagrange Relaxation) that minimize cost of paths between source and each destination node using Lagrange relaxation, and finally, minimize the total cost of multicast tree. A wide range of simulation research carried out by the authors, confirmed both the accuracy of new methodology and the effectiveness of the MLRA algorithm proposed by authors in earlier works.