Zsolt Alfred Polgar

Cross-layer QoS and its application in congestion control

The paper proposes a preliminary design of cross-layer quality of service applied to congestion control in future Internet. This is an alternative solution to QoS-aware routing, whenever the infrastructure operator cannot add new resources, and/or when re-routing is not possible. Dedicated software, running in each node, collects a list of local parameters such as available transfer rate and one-way delay between all neighbors. Then this real-time status information is distributed to all the in-network management enabled nodes that are allowed to be reached. Due to the statistics regarding individual link traffic, a minimal network coding scheme, triggered by cross-layer quality of service, is temporarily activated. This system presents an enhanced distributed routing that preserves the performances of the running services, despite the congestion which cannot be eliminated.

Improving transmission reliability in wireless sensor networks using network coding

Wireless sensor networks employed in industrial and other special applications have strict requirements concerning the transmission reliability, delays and energy efficiency. This paper proposes a scalable approach for increasing transmission reliability in wireless sensor networks, based on a cooperative scheme that uses Reed–Solomon codes as network code. The block error rate of the proposed coded transmission technique is analyzed in several scenarios and it is shown that our solution improves the error performance even for high coding rates. The paper proposes also a genetic algorithm based optimization of the network code functionality by selecting the most cooperation capable devices. The proposed network coding based solution is compared with automatic repeat request transmissions from the point of view of the resource usage, which influences the energy efficiency and the transmission delays. The evaluations performed show that network coded transmissions can ensure better error performance with significantly less resources.

Analysis of a transport protocol based on rateless erasure correcting codes

This paper presents a protocol designed as an alternative to classical TCP for channels which experience high loss-rates. The protocol is simplified with respect to TCP by eliminating the need of retransmissions and the associated buffers. This is achieved by applying a rateless erasure correcting code to the data that is going to be transferred. A modified version of the TCP congestion control algorithms is used in order to better differentiate between losses caused by errors on the channel and losses caused by congestion in the network. A statistical model for the steady-state throughput of the protocol is included in the paper as well. Using simulations performed in ns-2 the throughput model is validated. Other aspects of the behavior of the protocol are also investigated. The results are promising, mainly showing that the protocol does not experience any significant performance degradation in terms of steady-state throughput, even if the loss rate on the channel is high.

Network coding solution for improving transmission reliability in wireless sensor networks employed in industrial monitoring

One of the most appropriate techniques to increase the reliability of wireless sensor networks used in industrial environments are the network coding techniques. This paper proposes an effective, yet simple and scalable approach based on a relay-assisted cooperative scheme that uses Reed Solomon codes as network codes for such wireless sensor networks with cluster-tree topologies. The global Block Error Rate performances of this approach are analyzed in three different scenarios, characterized by different Block Error Rate distributions of the component paths. The results obtained show that this solution significantly improves the performances even for great coding rates. The paper also proposes an optimization of the network code functionality, based on a genetic algorithm, and concludes that it is effective in improving the performances for high coding rates.

Combined distributed turbo coding and space frequency block coding techniques

The distributed space-time (frequency) coding and distributed channel turbo coding used independently represent two cooperative techniques that can provide increased throughput and spectral efficiency at an imposed maximum Bit Error Rate (BER) and delay required from the new generation of cellular networks. This paper proposes two cooperative algorithms that employ jointly the two types of techniques, analyzes their BER and spectral efficiency performances versus the qualities of the channels involved, and presents some conclusions regarding the adaptive employment of these algorithms.

Network and Channel Coded Cooperation Algorithms for Cellular Networks

The paper analyzes the performances provided by two algorithms that combine the network and distributed channel coding in cooperative schemes with a relay-node serving two mobile stations, placed symmetrically and asymmetrically vs. the base-station. The analysis is performed in scenarios that consider error-affected mobile - relay node channels. It also proposes a low complexity hybrid coded cooperation algorithm that employs adaptively the cooperative or the non-cooperative transmissions. The selection of the cooperation mode is based on the bit error probability estimation on the mobile - relay node channels. I. INTRODUCTION Relaying and cooperation between terminals are considered as some of the most promising approaches for the improvement of the wireless networks performance. The channel-coded (CC) cooperation included in schemes where a relay-node (RN) serves only one mobile station (MS) in its transmission to the base station (BS) is one of the techniques proposed in literature to accomplish those improvements (1) (2). Though this approach is shown to bring performance improvements for the served MS in terms of bit error rate (BER), packet error rate (PER) and/or coverage, the additional time-frequency resources (TFR) required by the RN are used to serve only one MS leading to a loss of performances in terms of spectral efficiency. In order to decrease the effect of the additional TFR upon the spectral efficiency of the MS-BS transmission, Network Coding (NC) techniques were included in coded cooperation algorithms. Since the NC techniques allow cooperation structures within which the RN serves more MSs, such an approach leads to a more efficient employment of the additional TFR of the RN. But, making these techniques effective raises new questions that have to be addressed. The combined use of NC and channel coding was considered in several papers, e.g. (3) (4). NC-based or joint NC-CC coding cooperation algorithms were proposed and their performances were studied in different scenarios, but some practical aspects are still not completely addressed. This paper considers the cooperative scheme within which one RN serves the uplink connections of two MSs, using combined NC and distributed CC (DCC) techniques. It studies some practical aspects related to the selection of the best NC-DCC cooperation algorithm, the simplification of the cooperation techniques for a better and easier integration into cellular systems. The NC-DCC based cooperation algorithms are compared to cooperative algorithms based on DCC and on non-cooperative coded transmissions, in several scenarios. The paper is organized as follows: section II presents briefly the cooperative coding algorithms employed, as well as the scenarios within which their performances are evaluated. Section III presents a comparative study of these cooperative coding algorithms performances in ideal and more realistic transmission scenarios and discusses briefly the possibility of their adaptive employment. Section IV presents a solution proposed by the authors for a simplified and adaptive NC-CC based cooperation algorithm. Finally, section V concludes the paper.

Vertical Handover Decision Algorithm for Heterogeneous Cellular-WLAN Networks

Abstract Multi-access and heterogeneous wireless communications are considered to be one of the solutions for providing generalized mobility, high system efficiency and improved user experience, which are important characteristics of the Next Generation Networks. This paper proposes a Vertical Handover (VHO) decision algorithm for heterogeneous network architectures which integrate both cellular networks and Wireless Local Area Networks (WLANs). The cellular-WLAN and WLAN-WLAN VHO decisions are taken based on parameters which characterize both the coverage and the traffic load of the WLANs. Computer simulations performed in complex scenarios show that the proposed algorithm ensures better performance compared to “classical” VHO decision algorithms.

A cellular — WLAN vertical handover management system for public transport

This paper presents an ubiquitous connectivity solution for public transportation services and proposes a vertical handover (VHO) algorithm between cellular networks and WLANs, used to implement the ubiquitous connectivity in a heterogeneous wireless network. The system architecture, on which our solution relies, is also presented. The novelty of our approach is that the VHO algorithm takes the decision on the target network based on the background traffic and the link quality, besides the received signal level. Our algorithm exploits the fact that the communication device of the vehicle is equipped with several Wi-Fi interfaces which allow the measurement of the available WLANs parameters. The performance of our algorithm is significantly better than those of a classical VHO algorithm which selects the target network based only on the level of the received signal and is similar to that of an optimal VHO algorithm which has complete knowledge of the network parameters.

Cooperation protocol for the uplink of relay assisted cellular networks

The paper proposes a network coded cooperation protocol for the uplink transmission of relay assisted cellular networks characterized by non-ideal source - relay links. The proposed protocol employs Reed Solomon codes as network codes in order to improve the Block Error Rate (BLER) and Bit Error Rate (BER) performance over the slow varying fading channels. The paper presents also an algorithm for the computation of the BLER ensured by the cooperation protocol when the cooperative links are modeled as Block Erasure Channels (BLEC), as well as an analysis of the performance obtained, showing the significant improvement brought by the employment of RS network codes.

ADS-B based real-time air traffic monitoring system

This paper proposes an implementation of an Automatic Dependent Surveillance - Broadcast (ADS-B) based real time air traffic monitoring and tracking system. ADS-B system is a relatively new technology that is redefining the paradigm of COMMUNICATIONS - NAVIGATION - SURVEILLANCE in Air Traffic Management today, and it is an important component of the communication system of the Internet of Things which is harnessed to revolutionize the aerospace industry. ADS-B technology has already proven and certified as a viable low cost replacement for conventional radar systems. The paper describes a low cost solution for ADS-B based real-time air traffic monitoring system implemented on a software defined radio platform, which provides an integrated hardware and software solution for rapidly prototyping high-performance wireless communication systems.