Zsuzsanna Ilona Kiss

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.

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.

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.

FECTCP for high packet error rate wireless channels

Current Internet protocols like TCP have been designed to work well on channels with low channel error rates. Wireless channels on the other hand exhibit high loss rates when compared to wired channels. Current TCP implementations usually attribute packet losses caused by channel errors as being actually caused by congestion. The result is an unnecessary reduction of the sending rate which leads to a performance degradation. For channels with high packet error rates a discrimination mechanism between channel loss and congestion loss is needed in order to make TCP perform better over such links. This paper presents an approach for the implementation of a TCP-like transport protocol1 by using rateless erasure correcting codes for the error handling mechanism. Based on the distribution of packet losses on the channel the classical congestion control mechanism of TCP is modified as to better differentiate between packet losses caused by the wireless link and packet losses caused by congestion.

Load balancing solution for heterogeneous wireless networks based on the knapsack problem

This paper proposes a practical approach to load balancing in heterogeneous wireless networks, which is based on the adaptation of the multiple knapsack problem to this specific scenario. Several algorithms capable of solving the knapsack problem are considered, namely a brute force, a dynamic programming and a greedy approach. The algorithms are evaluated by computer simulations in terms of the capability of finding the optimal solution and of computational complexity. The best algorithm identified, capable to generate near to optimal solutions while keeping low the computational complexity, is integrated into a load balancing mechanism intended to be used in real communication networks. The test scenario and the results obtained by practical experiments are presented and analyzed.

Load balancing algorithms in heterogeneous networks for intelligent transportation systems

Nowadays the Always Best Connected paradigm becomes more and more important, but fulfilling the requirements of this paradigm is not an easy task. Providing ubiquitous connectivity in the particular case of intelligent transportation systems requires, in most of the cases, the joint usage of the transmission capacities offered by several wireless access technologies. This paper proposes a Game Theory based load balancing algorithm capable to distribute efficiently the data flows generated by various services used by the passengers of the transportation vehicles over the transmission channels of several wireless networks. The paper proposes also two reference load balancing algorithms, the Round Robin and the Multiple Knapsack algorithms, for assessing the performance improvement brought by the Game Theory based algorithm. Simulations performed in a realistic scenario validate the good performance of the proposed algorithm and show that this algorithm is a good alternative for load balancing operations.

Network coding based resource efficient congestion control for video streaming

The paper proposes a resource efficient solution for Network Coding (NC) based congestion control consisting in identification around the congested links of multiple butterfly or other low complexity NC-capable topologies by using the Discrete Lagrange Multiplier optimization algorithm. The identification of the NC-capable topologies is based on the resource management capabilities foreseen for the network entities of the Future Internet. The congestion control issue is tackled by separate encoding of appropriately selected groups of data flows passing through the bottleneck link. By optimal selection of the data flows to be encoded, the additional network resources required by the NC operations can be minimized. The encoding is realized by using an XOR-based algorithm adapted for unequal bit rate data flows, and the experimental performances are reported here. Due to its efficient usage of the network resources and high degree of scalability, the congestion control solution proposed in this paper is suitable for large bit rate transmissions, like video streaming.

Seamless connectivity platform architecture for public transportation

Providing ubiquitous connectivity to the passengers of public transportation vehicles is an important goal of the communication system designers in the context of fast development of the intelligent transportation systems and of Future Internet communication technologies. Efficient usage of transmission resources available in the heterogeneous networking environment, characteristic to todays wireless networks, and effective routing over these networks with minimal involvement of the operators core networks are some of the requirements for a fast and cost effective deployment. This paper proposes the architecture of an ubiquitous connectivity system for public transportation, the architecture design being considered on three distinct levels: system, functional and platform level. The proposed system architecture specifies a minimal set of entities required to implement envisaged connectivity solution and based on a functional analysis the subsystems and modules are derived. By mapping the functional architecture on the hardware components intended to be used the platform architecture is developed.