Showing papers by "Fabrizio Granelli published in 2007"

Enhanced GPSR Routing in Multi-Hop Vehicular Communications through Movement Awareness

Abstract: Providing reliable and efficient routing in presence of relative movement motivates the introduction of movement awareness to improve performance of existing position-based routing schemes in vehicular ad-hoc networks. The proposed algorithm represents a modification of well-known GPSR which exploits information about movement in order to improve the next forwarding node decision. Performance evaluation of the proposed protocol underlines a promising and robust basis for designing a routing strategy suitable for the automotive scenario.

Cross-Layer Error Control Optimization in 3G LTE

Abstract: 3G long-term evolution (LTE) is a recent effort taken by cellular industries to step into wireless broadband market. The key enhancements target an introduction of new all- IP architecture, enhanced link layer and radio access with OFDM modulation and multiple antenna techniques. In this study, we focus on the overhead deriving from the multilayer ARQ employed at the link and transport layers. To the aim of reducing unnecessary burden on the wireless link, we propose a cross-layer ARQ approach, called ARQ Proxy, which substitutes the transmission of TCP ACK packet with a short MAC layer request on the radio link. Packet identification is achieved through association of a hash function to the raw packet data. Performance of the ARQ Proxy is evaluated using EURAE extensions for ns2 simulator. Results demonstrate significant improvements in terms of system capacity, TCP throughput performance, and higher tolerance to transmission errors.

Self-Adjusting Grid Networks

Abstract: This paper introduces a procedure called traffic engineering for grids for enabling grid networks to self-adjust to resource availability. The proposal is based on monitoring the state of resources and on task migration. It involves several layers of the Internet architecture. Experiments executed in NS-2 are used to illustrate the efficacy of the procedure proposed.

Hierarchical secret sharing in ad hoc networks through Birkhoff interpolation

Abstract: Secret sharing schemes provide a natural way of addressing security issues in mobile ad hoc networks. This paper introduces a flexible framework for secure end-to-end transmission of confidential information which exploits multipath source routing and hierarchical shares distribution. Such a goal is achieved by designing a ideal, perfect, and eventually verifiable secret sharing scheme based on Birkhoff polynomial interpolation and by establishing suitable hierarchies among independent paths.

Performance Limitations of IEEE 802.11 Networks and Potential Enhancements

Abstract: The IEEE 802.11 standard is a significant milestone in the provisioning of network connectivity for mobile users. However, due to the time-variant characteristics of wireless links, interference from other devices and terminal mobility, 802.11-based WLANs suffer from performance drawbacks in relation to wired networks. This chapter surveys the performance issues related to throughput and delay in 802.11 networks and describes proposals to overcome such shortcomings.

Performance optimization of single-cell voice over WiFi communications using quantitative cross-layering analysis

Abstract: Cross-layer design has been proposed to optimize the performance of networks by exploiting the inter-relation among parameters and procedures at different levels of the protocol stack. This may be particularly beneficial in wireless scenarios, and for quality-of-service support. This paper proposes a quantitative study of cross-layer performance optimization for Voice over WiFi communications, which enables design engineers to analyze and quantify interlayer dependencies and to identify the optimal operating point of the system, by using cost-benefit principles. Furthermore, insight gained on the problem enables the proposal of design principles for a Call Admission Control scheme able to enhance the overall system performance by limiting the number of users in the system and signalling to the active terminals of the proper parameter settings to optimize overall performance.

Cross-Layer Error Recovery Optimization in WiFi Networks

Abstract: This paper presents a novel approach for cross-layer error control optimization in WiFi networks. The focus is on the reduction of the overhead deriving from the duplicate ARQ strategies employed at the link and transport layers. The proposed solution, called ARQ proxy, substitutes the transmission of a transport layer acknowledgement with a short request sent at the link layer. Specifically, TCP ACKs are generated based on in-transit traffic analysis and stored at the Access Point. Such TCP ACKs are released towards TCP sender upon a request from the mobile node, encapsulated into link layer acknowledgement frame. TCP ACK identification is computed at the Access Point as well as at the mobile node in a distributed way. ARQ proxy improves TCP throughput in the range of 25-100% depending on the TCP/IP datagram size used by the connection. Additional performance improvement is obtained due to RTT reduction and higher tolerance to wireless link errors.1 2

A study on the usage of cross-layer power control and forward error correction for embedded video transmission over wireless links

Abstract: Cross-layering is a design paradigm for overcoming the limitations deriving from the ISO/OSI layering principle, thus improving the performance of communications in specific scenarios, such as wireless multimedia communications. However, most available solutions are based on empirical considerations, and do not provide a theoretical background supporting such approaches. The paper aims at providing an analytical framework for the study of single-hop video delivery over a wireless link, enabling cross-layer interactions for performance optimization using power control and FEC and providing a useful tool to determine the potential gain deriving from the employment of such design paradigm. The analysis is performed using rate-distortion information of an embedded video bitstream jointly with a Lagrangian power minimization approach. Simulation results underline that cross-layering can provide relevant improvement in specific environments and that the proposed approach is able to capitalize on the advantage deriving from its deployment.

On Connectivity and Capacity of Wireless Mesh Networks

Abstract: Wireless Mesh Networks represent an interesting technology due to their reliability, broad coverage and relatively easy and inexpensive scalability. The architecture is mainly a hybrid solution between ad-hoc and infrastructure networking, where each node potentially acts as a relay, forwarding traffic generated by other nodes. Even if solutions are already available, many research topics have yet to be investigated, as no theoretical studies are available to determine the performance of such networking paradigm. In this work, we aim at providing mathematical expressions for connectivity and cumulative capacity of a mesh network on the basis of the network configuration, in order to provide guiding principles in mesh networks' design and development. An analytical approach is used in determining the connectivity probability, while the "bottleneck collision domain" concept is adopted to estimate capacity. The framework is further validated through comparison with simulation results.