Laurie G. Cuthbert

On-demand node-disjoint multipath routing in wireless ad hoc networks

An on-demand node-disjoint multipath routing protocol is proposed to overcome the shortcomings of on-demand unipath routing protocols like AODV and DSR. The protocol has two novel aspects compared to the other on-demand multipath protocols: it reduces routing overhead dramatically and achieves multiple node-disjoint routing paths. Simulation results show that the proposed protocol achieves lower data delay and control overhead as well as higher packet delivery ratio.

Stable node-disjoint multipath routing with low overhead in mobile ad hoc networks

Mobile ad hoc networks are characterized by the use of wireless links with limited bandwidth, dynamically varying network topology and multi-hop connectivity. AODV and DSR are the two most widely studied on-demand ad hoc routing protocols. Previous work has shown some limitations of the two protocols: whenever there is a link break on the active route, each of the routing protocols has to invoke a route discovery process. This leads to an increase in both delay and control overhead as well as a decrease in packet delivery ratio. To alleviate these problems, we modify and extend AODV to include the path accumulation feature of DSR in route request/reply packets so that lower route overhead is employed to discover multiple node-disjoint routing paths. The extended AODV is called stable node-disjoint multipath routing (NDMR) protocol, which has two novel aspects compared to the other on-demand multipath protocols: it reduces routing overhead dramatically and achieves multiple node-disjoint routing paths. Simulation results show that performance of NDMR is much better than that of AODV and DSR.

A reliable node-disjoint multipath routing with low overhead in wireless ad hoc networks

Wireless ad hoc networks are characterized by the use of wireless links with limited bandwidth, dynamically varying network topology and multi-hop connectivity. AODV and DSR are the two most widely studied on-demand ad hoc routing protocols. Previous work has shown some limitations of the two protocols: whenever there is a link break on the active route, each of the two routing protocols has to invoke a route discovery process. This leads to increase in both delay and control overhead as well as decrease in packet delivery ratio. To alleviate these problems, we modify and extend AODV to include the path accumulation feature of DSR in route request/reply packets so that much lower route overhead is employed to discover multiple node-disjoint routing paths. The extended AODV is called Reliable Node-Disjoint Multipath Routing Protocol (NDMR), which has two novel aspects compared to the other on-demand multipath protocols: it reduces routing overhead dramatically and achieves multiple node-disjoint routing paths. Simulation results show that performance of NDMR is much better than that of AODV and DSR.

Node-disjointness-based multipath routing for mobile ad hoc networks

Mobile ad hoc networks are characterized by the use of wireless links with limited bandwidth, dynamically varying network topology and multi-hop connectivity. AODV and DSR are the two most widely studied on-demand ad hoc routing protocols. Previous work has shown some limitations of the two protocols: whenever there is a link break on the active route, each of the two routing protocols has to invoke a route discovery process. This leads to increase in both delay and control overhead as well as decrease in packet delivery ratio. To alleviate these problems, we modify and extend AODV to include the path accumulation feature of DSR in route request/reply packets so that lower route overhead is employed to discover multiple node-disjoint routing paths. The extended AODV is called Node-Disjointness-Based Multipath Routing Protocol (NDMR), which has two novel aspects compared to the other on-demand multipath protocols: it reduces routing overhead dramatically and achieves multiple node-disjoint routing paths. Simulation results show that performance of NDMR is much better than that of AODV and DSR.

Energy-efficient multimedia transmissions through base station cooperation over heterogeneous cellular networks exploiting user behavior

Wireless multimedia traffic has increased considerably in recent years, and it has become urgent to propose new approaches to deliver multimedia application in an energy-efficient manner. In wireless networks, observations show that some multimedia streams requested by users in a certain geographical area for a certain period exhibit very similar behavior. By exploiting the similarity, we can significantly reduce power consumption in wireless cellular networks. In this article, we present the description of user behavior in HCN and then propose an architecture for multimedia transmission over HCN. Based on this architecture, an energy-efficient multimedia transmission scheme is proposed to optimize energy efficiency by exploiting user behavior. In this scheme macrocells and small cells cooperatively multicast/unicast multimedia steams without QoS degradation. Illustrative results indicate that the exploitation of user behavior and base station cooperation is able to bring green multimedia transmission for HCN.

Resource management for service providers in heterogeneous wireless networks

In current commercial wireless networks the service providers mediate between end users and network operators. The service provider can be a good candidate to integrate the different network technologies in a flexible and expandable platform. This paper presents a framework for a service provider to perform resource management in heterogeneous wireless networks. We analyse the characteristics of the service provider, summarize the required management functions and propose an architecture that allows the service provider to support real time resource management and seamless service handover in heterogeneous wireless networks. Additionally, the resource management functions based on two service level agreements are described, and an algorithm to perform QoS degrades of live connections has been implemented. A computer simulator has been developed to demonstrate the functionality and evaluate the performance of the architecture.

Multipath QoS routing of supporting DiffServ in mobile ad hoc networks

Future mobile ad hoc networks (MANETs) are expected to be based on all-IP architecture and be capable of carrying multitudinous real-time multimedia applications such as voice, video and data. It is very necessary for MANETs to have a reliable and efficient routing and quality of service (QoS) mechanism to support diverse applications which have varying and stringent requirements for delay, jitter, bandwidth, packets loss. Providing multipath routing is beneficial to avoid traffic congestion and break in communication in MANETs where routes are disconnected frequently due to mobility. Differentiated Services (DiffServ) which have simple, efficient and scalable characteristics can be used to classify network traffic into different priority levels and apply different scheduling and queuing mechanisms to obtain QoS guarantees. In this paper, we propose a practical node-disjoint multipath QoS routing protocol of supporting DiffServ (MQRD), which provides low routing overhead and end-to-end QoS support. Simulation results show that MQRD achieves better performance in terms of packet delivery ratio and average delay.

Intelligent radio resource management for IEEE 802.11 WLAN

IEEE 802.11 based WLANs have been widely deployed. Currently research is concentrating on how to find the best location for these access points plus tuning their antennas in order to seamlessly cover large areas. With more and more WLAN users, the air interface acts as bottleneck even in high-speed WLAN systems such as IEEE 802.11a. To improve the overall performance of IEEE 802.11 WLAN systems under congestion conditions, an agent-based radio resource management system is proposed that can dynamically change an APs radio coverage pattern in cooperation with surrounding APs. A low-cost four sector semismart antenna array is used for access points. In this paper we present results from a simulation showing system performance. The use of intelligent agents and negotiations for indoor radio resource management is presented and discussed.

Cell size and shape adjustment depending on call traffic distribution

In this paper the potential of a smart antenna based dynamic cell size and shape control scheme is assessed. By intelligent control of antenna pattern, the whole cellular network performance can be improved by contracting the antenna pattern around the source of peak traffic and expanding adjacent cells coverage to fill in the coverage loss. We perform a constrained optimization of antenna patterns by using real-coded genetic algorithms (RCGA), and develop a CDMA cellular system simulator to evaluate the overall improvement of the system performance. A transformation of the problem space is used to remove the principal power constraint. A problem with the intuitive transformation is shown and a revised one is presented. This highlights a problem with transformation-based methods in genetic algorithms. While the aim of transformation is to speed convergence, a bad transformation can be counter-productive. Optimization results for two scenarios show potential capacity improvement exceeding 20%.

Research on network coding based Hybrid-ARQ scheme for wireless networks

In a downlink wireless network, the XOR network coding method was used to combine with the Hybrid-ARQ (HARQ) scheme, which can improve the retransmission efficiency of the wireless network. The average number of transmissions and the average packet delay metrics were used to evaluate the performance of the network coding based HARQ (NC-HARQ). The theoretical analysis was given to compare the NC-HARQ scheme with traditional HARQ scheme, both in the broadcast and unicast scenarios. The theoretical analysis and simulation results show that the NC-HARQ can reduce the average number of trans-missions and benefit the retransmission efficiency with some packet delay expense.