During the recent years, research efforts have been made to study how to deploy the WLAN in a multi-hop manner. One of the many challenges to deploy a multi-hop network is how to provide delay-sensitive application support. Research have been done to study how to use DCF mode in a multi-hop network to provide delay-sensitive application support. However, few research have been made to study how to use PCF mode in a multi-hop network. In this paper, we first propose a CFP leasing scheme based on the PCF mode of 802.11 and a conservative scheduling scheme to enable voice service in a multi-hop network. Then we theoretically and numerically evaluate the performance of proposed scheme. Results show that with the proposed scheme, we can provide real-time application support for a small scale multi-hop network.

Mobile IP protocol has been proven to be problematic when it is used to support global-wide roaming due to the end-to-end signalling scheme used during the handover process which might lead to significant packet loss and generates a large amount of signaling messages. In order to solve these problems, micromobility protocols have been proposed which limit the signalling messages within a domain, i.e. a micromobility domain. The structure of the micromobility domain is directly related to the performance of the micromobility protocols. In this paper, we propose a dynamic micromobility domain construction scheme which dynamically constructs each micromobility domain according to the aggregated traffic information. Furthermore, the proposed scheme supports mobile network. Simulation results show that the proposed scheme reduces the average signalling messages significantly.

The TCP-R (TCP Redirection) is an extension of TCP, which maintains active TCP connections when the disconnection occurs due to the change of the IP address or the change of the network device. In mobile computing environments, the IP address may be changed frequently as the host moves across subnets or changes a network device. However, it is difficult for most network applications to work continuously in such a situation. There is much research to support such dynamics in the network layer, but these attempts in the IP layer tend to incur some complexity. This paper is intended as an investigation of the end-to-end mobility support in transport layer. We developed the simple and secure redirection mechanism in TCP, which enables us to keep our working activities without any intermediate agents. We also show that TCP-R can serve as a solution to the retransmission timeout problem which frequently occurs in mobile environments. We implemented and evaluated a prototype of TCP-R by modifying FreeBSD. The measured performance indicates that TCP-R can maintain operation continuously with minimal overhead and complexity.