دانلود رایگان مقاله هندآف از پیش زمانبندی شده برای خدمات آگاه و دسترسی به اینترنت

Abstract

Existing handoff techniques connect a user to a nearby access point whenever it is available along the user’s moving path. If the path is not fully Wi-Fi covered, the user may suffer from frequent disconnections. In this work, we propose a pre-scheduled handoff scheme, which determines a quality-aware path so a mobile user can move across an Urban Wi-Fi Mesh network with uninterrupted Internet access at a required data rate. This scheme has several novel techniques. Firstly, by concurrently considering the received signal strength at mobile users and the load of mesh routers (MRs), we design two path finding metrics, contact weight and handoff count, according to the coverage information. Secondly, to measure the path metric in a practical mesh network with irregular and dynamic MR coverage, we propose a light-weight Bloom-filter-based polling algorithm to discover the mobile stations (called STAs) covered in MR, and a Bloom-filter-based probabilistic algorithm to estimate the degree of coverage overlapping among MRs. Thirdly, based on the path metrics, our proposed scheme supports flexible rate requirements from mobile users through a fully distributed multi-service-class path finding algorithm. Our pre-scheduled scheme considers both mobility and connection requirement, so that the mobile user can continuously access the Internet with the expected data rate. To our best knowledge, this is the first work to ensure seamless Internet access with rate consideration by finding a Wi-Fi covered geographic path in a practical wireless mesh network. We have carried out extensive simulations, and the simulation results show that the pre-scheduled handoff scheme can provide appealing high data rate to mobile user with minimum handoff delay.

9. Conclusion

In this paper, we study a novel service-aware and seamless Internet access problem, and propose a fully distributed and prescheduled handoff scheme to solve the problem. In our scheme, mobility and connection are well scheduled for the mobile users to continuously access Internet with his expected data rate. Several novel techniques are proposed. First, we propose two novel path finding metrics (contact weight and handoff count) which are closely related to the quality of data service that a mobile user might experience when moving through the network. Second, to measure the path metric in a practical mesh network with irregular and dynamic MR coverage, we first propose a light-weight polling algorithm which exploits Bloom filter to quickly discover the STAs covered in MR, and then further apply the Bloom filter to estimate the degree of coverage overlapping among MRs. Third, based on the metrics, to flexibly support performance requirements of mobile users, we propose a fully distributed multiservice-class path finding algorithm. Finally, we propose a crosslayer pre-scheduled connection strategy where both L2 and L3 handoffs are pre-scheduled on the path for the mobile users. The performance results demonstrate that our pre-scheduled handoff scheme can effectively support network connectivity and with a much higher data rate, as compared with the reference schemes. Instead of relying on the current opportunistic handoff schemes, providing a better-covered path may allow the support of some advanced wireless applications which have higher requirements on network connectivity and transmission quality. For ex-ample, a user may hold a wireless terminal to monitor a remote site. With the support of the pre-scheduled handoff, the user can obtain a seamless network access and high quality surveillance video. This application can be used by policeman on the move to better monitor a public space for security. In this paper, we focus on finding a Wi-Fi covered path to provide the mobile user seamless and high received date rate. To provide the mobile users with flexible QoS support, in our future work, we will take account the delay and jitter into path finding procedure.