Abstract-The recent advent of high speed trains introduces new mobility patterns in wireless environments. The LTE-A (Long Term Evolution of 3GPP -Advanced) networks have largely tackled the Doppler effect problem in the physical layer and are able to keep wireless service with 100Mpbs throughput within a cell in speeds up to 350 km/h. Yet the much more frequent handovers across cells greatly increases the possibility of service interruptions, and the problem is prominent for multimedia communications that demand both high-throughput and continuous connections.In this paper, we present a novel LTE-based solution to support high throughput and continuous multimedia services for high speed train passengers. Our solution is based on a Cell Array that smartly organizes the cells along a railway, together with a femto cell service that aggregates trafc demands within individual train cabins. Given that the movement direction and speed of a high-speed train are generally known, our Cell Array effectively predicts the upcoming LTE cells in service, and enables a seamless handover that will not interrupt multimedia streams. To accommodate the extreme channel variations, we further propose a scheduling and resource allocation mechanism to maximize the service rate based on periodical signal quality changes. Our simulation under diverse network and railway/train congurations demonstrates that the proposed solution achieves much lower handover latency and higher data throughput, as compared to existing solutions. It also well resists to network and trafc dynamics, thus enabling uninterrupted quality multimedia services for passengers in high speed trains.
Abstract-The popularity of wireless local area networks has led to a dramatic increase in the density of access points, especially in urban areas. These access points are individually owned, placed, and power-tuned for their local users and are generally oblivious to others. On the other hand, the abundance of access points that mostly share the same upstream provider, offers opportunities for optimization of association to mitigate the negative impact of the overlapped coverage. We use this opportunity to enable collaboration by using a share of each access point's bandwidth to serve non-local users and gain access to their bandwidth in return. We extend the conventional proportional fair association through sharing and collaboration among individual networks, and present centrally optimized solutions. Our performance evaluation, based on data traces collected in 100 residential locations, demonstrate the superiority of our solution, outperforming the throughput of non-collaborative optimal access by up to 140%1 .
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