Cross-Layer Architecture for a Satellite–Wi-Fi Efficient Handover

Abstract

To achieve fully mobile communications, considering different environments and modern service requirements, a multiple-segment architecture is the most suitable to guarantee service continuity with acceptable performance. Handover (HO) procedures can be invoked either out of necessity (if the current network connection is going off) or to improve performance (if different bandwidth or quality of service is required). In this scenario, to provide uninterrupted communication services, efficient intersegment HO capability must be implemented. The architecture considered includes a satellite segment and a number of Wi-Fi hot spots. A mobile node (MN) can switch from a segment to other exploiting services of mobile Internet protocol (MIP). This architecture introduces great flexibility and ensures capillary coverage; it also strongly affects Transmission Control Protocol (TCP)-based application performance. To efficiently face HO consequences, particularly when the TCP runs as a transport protocol, an innovative protocol architecture based on cross-layer (CL) exchange of information is proposed. Analyses of TCP dynamics during HOs and the performance improvement introduced with the proposed CL architecture, evaluated through the network simulator Ns-2, are presented.

TCP Performance Issues in Satellite and WiFi Hybrid Networks for High-Speed Trains

“…We examine below the detailed effects on TCP behavior in the two possible VHO cases for our train scenario [14], [15]: from satellite to WiFi and from WiFi to satellite. We refer to a mobile collective terminal on the train that receives TCP downstream flows.…”

“…In particular, we focus on those studies adopting cross-layer methods involving L2, L3, and L4 signalling. The work in [15] proposes to close cwnd at the sender before the VHO execution (hard handover), through cross-layer signalling, based on transport layer ACK. When the VHO procedure re-establishes a connection in the new segment, cwnd is reset to 1 and ssthresh is set equal to the estimated bandwidth for the new link.…”

Cross-Layer Schemes for TCP Performance Improvement in HetNets for High-Speed Trains

“…In particular, we focus on those studies adopting cross-layer methods to improve TCP performance. For instance, the work in [7] proposes to close the congestion window (cwnd) at the TCP sender before the VHO execution (hard handover), through cross-layer signalling, based on transport layer ACK. When the VHO procedure re-establishes a connection in the new segment, cwnd is reset to 1 and ssthresh is set equal to the estimated pipe size of the new link.…”

“…As soon as the e2e signalling is completed for the new path, the receiver (mobile node) sends two duplicate ACKs (for redundancy reasons) that include the bandwidth estimation of the new link to be used for ssthresh update; then, cwnd = 1 and a slow start phase is performed. This approach can be considered as an improvement of [7]. Finally, RTO is updated via signalling at the terrestrial-to-satellite VHO.…”

Proactive TCP Mechanism to Improve Handover Performance in Mobile Satellite and Terrestrial Networks

“…Therefore a new Proactive TCP mechanism, aware of the flows' characteristics and ongoing changes that can adapt their behaviour to these changes, is an effective and efficient approach to solve such problem [6]. Hence here the attempt is to make the seamless handover more efficient by proactively adapting the TCP transmission windows to adapt the network environment so that congestion and buffer overflow situations can be prevented effectively and Mobile Nodes (MN) can experience the seamless mobility with consistent quality.…”