A New TCP-friendly Link-Layer Protocol for Wireless WAN and Satellite Networks
Davide Astuti · Työväentutkimus Vuosikirja · 2014
The provision of wireless access to voice and data services experienced an impressive growth of importance during the last 20 years. Most of the Internet applications employ the TCP/IP protocol suite to deliver their services. TCP has been developed to operate in a terrestrial network environment. However, with the rapid rise in wireless communication in recent years, it has become important to adapt TCP to heterogeneous environments that include both wireline networks and Wireless Wide-Area Networks (W-WANs), such as satellite and terrestrial wireless networks, in order to optimize performance. The specific link characteristics of wireless and satellite links, in particular high latencies and frequent frame losses due to bit-corruption, affect performance of transport protocols. TCP suffers because of low bandwidth, long connection set-up times, high latency and error rate, inefficient use of air link capacity. Most of next generation satellite systems utilizes Bandwidth-on-Demand (BoD) mechanisms to efficiently share radio resources among a large number of users. BoD mechanisms often causes additional link delay, which has a detrimental effect on TCP performance. In this thesis, we propose a new TCP/IP-friendly link level protocol, namely Satellite Link Aware Communication Protocol (SLACP) which incorporates a novel error-recovery mechanism aimed at drastically reduce the residual Packet Error Rate (PER) as seen by higher layers without producing significant extra delay. The protocol has been validated with experimental evaluations conducted in a Digital Video Broadcasting-Return Channel System (DVB-RCS) satellite environment, where the BoD technique Demand Assignment Multiple Access (DAMA) is employed to regulate the access to the satellite channel. Cross-layer interactions between link layer and transport layer as well as the impact of BoD mechanisms on TCP dynamics are investigated. Furthermore, experiments using a selected set of state-of-the-art TCP enhancements in conjunction with our TCP/IP-friendly link-level protocol have been carried out. The proposed mechanisms and improvements of the link and transport layer would be relevant for many wireless WAN systems.