Routing exploiting multiple heterogeneous wireless interfaces: A TCP performance study

Abstract

This paper proposes a routing scheme that exploits multiple heterogeneous wireless interfaces on a node: a primary 802.11a interface and a secondary 802.11b (or 802.11) interface. In normal conditions, a TCP flow uses a primary path over the 802.11a interface discovered by a reactive routing protocol. But in presence of route breakage due to node mobility, it resorts to its backup path over the 802.11b interface which is already maintained by a proactive routing protocol and is being used for delivery of control or management packets. The secondary interface exhibits different property than the primary interface (i.e., slower rate but larger transmission range). This helps keep TCP flows alive and preserve the TCP window size, thereby making them more resilient to route breakage induced by mobility. ns-2 implementation and simulations reveal several potential benefits of the proposed routing scheme: (1) recovering packets immediately in the event of link failures, (2) maintaining TCP connections while the higher-rate 802.11a path is not available, and even making the 802.11a path more available, (3) preserving the TCP window size during route breakage, which can lead to preservation of throughput, especially when the round trip delay between a source and a destination is large (e.g., either for long-hop connections or in high queueing delay conditions caused by network congestion, or both).