Opportunistic Routing for Interactive Traffic in Wireless Networks

To take advantage of the broadcast nature of wireless communication, a number of opportunistic routing protocols have recently been proposed. In order to manage the extra signaling overhead associated with operation of the opportunistic routing, these schemes work in terms of `batches' that consist of multiple packets. While these opportunistic protocols can dramatically improve the total throughput, the use of batches means that they are best suited to bulk UDP transfer. However, in the Internet and wireless networks, the vast majority of the traffic is interactive (e.g., TCP/VoIP which requires close interactions and feedback between the two communicating end points). To effectively support interactive traffic, we develop a new opportunistic routing protocol, called RIPPLE. RIPPLE uses an expedited multi-hop transmission opportunity mechanism to achieve low signaling overhead and eliminate re-ordering, and uses a two-way packet aggregation technique to further reduce overhead. We implement the RIPPLE in NS-2 along with several existing routing protocols, including predetermined routing, shortest path routing, the early version of ExOR, MCExOR, and an IEEE 802.11n-like single-hop packet aggregation scheme called AFR. We compare their performance for long-and short-lived TCP transfers and VoIP traffic over a wide range of network conditions, including varying wireless channel states, collision levels, and types of network topologies. Our results show that the RIPPLE scheme consistently achieves 100% - 300% performance gains over other approaches.