Ad hoc networking uses wireless technologies to construct networks with no physical infrastructure and so are expected to provide instant networking in areas such as disaster recovery sites and inter-vehicle communication. Unlike conventional wired networks services, services in ad hoc networks are easily disrupted by the frequent changes in traffic and topology. Therefore, solutions to assure the Quality of Services (QoS) in ad hoc networks are different from the conventional ones used in wired networks. In this paper, we propose a new queue management scheme, Interference Drop Scheme (IDS) for ad hoc networks. In the conventional queue management approaches such as FIFO (First-in First-out) and RED (Random Early Detection), a queue is usually managed by a queue length limit. FIFO discards packets according to the queue limit, and RED discards packets in an early and random fashion. IDS, on the other hand, manages the queue according to wireless interference time, which increases as the number of contentions in the MAC layer increases. When there are many MAC contentions, IDS discards TCP data packets. By observing the interference time and discarding TCP data packets, our simulation results show that IDS improves TCP performance and reduces QoS violations in UDP in ad hoc networks with chain, grid, and random topologies. Our simulation results also demonstrate that wireless interference time is a better metric than queue length limit for queue management in multi-hop ad hoc networks.

In multi-hop ad hoc wireless networks, it is well known that TCP suffers severe performance degradation. This is due to its window-based approach to transmission control, which injects traffic bursts into the network. These bursts increase the frequency of contention in the MAC layer which forces the dropping of some packets. This paper proposes an efficient TCP with pacing, Paced TCP, to alleviate MAC contention and thus achieve better performance than the traditional TCP variants. Our design approach is a TCP that probe the available bandwidth of the network without affecting the stability of the network. Simulations show that Paced TCP not only achieves better performance but is also friendly to UDP traffic.