We consider the problem of improving network capacity in wireless mesh networks from the angle of multi-flow diversity. As consecutive packets on a multihop path can interfere with one another within their interference range, the number of concurrent transmissions is limited, thereby degrading throughput performance. This intra-flow interference can be alleviated by enhancing multi-flow diversity in wireless mesh networks. Hence, we propose the use of a fair queueing policy to evenly distribute the traffic load to achieve fair bandwidth allocation among the flows. Through ns-2 simulations we subsequently show that CHOKe can effectively reduce intra-flow interference and improve throughput performance.

In wireless mesh networks, the end-to-end throughput of a flow over a multiple-hop wireless link rapidly decreases as the hop-count between the source and destination nodes increases, and the flows that travel over a path of more than 4-5 hops from its source node eventually starve. To alleviate this unfairness, we propose a weighted random early detection (RED) mechanism that has a different dropping preference according to the hop-count information. When the network is congested, it forwards packets that come from a farther source node with a higher priority. Through extensive simulations, we show that the proposed queue management policy can improve the fairness performance effectively and alleviate the starvation problem in multihop wireless networks.

Despite years of research and development, pioneering deployments of multihop wireless networks have not proven successful. The performance of routing and transport is often unstable due to contention-induced packet losses, especially when the network is large and the offered load is high. In this paper we propose RAIN, a reliable wireless network architecture for large-scale multihop wireless networks. A RAIN network enforces contention control by limiting the queue length at intermediate wireless routers to the minimum. To keep the queue short a RAIN network enforces congestion control through in-network implicit back-pressure. RAIN congestion control is built on wireless datalink layer mechanisms, e.g., mandatory per-frame acknowledgement and inter-frame backoff in popular CSMA/CA wireless transceivers, therefore very efficient and effective compared with those defined at the network or transport layer for the wired Internet. As a result of the built-in contention and congestion control, RAIN presents the end hosts a highly reliable network service model, even more reliable than that of the wired Internet. The end hosts only need to deal with packet losses due to router or routing failures. Therefore, the transport protocol can be significantly simplified. This is in stark contrast to the existing approach of adding more and more complexity to adapt TCP for multihop wireless networks. We propose the details of RAIN datalink layer protocol, and a simple transport protocol at the end hosts. Performance evaluation through intensive simulations shows that RAIN improves the throughput by up to 92% and fairness by up to 48%, with packet losses due to contention and congestion significantly reduced.

In this paper, we consider the problem of mitigating interference and improving network capacity in wireless mesh networks from the angle of temporal-spatial diversity. In a nutshell, while the achievable throughput on a multihop wireless path is limited by intra-flow interference, the overall capacity of a multihop wireless network can be increased by exploiting temporal-spatial diversity of concurrent transmissions that exist among a number of wireless links. Connections that are routed along multihop wireless paths can be scheduled to take place simultaneously if their transmissions do not interfere with each other (significantly).To make a case of exploiting the temporal-spatial diversity to improve network capacity, we focus on transporting downstream traffic at gateway nodes with Internet access. We propose to construct, based on measurements of received signal strengths, a virtual coordinate system that is used to determine the sets of paths along which transmissions can take place with the least inter-flow interference. Based on the sets of non-interfering paths, the gateway node then determines the order with which a gateway node schedules frames of different connections to be transmitted. Through extensive simulation (with real-life measurement traces on an operational, city-wide wireless community network), we show that the downstream throughput of a gateway node in a wireless mesh network can be improved by 10-35% under a variety of network topologies and traffic distributions. This, coupled with the fact that the proposed approach requires only minor code change in the gateway nodes and does not require any additional hardware, makes it a viable option to improving network capacity in existing wireless mesh networks.

IEEE 802.11 has become a dominant standard for wireless local area network (WLAN), and the users' demand for high throughput of IEEE 802.11 is continuously increasing. We propose a new medium access control scheme, TDM-based coordination function (TCF), which can be used when all the stations are within the radio transmission range. TCF uses information on the number of active stations explicitly to eliminate the contention period in the DCF (distributed coordination function) of IEEE 802.11. TCF can improve overall throughput and provide fair sharing of resources among active stations. Also, TCF is simple and can be implemented distributively. Simulation is performed to compare TCF with DCF and FCR (fast collision recovery) in terms of performance.