Fengji Ye

Distance-aware virtual carrier sensing for improved spatial reuse in wireless networks

In this paper we address the issue of improving the spatial reuse in virtual carrier sensing (VCS) mechanisms for wireless networks. The paper examines in detail the channel reservation mechanisms of IEEE 802.11 VCS and shows that its spatial reuse is sub-optimal in a number of scenarios. We also show that the area that should be reserved by the VCS depends on the distance between the transmitter and receiver. We then present a novel VCS scheme that optimizes spatial reuse by incorporating this distance information in the decision making process for the channel reservation. Unlike existing proposals for improving spatial reuse, our scheme does not rely on special hardware design such as directional antennas, power adaptable or dual-channel devices etc., and is thus easily implementable. Simulation results quantify and demonstrate the substantial performance improvements obtained by the proposed scheme.

A Swarm-Intelligence-Based Protocol for Data Acquisition in Networks with Mobile Sinks

This paper addresses the problem of data acquisition in ad hoc and sensor networks with mobile sinks and proposes a protocol based on swarm intelligence, SIMPLE, to route data in such environments. The proposed protocol is based on a swarm agent that integrates the residual energy of nodes into the route selection mechanism and maximizes the networks lifetime by evenly balancing the residual energy across nodes and minimizing the protocol overhead. The protocol is robust and scales well with both the network size and in the presence of multiple sinks. An information theoretic lower bound on the protocol overhead associated with the swarm agent advertisement is also obtained. SIMPLE is also shown to have a lower message complexity compared to similar algorithms previously proposed in literature. Simulation results are used to verify SIMPLEs performance and robustness and also to demonstrate its superior performance over existing algorithms.

SIMPLE: Using Swarm Intelligence Methodology to Design Data Acquisition Protocol in Sensor Networks with Mobile Sinks

This paper addresses the data acquisition problem in sensor networks using mobile sinks. Sensor nodes’ low computational capabilities and limited energy motivate our design of a swarm intelligence based, energy aware protocol, SIMPLE, to route data to the mobile destination via the shortest paths. Using a swarm agent technique to integrate nodes’ residual energy as a metric for the shortest path selection, SIMPLE maximizes the network’s lifetime by evenly balancing residual energy across the network and minimizing the protocol overhead. The protocol’s resilience against node failures is guaranteed by the multiple path technique. It scales well with both the network size and multiple sinks. Simulation results are presented to observe and verify SIMPLE’s performance and robustness. Compared with existing algorithms, SIMPLE is shown to have superior performance. A general tradeoff model is presented to evaluate the performance tradeoffs associated with different protocol parameters.

Distributed Mobility Transparent Broadcasting in Vehicle-to-Vehicle Networks

In this paper, we propose a distributed mobility transparent broadcast (DMTB) protocol to achieve efficient and effective broadcasts in vehicle-to-vehicle networks. The protocol is fully distributed and highly adaptive to node mobility. Although distributed, DMTB does not suffer from the performance degradation induced by the unavailability of global information. The protocols performance is proven to be within a constant of the optimum. A detailed analysis regarding the protocols performance is presented. The simulation results clearly verify that the protocol maintains its performance under high node mobility.

Evaluation of spatial reuse in wireless multiple access networks

In wireless multi-hop networks, the spatial reuse determines the number of simultaneous connections allowed in a given region. It has a strong influence on the throughput and delay characteristics of the network and is thus an important metric in performance evaluation. This paper presents an analytic model for the spatial reuse in a wireless multi-hop network with a random access MAC protocol that uses a fair scheduler to accomplish collision avoidance. We employ a purely probabilistic model to derive the closed form solution for the achievable throughput. Using our model we are able to show the maximum saturation throughput obtainable as a function of the node density.

Enhancing MAC Coordination to Boost Spatial Reuse in IEEE 802.11 Ad Hoc Networks

In a wireless ad hoc network where multi-hop traffic dominates the network, spatial reuse has an enormous impact on the network performance in terms of end-to-end throughput and delay characteristics. In this paper, we investigate the MAC coordination of persistent flows in 802.11 ad hoc networks and point out that the aggressive behavior of 802.11 MAC can throttle the spatial reuse and reduce bandwidth efficiency. We thus propose an adaptive layer-2 pacing scheme fully compatible with 802.11 MAC using explicit MAC feedback to balance the transmissions on adjacent nodes. By promoting MAC coordination, our scheme can assist the MAC to operate around its saturation state while minimizing resource contention. Experiment results demonstrate that our scheme significantly outperforms the original 802.11 MAC by boosting the throughput while still maintaining latency at a low level.

WLC07-6: Distributed Mobility Transparent Broadcast in Mobile Ad Hoc Networks

In this paper we propose a distributed, mobility transparent broadcast (DMTB) protocol to achieve efficient and effective broadcast in mobile ad-hoc networks. The protocol is fully distributed and highly adaptive to node mobility. It does not demand any neighborhood information and incurs little overhead. On one hand, the cross-layer design approach helps achieve effective broadcast with higher efficiency and alleviated interference; on the other hand, the proposed protocol achieves network energy balance by randomly rotating the set of relay nodes in different broadcast events even when the network topology stays unchanged. The protocols performance is proved to be within a constant of the optimum. Detailed analysis regarding the broadcast interference, node density and protocol overhead is presented. DMTB is not only efficient, but also robust against node failures and scalable with the node density or the network area size.