Increasing the capacity of wireless mesh networks has motivated numerous studies. In this context, the cross-layer optimization techniques involving joint use of routing and link scheduling are able to provide better capacity improvements. Most works in the literature propose linear programming models to combine both mechanisms. However, this approach has high computational complexity and cannot be extended to large-scale networks. Alternatively, algorithmic solutions are less complex and can obtain capacity values close to the optimal. Thus, we propose the REUSE algorithm, which combines routing and link scheduling and aims to increase throughput capacity in wireless mesh networks. Through simulations, the performance of the proposal is compared to a developed linear programming model, which provides optimal results, and to other proposed mechanisms in the literature that also deal with the problem algorithmically. We observed higher values of capacity in favor of our proposal when compared to the benchmark algorithms.
Spectrum handoff is a key mechanism for proper and efficient operation of cognitive radios. A handoff occurs when the current operating channel must be freed by secondary users due to the arrival of a primary user. This mechanism is responsible for searching for a new idle licensed channel for secondary use, a task known as channel selection. The order in which the channels are sensed during the handoff has a great impact on performance. This paper proposes a new spectrum handoff scheme that considers the existence of errors in primary user detection to achieve a better channel ordering in terms of spectrum utilization efficiency and primary user interference. Simulation results show that the proposed mechanism outperforms other mechanisms from the literature.
Abstract. In IEEE 802.11 networks composed by multiple APs, before a station can access the network it needs to make a decision about which AP to associate with. Usually, legacy 802.11 stations use no more than the signal strength of the frames received from each AP to support their decision. This can lead to an unbalanced distribution of stations among the APs, causing performance and unfairness problems. This work proposes a new approach that combines the number of associated stations and the current load of each AP plus the virtualization of client wireless interfaces. In this approach, stations permanently switch of association among the APs, staying on each AP for a time that takes into account the number of associated stations and the current load in each AP. Simulation results confirm the improvement obtained in the load balancing and fairness on network capacity allocation, while keeping the maximum network utilization.
In the last few years, IEEE 802.11 applications has experienced a significant growth. This expansion creates scenarios where distinct administrators manage wireless networks. These scenarios lack of a unique authority to perform an adequate channel allocation that minimizes the performance degradation generated by medium access sharing and co-channel interference. This work proposes a new dynamic channel selection mechanism that focuses on the restrictions imposed by scenarios with independent IEEE 802.11 networks and adapts faster to the interference pattern variations. Besides, the performance of the new mechanism is evaluated and compared to others through simulations.
Cognitive radios (CRs) are devices that access spectrum opportunistically taking advantage of unused portions of licensed spectrum. Therefore, depending on the licensed radios activity, cognitive devices may suffer from constant communication disruptions or even lack of opportunities in the access of the spectrum. To solve this problem, we propose a new paradigm of interaction between 802.11 radios and CRs to build hybrid mesh networks. In this architecture every node has 802.11 interfaces, which offer minimum spectrum access guarantees, and some special nodes possess additional CR interfaces, which may be opportunistically used to create "cognitive shortcut links". These shortcuts improve the hybrid network performance reducing the number of hops in routes and alleviating spectrum sharing in 802.11 channels. In order to create these shortcuts, we propose a shortcut discovering and selecting mechanism that presents a good performance when compared to an optimal case.
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