Structure-Free General Data Aggregation Scheduling for Multihop Battery-Free Wireless Networks
Abstract : With advances in wireless power transfer techniques, Battery-Free Wireless Sensor Networks (BF-WSNs) which can support long-term applications, has been attracting increasing interests in recent years. Unfortunately, the problem of Minimum Latency Aggregation Scheduling (MLAS) is not well studied in BF-WSNs. Existing works always have a rigid assumption that there is only one single query which is targeted at the whole network. Aiming at making the work more practical and general, we investigate the general MLAS problem in BFWSNs, which is targeted at any subset of nodes in the network and aimed for an arbitrary number of aggregation queries. Firstly, the general MLAS problem when there is one single query is studied. To control the number of nodes participating in the aggregation process, a node selection algorithm is proposed to cover and connect the whole target nodes. Then, a latency and energy aware scheduling algorithm is proposed to integrate the construction of aggregation tree with the chosen nodes, and the computation of a conflict-free schedule simultaneously, relying on non-predetermined structures. Secondly, the general MLAS problem when there is a group of aggregation queries is studied. Through designing some special structures to avoid collisions between both current and existing aggregation schedules, an algorithm without any waiting time is proposed. Additionally, the algorithm under physical interference model and dynamic energy arrival model are also presented. The theoretical analysis and simulation results verify that the proposed algorithms have high performance in terms of latency and energy efficiency.
? Vehicular networks as a special case of mobile ad-hoc networks make use of the frequently existing communication equipment in cars (either pre-installed or enabled by equipment carried by passengers).
? Wireless Mesh Networks (WMNs) provide a cost efficient way to interconnect existing wireless networks as well as to supply larger areas with network access.
? However, due to the large number of users and existing equipment, one cannot change TCP completely.
? All these existing wireless mesh networks share one important characteristic – they are distributed over large areas.
? In traditional battery-powered WSNs, the MLAS problem has been studied by, where the authors try to minimize the interference between wireless communication links to reduce the latency.
? Due to the limited communication range of sensor nodes, the problem of Minimum Latency Aggregation Scheduling (MLAS) is proved to be NP-hard and has attracted extensive attentions from researchers.
? To address the above problems, we study the coverage aware MLAS problem in multi-hop BF-WSNs in this paper.
? On the basis of the 1-coverage MLAS problem, the q-coverage MLAS problem is also defined and proved to be NP-hard, in which the arbitrary coverage requirement q can be ensured while the aggregated nodes are distributed evenly
• The performance of DDB has been compared with the protocol proposed by [Ni99] and MPR, which uses neighbour knowledge obtained through hello messages. The protocol proposed by [Ni99] was not able to perform well over a wide range of network conditions.
• To evaluate the performance of the proposed routing protocol, we used a generic data transfer application.
• The author proposed two mechanisms to handle the side effects of delayed ACKs: delayed ACKs after slow start and byte counting.
• Unfortunately, the joint channel assignment and routing problem is NPcomplete, thus only approximate solutions have been proposed.
? The theoretical analysis and simulation results verify that the proposed algorithms have high performance in terms of latency.
? Through extensive simulations, it is shown that the proposed algorithms have high performance in terms of both aggregation latency and coverage quality.
? To further understand the performance of the proposed methods, we investigate the coverage quality of each method.
? We evaluate the empirical performance of the proposed algorithms for both the 1-coverage and q-coverage MLAS problem through extensive simulations.
? Specially, the following algorithms are compared to verify the performance of the proposed methods.
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