具有睡眠-唤醒循环节点的无线传感器网络可调局部最优地理转发
Tunable locally-optimal geographical forwarding in wireless sensor networks with sleep-wake cycling nodes
摘要：
我们考虑一个无线传感器网络，其主要功能是检测某些罕见的报警事件，并将报警数据包转发到基站，使用地理转发。节点知道它们的位置，它们会进行睡眠-唤醒循环，周期性地醒来，但不是同步的。在这种情况下，当节点具有要转发到信宿的分组时，在该节点等待合适的邻居唤醒的时间与分组一旦被转发到该邻居就朝向信宿进行的进展之间存在折衷。因此，在选择一个中继节点，我们考虑的问题，最小化平均延迟的平均进度的约束。通过约束松弛，涉及拉格朗日乘子，我们制定这个下一跳中继选择问题作为一个马尔可夫决策过程（MDP）。可以找到精确的最优解（BF（最佳正演）），但计算量很大。接下来，我们考虑一个数学上简化的模型，其最优策略（SF（Simplified Forward））原来是一个简单的一步前瞻规则。仿真结果表明，SF是非常接近BF的性能，即使是合理的小节点密度。然后，我们研究了SF的端到端的性能相比，两个极端的政策：最大转发（MF），这使得每跳的最大可能的进展，从而降低网络能耗，和第一转发（FF），转发数据包的第一个节点唤醒，从而往往使端到端的转发延迟小。我们发现，通过适当选择一跳平均进度约束，SF可以被调谐以提供端到端分组延迟和转发路径中的跳数之间的有利权衡。
英文摘要：
We consider a wireless sensor network whose main function is to detect certain infrequent alarm events, and to forward alarm packets to a base station, using geographical forwarding. The nodes know their locations, and they sleep-wake cycle, waking up periodically but not synchronously. In this situation, when a node has a packet to forward to the sink, there is a trade-off between how long this node waits for a suitable neighbor to wake up and the progress the packet makes towards the sink once it is forwarded to this neighbr. Hence, in choosing a relay node, we consider the problem of minimizing average delay subject to a constraint on the average progress. By constraint relaxation, involving a Lagrange multiplier, we formulate this next hop relay selection problem as a Markov decision process (MDP). The exact optimal solution (BF (Best Forward)) can be found, but is computationally intensive. Next, we consider a mathematically simplified model for which the optimal policy (SF (Simplified Forward)) turns out to be a simple one-step-look-ahead rule. Simulations show that SF is very close in performance to BF, even for reasonably small node density. We then study the end-to-end performance of SF in comparison with two extremal policies: Max Forward (MF), which makes the maximum possible progress per hop and thus reduces network energy consumption, and First Forward (FF), which forwards the packet to the first node to wake up, and thus tends to make end-to-end forwarding delays small. We find that, with appropriate choice of one hop average progress constraint, SF can be tuned to provide a favorable trade-off between end-to-end packet delay and the number of hops in the forwarding path.
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