| dc.description.abstract | Among various types of network architectures, the mobile ad hoc network (MANET) and the wireless sensor network (WSN) are two of the most attractive wireless networks. One critical issue for almost all kinds of wireless devices supported by battery powers is power saving (PS). Without power, any wireless device will become useless. Battery power is a limited resource. Hence, how to lengthen the lifetime of batteries is an important issue, especially for MANETs and WSNs, those are supported by batteries only. The PS protocols design for MANETs can also be applied to irregular WSNs. However, when applied to regular WSNs, these protocols are more complicated and less efficient than the protocols design for regular WSNs. Therefore, besides the PS protocols of MANETs, we also design PS protocols for regular WSNs.
For irregular wireless networks, several novel power saving protocols for multi-hop MANETs are proposed. The PS protocols for MANET can be categorized into synchronous, and asynchronous ones. The synchronous PS protocol (e.g. IEEE 802.11’s PS protocol) can not be applied to a multi-hop MANET, because it will cause three problems: namely clock synchronization, neighbor discovery, and network partitioning. To solve these problems, we propose three asynchronous PS protocols for IEEE 802.11-based multi-hop MANETs, namely dominating-awake-interval, periodically-fully-awake-interval, and quorum-based protocols.
The basic idea is twofold. First, we enforce PS hosts sending more beacon packets than the original IEEE 802.11 standard does. Second and most importantly, we carefully arrange the wake-up and sleep patterns of PS hosts such that any two neighboring hosts are guaranteed to detect each other in finite time even under PS mode. Based on our powersaving protocols, we then show how to perform unicast and broadcast in an environment with PS hosts. Simulation results are presented, which show that our protocols can save lots of power when the traffic load is not high.
Although asynchronous solutions are attractive, yet, the cost is high as opposed to synchronous protocols. Hosts in asynchronous protocols need to keep awake for longer time, so as to discover asynchronous PS neighbors. Besides, a broadcasting message has to be sent multiple times if a sending host’s neighbors wake up asynchronously. To conquer the deficiency of asynchronous PS protocols, we propose several cluster-based semiasynchronous PS protocols for multi-hop MANETs. The basic idea is to cluster neighboring hosts such that synchronous PS protocols can be adopted within each individual clusters, and thus conserves more power. Several schemes are provided in our inter-cluster strategy, including probability-based, SNR-probability-based, round-robin-based, neighbor coverage-based and location-based schemes. Simulation results show that, the proposed
semi-asynchronous approaches outperform the asynchronous PS protocols when applied to a multi-hop MANET.
As for regular wireless networks, since the PS protocols for regular WSNs have not been proposed before, we propose several novel power management protocols for regular WSNs. The goal of our protocols is to let as many sensor nodes as possible switch to PS mode while still maintaining the connectivity of the network so that if any emergency occurs, the sensor node, which senses the event, may transmit this information to the base stations through the active sensor nodes without need to wake up any node in PS mode. Besides, each sensor node should switch to PS mode in turn, so that the power consumption of each node can be balanced. Our protocols work as follows: first, choose several different connected dominating sets according to the network topology and assign an id to each of the connected dominating set, and then the nodes in each connected dominating set will switch to active mode to serve the other hosts in PS mode according to which dominating set they belong to in a round robin manner. Each node can decide which connected dominating set it belongs to according to its own id. In our power management protocols, each sensor node should belong to at least one connected dominating set and most of the sensor nodes should belong to the same number of connected dominating sets so that the power consumption can be balanced. Our protocol can still work properly even there are faulty nodes. Performance analysis shows that the ratios of active nodes of our protocols are near optimal and much lower than those of GAF and SPAN, those are designed for high density irregular networks. Simulation results show that our power management protocols can conserve lots of power and greatly extend the lifetime of the network with a reasonable extra transmission delay. | en_US |