Energy-efficient randomized routing in radio networks

Abstract

The main contribution of this work is to present an energy-efficient routing protocol for single-channel, single-hop radio networks (RN, for short). Such networks are usually deployed in support of special events including search-and-rescue, disaster relief, law enforcement, and collaborative computing, among many others. An RN is typically populated by hand-held, commodity devices, running on batteries. Since recharging batteries may not be possible while on mission, we are interested in designing protocols that are highly energy-efficient. One of the most effective energy-saving strategies is to mandate individual stations to go to sleep whenever they are not transmitting or recieving messages. Consequently, we are interested in protocols that allow stations to power off their transceiver to the largest extent possible.Suppose that station S(i), (1 ≤ i ≤ p), of the RN stores si items. Each item has a unique destination which is the identity of the station to which the item must be routed. The routing problem asks to route all the items to their destinations, while expending as little energy as possible. Since, in the worst case, each item must be transmitted at least once, every routing protocol must take at least n = s1 + s2 ··· sp time slots to terminate. Similarly, each station S(i), (1 ≤ i ≤ p), must be awake for at least si + di time slots, where di denotes the number of items destined for S(i).It is well known that a station is expending power while its transceiver is active that is, while transmitting or receiving a packet. It is perhaps surprising at first that a station expends power even if it receives a packet that is not destined for it. Since in single-hop radio networks every station is within transmission range from every other station, the design of energy-efficient protocols is highly nontrivial! An additional complication stems from the inherent asymmetry of the routing problem: no destination knows the identity of the sender, precluding a priori arrangements between senders and receivers.We show that for every ƒ ≥ 1, the task of routing n items can be completed, with probability exceeding 1 - 1/ƒ, in n + O(q + ln ƒ) time slots and that no station S(i), (1 ≤ i ≤ p), has to be awake for more than si + di + O(qi + ri log p + log ƒ) time slots, where qi is the number of stations that have items destined for S(i), q = q1 + q2 + ··· + qp, and ri is the number of stations for which S(i) has items. Since qi ≤ di, ri ≤ si, and q ≤ n our protocol is close to optimal.