2015 IEEE 26th International Symposium on Personal, Indoor and Mobile Radio Communications - (PIMRC): Mobile and Wireless Networks
Maximum Lifetime Routing with Guaranteed Throughput in LEO Satellite Networks Yu Wang1 , Min Sheng1 , King-Shan Lui2 , Lei Zhou3 , Xijun Wang1 and Yan Zhang1 1
State Key Laboratory of ISN, Institute of Information Science, Xidian University, Xi’an, Shaanxi, 710071, China 2 Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong 3 Beijing University of Posts and Telecommunications, Beijing 100876, P.R.China Email:
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Abstract—An important consideration for LEO satellite networks is choosing suitable routes to prolong the network lifetime while stringently guarantee the throughput requirement. However, both the highly dynamic network topology and intrinsically time-varying renewable energy availability pose great constraints and challenges in designing such routing schemes. To solve the problem, we resort to Capacity Region Evolving Graph (CREG) and formulate the throughput constrained maximum lifetime routing problem. Unfortunately, solving the problem without exploiting its special structure is indeed time-consuming, since multiple time intervals must be jointly handled. Two efficient routing algorithms, namely, Maximum Lifetime Routing (MLR) and Shortest Path-based Progressive Routing (SPPR), are thus proposed to reduce the execution time of solving the routing problem. Specifically, MLR decomposes the problem into multiple independent subproblems without trading its optimality, while SPPR exploits the deterministic mobility of satellite networks without solving the optimization problem. Simulation results verify that prolonged network lifetime and balanced traffic distribution can be obtained for both the routing algorithms.
I. I NTRODUCTION The inherent broadcast nature of satellites, their intrinsic global coverage (air, land, and sea), and reliable wireless access to a large number of subscribers imply that satellites have unrivalled advantages in providing global ubiquitous broadband communication. Specifically, they are regarded as an indispensable part of the Next Generation Networks (NGN) to accommodate the burgeoning communication demands [1]. This is particularly the case for LEO satellite networks which can support innovative applications with high throughput and low end-to-end delay requirements. Typically, a LEO satellite revolves around the earth and is normally powered by solar panels when exposed to the sun, i.e., the sun phase. However, after moving to the earth’s eclipse, i.e., the eclipse phase, a satellite is powered by battery, and hence operates on a limited energy budget. Nevertheless, the satellite should still support data relay for other satellites and serve terrestrial users under its coverage with throughput guarantee as when the satellite has abundant energy supply. This paper is supported by NSFC (91338114, 61231008, 61172079, 61201141, and 61301176), 863 project (No. 2014AA01A701), 111 Project (B08038).
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Although battery can be charged repeatedly through solar panels in the sun phase, the Depth of Discharge (DoD) for the battery directly dominates its lifetime [2]. To this end, excessive utilization of energy in the battery will inevitably reduce its lifetime. Studies have shown that for every 15% increase in DoD, the lifetime for nickel hydrogen battery, which powers current Iridium satellite network, should halve. Coupled with the fact that replacing batteries on satellites is generally very hard or even impossible, the battery lifetime is thus essential to the service time of LEO satellites, and eventually the network lifetime1 . In practice, network lifetime is, indeed, a critical issue for LEO satellite networks, since it directly translates into cost savings [3]. Through proper lifetime-efficient strategy, a satellite requires a smaller energy source (solar panel, reactor, etc.) and a lighter battery pack, both of which result in weight savings and accordingly an economic benefit. In this paper, we concentrate on the particular problem of routing for lifetime maximization in LEO satellite networks, while at the same time guaranteeing the network throughput. However, a daunting challenge for the maximum lifetime routing in LEO satellite networks is the highly dynamic topology. Due to periodic rotation of satellites around the earth, frequent link switching and interruption should occur. Along with that, renewable energy sources are intrinsically dynamic with time varying availability. To be specific, satellites in the sun phase will enjoy continuous sunshine for their solar cells, and thus more energy can be consumed for data transmission. On the contrary, satellites in the eclipse phase should be disfavored to conserve energy in the battery. In this regard, an efficient routing scheme should be confronted with both the dynamics imposed by the LEO environment. The first effort towards routing for satellite network lifetime extension is made recently. In [2], the authors present two simple but qualitative routing metrics to route traffic over satellites exposed to the sun, thereby decreasing the average DoD and prolonging the network lifetime. However, they do not fundamentally address what the maximum lifetime is through the optimal routing strategy. For this purpose, we first employ 1 The network lifetime is determined by the minimum battery lifetime among all satellites in the network.
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