Throughput Distribution Analysis of Return Link Multi-Gateway Interference Cancellation Strategies for Multi-Beam Broadband Satellite Systems F. Lombardo, A.Vanelli-Coralli, E.A. Candreva, and G.E. Corazza DEIS/ARCES - University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy e-mail: {flombardo,ecandreva}@arces.unibo.it, {alessandro.vanelli, giovanni.corazza}@unibo.it Abstract—This paper presents the study of the throughput distribution for several interference cancellation and gateway co- operation strategies for the return link of a multi-gateway multi- beam broadband satellite system. Different coverage schemes and frequency reuse patterns are considered, taking into account practical system parameters and antenna design. Aim of this work is to provide a tool to ease the seek of design trade-offs, as between spectral efficiency and system complexity. This is ad- dressed showing the distribution of SINR (signal-to-interference plus noise ratio) and the throughput distribution considering different interference cancellation techniques, leveraging on dif- ferent degrees of cooperation between gateways. Index Terms—Interference Cancellation, Satellite Systems, Multi-Gateway, Multi-Beam, Throughput Distribution. I. I NTRODUCTION Satellite communications are undergoing a series of rapid innovations: satellite coverage is instrumental to provide ubiq- uitous connectivity, and the user bit-rate requirements are increasing, as a consequence of the evolution in services and users habits. This situation is stimulating significant research efforts to improve the efficiency of satellite communications, and to overcome present-day liming factors. Moreover satellite systems are leveraging on both a conver- gence and a competition with terrestrial networks, in the aim of meeting the requirements of a digital and fully connected citizenship. This has further boosted the requirement for the satellite capacity, and several advanced signal processing techniques are being studied to meet such requirements by improving the spectral efficiency. Current multi-beam satellites are heavily affected and lim- ited by the inter-beam interference, which is an unavoidable consequence of the overlap of beam patterns. Present-day typical solution is to employ a frequency reuse pattern, in order to provide a spatial separation between beams operated on the same frequency. Several studies, as [1]-[3], on the other hand, are focusing on a more promising approach, i.e. to operate with full frequency reuse and processing the signal in order to mitigate the interference. In this way the throughput is increased by several times, at the only expense of a slightly decreased availability [2]. Nevertheless, these advanced signal processing strategies pose additional challenges to the satellite network design, since the processing is performed at the gateway (GW) side, and it has to be designed considering a limited information exchange amongst gateways. As a matter of fact, the feeder link is one of the system’s bottlenecks in case of high throughput multi-beam satellite systems, since it represents the mean to carry the entire aggregated user generated traffic from the satellite towards the on ground core network. For this reason the total traffic at the satellite is split on different feeder links each one feeding a different and geographically separated gateway. In this paper, building upon [1]-[4], we analyze the impact on user throughput of different interference cancellation (IC) strategies, requiring various levels of gateway coordination. We will first consider a simpler MF (matched filter) processing and a MMSE (minimum mean square error) processing, and then we will evolve up to a centralized MMSE-SIC (successive interference cancellation), the focus being mainly on intra- GW and inter-GW interference cancellation. Performance is provided for a realistic antenna pattern and actual values of number of beams and gateways in terms of user SINR PDF (probability density function) and throughput CDF (cumulative distribution function). In the following, we will start with definition of the refer- ence scenarios and the system model. We will then discuss interference cancellation and gateway cooperation strategies, evaluating and comparing them. II. SCENARIOS DEFINITION The focus of this paper is on the return link of a broadband system based on a Ka-band geostationary satellite having B beams, obtained by a single feed per beam antenna architec- ture. Concerning the ground segment, two assumptions on the GWs are of fundamental importance for this analysis: we assume that the GWs are connected through a high-capacity network, to allow for the information exchange between them, and we assume that each gateway is able to control N BGW beams, due to the available feeder link bandwidth. Users are assumed to be randomly located within each beam and that an MF-TDMA channelisation [5] is adopted with a GC'12 Workshop: The 8th Broadband Wireless Access Workshop 978-1-4673-4941-3/12/$31.00 ©2012 IEEE 95