In initial random access, base station (BS) estimates the distance between the user equipment (UE) and BS. In the mobile satellite system (MSS), however, the characteristics of large transmission delay makes the estimation method used in the terrestrial system not applicable in the MSS. To solve this problem, a two-step time delay difference estimation scheme is proposed for orthogonal frequency division multiple access (OFDMA) multi-beam satellite system. We first divide a beam cell into some layered small sub-areas according to the different delay difference values. Then, two types of Physical Random Access Channel (PRACH) preamble burst format are performed: the first one is for the fractional delay difference value measurement and the second one is for the integer part. Further, complete criteria for the designation of PRACH parameters are proposed and closed-form expressions of the system performance are also derived, including the false alarm probability and the missed detection probability. Finally, according to the numerical analysis, the method shows good performance.
Abstract-A resource scheduling scheme which is based on interference pre-cancellation is proposed in this paper for orthogonal frequency division multiple access (OFDMA) multibeam satellite system. Firstly, in order to reuse same channel among beams, Tomlinson-Harashima precoding (TH-Precoding) is introduced to pre-cancel downlink interference of users from different beams. Then, several resource scheduling algorithms are proposed to jointly work with TH-Precoding. Finally, simulations are executed to validate the proposed scheme, which suggest that compared to traditional single frequency reuse scheme, the proposed scheme can successfully eliminate cochannel interference and improve user SINR significantly.
In multi-beam satellite systems, users suffer from 3dB power attenuation in beam-edge area. Joint transceiving can be used to improve this situation. It requires signals of several beams (downlink) or several users (uplink) to be equal-phase, which needs channel estimation and seems to be complex. The purpose of this paper is to reduce complexity of joint transceiving by compositing quasi-equal-phase beams. Firstly, radiation pattern of original component beams are discussed and calculated. Then a modified Least Mean Square (LMS) algorithm is presented to composite quasi-equal-phase beams from component beams calculated above. Lastly a numerical calculation is presented to show that quasi-equal-phase beams are composited with phase error smaller than 0.32 radian.
Abstract-In multi-beam satellite communication systems, users suffer from 3dB power attenuation in beam-edge area. This problem also exists in terrestrial cellular network. To solve this problem, terrestrial system employs joint transceiving that makes adjacent cells transmit signals together. The purpose of this paper is to propose a method of joint transceiving by compositing beams for satellite systems. The equal-gain combination algorithm is presented to simplify beams from component beams. Then we propose a joint transceiving scheme based on component beams based on a simplified processing algorithm. Simulation results show that SIR of users in beamedge increases by 6dB when using the joint transceiving scheme.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.