Shubo Ren

Selection of sub-carrier bandwidth in OFDM based mobile satellite communication

In mobile satellite communication systems, Doppler shift is caused by the movement of both unified equipment and satellite, and differs from that in terrestrial mobile communication. Therefore, in OFDM based mobile satellite communication systems, the selection of sub-carrier bandwidth should be different. In this paper, the characteristic of Doppler shift in the satellite communication is analyzed, and then a formula is represented to explain the influence on the theoretical system capacity from sub-carrier bandwidth with specific Doppler shift. Using the formula, this paper gives a practicable means to select the optimal sub-carrier bandwidth, and obtains the optimal range of sub-carrier bandwidth in GEO and LEO circumstances through the simulation.

Multi-Cell Interference Cancellation for TD-SCDMA Compatible Mobile Satellite System

In this paper two multi-cell interference cancellation (MCIC) schemes are proposed for the TD-SCDMA compatible mobile satellite service (MSS) system, including the parallel scheme and the serial scheme. In the MCIC schemes inter-cell interference is reconstructed and cancelled with the initial data, which is obtained through traditional single-cell joint detection (SCJD). Both intra-cell and inter-cell interference can be eliminated through the MCIC schemes and the uplink system performance is greatly improved compared with traditional SCJD scheme.

A Reduced Complexity K-Best SD Algorithm Based on Chi-Square Distribution for MIMO Detection

A reduced K-best sphere decoding (K-best SD) algorithm for Multiple-Input Multiple-Output (MIMO) detection is proposed. The algorithm reduces the complexity of the K-best SD by combining the statistics character of the signal and the requirement of the quality of service (QoS). In the reducing processing of the proposed algorithm, the chi-square distribution (CSD) property of the signal, the optimal symbol error rate (SER) property and the loss of pruning are considered together to give a theoretic error bound and then a threshold to determined which route can be pruned to reduced the calculation complexity. The algorithm reduces the complexity with a controllable cost of performance decrease. Simulation results on a 16QAM system with 4×4 antennas show that the algorithm can attain the near-optimal performance with a significant complexity reduction comparing to the original K-best SD or maximum likelihood (ML) algorithm.

Analysis of other spot-beam interference in TD-SCDMA compatible satellite system

In this paper, other spot-beam interference value is studied based on a mobile satellite system (MSS) compatible with TD-SCDMA by theoretical analysis and numerical simulation. A system model to calculate the interference value is presented by making assumptions such as perfect power control and uniformly distributed users. Numerical results of other spot-beam interference value with different frequency reuse factors and different spot-beam overlap values are obtained. Additionally, the influence of other spot-beam interference value is shown by an example of network design, which shows the mobile satellite system compatible with TD-SCDMA should use frequency reuse factor 1.

Propagation delays computation in GEO multi-beam satellite communications system

In order to overcome delay-sensitive shortcoming of satellite communications system based on Time Division Duplex mode, a scheme of acquiring propagation delay of any place within a spot beam is proposed. It is accurately calculated by space geometric model according to the satellite position ranging results by three calibration stations. Based on actual system parameters in China, the influence on radio frame design and synchronization problem by using midpoint propagation delay as synchronization reference time instead of average propagation delay is analyzed. The result shows that this approximation can not only reduce the computational complexity, but also ensure the adaptability of TD-SCDMA radio frame structure in GEO satellite communications system.

Joint Channel Estimation and Data Detection Based on Pilot Assisted Two-Way Relay Network Single-Carrier System

In this paper, we present a pilot assisted two-way relay network (TWRN) single-carrier frequency domain equalization (SCFDE) system with no cyclic prefix (CP), where two source terminals exchange their information through a relay terminal using the amplify-and-forward relaying scheme. During Phase I of the proposed system, two source terminals transmit the orthogonal pilot sequence and the single-carrier data blocks alternately. During Phase II, the relay terminal amplifies and forwards the combined data from the two source terminals, and both source terminals utilize a certain interference cancellation based algorithm of joint time domain circularly correlated channel estimation and data detection proposed for the non-CP single-carrier data structure. Simulation results show that, compared with TWRN SCFDE based on iterative reconstruction RR channel estimation, the proposed system based on non-CP TWRN SCFDE improves the performance of detection and achieves good channel estimation and tracking at the same time.

Movement Compensation for Uplink Synchronization in SCDMA Mobile Satellite Communication System

In this paper, a new compensation scheme for timing deviation is proposed in the SCDMA mobile satellite communication system. Instead of adjusting the timing deviation directly, the scheme adjusts the timing deviation according to the timing deviation of the current period and the last period. Simulation results show that the proposed scheme performs better than the traditional scheme.

Propagation Delay Characteristics Within Multi-beam Antenna Coverage of LEO Satellite Systems

In this paper a calculation model of propagation delays of satellite beams is introduced according to the analysis of propagation delay characteristic in the LEO multi-beam satellite communications system. Based on actual parameters and beam coverage patterns of the Iridium and Globalstar system, the maximum propagation delay differentials in several typical beams from the center to the edge of the satellites coverage are calculated. Analysis of these results can provide reference for analyzing the feasibility of LEO multi-beam satellite system compatible with uplink synchronization in LTE, and thereby make theoretical preparation for further study of the satellite system compatible with LTE.

Multi-beam Joint Detection Combination for TD-SCDMA Compatible Mobile Satellite Communication System

Based on the characteristic that received signals of different beam cells are sent to the same gateway station in the multi-beam satellite system, this paper introduces a technique of multi-beam joint detection combination for TD-SCDMA compatible mobile satellite communication system. The proposed technique adopts Adjacent Beam Assisted Single-beam Joint Detection (ABA-SB-JD) technique to get the detection signals of users in each target-beam cell and adjacent beam cells from the interference signals of users in adjacent beam cells, and detects the signal of the same user in each beam cell according to the maximal ratio combining principle. The simulation results show that this technique gets a good system bit-error rate performance, significantly reduces the SNR threshold of the system, and greatly improves multi-user detection performance of the multi-beam satellite communication system.

Layer reduced K-best sphere decoding

The detection of multiple-input multiple-output (MIMO) system is an important issue. The K-best sphere decoding (K-best SD) is a promising technology for the MIMO detection. But the complexity of the K-best SD is very high. In this article, a new algorithm is proposed to simply the complexity of the K-best SD. Through analyzing the statistics character of the channel matrix, we propose that the number of K can be reduced with the increasing of the detection layers. Simulation results show that with the price of slight performance drop the proposed algorithm can reduce the complexity of the K-best SD efficiently.