Research on the improved cooperative cellular system capacity

Recently, the multi-hop cellular networks have been widely studied in order to enhance the cell performances such as the cell capacity. While most of these works merely use the multi-hop methods instead of direct transmission without considering the co-channel inter-cell interference, signal transmission mode and the effects of the number of antennas. With the consideration of above important elements, this paper proposed an improved cellular system with multi-relay amplifies-and-forward (AF) cooperative transmission scheme and the corresponding capacity expression is derived under the corresponding environment. By using the potential space diversity and selecting relays based on maximizing the capacity, the cellular system capacity can be improved effectively. The simulation results show that with the assistance of optimal selected relays, the improved cooperative cellular system capacity with multi-relay AF transmission scheme performs better than single-hop cellular system.     

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Interference cancellation technique under imperfect synchronization in cellular systems

In this paper, an asynchronous cooperative cellular system applied with space-time block coding(STBC)is investigated. A signal detector is proposed based on parallel interference cancellation(PIC), to cancel the inter-symbol interference(ISI)caused by the imperfect synchronization. Simulation results show that the proposed PIC detector can effectively suppress the ISI, but there is still a comparatively high error floor, due to the co-channel interference(CCI)of the cellular system.     

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建设项目设计阶段投资控制的科学管理

设计阶段投资控制是影响工程项目投资的重要阶段,但是至今仍未引起有关部门广泛的重视。从政府主管部门、业主单位、设计单位三个角度分析了设计阶段投资控制存在问题,并提出了解决方法。     

Joint channel and power allocation scheme for cognitive wireless networks

Cognitive radio (CR) is a promising technology deemed to improve the efficiency of spectrum utilization. This paper considers a spectrum underlay cognitive radio network, in which the cognitive users (CUs) are allowed to use the radio spectrum concurrently with the primary users (PUs) under the interference temperature constraint. We investigate the system performance by using the proposed joint channel and power allocation scheme under two transmit strategies to achieve higher data rates and performance diversity gain respectively. Simulation results show that the proposed scheme provides a significant improvement on the bit error rate (BER) performance and spectrum efficiency of a cognitive wireless network.     

Interference cancellation scheme for uplink cognitive radio systems

This paper investigates the interference cancellation (IC) scheme for uplink cognitive radio systems, using the spectrum underlay strategy where the primary users (PUs) and the secondary users (SUs) coexist and operate in the same spectrum. Joint MMSE-based parallel interference cancellation (PIC) and Turbo decoding scheme is proposed to reduce the interference to the PUs, as well as to the SUs, in which the minimum mean square estimation (MMSE) filter is only employed in the first iteration, regarded as the “weakest link” of the whole detection process, to improve the quality of the preliminary detections results before they are fed to the Turbo decoder. Simulation results show that the proposed scheme can efficiently eliminate the interference to the PUs, as well as to the SUs.