Cooperative diversity is a new technology to improve bit error rate （BER） performance in wireless communications, A new power allocation algorithm to improve BER performance in cellular uplink has been proposed in this paper. Some existing power allocation schemes were proposed for the purpose of maximizing the channel capacity or minimizing the outage probability. Different from these schemes, the proposed algorithm aims at minimizing the BER of the systems under the constraint of total transmission power. Besides this characteristic, the proposed algorithm can realize a low complexity real-time power allocation according to the fluctuation of channels. Simulation results show that the proposed algorithm can decrease the BER performance of the systems effectively.
Customers＇ satisfaction with services is reflected by quality of experience（QoE）.Insofar,most studies on cooperative communication have been focused on improving the QoE of source users.However,the improvement of a source user＇s QoE is obtained at cost of degradation of the relay user＇s QoE.On the other hand,cooperative communications can achieve performance similar to that of a conventional multiple-input multiple-output（MIMO） system by forming virtual MIMO arrays.Hence,to improve the QoE performance of relay users,this article proposes the concept of a belief threshold at the destination user and a new cooperative scheme based on the belief threshold destination（BTD） technique,while without decaying the BER performance of the communication system.
WANG Liang,XIE Wei-hao,CHEN Hui-min,WU Zhuo Key Laboratory of Specialty Fiber Optics and Optical Access Networks,School of Communication and Information Engineering, Shanghai University,Shanghai 200072,China
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-andforward （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.
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.
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 effiectively suppress the ISI, but there is still a comparatively high error floor, due to the co-channel interference (CCI) of the cellular system.
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.
