A compressed sensing(CS) based channel estimation algorithm is proposed by using the delay-Doppler sparsity of the fast fading channel.A compressive basis expansion channel model with sparsity in both time and frequency domains is given.The pilots in accordance with a novel random pilot matrix in both time and frequency domains are sent to measure the delay-Doppler sparsity channel.The relatively nonzero channel coefficients are tracked by random pilots at a sampling rate significantly below the Nyquist rate.The sparsity channels are estimated from a very limited number of channel measurements by the basis pursuit algorithm.The proposed algorithm can effectively improve the channel estimation performance when the number of pilot symbols is reduced with improvement of throughput efficiency.
Aimed at the problem of unbalanced energy existed in sensor networks, the clustered method is employed to enhance the efficient utilization of limited energy resources of the deployed sensor nodes. In this paper, we describe the network lifetime as a function of the communication and data aggregation energy consumption and analyze the lifetime of different transmission schemes in the homogeneous and heterogeneous sensor networks. The analysis carried out in this paper can provide the guidelines for network deployment and protocol design in the future applications.
In this letter, the problem of blind source separation of Multiple-Phase-Shift-Keying (MPSK) digital signal is considered. The geometry of received MPSK signals constellation is exploited. The column vectors of received signals can be regarded as the points of hyper-cube. All the possible distinct vectors of received signals are found by clustering, and mixing matrix and sources are estimated by searching out the pairing vectors and eliminating redundant information in all possible distinct vectors. Simulation results give the polar diagram of estimated original signals. They show that the proposed algorithm is effective when the original signals is Quadrature-Phase-Shift-Keying (QPSK) or 8-Phase-Shift-Keying (8PSK).
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
