Lianguo Wu

Carrier frequency offset estimation approach for multicarrier transmission on hexagonal time-frequency lattice

In this paper, a novel carrier frequency offset estimation approach, including preamble structure, carrier frequency offset estimation algorithm, is proposed for hexagonal multi-carrier transmission (HMCT) system. The closed-form Cramer-Rao lower bound of the proposed carrier frequency offset estimation scheme is given. Theoretical analyses and simulation results show that the proposed preamble structure and carrier frequency offset estimation algorithm for HMCT system obtains an approximation to the Cramer-Rao lower bound mean square error (MSE) performance over the doubly dispersive (DD) propagation channel.

Efficient cooperative spectrum sensing with minimum sensing error in cognitive radio networks

Spectrum sensing is one of the most important components of cognitive radio technology. Due to fading or shadowing effects of the channel, a cognitive radio (CR) may fail to sense the presence of the primary user (PU). Cooperative spectrum sensing is a good solution to this problem. In this paper, we focus on the optimization of cooperative spectrum sensing in which multiple CRs efficiently cooperate to achieve superior detection accuracy with minimum sensing error. We derive the optimal randomized rule for different decision threshold. Then, the optimal final decision threshold is derived according to minimum sensing error (MSE) rule. By simulations, our proposed strategy shows better performance on ameliorating the final probability of false alarm and the probability of detection simultaneously.

Broadcasting efficient opportunistic network coding for multisource-multidestination scenarios

Network coding across multicast transmission can significantly reduce the number of retransmissions for wireless broadcasting. However, most of the existing network coding schemes for these scenarios base on the assumption that each source has priori knowledge of the others, which restricts the application of network coding seriously. In this paper, we propose a multi-relay opportunistic network coding (MR-OPP-NC) scheme for multisource-multidestination (MSMD) broadcasting scenarios without the above mentioned assumption. In specific, a joint network coding and opportunistic selected scheme is designed in decode-and-forward strategy. Simulation results show that the MR-OPP-NC scheme proposed outperforms the pure opportunistic relaying scheme in delay performance.

An energy-efficient sensor selection strategy based on spatial correlation for wireless sensor networks

In wireless sensor networks (WSNs), power-conserving MAC design is vitally important for sensors which use a power source from a fixed utility or manual battery recharging. In this paper, we propose an energy-efficient sensor selection algorithm with two-hop cooperating transmission, which minimizes the total energy consumption of WSNs by exploiting spatial correlation between sensors without compromising distortion performance. A convex optimization model is set up and we solve this convex optimization problem by adopting a priority ordering method instead of solving complicated equations. The simulation results indicate the necessity of our work for WSNs.

Performance analysis of distributed space-time coded cooperative multicast

Cooperative multicast/broadcast technique which can improve performance of traditional wireless multicast communications system has been paid a broad attention. However, in 2-hop Cooperative multicast system [8], it is easy to arise interference in destination node if all the nodes who decode message correctly in phase 1 forward information to other users simultaneously. In this paper, to solve this problem, we propose the distributed space-time coded cooperative multicast (DSTC-CM) scheme based on coded cooperation, where the base station (BS) sends a part of the information and the relays transmit the rest. The system performance is improved by making use of coding gain provided by the DSTC coded cooperation. The capability of the proposed scheme is evaluated in terms of the outage probability and diversity-multiplexing tradeoff (DMT). The closed-form of the average outage probability is derived. Asymptotic behavior of the average outage probability in high SNR regions is analyzed and it confirms that the proposed scheme is efficient in the sense of achieving full diversity. Finally, we compare the average outage probability and DMT for different transmission protocols in the simulations.

An opportunistic network-coded cooperative uplink transmission scheme for wireless multi-relay networks

In this paper, a feedback-based opportunistic network-coded cooperative scheme is proposed to be combined with cooperative communication in wireless uplink multi-relay networks. Different from previous network-coded schemes that conduct network coding all the time, we propose a scheme that conducts network coding and direct transmission alternately according to the quality of the channels. The outage probability is analyzed theoretically and the approximate expression of outage probability is derived. Compared with the previous schemes, the proposed scheme achieves a performance gain in terms of outage probability. The validity of the proposed scheme is verified by theoretical analysis and simulation results.

Cooperative scheme using STNC for uplink SC-FDMA and downlink OFDMA system

Orthogonal frequency-division multiplexing (OFDM) has recently developed as one of the most popular schemes to overcome multipath fading. Single carrier frequency division multiple access (SC-FDMA) has also been adopted as an alternative of OFDMA for uplink transmission in UTRA LTE. To improve the performance of OFDMA and SC-FDMA, cooperative communication can be used. However, traditional cooperative protocol for multi-carrier system suffers with the issue of imperfect synchronization. TDMA scheme in which each node in the network transmits symbols in its dedicated time slot can solve the asynchronous problem but gives rise to large time delay. In this paper, a novel cooperative scheme by using space-time network coding (STNC) for uplink SC-FDMA and downlink OFDMA system is proposed. For a SC-FDAM/OFDMA system consists of N users and R relay nodes, a full diversity order of R +1 can be achieved while keeping the delay low and the issue of asynchronization is eliminated. Compare with the TDMA scheme where N(R + 1) time slots is required to complete the transmission of a symbol frame, only N+R time slots is needed in our proposed scheme by using STNC at relay nodes.

A novel self-localization algorithm based on RSS for wireless sensor networks

Self-localization is one of the basic problems in wireless sensor networks. In this paper, we propose a new localization algorithm using received signal strength (RSS) with seven anchors in order to balance the complex technology for distance estimation and the accuracy of the localization. First, based entirely on comparison of received signal strength transmitted by mobile anchors, the static nodes can acquire their positions without estimating these distances directly from other nodes. Then the unknown nodes can estimate the path loss exponent nearby with the estimated positions. Finally, the more accurate positions are achieved through log-distance path loss model. This proposed algorithm decreases the complexity of the hardware equipment, and improves the accuracy of localization result.