Applied Mechanics and Materials Vols. 631-632

Abstract: In order to meet the requirements of low bit error-rate of the channel code in the space optical communication system, a construction method of low density parity check ( LDPC) codes with excellent performance is proposed based on protograph and quasi-cyclic expansion. It can be applied in high-speed encoding and decoding with efficient quasi-cyclic expansion. According to the proposed method, a LDPC ( 8832, 1472) suitable for the space optical communication system is constructed, in which the LDPC codes of the protograph perform very well. Simulation shows that the LDPC codes have superior error-correction performance and show no sign of error floor when the BER is in the order of 10-9, which are suitable for the long-distance space optical communication systems.

Abstract: This paper proposes an alternative solution for Long-Reach Ethernet passive optical networks. The proposed scheme enables directly communication between ONUs for the transmission of local traffic and control messages, and each ONU calculates bandwidth allocation independently without participation of OLT to remedy the long propagation delay of LR-PON. This scheme also supports centralized control by OLT to change ONUs’ parameters synchronously. Simulation results show that this scheme can effectively reduce the end-to-end packet delay, while maintaining high throughput in uplink channel.

Abstract: This paper analyzes a MAC (Medium Access Control) layer throughput over error-prone channel in the IEEE 802.11ac-based wireless LAN with DCF (Distributed Coordination Function) protocol and A-MPDU (MAC Protocol Data Unit Aggregation) scheme, using theoretical analysis method. The MAC saturation throughput is evaluated by using a PER (Packet Error Rate) on the condition that the number of station, transmission probability, the number of parallel beams and the number of frames in each A-MPDU are variables. When the PER is 10^-2 and the number of aggregated MPDUs in each A-MPDU is 20, it is identified that the MAC layer throughput of IEEE 802.11ac can be maximally attained up to a 92.8% of physical transmission rate.

Abstract: A polarization stabilization control system based on digital signal processor (DSP) is proposed in this paper. The system uses low frequency radio frequency (RF) power as control signal for polarization stabilization, and it does not need high-speed circuit to track fast polarization change. Modified particle swarm optimization algorithm is utilized and the effectiveness of polarization stabilization control is experimentally verified.

Abstract: The basic characteristics for the WCDMA system, several typical scheduling algorithms are analyzed, and focused on the proportional fair algorithm, in order to maintain good performance of proportional fair algorithm in terms of throughput and fairness,and make it better adapt to the multi-service environment, this paper proposed a QoS-based proportional fair algorithm, using OPNET network simulation software to build a WCDMA network, respectively in different business environments to verify and compare the algorithm performance.The results show that under the multi-service environment, the performance of QoS-based proportional fair algorithm is better than the basic proportional fair algorithm in terms of throughput and average latency.

Abstract: Recursive system convolutional codes (RSC codes) are the commonly used coding form for Turbo sub-encoders. For blind recognition problem of RSC codes, a novel method is proposed to recognize code parameters and generator polynomials. Firstly, code parameters are estimated by analyzing matrix constructed from the received codeword. Then, the mathematical model for recognition of generator polynomials is derived according to RSC codes’ characteristics, and the specific implementation steps are introduced. Finally, simulation results from Matlab show that the performance of the method is obviously more excellent than other methods, which indicates great significance to further research on Turbo codes.

Abstract: This article first describes the position and role of the communication system in the commodity trading system. According to TCP communication protocol, comprehensive using JSON and related technology,designes a communication program which used to connect the client to server. In this paper, the communication protocol, the design of the communication class, loading balancing strategy, improving the efficiency of the communication methods are expounded in detail.

Abstract: The paper present new approach for improving the steady-state error performance of Constant Modulus Algorithm (CMA), it is well known that for higher level modulations such as QAM, CMA does not perform well. Several techniques have been proposed in recent years to deal with slow convergence and MSE performance of CMA. Constellation matched error has been seen to offer best performance by providing the cost function with the knowledge of the constellation symbols. New constellation match error function is studied, simulation is performed, it can be witnessed that 4dB improvement stead state error performance.

Abstract: This paper discusses the wideband array pattern synthesis based on filter banks, and the system output error is considered form time to frequency adaptive pattern synthesis. The novel structure is suitable to be used for the interference suppression in the downlink filter banks multicarrier system.

Abstract: In wireless communication systems, frequency hopping (FH) spread spectrum and direct sequence spread spectrum are two main spread coding technologies. In this paper,by the Cartesian product, we construct one class of one-coincidence frequency-hopping sequence set. It is shown that this set has optimal balance property, optimal average periodic Hamming correlation properties and optimal average periodic partial Hamming correlation properties according to the bounds.