基于数字化校区道路二维码系统的自主学习途径研究

利用信息化技术以及互联网平台提高学生自主学习能力是现代教育发展的趋势。数字化校区道路二维码系统是在收集校区道路信息的基础上构建道路信息资源库。将道路信息转化为二维码,将包含道路信息资源库学习资料的二维码标在校区道路牌上,构建数字化校区道路二维码系统,方便学生自主学习。通过二维码通关测试题激发学生的探索欲,检验学生的自学情况。开发数字化校区道路系统,校园处处可学习,营造智慧校园。对于开设交通专业的学校有借鉴意义。

利用软解调序列的LDPC码闭集识别方法

为实现对包括低密度奇偶校验（LDPC）码在内的一系列“稀疏几何编码冶的识别,基于软解调序列,设计和实现了一种闭集集合应用背景下的识别方法.以校验约束关系作为切入点,首先回顾了基于硬解调序列的传统识别策略;接着分析和推导了软解调序列所应满足的校验约束形式;通过引入后验校验对数似然比（CLLR）这一统计量,最终设计了相应识别算法.在事先给定先验编码集合的闭集应用模式下,仿真结果显示,算法明显占优,识别增益在低信噪比环境下可达2~6dB.

橡胶轮码盘在谏壁站液压启闭机上的应用

根据谏壁站液压启闭机传感装置在运行中存在的问题 ,分析对比研究了四种传感技术的优缺点 ,重点介绍了橡胶轮码盘传感装置的应用。通过应用实践证明 ,选用该装置作为启闭机的开度显示控制是科学、合理的 。

相位推算法瞬时测频研究

相位推算法瞬时测频是基于数字接收机的计算方法。本文介绍了该算法的原理,分析、仿真了其误差,给出了校码处理原则,并进行了技术验证。结果表明,该算法具有测频精度高、瞬时性好的优点。

Modbus通讯协议在液位监测系统中的应用

本文简要介绍了Modbus通讯协议的技术要点和具体规定及错误校验方法,然后通过基于Modbus协议的储油罐液位远程监测系统实例,说明了整个监测系统的硬件构成,监测软件的相关设计和开发以及Modbus协议的实现。

一种自动补偿相位的波束控制系统设计

针对相控阵系统相位一致性要求高,阵元数量巨大,相位校准与测试困难的问题,设计了一种自动补偿相位的波束控制系统,系统基于CAN总线通信,采用FPGA和单片机作为补偿算法核心,具有结构简单、可靠性高、波控速度快的特点。

Performance analysis of coded OFDM systems using a novel class of LDPC codes

A new method of constructing regular low-density parity-check (LDPC) codes was proposed. And the novel class of LDPC codes was applied in a coded orthogonal frequency division multiplexing (OFDM) system. This method extended the class of LDPC codes which could be constructed from shifted identity matrices. The method could avoid short cycles in Tanner graphs with simple inequation in the construction of shifting identity matrices, which made the girth of Tanner graphs 8. Because of the quasicyclic structure and the inherent block configuration of parity-check matrices, the encoders and the decoders were practically feasible. They were linear-time encodable and decodable. The LDPC codes proposed had various code rates, ranging from low to high. They performed excellently with iterative decoding and demonstrate better performance than other regular LDPC codes in OFDM systems.

Modified Benes network architecture for WiMAX LDPC decoder

A modified Benes network is proposed to be used as an optimal shuffle network in worldwide interoperability for microwave access （WiMAX） low density parity check （LDPC） decoders, When the size of the input is not a power of two, the modified Benes network can achieve the most optimal performance. This modified Benes network is non-blocking and can perform any sorts of permutations, so it can support 19 modes specified in the WiMAX system. Furthermore, an efficient algorithm to generate the control signals for all the 2 × 2 switches in this network is derived, which can reduce the hardware complexity and overall latency of the modified Benes network. Synthesis results show that the proposed control signal generator can save 25.4% chip area and the overall network latency can be reduced by 36. 2%.

Efficient construction and encoding of QC-LDPC codes by cyclic lifting of protographs

Quasi-cyclic low-density parity-check （QC-LDPC） codes can be constructed conveniently by cyclic lifting of protographs. For the purpose of eliminating short cycles in the Tanner graph to guarantee performance, first an algorithm to enumerate the harmful short cycles in the protograph is designed, and then a greedy algorithm is proposed to assign proper permutation shifts to the circulant permutation submatrices in the parity check matrix after lifting. Compared with the existing deterministic edge swapping （DES） algorithms, the proposed greedy algorithm adds more constraints in the assignment of permutation shifts to improve performance. Simulation results verify that it outperforms DES in reducing short cycles. In addition, it is proved that the parity check matrices of the cyclic lifted QC-LDPC codes can be transformed into block lower triangular ones when the lifting factor is a power of 2. Utilizing this property, the QC- LDPC codes can be encoded by preprocessing the base matrices, which reduces the encoding complexity to a large extent.

A Joint Encryption and Error Correction Method Used in Satellite Communications

Due to the ubiquitous open air links and complex electromagnetic environment in the satellite communications,how to ensure the security and reliability of the information through the satellite communications is an urgent problem.This paper combines the AES(Advanced Encryption Standard) with LDPC(Low Density Parity Check Code) to design a secure and reliable error correction method — SEEC(Satellite Encryption and Error Correction).This method selects the LDPC codes,which is suitable for satellite communications,and uses the AES round key to control the encoding process,at the same time,proposes a new algorithm of round key generation.Based on a fairly good property in error correction in satellite communications,the method improves the security of the system,achieves a shorter key size,and then makes the key management easier.Eventually,the method shows a great error correction capability and encryption effect by the MATLAB simulation.

VARIABLE NON-UNIFORM QUANTIZED BELIEF PROPAGATION ALGORITHM FOR LDPC DECODING

Non-uniform quantization for messages in Low-Density Parity-Check(LDPC)decoding canreduce implementation complexity and mitigate performance loss.But the distribution of messagesvaries in the iterative decoding.This letter proposes a variable non-uniform quantized Belief Propaga-tion(BP)algorithm.The BP decoding is analyzed by density evolution with Gaussian approximation.Since the probability density of messages can be well approximated by Gaussian distribution,by theunbiased estimation of variance,the distribution of messages can be tracked during the iteration.Thusthe non-uniform quantization scheme can be optimized to minimize the distortion.Simulation resultsshow that the variable non-uniform quantization scheme can achieve better error rate performance andfaster decoding convergence than the conventional non-uniform quantization and uniform quantizationschemes.

A New Design and Implementation of an Attendance Checking Node for Coal Mines

A novel design and implementation of an attendance checking node for coal mines based on the CAN bus is presented in this paper. Hardware circuits and programming methods for the attendance checking node are discussed,including the single-chip computer with CAN controller AT89C51CC03,the CAN bus transceiver TJA1050,the large capacity DataFlash memory,the real-time clock DS1302,the voice chip ISD2560 and the card-reading circuit in Wie-gand format. All the extended hardware satisfies the requirements for intrinsically safe circuits (GB3836.4-2000) and intrinsically safe authentication promoted by the national explosion-proof institute. Further,the software programming methods for the CAN controller (AT89C51CC03) and the implementation of the CAN communications protocol are presented as well.

Construction of LDPC Codes for the Layered Decoding Algorithm

Abstract： The layered decoding algorithm has been widely used in the implementation of Low Density Parity Check （LDPC） decoders, due to its high convergence speed. However, the pipeline operation of the layered decoder may introduce memory access conflicts, which heavily deteriorates the decoder throughput. To essentially deal with the issue of memory access conflicts,

Regular Quasi Cyclic Low Density Parity Check Codes with Girth 8 from Elementary Number Theory

This paper is concerned with (3,n) and (4,n) regular quasi-cyclic Low Density Parity Check (LDPC) code constructions from elementary number theory.Given the column weight,we determine the shift values of the circulant permutation matrices via arithmetic analysis.The proposed constructions of quasi-cyclic LDPC codes achieve the following main advantages simultaneously:1) our methods are constructive in the sense that we avoid any searching process;2) our methods ensure no four or six cycles in the bipartite graphs corresponding to the LDPC codes;3) our methods are direct constructions of quasi-cyclic LDPC codes which do not use any other quasi-cyclic LDPC codes of small length like component codes or any other algorithms/cyclic codes like building block;4)the computations of the parameters involved are based on elementary number theory,thus very simple and fast.Simulation results show that the constructed regular codes of high rates perform almost 1.25 dB above Shannon limit and have no error floor down to the bit-error rate of 10-6.

JOINT SOURCE-CHANNEL DECODING OF HUFFMAN CODES WITH LDPC CODES

In this paper, we present a Joint Source-Channel Decoding algorithm (JSCD) for Low-Density Parity Check (LDPC) codes by modifying the Sum-Product Algorithm (SPA) to account for the source redun-dancy, which results from the neighbouring Huffman coded bits. Simulations demonstrate that in the presence of source redundancy, the proposed algorithm gives better performance than the Separate Source and Channel Decoding algorithm (SSCD).

Low-Density Parity-Check Codes for Noncoherent UWB Communication Systems

In order to guarantee reliable data transmission, powerful channel coding techniques are usually required in noncoherent ultra-wideband(UWB) communication systems. Accordingly, several forward error correction(FEC) codes, such as Reed-Solomon and convolutional codes have been used in noncoherent UWB systems to improve the bit error rate(BER) performance. In this paper, low-density parity-check(LDPC) codes are further studied as more powerful FEC candidates for noncoherent UWB systems. Two LDPC codes and the corresponding decoding procedures are presented for noncoherent UWB systems. Moreover, performance comparison between the LDPC codes and other FEC codes are provided for three major noncoherent UWB communication systems, namely, noncoherent pulse position modulation(NC-PPM), transmitted reference(TR) and transmitted reference pulse cluster(TRPC). Both theoretical analysis and simulation results show that the two investigated LDPC codes outperform other existing FEC codes with limited penalty in terms of complexity and therefore they are promising FEC candidates for noncoherent UWB systems with low-cost and low-power consumption.

A front-end automation tool supporting design, verification and reuse of SOC

This paper describes an in-house developed language tool called VPerl used in developing a 250 MHz 32-bit high-performance low power embedded CPU core. The authors showed that use of this tool can compress the Verilog code by more than a factor of 5, increase the efficiency of the front-end design, reduce the bug rate significantly. This tool can be used to enhance the reusability of an intellectual property model, and facilitate porting design for different platforms.

Design and implementation of LDPC encoder based on FPGA

A low density parity check(LDPC)encoder with the codes of(8176,7154)and encoding rate of 7/8 under CCSDS standard for near space communication is designed.Based on LDPC encoding theory,the FPGA-based coding algorithm is designed.Based on the characteristics of LDPC generating matrix,the cyclic shift register is introduced as the core of the encoding circuit,and the shift-register-Adder-Accumulator(SRAA)structure is adopted to realize the fast calculation of matrix multiplication,so as to construct the encoding module with partial parallel encoding circuit as the core.In addition,the serial port input and output module,RAM storage module and control module are also designed,which together constitute the encoder system.The design scheme is implemented by FPGA hardware and verified by simulation and experiment.The results show that the test results of the designed LDPC encoder are consistent with the theoretical results.Therefore,the coding system is practical,and the design method is simple and efficient.

Practical Polar Code Construction For Degraded Multiple-Relay Networks

In this paper, based on the characteristics of polar codes, a new decode-and-forward strategy called generalized partial information relaying protocol is proposed for degraded multiple-relay networks with orthogonal receiver components(MRNORCs). In such a protocol, with the help of partial information from previous nodes, each relay node tries to recover the received source message and re-encodes part of the decoded message for transmission to satisfy the decoding requirements for the following relay node or the destination node. In order to construct practical polar codes, the nested structures are developed based on this protocol and the information sets corresponding to the partial messages forwarded are also calculated. The proposed scheme is proved to be capable of achieving the theoretical capacity of the degraded MRN-ORCs while still retains the low-complexity feature of polar codes. We perform simulations to testify the practicability of the proposed scheme and compare polar codes by using successive-cancellation list decoder(SCLD) with traditional low-density parity-check(LDPC) codes. The results show that the obtained polar codes provide significant gain.