Performance Analysis of Repeat-Accumulate Codes over Shallow Water Acoustic Channels

针对浅海水声信道的强多途、长时延、严重衰落等特点,需采用性能好、能够实现线性编译码便于实时处理的信道纠错码技术以提高水声通信系统可靠性的问题,提出重复累积(rEPEAT-ACCuMulATE,rA)码作为浅海水声信道的纠错码方案。建立rA码在浅海水声信道中的仿真模型,比较其在不同浅海水声信道模型下的性能,通过水池数据传输实验研究编译码参数对rA码性能的影响,并以水下图像传输实验进一步验证该编码方案。仿真和实验结果表明:rA码在浅海水声通信系统中具有较强的纠错能力,选择合适的参数会进一步提高编码增益。与TurbO码和ldPC码的编译码复杂度对比,rA码能够实现线性时间编译码,算法复杂度低,硬件实现简单,在水声通信中具有非常好的应用前景。Due to a large delay spread caused by multipath propagation and severe attenuation of the channel conditions,the Repeat-Accumulate(RA) code with short length codes,good performance and easy implementation has been proposed to enhance the reliability of the shallow water acoustic(SWA) communication system.A system model including RA coding over the SWA channels was established.As a comparison,the performance of RA codes under different ocean acoustic channel conditions was presented.The experiment in the pool was carried out to show how the encoding and decoding parameters affect the performance of RA codes,which was verified by the image transmission over channels in the pool tank.The simulation and experimental results show that RA codes have a strong error correction capability and the codes with appropriate parameters would further improve the coding gain,while they enjoy encoding and decoding in linear time and have simple hardware implementation,which have a good applied prospect in underwater acoustic communication system.国家自然科学基金资助项目(41176032);中央高校基本科研业务费专项资金资助项目(2010121032)(20112G020);厦门大学基础创新科研基金资助项目(201112G020

厦门市儿童溺水死亡流行病学调查分析

目的了解厦门市儿童溺水死亡(溺死)的流行病学特征及危险因素,探索有效的干预措施。方法采用问卷调查收集溺死儿童资料,用HIErArCHICAl MOdEl法和gEnErAl MOdEl法对危险因素进行筛选分析。结果共收集2001-2009年溺水死亡儿童95例,其中男孩占74.7%,小学生占63.2%,不会游泳者占78.9%;主要发生地在池塘、溪流或沟渠;70.5%发生在夏秋季;80%儿童溺死时无人监管;溺死儿童的父母多数文化程度低,家庭收入偏低;死亡的危险因素为:男孩、4~6年级小学生、父亲在40岁以上和下午。结论应采取有针对性的干预措施,控制危险因素,减少儿童溺死的发生

Effects of Different Sallow Water Acoustic Channel Models on Error-correction Code Performance Analysis

由于水声信道复杂多变,很难进行信道建模,迄今为止并没有一个标准的统计信道模型。针对不同的研究对象,往往需要采用不同的水声信道模型,而评估信道建模差异对研究结论的影响则具有重要意义。从信道纠错码角度,在分析时不变信道模型、时变信道模型和准静止衰落信道模型的基础上,结合高效信道纠错码(以ldPC码为例),讨论了水声信道模型差异对研究纠错码性能可能带来的影响,为实际设计水声通信系统提供参考。仿真结果表明,尽管不同信道建模方式对系统解码的具体信噪比数值要求不大相同,但编译码参数优化设计的方案基本一致,海试数据则进一步验证了上述结论。There have been no standard statistical channel models for the underwater acoustic( UWA)channel as a result of the complex and variability of UWA channel.Different UWA channel models are required for different purposes during the UWA communication research.It is important to evaluate the effect of different UWA channel modeling on research conclusions.From the perspective of channel errorcorrection code,the effects of different channel models on channel error-correction code( taking LDPC codes as an example) design are investigated by analyzing several UWA channel models,including timeinvariance model,time-variance model and quasi-static fading model adopted in UWA communication simulation.The simulation results show that the optimized designs of coding parameters are almost the same,although different channel modeling usually requires different signal-to-noise ratio for decoding.The sea test data are adopted to further verify the conclusions.国家自然科学基金项目(41176032、41376040); 中央高校基本科研业务费专项基金; 厦门大学基础创新科研基金项目(201112G020、201212G012); 高等学校博士学科点专项科研基金项目(20130121120033

Irregular QC-LDPC Coding Joint Adaptive Equalization for Shallow Water Acoustic Communications

浅海水声信道具有长时延、多途强、起伏快等特点,为提高数据传输可靠性,采用纠错能力强、编译码复杂度低的非规则准循环低密度奇偶校验(QC-ldPC)码作为信道纠错码方案,并联合自适应判决反馈均衡器(dfE)作为接收机结构以消除码间干扰(ISI).综合考虑非规则QC-ldPC码编译码参数选择、自适应均衡器中的最小均方差(lMS)、可变步长lMS(SVSlMS)和递归最小二乘(rlS)等3种算法的性能与复杂度权衡问题,结合福建泉港浅海域实测水声信道特性,研究了该接收机的性能.仿真结果表明:非规则QC-ldPC码的性能优于随机构造的规则ldPC码;联合自适应均衡的非规则QC-ldPC码可显著提高浅海水声通信系统性能,在较高信噪比(Snr)下,选用rlS算法时,误码率(bEr)可降为0(15db),选用低复杂度的SVSlMS算法bEr可达到10-4(18db).Shallow water acoustic channel is characterized by long transmission delay,strong multipath interference,and large fluctuation.To improve reliability of underwater acoustic data transmission,this paper use irregular quasi-cyclic low density parity check(QC-LDPC)codes as an error-correcting coding scheme,which have strong error correction capability and low coding and decoding complexity,joint adaptive equalization as a receiver structure for eliminating inter-symbol interference caused by strong multipath effect.This paper makes comprehensive considerations of optimal design problem,such as the choices of coding and decoding parameters for irregular QC-LDPC codes,the balances of performance and complexity for least mean square,recursive least squares and sigmoid variable step-size least mean square algorithms in adaptive decision feedback equalizer;combining the measurement shallow water acoustic channel of characteristics Fujian quangang Xiaocuo harbour to analyses the performance of the receiver.Simulation results show that the irregular QC-LDPC codes perform better than random structure regular LDPC codes;irregular QC-LDPC coding joint adaptive equalization can significantly improve the performance of shallow water acoustic communication system.At high SNR,when select RLS algorithm,bit error rate can be reduced to 0;when select SVSLMS algorithm with low complexity,error rate can reach 10-4.国家自然科学基金(41176032;41376040

Applications of rate-compatible QC-LDPC codes in underwater acoustic communication

针对水声信道复杂多变、强多途和大起伏干扰等特点,提出采用码率兼容QC-ldPC码的自适应信道编码技术,以提高水声数据传输的可靠性和水声信道的信道吞吐率。建立了码率兼容QC-ldPC码在水声信道中的仿真模型,构造码率为1/2、2/3…5/6等一系列QC-ldPC码,在三种典型的水声信道中对其性能进行仿真。结果表明所设计的码率兼容QC-ldPC码在三种不同信道下可行有效,能较大地提高水声通信系统的性能。由于信道时延越长、信噪比越低,满足通信指标的码率就越低;并给出码率兼容QC-ldPC码在浅海水声信道中不同信噪比下满足通信性能指标的编码码率的查找表。码率兼容QC-ldPC码提高了水声通信的信道利用率,具有灵活的编译码性能,在水声自适应通信中具有很好的应用前景。The underwater acoustic(UWA) channel is characterized as a complex variable, strong multipath and fluctuation interference channel.Adaptive channel coding techniques which use rate-compatible QC-LDPC(RC QC-LDPC) codes are proposed to enhance the reliability of UWA data transmission and channel throughput.A system simulation model including RC QC-LDPC codes for the UWA channels is built.With constructing a series code-rates(such as 1/2, 2/3, …, 5/6) of QC-LDPC codes, the performance of the system is simulated over three different kinds of UWA channels.The simulation results show that the designed RC QC-LDPC codes are feasible and effective, can dramatically improve the performance of UWA communication system, have good applicability in UWA channels.In the case that the worse the channel, due to longer channel delay and lower signal-to-noise ratio, the lower the code-rate is taken to meet system communication indicators.The lookup table(LUT) of the rate compatible QC-LDPC codes, which meet the communication indicators of the shallow water acoustic communication system under different signal-to-noise ratios, is given.The RC QC-LDPC codes with flexible encoding and decoding performances can improve the utilization of UWA communication channel and have good application prospects.国家自然科学基金(41176032、41376040)资助项

Effect of Community-hospital Integrated Management Model on Patients with Diabetes Mellitus

目的探讨糖尿病社区-医院一体化管理模式。方法对中华、厦港两个社区医疗中心所管辖的701例糖尿病患者实施社区、医院一体化管理,通过社区-医院的双向转诊,让患者得到“无缝化“的医疗服务。比较管理前后糖尿病患者的血糖、生活方式变化情况。结果 701例糖尿病患者建档时空腹血糖平均为(7.6±2.3)MMOl/l,餐后2H血糖平均为(9.9±2.5)MMOl/l,管理2年后空腹血糖降至(6.9±1.7)MMOl/l,餐后2H血糖降至(9.0±2.0)MMOl/l,随着管理时间的延长,空腹血糖、餐后2H血糖均呈下降趋势(P<0.05);糖尿病患者的生活方式(限盐、运动、饮酒控制、体质量控制)有明显改善,与管理前比较,差异均有统计学意义(P<0.01)。结论社区、医院一体化糖尿病规范化治疗和管理服务模式中双向转诊是重要内容和关键环节,是提供无缝式管理和连续性服务的重要手段,“院办院管“能有效消除医院与社区间双向转诊、技术支持和信息共享等一体化协作的阻碍。Objective To observe the effect of community-hospital integrated model on diabetes management.Methods From 2004 to 2009,701 patients with diabetes were selected from Zhonghua and Xiagang community health centers and managed with the community-hospital integrated management model.Their blood glucose levels and changes of lifestyle were compared between before and at the end of the management.Results The levels of fasting blood glucose [(6.9±1.7)mmol/L] and 2 h postprandial blood glucose[(9.0±2.0) mmol/L] at the end of 2 years management were significant lower that those[(7.6±2.3) mmol/L and (9.9±2.5) mmol/L ]before the management.And there was a declining trend of the fasting blood glucose and 2 h postprandial blood glucose with the time of the management.The lifestyle of them,including salt restriction,exercise,alcohol drinking restriction and body weight control,was improved significantly (P<0.01).Conclusion The community-hospital integrated management model for diabetes plays an ideal role on the management and control of diabetes in communities

Rate compatible LDPC codes design for shallow water acoustic communications

Conference Name:2012 International Applied Mechanics, MechatronicsAutomation and System Simulation Meeting, AMMASS 2012. Conference Address: Hangzhou, China. Time:June 24, 2012 - June 26, 2012.The fast temporal variations shallow water acoustic (SWA) channels need the temporal variations channel coding scheme at the acceptable cost. Hence, flexible channel coding rate, adjusted according to different ocean channel characteristics, should be desired in the design of practical error control SWA communication system. In this paper, we propose rate-compatible LDPC (RC-LDPC) codes to improve the communication system reliability for SWA communications. The proposed SWA system adopting RC-LDPC codes consists of three important preprocessing: channel state information (CSI) estimator, signal-to-noise ratio (SNR) estimator and RC-LDPC pattern. For the estimation error, we define and derive the sensitivity to imperfect CSI and imperfect SNR. Then the design of RC-LDPC codes and SWA channel profile are described. Furthermore, the RC-LDPC performance pattern is given and sensitivity to estimation error of CSI and SNR are analyzed via simulation. It is shown that RC-LDPC codes have good performances with wide range of rates in SWA channels. Finally, coding rate distributions of RC-LDPC codes in different SNR at BER below 10-4 for SWA channel are investigated. 漏 (2012) Trans Tech Publications, Switzerland

Design of RC-LDPC codes and its application for shallow water acoustic communications

According to fast temporal variations shallow water acoustic (SWA) channels, dynamic channel coding, adjusted according to different ocean channel characteristics, should be desired in the design of practical error control SWA communication system. In this paper, we propose a dynamic channel coding scheme where rate-compatible (RC) LDPC (RC-LDPC) codes is adopted as an example to improve the system reliability for SWA communications. Based on the automatic repeat request (ARQ) mechanism, the proposed SWA system consists of three important preprocessing: channel state information (CSI) estimator, signal-to-noise ratio (SNR) estimator and RC-LDPC pattern. For ARQ-SWA system, we firstly derive the throughput of the ARQ-SWA system adopting RC-LDPC codes. The SWA channel model profile is then given, and the description of RC-LDPC codes is also presented. The RC-LDPC performance patterns, effects of different mother code design and throughput analysis of the system are also discussed via simulation. It is shown that, RC-LDPC codes constructed using extending demonstrates good performances with wide range of rates in SWA channels. Furthermore, combining Quangang Xiaocuo harbor SWA channel data, coding rate distributions of RC-LDPC codes in different SNR at BER below 10-4 are investigated