分簇无线传感器网络中根校验全分集LDPC码设计与能效分析

高效的差错控制编码技术(ECC)可以增强无线传感器网络传输稳定性、网络的能量利用效率。为了充分利用无线传感器网络中蕴含的分集资源应对恶劣信道环境导致的高差错概率,该文研究了基于根校验全分集LDPC码的差错控制编码技术。首先,提出在分簇无线传感器网络中,基于根校验全分集LDPC码的编码方案;其次,设计了适用于所提方案的速率兼容全分集LDPC码字结构。最后,分析了所提编码系统的能效。仿真结果表明,在信道条件较差的环境中(仿真中,信道噪声大于410-4 mW),采用该文的编码方案,能够显著提高无线传感器网络的能效。     

Analyzing and improving the energy efficiency of IEEE 802.15.4 wireless sensor networks using retransmissions and custom coding

This paper analyzes the performance of error control strategies in IEEE 802.15.4 wireless sensor networks. ARQ schemes of the IEEE 802.15.4 are used and also we propose custom coding using BCH codes. The performance is analyzed through simulation using the energy efficiency parameter. Performance results are obtained for multi-hop networks with different channel conditions and packet sizes. The results have shown that the ARQ scheme and BCH codes are energy efficient for networks with high number of hops and low values of signal-to-noise ratio.     

Error Control in Wireless Sensor Networks: A Cross Layer Analysis

Error control is of significant importance for Wireless Sensor Networks (WSNs) because of their severe energy constraints and the low power communication requirements. In this paper, a cross-layer methodology for the analysis of error control schemes in WSNs is presented such that the effects of multi-hop routing and the broadcast nature of the wireless channel are investigated. More specifically, the cross-layer effects of routing, medium access, and physical layers are considered. This analysis enables a comprehensive comparison of forward error correction (FEC) codes, automatic repeat request (ARQ), and hybrid ARQ schemes in WSNs. The validation results show that the developed framework closely follows simulation results.      

A Comparison of Block and Convolutional Codes in ARQ Error Control Schemes

ARQ methods of error control can considerably improve the reliablity of data transmission in such areas as satellite communications, computer networks, etc. A number of ARQ schemes using both block and convolutional codes have appeared in the literature. In this paper, the following problem is addressed. Given two different implementations of an ARQ scheme, one using a block code and the other using a convolutional code, such that the bit error probability of both implementations does not exceed some specific value, which implementation has the higher throughput and under what conditions will it be attained? The comparison is made for three basic retransmission schemes using both hybrid and pure ARQ: stop-and-wait, go-back-N, and selective repeat. Numerical estimates of the throughput were obtained using approximate theoretical expressions for BCH codes and simulation results for sequential decoding of rate 1/2 convolutional codes. Parameters optimizing the performance of both block and convolutional codes for different channel conditions and round trip delays were found and were used to obtain these numerical estimates. Comparison of the quantitative results indicates a trend toward preferring convolutional codes as delay and/or block length increases. A binary symmetric channel with noiseless feedback was assumed. Possible implications for the Gaussian channel are also discussed.     

Energy Efficient Raptor Codes for Error Control in Wireless Body Area Networks

WBAN consists of several tiny sensors that are located inside and outside human body for continuous monitoring of vital parameters of patients suffering from chronic diseases. The wearable sensor unit consists of transmitter, receiver and central process unit (gateway). The gateway is used to connect wearable sensors on human body to the internet. To increase the lifetime of such networks, the energy spent by the sensors has to be minimized. In this work we analyzed the feasibility and performance of fountain code based raptor code for error correction to overcome the energy and reliability issues. Versatility of raptor code in terms of code rate and coding gain is advantageous to increase the energy efficiency of WBAN network. Simulation results considering different fading channels show that the raptor coded packet transmission is more energy efficient than that of LT code, traditional BCH code and ARQ error control technique.     

Separate codes on type-II hybrid ARQ systems

A hybrid automatic repeat request (ARQ) system (HARQ-II) with parity retransmission for error correction, which combines ARQ and forward error correction is discussed, and the successful application of these codes to HARG-II is illustrated. A method of constructing the codes whereby conventional BCH codes can be changed into separable codes is proposed. A scheme is presented that has the advantages that, the code lengths are always made equal and that even in parity retransmission new information symbols can be sent along with the necessary parity-check symbols. The performance of the proposed schemes on the binary symmetric channel is discussed. The numerical results show that they outperform conventional schemes     

A novel adaptive hybrid ARQ scheme for wireless ATM networks

This paper describes the design and performance of a novel adaptive hybrid ARQ scheme using concatenated FEC codes for error control over wireless ATM networks. The wireless links are characterized by higher, time‐varying error rates and burstier error patterns in comparison with the fiber‐based links for which ATM was designed. The purpose of the hybrid ARQ scheme is to provide a capability to dynamically support reliable ATM‐based transport over wireless channels by using a combination of our ARQ scheme (called SDLP) and the concatenated FEC scheme. The key ideas in the proposed hybrid ARQ scheme are to adapt the code rate to the channel conditions using incremental redundancy and to increase the starting code rate as much as possible with the concatenated FEC, maximizing the throughput efficiency. The numerical results show that our proposed scheme outperforms other ARQ schemes for all SNR values. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improved FEC Code Based on Concatenated Code for Optical Transmission Systems

The improved three novel schemes of the super forward error correction(super-FEC) concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existing FEC codes have been analyzed. The performance simulation of the Reed-Solomon(RS)+Bose-Chaudhuri-Hocguenghem(BCH) inner-outer serial concatenated code is implemented and the conceptions of encoding/decoding the parallel-concatenated code are presented. Furthermore, the simulation results for the RS(255,239)+RS(255,239) code and the RS(255,239)+RS(255,223) code show that the two consecutive concatenated codes are a superior coding scheme with such advantages as the better error correction, moderate redundancy and easy realization compared to the classic RS(255,239) code and other codes, and their signal to noise ratio gains are respectively 2～3dB more than that of the RS(255,239)code at the bit error rate of 1×10 -13 . Finally, the frame structure of the novel consecutive concatenated code is arranged to lay a firm foundation in designing its hardware.     

Euclidean Geometry LDPC-VBLAST System Design and Performance Evaluation

Among popular multi-transmit and multi-receive antennas techniques, the VBLAST (Vertical Bell Laboratories Layered Space-Time) architecture has been shown to be a good solution for wireless communications applications that require the transmission of data at high rates. Recently, the application of efficient error correction coding schemes such as low density parity-check (LDPC) codes to systems with multi-transmit and multi-receive antennas has shown to significantly improve bit error rate performance. Although irregular LDPC codes with non-structure are quite popular due to the ease of constructing the parity check matrices and their very good error rate performance, the complexity of the encoder is high. Simple implementation of both encoder and decoder can be an asset in wireless communications applications. In this paper, we study the application of Euclidean geometry LDPC codes to the VBLAST system. We assess system performance using different code parameters and different numbers of antennas via Monte-Carlo simulation and show that the combination of Euclidean geometry LDPC codes and VBLAST can significantly improve bit error rate performance. We also show that interleaving data is necessary to improve performance of LDPC codes when a higher number of antennas is, used in order to mitigate the effect of error propagation. The simplicity of the implementation of both encoder and decoder makes Euclidean geometry LDPC codes with VBLAST system attractive and suitable for practical applications.     

Reliability/energy trade-off in Bluetooth error control schemes

Two important objectives in wireless sensor networks are reliability and reducing energy consumption. Hence, overcoming energy constraints and utilizing error control schemes such as Automatic Repeat Request (ARQ) and Forward Error Correction (FEC) are necessary to improve the energy efficiency and reliability. However, these two concerns are at odds, so there is a trade-off between them. Considering this point, the impact of various error control schemes on these objectives and the trade-off between them has been considered in Bluetooth networks recently. However, all these works consider ideal assumptions (e.g., perfect error detection) only. This work evaluates the energy-efficiency of Bluetooth error control schemes in Rayleigh fading channels taking into consideration both ideal assumptions and residual error probability of the CRC code in ARQ schemes. A comparative analysis of coding techniques using different BCH codes on the AUX1 packet is provided. In addition, the impact of variations in number of hops and SNR on the effectiveness of proposed coding techniques is analyzed through simulation. This analysis provides information that help network designers to choose suitable packet types and coding techniques for Bluetooth networks depending on the network situation.     

Extended Hamming and BCH soft decision decoders for mobile dataapplications

A methodology is presented for the design and development of efficient trellis-based soft decision decoders for extended Hamming and BCH codes. A new metric for noncoherent discriminator detection is proposed that substantially improves the performance of trellis-based decoders over additive white Gaussian noise (AWGN) channels. Minimal edge trellises are then presented for the class of extended Hamming codes and the (32, 21) extended BCH code. The latter is in extensive use in narrow-band wireless data systems. An automatic request (ARQ) protocol is described that allows the soft decision decoders to outperform their hard decision counterparts in both reliability and throughput     

Optimal coding rate of punctured convolutional codes inmultiservice wireless cellular systems

The microcellular link performance of future multimedia wireless systems could he improved by using error-correcting punctured convolutional codes in conjunction with slow-frequency hopping. However, the bandwidth expansion due to coding leads to a decrease in the signal-to-interference ratio (SIR) of a frequency-division time-division multiple-access (FD-TDMA) cellular radio link if the system capacity is to be maintained for a given bandwidth allocation. This work determines the best compromise between the power of error correction due to coding and the strength of the self-induced system interference in terms of numerous criteria for speech and data transmission. The aforementioned tradeoff is evaluated in terms of the average bit error rate (BER), the frame error rate, and the burst error distribution for voice transmission. For data transmission with a type 1 hybrid selective-repeat automatic repeat-request (ARQ) protocol, the criteria are average throughput and throughput distribution, the round-trip acknowledgment transmission delay distribution, and the buffering requirements at the transmitter and receiver. The study highlights that punctured codes can significantly improve performance for wireless data links in comparison with the rate 1/2 convolutional coding case or the no-coding case     

Error control for multimedia communications in wireless sensor networks: A comparative performance analysis

The emerging multimedia applications of Wireless Sensor Network (WSNs) impose new challenges in design of algorithms and communication protocols for such networks. In the view of these challenges, error control is an important mechanism that enables us to provide robust multimedia communication and maintain Quality of Service (QoS). Despite the existence of some good research works on error control analysis in WSNs, none of them provides a thorough study of error control schemes for multimedia delivery. In this paper, a comprehensive performance evaluation of Automatic Repeat Request (ARQ), Forward Error Correction (FEC), Erasure Coding (EC), link-layer hybrid FEC/ARQ, and cross-layer hybrid error control schemes over Wireless Multimedia Sensor Network (WMSNs) is performed. Performance metrics such as energy efficiency, frame Peak Signal-to-Noise Ratio (PSNR), frame loss rate, cumulative jitter, and delay-constrained PSNR are investigated. The results of our analysis show how wireless channel errors can affect the performance of multimedia sensor networks and how different error control scenarios can be effective for those networks. The results also provide the required insights for efficient design of error control protocols in multimedia communications over WSNs.     

Medical data transmission using the product of TLDPC and BCH error control coding systems with two interleavers

Medical data are very precious since it has the most sensitive data of patient which can save them. If it is handled wrongly or it is manipulated, then it could result in permanent problems or even it can result in fatal. So medical data widely used in a digital format with error detection and correction codes (EDC) in its transmission and storage process. EDC is a method of adding redundant bits to the static message bits to enhance the reliability of binary digital data broadcast while the medical data communication medium adds the errors in the course of transmission. In the proposed method, we use Bose–Chaudhuri–Hocquenghem codes (BCH) as an outline algorithm and trellis Low‐Density Parity Check code (TLDPC) as an inner algorithm along with two interleavers. Product of BCH code and TLDPC code with interleavers can control more errors as compared with its plain code and product of RS‐Hamming code. MATLAB used as a simulation tool. Plain BCH code is simulated first, and then plain LDPC code is simulated for the same information. Finally, the product of BCH and TLDPC with two interleavers is imposed on the same information. The result of our research work shows enhancement in bit error rate (BER) compared to other plain and product codes from 10^?2 to 10^?3. Also, frame error rate (FER) is improved in 0.5 scaling factors when compared with other trellis decoders. Hence, this proposed system can be utilized in an application where less error rate and high accuracy of information transmission between medical data processing systems are required.     

Enhanced Low Complex Double Error Correction Coding with Crosstalk Avoidance for Reliable On-Chip Interconnection Link

As the technology scales down, shrinking geometry and layout dimension, on- chip interconnects are exposed to different noise sources such as crosstalk coupling, supply voltage fluctuation and temperature variation that cause random and burst errors. These errors affect the reliability of the on-chip interconnects. Hence, error correction codes integrated with noise reduction techniques are incorporated to make the on-chip interconnects robust against errors. The proposed error correction code uses triplication error correction scheme as crosstalk avoidance code (CAC) and a parity bit is added to it to enhance the error correction capability. The proposed error correction code corrects all the error patterns of one bit error, two bit errors. The proposed code also corrects 7 out of 10 possible three bit error patterns and detects burst errors of three. Hybrid Automatic Repeat Request (HARQ) system is employed when burst errors of three occurs. The performance of the proposed codec is evaluated for residual flit error rate, codec area, power, delay, average flit latency and link energy consumption. The proposed codec achieves four magnitude order of low residual flit error rate and link energy minimization of over 53 % compared to other existing error correction schemes. Besides the low residual flit error rate, and link energy minimization, the proposed codec also achieves up to 4.2 % less area and up to 6 % less codec power consumption compared to other error correction codes. The less codec area, codec power consumption, low link energy and low residual flit error rate make the proposed code appropriate for on chip interconnection link.     

Design of Rate-Compatible Irregular Repeat Accumulate Codes

We consider the design of efficient rate-compatible (RC) irregular repeat accumulate (IRA) codes over a wide code rate range. The goal is to provide a family of RC codes to achieve high throughput in hybrid automatic repeat request (ARQ) scheme for high-speed data packet wireless systems. As a subclass of low-density parity-check codes, IRA codes have an extremely simple encoder and a low-complexity decoder while providing capacity approaching performance. We focus on a hybrid design method which employs both puncturing and extending. We propose a simple puncturing method based on minimizing the maximal recoverable step of the punctured nodes. We also propose a new extending scheme for IRA codes by introducing the degree-1 parity bits for the lower rate codes and obtaining the optimal proportions of extended nodes through density evolution analysis. The throughput performance of the designed RC-IRA codes in hybrid ARQ is evaluated for both AWGN and block fading channels. Simulation results demonstrate that our designed RC codes offer good error correction performance over a wide rate range and provide high throughput, especially in the high and low signal-to-noise ratio regions.     

On the performance of hybrid FEC/ARQ systems using rate compatiblepunctured turbo (RCPT) codes

This paper introduces a hybrid forward-error correction/automatic repeat-request (ARQ) system that employs rate compatible punctured turbo (RCPT) codes to achieve enhanced throughput performance over a nonstationary Gaussian channel. The proposed RCPT-ARQ system combines the performance of turbo codes with the frugal use of incremental redundancy inherent in the rate compatible punctured convolutional codes of Hagenauer (1988). Moreover, this paper introduces the notion of puncturing the systematic code symbols of a turbo code to maximize throughput at signal-to-noise ratios (SNRs) of interest. The resulting system provides both an efficient family of achievable code rates at middle to high SNR and powerful low-rate error correction capability at low SNR     

DTMB标准中BCH译码算法及其FPGA的实现

首先证明了DTMB标准中采用的BCH码是纠错能力为1的循环汉明码,并基于此提出了适用于该BCH码的译码算法,及其串行和并行两种FPGA实现电路。考虑到该BCH码缩短码的特性,通过修改差错检测电路,使其译码时延缩短34%。实现结果表明,译码器译码正确无误,FPGA资源占用极少。串行译码器总时延为762个时钟周期,最大工作时钟频率可达357MHz。并行译码器总时延仅为77个时钟周期,最大工作时钟频率可达276MHz。     

Adaptive type-II hybrid broadcast ARQ system

In this letter, a type-II hybrid broadcast automatic-repeat-request (ARQ) scheme with adaptive forward error correction (AFEC) using BCH codes is proposed and analyzed. The basic idea in the proposed scheme is to increase the error correcting capability of BCH codes according to each channel state using incremental redundancy. The numerical results for the analysis and the simulation show that the proposed scheme maintains high throughput even if channels become noisy and the number of receivers is large     

Power control and capacity analysis for a packetized indoormultimedia DS-CDMA network

This paper proposes a packetized indoor wireless system using direct-sequence code-division multiple-access (DS-CDMA) protocol. The indoor radio environment is characterized by slow Rayleigh fading with or without lognormal shadowing. The system supports multimedia services with various transmission rates and quality of service (QoS) requirements and allows for seamless interfacing to asynchronous transfer mode (ATM) broadband networks. All packets are transmitted with forward error correction (FEC) using convolutional code for voice packets and Bose-Chaudhuri-Hocquenghem (BCH) code for data packets with an automatic retransmission request (ARQ) protocol and for video packets without ARQ. A queueing model is used for servicing data transmission requests. A power control algorithm is proposed for the system, which combines closed-loop power control with channel estimation to give the best performance. The cell capacity of each traffic type and various multimedia traffic configurations in both single-cell and multiple-cell networks are evaluated theoretically under the assumption of perfect power control. The effect of power control imperfection on the capacity using the proposed power control algorithm is investigated by computer simulation