Forward Error Correction Scheme Research Articles

Terminated and Tailbiting Spatially Coupled Codes With Optimized Bit Mappings for Spectrally Efficient Fiber-Optical Systems

We study the design of spectrally efficient fiber-optical communication systems based on different spatially coupled (SC) forward error correction (FEC) schemes. In particular, we optimize the allocation of the coded bits from the FEC encoder to the modulation bits of the signal constellation. Two SC code classes are considered. The codes in the first class are protograph-based low-density parity-check (LDPC) codes which are decoded using iterative soft-decision decoding. The codes in the second class are generalized LDPC codes which are decoded using iterative hard-decision decoding. For both code classes, the bit allocation is optimized for the terminated and tailbiting SC cases based on a density evolution analysis. An optimized bit allocation can significantly improve the performance of tailbiting SC codes codes over the baseline sequential allocation, up to the point where they have a comparable gap to capacity as their terminated counterparts, at a lower FEC overhead. For the considered terminated SC codes, the optimization only results in marginal performance improvements, suggesting that in this case a sequential allocation is close to optimal.

Transmission Performance of 4D 128SP-QAM With Forward Error Correction Coding

The performance of the 4-D 128SP-QAM format is experimentally investigated in a Nyquist-wavelength division multiplexing system for two different forward error correction (FEC) scenarios. Two soft-decisions FEC schemes are experimentally evaluated for 128SP-QAM, namely, a turbo product code (TPC) and a low-density parity-check (LDPC) code. The results show that after full convergence the LDPC code outperforms the TPC with respect to coding gain at a bit error ratio of $10^{\mathrm {\mathbf {-8}}}$ . However, it requires more decoding iterations to achieve convergence toward an optimum performance state.

Scalable Video Transmission Over Wireless Networks Based on Loss Distribution and Layer Information

We propose an efficient scalable video transmission method using unequal forward error correction (FEC) scheme based on loss distribution and layer information. The actual packet loss rates over wireless networks are variable due to the clustered packet losses. First, we deduce the expected packet loss recovery rate from the estimation of the effective packet loss rate using loss distribution statistics. Second, layer-based distortion metric is presented including error propagation effects from hierarchical prediction structure in compressed scalable video packets. Third, the performance metric for FEC assignment is proposed from the layer-based distortion metric and the expected packet loss recovery rate. Finally, the FEC assignment algorithm is proposed for maximizing the performance metric. The proposed unequal FEC assignment method demonstrates robustness and significantly improved performance for scalable video transmission in various channel conditions compared to previous FEC assignment schemes.

Bit Error Rate Analysis of RS (7, 3) Coded Frequency Shift Keying Using Simulink

Bit Error Rate is an essential parameter to quantize the effectiveness of transceiver circuits used in low power, low duty cycle sensor nodes. BER can figure out their performance in terms of number of retransmissions, which keeps the node to consume its battery power undesirably rather than conserving it. Forward Error Correction schemes ensure the transceiver circuit to effectively perform its operations over a noisy bandwidth like ISM and under harsh/unpredictable channel conditions. As none of the coherent M-ary modulation schemes are 100% efficient, non-coherent schemes can be considered as power-efficient choice for power limited sensor nodes. BFSK helps the sensor no des to have quicker transition from sleep mode to active mode. Otherwise, this will also force the transceiver to waste considerable amount of power. In this paper, by developing a SIMULINK model for RS (7, 3) coded BFSK in its non-coherent detection mode is analyzed for its bit error rate performance under various channel and coding conditions. Simulation results show that, this model gives its best BER performance as 16.67% under suitable conditions.

Optimized WiMAX System over Fading Channels Using FEC Codes

The Wireless Interoperability Microwave Access (WiMAX) system in this paper makes use of various forward error correction codes to improve and hence optimize the performance of the system. Two diverse fading channels have been used to study the response of the WiMAX system based on Forward Error Correction (FEC) encoding and M-ary Phase Shift Keying (M-PSK) modulation. Since WiMAX is used for both Line Of Sight (LOS) and Non Line-Of-Sight (NLOS) communication so, Rayleigh and Rician channels have been used, out of which one has LOS component, and other has no LOS component. The performance of WiMAX system has been studied by analyzing the graphs between Bit Error Rate (BER) and Signal to Noise Ratio (SNR) for all the different cases. It is observed that out of all coding techniques reed Solomon (RS) encoding techniques performs better at lower order modulation schemes by providing the BER of 10-3 at lower values of SNR in comparison to all other FEC encoding techniques. But, at higher order modulation level turbo encoding scheme outperform all other FEC schemes. Also, out of channels rician channel has a better response because of one strong line of sight constituent in comparison to Rayleigh fading channel. Further, modified FEC encoding schemes can be incorporated to enhance the BER performance of the WiMAX system.

Layer‐based RED‐FEC (L‐RED‐FEC) method for wireless scalable video streaming

A layer-based random early detection (RED) forward error correction (FEC) method for scalable video streaming over wireless networks is proposed. The proposed method determines the FEC rate in accordance with the layer-based error propagation effect as well as network traffic load. Furthermore, a packet importance model based on layer information of scalable video coding (SVC) has been developed for efficient FEC assignment considering the video quality. Simulation results show that the proposed method achieves higher peak signal-to-noise ratio (PSNR) values compared with the conventional FEC schemes under various network conditions.

Modeling and Analysis of Frame-Level Forward Error Correction for MPEG Video over Burst-Loss Channels

Forward error correction (FEC) is a common error control technique to improve the quality of video streaming over lossy channels. To optimize the data recovery performance, frame-level FEC schemes have been proposed for streaming video to maximize playable frame rate (PFR) within transmission rate constraint on a random binary symmetric channel (BSC). However, burst loss is a commonplace in current Internet architecture, and the FEC efficacy c an be degraded since the burst data losses easily exceed the error correction capacity of FEC. Accordingly, an estimated video quality model over burst loss channels is proposed in this paper to evaluate the impact of burst loss for FEC-based video applications. In addition to th e model analysis, the simulation experiments on the NS-2 network simulator are conducted at a given estimate of the packet loss probability and average burst length. The results suggest a useful reference in designing the FEC scheme for video applications, and as the video coding and channel parameters are given, the proposed model can provide the optimal FEC solution to achieve a better reconstructed video quality than the FEC model based on a random BSC channel.

Cross-Layer Forward Error Correction Scheme Using Raptor and RCPC Codes for Prioritized Video Transmission Over Wireless Channels

The unequal error protection (UEP) has shown promising results for transmitting video over error-prone wireless channels. In this paper, we investigate the cross-layer design of forward error correction (FEC) schemes by using the UEP Raptor codes at the application layer (AL) and UEP rate compatible punctured convolutional (RCPC) codes at physical layer (PHY) for prioritized video packets. The video packets are prioritized based on their contribution to the received video quality. A genetic algorithm (GA)-based optimization algorithm is proposed to find the optimal parameters for both Raptor and RCPC codes, to minimize the video distortion and maximize the peak signal-to-noise-ratio for the given video bit rates and channel constraints (i.e., SNR and available bandwidth). We evaluate the performance of four combinations of the UEP schemes for H.264/AVC encoded video sequences over the AWGN and Rayleigh fading channels and show the superiority of the optimized cross-layer UEP FEC scheme. For Rayleigh fading channel, the proposed cross-layer optimization uses two different time-scales at AL and PHY which allows PHY to adapt faster to the changing channel quality.

Layered Wireless Video Relying on Minimum-Distortion Inter-Layer FEC Coding

Layered video coding is capable of progressively refining the reconstructed video quality with the aid of multiple layers of unequal importance. When the base layer (BL) is corrupted or lost due to channel impairments, the enhancement layers (ELs) must be discarded by the video decoder, regardless whether they are perfectly decoded or not, which implies that the transmission power assigned to the ELs is wasted. To circumvent this problem, we proposed a bit-level inter-layer forward error correction (IL-FEC) scheme for layered video transmission in our previous work, which implanted the systematic bits of the BL into the systematic bits of the ELs using exclusive-OR operations (XOR). This allowed the receiver to exploit the implanted bits of the ELs for assisting the BL's decoding and hence improved the overall system performance of our IL-FEC aided layered video scheme. In this treatise, we find the specific FEC coding rates in a real-time on-line fashion for the sake optimizing the overall system performance. The proposed procedure is widely applicable to diverse wireless transceivers and FEC codecs. Our simulation results show that the proposed optimized IL-FEC system outperforms the traditional optimal UEP by about 1.9 dB of Eb/N0 at a peak signal-to-noise ratio (PSNR) of 38 dB. Viewing the improvements in terms of the video quality, 3.3 dB of PSNR improvement is attained at an Eb/N0 of 10 dB, when employing a recursive systematic convolutional (RSC) code.

3G 네트워크에서 MPEG-4 스케일러블 비디오의 실시간 방송을 위한 실행시간 예측 기반 MAC계층 오류제어

본 논문에서는 CDMA2000 1xEV-DO의 매체 접근 제어 계층에서 현재 순방향 오류 정정 방법으로 사용되고 있는 리드-솔로몬 복호화 과정의 수행 시간을 다양한 채널 조건에서 분석하였다. 그 결과, 트래픽 채널의 패킷 손실률이 특정 수준 이상으로 높을 경우 리드-솔로몬 복호기의 수행 시간이 길어져 MPEG-4 비디오의 시간 제약을 보장할 수없음을 확인하였다. 이러한 문제를해결하기 위해서본 연구에서는3가지의 기법을제시하였다. 첫째, 정적기법은 패킷 손실률이 특정 임계값 이상일 경우 리드-솔로몬 복호를 생략함으로써 MPEG-4의 시간 제약을 맞춘다. 두 번째 동적 기법은 패킷 손실률이 높더라도 모든 리드-솔로몬 복호를 생략하지는 않고MPEG-4의 시간 제약을 맞출 수 있는 범위 안에서 최대한으로 복구를 수행한다. 마지막 기법인 비디오 인지 동적 기법은 동적 기법과 비슷하지만 비디오 복호에 대한 기여도에 따른 우선 순위 기반으로 복구를 함으로써 비디오의 품질을 더욱 향상시키는 것이다. 우리는 본 논문에서 제안한 기법들을 활용하는 것이 실시간 비디오방송의 서비스 품질을 크게 향상시킬 수 있음을 다양한 실험을 통해 입증하였다. We analyze the execution time of Reed-Solomon coding, which is the MAC-layer forward error correction scheme used in CDMA2000 1xEV-DO broadcast services, under different air channel conditions. The results show that the time constraints of MPEG-4 cannot be guaranteed by Reed-Solomon decoding when the packet loss rate (PLR) is high, due to its long computation time on current hardware. To alleviate this problem, we propose three error control schemes. Our static scheme bypasses Reed-Solomon decoding at the mobile node to satisfy the MPEG-4 time constraint when the PLR exceeds a given boundary. Second, dynamic scheme corrects errors in a best-effort manner within the time constraint, instead of giving up altogether when the PLR is high; this achieves a further quality improvement. The third, video-aware dynamic scheme fixes errors in a similar way to the dynamic scheme, but in a priority-driven manner which makes the video appear smoother. Extensive simulation results show the effectiveness of our schemes compared to the original FEC scheme.

Improved Energy Efficiency for Optical Transport Networks by Elastic Forward Error Correction

In this paper we propose a scheme for reducing the energy consumption of optical links by means of adaptive forward error correction (FEC). The scheme works by performing on the fly adjustments to the code rate of the FEC, adding extra parity bits to the data stream whenever extra capacity is available. We show that this additional parity information decreases the number of necessary decoding iterations and thus reduces the power consumption in iterative decoders during periods of low load. The code rate adjustments can be done on a frame-by-frame basis and thus make it possible to manipulate the balance between effective data rate and FEC coding gain without any disruption to the live traffic. As a consequence, these automatic adjustments can be performed very often based on the current traffic demand and bit error rate performance of the links through the network. The FEC scheme itself is designed to work as a transparent add-on to transceivers running the optical transport network (OTN) protocol, adding an extra layer of elastic soft-decision FEC to the built-in hard-decision FEC implemented in OTN, while retaining interoperability with existing OTN equipment. In order to facilitate dynamic code rate adaptation, we propose a programmable encoder and decoder design approach, which can implement various codes depending on the desired code rate using the same basic circuitry. This design ensures optimal coding gain performance with a modest overhead for supporting multiple codes with minimal impact on the area and power requirements of the decoder.

Generalized Analytical Framework for the Performance Assessment of Slotted Random Access Protocols

This manuscript provides a general analytical framework to accurately predict the performance of several slotted Random Access (RA) schemes such as Slotted Aloha and Diversity Slotted Aloha. Compared to past literature the proposed analytical framework allows to perform accurate performance estimation of these RA schemes exploiting state-of-the-art forward error correction schemes in the presence of packet power unbalance as it is the case in many practical systems. Furthermore, the analytical framework is also capable to accurately approximate the performance of more recent RA schemes particularly suitable for satellite communications such as Contention Resolution Diversity Slotted Aloha exploiting iterative interference cancellation techniques on top of packet repetition within the frame to further improve the RA scheme performance. The analytical results have been successfully verified against a comprehensive set of simulations covering cases of practical interest.

Improving the Packet Delivery Performance for Concurrent Packet Transmissions in WSNs

In this letter, we investigate the properties of packet collisions in IEEE 802.15.4-based wireless sensor networks when packets with the same content are transmitted concurrently. While the nature of wireless transmissions allows the reception of a packet when the same packet is transmitted at different radios with (near) perfect time synchronization, we find that in practical systems, platform specific characteristics, such as the independence and error of the crystal oscillators, cause packets to collide disruptively when the two signals have similar transmission powers (i.e., differences of <;2 dBm). In such scenarios, the packet reception ratio (PRR) of concurrently transmitted packets falls below 10%. Nevertheless, we empirically show that the packet corruption patterns are easily recoverable using forward error correction schemes and validate this using implementations of RS and convolutional codes. Overall, our results show that using such error correction schemes can increase the PRR by more than four-fold.

Protection of HEVC video delivery in vehicular networks with RaptorQ codes.

With future vehicles equipped with processing capability, storage, and communications, vehicular networks will become a reality. A vast number of applications will arise that will make use of this connectivity. Some of them will be based on video streaming. In this paper we focus on HEVC video coding standard streaming in vehicular networks and how it deals with packet losses with the aid of RaptorQ, a Forward Error Correction scheme. As vehicular networks are packet loss prone networks, protection mechanisms are necessary if we want to guarantee a minimum level of quality of experience to the final user. We have run simulations to evaluate which configurations fit better in this type of scenarios.

Performance Analysis of Viterbi Decoder using different Digital Modulation Techniques in AWGN Channel

Error detection and correction has got a great practical importance in maintaining information (data) integrity across noisy channels. Convolutional encoding is considered as one of the forward error correction (FEC) schemes. A Viterbi decoder (VD) uses the Viterbi algorithm for decoding a bit stream that has been encoded using FEC based on a convolutional code. In this proposed work, a simulation of convolutional encoder and Viterbi decoder presented. This paper focuses on the performance study of Viterbi algorithm by varying parameters like constraint length, generating polynomials, traces back lengths and also modulation technique. The code rate considered is ½. In each case the Signal to Noise ratio (SNR) is varied from -2 to 6 and the computation of Bit Error Rate (BER) is performed.

오류 강인 SVC 비디오 전송을 위한 Exclusive-OR 기반의 FEC 부호화 시스템 설계 및 성능 분석

In this paper, we design and analyze performance of Exclusive-OR based FEC (Forward error correction) system to deploy SVC video transmission service over packet-loss prone IP network. In the designed system, we adopt standard compliant Exclusive-OR based FEC scheme and apply it to be appropriate to the hierarchical layer structure of SVC video. To verify the performance of the designed Exclusive-OR based FEC system for SVC video transmission, we employ NIST-NET based transport simulator. By the SVC video transmission using the NIST-NET based simulator, we confirm the error resilient transmission performance of the designed Exclusive-OR based FEC system.

Interleaving-based Forward Error Correction Scheme for Scalable Video Wireless Transmission

본 논문은 무선 채널 상의 스케일러블 비디오 전송을 위한 인터리빙 기반의 순방향 오류 정정(forward error correciton, FEC) 알고리즘을 제안한다. 무선 채널상의 스케일러블 비디오 전송은 연속적인 패킷 손실로인하여 급격한 화질 열화를 발생시키기 때문에, 효율적인 손실 보호 알고리즘이 필요하다. 제안된 FEC 알고리즘은 우선 계층내의 연속적인 패킷 손실을 여러 스케일러블 계층으로 분산시키기 위해서, 새로운 계층 기반 인터리빙 블록 구조를 제안한다. 또한 계층적 예측 구조의 에러 전파 특성을 이용한 FEC 할당 알고리즘이 패킷 손실로 인한 화질 열화를 최소화하기 위해서 제안된다. 실험 결과에서 제안된 알고리즘은 다양한 채널 환경에서 기존의 FEC 알고리즘과 비교하여 성능 향상을 보여주었다.

Improving Network Life Time of Wireless Sensor Network Using LT Codes Under Erasure Environment

In recent years, Wireless Sensor Network (WSN) finds application in Multimedia Broadcast and Multicast Service (MBMS). Reliability is the prime concern as some of the transmitted information gets lost in the erasure channel. As the application involves broadcast or multicast delivery of multimedia data through an erasure channel, Automatic Repeat request (ARQ) will not be good choice for improving the reliability as it leads to more energy wastage. Therefore, in this paper, we investigate the use of forward error correction scheme for energy conservation in WSN under erasure channel conditions. We found that the use of Luby Transform (LT) codes for IEEE 802. 15. 4 compliant WSN conserves more energy when compared to retransmission strategy. Other performance measures such as Bit Error Rate (BER) and throughput also showed improved results.

Packet Loss Recovery Scheme with Uniquely-Decodable Codes for Streaming Multimedia over P2P Networks

This paper presents an effective packet loss recovery scheme for Internet Protocol (IP) based peer-to-pear (P2P) networks that deliver multimedia streaming contents. The proposed scheme consists of two key components, a packet forward error correction (FEC) scheme and a uniquely decodable coding (UDC) scheme. The FEC scheme is devised to recover network packet loss over the transport layer to improve link transmission reliability at the user-ends of the P2P networks. The UDC scheme is employed to allow multiple sources to transmit data streams simultaneously in such a way that the combined data streams can be separated uniquely without ambiguity at the user-ends. This simultaneous multiple sources data transmission increases the throughput at the user-ends. Theoretical analysis and computer simulations show that the proposed scheme can achieve the commonly acceptable of 10^{-6} end-to-end packet loss rate for input packet loss rate of up to 10%with a reasonably small bandwidth expansion factor, while maintains a high throughput at the user-ends.

Optimized cross-layer forward error correction coding for H.264 AVC video transmission over wireless channels

Forward error correction (FEC) codes that can provide unequal error protection (UEP) have been used recently for video transmission over wireless channels. These video transmission schemes may also benefit from the use of FEC codes both at the application layer (AL) and the physical layer (PL). However, the interaction and optimal setup of UEP FEC codes at the AL and the PL have not been previously investigated. In this paper, we study the cross-layer design of FEC codes at both layers for H.264 video transmission over wireless channels. In our scheme, UEP Luby transform codes are employed at the AL and rate-compatible punctured convolutional codes at the PL. In the proposed scheme, video slices are first prioritized based on their contribution to video quality. Next, we investigate the four combinations of cross-layer FEC schemes at both layers and concurrently optimize their parameters to minimize the video distortion and maximize the peak signal-to-noise ratio. We evaluate the performance of these schemes on four test H.264 video streams and show the superiority of optimized cross-layer FEC design.