Adaptive Low-density Parity-check Research Articles

Fast Adaptive Low-density Parity Check Coding Based on Confidence Criteria

Fast Adaptive Low-density Parity Check Coding Based on Confidence Criteria

Real-Time Verification of Soft-Decision LDPC Coding for Burst Mode Upstream Reception in 50G-PON

Forward error correction (FEC) with high coding gain is needed to achieve PR30 (29 dB) link budget in 50G-PON. In particular, the stringent capacity and latency requirements of the 50G PON call for innovations in the design of FEC codes to go against the noise in the channel. In this paper, we propose a generic FPGA design for an adaptive irregular LDPC coding emulator that supports hard-decision, soft-decision, shortening, and puncturing. We evaluate the error-correction performance of the low-density parity-check (LDPC) forward-error correction (FEC) code that is currently under study by ITU-T's 50G-PON group for burst-mode upstream reception. Through experimental measurements based on a real-time FGPA platform, we found that soft-decision (SD) offers ∼1.3 dB more gross coding gain than hard-decision (HD). The SD LDPC performance is well maintained for non-uniform input bit error distributions where the errors are concentrated at the first 1/8 of each code word, corresponding to ∼44 ns (∼88 ns) for a 50-Gb/s (25-Gb/s) upstream signals. This indicates the suitability of the use of the SD-LDPC for burst-mode upstream reception in 50G-PON.

Energy Efficiency of a Decode-and-Forward Multiple-Relay Network with Rate Adaptive LDPC Codes.

This paper presents cooperative transmission (CT), where multiple relays are used to achieve array and diversity gains, as an enabling technology for Internet of Things (IoT) networks with hardware-limited devices. We investigate a channel coding aided decode-and-forward (DF) relaying network, considering a two-hop multiple-relay network, where the data transmission between the source and the destination is realized with the help of DF relays. Low density parity check (LDPC) codes are adopted as forward error correction (FEC) codes to encode and decode the data both at the source and relays. We consider both fixed and variable code rates depending upon the quality-of-service (QoS) provisioning such as spectral efficiency and maximum energy efficiency. Furthermore, an optimal power allocation scheme is studied for the cooperative system under the energy efficiency constraint. We present the simulation results of our proposed scheme, compared with conventional methods, which show that if decoupled code rates are used on both hops then a trade-off has to be maintained between system complexity, transmission delay, and bit error rate (BER).

Low-Complexity High-Throughput Bit-Wise LDPC Decoder

Emerging standards for wireless communications in the 60-GHz band, such as WiGig and IEEE 802.11ad, require high throughput between 1.5 and 6 Gb/s. These standards use adaptive low-density parity-check (LDPC) codes for high error correction capability. Most research studies on LDPC decoders have focused on low area implementations, to improve throughput. We previously developed a bit-serial first two minimum-value generator without bit error rate (BER) performance degradation. This paper presents a low-complexity bit-wise LDPC decoder based on bit-serial first two minimum-value generator for a high-data-rate LDPC decoder. We use the throughput-to-area ratio (TAR) metric to compare with other 802.11ad LDPC decoders.

Performance optimization of PM-16QAM transmission system enabled by real-time self-adaptive coding.

We experimentally demonstrate self-adaptive coded 5×100 Gb/s WDM polarization multiplexed 16 quadrature amplitude modulation transmission over a 100km fiber link, which is enabled by a real-time control plane. The real-time optical signal-to-noise ratio (OSNR) is measured using an optical performance monitoring device. The OSNR measurement is processed and fed back using control plane logic and messaging to the transmitter side for code adaptation, where the binary data are adaptively encoded with three types of low-density parity-check (LDPC) codes with code rates of 0.8, 0.75, and 0.7 of large girth. The total code-adaptation latency is measured to be 2273ms. Compared with transmission without adaptation, average net capacity improvements of 102%, 36%, and 7.5% are obtained, respectively, by adaptive LDPC coding.

Skip block based distributed source coding for hyperspectral image compression

Due to the involvement of massive amount of information in processing and transmission operations, reduction of encoder complexity is a key requirement for lossy compression methods of hyperspectral images. Distributed Source Coding (DSC) is the enabling technology which reverses the encoder-decoder complexity and provides error resilience. In this work, for complexity reduction, the adaptability of block based design to spatially varying characteristics is exploited and combined with DSC. Blocks of size 8x8 with Mean Absolute Error (MeanAE) less than 3.0 and Maximum Absolute Error (MaxAE) less than 4 are identified and skipped from coding, and the remaining portion has been 2D (2-Dimensional) DCT (Discrete Cosine Transform)/SPIHT (Set Partitioning in Hierarchical Trees) coded. Skip block based DSC scheme results in variable source statistics and this is handled with rate adaptive Low Density Parity Check (LDPC) codes. This new block based algorithm, together with rate adaptive codes results in better compression with reduced coding complexity. Our experimental results show that skip block based DSC coded scheme, in addition to being very flexible, retains all the desirable features of compared well-known algorithms. This is also highly competitive to 3D-SPIHT, and better than 2D SPIHT both in terms of compression efficiency and classification.

Dynamic voltage and frequency scaling scheme for an adaptive LDPC decoder using SNR estimation

Abstract In this paper, we propose a low-power adaptive low-density parity check (LDPC) decoder that utilizes dynamic voltage and frequency scaling to reduce power consumption. Most existing adaptive LDPC decoders have focused only on the decoding performance based on the signal-to-noise ratio (SNR) estimation. However, significant idle power is consumed when the decoder awaits the next frame after processing a frame. In mobile communication standards such as China Mobile Multimedia Broadcasting and Digital Video Broadcasting Satellite Second Generation, adaptive coding and modulation has been adopted. Thus, it is possible to reduce the power consumption efficiently by using the SNR estimation. In this paper, we apply a customized frequency selection scheme and a variable voltage generation scheme to an adaptive LDPC decoder to reduce the dynamic power consumption. The proposed schemes result in a reduction of 44% in the energy consumption of an LDPC decoder implemented using 0.18-μm complementary metal-oxide-semiconductor technology.

Analysis and Evaluation of Adaptive LDPC AL-FEC Codes for Content Download Services

This paper proposes the use of adaptive low density parity check (LDPC) application layer-forward error correction (AL-FEC) codes for content download services over erasure channels. In adaptive LDPC codes, clients inform the content download server of the losses they are experiencing. Using this information, the server makes forward error correction (FEC) parity symbols available to the client at an optimum code rate. This paper presents an analytical model of the proposed adaptive LDPC codes. The model is validated through measurements realized with an application prototype. In addition, results show the performance of these codes in different scenarios, compared to the performance of nonadaptive AL-FEC, optimum LDPC AL-FEC codes, and an almost ideal rateless code. Adaptive LDPC AL-FEC codes achieve download times similar to almost ideal rateless codes with less coding complexity, at the expense of an interaction channel between server and clients.

PEEC: a channel-adaptive feedback-based error

Reliable transmission is a challenging task over wireless LANs since wireless links are known to be susceptible to errors. Although the current IEEE802.11 standard ARQ error control protocol performs relatively well over channels with very low bit error rates (BERs), this performance deteriorates rapidly as the BER increases. This paper investigates the problem of reliable transmission in a contention free wireless LAN and introduces a packet embedded error control (PEEC) protocol, which employs packet-embedded parity symbols instead of ARQ-based retransmission for error recovery. Specifically, depending on receiver feedback, PEEC adaptively estimates channel conditions and administers the transmission of (data and parity) symbols within a packet. This enables successful recovery of both new data and old unrecovered data from prior transmissions. In addition to theoretically analyzing PEEC, the performance of the proposed scheme is extensively analyzed over real channel traces collected on 802.11b WLANs. We compare PEEC performance with the performance of the IEEE802.il standard ARQ protocol as well as contemporary protocols such as enhanced ARQ and the hybrid ARQ/FEC. Our analysis and experimental simulations show that PEEC outperforms all three competing protocols over a wide range of actual 802.11b WLAN collected traces. Finally, the design and implementation of PEEC using an adaptive low-density-parity-check (A-LDPC) decoder is presented.

Study of adaptive modulation and LDPC coding in multicarrier systems

An adaptive modulation (AM) algorithm is proposed and the application of the adapting algorithm together with low-density parity-check (LDPC) codes in multicarrier systems is investigated. The AM algorithm is based on minimizing the average bit error rate (BER) of systems, the combination of AM algorithm and LDPC codes with different code rates (half and three-fourths) are studied. The proposed AM algorithm with that of Fischer et al is compared. Simulation results show that the performance of the proposed AM algorithm is better than that of the Fischer's algorithm. The results also show that application of the proposed AM algorithm together with LDPC codes can greatly improve the performance of multicarrier systems. Results also show that the performance of the proposed algorithm is degraded with an increase in code rate when code length is the same.

Approaching V-BLAST Capacity With Adaptive Modulation and LDPC Encoding

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents a practical implementation of the vertical Bell Laboratories layered space-time (V-BLAST) type system, in which the multiple-input multiple-output (MIMO) open-loop capacity can be approached with conventional scalar coding, using adaptive modulation with appropriate channel codes, e.g., low-density parity-check (LDPC) codes and optimum successive detection (OSD). The density evolution (DE) technique is employed to determine the maximal achievable rate of an LDPC code for each transmit antenna for a given channel realization at a given SNR. Numerical results show that the average sum rate of the adaptively modulated LDPC-encoded system is quite close to the V-BLAST capacity with both rate and power adaptations. Considering the performing degradation caused by error propagation due to the imperfect feedback and relatively long decoding delay in the OSD, we use parallel interference cancellation (PIC) followed by minimum mean square error (MMSE) filtering in the bit error rate (BER) performance simulation. Simulation results show that a target BER of 10-5 can be achieved by the optimally designed LDPC codes. To simplify the code design, we replace the LDPC codes optimally designed for each channel realization with rate-compatible punctured LDPC codes, at the cost of a slight sum rate loss. If the fading process is nonergodic, the outage capacity corresponding to a given outage probability is used to measure the channel performance. As an example, we design the LDPC codes for an adaptively modulated 2 <formula formulatype="inline"><tex>×</tex></formula> 2 V-BLAST system to approach its outage capacity for a given outage probability. </para>