Forward Error Correction Codes Research Articles

Design of a 40/50 GHz satellite ground station for fade mitigation experiments

Due to the increasing demand in satellite capacity, driven by applications such as high-definition television (HDTV), 3D-TV and interactive broadband services, higher frequency bands will have to be exploited. The capacity on Ku-band is already becoming scarce and Ka-band systems are more commonly used. It can be expected that 40 and 50GHz (Q and V band) will have to be used in the future. At these frequencies the wave propagation effects have a significant impact on the performance. The traditional approach of implementing large fade margins in the system design is not suitable as it leads to expensive ground terminals. Fade mitigation by adaptive coding and modulation (ACM) is a cost-efficient method. To investigate the Q/V-band for future commercial exploitation, ESA's ALPHASAT satellite will provide experimental payloads for communications and wave propagation experiments. In Graz a Q/V-band ground station is currently under development. It will be equipped with a 3m tracking antenna, a 50W Klystron amplifier and a 290K LNA. Fade mitigation experiments will be conducted, initially using DVB-S2 modems which allow to vary the modulation scheme, the Forward Error Correction code and the symbol rate under control of the ACM computer. In addition, uplink power control can be combined with the ACM methods. A specially developed signal analyser provides precise measurement of the signal/noise ratio. In addition, propagation data will be available from a beacon receiver, also developed by Joanneum Research. Important goals of the experiment are to investigate the reliability of links under realistic operating conditions using ACM and to develop efficient ACM and signal/noise ratio measurement algorithms which can be later implemented in optimised modems for Q/V-band.The paper describes the ground station design and addresses the planned fade mitigation experiments.

Forward error correction supported 150 Gbit/s error-free wavelength conversion based on cross phase modulation in silicon

We build a forward error correction (FEC) module and implement it in an optical signal processing experiment. The experiment consists of two cascaded nonlinear optical signal processes, 160 Gbit/s all optical wavelength conversion based on the cross phase modulation (XPM) in a silicon nanowire and subsequent 160 Gbit/s-to-10 Gbit/s demultiplexing in a highly nonlinear fiber (HNLF). The XPM based all optical wavelength conversion in silicon is achieved by off-center filtering the red shifted sideband on the CW probe. We thoroughly demonstrate and verify that the FEC code operates correctly after the optical signal processing, yielding truly error-free 150 Gbit/s (excl. overhead) optically signal processed data after the two cascaded nonlinear processes.

Free space laser communication experiments from Earth to the Lunar Reconnaissance Orbiter in lunar orbit

Laser communication and ranging experiments were successfully conducted from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit. The experiments used 4096-ary pulse position modulation (PPM) for the laser pulses during one-way LRO Laser Ranging (LR) operations. Reed-Solomon forward error correction codes were used to correct the PPM symbol errors due to atmosphere turbulence and pointing jitter. The signal fading was measured and the results were compared to the model.

Performance of COFDM in Underwater Acoustic Channel with Frequency Selective Fading

In this paper, performance of COFDM (Coded Orthogonal Frequency Division Multiplexing) which is OFDM with a forward error correction code, is studied in frequency selective fading underwater acoustic communication channel. The OFDM is a multiplexing technique resistant to frequency selective multipath channel. In OFDM, a broadband information signal is transformed into several narrow band signals and transmits narrow band signals whose bandwidths are less than the channel coherence bandwidth. However, its performance is degraded in a specific narrow band signal due to its deep fading by multipath. To mitigate this degradation, COFDM which is OFDM with convolution code as a forward error correction code, is evaluated. The performance of COFDM is found to be better than that of OFDM in multipath channel.

Performance Analysis Of A Cellular System Using C-Ofdm Techniques

The basic idea of COFDM is to split the modulation samples of incoming data stream onto a large number of carriers instead of modulating a unique carrier. Therefore, COFDM is an effective technique for combating multi-path fading and for highbit- rate transmission over wireless channel. In a single carrier system a frequency Selective fading can cause the entire transmission link to fail, but in an COFDM multi carrier system, only a small percentage of the sub-carriers will be corrupted. Frequency and time interleaving in conjunction with forward error correction coding can then be used to correct for erroneous subcarriers. The background information with the aim to provide an intuitive explanation of our research motivation. C-OFDM is the modulation scheme of choice , as enshrined in International standard for all forms of digital broadcasting both audio and video and including satellite, terrestrial, and cable. In the existing standard the “coding” referred to consists of an inner convolutional code concatenated with an outer R-S code; here in this thesis, we replace the inner code with the coding like space time trellis code for analysis.

Modified Reed–Muller Coding Scheme Made From the Bent Function for Dimmable Visible Light Communications

In this letter, we propose a new forward error correction (FEC) coding method using a coset constructed from a bent function and a Reed-Muller (RM) code for providing accurate dimming control in on-off keying-based visible light communication (VLC) systems. By partitioning the coset made from bent function and the first-order RM codes, the new FEC scheme can be made to be suitable for dimming close to 0% or 100%. Therefore, it can contain minimal compensation symbols in supporting multiple dimming target values, which causes improved coding gain when the total amount of frame data is fixed. Simulation results for various dimming target values show that the proposed scheme leads to about 1-dB signal-to-noise ratio gain in 10-2 bit error rate compared with other three FEC codes.

Error Control and performance Analysis of MIMO-OFDM Over Fading Channels

Multiple Input Multiple Output is a wireless technology that uses multiple transmitters and receivers to transfer more data at the same time. Orthogonal Frequency Division Multiplexing, an FDM modulation technique which splits the signal into multiple smaller sub-signals that are then transmitted simultaneously at different frequencies to the receiver. OFDM technique spreads the data over number of carriers which are at specific predefined frequencies. This reduces or eli minates the ISI. Forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The objective of our proposed paper is to implement the FEC into the MIMO OFDM systems and its performance is analysed by using MATLAB over different fading channels. For modulation it employs M-QAM which combines both ASK and PSK thereby enabling several bits to be transmitted per symbol. The performance of MIMO-OFDM system is evaluated by BER Vs SNR when the bits propagates through the different fading channels. Keywords- OFDM, MIMO, QAM, FEC , BER .

On the design of full-rate full-diversity space-time block codes for multiple-input–multiple-output systems with a turbo minimum mean square error equaliser at the receiver side

Non-orthogonal space-time block (STB) code structures used to be optimised considering a maximum-likelihood detection, but depending on the modulation order and/or the antenna number, the prohibitive complexity of such a receiver makes it infeasible in practice. Suboptimal low-complexity receiver structures like linear detectors can be applied instead, yielding degradation of performance compared with the predictions. When a forward error correction (FEC) code is used upstream of the STB code, an iterative receiver consisting of a FEC decoder and an interference canceller (IC) co-operating according to the turbo equalisation principle, can achieve near-optimal performance. This study aims to define the construction of full-rate full-diversity linear dispersion codes with reduced peak-to-average power ratio (PAPR), taking into account the serial concatenation with a FEC at the transmitter and a minimum mean square error (MMSE) turbo equaliser at the receiver. Optimisation criteria are mutual information maximisation, symbol error rate minimisation at the MMSE–IC output, full-diversity thanks to the threaded algebraic space time concept and PAPR minimisation. Explicit constructions are given and the resulting code efficiency is analysed through comparison with equivalent perfect STB codes.

Impact of Nonideal Phase Reference on Soft Decoding of Differentially Encoded Modulation

The performance of coded modulation schemes based on the concatenation of a forward-error correction (FEC) code and differentially encoded quadrature amplitude modulations (QAMs) in the presence of Wiener phase noise is considered. Log-likelihood ratios, required to perform soft decoding, are first derived for the case in which the phase of the received carrier is assumed to be perfectly known, and then used to obtain the performance for nonideal reference of phase. Simulation results of the post-FEC bit-error rate are presented for a near-Shannon limit low-density parity check code with an overhead of 20%. The performance loss, compared to ideal coherent demodulation, is evaluated for two different linewidths of the phase noise in case of quadrature-phase shift keying and 16-QAM transmission.

Experimental Investigation of 126-Gb/s 6PolSK-QPSK signals

We experimentally generate 28-GBd 6-ary polarization-shift keying quadrature phase-shift keying (6PolSK-QPSK) signals by utilizing a high-speed 4-channel digital-to-analog converter and an integrated dual-polarization I/Q modulator. In WDM transmission experiments over up to 4800 km standard single-mode fiber, we compare the performance of 126-Gb/s 6PolSK-QPSK and 112-Gb/s polarization-division multiplexing (PDM) QPSK signals. Furthermore, we discuss the implications of applying an inner Reed-Solomon RS(511,455) forward error correction code in order to correct burst errors due to the anti-Gray mapping of 6PolSK-QPSK.

1-Gb/s Transmission Over a Phosphorescent White LED by Using Rate-Adaptive Discrete Multitone Modulation

Light-emitting diodes (LEDs), which will be increasingly used in lighting technology, will also allow for distribution of broadband optical wireless signals. Visible-light communication (VLC) using white LEDs offers several advantages over the RF-based wireless systems, i.e., license-free spectrum, low power consumption, and higher privacy. Mostly, optical wireless can provide much higher data rates. In this paper, we demonstrate a VLC system based on a white LED for indoor broadband wireless access. After investigating the nonlinear effects of the LED and the power amplifier, a data rate of 1 Gb/s has been achieved at the standard illuminance level, by using an optimized discrete multitone modulation technique and adaptive bit- and power-loading algorithms. The bit-error ratio of the received data was $1.5\cdot 10^{-3}$ , which is within the limit of common forward error correction (FEC) coding. These results twice the highest capacity that had been previously obtained.

Ultranarrow Spectrum-Sliced Incoherent Light Source for 10-Gb/s WDM PON

We report on the use of an ultranarrow ( ~0.01 nm) spectrum-sliced incoherent light source for transmission of 10-Gb/s nonreturn-to-zero signals over 20-km dispersion-uncompensated standard single-mode fiber and 0.2-nm-bandwidth optical band-pass filter. A wideband amplified spontaneous emission is first generated using an erbium-doped fiber amplifier and then spectrum-sliced by an ultranarrow fiber Fabry-Perot filter (3-dB bandwidth: ~0.006 nm). The spectrum-sliced light is intensity-smoothed by using a gain-saturated reflective semiconductor optical amplifier and then modulated at 10.7 or 12.5 Gb/s, assuming forward error correction (FEC) with 7% or 25% overheads, respectively. Thanks to the narrow linewidth of the source, we are able to retain the intensity smoothing after the transmission, achieving uncorrected bit-error ratios better than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> and 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> at 10.7 and 12.5 Gb/s, respectively. We discuss the applicability of the proposed light source to wavelength-division-multiplexed passive optical networks and the choice of FEC codes for the proposed scheme.

Rate-Adaptive Modulation and Low-Density Parity-Check Coding for Optical Fiber Transmission Systems

We propose a rate-adaptive optical transmission scheme using variable-size constellations at a fixed symbol rate and variable-rate forward error correction (FEC) codes with soft-decision decoding (SDD), quantifying how achievable bit rates vary with transmission distance. The scheme uses outer Reed&#x2013;Solomon codes and inner extended irregular repeat-accumulate low-density parity-check (LDPC) codes to vary the code rate, combined with single-carrier polarization-multiplexed M-ary quadrature amplitude modulation with variable M and digital coherent detection. LDPC codes are decoded iteratively using belief propagation. Employing M=4,8,16, the scheme achieves a maximum bit rate of 200&#x00A0;Gbit/s in a nominal 50-GHz channel bandwidth. A rate adaptation algorithm uses the signal-to-noise ratio (SNR) or the FEC decoder input bit-error ratio (BER) estimated by a receiver to determine the FEC code rate and constellation size that maximize the information bit rate while yielding a target FEC decoder output BER and a specified SNR margin. We simulate single-channel transmission through long-haul fiber systems with or without inline chromatic dispersion compensation, incorporating numerous optical switches, evaluating the impact of fiber nonlinearity and bandwidth narrowing. With zero SNR margin, we achieve bit rates of 200/100/50/20&#x00A0;Gbit/s over distances of 960/2800/4400/9680&#x00A0;km and 1920/4960/8160/19,360&#x00A0;km in dispersion-compensated and -uncompensated systems, respectively, corresponding to an increase of about 50&#x0025; in reach compared to a reference system that uses a hard-decision FEC scheme. Compared to an ideal coding scheme, the proposed scheme exhibits a performance gap ranging from about 4.0&#x00A0;dB at 960&#x00A0;km to 2.7&#x00A0;dB at 9680&#x00A0;km in compensated systems, and from about 3.9&#x00A0;dB at 1920&#x00A0;km to 2.9&#x00A0;dB at 19,360&#x00A0;km in uncompensated systems. Observed performance gaps are about 2.5&#x00A0;dB smaller than for the reference hard-decision FEC scheme, close to the improvement expected when using SDD.

Performance analysis of zigzag-coded modulation scheme for WiMAX systems

WiMAX is an OFDM-based technology that supports point-to-multi-point broadband wireless access for next-generation radio access such as 4G. In this paper, we evaluate bit-error-rate performance of fixed WiMAX (IEEE 802.16d) and mobile WiMAX (IEEE 802.16e) transmission systems with various modulations and channel coding techniques. In the digital communication phenomenon, coding schemes are broadly used as a term mostly referring to the forward error correction code. The advantage of the forward error correction code is that retransmission of data can often be avoided. The simulation results include performance analysis based on bit-error-rate versus signal-to-noise-ratio plots and spectral efficiency of different modulation and coding schemes according to the IEEE 802.16 general standard. The results show that the proposed zigzag-coded modulation possesses a stronger error correcting capability according to the Reed Solomon with Convolutional code for both fixed WiMAX and mobile WiMAX standards.

A novel genetic probability decoding (GPD) algorithm for the FEC code in optical communications

A new genetic probability decoding (GPD) algorithm to be fit for forward error correction (FEC) codes of optical communications, based on the genetic algorithm, is proposed through the characteristic analysis of optical communications. This novel algorithm can further optimize the matched filter's output of demodulator by applying the channel interference probability statistics and taking the advantage of the genetic algorithm's heuristic parallel search capability to restore a more likelihood transmission code. The theoretical performance analysis and the simulation result of the GPD algorithm show the proposed GPD algorithm has a relatively low decoding complexity because it won’t be affected by the number of code symbols, as well as a faster decoding speed and a better decoding correction-error performance. Therefore, the proposed GPD algorithm is a better practical decoding algorithm.

Spectral Efficient Coding Schemes in Optical Communications

Achieving high spectral efficiency in optical transmissions has recently attracted much attention, aiming to satisfy the ever increasing demand for high data rates in optical fiber communications. Therefore, strong Forward Error Correction (FEC) coding in combination with multilevel modulation schemes is mandatory to approach the channel capacity of the transmission link. In this paper we give design rules on the joint optimization of coding and signal constellations under practical considerations. We give trade-offs between spectral efficiency and hardware complexity, by comparing coding schemes using capacity achieving constellations with bit-interleaved coded modulation and iterative decoding (BICM-ID) against applying conventional square quadrature amplitude modulation (QAM) constellations but employing powerful low complexity low-density parity-check (LDPC) codes. Both schemes are suitable for optical single carrier (SC) and optical orthogonal frequency-division multiplexing (OFDM) transmission systems, where we consider the latter one in this paper, due to well-studied equalization techniques in wireless communications. We numerically study the performance of different coded modulation formats in optical OFDM transmission, showing that for a fiber optical transmission link of 960 km reach the net spectral efficiency can be increased by ≈0.4 bit/s/Hz to 8.61 bit/s/Hz at a post FEC BER of <10-15 by using coded optimized constellations instead of coded 64-QAM.In this paper we propose a high spectral efficient coded modulation scheme for implementation in future optical communication systems operating at data rates beyond 400 Gb/s. In detail, we adapt the “Turbo Principle” to BICM-ID[8] and combine it with a high-rate outer algebraic code to obtain a post-FEC BER <10-15, which is a typical demand in optical transponders. Furthermore we give simple design principles for the design of BICM-ID based on the extrinsic information transfer (EXIT) chart analysis[9]. The optical channel is considered to be weakly-nonlinear. Therefore the proposed techniques are also applicable for single-carrier transmission; however we consider OFDM since it appears to be more appropriate for the high order modulation formats and efficient equalization algorithms that are well established in wireless communications.

Nonbinary LDPC-Coded Modulation for Rate-Adaptive Optical Fiber Communication Without Bandwidth Expansion

A rate-adaptive nonbinary low-density parity-check-coded modulation scheme is proposed to enable fiber-optic transmission at variable bit rates by adjusting the spectral efficiency (SE) of transmission while keeping the occupied bandwidth fixed. To achieve a given SE within a fixed bandwidth, both the underlying signal constellation size and the forward error correction code rate are adjusted. Using the scarce resource of bandwidth more effectively, the proposed scheme is expected to find applications in both current fixed-grid networks and in future networks that might adopt flexible grid approach.

부호화된 MIMO 시스템에서 QR 분해를 이용한 효율적인 연판정 검출

무선통신시스템에서의 고용량 데이터 전송을 위해 MIMO 전송은 필수적인 기술의 하나로 자리매김하였다. 더불어 열악한 채널환경에서 요구되는 성능을 만족하기 위해서는 반드시 고효율 오류정정부호를 사용하여야하며, 반복적인 복호 기법을 사용하는 터보부호나 저밀도 패리티 검사부호 등이 그 예라고 할 수 있다. 이러한 오류정정 부호들의 우수한 성능은 반드시 MIMO 검출 단에서의 정확한 연판정 검출 값이 전제되어야 한다. 본 논문에서는 매우 적은 복잡도로 효과적으로 연판정 검출 값을 복호기에 전달 할 수 있는 방법으로써 채널 행렬의 QR 분해기법을 적용한 연판정 검출 기법을 제안한다. 본 논문에서 제안하는 방식은 먼저 연판정 MIMO 검출 단계를 두 단계로 나누어 복잡도를 획기적으로 감소시킬 수 있는 방법과 결합하였으며, 채널 행렬에 대하여 직접 역행렬을 구하는 방식에 비해서 안테나 수가 증가할수록 훨씬 더 적은 복잡도로 동일한 성능을 얻을 수 있다. Multi-Input Multi-Output (MIMO) transmission is now considered as one of essential techniques enabling high rate data transmissions in wireless communication systems. In addition, severe channel impairments in wireless systems should be compensated by using highly efficient forward error correction (FEC) codes. Turbo codes or low density parity check (LDPC) codes, using iterative decoding with soft decision detection information (SDDI), are the most common examples. The excellent performance of these codes should be conditioned on accurate estimation of SDDI from the MIMO detection process. In this paper, we propose a soft MIMO detection scheme using QR decomposition of channel matrices as an efficient means to provide accurate SDDI to the iterative decoder. The proposed method employed a two sequential soft MIMO detection process in order to reduce computational complexity. Compared to the soft ZF method calculating the direct inverse of the channel matrix, the complexity of the proposed method can be further reduced as the number of antennas is increased, without any performance degradation.

A novel RS BTC coding scheme for optical communications

A novel Reed Solomon (RS) block turbo code (BTC) coding scheme of RS(63,58)×RS(63,58) for optical communications is proposed. The simulation results show that the net coding gain (NCG) of this scheme at the sixth iteration is more than that of other coding schemes at the third iteration for the bit error rate (BER) of 10−12. Furthermore, the novel RS BTC has shorter component code and rapider encoding and decoding speed. Therefore, the novel RS BTC coding scheme can be better used in high-speed long-haul optical communication systems, and the novel RS BTC can be regarded as a candidate code of the super forward error correction (super-FEC) code. Moreover, the encoding/decoding design and implementation of the novel RS BTC are also presented

Transmission Power Analysis of Optical Wireless Based Mobile Healthcare Systems

In the context of healthcare monitoring, it is necessary to transmit vital information from the patient to an interface managed by the hospital staff. In this work we consider a system where the patient can move within a hospital room and the data collected by sensors are transmitted to a distant receiver placed on the ceiling. We investigate the potentiality of using infrared (IR) communication for the transmission of information in this mobile context. Considering two main IR propagation types (line of sight and diffuse), we characterize the IR mobile channel by using a random waypoint mobility for a realistic scenario. Thanks to the mobility model, we evaluate the outage probability of this mobile monitoring scheme. From the results, the power efficiency of IR technology to ensure the communication between sensors and the collecting point is established. Moreover, to minimize the system performance and ensure the highest power autonomy, we investigate the possibility of using channel coding. The analysis shows that for a typical data rate of 500 Kbps, it is theoretically possible to minimize the transmission power considering the use of a forward error correction code while maintaining the targeted information rate.