ARO scheme with combined channel coding and modulation using noncoherent detection

A new method for the combination of channel coding and modulation with noncoherent detection in automatic-repeat-request protocols is described. This scheme can be used in automatic-repeat-request protocols in which each codeword is transmitted m >or= 2 times consecutively. Theoretical analysis shows that this scheme offers a net increase in the performance with respect to other similar protocols.<>     

A new method for the integration of modulation and channel codingin an ARQ protocol

A method for the integration of the modulation operation in an automatic-repeat-request (ARQ) scheme is described. This method uses a memory for the successive transmissions of a codeword and, through a suitable encoding operation, the Euclidean distances among the codewords are significantly increased with the number of transmissions. The application of the described method to some different modulation schemes, such as M-ary PSK with M>2 and continuous-phase frequency shift keying modulation, is described. The optimum combination of the modulation and channel coding operations for some short block codes is also presented. The results of the theoretical analysis show that the method described permits improving both the error probability and the throughput of an ARQ protocol with respect to similar schemes     

Hybrid ARQ schemes employing coded modulation and sequencecombining

In this paper, we propose and analyze two hybrid automatic-repeat-request (ARQ) schemes employing bandwidth efficient coded modulation and coded sequence combining. In the first scheme, a trellis-coded modulation (TCM) is used to control channel noise; while in the second scheme a concatenated coded modulation is employed. The concatenated coded modulation is formed by cascading a Reed-Solomon (RS) outer code and a block coded modulation (BCM) inner code. In both schemes, the coded modulation decoder, by performing sequence combining and soft-decision maximum likelihood decoding, makes full use of the information available in all received sequences corresponding to a given information message. It is shown, by means of analysis as well as computer simulations, that both schemes are capable of providing high throughput efficiencies over a wide range of signal-to-noise ratios. The schemes are suitable for large file transfers over satellite communication links where high throughput and high reliability are required     

New ARQ protocols using concatenated codes

Two automatic-repeat-request (ARQ) protocols using a concatenated coding scheme are described. The structure, introduced in a codeword of a concatenated coding scheme, is used to improve the performance of ARQ protocols, especially for high error rates in the communication channel. The performance of the scheme described herein is derived through theoretical analysis. The results show that the proposed scheme outperform other similar ARQ protocols     

Analysis of memory and incremental redundancy ARQ schemes over anonstationary channel

A generalized type II automatic-repeat-request (ARQ) scheme using punctured convolutional coding on a two-state Markov model of a nonstationary channel is analyzed. A simple ARQ scheme with memory is also analyzed. It is shown that the simple memory ARQ scheme offers a substantial throughput improvement over a conventional ARQ scheme at severe channel conditions. Furthermore, the generalized type II ARQ scheme yields a better performance than the conventional type II ARQ scheme under all channel conditions, thus making it attractive for use over time-varying channels     

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     

An ARQ scheme using combined QPSK and BPSK transmissions

We propose a hybrid ARQ scheme which uses QPSK modulation for the first transmission and BPSK modulation for retransmissions. The throughput performance of the proposed ARQ scheme is better that those of ARQ schemes purely using QPSK modulation or purely using BPSK modulation for transmissions. Furthermore, the proposed scheme does not require any operation of error correction as usually required in hybrid ARQ schemes. Therefore, the ARQ scheme proposed in this paper can be easily implemented     

Modified majority logic decoding of cyclic codes in hybrid-ARQsystems

Reliability information provided by sets of orthogonal check sums in a majority logic decoder for block codes is used in a type-I hybrid automatic-repeat-request (ARQ) error control scheme. The reliability information is obtained through a simple modification of the majority logic decoding rule. It is shown that the reliability performance of Reed-Muller and other majority logic decodable codes can be substantially improved at the expense of a very small reduction in throughput. The simplicity of the decoding circuit permits implementation in systems with very high data rates     

Analysis of a type II hybrid ARQ scheme with codecombining

An analysis is presented of the selective-repeat type II hybrid AR Q (automatic-repeat-request) scheme, using convolutional coding and exploiting code combining. With code combining, at successive decoding attempts for a data packet, the decoder for error correction operates on a combination of all received sequences for that packet rather than only on the two most recent received ones as in the conventional type II hybrid ARQ scheme. It is shown by means of analysis and computer simulations that with code combining, a significant throughput is achievable, even at very high channel error rates     

基于非编码信息匹配的自适应Turbo TCM编码调制方案

本文提出了一种通过调整非编码信息量,并与信号映射相结合来改变编码、调制模式的自适应Turbo TCM编码调制方案,称之为基于非编码信息匹配的自适应Turbo TCM编码调制方案.由于将Turbo码和TCM编码调制技术相结合得到的Turbo TCM编码调制方案的带宽效率高,所以,在慢时变无线衰落信道中,自适应Turbo TCM编码调制的平均频谱效率也将很高.给出了该方案的工作原理、设计方法,并通过蒙特卡洛(Monte Carlo)仿真研究了该方案的性能.与现有编码调制方案相比,该方案具有频谱效率高、易于设计和实现的优点.     

Superposition of DQPSK over inverse-RZ for 3-bit/symbol modulation-demodulation

We successfully demonstrated overwriting of differential quadrature phase-shift keying (DQPSK) on inverse return-to-zero (RZ) pulses for simple 3-bit/symbol operation at a 10-Gb/s symbol rate (30-Gb/s bit rate). We adopted cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) for inverse-RZ generation, which allows both low and high levels of RZ optical signal to have a finite pulse energy in a bit time slot. We verified a wide tolerance of 20% of the bit-slot for time slot alignment between amplitude-shift keying and differential phase-shift keying modulation in the proposed scheme. We also demonstrated wide dynamic range characteristics at the extinction ratio for both 2- and 3-bit/symbol operation, compared to the conventional scheme. The proposed scheme allows a cross-modulation penalty, due to the intensity to phase modulation, of less than 1.5 dB in 2-bit/symbol and less than 5 dB in 3-bit/symbol operation.     

Performance evaluation of multiple access techniques in land mobilesatellite networks

The performances of four different multiple-access techniques for land-mobile satellite networks are compared. These multiple-access techniques are: slotted ALOHA, slow frequency-hopping and two reservation schemes. A hybrid automatic-repeat-request (ARQ) scheme based on Reed-Solomon codes is used to combat the error bursts resulting from multipath fading and shadowing. The advantages of using symbol interleaving and erasure decoding are demonstrated. The effect of such parameters as the rate of the forward error correction code, the guard time, and the error rate on the acknowledgment channel is evaluated     

Approaching intraband relaxation rates in the high-speed modulation of semiconductor lasers

This paper uses a nonequilibrium semiconductor laser model to investigate high-modulation bandwidth operation in semiconductor lasers. In particular, limitations to /spl gsim/100GHz modulation response, which approaches the carrier-phonon scattering rate, are analyzed. It is found that plasma heating leads to a dynamic carrier population bottleneck, which limits scaling of modulation bandwidth. An optical injection scheme is proposed to verify this phenomenon experimentally.     

Enhanced control scheme for three-phase three-level rectifiers at partial load

A prominent boost-type three-level topology (VIENNA Rectifier I), which proved to represent a cost-effective and highly efficient solution for switched-mode rectifiers is inspected toward its operation at discontinuous conduction mode (DCM). This mode of operation occurs not only at high input voltage in conjunction with low load currents but even at medium loading in the vicinity of mains voltage zero crossings. When this circuit is operated in DCM, additional measures are required for improved behavior to avoid conflicts with requirements on total harmonic distortion and regulations as well as safe operation in terms of voltage balancing and overvoltage protection. A detailed analysis of DCM and associated states is performed enabling determination and location of error voltages. Basic rules for the location of error voltages can be found. This leads to a novel optimized modulation and control scheme, facilitating designs without additional inductance. Selected simulation and measurement results prove the enhanced modulation scheme.     

Hybrid ARQ schemes for point-to-multipoint communication overnonstationary broadcast channels

Hybrid automatic-repeat-request (ARQ) error control schemes make use of both error detection and error correction in order to achieve high throughput and low undetected error probabilities on two way channels. Two hybrid ARQ schemes, termed hybrid go-back-N (HGB- N) and hybrid selective-repeat (HSR), are proposed for point-to-multipoint communications over broadcast channels. Both schemes incorporate a concatenated code for error correction and error detection. The performance study of the hybrid schemes is based on a two-state Markov model of a burst noise channel. An analytic solution is derived for the throughput efficiency of the HSR scheme, while approximations and computer simulation are used to evaluate the throughput efficiency of the HGB-N scheme. It is shown that the schemes perform considerably better than the corresponding pure ARQ schemes in which a block code is used for error detection only, especially in environments with a large number of receivers and large channel roundtrip delays, such as satellite broadcast links     

ARQ protocols with adaptive block size perform better over a widerange of bit error rates

The throughput of conventional automatic-repeat-request (ARQ) protocols, such as the stop-and-wait, go-back-N, and selective repeat, can be improved by dynamically adapting the protocol block length so that it approaches the optimum value for varying channel bit error rates. A very simple algorithm to implement such an adaptive scheme is presented. The algorithm assumes a known block error rate, estimates the bit error rate, and determines the best block length. Results of a simulation study show that in spite of its simplicity, the algorithm performs well     

Multiplexed ARQ for time-varying channels. II. Postponedretransmission modification and numerical results

For pt.I see ibid., vol.46, no.1, p.41-51, 1998. A “postponed retransmission” (PR) modification to both go-back-N (GBN) and ideal selective repeat (ISR) automatic-repeat-request (ARQ) is discussed and analyzed. A scheme for reducing the number of states involved in the calculation for multiplexed GBN ARQ is also presented. Numerical results are then shown for stop-and-wait (SW), GBN, and selective repeat (SR) ARQ (as well as the PR modified versions), under both round-robin and adaptive multiplexing     

Linearity enhancement of an electroabsorption modulated laser bydual-parallel modulation

A novel linearization process in an electroabsorption-modulated laser (EML) is proposed and experimentally demonstrated. A dual-parallel modulation scheme is used to compensate the nonlinear component of the EML by controlling the dc bias voltages of each EML separately. The validity of the proposed modulation scheme is confirmed through simulations and experiments. From a dual-parallel modulation experiment at 8 GHz, a reduction of 23 dB in IMD3 and a following increase of linear dynamic range of 19.6 dB are achieved compared to those of a single EML operation     

Throughput analysis for two ARQ schemes using combined transitionmatrix

The authors investigate throughput efficiencies for two basic automatic-repeat-request (ARQ) strategies, go-back-N and selective repeat disciplines, assuming that forward and backward channels have Markov error characteristics and they are mutually independent. For the two ARQ schemes, simple analytical formulas for the throughput efficiency are obtained. Particularly, in the case of the go-back-N scheme the authors show that the result of throughput analysis can be extended to a general form that includes results presented by C.H.C. Leung et al. (1988)