Adaptive Modulation And Coding System Research Articles

Adaptive Modulation and Coding: a Brief Review of the Literature

This work provides a general review of Adaptive Modulation and Coding (AMC) techniques that optimize the utilization of available resources and parameters in wireless communication systems. AMC or link adaptation empowers communication systems to employ appropriate modulation and coding schemes in order to enhance link spectrum utilization over time-varying channels. In addition, the proper selection of Modulation and Coding Schemes (MCS) diminishes the Bit Error Rate (BER) of systems and reduces the required transmit power through which the interference to other users is minimized. This paper conducts a state-of-the-art review of the existing AMC technologies. The reviews provided in this paper shed light on the trends of research in AMC and bring focus to related techniques. First, the existing constraints and the related phenomena in advanced wireless communication, including channel capacity, path loss, fading, and interference, are thoroughly investigated to understand further and improve the AMC systems. Moreover, several scenarios of utilizing the AMC methods are provided in order to demonstrate the extent of the effectiveness and importance of accurate AMC. Lastly, the challenges, the likely problems, the research gaps, and the potential avenues for future work are declared.

Blind Recognition of LDPC Codes Over Candidate Set

Adaptive modulation and coding (AMC) techniques have attracted more attention recently because of flexible strategies and dynamic channel quality. Blind recognition of encoder is an important technology for AMC systems because it can improve communication efficiency very well. In this letter, we present a new algorithm to tackle blind low-density parity-check (LDPC) encoder identification over a given candidate set. Our proposed scheme establishes a cosine conformity (CC) of syndrome, which is a posterior probability that can measure the probability that all parity check relations of the codes are satisfied, and classifies the LDPC encoder leading to maximum average CC over the candidate set. Simulations show that the new method is effective for LDPC encoder identification; the theoretical correct ratio of recognition is consistent with the simulation results, and its performance is improved by nearly 1.5 dB when compared with the existing algorithm.

Unique faster‐than‐Nyquist transceiver of the ACM system

The link adaptive transmission system chooses the optimum combinations of modulation order and code rate according to the characteristics of wireless channels to make use of the channel resources. To improve the spectral efficiency further, the authors apply the faster-than-Nyquist (FTN) signalling to the adaptive coding and modulation (ACM) system. The ACM system based on FTN signalling can take advantage of the channel resources by adjusting the packing ratios, modulation orders and code rates. However, the variable packing ratios correspond to variable sampling rate, which challenges the receiver of the ACM system. They propose a new transceiver of the FTN-based ACM system which can detect the FTN signal at a constant sampling rate. Moreover, they search for the optimum modulation and coding schemes of ACM based on FTN by analysing the extrinsic information transfer diagram. The simulation results show that the FTN-based ACM system has additional gains compared with the traditional way and the proposed transceiver may be a better choice in the ACM system.

A learning approach to link adaptation based on multi-entities Bayesian network

Adaptive modulation and coding (AMC) is widely used in modern communications which attempts to predict the best available rate and select the most suitable modulation and coding scheme (MCS) by estimating the real-time channel quality to obtain higher throughput of communication system. However, due to the characteristics of wireless channel fading, there are a lot of uncertainties in the communication process, which makes deviation between the channel estimate and the true value and can affect performance of AMC system. Bayesian network is an important tool to research uncertainty. This paper considers learning with the multi-entities bayesian network (MEBN) as a new framework for adaptive modulation and coding which avoids the flaw of flexibility in traditional Bayesian network (BN). Simulation results show that our algorithm has more validity in the selection MCS and lower bit error rate (BER) by considering estimate deviation in MEBN-AMC system. We also provide the further simulation results by using Bayesian structure learning and parameter learning.

Proposal of an Algorithm for an Efficient Forward Link Adaptive Coding and Modulation System for Satellite Communication

This paper proposes the algorithm for forward link adaptive coding and modulation (ACM) and the detailed design for a satellite communication system to improve network reliability and system throughput. In the ACM scheme, the coding and modulation schemes are changed by as much as the channel can provide depending on the quality of the communication link. To implement the forward link ACM system in the Ka-band, channel prediction and modulation/coding decision methods are proposed and simulated. The parameters of the adaptive filter predictor based on the least mean square are optimized, the minimum mean square error of the channel predictor is 0.0608 when step size and the number of filter tap are 0.0001 and 4, respectively. A test-bed is set up to verify the forward link ACM system, and a test is performed using a Ka-band satellite (i.e., Communication, Ocean, and Meteorological Satellite [COMS]). This test verifies that the ACM scheme can increase the system throughput.

Adaptive Modulation and Coding for Underwater Acoustic OFDM

Underwater acoustic channels are fast varying spatially and temporally according to environmental conditions. Adaptive modulation and coding (AMC) is appealing for underwater acoustic communications to improve the system efficiency by matching transmission parameters to channel variations. In this paper, we construct an AMC system with a finite number of transmission modes in the context of underwater orthogonal frequency-division multiplexing (OFDM). We propose the effective signal-to-noise ratio (SNR) computed after channel estimation and channel decoding as a new performance metric for mode switching, which is shown to predict the system performance more consistently than the input SNR and the pilot SNR. Real-time AMC tests have been conducted in a recent sea experiment to maximize the transmission rate with a given transmission power.

Low complexity minimum mean square error channel estimation for adaptive coding and modulation systems

Performance of the Adaptive Coding and Modulation (ACM) strongly depends on the retrieved Channel State Information (CSI), which can be obtained using the channel estimation techniques relying on pilot symbol transmission. Earlier analysis of methods of pilot-aided channel estimation for ACM systems were relatively little. In this paper, we investigate the performance of CSI prediction using the Minimum Mean Square Error (MMSE) channel estimator for an ACM system. To solve the two problems of MMSE: high computational operations and oversimplified assumption, we then propose the Low-Complexity schemes (LC-MMSE and Recursion LC-MMSE (R-LC-MMSE)). Computational complexity and Mean Square Error (MSE) are presented to evaluate the efficiency of the proposed algorithm. Both analysis and numerical results show that LC-MMSE performs close to the well-known MMSE estimator with much lower complexity and R-LC-MMSE improves the application of MMSE estimation to specific circumstances.

Analysis of Optimal Spectral Efficiency with Adaptive Modulation Coding and Cooperative ARQ Protocols

In this paper aiming at maximizing the spectral efficiency, a cross-layer design which combines adaptive modulation and coding (AMC) at the physical layer and truncated automatic repeat request (ARQ) protocol at the data link layer in cooperation system is proposed. In order to analyze the system performance, we first derive a closed form expression of probability density function (PDF) of the received signal-to-noise (SNR) using maximum ratio combing (MRC) at the destination node, the theoretical results and simulation show that the new design outperforms the traditional AMC system especially at low SNR.

Performances of adaptive modulation and coding in satellite mobile channel

Given that satellite mobile channel is a time-varying channel, Adaptive Modulation and Coding (AMC) was proposed to provide robust and spectrally efficient transmission over satellite mobile channel. Three different kinds of channel environment were considered in this paper: the urban area, the rural area, and the open space. Four combinations of modulation and coding were designed to meet reliable communication on time-varying channel, and spectral efficiency and system throughput of these three kinds of channel environment were simulated. Based on the simulation results, this paper analysed the results and compared the performances of AMC with non-AMC system in these three kinds of channel environment. At last, we come to the conclusions: a system with AMC can achieve higher spectral efficiency and better system throughput; and the spectral efficiency and system throughput of AMC system will be higher on better satellite mobile channel.

Position-aided mobile communications

Capacity limits of position aware adaptive mobile communication systems exploiting channel state information (CSI) at the transmitter (CSIT) are presented. The position aware adaptive communication systems are benchmarked against state-of-the-art adaptive modulation and coding (AMC) systems that use only feedback CSI or additionally predict CSIT. Numerical results show that position aware adaptive systems achieve large capacity gains compared to state-of-the-art AMC systems for medium to large feedback delays.

AMC와 MIMO 기법이 결합된 Adaptive-MCM 시스템의 성능 분석

본 논문에서는 AMC(Adaptive Modulation and Coding) 기법에 MIMO(Multiple Input Multiple Output) 기법이 결합된 Adaptive-MCM(Modulation, Coding and MIMO) 시스템을 제안하고, 모의실험을 통해 그 성능을 분석한다. AMC 기법은 채널 환경에 따라서 변조방식, 코드율을 적응적으로 변화시켜 전송률과 신뢰도의 향상을 가져온다. 제안된 Adaptive-MCM 시스템은 채널 환경에 따라서 MIMO 기법을 적응적으로 활용함으로써 기존의 변조방식과 코드율의 조합에 국한된 AMC 기법보다 더욱 향상된 전송률과 에러 성능을 가져 오게 한다. 제안된 시스템의 성능 분석은 Adaptive-MCM 시스템을 적용한 시스템과 적용하지 않은 시스템의 각 전송률 결과를 바탕으로 비교 수행되었다. 실험결과, Adaptive-MCM 시스템을 적용함으로써 각 MCMS(Modulation, Coding, and MIMO Scheme) 레벨에 해당하는 조합을 고정적으로 사용하는 시스템에서 나타났던 SNR(Signal to Noise Ratio) 확보와 데이터율 증가 사이의 Trade-Off 관계 개선이 이루어졌으며, 이를 통해 평균 데이터율의 향상을 가져올 수 있었다. The proposal set out in this paper, is the Adaptive-MCM(Modulation, Coding and MIMO) system, which results from the combination of adaptive modulation and coding (AMC) and multiple input multiple output (MIMO) schemes. The performance of this system is analyzed through computer simulation. By using the MIMO scheme adaptively as well, the proposed Adaptive-MCM system, presents a better improvement of data rate and error performance compared to the AMC system. The throughput performance of the Adaptive-MCM system is analyzed and compared with the throughput performance of Non-Adaptive-MCM Systems. As a result of the simulation, we can infer that, at a fixed MCM level, there is an improvement of the trade-off between secure Signal to Noise Ratio (SNR) and a high data rate. Consequently, this trade-off improvement results in a better average data rate.

A simple SNR representation method for AMC schemes of MIMO systems with ML detector

Adaptive modulation and coding (AMC) is a powerful technique to enhance the link performance by adjusting the transmission power, channel coding rates and modulation levels according to channel state information. In order to efficiently utilize the AMC scheme, an accurate signal-to-noise ratio (SNR) value is normally required for determining the AMC level. In this paper, we propose a simple method to represent the SNR values for maximum likelihood (ML) detector in multi-input multi-output (MIMO) systems. By analyzing the relation between the upper bound and the lower bound of the ML detector performance, we introduce an efficient way to determine the SNR for the ML receiver. Based on the proposed SNR representation, an AMC scheme for single antenna systems can be extended to MIMO systems with ML detector. From computer simulations, we confirm that the proposed SNR representation allows us to achieve almost the same system throughput as the optimum AMC systems in frequency selective channels with reduced complexity.

Adaptive Modulation and Coding Scheme with Independent MCS Level Selection in MIMO Systems

In this paper, we propose a system that adopts the independent MCS (modulation and coding scheme) level for each layer in the AMC (adaptive modulation and coding) scheme combined with the V-BLAST (vertical Bell lab layered space time) system. From the simulation results, we observe that since the independent MCS level case adapts modulation and coding rate for maximum throughput to each channel condition in separate layers, the combined AMC-V-BLAST system with the independent MCS level selection results in improved throughput compared to the combined AMC-V-BLAST system with the common MCS level selection and the conventional AMC system based on the 1x EV-DO standard. Especially, the combined AMC-V-BLAST system with the independent MCS level achieves a gain of 700 kbps in 7–9 dB SNR (signal-to-noise ratio) range.

Performance Analysis of an AMC System with an Iterative V-BLAST Decoding Algorithm

In this paper, the iterative Vertical-Bell-lab Layered Space-Time (V-BLAST) decoding algorithm of an Adaptive Modulation and Coding (AMC) system is proposed, and the corresponding MIMO scheme is analyzed. The proposed decoding algorithm adopts iteratively extrinsic information from a Maximum A Posteriori (MAP) decoder as an a priori probability in the two decoding procedures of the V-BLAST scheme of ordering and slicing in an AMC system. Furthermore, the performance of the proposed decoding algorithm is compared with that of a conventional V-BLAST decoding algorithm and a Maximum Likelihood (ML) decoding algorithm in the combined system of an AMC scheme and a V-BLAST scheme. In this analysis, each MIMO schemes are assumed to be parts of the system for performance improvement.

DVB‐S2 ACM modes for IP and MPEG unicast applications

AbstractThe DVB‐S2 standard (ETSI: EN 302 307. Digital Video Broadcasting (DVB): second generation framing structure, channel coding and modulation systems for Broadcasting, Interactive Services, News Gathering and other broadband satellite applications (DVB‐S2)) has been conceived for several satellite broadband applications: Television Broadcast Services, Interactive Services including Internet Access by consumers, Professional Applications such as Digital Satellite News Gathering (DSNG) and TV distribution, data trunking. This paper focuses on the profiles supporting interactive type of services, for which Adaptive Coding and Modulation (ACM) has been included in the new generation of the standard. Following the DVB‐S2 specifications, a number of modem configurations and tools are made available for implementing ACM in interactive systems. However, the different approaches have important impacts on the design of the system architecture and of the scheduling/resource management algorithms. The aim of the present contribution is providing a first discussion on the critical issues at system and MAC level, which need to be addressed when implementing a DVB‐S2 ACM system. A general introduction to ACM is also provided, as well as an illustration of the key elements included in the DVB‐S2 standard for supporting physical layer adaptivity. Copyright © 2004 John Wiley & Sons, Ltd.

Capacity analysis and system optimization for the forward link of multi‐beam satellite broadband systems exploiting adaptive coding and modulation

AbstractThis paper proposes a methodology for designing and optimizing the performance of adaptive coding and modulation (ACM) schemes for the forward link of unicast satellite broadband networks. The proposed technique of general applicability is based on the overall system capacity maximization conditioned on meeting a certain service area coverage for a given outage probability. The paper first derives in detail the method for computing the Shannon‐based capacity of a multi‐beam satellite system adopting ACM. Then the link efficiency is optimized under different physical layer constraints allowing a more realistic system performance assessment. Finally, to exemplify the methodology application and to quantify the ACM system performance improvement capabilities a study case corresponding to a Ka‐band state‐of‐the‐art bent pipe satellite network is provided. The example illustrates the very substantial capacity gain offered by state‐of‐the‐art adaptive modulation and coding schemes utilization compared to current broadband satellite system design approach. Copyright © 2004 John Wiley & Sons, Ltd.

Comparative Performance of Cellular Communication Systems with Adaptive Modulation and Coding and Systems with Power Control

We carry out a comparative analysis of performances of a cellular communication system with adaptive modulation and coding (AMC) and a system with power control (PC). It is shown that the performance of an AMC system is higher than the performance of a PC system for an arbitrary probability density function of the signal fading. To achieve identical throughputs of the two systems, the mean transmitted power for PC must be greater than that for AMC. For identical mean transmitted powers, the throughput of an AMC system is always greater than that of a PC system. We consider code division multiple-access (CDMA) systems with arbitrary numbers of fading time-taps (paths), having a statistically independent Rayleigh fading of signals from path to path. The influence of self-interference on AMC and PC performance is studied. This self-interference results from the nonideal path separation in the receiver.