Reduced Complexity Blind Recognition Method of LDPC Codes over a Candidate Set

A low-density parity-check (LDPC) coded adaptive modulation and coding (AMC) strategy is presented for orthogonal frequency division multiplexing (OFDM) systems. Since system performance is improved as the maximum iteration times for LDPC decoding increase, iteration times for decoding reflect channel quality. We first propose an AMC strategy to utilize the information of iteration times for decoding to adopt higher order modulation and coding schemes (MCS) than the conventional strategy, so as to improve system throughput. Since it may bring worse reliability, hybrid automatic repeat request (H-ARQ) is used in a second strategy. Simulation under typical urban channel is carried out, and the results show the proposed strategies can bring higher throughput, and the strategy with H- ARQ can improve throughput and guarantee reliable transmission simultaneously.

A New Adaptive Modulation and Coding Method for Communication-Based Train Control Systems using WLAN

Objectives: The objective of using cross layer approach in Adaptive Modulation and Coding (AMC) based wireless systems is to enhance the spectral efficiency and reliability of transmission n time varying MIMO channel. Methods: A cross layered design using k-NN based AMC with Improved Low-Density Parity Check Accumulate codes (ILDPCA) that opt for nonuniform division of check nodes at the physical layer and Incremental Redundancy Hybrid Retransmission Request (IRHARQ) at the link layer is implemented. The encoded symbols are routed consecutively over MIMO fading channels. The MIMO channel is predicted at the receiver and is forwarded to the AMC controller. IR-HARQ regulates packet retransmission with new codeword on failure. Findings: The performance of the cross layer design is assessed in terms of BER, packet loss and spectral efficiency. The proposed cross layer with ILDPCA coders improves the spectral efficiency by 45% compared to the conventional systems but still maintaining acceptable PLR. Application: Therefore the proposed adaptive system can be adopted for reliable adaptive transmission over MIMO network and is suitable for multimedia applications. Keywords: Cross Layer, Multiple Input Multiple Output, Reliability, Wireless System Design

Cross-layer techniques represent efficient means to enhance throughput and increase the transmission reliability of wireless communication systems. In this paper, a cross-layer design of aggressive adaptive modulation and coding (A-AMC), truncated automatic repeat request (T-ARQ), and user scheduling is proposed for multiuser multiple-input-multiple-output (MIMO) maximal ratio combining (MRC) systems, where the impacts of feedback delay (FD) and limited feedback (LF) on channel state information (CSI) are also considered. The A-AMC and T-ARQ mechanism selects the appropriate modulation and coding schemes (MCSs) to achieve higher spectral efficiency while satisfying the service requirement on the packet loss rate (PLR), profiting from the feasibility of using different MCSs to retransmit a packet, which is destined to a scheduled user selected to exploit multiuser diversity and enhance the system's performance in terms of both transmission efficiency and fairness. The system's performance is evaluated in terms of the average PLR, average spectral efficiency (ASE), outage probability, and average packet delay, which are derived in closed form, considering transmissions over Rayleigh-fading channels. Numerical results and comparisons are provided and show that A-AMC combined with T-ARQ yields higher spectral efficiency than the conventional scheme based on adaptive modulation and coding (AMC), while keeping the achieved PLR closer to the system's requirement and reducing delay. Furthermore, the effects of the number of ARQ retransmissions, numbers of transmit and receive antennas, normalized FD, and cardinality of the beamforming weight vector codebook are studied and discussed.

In this study, we propose a cooperative transmission framework based on Adaptive Modulation and Coding (AMC) cooperative food communication system in Multiple-Input Multiple-Output (MIMO) fading channels. We consider the scenario that consists of one source node, one relay node and one destination node, they all equipped with multiple antennas and employed the adaptive modulation and coding schemes. The relay node follows the decode-and-forward strategy, forwarding the information received from the source to the destination in case of correct decoding. Through computer simulation, we got the effective capacity of the adaptive cooperative transmission cooperative food communication system according to different Qos requirement.

Long Term Evolution (LTE) is the new upgrade path for carrier with both GSM/UMTS networks and CDMA2000 networks. The LTE is targeting to become the first global mobile phone standard regardless of the different LTE frequencies and bands use in other countries barrier. Adaptive Modulation and Coding (AMC) is used to increase the network capacity or downlink data rates. Various modulation types are discussed such as Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM). Spatial multiplexing techniques for 4×4 MIMO antenna configuration is studied. With channel station information feedback from the mobile receiver to the base station transmitter, adaptive modulation and coding can be applied to adapt to the mobile wireless channels condition to increase spectral efficiencies without increasing bit error rate in noisy channels. In High-Speed Downlink Packet Access (HSDPA) in Universal Mobile Telecommunications System (UMTS), AMC can be used to choose modulation types and forward error correction (FEC) coding rate.

Spectrum efficiency (SE) and QoS guarantee are two critical issues in wireless communication systems. The truncated ARQ and the adaptive modulation and coding (AMC) are often used to improve the SE and transmission reliability in wireless communications. In this paper, we study the SE and QoS performance of a system with a cross-layer combining of the truncated ARQ with the AMC. First, we analyze the performance of current combinations of the ARQ and the AMC. The analysis results indicate that the current combination is too “ineffectiveness” or “conservative.” Then, based on the analysis, we design a new rule for the AMC, which is used to adaptively choose transmission mode. Through analyzing the AMC and the combination algorithm using the proposed rule, both the SE and the packet dropped probability of the system are improved. Furthermore, the analysis result also point outs the suitable scenario of each algorithm. Simulation results verify the analysis result and demonstrate that the proposed algorithm can achieve higher SE while the QoS requirement is guaranteed. At last, to further improve the SE of the system, we propose an algorithm jointing power control and the combination of the ARQ with the AMC under the QoS constraint.

Based on adaptive theory, an adaptive modulation and coding (AMC) multiple input multiple output (MIMO) system with adaptive Turbo receiver is designed to increase the overall capacity and decrease the processing delay. The scheme sets several factors including channel coding rate, modulation mode and iteration times of Turbo receiver as adjustable elements. To guarantee the superiority of the proposed adaptive Turbo receiver in terms of decreasing processing delay and power consuming, an MMSE based no-ordered parallel soft interference cancellation (NOPSIC) MIMO detector which takes error propagation into account is explored for the non-first iteration. Simulation results reveal that the proposed scheme could significantly raise the system capacity, meanwhile bring down overall times of iteration processing by nearly one third.

This paper presents capacity limits of novel position aware adaptive cellular communication systems exploiting channel state information (CSI) at the transmitter (CSIT). The position aware adaptive communication systems are benchmarked against state-of-the-art adaptive modulation and coding (AMC) systems that use only feedback or predict CSIT in addition to the feedback CSI. We analyze the position aware adaptive communication systems both with perfect and imperfect position information. Numerical results demonstrate that position aware adaptive systems operate close to the channel capacity over a large range of feedback delays and channel variability with perfect position information. Further, position aware adaptive communication systems can outperform state-of-the-art AMC systems for Gaussian distributed position errors with standard deviations smaller than 2.5 m by more than 0.6 bits/s/Hz.

In this paper, an energy-efficient cross-layer design framework is proposed for cooperative relaying networks, which takes into account the influence of spectrum utilization probability. Specifically, random arrival traffic is considered and an adaptive modulation and coding (AMC) scheme is adopted in the cooperative transmission system to improve the system performance. The average packet dropping rate of the relay-buffer is studied at first. With the packet dropping rate and stationary distribution of the system state, the closed-form expression of the delay is derived. Then the energy efficiency for relay-assisted transmission is investigated, which takes into account the queueing process of the relay and the source. In this context, an energy efficiency optimization problem is formulated to determine the optimum strategy of power and time allocation for the relay-assisted cooperative system. Finally, the energy efficient switching strategy between the relay assisted transmission and the direct transmission is obtained, where packet transmissions have different delay requirements. In addition, energy efficient transmission policy with AMC is obtained. Numerical results demonstrate the effectiveness of the proposed design improving the energy efficiency.

This paper proposes a novel machine learning (ML) assisted low‐latency low density parity check (LDPC) coded adaptive modulation (AM) system, where short block‐length LDPC codes are used. Conventional adaptive modulation and coding (AMC) system includes fixed look‐up table method, which is also called inner loop link adaptation (ILLA) and outer loop link adaptation (OLLA). For ILLA, the adaptive capability is achieved by switching the modulation and coding modes based on a look‐up table using signal‐to‐noise ratio (SNR) thresholds at the target bit error rate (BER), while OLLA builds upon the ILLA method by dynamically adjusting the SNR thresholds to further optimize the system performance. Although both improve the system overall throughput by switching between different transmission modes, there is still a gap to optimal performance as the BER is comparatively far away from the target BER. Machine learning (ML) is a promising solution in solving various classification problems. In this work, the supervised learning based k‐nearest neighbours (KNN) algorithm is invoked for choosing the optimum transmission mode based on the training data and the instantaneous SNR. This work focuses on the low‐latency communications scenarios, where short block‐length LDPC codes are utilized. On the other hand, given the short block‐length constraint, we propose to artificially generate the training data to train our ML assisted AMC scheme. The simulation results show that the proposed ML‐LDPC‐AMC scheme can achieve a higher throughput than the ILLA system while maintaining the target BER. Compared with OLLA, the proposed scheme can maintain the target BER while the OLLA fails to maintain the target BER when the block length is short. In addition, when considering the channel estimation errors, the performance of the proposed ML‐LDPC‐AMC maintains the target BER, while the ILLA system's BER performance can be higher than the target BER.

Rain attenuation can cause a serious problem that an availability of space communication link on Ka band becomes low. To reduce the effect of rain attenuation on the error performance of space communications in Ka band, an adaptive coding and modulation (ACM) scheme is required. In this paper, to achieve a reliable telemetry data transmission, we propose an adaptive coding and modulation level using turbo code recommended by the consultative committee for space data systems (CCSDS) and various modulation methods (QPSK, 8PSK, 4+12 APSK, and 4+12+16 APSK) adopted in the digital video broadcasting-satellite2 (DVB-S2).

One of the most important features of the IMT-Advanced system is to utilize adaptive modulation and coding (AMC) in order to counteract time and/or frequency varying channel conditions. Due to increasing importance of integrated satellite and terrestrial networks, a satellite system specification needs to be designed by considering compatibility with terrestrial systems. In this paper, we propose an efficient utilization of AMC scheme for mobile satellite systems compatible with the LTE-Advanced. Due to a long round-trip delay (RTD) of a satellite system, the adaptation strategy of a satellite system should be quite different from that for the terrestrial system. In our scheme, a variable margin is allocated along with AMC in a comparatively slow fading condition such as open environment, while a long time interleaver is utilized along with AMC in a comparatively fast fading condition such as sub-urban area.

This paper is concerned with a wireless access system with adaptive modulation and coding (AMC) at the physical layer (PHY), Type-Ill hybrid automatic repeat request (HARQ) at the data link layer (LL) and transport control protocol (TCP) at the transport layer. In order to evaluate the quality-of-service (QoS) of TCP, we analyze the queueing behavior induced by both AMC and Type-Ill HARQ with an embedded Markov chain and study the interaction between AMC, Type-Ill HARQ and TCP via a fixed-point procedure. To maximize the TCP throughput for QoS-guaranteed traffic, we propose a cross-layer design which optimizes the target packet error rate (PER) for AMC at the PHY as well as the maximum number of retransmission for Type-III HARQ at the LL.

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.