Rateless codes with adaptive parity allocation for satellite systems

The challenge of the adaptive modulation and coding (AMC) scheme is to make a decision when to switch between different modulation and coding scheme. This is difficult because the performance of the AMC system is very sensitive to channel quality estimation errors and other channel impairments. In this paper, block error rate (BLER) performance of the wideband code division multiple access (WCDMA) system using AMC techniques are studied with nonideal channel and signal-to-interference-and-noise ratio (SINR) estimation and with the presence of multiuser interference. Also, the throughput of the adaptive system is simulated.

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).

Due to the time variant characteristic of wireless communication channels, channel-state-information (CSI) becomes out-of-date if we consider the CSI feedback delay. Thus, channel prediction is required to mitigate this phenomenon. In this paper, we propose an adaptive modulation and coding (AMC) scheme using channel prediction on multipath Rayleigh fading channels and evaluate the performance of the proposed scheme. For a given modulation and coding set (MCS), the average packet error rates are derived as functions of the predicted channel information and the prediction error variance. Based on CSI's, the required transmit power is obtained for each MCS option, simulation results show that the performance degradation due to feedback delay can be compensated by the proposed scheme

Due to directional propagation of light signals, visible light communication (VLC) channel quality is sensitive to the distance and the angle between a VLC access point (AP) and a VLC terminal. When a terminal is mobile, VLC channel gain varies with the position of the terminal. Considering rotations of a terminal during mobility, channel variations are even more severe. As a result, data rates need to be adapted according to variable link qualities. The commonly used feedback-based adaptive modulation and coding (AMC) scheme cannot catch up with channel variations in VLC, resulting in staircase-shaped adaptation results. Smoother adaptation can be achieved by the seamless rate adaptation (SRA) scheme via rate compatible modulation (RCM). However, SRA does not provide an effective way to increase symbol distances, so the improvement on spectral efficiency is small. To address the shortcomings in the existing schemes, rateless adaptation (RLA) is developed for VLC systems in this paper based on spinal codes. With RLA, smooth rate adaptation is accomplished without channel state information (CSI) feedback, and spectral efficiency is also greatly improved. Simulation results show that, in mobile scenarios, RLA achieves at least 46% improvement over AMC and 19% improvement over SRA in terms of spectral efficiency.

This paper extends the work on cross-layer design which combines adaptive modulation and coding at the physical layer and hybrid automatic repeat request protocol at the data link layer. By contrast with previous works on this topic, the present development and the performance analysis as well, is based on rate compatible punctured turbo codes. Rate compatibility provides incremental redundancy in transmission of parity bits for error correction at the data link layer. Turbo coding and iterative decoding gives lower packet error rate values in low signal-to-noise ratio regions of the adaptive modulation and coding (AMC) schemes. Thus, the applied cross-layer design results in AMC schemes can achieve better spectral efficiency than convolutional one while it retains the QoS requirements at the application layer. Numerical results in terms of spectral efficiency for both turbo and convolutional rate compatible punctured codes are presented. For a more comprehensive presentation, the performance of rate compatible LDPC is contrasted with turbo case as well as the performance complexity is discussed for each of the above codes.

In this paper, we propose a throughput optimization scheme for relay protocols based on Adaptive Modulation and Coding (AMC). The performance of relay protocols with the AMC scheme and show that relay protocols with the AMC scheme are capable of providing better average throughput at a lower Signal to Noise Ratio (SNR) level as compared to the conventional scheme with no AMC. We perform 3GPP Long Term Evolution-Advanced (LTE-A) parameters based simulations to prove the performance comparison of adaptive Modulation and Coding Scheme (MCS) relay protocols with non-adaptive MCS relay protocols. The simulation results of the proposed system with adaptive MCS prove that among the Amplify-and-Forward (AF), Decode-and-Forward (DF) and De-Modulate-and-Forward (DMF), the DMF protocol performs best, at a lower SNR value and higher average throughput.

With the development of the underwater acoustic (UWA) adaptive communication system, energy-efficient transmission has become a critical topic in underwater acoustic (UWA) communications. Due to the unique characteristics of the underwater environment, the transmitter node will almost always have outdated channel state information (CSI), which results in low energy efficiency. In this paper, we take full advantage of bidirectional links and propose an adaptive modulation and coding (AMC) scheme that aims to maximize the long-term energy efficiency of a single link by jointly scheduling the coding rate, modulation order, and transmission power. Considering the complexity characteristics of UWA channels, we proposed a bit error ratio (BER) estimation method based on deep neural networks (DNN). The proposed network could realize channel estimation, feature extraction, and BER estimation by using a fixed pilot of the feedback link. Then, we design a channel classification method based on the estimated BERs of the modulation and coding scheme (MCS) and further model the UWA channels as a finite-state Markov chain (FSMC) with an unknown transition probability. Thus, we formulate the AMC problem as a Markov Decision Process (MDP) and solve it through a reinforcement learning framework. Considering the large state-action pairs, a double deep Q-network (DDQN) based scheme is proposed. Simulation results demonstrate that the proposed AMC scheme outperforms the fixed MCS with a perfect channel information state, and achieves near-optimal energy efficiency.

Erlang capacity is traditionally defined as the maximum value of offered traffic among different service classes that the system can support when the blocking probabilities at the call admission control (CAC) level do not exceed certain thresholds. That is valid when a fixed amount of bandwidth is allocated to each user in each frame during the whole service time. However, with the introduction of adaptive modulation and coding (AMC) scheme employed at the physical layer, outage might occur due to the fact that the allocation of bandwidth is dynamic based on the time-varying wireless channel conditions. In this paper, we evaluate the Erlang capacity of a TDMA system with AMC supporting voice and data traffics, by taking both the blocking and the outage probabilities into account. The analytical models for calculating the blocking and the outage probabilities are developed separately, and a joint algorithm for determining the Erlang capacity of the system is proposed with some numerical examples.

This paper presents a cross-layer design of adaptive modulation and coding (AMC) with truncated hybrid automatic repeat request (HARQ) for one-to-many multicast transmission, in order to increase the spectral efficiency under the quality-of-service (QoS) constraints. For adaptive transmission over the channel common to the multicast group users, the AMC mode is chosen with the minimum SNR among the users to guarantee the target performance of all users. In the meanwhile, the minimum SNR required to support an AMC mode is aggressively designed by allowing retransmission with HARQ schemes. For the proposed design, we derive the average packet error rate, average number of transmission, and spectral efficiency and provide the performance numerically obtained. Numerical results show that the cross-layer design for multicast provides a significant performance gain at a small number of retransmissions as in unicast. In particular, it is observed that AMC design with HARQ is more beneficial in the low SNR region where multicast performs worse than unicast.

This paper proposes a cross-layer design which combines adaptive modulation and coding (AMC), cooperative diversity at physical layer (PHY) and hybrid automatic repeat request (HARQ) at data link layer (LL) for wireless ad-hoc networks. First, we provide theoretical analyses of conventional direct transmission scheme and cooperative transmission scheme with AMC and HARQ that include analytical expressions for the packet error rate (PER) and spectral efficiency. Then we propose a novel hybrid transmission scheme which invokes cooperation based on the feedback AMC information. Numerical results demonstrate that the performance of the hybrid transmission scheme is equivalent to the cooperative transmission scheme while its cooperation cost is kept much lower compared with that of the cooperative transmission scheme.

This paper proposes a spectral efficient multiuser scheme for single-carrier transmission. In the proposed scheme, a combination (hybrid) of localized and distributed subcarrier mapping types is employed, where the signals of users with different subcarrier mapping types are superimposed on a common set of subcarriers. We first present mathematical formulations of multiuser detection and derive the equalization coefficients for the hybrid type. In fading environments, the proposed scheme allows users to employ any subcarrier mapping types (localized, distributed, hybrid types), which can support low and high speed users. To estimate the performance of the proposed scheme, we develop a density evolution technique and show that the predicted performances are consistent with simulated performances. Further, based on the performance estimation of the proposed scheme, we discuss channel-dependent resource allocation algorithms: opportunistic scheduling and adaptive modulation and coding (AMC) schemes. These resource allocation algorithms increase the spectral efficiency of the proposed scheme with guaranteed quality-of-service (QoS). Simulation results show that the proposed multiuser scheme achieves both multiuser and frequency diversity gains in fading environments.

In this paper, we propose a cross-layer design which combines adaptive modulation and coding (AMC) at the physical layer with a hybrid automatic repeat request (HARQ) protocol at the data link layer to minimize the packet error rate (PER) and maximize the spectral efficiency. By using Markov model to predict the channel condition of next frame according to the second order statistics characteristics of the former frame, we calculate the conditional probability density function and joint probability density function of signal to noise ratio (SNR). Further, we derive the packet error rate and average spectral efficiency in closed-form for transmission over Nakagami-m fading channels. Numerical results show that the proposed scheme can obtain lower PER and higher spectral efficiency c ompared with traditional HARQ protocol s. The cross-layer design scheme combing type-III HARQ with AMC can achieve the highest spectral efficiency and the lowest PER than type-I HARQ and type-II HARQ.

In this paper, a joint cross-layer design of adaptive modulation and coding (AMC) and cooperative automatic repeat request (C-ARQ) scheme is proposed for a secondary user in a shared-spectrum environment. First, based on the statistical descriptions of the channel, closed-form expressions of the average spectral efficiency (SE) and the average packet loss rate (PLR) are presented. Then, the cross-layer scheme is designed, with the aim of maximizing the average SE while maintaining the average PLR under a prescribed level. An optimization problem is formed, and a sub-optimal solution is found: the target packet error rates (PER) for the secondary system channels are obtained and the corresponding sub-optimal AMC rate adaptation policy is derived based on the target PERs. Finally, the average SE and the average PLR performance of the proposed scheme are presented.

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.

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.