Adaptive Coding And Modulation Scheme Research Articles

Rateless codes with adaptive parity allocation for satellite systems

SummaryIn this paper, we propose efficient parity allocation schemes when rateless codes are used in satellite communication systems in conjunction with an adaptive coding and modulation (ACM) scheme. ACM schemes are widely used in modern satellite communication systems to maintain the required error rate performance under channel impairment (such as rain fading observed in high‐frequency bands). The performance enhancement of ACM can be achieved by providing a good channel prediction and mode allocation method. In the case of a channel prediction or allocation error, rateless codes can be used as an effective means of retransmission to compensate for the performance degradation. After investigating the performance behaviour of rateless codes combined with ACM, we derive a mathematical formula to find the optimum parity length of the rateless code to be retransmitted to satisfy the target performance requirements. Simulation results described in this paper show that the proposed method can be used to enhance the error performance as well as spectral efficiency.

Adaptive Coding and Modulation for Robust Optical Access Networks

We introduce adaptive coding and modulation (ACM) to direct-detection passive optical networks (PONs) operating beyond 10 Gb/s per wavelength to allow each user to transmit at the highest possible bit rate and improve network reliability. Current fixed-rate PONs must allocate significant power margin to ensure reliable long-term operation over channels that vary over time and between users. Introducing adaptive-rate transceivers with ACM is a promising low-cost solution to increasing the overall capacity of optical access networks. The proposed ACM scheme uses two-, three-, or four-level pulse-amplitude modulation (2-, 3-, or 4-PAM) at a fixed symbol rate with direct detection and low-density parity check (LDPC) codes derived from a mother code by shortening and puncturing, decoded using fixed-initialization normalized min-sum decoding. The scheme supports received optical powers spanning a 10-dB range at bit rates of 20–54 Gb/s. In a PON with 64 users transmitting at a symbol rate of 30 Gbaud and a maximum transmission distance of 25 km, the ACM scheme demonstrates more than 3 dB improvement in overall optical power budget. For a fixed margin, ACM can increase throughput up to 60% compared to fixed-rate transmission, from 25 Gb/s to 39.7 Gb/s, or from 37.5 Gb/s to over 50 Gb/s, depending on the received optical power.

Adaptive hierarchical coding and modulation scheme over satellite channels

In this study, a new scheme called adaptive hierarchical coding and modulation has been proposed, based on Adaptive Coding and Modulation (ACM) and hierarchical modulation (HM). The primary contribution of this study is summarised as the following aspects. Firstly, 16- to 64-APSK constellations with size and labelling optimisation method are proposed for HM, which can be adapted to transmitting multiple hierarchies with different QoS streams and to the non-linear satellite channels due to a lower peak-to-average power ratio compared to traditional hierarchical QAM modulation. Bit channel capacity and Chernoff error bound are introduced to optimise size and labelling of the constellation with interior-point algorithm and modified binary switch algorithm for a specific channel model to get a better performance. Secondly, combining with optimised constellations, coding and modulation modes set is obtained from using constellation design and optimisation method, with different modulation orders and code rates. And over satellite channels with rain and location attenuation, the proposed scheme is able to adapt itself to a changing channel condition and increase the transmission rate compared with ACM schemes of DVB-S2 and DVB-S2X standard.

Regularized Zero-Forcing Precoding-Aided Adaptive Coding and Modulation for Large-Scale Antenna Array-Based Air-to-Air Communications

We propose a regularized zero-forcing transmit precoding (RZF-TPC)-aided and distance-based adaptive coding and modulation (ACM) scheme to support aeronautical communication applications, by exploiting the high spectral efficiency of the large-scale antenna arrays and link adaption. Our RZF-TPC-aided and distance-based ACM scheme switches its mode according to the distance between the communicating aircraft. We derive the closed-form asymptotic signal-to-interference-plus-noise ratio (SINR) expression of the RZF-TPC for the aeronautical channel, which is Rician, relying on a non-centered channel matrix that is dominated by the deterministic line-of-sight component. The effects of both realistic channel estimation errors and of the co-channel interference are considered in the derivation of this approximate closed-form SINR formula. Furthermore, we derive the analytical expression of the optimal regularization parameter that minimizes the mean square detection error. The achievable throughput expression based on our asymptotic approximate SINR formula is then utilized as the design metric for the proposed RZF-TPC-aided and distance-based ACM scheme. Monte-Carlo simulation results are presented for validating our theoretical analysis as well as for investigating the impact of the key system parameters. The simulation results closely match the theoretical results. In the specific example that two communicating aircrafts fly at a typical cruising speed of 920km/h, heading in opposite direction over the distance up to 740km taking a period of about 24 min, the RZF-TPC-aided and distance-based ACM is capable of transmitting a total of 77 GB of data with the aid of 64 transmit antennas and four receive antennas, which is significantly higher than that of our previous eigen-beamforming transmit precoding-aided and distance-based ACM benchmark.

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.

Two-Step Scheduling Scheme to Support Fairness and QoS in DVB-S2 System

The use of an efficient packet scheduling scheme for a forward link in satellite communication networks is very important to support fairness for each return channel satellite terminal (RCST) and the service differentiations for user traffics. To support fairness and QoS for each RCST with service-level agreement (SLA), the Adaptive Coding and Modulation (ACM) system in a satellite hub has to process packets with considering modulation and coding (MODCOD) and packet types. Although a DVB-S2 system with ACM scheme has higher transmission efficiency, it cannot offer fairness or quality of service (QoS) to RCSTs. Because the data are transmitted with high MODCOD in regions with clear skies, while data are transmitted using low MODCOD in regions experiencing rain events. In this paper, we propose a two-step scheduling scheme offering fairness and QoS to RCSTs, while minimizing a decrease in throughput. The proposed scheme is carried out performance evaluations using a computer simulation. As results of this simulation, the proposed scheduler was shown to support bandwidth fairness to an individual RCST, and provide a level of QoS differentiation for user traffics.

Subset Optimization of ACM Schemes Based on DVB-S2 Standard

A rain fading mitigation technique, called Adaptive Coding and Modulation (ACM), is supported by the DVB-S2 standard. But the number of Coding and Modulation Schemes is over dimensioned. It is shown that by a careful selection of the ACM schemes, with one fourth of the total number of schemes, it is possible to get performance close to the optimum, but with a much lower terminal complexity.

TCP Throughput Adaptation in WiMax Networks Using Replicator Dynamics

The high-frequency segment (10-66 GHz) of the IEEE 802.16 standard seems promising for the implementation of wireless backhaul networks carrying large volumes of Internet traffic. In contrast to wireline backbone networks, where channel errors seldom occur, the TCP protocol in IEEE 802.16 Worldwide Interoperability for Microwave Access networks is conditioned exclusively by wireless channel impairments rather than by congestion. This renders a cross-layer design approach between the transport and physical layers more appropriate during fading periods. In this paper, an adaptive coding and modulation (ACM) scheme for TCP throughput maximization is presented. In the current approach, Internet traffic is modulated and coded employing an adaptive scheme that is mathematically equivalent to the replicator dynamics model. The stability of the proposed ACM scheme is proven, and the dependence of the speed of convergence on various physical-layer parameters is investigated. It is also shown that convergence to the strategy that maximizes TCP throughput may be further accelerated by increasing the amount of information from the physical layer.