Adaptive Modulation and Coding for Hybrid Cooperative Networks

Wireless transmission can be affected by severe weather conditions such as heavy rain. Such a temporary weather condition leads to decrease the received power and thus reduce the signal-to-noise ratio, which degrades the overall performance. In some cases, in which a high bit rate is being transmitted where a specific amount of signal-to-noise ratio is required, the wireless transmission drops down completely. Adaptive Coding and Modulation technique could provide the feature of adaptation during transmission. In Adaptive Coding and Modulation, transmission parameters such as modulation scheme and/ or code rate can be altered based on signal-to-noise ratio measurements. In this paper, a survivable point-to-point wireless transmission was established using Adaptive Coding and Modulation technology. A concentration on the Adaptive Modulation was made in this work by using the AF-11FX equipment which is capable of modulate carriers using different modulation schemes (QPSK, 16QAM, 64QAM, 256QAM, and 1024QAM). In this context, the wireless point-to-point link was examined with and without the use of Adaptive Modulation. A survivable transmission was achieved in which an automatic switching mechanism is performed among the aforementioned modulation schemes based on signal-to-noise ratio measurements, which led to increase the average transmission rate.

In this paper, an adaptive coding and modulation (ACM) technique is introduced in an attempt to maximize the channel throughout. This technique suggests five different pairs of coding and modulation techniques, starting from low modulation orders and code rates going through higher values. Simulation over additive white Gaussian noise (AWGN) of the physical layer of the system is performed using M-phase shift keying (M-PSK) modulation and convolutional codes with soft Viterbi decoding algorithm. In addition, the channel throughput for each Modulation and coding pair is obtained using specific packet retransmission mechanism. An algorithm for adaptive coding and modulation is developed and the overall throughout of the adaptive system is determined with respect to the received Eb/No values.

One of the major factors which degrades the Free Space Optics (FSO) link performance is the atmospheric turbulence. Turbulence manifests in increased Bit Error Rate (BER) leading to degradation in the link performance. Adaptive Coding and Modulation (ACM) technique is used to mitigate this effect. This technique is an adaptive transmission scheme wherein transmission parameters such as modulation scheme, code rate, etc., are adjusted based on Channel State Information (CSI). In this paper, we have considered lognormal channel model in low turbulence conditions. Three adaptive transmission schemes viz., variable data rate, variable modulation schemes and variable coding rate are considered. The entire work has been carried out in MATLAB. We see improvement in FSO link performance in terms of average transmitted data rate when variable data rate adaptation scheme is used. Improvement in spectral efficiency is observed when the other two adaptation schemes are used. Design of adaptive transmitter for all the three schemes is presented and data rate of RF feedback channel is determined.

We study the problem of routing packets to the nearest server in a ubiquitous environment. An Anycast Routing Protocol using Swarm Intelligence, denoted as ARPSI, is proposed to route packets dynamically in a mobile, ad hoc, wireless network. Based on swarm intelligence, which consists of route discovery and route maintenance, ARPSI finds a short path to a neighboring server efficiently and quickly. Simulations show that ARPSI achieves a higher packet delivery ratio, shorter routing path, and lower control overhead.

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.

Recently, LTE-based femtocell system has received significant attention as a promising solution offering high-speed services, enhanced indoor coverage and increased system capacity. Intelligently allocate resources in multi-user OFDMA-based network is the substantial aim towards interference mitigation and enhancing power and spectral efficiencies. In this paper, we propose a downlink joint resource allocation with Adaptive Modulation and Coding (AMC) technique for such system, namely AMC-QRAP. The proposal core is adjusting the transmission link to the channel status and users demand through the power control and suitable selection of the modulation/coding scheme. Clustered network is adopted and users differentiation is considered providing Quality of Service (QoS) in the network. Our resolution model is solved as an optimization problem using the linear programming. We show through extensive simulations the outperformance of our method compare to different state-of-the-art methods using different evaluation metrics.

Abstract: OFDM (Orthogonal Frequency Division Multiplexing) as a special multi-carrier transmission technology has good resistance to narrow-band interference and frequency selective fading ability. Using adaptive modulation and coding in an OFDM systems in comparison with traditional fixed modulation techniques, it becomes possible to take full advantage of spectrum resources enhancing bandwidth efficiency and system capacity making it suitable for the high-speed and reliable mobile communication systems in the future. In AMC (Adaptive Modulation and Coding) technique, modulation method, coding rate, and/or other signal transmission parameters are dynamically adapted to the channel conditions to increase the system performance in terms of Bit Error Rate (BER) and throughput (bps) in various conditions such as channel mismatch, Doppler spreads, fading, etc. The purpose of this paper is to investigate the effect of adaptive modulation and coding in an OFDM system in terms of bit error rate and SNR over fading communication channels. In this paper, we have considered fixed and adaptive modulation technique in an OFDM system over AWGN and RICEAN channel with convolutional and BCH coding. An OFDM system model is simulated in MATLAB programming environment to obtain the simulation result. From the comparative simulation result analysis in terms of BER v/s SNR, it can be concluded that Adaptive modulation with Convolutional coding over RICEAN channel significantly reduces bit error rate giving better trade-off between SNR and BER than all other options considered here.

Systems with an adaptive physical layer make use of the channel conditions information in order to adapt their transmission to the channel with adaptive coding and modulation (ACM) techniques. This adaptability also has a huge impact in the capacity allocation since the amount of resources is not constant anymore, and therefore the solution region becomes variable. This situation requires the development of powerful and dynamic strategies for adaptive capacity allocation. Game theory approaches have been proposed for addressing the resource allocation problem for ACM systems, either with cooperative or noncooperative game models. One of these approaches is the use of a resource pricing approach for non-cooperative games. This approach has the advantage of introducing a control mechanism that increases fairness between users. This results in a non-cooperative algorithm that converges to the theoretical cooperative solution. In this paper we present a resource allocation mechanism for ACM systems that implements a price-based multi-player game. The system converges to equilibrium by varying the resource units’ price. Since this equilibrium is found over a few resource allocation cycles, this could be considered as a Stackelberg game. The convergence of this mechanism is quite important because when system conditions change, the resource allocation equilibrium is quickly reestablished. In this system, the pricing is not intended to reflect the real cost paid by the user but rather as a virtual resource market that is designed for resource allocation. Nonetheless, this framework may provide an insight into the cost of providing different services, especially when these have strict QoS requirements. Finally, the use of different pricing policies is presented as a mechanism for controlling the social welfare. This mechanism allows for resources to be distributed according to ACM modes of each terminal. These policies are implemented in a multi-agent simulator that provides a dynamic resource allocation scenario for testing different policies. Our results show interesting properties and a number of conclusions have been drawn.

AMC has been adopted at the physical layer of several standard e, g 3GPP, 3GPP2, HIPERLAN/2, IEEE802.11a, IEEE 802.15.3 and IEEE 802.16. MIMO technology in coordination with Adaptive Modulation and Coding (AMC) scheme further enhances spectral efficiency by adjusting transmission parameters to the channel condition while satisfying a target error performance. Consequently, the combined MIMO-AMC technology is a promising solution to offer high throughput for next generation wireless systems. The system still has limitations in terms of channel estimation error, periodic performance drop, channel correlation resulting in reduced throughput and packet loss rate A cross layer design using Improved Low Density Parity Check Code (ILDPCA) in AMC on the physical layer and Incremental redundancy Hybrid ARQ (IR-HARQ) in the data link layer is proposed. ILDPCA coder in AMC enhances the performance of the system in terms of bit error rate,packet loss rate and spectral efficiency.

The exploitation of adaptive coding and modulation (ACM) techniques for satellite communication (SATCOM) has been shown to provide large system capacity gains, the technique of how to adapt the modulation and coding scheme (MCS) play a key role to ACM performance. This paper presents an effective threshold switching algorithm exploiting a hysteresis threshold techniques for satellite ACM. Simulation results demonstrate that the algorithm can take an excellent balance between performance and system complication.

An integrated cross-layer framework of adaptive FEedback REsource allocation and Prediction for OFDMA systems

As underwater acoustic channels are highly variable, both temporally and spatially, it is impossible to design a single communication scheme that works well everywhere and at all times. Adaptive modulation and coding (AMC) techniques can help determine the best communication scheme to use for a particular channel, but require an accurate model to predict communication performance. We propose a bit error rate (BER) estimation model that fuses domain knowledge with experimental data, yielding BER estimates that are consistent with experimental observations. Predictions from such a model are used to drive an AMC algorithm to maximize communication throughput. For AMC, regular feedback from the receiver to the transmitter is necessary to gather channel state information (CSI). On the one hand, obtaining feedback too often drastically impacts the communication throughput in channels with long propagation delays, but on the other hand, insufficient feedback leads to poor AMC decisions and hence poor throughput. We propose a dynamic feedback strategy to automatically find the right balance and maximize communication performance.

In this study, a field-programmable gate array (FPGA) based high rate transmitter is developed for low earth orbit satellite communication links using adaptive coding and modulation (ACM) techniques. The developed transmitter structure is modeled in MATLAB. Then, the MATLAB model is taken as reference for developing an FPGA design. This design is implemented on Xilinx Kintex Ultrascale XCKU060 FPGA which provides high performance and whose space grade model will be on product line in December 2020. It is shown that the developed transmitter structure can reach a spectral efficiency of 7.068 bits per second per Hertz (bps/Hz) with a code rate of 0.8889 in the highest rate mode. The implemented FPGA design of the transmitter structure can support input data rates from 50.7225 megabits per second (Mbps) to 530.1 Mbps with a baud rate of 75 mega symbol per second (Msps) and a sampling rate of 300 mega sample per second (MSps) at the output.

Adaptive modulation and coding (AMC) technique is integrated with WiMAX to provide higher data rates with error free transmission. AMC schemes employ the channel state information (CSI) to utilize the channel efficiently and maximize the throughput with better spectral efficiency. In this paper, least square error (LSE) and minimum mean square error (MMSE) estimators are suggested and bit error rate (BER) performance has been analyzed. Channel equalization is also integrated with with AMC-OFDM system and presented with constant modulus algorithm (CMA) and least mean square (LMS) algorithms in terms of convergence rates analysis. Simulation results proved that increment in modulation scheme size causes to improvement in throughput along with BER value. There is a trade-off among modulation size, throughput, BER value and spectral efficiency. Results also reported the requirement of channel estimation and equalization in high data rate systems.

In order to reduce the complexity when adaptive coding and modulation (ACM) technique is applied in the low and medium-orbit remote sensing satellite with Ka band TT&C and communications systems, this paper presents a novel ACM technic optimization method based on system characteristics (e.g., the earth station location, trajectory of the satellite and communication frequency.). The algorithm exploits the existed modulation and coding schemes (MODCODs) and the probability density function (PDF) of signal to noise ratio (SNR). We can examine the utilizing probability of the existed MODCODs according to the PDF of SNR which is estimated from the characteristics of presented system model. Based on the MODCODs' utilizing probability, the most useful MODCODs combinations will be picked out. Although, the system transmission efficiency will be decreased to some extent when the number of MODCODs is reduced, it is worthy considering that the complexity is significantly depressed. Simulation results show that the number of MODCODs is decreased of 86.1% at the cost of 4.2% transmission efficiency when compared with DVB-S2X system.