Analysis of wireless transmission efficiency and its application: efficiency-based adaptive coding

Digital video broadcasting network facilitates distribution of real time video and video on demand services to global end users. This network has significant limitations stemming from scarced network resources to meet users popular demand of improved received quality. This research, presents a thorough investigation of variable content characteristic and application of variable network coding on digital video quality performance over wireless channel to enhance received video quality performance. In the proposed scheme, variable channel coding-rate is deployed to provide significant received quality performance gain by intelligently avoiding waste of limited network resources related to the fixed resource allocation necessary to guarantee acceptable quality performance. In order to assess the performance of the proposed scheme, experimental set up consisting of H.264 reference software for source coding, motion rate classifier and simulated wireless channel consisting of various channel coding and modulation schemes were adopted for this study. The test video samples were classified into high and low motion rate videos. In contrast, investigation of extension from fixed channel coding scheme to the application of variable channel coding-rate and modulation schemes in response to variable content motion-rate is analyzed over error free and poor channel conditions. The quality performance of received video quality over various wireless channel conditions is measured using standard objective algorithm, Peak-Signal-to-Noise-Ratio (PSNR). For the Soccer test video sample representing high motion rate videos, the 16QAM;1/2, the lower channel coding rate recorded the highest received video quality performance with PSNR value of 37.95dB compared to PSNR values of 33.29dB for 64QAM;1/2, and 24.40dB for the 64QAM;2/3 modulation and channel coding technique. Whereas, Akiyo test video sample representing low motion rate videos recorded significant quality performance of 51.19dB, 50.97dB and 39.93dB for 16QAM;1/2, 64QAM;1/2 and 64QAM;2/3 channel coding and modulation schemes, respectively.

This paper proposes a novel approach to energy efficient data transmission based on radio link estimation and adaptive channel coding. A channel protection algorithm is proposed to achieve efficient transmission (in terms of bit error rate), while reducing as much as possible power consumption and transmission bandwidth. The algorithm has been implemented and integrated within an experimental set-up based on a narrowband ad hoc network. It has been evaluated through field trials carried out in a hilly region with terrain characteristics that reproduce a variety of situations. The adopted simplified propagation model is based on the well-known knife-edge approximation while the radio link budget is computed by the mobile terminals thanks to 3D map information locally available. The level of channel protection is adaptively matched to the estimated radio link by tuning the transmission parameters and by configuring the Reed-Solomon protection code. Theoretical background and preliminary experimental results are presented in detail.

Mobile image transmission using combined source and channel coding with low complexity concealment

We propose a novel joint source and channel coding (JSCC) scheme for wireless image transmission that departs from the conventional use of explicit source and channel codes for compression and error correction, and directly maps the image pixel values to the complex-valued channel input signal. Our encoder-decoder pair form an autoencoder with a non-trainable layer in the middle, which represents the noisy communication channel. Our results show that the proposed deep JSCC scheme outperforms separation-based digital transmission at low signal-to-noise ratio (SNR) and low channel bandwidth regimes in the presence of additive white Gaussian noise (AWGN). More strikingly, deep JSCC does not suffer from the cliff effect as the channel SNR varies with respect to the SNR value assumed during training. In the case of a slow Rayleigh fading channel, deep JSCC can learn to communicate without explicit pilot signals or channel estimation, and significantly outperforms separation-based digital communication at all SNR and channel bandwidth values.

Long-distance wireless energy transmission is realized by photoelectric conversion through lasers and photovoltaic cells. However, existing devices have low transmission power and low transmission efficiency. Exploring the main factors that limit the transmission efficiency during transmission is necessary to improve the transmission power and efficiency, and theoretically analyze these factors that affect transmission efficiency, such as beam quality, divergence angle, wavelength and so on. This will provide research directions for subsequent work. A multiwavelength laser wireless energy transmission experimental platform was built by using powersphere, laser with three different wavelengths and other devices. This platform was used for transmission efficiency verification experiment. The total electro-optical-electric conversion efficiency values obtained by the 532, 1030, and 808 nm lasers are 0.01%, 0.08%, and 0.11%, respectively. The corresponding laser-to-electric conversion efficiency values are 1.37%, 1.60%, and 0.73%, respectively. Experimental results show that the electro-optic conversion efficiency of the laser and the photoelectric conversion efficiency of the photovoltaic receiver is the main reasons for the low conversion efficiency of the system. In addition, factors such as the expansion ratio of the beam expander, laser collimation, laser uniformity at the photovoltaic receiver end, and circuit structure, affect the conversion efficiency of the system.

Multiantenna transmission using load modulated arrays (LMAs) is gaining recent research interest. LMAs use a single central power amplifier and tune the antenna loads according to the information signal. In this paper, we propose a novel multiantenna transmitter architecture that can enable high-rate transmissions using LMAs. The proposed architecture uses channel modulation with RF mirrors in conjunction with antenna load modulation to transmit information bits. The proposed architecture has two key advantages: 1) it facilitates simple construction of high-rate signal sets suited for LMAs, and 2) it requires significantly fewer channel coefficients to be estimated at the receiver compared to conventional channel modulation architectures. The proposed architecture is shown to achieve improved bit error performance compared to conventional load modulation as well as spatial modulation, which are also single power amplifier transmission schemes. We also investigate the use of the proposed transmission scheme in a multiuser setting on the uplink. The proposed scheme not only offers the advantage of RF hardware simplicity at the user equipment but also requires fewer receive antennas at the base station to achieve a target bit error performance.

In this paper, we investigate a novel beam direction-based modulation transmit scheme for millimeter-wave (mmWave) communication systems equipped with distributed antennas, and propose an enhanced space-domain index modulation (ESDIM) scheme, in which the number of beamforming directions (BDs) for transmitting information bits can be one or two. The ESDIM system jointly utilizes the combination of the index of BDs and signal constellations to transmit information bits, in which one or two beam directions are considered. In addition, we propose power allocation (PA) aided schemes for ESDIM to further improve the system reliability by reducing the system symbol error rate (SER), where three constraints to the transmit power for beamforming are investigated. To be specific, a total transmit power constraint (TTPC) and two per-beamforming power constraints (PBPC) are considered. We first propose a suboptimal PA algorithm for the TTPC-PA aided ESDIM scheme using a powerful solver based on advanced algebra theories, which only considers the PA aspects for a given selected beamforming pair. Then, we extend the TTPC-PA aided scheme to the average per-beamforming power constraint (APBPC)-PA aided scheme and the strict per-beamforming power constraint (SPBPC)-PA aided scheme. Simulation results show that the proposed schemes improve the system SER performance compared to other existing counterparts.

Sparse vector coding (SVC) is a promising short-packet transmission method for ultra reliable low latency communication (URLLC) in next generation communication systems. In this paper, a dual-mapping SVC (DM-SVC) based short packet transmission scheme is proposed to further enhance the transmission performance of SVC. The core idea behind the proposed scheme lies in mapping the transmitted information bits onto sparse vectors via block and single-element sparse mappings. The block sparse mapping pattern is able to concentrate the transmit power in a small number of non-zero blocks thus improving the decoding accuracy, while the single-element sparse mapping pattern ensures that the code length does not increase dramatically with the number of transmitted information bits. At the receiver, a two-stage decoding algorithm is proposed to sequentially identify non-zero block indexes and single-element non-zero indexes. Extensive simulation results verify that proposed DM-SVC scheme outperforms the existing SVC schemes in terms of block error rate and spectral efficiency.

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.

Demands for video access and services are getting higher every day. To support this service remains reliable and robust, the improvement of data rate and bandwidth capacity as well as a large amount of energy is required. A cooperative communication system as an alternative solution is needed. The advantage of a cooperative communication system is utilizing the neighborhood user as the relay. The relay is aimed to improve the performance of network transmission as well as an energy saver. This study develops the numeric simulation model of energy efficiency for video transmission using four network models: without-relay, one relay, two relays, and three relays. The numerical simulations are to analyze the impact of relay utilization for energy consumption, and Signal Noise to Ratio (SNR) effect on throughput and energy efficiency. The simulation results confirm that the more relays used could reduce energy consumption and increase energy efficiency. The relays utilization also has an impact on the increment of SNR and enhancing the throughput of video transmission.

Optical communications, both fiber-optics and optical wireless (OWC), have a proven potential for high speed data transmission due to the vast optical spectrum. Given the ever increasing wireless data demand, we look towards OWC as a supplemental medium in heterogeneous networks (HetNets). In such networks, fair comparison of available connections is required for optimal allocation of resources. This comparison is essential for provisioning and analysis as well as in the decision metrics for handover and aggregation. As the optical communications field has developed, Signal to Noise Ratio (SNR) has been defined in various ways. Instantaneous optical power constraints have led the fiber- optics community to define SNR relative to peak- to-peak optical signal power. Additional average optical power constraints have led the OWC community to observe SNR relative to average optical signal power rather than average electrical signal power. Accordingly, the relationship between SNR and link performance has also changed. While the various definitions offer fair comparison under similar constraints, relative analysis is necessary when comparing the quality of multiple links in a HetNet or performance of networks operating under different constraints. In this paper, we reconcile three common SNR definitions and use symbol error rate (SER) analysis for pulse amplitude modulation in order to exemplify how different definitions affect the SER versus SNR curves.

This work studies the performance of a cooperative network which consists of two channel-coded sources, multiple relays, and one destination. To achieve high spectral efficiency, we assume that a single time slot is dedicated to relaying. Conventional network-coded-based cooperation (NCC) selects the best relay which uses network coding to serve the two sources simultaneously. The bit error rate (BER) performance of NCC with channel coding, however, is still unknown. In this paper, we firstly study the BER of NCC via a closed-form expression and analytically show that NCC only achieves diversity of order two regardless of the number of available relays and the channel code. Secondly, we propose a novel partial relaying-based cooperation (PARC) scheme to improve the system diversity in the finite signal-to-noise ratio (SNR) regime. In particular, closed-form expressions for the system BER and diversity order of PARC are derived as a function of the operating SNR value and the minimum distance of the channel code. We analytically show that the proposed PARC achieves full (instantaneous) diversity order in the finite SNR regime, given that an appropriate channel code is used. Finally, numerical results verify our analysis and demonstrate a large SNR gain of PARC over NCC in the SNR region of interest.

This paper proposes a highly accurate signal to noise ratio (SNR) estimation method for adaptive modulation and coding (AMC) by learning power spectral density (PSD) images with a convolutional neural network (CNN). Accurate SNR estimation is indispensable for adaptive control schemes such as AMC. Proposed method trains the CNN using PSD images and the corresponding SNR value as a teacher signal, and outputs the SNR in response to an input of unknown PSD image. Once trained, the SNR can be estimated with high speed and high accuracy, so AMC performance can be improved. Furthermore, since PSD is hardly affected by the Doppler shift, proposed method is resistant to high-speed environment. Compared with the previously proposed method which estimates SNR from a PSD data using a neural network, the proposed method can improve the estimation accuracy, bit error rate (BER) and throughput performance when AMC is applied.

The advance in wireless sensor networking technology is increasing the number of control systems that use these networks to transmit the relevant variable to be measured and controlled, despite of the more intense distortions caused by wireless channels. The performance of wireless communications systems is mainly limited by fading produced by multipath propagation. In order to minimize the fading effects, channel coding and diversity techniques are often used in wireless systems. Among the known coding techniques in the literature, the wavelet coding presents an interesting alternative to overcome the multipath fading, since it gets performance gain by transmitting in time diversity without compromising spectral efficiency. This paper investigates the use of wavelet coding in a system that operates over a wireless channel to control the rotation frequency of the direct current motor. Aspects such as packet error probability performance, hardware complexity and processing delays due to wavelet coding are analyzed, as well as its beneficial effects on the control system. In the proposed system, the wavelet coding was embedded in PIC microcontroller and a radio transceiver XBee is used to establish a wireless link. The obtained results demonstrate a reduction of fading effects on the control signal, as well as, a low cost for hardware implementation and a small impact on system processing time.

This paper presents a performance model of a wireless network with one-antenna transmitter scheduling information towards a set of terminals in a time-division fashion. Each terminal is enabled with a multiple-antenna maximum ratio combining (MRC) receiver. The objective of this model is to evaluate the performance of adaptive modulation and coding (AMC) in Rayleigh fading channels under two assumptions: 1) correlation between antennas, and 2) user scheduling based on maximum channel gain. The model is useful for cross-layer design purposes, as it provides a relatively low-complex representation of the physical-layer. Closed-form expressions are here derived of correct packet reception probabilities for different modulation and coding schemes (MCSs) with different values of block error rate (BLER) and spectral efficiency. Analytic expressions are derived with the help of the theory of order statistics, which allows for the study of the statistics of channel-aware scheduling. The results indicate that correlation does not always reduce performance. At low signal-to-noise ratio (SNR), correlation can improve performance rather than reducing it. By contrast, at high SNR, correlation is shown to always reduce the performance of the receiver. This low-SNR behavior is less evident as the number of antennas increases and more evident when the number of users included in the scheduling process increases.