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A new method for capacity and spectral efficiency increases is a full-duplex communication, where sending and receiving are done simultaneously. Hence, severe interference leaked from the transmitter to the receiver, which can disrupt the system's operation completely. For interference reduction, the transceiver tries to estimate the interfering symbols to remove their effects. A typical method is to use the Hammerstein model. In this method, nonlinear power amplifier (PA) and multipath channel are modeled with a successive nonlinear system and a finite impulse response filter. Then, the model parameters are adjusted, and interference symbols are estimated from the transmitted symbols. In the Hammerstein method, the interference symbols are estimated directly from the transmitted symbols. But practically, the transmitted symbols first pass through the pulse-shaping filter and become a signal. Then, this signal passes through the nonlinear PA and communication channel. Finally, the received signal is filtered by the matched filter (MF) at the receiver and converted to the symbols again. In this procedure, the amplifier and the communication channel affect the transmitted signal directly and distort transmitted symbols indirectly. Therefore, in the practical situation, when we consider the transmitter's pulse-shaping filter and the receiver's MF, the estimated symbols with the Hammerstein method are erroneous. To solve this problem, a new MF at the receiver is proposed and adjusted according to the interfering signal. We have shown that this method is far better than the Hammerstein method. [ABSTRACT FROM AUTHOR]

Underwater visible light communication emerges as a promising technique to enhance the capacity of underwater wireless communication networks for upcoming generation. Major technical problem with underwater visible light communication systems in motion is the pointing, acquisition, and tracking. To ease pointing, acquisition, and tracking, hence it is important to navigate optical information beam over broad range and adjust the transmitter beam divergence angle according to the link condition, which is adjusted by the Optisystem software. In this paper, performance comparison among wide range of transmittance optical beams in underwater visible light communications system for high-speed communication is presented for PIN as well as for Avalanche photodiode. The effect of using variable transmittance beam-divergence angle on the bit-error rate, signal-to-noise ratio, communication link distance is also investigated. OptiSystem and MATLAB software is used to implement the underwater visible light communication transceiver system. Finally, it is shown in the paper that in the presence of pointing errors, adaptive beam control techniques improve the performance of high-speed Underwater visible light communication system. [ABSTRACT FROM AUTHOR]

Free space optics (FSO) communication is a very recent mechanism. It is mainly needed when physical connection between the transmitter and the receiver is practically impossible and when high bandwidth data transmission is expected. This paper walks through the investigation of the performance of FSO communication adopting spectral amplitude coding optical code division multiple access (SAC-OCDMA) systems at different weather scenarios. The suggested system uses enhanced double weight codes as signature codes by 3 clients, simultaneously. To eliminate multiple access interference and phase induced intensity noise, two different detection schemes are used; single photodiode (SPD) and modified-AND subtraction detection schemes. Furthermore, a comparison between PIN and APD detectors is performed. The performance is evaluated through its propagation distance, received power, Q-factor and bit error rate (BER). The obtained numerical results reveal both Q-factor and BER are modified by 30%. Accordingly, the system performance is enhanced by 30%, when using SAC-OCDMA-FSO with SPD detection technique compared with modified-AND subtraction technique. [ABSTRACT FROM AUTHOR]

The implementation of beamforming schemes on the base station side has been widely employed in recent communication networks. Thanks to the small size of microstrip antenna elements in millimeter-wave (mmWave) frequencies, the implementation of uplink beamforming in small-size user equipments (UEs) is now available and recently becoming popular. The practical implementation of beamforming on the UE side is limited by a variety of challenges and bottlenecks, of which the most significant are the hardware and software complexity as well as power consumption, and hence the low-complexity beamsteering techniques such as analog beamsteering is generally preferred to other schemes on the UE side. In this paper, we consider a mmWave D2D underlaid cellular network, wherein D2D UEs are equipped with low-complexity beamsteering capable antennas. The problem is then formally defined as to find the channel scheduling together with assigning optimal directivity angle and transmit powers of D2D UEs corresponding to the maximum throughput of D2D network. We will employ novel distributed solution approach based on generalized benders decomposition scheme. More specifically, we manage to obtain the closed-form solutions of the primal and master subproblems through which the optimal solution variables can be obtained in a low-complexity distributed scheme. [ABSTRACT FROM AUTHOR]

A scheme for transportation of information with minimum Rayleigh backscattering (RB) noise to the multi-users by employing Qdash laser diode as a source is designed and evaluated. In this paper, employing digital phase shift keying, millimeter wave, 16-quadrature amplitude modulation orthogonal frequency division multiplexing (16-QAM OFDM), and 32-QAM OFDM techniques, the data rates of 4 × 10 Gbps are transmitted simultaneously over 50 km single mode fiber, plus 15 m wireless link, 50 m free space optical (FSO) link, 10 m wireless respectively. Four selective self-injection locked modes of Qdash laser are utilized as optical carriers for downstream and upstream transmission. To ensure the matter of mitigation of RB noise, which mainly arises due to the transmission of light-wave of same wavelengths in bidirectional transportation, the carrier signals of different wavelength are used for modulation and remodulation in optical line terminal and optical network unit. Besides being a strong support to increase the tolerance level against RB noise, this architecture is capable to transmit less noisy information wirelessly in radio frequency sensitive areas too. The constancy of the proposed architecture is evaluated by very low power penalty (~ 1.5–1.7 dB, ~ 2.4–2.6 dB, ~ 1.4–1.6 dB, ~ 1.7–1.8 dB for four channels respectively), clear constellation, prominent eye opening, low bit-error-rate (< 10–9 for pseudo random bit sequence data stream and < 3.8 × 10–3 for OFDM signal) and low error vector magnitude (< 12.4% for 16 QAM, < 10% for 32 QAM). Therefore, the proposed architecture could be promising alternative not only due to the scheme for mitigation of RB noise but also be a potent in the field of applications of the communication world to provide less noisy information to the multi-users (wired/wireless/FSO). [ABSTRACT FROM AUTHOR]

Millimeter-wave (mmWave) and massive multi-input–multi-output (mMIMO) communications are the most key enabling technologies for next generation wireless networks to have large available spectrum and throughput. mMIMO is a promising technique for increasing the spectral efficiency of wireless networks, by deploying large antenna arrays at the base station (BS) and perform coherent transceiver processing. Implementation of mMIMO systems at mmWave frequencies resolve the issue of high path-loss by providing higher antenna gains. The motivation for this research work is that mmWave and mMIMO operations will be much more popular in 5G NR, considering the wide deployment of mMIMO in major frequency bands as per 3rd generation partnership project. In this paper, a downlink multi-user mMIMO (MU-mMIMO) hybrid beamforming communication system is designed with multiple independent data streams per user and accurate channel state information. It emphasizes the hybrid precoding at transmitter and combining at receiver of a mmWave MU-mMIMO hybrid beamforming system. Results of this research work give the tradeoff between multiple data streams per user and required number of BS antennas. It strongly recommends for higher number of parallel data streams per user in a mmWave MU-mMIMO systems to achieve higher order throughputs. [ABSTRACT FROM AUTHOR]

Body channel communications (BCCs) were investigated, to enhance requirements for low power and high-reconfiguration power within permitting technology of wireless measurement systems for wireless communication applications. Standard options for BCC are targeted totally toward channel modeling with a potency measuring technique, a transmission technique, and a wireless transceiver style. Wireless digital transmission designed as a personalized methodology meant for the body channel offers significantly the necessary pathway to implement versatile and low-power BCC systems. In addition to the developing level of wearable communication protocol and applications, there is also an increasing reliability on a flexible BCC transmitter which helps to reconfigure power and meet power reduction conditions. This paper proposes an ultra-low-power, Hamming encoding-based, and body channel communication receiver for wireless body area network applications. Proposed BCC transmitter uses a channel of 1–100 MHz frequency to enhance the transmitter frequency and time domain properties. Hamming-based BCC transmitter makes use of a two-stage low-power analog processing circuit and digital information restoration circuit. Analog processing circuit consists of a dual op-amp adjustable preamplifier. Proposed BCC transceiver has higher data reliability because of the orthogonal characteristic of the Hamming codes. Moreover, the proposed Hamming code concatenated method strengthens the jitter tolerance and improves the code rate. Proposed BCC transceiver was verified using a field-programmable gate array board. Proposed data transceiver achieves a data speed rate of 20 Mbps. Bit error reduction values achieved were < 10−6 and < 10−5 at 60 Mbps and 100 Mbps, respectively. It uses a primary space of 0.14 mm × 0.2 mm when it is functioning below a 15 Mb/s data rate (low-power) condition. BCC transmitter utilizes the power of only 1.0 mW. [ABSTRACT FROM AUTHOR]

In this paper, we consider an energy harvesting device-to-device (D2D) communication system, where D2D transmitter can use mode A to directly communicate with D2D receiver or use mode B as a relay to assist cellular communication while communicating with D2D receiver by adopting non-orthogonal multiple access technology. Firstly, the outage probability expression in two modes is derived, and the communication mode is determined according to outage performance. Then, assuming that the full system information is available, the channel allocation and relay selection are completed by Kuhn–Munkres algorithm, and the offline power allocation of D2D users is realized by reinforcement learning. Next, the offline optimization results are taken as the training data set to train the neural network, and the optimal model of the transmission power is obtained. Considering the transmission power constraint, the online power allocation optimization algorithm is further proposed. Numerical results demonstrate the accuracy of derived outage probability, and the proposed resource allocation algorithm can improve the performance of hybrid system. [ABSTRACT FROM AUTHOR]

The possibility of using acousto-optic multiband filters for construction of code division multiple-access communication networks has been experimentally proved. Correlation interference has been studied for a set of bands with a spectrum close to sin(x)/x function which are used for encoding/decoding. For the case of several transmitters, a special technology was developed and realized that made it possible to perform studies on a transmission line based on two filters. The key component of this technology lies in emulating the sum signal from two to five transmitters on the first filter. The measured signal-to-interference ratio was more than 11 dB and decreased by less than 3 dB due to correlation interference from the network neighborhood and the emulation error of the sum signal. [ABSTRACT FROM AUTHOR]

Standard power control techniques are not deployable in Aloha networks due to lack of central controlling entity and/or inefficiency of such algorithms in large networks with bursty traffic. To handle this problem in practice, simple transmission power selection algorithms are used for ranging and/or combating harsh channel conditions. In such algorithms, the transmission power is steadily increased by an amount called power step, until the packet is successfully transmitted. Noting that ranging is the major concern of this approach, small power steps are ideal for its operation. However, as we will show in this paper, using small power steps with this algorithm causes a throughput collapse in large networks, when capture effect is considered in the analysis. In the asymptotic case, the throughput of this algorithm will be less than the throughput of the Binary Exponential Backoff (BEB) scheme which only uses a single power level. To show these results, we will present an asymptotic analysis of this algorithm with small power steps in an ideal communication channel where BEB is used as the retransmission scheme. In order to strengthen the results, we will prove the existence of better choices for power steps by extending the analysis for large power steps and we will show that properly chosen large power steps guarantee higher throughputs and require approximately the same average powers as small power steps. Our analysis and simulation results show that small power steps should be avoided with the mentioned power selection algorithm except probably for ranging and once the ranging process is complete, larger power steps should be used to exploit the capture effect. [ABSTRACT FROM AUTHOR]