Multi-path Penalty metric in underwater acoustic communication for autonomy and human decision-making

A novel performance metric to improve underwater digital acoustic communication, called Multipath Penalty (MPP), is proposed as an alternative to traditional signal-to-noise ratio (SNR) methods in the context of the Arctic Beaufort Sea. MPP and SNR are compared alongside a third performance metric, Minimum Achievable Error (MAE), which replicates the operation of a channel estimate-based decision feedback equalizer in an acoustic modem. The three metrics are then tested in a hardware-in-the-loop Virtual Ocean simulator for an autonomous undersea vehicle (AUV) communicating with a collaborator. Using field data of modem statistics obtained duringICEX20 and expanded data supplied by the simulator, calibration of the three metrics to modem packet success is evaluated, resulting in a proposed recalibration for MAE. The AUV’s ability to communicate when adaptively choosing its depth is analyzed above and below the Beaufort Lens, and settings for MPP’s engineering variables are obtained. The results show MPP generally improves reception and demodulation of acoustic transmissions over SNR by approximately 5% within an operational range of 8 km, while achieving similar results to the more robust metric MAE. MPP is an improved utility for underwater digital acoustic communication in both marine autonomy and as a tactical decision aid.

Performance Evaluation of FBMC for Future Communication

The current mobile telecommunication system is grew in a massive way, and in upcoming days requires a good supervision and enactment evaluation in addition to analysis. Filter-Bank-Multi-Carrier (FBMC) stands a method of multicarrier cadence method that is been extremely used for high date rate cellular network system as well as wireless systems. This entails a supple distribution of the obtainable time-frequency possessions, which is problematic over conservative Orthogonal Frequency Division Multiplexing (OFDM). Consequently, alterations of OFDM, such as windowing otherwise filtering, develop essential. The intention of current investigation exertion grounded on mobile expertise remains to upsurge the bandwidth in lieu of altogether users, huge bandwidth, further effectual also easily wieldy also continual unchanging connectivity. The projected paper benevolences, a coalescing outline, and discussion also performance estimation of FBMC also associate it toward OFDM grounded patterns. We develop that several antennas also channel estimate, two of the chief defies allied by FBMC, be able to be proficiently dealt through.

Analysis and Optimization for Downlink Cell-Free Massive MIMO System with Mixed DACs

This paper concentrates on the rate analysis and optimization for a downlink cell-free massive multi-input multi-output (MIMO) system with mixed digital-to-analog converters (DACs), where some of the access points (APs) use perfect-resolution DACs, while the others exploit low-resolution DACs to reduce hardware cost and power consumption. By using the additive quantization noise model (AQNM) and conjugate beamforming receiver, a tight closed-form rate expression is derived based on the standard minimum mean square error (MMSE) channel estimate technique. With the derived result, the effects of the number of APs, the downlink transmitted power, the number of DAC bits, and the proportion of the perfect DACs in the mixed-DAC architecture are conducted. We find that the achievable sum rate can be improved by increasing the proportion of the perfect DACs and deploying more APs. Besides, when the DAC resolution arrives at 5-bit, the system performance will invariably approach the case of perfect DACs, which indicates that we can use 5-bit DACs to substitute the perfect DACs. Thus, it can greatly reduce system hardware cost and power consumption. Finally, the weighted max–min power allocation scheme is proposed to guarantee that the users with high priority have a higher rate, while the others are served with the same rate. The simulation results prove the proposed scheme can be effectively solved by the bisection algorithm.

Channel Estimation and Equalization for Vehicular Network by Novel Pilot

In this paper, we proposed a new technique for channel estimation using Orthogonal Frequency Division Multiplexing, (OFDM). Channel estimation is an integral part of the OFDM system based on the latest high speed transmission technology. Channel estimation is a vital technique used at the receiver side in order to estimate actual transmitted signal which gets affected by Interference. In OFDM, the known pilot signal is inserted to get a channel estimate and then the channel response is obtained by interpolation algorithms. We propose two algorithms and studied their characteristics qualities in channel estimation by simulation in NS-2. Firstly, the channel estimation scheme named Frequently Constructed Pilot Based Channel Estimation(FCPCE), which fully utilizes the pilot symbols is used to estimate the channel response and then the equalizer technique Maximum Minimizing Null Adaptive filters(MMNF) is used to completely remove the inter-symbol interference (ISI) and noise at the receiver side. Further, analysis and simulations show better performance of the proposed techniques based on 802.11p standard.

Robust Beamforming Design for SWIPT-Based Multi-Radio Wireless Mesh Network with Cooperative Jamming

Wireless mesh networks (WMNs) can provide flexible wireless connections in a smart city, internet of things (IoT), and device-to-device (D2D) communications. The performance of WMNs can be greatly enhanced by adopting a multi-radio technique, which enables a node to communicate with more nodes simultaneously. However, multi-radio WMNs face two main challenges, namely, energy consumption and physical layer secrecy. In this paper, both simultaneous wireless information and power transfer (SWIPT) and cooperative jamming technologies were adopted to overcome these two problems. We designed the SWIPT and cooperative jamming scheme, minimizing the total transmission power by properly selecting beamforming vectors of the WMN nodes and jammer to satisfy the individual signal-to-interference-plus-noise ratio (SINR) and energy harvesting (EH) constrains. Especially, we considered the channel estimate error caused by the imperfect channel state information. The SINR of eavesdropper (Eve) was suppressed to protect the secrecy of WMN nodes. Due to the fractional form, the problem was proved to be non-convex. We developed a tractable algorithm by transforming it into a convex one, utilizing semi-definite programming (SDP) relaxation and S-procedure methods. The simulation results validated the effectiveness of the proposed algorithm compared with the non-robust design.

An Improved Channel Estimation Technique for IEEE 802.11p Standard in Vehicular Communications

IEEE 802.11p based Dedicated Short-Range Communication (DSRC) is considered a potential wireless technology to enable transportation safety and traffic efficiency. A major challenge in the development of IEEE 802.11p technology is ensuring communication reliability in highly dynamic Vehicle-to-Vehicle (V2V) environments. The design of IEEE 802.11p does not have a sufficient number of training symbols in the time domain and pilot carriers in the frequency domain to enable accurate estimation of rapidly varying V2V channels. The channel estimation of IEEE 802.11p is preamble based, which cannot guarantee a suitable equalization in urban and highway scenarios, especially for longer length data packets. This limitation has been investigated by some research works, which suggest that one major challenge is determining an accurate means of updating channel estimate over the course of packet length while adhering to the standard. The motivation behind this article is to overcome this challenge. We have proposed an improved Constructed Data Pilot (iCDP) scheme which adheres to the standard and constructs data pilots by considering the correlation characteristics between adjacent data symbols in time domain and adjacent subcarriers in frequency domain. It is in contrast to previous schemes which considered the correlation in the time domain. The results have shown that the proposed scheme performs better than previous schemes in terms of bit error rate (BER) and root-mean-square error (RMSE).