Power-trading in wireless communications: a cooperative networking business model

Managing the power resource in battery operated wireless devices is very crucial for extending the lifetime, here we propose the concept of power trading in wireless communications. We present a business model using sealed bid procurement auction based game theory for power-trading in cooperative wireless communication with quality of service (QoS) constraints. We formulate the problem as an auction in a buyer's market sequentially/repeatedly played with a single source and a multiple relay network. The source, in-need of cooperation of a relay due to lack of battery power to communicate with the destination, broadcasts a cooperation-request specifying its QoS requirements. The QoS that we consider here are the bit error rate and the total delay associated with relaying the source data. The relays respond with their bids in terms of Euros/bit, and the source selects the best relay based on the bids. The relays compete with each other to win the game and profit from power trading. Each relay updates its pricing index via reinforcement learning to win the game during successive bidding intervals of the repeated game. Based on this model our results show that the relay node with the best features such as a better wireless channel and a better geographical position with respect to the source and destination nodes has a better chance of winning the game, and hence giving rise to a dominant strategy. More importantly, we show that the gains from the wireless channels can be converted into economic profits which is an attractive feature of the proposed business model for power trading

Deep Learning Methods for Device Identification Using Symbols Trace Plot

Devices authentication is one crucial aspect of any communication system. Recently, the physical layer approach radio frequency (RF) fingerprinting has gained increased interest as it provides an extra layer of security without requiring additional components. In this work, we propose an RF fingerprinting based transmitter authentication approach density trace plot (DTP) to exploit device-identifiable fingerprints. By considering IQ imbalance solely as the feature source, DTP can efficiently extract device-identifiable fingerprints from symbol transition trajectories and density center drifts. In total, three DTP modalities based on constellation, eye and phase traces are respectively generated and tested against three deep learning classifiers: the 2D-CNN, 2D-CNN+biLSTM and 3D-CNN. The feasibility of these DTP and classifier pairs is verified using a practical dataset collected from the ADALM-PLUTO software-defined radios (SDRs)

Fast doppler tracking DSP-based earth station modem for LEO satellite applications

A fast Doppler (carrier frequency drift) tracking earth station modem is presented in this paper. The modem is designed to track high carrier frequency offsets for low-earth orbital (LEO) satellite applications. LEO satellites have very high Doppler offsets with considerable Doppler rates (rate of change of frequency). The earth station modem tracks Doppler offsets at a data rate of 128ksym/s for QPSK modulation. The synchronisation circuit of the modem consists of, frequency synchronisation, symbol timing synchronisation and phase synchronisation. We look into the design and performance analysis of the modem, in particularly the synchronisation system of the modem

Performance analysis of a correlator based maximum likelihood frequency estimator

In this paper we discuss the performance of a correlator based frequency estimator (CE). The estimator is statistically analysed for single-tone frequency estimation for an additive white Gaussian noise (AWGN) channel. The CE is a maximum likelihood estimator (ML) [7] which theoretically achieves the Cramer-Rao lower bound (CRB) [7] if properly implemented. Frequency estimates on the received single-tone signal are made by correlating the received signal with a locally generated signal by varying the frequency, and maximizing the energy at the output of the correlator. The statistical distribution of the frequency estimates, made by the CE is studied; we consider four different cases as discussed in the paper for the distribution, whilst providing simulation results to verify the analysis

Performance analysis of a logarithmic based phase detector for tan-locked loops

Nonlinear system design is a common practice in communication engineering for improved performances in advanced receivers. Here we look into a logarithmic based nonlinear loop for a second order arctan based digital phase locked loop (DPLL) for frequency synchronisation. The steady state and the acquisition performances of the loop are analyzed. The logarithmic nonlinearity is intentionally introduced to have improved phase noise performances during the steady state tracking mode. We present a close form expression for the open loop statistical distribution of the phase noise process and compare it with the linear PLL model on its performances. We also study the acquisition process of the loop by looking at the phase plane trajectories

Acquisition Performance of a Digital Phase Locked Loop with a Four-Quadrant Arctan Phase Detector

The acquisition performance of a digital phase locked loop (DPLL) with a four-quadrant arctan based phase detector (PD) is discussed. In the noiseless case, unlike the traditional sine function based phase locked loops, the acquisition process of the four-quadrant arctan based phase locked loops is less tedious. We look into the pull-in process together with a time-series analysis of the DPLL for the noiseless case. The phase-plane portrait of the loop is also discussed, for both the noiseless and the noisy conditions

DSP Based Symbol Timing Estimation Techniques

This paper presents three symbol timing estimation techniques, using DSP (digital signal processing) methods. The techniques are easily implemented on digital signal processors or FPGAs (field programmable gate arrays). Two feedforward techniques and one feedback technique are presented. The relative performances of the techniques are compared, and the advantages and the disadvantages of the techniques are discussed as well

Frequency error correction for OFDM based multicarrier systems and performance analysis

The presence of frequency offsets in the received signal for an orthogonal frequency division multiplexing (OFDM) based multicarrier system leads to inter carrier interferences (ICI). The degradation in the performance of an OFDM system is severe when there is frequency error, which is caused by the loss of orthogonality in the received carrier frequencies. Here, we look into the correction of frequency errors in the received OFDM signal, by means of a correlator based maximum likelihood (ML) frequency estimator. We analyse the system performance of the frequency corrected OFDM system and study the statistical nature of the frequency uncertainty in the receiver when the ML frequency estimator is used. The statistical distribution of the estimates made by the receiver is also determined

Analysis of a discrete complex sinusoid frequency estimator based on single-delay multiplication method

A statistical analysis of the single-delay multiplication based frequency estimator is treated here. The single-delay multiplication frequency estimator for complex single sinusoid signals is a phase averaged estimator, which is similar to the Kay's estimator. Here we provide a study on the statistical distribution of the frequency estimates made by the estimator, and verify the analytical results using simulations. It is shown that the analytical results hold true even at very low signal to noise ratio levels. In deriving the probability density function of the frequency estimates, we explore the cross product noise terms resulting due to the multiplication operation of the estimator by making valid assumptions