Duplex Communication System Research Articles

A Machine Learning Based Full Duplex System Supporting Multiple Sign Languages for the Deaf and Mute

This manuscript presents a full duplex communication system for the Deaf and Mute (D-M) based on Machine Learning (ML). These individuals, who generally communicate through sign language, are an integral part of our society, and their contribution is vital. They face communication difficulties mainly because others, who generally do not know sign language, are unable to communicate with them. The work presents a solution to this problem through a system enabling the non-deaf and mute (ND-M) to communicate with the D-M individuals without the need to learn sign language. The system is low-cost, reliable, easy to use, and based on a commercial-off-the-shelf (COTS) Leap Motion Device (LMD). The hand gesture data of D-M individuals is acquired using an LMD device and processed using a Convolutional Neural Network (CNN) algorithm. A supervised ML algorithm completes the processing and converts the hand gesture data into speech. A new dataset for the ML-based algorithm is created and presented in this manuscript. This dataset includes three sign language datasets, i.e., American Sign Language (ASL), Pakistani Sign Language (PSL), and Spanish Sign Language (SSL). The proposed system automatically detects the sign language and converts it into an audio message for the ND-M. Similarities between the three sign languages are also explored, and further research can be carried out in order to help create more datasets, which can be a combination of multiple sign languages. The ND-M can communicate by recording their speech, which is then converted into text and hand gesture images. The system can be upgraded in the future to support more sign language datasets. The system also provides a training mode that can help D-M individuals improve their hand gestures and also understand how accurately the system is detecting these gestures. The proposed system has been validated through a series of experiments resulting in hand gesture detection accuracy exceeding 95%.

A FULL DUPLEX 5G WIRELESS COMMUNICATION SYSTEM USING NI USRP 2944

Full-duplex (FD) transmission is an emerging wireless technology that holds a great promise in improving the wireless throughput. The concept of fullduplex communication is simple. A single device can simultaneously transmit and receive on the same frequency channel. However, as the transmitted signal is many orders of magnitude stronger than the desired signal at the input of the receiver, it is extremely challenging to recover the desired signal and enable such a communication. In particular, the self-interfering (SI) signal needs to be suppressed by a factor of a billion to a trillion, requiring 90 − 120 dB of self-interference cancellation (SIC). Full-duplex wireless transceivers are typically operated over two concurrent half duplex channels, one for the transmitter (Tx) and one for the receiver (Rx). These half-duplex links have RF carriers separated in the frequency domain, namely using a TDD or Frequency Division Duplexing (FDD) scheme. This allows the receiver’s sensitive front-end to be isolated from the high power generated by the co-located transmitter. In this paper, a full duplex communication system is implemented using Universal Software Radio Peripheral (USRP) and interfaced to a system installed with LabVIEW software. IQ signals transmission scenario was applied and tested.

Ultra-Wide Band On-Chip Circulator With Sequentially Switched Delay Lines (SSDL)

The Sequentially-Switched Delay Lines (SSDL) consists of a set of RF switches and transmission lines of equal length which provides magnetless nonreciprocity with no theoretical bandwidth limit. SSDL circulator architectures are presented in this paper on a GaN MMIC. The SSDL circulators presented here demonstrate nonreciprocity from 10MHz to 1.2GHz with isolation between the transmitter and receiver which is greater than 20dB for most of the measured frequency range. The insertion loss of the GaN MMIC SSDL circulator is reduced to below 3dB from 10MHz to 800MHz, by using matching circuits at the gates of the switching transistors. The spurious-free operation of the SSDL circulator is also verified from 10MHz to 1GHz. It is also demonstrated that with passive bootstrapping, SSDL insertion loss is further reduced to about 2dB and P1dB performance can be significantly enhanced by an additional 10dB. The time-modulation/switching strategy to achieve broadband magnetless nonreciprocity has the potential to be used in future STAR and full duplex communication systems.

Digital SI Cancellation Based on LSTM for Co-frequency Co-time Full Duplex Communication Systems

To address the high self-interference (SI) in co-frequency co-time full duplex (CCFD) communication systems, a digital SI suppression method based on deep learning is proposed. A memory polynomial is firstly utilized to simulate the SI channel. Then a long short-term memory network (LSTM) is used to reconstruct the SI signal. The clean signal after interference suppression can be achieved by subtracting the SI signal at the receiver. To better reflect the changes of the SI signals after being transmitted through the multiple channels and reduce dependence on data volume, feature preprocessing and feature reconstruction are performed at the input of the LSTM. We use the multi-segment delayed transmitted signal as the multiple features and utilize the brainstorm optimization (BSO) technique to estimate the ideal time delay. We verify the proposed SI suppression scheme in the OFDM transmission system. The experimental results show that compared with the traditional least squares estimation (LS) and adaptive filter least mean square (LMS) algorithms, the proposed scheme has a significant performance boost. A SI signal suppression capability of 47.19 dB is achieved.

Bi-directional photonic switch and optical data storage in a hybrid optomechanical system

We propose to achieve quantum optical nonreciprocity in a hybrid qubit-optomechanical solid-state system. A two-level system (qubit) is coupled to a mechanically compliant mirror (via the linear Jaynes–Cummings interaction) placed in the middle of a solid-state optical cavity. We show for the first time that the generated optical bistability exhibits a bi-directional photonic switch, making the device a suitable candidate for a duplex communication system. On further exploring the fluctuation dynamics of the system, we found that the proposed device breaks the symmetry between forward and backward propagating optical modes (optical nonreciprocity), which can be controlled by tuning the various system parameters, including the qubit, which emerges as a new handle. The device thus behaves like an optical isolator and hence can store optical data in the acoustic mode, which can be retrieved later.

Miniaturized microstrip patch antenna with high inter‐port isolation for full duplex communication system

In this paper, an antenna is presented for in-band full duplex technology. This antenna includes a microstrip patch and a new 180° hybrid coupler. The designed 180° hybrid coupler has new structure that miniaturizes the entire system and also eliminates the self-interference signal that leaks from transmitter to receiver. In this antenna, at 2.4 GHz, an isolation between transmit and receive ports is more than 79 dB. Additionally, in this antenna, the measured inter-port isolation is better than 68, 72, and 74 dB for 80, 50, and 20 MHz bandwidths respectively in 10 dB return loss impedance. The dimensions of the designed antenna are 68 mm × 60 mm, and in compare with similar designed antenna is considerably smaller (more than 60%) with acceptable isolation.

On-chip broadband nonreciprocal light storage

AbstractBreaking the symmetry between forward- and backward-propagating optical modes is of fundamental scientific interest and enables crucial functionalities, such as isolators, circulators, and duplex communication systems. Although there has been progress in achieving optical isolation on-chip, integrated broadband nonreciprocal signal processing functionalities that enable transmitting and receiving via the same low-loss planar waveguide, without altering the frequency or mode of the signal, remain elusive. Here, we demonstrate a nonreciprocal delay scheme based on the unidirectional transfer of optical data pulses to acoustic waves in a chip-based integration platform. We experimentally demonstrate that this scheme is not impacted by simultaneously counterpropagating optical signals. Furthermore, we achieve a bandwidth more than an order of magnitude broader than the intrinsic optoacoustic linewidth, linear operation for a wide range of signal powers, and importantly, show that this scheme is wavelength preserving and avoids complicated multimode structures.

Application of ICA on Self-Interference Cancellation of In-Band Full Duplex Systems

In this letter, we propose a modified version of Fast Independent Component Analysis (FICA) algorithm to solve the self-interference cancellation (SIC) problem in In-band Full Duplex (IBFD) communication systems. The complex mixing problem is mathematically formulated to suit the real-valued blind source separation (BSS) algorithms. In addition, we propose a method to estimate the ambiguity factors associated with ICA lumped together with the channels and residual separation error. Experiments were performed on an FD platform where FICA-based BSS was applied for SIC in the frequency domain. Experimental results show superior performance compared to least squares SIC by up to 6 dB gain in the SNR.

Microstrip antenna with high self‐interference cancellation using phase reconfigurable feeding network for in‐band full duplex communication

AbstractThis article presents a bistatic microstrip circular patch antenna with high self‐interference cancellation (SIC) through phase reconfigurable differential feeding network. The proposed microstrip antenna consists of closely spaced transmitter and receiver patches having orthogonal polarization with respect to each other. To achieve high SIC, the phase reconfigurable of feeding network can assist in tracking the phase offsets of self‐interference signal caused by fabrication error or scattering nearby objects. From the experiment, the proposed antenna provided higher than 75 dB (65 dB) SIC bandwidth for 36 MHz (50 MHz) at the center frequency of 2.50 GHz. The proposed antenna is a good candidate for in‐band full duplex communication system because of its simple design.

Bidirectional MDRZ Downstream and NRZ OOK Upstream SS-WDM RoFSO Communication System

Abstract A cost-effective spectrum sliced wavelength division multiplexing radio over free space (SS-WDM RoFSO) full duplex communication system architecture has been proposed and analyzed. For the downlink, a 10 Gbits/s high spectrally efficient and amplitude maintaining modified duobinary return to zero (MDRZ) modulated the filtered slices from the light source. The free space optical (FSO) channel was modeled by the well-known Gamma-Gamma model and was further subjected to moderate rain attenuation conditions. Four FSO transceivers were used to mitigate against laser beam scintillation, geometrical losses and rain attenuation. For uplink, a reflective semiconductor optical amplifier (RSOA) was used both as a modulator and an amplifier. Its amplitude squeezing effect was used to erase the information in the MDRZ modulated downstream seeding wavelength for uplink transmission of 10 Gbits/s NRZ OOK signals. At a bit error rate (BER) of 1.262 × 10 − 9 $1.262\times 10^{-9}$ , our proposed architecture revealed that 10 Gbits/s symmetric SS-WDM RoFSO can achieve 4.167 km of free space transmission. Power penalty of approximately 0.2 and 3 dB was achieved for downstream and upstream, respectively, which assures the feasibility of the proposed architecture. Such a system is meant to co-exist with the forthcoming fifth generation long-term evolution urban systems.

Wireless local data transmission network through LED lighting compatible with IEEE 802.11 protocol communication systems

We developed a wireless duplex communication system using visible light communication concept. In this work we investigated a downlink data transmission channel. We modelled the optical configuration of the system, calculated optical losses, fabricated the system and measured downlink channel parameters under test of analog and digital signals. The analysis showed that with a heterodyne scheme used for transmitting signals through visible light, the model of additive Gaussian noise is applicable to the channel and there are no phase distortions in the system. The system has shown the capability to operate with modulation types according 802.11 IEEE protocol.

A secret key establishment in frequency division duplex communication systems under active attacker

Most of the current research on generating a secret key from wireless fading channels relies on the channel reciprocity feature of the time division duplex link between legitimate entities so that they can acquire related information from the joint wireless connection. This paper investigates the challenge of generating a shared secret key in frequency division duplex communication systems, in which there is no reciprocity between the two nodes, in the presence of an active opponent. We suggest a key generation algorithm that depends on the product of two fading coefficients. We additionally look at the effects of an interfering adversary on the suggested key establishment scheme and solve the problem of evaluating the key rate for a scheme depending on virtual channel gain. We illustrate an adversary model using an optimal attacking strategy to minimize the rate of generating a shared secret key for our suggested algorithm. Additionally, we identify the suitable channel conditions for the non‐zero rate in the existence of an interfering adversary using simulation results.

An Investigation of Using Loop-Back Mechanism for Channel Reciprocity Enhancement in Secret Key Generation

Physical layer security key generation exploits unpredictable features from wireless channels to achieve high security, which requires high reciprocity in order to set up symmetric keys between two users. This paper investigates enhancing the channel reciprocity using a loop-back scheme with multiple frequency bands in time-division duplex (TDD) communication systems, in order to mitigate the effect of hardware fingerprint interference and synchronization offset. The scheme is evaluated to be robust to passive eavesdropping and active Man-in-the-Middle attack through both theoretical analyses and practical measurements. A secret key generation protocol is subsequently designed. The performance of the proposed secret key generation method is then evaluated through both numerical simulation and experiments. Results demonstrate that the proposed scheme can effectively mitigate non-reciprocity and outperforms the classical TDD scheme in both key disagreement rate and key generation rate.

Self Interference Cancellation in Co-Time-Co-Frequency Full Duplex Cellular Communication

The performance of co-time co-frequency full duplex (CCDF) communication systems is limited by the self-interference (SI), which is the result of using the same frequency for transmission and reception. However, current communication systems use separate frequencies for transmission and reception, respectively. Therefore, SI is an important issue to be fixed for future-generation systems. As the radio frequency (RF) spectrum is very scared and a CCDF system has the potential to reduce the current spectrum use by half. In this paper, a CCDF communication system is modeled and a combination of RF and digital cancellations is used to mitigate the SI. The simulation results reveal that the proposed combination of RF and digital cancellation achieve the bit-error-rate of 10-11 at an interference-to-signal ratio of 10 dB, which is satisfying value for CCDF communication. The achieved efficiency of the proposed system is 13 bits/sec/Hz at a signal-to-noise ratio of 50 dB. The antenna separation of 35 dB is considered for the proposed model to keep the data loss as minimum as possible. The performance can be improved further by increasing digital-to-analog converter bits but with added complexity.

Double Balanced Feed Network for the Self-Interference Cancellation in Full Duplex Communication System

Recently, there have been hot issue and many research activities on the In-band full duplex (IBFD) for the spectral efficiency improvement in wireless and mobile communication system. In IBFD syste...

Performance of a bi-directional relaying system with one full duplex relay

Full duplex communication system has the potential to double the spectral efficiency compared to traditional half duplex communication system. However self interference in full duplex relay is considered as the major concern to the performance of system. In this paper, performance of two way relaying communication system is studied with a full duplex relay. Specifically, the probability density function (PDF) of the signal-to-interference-plus-noise ratio (SINR) is derived. By using the derived PDF, closed form expressions for average bit error rate (BER) is derived for various binary modulation schemes such as, coherent binary phase shift keying (BPSK), differential BPSK, coherent binary frequency shift keying (BFSK), and non-coherent BFSK. Moreover, the ergodic capacity of the considered system is also analyzed.

Single laser free-space duplex communication system with adaptive threshold technique and BER analysis in weak turbulent atmosphere.

A free space duplex communication system with a single laser and a modulated retro-reflector is presented. A method to minimize the echo wave bit error rate (BER) of this system is proposed by setting the optimum threshold automatically based on the measured mean power and irradiance variances with log-normal distribution and the Bayes minimum classification error criterion. Experiments were taken at a distance of 1.55 km in a weak turbulence and the measured BER was 0.0213. The BER performance of this system is studied and the result shows the experimental BER is in good accordance with the theoretical value.

Image and Video Error Rate Analysis in Full Duplex Communication Using Phase Offset

ne of the most efficient way to utilize the bandwidth in wireless communication systems is Full- duplex communication. It is proposed for full duplex wireless communication over a single channel. The signals are transmitted and received at a same time and same frequency. It creates the large self-interference over the transmitted and received signals and lead to large loss of data. We used different values of phase offset to reduce the self-interference between the transmitted and received signals. The full duplex communication system is designed for input as image and by using wavelet transform. The performance of full-duplex communication system using various modulations like 16-QAM, QPSK and 64-QAM along with Haar, Daubechies2 and Daubechies 4 wavelets over different values of phase offset are evaluated by bit error rate.

16-QAM OFDM-Based W-Band Polarization-Division Duplex Communication System with Multi-gigabit Performance

This paper presents a novel 90 GHz band 16-quadrature amplitude modulation (16-QAM) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 6 Gbps through six channels with a bandwidth of 3 GHz. Each channel occupies 500 MHz and delivers 1 Gbps using 16-QAM OFDM. To implement the system, a low-noise amplifier and an RF up/down conversion fourth-harmonically pumped mixer are implemented using a 0.1-μm gallium arsenide pseudomorphic high-electron-mobility transistor process. A polarization-division duplex architecture is used for full-duplex communication. In a digital modem, OFDM with 256-point fast Fourier transform and (255, 239) Reed-Solomon forward error correction codecs are used. The modem can compensate for a carrier-frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of 10–5 at a signal-to-noise ratio of about 19.8 dB.

ACTIVE SELF INTERFERENCE CANCELLATION TECHNIQUES IN FULL DUPLEX COMMUNICATION SYSTEMS - A SURVEY

In this paper we present a survey based on vast res earch done in the area of various important factors relating to full duplex communication revealing several facts. In fact thes e revelation has served to be vital in the future d esign of any full duplex communication system . The major problem or challen ge faced in such a system was the interference caus ed from the transmitting antenna on the receiver antenna placed at the same node. The interference was termed as ' self interfe rence'. Wireless transceivers nodes can select between transmit and receive funct ions on the same frequency band at different time ( Time Division Duplex-TDD) or they can transmit at the same time at different frequencies ( Frequency Division Duplex-FDD). Recen tly researchers have put forth a new radio system, that can operate full duplex ov er a single channel , that is transmitting and rec eiving at the same time on the same frequency band. This kind of system is overwhe lmed by interference. Interference need to be redu ced to the point where the receiver can detect even the weakest signal of inte rest. Several active interference cancellation tech niques that can help in self interference reduction have been proposed. The in d epth survey was helpful enough to come out with a n ovel solution to an antenna design based on passive suppression techniques usin g polarization and other diversity techniques so a s to reduce the self interference problem.