Duplex Channels Research Articles

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.

Fiber-Extended Copper Line Architecture With End-to-End Data Transmission and Link Monitoring

We demonstrate a prototype hybrid, full duplex fiber-extended copper line with frequency-reusability and simultaneous fiber and copper line monitoring. The link architecture is composed of three main units: a central office; a remote-node copper to fiber converter (CuFiC); and a radio head. A fiber optical link connects the central office to the remote node, while the remote node is connected to the radio head by a copper line. Even though the prototype is built with two full duplex channels, more channels can be supported by the architecture, and an optical feedforward linearization scheme for the transmitter is demonstrated for that purpose. In-service simultaneous multi-copper and fiber monitoring is possible with the right choice of frequency bands, a result backed by the Error Vector Magnitude measurement of data channels in simultaneous coexistence with monitoring channels. A frequency multiplication unit, built into both the transmitter and the remote node, allows for a single seed tone to generate all the sub-carrier multiplexed channels for up and downstream in both the fiber and in the copper links without the need of local oscillators. This not only simplifies the architecture, but also allows for optimal homodyne up- /down-conversion. The demonstrated prototype figures as a potential candidate for interfacing fiber to the home and fiber to the building (FTTH/FTTB) links with legacy copper infrastructure currently allowing for: up to eight 20MHz LTE 64QAM channels to be subcarrier-multiplexed onto a single optical carrier and seemlessly demultiplexed into individual copper channels, backed by a ≤8% EVM measured at the radio head; concurrent 7dB dynamic range 10 meter spatial resolution intermediate-haul fiber monitoring (up to 15 km) as well as copper line monitoring both available at the central office. The next steps beyond the presented proof of concept include simultaneous bi-directional transmission among multiple receivers, automated feed-forward linearization, and the study of factors that may limit the achievable dynamic range.

An Interactive Real-Time SCADA Platform With Customizable Virtual Instruments for Cloud Control Systems

This paper studies the design and implementation of an interactive real-time cloud supervisory control and data acquisition (SCADA) platform. The platform relying on C# and client/server architecture provides full support for data supervision of the cloud control system (CCS). Users are allowed to design supervisory interfaces by dynamically creating and customizing virtual instruments, which are seamlessly integrated into the platform by reconstructing it. Both the scalar and matrix data from different cloud nodes are supported for supervising simultaneously in real-time through receiving data asynchronously. The user can tune the parameters of the CCS online via duplex channels based on the transmission control protocol/internet protocol (IP). To overcome the disturbance of network delays to data display, a stable data and real-time data communication scheme are proposed. All the supervised data can be stored in separate files for further analysis. Finally, the online simulation and experiment are provided to demonstrate the feasibility of the designed SCADA platform.

Secret Key Exchange Using Private Random Precoding in MIMO FDD and TDD Systems

Along with the ongoing evolution of multiple antenna communication systems, new physical layer security techniques are continuing to achieve higher levels of secrecy. Most physical layer approaches, however, concern time division duplex (TDD) channels which rely on using the channel reciprocity feature as a shared randomness and tend to be associated with a large computational burden. In this paper, we propose a new physical layer method which utilizes private random precoding for exchanging the secret key bits in multiple-input–multiple-output (MIMO) systems. The principle of this method is to exploit the precoding matrix index in a manner that produces low correlation at the adversary. A robust key exchange between the transmitter and the receiver is established by uniquely relating the secret key bits to the channel precoding matrix using a private version of the universal codebooks. What is more is that the proposed method is applicable in both frequency division duplex (FDD) and TDD channels. The results demonstrate that the proposed method can offer superior performance in terms of the key agreement, secrecy level, and computational load.

Channel Training for Analog FDD Repeaters: Optimal Estimators and Cramér–Rao Bounds

For frequency division duplex channels, a simple pilot loop-back procedure has been proposed that allows the estimation of the UL & DL channels at an antenna array without relying on any digital signal processing at the terminal side. For this scheme, we derive the maximum likelihood (ML) estimators for the UL & DL channel subspaces, formulate the corresponding Cram\'er-Rao bounds and show the asymptotic efficiency of both (SVD-based) estimators by means of Monte Carlo simulations. In addition, we illustrate how to compute the underlying (rank-1) SVD with quadratic time complexity by employing the power iteration method. To enable power control for the data transmission, knowledge of the channel gains is needed. Assuming that the UL & DL channels have on average the same gain, we formulate the ML estimator for the channel norm, and illustrate its robustness against strong noise by means of simulations.

A holistic mathematical modelling and simulation for cathodic delamination mechanism – a novel and an efficient approach

This paper addresses a holistic mathematical design using a novel approach for understanding the mechanism of cathodic delamination. The approach employed a set of interdependent parallel processes with each process representing: cation formation, oxygen reduction and cation transport mechanism, respectively. Novel mathematical equations have been developed for each of the processes based on the observations recorded from experimentation. These equations are then solved using efficient time-iterated algorithms. Each process consists of distinct algorithms which communicate with each other using duplex channels carrying signals. Each signal represents a distinct delamination parameter. As a result of interdependency of various processes and their parallel behaviour, it is much easier to analyse the quantitative agreement between various delamination parameters. The developed modelling approach provides an efficient and reliable prediction method for the delamination failure. The results obtained are in good agreement with the previously reported experimental interpretations and numerical results. This model provides a foundation for the future research within the area of coating failure analysis and prediction.

Design and Verification of an FPGA-based Bit Error Rate Tester

Abstract Bit error rate (BER) is the principle measure of performance of a data transmission link. With the integration of high-speed transceivers inside a field programmable gate array (FPGA), the BER testing can now be handled by transceiver-enabled FPGA hardware. This provides a cheaper alternative to dedicated table-top equipment and offers the flexibility of test customization and data analysis. This paper presents a BER tester implementation based on the Altera Stratix II GX and IV GT development boards. The architecture of the tester is described. Lab test results and field test data analysis are discussed. The Stratix II GX tester operates at up to 5 Gbps and the Stratix IV GT tester operates at up to 10 Gbps, both in 4 duplex channels. The tester deploys a pseudo random bit sequence (PRBS) generator and detector, a transceiver controller, and an error logger. It also includes a computer interface for data acquisition and user configuration. The tester's functionality was validated and its performance characterized in a point-to-point serial optical link setup. BER vs. optical receiver sensitivity was measured to emulate stressed link conditions. The Stratix II GX tester was also used in a proton test on a custom designed serializer chip to record and analyse radiation-induced errors.

Low-Cost, Precision, Self-Alignment Technique for Coupling Laser and Photodiode Arrays to Polymer Waveguide Arrays on Multilayer PCBs

The first, to our knowledge, passive, precision, self-alignment technique for direct coupling of vertical cavity surface emitting laser (VCSEL) and photodiode (PD) arrays to an array of polymer buried channel waveguides on a rigid printed circuit board (PCB) is reported. It gives insertion losses as good as the best achieved previously, to within experimental measurement accuracy, but without the need for costly active alignment nor waveguide facet polishing and so is a major step towards a commercially realizable low cost connector. Such an optical connector with four duplex channels each operating at 10 Gb/s (80 Gb/s aggregate) was designed, constructed, and its alignment precision assessed. The alignment technique is applicable to polymer waveguide interconnections on both rigid and flexible multilayer printed circuit boards (PCBs). The dependence of optical coupling loss on misalignments in , and of the VCSEL and PD arrays allows the precision of alignment to be assessed and its reproducibility on multiple mating cycles of the connector is reported. The first recorded measurements of crosstalk between waveguides when the connector is misaligned are reported. Lateral misalignments of the connector to within its tolerance are shown to have no effect on the signal to crosstalk ratio (SCR), to within experimental measurement accuracy. The insertion loss repeatability is similar to that of single mode fiber mechanically transferable (MT) connectors.

Medium- and Large-Scale Characterization of UMTS-Allocated Frequency Division Duplex Channels

A dual-band sounder is used in both trolley and van measurements in the dense urban environment of Manchester city center to characterize the uplink (1920-1980 MHz) and downlink (2110-2170 MHz) frequency-division duplex (FDD) channels allocated to third-generation (3G) mobile radio systems. The data are analyzed with 60- and 5-MHz resolutions, as used for 3G wideband code-division multiple-access systems. Root-mean-square (rms) delay spread and 15-dB widths of mainly temporally averaged delay profile are presented either as cumulative distribution functions (cdfs) for each individual frequency band or as histograms of the difference between uplink and downlink on a local area basis. It was found that the histograms show larger differences between the two bands than the individual cdf and that the differences between the FDD channels are more pronounced on circumferential routes and shadowed locations. Correlations of rms delay spread with excess path loss and distance are on the order of 0.5 and 0.4, respectively.

Robust Control of Information Networks

A problem of robust control of routing for preventing the congestion in digital information networks is considered. Models for both duplex and semiduplex data communication channels (data channels) are suggested. For the problem of robust control of routing, the factorization operation of the traffic matrix of an information network is proposed, which plays an important role in the development of a control algorithm. Robust control algorithms are proposed, in which use is made of alternate paths with an arbitrary number of links. Properties of the suggested algorithm are studied. Model examples of information networks are given, which display the effectiveness of the suggested algorithms of robust routing.

Basic capacity calculation methods and benchmarking for MF‐TDMA and MF‐CDMA communication satellites

AbstractThis paper introduces basic capacity calculation methods for circuit switched, multiple‐beam, low earth orbit (LEO) communication satellites that use MF‐TDMA and MF‐CDMA schemes. Capacity is defined as the number of simultaneous duplex channels that a satellite can support for a given data rate and bit error rate. This paper integrates the bandwidth limit and the power limit on capacity, and derives the equations by which the capacity of a MF‐TDMA or a MF‐CDMA system can be calculated using key system parameters. Therefore, these methods enable system designers to quickly estimate the communication system capacity when key system parameters are known. The paper uses the Iridium and Globalstar systems for benchmarking by comparing the results obtained from the analytical methods with the 1100 and 2500 simultaneous channels reported by Iridium and Globalstar, respectively. The analytic capacity estimate matches reported single satellite capacities to within 6%, but the predictions are sensitive to various loss assumptions made in the link budget. Copyright © 2005 John Wiley & Sons, Ltd.

Link-Level Traffic Scheduling for Providing Predictive QoS in Wireless Multimedia Networks

A set of centralized burst-level cell scheduling schemes, namely, First Come First Served with Frame Reservation (FCFS-FR), FCFR-FR+, Earliest Deadline First with Frame Reservation (EDF-FR), EDF-FR+, and Multitraffic Dynamic Reservation (MTDR), are investigated for transmission of multiservice traffic over time division multiple access (TDMA)/time division duplex (TDD) channels in wireless ATM (WATM) networks. In these schemes, the number of time slots allocated to a virtual circuit (VC) during a frame-time is changed dynamically depending on the traffic type, system traffic load, the time of arrival (TOA)/time of expiry (TOE) value of the data burst and data burst length. The performances of these schemes are evaluated by computer simulation for realistic voice, video and data traffic models and their quality-of-service (QoS) requirements in a wireless mobile multimedia network. Both the error-free and the correlated fading channel conditions are considered. Simulation results show that the EDF-FR+ and MTDR schemes outperform the other schemes and can provide high channel utilization with predictive QoS guarantee in a multiservice traffic environment even in the presence of bursty channel errors. The EDF-FR+ scheme is found to provide better cell multiplexing performance than the MTDR scheme, Such a scheme would be easy to implement and would also result in a power conservative TDMA/TDD medium access control (MAC) protocol for broadband wireless access. Burst-level cell scheduling schemes such as EDF-FR+ can be easily adapted as MAC protocols in the emerging differentiated services (DS) enhanced wireless Internet protocol (IP) networks.

Dual-frequency sounder for UMTS frequency-division duplex channels

A single-frequency wideband chirp sounder designed and implemented at UMIST was modified to carry out simultaneous measurements at the uplink and downlink frequencies of the UMTS bands. Measurements in the dense urban environment of Manchester city centre were carried out using both a trolley and a van, and power delay profiles were obtained over the two 60 MHz channels allocated for the frequency-division duplex links. Small-scale characterisation is determined from scattering functions and from power delay profiles. Both functions showed differences in the multipath structure between the two channels. Scattering functions with both sparse scattering and dense scattering were detected. The effects of moving vehicles on a stationary user are also presented. These results are preceded by a presentation of the sounder architecture and various back-to-back tests demonstrating its performance capabilities. These include linearity tests with multiple tones, and ambiguity functions of the two frequency bands.

Advanced Synchronous Communication PC-Add on Card

Serial Communication is one area where a lot of improvement is desirable. This paper describes an advanced synchronous communication PC/PC-XT/PC-AT add on card, designed and developed for SHAR computer facilities, SHAR centre, ISRO, Sriharikota, to provide synchronous communication in personal computers. This card is developed as an intelligent one, having on-board CPU, memory and interrupt controller to save the PC CPU time. Two independent full duplex channels, fully compatible with RS232-C standards with maximum speed of 19200 bps are provided by this card. The on-board firmware allows to program the channels in asynchronous/synchronous mode of communication, at different baud rates (SO bps to 19200 bps) and in different operation modes. A driver software is provided to run in PC to transmit/receive the data to/from the external world. Also a diagnostic software is provided to run in PC as well as in the card to test all the major components or hardware subsystems in the card individually.

The pan‐European mobile radio system: Part II

AbstractHaving considered the mapping of logical traffic and control channels onto physical channels, speech and error correction coding, interleaving as well as the TDMA hierarchy and synchronisation problems in Part I of this contribution, here mainly transmission issues are addressed [1–6] and some performance figures are provided. Constant envelope partial response Gaussian Minimum Shift Keying (GMSK) with a channel spacing of 200 kHz is deployed to support 125 duplex channels in the 890 ‐ 915MHz uplink and 935 ‐ 960 MHz downlink bands, respectively. At a transmission rate of 271 kbit/s 1.35 bit/s/Hz spectral efficiency is achieved. The controlled GMSK‐induced and un‐controlled channel‐induced inter‐symbol interferences are removed by the channel equaliser. The set of standardised wide‐band GSM channels is introduced in order to provide bench‐markers for performance comparisons. Efficient power budgeting and minimum co‐channel interferences are ensured by the combination of adaptive power‐ and handover‐control based on weighted averaging of up to eight uplink and downlink system parameters. Discontinuous transmissions (DTX) assisted by reliable spectral‐domain voice activity detection (VAD) and comfort‐noise insertion further reduce interferences and power consumption. Due to ciphering, no unprotected information is sent via the radio link. As a result, spectrally efficient, high‐quality mobile communications with a variety of services and international roaming is possible in cells of up to 35km radius for signal to noise‐ and interference‐ratios in excess of 10 ‐ 12 dBs.

New reflective type star couplers for full duplex channels

A new reflective-type singlemode fibre-optic passive star coupler is described. For this new type of coupler, power entering any one of the ports is divided to all ports except the input port, and thus the optical signal is prevented from returning to its own source.

A custom VLSI architecture for the CCITT wideband coding standard

A custom VLSI architecture for implementing the CCITT G.722 64-kb/s (7-kHz) wideband audio coding standard is presented. By tailoring the architecture to the algorithm, an architecture was designed that is capable of processing a full duplex channel in less than 625 cycles. That is 71-73% less cycles than are required by the reported general-purpose DSP implementations. In a 1.5- mu technology with a 100-ns cycle time, it is estimated that the architecture would consume 95000 mL/sup 2/ of silicon and support two full duplex channels on a single chip. The authors wrote a behavioral simulation of the architecture and its implicit microcode. This simulates the architecture's behavior at the bit level. The simulation passes the CCITT G.722 test vectors, demonstrating that the implementation conforms to the standard. >

Channel Requirements for a Cordless Telephone Spectrum Allocation

Planning for a permanent cordless telephone spectrum allocation requires that the number of channels necessary to meet the long-term needs of cordless telephones be estimated. To provide the analytical basis for such an estimate, we determine the relationship between the number of channels available to cordless telephones and their performance in a suburban residential environment. Multiple cordless telephones in a community can use the same channel simultaneously, so performance ultimately will be limited by cochannel interference. We therefore develop a mathematical model of the carrier-to-interference ratio. This model accounts for shadowing, polarization, and multipath propagation effects observed in field measurements, as well as the random locations of cordless telephones. A performance measure is developed and evaluated for cordless telephones that can access all available channels and are operating in a suburban residential environment. The results indicate that for carrier frequencies in the low UHF band (300 MHz to 1 GHz), an allocation of 30-40 duplex channels can accommodate universal use of cordless telephones in that environment. For lower carrier frequencies, shadowing is less severe and fewer channels would be necessary. For example, at 50 MHz, 20 duplex channels would suffice.

New transmissive star couplers for full duplex channels

The letter describes a new type of optical transmissive star coupler which allows full duplex operation to be achieved with half the transmission channels of conventional transmissive star networks.

An error-controlling device for HF channels

Practical biprocessor error-controling equipment (ECE) realised by the INTEL 8085 micro-processors has been demonstrated. Several shorter BCH codes for correction of 1 to 3 errors (codeword length is less or equal to 15) are chosen. The look-up table method both for the encoding and for the decoding is used. The ECE is intended for use on simplex, half and full duplex channels for the transmission rates of 50–9600 b/s, so both forward error correction and hybrid techniques are implemented. Variable modes of operation such as synchronous and asynchronous transmission with variable stop bit length, different character lengths with or without parity control, different transmission rates can be easily chosen by the switches on the front panel.