Analog Carrier Research Articles

Digital-carrier multi-band user codes for baseband UWB multiple access

The growing interest towards ultra-wideband (UWB) communications stems from its unique features such as baseband operation, ample multipath diversity, and the potential of enhanced user capacity. But since UWB has to overlay existing narrowband systems, multiple access has to be achieved in the presence of narrowband interference (NBI). However, existing baseband spreading codes for UWB multiple access are not flexible in handling NBI. In this paper, we introduce two novel spreading codes that not only enable baseband UWB multiple access, but also facilitate flexible NBI cancellation. We construct our codes using a single carrier or multiple carriers (SC or MC), which can be implemented with standard discrete-cosine transform (DCT) circuits. With our SC/MC codes, NBI can be avoided by simply nulling undesired digital carriers. Being digital, these SC/MC codes give rise to multi-band UWB systems, without invoking analog carriers. In addition, our SC/MC codes enable full multipath diversity, and maximum coding gains. Equally attractive is their capability to reduce the number of interfering users, with simple matched filter operations. Comprehensive simulations are also carried out to corroborate our analysis.

Designing optimal pulse-shapers for ultra-wideband radios

Ultra-wideband (UWB) technology is gaining increasing interest for its potential application to short-range indoor wireless communications. Utilizing ultra-short pulses, UWB baseband transmissions enable rich multipath diversity, and can be demodulated with low complexity receivers. Compliance with the FCC spectral mask, and interference avoidance to, and from, co-existing narrow-band services, calls for judicious design of UWB pulse shapers. This paper introduces pulse shaper designs for UWB radios, which optimally utilize the bandwidth and power allowed by the FCC spectral mask. The resulting baseband UWB systems can be either single-band, or, multi-band. More important, the novel pulse shapers can support dynamic avoidance of narrow-band interference, as well as efficient implementation of fast frequency hopping, without invoking analog carriers.

A telemetric measurement system for flow diagnostic after bypass surgery.

In medical applications minimal invasive techniques become more and more important. This paper is focused on the results of vascular flow measurements based on micromachined acceleration sensors. A telemetry circuit will be designed to transmit energy to the system and transmit data from it. The sensors were placed outside on artificial blood vessels. With special prepared measuring equipment we have varied the flow through elastic flexible tubes. The tubes were narrowed to different levels to simulate different states of a stenosis. The duty cycled output signals of the acceleration sensors modulates the amplitude of an analogue carrier frequency. The demodulator in the receiving module rebuilds the transferred sensor signals which are evaluated by a microcontroller.

Analog carrier recovery circuits for six‐port direct digital receivers

AbstractIn this paper, simple analog carrier recovery circuits are proposed for BPSK and QPSK reception. Theoretical analysis and simulations using an SPW (signal processing workstation) validate the feasibility of these circuits. Practical circuits are also given to implement the control signal. The proposed circuits are especially suitable for receivers using compact analog signal processing means to receive high data bit‐rate signals. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 454–457, 2001.

Approaches to Planning and Deploying MRC's Innovative Dual (Analog and Digital) Carrier Microwave System

Microwave Radio Communications' (MRC) TwinStream radio is the first dual carrier radio for transmission of uncompressed legacy NTSC plus ATSC signals in a single 25-MHz radio frequency (RF) channel. Featuring a proprietary, patent-pending approach to microwave system design, the TwinStream radio is ideal for studio-to-transmitter links (STLs), transmitter-to-studio links (TSLs), and satellite backhaul requirements. MRC has worked closely with major network broadcast groups to provide the TwinStream radio for the November 1998 digital television (DTV) sign-on requirements. MRC's support of these demanding new applications is the latest in its long history of providing market innovations for television broadcasting. The TwinStream radio also is ideal for digital and analog programming feeds to cable headends and digital and analog newsgathering backhauls.

Frequency and symbol rate offset compensating algorithms for simultaneous estimation of echo and channel responses

This article addresses two critical problems in designing new full-duplex fast training algorithms for simultaneously estimating echo and channel responses. Although algorithms of this type have been discussed and evaluated in previous work, the proposed algorithms concentrate on coping with the following two problems that were not solved in the previous approaches: (1) the symbol rate difference between the local transmitter and the remote transmitter, and (2) the frequency offsets in both far echo and far signal that are caused by the analog carrier network. The performance of the new methods is analyzed in terms of the mean square error. Simulation results are presented to confirm the analysis.

Full-duplex fast estimation of echo and channel responses in the presence of frequency offsets in both far echo and far signal

In a previous publication, we proposed a full-duplex fast training procedure for simultaneously estimating echo and channel responses. It reduces the tap-setting time to half of that required by the traditional half-duplex fast training schemes. However, its estimation accuracy may be degraded by the frequency offsets in both far echo and far signal that are caused by the analog carrier network. We extend the previous work and develop a new algorithm that can compensate for the phase rotation components introduced by these frequency offsets. The performance of the new method is analyzed in terms of mean-square error. Simulation results are presented to confirm the analysis.

The effect of analog video modulation on laser clipping noise in optical video-distribution networks

Laser clipping distortion has been shown to cause potentially severe bit-error-rate (BER) floors in hybrid fiber/coax (HFC) networks carrying a combination of analog and digital video signals. Previous experimental investigations have generally used unmodulated analog carriers to quantify the effects of laser clipping. This paper provides experimental measurements of clipping noise and BER performance when the analog carriers are modulated, as they would be in actual systems. Comparisons with the case of unmodulated carriers are also given. Dramatic reductions in clipping-related degradation are observed once the carriers are modulated, suggesting that laser clipping will not pose a significant impediment to digital transmission in future HFC networks.

The evolution of digital loop carrier

The development of systems that apply digital multiplexing technology to the loop is examined. The analog carrier foundations of the present loop are reviewed, and the introduction of digital technology is described. The maturing of digital loop carrier (DLC) systems, integration of digital switching and loop transmission, operations issues, and factors that could constrain deployment of DLCs on a large scale are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The analog local loop: a growing revolution in optical transmission

To provide an economic justification for the widespread deployment of optical fiber in the local loop, it may be necessary in some situations to install networks which will carry only telephony but can be upgraded to provide broadband services. Methods by which this may be achieved using analog carrier techniques are discussed. Passive optical networks (PONs) are considered, and the application of plain old telephone service (POTS) and broadband services over PONs is considered. Frequency planning and future trends are summarized. >

No. 4 ESS: Digital Interface

This article describes the hardware and maintenance software implementation used for the Digital Interface (DIF), a new transmission interface for the No. 4 ESS. The DIF replaces the Digroup Terminal (DT) and the Signal Processor 2 (SP2) used for terminating digital carrier trunks. It also provides a more economical transmission interface for the No. 4 ESS, enhances the use of the LT-1 connector for terminating analog carrier facilities, and provides a standard peripheral/processor interface for maintenance. In conjunction with the DIF, a hierarchical modularly structured maintenance software system was introduced to support the new No. 4 ESS peripherals. Incorporated into this system were the mechanisms required to support the introduction of microcomputer-based peripherals such as DIF.

Loop Plant Electronics: Overview

The dramatic improvement of semiconductors and other electronic components has yielded the low costs and high reliability long sought in electronic loop systems. The scope of existing systems includes range extension, analog and digital carrier, and loop switching systems. Use is accelerating and procedures are evolving to make such systems a fully accepted substitute for traditional cable pairs in telephone company operations.

Loop Plant Electronics: Physical Design Considerations

The introduction of electronics into the loop plant has created the need for mounting electronic systems in the outdoors as well as in the central office. This article details the physical design considerations and requirements for the plug-in circuit boards, cabinets, closures, and hardware, and their interconnection to the telephone plant. Of particular interest is the product-line diversity from the small voice frequency range-extension devices and analog carrier systems to the large digital carrier and voice frequency loop switching systems. Each requires unique electrical and mechanical partitioning to optimize performance. Other critically important considerations are the cost-performance tradeoffs in a cost-sensitive market; the analysis, testing and evaluation of the system in environmental extremes of temperature, humidity, and atmospheric pollutants; the need to be compatible with existing loop plant hardware; and, lastly, the human factors considerations necessary to provide an effective interface with the telephone craftsperson. Specific designs are discussed which illustrate the practical problems encountered in meeting these requirements. In addition, the future thrust of loop electronics is discussed.

System Considerations for Short-Haul Multichannel Subscriber Carrier

Solid-state technology is available to permit the design of multichannel station carrier systems with "prove-in" distances of 18 kft or less. Customer acceptance of these systems will depend on transmission performance, installation and maintenance ease, service reliability, and application restriction, as well as the per-channel installed cost. This paper discusses these parameters with regard to digital and analog carrier and carrier-concentrator systems.

Transmission Facilities for General Purpose Wideband Services on Analog Carrier Systems

Three new general purpose wideband data facilities provide for the transmission of synchronous and nonsynchronous, 2-level data at bit rates ranging from 19.2 to 250 kb/s. These facilities make use of half-group, group, and supergroup bandwidth telephone facilities. The major components involved are the type 303 wideband data station, the exchange area transmission systems (local loop, N-Carrier, T1 Carrier), and the long-haul transmission systems [L-type multiplex (LMX) terminals, and coaxial cable and microwave radio circuits]. The group band system is representative and is discussed in some detail. The analog carrier systems were designed principally to handle voice frequency transmission and they present special problems when they are adapted to accommodate wideband signals. For example, up to eight LMX group connector filters may be encountered in a 4000 mile circuit and each connector introduces over 150μs of delay distortion in the transmission band. Special delay equalizers are added to each connector which reduce the distortion to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\pm 3\mu</tex> s in the band 64 to 104 kHz. The modulation schemes utilized in the various wideband modems were carefully tailored to the respective carrier systems. The LMX modem, used as an example in this paper, utilizes vestigial sideband, suppressed carrier, amplitude modulation. A carrier frequency pilot is added to the transmitted signal to facilitate carrier recovery in the receiver. The pilot is separated from the wideband signal in the receiver by a crystal bandpass filter. The filtered pilot is used for two functions; it is used to control an AGC circuit and hence the level of the received signal, and it is used in a multiple loop APC circuit to coherently demodulate the wideband signal. The APC circuit is new and promises improved performance over the conventional phase-locked oscillator when used in a coherent detector. It is capable of maintaining smaller phase errors in the presence of phase perturbations and, furthermore, the recovered carrier is always at exactly the correct frequency and hence the circuit is incapable of breaking lock.