This paper presents a new blind equalization algorithm called multimodulus algorithm (MMA). This algorithm combines the benefits of the well-known reduced constellation algorithm (RCA) and constant modulus algorithm (CMA). In addition, MMA provides more flexibility than RCA and CMA, and is better suited to take advantage of the symbol statistics of certain types of signal constellations, such as nonsquare constellations, very dense constellations, and some wrong solutions.

We propose a dual-mode receiver capable of blindly demodulating both carrierless amplitude modulation/phase modulation (CAP) and quadrature amplitude modulation (QAM) line codes. Our work is motivated by some emerging broad-band access standards which require a receiver that can first blindly start up, then blindly distinguish between CAP and QAM, and finally decode the signal. The "brute force" solution to this problem would be to implement CAP and QAM receivers in parallel. However, we propose a single novel receiver based on a single equalizer that accommodates both line codes, yielding significant computational savings. We describe the receiver architecture, blind start-up methods, and line code identification algorithms, as well as computer simulations and a laboratory experiment to verify the theoretical receiver behavior.

Some emerging broadband access standards require a receiver that can first blindly start up, then blindly distinguish between carrierless amplitude modulation/phase modulation (CAP) and quadrature amplitude modulation (QAM), and finally decode the signal. The "brute force" solution to this problem would be to implement CAP and QAM receivers in parallel. However, we propose a novel dual-mode receiver based on a single equalizer which accommodates both line codes, yielding significant computational savings. We describe the receiver architecture, blind start-up methods, and line code identification algorithms, as well as computer simulations and a laboratory experiment to verify the theoretical receiver behavior.

This paper presents theoretical and numerical results on the effect of bridged taps on the channel capacity of unshielded twisted pair telephone wiring used in very-high-speed digital subscriber line broadband access systems.

The fundamental limits of the outside loop plant to carry high-speed digital (bi-directional HDSL and ADSL) data are reported. The paper focuses on the copper wire pairs, drop lengths, and interconnects that convey data over the “last mile” to almost all businesses and residences in the US. The two major customers, businesses and households, are classified, characterized, and categorized by the distance to the central office or the remote terminal. Their spectral capabilities are computed and their ultimate digital capabilities are reported. The crosstalk limitations inherent in the plant are also computed and verified against the loss of signal due the distance and spectral constraints. The signal to noise ratio can thus be estimated to ascertain the transmission quality through the plant. Accordingly, the paper reports on losses, bandwidths, and bit rates in the first half, and discusses the major bottlenecks in the second half

The paper describes the characteristics and performance of the 16-CAP transmission scheme that has been chosen by the Technical Committee of the ATM Forum as the ATM LAN physical layer interface standard at 51.84 Mb/s for category 3 unshielded-twisted-pair (UTP) wiring. The two most attractive features of the 16-CAP transceiver are its capability of operating in the presence of multiple users in a voice-grade UTP cable and the straightforward way in which it can provide scalability to lower speeds. It is also shown in the paper how the carrierless AM/PM (CAP) modulation scheme used for the ATM LAN standard can be utilized to provide substantially higher data rates than 51 Mb/s when there is only one user in a cable. Under this condition, data rates up to 155 Mb/s can be achieved over category 3 wiring and significantly higher rates can be achieved over high-performance category 5 wiring.>

Describes techniques for achieving data rates up to 155 Mb/s over unshielded twisted-pair (UTP) wiring for local area network (LAN) applications in premises distribution systems. Duplex operation at these high data rates is achieved over two pairs of UTP wiring and with a bandwidth utilization that is less than 30 MHz, thus avoiding potential problems with radiation limits. The transmission scheme used for these LAN applications is carrierless AM/PM (CAP), which is a bandwidth-efficient two-dimensional passband encoding scheme. The paper also discusses in some detail a technique called NEXT equalization, which allows several users to share the same cable

Higher-speed data transmission over the embedded network of cables, specifically, Category 3 unshielded twisted-pair developed primarily for voice communications, is addressed. To provide robust transmission systems at high data rates for distances of 100 m, bandwidth-efficient encoding schemes utilizing adaptive noise cancellation techniques are required. One such scheme, carrierless AM/PM (CAP), is described.>

Analytical and experimental results are presented for the performance of one echo canceller arrangement. It consists of a data-driven echo canceller having a so-called cross-coupled structure, which is followed by a rotator and a phase-locked loop (PLL). A cross-coupled echo canceller structure without a PLL is analyzed first. Expressions for speed of convergence and achievable echo-return-loss enhancement (ERLE) in the presence of frequency offset are derived. These results are compared in previously published results for a noncross-coupling echo canceller structure. Specifically, it is shown that the cross-coupled structure converges twice as fast as the noncross-coupled structure and provide an achievable ERLE that is about 6 dB better. The joint adaptation of the echo canceller and the PLL is then studied. It is shown that it is always possible to choose design parameters for the echo canceller which are consistent with adaptation requirements under double-talking conditions, provided that the PLL is properly engineered. The sensitivity of the performance of PLL to the power level of the far echo, as well as possible solutions to this problem, are discussed.>

In this paper we describe an experimental 4800 bit/s fullduplex DDD modem which has been constructed at Bell Laboratories and AT&T Information Systems. The modem achieves full-duplex operation by using echo cancellation techniques. The main features of the modem's architecture and start-up procedure are discussed in the paper. We also study in detail the characteristics of an echo canceller structure which was found to be particularly attractive for this application. Finally, we present experimental performance results obtained over simulated channels in the laboratory and over telephone loopback facilities.

We analyze an echo canceler structure which has dispersion and/or delay in the tap adjustment loop. Such a structure has the potential of providing a saving in the analog filtering requirements, when the cancellation is performed in the sampled-data domain. We derive the optimal coefficient vector, in the mean-square error sense, and we derive conditions for a unique solution. It is observed that this problem is somewhat similar, but not equivalent, to the mean-square equalizer problem. Similarities and differences between the two are discussed. We also propose an adaptive algorithm which is well suited for this canceler structure. It is shown that the computational complexity of this algorithm is significantly greater than that of the conventional updating algorithm.

In this paper the recovery of the modulation signal from filtered versions of single-sided angle modulation (SSBØM) by using a simple angle detector is investigated. A general analysis is made which suggests that for modulation signals of small amplitude and for relatively well behaved filters distortionless reception of the modulation signal is possible at the receiver if the angle detector is followed by an ideal low-pass filter. This result is proved for modulation signals which are band-limited and square-integrable functions of time, and for the pure sinusoid, when the modulated signals are ideally band limited. Of special practical and theoretical interest is the case where the ideally filtered SSBØM signal has the bandwidth saving of conventional single-sideband amplitude modulation (SSBAM). In this case a sufficient condition for distortionless reception of a signals(t)with energy Esand one-sided bandwidthWis that(2E_{s}W)^{1/2} < 0.8, the maximum amplitude of the unmodulated carrier being 1. A necessary and sufficient condition for distortionless reception of the pure sinusoids(t) = d \cos w_{1)tis:d < 1.