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An architecture of an externally modulated AM-VSB CATV 77-channel erbium-doped fiber amplifier (EDFA)-repeated system which use the combination of single-mode fiber (SMF) and reverse dispersion fiber (RDF) as dispersion compensation device is proposed and demonstrated. Compared to the conventional externally modulated fiber optical CATV systems with or without dispersion compensation fiber (DCF), excellent performance of composite second order (CSO) [greater than or equal to] 78 dB accompanied by satisfied carrier-to-noise ratio (CNR) [greater than or equal to] 50 dB and composite triple beat (CTB)[greater than or equal to] 65 dB was obtained in the proposed system. Index Terms--Dispersion compensation, dispersion compensation fiber, reverse dispersion fiber.

One way to broadcast a popular/hot video is to let multiple users share a few channels. The stress on the scarce channels can be alleviated without sacrificing viewer waiting time. One common approach is to partition the video into fixed-length segments, which are broadcast on several channels periodically. Two representative approaches are the Fast Broadcasting scheme and the PAGODA scheme, which can broadcast a video using k channels by having new viewers wait no longer than [THETA](D/[2.sup.k]) and [THETA](D/[5.sup.k/2]) time, respectively, where D is the length of the video. In this paper, we propose a new scheme, called Recursive Frequency Splitting (RFS), that significantly improves on existing schemes in terms of viewer waiting time. Some lower bounds on the viewers' waiting time are also developed. Index Terms--Broadband networks, broadcasting, cable TV, digital video broadcasting, scheduling, video-on-demand (VOD).

This article describes the measurements of composite second order (CSO), composite triple beats (CTB) frequency spectrum and time-varying distortion in basic bandwidth (BB) (0 - 4 MHz) of the 64-QAM digital channels by multichannel AM/64QAM both optical and coaxial transmission systems. For any regular standard frequency plans (Europe, USA NCTA etc.) there is, for I and Q components in BB of the QAM channels, harmonic series of CSO/CTB with first harmonic [f.sub.1]. It has been showing that for all the same laser-optics or coaxial transmission systems CSO/CTB distortions spectrum form in QAM BB the 60-80[[micro]seconds] duration bursts of series pulse with pulse periode T = 1/[f.sub.1] and the pulse duration [Tau] [approximately equal to] 0.4/[f.sub.m], where [f.sub.m] is the CSO/CTB harmonic with max. amplitude in BB of QAM. The bursts result in the essential unevenness of error bits in time domain distribution. These bursts can deteriorate essential of Error Correction by Interleaver-Deinterleaver and Reed-Solomon (RS) Forward Error Correction (FEC) Code of the transmission systems also with a relative low. Bit Error Rate (BER) about [10.sup.-5] before FEC. There is, white Gaussian noise like, intermodulations .distortion from interaction of digital-, digital-analog channels too, that have summed with white Gaussian noise. Indexing terms: CATV, Distortion, Noise, Optical communication, CNR, CSO, CTB, QAM.

The discrete CSO/CTB intermodulations distortion has a big influence on the CATV net quality. This article describes a new method to calculate the composite second order (CSO) and composite triple beats (CTB) intermodulation distortions spectrum for fully frequency range of coaxial cable CATV- amplifier for any input frequency plan. The calculation takes into account the output level ripple and preemphasis, using frequency dependent intermodulation coefficients. These coefficients have been established through CSO/CTB measurements on multichannel test systems for standard frequency plans at 5-8 intermodulation frequencies or on distortion arrays for the two (three) oscillator measuring test system. The defined intermodulation coefficients are unrelated to the frequency plan and the input/output level ripple. It is also possible to calculate the CSO/CTB spectrum caused by analogue channels within digital QAM channels. The results equally apply to optical CATV-receivers. Simulation results have been verified using extensive data from multichannel measurement systems. Indexing terms: Distortion, Cable television, Optical communication, CSO, CTB,QAM.

To achieve smooth display of MPEG-II programs in the residential cable TV networks, we present a timestamp-sensitive scheduling algorithm for MPEG-II multiplexers. The deadline-driven scheduler maintains, for each program stream, a counter and a timestamp to record and determine how many Transport Stream (TS) packets should be transmitted before the current scheduling cycle ends. The decoding timestamp (DTS) of TS packets is used to update the counter in order to prevent deadline violation. This algorithm is compared numerically with the timestamp-insensitive algorithm which runs constant-bit-rate (CBR) scheduling. The trace-driven simulation shows that the deadline violation of our timestamp-sensitive scheduling is much lower than CBR's and well controlled for programs with various degrees of burstiness. We also show that the algorithm can be further improved by adding a scheme to prevent buffer underflow and overflow at multiplexers and set-top-boxes, respectively. Keywords - timestamp-sensitive, deadline, scheduling, MPEG-II, multiplexer, CATV

Analogue video cavalcade services in cable access television (CATV) networks usually require a very high carrier-to-noise ratio (CNR) in order to provide a good quality picture. In consequence, practical lightwave hybrid amplitude modulation (AM)/M-ary quadrature amplitude modulation (M-QAM) systems are found to suffer only infrequent clipping impulse noise, which can be provably modeled as a Poisson arriving pulse train. Based on this knowledge, a new expression for the probability density function (pdf) of the clipping noise at the output of a QAM demodulation matched filter is given which can be numerically evaluated with high accuracy. Bit-error rate (BER) performance prediction is then carried out for M-QAM signals within the hybrid system in the presence of an additive mixture of Gaussian and clipping impulse noise. Agreement between the analytical results and the experimental data is quite good.

We present the design and the basic features of variable symbol-rate demodulators for digital TV broadcasting by cable and satellite. The demodulators are fully compliant with the DVB Recommendations which were later published as ETSI standards. The satellite demodulator employs the QPSK signal constellation and can handle symbol rates up to 30 Mbaud. The cable demodulator is configurable to operate with all QAM signal formats from 16-QAM to 256-QAM, and handles symbol rates up to 7 Mbaud which is the maximum possible symbol rate in an 8MHz channel. Both demodulators employ polyphase filtering for variable symbol rate operation and fully-digital carrier recovery loops with an extended frequency acquisition range. In addition, the cable demodulator includes a blind equalizer with smooth transition to a conventional adaptation algorithm after convergence.

An infrastructure shared 802.6 MAN based personal communication network(PCN) is to be discussed. Considering the network configurations of CATV and 802.6 MAN based PCNs, a possible architecture is proposed. It is shown that the unidirectional dual buses can be implemented over star topological CATV distribution cable networks with only two cores. The design considerations related to the network capacity and the signaling loads for wireless personal communications are investigated with numerical example. The MAN partitioning is considered to extend the capacity of the network. An analytical method to evaluate the signaling loads of 802.6 MAN based PCNs is presented with a new mobility model. It is shown that the signaling traffic increased by partitioning is not the critical constraint for the feasibility of 802.6 MAN based PCN.

There are two competing transmission systems for downstream digital transmission on hybrid fiber/coax cable networks: quadrature amplitude modulation (QAM), and vestigial sideband modulation (VSB). Both QAM and VSB are bandwidth efficient, and have the same bandwidth efficiency. Detailed calculations and simulations of QAM and VSB transmission on hybrid fiber/coax are reported here. It is shown that, since VSB has a higher symbol rate, it has at most 1/2 dB less received SNR than QAM at low frequencies because of dispersion and symbol timing jitter. This difference is negligible. Vendors proposing VSB recover the carrier with a pilot tone and a PLL, and vendors proposing QAM use all-digital data-directed carrier recovery. Simulations reported here show that QAM and VSB have very similar carrier recovery performance. It is concluded that for hybrid fiber/coax, VSB and QAM have practically the same overall performance, and the choice between these transmission systems should he based on considerations other than performance.

Existing cable television (CATV) networks are proposed as a means to interconnect wireless terminals to terrestrial networks and services. Discrete antennas, each controlled by a remote antenna driver (RAD), are separated by 250 m along a cable to provide wireless access. RAD's transceive as a group on any active channel, and are controlled by a remote antenna signal processor (RASP) which interconnects to the public switched telephone network, or other broad-band network. Simulcast interference caused by transmissions involving the RAD's is analyzed. It is determined that communication is feasible, even in the simulcast interference zone, provided the time delay difference caused by differences in path length traveled by simulcast signals with comparable power levels is a small fraction of the signal pulse duration. Emphasis here is on the CT2 air interface with its 72 kb/s baud rate. The possible effects of cable transmission delay on the time-division duplex (TDD) transmission algorithm are considered. Some discussion involving communications through walls or around obstructions is included.

Based on a unified analysis of both pure and slotted ALOHA systems, a new control algorithm for ALOHA systems is proposed. A feature of great practical importance is the algorithm's automatic adjustment to changes in average traffic intensity or the (finite or infinite) number of active stations in the system. In addition, the algorithm has a low-complexity implementation. Computer simulations, concentrating on the use for two-way data communication in a cable television network, have demonstrated that the practical performance of the algorithm closely approximates the theoretical optimum, even under extremely heavy traffic load conditions. Furthermore, dynamic performance simulations have shown that the algorithm assures swift recovery from overload situations.

Cable television (CATV) used for television broadcasting in the Netherlands ensures broad frequency spaces for mobile telephony applications but interferes with television channel transmission of neighboring countries. Use of CATV through 'Negroponte switch' enhances the scope of the telephony communications and mainly depends on the generation of radiation spectrum.