PCUP: pipelined cyclic upstream protocol over hybrid fiber coax

In order to bring the NII (National Information Infrastructure) into the home, the community cable TV networks have to be reengineered to support two-way interactive services. The authors propose the PCUP (pipelined cyclic upstream protocol) as the upstream MAC (medium access control) protocol for the HFC (hybrid fiber coax) community access network. The PCUP is designed with the intention of pipelining the upstream channel. This is achieved by proper station positioning, which measures the station propagation offset from the headend, and transmission scheduling which assigns each station a transmission starting time and duration in a cycle. By taking into account the propagation offsets and transmission lines, transmitted cells can appear back-to-back (i.e., pipelined) at the headend. Since only the active stations are scheduled to transmit in a cycle, a membership control mechanism, which runs a contention-based tree walk algorithm, is executed periodically to allow the stations to join or leave. The authors also compare the PCUP with various schemes proposed to the IEEE 802.14 committee     

A comparison of UPS for powering hybrid fiber/coaxial networks

Four distinct uninterruptible power supply topologies are presented here for powering hybrid fiber/coaxial (HFC) networks. Topologies based on a low frequency isolation transformer are found to have better efficiency than the topologies with high frequency transformer. However, the latter topologies have much better performance in terms of transient response, quality of the output voltage, input power factor, total harmonic distortion of the input current, size and weight. The series-parallel resonant based UPS topology is found to have best overall performance for the emerging HFC applications     

Hybrid fiber/coax in the public telecommunications infrastructure

The benefits of the hybrid fiber/coax (HFC) architecture for the delivery of interactive broadband services have been widely discussed in the past few years. The cable television industry began deployment of this infrastructure in 1989 to support the broadcast video business. Recently, domestic telephone companies have looked at various degrees of HFC implementation, ranging from the delivery of broadcast video only to full telephony integration. The article looks at the HFC network evolution from a broadcast, non-essential, isolated architecture to a robust, interactive, broadband element within the public telecommunications fabric. Regional networks, interface to the public network and network management systems are a few of the significant issues with respect to the viability of HFC as the access layer to the “information superhighway.” If the HFC platform proves viable, telephone companies will adapt it to meet their needs in a fully integrated system     

Performance analysis preclipping AM/QAM hybrid lightwave systems

A model is presented for the analysis of the clipping noise in preclipping AM/QAM hybrid lightwave systems. It is shown that the clipping-induced degradation of BER performance can be reduced by preclipping the signal. It is also shown that the recurrence of the signal tips after passing through the low-pass filter presents a serious limit to the performance improvement achievable by the preclipping technique     

A hybrid adaptive blind equalization algorithm for QAM signals in wireless communications

A hybrid adaptive channel equalization technique for quadrature amplitude modulation (QAM) signals is proposed. The proposed algorithm, which is referred to as the modified constant modulus algorithm (MCMA), minimizes an error cost function that includes both amplitude and phase of the equalizer output. In addition to the amplitude-dependent term that is provided by the conventional constant modulus algorithm (CMA), the cost function includes an additive signal constellation matched error (CME) term. This term can be designed to satisfy a set of desirable properties. The MCMA is compared with the CMA for blind equalization. The performance is measured for wireless channels using both transient and steady-state behavior of the mean square error (MSE). It is shown that MCMA is superior and more robust in low signal-to-noise ratio (SNR) environments. Simulation results demonstrate that using MCMA improves adaptive channel equalization by increasing the convergence rate and decreasing the steady-state mean square error.     

A protocol for efficient transfer of data over hybrid fiber/coaxsystems

The cable TV plant is a broad bandwidth channel into the home and community that has been used primarily for the distribution of television. As the plant is upgraded, there is an opportunity to use it for the transport of high-speed digital signals. While the downstream channel is relatively easy to exploit, the topology and physical characteristics of the upstream channel present new challenges at both the physical and the media access layers. We present a media access protocol that efficiently transfers data on this channel. A primary goal of the design is to keep that portion of the protocol resident in the station as simple as possible. Thus, we use centralized control located in the cable head-end. A station wishing to transmit sends a request to the head-end using a contention channel. The head-end acknowledges the request and then schedules the request, informing the station, by means of a grant message, exactly when to transmit. The protocol performs efficiently under a wide range of conditions, and is robust in the presence of channel errors     

Physical layer characterization of hybrid fibre coax (HFC) networks

This paper reviews the future prospects of cable television networks through their evolution towards HFC topology. This upgrade will allow cable operators to provide full broadband bi-directional communications (image, data and voice) and generate new revenues from their existing network. This article focuses on: what is an HFC topology, what are the relevant parameters to characterize its physical layer, what are the technological key issues and future trends?     

A simple formula for calculation of power loss in digitaltransmission lines

Presented is a two-parameter model of line loss in which the frequency dependence of loss is determined by way of the loss at the selected frequency and the conductor diameter. The model quite faithfully represents the actual loss of the line, and is much better than the often used √f model     

Simplified analysis of QAM BER impairment in hybrid AM/QAMlightwave systems

A new simplified approach for QAM signal error analysis in hybrid AM/QAM lightwave systems is proposed. The method allows fast and accurate BER calculation     

Bit-error rate of M-QAM signal and its analysis model for compositedistortions in AM/QAM hybrid transmission

In cable television (CATV) systems that deliver digital video services by employing a hybrid fiber and coaxial network, it is important to consider digital channel deterioration due to composite distortions, as well as the amplitude-modulation vestigial-sideband channel. Furthermore, it is essential to clearly estimate a digital channel's quality in designing CATV transmission systems. However, there have been few studies on statistical models and an analysis method to estimate the bit-error rate (BER) of M-ary quadrature amplitude-modulation signals for composite distortions. This paper shows statistical properties of composite distortions and a new BER analysis method to handle them. In the evaluations, the amplitude distributions of composite distortions are given by Weibull distributions with skewness levels of 2.3 for composite second-order distortion and 1.5 for composite triple-beat distortion. We propose a new BER analysis method that uses the Weibull distributions for the composite distortion statistical features and demonstrate the effectiveness of the new BER analysis method in estimating BER by comparing its measurement results to calculation results     

Modeling and performance of a power distribution system for hybridfiber/coax networks

This paper presents the performance of a power distribution system for hybrid fiber/coax networks. The power scheme uses 90 V 60 Hz trapezoidal voltage distribution over the network. A simulation model of the proposed distribution system is developed, and the performance under steady-state, transient, and dynamic conditions is studied. The system loading capability as a function of cable size and distribution length is presented. It is shown in the paper that synchronous power sources can provide a much larger distribution reach than asynchronous sources. In order to ride through a fault in the system, it is found that the power supplies used in the coax node and the home termination unit should have enough holdup time capability. A system designed in this manner is inherently stable     

Resource planning and bandwidth allocation in hybrid fiber–coax residential networks

The introduction of new high bandwidth services such as video-on-demand by cable operators will put a strain on existing resources. It is important for cable operators to know how many resources to commit to the network to satisfy customer demands. In this paper, we develop models of voice and video traffic to determine the effect of demand growth on hybrid fiber–coax networks. We obtain a set of guidelines that network operators can use to build out their networks in response to increased demand. We begin with one type of traffic and generalize to an arbitrary number of high-bandwidth constant bit rate (CBR) like services to obtain service blocking probabilities. We consider the effect of supporting variable bit rate (VBR) packet-switched traffic in addition to CBR services. These computations help us to determine how cable networks would function under various conditions (i.e., low, medium, and heavy loads). We also consider how the growth rate of the popularity of such services would change over time, and how this impacts network planning. Our findings will help cable operators estimate how much bandwidth they need to provision for a given traffic growth model and connection blocking requirement.     

A MSE optimized polynomial equalizer for 16QAM and 64QAM constellation

Recently, a Maximum Entropy (MaxEnt) algorithm and its derivation called WNEW algorithm were presented by the same author. It was shown that the MaxEnt and WNEW algorithm have improved equalization performance compared with Godard’s, reduced constellation algorithm and the sign reduced constellation algorithm. In this paper, a new equalization method is proposed for the 16QAM and 64QAM input constellation based on the WNEW algorithm which is extended with some polynomials of the equalized output and optimized with the mean square error criteria. According to simulation results, the new equalization method leads to over 15 dB advantage in the residual Intersymbol Interference compared to the results presented by Godard, 10 dB advantage compared with the WNEW algorithm and 5 dB advantage compared with the MaxEnt algorithm.     

采用16QAM的GSM/EDGE调制技术

分析了GSM/EDGE信号的8PSK调制方案,在兼容现有GSM/EDGE系统、不改变该系统发送和接收滤波器的基础上,将GSM/EDGE的8PSK调制方式改进为16QAM调制方式,使得在相同的信噪比情况下,每时隙数据速率达到91.2 kbit/s,比现有的EDGE系统每时隙传68.4 kbit/s的传输速率多22.8 kbit,从而提高了数据传输速率,进一步改善了GSM/EDGE系统性能.     

一种重构多信道布拉格光栅的混杂算法

由于光纤光敏性的限制,当信道数N变得很大时,采用幅度取样方式制作多信道光栅将变得非常困难.通过相位取样来制作多信道光栅被证明是一种能有效降低峰值折变量的方法.提出一种采用逆散射技术和优化策略的混杂算法有效地设计多信道光栅.由遗传算法进行优化,得到每一个信道相应的相位因子的最优值,改进了多信道光栅复杂的反射谱.再由Layer-peeling算法为依据引入了相位因子后的频谱响应重构光栅.通过对信道间相对相位的优化,制作这种多信道光栅所需的峰值折变量降低为单信道光栅的√N倍.经过数值仿真,得到8信道光栅的峰值折变量大约为单信道光栅的√8倍.     

8VSB芯片的层次式设计方法

提出了深亚微米下系统级芯片层次式版图设计的方法，并用该方法设计了HDTV信道解码芯片8VSB的版图。实例设计结果表明，该方法在节约面积、加速时序收敛方面效果明显，大大缩短了芯片设计周期。     

Controlled-Carrier Transmission of AM/VSB Television From Space

Television broadcasting from space, using AM/vestigal sideband (VSB) modulation, requires high satellite power. A method of reducing the necessary prime power, while maintaining signal quality, is described. The method, termed controlled-carrier transmission, is a form of automatic level control at the transmitter that permits the power supply (e.g., solar array plus power conditioner) to be designed for the average long-term power demand rather than for the maximum average power demand, for which ground transmitters are conventionally designed. By this means, power reductions on the order of 30 percent, depending on the type of power amplifier used, may be obtained resulting in significant cost and weight savings for AM broadcasting satellites. A laboratory simulation of the proposed method was set up and the resulting pictures were subjectively evaluated. These tests indicate that, for practical purposes, the average viewer found no difference between conventional and controlled-carrier transmission.     

A multicarrier QAM modulator for WCDMA base-station with on-chip D/A converter

In this paper, design and implementation of a multicarrier quadrature amplitude modulation (QAM) modulator for a wideband code division multiple access (WCDMA) base-station with a 14-bit on-chip D/A converter is described. The modulator is capable of modulating four carriers with four independent in phase (I) and quadrature (Q) data streams. The proposed modulator structure consists of an interpolation chain for data streams and four digital frequency synthesizer/modulators, which are based on a coordinate rotation digital computer (CORDIC) vector rotation algorithm. The interpolation chain consists of a root-raised cosine pulse shaping filter and three half-band filters for image filtering. The modulated carriers are combined to form a multicarrier WCDMA signal. The SINC-attenuation effect of a digital/analog (D/A) converter is canceled by an inverse-SINC predistortion filter. The multicarrier signal is converted to the analog domain with a 14-bit current steering D/A converter, which is integrated on the same silicon chip. The modulator is implemented with a 0.35-mum BiCMOS process with CMOS transistors only     

CCK调制与16QAM调制的干扰抑制能力比较

对相同的频带利用率(BE)的两种调制方式进行了分析:第一种方式是CCK调制,另一种是为直扩条件下的16QAM(DS-SS 16QAM)调制。考虑采用不同的干扰类型(CW(连续波干扰)、多径干扰、多址干扰),在Matlab6.1中的Simulink环境下进行仿真。仿真结果显示,CCK的干扰容限在大多数情况下比DS-SS 16QAM的干扰容限高,但DS-SS 16QAM也有其优点。     

A New Carrier Recovery Technique for Vestigial-Sideband (VSB) Data Systems

In this concise paper we have developed a new carrier recovery system for vestigial sideband amplitude modulation (VSB-AM) data sets. Neither dc restoration nor extra bandwidth is required for the proposed system. A pilot tone is transmitted at the carrier frequency and the phase jitter is derived from the quadrature chnnnel. "Artificial" phase jitter which is introduced by the data signal can be eliminated by properly shaping the transmitted signal. We have also shown that even in the presence of channel distortion and white Gaussian noise, the proposed system can faithfully track up to 60-Hz phase jitter.