An innovative cable modem system for broadband communication

The combination of optical fiber and coaxial cable is referred to as Hybrid Fiber Coax (HFC) network. The HFC CATV network is considered a promising infrastructure and the most general access path to connect the residential with the Internet. The advantages of the HFC network include using a less number of signal amplifiers, furnishing more bandwidth, and reducing signal attenuation. In this paper, we reported the realization of the Broadband Information System Based on HFC CATV Networks. In such a system, the characteristics of upstream channel noise are the most important. We studied the causes of the noise and interference, and discussed the solution by using Synchronous Code Division Multiple Access (S-CDMA), trellis coded modulation and Interleaver. We used the cable modem equipment based on S-CDMA for the access method, adopted 1550nm and 1310nm fiber optic cables to combined a HFC CATV network and provided Internet services. This Scheme has been used in several districts in Tianjin. It is welcomed for its high-performance and cheaper in prices.

Using proxies to enhance TCP performance over hybrid fiber coaxial networks

Hybrid fiber coaxial (HFC) network has recently emerged as a promising access network infrastructure for the delivery of voice, video and high-speed data traffic. This paper first described the activity of cable modem termination system (CMTS) and cable modem (CM). Then the effect of the upstream bandwidth resource allocation mechanism based on request/transmit policy on the performance of asymmetric data application is analyzed. An active grant upstream bandwidth allocation policy is proposed to improve the performance of asymmetric data application over the HFC networks. The simulation result is also given.

Cable TV network's ability to provide fast data transmission using cable modems is receiving much attention these days. A cable modem (or cable TV modem) is a device that connects your computer to the cable TV network. The cable television (CATV) industry was born in 1948 as a way to provide TV reception to remote viewers. However, CATV's marriage to television basically obscured the fact that it can provide high-speed two-way data communication services. A cable modem is a modem in the sense that it MOdulates and DEModulates signals. However, a cable modem is far more complex than a typical telephone dial-up modem. A cable modem is partly modem, partly bridge, partly router, partly encryption/decryption device, partly NIC card, and partly Ethernet hub. A single cable modem connection speed is about 500 kbp-1.5 Mbps, and is used for point-to-point. The distance can be 100 km or even more.

In this paper, an efficient blind equalization with two‐stage single/multilevel modulus and decision directed (DD) least mean square (LMS)‐like algorithm is proposed for high‐order QAM (64/256/1024QAM) cable modem systems. In wire‐lined cable systems, it seems that the cable channel may display a nearly invariant multi‐path effect over a considerable time, and then the blind equalizer can have the capability to recover the received high‐order QAM symbols on wired cables. The proposed blind equalization algorithm applies a two‐stage convergence scheme, which results from the multi‐modulus algorithm (MMA), sometimes called the modified constant modulus algorithm (MCMA), and the DD LMS‐like method. In the first equalization stage, the joint MMA and DD LMS‐like methods are applied for the purpose of fast convergence. When the convergence process reaches an acceptably steady condition, the convergence detector changes the process into the second stage. In the second equalization stage, the enhanced DD LMS‐like method with the generalized multi‐modulus is applied to reduce the mean square error (MSE) of equalizations further. For high‐order QAM cable systems, the proposed method performs faster than the previous well‐known blind methods do. Simultaneously, the proposed algorithm also provides less MSE and lower symbol error rate (SER) than the other blind methods do at the same signal‐to‐noise ratio (SNR).

This paper deals with the design of impulse noise resistant receivers for providing telephony-over-cable (ToC) services over hybrid fiber coax (HFC) networks. We first discuss the overall scenario of ToC services and the impulse noise problems faced by such systems in HFC networks. We then briefly describe the time-frequency characteristics of impulse interference and derive the probability of error for binary and quadrature PSK signalling schemes for impulse noise afflicted channels. In light of the constraints imposed by the ToC problem, the performance of the proposed solution strategies which make use of non-linear processing and channel coding, is evaluated in detail along with simulation results.

FiberVista is a fiber-to-the-home (FTTH) or fiber-to-the-curb (FTTC) system that provides more bandwidth for emerging broadband services, such as Internet data, than existing deployed residential systems, while tapping predictable revenue streams from telephony and analog- and digital-video broadcast television service. At the same time, FiberVista minimizes development costs by reusing existing or emerging technology from other systems, such as cable modems and low-cost residential optical transceivers. It also allows for incremental, “pay-as-you-grow” provisioning of capacity. Like cable-television (CATV) hybrid fiber-coax (HFC) networks, FiberVista uses subcarrier multiplexing to offer a flexible mix of services. The system is superior to HFC in that it offers more total bandwidth, both upstream and downstream, which can be shared among fewer homes. By limiting the coax plant to a small passive run in FTTC, or eliminating it altogether in FTTH, FiberVista minimizes the most unreliable and maintenance-intensive portion of the HFC network. Furthermore, it utilizes new technologies, such as high-power erbium-doped fiber amplifiers (EDFAs), coarse wavelength division multiplexing (CWDM), and passive optical networks (PONs), to make the extension of optical fiber deep into the network practical. In this paper, we describe the FiberVista network architecture, potential upgrade scenarios, and experimental system demonstrations.

In the past CATV networks were used for broadcasting television signals. Since the deployment of fiber, the CATV networks are being upgraded to so-called hybrid fiber coax (HFC) networks, providing the possibility to use the return channel as well. The presence of such a channel challenges the operators to implement bi-directional services, such as telephony, Internet or interactive television. State-of-the- art products are in most cases ad hoc solutions implementing a single service on a dedicated system. This means that if a customer subscribes to a telephone service and a data service he ends up with two cable modems. In such a scenario also the number of interfaces at the head-end increases, so that the complexity of the total system increases for the operator. Although ATM is meant to be the multiplexing method to support all services, it is still not cheap enough to provide the wide variety of quality of services (like delay requirements for telephony in combination with efficiency and reliability requirements for data). In this paper a concept is presented that can deal with this problem in a cost effective way. The concept can be used to implement STM traffic (e.g. telephony) and ATM traffic in an efficient way. It is also shown that the system can be used for ATM traffic only so that it can be used as an intermediate step in the evolution of HFC networks to a full service network. Simulation results show a very good overall performance. This is partly due to the flexibility that is inherent to the system concept.

The Empirical Case Against Asymmetric Regulation of Broadband Internet Access

Multiple Input Multiple Output (MIMO) communication technology has received recently significant attention triggered by the rapid development of Orthogonal Frequency Division Multiplexing (OFDM) broad-band wireless and high speed wireline communication systems. Such systems are very sensitive to Narrowband Interferences (NBI) due to their relatively low transmission power. This type of signal interference can be found in the new unlicensed frequency bands, e.g., the Industrial Scientific Medical (ISM) band, coming from systems such as Bluetooth or microwave ovens which interfere with OFDM based Wireless Local Area Networks (WLAN), like Hiperlan II. Other examples of NBI, typical for Digital Subscriber Line (DSL) communications, are strong Radio Frequency Interferences (RFI) from short-wave radio, Citizen's Band (CB) radio and amateur “ham” radio which interfere with Hybrid Fiber Coaxial (HFC) networks and high speed DSL. Ineffective shielding of a cable network may also cause the ingress from external home electrical devices, such as cordless phones, TVs and computers. Let’s consider a strong NBI signal which resides within the same frequency band as a wideband OFDM signal. In this case, severe Signal to Noise Ratio (SNR) degradation is likely to occur across all OFDM subcarriers due to spectral leakage of the NBI signal from block processing in the OFDM receiver. In Fig. 1, the magnitude-squared of the received

There are many problems regarding the performance of the return channel of a hybrid fiber-coaxial (HFC) network, as cable operators know well. These problems are mainly due to the branch-tree architecture of the coaxial part of the network, which causes all the noise from any point to add in the upstream direction, an effect called noise funneling. The present work has focused on the controlled insertion of selected types of noise into a part of a coaxial network, simultaneously with the data transmission of a cable modem towards the head end. As a result, the upstream (return) data transmission will be affected, depending on the various changing and controlled noise characteristics. Monitoring several parameters shows the effect on the transmitted signal, thus giving an idea of the quality of the transmission.

In this paper, we present a new all-digital carrier recovery loop for high-order quadrature amplitude modulation (QAM) signal constellations. The proposed approach is a blind phase-frequency detector structure that consists of a phase detector, a phase offset estimator, a frequency offset estimator, and a digital control oscillator. Compared to previous related approaches, the proposed algorithm provides a wider acquisition range and a more accurate estimation of frequency and phase offsets. These features are demonstrated by simulation results of the DOCSIS (Data-Over-Cable Service Interface Specifications) cable modem system.

In this paper, we present a new all-digital carrier recovery loop for high-order quadrature amplitude modulation (QAM) signal constellations. The proposed approach is a blind phase-frequency detector structure that consists of a phase detector, a phase offset estimator, a frequency offset estimator, and a digital control oscillator. As compared with previous related approaches, the proposed algorithm provides a wider acquisition range of /spl plusmn/400 kHz and a more accurate estimation of frequency and phase offsets. These features are demonstrated by simulation results of the DOCSIS (Data-Over-Cable Service Interface Specifications) cable modem system.

A hybrid fiber coaxial (HFC) network uses both optical fibers and coaxial cables for cable TV networks. Coaxial cables are mainly used for access networks. Recently, fiber to the home (FTTH) is being widely deployed. For cable TV companies to utilize readily deployed FTTH, legacy coax network-based customer premise equipment (CPE) such as cable modems and set top boxes may have to be replaced with fiber network based CPE. In order to reduce the expenditure incurred in this process, radio over Internet Protocol (RoIP) technology has been proposed. In the RoIP system, RF signal for coax generated by legacy CPE toward the headend is first sampled, and digitized, and then encapsulated in IP packets, which are then sent to the headend using FTTH access technologies such as passive optical network (PON). In the process of digitizing RF signal, a huge amount of data much more than the base band data is generated. So, a data compression method is required to lower the upstream bit rate maintaining the signal quality. Most compression methods are significantly degraded due to the interference caused by burst noise in the upstream link. Therefore, this paper proposes a new compression method which combines linear predictive coding (LPC), block scaling and non-linear quantization for CATV upstream links. The proposed method is demonstrated to greatly reduce the impact of burst noise while maintaining the compression performance.

This paper analyzes zero-forcing (ZF) code-aided narrow-band interference (NBI) rejection in synchronous direct-sequence code-division multiple access (DS-CDMA) systems of complex channel circumstance. The performance of decoding is badly affected based on general ZF code-aided techniques because of the phase of complex gain accounting for channel effects. The system based on modified ZF code-aided technique could cancellate or relieve the effects but attend by high computational complexity. So this paper designs a new optimal restrictive ZF code-aided technique to solve this problem without the increasing of computational complexity. The conclusion is approved by experiments.