Cable Modem Research Articles

Cable Modems and DSL: Broadband Internet Access for Residential Customers

Cable Modems and DSL: Broadband Internet Access for Residential Customers by Jerry A. Hausman, J. Gregory Sidak and HalJ. Singer. Published in volume 91, issue 2, pages 302-307 of American Economic Review, May 2001

The wireless art and the wired force of subscriber access

Different technologies for subscriber access are put side by side. Starting from the various transmission media characteristics of all systems, the well-known twisted pair lines with their corresponding digital subscriber line services are evaluated against wireless local loops, communications over ubiquitous power lines, high-bandwidth cable modems, and mobile radio. Each technology has its advantages and disadvantages. The different technologies will find their fields of applications. Most networks will have to provide a mixture of solutions for individual subscribers and customer segments to meet their boundary conditions. As a result, the future of subscriber access is a hybrid solution.

How network asymmetry affects TCP

Several emerging wireline and wireless access network technologies exhibit asymmetry in their network characteristics. For instance, cable modem networks exhibit significant bandwidth asymmetry, while packet radio networks exhibit media access asymmetry. A high degree of asymmetry can have an adverse effect on the performance of feedback-based transport protocols. We study the effects of bandwidth and media access asymmetry on the performance of the TCP protocol. We identify the fundamental reasons for the mismatch between TCP and asymmetric networks, and then present several techniques to address this problem.

DOCSIS/sup TM/ cable modem technology

An overview of the cable modem interface standard is presented. This standard is the foundation for high-speed access to content on the Internet being offend by North American cable operators. It also facilitates retail sales of modems and integration into computers, is being adopted by international operators, and provides a path for convergence of video, data, and voice services on a broadband cable system. The details of the protocol stack and evolution of the standard are discussed.

Recovery analysis of the DOCSIS protocol after service disruption

Wide scale power outages can cause serious disruptions to digital services over community antenna television (CATV) networks. This can result in long service recovery times for some or all of the cable modems (CMs). In this paper, the recovery mechanisms of the Data Over Cable Service Interface Specification (DOCSIS) protocol, due to service disruption, are studied. We propose a new scheme for the ranging of modems, namely persistent ranging algorithm (PRA) and two different simulation models have been developed for this purpose. The simulation results show that the static nature of the registration and initialization parameters can introduce an excessive delay in the recovery time of the system. Minimum recovery times of 820 s and 975 s (two ranging opportunities/second) for network architectures with 400 CMs and 500 CMs, respectively, on a single upstream channel were obtained. In order to validate the accuracy of the simulation models a set of experiments was performed on a CATV network testbed. The testbed results revealed that the simulation models produced are realistic and offer reliable estimates of large-scale network topologies. Extensions to the DOCSIS MAC protocol in which the status of the system prior to disruption is used have reported a decrease of up to 42% in the recovery time of the system.

Panel 2: finding solutions through partnerships, education, and technology: Speaker 1

Panel 2: finding solutions through partnerships, education, and technology: Speaker 1

Virtual private networks

A virtual private network (VPN) can help resolve many of the issues associated with today's private networks. A VPN facilitates an agile IT infrastructure. Global VPNs enable connectivity to all locations anywhere in the world at a fraction of the cost of dedicated links. VPN services enable remote access to the intranet at significantly lower cost, thus enabling support for a mobile workforce. Additionally, the VPN architecture support a reliable authentication mechanism to provide easy access to the intranet from anywhere using any available access media including analog modems, ISDN, cable modems, DSL and wireless. There are primarily three types of VPN services: (1) local area network (LAN) interconnect VPN services, (2) dial-up VPN services, and (3) Ethernet VPN services.

Architecting the services optical network

In this new millennium, the most valuable commodity will be information, as seen by the surge in demand for faster access technologies such as cable modems, xDSL, and wireless data. The tremendous growth in data traffic, particularly that associated with the Internet, is changing the way it is carried over public and private networks. Together with the rapid advances in optical networking technology and the spawning of a new category of wavelength services stimulated by new high-speed data requirements, this is dramatically changing network architectures and the relationship between network service providers and their customers. Incumbent carrier globalization and new carrier entry require support for a broader set of business models and range of service interfaces. The growth and expansion of networks imply a greater need for more scalable solutions and more automation for network maintenance. An intelligent optical core optimized for service optical networking, the services optical network, needs to take the best aspects of both the transport and data networking domains to meet the above needs. This article focuses on architecting the services optical network to meet the challenges of optical data networking, and includes a snapshot of supporting standardization activities.

High-bandwidth interface for multimedia communications over fixed wireless systems

Over the past two decades, cable television has largely supplanted over-the-air broadcast as a TV distribution medium. Several years ago, enterprising companies concluded that they could leverage the extremely wide bandwidth of cable TV systems required to deliver broadcast-quality television as a high-speed conduit for broadband data communications. This led to the birth of the cable modem. Early cable-modem equipment was vendor proprietary, so interoperability between different vendors' products was largely nonexistent. To promote interoperability, Cable Labs (the cable TV industry research arm) developed the Data Over Cable Service Interface Specification (DOCSIS 1.0), an IP-centric, point-to-multipoint standard that quickly replaced the proprietary solutions that preceded it. DOCSIS has now become the accepted cable standard. The newly released DOCSIS 1.1 is destined to play an important role in the delivery of high-quality multimedia across fixed wireless communications networks. With this approach, we can take advantage of all the DOCSIS technology modules that exist in the market today, allowing the wireless platform to migrate toward emerging services such as Internet protocol multicasting and voice over IP (VoIP). We describe the state of current technologies that have made fixed-wireless access a viable and compelling choice. We also discuss some emerging technologies that will bring exciting new fixed-wireless services and capabilities into homes and small businesses in the near future.

Next-generation modems: a professional guide to DSL and cable modems [Book Review

Next-generation modems: a professional guide to DSL and cable modems [Book Review

Telecommunications alternatives in accessing image intensive digital libraries

Digital libraries are becoming vital in basic research and general surfing of the Internet and the Web. Unlike text‐based digital libraries, image intensive digital libraries have inherent problems of slow downloading and uploading. These bottlenecks are caused by low bandwidth at the “last mile”, the distance between the telecommunications carriers’ distribution center – or central office and the user premises. Telecommunications technologies which are commonly used to alleviate this problem are: high end analog modems, T… series, frame relay, ISDN, cable modems, digital subscriber line and satellites. The article summarizes the latest developments of these technologies and how they can be used by various types of information professionals and end‐users in accessing digital libraries.

Coding and Modulation for LMDS and Analysis of the LMDS Channel.

Local Multipoint Distribution Service (LMDS) has the potential to become a viable alternative to coaxial cable, fiber and other wired and wireless technologies providing “last mile” communication services. A major obstacle, however, is the high equipment cost. While for example cable modems supporting two-way services are available for $200 to $300, LMDS modem providing similar services will cost over $1000. The major cost driver of LMDS equipment is the radio frequency (RF) unit, as Ka-band technology still is quite expensive. The modem design must minimize the overall architecture cost, and low-cost modems requiring an expensive architecture should not be used. The channel characteristics of LMDS systems are very different from those of fiber, coaxial cable, and lower frequency wireless links, major channel impairments being non-linear high power amplifier (HPA), high phase noise and high co-channel interference. Modems should therefore be developed specifically for LMDS systems. This report deals with the choice of coding and modulation schemes, the LMDS channel, and how the channel impairments should be overcome by digital signal processing algorithms.

White House unveils new cyber-crime, crypto export policies

In the United States, on 17 July 2000, the White House announced sweeping new policy changes that ease law enforcement access to E-mail and cable modem traffic. The policy change also permits the license-free export of US encryption products to the European Union, Australia, Norway, Czech Republic, Hungary, Poland, Japan, New Zealand and Switzerland. Canada is already covered by such an exception. The new policy eliminates previous distinctions between government and non-government end-users. This move mirrors that taken in early July by the EU nations that involves the same list of countries.

FIR parity check codes

This paper describes a method for packet synchronization and error detection for use in a synchronous digital communications system. The method relies upon a class of linear block codes that have parity checks that are expressed in terms of a finite-impulse response (FIR) filter. This system is incorporated in the newly established ITU standard of digital cable television standard, J.83 appendix B, which is based on an MPEG 2 transport packet data stream. This technique is also the basis for cable modem downstream transmission defined in the IEEE 802.14 and MCNS standards. The parity check structure is based on a pseudonoise sequence generated by a (binary) primitive polynomial. This structure allows for a computationally efficient implementation of the parity check FIR filter, in a recursive manner, that is none the less self-synchronizing. The FIR parity check codes that are described are characterized as the dual of a CRC-type, shortened cyclic code. The theory and computational structure of these codes are presented here; the J.83R code is used as an example of the general theory.

Improving TCP performance over asymmetric networks

Bandwidth asymmetry is quite common among modern networks; e.g., ADSL, cable TV, wireless, and satellite link with a terrestrial return path. In these networks, the bandwidth over one direction can be orders of magnitude smaller than that over the other. The performance of TCP transfer in the high bandwidth direction can be severly reduced by the delay acknowledgment packets experienced in the reverse direction. In this paper, we describe our proposed solution ACE (Acknowledgement Based on Cwnd Estimation). In comparison to other solutions, ACE requires only modification of the TCP stack at terminals attached to an asymmetric network. We evaluated the performance of ACE over a cable modem network by simulation. We have also implemented ACE on the Linux platform and tested it on a small testbed network with an emulated asymmetric link. The performance improvement was significant especially when there is a high degree of asymmetry.

Cable modem access to picture archiving and communication system images using a web browser over the Internet.

This presentation describes our experiences using a web-based viewing software and a browser to view our picture archiving and communication system (PACS) images at a remote site with cable modem-internet communications. Our testing shows that using a cable modem to access our radiology webserver produces acceptable transmission speeds to remote sites. The average time-to-display (TTD) for 16 computed tomography (CT) images on the web-based intranet system in our hospital was 7 to 8 seconds. Using a cable modem and comparable equipment at a remote site, the average TTD is 16 seconds over the internet. The TTD does not significantly change during various hours of the day. Security for our hospital-based PACS is provided by a firewall. Access through the firewall is accomplished using virtual private network (VPN) software, a secure ID, and encryption. We have found that this is a viable method for after-hours subspecialty radiology consultation.

Evaluating content management techniques for Web proxy caches

The continued growth of the World-Wide Web and the emergence of new end-user technologies such as cable modems necessitate the use of proxy caches to reduce latency, network traffic and Web server loads. Current Web proxy caches utilize simple replacement policies to determine which files to retain in the cache. We utilize a trace of client requests to a busy Web proxy in an ISP environment to evaluate the performance of several existing replacement policies and of two new, parameterless replacement policies that we introduce in this paper. Finally, we introduce Virtual Caches, an approach for improving the performance of the cache for multiple metrics simultaneously.

Embedded Processors for Networking and Communications

This paper shortly introduces the PowerQUICC microcontroller family. The PowerQUICC devices provide support for communications protocols such as ATM, HDLC, ISDN, multi-channel HDLC and 10BaseT Ethernet. The flexibility of the devices makes them ideal for equipment such as: SOHO and branch office routers; ADSL and cable modems; and intelligent switching hubs.

Performance evaluation of Web proxy cache replacement policies

The continued growth of the World-Wide Web and the emergence of new end-user technologies such as cable modems necessitate the use of proxy caches to reduce latency, network traffic and Web server loads. In this paper we analyze the importance of different Web proxy workload characteristics in making good cache replacement decisions. We evaluate workload characteristics such as object size, recency of reference, frequency of reference, and turnover in the active set of objects. Trace-driven simulation is used to evaluate the effectiveness of various replacement policies for Web proxy caches. The extended duration of the trace (117 million requests collected over 5 months) allows long term side effects of replacement policies to be identified and quantified. Our results indicate that higher cache hit rates are achieved using size-based replacement policies. These policies store a large number of small objects in the cache, thus increasing the probability of an object being in the cache when requested. To achieve higher byte hit rates a few larger files must be retained in the cache. We found frequency-based policies to work best for this metric, as they keep the most popular files, regardless of size, in the cache. With either approach it is important that inactive objects be removed from the cache to prevent performance degradation due to pollution.

Cable modem technology

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.