The New Market in Software

Painting QR in Software The New Market

The cable television companies are in the midst of a transition from their traditional core business of entertainment video programming to a position as a full-service provider of video, voice, and data telecommunications services Among the elements that have made this transition possible are technologies such as the cable data modem These companies have historically carried a number of data services These services have ranged from news and weather feeds, presented in alphanumeric form on single channels or as scrolling captions, to one-way transmission of data over classic cable systems as discussed in 13 Information providers are targeting upgraded cable network architecture as the delivery mechanism of choice for advanced high-speed data services These changes stem from the commercial and residential data communications markets The PC and LAN explosion in the early 1980s was rapidly followed by leaps in computer networking technology More people now work from home, depending on connectivity from commercial online services (such as AOL, CompuServe, and Prodigy) to the global Internet Increased awareness has led to increasing demand for data service, and for higher speeds and enhanced levels of service Cable is in a unique position to meet these demands The same highly evolved platform that enables cable to provide telephony and advanced video services also supports high-speed data services There appear to be no serious barriers to cable deployment of high-speed data transmission

The cable platform is steadily evolving into a hybrid digital and analog transmission system Cable television systems were originally designed to optimize the one-way, analog transmission of television programming to the home The underlying coaxial cable, however, has enough bandwidth to support the two-way transport of signals The hybrid network is shown in Figure 14-4

Figure 14-4: The new hybrid data network Growth in demand for Internet access and other two-way services has dovetailed with the trend within the industry to enhance existing cable systems with fiber optic technology Many cable companies are in the midst of the upgrade to HFC plants to improve the existing cable services and support data and other new services Companies are taking different approaches to online service access For some applications, customers may be accessing information stored locally at or near the cable head-end or regional hub such as the @Home [ 1 ] services being offered in many cities This may be temporary until wide area cable interconnections and expanded Internet backbone networks are in place to allow information access from any remote site

Digital data signals are carried over Radio Frequency (RF) carrier signals on a cable system Digital data utilizes cable modems, devices that convert digital information into a modulated RF signal and convert RF signals back to digital information The conversion is performed by a modem at the subscriber premises, and again by head-end equipment handling multiple subscribers Look at Figure 14-5 for a block diagram of the cable modem

Figure 14-5: Block diagram of the cable modem A single 6 MHz channel can support multiple data streams or multiple users through the use of shared Local Area Network (LAN) protocols such as Ethernet, commonly used in business office LANs today This is where the industry began in the late 1970s when Ethernet networks were applied to the broadband coaxial networks Different modulation techniques are being tried to maximize the data speed that can be transmitted through a 6-MHz channel Modulation techniques include Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), and Vestigial Side Band (VSB) amplitude modulation Comparing the data traffic rates for different types of modems shows why the cable modem is so popular under today s environment Table 141 is a comparison of a file download of 500 Kbytes using different techniques Table 14-1: Comparison of transmission speeds Time to Transmit a Single 500 Kbytes Image Telephone Modem ISDN Cable Modem Source: CableLabs 288 kbps 64 kbps 10 Mbps 6 8 minutes 1 15 minutes Approximately 1 second

Careful traffic engineering is being performed on cable systems so that data speeds are maximized as customers are added Just as office LANs are routinely subdivided to provide faster service for each individual user, so too can cable data networks be custom tailored within each fiber node to meet customer demand Multiple 6-MHz channels can be allocated to expand capacity as well Some manufacturers have designed modems that provide asymmetrical capabilities, using less bandwidth for outgoing signals from the subscriber Cable systems in some locations may not have completed system upgrades, so manufacturers have built migration strategies into such modems to allow for eventual transmission of broadband return signals when the systems are ready to provide such service and customers demand it A representative sample of the way data speeds are provided on cable modems is shown in Table 14-2 Table 14-2: Representative asymmetrical data cable modem speeds Sample Cable Modem Speeds General Instrument Hybrid/Intel LANcity Motorola Zenith Upstream 15 Mbps 96 kbps 10 Mbps 768 kbps 4 Mbps Downstream 30 Mbps 30 Mbps 10 Mbps 30 Mbps 4 Mbps