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, at least in most urban and suburban areas. 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 an IP-centric, point-to-multipoint standard that quickly replaced the proprietary solutions that preceded it. DOCSIS has now become the accepted cable standard. Although it’s successful, DOCSIS 1.0 is a dataonly specification, with no support for voice or other latency-sensitive multimedia applications. The newly released DOCSIS 1.1 remedies this with quality-of-service (QoS) support for proper handling and delivery of multimedia and voice applications. DOCSIS has thus provided a standards-based way to deliver a rich variety of data types across cable TV systems. Many areas still exist, however, that don’t have cable TV service. To fill these gaps, other carriers are fielding fixed-wireless broadband networks. The attraction that wireless technology holds for carriers is it eliminates the need to cable tens of thousands of subscribers. Although it was intended for coaxial networks, many manufacturers of fixed-wireless communications equipment have found that they can effectively leverage the DOCSIS standard for the wireless environment, provided that they understand and compensate for the unique qualities and sometimes hostile environment of radio-frequency communications. With the necessary wireless enhancements, DOCSIS 1.1 is destined to play an important role in the delivery of high-quality multimedia across fixedwireless 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). In this article, 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. Fixed-wireless spans a significant portion of the spectrum from ultrahigh frequency (UHF) to unlicensed bands to multichannel–multipoint distribution service (MMDS), 3.5 GHz, and low multipoint distribution service (LMDS) at frequencies up to 40 GHz. Here, we primarily concentrate on bands under 11 GHz, including the 3.5-GHz band.