Wireless telecommunications, that is, telecommunications through the medium of radio waves, is rapidly emerging as the dominant force in development of infrastructure in emerging economies.
The use of radio for mobile services, microwave links, cellular telephone and broadcasting is well known and fairly widely deployed. Only recently coming on the scene are broadband radio services that not only provide the previously familiar wired services like telephone, but go beyond to high speed data and digital television access. Released from the bandwidth constraints, deployment costs, and security concerns of copper wires wireless digital services can provide public services not even imagined a few years ago.
Furthermore, the rate of adoption of these services even as submarket segments in many industrialized economies has been sufficient to drive technological development and device pricing to the point of affordability in less developed economies. Indeed, the deployment cost of wireless technologies is now well below that of conventional copper wire systems.
From a technical standpoint, three wireless telecommunications opportunities exemplify the trend. Wireless local loop, otherwise known as "WLL" is a direct stand-in for the familiar telephone line to the home or business. High speed data transmission called Wireless Digital Data or "WDD" permits business and Internet data connectivity at rates unavailable over telephone lines. Multichannel digital television distribution, frequently known as "MMDS" allows a direct path to home television receivers with dozens of program choices.
An added feature of these technologies is that a properly designed network, with adequate frequency spectrum, can often support implementations of all modes simultaneously. In fact, the most cost effective approach to making these advanced services available in developing markets will be to share digital bandwidth to the greatest possible extent. This has been recognized recently by the United States Federal Communications Commission, which is authorizing spectrum with no content or use restrictions save those necessary to protect other services from direct frequency interference.
All of these services best operate over frequencies in the area of 2000 to 3000 megahertz. An allocation of 200 megahertz of this spectrum permits effective development of systems that can deliver maximum services at minimum initial cost. Many already developed low cost consumer hardware devices are configured to operate from 2500 to 2700 megahertz, a frequency range that avoids conflict with satellite signals worldwide. In addition, additional spectrum is typically needed on a limited basis to support microwave interconnect links between infrastructure transmitting nodes. This should be readily available, based upon local design needs.
Wireless local loop is analogous with local telephone service, but much more capable. A WLL system serves a local area by deploying a multiplicity of multichannel transmit/receive base stations which are within line-of-site of the intended customers. Each customer is equipped with a mini-station of low power, into which the telephone (or PBX) is connected. When calls are made from the telephone, it signals the base station for a connection, which is subsequently established through a switch center, exactly as in conventional telephony. An incoming call is identified at the switch center and routed to the base station assigned to serve the telephone being called. The wireless connection is then made, and the call completed in a conventional manner.
In the manner described, a complete metropolitan or rural telephone system can be set up and operated in a manner transparent to the users. No wires are needed, no access to public ways is required, and all problems of theft and security of plant are avoided. Lacking exterior plant, reliability is greatly enhanced, as well designed WLL facilities do not significantly suffer from weather damage, vandalism, and accidents.
Most important, because the WLL system has much better bandwidth than traditional telephone systems, superior customer service features and quality can be provided. WLL systems support high quality data transmission, signaling services, and all the most advanced customer service features.
The infrastructure design of a WLL system typically uses an advanced transmission technology such as CDMA which permits support of large subscriber bases through orderly expansion of the base station clusters. Such systems can support a mixture of rural and urban coverage, permitting modern telephone services to be economically extended to less advantaged population groups. Services like public payphone can also be supported.
High-speed data is becoming an important part of the modern business and personal lifestyle. Until the advent of Wireless Digital Data there was no economical method available for the delivery of megabyte datastreams. However, the huge data demands of modern business, as well as the personal and business adoption of the Internet, have made such delivery crucial.
WDD is a wireless network technology that can be implemented in several forms. A typical configuration consists of broadband data transmitters located at strategic sites to transmit broadband data streams to antennas located at the sites of primary users in a market area. Receiving facilities of less bandwidth, WLL, or telephone access are established to permit a return path to complete a two-way data connection. Typically, more economical low bandwidth connections are feasible for one half of the WDD connection, although full broadband connectivity can be supplied to users desiring it.
The WDD network is connected to its own internal computer servers and routers which determine the flow of customer data and interconnection with external satellite, microwave, or fiber optic high speed data backbone networks.
Multichannel wireless digital television or MMDS is a technology that permits the simultaneous distribution of dozens of television programs to subscribers. Using strategically located, relatively low power, transmitters to broadcast multichannel signals, MMDS can "blanket" a region with reception capability that would not be physically or economically practical with conventional wired cable television.
The subscriber receive equipment is low cost, easily installed, and quite maintenance free. It can be programmed to respond to only authorized channels, making opportunities for the same network to support entertainment, private conferencing, education, and government channels without conflict and in full security. Moreover, the system technology will be capable of supporting high quality "high definition TV" in the future.
MMDS systems can also support a mix of analog and digital transmission, which provides for a migration path from an initial "conventional" analog TV offering to a "state-of-art" full digital facility in response to subscriber demand.
