Smart Radio is a Brain Behind the Antenna
To conceive of Baran's model of wireless, begin by thinking of the human eye and comparing it to a radio. Like a radio, the eye is essentially a device for converting photons into electrons, pulses of electromagnetic energy into electrical currents. Geared for visible light rather than radio frequency signals, the eye is a receiving antenna. As radio technology moves up through the microwaves toward the infrared realm-with infrared wireless links from Canon now reaching 155 megabits per second-many of the differences are dissolving.
Yet, in the crucial index of performance, the radio is drastically inferior to the eye. While most radios can receive signals across a span of frequencies ranging from the kilohertz to the megahertz, from thousands to a few million cycles a second, the eye can grasp signals with a total bandwidth of more than 350 trillion hertz (terahertz). That is the span of visible light, from 400 terahertz to 750 terahertz, red to purple.
How is it that your eyes command 350 terahertz of bandwidth and your FM radio around 20 megahertz, 17 million times less? It is not chiefly the special powers of the retina and other optical faculties. Radio antennas can collect an even larger span of frequencies. The difference is mostly behind the receiver. Backing up the eyes is the processing power of some 10 billion neurons and trillions of synapses. Backing up the radio antenna is a lot of fixed- analog hardware. Eyes are smart and aerobatic while the radio is dumb and blind.
In Baran's vision, the future of wireless is the replacement of current dumb radios by smart digital radios that resemble eyes. Coupling radio technology with computer technology, the antenna can acquire a brain. Smart radios can eventually process gigahertz of spectrum (billions of cycles a second). They can sort out the frequency channels much as eyes sort out arrays of color, and pin down codes and sources of radiation much as the eyes descry different sources, shapes, and patterns of light. For example, a smart radio could process phone calls, videos, teleconferences, geopositioning codes, speed-trap lasers, and emergency SOS's.
The result will be a transformation of the nature of the spectrum. The current real estate model will give way to a new view. Rights to spectrum will roughly resemble drivers' licenses for use on the highways. Today you use your 350-terahertz eyes to survey the highway in front of you and avoid other traffic. As long as you do not collide with other users, pollute the air, or go too fast (use excessive power), you can drive anywhere you want. As radios are computerized, they will be able to "see" the radio frequency spectrum as your eyes see the roads. Smart radios will be licensed to drive in open spaces in the air as long as they don't collide with other radios, overpower them, or pollute the airwaves.
As Baran argues, the fulfillment of this dream is at hand. It is the broadband digital radio or software radio. Essentially, the radios used in cellular or PCS (personal communications services) phones will be able to differentiate among frequencies; they will be able to tell which direction a signal is coming from and isolate it in space; they will be able to identify the language of codes and protocols and waveforms that it is using and download software translators. No longer caught in a dedicated set of channels, time slots, protocols, data types, and access standards, radios will be smart and agile rather than dumb and fixed frequency.