As more power-line products move into the marketplace, the competition becomes intense for this technology's sweet spot, a coveted frequency range from 2 to 30 MHz that promotes optimal performance. Success depends on each product's ability to reliably operate within this spectrum. Thus, the industry's challenge lies in preserving the integrity of the medium to avoid problems between technologies vying for the same frequency.

Power line is inherently attractive for networking consumer products in four basic categories: control, data, multimedia and "last mile." Typically, power-line devices are built to address a specific market category but do not scale well into others. This results in numerous technologies occupying the same frequency spectrum, on the same wire, each supporting a different set of applications. For instance, data networks try to drive as much information onto the same medium as they can in a nondeterministic fashion not conducive to multimedia traffic, which needs guaranteed latency, bandwidth and prioritization. And last-mile networks must be capable of hosting and routing various services, so flexibility and high bandwidth are critical.

The industry must embrace power-line coexistence, to allow all devices-regardless of vendor or purpose-to utilize the same frequency range and co-inhabit the same wire. To accomplish that, the industry must embrace two main ideas: frequency-division and time-division multiple access.

FDMA is the solution of choice for allowing coexistence between in-home networking systems and last-mile access systems. This solution splits the frequency spectrum between isolated systems to eliminate contention. This is fairly effective, but minimizes overall throughput and potentially favors one system over another. Given these limitations, a coexistence mechanism that allows reuse of an unused neighboring system must be aggressively pursued.

TDMA would create virtual time slots, allocated to each compliant node through a "universal language." Each node could then communicate using its own native protocols and language during its time slot. It is imperative that a common TDMA mechanism be deployed to facilitate interaction between two in-home technology providers.

In short, two separate coexistence mechanisms must be deployed to solve two separate coexistence problems between in-home and last-mile access systems as well as between two in-home systems. The industry cannot afford to ignore the traffic jam that looms on the horizon.

Power line has tremendous promise, as long as its integrity stays intact. Any rogue effort claiming absolute supremacy on the power line will only damage its potential. The industry must embrace and implement a set of universal attributes to ensure the long-term viability of power line as a networking medium.

Alan Walbeck is founder and chief technology officer at Inari Inc. (Draper, Utah).