xG Technology was exhibiting at the WISPA conference in St. Louis July 21-22, as they also did at the 4G Wireless Evolution conference in Miami in January. In January, I visited their facilities in Fort Lauderdale and talked at length with their founder, Joe Bobier. This is a company that, back in 2006, made some outrageous claims for a new kind of radio modulation. At the time, some friends asked me to look into their claims. I read their literature and their patent filings and concluded it couldn’t work as claimed without violating either the laws of physics or FCC regulations or both, and I wrote a blog post to that effect. Indeed my original conclusions appear to have been true. In 2006, they naively thought they could get the FCC to change specs for out-of-band signal levels.
What’s interesting is how they have completely reinvented their company. They have dropped the magic modulation ideas of 2006. Today, they are in alpha test with a mobile voice telephony system that uses conventional first order modulation. I don’t know whether they will succeed in the market, but today’s product is at least built on credible technology, they are going after plausible customer sets, and what they’ve done is cute enough (from a techie point of view) to be worth some discussion.
Their system allows a service provider to delivery a cellular mobile voice service much like any other mobile voice service plus it can support optional data services at GPRS-like data rates. The key difference is their system uses license-exempt spectrum in the 900 MHz band, thus avoiding big bucks for spectrum licenses. They deal with interference from other users of the 900 MHz band by monitoring in both frequency and time and rapidly switching channels (up to 33 times/second) to avoid interfering signals.
Of course there are no standards for such a system so, while the RF technology is now very conventional, the base stations and handsets are proprietary. They have adapted VoIP and SIP standards where possible, so their MSC is just a conventional 3rd party softswitch. However, some of how they handle channel hopping, roaming and handoffs is inconsistent with IETF standards, so they have a SIP proxy and a DHCP proxy that together isolate their proprietary protocols (used over the air) from the rest of the system which use standard IP components and standard SIP.
I don’t know whether their business will work or not. Their current system delivers mobile voice telephony plus data at 2G speeds, but it doesn’t roam. It might be a good fixed line replacement providing city-wide cordless telephony, not unlike the PAS systems deployed in China, but with no need for spectrum licenses. I wish them luck.