Business, Enterprise, Technology Security

The Future of VoIP? xMax Runs on Unlicensed Frequencies

Proving any new technology can be a daunting task, even if you have world changing technology, and xMax is exactly one such technology, that could significantly increase signal range of our mobile devices. xG Technology announced a contract to deploy on a trial basis its xMax cognitive mobile network over a large part of the US Army’s Fort Bliss Desert Training areas in Texas and New Mexico. xMax is a cognitive radio based mobile VoIP and data system that uses an end-to-end Internet Protocol [IP] system architecture and operates in the license-free ISM 900MHz band [902-928MHz].

How xMax works
How xMax works – Low power, low interference technology
Fort Bliss is the US Army’s largest training facility and a leading center for the testing of new weapons and communications systems. With an area of about 1,700 square miles [4,400 km2], it is the Army’s second-largest installation behind the adjacent White Sands Missile Range in New Mexico. Fort Bliss also provides the largest contiguous tract [1,500 sq mi, 3,900 km2] of virtually unrestricted airspace in the continental United States; the airspace is used for missile and artillery training and testing.
xMax Test PhonexG Technology is headquartered in Sarasota, Florida with central engineering facilities located in Fort Lauderdale, Florida. They will install a comprehensive xMax network solution at Fort Bliss consisting of several xMax BSN 250 base stations, an xMSC mobile switching center, and trial TX 70 handsets. This will allow the Army to evaluate xMax’s capabilities as a wide area and tactical cellular system. xG Technology will provide training and ongoing maintenance support after the initial setup of the network to ensure seamless transition of operational responsibilities to Army support staff.

Rick Rotondo, xG Technology’s VP of Marketing, explained that "xMax technology is a frequency-agile radio capable of detecting interference in real time, then handing off from channel to channel 33 times a second. Rather than looking at the frequency domain for interference, xMax also senses the time domain to slice the interference even further." xG Technology has developed a broad portfolio of IP [Intellectual Property] that covers wired and wireless communications systems. The company counts 52 patents or patent applications in the US, and almost 120 internationally.
Lieutenant Colonel John Moelter, Chief of Integrations, US Army Signal Center of Excellence, Fort Gordon, Georgia, said: "xG brings a capability we have not seen in any other products available today, especially in a cellular form factor."
Andrew Seybold, CEO and Principal Analyst of Andrew Seybold, Inc. said: "The US Army’s CERDEC is constantly evaluating new wireless technologies, and the fact that they believe that cognitive radio techniques have now matured enough to be considered as a viable option is not only good news for xG Technology, but also for better management of spectrum for all wireless customers moving forward."  
Cognitive [smart] radios are able to identify spectrum [i.e. radio frequencies] that is not being used, and to quickly tune to that frequency to transmit and/or receive radio signals. They also have the ability to instantly find other spectrum if interference is detected on the frequencies being used. Depending on the radio technology being employed, the detection and decision process can take a few seconds ? with the xMax system that time frame is only a matter of milliseconds.
Over the years, DARPA [Defense Advanced Research Projects Agency] has shown that SDR [software defined radio] cognitive radio tests demonstrated the ability to form an infrastructureless network automatically and without preplanned spectrum coordination that limits the present LMR [land mobile radio] based public safety networks.
The military and public safety use old style LMR based push-to-talk technology that requires an operator to change radio channels. With a cognitive radio, the radio is aware of its environment and location, then alters its power, frequency, modulation, and other parameters so it dynamically reuses available radio spectrum. This is critical for the military and public safety during a major disaster.
Joseph Bobier invented "xG" core technology. He also holds several additional patents for wireless technology. Bobier co-founded xG Technology with Rick Mooers and Roger Branton in August 2002. Bobier explains the xMax Network Architecture [PDF Download] as follows:
"The primary consideration in the design of the xMax system is the desire to provide robust, scalable, and full-featured voice and data services to mobile subscribers at a fraction of the cost of traditional approaches. A reference model form of the resulting Internet protocol centric network architecture is shown in Figure 1. As the diagram indicates, the network architecture includes the following elements:
xMax Network Architecture Reference Model
xMax Network Architecture Reference Model.

  • Air-interface designed for operation in unlicensed as well as licensed bands.
  • Base Station Node [BSN], which provides radio to network access to handsets, and Access Network Gateway [ANG], which provides call process and IP packet delivery services. The xMax BSN is a 3 sector, 18 channel VOIP basestation transceiver device. The BSN channelizes the 902-928 MHz band into 18 discrete channels, which are used only when there is traffic to mobile devices that are registered with a particular channel.
  • Radio spectrum util
    ization is highly efficient in that the system occupies only that spectrum which is necessary for individual data streams. The bandwidth of each channel is 1.44MHz with sufficient guard band between channels.
  • Technology agnostic backhaul links from BSN sites and the ANG [Fiber, Metro Ethernet, PTP [point-2-point] Wireless, etc.].

While the xMax BSN is conventional in both architecture and functionality, the ANG is a novel piece of wireless infrastructure equipment that consists of the following:

  • Ethernet Switch which aggregates BSN links.
  • Firewall which provides private to public network address translation [NAT] services SIP.
  • Proxy Server which supports SIP call control, SIP message compression, and E911 services.
  • Proxy DHCP Server which is used for IP address services.
  • Network Monitor which is responsible for end-to-end network management and monitoring services.

Sprint Nextel is presently the commercially available wireless technology which does some of what a true cognitive radio will do. If you are carrying a Nextel push-to-talk radio handset in the field, you can reach a nearby mobile radio tower. The mobile system telephone-based backbone [operated by Sprint] will haul your conversation to another Nextel mobile radio base station and deliver the voice call to another Nextel user.
xG Technology’s xMax has tremendous potential for deployment throughout the world. We asked Fernando Cassia, a technology writer in Argentina what is happening in their ISM 900MHz band. Cassia said: "here, we have a single operator in the Buenos Aires and Greater Buenos Aires area with a 900MHz license. It is Hong Kong’s Hutchison Whampoa. They use the 900MHz GSM equipment to provide "fixed wireless" service, that very same service is restricted to a single cell where your home is, and your number has a POTS, fixed line area code and land line rates-as an alternative to land lines in poorer neighborhoods. So for broadcast or providing mobile services, you have to request a license down here. However, for point-to-point links with directional antennas, nobody seems to complain, as long as you don’t interfere with someone else with a legit license."

Challenges faced by xMax technology: Open opposition by legacy carriers of mobile phone and TV signals, gathered around CTIA and lobbys that pressure FCC
Challenges faced by xMax technology: Open opposition by legacy carriers of mobile phone and TV signals, gathered around CTIA and lobbys that pressure FCC

There are several homebrew SDR systems available including Flexradio for techy types to experiment with the ideas behind cognitive radios. Bottom line on this story is very simple: if tests at Fort Bliss with different equipment prove that xMax can be used without major issues and will not interfere with the existing networks, rather supplement them, opposition formed around CTIA and TV networks might lose their teeth. And that would open the opportunity for worldwide implementation.