It used to be that the obstacles that prevented a fixed-wireless signal from reaching its destination were ultimately the obstacles that kept the industry’s service providers from reaching all their potential customers.
The creation and maturation of non-line-of-sight technology however, is changing the face of the wireless broadband industry by working over, above and around objects that traditionally have stood in the path of a signal’s transmission.
Among those companies that are either developing or currently offering non-line-of-sight systems are Cisco Systems Inc., Iospan Wireless, Hybrid Networks Corp., NextNet Wireless Inc. and relative unknowns such as WaveRider Communications Inc. and Wave Wireless Networking, a division of Speedcom Wireless Corp. Each produces non-line-of-sight systems for various frequencies, including licensed-exempt and multichannel multipoint distribution service.
None-line-of-sight antennas work by reusing the same frequencies among various cell sectors. If something is standing in the way of a transmission path in one sector, the signal will hop to the same frequency in another sector to circumvent the problem, “producing the greatest aggregate throughput for the least amount of spectrum allocated,” according to NextNet, which was among the first companies to demonstrate an MMDS non-line-of-sight fixed-wireless product in January.
For example, NextNet’s multicell, sectorized system architecture typically uses a six-channel set of MMDS spectrum, with each of the six, 60-degree sectors occupying one channel.
At the heart of non-line-of-sight technology is Orthogonal Frequency Division Multiplexing, and each company has tweaked it a little to differentiate its product from its competitors. OFDM is a technique that divides a digital message stream into parallel streams, with each stream being carried by a separate frequency.
Iospan uses Multi Input Multi Output OFDM, which transmits data using multiple antennas at slightly different points in space. The data is broken into pieces and transmitted. Then the receiver processes the separate data flows and puts them back together, Iospan said.
BeamReach Networks, formerly Radix Wireless, combines OFDM with stacked carrier spread spectrum, which increases frequency diversity, and Cisco uses its own version of OFDM, called vector-OFDM. V-OFDM increases the tolerance of a wireless system to noise, interference and multipath, and can deliver multiple signals on a single antenna and receive the signals on multiple antennas. BeamReach has yet to launch a product, but Cisco’s WT-2700 multipoint and point-to-point systems are available.
Toronto-based WaveRider also has product in action. The company designs systems for use in the unlicensed 900 MHz frequency band, a frequency not typically used in the United States, but seemingly well-suited for wireless broadband connectivity, according to Charles Brown, vice president of sales and marketing for WaveRider.
“The 900 MHz band offers very good propagation characteristics. We get connectivity through the utilization of good spectrum,” Brown said.
The company debuted its LMS3000 non-line-of-sight wireless broadband system in late March at the International Wireless Communications Expo in Las Vegas. Platinum Communications Corp. in southern Alberta is using the system.
On May 8, Wave Wireless will unveil its PH9000 point-to-multipoint, non-line-of-sight product line for the unlicensed 2.4 GHz frequency band, and trials are taking place around the country of other non-line-of-sight systems, including those from Aperto Networks, Hybrid and Iospan.
