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3G/HSPA

ArrayComm's Highspeed Handoff

Belt up, readers! ArrayComm Inc. has demonstrated the capability to hand off between its i-Burst basestations while driving around at speeds of between 30 to 40 miles per hour (see ArrayComm Hands Off Session).

For the demonstration, ArrayComm used an i-Burst wireless modem attached to a laptop computer. While driving between the basestation at its San Jose headquarters and another three miles away, the team streamed a live video feed, transferred a large file via FTP, and conducted several other typical Internet sessions.

ArrayComm's technology is different from standard 3G systems because it uses "unpaired" spectrum. Unpaired, or time-division duplex (TDD), technology allows one communications channel to be used for both upstream and downstream traffic, and is well-suited for data packet delivery and Internet connectivity. Frequency-division duplex (FDD) transmission, the flavor used by the major 3G systems, uses two separate channels for sending traffic back and forth. This makes it somewhat of a spectrum glutton compared with TDD.

Nitin J. Shah, executive vice president and general manager of business development and strategy at ArrayComm, says the vendor has been working on upgrading handoff capabilities for a while. "We've had this in design for a year, implemented it several months ago, and have been testing it on and off for a while," he says. "It's one of the last items we had to tick off on our feature set list."

Rivals such as Flarion Technologies and IPWireless Inc. say they already have high-speed handoff capabilities. In fact, your correspondent nearly got into a nasty accident during IPWireless's demonstration of drivin' and surfin' in Las Vegas earlier this year (see IPWireless Does Mobile 3-Step).

So, we wondered, exactly how new is all of this? "Well, say if you'd wanted to see this in the labs a year ago, we could have demonstrated it to you then," says Shah. "These are now fully installed units we're talking about." Basically, ArrayComm can now do it in the field (or on the road, or at the office…).

The firm is using the simple IP protocol for transfer between basestations. The call setup time – basically the time it takes the network to wake up after it has been pinged – is around 20ms to 30ms after a "complete cold start," says Shah. Similarly, network latency – the time it takes to send packets from one point to another on a network – is around 20ms.

Contrast this with a standard CDMA cellular network, where call setup can take up to four seconds and latency is typically somewhere under a second.

All well and good. However, we did wonder if this might currently be a technology in search of an application. After all, how many people are going to be surfing data on a wireless device while walking, driving, or cycling? However, Shah says that as network traffic increases, this handoff capability could almost be used as a load-balancing tool in a fixed environment, transferring users between basestations so they all handle roughly the same amount of traffic.

— Dan Jones, Senior Editor, Unstrung
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