Fixed Wireless Equipment

Next Generation Backbone Radio

DragonWave has updated its product line and now offers 1.6 Gbps throughput using two signals, one on each polarization.

by Alex Goldman ISP-Planet Managing Editor [March 17, 2008]

In conjunction with the opening of the CTIA show, Ottawa, Canada-based high end radio manufacturer DragonWave is announcing its newest line of radios, the Horizon Duo, featuring throughput of up to 1.6 Gbps, and a new box it calls the Service Delivery Unit, built to assist in the convergence of IP and TDM networks.

"The Horizon Duo has twice the capacity of any competitor," says Alan Solheim, DragonWave vice president of product management (of course it would because it delivers two RF signals, each carrying 800 Mbps).

The radio
The radio operates at frequencies from 11 GHz to 38 GHz. Channel size can rage from 7 MHz to 56 MHz, but throughput will be less in channels smaller than 56 MHz.

"Another subtlety," says Solheim, "is that in a packet based network, you have idle packets, so if the system is smart enough, you can avoid transmitting redundant information and increase throughput. In addition, smaller packets require less overhead (VoIP and video generate small packets; file transfers generate large packets). In optimum conditions, the radio can generate up to 900 Mbps of throughput per channel.

DragonWave is maintaining what it calls "flex", a fancy name for the fact that all radios are shipped fully capable, and customers buying cheaper products can unlock their potential by buying the appropriate software key.

In addition, for customers upgrading from other DragonWave products, the antennas don't need to be changed. "Service providers don't need to climb the tower or license new links," says Solheim. "They just unplug the cables on the existing indoor rackmount, plug in the Horizon Duo, and upgrade their capacity. It costs money to climb the tower, and then when you're done, you have to go back to the regulator and obtain permission for the spectrum."

Solheim adds that sending two signals through one radio cuts all hardware costs in half.

He sees the product being used in new high capacity wireless networks, both fixed and mobile, such as WiMAX and LTE. Traffic should rise faster than revenues, forcing ISPs to focus on costs, especially OPEX and cost per bit.

Another key market is fiber replacement. Fiber installs are both slow and expensive. Of course, we could also see this product being used as a temporary fiber replacement (over a period of 3 months to however long the install takes), with the radio removed once the fiber's available.

The Service Delivery Unit (SDU)
The SDU uses pseudowire technology to deliver a pure Ethernet packet flow to the radio. It can handle jumbo frames, an has a wide variety of optional interfaces (including fiber).

But the highlight is the handling of TDM, says Solheim. "In the past," he says, "encapsulated TDM circuits were not high enough quality, much like the difference between early VoIP and what we have now. We adopted timing over packet to allow the output signal to faithfully track the input signal."

Asked to elaborate, he later writes by e-mail, "Really what we are talking about is circuits which have been converted to packets, transported across a packet based network, and then reconstructed at the far end into a circuit again. This is done by taking the incoming circuit data stream (continuous bit stream), breaking it up into segments (packets), and then encapsulating each segment with a header to create a packet so the network knows what to do with that particular packet. It sounds complex, but it is all done in the hardware and is transparent to the user."

But doesn't TCP/IP have a retransmission component that could handle this issue adequately? "If you retransmit packets, you mess up the buffer," explains Solheim. "You need a mechanism to measure the network delay and subtract it from the input timing. This is not a solution for an arbitrary Ethernet network, but in a constrained subset, such as between the radio and substation, it works."

The result, DragonWave claims, is over 25 percent more T-1/E-1 circuits per RF channel.

The SDU combines the functions of what were several boxes in older networks. "Now you don't need a stand alone pseudowire box, an Ethernet switch, etc. Less hardware means less space and power used."

In addition, you don't need TDM components deep within your IP network, says Solheim. "You avoid needing separate Add Drop Multiplexers (ADMs) at repeater sites," he says. "This can represent a 35 percent to 45 percent cost reduction, if you include the lower price of Ethernet transit."

The bottom line
The goal of the system is to be future-proof, to deliver more bandwidth than you need now or in the near future. Of course, you don't know how much bandwidth you'll need in the future, so you want to have a network you can scale easily. Scaling a pure IP network, Solheim says, is far easier than scaling a hybrid network.

Pricing and availability
The Horizon Duo and Service Delivery Unit are available now from DragonWave and its distributors. Pricing is not disclosed.

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