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Backhaul

Verizon's Backhaul Speed Race

Verizon Wireless said at the recent CTIA show that it aims to get 100-Mbit/s links to its cell sites as it moves to Long-Term Evolution (LTE), matching the current maximum speeds offered by the proto-4G base stations but not the some of the prototypes that vendors are already showing off at tradeshows and other events.

Backhaul -- the part of the network that links the radio elements to the wired Internet -- is the largest and most often overlooked gating factor for mobile broadband services. "You can’t simply have very fast links on the airlink side and really have it constrained on the backhaul side," Brian Higgins, executive director of the Verizon Wireless LTE Innovation Center, told LR Mobile in Vegas. (See CTIA 2010: Verizon LTE Gets Friendly.)

Verizon is trying to head off any backhaul issues upfront with fiber and -- occasionally -- microwave links to its LTE cellsites. As we have seen with AT&T Inc. (NYSE: T)'s iPhone 3G issues, having inadequate backhaul in place can result in bad publicity from big-ticket users. (See AT&T to Spend $2B More on Wireless in 2010 and AT&T Mobile Boss: NYC & San Fran Are 'Underperforming'.) "The view right now is that we're targeting to get 100-Mbit/s connections to each individual cell site," Higgins said of Verizon's backhaul plan. Click on the video for more:

Many US cellular networks use T1 lines, which provide 1.5 Mbit/s and can be bonded together for better performance. As we've already seen, this old, copper-based technology sometimes can't keep pace with 3G data demands, let alone a network that Verizon is hoping will get 5- to 12-Mbit/s downloads on average. Higgins claims that LTE performance will represent "a 10x increase over 3G."

The backhaul speed race, however, likely won't end there for Verizon or other carriers deploying proto-4G services. Infrastructure vendors, looking to capitalize on fast-growing demand for data services, are pushing LTE beyond its originally planned maximum speed of 100 Mbit/s downlinks from a base station.

NTT DoCoMo Inc. (NYSE: DCM) was already showing off 250-Mbit/s links on LTE in 2008. Huawei Technologies Co. Ltd. claims to have a commercial basestation that will support 150 Mbit/s. The technology has been pushed beyond 300 Mbit/s in tests. (See DoCoMo Takes LTE to 250 Mbit/s and LTE Hits 300 Mbit/s.)

It is questionable what some of these speed increases will actually mean in the real world. The 100-Mbit/s link that Verizon is talking up certainly accounts for the top line of LTE infrastructure performance for now. There are other factors to take into consideration, however, such as how many base stations are located at a cell site and how RF conditions for a particular location might actually affect the end performance of the radio network itself.

Hence, the difference between the base station performance and the link speed users can expect from this faster -- but still shared -- medium.

— Dan Jones, Site Editor, Light Reading Mobile

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