LG Telecom's new CDMA-LTE network offers a glimpse of Sprint's future

For a sneak peak of Sprint’s new Network Vision architecture, one needs only look over the Pacific at the multi-radio network Samsung just deployed for LG Telecom’s U+ in Korea. LG, which is in the rather odd position of buying equipment from a company it competes with in many other industries, turned on its CDMA network this month, but plans to have long-term evolution (LTE) built on the same network nationwide by this time next year.

Sprint hasn’t officially announced its future mobile broadband plans, but all signs point to it beginning a large-scale LTE build this summer. Its WiMAX partner Clearwire is in discussions with Sprint about building a shared network over the former’s 2.5 GHz spectrum (CP: Clearwire hints at LTE build with Sprint), while LightSquared has penned a similar deal to build its wholesale LTE network on Sprint’s towers (Unfiltered: Sprint-LightSquared network sharing plans are a go).

Whatever partner or partners it chooses and whatever 4G technology it settles on, Sprint will have the right infrastructure in place, and that infrastructure will look very similar to the U+ network, said Tom Jazny, vice president of wireless broadband for Samsung. Along with Ericsson and Alcatel-Lucent, Samsung is building Sprint’s new Network Vision radio-agnostic architecture (CP: Sprint lays out a vague path to LTE).

LG and Sprint will use “the same basic hardware platform, which we’ve been calling our multi-mode, multi-technology base station,” Jazny said. “It’s a shared base station infrastructure, supporting multiple technologies at multiple frequencies. A lot of common hardware can be shared, and you can add or change over a technology without a new base station.”

Sprint and LG aren’t getting two networks for the price of one. Only certain elements can perform dual-duty. For instance, a single remote radio head can be used if both LTE and CDMA are on the same frequency, but in most cases, the two networks operate on separate bands, meaning separate radio heads need to be tuned to those distinct frequencies.

The baseband units, however, are radio interface agnostic, meaning they can support LTE or CDMA or a combination of both. But that doesn’t mean you can juice two networks worth of capacity out of baseband unit designed to power one network, Jazny said. Unless an operator is replacing one technology wholesale with another, it will have to add more baseband processing resources. An operator, however, can expand that baseband capacity through installing new line cards and software upgrades. It doesn’t have to install a new base station, which is what they would have been forced to do with older generation equipment, Jazny said.

While LG’s plans are fairly straightforward—a new CDMA network today followed by an LTE network tomorrow—Sprint’s cloudier network plans could benefit tremendously from the flexibility of the multimode architecture. For instance, its deployment with LightSquared is far from certain. If the FCC pulls LightSquared’s terrestrial network waiver, there will be no network-sharing deal of any sort (CP: LightSquared lashes back at GPS industry). If Sprint were to start building LightSquared’s LTE network, it could always change course and allocate those baseband resources to another technology or another frequency, though it would have to toss the radio heads.

Sprint is also shutting down its Nextel iDEN network, presumably moving those frequencies over to CDMA. If later Sprint wanted to use those 800 MHz frequencies for LTE, it could switch radio technologies with a software upgrade. The same goes for its CDMA network at PCS. Sprint could even continue Clearwire’s WiMAX expansion on its new network and switch over to LTE at a later date.

Apart from the flexibility there’s also a sizable savings in the new architecture, Jazny said. Even though carriers still have to add baseband capacity to support new technologies, the networks share the same cabinet and thus the same footprint, the same cabling, the same power supplies and cooling units and the same backhaul. Jazny wouldn’t put an exact percentage amount on those savings, saying only that deploying the multi-radio architecture would cost some fraction of the cost of deploying two discreet networks.

“The savings will always be somewhat carrier specific, depending on how many technologies you plan to deploy and how many frequencies plan to use,” Jazny said.