An Incremental Approach to LTE: Why and When HSPA+ Makes Sense

Wireless Broadband

An Incremental Approach to LTE: Why and When HSPA+ Makes Sense

By Paula Bernier, Executive Editor, IP Communications Magazines  |  September 01, 2010

This article originally appeared in the Sept. 2010 issue of INTERNET TELEPHONY.

If you’re a regular reader of INTERNET TELEPHONY, you may remember a March piece I did about how, while there’s a ton of talk about LTE (News - Alert) and 4G, many wireless service providers expect to invest in 3G for at least a little bit longer. Specifically, the article talked about how AT&T had announced Alcatel-Lucent and Ericsson as its 4G suppliers, yet stipulated that the 3G equipment it received by those vendors this year would have to be software-convertible to LTE.

Fabricio Martinez, service product management director for AIRCOM, a global company that specializes in network planning and optimization and OSS solutions for mobile operators, indicates that makes perfect sense given the traffic to justify a move to LTE simply does not yet exist.

As a result, he says, carriers that have an embedded base of GSM/UMTS (News - Alert) technology can first move from current HSPA technology to what’s known as HSPA+. Taking this increment path to 4G, he says, will allow wireless service providers to invest just a third (not including the cost of spectrum, if you still need that) of what it would cost them to jump right to LTE.

“What we are saying is that even though you will need the capacity [of LTE] in the future, it would be like buying a whole train to transport goods from one point to another and have the train pretty much empty,” says Martinez, noting that given most broadband cellular networks today deliver between 3.6mbps and 7.2mbps, the move to 21mbps-based LTE would be a two-and-a-half to three-times increase.

Martinez adds that the cost per new subscriber on a cellular network is typically in the $75 to $100 range. That cost is about $450 for HSPA+ networks, and a smaller $350 for LTE networks. The catch, he explains, is that this last figure is based on the assumption that the LTE network is working at full capacity.

“The benefits you get from LTE will come when you build up the traffic that LTE has been designed for,” he says.

Before we go any further with this discussion, let’s sort through the alphabet soup of air interfaces and what kind of bandwidth each can deliver. Companies like AT&T and T-Mobile (News - Alert) launched their 3G strategies about 10 years with the introduction of UMTS networks, which initially delivered 1mbps to 2mbps downstream speeds and about 384kbps upstream. Around the 2006 time frame HSPA came into vogue; it started out offering 1.8mbps or 3.6mbps downstream and kept the upstream at 384kbps. HSPA in the last two to three years expanded to support up to 3.6mbps upstream and 14.4mbps downstream. And HSPA+ delivers 21mbps to 84mbps downstream and 5.6mbps upstream, says Martinez.

“One of the key findings that we are presenting is when you go above 21mbps, because of the different changes you need to make in the network you will probably be doing what is needed to go into LTE. And LTE starts around 42mbps, 100mbps,” he says.

While HSPA+ will move a carrier more incrementally toward the much-vaunted evolved packet core, which is a key component of the LTE architecture, Martinez adds, it is still moving that service provider in the right direction.

So who is deploying HSPA+? Well, AT&T expects to. T-Mobile recently did. And several carriers in Asia and Europe have as well. In all, Martinez says, we’ve seen 110 deployments of HSPA+ worldwide.

“HSPA+ is happening in networks now,” he says. “It’s a reality now.”

In the U.S., T-Mobile is using HSPA+ in some markets today, says Martinez, adding” “I think it’s just a matter of time until AT&T will follow.”

And while Martinez doesn’t necessarily recommend it, there are a least a couple of deployments of HSPA+ at rates above the 21mbps HSPA+ cap AIRCOM prescribes. That includes SingTel (News - Alert), which is offering 42mbps HSPA+, and Telstra, which has announced HSPA+ at 84mbps.

Of course, not everybody is running to HSPA+. In fact, for some wireless operators like Verizon (News - Alert), it’s not an option, given they are coming from a CDMA background, says Martinez. That means they’ll have to advance straight to LTE.

However, he concludes, in this day and age in which funding new capital projects can be a hard sell, taking the incremental approach seems to make sense to many companies.

“The message is very simple: You can go to LTE in a cost-effective way by doing this,” he says. “By going to HSPA+ you solve the short-term issue, and still you keep your direction to what you want to achieve, which is LTE.”

Edited by Stefania Viscusi


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