Skip to main content

LTE deployment options: Make the best choice

LTE deployment using a network overlay for rapid wide area deployment is a more efficient approach than adding LTE support as part of an overall cell site upgrade using single radio access network (RAN). In this article, I’ll review both options and share projected implementation data that supports choosing the overlay model.


Among the 1st things to consider is the difference in market potential between deploying 3G and LTE. When 3G arrived there were very few 3G phones available, but today a big percentage of new phones are already LTE-enabled -- even in markets without LTE service. This means that an operator might have a big potential market of LTE users waiting even before he begins to offer LTE service.

Other considerations include the mix of feature versus smart phones and pre-paid versus post-paid service contracts which, when taken together, will give a good indication of the number of users who will jump to LTE once service is launched. Also the legacy network design and equipment age.

Another issue is whether or not there are any regulatory requirements. For example, are there any minimum coverage rules associated with the new LTE licenses?

And do you have a large data traffic load from LTE-ready dongles? Then it’s probably a good time to rapidly deploy LTE to shift off a big part of your data traffic and free up legacy capacity for voice services.

In terms of network design, how much spectrum do you have and how much refarming can you potentially do? Spectrum is a key factor. For LTE coverage it’s good to have a low band, while for adding capacity it’s useful to also have a high band.

And for additional capacity in high usage areas:

  • Where do small cells figure in your planning?
  • Do you have lots of cell sites in high traffic areas?
  • Do your sites have enough room for additional LTE kit?
  • How old is your legacy 2/3G radio gear?
  • Can you keep it in place to carry the remaining legacy users while you switch investment to LTE? Or are you going to be forced to also swap out 2/3G radios despite declining traffic loads?


There are 2 distinct options for operators to consider when deploying LTE:

  1. Gradual rollout with selected cell site upgrades driven by capacity needs
  2. Rapid wide area deployment

Likewise, there are 2 distinct ways to install LTE at a cell site. LTE can be added as an overlay while leaving the legacy gear in place. Or the existing legacy network infrastructure can be replaced with a new radio system that can carry 2G, 3G, and LTE – the single RAN approach.

Single RAN renovation is often used during gradual rollout approaches while LTE overlay provides a faster path to achieving rapid deployment.

Gradual rollout using single RAN
With this option, the operator deploys LTE into the cell sites where extra capacity is needed while continuing to grow the 3G network.

Single RAN means you have to plan a 2-step upgrade process:

  1. Replace your legacy 2G and 3G gear with a new 2G/3G single RAN
  2. Go back and upgrade the cell site to also support LTE once it’s stable and you are sure the legacy network quality has been retained

In a nutshell, it’s more work.

However, there is a trade-off here. Since you now have more modern equipment in place, you’ll expect to see a reduction in OPEX on your 2G and 3G service. But you also have to think about how long you’ll leave your legacy kit switched on for as traffic declines, how much longer it will take to do this 2-step process, and how much you really will save compared to how much more you have to spend on upgrades.

Rapid wide area deployment using network overlay
This method involves a “big bang” deployment, where the operator seeks to cover as much ground as possible as quickly as possible. With this option, operators actively move as many subscribers as they can onto LTE – and so may rapidly stop the need for continued CAPEX on legacy access technologies.

What overlay means in real terms is that you leave your legacy 2G and 3G gear in place and add new LTE gear to the network. You don’t need to reengineer anything beyond potentially freeing up legacy bands like 1800 MHz for refarming.

This deployment method means you don’t negatively impact ongoing operations, and the well-defined interworking processes mean you ensure seamless mobility. It’s a way of rapidly deploying LTE while at the same time stopping legacy CAPEX spending on your RAN. And it’s the method that most of our tier 1 customers have used.


Alcatel-Lucent used a long term network dimensioning simulation tool built by our Wireless CTO Office that uses public information to compare LTE deployment estimates around the world. In 1 test case, using a Tier 1 North American operator:

  • Deployment was rapid
  • LTE adoption was aggressively marketed
  • 2G and 3G subscriber numbers began to decline quite quickly as 1st power users and then a majority of smart phone users migrate to LTE

This is the LTE overlay approach. It targets fast rollout, getting to sites quickly, and adding LTE service. It’s also about investing in the future and lets the operator quickly halt legacy CAPEX spending.

We can see this case illustrated in the following graphs showing our estimates for 2010-2018 for subscriber mix, LTE rollout, and the corresponding change in relative annual investment on radio gear.

With this approach, overlay, the migration path is fast and LTE is also getting to a large number of sites very quickly.

Alternatively, a European operator took the opposite approach: A slow rollout driven by capacity relief, slow adoption route with minimal marketing, and a single RAN network design. They swapped legacy gear in about 50% of cell sites — with the net effect of continuing traffic growth on 3G that required continued investment in legacy gear while also investing in LTE.

The graphs below show these estimates.

To further clarify the impact of this strategy, we then looked at what would happen if this operator had taken a different track -- with accelerated adoption and rollout and an LTE overlay approach. The following charts illustrate the change.

What this means is that the operator would have ceased 3G investment sooner and could have gone from 38% total investment in LTE to almost 46% while reducing the peak spending rate by 30%.


Ultimately, we come down on the side of overlay for deploying LTE most effectively.

Single RAN takes longer to deploy – at least an extra year -- and in the meantime traffic on your 3G network will keep climbing. The net effect is higher costs. You need to swap out your legacy gear for single RAN, increase your 3G capacity to handle the delayed rollout, and still invest in LTE.

If you choose overlay for LTE deployment, you maximize your CAPEX for the long-term, and you don’t have to touch legacy networks either – meaning a faster, more efficient rollout, more immediate benefits, and a genuine ROI.


LTE overlay: Better for your customers, better for your bottom line blogAmerica Movil selects Alcatel-Lucent’s LTE overlay technology for its 4G rollout in the Dominican Republic press releaseOverlay LTE networks: The quickest way to mainline your 4G

To contact the author or request additional information, please send an email to

Alistair Urie

About Alistair Urie

Alistair URIE is currently Architecture Strategy Director and lead for 5G Strategy in the Alcatel-Lucent Wireless Product Division and Bell Labs Fellow. His main interests include 5G mobile systems, LTE/EPC networking, legacy and IMS interworking, small cell systems, cellular/WLAN interworking and spectrum management. He has previously worked in Alcatel-Lucent on end-to-end network solutions, network strategy, hybrid terrestrial-satellite broadcast networks, standardisation management, mobile systems product strategy and international research programmes (European RACE Programme) for GSM and UMTS systems.
Prior to joining Alcatel in 1991 he had been involved in both line and radio transmission system research at the Telecom Australia Research Laboratories and had also worked at the Dept. of Science Antarctic Division in Australia.
Mr. URIE was Vice-Chair of the ETSI Board and Chair of ETSI OCG. He has published numerous papers in conferences, IEEE magazines, Alcatel Telecommunications Review (ATR) and Bell Labs Technical Journal (BLTJ) and was guest editor for special editions of both ATR and BLTJ.

Article tags