Enterprise Small Cell Technology Choice: 3G or LTE or both?

3G LTERelatively few subscriber devices deployed today are LTE capable and even with the strong take-up of the latest smartphones, it will be some years before LTE becomes predominant. The wide range of different frequency bands available for LTE, as well as the choice between FDD and TDD modes, further complicates matters. Early LTE capable devices may be incompatible with the full range of frequencies becoming available to their service providers. LTE roaming is still in its infancy.

Operators are faced with a dilemma of whether to wait until LTE is more mature, deploying 3G/LTE multi-mode or even just LTE only. For outdoor/urban areas, it seems they are content to wait for LTE. Indoor/Enterprise seems to be another matter, with  3G readily available and able to address the real coverage issues facing in-building cellular service today.

 

Despite rapid adoption, it will still take a few years for LTE and VoLTE to grow

While LTE has been adopted more rapidly than any other cellular technology, it still only forms 3% of global connections. There is a strong regional variation: North America dominated with 50% of world's LTE connections at the end of 2013, totalling some 100 million = 25%. [Update: This dropped to 38% share at end 2014]. Worldwide, LTE is forecast to grow to 24% of mobile broadband connections by 2018. The majority of these will be in the higher value markets of North America, Europe and Asia which will pull through demand from other regions.

Perhaps the most important cellular service to address indoors is traditional voice, which is perceived to have been dropping in performance and quality over recent years. In 2013, voice service still generated 58% of mobile service revenues worldwide. With more voice calls minutes now being made over cellular than landline, it is this service that is most critical to protect.

VoLTE (Voice over LTE) is not yet widely deployed, and 2G/3G will continue to carry the majority of voice traffic for some years. Deployed extensively in a few countries such as South Korea, would not be so worthwhile until VoLTE service is widespread and the majority of the installed base of smartphones supports it. In Japan, NTT DoCoMo has only just announced the launch of VoLTE voice and video services from next month, with an initial device choice from four smartphones and two tablets. Singtel announced its VoLTE service launch at end of this month, featuring better voice quality and faster call setup times than using 2G or 3G. Call charges will be the same as for traditional voice, and can work using your bundle of voice minutes as before.

That "old chestnut" concern of RF interference from Small Cells

A serious concern raised by many RF planners relates to potential interference between Small Cells and Macrocells. With spectrum at such a premium, the industry wants to share and reuse the same spectrum for both. 3G wasn't originally designed with this in mind, and despite extensive studies and trials, some concerns remain about the viability of this model of operation. LTE was designed from the outset to cater for multi-layer HetNets, with features such as ABS (Almost Blank Subframes) and eICIC (enhanced InterCell Interference Co-ordination) built in to deal with these situations. For outdoor/urban use cases, it seems likely the industry will widely adopt LTE Small Cells and ensure these are tightly integrated with their existing macrocell assets.

Indoor service differs. The additional RF isolation provided by most buildings – especially those where in-building coverage is poor – generally satisfies the most sceptical RF planners that in-building 3G Small Cells won't disrupt the operation of their outdoor network. It is precisely inside those buildings that demand for better service is strongest.

Practical options for protecting the future

Deploying proven 3G technology is the simplest and cheapest short term option. Cautious operators looking for solutions that cater for both 3G and LTE to allow investment to be amortised over longer periods could choose from:

  • Multi-Mode Small Cells, capable of 3G, LTE and Wi-Fi simultaneously
  • Remotely upgradeable Small Cells, which can be software updated and reconfigured between 3G and LTE without a site visit or hardware change. These would typically not handle remote upgrade between significantly different frequency bands.
  • Modular upgradeable Small Cells, where a cartridge or pluggable module can be swapped and replaced.

Many of the latest underlying silicon chipsets from vendors such as Broadcom, Qualcomm and TI support these capabilities. These have been used within Enterprise Small Cell products from vendors such as Cisco, SpiderCloud and (coming soon) Alcatel-Lucent amongst others.

Jump now... or continue to wait

The cellular industry is often cautious to await the next big technical leap before investing in the current one. It's a bit like waiting for the next model of laptop or smartphone before upgrading. At some point, you just have to make a commitment and those operators who have already done so may find themselves ahead of the game.

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