Case Study: Expanding LTE to 3G/LTE Multimode Small Cell Solution

Case StudyThere are several 3G only small cell products, and quite a few LTE only ones. But today’s market requirement in many regions for small cells is for multi-mode 3G/LTE. Here we describe how one vendor approached the task of expanding the scope of their solution to match that requirement, shortening development timescale, cost and risk by building it using mature 3rd party software.



Scope expansion

While there are a number of large networks happy to roll out LTE only solutions (e.g. Verizon USA, China Mobile, Reliance Jio India, South Korean operators), the reality is that the majority of today’s users and smartphones are 3G. VoLTE is still relatively in its infancy and many LTE networks still rely on 3G for voice service using CSFB. The industry requires 3G compatibility today for voice to support existing handsets while also wanting LTE for high speed data and future evolution.

Parallel Wireless had launched an LTE only small cell rural/outdoor solution but quickly recognised that there’s still a need for 3G capability. A true multi-mode solution would also allow them to enter the indoor/Enterprise market. The scope would include both the small cell and the small cell gateway. [I’d note that the complexity of a 3G small cell gateway is considerably greater than an LTE one.]

The market window is relatively short – perhaps it will be a few years before LTE only will become widely accepted – so if a 3G development was to be undertaken, it was critical to complete it in a short timescale.

Technical Options

There was a clear choice between

  1. Developing their own 3G software stack from scratch
  2. Integrating an existing 3G stack from a 3rd party

The latter was selected because it would achieve much faster time to market, with lower risk (the mature software is already proven in the field, successfully interworking with other vendors). The development cost has been spread across many small cell vendors and a wide level of expertise captured from many different deployment scenarios in different regions.

The approach is future-proofed in that the software continues to evolve to support 3GPP standards. Vendors can select which subset of features they incorporate and enable/add others quickly when the need arises.

Why Radisys?

Parallel Wireless selected Radisys for the 3G software used in both their small cell and HetNet gateway. They valued Radisys’ market leadership in the small cell stack business, a mature feature rich small cell software solution with over 150 person-years of investment and more than 80 3G/LTE small cell vendor customers.

The software is hardware vendor agnostic and actively supported on all the leading chipsets. This meant it not only supported Parallel Wireless’ current hardware platform but is future-proofed should a decision be made to move to a different one later.

Radisys continues to invest in their software with a strong roadmap that tracks 3GPP standards. They are agile enough to respond to specific operator requirements while retaining long term focus with a single consolidated codebase. For example, they already have LAA demos and are well positioned for the latest Release 13 features. Any of their customers can take advantage of this in their own roadmaps and release cycles as and when they choose to do so.

Hardware (re)design

Parallel Wireless small cell hardware (called the CWS or Converged Wireless System) has been originally designed to support both 3G and 4G/LTE in a single footprint, sharing common backhaul and power.

Their small cell HetNet gateway is based on standard off-the-shelf servers without any customisation.

This meant that no new hardware development was required for 3G, considerably shortening the development timescale.


True multimode solutions aren’t just two independent parallel systems – a lot of interworking is needed between them to be effective. That includes handover and fallback, such as where a voice call is redirected to 3G when a device is using LTE.

One area where Parallel Wireless have added their own “secret sauce” is for SON (Self-Organising Network). The Radisys platform offers considerable choice here – you can use theirs or integrate your own as a third party SON.

Parallel Wireless HetNet gateway also integrates carrier Wi-Fi too, so this meant a three-way co-ordination with features such as traffic balancing making best use of all available resources.

The provisioning and management system was extended to enable “plug and play” installation and commissioning for both 3G and LTE.

Interoperability Testing

This was minimised by using the Radisys stack which had already been extensively tested between many different vendors. IOT testing with several leading core networks found very few issues that were quickly resolved. Testing with leading 3G RAN proved operation of hard handover using the Iu-h interface and automated neighbour list configuration.

Both companies praised the initiative by the Small Cell Forum and ETSI to hold and manage interoperability plugfests, which have proved a great success.


Good products are nothing without trained staff who know how to install and support them. The training and documentation was expanded to include 3G.

Operator specific aspects would include provisioning and integration for e911 (emergency) call routing and location services, so that these calls are directed to the correct answering call centres.[LM1] 

Parallel Wireless combined 3G/4G SON eliminates a lot of deployment challenges, making it as easy as installing Enterprise Wi-Fi.

Customer Approval

Operators have been quick to sign up for testing and live field trials to assess and prove the solution in the field.

The solution is currently in the trial stage worldwide including Europe, APAC, North America and LATAM. Watch this space for upcoming press announcements.

Learning points

3G is still king for voice. VoLTE has not yet been adopted so widely worldwide. While aiming for an entry point into the market, Parallel Wireless initially thought that VoLTE would be more mature by this time and invested in LTE on that basis. Although 3G was on the roadmap, it wasn’t so obvious a few years ago that 3G would remain critical for so long.

A 3G/LTE multimode product matches the market requirement today far more than any of the (excellent) 3G only or LTE only solutions commercially available. Accelerating the development of 3G into the portfolio by building on a proven 3G software stack from Radisys has allowed Parallel Wireless to deliver that capability quickly, cost effectively and with low risk for all.

We’ve illustrated the journey as an Infographic below (and a larger standalone version here), spelling out the  considerations for each of the 10 decision steps and the consequences in time and cost of taking the wrong path.

10 steps 3G MultiMode

Our thanks to Eugina Jordan, Parallel Wireless and Renuka Bhalerao, Radisys for their contribution in preparing this article. Both companies are sponsors of ThinkSmallCell.

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