I attended the Telecom Infra Project Summit last week in Santa Clara where the OpenCellular Project (yes, a project within a project) announced a new grants program to make their OpenCellular base stations available for testing and piloting to organisations researching and/or implementing affordable access solutions.  This is a great opportunity for groups who may already be doing work with WiFi or dynamic spectrum but see the need for affordable GSM services in the areas in which they work, also for universities in the Global South to research cutting-edge low-cost access technologies.  For the time being, this will only apply to the 2G OpenCellular base stations that are currently in production but will soon be extended to LTE.  The prototype LTE OpenCellular (OC-LTE) base station was on display at the event.  The LTE platform is currently undergoing testing in preparation for production within a few months.

The fact that the OpenCellular project has chosen to develop 2G and LTE platforms but not 3G is what I want to dwell on in this article.  2G networks are mostly oriented around voice services although they are capable of data services at basic speeds and capacity.  There are still millions and millions of people without access to simple voice services in the world and the OpenCellular 2G base station directly addresses the economic limitations of extending access into sparsely populated areas where traditional mobile network operator models are unsustainable.  The decision to develop an LTE version of the OpenCellular base station makes perfect sense as LTE is the current standard for mobile broadband and offers better digital performance than 3G networks.

In the course of the event, I watched Navindran Naidoo present MTN’s plans for OpenCellular in which he emphasised the importance of legacy mobile technologies in Africa and the continuing need for 2G networks.  He also urged the OpenCellular project to develop a 3G version of their technology. Interesting!  And it is not just MTN that continue to see 3G as a relevant technology.  Only last week, Airtel in Tanzania announced a significant investment in expanding their 3G network coverage in the 900MHz band into rural areas.  In September, the Ghanaian regulator actively encouraged licensed operators to offer 3G services in the 900MHz band.  Airtel in Uganda completed a massive upgrade to 3G on their network in 2016, again in the 900MHz band.  Perhaps you’re like me and wondering, why would you choose 3G when you could have LTE? The answer is not as simple as it appears.

Slide from MTN presentation at TIP Summit 2017. Red ellipse emphasis is mine.

LTE Is A Leap

LTE stands for Long Term Evolution and in evolutionary terms it is a significant change.  The voice components of 2G and 3G networks are based on circuit-switched networks which allocate a dedicated ‘circuit’ for every call on the network.  The part of 2G/3G networks that serves data is separate from the voice and SMS side of the network.  LTE on the other hand is a completely packet-switched (IP-based) network where all services voice, SMS, data are delivered via IP packets. This allows for much more efficient use of the wireless network but means that a new protocol, Voice over LTE (VoLTE) is needed to deliver voice services over the network.  This can present a problem for network operators who still want to deliver basic voice and SMS services to the millions of users in African countries who still have feature phones that are only designed to operate on 2G or 3G networks. In many cases, operators deploying LTE networks are obliged to maintain 2G networks in parallel in the same areas in order to ensure full service delivery.

Deploying a 3G network might seem like a better option to operators in that 3G technology is usable by feature phones while still providing data services that can be considered broadband; a cost-effective compromise.  They downside is that it may end up costing the operators more in the future when they inevitably have to upgrade to LTE as smartphones proliferate and demand for broadband increases.

Voice call quality may also be a factor in decision-making on LTE vs 3G in that VoLTE is not regarded by some as delivering the same level of quality and reliability of voice services as 2G/3G circuit-switched networks.  Naturally opinions vary on this and VoLTE is only likely to improve over time but for operators that are already under pressure from their regulators on Quality of Service, this may be a near-term factor.

Spectrum Re-Use

Another motivation for operators to deploy 3G networks, especially in the 900MHz band, is that it is typically spectrum they already have a license for.  Regulators have been slow to make new spectrum frequencies available to operators to enable more broadband services.  Re-using existing GSM spectrum allows the operator to move forward in upgrading their broadband services without having to wait for regulatory approval of new frequencies.  Given the millions of dollars in fees that are being levied for new spectrum bands, re-using existing frequencies also represents a significant cost savings for operators.  The rub is that using the 900MHz band may mean taking down some of their existing 2G network.  Some operators will need to implement a technology that offers backward compatibility for feature phones and 3G fits that bill.  I also have the impression that new 3G technologies can be upgraded to LTE at a lower cost than older 3G networks.

It Depends

Thus there is no right or wrong as to whether low-cost 3G or LTE is the right technology to develop and deploy.  It depends on the operator’s existing networks, how old they are, what technologies dominate in terms of handsets, and what radio frequencies are available to the operator.  It also depends to some degree on how bold and disruptive the view of the operator is.  Consider Reliance Jio in India who have bet everything on LTE and an all IP-based platform. This forward-looking approach has allowed them huge efficiencies in moving billing and other services into the cloud.  It also positions them for future network growth and evolution.  This is an easier decision for a newer operator entering into a massive build-out than it is for an older operator with a vast legacy network.  Now, a dual-radio OpenCellular base station that can serve 2G and LTE, that would be an interesting idea.

Posted by Steve Song

@stevesong local telco policy activist. social entrepreneur. founder of @villagetelco #africa #telecoms #opensource #privacy #wireless #spectrum #data