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Spectrum is one of the most critical assets for mobile network operators (MNO) to support the exponential growth of data traffic driven by social media such as Facebook, YouTube and Twitter. Adding new spectrum is one way of increasing capacity to a wireless network. However, new spectrum is not always available and can be expensive to license when auctioned by regulators.
For these reasons, MNOs need to make the best use of their available spectrum. They are always striving to improve their networks to achieve better spectral efficiency. Spectral efficiency is measured as the number of bits per second that can be transmitted in a given single hertz of used spectrum.
It’s a known fact that 4G has better spectral efficiency than 3G -- up to almost 6 times better according to Ofcom -- because it uses more advanced techniques to improve the number of bits transmitted per single hertz of spectrum. Some of these techniques include higher modulation schemes such as 64 QAM (which means that a single transmitted symbol contains six bits of information) and radio techniques such as MIMO (Multiple-Input Multiple-Output).
So why don’t MNOs switch off their 2G and 3G networks today and move all their systems to 4G to gain spectral efficiency?
It is not that simple because mobile networks still have to support legacy services. It is ironic that today we may need to consider voice calls as a legacy service because that was the reason why mobile networks were designed in the first place. However, when I look at how my teenage children use mobile phones, I really feel this.
Today 4G does not support voice call functionality, and on some networks you can see this if you look at your smartphone when starting a voice call. You will see the 4G icon changing to 3G before the call is established. This network feature is called CSFB (Circuit Switch Fallback). However MNOs are quickly deploying a network function called VoLTE (Voice over LTE) that supports voice calls over 4G, thus solving this issue. Every MNO is setting up a date during the next two to three years when 3G will be completely replaced by 4G.
What about 2G? Here surprisingly the challenge is more difficult to solve because there are some other legacy services that totally rely on 2G. You may be surprised to know how many machines today use connectivity to 2G networks to operate. For example, the waiter taking the bill to your table most likely uses a credit card machine connected to a 2G network to conduct the wireless transaction. Another example is if you find your preferred vending machine out of coffee, then that vending machine is likely sending a SMS text via 2G to the company in charge of refilling it. This is the reason I believe it will take longer to switch off 2G networks.
So for at least the near future and likely longer, MNOs are going to need to support multiple technology services in their networks. Technology like 4G will continue to provide the best possible data service and 3G will likely be going away, but 2G will stay around longer. Subscribers will be on 4G networks for checking emails, but to purchase coffee, a 2G network will likely need to be in place for machine-to-machine (M2M) communications. MNOs will need solutions to make adding and managing multiple technologies more effective both indoors and out.
What challenges do you face in supporting multiple wireless technologies?