Mobile Phone Technology

The latest version of 3G technology (3G-HSPA+) has enabled faster speeds and greater capacity on the mobile phone network. However, there was still a demand for greater speed and capacity within the network. To address this, a new generation of network was implemented with an advertised speed of 100 Mbps. By its nature, 4G LTE is an evolution of the previous 3G HSPA+ technology. Although there were a number of potential technologies capable of delivering 4G, the evolution from previous networks was seen as the best solution. The aim of 4G LTE is to achieve higher capacity, reduced latency, and more efficient use of the spectrum.

4G LTE is an IP (data) network only, with no provision for a separate phone channel. Initially, the phone function was covered by the earlier 2G network. Therefore, to make a phone call, the original 4G network would drop the 4G connection and connect to an available 2G network instead. This led to complaints early on that 4G phones could not make phone calls, which was caused by the phone being unable to find a suitable 2G network. Even 15 years after the start of the 4G revolution, if a VoLTE connection cannot be found, the phone will resort to 2G calling. You can tell whether the phone is using 4G or 2G calling: on 4G calling, the "VoLTE" image appears on the screen and the call quality is better.

Two new frequencies were made available for MNOs to bid for when 4G was introduced. The 800 MHz frequency was seen as ideal for nationwide coverage, backed up by the 2.6 GHz frequency to provide additional capacity in congested areas such as city centres. EE and Three also use the 1800 MHz frequency for 4G, as there was spare capacity on this frequency. 1800 MHz was previously used by EE's predecessors for 2G.

As part of the frequency bidding process in the UK, one bundle included the additional requirement of a Public Service Obligation: one operator must guarantee 98% population coverage for 4G. O2 purchased this bundle.

In a 3G network, communications typically split the frequency into channels of an equal size. In 4G, however, the channels can be of different sizes and multiple channels can be used, even over different frequencies. Mixing and matching these technologies to implement this gives 4G better performance, as it uses the available frequencies more efficiently.

4G LTE is an evolution of the previous 3G HSPA+ network. Three key technologies underpin 4G:

• SAE - System Architecture Evolution
• OFDM (Orthogonal Frequency Division Multiplexing)
• MIMO (Multiple Input Multiple Output)

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