LTE was designed mainly for the delivery of mobile broadband over smartphones. However, a progressive flattening of broadband revenues has led network operators to seek out new markets and new use cases, in which connectivity can provide economic benefits. These use cases often have different use cases from those of mobile broadband. Some of them, for example mMTC (Massive Machine Type Communications), can be addressed by enhancing the LTE specifications. However, other use cases cannot be supported so easily over LTE, and require a new technology to address them properly. The technology is known as the 5G New Radio (NR).
Most of the use cases envisaged for 5G, including the continued evolution of mobile broadband, demand higher data rates from the network. That is provoking a drive towards higher radio bandwidths, and hence to higher radio frequencies: millimetre waves at frequencies of tens of GHz. The nature of radio propagation is different in these frequencies from traditional UHF (Ultra High Frequency), and requires a new technology, that being the main driver for the development of the 5G New Radio. The US FCC’s (Federal Communication Commission) 2016 allocation of millimetre wave bands for mobile telecommunications has been an additional driver in this respect.
Similarly, some of the use cases envisaged for 5G, namely ultra-reliable low-latency communications and vehicle communications, require very low latencies, of order milliseconds. Although the LTE specifications have been enhanced to address this use case in part, the 5G New Radio can reduce the latency and increase the reliability further.
Another limitation of LTE is the amount of power that the base stations and mobiles consume. This is expressed using a quantity called the energy efficiency, which is the amount of energy required to transmit each bit of data. Even if LTE could be enhanced to deliver the high data rates that are envisaged for 5G, its underlying design means that the power consumption would be excessive. Once again, a new radio communication technology, with a lower power consumption, is required.
As each generation evolves, it becomes constrained by the need to maintain backwards compatibility with legacy devices and networks, and the specifications become increasingly complex. Such issues limit the extent to which LTE can evolve. By introducing a new generation, the specification process can begin from a clean slate, and can properly address all the use cases that are envisaged, both now and in the future, in a more efficient and flexible way.
It is expected that early 5G networks will combine the 5G New Radio with an enhanced version of LTE. This will allow operators a smooth upgrade path from their existing LTE networks, and will ensure a smooth improvement to the consumer’s mobile broadband experience.