5G / New Radio Use Cases
5G or New Radio (NR) is a next (fifth) generation of mobile networks after LTE (the forth generation). While next versions of LTE specifications are under development and there will be further LTE evolution, there is a new standard published that defines 5G. During early days of LTE it was developed primary to provide subscribers with Mobile Broadband services (MBB) based on IP connectivity. Later LTE specifications were extended with new functionality to support another use cases as well. For example new functionality includes an ability to support a massive number of low cost devices for IoT (Internet of Things) use cases that have specific and different requirements comparing to initial MBB use cases. In contrast to LTE 5G covers the following three classes of use cases from the beginning:
- enhanced Mobile BroadBand (eMBB)
- massive Machine-Type Communication (mMTC)
- Ultra-Reliable and Low-Latency Communication (URLLC)
eMBB (enhanced Mobile BroadBand)eMBB is more or less straightforward evolution of mobile networks (as it was mentioned above MBB is an initial use case for LTE). 5G should push further network throughput and enhance user experience. For 5G target throughput is up to 20 Gbps in downlink channel (i.e. from a base station to user equipment). To meet this requirement new frequency bands are needed for 5G to form channel with bandwidth of up to 1 GHz. Another enablers of such high throughputs are multi-antenna transmission and beamforming. There are not so many free bands in low frequencies (<6 GHz) as most of bands are allocated already. So to have ultra wide channels 5G networks can be launched using millimeter waves (e.g. 28 GHz). In this range there are quite many free bands that can be allocated to provide mobile wireless services. While low frequencies (ideally <1 GHz) are used to provide appropriate network coverage.
Multi-antenna transmission is an important component of 5G network especially in high bands where waves propagation is very limited. Multi-antenna transmission improves network coverage and increases spectral efficiency. Below there is a table that shows an order of peak rates per frequency band (source).
|Peak Rate, Gbps
|24 - 28
|2х2 / 4х4
|10 / 20
|3.3 - 4.9
mMTC (massive Machine-Type Communication)mMTC is about a massive number of devices such as various sensors and meters, remote equipment monitoring and so on. Typically these devices are low cost (<5$). Another distinctive feature of such devices is very low energy consumption and relatively small amount of transmitted data. So high rates are not required for this use cases. While an ability to support a lot of devices that infrequently transmit small packets (usually delay tolerant) and effective UE (User Equipment) energy saving features are key building blocks in this area.
URLLC (Ultra-Reliable and Low-Latency Communication)These class of use cases is partially (or even mostly) about machine-to-machine communication as well as the one above. But in contrast to the previous one this class is also about ultra low latency (<1 ms in one direction) and extremely high reliability. Examples that fall into this bucket are factory automation, traffic safety and Vehical to Everything (V2X), robots control and remote medicine and so on. To meet requirements raised by this class of use cases there is a specific set of 5G features specified. For example support of mini-slot that allows to transmit data within a part of slot (aka TTI in LTE). That reduces transmission time on radio link between gNB (base station) and UE (user equipment). Moreover in 5G there are much more strong requirements on data processing time in gNB and UE, i.e. allowed time to process data is much shorter (comparing to LTE).
5G / New Radio RequirementsAs it can be noticed from listed above classes of use cases there is quite wide set of requirements for 5G. Moreover there are some contradicting requirements. This aspect brings additional difficulties and challenges for specification designers and network equipment vendors when they implement these specifications (as well as there are certain challenges during 5G networks deployment). Below in a table key 5G requirements are listed. It should be mentioned that it's hardly possible that all listed below requirements will be met simultaneously (e.g. all subscribers in a network have 20 Gbps rate and latency <1 ms). So the most part of below requirements represent corner cases that theoretically achievable with certain conditions or limitations.
|Peak Data Rate
|DL: 20 Gbps
UL: 10 Gbps
|assuming error-free radio conditions, all radio resources are in use
and assigned to a single user equipment
|Peak Spectral Efficiency
|DL: 30 bps/Hz
UL: 15 bps/Hz
|see comment above
|between MHz and GHz
|5G specifications are very flexible that allows efficient channels utilization of different bandwidth from MHz and up to GHz
|User Plan Latency
|URLLC: 0.5 ms
eMBB: 4 ms
|These values are defined for one way data transmission
|It sets the success probability of transmitting X bytes within a certain delay.
URLLC: X = 32 bytes, user plane latency 1 ms
eV2X: X = 300 bytes, user plan latency 3-10 ms
|This parameter sets MaxCL (Maximum Coupling Loss) that represents the maximum loss that a system can tolerate to correctly decode data. MaxCL is a difference between transmission power and receiver sensitivity. Current value is set assuming data rate of 160 bps
|UE Battery Life
and 15 years is desirable
|This KPI is defined for mMTC use case only. UE battery life is defined as the battery life of the UE without recharge. Here the following data rates assumed: UL <200 bytes and DL <20 bytes per day.
|User Experienced Data Rate
|DL: 100 Mbps
UL: 50 Mbps
|User experienced data rate is the 5% of the user throughput.
|1 000 000 device/km2
|Mobility is defined as the maximum user speed at which a defined QoS can be achieved.
The table above contains only key 5G requirement the rest and further details can be found at 3GPP TR 38.913 "Study on Scenarios and Requirements for Next Generation Access Technologies".