5G NR Spectral Efficiency vs 5G NR Energy Efficiency

5G NR Spectral Efficiency vs 5G NR Energy Efficiency provides difference between 5G NR spectral efficiency and energy efficiency and its formulas as per 3GPP 5G NR standard.

What is 5G NR ?

As we know, 5G NR (New Radio) technical specifications have been published by 3GPP release 15 and beyond. It operates in FR1 and FR2 frequency bands. FR1 has 450 to 6000 MHz range. FR2 has 24250 to 52600 MHz range in mmwave spectrum. 5G NR frame is 10 ms in duration.

The figure-1 depicts 5G NR architecture and its components. There are two modes in 5G NR viz. non-standalone and standalone. In non-standalone mode, it utilizes LTE network for control signaling. In standalone mode, 5G network handles both control signaling and data transfer part.

5G NR Spectral Efficiency

It specifies amount of information or how much data can fit in the given BW (Bandwidth). This limit is also called shannon limit as mentioned in the below equation.

From Shannon Hartley theorem, we can derive following points.
• Increase in channel bandwidth can help in increasing network capacity.
• Increase in number of channels can increase data rates and consecutively its capacity.
• Due to SNR in the equation, we can conclude that increase in output power from femtocells or eNBs can lead to improvement in energy efficiency of the network.

Spectral efficiency can be expressed as ratio of net data rate to channel bandwidth as shown in the following formula.

Example of 5G NR Spectral efficiency (downlink) :
INPUTs : Net data rate = 2.31 Gbps, Bandwidth = 100 MHz
Output : Spectral efficiency = 2.31 x 10⁹/100 x 10⁶ = 23 bits/second/Hz

Simiarly uplink spectral efficiency can also be calculated in 5G NR system.

5G NR Energy Efficiency

In general, energy efficiency refers to use of less energy to perform the same task or function. In other words, it means elimination of energy waste.

In traditional cellular network, one base station is used to transmit energy throughout the wide area coverage. Usually 120 degree of angular region is covered by one BS (i.e. Base Station or eNB). In 5G NR, one signal Base Station Antenna is replaced by 120 antenna array. The concept is known as Massive MIMO. The massive MIMO helps in achieving higher energy efficiency due to concentration of radiated energy on Mobile Subscriber (MS) or User Equipment (UE). Also refer difference between massive MIMO and mmwave MIMO.

Figure below depicts 5G NR energy efficiency using beamforming and using massive mimo antenna array.

Image Courtesy: Microwave Journal

Theoretically, when single antenna is replaced by 120 antenna array to target energy to individual users, required BS power is decreased by 0.1 % of original output power.
Practically, due to the efficiency and losses of RF components used in the BS, the output power decreases by only 30% of original power for the same capacity.

Difference between 5G NR spectral efficiency and energy efficiency

➨Spectral efficiency describes how much capacity can be provided. It is measured in bps/Hz (i.e. Bits per second per Hertz)
➨Energy efficiency characterizes how much it costs to run the 5G network for given capacity.