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Spectral efficiency

It is also referred to as Spectrum efficiency or bandwidth efficiency. It refers to the information rate that can be transmitted over a given bandwidth in a communication system. It is a   measure of how efficiently a limited frequency spectrum is utilized by the physical layer protocol and sometimes by the medium access control protocol. The link spectral efficiency of a digital communication system is measured in bit/s/Hz. 

Spectral efficiency is an important consideration for 5G-NR radios, as it was for 4G/LTE. The amount of information that fits in a given channel bandwidth or one just say how efficiently can that piece of spectrum be used to transmit information. Net data rate and symbol rate are related to the raw data rate which includes the usable payload and all overhead. 

  • Raw data rate: Payload + Overhead
  • Net data rate: raw data rate - Overhead
  • Spectral efficiency = net data rate in bps/channel Bandwidth in Hz 

Calculating spectral efficiency for 5G New Radio

5G NR is capable of providing a downlink throughput of 2.31Gbps and uplink throughput of 2.47Gbps with certain configurations. Let’s assume 100 MHz channel bandwidth (Single Carrier Component)

  • Downlink Spectral efficiency: 2.31 * 109 bps / 100 * 106 Hz = 23 bits/second/Hz
  • Uplink Spectral efficiency: 2.47 * 109 bps / 100 * 106 Hz = 24 bits/second/Hz 

5G NR Spectral efficiency calculation is based on the 3GPP recommendations

  • Calculate 5G NR throughput which depends upon the number of MIMO layers, bandwidth, frequency range,  modulation types, etc.
  • For correct results, the number of aggregated component carriers should be 1. 
  • Divide the 5G NR throughput, bps by channel(band) bandwidth, Hz.