What is SNIR?
SNIR (Signal-to-Noise and Interference Ratio), also written SINR, is the ratio of the desired signal power to the combined power of interference from other transmitters and thermal background noise. SINR is the most relevant metric for determining achievable data rates in cellular networks, where inter-cell interference is typically the dominant impairment rather than noise alone. In 5G NR, SINR measurements drive link adaptation, scheduling decisions, and handover triggers.
How Does SNIR Work?
SINR = P_signal / (P_interference + P_noise), expressed in dB. In a cellular network, the desired signal comes from the serving cell’s gNB, while interference comes from neighbouring cells transmitting on the same frequency (co-channel interference). At the cell centre, SINR is high (20–30+ dB) because the serving cell signal is strong and interference from distant cells is weak. At the cell edge, SINR drops to 0 dB or below as interference from adjacent cells becomes comparable to the serving signal. The achievable spectral efficiency follows Shannon’s bound: C = B·log₂(1 + SINR). In 5G NR, the gNB uses CQI (Channel Quality Indicator) reports from the UE — which are based on SINR measurements — to select the optimal MCS (modulation and coding scheme).
Use Cases
5G NR link adaptation and MCS selection, cell-edge performance analysis, inter-cell interference coordination planning, network capacity dimensioning, and handover threshold configuration.
3GPP / Standards Reference
3GPP TS 38.214 (NR physical layer procedures — CQI/MCS tables), 3GPP TS 38.133 (NR RRM requirements — SINR thresholds)
Related Terms
SNR | QoS | MIMO | Beamforming | KPIs
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