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Article
Introduction to Uplink Power Control for 3GPP RAN Developer
by
Samir Amberkar
(published on 26-Oct-2023)
Though important, uplink power control is often ignored and less understood topic.
In this article, we shall make an attempt to understand the concepts behind uplink power control.
This will help both junior and senior RAN developers.
Though we will use 5G NR (Rel 15) as a reference, the principals will apply equally well to LTE.
Receiving the signal at optimum power (SINR) is desirable for successful decoding (reception).
If we can control transmission power to maintain SINR at receiver, we can maintain the desired date rate.
In a way, power control is a link adaptation technique wherein power is controlled to get the best data rate [5] .
During propagation, signals face gradual attenuation (loss of power due to the medium).
This is known as "path loss (PL)".
To compensate the path loss, transmission power need to be increased.
This may lead to increased interference/noise to other transmissions.
Ensuring that the interference/noise is within certain limits is also a consideration behind power control.
UE is power limited, so we need to ensure its power efficiency.
Though this is not a prime factor, it is of importance in designing power control techniques/protocols.
Fig "ULPC"
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