For the High Luminosity LHC, the Beam Radiation Instrumentation and Luminosity (BRIL) project will employ CMS tracker modules for precision luminosity measurement with an ambitious target offline luminosity precision of $1\%$.
Inner tracker endcap (TEPX) luminosity will be based on the online clustering algorithm.
An FPGA-based clustering algorithm has been developed to count hit clusters detected by RD53B readout chips.
Simulations and beam tests have been conducted to validate the algorithm under realistic conditions.
Disk 4 Ring 1 (D4R1) of the TEPX will be fully dedicated to luminosity, while the rest of TEPX will allocate $10\%$ of the trigger rate for luminosity.
The Outer Tracker (OT) system will be utilized for high-statistics online luminosity measurements by providing high-rate physics objects known as Level-1 (L1) track stubs.
Stubs are formed by detecting two-hit coincidences on closely spaced silicon sensors using front-end ASICs and are transmitted at a frequency of 40 MHz to the L1 track reconstruction system.
For luminosity measurement, stubs will be aggregated in the histogramming firmware block.
Currently, common mode noise within OT modules is being studied to evaluate its impact on the luminosity measurement using comparisons between a toy strip-strip (2S) module simulation and noise data from real 2S production modules.