The approval is considered a boon for AT&T which entered into an agreement to acquire NextWave Wireless earlier this year for its WCS and AWS licences.
WCS spectrum has largely been unused for the past few years due to concerns over interference with satellite radio devices.
AT&T and Sirius first submitted their proposal in June, which protects satellite radio service through the use of guard bands of unused spectrum next to the spectrum used by Sirius.
Now that approval has been granted, the US carrier is expected to be able to begin initial deployments of 20MHz of its 30MHz of WCS within the next three years.
The new spectrum source could prove crucial for AT&T, which lags behind its rival Verizon in its LTE deployments and coverage in the US.
Verizon has announced that it expects to reach its goal of providing LTE service in 400 US markets next week.
