WCS Spectrum Compromise Avoids LightSquared Issues

The joint AT&T and Sirius XM proposal regarding use of spectrum in the  2.3 GHz Wireless Communication Services (WCS) spectrum band seemingly avoids an issue LightSquared was unable to address, namelhy interference between a high-power Long Term Evolution mobile network and an adjacent low-power satellite service.


AT&T has owned its WCS spectrum since 1997, but there have been concerns about whether WCS licensees could peacefully co-exist with neighboring licensees in the Satellite Digital Audio Radio Service (SDARS) band, just as there were interference issues with LightSquared and neighboring GPS applications.


Apparently, AT&T and Sirius XM now are satisfied that a 10-MHz guard band will prevent any service-impairing interference, clearing the way for AT&T to use its spectrum. Only an engineer could tell you why the WCS interference issues could be resolved by instituting a 10-MHz guard band, where LightSquared could not do the same.


One suspects that the difference is transmitted power levels required for the higher-frequency LightSquared LTE signals. Since higher-frequency signals do not propagate as well as lower-frequency signals, the proposed LightSquared network presumably required higher power levels, and therefore, more interference risk, compared to power levels for the WCS signals.