XM Satellite Radio Upgrades Sound Quality 
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Written by AVRev.com   
Friday, 19 April 2002

When first launched, XM Satellite Radio boasted that it’s sound quality was far superior to that of standard radio. Not resting on their laurels XM has just unveiled an upgrade in an attempt to achieve near-CD quality sound.

This new technology called Customized CT-aacPlus is the combination of Advanced Audio Coding (AAC), a highly efficient global standard combining the work of the world's foremost experts on perceptual audio encoding -- AT&T, Dolby, Fraunhofer (main developer of audio coding schemes such as MPEG Layer-3 (mp3) and MPEG-2 AAC) and Sony -- with Coding Technologies' Spectral Band Replication technology.

The XM signal is then optimized by Neural Audio, a Seattle-based research lab, using customizing pre-processing software that implements algorithms based on models of the brain's perception of sound. In addition, Neural Audio's "stereo transcoder" algorithm preserves the imaging and spatiality of stereo and surround-sound content that XM broadcasts. This allows XM customers with matrix-style surround sound equipment, including Dolby technology to receive a full surround sound experience.

XM's digitally compressed audio content is uplinked into outer space.
XM claims they are able to deliver sound quality that is superior to traditional radio anywhere in the lower 48 states using two of the most powerful commercial satellites ever built. These satellites are augmented by a nationwide network of more than 800 repeaters in 70 cities, the most extensive SDARS repeater network available.

XM's two Boeing 702 satellites, "Rock" and "Roll," deliver more than twice as much total satellite power of any other satellite radio service, thus only two are needed. The satellites are "parked" in geostationary orbits aligned with the east and west coasts of the United States and each broadcasts the full 100-channel service to all XM radios across the country.

XM also devotes bandwidth to error correction and concealment. This is done in an attempt to create a reliable delivery system that minimizes momentary signal losses from interfering with the continuous flow of music.

In an upcoming issue of AudioRevolution.com, our publisher Jerry Del Colliano will give you his real world evaluation of XM Satellite Radio. Stay tuned…







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