Among other things, it lacked a memory "buffer" which banks audio in a separate storage area that can be drawn on if line-of-sight reception is blocked.A closer look at XM's chipset reveals two unique integrated circuits, each assigned to different tasks.
In addition, being able to buy DSPs off the shelf has saved the company a fortune in not having to create a custom-built chipset from scratch.The company's co-founder and chief executive, Paul Heinerscheid, talks of adding a GPS (global positioning system) feature to the receivers.
A poorly designed chipset will corrupt the sound with pops, clicks or dead air.Working with Germany's Fraunhofer Institute (the birthplace of MP3) and STMicroelectronics, XM essentially re-engineered an existing chipset.
Eschewing the "hard-wired" design that is difficult to upgrade, Global Radio has set out to create a software-driven chipset that is based on a generic digital signal processor (DSP).
More than any other factor, the chipset defines the audio experience.
The second circuit also buffers four seconds' worth of incoming data, so that tunnels, underpasses or other blind spots do not hinder reception.By contrast, the Sirius chipset, which is manufactured by Agere Systems (formerly part of Lucent Technologies), encompasses eight integrated circuits.
What engineers at iBiquity found was that they could squeeze a compressed digital signal into that buffer and still have 100 kilohertz left over to prevent their signal from interfering with a neighbouring station's.The company has designed a chipset that can not only process the old analogue signal, but also combine it with two new digital streams.
Supplied by SGS-Thomson, the earlier chipset had been used by WorldSpace since 1997, but could not get mobile reception.
This chipset then decompresses the stream into clean, crisp audio.
In doing so, Global Radio can upgrade the software or replace the hardware whenever newer and better technology become available, allowing its chipset to improve steadily with time.
With Global Radio's transmissions and GPS signals being neighbours in the radio spectrum, it ought not to be too difficult to make a dual-function chipset for an all-purpose, music-everywhere, never-get-lost gizmo.
