| "Software-only" GPS supports WIndows |
May 15, 2008
 Finnish company Fastrax Ltd. has announced a "completely software based" GPS receiver solution, said to add less than $3 to the cost of a device. "Fastrax Software GPS" runs on both x86 and ARM processors, supports Windows, and requires only an RF front end, says Fastrax.
As the company explains, a traditional GPS receiver consists of an antenna, an RF front end, and a baseband IC. The RF front end converts the RF signal into a digital IF (intermediate frequency) signal to be processed by the baseband IC. The latter typically consists of an application processor, some memory, and dedicated HW modules for both communication (UART, SPI) and signal processing (correlators, acquisition engine).
A number of designs -- which Fastrax terms "measurement front end receivers" -- have sought to reduce the size and complexity of the baseband IC by moving navigation algorithms to the host CPU. But Fastrax Software GPS is claimed to be the first GPS solution that eliminates the baseband IC entirely, accomplishing all digital signal processing on the host processor.
Fastrax touts its software solution as offering a similar level of performance to hardware-based receivers. For example, cold start sensitivity is rated at -144 dBm, and navigation sensitivity is rated at -162 dBm. The software requires approximately 10 MIPS (millions of instructions per second) per tracked satellite, for a total of around 100 MIPS in typical usage.
Software-only GPS (left) costs less but requires more from a host processor
Source: Fastrax
(Click to enlarge)
As the above illustration suggests, standalone GPS receivers (right) ask little -- only about 1 MIPS -- of a host processor, while measurement front end receivers require about 10 MIPS. The software-only solution (left) might need 100 MIPS, but this is easily handled by modern processors running at 500MHz and above, says Fastrax.
Mindful of lower-end devices that still only have processors clocked at 200MHz or 300MHz, the company also offers its "Fastrax Accelerated Software GPS" (shown second-from-left in the above illustration). This reduces CPU load to around 20 MIPS by performing the correlation process on hardware that is integrated into the RF front end or in the host processor. However, most operations are still performed on the host, unlike with previously available products, according to Fastrax.
Both the software-only and hardware-assisted versions of Fastrax cut a device's bill of materials substantially, the company says. It's claimed the software-only version would add GPS to a device for about $3, while the hardware-assisted solution would cost about $4 per unit.
Fastrax's Software GPS stack
(Click to enlarge)
Fastrax's Software GPS stack, illustrated above, is based on the company's iSuite architecture. Written in C, the code was originally designed to run on the company's own iSys real-time operating system, but has now been ported to Windows CE, Windows, and Linux.
Fastrax Software GPS runs on both x86 and ARM processors, and porting it to new operating systems and hardware platforms is said to be quick and straightforward. Another claimed advantage is easy adaptation to future iterations of GPS, or to alternative satellite networks such as Europe's Galileo and Russia's GLONASS.
In the case of Fastrax Accelerated Software GPS, systems can presently be emulated via an FPGA platform (Altera Stratix II). In addition, says Fastrax, RTL (register transfer level) information is available, to assist in designing silicon.
The Fastrax Software GPS and Accelerated Software GPS solutions solution are currently available for demonstration to prospective customers. The company did not estimate when the technology might go on sale to consumers.
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