[Tinyos-help] FW: [Tinyos-devel] 900 MHz vs ZigBee

Joe Polastre joe.polastre at gmail.com
Sun Mar 20 19:09:42 PST 2005


> Is there a marketing advantage? Wouldn't a vendor that offers a
> 900 MHz design just as easily be able to offer an 802.15.4 design?

Well, no, not necessarily.  It depends on how the synchronization is
implemented; the 900mhz radios tend to be bit or byte based radios,
whereas 15.4 radios are packet based.  This means you lose a lot of
flexibility in exchange for higher data rates and encoding features,
which hinders many synchornization implementations.  VU has managed to
port their code to the CC2420, but the method is a specific hack to
the CC2420 and may not be possible on other 15.4 radios, such as the
one from Freescale.  Regardless of the implementation details, some
form of synchronization is possible on pretty much any transceiver;
however, the protocols may be drastically different.

The other part here is that RF circuits are very picky and tend to
take a few months of revisions in order to get them tuned correctly to
the transmission and reception frequency.  As a result, a company that
offers a 2.4GHz solution may be very reluctant to create a 900MHz
solution since it requires a costly hardware design cycle.

Then the software interface (SPI, UART, register access, etc) to
different radios with different frequencies is a decent amount of
software work to create a robust radio stack.

These are just a short, and incomplete, summary of the issues.

-Joe


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