WPAN as innovation?

Werner Almesberger werner at almesberger.net
Thu Apr 14 13:25:20 EDT 2011


I wrote:
> With my ATBEN/ATUSB prototypes, I've obtained good to acceptable BER
> for a distance between stations of 4-7 m indoors in a residential
> area with relatively few interferences.

A clarification on the error rate (BER = Bit Error Rate, PER = Packet
Error Rate):

IEEE 802.15.4 defines a maximum PER of 1% for a PSDU of 20 bytes.
This means that all bits of the PSDU, the length (1 byte) and the SFD
(1 byte) be received without errors, and that enough bits of the
preamble (4 bytes) must be received for the receiver to synchronize.
To keep the numbers simple, let's assume that's 200 bytes in total.
Thus

1-PER = 1-(1-BER)^200

With PER = 1%, we get a BER of about 50 ppm.

Since our primary usage scenario, Internet access, would often use
maximum-sized packets, I used max-sized packets for my measurements as
well. The maximum PSDU size is 127 bytes. So we get 200+8*(127-20) =
1056 bits.

Aiming for a PER of 1% with full-sized packets, the BER has to be
lower, about 9.5 ppm.

- Werner




More information about the discussion mailing list


interactive