Sleep Timing, Retry Timing, and Encryption Throughput

Below are timing charts showing details associated with transmit/receive timing of our modules. Note that next to each module type is the firmware version. Timing schemes may vary by firmware version.



Sleep Mode Timing


Modem
(firmware version)
XCite (111) XStream (42B0) XTend (2001) XBee/XBee-PRO (1061)
Power up 68.5 ms 40 ms 45.2 ms 25 ms
/SHDN n/a n/a 37.3 ms n/a
SM=1 Pin Sleep/Pin Hibernate 69 ms 40 ms 1 ms 9.5 ms
SM=2 Serial Port Sleep/Pin Doze 88 ms 45 ms 83.2 ms 1.8 ms
SM=3,4- Cyclic Sleep
(pin wakeup)
69 ms 40 ms 1 ms 1.8 ms
SM=3,4- Cyclic Sleep
(RF wakeup)
n/a* n/a* n/a* 1.1 ms
SM=3,4- Cyclic Sleep
(RF "sniff time")
52 ms 100 ms 80 ms 30.5 ms
* These times are deemed invalid due to the RF "header" of the coordinator

Retry Timing

This timing chart shows the inter-packet time spacing of each redundancy modes.

Modem
(firmware version)
XStream
(42B0)
XTend
(2001)
RF Data Rate (bps) 9600 19200 9600 115200
RR- Retries 1 byte 63 ms 51 ms 86 ms 9.1 ms
RR- Retries 32 bytes 88 ms 63 ms 110 ms 11.1 ms
MT- Multiple Transmit 1 byte n/a n/a 69 ms 7 ms
MT- Multiple Transmit 32 bytes n/a n/a 94 ms 9 ms
* Retry times are based on time spacing with no received ACK


XBee & 9XTend Encryption Throughput


Encryption (256 bit AES for the 9XTend and 128 bit AES for the XBee) will slow down throughput for the XBee only. The 9XTend has a much more powerful processor which allows the 9XTend to process the encryption "real time" while the XBee which must perform an additional operation to process the encrypted data.


Measured Throughput Encrypted Not Encrypted
XBee ~47Kbps ~80Kbps
9XTend ~111Kbps ~111Kbps

The throughput figures were measured with HyperTerminal''''s Zmodem (Zmodem was chosen because of the low associated overhead). It is important to note that these measurements were done by sending large files of data and averaging the throughput based on the entire file. It is also important to note that smaller packets will reduce throughput with encrypted data.

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