SparkFun Forums

[sebmadgwick]

I am creating a system where multiple wireless sensors stream data to a host computer displaying real-time graphics. I am using XBee series 1 modules in a P2P arrangement with one USB dongle per sensor (due to bandwidth limitations). Each XBee sensor will operate on a different channel.

I have left the PAN as the default as each sensor is on a different channel. However, the system will be deployed in public locations and I am concerned that a 3rd party wireless system might interfere. I want to choose a PAN that is 'least likely' to be used by other systems. Can anyone offer some advice on this?

[stevech]

I am creating a system where multiple wireless sensors stream data to a host computer displaying real-time graphics. I am using XBee series 1 modules in a P2P arrangement with one USB dongle per sensor (due to bandwidth limitations). Each XBee sensor will operate on a different channel.

I have left the PAN as the default as each sensor is on a different channel. However, the system will be deployed in public locations and I am concerned that a 3rd party wireless system might interfere. I want to choose a PAN that is 'least likely' to be used by other systems. Can anyone offer some advice on this?

Normally, all sensors would be on the same RF channel so that the receiving device need not scan/search. Each 802.15.4 (XBee series 1) has a unique 64 bit address. If you configure it for 64 bit addresses rather than 16 bit, and if you do not need/use a coordinator, then the problem is simple... the Digi Binary API (see OEM manual) allows for 64 bit addressing. A received data frame includes the sender's 64 bit MAC address. A sender transmits data frames to a specific 64 bit destination MAC address (the data logger?), or sends to a broadcast address so it doesn't need to know the destination address... however broadcasts don't use error correcting ACKs. All transmissions use CCA (listen before transmit), so all are on the same channel and PAN ID. Odds are, no one is using the same PAN ID and channel with 802.15.4.

Using the binary API assumes you have an attached microprocessor with your program. If instead, you are using bare XBees with the sensors wired directly to it, and no microprocessor, then there's less flexibility.

No matter the addressing method, You could enable encryption (shared key AES) that's an option in 802.15.4 and XBees.

[Microguy]

For more information about XBee Series-1 modules in networks, see: "The Hands-On XBee Lab Manual," by Jon Titus. There are experiments with networks and MCUs here.

[sebmadgwick]

Thanks for the info but this is not quite the answer I am looking for. I understand how the XBee modules work and how various configurations can be useful to me. I want to know if certain channels and/or PAN IDs are more likely to be a problem than others in public environments.

For example, it is obvious that the default XBee settings (chan 12, PAN ID 3332) could be a problem. Are other channels and/or PAD IDs (I’ll be using 16-bit) known defaults for certain publicly used systems?

[stevech]

PAN IDs ... don't matter. As in WiFi, just change the factory default to an oddball 16 bit number.
Channel: Doesn't matter .. PAN ID would be unique even for the unlikely case where there's other 802.15.4 gear in range on the same channel.