Just for future reference, from the Kickstarter Project Update #9:
The TTN gateway will not include a GPS module (but will have Bluetooth 4.2 and an XBee interface). So, if ever needed, it needs to get time synchronisation from the internet, not from GPS.
We were hoping also to announce we would support positioning over LoRaWAN. But as the current LoRaWAN specifications and chips do not allow positioning to properly work we will not add this feature.
Positioning over LoRaWAN
We would have loved to offer you the potential positioning features as a third extra as well but this was unfortunately not possible.
This would have been a very nice feature we worked hard on to include. But due to the lack of support in both the LoRaWAN chips and specifications this is not possible at the moment. Please find below our considerations with regards to this topic.
When we started out with the gateway design we wanted to make the specifications comparable with all LoRa gateways out there, only for a fraction of the price. When doing our research and testing different gateways we noticed a lot of them had, or had place for, a GPS module. This GPS module is intended to enable triangulation based on triangular time of flight calculations as well as to sync the internal clocks over GPS. With a rather complex set of calculations one could, in theory, calculate the location of a node in a LoRa network.
That looked very promising. Well the problem is that this is in theory and after some thorough testing we have concluded that the current version of LoRaWAN compliant chips are not capable of providing the information required for calculating usable positioning data of the nodes. We always saw this as a future possibility and while not pitching localization use cases in this Kickstarter we felt the strong need to explore this possibility.
Since we started working on LoRa more and more research has been carried out on this localization challenge it is now safe to say that with the current layout of components that all available gateways use it won’t be possible to carry out triangulation and still be LoRaWAN compliant. There is a new reference design currently being developed by the LoRa Alliance with better support for this functionality. There are no guarantees that this will be achieved or if so in which time frame.
The way we see it, we had 2 options:
Option 1, wait till this new design is finalized, pushing our deadline easily another 12 months, but do the best we can and support the feature of localization, with no guarantees that it will be even possible in this new reference design. So extending the delivery to an unacceptable date for an add-on of which does not yet have proof of working.
Or option 2. Stick to our deadline, and stick to the current reference design we have always been using, make it the cheapest, best working, plug and play, open source LoRaWAN gateway available to start building this network.
We choose option 2 because we are not prepared to accept an uncertain delay for an uncertain design feature; leading us to the conclusion that the use of the GPS chip for this purpose in our gateway has been rendered useless.
Good to know is that for the ones that had a use case in mind that required positioning. It is still very good possible to make it with a GPS chip on your node. These products are emerging at the moment and are easily to find.