In the Eddystone beacon spec the word 'slot' is used

[Mahendra Tailor]

The term 'slot' is used in the context of the Eddystone beacon specification.

I cannot find a definition of that word.

For example, the sample app from Nordic says "The example provides five advertising slots" and despite working in Bluetooth for 17 years I am confused :-)

Does it mean that if you have 5 slots, then each advert will contain one frame and so 5 adverts are required to advertise all of them, OR Does it mean that you can fit 5 AD elements in a single advert ( which means it will not fit in pre v5 adverts)

I think in my case the confusion comes from a little bit too much knowledge to be able to perceive the ambiguity.

Look forward to hearing from someone.

Note to Nordic guys: it may be worth putting whatever feedback comes back as a response to this in the Nordic Inforcenter page related to "Eddystone Beacon Application"

[AmbystomaLabs]

Time slotting is a standard approach for time division duplexing (TDD) for many wireless transmission systems and Bluetooth supports it. You can find it discussed in the Core spec v4.2 section 2.2.3.

[Mahendra Tailor]

Thank you for a quick response, unfortunately this does not answer my question as my reading of the eddystone documentation is that the designers had something something specific in mind when they used the word 'slot' in their narrative.

Your response is true about TDD in wireless - just that it is all so implied that why should something like eddystone which is an application even bother to mention :-)

[AmbystomaLabs]

Well now I'm curious too. I'll do some reading today to see if there is anything specific to Eddystone.

[AmbystomaLabs]

I noticed you were looking around on github too. Yes fascinating question. I would say your knowledge is considerably better than mine on this subject but I will give you my take anyway. I hope what I say doesn't sound stupid... It seems the eddystone folks are reusing the term slot and just not defining it well. Even the spec doesn't define it. As far as I can tell "slot" refers to the encryption time slot used for the EID beacon broadcast. Once the beacon negotiates encryption with its host the timestamp is used to create the following encryption keys. Therefore each "slot" has a unique key. There are 8 slots allowed in an EID frame. Then these data are broadcast over multiple bluetooth TDD slots.

I hope that helps a little and wasn't painfully obvious to you. I must say eddystone is a complicated protocol.

[Mahendra Tailor]

I like your thinking. However, I seem to recall that the term 'slot' has also been used in the context of the other frame types which don't have the encryption time cycling. So if my memory is correct (which I would not bet on ) would mean that your interpretation would not apply.

I am hoping the developer of the sample app at Nordic can comment as he is obviously much higher up the learning curve