In part 4 of my mini-series about 3GPPs Internet of Things standardisation for cellular networks I’ve given an overview of the currents state of the NB-IoT standardization in 3GPP. Most of what I’ve written in there is based on a 3GPP Technical Report that summarizes the different options that were studied and RP-151621 which contains the Work Item Description for NB-IoT in which the resulting compromise was detailed. But where in the 3GPP Specs is NB-IoT now actually specified?
The answer is: Nowhere YET! That is because it was decided that NB-IoT will not get its own specification documents. Instead NB-IoT is based on LTE and hence all additions will go into already existing specification documents. The current Release 13 versions of relevant documents such as for example for the physical layer, MAC or RRC, do not contain anything on NB-IoT yet.
NB-IoT Protocol Enhancments
It looks like the details are mostly hammered out in RAN ad-hoc meetings on NB-IoT and everything is collected in a few big CRs that will at some point in the not too distant future be folded into the real specification documents. The current version of one of these big CRs that is of particular interest can be found in R2-163218 for 3GPP TS 36.300 (E-UTRAN Overall Description – Stage 2). But this is just one document, there are many more that can be found in the list documents of the RAN2 ad-hoc on NB-IoT here.
The last document in the list is an Excel document that contains an overview of all the documents.Have a closer look at column “U” in that document as it contains the 3GPP specification number the CR is intended for. Those documents which have a specification number in that column are worth to be looked at first.
NB-IoT Physical Layer Enhancements
While the 3GPP RAN2 NB-IoT ad-hoc is responsible for Layer 2 and 3 of the radio network, RAN1 deals with the physical layer, i.e. Layer 1. This group has also formed an ad-hoc for NB-IoT and the current state of specification activity can be found here. There’s also an Excel document at the end of that list but they seem to do things a bit differently as there are no “rolling CRs” that capture all changes.
Even in the future the final output documents of these ad-hocs might be quite useful as all NB-IoT related addition and changes are marked so it’s easy to get an overview quickly.