5G NSA option 3a versus 3x

Carriers using higher frequency bands for 5G than that of existing 4G may have to very carefull about choosing the NSA option 3a versus 3x.


Option 3a 5G data will be sent by SCG (Slave Cell Group) Only, that is only through gNB, while in option 3x SCG Split bearer is used, that is part of the data can go through eNB in addition to gNB.


If you are using higher frequency band for 5G than that of 4G then the footprint of gNB will be smaller than that of eNB. And in case you end selecting option 3a then at gNB cell edge Ue might end up having lower throughput than that if its being served eNB at that point.


But if you are using option 3x then SCG split bearer functionality will keep the Ue served by eNB.


attached picture is taken from:
https://www.3gpp.org/ftp/Information/presentations/presentations_2018/2018_10_17_tokyo/presentations/2018_1017_3GPP%20Summit_03_TSG-RAN_Bertenyi_Nagata.pdf

5G is the First Gen of Cloud Only Networks, 4G was the Last Gen of Telecom Networks

Digital Communications is apparently settling down to cloud, fiber, and OFDMA fueled with deep-learning enabled AI.




let's take a look at some of the victims of 5G, Telecom network vendors/operators and Cell Phone vendors. When I call them victims, I ain't mean that they are going out of business 😊 but I mean they have to discover new ways of business and , at least, they can exploit their Telecom Brand names while pursuing new dimensions to their current business that's heavily Telecom based.




Telecom operators are happy on one side, as they don't have to pay billions of dollars to Telecom vendors for dedicated hardware and software and on the other side may be struggling, how to force existing customers (cell phone subscribers) to pay more just for having 5G on their displays instead of 4G.


As competition forced the major US carriers to offer unlimited plans, same may gonna happen on lowering down the price further due to reduction in employees and negligible cost of white box & open source software. Forgot to mention almost free spectrum too (CBRS/WiFi).




Telecom operators are exploring new dimensions to attract new customers for new services (slices) , including industrial IoT (one of the most promising new slice at the moment, rest are in testing phase yet or not matured yet).






When you have a white box and open source software at Network End, it's natural to have the same kind of device (white box with open source software) at the consumer end, so apparently the major cell phone vendors making iPhone/Galaxy will be having a hard time to force the existing consumers to continue buying annually an upgraded version of their cell phones.


Telecom Network vendors are the ones affected mostly because they were selling Telecom dedicated hardware and software. And now they have re-align their hardware and software product line from Telecom dedicated hardware & software to Cloud native hardware & software product line. Fiber devices & active antennas would be their hot items in 5G.


Industrial IoT is the target of both Telecom Network vendors and operators, let's how this market grows and which way it sways.

LTE Idle Mode Mobility in One Diagram

Concept of Events in Idle mode mobility, role of Cell Edge in mobility and hence an introduction of a new quantity Srxlev.


qRxLevMin defines the Cell Edge, can be configured at cell level, usually depends on signal characteristics of a particular band.


Srxlev is a quantity measured from Cell Edge towards Base Station and is Zero at cell edge while highest next to the base station. That may be the reason that all the thresholds in idle mode are relative to Cell Edge (qRxLevMin) and correspondingly Ue makes a decisions when it crosses any of those thresholds.


Pcomensation is a penulty for low powered Ues (Reducing the Cell Size for low Powered Ues with respect to the configured power)


Intrafreq reselection (A3 based) is better cell reselection means reselecting the target cell when Srxlev of target cell becomes better than Srxlev of serving cell.


Interfreq reselection to low/equal priority cell (A5 based) needs to meet two conditions A51 & A52, means reselecting the target cell when Srxlev of serving cell goes below threshServingLow (A51) and that of target goes above threshXlow (A52).


Interfreq reselection to high priority cell (A4 based) needs to meet only one condition, means when Srxlev of target cell goes above threshXhigh.


If the Ue is not at highest priority (7) cell, it continues to look for highest priority cell periodically.


When Srxlev of serving cell goes below SintraSearch And SnonintraSearch thresholds, intrafreq and interfreq towards low/equal priority target cell measurements are triggered respectively.


In connected mode, as we all know, the mobility (from one cell to another) is controlled by base station and assisted by Ue (by sending Measurement Reports).


In Idle mode, it's just the opposite of that, the mobility (from one cell to another) is controlled by Ue and assisted by base station (by sending SIBs).


In idle mode to get a little bit more control over Ue's mobility in interfreq environment (multi-carrier sites), the concept of cell reselection priority is introduced. It's my own visualization to understand these few things, less talked about.


Srxlev = Qrxlevmeas - qRxLevMin 


Note: Often Rel9 is mentioned in literature because Squal is not recognized by UEs < Rel9