5G NBIOT LTE Question Answers

Home                 LTE                NB-IoT               5G(NR-NSA) In this section we will learn about SRB and its basics as well as interview questions. Please read our previous SRB article basic Part-2. Signaling Radio Bearer's: In ENDC, for SRB1, the random access is triggered by RRC layer itself because there is not necessarily other UL transmission. Also for SRB3 the random access is triggered by MAC layer because of arrival of RRC reconfiguration complete. There are 4 SRB's – SRB 0, 1 ,2 & 3 SRB0: SRB0 is mapped to CCCH in Downlink and Uplink. The RRC messages, RRC Connection Setup & RRC Connection request ( in NR Case RRCResumeRequest ) will be transmitted in SRB0. Signaling Radio Bearer 0 is for RRC messages using the CCCH logical channel. SRB0: Direction: UL/DL RLC - Mode: TM (Transparent Mode) Logical Channe...

Home                 LTE                NB-IoT               5G(NR-NSA) In this section we will learn about SRB and its basics as well as interview questions.  Please read our previous  SRB article basic Part-1. SRBs (Signaling Radio Bearers) are nothing but the Radio Bearers that are used only for the transmission of NAS and RRC messages. In more convenient way SRBs can be defined as follow: In downlink piggybacking of NAS messages is used only for bearer establishment or modification or release. Whereas, in uplink piggybacking of NAS message is used only for transferring the initial NAS message during connection resume and connection setup. FFS Piggybacking of NAS messages in other procedures than bearer establishment or modification or release. NOTE: The NAS messages transferred through SRB2 are also contained in RRC messages, wh...

Home                 LTE                NB-IoT               5G(NR-NSA) In this section we will learn about PRACH and its basics as well as interview questions. To handle the wide range of deployments for which NR is designed, NR RA preamble supports two different sequence lengths with different format configurations.  For the long sequence of length 839, four preamble formats that is generated from LTE preambles and these supports mainly large cell deployment scenarios. These formats have subcarrier spacing of 1.25 or 5 KHz and can be used only in FR1.  For the short sequence, nine different preamble formats (of length 139) are introduced in NR. This mainly targets the small or normal cell and indoor deployment scenarios.tis short preamble formats can be used in both FR1 with sub carrier spacing of 15 or 30 KHz and FR2 with sub...

Home                 LTE                NB-IoT               5G(NR-NSA) In this section we will learn about PRACH and its basics as well as interview questions.               To obtain the UL synchronization, a preamble is send by UE to gNB over PRACH channel. As LTE, in 5G NR also there are 64 preambles defined in each time frequency PRACH accession. After the cell search process, UE has obtained DL synchronization with cell, so UE can receive DL data. But UE can perform UL transmission only when it obtains UL synchronization with the cell. The UE forms the connection with cell and obtains UL synchronization through random access procedure. The main purpose is: Achieve uplink synchronization between eNB and UE Obtain the resource from Msg3 (obtain uplink grant, the uplink resource request) Assign CRNTI(unique i...

Home                 LTE                NB-IoT               5G(NR-NSA) In this section we will learn about SRB and its basics as well as interview questions. Signaling Radio Bearer's: ENDC (EUTRA-NR dual connectivity- 3gpp release-15 feature- deployment Option-3) is a feature that is introduced to support new radio NR (5G) data with existing LTE core and radio networks and without introducing 5G core network.   This ENDC (EUTRA New Radio dual connectivity) can be a useful feature for heterogeneous network where LTE provides reliable coverage and NR can be used for improving data rates. In ENDC, the schedulers in the eNB and en-gNB are independent from each other and make their own decisions how much and when the data is to be send or receive from UE. This is also applicable to RRC, and the device now has one RRC context to the eNB and another ...