03. RACH Setup Analysis & Case Study_Wk50v1

RACH Setup Analysis & Case Study 1

1/28/16

Confidential

© Nokia 2014

Summary Objectives: To study what is RACH & its types. Compl RACH stp SR counters used & calculations. To study Small message & Large message. Compl RACH stp SR trend for N2 (City wise). As per request PrachCS (10 13) , prachConfIndex (319 ) and RootSeqIndex(613) changed for 244B1LN1 on 18th Nov & KPI was monitored. Compl RACH stp SR Analysis & Case Study done for Worst Cells (Top 10 Cells of N2 region & Top 5 cells of Hsinchu).

Analysis &Troubleshooting Results: N2, New Taipei city, Hsinchu & Taoyuan is having 87% Small message & 13 % Large message. Suggest to pre-check PCI confusion/collision after found some Top 10 worst cell cases of very low Compl RACH stp SR. Layer1 optimization is required based on the case study 242H2LN1 which is overshooting to Shulin. Compl RACH stp SR improved for 244B1LN1 after parameter changes on 18th Nov due to Preamble format change from 01 causing the cell radius increased. 2 1/28/16 © Nokia 2014  Confidential To further study & implement the three parameters in 31304LN1_112 & 30314LN1_111.

Random Access Procedure (#1)  RACH has very important functionality especially in LTE (and in WCDMA as well). The main purpose of RACH can be described as follows. • Achieve UP link synchronization between UE and eNB • Obtain the resource for Message 3 (e.g, RRC Connection Request)  The use cases are usually: • Initial access when establishing a radio link (RRC_IDLE to RRC_CONNECTED) • To re-establish a radio link after a radio link failure • During the handover process to establish uplink synchronization to the target cell

No Retransmission 3

1/28/16

Confidential

© Nokia 2014

Random Access Procedure (#2)  There are two forms of Random Access procedures : (a) Contention based (risk of collision). If the same PRACH preamble from multiple UE reaches the NW at the same time, this kind of PRACH collision is called "Contention" and the RACH process that allows this type of "Contention" is called "Contention based" RACH Process. In this kind of contention based RACH process, Network would go through additional process at later step to resolve these contention and this process is called "Contention Resolution" step. i) UE --> NW : RACH Preamble (RA-RNTI, indication for L2/L3 message size) ii) UE NW : L2/L3 message iv) Message for early contention resolution

(b) Contention free. In this case RACH Preamble is assigned to UE by the eNB. i) UE NW : RACH Preamble (RA-RNTI, indication for L2/L3 message size) iii) UE