4G LTE KPI - Accessibility

Accessibility KPIs

Accessibility is one of the key performance indicators in providing services to end-users by giving access to the network in an appropriate manner.
It is used to measure whether users are able to access the network and obtain the service efficiently or not.

Accessibility can be analyzed through : RACH, RRC & ERAB success rate.

a. Random access is a basic procedure of uplink synchronization between UE & Network, and it helps to enable uplink transmission. UE sets the initial Power of RACH (random access channel) & sends preamble signal. If UE doesn’t get response from BS, UE Tx power is increased in steps to ensure that RACH procedure is successful. There are different preamble formats depending upon the target cell radius, which is derived by timing advance (TA). Ratio of RACH setup complete to setup attempts is termed as RACH success rate.

b. Radio resource control (RRC) exists at IP level (layer 3) between UE and ENB. It ensures that control plane is successfully established between UE and network. The major functions of the RRC protocol include connection establishment/release functions, broadcast of system information, radio bearer establishment/reconfiguration/release, RRC connection mobility procedures and paging notification/release. The operation of the RRC is guided by a state machine which defines certain specific states that a UE may be present in – Idle or connected mode. Ratio of RRC setup complete to setup attempts is termed as RRC success rate.

c. Radio access bearer (RAB) is the user plane between UE and Radio access network to carry the data for the services requested by the user. And, once radio bearer is established, then there is a end to end EPS bearer (Radio Bearer + S1 Bearer + S5 Bearer) is established. Ratio of RAB setup complete to setup attempts is termed as RAB success rate.

Accessibility related KPIs success rate can degrade due to failures in Radio layer – Coverage/Quality/Interfere, unavailability of resources – Radio/MME/Tx, or other reasons – HW/SW/VSWR/Ant line etc.

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