LTE KPI test procedure : Latency

1.1    Latency

1.1.1      Round Trip Time

Name:  Maximum round trip latency
Purpose: To verify that Round Trip Time  remains within acceptable range
Measurement method	Time stamp of “PING Response received by the UE" - Time stamp of “PING Request sent by the UE
Acceptable range	Average time less than 40 ms

 

1.1.1.1      Test conditions and requirements

This test is to measure round trip time (RTT) in given test network in stationary conditions

Specifically the procedure starts at transmission of PING Request by the UE and ends at the reception of PING Response at the UE.

Radio latency is round trip time between PDCP layer of UE and PDCP layer of eNB. Single user per cell scenario is to be considered.

Radio latency will be measured using ordinary ping.

As shown in the figure below, end-to-end latency is the sum of radio latency and core latency.

But there can be some uncertainties in core latency because the backhaul delay and delay induced in PDN are variable.

Core latency shall be separately measured and radio latency is calculated by end-to-end latency minus core latency.

Ÿ A vehicle for moving, a test UE, and a test laptop computer connected with GPS and the UE are required.

Ÿ 2ms backhaul delay between eNB and EPC is assumed.

Ÿ Assumes UE processing time = 1ms. (one way)

Ÿ The network stability is certainly guaranteed.

1.1.1.2       Test description

1.     Locate the test UE at a predefined place with good link condition.

2.     The test point should be over the cell edge RF conditions. (RSRP: higher than -100dBm, SNR: higher than 5)

3.      Connect the UE to eNB. (Initial attachment)

4.      Generate 32-bytes ping packet 100 times using DOS windows.

5.      Calculate the min, average and max value of Round trip time.

6.      Average Round trip time is calculated using measured data between 5th percentile and 95th percentile.

1.1.1.3      Pass/Fail Criteria

Ÿ The average round trip time shall be less than 40ms. (median of 95% tile)

Appendix A – Acronyms

DM                   Diagnostic Monitor

eNB                  E-UTRAN NodeB

EPC                 Evolved Packet Core

FTP                  File Transfer Protocol

GBR                  Guaranteed Bit Rate

KPI                   Key Performance Indicators

LTE                  Long Term Evolution

MIMO               Multiple Input Multiple Output

MME                Mobility Management Entity

OCNS               Other Cell Noise Simulator

PCRF               Policy and Charging Rules Function

PDN                 Packet Data Network

P-GW               PDN Gateway

QCI                    QoS Class Identifier

RRC                 Radio Resource Control

RSRP               Reference Signal Received Power

S-GW               Serving Gateway

SIMO                Single Input Multiple Output

SINR                 Signal to Interference and Noise power Ratio

TCP                  Transmission Control Protocol

UE                    User Equipment

UDP                 User Datagram Protocol