TTCN-3 Based Automation Framework
for
LTE UE Protocol Stack Testing
Theofanis Vassiliou-Gioles
Testing Technologies
Ranganath Mahapatra
Larsen & Toubro Infotech
1
LTE Network Architecture
GERAN
SGSN
HSS
UTRAN
S3
S6a
S7
MME
LTE-Uu
UE
LTE-Uu
Operator IP
Services
PCRF
S10
eNB
S4
S11
Serving GW
S1u
S2a
X2
S5
Internet
PDN GW
S2c
SGi
S2b
ePDG
Trusted non 3GPP IP
Access
Trusted/Untrusted non3GPP/3GPP IP Access
Wn*
Untrusted
non 3GPP IP Access
UE
2
Network Simulator
Need for Simulated Environment
• Before porting a UE protocol stack to a Modem, a simulated environment is required for
test and verification
• Network simulator is implemented on a host environment consisting of an automation
framework, test scripts and the UE side interface.
Emulating Network Element Functionality
• Test environment emulates the functionality of the network elements.
• It interacts with the UE protocol stack through a common interface in a pre-determined
manner as per the test cases.
Manager, Logger, Debugger
• The frame work consists of a test manager, mechanism to capture logs, data analysis
and debugging capability in text and graphical mode.
• It provides scope for integration of external codec and plug ins.
3
Protocol Stack Functionality
NAS
NAS
Relay
RRC
RRC
PDCP
PDCP
SCTP
SCTP
RLC
RLC
IP
IP
MAC
MAC
L2
MAC
L1
L1
L1
L1
UE
LTE-Uu
S1-AP
eNobeB
S1-AP
S1-MME
MME

UE protocol stack communicates with multiple elements in the network side though eNodeB.

UE control plane protocol layers are mapped to eNodeB and MME.

Except for the NAS layer messages, the other layers of UE interact directly with eNodeB
protocol stack.
4
Testing Architecture
Test Management
Control & Logging
Automation Framework
TCI
UE Protocol Stack
ETSI Test Scripts in TTCN-3
TRI
RRC
DRB Codec
SRB Codec ASN.1
Codec Layer
PDCP
RLC
PDCP
RLC
MAC
L2 Layer Stubs
MAC
MAC-Phy
MAC-Phy
System Adaption Layer
UDP / IP
5
Components
Codec
• Encodes and decodes the RRC messages which are defined in EUTRA_RRC_ASN1_Definitions.
• The default technique for encoding and decoding is as per RRC standard 36.331 is “PER-BASICUNALIGNED: 2002”.
L2 Layer Stubs
• PDCP, RLC and MAC header encapsulation and de-capsulation of messages and PDUs are some of
the functionalities of this module.
• Other basic functionalities/procedures of PDCP, RLC and MAC, ex - RACH procedure, broadcast
etc are also implemented.
System Adaptation Layer
• defines the communication protocol between eNodeB and UE protocol stack.
• The function of MAC-Phy interface is for the synchronization of eNodeB with UE protocol stack on
UDP/IP.
Wireshark Dissection Implementation
• MAC-Phy layer encapsulates its header into the messages.
• Wireshark doesn’t support these headers, so required dissectors are implemented in wire-shark
to dissect and understand the LTE messages sent via PHYSAP interface.
ETSI Test Script
• Consists of test cases, templates, records, functions, interfaces and TTCN3 ports (TCI & TRI
Ports).
• Additional test cases were also developed to improve the coverage.
6
Incremental Development & Testing
7
Test Execution
 Test case drives the specified procedures for
validation of the stack.
 The Test Manager of IDE provides a GUI interface to
run the test cases individually or in batches.
 The frame work provides log capturing and debugging
mechanism both in text and graphical representation
8
Our Value Adds on ETSI’s Solution

ETSI’s Solution
–
ETSI Test suite provides TTCN-3 scripts for protocol conformance testing.
–
It provides parallel test components and ports for seamless mapping of protocol layers for
network side entities.

Our Value Adds
–
In order to optimize the development cycle, we have utilized ETSI test suites,
commercially available IDE and external plug ins.
–
Adaptation layers were developed
–
A pseudo MAC-Phy interface layer was implemented.
9
Challenges
Codec’s and Adaptation Layers : Requires good understanding of protocol stack layers
and specification
Debugging and classification of issues: Differencing between test framework and UE
issues
Concurrent Development : Development of Test Framework (IDE), ETSI test cases and
UE Protocol stack
Identification of suitable commercial IDE
10
Thank You
Experts in Test
Automation
Our Business Knowledge,
Your Winning Edge.