1. TTCN-3 Based Automation Framework for LTE UE Protocol Stack Testing
Theofanis Vassiliou-Gioles
Testing Technologies
Ranganath Mahapatra
Larsen & Toubro Infotech

2. LTE Network Architecture
GERAN
SGSN
HSS
Operator IP Services
UTRAN
PCRF S3
S6a
MME S7 S4
LTE-Uu
S10
S11
Internet
eNB
Serving GW
PDN GW UE
LTE-Uu
S1u S5
SGi
S2a X2
S2b
S2c
ePDG
Trusted non 3GPP IP Access
Trusted/Untrusted non-3GPP/3GPP IP Access
Wn*
Untrusted
non 3GPP IP Access UE

3. 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.
Need for Simulated Environment
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.
Emulating Network Element Functionality
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.
Manager, Logger, Debugger

4. Protocol Stack Functionality
RRC
S1-AP
PDCP
SCTP
RLC IP
MAC L2 L1
NAS
RRC
PDCP
RLC
MAC L1
NAS
S1-AP
SCTP IP
MAC L1
Relay UE
LTE-Uu
eNobeB
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.

5. ETSI Test Scripts in TTCN-3
Testing Architecture
Test Management
Control & Logging
Automation Framework
TCI
ETSI Test Scripts in TTCN-3
UE Protocol Stack
TRI
RRC
PDCP
RLC
MAC
MAC-Phy
SRB Codec ASN.1
DRB Codec
Codec Layer
PDCP
RLC
MAC
L2 Layer Stubs
MAC-Phy
System Adaption Layer
UDP / IP

6. Components
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 is “PER-BASIC-UNALIGNED: 2002”.
Codec
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.
L2 Layer Stubs
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.
System Adaptation Layer
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.
Wireshark Dissection Implementation
Consists of test cases, templates, records, functions, interfaces and TTCN3 ports (TCI & TRI Ports).
Additional test cases were also developed to improve the coverage.
ETSI Test Script

7. Incremental Development & Testing

8. 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

9. Our Value Adds on 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.

10. 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

11. Thank You Our Business Knowledge, Experts in Test Automation
Your Winning Edge.