Design of an Autonomous Remote Cellular Network

Service Tester

Sharvin Vijayakumar, Suhanya Jayaprakasam, Sivajothi

Paramasivam

School of Engineering

KDU University College,

43400 Damansara Jaya, Selangor D.E., Malaysia

Quan Zee Teng Quantum Engineering Solutions Sdn. Bhd

Centrio Pantai Hillpark, 59200 Kerinchi,

Kuala Lumpur Malaysia

zee@quanteng.my

Abstract— This paper presents an autonomous cellular testing

system, which gathers wireless Quality of Service (QoS) data

remotely, for the purpose of network optimization activities by

network service providers. We have proposed and designed a

proof of concept prototype of an autonomous testing device

that could be installed in public vehicles and static locations to

enable continuous testing and monitoring of cellular wireless

networks. This leads to a more accurate and up to date quality

of service data for the wireless service provider’s quick action.

Data would be collected autonomously while the vehicles are

on the move and will be sent to a server periodically where

engineers can analyze and process the data in near real time.

All radio and service test parameters are captured with geo-

location and accurate time stamping from GPS satellite time to

produce geo-reports, and statistical analysis with cross

reference capability against core network counters and logs by

the wireless service provider. Service testing conditions are

around typical subscriber usages; ping, file transfer protocol

(ftp) upload and download, http download, call and short

messaging service (SMS). Initial testing proves that our device

is able to provide detailed QoS data to the service provider for

optimization purposes.

Keywords- autonomous; remote testing; cellular networks.

I. INTRODUCTION

Wireless cellular communications offer a host of services to subscribers, from the traditional voice telephony and short message service (SMS), to a richer variety of services over the internet protocol (IP) such as web browsing, instant messaging, streaming and video telephony. While the older GSM (2G) systems were based on traditional circuit switched technology for voice and SMS services, the current 3G systems, and going further forward into the future, the LTE (4G) wireless systems are evolving toward more packet switched services over standard internet protocol [1]. As a result, spectrum efficiency is greatly increased and access to existing IP services and rich digital content will be more seamless to the subscriber. These networks require continuous tuning and optimization to cater to the changes in usage patterns, movements of subscriber population densities, changes in terrain and man-made structures, equipment failures and faults.

The explosive growth of cellular network service providers over the past few years has boosted healthy competition among service providers, which in turn

positively affects the quality of the service provided to the subscribers.

In order to stay ahead of the competition, service providers continuously monitor and maintain the quality of their network, ensuring that their subscribers enjoy top notched services at all times. This monitoring must be done through continuous testing of the services provided by the cellular network.

Cellular testing has now become a central measure in maintaining the standard of a network. The most common tests carried out by cellular testers are [2]:

1. Locating the pockets of bad or no service.

2. Determining the quality of service (QoS) of various services offered by the network to the customers, like voice quality, download / upload throughput and etc..

3. Accessibility of the network- the ability to obtain services at all times

4. Retainability of the network- the ability to deliver said services uninterrupted.

Currently, testing of cellular networks are done on a periodic quarterly or yearly basis, complimented by ad-hoc testing spurred typically by user complaints. Problems arising from the network typically manifests itself via complaints from subscribers. Cellular service providers will then dispatch engineers and technicians to test the network at that particular location to troubleshoot the problem. Existing solutions in the market involve engineers taking a laptop and a test device to that particular location to perform testing.

This method suffers several drawbacks:

1. Time Consumption: Time is wasted to gather relevant data. Engineers need to go on location to collect the data they need for processing and analysis. Troubleshooting and rectification work then is required with several rounds of changes and testing to correct the problem. As a result, engineers spend a large amount of time collecting data rectifying the problem, and then verifying the fix.

2. High Cost: High cost of Engineer’s time needed to travel to location to collect data and incurredtransportation fees.

2012 IEEE Symposium on Industrial Electronics and Applications (ISIEA2012), September 23-26, 2012, Bandung, Indonesia

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We have therefore proposed an autonomous remote cellular service tester in this paper, to alleviate the problems caused by the current solutions for cellular testing.

II. SYSTEM DESIGN

Our device, hereafter called the test set, has the onus of being both autonomous and remotely accessible. The test set can be installed in either vehicles or static locations. Designated tests are conducted continuously by the test set and the collected test data are logged into a remote server. In case a specific test needs to be conducted, test engineers could remotely send a control to the test set via the web server. Figure 1 depicts the basic operation of the test set.

A. Hardware Requirement

The main objective of the hardware design is to keep the test set as small as possible as it would be installed in vehicles. The test set has to be able to be connected to the car battery which runs at 12 volts (V) direct current (DC). Figure 2 illustrates the functional blocks of the test set.

This test set will be connected into a car or a public vehicle. The power source is the vehicle’s battery which operates at 12VDC and connection made is via the cigarette lighter power socket, which provides a direct connection to the car battery.

The equipment required to assemble the test set are summarized in Table I.

B. Software Requirement

The software’s that are used to develop this test set are:

1. Ubuntu Linux Operating System This operating system is a freeware, user friendly and

comes with support for various devices. Linux is used as the platform to develop bash scripts to send AT commands, the control language of the serial modem devices.

2. Ruby on Railson Nginx Web Server This software is an open source application that runs on

the Ruby programming language. The logged data of the test results are presented in a web based Graphical User Interface (GUI) built using this framework.

3. MySQL Database Server This open source relational database system is used to

store the collected service test and radio parameters.

Test 1

Test 2

log

control

serverTest set

Base

station 1

Base

station 2

Figure 1. Basic operation of the autonomous remote service tester

Figure 2. Block diagram of the autonomous cellular tester circuit

III. TESTING METHODOLOGY

Multiple testing is done on the network using the developed test set. Services tested are Ping, FTP, Call, SMS and HTTP. Having received instructions from the server, tests are performed continuously and autonomously by the test set. Table II shows all the test cases that are available for testing by the test set. It describes the parameters required from the user via the web interface and also the data that will be logged from said test case.

The drive test is conducted with the test set installed in a vehicle along a route. While the vehicle is on route, the test set will perform multiple tests and collect data from the network, as determined remotely from the configuration page on the server’s web interface. The test cases configured on the web interface is translated to a command file which gets synchronized to the test over the data network. As the test cases are run, service QoS data and radio parameters are collected into files which are synchronized back to the server, and also over the cellular data network.

IV. TEST RESULTS AND DISCUSSIONS

The autonomous testing device collects data and logs the data to be sent to the server for processing into a web based Graphical User Interface (GUI).

Figure 3 and Figure 4 illustrate the geolocated radio and service data collected by the test set, displayed on a map using the web interface. The easy interface to collected QoS data facilitates very quick troubleshooting. Apart from geolocated data viewable on maps, we are able to (with the wide range of collected data) tabulate a range of statistical charts and graphs to represent and mine the collected data for intelligence on the nature of QoS degradation experienced by cellular network users. The statistical information is useful for management to obtain an overall understanding of the network problems faced and the severity of the degradation as shown in Figure 5 to Figure 8.

2012 IEEE Symposium on Industrial Electronics and Applications (ISIEA2012), September 23-26, 2012, Bandung, Indonesia

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TABLE I. SUMMARY OF EQUIPMENT USED TO ASSEMBLE THE TEST SET

Device Specification Function

Motherboard Intel

D525MW

Intel D525MW Fanless Dual Core Atom Mini-

ITX Board

Hardware host of the

Linux Operating System

Intel Atom

Processor D525

-1.8 Giga Hertz (GHz)

-64-bit instruction set

Processor for all the

activity done by the device

Toshiba Hard Disk -Memory of 320GB Stores all the data and

log files

Sierra Airprime MC8704

- PCI Express

- GpsOne from Qualcomm for

positioning and time

Determines the location

of the device via

GpsOne technology

Ericsson F3507G

Mobile Broadband

- PCI Express

- WCDMA

2100/1900/850 GPRS/EDGE

850/900/1800/1900

Executes all the test

cases from the scripts to the cellular network

BQ656 (Casing) -Small ATX form factor chassis

The casing to cover all

the modems and the

motherboard.

TABLE II. SUMMARY OF USER INPUT AND LOGGED DATA IN A TYPICAL

TEST

Test User Input Data Logged

Ping IP address

Intervals

Number of

pings

Sending duration

Receiving duration

IP address

Test time

Number packets send and received

FTP IP address

Username

Password

Time taken to upload

Time taken to download

Upload/ Download acknowledgement

Test time

FTP server IP address

Call Base Station (B)

number

Delay between

calls

Hang time

Connection time

Test time

Target (B) number

Call duration

SMS B number

Single text or

continuous text

Send acknowledgement

Receive acknowledgement

HTTP Website address

Duration

Interval

Test time

File size

Speed

Figure 3. Geolocated radio data displayed on web interface

Figure 4. Geolocated service test data for calls

Charts and statistical data are also useful for engineers to

troubleshoot problems by providing a large sample size of data from which they may draw statistical conclusions to judge the impact of problems into perspective, and to view them by varying levels of resolution. Figure 9 and Figure 10 gives an example of service level degradation separated by geographical areas around Kuala Lumpur, Malaysia, which are defined in the database by means of geographical ranges

For benchmarking purposes it is also useful to make

comparative analysis between operators to understand service quality comparison between competing providers. This helps ascertain market position and devise strategy for increasing market penetration and reducing subscriber churn. Figure 11 and Figure 12 illustrate collected comprative data between multiple operators which show comprative strengths and weaknesses in various geographical locations.

V. CONCLUSIONS AND RECOMMENDATIONS

Autonomous testing devices like the one described in this paper, installed in public vehicles and static locations can yield considerable amount of quality of service data to wireless service providers for optimization efforts. The data is collected continuously providing the cellular service provider with a near real time view of subscriber quality perception.

Data provided through these devices facilitate detection of problems in the network. The test cases can be changed easily from a remote location to meet more customized test conditions. Reports generated can be done for a single wireless service provider or used as a benchmark of all service providers in an area. This device is also very compact and mobile and can fit unobtrusively inside a vehicle without occupying a lot of space. It also does not need to be serviced on site as the maintenance of the software can be done remotely, thereby greatly increasing efficiency while lowering running costs of network optimization.

2012 IEEE Symposium on Industrial Electronics and Applications (ISIEA2012), September 23-26, 2012, Bandung, Indonesia

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Figure 5. Total call and SMS tests

Figure 6. Blocked and dropped call rates

Figure 7. Data tests

Figure 8. Data Test Speeds

Figure 9. Dropped call rate by area

Figure 10. Blocked call rate by area

Figure 11. Signal Strength (dBm) by Area for different Operators

Figure 12. Interference (Ec/No) (dB) by Area for different Operators

A. Problems encountered, expected and anticipated

There are some inherent problems with this methodology which require our consideration:

1. Synchronization of collected data being over the cellular network itself introduces a traffic load on the network being observed. Careful planning must be used to ensure data synchronization load is low and if possible, on a different network than the one which is being measured.

2. Certain manufacturers of commercial radio modems do not allow interrogation of low level physical and medium access control signaling and parameters, which are required for the collection of parameters required.

2012 IEEE Symposium on Industrial Electronics and Applications (ISIEA2012), September 23-26, 2012, Bandung, Indonesia

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B. Current Work

We have embarked on ongoing developments to improve the automation and reliability of the test set to increase the fault tolerance and automatic recoverability. Furthermore, improved geolocated and statistical reporting options are being developed to improve the usability and quality of reports generated for assisting optimization effort. Current efforts also include engagement with local operators for trial, testing and feedback.

C. Recommendations for Future Development

Among the improvements that can be done on this project are:

1. Utilize and improved external reception antenna mounted on vehicle body.

2. More compact casing, with higher tolerance to mechanical vibrations while reducing energy footprint

3. Increased modems on the device for concurrent testing of services.

4. More streamlined code using C and assembly

5. Battery systems for sustained operation during engine off scenario, and for graceful shutdown of systems

REFERENCES

[1] Poole, I., Cellular Communications Explained: From Basics to

3G. 1 ed. 2006: Newnes. [2] Fitts, R., Cellular Network Testing. 2006, Consultronics

Ontario, Canada.

[3] uOttawa. EMF Primer- Base Stations [Online] Available at: <http://www.rfcom.ca/primer/bases.shtml> [Accessed March

2012]

[4] Docomo. 1999, A Brand New Mobile Millennium Ericsson/CATT/DoCoMo jointly demonstrate pioneering W-CDMA technology at PT/Wireless [Online] Available at: <http://www.nttdocomo.com/pr/1999/001070.html> [ Accessed 20 January 2012]

[5] Radio-Electronics. Cellular Concepts and Basics [Online] Available at :<http://www.radio-

electronics.com/info/cellulartelecomms/cellular_concepts/mobile-basics-concepts.php>[Accessed 1 March 2012]

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