The 8th International Conference on Computer Science & Education (ICCSE 2013) April 26-28, 2013. Colombo, Sri Lanka SaB2.3

Implementation of Concatenated Short Messaging Service in a Campus Environment

H.K.S. Premadasa Centre for Computer Studies

Sabaragamuwa University of Sri Lanka Belihuloya, Sri Lanka

salinda@sab.ac.lk

Abstract-Integrating a secure short messaging system with message concatenation into a learning management system (LMS), provides a facility for teachers to communicate with students effectively. In this paper, we propose an open-source mobile-based short messaging system with message concatenation that can be easily integrated into the MoodIe LMS. Initially, a database is integrated into the LMS that holds message information such as recipient's phone number, message body, user data header (UDH), etc. The UDH associated message concatenation with short messaging service is used to transmit data in the SMS for the students. Authenticated users can create extensive text messages using a mobile device connected to the Internet. Statistical analysis of results during a campus-wide implementation of the system reveals positive feedback of students in using SMS for academic activities.

Index terms- Message concatenation, mobile learning, SMS, UDH

I. INTRODUCTION

Recent reports indicate that more than 6.6 trillion text messages were sent out over carrier networks worldwide in the year 2010 which includes messages used in learning environments [1, 2]. Moreover, stereo images, colour images, animations and voice can be sent over SMS using a number of consecutive messages through mobile devices that do not even support 3G or GPRS technologies [7, 8]. The use of mobile technologies for distance learning has become a popular tool in higher education across the globe due to its ever-increasing demand for student-centric learning [3]. In this scenario, an SMS system can be established for university students as a supportive tool to capture students' retention in the existing LMS that provides a blended learning environment [4].

The teacher and the student are crucial entities in the learning process and moreover, supporting students in teaching is considered as an indirect form of supporting a student's learning ability [5]. A majority of university students use a mobile phone for routine voice and text message communication. Consequently, SMS can be used as a trusted technology to form a better learning environment having a huge potential in higher education with active (sending a message) and passive (reading a message) interactions [I, 6].

R.G.N. Meegama Department of Statistics and Computer Science

Faculty of Applied Sciences University of Sri Jayewardenepura Gangodawila, Nugegoda, Sri Lanka

rgn@sjp.ac.lk

In mobile telephony, the Short Message Service Centre (SMSC) is the intermediate controlling unit in both parties (sender and receiver) when sending and receiving text messages [20]. The mobile phone is handled by an inbuilt GSM (Global System for Mobile Communication) modem controlled by AT (ATTENTION) commands to pursue text messaging [9, 10].

Teachers who work with Moodie are assigned to facilitate and monitor academic progress of the learners. The teachers use a concatenated SMS system integrated with Moodie through a secure channel. This system provides a facility for the teachers to communicate with students effectively. Moreover, teacher can send brief lecture summaries, assessment schedules or feedbacks, detailed news and notices at any time anywhere using consecutive messages at once.

There are number of web-based paid SMS systems available in the Internet at present that facilitate sending secure messages through an LMS, such paid services restrict the number of outgoing messages as well as the number of users [II, 12]. Teachers who work with this LMS can send messages to a relevant course unit so that students who are currently logged in will receive this message on their mobile devices.

In contrast, our proposed system is a secure, open source

SMS system with message concatenation technique using

UDH that can be easily integrate into Moodie for monitoring

academic progress and performing administrative tasks using

consecutive messages at once where the cost involved is only

for sending messages. Furthermore, we have used only an

SMS gateway and the database of the LMS for this proposed

system.

II. RELATED WORK

Khan and Beg [7] have presented a methodology where stereo images can be sent through a number of consecutive short messages over a GSM network. A stereo image is converted into characters and then set these characters as the payload text of the short message. This payload text is sent as concatenated short messages on a specified port of the mobile device. Moreover, Khan and Beg [13] have used this invention to propose a technique to transfer voice over a short

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message by concatenating short messages defined on a specific messaging port in the device.

A method concerning multiple-choice qUlzzmg over concatenated messages is revealed by Shirali-Shahreza [14] where students receive questions via short messages and after answering these questions, the results can be obtained in the client side. [n this research, the authors have used steganography (hiding information in a cover media) in a picture message to hide quiz answers. There are apparently two programs running on instructor-side and student-side where the instructor prepares and sends quizzes over messages and answers over steganography picture message. The student in turn takes the quiz, answers it, finds the quiz grade and sends answers back to the instructor.

In recent literature, as presented in the previous section, applications were developed based on concatenation of messages and also complex data conversion techniques mainly to send voice, image, animation as well as to perform MCQ tests only between two mobile devices where large amounts of messages (i.e. 30 messages) are required increasing the cost of implementation. Our proposed system is capable of monitoring academic progress and performing administrative tasks using consecutive text messages at once without sending such large amount of messages and concealing data. For this purpose, we have used an open source SMS gateway, a messaging daemon and UDH associated software in the teacher's end. The system is fully functional at anytime anywhere between both parties (teacher and student) in a secure, cost effective and time efficient manner providing a mobile learning environment for assessing students' and performing administrative work.

III. THEORETICAL FRAMEWORK

[t is traditionally known that an SMSC performs a "store and forward' mechanism for sending and receiving messages [15]. The mobile originated (MO) text message is transported from a mobile station to the SMSC where these MO text message may be destined to other mobile stations or other services. [n contrast, the mobile terminated (MT) text message is transported from an SMSC to a mobile station.

Two approaches, namely, PDU (Protocol Description Unit) and Text can be applied to send and receive text messages using AT commands. The text mode (unavailable on some phones) is just an encoding of the bit stream represented by the PDU mode [16]. A majority of network services such as Wireless Application Protocol (W AP), Multimedia Messaging Service (MMS), mobile banking and Over-the-Air (OT A) makes use of the PDU messaging standard. Because this PDU mode is used to encode the message header and user data (payload) hexadecimal or decimal semi-octet format, it is

SMS-SUBMIT and SMS-DELIVER Protocol Description Unit

(PDU) The SMS-SUBM[T PDU can be expressed as with Service

Centre Address (SCA) and the rest of Transport Protocol Data Unit (TPDU). The PDU format is a hexadecimal encoded

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binary format, which means that two hexadecimal digits represent a byte of data. A header with control information and user data make up a TPDU [18].

As some mobile phones do not supported the PDU format but only the TPDU format, the SCA is removed from the PDU and stored in the S[M card by the network operator. This information can be modified using AT commands and hence, the default SCA information (from the S[M card) can be used to implement SMS-SUBMIT to insert any type of SCA supported by the network operator. As a result of this implementation, the SCA part of the PDU can be replaced with a 00 Octet.

<:: ________ S_M

__ S-_S _U_B _MI

__ T _P _D _U ______ �::>

Service Center Tra nsport Protocol Data Unit Address (SCA ) (TPDU)

069149170000F3 41000A8170416998870000A715 050003010801 ..... . . user data ......

Fig. I. The architecture ofthe SMS-SUBMIT protocol description unit (PDU) and its data values

The mobile phone receives an SMS-DELIVER PDU from the SMSC as a Mobile Terminated (MT) message. For this architecture, the same method as described above performs both SMS-DELIVER and SMS-SUBM[T type messages [15]. The architecture and the data values contained in an SMS­SUBMIT PDU associated with message concatenation (with SCA) are represented in Figure l. Various fields that are associated with this SMS-SUBMIT PDU are shown in Table 1. These concepts allow us to understand the theoretical background of generating and sending text messages [21].

A. User Data Header (UDH) The UDH is divided into two parts, the first part, which is

only one byte in length, is identified as a User Data Header Length (UDHL) of the UDH. Following this UDHL, an Information Elements (IE) instructs the mobile phone to perform some action based on the information received. The most common Information Element Identifier (lEI) of Message Concatenation is representing a byte 00. Each concatenated message reference is addressed to a phone that provides clear instruction on putting together two or more text messages to make a single message during concatenation of several text messages.

The second byte of the IE is the Information Element Data Length (lEDL) that tells the phone how many of the following bytes are part of the Information Identifier. The subsequent bytes of the [E are the actual information being conveyed and is referred to as the Information Element Data (lED) [15, 17]. Figure 2 illustrates that the architecture of the standard SMS payload and the concatenated SMS payload.

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TABLEr

SMS-SUBMIT PROTOCOL DESCRIPTION UNIT (PDU) FIELDS

SMS-OCTETS Field Name Length (bytes)

06 Address Length 1

91 Type of address 1

49 17 00 00 F3 Address value variable

41 First octet of SMS-SUBMTT 1

00 TP-MR 1

OA Address Length 1

81 Type of address 1

70 41 69 98 87 Address value Variable

00 TP-PID 1

00 TP-DCS 1

A7 TP-VP 1

15 TP-UDL 1

0 5 TP-UDHL 1

00 03 010801 TP-UDH Variable

------- user data

(in octets) -------TP-UD Variable

B. Concatenated SMS The concatenated SMS (CSMS) is completely related to the

User Data Header (UDH), a collection of bytes that can be placed at the beginning of the text message [15]. To indicate that the SMS-SUBMIT POU contains a UOH, a flag on the text message, called TP-UOHI, must be turned on. This signal instructs the mobile phone that it must separate the UOH from the rest of the POD.

r 140 Bytes """ �----V 1 [� ____________________ s_ m_n _dM_ d_ S_M_S _h _� _oa�dl l Message Data

I 6 Bytes II II User Data Header (UDH) 11 II UDHL I IE II Il I lEI I IEDL I lED JI

• • • •

II User Data Header (UDH) II II UDHL I IE II Il I lEI I IEDL I lED J I

UDHL • User Data Header Length

IE - Information Element

Concatenated SMS Payload

134 Bytes

Message Data

(SMS part I of N)

• • • •

Message Data (SMS part N ofN)

lET - Information Element Identifier

mDL - Information Element Data Length

lED - !ofonnation Element Data

I I j

Fig. 2. The architecture of the standard SMS payload and UDH associated SMS payload

Description

number of octets to follow

SMSC number format (international format)

address of an SMSC (947100003)

User Data Header (UDH ) turned on

ID assigned to a SMS in SMS-SUBMTT format by a local GSM

modem

number of digits in the destination mobile number

destination phone number format (national format)

destination phone number (0714968978)

informs about networking protocol and nature of SMS data

user data encoding scheme

validity period (amount of time that the SCA will hold submitted

SMS if the destination address is unreachable

size of the user data (payload)

user data header length (Depicts in a Table 2) user data header (Depicts in a Table 2) user data (PDU message),

153 (character length per message when UDH exist) x 8 (number a/messages) = 1224 characters

160 characters = 140 octets

(Therefore 10710ctets need maximum as user data)

For the CSMS, the UDHL (06 octets) specifies that the remaining six bytes are for the UDH. The lEI points out that the rest of the message is a CSM (0 I represents an 8 bit message reference number of CSMS) while the Information Element Oata Length (IEOL) indicates the nmnber of bytes (03) containing the lEO. The first byte (01) is allocated to CSMS reference number, next byte (08) is for the total number of fragments of the CSMS and the final byte (01) is for the number of currently received fragment of the CSMS)

When transmitting an extensive text (more than 160 characters as user data) through a GSM network, the message is split into fragments of text messages (153 characters for user data and the rest for UDH in each part of the text message)[ I 9]. Even though, these fragmented text messages are concatenated as a single text message in the recipient's mobile phone, the recipient is unable to recognize this back­end functionality. According to CSMS concept, the reference number of the UOH-IEO must be same in each text message fragment. The total number of text message fragments and current fragment number of the text message must be indicated accordingly in the UOH-IEO for each text message fragment. This is achieved by setting up the fields to 08 (total number of text message fragments) and 01 (fragment number of the current text message) allowing the receiving device to recognize that the concatenated text message consists of just one fragment which is the current actual text message. Table 2 illustrates the fields of the UDH with message concatenation [15, 17].

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TABLE II

FIELDS OF USER DATA HEADER (UDH) FOR CONCATENATED SMS

Fields Description

05

00

03

01

08

01

User Data Header Length -UDHL(5

octets contained in this UDH)

TET: Concatenated SMS 8-bit

(IEDL: Indicates the number of Message fields in UDH Concatenation Concatenated message reference

Total message parts

Message part number (up to 08)

IV. SYSTEM FUNCTION AND ARCHITECTURE

The theoretical concept behind this system flllctionality is built upon the convention of message concatenation and the UDH of the SMS PDU. In the standard format of the text message, only 160 characters (140 octets) can be sent without UDH information to the recipient. However, the UDH with the message concatenation technique can be used to send more characters (rather than 160 characters) using consecutive messages to the recipient.

As illustrated in Figure 3, the proposed system enables a teacher to post extensive text messages to students for monitoring academic progress and performing administrative tasks using consecutive messages at once via a mobile browser interface through an Internet-enabled mobile device. Once a teacher logs in to the system relevant to a particular course unit, he/she can create extensive text message and send brief lecture summaries, assessment schedules or feedbacks, detailed news and notices to obtain more academic expectations such reading, learning or working to gain the preeminent learning outcome from students before the scheduled class.

� 1 Sphts the smgle >-)J �:t�"t:����:

t�sage

� by the software

� Insert message fragments � to the database With UDH

•... �

" : Students

• ...

Can be seen as a single extensive message

Concatenated message I � fragments �

Short Message Service Centre

Concatenated message fragments

(SMSC) SMS Gateway and SMS Daemon

MO-SMS receive and MT·SMS transfer

by the SMSC

Fig. 3. The architecture ofthe proposed system

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The length of the message (number of characters containing the message) is pre-defmed by the system administrator.

When the teacher creates and ready to insert the extensive text, the front-end software splits this extensive text into number of consecutive messages and concatenation technique associated UDH is added for each message part. At this point, the concatenated message reference is the same as every message part assigned by the software. Thereafter, these consecutive messages are inserted into a database where an SMS daemon checks the database periodically and sends out stored messages through an SMS gateway to a GSM modem. Using 'AT' commands, the modem in tum sends out these text messages to all the recipients having access to that particular course unit through the SMSC. Finally, these consecutive messages are merged in the recipient's mobile device and viewed as a single extensive text message in the standard INBOX.

The front-end design of the system provides the teacher the ability to select a single or multi-recipient phone numbers in addition to students' mobile phones numbers previously added. In order to mitigate system abuse, restriction can be enforced to limit the number of messages that can be sent by each teacher for a given month. System logs allow a teacher to view delivery information such as recipient phone numbers, delivered times, message contents about each text message.

V. METHODOLOGY

The Students' feedback is a vital factor to evaluate the effectiveness of the proposed system integrated with the MoodIe in an academic environment. Two groups of students, from Sciences and Non-Sciences, were asked to fill out two questionnaires according to pre and post usage of the proposed system.

Detailed notices were placed in the notice board by informing assessment schedules and administrative activities. On the other hand, lecture summaries and student feedbacks were given by the lecturer in the classroom. At first, a pre­questionnaire was given to the students after following the above process. Secondly, extensive text messages with lecture summaries, student feedbacks, informing assessment and detailed notices were sent to the students from the system. The post-questionnaires were given to the students after those messages had been sent.

The signal strength of the mobile phone is not dependent on the reception of extensive text message, because the reception of an extensive text message is a passive interaction. It means, if the mobile phone is not in the area of network coverage or switched off, the reception of extensive text message is temporally ignored. However, the short messaging service centre (SMSC) will continuously attempt to send the messages llltil an acknowledgement is received.

The proposed system is tested with a series of smart phones as well as basic phones (i.e. Nokia 6720, 3120, 6210, Sony Ericsson W508, T700) having connectivity to several GSM networks. The pre-questionnaire was primarily focused on

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both groups of students to obtain an evaluation of the level of satisfaction among the following aspects, separately:

a) Come across existing methods for achieving their academic and administrative activities.

b) Obtain a preference order of mobile phone's features.

These factors help us to ascertain whether the students are willing to use the proposed system or not for their academic and administrative activities.

Basically, any kind of existing mobile device is well supported for receiving extensive text messages at present. Hence, the following aspect of both groups was taken into account to obtain an evaluation of the effectiveness of the students' adaptation to academic and administrative activities using the proposed system:

a) Suitability of the proposed system for academic and administrative activities

Several statistical approaches, namely, paired sample T-test (parametric) and descriptive statistical analysis, were applied to pre and post intervention data to analyse the appropriateness of the proposed system and its effect on enhancing the efficiency in academic notification of students. The analysis was carried out using both samples separately at first and finally, as an overall sample.

VI. PRE- AND POST-INTERVENTION SURVEY

A. Pre-survey results: Existing methods of academic and administrative activities and mobile phone usage.

Two samples were selected to carry out this survey from Science and Non-Science students with 75 students per each group. At the pre-survey, 97% of the sample responded that they were familiar with mobile phone usage with the precedence of calling (84.33%), sending text messages (73.92%) and other (10.15%) activities.

As highlighted in Figure 4, a majority of the students preferred traditional methodologies, such as notice board for administrative activities and verbal access for academic information in the class room. Non-science students were significantly more dependent on notice boards than Science students.

The pre-survey results initially exhibit students' existing methods of accessing academic and administrative information.

B. Post-survey results: Suitability of the proposed system to obtaining academic and administrative information

The paired sample T-test (parametric) was carried out to analyse the suitability of the extensive text messaging system by comparing data obtained during pre and post intervention surveys with the same sample of students. The post-survey was mainly focused on the importance, efficiency, its effect in changing the learner's traits and social skills and the level of

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satisfaction shown by the students in using the proposed system.

A score value was assigned to each option in list of answers the pre and post survey. A paired sample T-test (parametric) was applied, after defining a null hypothesis (Ho), to compare these two final score values. Ho was accepted or not by considering the p-value of the test (i.e. if p-value > 0.05 then reject Ho or accept otherwise).

• Administrative activities by notice board

• Other technological methods

76.00

67.33

58.67

41.33

32.67

24.00

Sciences Non-Sciences Overall

• Academic activities by lecturer within

the class room

• Other technological methods

77.33 74.00 70.67

29.33 26 .00

Sciences Non-Sciences Overall

Fig. 4. Methods obtained to access academic and administrative information

1) Suitability of proposed system to access information in academic and administrative activities:

We assume a null hypothesis Ho as,

Ho = Students are not satisfied with the proposed system to access information in academic and administrative activities

According to the pre-intervention survey, students preferred administrative activities on notice boards (67.33%) than other technological methods (32.67%). This is followed by having the lecturer in the class room for face-to-face interaction (74.00%) rather than distance learning methods (26.00%). Questions focusing on pre and post surveys were verified using a 5-point Likert scale with strongly disagreed as -10, disagreed as -5, neutral as 0, agreed as 5 and strongly agreed as 10 on the scale. Table 3 gives statistical results obtained after applying paired sample t-test.

TABLE III

RESULTS OF PAIRED SAMPLE T-TEST FOR SMS NOTIFICATION SYSTEM.

Sample Variable N Mean St. Dev p-Value

pre 75 3.83333 4.29750

Science post 75 2.80000 5.14913 0.033

difference 75 1.03333 4.81224

Non-pre 75 3.70000 5.56534

Science post 75 2.26667 5.82941 0.035

difference 75 1.43333 6.74303

pre 150 3.76667 4.95573

Overall post 150 2.46667 5.57880 0.00 4 difference 150 1.30000 5.88423

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As seen in Table 3, of the overall sample as well as of each sample, the related p-value was less than the significant level (0.05). This results in Ho being rejected and HI accepted. This shows that the chance of accepting the proposed system for academic and administrative activities is significantly higher than previous traditional methods.

VII. CONCLUSION AND FUTURE WORK

The proposed system is a prototype developed to communicate administrative details such as detailed notices and assessment/teaching schedules to students and perform academic activities such as lecturer feedbacks and lecture summaries using extensive text messages.

Statistical analysis of students' feedback during a campus­wide implementation of the proposed system pointed out that the students' preference of using proposed system in academic activities is highly significant. As such, it is evident students are eager to be reminded of lecture summaries and feedbacks using extensive text messages to gain pre-eminent learning outcome from a lecture session at any time before the scheduled class from outside the boundaries of a traditional classroom.

We have also identified certain limitations that are beyond the theoretical and technical implementation of the proposed system. This original survey was conducted in the university at four different faculties, namely, Agricultural Sciences, Applied Sciences, Management Studies and Social Sciences. Social issues concerning the usage of modern technology are

somewhat different among the two groups of students. Language skills played a major role during the introduction of this technology. As such, we must pay attention to isolate social difference and language skills during implementation of the project.

Future research directions will certainly discover solutions to mitigate the above limitations by inventing a demand based mobile learning environment useful for lifelong learning.

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