Study About Mobile Computer Communications Systems Computer Science Essay

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Nowadays Mobile communication network allows real time and fast access to information by using hand held devices and others mobile devices. This report discusses about a Regulatory Agency named STARfruit Communications Sdn. Bhd based in Malaysia Kuala Lumpur. Actually STARfruit Communications has Head quarter and one satellite branch in Malaysia. STARfruit Communications is a regulatory agency which regulate electricity, water and telecommunication sector in Malaysia. However to facilitate communication and easy access to consumers complaints the management of STARfruit Communications suggested to mobilize some staff of consumer and Transport department by using PDAs. The agency is using a traditional client-server application over its local area network. Moreover the management of the Agency decided to mobilize some of the desktop client to be used on PDA devices. However it should be noted that to communicate between Wireless LAN and cellular network all PDAs should support 3G UMTS technologies. The use of EDGE, GPRS is also considered in this research. Hence the use of PDA allows users mobility advantage and increase work performance. The users will have access to wireless network through access points. STARfruit Communications has the following department respectively Information System Department, Human Resource Department, Consumer Department, Transport Department. Moreover 10 staff of consumer department and 15 staff of transport department will use PDAs to facilitate communication with consumers as well as communicate with other staff internally inside the local area network. Other remaining staff will continue to use desktops for their work.


The objectives of this research are to analyses and suggest STARfruit communications Sdn. Bhd to mobilize their desktop clients to be used in PDA devices by their remote workforce. This study will explain the wired network and wireless LAN STARfruit use currently and suggest the suitable applications for the PDA devices. The study will explain the issues of wireless LAN faced by STARfruit and the proposed solutions to solve those issues.

However the research focused on the bearer technologies supported by the PDAs and explains the advantages of bearer technologies to the mobile infrastructure of STARfruit.

This research will describe the advantages of Mobile IP which will be the protocol used for communication between the mobile client and the organization's server.

The study will focus to identify suitable client development technology for PDA.


This study describes the way the agency STARfruit Communications will connect its network infrastructure to the operator's network. However this study describes the mobile technologies EDGE, UMTS, GPRS to connect the PDA devices to the internet. In addition this study describes how the PDA device will connect to the operator network and some measures to prevent wireless security issues which could affect mobile communication.


STARfruit Communications Agency ensures that some utilities companies provide good services to the consumers in the country. STARfruit Communications ensures the protection of the consumers from the abuse of some utility companies because they have monopoly. However every time STARfruit Communications receives complaints from consumers and the company needs PDA devices to collect the complaints and update information to their complaint application at any time and in anywhere.

STARfruit Communications has a complaint application in house for storing consumer's complaints. Actually the information is collected through forms.

The connectivity of the PDA to the STARfruit Communications network will allow mobile staff to collect information from the consumers anywhere and update them to the complaint application.

Hardware architecture

STARfruit Communications Agency uses blade server IBM HX5 which run Microsoft Windows Server 2008 as Operating System, processor IntelRxeon 2.7 GHz, storage capacity up to 300GB and it is connected to the internet. However the mobile terminals used by remote workforce are

HTC Touch 3G PDA Phone with Windows Mobile version 6.1 as operating system installed;

EDGE, UMTS, GPRS, Wireless LAN are the mobile technologies used by STARfruit Communications to connect mobile devices to the internet.

Softwares installed inside the blade server IBM HX5 are:

Microsoft Outlook Exchange for mail communication.

Database for Transport department and Consumer affairs build in SQL Server 2008 and PHP.

Database for telecommunication operators. The database contains the type of links that connect the company to outside, their capacity. For example the company is connected to outside by fiber or satellite. Their link is protected or not.

The database of telecommunication operators contains information about the company, their traffic it means the number of clients who call per hour and the average duration of call.

The database of telecommunication operators contains the capacity of their systems; it means the number of customers that their system allows calling at the same time.

Software applications for mobile devices to synchronize to the mobile phones: HTC Touch 3G PDA Phone.

Figure 1: Wireless LAN (

STARfruit Communications decides to choose Windows Mobile operating System for their PDAs. Here are some reasons they chose Windows Mobile Operating system.

Windows mobile gives option to the owner of the mobile device to set up a password to avoid others unauthorized users to get access to data. An unauthorised users will be prompted for a password before to use the phone.

Most of the users are familiar with windows applications like word, excel, powerpoint. However windows mobile can provide mobile version of office applications which most users are familiar.

The figure below shows some advantages of Windows mobile to Blackberry

Figure 2: (

Figure 3: HTC Touch 3G PDA Phone (

Figure 4: Specifications of the proposed HTC Touch 3G (

Memory and storage


GSM/WLAN Convergence

Operating system


Flash ROM: 256M

RAM: 192M

2.8" TFT LCD Flat Touch-sensitive screen with QVGA resolution


Europe/Asia:900/2100 MHz

Up to384kbps up-link and 7.2 Mbps down-link speeds

Windows Mobile 6.1 Professional

Qualcomm MSM7225, 528MHz

MicroSD memory card(SD 2.0 compatible)



STARfruit Communications Sdn.Bhd chose HTC Touch 3G for their remote workers for some reasons like its features and specifications. Here are some specifications of HTC 3G mobile phone.

Screen size: 2.8" TFT LCD Flat Touch sensitive. This screen is enough large and good for mobile workers and the resolution with QVGA is better.

Battery life: Li-ion 1100 mAh. Standby up to 450h. You may talk up to 6h 30min. Field workers need mobile phone which keep battery power for long time. Therefore they will avoid charging it while they are in the field. However these PDAs are suitable for mobile workers because they do not need to charge it every day.

Overview of Wireless LAN of STARfruit Communications Sdn. Bhd

STARfruit Communications Sdn.Bhd has a local area network and wireless LAN as well. This infrastructure is described in figure 1. However there are four departments respectively Information system department, Human Resource department, Consumer Affair department and Transport department inside the agency. All departments are connected to a switch which connects them to the local area network. Then the switch is connected to a router and plays a role of gateway by connecting the organization to the internet. Moreover access points are connected to a switch to form a Wireless LAN. The access points connect staff that has laptops with wireless card integrated, mobile users as well as desktops users to the internet. Furthermore all the staff can access the resources and applications of the server like SQL database, by the client outlook installed on their desktops and PDAs they can download their emails from the server.

Connecting STARfruit Communications' s network to operator network

Figure 2: Office network connecting to Mobile Operator Network

According to the figure 2 the network of the organization is composed of the following infrastructure access points, router, switch, firewall, server, and modem. However inside the organization there is wirelesses LAN which connect different staff to the internet. Outside the organization network the mobile users will connect through the BTS to transmit and receive data.

However to connect organization network which use Wireless LAN to the operator network (GPRS, UMTS) there should be two separate authentication, authorization and accounting(AAA) on two accounts. Moreover PDAs allocated to mobile staff should have an account to the operator network. Therefore Wireless LAN network interfaces cards, SIM cards for GPRS and UMTS SIM is needed. Needless to say that the entire PDA must have dual mode interfaces in order to support both Wi-Fi and cellular networks.

According to Stemm (1996) vertical handoff occurs between base stations that are using different wireless network interfaces. This is why in this figure 2 if a mobile user is situated inside network organization he will be connected to the wireless LAN of the organization with his PDA to get connected to the internet and keep communicating with other staff of the network. However it may happen that the mobile staff roams from the organization network to outside the coverage of the organization Wireless LAN. The PDA's mobile staff will handoff and get connected to the nearby base station because of seamless vertical handoff. He will keep his communication without interruption of the call.

Wireless LAN security issues inside the organization

Even if wireless LAN is nowadays become popular and most company opt to install it there is a lot of risks that wireless LAN be compromised by attacks. Because of the way radio wave is transmitted over the air and it is open make wireless communication susceptible to different kind of attacks. Moreover this research describes some of the attacks susceptible to over overwhelm wireless LAN of STARfruit Communications Sdn.Bhd.

Denial service attack

In this kind of attack the intruder can flood with invalid messages the wireless access point of the organization, preventing legitimate hosts to get access to information from the access points. Therefore there will be a lot of traffic inside the network. By flooding the network with invalid messages, the attacker will consume a lot of bandwidth, slowing the speed of the wireless LAN and affecting others hosts.

Figure 3: Denial Service Attack (


In this attack the sender may communicate with the receiver. However the attacker can intercept the information by using its antenna and modify its content.


DHCP could be a problem to wireless LAN because it allocates dynamically IP addresses to legitimate hosts inside the network. Therefore DHCP server could allocate IP address unintentionally to an attacker.

Some solutions to the issues

Change default SSID of the wireless access point.

Set up a Virtual Private Network to encrypt data communication

Every time check the security of your WLAN

Set up encryption key to WLAN WEP.

Connecting PDA to operator network

In this scenario the management of STARfruit Communications need to identity the number of PDAs needed to be connected to the operator network. In the case of STARfruit Communications Sdn.Bhd they need to mobilize 25 staff from Consumer and Transport department. Therefore subscription of 25 PDAs to one Telecommunication company is necessary to allow remote workforce to communicate. However the need to identify a suitable telecommunication company in term of cost, bandwidth is needed.

Figure 4: Postpaid Plans Comparison Celcom Vs Digi Vs Maxis (

For example in supplementary plans off-net calls for DIGI is 13 sen, for Maxis it is 20 sen, for Celcom it is 30 sen. While on-net calls for Digi is 13 sen, for Maxis it is 15 sen and for Celcom is 30 sen. In this figure 4 the cheapest voice call is Digi. Based on this figure Digi operator is the best suitable Telecom company STARfruit Communications need to make a contract for subscription for their PDAs simcards because of the cheapest price for calls.


Monthly access


Average speed



RM 68






RM 80

Explore 10GB

RM 108


Explore 16 GB

RM 158


Figure 5: DiGi Broadband pricing per (


Monthly access




Celcom broadband entry

RM 48

For those with basic surfing needs

Up to 384 kbps

1 GB

Celcom Broadband Basic

RM 68

Surfing every day fro email, news and general browsing

Up to 512 kbps

3 GB

Celcom Broadband Advance

RM 98

Advanced user who has download, movie streaming & other heavy internet needs

Up to 3.6 Mbps


Figure 6: Celcom broadband pricing as per (

According to the figure 5 the different plan ranging from RM68 for discovery plan, to RM108 for explores 10 and for explore 16 plan RM158 DiGi has a competitive price compared to mobile broadband from celcom. However the need to identify a suitable telecommunication company in term of cost, bandwidth is needed. This is why STARfruit chose DiGi as a telecommunication company to go for subscription for their PDAs.

Bearer technologies

STARfruit Communications Sdn.Bhd opts to mobilize its remote workers mostly who work in consumer and transport departments to increase the efficiency and effectiveness of the work. The mobility of the remote workers will facilitate them to reach consumers easily. Therefore they will be able to collect their complaints to their PDAs devices and update complaint's database installed in the STARfruit Communications Sdn.Bhd 's server accordingly. But to realize the need of telecommunication technologies such as EDGE, UMTS and GPRS is paramount. As those cellular technologies are proposed for this study therefore there is a need to explain the following bearer technologies and their advantages.

The bearer technologies used in this scenario to connect Wireless LAN to the operator network are the following:

UMTS: its stand for Universal Mobile Telecommunication System. UMTS is a third generation. UMTS has a high speed compared to other mobile telecommunications technologies. UMTS as a 3G technology allow users to change the network (handover) from Wireless LAN to cellular network while communicating. Because of the high speed rate it has UMTS can support videoconferencing and download video and music. UMTS technology has a wide coverage area than many of other telecommunication technologies.

EDGE: stands for Enhanced Data for Global Evolution. EDGE is a third generation mobile telecommunication technology and was developed to enhance GSM. EDGE is a new version of GSM but with high speed data transmission than GSM. With EDGE you can browse to the internet by using wireless connection through mobile phones. EDGE offer high data speed rate than GSM networks. EDGE was released to the public in 2000. In EDGE data transmission is made at speed of 384 kbps.

"GPRS: stands for General Packet Radio Service is a packet-based data network, which is well suited for non-real time Internet usage, including the retrieval of email, faxes, and asymmetric web browsing, where the user downloads much more data than it uploads on the internet" (Rappaport, 2002). GPRS is a second generation technology and can support more users than High Speed Circuit Switched Data.

Coverage of DiGi

Figure 7: Coverage (

According to the above figure it is obvious that DiGi 3G (EDGE) is present in some towns. As STARfruit Communications Sdn.Bhd is located in Kuala Lumpur and would like to mobilize its remote workers with PDA, 3G (EDGE) will be the good choice for mobile communication.

Protocols used between the mobile client to the organization server

Needless to say that to communicate with the organization server PDAs should use the same protocol with the organization's server. However while mobile workers communicate using PDAs from one region and roam to another base station communication should be maintained. However this mobility can be facilitated by using the mobile IP. This study describes the protocols used in 3G mobile communication.

Mobile IP:

Mobile IP is an internet protocol and was designed to support mobility of handheld devices. Mobile IP allow mobile host to stay connected even if the mobile node has changed its point of attachment. It means that mobile workers of STARfruit Communications Sdn.Bhd can communicate each other by using PDAs and stay connected even while they roam from one base station to another base station and it is done by mobile IP.

Mobile IP will allow remote workers after collecting complaints with their PDAs from the consumers at field to update information to the organization's server without interruption; therefore data loss will be reduced.

Another benefit of mobile IP in STARfruit Communications Sdn. Bhd as a regulatory agency which controls Telecom Companies of Malaysia. Sometimes Telecommunication companies make some changes to their networks without inform STARfruit Communications Sdn. Bhd. Therefore STARfruit is not updated for these changes. However if STARfruit Communications Sdn.Bhd set up requirements to Telecommunication operators when they make some parameter changes to their network they automatically inform remote workers of STARfruit Communications Sdn.Bhd through PDAs. Therefore remote workers will update information to the organization's database server accordingly.

Mobile IP will allow remote workers to read their emails wherever they are, at anytime and anyplace. However they will be able to pull emails from the server to their PDAs.

The communication is done without interruption because Mobile IP allows a mobile node (PDA) to keep its permanent IP address when it moves to another network.

Mobile IP will allow remote workers to stay connected, keep communicating efficiently and increase productivity of the agency.

Suitable client development technologies and strategies

To identify better mobile platform we should consider the following four key criteria (Drake. 2008). We assume that Mobile platform for STARfruit Communications Sdn. Bhd is .NET.

Choose a platform provider who already deployed a mobile enterprise platform to other companies and verify the feasibility of the company to ensure the longevity of the company. In this case, .NET platform has deployed for many enterprises level companies. Because, it has such features like (security, reliability, performance, mobility support). That's these companies are using it for a long time.


Development language

Application framework


Operating System


Unique.NET CF

Classes, device specific& third-party extensions

Common Language Runtime

Windows CE, Windows Mobile

Core components(subsets of the full .NET class library

Figure (Gavalas, D & Economou, D)