Police Department Examination Cycle Computer Science Essay

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In the terms of network topology, physical topology is the physical layout, or pattern, of the nodes on a network and logical topology is the way in which data is transmitted between nodes. Although we have known topology as physical and logical, the word 'topology' often refers to a network's physical topology.

Network topologies are categorized into the following types:

Bus Topology

Ring Topology

Star Topology

Mesh Topology

Tree Topology

Hybrid topology

Except in very small networks, a pure bus, ring or star topology is hardly found. As simple topologies are too restrictive, it cannot accommodate a large number of devices. In order to fulfill these, we will need to work with a complex combination of these topologies, know as hybrid topology.

Bus Topology

A bus topology consists of a single cable connecting all nodes on a network without intervening connectivity devices. The single cable is called the bus and can support only one channel for communication. When one node wants to transmit data to another node, it broadcasts an alert to the entire network, informing all notes that a transmission is being sent; the destination node then picks up the transmission. Nodes other than the sending and receiving nodes ignore the message. At the ends of each bus network are 50-ohm resistors known as terminators. Terminators stop signals after they have reached the end of the wire. Without these devices, signals on a bus network would travel endlessly between the two ends of the network and new signals could not get through.

Fig (1.1) A terminated bus topology network

Ring Topology

In a ring topology, each node is connected to the two nearest nodes so that the entire network forms a circle. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). Each workstation accepts and responds to packets addressed to it, then forwards the other packets to the next workstation. Each workstation acts a repeater for the transmission. But unlike bus topology, it has no ends and data stop at its destination. The major drawback of a ring topology is that a single malfunctioning workstation can disable the network. So the double ring is suited to use as a backbone network.

Fig (1.2) A typical ring topology network

Star Topology

In a star topology, every node on the network is connected through a central device, such as a hub or switch. Any single cable on a star network connects only two devices (for example, a workstation and a hub), so a cabling problem will affect two nodes at most. Devices such as workstations or printers transmit data to the hub, which then retransmits the signal to the network segment containing the destination node. As each node is separately connected to a central connectivity device, a single malfunctioning workstation cannot disable an entire star network. However, a failure in the central connectivity device can take down the network.

Fig (1.3) A typical star topology network

Mesh Topology

A fully connected or mesh topology is a network topology that has a direct link between all pairs of nodes. Unlike other topology, messages sent on a mesh network can take any several paths from source to destination. Mesh network provides many redundant paths to be used to ensure that alternative data paths between nodes are always available. Networks designed with this topology are usually very expensive to set up, but provide a high degree of reliability due to the multiple paths for data that are provided by the large number of redundant links between nodes.

Fig (1.4) A typical mesh topology network

Tree topology

A tree topology or hierarchical topology can be viewed as a collection of star networks arranged in a hierarchy. Unlike star topology, the functionality of its central node may be distributed. The nodes in a tree topology transmit data to its intended destination nodes and do not need to act as repeaters or regenerators. So, it was supported by many network vendors and even hardware vendors. However, the tree topology is entirely dependent on the trunk which is the main backbone of the network. If this backbone fails then the entire network would fail.

Fig (1.5) A typical tree topology network

Hybrid Topology

Hybrid network is a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g. bus, star, ring, etc.). This hybrid network is produced when two different basic network topologies are connected. Tow common examples of hybrid network are: Star-wired ring topology and star-wired bus topology. The following figures show the two examples of hybrid topology.

Fig (1.6) A star-wired ring topology network

Fig (1.7) A star-wired bus topology network

b) Advantages and disadvantages of medium

In order to connect one network device to other or to connect two or more computers to share printer or scanner, we need a network medium. Different types of network media exist, both wire and wireless. Below are the types of media that are commonly used for LANs.

Coaxial cable

Twisted pair cable (UTP or STP)

Fiber-optic cable

Wireless media

Coaxial cable


Can transport video and high data rate digital information

Can be run with fewer boosts from repeaters for longer distances between network nodes than either STP or UTP cable

Flexibility as it can bend easily

Durability as the outer layer protects the wiring inside from weather and the elements


Damage cable can result the entire network break down

Distance limited

It breaks easily though and has to replaced regularly

More expensive than twisted pairs and not supported for some network standards

Twisted pair cable (UTP or STP)


UTP is the least expensive transmission media

UTP is thin, flexible and easy to install

STP reduces crosstalk

STP can carry data a faster speed than UTP


UTP is susceptible to interference

STP is difficult to connect to a terminating block

Both STP and UTP can cover only a limited distance

Fiber-optic cable


Wide bandwidth

Smaller and lighter than copper wires

Can transmit large amount of data

Offer more secure communication as they are highly resistant to tapping, radio frequency interference and jamming

Very little data loss even over long distances (low attenuation)


High investment cost

Susceptibility to physical damage

Fiber-optic connections are not available in many areas

More difficult and expensive to splice

Cannot carry electrical power to operate terminal devices

Wireless media


Implementation cost is cheaper than wired network

Easy to add stations as there are no cables required

Can surf from anywhere in the house without a new configuration

Can access files and printers from anywhere in your home


Distance limited

Lower speed compared to wired network

More complex to configure than wired network

Risk of outsiders accessing your network unless robust security protocols are enabled (e.g. WPA, WPA2)

Radio interference due to weather, other wireless devices, or obstructions like walls

c) Recommendation

To create the in-house network (LAN) for the Police Department, I will use star topology as any single failure of the port will not impact the whole network, management is easy through the Switch at the port level, administration and management can be done remotely by the authorized administrator, and installation of the cable in each port will not disrupt LAN services. For network media, I will use fiber-optic cable and UTP Category 5e cable. Although fiber-optic cable is expensive, they can transmit data at greater speeds and higher bandwidths, so I use it for connecting from the server switch to the department switch. Furthermore, UTP cable is the least expensive transmission media and easy to install, so for distributing network in in-house, I choose the UTP cable.

The following figure is the design of in-house LAN that I will configure.

Fig (1.8) design of in-house LAN

Task 2

Task 2

a) Internet services required for police department

For one police department, security is one of the most important aspects to be considered no matter which internet services we will use. The internet services that we will use can be grouped into four categories:


File transfer

Communication and


Information - the information used in police department need to be protected by password or encrypted in order to make it difficult or impossible for unauthorized people to read or decode the information.

File transfer - using FTP (File Transfer Protocol) can make the copying of files from one computer to another convenient and efficient. And while transferring files over the internet, VPN (virtual private network) is suitable to use to enhance security.

Communication - communication services includes email and telephony. Mail services coordinate the storage and transfer of e-mail between users on a network and SMTP (Simple Mail Transfer Protocol) supports mail services. For internet telephony, VoIP is the internet communication and it can be free or cost much less than a traditional telephone call, especially over long distances and for those with always-on Internet connection.

Management - if network were small, they can be managed by a single network administrator. However, as networks grow larger and more complex, they become more difficult to manage. Using network management services can help in keeping track of a large network.

b) Connection speed that are suitable for police department

As we have use mail, telephony, files transfer and communication services for the police department, the connection speed for email is adequate with 64 kbps and 256 kbps is preferable. For file transfer, 128 kbps will be adequate and 1 Mbps is preferable. For communication, 64 kbps is adequate for normal conversation and 512 kbps is preferable for peak hours. The overall connection speed for internet services is adequate with 2Mbps.

There are many access services to meet the above services. Among them, using wire, ADSL is a data communications technology that enables faster data communication. It uses separate transmission frequencies to provide what are effectively a voice channel and a data channel on a single standard telephone line. Using ADSL, downstream rate is basically 8Mbit/s and upstream rate is 1Mbit/s.

Wireless can also be used for the above services. WiMax (Worldwide Interoperability for Microwave Access) is a telecommunications technology that provides wireless transmission of data using a variety of transmission modes. Without using cable, WiMax provides up to 10Mbps.

2. c) Internet Service Providers (ISPs)

There are two service providers in Myanmar, Myanmar Teleport (formerly Bagan Cyber Tech) and the Ministry of Post and Telecommunication (MPT).

Myanmar teleport offers:


Access Prepaid Dial-Up Kit

Internet & e-mail Dial-Up Service


IPSTAR Broadband Satellite Service

Broadband ADSL Service

Broadband Wireless Service

MDU/ MTU Broadband Service

Ministry of Post and Telecommunication (MPT) offers:

Dial-up Internet Account

High-speed Internet Access

Domain Name Registration

Virtual Web Hosting Service

Public IP Address

Galileo Online Reservation

Server CO-Location

X-25 Service

d) Recommendation

The access service I will use is ADSL and WiMax services. Both of them are available in Myanmar teleport. And the price range offers in Myanmar teleport are suited with the design we would configure and get more services than MPT. So, l chooses Myanmar teleport for the police department. The following figures are the price range of ADSL and WiMax offer by Myanmar teleport.

Fig (2.1) price range of ADSL

Fig (2.2) price range of WiMax

Task 3

Task 3

For the police department, two-way voice communication is needed for patrolling the area in each district. There are two methods for implementing two-way voice communication. One is using cordless phones both for the police officer and patrolling car. The other is using cordless phones for police officer and vehicle mounted two-way radio for patrolling car.

If using the former method, it is suitable to use EnGenius Durafon Long Range Cordless Phones - 1 line (SN902). If the later method is used, Motorola CM300 vehicle mounted mobile two-way radio and Motorola's MTP850Ex cordless phone is suitable for implementing the method.

a) How each method works

EnGenius Durafon 1x cordless phone system

Fig (3.1) EnGenius SN902 DuraFon 1x cordless phones and its base unit

EnGenius Durafon is the revolutionary cordless phone system and uses two-way radio technology. The system provides mobility, flexibility, freedom, crystal clear over long distances and ideal where a number of handsets are required. And additional handsets and base units are available separately and give handset to handset communication, so we can build a system that can extended as we need.

The EnGenius Durafon 1x (SN 902) supports 1 PSTN line and combined with up to 9 Handsets per base and a maximum of 4 bases. The available frequency is between 902 MHz and 928 MHz and channel spacing is 200 kHz. The DECT cordless phone provide frequency hopping spread spectrum over TDMA structure and its frequency hopping rate is 100 times per second. Moreover, the channel is available up to 128 lines and its broadcast facility is direct announcement to all handsets or a group of handsets.

This cordless phone is work with half or full duplex. It has six hours talk time and 50 hours standby time. The major advantage is it is compatible with PABX and programmable with PABX option key. As the EnGenius Durafon 1x is along with car charger socket, it is also suitable for the police officer patrolling with the car.

Motorola's MTP850Ex ATEX TETRA Radio

Fig (3.2) Motorola's MTP850Ex ATEX TETRA Radio

The Motorola's MTP850Ex is designed typically for specialist users from industry or public safety operate. It is supported by TETRA technology and the frequency band is between 380 MHz and 430 MHz and available up to 25 channel spacing. And its switching bandwidth is 50 MHz and receiver class is A & B. For telephony, the MTP850Ex works with full duplex and for private call, it can be half or full duplex. Moreover, it can configure timers, set emergency target address to individual or group and has an alarm for emergency status.

The MTP850Ex has 12 hrs battery life and its power consumption is 1 W. What is more, the keypad with large button surface makes the MTP850Ex easy to use with gloves. And because of large scalable display fonts and icons, the MTP850Ex facilitates operation in difficult environments with limited visibility.

On top of that, the MTP850Ex is integrated with GPS receiver which provides the ability to locate personnel through the radio. In GPS, it has 12 simultaneous satellites and GPS antenna is integrated in TETRA antenna. Its accuracy is 5 meter (50% probable). So, the MTP850Ex along with GPS receiver can improve user safety and resource management.

Motorola CM300 vehicle mounted mobile two-way radio

Fig (3.2) Motorola CM300 mobile two-way radio

The Motorola CM300 uses UHF (Ultra High Frequency) radio frequency as it is less likely to have interference from other systems. Its frequency range is between 438 MHz and 470 MHz. The CM300 uses TETRA technology as it is ideally designed for government agencies, emergency services, police force and fire departments. It has 32 channels and 8 characters Alphanumeric Display.

The CM300 works with half or full duplex. Moreover, it is along with 4-watt speaker faces forward so it provides the best audio quality. Its power consumption is 40 Watts. The CM300 provides unit to unit communication bypassing the repeater and its local mode reduces interference from nearby radios and distance mode helps improve range. It also adjusts transmit power to accommodate user environments. And it can be adapted an external alarm, so it is suitable to use for patrolling car.

b) Legal requirements for operating the system

The Myanmar Posts and Telecommunications (MPT), is the sole provider of telecommunication services in Myanmar. It is a Government Agency, operating under the Ministry of Communications, Posts and Telegraphs. Before applying license for using two-way voice communication to the MPT, we need the agreement of the Chief Constable of the police department. Moreover, we need to know the range of frequencies that the MPT offers for choosing which frequencies we will use. MPT offers 6 to 7 GHz for analogue and digital microwave link. For analogue UHF link it offers 400 and 900 GHz and for digital UHF link, MPT offers 800 GHz and 1800GHz. The frequency we used is under the range of MPT. So, it is legal for us to apply for licensing. With the Chief Constable agreement, we need to fill forms that include which type of equipments we will use, the frequency range we need and reasons for using. After that, apply the forms to MPT for legal in getting license for two-way voice communication.

Licensing obligation

Operating a radio communications network in most countries is subject to licensing by national telecommunications regulators, both for its type of use and the radio frequency spectrum it utilises, especially as radio frequency spectrum is a scarce resource and needs to be used efficiently.

Operating license

Operating a commercial mobile radio network practically always requires a specific operating license. In case of private radio networks, i.e. Professional Mobile Radio (PMR), the interpretation of the licensing requirements is country specific and the opinion of the national regulator should thus always be consulted before setting up a radio communication network. In most cases a private radio system requires only a frequency license.

Radio Frequency license

Usage of radio frequencies is practically always controlled either by the national radio communications regulator, which is Ministry of Defense, Myanmar. In the Application, we must clearly mention about (1) Model and type of Radio communication devices. (2) Frequency range (3) Number of units and (4) Purpose of Radio communication network.The national radio communications regulator will review the application. Upon successful application, the regulator will grant right to use specific radio frequencies for a specified purpose within a specified region. Radio frequency licenses are not normally issued free of charge and the cost of the license can vary greatly depending on country and type of usage. For details of the procedures and fees regarding a radio frequency license the national regulator should be consulted. For police department, it will not charge fees radio frequency license.

c) Cost of setting up and operating the system

I would use EnGenius SN902 Durafon 1x both for police officers and patrolling cars and one handset for one group- three police officers and one handset for one patrolling car. As EnGenius SN902 Durafon 1x base unit can offer up to 9 handsets, we need two base units for each district. In each district, there are 24 police officers who will patrol the area and five patrolling cars, so we need 13 handsets for each district. So, for all district, we need 8 base units and 52 handsets. Below is calculating the cost of using EnGenius Cordless phone.

EnGenius SN902 Durafon 1x base unit = $315.5

Need 8 base units, so 315.5 * 8 = $2524

EnGenius SN902 Durafon 1x handset = $293.12

Need 52 handsets, so 293.12 * 52 = $15242.24

Total cost of EnGenius Cordless phone $17766.24

We also need to calculate the cost of RJ11 cable for connecting the base units. As I will use the GE Jasco TL 26119 RJ 11 phone cable, it will cost $2 for one cable. The RJ 11 phone cable has 25 ft in length, so we need 2 cables for one district and 8 cables for all districts. Then, the total cost of phone cable is $16.

For setting up the base units and cordless phones, we need to call a technician. So, for technician, it costs $750.

In dealing with licensing costs, if it is a government organization, the licensing costs is paid in Kyats. If it is for personal or company, the licensing costs is paid in US$. As the police department is part of the government organization, the licensing cost is 700000 Kyats and annual fee is 25000 Kyats. If calculate in US$, licensing cost is $650 and annual fee is $ 25. So, the total license cost is $675.

So, the total cost (including equipments costs, licensing costs and setting up costs) is $19207.24.

d) Limitation of each method

EnGenius Durafon 1x cordless phone system

The EnGenius Durafon 1x SN 902 will not operate under 14 degree Fahrenheit and upper 140 degree Fahrenheit. The storage temperature is between 14 and 158 degree Fahrenheit. It range is not over 5 km in rural areas. One base unit is available only one PSTN line and can support only up to 9 handsets, so extra base unit is required for large department.

Motorola's MTP850Ex ATEX TETRA Radio

The Motorola MTP850Ex will operate between -20 to +50 degree Celsius in hazardous environments and between -20 to +60 degree Celsius in non-hazardous environments. The storage temperature is between -40 to +85 degree Celsius. It can accept the message only up to 20.

Motorola CM300 vehicle mounted mobile two-way radio

The Motorola CM300 will not operate under -30 degree Celsius and upper +60 degree Celsius. The storage temperature is between -40 and + 85 degree Celsius. The thermal shock is between -40 to +80 degree Celsius.

e) Recommendation

Task 4

Task 4

a) Main Equipment that would be installed

The main equipments that I would install for the telephone system are

One IP PBX Exchange (Mitel 3300 CX II Controller)

74 IP Phones (Cisco Unified IP Phone 7970G)

IP PBX switch (Mitel 3300 CX II Controller)

IP PBX is a complete telephone system that provides telephone calls over IP data networks. All conversations are sent as data packets over the network. It can also connect to the traditional PSTN lines via an optional gateway. For all forms of telecommunications, IP PBX uses the same Ethernet networks. This eliminates the need for separate data and voice cabling installations. Moreover, we can plug IP phone into any outlet without the involvement of any telecom professional. As IP PBX acts as a centralized, reliable call-processing server, we do not need to deploy other voice switches at the remote. By deploying IP PBX, many benefits are available - they can easily use a VOIP service provider for long distance and international calls and connect hardware phones directly to a standard computer network port. Because of these reasons, I would us IP PBX switch from Mitel for telephone system of police department.

Mitel 3300 CX II controller allows the system to be deployed into many varied environments and offers great flexibility and everything needed to support phones, fax machines, and with a choice of connectivity all in one compact box and over one line. It is also act like a media gateway for lager networks. Below is the image of IP PBX switch form Mitel.

Fig (4.1) MITEL 3300 CX II Controller

IP Phones (Cisco Unified IP Phone 7970G)

IP telephony provides a way for organizations to extend consistent communications services to all employees in their workspaces. It transmits voice and video communications over the network using the open-standards-based Internet Protocol. It reduces telephone costs and allows for greatly enhanced capabilities such as unified messaging.

The following figure is the Cisco Unified IP Phone 7970G for police department.


Fig (4.2) Cisco Unified IP Phone 7970G

Fig (4.3) configuration of IP PBX switch and IP Phones

b) Features available with each system

MITEL 3300 CX II Controller

MITEL 3300 CX II Controller can be used for the small business or deployed into many varied environments. And it offers full IP-PBX services, like a media gateway for Industry Standard Network, as a centralized network, and as a PBX operating as part of a distributed network. It provides lots of features to be used for the Single-Site Organizations like for using the Police Department. The following are the specific features of MITEL 3300 CX II Controller:

Maximum numbers of IP phones are 150.

Maximum ACD (Automatic Call Distribution) Agents are 50.

Maximum numbers of analog phones are 104.

Maximum numbers of SIP (Session Initiation Protocol) devices / users are 100.

Having 8GB SATA Solid State Drive | 80GB SATA Hard Drive for Main Software Storage Media.

512 MB of RAM will be available.

MMC (MITEL Mezzanine Card) Slots for Quad CIM, Single T1/E1, Quad BRI and DSP II.

It used IEEE 802.af technology and provides connection with the additional switch ports and router. Moreover, 10/100 WAN port is available for the Internet Gateway, also supports NAT and firewall capabilities but it doesn't support the IP Networking.

Maximum numbers of IP trunks between controllers are 200.

STP (Session Initiation Protocol) and RSTP are also supported.

Maximum mailboxes are 750 and Maximum messages per mailbox are 100.

It also has Analog Option Board for 6 LS trunks and 4 ONS ports.

Operational Environment

Temperature : need to be between 400 to 1220F (40 to 500C)

Humidity : 5-95% relative humidity, non condensing

Max. Heat Dissipation : 170 BTUs (British Thermal Unit) per hour

Air Flow : 46 cubic ft. / min. at maximum output of fans

System Input Power Requirements

Frequency Range : 47 - 63 Hz

Input Power : 250 W

Voltage : 100 - 240 VAC

Cisco Unified IP Phone 7970G

Cisco Unified IP Phone 7970G offers the advanced technology in IP telephony features. It is not only the decision makers and addressing the execution but also send the data of applications to the need of users without having PCs. It also uses the Extensible Markup Language (XML), enables customers and developers to be innovative and enhancing the productivity, to display.

The following lists are the features provide for using the Cisco Unified IP Phone 7970G:

a great resolution in display with touch-screen

using the streaming technology to communicate information

provide to access eight telephone lines and also access directly to the feature of telephony

having a hands-free speakerphone with built-in headset utility

provides to use over Ethernet(PoE) and IEEE 802.3af(PoE) for inline power

direct access to voicemail for messages

using direct dial-back capability with the Lightweight Directory Access Protocol Version 3 (LDAPv3) standard directory

Supports the user with adjustable display, lots of ring sounds, settings for all audio components like handset and headset. It can be configured the network configuration in either automatically or manually setting up the Dynamic Host Control Protocol (DHCP) and Trivial File Transfer Protocol (TFTP) in Cisco Unified CallManager software.

It can easily access the latest information such as weather, exchange rate, or any other Web-based information. Plus, using the latest technology of XML to access the information.

Can also get the help from the new feature in online about the specific phone keys, buttons and features. For example, if the user clicks the Directory button, the display will show not only the local but also server-based directory information.

For Volume Control, It provides the easiest way of on off button in speaker and mute button in microphone. Moreover, supporting the flexible, convenient volume adjustment control button.

Having a 3.5-mm stereo jack socket to be used with a stereo microphone. It can also connect with auxiliary speakers or headphones but still need an external power adapter to connect.

LCD (liquid crystal display) can access easily to previous pages and opened applications.

c) Cost of Equipment and installation

Administration costs

Training costs

d) Cost of operating the system

e) Recommendation

Task 5