The network topologies and media
This task is considered the network topologies and media that can be used to build the in-house network (LAN) for the police department. Also given the advantages and disadvantages of each medium and appropriate reason why this topology and medium is used.
1.1 Explain how the topologies operate.
There are many topologies in the network media. The topologies are given below:
- Bus topology
- Ring topology
- Mesh topology
- Star topology and
- Extended star topology
For the network of police department bus topology is not suitable for this because it has a minimum space to operate a network and it is has also limited space up to 500m and only 30devices can be connected. Police department need to cover 100 square kilometer so bus topology can not covered the network. Moreover, ring topology has no begging or ending part and more cable required and the devices are not available so it can not reliable for police department network. In addition, for this network star topology can be used but the cost of it is really high so it can not be chosen. Furthermore, the device of a mesh topology has a dedicated point-to-point link to every other device but it is difficult to manage, install and it is highly expensive so this topology can be acceptable for this network.
However, the network of police department it requires a large and cost effective topology that can cover the whole area of 100 square kilometers. As a result extended star topology can be chosen as it is bigger, extended and also cost effective. This topology is easy to install, there is no disruption to the network when connecting or removing devices, easy to detect faults and to remove parts with no trouble.
1.2 Explain the advantages and disadvantages of each medium.
As though there are different kinds of medium in the network media. For example optical fiber, Coaxial cable, twisted pair cable, Cat1, Cat2, Cat5 and Cat6. Every medium has some advantage and disadvantage. While it is an in house network so optical fiber can not be preferred. Optical fiber supports high bandwidth, more reliability and security but components parts are expensive, it is not easy to install and easily broken than other cables. Coaxial cable is too much resilience and hard to install and expensive so this can not match to make the network. Cat1 carry out voice but can not carry out data so this is not acceptable for may network. Moreover, Cat2 and Cat5 are less expensive but the speed of the network is low so this not reliable for this network.
But the data speed, the size and shape of the network and the construction of LAN is similar to Cat6. It can cover and protect the whole area. Cat6 is preferable for this network from other medium. Cat6 is used when network is carried out within a building.
For the network of police department I use cat6.The advantages of Cat6 are given below:
- It has more speed than cat5
- Cat6 supports Gigabit (1000 Mbps) Ethernet
- Capable of multimode applications
- Very robust locking lever protection and unlocking latch
- Cat-6 features more stringent specifications for crosstalk nd system noise
- It is easy to install
Disadvantages of Cat6:
It is more expensive than cat5
In this network, wireless media is used for two way voice communication and also used private frequency because there is some limitation.
The advantages and disadvantages of wireless media given below:
- The wireless infrastructure can permit roaming for mobile devices.
- It is designed to minimize the need for complex configuration.
- Play is feasible in many cases.
- Does not require installation of media
- It is easy to install
- Transmission speed is limited for current devices and it is less than from cat5 copper.
- Interference may be occurred
- It is expensive
- Wireless frequencies range from 3 kHz to 300 GHz
- With wireless devices security is achieve too much harder
1.3 Provide a recommendation for which topology and medium to use including reasons for this recommendation.
From the above discussion, though there are different kinds of topology and medium. Topology such as bus, ring, star, mesh and extended star topology. From them I chose for my network extended star topology, it is the best suited topology for my network. It is large and extended topology that's why it can cover 100 square kilometer. It is easy to install and less expensive so it is great for my network. On the other hand, there is a lot of medium also. For example optical fiber, Coaxial cable, twisted pair cable, Cat1, Cat2, Cat5 and Cat6. From these cable I select Cat6, it is reliable both technically and economically and it also provides a lot of facility that is required for my network. To investigate the LAN network of police department, it is decided that Cat6 is best option for this. For two way voice communication I opt for wireless media not microwave. It means private frequency is best approach for my network. In the world, for police network PMR is used generally because it is suitable.
In task 2 there need some requirements for internet connection for the police department. In the police department there may be required some internet services, the connection speeds to fulfill this requirements, the examples of Internet Service Providers (ISP) , recommendation to use one ISP based upon the services and price charged.
2.1 Describe the internet services that may be required.
For this network of police department there should be need broadband Internet service because it provides high speed data transfer rates. To provide internet service it is required high speed for communication and also other purpose. Broadband services are available in half and full duplex communications. For this kind of organization, Full Duplex communication is best suitable so that incoming transmission does not hamper outgoing transmissions. The service must be dedicated so that outside person can not access it. To put the information is secured the mail server, web server and DNS server must be kept in own server. But for the detective branch, it requires video conferencing to prove any serious crime or murder and the video conferencing must be uninterrupted. For the video conferencing it must require high bandwidth for additional information and it must get from the ISP. For the chief commander or for the chief constable there must be kept approximately 1 MB redundant data.
2.2 Explain the connection speeds that are suitable for these requirements.
To fulfill the requirements the connection speed is required:
No of pc
Deputy District Commander
Internet browsing, file upload and download, mailing, share file and video conferencing
Internet browsing and share file
Detective chief inspector
Internet browsing, file upload and download, mailing, share file and video conferencing
Internet browsing, mailing, share file and video conferencing
Internet browsing and share the file
=7168 kbps (7 MB)
So the connection speed requires seven (7) MB and 1 MB required for redundant data. This connection speed should be dedicated. It can not be shared by anyone.
2.3 Find examples of Internet Service Providers (ISPs) that can meet these requirements in your country.
In our country there is a lot of Internet Service Providers that is useful for our network management system. Like wise:
- Mango ISP
- BDCOM Online Ltd
- Agni Systems Ltd
- Akij Online Ltd (AOL)
- Brac BDMail Ltd (BBL)
2.4 Make a recommendation to use one ISP based upon the services offered and price charged.
Mango ISP provides line to different organization that is well known in our country. Already they have shown their trust and competency over the year. So I select Mango ISP because it is well known and also it provides service extremely well. The price charge of this ISP is given below:
In task 3, to investigate how each method works for the police department to implement the two way voice communication, the legal requirements for operating the system, costs of setting up and operating the system with license cost and equipment cost and limitation of each method. Finally provide a recommendation for how voice communication should be set and reason for this recommendation.
3.1 How each method works (frequencies, full/half duplex, etc?)
Method: The method of PMR (Private Mobile Radio) is appropriate for two way voice communication in this police department. PMR is used for businesses as a very convenient way of communicating. The working methods are given below:
- The coverage area is limited
- Communications are half duplex using over and out for controlling the conversation flow
- Required license from the appropriate government department
- Communications on a single channel
- Communication between a fixed set of users or closed user groups
- It is used in cell phones which are point to point communication
- Multi-site capability for wide area
- Availability of bandwidth and channel is limited
- In PMR the frequency range is 446,000 - 446,100 MHz (According ERC/DEC 98/25 i 98/26)
- The radio communication systems can be portable
- Mobile as repeater operation
3.2 Details of the legal requirements for operating the system in your country (e.g. allocation of frequencies, licensing requirements, etc)
Legal requirements for operating the system are given below:
The following are the principal legal statutes governing the telecommunication industry in Bangladesh:
- The Bangladesh Telecommunication Act, 2001 (Act No. 18 of 2001).
- The Wireless Telegraphy Act, 1933 and The Telegraph Act, 1885, for matters that are not covered by the Bangladesh Telecommunication Act, 2001
- Any Regulation made or to be made by the Commission.
- The domestic VSAT-HUB operator (Licensee) shall develop, build, own, operate and maintain the Domestic VSAT-HUB and RT as provided in these guidelines
- The Licensee shall install, operate and maintain the BWA Services as provided in the License.
- In order to ensure proper competition among the BWA Services licensees, total 3 (three) licenses will be issued to provide nationwide BWA Services in 2.3 GHz and 2.5 GHz spectrum bands.
- Two licenses will be awarded to the prospective Applicant(s) to provide nationwide BWA Services in 2.3 GHz and one license will be awarded in 2.5 GHz spectrum bands
- The duration of the license shall initially be for a term of 15 (fifteen) years. Upon expiry of the initial term, the License(s) may be renewed for subsequent terms, each of 5 (five) years in duration, subject to the approval from the commission and to the conditions of the license.
Allocation of frequencies:
The eight frequencies used:
- 697, 770, 852, 941 Hz
- These are termed the “low tones”
- 1209, 1336, 1477, 1633 Hz
- These are termed the “high tones”
One high and low tone is used together and the various combinations are used to represent numbers.
The lowest frequency of which is 67 Hz and the highest 250.3 Hz. This enables a variety of different mobiles to be called selectively.
3.3 Costs of setting up and operating the system, including licensing costs, equipment costs, etc.
Cost of setting up and operating the system and equipment cost;
For the setup of PMR and operating the system there should be need the PMR device, hardware, software, walkie talkie and etc. To install PMR, the IT people should give the installation charge and also the maintenance cost of the device.
The equipments are:
Cobra Micro Talk CXT (per piece 2700 taka)
54 ,000 taka (BDT)
Total equipment cost
Total installation cost
Total operating cost
1, 20, 000 taka (BDT)
30, 000 taka (BDT)
45,000 taka (BDT)
In total, the cost of setting up and operating the system is approximately 75, 000 taka.
If to set up the PMR properly it can feasible to every people of the police department for voice communication.
Charges of frequencies:
Channel Frequency in MHz
Tk. 50,000.00 (Taka fifty thousand) only
License acquisition Fee
To be fixed be auction
Annual License Fee
Tk. 3 (Three) crore only
Gross Revenue Sharing with the
To be fixed through Auction
Tk. 15 (Fifteen) crore only
3.4 Limitations of each method (interference, range, etc)
To use PMR there are some limitation both in interference and range. The limitations are given below:
- Exact frequency allocations differ, so equipment legal to operate in one place may cause unacceptable interference in another.
- It does not suffer the interference effects at 27 MHz, or the 49 MHz band
- It is used frequency modulation instead of amplitude modulation
- PMR manufacturers generally claim exaggerated range
- The presence of large buildings, trees, etc. will reduce range
- Under the exceptional conditions (such as hill-top to hill-top) communication is possible over 60 km (40 miles) or more but that is rare
- In normal conditions with line-of-sight blocked by a few buildings or trees
3.5 Provide a recommendation for how voice communications should be set up and run including reasons for this recommendation
PMR must be set up for voice communication in police department. To implement PMR a network of stations is set up. There is also need repeater to set up the PMR. These stations are linked with using land lines; Cat6 and point to point radio are also used. In this way the different base stations are able to communicate with each other. A single base station with a number of different channels can be run by one operator for a number of different users and this makes efficient use of the base station equipment. The base station site can also be located at a position that will give optimum radio coverage. The PMR supports up to 1024 different traffic channels to be used. In this way a base station can support a large number of different mobile stations that are communicating at the same time. Moreover, PMR can increase intelligence exchange, greater knowledge of criminals, public safety and it can help to take quicker decision. So it is perfect for the network of police department.
In this network, through the use of private frequency for the police department, it can create a best suited network for this because it is dedicated so this private frequency can not be used in another side. The noise level is lower in this frequency and the effect of this is less in environment. To create the network of police department, the component that is used for the network is appropriate.
In this task, to investigate the telephone system that is available in our country for single site organization like police department. To install all the equipment that is required for the telephone system and also gives the feature of this. The equipment and installation cost and also give the cost of operating the system. Finally provide a recommendation why I purchase this equipment.
4.1 The main equipment that would be installed.
For the police department is given the telephone number. It is divided into two categories one is direct number and another one is PBX number. Direct numbers are given to top level of officer. Like:
- Chief constable - Two direct number or main line
- Assistant chief - One direct number or main line
- District commander - Four direct number or main line
- Deputy district commander - Four direct number or main line
- Detective - Three direct number or main line
- General administration - one direct number or main line and another line PBX
- Sergeant - PBX number
- Another constable - PBX number
At least three direct numbers must be allocated to use in future if any new department will add in the police department.
To install the main equipment, at first the telephone set and the PBX machine that is required for the installation and also a cable is required for this. Then from the local exchange, the local divi point is put into the police head quarters. The capability of this must be high because at first it provides a main line then it is distributed into the PBX line.
To set up a PBX machine these criteria should follow:
- At first the area should be selected that which area the PBX machine will be installed.
- The area where PBX machines would be installed should be well protected all around from rain
- It should be air conditioned area
- Power back, power connections and earthing must be checked and verified. Earthing is very important for any PBX machines to work.
- The room should be dust free.
- Wiring should normally sealed always
- If wires are not sealed, than probability of cable cutting or disconnection would increase.
- Once the wiring is complete, the PBX machine should be configured
- Once it is completed, the programming data should be backed up and stored for future restoration if any problem occurs.
4.2 The feature available with each system
The feature of PBX:
- Account Code: Account code for dialing calls
- Alternate Number Ring: Assign a different number to same line that rings with a different cadence
- Attendant: Main Operator extension
- PBX Automatic Line Selection
- PBX Automatic Redial
- Automated directory: Automatically connect to an extension by name
- PBX Automatic Redial
- Call Forwarding: Redirects all incoming calls towards other extension
- Call Trace: mark a call in system logs as requiring tracing or special attention
- Call Transfer: Hand a call off to another extension
- Call Waiting: Receive a tone indicating another call is waiting for attention
- Calling ID: Identify (or block identification) of caller's phone number or phone number and name
4.3 The cost of equipment and installation
The costs of the equipments are given below:
- Quantity - 48
- Brand name-Samsung (per piece 1200 taka (BDT))
- Total price 57,600 taka (BDT)
- Quantity - 1
- Brand name - Yawarra
- Price 14,000 taka (BDT)
Cable - price 5000 taka BDT)
The installation cost is: 36,000 taka (BDT)
The total cost of equipment and installation is 1, 76, 000 taka (BDT)
4.4 The cost of operating the system
The cost of operate the system including monthly bill of use PBX and maintenance the PBX machine properly. So an operator should maintain and monitor the PBX machine. If any problem occurred in the PBX machine instantly it must be solved. If any telephone set is damaged after that a new telephone set is installed. So the cost of operating the system may be required
- Monthly bill - 30, 000 taka (BDT)
- Maintenance cost - 24, 000 taka (BDT)
- If a new telephone set is add its price - 1200
In total the cost is 55, 200 taka (BDT)
4.5 Provide a recommendation for which system to purchase including reasons for this recommendation
There is a lot of reason to choose PBX because it has all the function that is required for police headquarters. The PBX is the best approach that any organization can accept it. A hosted PBX usually can handle a higher number of calls. The most important advantage of PBX is that it has the ability to route calls to any phone rather than just phones wired to the PBX inside the office. PBX telephone system is the power hub for a business internal phone system and automatically provides switching connections between two or more telephone users. This type of phone system serves as the operator for phone call transactions without the need for a live person and is owned and operated by the company itself. Other advantages are given below:
- It allows all employees to share phone system lines, thus reducing the overall telecommunication expenses.
- The PBX system is totally programmable and can support complex installation or integration requirements.
- The physical PBX hub is low profile and does not require a large amount of space
- Easily transfer calls between stations (internal phones)
- Setup Individual Voice Mail boxes for every employee
- Network as few as 4 to over 1000 phones
- It is much easier to install and configure than a normal home line
- It is easier to manage
- Easily connect phone systems between branches and make free phone calls
- The quality of calls standard is high
Hosted PBX includes lower cost, support cost, greater use of management, flexibility and improved scalability. From the above advantages it is recommend that PBX is best suited for voice communication and if a new department is added in the police department the PBX numbers can be increased.
Detail discussion and solution of task 1-4:
- To make an in-house network, topology and media is the best suited approach
- How topologies operate in the network.
- Every media has some advantage and disadvantage.
- Recommendation for topology and medium that is selected.
- The internet connection requirements for police department
- Type of internet service that is required for communication
- Connection speeds or bandwidth that fulfills the requirements
- Providing the ISPs name that is available in our country
- Recommendation of an ISP and the price of this
- The method of two way voice communication that need to implemented
- The working methods of PMR that is selected for two way voice communication
- Legal requirements (allocation of frequencies and license requirements)
- Licenses, equipment cost and cost of setting up and operating the system
- Limitation of PMR
- Recommendation for PMR
- Telephone system that is used for single site organization like police department
- Equipments required for installation
- Features available with the system
- Cost of equipment, operation and maintenance
- Recommendation for purchase telephone system or PBX
Professional Presented Report:
Report on how to make a network of police department
The aim of this task is to define the whole network structured. That is used to operate a single site organization like police headquarters. To make a large network there are lot of things that need to operate. Government approval must require when a big network is created including legal requirements. For making this networks of police department, topology, media, connection speed, PMR methods and the telephone system all the things that are clearly defined.
Topology and media for the network:
For the network of police department topology is selected. Topology of a network refers the logical and physical connection between nodes (workstations). The topology has a great impact on network to specify the network structure. Every topology has some advantage and disadvantage also. Bus topology has minimum space, the device of ring topology is not available, the cost of star topology is high and mesh topology is difficult to manage and install and also expensive. So for police headquarters extended star topology is selected. It is extended and bigger and it is easy to install, there is no disruption to the network when connecting or removing devices, easy to detect faults and to remove parts with no trouble. However as a media Cat6 cable is preferred. it is reliable both technically and economically and it also provides a lot of facility that is required for the network. To investigate the LAN network of police department, it is decided that Cat6 is best option for this. For two way voice communication I opt for wireless media not microwave. It means private frequency is best approach for the network.
Internet connection requirements:
Police headquarters is required Internet service that is get from the broadband services. They provided high speed for communication purpose. The internet service should be dedicated and the web server, DNS server and mail server must be kept in their own server but for detective branch they making video conferencing so it requires high bandwidth that is get fro the ISP.
The connection speed that is required for the Townsville police headquarters are given in the above.
There are different kinds of ISP in Bangladesh. From them I select Mango ISP. It is well known and trusted ISP. The price of 1 MB is 22000 taka (BDT) per month. So the price of 8 MB is 1, 76,000 BDT (per month)
Method of police department for two way voice communication:
There are many methods through which the two way voice communication can be formed such as PTMR, cellular Radio, MPDN, PMR and etc. From them PMR is more popular. To build up the voice communication of police headquarters, PMR (Private Mobile Radio) is preferred. Its function is more reliable than other. Communications are half duplex in PMR and it has multi-side capability for wide area. The coverage area of PMR is limited and communications on a single channel. To use PMR must be permission from appropriate government. Every police officer will be carrying one of the radio devices and base stations will be set up in the district offices and the headquarters. If signals are distorted repeaters can be used and repeaters can increase the radius of signal that is covering large distance. Encryption is encouraged because Police conversation is very important and sensitive so its leak can create havoc and increase crimes. Signals can be protected through Encryption and prevent from getting captured by Scanners.
To use PMR legal requirements must be achieve. The legal requirements are given in the above.
The equipment cost and setting up and operating the system cost gives in the above
The PMR has some limitation that is given in the above.
The PMR should be set up for voice communication. To implement PMR a network of stations is set up. In this way the different base stations are able to communicate with each other. As though this is a private frequency so the noise level is less and it is less effective on environment. That's why it is selected for police department.
Telephone system for police department:
The telephone set and the PBX machine that is required for the installation and also a cable is required for this. Then from the local exchange, the local divi point is put into the police head quarters. The capability of this must be high because at first it provides a main line then it is distributed into the PBX line.
The features of PBX machine are many are given in the above description.
The total cost of equipment and installation is 1, 76, 000 taka (BDT). The cost of operating the system is 55, 200 taka (BDT).
To purchase the PBX, there is a lot reason such as it is much easier to install and it is easier to manage, easily connect phone systems between branches and make free phone calls and the quality of calls standard is high etc.
- BTRC provides license of PMR in the way of BWA licenses.
- ISP will fulfill the requirements if the price given timely
- The legal requirements that is given in the above from BTRC is accurate
- PMR is implemented in Bangladesh if they fulfill the requirements that is given in the above
- PMR is used in Bangladesh for two way voice communication in mostly single site organization
- Equipments that are required for PBX are about the same as denoted above.
- Hosted PBX in Bangladesh is at the price declared above
- Enterprise networking provided by NCC education.
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