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    Electrical Engineering




    Part A

    Question 1: active   redundant generator at the main exchange of Telecommunication Company


    In the problem statement the used generators which are used at the main exchange of telecommunication company ar4e in redundant in nature. The generators are connected in parallel.

    1.a) Calculate the reliability of the overall system Rs as a   function of R assuming the reliability of each subsystem (or   component) i has the reliability of   R


    The probability of survival of all items is the probability of survival of the system is

    Thus, Rs = R1 * R2 * …….. Rn

    Let Riare all equal

    Hence, Rs= RN

    Let the R is represented as the function of f.

    Hence, R= m.f

                   R1 = m1 . f1    &     R2 = m2 . f2

    Case 1: When m = 1

    The failing probability = (1 – Ri), (this is for an individual item)

     The probability of failing is,

    Let all Riare equal

    Hence, RS = 1 – (1 – Ri)N

    Case 1: When m ≠ 1

    In order to analyze the situation calculating the probability of occurrence of each state is needed. There are fewer down states which are lesser in number than up states if m > ½(n+1).

    Case 1: When m =2, n= 3
    since m is not less than 1/2(n+1) the results will be aw below.

    ·         Survives 1,2, and 3

    ·         Survives 1,2, while 3 fails

    ·         Survives 1,3, while 2 fails

    ·         Survives 3,2, while 1 fails

    The probabilities can be such as P(i) = R1 . R2 . R3;  P(ii) = R1 . R2 . (1 - R3);  P(iii) = R1 . R3 . (1 - R2);  P(iv) = R2 . R3 . (1 - R1).

    The number of events is four.

    Hence, RS = P(i) + P(ii) + P(iii) + P(iv)

    For m=2, and n=3;

    RS = R1R2R3 + R1R2(1 - R3) + R1R3(1 - R2) + R2R3(1 - R1)

    Assume all Riare equal to R

    RS = R3 + 3R2 (1 - R)

    1.b) What is the reliability function of the overall system at time t if the reliability of component i at time t is Ri(t)=e-λit ?

    1.c) Evaluate the mean time to failure (MTTF) of the overall system as a   function of λi using the reliability function in part (b).

    1.d) Calculation of the failure rate of the overall system with exponential reliability.

    The probability of an individual item failing is (1 – Ri).

    In order to calculate for Pf,probability of failure rate is


    Question 2: Digital Microwave   Radio System

    Trans mission speed= 2.048 Mbps

    MTBF = 100000 hours

    MTTR = 2 hours

    BER = 10-8 

    2.a)Calculation of overall availability

    The overall system availability, A (%)= 100(total usage time – downtime) / total usage time

            Availability = 99.998 %

    2.b)Draw the reliability diagram of   the system 

    2.c) How would you increase the availability of the system required by the bank?

    Satellite links involve an additional round-trip latency which is approximately one second,

    Limit of the speed=TCP/IP communication.

    Transmission speed= 2.048 Mbps

    If the latency is of 2.1 second

    The speed achieves a maximum through out of 200Kbit/sec. TCP will accelerate and will remove that bottleneck. Due to this the line will be allowed to run at its nominal speed.

    2.4) The useful life of the equipment shown in Figure 2 is 15 years. Calculate the reliability of the one radio   terminal at the end of it life

    It is taken as at the end of the life reliability of the radio terminal increases as given below. Reliability of a radio terminal depends on the time of availability and the maintenance breakdown. Generally, the number of break down is taken in the count.

    Using the reliability demonstration method,  = x2 (α,β) / (2 * time * Af)

    As the availability is high the reliability will be 99.99%

    Question 3:High-Speed Connectivity

    In order to give a high-speed internet service in Australia, the government has introduced the National Broadband Network service. It is a National open-access data network project by the government of Australia. The distribution technology used by the NBN is of four types which are FTTN, FTTP, HFC and FTTC (sars.org.uk, 2018). FTTN is fiber to the nodewhereas the cable optical fiber is used generally. FTTP is fiber to the premises which is used in the development of the green field. HFC is hybrid fiber- coaxial but recently this system got shut down. As mentioned by Alizadeh (2015), FTTC is fiber to the Curb which was introduced in the year 2017.

    Question 4 Functions of a   Telecommunication Network

    4.a) Limitation to the size of the coverage area of a telephone exchange

    The factor that limits the size of the coverage area of a telephone exchange is due to less transmitting channels base station occurs(acma.gov.au, 2018). The bandwidth allocated is fixed for uplink and downlink transmission.

    4.b) Limitation to the traffic carrying capacity of a telephone exchange

    The factors that limit the traffic carrying capacity of a telephone exchange are as given below.


    ·         MA transmits data when it is polled to do and it is controlled by BS. If the rate of transmission is too high then in the BS received buffer for the MS would get congested

    ·         Transmission of a signal through different may result in Fading.

    ·         When the same channel is used by different cells it limits the traffic carrying capacity and it is called Co-Channel Interface.

    Part B

    Reflective Journal

    Week 1



    Week No 1



    In this week, I came to know system engineering has become integral part of modern business world.


    The modern day business organisations are using system engineering in order to design or maintain their processes and products.


    Here, I realized that, the role of system engineer is to help the organisation to improve their product quality so that they can be able to meet their customer satisfaction.


    System engineering needs to be govern by laws and fundamental truths related to it.


    Week 2



    Week No 2



    In week 2, I have understood the application of public switched telephone network i.e PSTN. This can be defined as the aggregate of circuit switched network of telephone that can be used in order to operate local, regional along with national operators offering proper services and infrastructure for public telecommunication.


    I found that, PSTN contains fibre cable, telephone lines, and communication satellites along with underwater sea cable that can help to communication the world together.


    PSTN is digital in nature and it contains mobile along with different networks and fixed telephones as well.


    PSTN needs to adhere the standards developed by ITU-T. Moreover, single numbering plan can be effective to make a combination of interconnected networks.


    Week 3



    Week No 3



    In week 3, I tried to gather few theoretical knowledge. I came to know the most important element of telephone is to speak with the microphone and hear from earphone.


    Old landlines phones were connected by pair of cords with the telephone network. The whole process can be considered as radio transmission.


    Landline phones helped the people to communicate with each other effectively. The whole process was done dialling a number using keypad of the phone.


    I need to gather more information to understand how smart phones are dominating this land phones in modern days.


    Week 4



    Week No 4



    In this week, I found that, as a system engineers, it helps to create the attention of engineering discipline.


    Most of the system engineers are associated to many projects from chip design to spacecraft maintence.


    I found that, as a system engineer, it is important to work as interdisciplinary team with the specific components.


    I need to work more effective as a team in order to fulfil projects successfully.


    Week 5



    Week No 5



    In week 5, a discussion is done on the active redundant generator and the questions related to that.


    It has presented a detailed discussion which is based on the availability factor and the reliability factor. It has performed an evaluation considering the Digital Microwave Radio System.


    A brief discussion is done on the high-speed connectivity of LAN as well as on the functions of the telecommunication network.


    I need to be more attentive to understand the way of using active redundant generator.


    acma.gov.au (2018), What technology will connect my premises, Retrieved on : 2nd Jan,2018  From:


    Alizadeh, T. (2015). The spatial justice implications of telecommunication infrastructure: The socio-economic status of early National Broadband Network rollout in Australia. International Journal of Critical Infrastructures11(3), 278-296.Retrieved on : 2nd Jan,2018  From:                                                       https://www.inderscienceonline.com/doi/abs/10.1504/IJCIS.2015.072156

    De Vos, K. (2015). Actors and roles in electricity markets.Retrievedon : 2nd Jan,2018  From: https://lirias.kuleuven.be/bitstream/123456789/514347/1/2015_Roles%26ActorsSGF_Kristof.pdf

    Halat, M., Clotet, X., Gaitán, V., &Bechrakis, D. (2015). Protection elements and methods in Energy and Telecom infrastructure. Retrieved on : 2nd Jan,2018  From:                                                                                                                                      http://rain-project.eu/wp-content/uploads/2015/11/D4.2-Protection-on-Electrical-and-Telecomunication.pdf

    Kumar, A. R., & Krishnan, V. (2017). A Study on System Reliability in Weibull Distribution. METHODS5(3).Retrieved on : 2nd Jan,2018  From: https://www.researchgate.net/profile/Krishnan_V/publication/314950931_A_Study_on_System_Reliability_in_Weibull_Distribution/links/58c7be4ba6fdcc550cab38e2/A-Study-on-System-Reliability-in-Weibull-Distribution.pdf

    sars.org.uk (2018), PROBABILISTIC R&M PARAMETERS AND REDUNDANCY CALCULATIONS, Retrieved on : 2nd Jan,2018  From: http://www.sars.org.uk/BOK/Applied%20R&M%20Manual%20for%20Defence%20Systems%20%28GR-77%29/p4c06.pdf