ME503 Assignment: Reliability Analysis in Telecommunication Systems

This assignment solution covers key aspects of telecommunication engineering reliability, including the analysis of parallel systems, digital microwave radio systems, and the National Broadband Network (NBN) technology. It delves into the calculation of system reliability, mean time to failure (MTTF), mean time to repair (MTTR), and the factors limiting the coverage area and traffic carrying capacity of a telephone exchange. The NBN discussion is based on research findings, referencing journals to explain the various technologies used in its deployment. The document also addresses the functions of a telecommunication network and the parameters defining its performance, such as quality of service. The solution utilizes mathematical models and concepts from reliability engineering to provide a comprehensive understanding of the subject.

Telecommunication Engineering
Reliability
Name:
Professor:
Date:

a) RELIABILITY
If the components are in parallel, system performs if any one component remains operational
If there are n components in parallel, where the reliability of the i-th component is denoted by
ri , the system reliability is
Rp=1-(1-r1) (1-r2)… (1-rn)
For our case
Assume that the reliability of each subsystem (or component) i has the reliability of Ri. Calculate
the reliability of the overall system RS as a function of Ri.
RS=1-(1-RI) (1-RI)
RS=1-(1-RI) 2
a) If the reliability of component i at time t is Ri (t) =e-λit, what is the reliability function of the
overall system at time t?
Qi (t) = 1-e-λit
f (t) = dQ (t )
dt = d (1−e− λit)
dt = λe -λit

b) Evaluate the mean time to failure (MTTF) of the overall system as a function of λi using the
reliability function in part (b).
Mean Time to Failure, MTTF= ∫
0
∞
f (¿)dt = 1/λ
=1/λ
c) Calculate the failure rate of the overall system with exponential reliability. Hint use binomial
distribution.
Qi (t) = 1-e-λit
d) What is the mean time before failure (MTBF) of the above system?
= ∫
0
∞
f (¿)dt = 1/λ
Question 2 Digital Microwave Radio System
A point-to-point digital microwave radio system is required by a bank to link the LANs of two
of its branches at 2.048 Mbps transmission speed. The handbook delivered by the manufacturer
has dimensioned the entire radio terminal with the reliability:
MTBF (mean time between failures): 100,000 hours
MTTR (mean time to repair): 2 hours (equipment only).
The radio path availability was calculated for 𝐵𝐸𝑅=10-8 and found to be 99.999% for the
average worst case. The system configuration is shown in Figure 1.
a) Calculate the overall system availability
Availability =MTBF/ (MTBF+MTTR)
=99.998%
b) Draw the reliability diagram of the system
NODE 1 NODE 2SYSTEM BLOCK

c) How would you increase the availability of the system required by the bank?
FINDING AND IMPLIMENTING THE MEAN TIME TO REPAIR (MTTR)
Mean time to repair (MTTR) is the typical time necessary to deduce and mend failed
equipment and return it to standard working settings [7]. It is a fundamental technical measure
of the maintainability of equipment and repairable parts. Maintenance time is referred to as the
time interval between the beginning of the incident and when the system is returned to
production (i.e. time when the equipment is inactive). This comprises of the notification time,
investigative and problem-solving time, cool down time, reassembly, configuration,
standardization, experiment time, back to production, etc. It usually does not incorporate lead-
time for parts. Mean time to repair eventually depicts how well an organization can react to a
technical itch and restore it.
d) 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.
Figure 2: Microwave system
Question 3 High Seed Connectivity
Access to the Internet has arguably become an essential service. However, the quality of the
service varies widely in Australia. Multiple governments had promised (and begun to deliver) a
high-speed connectivity throughout Australia via the NBN. Discuss and briefly explain the NBN
Terminal
A
Terminal
B

technology. The discussion must be based on research findings, e.g. reference must be made of
at least two journals.
The NBN (National Broadband Network) is an Australian domestic extensive open-access
data linkage project. It consists of both wired and radio communication mechanisms rolled out
and activated by NBN Co Limited. Retail service providers (RSPs), normally Internet service
suppliers, sign agreement with NBN for the right to use the network and sell secure internet
access to consumers [4].Logics for this countrywide telecommunications set-up project
encompassed replacing the current copper cable telephony system that is approaching extinction,
and the swiftly rising demand for internet access[2]. As initially planned, wired networks would
have delivered up to 100 Mbit/s, later amplified to 1 Gbit/s; after the election of the Abbott
government in 2013 this was reduced to a minimum of 25 Mbit/s [5].
There are 4 types of NBN technologies used namely:
 Fibre to the premises (FTTP): A fibre optic cable transmits the NBN signal from the
interchange, over the adjoining fibre node and to a mounted link device on your
properties.
 Fibre to the node (FTTN): A fibre optic cable transfers the NBN signal from the
interchange to the adjoining node, then depend on the copper cabling to transmit it to
your property.
 Fibre to the building (FTTB): This selection is usually used to link apartment. The signal
runs over the fibre optic cable to the structure’s communications room, and from there
the existing network technology carries it to the individual apartments.

 Hybrid fibre coaxial (HFC): A current ‘pay TV’ or cable network is utilized to transmit
the NBN signal from the bordering fibre node to a connected device on your properties.
Question 4 Functions of a Telecommunication Network
The functions of a telecommunication network, whether it is wired or wireless, are specified by
the size of its coverage area and traffic carrying capacity. On the other hand, the performance of
the network is specified by its quality of service.
a) What limits the size of the coverage area of a telephone exchange?
The congestion of consumers in a zone that steered to the usage of cells in communication
interference impacts were not as a result of the distance between zones, but to the proportion of
the distance between areas to the mast power (radius) of the regions[8]. By decreasing the radius
of a region by 50%, service suppliers may perhaps increase the quantity of potential consumers
in a region fourfold. Systems centered on regions with a one-kilometer range would have one
hundred times more frequencies than systems with regions 10 kilometers range. Assumption led
to the decision that by decreasing the range to a few hundred meters, many calls may perhaps be
served [9].The cellular concept uses adjustable low-power intensities that permit cells to be sized
based on the subscriber concentration and demand of a given region. As the populace grows,
cells can be added to accommodate that growth. Frequencies used in one cell constellation can
be used again in other cells.
What limits the traffic carrying capacity of a telephone exchange?

 Traffic Load Measurement
Traffic load is the ratio of call arrivals in a definite period of time to the average amount of time
taken to service each call during that period. These measurement units are based on Average
Hold Time (AHT).
 Grade of Service
Grade of Service is defined as the likelihood that calls will be blocked while attempting to seize
circuits
 Type of traffic (modem versus traditional voice)
Apparent versus offered load

References
[1] Birolini, Alessandro. (2017). Reliability Engineering: Theory and Practice. Springer Verlag.
[2] Brown, Damien. “NBN Now 10 Times Faster.” The Mercury 13 Aug. 2010.
‹http://www.themercury.com.au/article/2010/08/13/165435_todays-news.html›.
[3] Carmines, E. G., & Zeller, R. A. (2008). Reliability and validity assessment. Newbury Park,
Calif: Sage Publ.
[4] Edwards, K., Rebecca G., Ratul M., and David W. (2010). “Advancing the State of Home
Networking.” Communications of the ACM 54.6 .62-71.
[5] Neumann, K.-H. (2010). Structural models for NBN deployment. Bad Honnef: WIK
Wissenschaftliches Institut fu [section] [u.a.
[6] Reliability Engineering Conference for the Electric Power Industry, & Institute of Electrical
and Electronics Engineers. (n.d.). Reliability. New York: Institute of Electrical and
Electronics Engineers.
[7] Tobias, P. A. (2012). Applied Reliability. CRC Press.
[8] Tucker, Rodney S. (2010). “Broadband Facts, Fiction and Urban
Myths.” Telecommunications Journal of Australia 60.3: 43.1 to 43.15.
[9] Wilken, R., Michael A., and Bjorn N. (2011). “Broadband in the Home Pilot Study: Suburban
Hobart.” Telecommunications Journal of Australia 61.1: 5.1-16.

[10] Zafar, M. Shaqfeh, M.-S. Alouini, and H. Alnuweiri, “A suboptimal scheme for multi-user
scheduling in Gaussian broadcast channels,” IEEE Trans. Signal Process., vol. 22, no. 2,
pp. 136–140, Feb. 2015