Wireless Networks & Communication
Part I: Encoding
and error control
Sam is a computer science student and
working on a new micro robot design. The robot continuously sends every two
seconds a status string comprising the accelerometer reading (4 bits),
ultrasound obstacle detection (6 bits), motor functionality (4 bits) and
battery power level (2 bits).
a) Calculate the data rate required for robot
to remote controller communication
b) Explain 3 types of suitable encoding
techniques could be used to encode the status string.
c) At a certain instance, the sensors provided
data as acceleration 5 m/s2, obstacle at 48 cm, all motors working
(i.e. motor functionality 1111), and battery is 75%.
i. Write the status string in binary for this
instance
ii. Represent the status string on ASK, FSK,
and PSK encoding techniques
d) Calculate the CRC for the status string
derived in c) with polynomial divisor 11001101
e) Briefly explain some other error control
and flow control techniques that Sam can use to ensure the accuracy of robot
control
Part II:
Multiplexing and multiple access
Multiplexing plays an important role in
communication as it allows the combination of multiple streams together.
Different multiplexing techniques are used for various applications.
a) Explain TDM, FDM and CDMA multiplexing
techniques with suitable diagrams
b) Main air interface in the change from 3G to
4G and WiMAX. Explain how OFDM is different from above techniques and the
special feature of signals used by OFDM
c) IEEE 802.11ac wireless LAN standard uses 40
MHz total bandwidth in OFDM scheme.
i. For 48 subscribers what should be the
subcarrier bandwidth ( fb ) ?
ii. Propose a suitable subcarrier bit time of T
to achieve orthogonality
iii. Explain
how OFDM overcomes the issue of inter symbol interference (ISI)
Part
III: Wi-Fi
Prime
Living is a real estate company based in Victoria and you work form them as a
consultant network engineer. The company has decided to open a new office in
South Eastern suburbs and the floor plan of the building is shown below. The
office consists of 5 rooms and on average 8 employees work at each room. The
lounge is used by both staff and customers and on average about 25 devices
connect to Wi-Fi. The clients wants you to design the network for them with at
least 100 Mbps data rate for all wireless connections. As resources you’ve got
one distribution system and few access points of 10 m range.
a) Design the network specifying the locations
of access points and distributions system showing the backbone network.
b)
Calculate the BSS and ESS sizes
c)
Calculate the throughput for the DS
d) Recommend a suitable IEEE substandard for
the network and give reasons for your choice
e)
Recommend suitable security strategies for
the network
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