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Sulanus Arinno Wirdatmedja
Ste Lanus. wirdatmadje E tut.fi

TLT-5706 Multicarrier Technigues Exam 17.04.2013

You may use either English or Finnish language.
Use of literature is not allowed.

Use of the Faculty calculator is allowed.
Compiler of the exam: Jukka Rinne.

1. Describe the basics of Filter Bank based Multicarrier (FBMC) systems. What are the advantages and limitations in
FBMC systems? Give also an example on prospective use of FBMC. How the channel egualization might be carried
out in these systems?

2. Why nonlinear distortion is more likely to occur in OFDM systems? What are the effects of nonlinear distortion on
the OFDM system? What is the peak-to-average power ratio (PAPR)? How can PAPR be reduced in OFDM
systems?

3. Answer to the following guestions:
a) Explain the basics of OFDM? (2p)
b) What are the advantages and drawbacks of OFDM? (1p)
€) Why Guard interval (GI) is used in OPDM systems? What condition the GI should satisfy with respect to the
maximum delay spread of channel? (1p)
d) What are the basic operations that the OFDM receiver should be able perform? (2p)

4. Study the Guard Interval Correlation (GIC) method. Write the mathematical derivations for the output of GIC in case
of multipath channel with one delayed component. The sampled channel response is k(1) = &(n)+ Aö(n- D) , where

ne ]-0,0] » &() is (Kronecker) delta function, A and D are arbitrary constants. Define and justify other needed
assumptions. Give also illustration of the output of GIC.

5. Design a multicarrier system for 15.0 MHz bandwidth. The reguired transmission rate is 40 Mbits/s and maximum
delay spread of the channel is 15 us. Guard band of 2: 0.5 MHz. is reserved for spectral shaping purposes and at least
5% of the carriers should be reserved to be used for synchronization (continual pilots) etc purposes. Channel is
supposed to change insignificantly in time. It can be also assumed that noise is not a limiting factor.

a) What are suitable symbol and guard interval durations in this case? (2p)

b) In FFT implementation, the number of carriers should be a power of 2. Give the length of FFT in your design.
(1p)

o) What kind of submodulation might be useful? (Ip)

d) What is the number of continual pilots in the design? (1p)

€) Describe possible and practical pilot configuration used for the channel estimation in the system. (1p)