168 S. K. CHRONOPOULOS ET AL.

PAPR

dB

CCDF

3

4

5

6

7

8

9 10

11 12

10

0

10

–1

10

–2

10

–3

Conv. Encoder only

M-LAW + conv. encoder

MLSR + conv.encoder

MLACP + conv. encoder

(b) 128 carriers

Figure 6. CCDF of the OFDM PAPR for 64 and 128 carri-

ers (For all μ-Law blocks: μ = 3 and PR = 2).

performance compared to all other techniques. Maximum

PAPR compared to μLSR, μ-Law and OFDM system

with convolutional encoder, has been decreased by al-

most 2 dB, 3 dB and 4.5 dB respectively (for theoretical

maximum PAPR). Hence, in order to understand μLaCP

better performance compared to all other schemes, we

can observe the probability of depressing PAPR under

various values. For example, decreasing PAPR less than

5 dB for μLaCP, μLSR, μ-Law and OFDM conv. system,

concludes to a probability of 90%, 40%, 20% and below

1% respectively for 64 carriers – from Figure 6(a).

6. Conclusion

In this paper we proposed two new techniques for de-

creasing Peak to Average Power Ratio. The primary

concern was to accomplish this with no BER deteriora-

tion and hence to keep complexity of the system as low

as possible. BER curves for μLSR and μLaCP which

were derived from simulations (in the absence of ADC

and DAC) showed clearly not a severe deterioration.

μLSR had a slightly better performance (0.5 dB) com-

pared to μLaCP, but the last exhibited a superior PAPR

performance in terms of probability and maximum PAPR.

Also, μLaCP is even simpler technique compared to

μLSR. Both techniques don’t include an expander in re-

ceiver’s part, for simplicity reasons. Additionally, these

two new methods in their present forms give the capabil-

ity in the final designer to implement them easily in a

DSP. This is also a future goal of us, along with the de-

sign of a final OFDM system (vast number of subccarri-

ers) introducing precise channel estimation.

7. Acknowledgements

The research Project is co-funded by the European Union

– European Social Fund (ESF) & National Sources, in

the framework of the program “HRAKLEITOS II” of the

“Operational Program Education and Life Long Learn-

ing” of the Hellenic Ministry of Education, Life Long

Learning and religious affairs.

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