.3 To Reduce The Papr In The Gpp Lte

The cellular technologies specified by 3GPP are the most widely deployed in the world. Nowadays, 3GPP is working on a project called Long Term Evolution (LTE). LTE will allow operators to achieve even higher peak throughputs in higher spectrum bandwidth.The initial possible deployment of LTE is targeted for 2010.On uplink, LTE uses an approach called SC-FDMA, which has some similarities with OFDMA but will have PAPR advantage over the OFDMA method used by other technologies such as IEEE 802.16e.Furthermore, a better measure of the impact on the required power-amplifier back-off and the corresponding impact on the power-amplifier efficiency is given by the so-called Cubic Metric(CM).In Chapter 2, we investigate the differences between DFT-S-OFDM based SC-FDMA signal's and OFDMA signal's PAPR/CM and BER performances under different modulation schemes. Furthermore, we considered the impact of applying spectrum shaping to DFT-S-OFDM signal generation. And from the analysis of Chapter 2 and the simulation results of Chapter 4, we can draw the conclusion that spectrum shaping allows for further reduction in the power variations of the transmitted signal, thus allowing for even higher power-amplifier efficiency.LTE uses Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink, which is well suited to achieve high peak data rates in high spectrum bandwidth. One of the drawbacks of multi-carrier transmission is the corresponding large variations in the instantaneous transmit power.Being a kind of multi-carrier transmission scheme, OFDMA is subject to the same drawback.In Chapter 3, we introduce two suitable reducing OFDM signal's PAPR methods for LTE downlink: Active Constellation Extension and Quantified Core Clipping method, which wouldn't be limited by LTE specifications and can obviously improve the system's PAPR performance. Furthermore, a new method to reduce OFDM signal's PAPR based on clipping is proposed and explained.In order to test the PAPR reduction performances of the mentioned above methods, in Chapter 4, based on the 3GPP related specifications to LTE system's frame structure as well as the uplink and downlink physical channel process request, we build the uplink and the downlink of the physical layer using MATLAB. In this chapter, the above mentioned spectrum shaping method in uplink and ACE, Quantified Core Clipping method and the new proposed method in the downlink are simulated and further conclusions are drawed by analyzing and contrasting the simulation results.Finally, some conclusions to the whole dissertation are given, and further research issues and possible research directions are pointed out.