Peak to average power ratio analysis for LTE systems

The 3rd generation partnership project (3GPP) long term evolution (LTE) standard uses single carrier frequency division multiple access (SCFDMA) scheme for the uplink transmissions and orthogonal frequency division multiplexing access (OFDMA) in downlink. SCFDMA uses DFT spreading prior to OFDMA modulation to map the signal from each user to a subset of the available subcarriers i.e., single carrier modulation. The efficiency of a power amplifier is determined by the peak to average power ratio (PAPR) of the modulated signal. In this paper, we analyze the PAPR in 3GPP LTE systems using root raised cosine based filter. Simulation results show that the SCFDMA subcarrier mapping has a significantly lower PAPR compared to OFDMA. Also comparing the three forms of SCFDMA subcarrier mapping, results show that interleave FDMA (IFDMA) subcarrier mapping with proposed root raised cosine filter reduced PAPR significantly than localized FDMA (LFDMA) and distributed (DFDMA) mapping. This improves its radio frequency (RF) power amplifier efficiency and also the mean power output from a battery driven mobile terminal.<br /

PAPR reduction in OFDM communications with generalized discrete Fourier transform

The main advantage of Generalized Discrete Fourier Transform (GDFT) is its ability to design a wide selection of constant modulus orthogonal code sets, based on the desired performance metrics mimicking the engineering specs of interest. One of the main drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) systems is the high Peak to Average Power Ratio (PAPR) value which is directly related to power consumption of the system. Discrete Fourier Transform (DFT) spread OFDM technology, also known as Single Carrier Frequency Division Multiple Access (SCFDMA), which has a lower PAPR value, is used for uplink channel. In this thesis, the PAPR of DFT spread OFDM was further decreased by using a GDFT concept. The performance improvements of GDFT based PAPR reduction for various SCFDMA communications scenarios were evaluated by simulations. Performance simulation results showed that PAPR efficiency of SCFDMA systems for Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK) and 16 Quadrature Amplitude Modulation (16-QAM), digital modulation techniques are increased

IMPLEMENTATION AND PERFORMANCE ANALYSIS OF LONG TERM EVOLUTION USING SOFTWARE DEFINED RADIO

The overwhelming changes in the field of communication brought about need for high data rates, which led to the development of a system known as Long Term Evolution (LTE). LTE made good use of Orthogonal Frequency Division Multiplexing Access (OFDMA) in its downlink and Single Carrier Frequency Division Multiplexing Access (SCFDMA) in its uplink transmission because of their robust performance. These multiple access techniques are the major focus of study in this thesis, with their implementation in the LTE system. GNU Radio is a software Defined Radio (SDR) platform. It comprises of C++ signal processing libraries. For user simplicity, it has graphical user interface (GUI) known as GNU Radio Companion (GRC), to build a signal processing flow graph. GRC translates any specific task flow graph to a python program which calls inbuiltC++ signal processing blocks. By leveraging this feature and existing modules in GRC, OFDMA and SCFDMA is implemented. In this study we made use of existing OFDMA flow graph of GNU Radio to study the behavior of downlink and general performing SCFDMA system was implemented with some modifications of the existing GNU Radio blocks. With the GNU Radio implementation, we tested the working mechanism of both the systems. OFDMA is used in downlink for achieving high spectral efficiency and SCFDMA was introduced in uplink due to its low PAPR feature. These multiple access schemes have to meet the requirement of high throughput with low BER and PAPR, low delays and low complexity. In this thesis we are focused on evaluating these multiple access techniques in terms of BER and PAPR with modulation techniques like QPSK, 16-QAM and 64-QAM. Performance analysis part is performed in MATLAB

A COMPARATIVE ANALYSIS OF PAPR OF SC-FDMA AND OFDMA FOR LTE SYSTEMS

Long Term Evolution is a new advancement in the era of cellular technology emerged in recent decade that can accommodate the features of quite efficient radio access with high peak data rates as well as high capacity for voice links. Actually it is a journey toward 4th generation with the recent 2G and 3G network operators. This revolution is an improvement over GSM, EDGE G, WCDMA/UMTS, and HSPDA and then HSPA+ to fulfil the demand of high speed mobile networks. This paper primarily describes a comparison of Single Carrier Frequency Division Multiple Access (SC-FDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) multiple access techniques.This comparison is carried out for the selection of multiple access schemes for the implementation of Long Term Evolution (LTE) systems. Also the advantages and disadvantages of SC-FDMA and OFDMA schemes are described. SC-FDMA is proved better than OFDMA in terms of Peak to average power ratio (PAPR).SCFDMA and OFDMA systems are modelled with MATLAB for PAPR analysis

Papr analysis and channel estimation techniques for 3GPP LTE system

High data rates and secured data communication has become an unavoidable need of every mobile users. 3G technology provided greater data speed and secured networks compared to its predecessor 2G or 2.5G. The highest bit rates in commercially deployed wireless systems are achieved by means of Orthogonal Frequency Division Multiplexing (OFDM) [1]. The next advance in cellular systems, under investigation by Third Generation Partnership Project (3GPP), also anticipates the adoption of OFDMA to achieve high data rates. But a modified form of OFDMA i.e. SCFDMA (Single Carrier FDMA) having similar throughput performance and essentially the same complexity has been implemented as it has an edge over OFDMA having lower PAPR (peak to average power ratio) [2]. SCFDMA is currently a strong candidate for the uplink multiple access in the Long Term Evolution of cellular systems under consideration by the 3GPP. In our project we have worked on PAPR analysis of OFDMA, SCFDMA and various other SCFDMA (with different subcarrier mapping). Though SCFDMA had larger ISI it has lower PAPR which help in avoiding the need of an efficient linear power amplifier. We have analyzed various modulation techniques and implemented various kinds of pulse shaping filters and compared the PAPR for IFDMA, DFDMA and LFDMA (kinds of SCFDMA). Like other communication systems, in SCFDMA we encounter many trade-offs between design parameters (such as roll-off factor) and performance. The project report also constitutes the channel estimation techniques implemented in OFDM systems. Due to multipath fading the channel impulse response fluctuates for different subcarriers in different time slots. But with channel estimation OFDM systems can use coherent detection instead of differential. For MIMO system like OFDM channel information is vital for diversity combining and interference suppression [3]. So we need to estimate the channel as accurately as possible. As we have taken a slow Rayleigh fading channel in our study we used block type pilot arrangement channel estimation which uses LS (least square), MMSE (minimum mean square error) estimator. Due to higher complexity of the MMSE estimator, modified MMSE is implemented where tradeoff is made with performance. Here we have compared various channel estimation techniques used in OFDM systems. There are various other adaptive estimation techniques like LMS and RLS for estimating blind channels and comb type pilot arrangement estimation techniques for fast fading channels

Channel Estimation And Correction Methods For Ofdma Based Lte Downlink System

In present era, cellular communication plays a vital role for communicating over long distance. The number of mobile subscribers is increasing tremendously day by day. 3GPP LTE is the evolution of the UMTS in response to ever-increasing demands for high quality multimedia services according to users\u27 expectations. The average data consumption exceeds hundreds of Megabytes per subscriber per month. To introduce, summarize and get acquainted with this new technology LTE is one of the main objectives of my thesis. The Downlink is always considered an important factor in terms of coverage and capacity aspects in between Downlink and Uplink factors for cellular communication. Orthogonal Frequency Division Multiple Access (OFDMA) and Multiple Input Multiple Output (MIMO) are the new technologies which enhance the performance of the traditional wireless communication experience for downlink. In this thesis, we considered the downlink system for channel estimation by using different algorithms and interpolation methods. Channel Estimation algorithms such as Least Squares Estimation (LSE) and Minimum Mean Square Error (MMSE) have been evaluated for different channel models. The interpolation method used in algorithms is Linear, Piecewise constant, Averaged and Pilot averaged. I measured the performance of these algorithms in terms of Bit Error Rate (BER) and Symbol Error Rate (SER). The results are presented to illustrate the salient concept of the LTE communication system

Performance evaluation of subcarrier mapping techniques for multiuser in presence of Doppler in LTE uplink

Advisors: Mansour Tahernezhadi.Committee members: Lichuan Liu; Donald S. Zinger.Orthogonal Frequency Division Multiplexing (OFDM) is an advanced 3G/4G scheme which achieves high data rate and combats multipath fading. However, OFDM systems suffer from nonlinear peak to average power ratio (PAPR) and Carrier Frequency Offsets (CFO). These two factors lead to degraded performance and thereby reducing the system efficiency. In order to reduce the PAPR, the Single Carrier Frequency Division Multiple Access (SCFDMA) in the Long Term Evolution (LTE) uplink was developed. In this thesis, the Bit Error Rate (BER) and PAPR for Localized Frequency Division Multiple Access (LFDMA), Modified Hybrid Frequency Division Multiple Access (MHFDMA) and Zero Interleaved Frequency Division Multiple Access (IFDMA) in the presence of multipath fading and Doppler have been evaluated and compared. The MHFDMA has been designed using the LFDMA and IFDMA subcarrier mapping techniques in SCFDMA. The multiuser SCFDMA system is simulated using different number of subcarriers and modulation schemes. In terms of PAPR, IFDMA gives a lower value compared to the MHFDMA and LFDMA but its implementation is complex for the base station. The LFDMA gives a higher PAPR value compared to the IFDMA and MHFDMA, but it gives a lower value compared to the conventional OFDM systems. The implementation complexity of LFDMA is very low. The MHFDMA gives a PAPR in between LFDMA and IFDMA with the implementation complexity also in between LFDMA and IFDMA. However, it extracts the multiuser diversity and frequency diversity of both the schemes. The system is simulated for four users and 1024 subcarriers, with each user accessing 256 subcarriers, in the presence of Doppler and multipath Rayleigh fading channel. The BER performance for all the three subcarrier mapping techniques was the same in no Doppler case and different percentage Doppler cases. The BER performance degraded as the constellation size in the modulation increased.M.S. (Master of Science

Impact of Adaptive Modulation and Coding Schemes on Bit Error Rate for System Performance in the Uplink LTE System

Long Term Evolution (LTE) is a cellular network technology aims to render enriched data services to users at lower latency and higher (multi-megabit) throughput. The higher system throughput with more reliable transmission is achieved by the support of Adaptive Modulation and Coding (AMC) schemes, scheduling algorithms, multi-antenna techniques etc. The AMC schemes substantially increases the system throughput by reducing the Bit Error Rates (BER) and by adjusting the transmission parameters based on the link quality. The scheduling algorithms also enhance the throughput of individual users, as well as the cell throughput by allocating the resources among the active users. Hence in this paper, an attempt has been made to study and evaluate the effects of AMC schemes such as QPSK, 16-QAM and 64-QAM on uplink LTE system performance for Proportional Fair (PF) and Round Robin (RR) scheduling algorithms using QualNet 7.1 network simulator. The performance metrics considered for the simulation studies are BER, cell throughput, average delay and average jitte

LTE Advanced: Technology and Performance Analysis

Wireless data usage is increasing at a phenomenal rate and driving the need for continued innovations in wireless data technologies to provide more capacity and higher quality of service. In October 2009, 3rd Generation Partnership Project (3GPP) submitted LTE-Advanced to the ITU as a proposed candidate IMT-Advanced technology for which specifications could become available in 2011 through Release-10 . The aim of “LTE-Advanced” is to further enhance LTE radio access in terms of system performance and capabilities compared to current cellular systems, including the first release of LTE, with a specific goal to ensure that LTE fulfills and even surpass the requirements of “IMT-Advanced” as defined by the International Telecommunication Union (ITU-R) . This thesis offers an introduction to the mobile communication standard known as LTE Advanced, depicting the evolution of the standard from its roots and discussing several important technologies that help it evolve to accomplishing the IMT-Advanced requirements. A short history of the LTE standard is offered, along with a discussion of its standards and performance. LTE-Advanced details include analysis on the physical layer by investigating the performance of SC-FDMA and OFDMA of LTE physical layer. The investigation is done by considering different modulation schemes (QPSK, 16QAM and 64QAM) on the basis of PAPR, BER, power spectral density (PSD) and error probability by simulating the model of SC-FDMA & OFDMA. To evaluate the performance in presence of noise, an Additive White Gaussian Noise (AWGN) channel was introduced. A set of conclusions is derived from our results describing the effect of higher order modulation schemes on BER and error probability for both OFDMA and SC-FDMA. The power spectral densities of both the multiple access techniques (OFDMA and SC-FDMA) are calculated and result shows that the OFDMA has higher power spectral density.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format