Implementation Of OFDM System Research Articles

The FPGA implementation of OFDM system on channel estimation and equalization on preamble

The FPGA implementation of OFDM system on channel estimation and equalization on preamble

An Implementation of Error Minimization Data Transmission in OFDM using Modified Convolutional Code

This paper presents about error minimization in OFDM system. In conventional system, usually using channel coding such as BCH Code or Convolutional Code. But, performance BCH Code or Convolutional Code is not good in implementation of OFDM System. Error bits of OFDM system without channel coding is 5.77%. Then, we used convolutional code with code rate 1/2, it can reduce error bitsonly up to 3.85%. So, we proposed OFDM system with Modified Convolutional Code. In this implementation, we used Software Define Radio (SDR), namely Universal Software Radio Peripheral (USRP) NI 2920 as the transmitter and receiver. The result of OFDM system using Modified Convolutional Code with code rate is able recover all character received so can decrease until 0% error bit. Increasing performance of Modified Convolutional Code is about 1 dB in BER of 10-4 from BCH Code and Convolutional Code. So, performance of Modified Convolutional better than BCH Code or Convolutional Code.Keywords: OFDM, BCH Code, Convolutional Code, Modified Convolutional Code, SDR, USRP

Reduction of PAPR using Modified PTS Technique Improvement: Simulation and Hardware Implementation

In this paper, the design and implementation of OFDM system along with Multi-Point Square Mapping combined with PTS (M-PTS) technique has received much attention in reducing the high peak to average power ratio (PAPR) of Orthogonal Frequency Division Multiplexing signals (OFDM). As compared to C-PTS technique, the proposed M-PTS technique needs not to submit side information but keeping almost the same performance of PAPR reduction as the C-PTS technique. A detailed Simulation of OFDM system is conducted and implemented using FPGA to validate the results.

Hardware Implementation of OFDM system to reduce PAPR using Selective Level Mapping on FPGA

OFDM is a modulation as well as multiplexing technique which is widely used in various high speed mobile and wireless communication systems because of its capacity of ensuring high level robustness against interference. In this paper the design and implementation of OFDM system along with SLM implementation to reduce PAPR(6)is illustrated and a detailed simulation of the OFDM system with 16-QAM. OFDM transceiver is implemented using FPGA Spartan6 kit. The hardware results show a detailed study of RTL schematics and Test Bench. In this paper, the software simulation results show 2dB reduction in the peaks. Keywords - Field Programmable Gate Array, Matlab Simulink, Orthogonal Frequency Division Multiplexing , Peak-to-Average Power Ratio, Selective level Mapping and Xilinx

Hardware Implementation of OFDM system to reduce PAPR using Selective Level Mapping on FPGA

Hardware Implementation of OFDM system to reduce PAPR using Selective Level Mapping on FPGA

FPGA Synthesis of VHDL OFDM System

This paper presents a novel Field Programmable Gate Array (FPGA) technique to gain approach in the problem of OFDM system implementation. The actual and next communication schemes tend to use OFDM systems in order to provide high baud rates, less intercarrier interference (IC), and less intersymbol interference (ISI). Some examples are IEEE-802.11, IEEE-802.15, IEEE-802.16, 3GPP, MC-CDMA, digital video broadcasting (DVB), wireless USB, and/or wireless firewire among others. Trying to provide a solution to the new devices emerging, slow standard adoption, poor spectrum use, etc. This work presents an FPGA design; validation, and implementation of an OFDM modulator for IEEE-802.16e using a high level design tool, also reports the resources requirements for the presented system. The proposed design is synthesized using high level design tools. The design flow is optimized for fast prototyping which is implemented on the latest generation of FPGA chips. Such an FPGA implementation has the added advantage to modify for changes and improved system performance, e.g. reducing propagation delay.

Theoretical and experimental investigation of compatible SSB modulation for single channel long-distance optical OFDM transmission

We present the first experimental demonstration of compatible single-sideband (compatible-SSB) modulated OFDM optical system at 11.1Gb/s data rate for long distance transmission over 675 km uncompensated standard single-mode fiber. Compatible-SSB modulation employing a simple dual-drive Mach-Zehnder modulator (MZM) in the transmitter and direct-detection at the receiver provides an OFDM system implementation with reduced complexity. It does not require a guard-band between the carrier and the OFDM sideband and so makes full use of available digital-to-analog converter (DAC) bandwidth. We demonstrate digital pre-compensation applied in the transmitter to correct MZM nonlinear transfer function and to improve the system transmission performance. We show that optimum modulation index value decreases with increasing transmission distance. We have also investigated the impact of self-phase modulation (SPM) on the system performance, and show that a compatible-SSB modulated system is less vulnerable to SPM in comparison to the conventional offset-SSB modulation at the same data rate.

Intercarrier Interference Cancellation with Frequency Diversity for OFDM Systems

The implementation of OFDM system suffers from the effect of phase noise (PHN) generated by local oscillator (LO), which disturbs the orthogonality among subcarriers and causes intercarrier interference (ICI). In frequency domain, the received signal can be formulated as the circular convolution of the transmitted signal and the ICI weighting function. In this paper, the symmetric conjugate property of the ICI weighting function is investigated. Based on that, the ICI self-cancellation of symmetric data-conjugate method is studied to suppress PHN. A new ICI cancelling demodulation (ICD) scheme with frequency diversity combining is proposed. Under flat fading channel, the carrier-to-interference ratio (CIR) improvement from this proposed method is larger than 22 dB, and can tolerate a phase noise with standard deviation of 7 deg when BER is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . In frequency selective fading channel, the proposed method is shown to be able to offer significant diversity gain

Estimation of Stationary Phase Noise by the Autocorrelation of the ICI Weighting Function in OFDM Systems

Phase noise resulting in common phase error (CPE) and inter-carrier interference (ICI) is a critical challenge to the implementation of OFDM systems. Modeling phase noise as a stationary Gaussian random process with the specified power spectrum density, different from conventional approaches which mostly relay on pilots to provide CPE estimation, we explore the statistical characteristics of the sufficient statistics then propose a pilot-aided decision-directed approach according to maximum-likelihood criterion. Numerical results demonstrate that the proposed algorithm enjoys 2 dB gain at moderate SNR and is quite robust against possible model mismatch

FPGA-based prototyping of IEEE 802.11a base band processor

In technical literature and especially in domestic, predominant way to examine performance of 802.11a-based systems are experiments in simulations. In this paper, we present FPGA based 802.11a prototype, which gave us a possibility to gain closer insight into the problems of OFDM system implementation. A specific design of base band modem physical layer is discussed, along with the presentation of the FPGA prototyping platform on which it was developed. Prototype is implemented on the latest generation of FPGA chips, using state-of-the-art tools for DSP development. Custom made development environment, and design flow optimized for rapid prototyping of software defined radios, are also presented in the paper.

Combination of DFT and Multitone Modulation in OFDM Systems

In the implementation of OFDM systems one of the most consolidated schemes consists of an N-point DFT processor and an N-input N-output polyphase network, where N is the number of channels. Another recently developed scheme, which is attractive for its conceptual simplicity, consists of a polyphase filter, a multitone modulator (MTM) with carrier exp(j2Π(Fot)2/2N), and an equalizer. In this paper we derive a combination of the two previous schemes, where the number of channels Nis factored in the form N = M· I. The composite scheme consists of: 1) an l-point DFT processor; 2) a bank of I different MTM and 3) a bank of I different polyphase filters; and 4) a bank of I identical MTM with carriers. The composite scheme degenerates into the previous schemes in the extreme cases provided by factorization M I. Specifically, the DFT scheme is obtained with M = 1 and I = N, and the MTM scheme with M = N and I = 1. Here the attention is for the intermediate cases of factorization.