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Abstract: The size, complexity and performances of modern wireless communication circuits are getting more and more challenging whereas marketing time and cost must be reduced as much as possible. In order to fill the current lack in CAD tools, this work is dedicated to the mixed simulation of complete communication systems driven by digital and digitally modulated RF signals. This paper describes a methodology for top-down design, modeling, and simulation of complete RF system using hardware description language VHDL-AMS (Very high speed integrated circuit Hardware Description Langage – Analog Mixed Signal). As application, we consider a complex M-QAM system (transmitter, channel, and receiver) and we show some details of

Wireless designers constantly seek to improve the spectrum efficiency/capacity, coverage of wireless networks and link reliability. Space-time wireless technology that uses multiple antennas along with appropriate signalling and receiver techniques offers a powerful tool for improving wireless
performance. More advanced MIMO techniques are planned for future mobile networks in wireless Local Area Network (LANs) and Wide Area Network (WANs). Multiple antennas when used with appropriate Space-Time Coding (STC) techniques can achieve huge performance gains in multipath fading wireless links. The Space Time Coding has evolved as a most vibrant research area in wireless communications. Recently, Space-Time Block Coding (STBC) has been trying to incorporate in the forthcoming generation of mobile communication standard which aims to deliver true multimedia capability. This paper presents the Space-Time Block Codes (STBC) for wireless networks that uses multiple numbers of antennas at both transmitter and receiver. The simulations have been done in MATLAB. The STBC which includes the Alamouti Scheme as well as an orthogonal STBC for 4 transmit antenna case has been simulated and studied.

In OFDM (Orthogonal frequency division multiplexing) systems, channel estimation and channel
equalization play a key role in overcoming distortions caused by phenomena like fading, delay spread and
multipath effect. In this paper, channel estimation and equalization techniques are analyzed to improve the
performance of OFDM system. The channel estimation techniques considered here are estimation using
wiener filter and frequency domain approach. Prior Channel estimation leads to simple equalization. The
channel equalization techniques employed here are based on LMS algorithm and one tap frequency domain
equalization, under different channels; AWGN, Rayleigh and Rician channels. Eye patterns for different
channels are compared in simulation. It is observed from simulation that wiener filter provides better
estimation and OFDM performance is better under AWGN channel than fading channels. SER curves
shows 6dB improvement in AWGN performance than fading channels to achieve 0.1 SER. In addition, MSE
performance shows fast convergence for AWGN channel.

ABSTRACT The paper presents the design and performance of a baseband modem for wireless LAN systems. The modem fully complies with the IEEE 802.11g standard draft 4.0. It is capable of operating in any of available modes such as ERP-DSSS/CCK, ERP-OFDM, Extended Rate PBCC, and CCK-OFDM. It offers different data rates from 1 Mbps to 54 Mbps and handles DBPSK, DQPSK, QPSK, 8-PSK, BPSK, 16-QAM, and 64-QAM modulation schemes. We show the BER performance of the presented modem as the result of simulation under AWGN and multipath channels.

We present bounds and a closed-form high-SNR expression for the capacity of multiple-antenna systems affected by Wiener phase noise. Our results are developed for the scenario where a single oscillator drives all the radio-frequency circuitries at each transceiver (common oscillator setup), the input signal is subject to a peak-power constraint, and the channel matrix is deterministic. This scenario is relevant for line-of-sight multiple-antenna microwave backhaul links with sufficiently small antenna spacing at the transceivers. For the 2 by 2 multiple-antenna case, for a Wiener phase-noise process with standard deviation equal to 6 degrees, and at the medium/high SNR values at which microwave backhaul links operate, the upper bound reported in the paper exhibits a 3 dB gap from a lower bound obtained using 64-QAM. Furthermore, in this SNR regime the closed-form high-SNR expression is shown to be accurate.

On of the main drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) is the significant increase in the Peak-to-Average Power Ratio (PAPR), due to the large dynamic range of its symbol waveforms, which in turn requires a wide dynamic range of power amplification. To overcome this problem, a novel selected mapping (SLM) based technique named Orthogonal-SLM (OSLM) is proposed, where each

Orthogonal Frequency Division Multiplexing (OFDM) is a special form of multicarrier modulation scheme, which divides the entire frequency selective fading channel into many orthogonal narrow band flat fading sub channels. Orthogonal Frequency Division Multiplexing (OFDM) is considered to be a promising technique against the multipath fading channel for wireless communications [1]. However, OFDM faces the Peak-to-Average Power Ratio (PAPR) problem that is a major drawback of multicarrier transmission system. We will be using Selected Mapping method (SLM) to reduce PAPR, improve BER while maintain high SNR. MATLAB® simulation is used to implement the proposed model.

Abstract In this paper MIMO (Multiple Input Multiple Output) configuration provides enhanced capacity with the same transmit power. OFDM (Orthogonal Frequency Division Multiplexing) is a multicarrier technique that offers high spectral efficiency. OFDM combined with MIMO offers increased reliable high data rate transmission, multiplexing gain, diversity gain, improve the link, system capacity and frequency variant over broadband wireless channels. MIMO- OFDM configuration is found to perform better against multi-path fading and the varying channel conditions, interferences, than the conventional technologies. In this paper, the channel estimation & BER performance of a MIMO-OFDM are evaluated on the basis of error reduction and better system designing using popular IFFT/FFT & 16- QAM modulation formats. The final performance of the system with different parameters is tested by using MATLAB code word. Keywords: MIMO-OFDM, 16-QAM, IFFT

We demonstrate the feasibility of Radio Over Fiber (ROF) transmission of 4 Sub-Carrier Multiplexed (SCM) 64-QAM data streams to a pair of low-complexity Radio Access Units (RAUs), which form part of a virtual MIMO architecture under the control of a Central Unit (CU). The ROF signal is transmitted over low frequency RF carriers and heterodyne detection is used at the RAUs. The 4 coherent optical carriers used for data transmission as well as for heterodyning at the RAUs are generated using a single laser rather than several inevitably non-coherent lasers. Our proposed system transmits duplex data of 480 Mbit/s and 240 Mbit/s in the downlink and uplink directions, respectively at mm-wave frequencies of 25 GHz or 50 GHz.

In this letter we propose simple and robust features to distinguish continuous-phase frequency shift keying from quadrature amplitude modulation and phase shift keying modulations. The features are based on sample mean and sample variance of the imaginary part of the product of two consecutive complex signal values. Root raised cosine pulses are used to generate the linearly modulated signals. Support vector machines are employed to distinguish the signals. One benefit of using support vector machines is that it requires very few realizations for training. Moreover, no a priori information is required about carrier amplitude, carrier phase, carrier offset, symbol rate, pulse shape, initial symbol phase (timing offset) and channel impulse response. Effectiveness of the features and signal separation by support vector machines is tested by observing the joint effects of additive white Gaussian noise, carrier offset, lack of symbol and sampling synchronization, and either fast or slow fading. In the course of doing that, the proposed classifier is compared to the wavelet based classifier, equipped by support vector machines.

Orthogonal Frequency-Division Multiplexing (OFDM) is essentially identical to coded OFDM (COFDM) and discrete multi-tone modulation (DMT). It is a frequency-division multiplexing (FDM) scheme, which is used as a digital multicarrier modulation method. The paper is aimed at analyzing the BER performance of the MIMO (Multi-Input Multi-Output) OFDM system for AWGN (Additive White Gaussian Noise) Channel, Rayleigh Fading Channel along with a simulation channel using different modulation technique. Also the result of the analysis suggest for the better technique in order to improve the BER characteristic of the MIMO-OFDM system.

Laboratoire d'Electronique et des Technologies de l'Information Ecole Nationale d'Ingénieurs de Sfax BP W, 3038 SFAX TUNISIE, Tel (+216) 74 274 088 - Fax: (+216) 74 275 595 ... Abstract: The size, complexity and performances of modern wireless communication ...

Main objectives of this paper is to design the PSK and QAM system for Symbol Error Rate (SER) performance analysis and to estimate the channels in OFDM. PSK & QAM syatems are designed for 64 Sbcarriers. In this paper we will compare the SER for both techniques for same modulation rate and same number of subcarrier. In this paper we will show how Symbol error rate is reduced as modulation rate increases for PSK & QAM. We will use three algotihms LS, LMMSE & Modified MMSE to compare the result parameters. Modified MMSE gives better results than LS & LMSE but computational complexity will be increased that is its major drawback.