FREQUENCY DIVISION MULTIPLEXING

Page 1. FAST ACTIVE CONSTELLATION EXTENSION FOR MIMO-OFDM PAR REDUCTION Brian S. Krongold ARC Special Research Centre for Ultra-Broadband Information Networks Dept. of Electrical & Electronic Engineering University of Melbourne, Australia ...

This paper examines the possibility of implementation of relaying in 3G cellular systems by allowing calls between a mobile terminal and base station to be forwarded by some other mobile device in the cell. This "stretched" call provides improvements in throughput, capacity, energy savings and coverage. The main contribution of this paper is to enumerate the problems that are introduced

: In this thesis, an optimal estimation algorithm, based on the Kalman Filter, is introduced for data recovery of orthogonal frequency-division multiplexed (OFDM) signals transmitted over fading channels. We show that the use of a zero prefix (ZP) along with a fast Fourier transform (FFT) operation zero padded to twice the data length allows for the recovery of subcarriers located next to a deep faded (at low signal-to-noise ratio [SNR]) values, exploiting all other subcarriers with higher SNR. The same approach is also shown to improve demodulation in the presence of signal clipping due to high peak to average power ratio (PAPR), as is often seen in OFDM signals. The proposed method assumes prior knowledge of the channel, usually estimated using the preamble. Testing was conducted for random channels with zero frequency response at a random frequency omega 0 and a signal in additive white Gaussian noise for various conditions. Further testing was done with typical Stanford Universi...

A Doppler estimation system using a maximum likelihood criterion is presented in the context of underwater acoustic communications between moving transmitter/receiver. We simulate the method for the estimation of the Doppler effect induced by an underwater acoustic channel (UWA) using Zero Padded-Orthogonal Frequency Division Multiplexing (ZP-OFDM). Among the wide range of physical processes that impact OFDM communications through the underwater environment, Doppler effect is an important cause of loss of orthogonality and must be compensated before discrete Fourier transform based demodulation can be performed. The proposed approach is based on the perfect knowledge of the emitted signal during one block and rely on the assumptions of a small variation of the Doppler effect induced by the canal between two ZP-OFDM blocks and, above all, during one block.

Sprott’s circuit, which is improved to crypt signals, is presented. Using Frequency Division
Multiplexing (FDM) technique, transmit the controlling signal and the secret signal via one single channel can be sent for chaos synchronization. The proposed method is
applied with Double Side Band – Sub Carrier (DSB-SC) modulation-demodulation.

... CRC Reserved (2 bytes) CLP Type CSN Control MVCI MVCI HEC CRC DATA (48 bytes) GFC PT CLS MVCI MVCI CRC PRM3 (2 bytes) PT PRM2 (2 bytes) PRM1 (2 bytes) WATM Data cell Signaling packet Figure 6. WATM packets formats ... [7] Tarek Bejaoui1, Véronique Vèque ...

... signaling due to the on-demand CQF, the associated total con-trol signaling is reduced ... Furthermore, by reducing the overall CQF feedback overhead per transmitted bit, it saves the scarce ... 3GPP TSG RAN WG 1, Tdoc R1-02-1051, Mitsubishi, "Additional CQI feedback," Seattle ...

: Since the beginning of this century, the Argentine Army has used Commercial Off-The-Shelf (COTS) wireless products, equipment, and communication systems to support Humanitarian Assistance and Disaster Relief (HA/DR) operations. The participation of Military, Governmental, and Non-Governmental Organizations in these activities requires more wireless coverage area. These communication systems are an integration of several subsystems that provide an initial Hastily Formed Network (HFN), but they do not provide enough coverage area to support Command and Control centers from different organizations. This thesis explores different solutions to address the lack of coverage area of the current wireless systems. It analyzes new COTS technologies that could be applied to the Argentine Military HFN Centers to satisfy the emerging requirements of HA/DR operations. This research is focused on Wireless Subsystems, and it gathers data from actual HA/DR experiments and exercises organized by NPS...

We propose an efficient algorithm that computes the maximum achievable rate of a decode-and-forward multi-relay cooperative system with orthogonal transmissions under total power constraint. In P.A. Angel et al. we have argued that in a system with Q relays the optimum rate can be found by solving Q convex problem despite the fact that the optimization problem is not convex

Optical fiber Bragg gratings (FBG) have numerous features making them very useful for sensing applications. In this work, we demonstrate a multiplexed sensor based on a serial array of twin-grating interferometers. The sensor employs low reflective Bragg gratings and is easy to manufacture. The combination of wavelength- and frequency-division multiplexing was tested experimentally and using a computer simulation. The approach

ABSTRACT In this paper, a method for estimating the maximum Doppler shift frequency is presented for Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems. This method uses the Autocorrelation Function (ACF) for estimating frequency shift that induces ICI between adjacent OFDM subcarriers. The simulation results investigate the BER performance of OFDM system that achieves transmit and receive diversity by using Alamouti/MRC, as well as the BER performance of MIMO linear detectors Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) under the effect of a Doppler spread channel.