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This paper proposes and designs a linear demapper which compares to a recently proposed non-linear demapper under different decoding schemes of dedicated short-range communications (DSRC) receivers. Modelling and simulations are carried out under common mobile vehicular channel conditions. It can easily be seen that multipath and Doppler shift has a detrimental effect on the transmitted modulated...
In-band pilot and cyclic prefix (CP)-based sensing, exploiting OFDM signal characteristics in the frequency domain and time domain respectively, are two effective techniques for low SNR spectrum sensing in cognitive radio communications. This paper seeks the theoretical performance improvement and optimal solution on the combination of these two techniques. The principles and performances of these...
It is developed a case study, unifying theoretical and practical aspects, concerning planning and implementation of orthogonal frequency division multiplexing (OFDM) point-to-multipoint (PtMp) links at Industrial, Scientific and Medical (ISM) 5 GHz band. The proposed design methodology is validated using analytical results and field measurements.
The acquisition of accurate channel estimation is important for Orthogonal Frequency-Division Multiplexing (OFDM) system to reliably recover the transmitted data symbols. Decision-directed channel estimation (DDCE) has been utilized to improve the accuracy of conventional training-based channel estimation. However, this method can only provide limited improvement when the data decision feedback comprises...
One of the issues of power amplifier used in satellite communications is its nonlinearity. Digital predistortion is used in a linearizer to inverse this undesired effect to achieve higher efficiency to the amplifier. Xilinx provides a predistortion core to be implemented in FPGA devices. The core is used in a linearizer to test its functionality and performance. Simulation results indicate a gain...
Adaptive modulation exploits the channel conditions to improve spectral efficiency of the wireless communication system. Moreover, channel characteristics also depend upon Dop-pler shift, due to the motion of the mobile station. In this paper, a new technique of adaptive modulation is proposed which takes into account the effect of varying speed receiver. For the purpose, mapping between channel correlation...
Signals transmitted through a wireless channel undergo distortion due to multi-path and Doppler shift effects which can be recovered at the receiver through channel state information (CSI). The variation of wireless channels causes outdated CSI to be used for optimization techniques. Channel prediction allows the system to adapt modulation methods to an estimated future CSI. But this becomes complex...
This paper deals with the sub-carrier and bit allocations for multi-user orthogonal frequency division multiplexing (OFDM) systems by a modified particle swarm optimization (MPSO) method for a specific bit error rate (BER). The resources (subcarriers and the number of bits per symbol per subcarrier) are allocated according to the instantaneous channel state information (CSI) which is assumed to be...
It is shown analytical and simulation results on the performance of legacy IEEE 802.11a time synchronization algorithms when the synchronization preamble is transmitted by IEEE 802.11n devices with multiple transmitting antennas using cyclic shift diversity. It is concluded that an auto-correlation synchronization scheme allows the legacy compatibility over AWGN and fading channels.
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