In this paper, we have investigated the effects of self-fields on gain in a helical wiggler free electron laser with axial magnetic field and ion-channel guiding. The self-electric and self-magnetic fields of a relativistic electron beam passing through a helical wiggler are analyzed. The electron trajectories and the small signal gain are derived. Numerical investigation is shown that for grou...

Communication in the presence of a priori known interference at the encoder has gained great interest because of its many practical applications. In this paper, additive exponential noise channel with additive exponential interference (AENC-AEI) known non-causally at the transmitter is introduced as a new variant of such communication scenarios‎. First, it is shown that the additive Gaussian ch...

In this paper a new adjacent channel interference (ACI) cancellation scheme for multi-channel signal reception with low-IF receivers is investigated through the experiment. In the low-IF receivers, the signal in the mirror frequency causes interference to the desired signal. In the proposed analog-digital signal processing scheme, channel selection is made by analog complex band pass filter and...

Recently, blind multi-user detection has become an important topic in code division multiple access (CDMA) systems. Direct-Sequence Spread Spectrum (DSSS) signals are well-known due to their low probability of detection, and secure communication. In this article, the problem of blind multi-user detection is studied in variable processing gain direct-sequence code division multiple access (VPG D...

The performance of video transmission over wireless channels is limited by the channel noise. Thus many error resilience tools have been incorporated into the MPEG-4 video compression method. In addition to these tools, the unequal error protection (UEP) technique has been proposed to protect the different parts in an MPEG-4 video packet with different channel coding rates based on the rate...

Audio signal information with high quality would help the television audience to increase the perception of the information displayed. Transmission channel capacity will become limited, while the need of channel communication is increased. The research aim is coding the audio signal on the low bit rate for saving the channel communication usage for digital television broadcasting. The research ...

Ultra-wideband (UWB) radio is a promising technology for low-cost, high-rate communications at short ranges. However, high bandwidth and low power of the UWB signals impose some difficult challenges in signal processing and implementation of the receiver. Acquisition of the signal timing is the first task to be performed in a coherent receiver. The high bandwidth of UWB signals demand for fine ...