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Simulation plays an important role in the performance evaluation of MAC protocols. Building simulation models which are able to accurately model physical behaviour is fundamental to the outcome of such techniques. Through both qualitative and quantitative comparison of experimental trace data against simulation results obtained using delay, power, and hybrid capture models, this paper investigates...
This paper presents the study, design and simulation of a multi-flow radio frequency transceiver based on a direct sequence spread-spectrum with a 2,4 GHz carrier. First, the functional model of differential QPSK modulation for digital transmission, and the different parts making up spread spectrum function (spreader, despreader, tracking and synchronising devices) have been studied, implemented,...
In this paper, the design of optimal receive filter banks for frequency division multiple access (FDMA) over frequency selective channels is investigated. A new design strategy based on the principle of memory truncation, rather than equalization, is presented. Through the receive filters, each subchannel is truncated to a pre-defined length, and the final data recovery is carried out via low complexity...
Soft-combining algorithms use retransmissions of the same codeword to improve the reliability of communication over very noisy channels. In this paper, soft-outputs from a maximum a posteriori (MAP) decoder are used as a priori information for decoding of retransmitted codewords. As all received words may not need the same number of retransmissions to achieve satisfactory reliability, a stop criterion...
The most important optical devices which can be used for controlling microwave circuits will be presented in the paper. The performance and the parameters of the devices such as semiconductor microwave optoelectronic switches, photodiodes and phototransistors were described. The influence of the optical illumination on their microwave parameters will be described in details, including the our own...
This paper is concerned with the issue of optimum detection of known signal in nonwhite noise and/or narrow-band interferences. The detection is carried out in three steps. First, some function related to the power spectrum of interfering process I(z) is estimated via adaptation. Second, the signal + interference is withened due to I(z). Third, the replica of signal is filtered via I(z) to match it...
The paper is focussed on the development of the method of analytical regularization (MAR) in electromagnetic wave scattering and absorption by imperfect scatterers shaped as thin screens.
In order to obtain precise complex permittivity of the dielectric materials obtained from the perturbation method a correction curve is made using the electromagnetic field simulator which applies transmission line modeling (TLM) method. In this experiment, generated microwave power with the frequency of 2.45 GHz is applied to heat dielectric material while measuring temperature dependence of complex...
The statistics of the error process generated by a discrete super channel formed by the concatenation of a constrained encoder, a non-renewal finite state channel (FSC), and a constrained decoder is studied in this paper. First, recursions are developed for the error weight distribution. This statistics is relevant to the design of coding schemes and interleaving in concatenated. systems. We also...
Linear prediction is the cornerstone of most modern speech compression algorithms. This paper proposes modifying the calculation of the linear predictor coefficients to incorporate a weighting function based on the simultaneous masking property of the ear. The resultant prediction filter better models the perceptual characteristics of the source and results in the removal of more perceptually important...
Envelope constrained filter design is concerned with the time domain synthesis of a filter whose response to a specified input signal stays within prescribed upper and lowe bounds and in addition has minimal noise enhancement. In many practical applications, a "soft" approach, such as least mean square, is not the most suitable and it becomes necessary to use "hard" constraints...
This paper deals with a new method to design polyphase spreading sequences for DS CDMA wireless applications. The method is based on weighting symbols of the orthogonal Walsh sequences by the complex factors being symbols of baseband chirp sequences. The resulting sequences possess good aperiodic correlation properties, while maintaining the orthogonality. Because of the parametric design, the sequences...
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