This paper presents a measurement system for indoor characterization of UWB channels. The presented method uses a scalar network analyzer (SNA) or a spectrum analyzer (SA) with tracking generator, connected to two antennas: a receiving and a transmitting one. This setup, which obtains only the magnitude data of the frequency response, makes the method less expensive when compared with other setups presented in the literature. From the magnitude data of the frequency response, a processing algorithm obtains the phase data of the frequency response making it possible to calculate the channel power delay profile. The tests for validation of the method are detailed herein.
measurements; indoor radio propagation; spectrum analyzerI.
Nowadays, low reuse factors are used in cellular systems because of high traffic demand, despite it produces high co-cell interference (CCI) levels. Consequently, soft-frequency-reuse (SFR) and sectorization are used to improve the spectral efficiency and to mitigate CCI. In addition, diversity techniques are necessary for a good system performance. Motivated by this scenario, for the uplink of orthogonal-frequency-division multiple access (OFDMA) systems, the bit error rate (BER) and the cellular spectral efficiency using multilevel-quadrature-amplitude-modulation (M-QAM) and maximalratio-combining (MRC) in Rician fading channels are analyzed, where diversity branches have different Rician K-factors (unbalanced diversity). SFR is used assuming non-ideal sectorized cells due to the irregular radiation pattern of base station antennas. An exact integral-form expression and a closed-form upper-bound to evaluate the BER are obtained. In addition, an algorithm, and an expression to calculate the cellular spectral efficiency are presented considering that a target BER must be guaranteed for all users in the cell. From the analysis, it is determined that the BER can be reduced and the spectral efficiency can be improved if some system operating parameters are selected in an adequate manner. Thus, it was noticed that the number of diversity branches, the sum of the K factors of these branches, and the antenna type, are decisive to guarantee the target BER and to maximize the cellular spectral efficiency.
Linear precoding can be applied to multicarrier systems to minimize the effect that a deep fade in one of the subchannels can have on the overall bit error ratio when the transmitter does not have channel state information (CSI). But for filterbank multicarrier (FBMC) systems, which were proposed to overcome the poor spectral characteristics and bandwidth/energy waste caused by the use of the cyclic prefix, there are very few proposals of precoded systems in the literature. This paper proposes a precoded SISO (single-input single-output) filterbank multicarrier system with zero-forcing (ZF) and minimum mean square error (MMSE) equalization. Results show that in a well-equalized system, the Monte Carlo simulation results match the ones provided by the BER approximation presented in this paper. However, in systems with residual interference, the Monte Carlo results drift from the approximation at high SNR values, with the error performance from precoded FBMC systems being more affected by the unequalized interference.
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