3:30, SPCOM-L12.1
LINEAR RF POWER AMPLIFIER DESIGN FOR TDMA SIGNALS: A SPECTRUM ANALYSIS APPROACH
C. LIU, H. XIAO, Q. WU, F. LI
One of the critical and costly components in digital cellular communication systems is the RF power amplifier. Theoretically, one of the main concerns in an RF power amplifier design is the nonlinear effect of the amplifier. Quantitatively, so far, no clear elationship or expression currently exists between the out-of-band emission level and the nonlinearity description related to the third-order intercept point (IP3). Further, in experiments and analysis, it was discovered that, in some situations, using IP3 only is not accurate enough to describe the spectrum regrowth, especially when the fifth-order intercept point (IP5) is relatively high compared to the third-order intermodulation. In this article, we analyze the nonlinear effect of an RF power amplifier in TDMA (IS-54 Standard) system, give an expression of the estimation of the out-of-band emission levels for a TDMA power spectrum in terms of the IP3 and the IP5, as well as the power level of the signal. This result will be useful in the design of RF power amplifier for a TDMA wireless system.

3:50, SPCOM-L12.2
COMPENSATION OF AMPLIFIER NONLINEARITIES ON WAVELET PACKET DIVISION MULTIPLEXING
K. TO, P. CHING, K. WONG
Wavelet packet division multiplexing (WPDM) is a high-capacity, flexible and robust orthogonal multiplexing scheme in which the message signals are waveform coded onto wavelet packet basis functions for transmission. However, WPDM suffers from severe performance degradation in the presence of high-power amplifier (HPA) nonlinearities. In this paper, data predistortion using the pth-order Volterra inverse is proposed to combat the amplifier nonlinearities in a WPDM system. A 5th-order Volterra inverse with truncated memory length is designed based on the Volterra series channel model. Computer simulations are presented to demonstrate the capability of the proposed technique in compensating amplifier nonlinearities even under system parameter discrepancy. Guidelines are also proposed for designing wavelet filter which leads to better predistortion with the truncated Volterra inverse.

4:10, SPCOM-L12.3
ANALYZING SPECTRAL REGROWTH OF QPSK AND OQPSK SIGNALS
R. RAICH, G. ZHOU
In this paper, a comparison is made between the spectral regrowth of quadrature phase shift keyed (QPSK) and offset QPSK (OQPSK) signals as they go through non-linear amplifications. Contrary to existing approaches that assume the power amplifier input is Gaussian, our analysis is carried out without the Gaussian assumption, by using higher-order statistics. We show that it is possible to assess quantitatively, whether and how much OQPSK is beneficial in reducing spectral regrowth. Simple closed form formulas are obtained when the pulse shape filter is time-limited. A particular measure of spectral broadening is also provided.

4:30, SPCOM-L12.4
OPTIMISATION OF THE INTERFERENCE COST GENERATED BY THE RANDOM ACCESS CHANNEL OF THE UMTS FDD SYSTEM
M. SIALA, H. BOUJEMAA
In this paper, we investigate the optimisation of the Random Access CHannel (RACH) energy of the UMTS FDD system in terms of generated interference. Conditional on open loop measurements, we search the best initial energy of the RACH in order to reduce the multiple access interference while keeping a reasonable mean access time.

4:50, SPCOM-L12.5
DESIGN OF A TOTALLY PASSIVE WIRELESS DIGITAL MICRO-TRANSCEIVER FOR PICOCELLULAR SYSTEMS
A. SCAGLIONE, J. ROHWER
We consider the problem of designing a wireless communication system where one of the two ends in the link is totally passive and can use simplified analog technology, such as filters and non-linearity. This study builds the background and proposes possible solutions for the design of future ultra-miniaturize wireless transceivers operating on ranges of picocells and may serve in a wide range of civil and military applications.

5:10, SPCOM-L12.6
USE OF KALMAN FILTERING IN DATA DETECTION IN OPTICAL COMMUNICATION SYSTEMS WITH MULTIPLICATIVE NOISE
H. BURRIS, A. REED, N. NAMAZI, M. VILCHECK, M. FERRARO
In optical communication systems with detectors that have a multiplicative noise component, bit error rates (BER) can be improved by orders of magnitude by using threshold detection based on a likelihood ratio test (LRT) instead of a matched filter. LRT detection of this type has been derived previously for optically encoded Manchester data; however, the threshold development required that the bit means and variances were known. In free-space optical communication systems, atmospheric turbulence causes large variations in optical transmission and subsequently in the bit level means and variances. A Kalman filter based method has been developed which uses an adaptive LRT threshold for detection while tracking the bit means and variances. The development of the Kalman filter will be discussed and the results of simulations comparing performance of the adaptive Kalman filter algorithm to a matched filter and a non-adaptive LRT detection scheme will be presented.