Diversity for indoor radio communications

Abstract

The impulse response of the indoor radio propagation channel is measured and the Angle-Of-Arrival of the distinct paths is resolved with a 5 degree resolution. The resolved AOA is used to model the indoor environment for the purpose of (computer) simulating a digital cellular system with diversity. The modulator consists of a ~1 4 shifted QPSK communication system with a choice of 3 symbol rates: 145.8 Ksymbollsec, 1 Msymbollsec and 10 Msymbol lsec , over a bandwidth of 180 KHz , 1.2346 M H z and 12.346 MHz respectively, accommodating 18, 123 and 1234 voice channels respectively. It is shown that equalization and Maximum Likelihood Sequence Estimation can be avoided for both the 2. Modeling of the Indoor Channel The mathematical model chosen in this paper is due to Turin [l], which expresses the channel as a linear filter with the complex-valued impulse responsem h ( t ) = a,(t) &(t-z,(t)) e j e , ( t ) (1) k= 0 The complete model is characterized by a set of path amplitudes {ak ( t ) }, path arrival times {zk ( t ) }, and path phases { e k ( t ) } , assuming that the channel is contaminated with additive white Gaussian noise of two-sided power spectral density N0/2; j = a. 00 m 0 0 m 0 145.8 Ksymbollsec and the 1 Msymbollsec symbol rates mIn a Doppler environment, the phases { e k ( t ) b are without significantly affecting the performance of the receiver. It is also shown that for those two rates, channe1 encoding improves the speech quality only slightly, able speech quality.

Phase modeling of indoor radio propagation channels

“…Therefore (4) For mobile channel ( ) were generated according to a uniform distribution. The power spectra of simulated CW data generated using a wide-band channel simulator (reported in [23]) showed better agreement with theory [18], when compared with the spectra obtained using the random phase increment model (which is described in Section III-C). For the indoor channel, ( ) were estimated with a 5 resolution based on measurements and by using Fourier transform method (details are reported in [19]).…”

“…In two other simulation applications, the deterministic phase model has been used for the mobile and indoor channels [18], [19]. In both applications, it was assumed that the angle of arrival of the th multipath component with respect to the direction of motion of vehicle (portable) remains the same for small spatial separations.…”

“…In the previous application of the deterministic phase increment model [6], [7], [18], [19], it was assumed that each multipath component results by reflection from a single reflector. This seems to be an oversimplification of the principal reality of the channel, since in practice there may be many indirect paths between transmitter and receiver for each multipath component.…”

“…In [17], empirical probability density function (pdf) of signal phase for a land mobile satellite channel is reported to be approximately Gaussian. References [6], [7], [18], and [19] have explored some aspects of phase modeling for the indoor (mobile) radio channels. Some simplifying assumptions have been made in these investigations.…”

“…For example, in [6] and [7] it was assumed that over a length of 1 m in space, all multipath components with the same delay are caused by reflection from the same fixed scatterer. In [18] and [19], it was assumed that for small spatial separations the angle of arrival of each multipath component remains the same with respect to the direction of motion of vehicle (portable). To date, however, no empirically driven model for signal phase has been reported in the literature.…”