Work reported in this paper contributes to the characterisation of 4.9 GHz radio channels in a scenario in which emergency vehicles are parked outside a building and operate as a communications centre for communications with rescue crews and equipment inside the building. Transmission loss, rms delay spreads, equivalent CW envelope fading characteristics, and frequency correlation characteristics are reported for the measured channels. Achievable IEEE 802.16 performance on the measured channels is also predicted, using simulations based on time series of 50 Mchps PN channel soundings.

A reduced-complexity time-domain equalization scheme for wideband turbo-multiple-input multiple-output (turbo-MIMO) systems is presented. This scheme, called iterative trellis search equalization, is based on a modified version of the M-Bahl-Cocke-Jelinek-Raviv (M-BCJR) algorithm, applied to a suitably chosen trellis representation of the wideband MIMO channel process. Exploiting the properties of quadrature amplitude modulation (QAM) signal constellations with block-partitionable labels, this modified M-BCJR algorithm has complexity per bit that is independent of the constellation size, and polynomial in the number of transmit antennas and channel memory. Results from computer simulations show that the new scheme successfully mitigates intersymbol interference even if only a very small fraction of trellis state transitions is considered. It is also demonstrated that asynchronous transmission of the spatially multiplexed symbol streams can result in considerable performance improvement compared to synchronous MIMO systems.

A key problem in high-resolution multidimensional parameter estimation via unitary ESPRIT is to jointly solve a set of invariance equations by means of least-squares minimization. It has been shown previously that existing least-squares techniques fail when applied to the category of cross arrays, which consist of perpendicular uniform linear arrays crossing at the center of the array. Cross array geometries are of special interest because they provide a larger aperture and, hence, better resolution for a given number of array elements than other multidimensional uniform array geometries. This letter proposes an improved structured least-squares method that enables successful application of unitary ESPRIT to cross arrays. Results of simulated direction-of-arrival estimation experiments using a three-dimensional cross array indicate that considerable performance improvements can be achieved if the new method is used.

This paper presents a reduced-complexity soft-input soft-output detection scheme, called iterative tree search detection, for multiple-input multiple-output wireless communication systems employing turbo processing at the receiver. In this scheme, a reduced search space is selected with the aid of the M-algorithm, and QAM signal constellations with block partitionable labels are used in order to make the detection complexity per bit almost independent of the modulation order, as well as asymptotically linear in the number of transmit antennas. Results from computer simulations are presented which demonstrate the capability of the scheme to approach optimal performance at considerably reduced complexity.

This work presents a reduced-complexity soft-input soft-output detection scheme for wideband space-time bit-interleaved coded modulation (ST-BICM) MIMO systems. This scheme, which is referred to as iterative trellis search detection, is based in part on a reduced-complexity variant of the BCJR algorithm. It also uses signal sets with block partitioning labeling, called multilevel mapping constellations, in order to achieve further complexity reduction for higher-order QAM modulation formats. Results from computer simulations of an iterative ("turbo") MlMO receiver employing the new scheme have shown that it successfully eliminates the error floor that occurs if inter-symbol interference is not mitigated. It is also shown that the optimum choice of the number of fingers employed by the detector is not only dependent on the channel characteristics, but also by the fraction of states considered in the trellis search.

This paper describes a procedure for combined time delay/angle of arrival (AOA) measurements, which are needed for the development of improved microcell propagation models. The procedure requires a spread-spectrum channel sounder equipped with a receive antenna which can be moved along a circle. Using angular superresolution algorithms such as UCA-MUSIC and UCA-ESPRIT, accurate azimuth/elevation AOA information of individual multipath contributions arriving within subsequent time delay intervals can be extracted from the measured data. Simulations indicate that good results can be obtained (RMS AOA errors smaller than one degree), except for the case of highly correlated ground-reflected signals at grazing incidence. Measurement results obtained in a simple multipath environment are presented.