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This paper considers the suitability of a range of multi-input-multi-output (MIMO) orthogonal frequency-division multiplexing architectures for use in urban hotspots. A ray-tracing propagation model is used to produce realistic MIMO channel data. This information is used to determine the expected throughput and area coverage for various physical (PHY) layer schemes. Site-specific throughput predictions are generated in a city-center environment. Link adaptation (LA) is shown to play a key role in the choice of space-time algorithm, the use of adaptive modulation and coding, and the number of antennas employed at both ends of the radio link. No single PHY layer scheme is suitable to cover the entire coverage area. Results demonstrate the need for MIMO LA under a wide range of channel conditions. For the area under test, 2% of covered locations selected a spatial multiplexing (SM) scheme, 50% selected a space-time block coding (STBC) scheme, and 48% selected a hybrid SM/STBC scheme. With suitable power control and LA, for the scenario under consideration, high peak capacities and good geographic coverage were achieved. [ABSTRACT FROM AUTHOR]

In this paper, an advanced site-specific image-based ray-tracing model is developed that enables multielement outdoor propagation analysis to be performed in dense urban environments. Sophisticated optimization techniques, such as preprocessing the environment database using object partitioning, visibility determination, diffraction image tree precalculation, and parallel processing are used to improve run-time efficiency. Wideband and multiple-input-multiple-output (MIMO) site-specific predictions (including derived parameters such as theoretic capacity and eigenstructure) are compared with outdoor site-specific measurements at 1.92 GHz. Results show strong levels of agreement, with a mean path-loss error of 2 dB and a mean normalized-capacity error of 1.5 b/s/Hz. Physical-layer packet-error rate (PER) results are generated and compared for a range of MIMO-orthogonal frequency-division-multiplexing (OFDM) schemes using measured and predicted multielement channel data. A mean EbNo error (compared to PER results from measured channel data) of 4 and 1 dB is observed for spatial-multiplexing and space- time block-code schemes, respectively. Results indicate that the ray-tracing model successfully predicts key channel parameters (including MIMO channel structure) and thus enable the accurate prediction of PER and service coverage for emerging MIMO-OFDM networks such as 802.lln and 802.16e. [ABSTRACT FROM AUTHOR]