Influence of antenna configurations on performance of STBC in urban microcells

Introduction: The performance of coded data transmission over multiple-input multiple-output (MIMO) channels depends on the spatial characteristics of antennas and the propagation environment. Even so, it is typically evaluated using idealised channel models, that are unable to capture the combined effect of real-world radio channels and handset antennas on wireless link performance. The three main factors degrading performance of real-world MIMO communications systems are spatial correlation, channel coefficient power imbalance, and SNR degradation owing to unfavourable antenna orientation. In particular, field patterns of realistic mobile handset antennas are not omnidirectional, and the received signal typically arrives from few dominating directions, or angular clusters. As a consequence, directivity and orientation of the antenna patterns play an important role in estimating system performance. In this Letter, we evaluate the effect of antennas on the bit error ratio (BER) performance of a quasiorthogonal space-time block code (QSTBC) for four transmit antennas in a practical urban microcell scenario. Channel measurements: Measurements were conducted in downtown Helsinki at 2.1 GHz carrier frequency. The transmitter had two dualpolarised patch antennas (four tx channels) with 45 cm (three wavelengths) element separation. The receiver was a spherical antenna with 32 dual-polarised elements. The receiver and the transmitter heights were 1.5 and 13 m, respectively. The height of the surrounding buildings was 15‐25 m. This is a typical urban microcell scenario. The measurement system and the environment have been explained in