Vipul Desai

Estimating Statistical Eigen-Beamforming Gains Using Spatial Channel Correlation

Statistical eigen-beamforming (EBF) is a widely used multiple antenna transmission technique in which one antenna weight is used over potentially a large bandwidth (e.g., all subcarriers in OFDM). With N transmit antennas, the maximum gain for EBF at a receiver is 20 log N decibels over a single antenna transmission (assuming a power unfair comparison where each transmit antenna has a fixed power so the addition of new antennas brings a beamforming gain as well as a total transmit power increase). Based on statistical analysis of field data and observations, this gain is nearly achievable with line-of-sight transmissions. While useful for characterizing the benefits of EBF, the statistical analysis does not indicate the realizable gain for a particular location. This paper presents a relationship between the EBF gain, spatial correlation of the channel, and the number of transmit antennas. The conjectured gain is compared to the expected gain based on an analysis of field data. The results of this comparison show that the spatial correlation as defined in this paper can be used to predict the EBF gain accurately for a variety of antenna spacings and polarizations.

Block product code design with the aid of union bounds

Applying soft-input soft-output iterative decoding allows block product codes (BPCs) to exhibit error-correcting capability close to that of convolutional code-based turbo codes. However, finding the best BPC design for a given target code size can be difficult. This paper analyzes BPC performance using weight distribution and union bounds, which leads to a systematic BPC design procedure. The analysis is supported by simulations and examples.

An Experimental 8x8 System Used to Characterize the Spatial Channel at 3.5 GHz

Motorola Labs has developed a 20 MHz experimental wide-area mobile multi-antenna system with which to characterize the spatial channel. This system transmits OFDM waveforms from an eight-element array in each of three sectors at the base to an eight-element mobile receive array. In addition, two carrier frequencies are simultaneously transmitted and received, thus providing both FDD and TDD data. The received waveforms are post-processed to extract various channel characteristics such as time of arrivals (TOAs), Doppler frequencies (DFs), and directions of departure (DODs) at the base. This paper describes key components and parameters of this system and describes the spatial characteristics uncovered from the collected field data.