Obtaining transmitter side channel state information in MIMO FDD systems

Abstract

Channel state information (CSI) in systems with multiple antennas at both sides of the transmission link (multiple input multiple output, MIMO) is beneficial for many transmission schemes. However, a transceiver station can only estimate the channel transfer functions (CTFs) of the channels over which the received signals propagate which are different from the channels over which the transmitted signals will propagate in FDD systems. This paper shows a technique to obtain the CSI of the channels over which the transmitted signal will propagate based on the CSI of the channels over which the received signals propagate. By means of estimating the directions of arrival (DOAs) and times of arrival (TOAs), the shift of the previously estimated CSI to the CSI which cannot be estimated based on training signals can be calculated. The quality of the proposed algorithm depends on the quality of the parameter estimation. In scenarios with many scatterers the estimation of the DOAs and TOAs may not be precise enough or there may be paths with similar parameters which cannot be resolved. Thus, the proposed algorithm performs better in non-rich scattering environments.

Fundamental Limits of Dynamic Interference Management With Flexible Message Assignments and Separate Deep Fading Block Coding

“…In practice, the channel coefficients are approximately estimated at the receivers by transmitting known pilot signals, and then they are fed back to the transmitters (see e.g. [15], [16] and [17]).…”

Eliminating Channel Feedback in Next-Generation Cellular Networks

“…al [19] observe that the channels at two cellular FDD bands are correlated and hence postulate that one can infer downlink channels from uplink channels. Some papers [18,20,36,37] propose theoretical models that use large antenna arrays to infer channels on the downlink from those on the uplink. Their models are either based on long-term channel statistics and do not account for fast variations, or are based on the angle of arrival power profile (used in RF localization), which we show in §8 to yield poor performance in practice.…”