Channel estimation and tracking for closed loop EO-STBC with differentially encoding feedback

Extended orthogonal space time block coding (EO-STBC) can achieve high transmit diversity over a multiple-input multiple-output (MIMO) channel. To do so, it requires channel state information on the transmitter side, which needs to be estimated and fed back from the receiver. Therefore, this paper explores an estimation and tracking scheme by means of a Kalman filter, which is integrated with EO-STBC detection and exploits the smooth evolution of the channel coefficients by applying differential feedback. For slow fading, we propose the inclusion of a drift vector in the Kalman model, which is motivated by a second order approximation of the underlying channel model and can be shown to offer advantages in terms of temporal smoothness when addressing channels whose coefficient trajectories evolve smoothly

Distributed closed-loop EO-STBC for a time-varying relay channel based on kalman tracking

This paper considers distributed closed-loop extended orthogonal space-time block coding (EO-STBC) for amplify-forward relaying over time-varying channels. In between periodically injected pilot symbols for training, the smooth variation of the fading channel coefficients is exploited by Kalman tracking. We show in this paper that the joint variation of both relay channels still motivates the use of a higher-order auto-regressive model for the a priori prediction step within a decision-feedback system, compared to a first-order standard Kalman model. Simulations results compare these two case and highlight the benefits of the proposed higher-order Kalman filter, which offer joint decoding and tracking

Comparative study for broadband direction of arrival estimation techniques

This paper reviews and compares three different linear algebraic signal subspace techniques for broadband direction of arrival estimation --- (i) the coherent signal subspace approach, (ii) eigenanalysis of the parameterised spatial correlation matrix, and (iii) a polynomial version of the multiple signal classification algorithm. Simulation results comparing the accuracy of these methods are presented

Extended orthogonal space-time block coded transmission with quantised differential feedback

Extended orthogonal space-time coding can use feedback of channel state information to increase the diversity gain of the transmission. This paper calculates the maximum attainable gain, and shows the effect that quantisation in the feedback channel has on the system performance. We demonstrate that for slow-fading channels, differential coding with a single feedback bit can achieve near-optimum performance and exceed the performance of non-differential feedback with higher word length. We also comment on combining differential encoding with channel estimation. Simulation results compare this approach to state-of-the-art systems with standard quantised and unquantised feedback

FrFT-based EO-STBC multicarrier system for transmission over doubly-dispersive channels

This paper focuses on the enhancement of extended orthogonal space-time block coding (EO-STBC) when transmitting over a doubly-dispersive channel. The frequency selective nature of the channel favours the combination with a multicarrier approach such as orthogonal frequency division multiplexing (OFDM). However, as Doppler spread increases, OFDM loses its orthogonality, resulting in severe inter-symbol (ISI) and inter-carrier interference (ICI). This is addressed firstly by the generalisation of OFDm to fractional Fourier transform (FrFT)-based multicarrier approaches, which can provide better resilience in the presence of Doppler spread. Secondly, in higher mobility scenarios, an equalisation scheme is employed, whose lower complexity in an FrFT-based multicarrier setting can further minimised by a reduction of the equaliser. Simulation results highlighting the potential performance improvements are presented