Biljana Badic

Extended Alamouti codes in correlated channels using partial feedback

In this paper we present a family of quasi-orthogonal space-time codes for correlated MIMO (multi-input/multi-output) channels using four and eight transmit antennas when only partial channel state information is sent back to the transmitter. Transmit diversity is improved up to nearly the optimum diversity value. This high diversity can be exploited with zero forcing receivers as well as with maximum-likelihood receivers.

Quasi-orthogonal space-time block codes on measured MIMO channels

In this paper we study the performance of quasi-orthogonal space-time block codes (QSTBCs) on measured MIMO channels using four transmit and four receive antennas. We use QSTBCs with and without partial channel state information at the transmitter At the receiver we compare a zeroforcing receiver and a maximum likelihood receiver We demonstrate that applying our simple feedback scheme, the QSTBCs are robust against different MIMO channel realizations and they perform very well even in case of spatial channel correlations.

Performance of various data transmission methods on measured MIMO channels

We discuss the performance of several data transmission schemes over measured MIMO-channels using four transmit antennas. We analyze uncoded and prefiltered data transmission with schemes using simple extended Alamouti codes, with and without partial feedback. Our simulations are based on channel measurements and measurement based channel models. It is shown that the extended Alamouti scheme using partial feedback is extremely robust against channel correlation and thus outperforms other transmission schemes.

Comparison of nonorthogonal space-time block codes using partial feedback in correlated channels

We analyze and compare transmission schemes that apply nonorthogonal space-time block codes in uncorrelated and correlated MIMO channels using four transmit antennas and a zero-forcing receiver. The ABBA code and a slightly different code, the so-called extended Alamouti code (EAC) are compared. For both codes, partial channel state information is sent back from the receiver to the transmitter quantized to one bit per code block. In this way, we improve the diversity of signal transmission and decorrelate the system using the ABBA code as well as the EAC.

Assessment of H.264 coded panorama sequences

The newest video coding standard, H.264, allows video streaming to be provided for low bit and frame rates in acceptable quality in 3G wireless networks due to significant video compression gain while preserving perceptual quality. This is specially suitable for video applications in 3G wireless networks. One of the most popular content types in 3G streaming is panorama (weather cams, traffic jams, city guides). The results for subjective perceptual quality evaluation of panorama sequences differ from other sequence types significantly. The differences of the panorama type are investigated and a prediction of a perceptual metric for panorama sequences based on different objective parameters is introduced.

Optimization of coded MIMO-transmission with antenna selection

The performance of a wireless system can be significantly improved by using multiple antenna elements at the transmitter and/or the receiver side. The major problems of such systems are high cost and complexity due to more than one radio frequency (RF) chains at both end links. An effective technique to reduce this overhead is to allow the transmitter and/or the receiver to select an optimum antenna subset according to some optimization criterion. In this paper, we analyze coded multiple-input/multiple output (MIMO) systems with antenna selection at the transmitter side. We propose an optimum selection criterion to minimize the bit error ratio (BER) when a channel adapted quasi-orthogonal space time code (QSTBC) and a low complexity zero forcing receiver (ZF) are used. We show that antenna selection is a promising low-cost technique that provides additional diversity and coding gain and therefore improves the system performance even if the simple linear receiver is used.

Impact of spatial channel correlation on super quasi-orthogonal space-time trellis codes

The error performance of a new family of super quasi-orthogonal space-time trellis codes (S-QSTTCs) for four transmit antennas on correlated MIMO channels is investigated. Two slightly different designs of S-QSTTCs, namely S-QSTTCs obtained by concatenating the extended Alamouti space-time code (EAC) with a simple outer trellis code and the concatenation of the ABBA code with a simple outer trellis code are compared in detail. It is shown that EA-type and ABBA-type S-QSTTCs perform quite different on spatially correlated MIMO channels. However, a unique labelling of the trellis diagram adapted to these two super quasi-orthogonal constituent code types, results in a very similar error performance even in spatially correlated channels.