9,263 research outputs found
Efficient Weight Vector Representation for Closed-Loop Transmit Diversity
For a closed-loop transmit (Tx) diversity, the Tx
weights are calculated at a receiver, and fed back to a transmitter.
As the number of Tx antennas increases, the potential gain of
closed-loop Tx diversity may be significant. However, the amount
of feedback information, which is the number of Tx weights
that should be fed back, linearly increases, and the performance
improvement of a closed-loop Tx diversity system may not be
as significant as expected due to delay in the feedback process.
Thus, an efficient Tx weight representation, which can reduce the
amount of feedback information, is needed. In this letter, a Tx
weight vector representation is presented, and its performance is
analyzed. Analysis shows that this weight vector representation,
referred to as basis selection, significantly reduces the amount of
feedback information with little performance degradation
Space-time coding techniques with bit-interleaved coded modulations for MIMO block-fading channels
The space-time bit-interleaved coded modulation (ST-BICM) is an efficient
technique to obtain high diversity and coding gain on a block-fading MIMO
channel. Its maximum-likelihood (ML) performance is computed under ideal
interleaving conditions, which enables a global optimization taking into
account channel coding. Thanks to a diversity upperbound derived from the
Singleton bound, an appropriate choice of the time dimension of the space-time
coding is possible, which maximizes diversity while minimizing complexity.
Based on the analysis, an optimized interleaver and a set of linear precoders,
called dispersive nucleo algebraic (DNA) precoders are proposed. The proposed
precoders have good performance with respect to the state of the art and exist
for any number of transmit antennas and any time dimension. With turbo codes,
they exhibit a frame error rate which does not increase with frame length.Comment: Submitted to IEEE Trans. on Information Theory, Submission: January
2006 - First review: June 200
Space time transceiver design over multipath fading channels
Imperial Users onl
MIMO-aided near-capacity turbo transceivers: taxonomy and performance versus complexity
In this treatise, we firstly review the associated Multiple-Input Multiple-Output (MIMO) system theory and review the family of hard-decision and soft-decision based detection algorithms in the context of Spatial Division Multiplexing (SDM) systems. Our discussions culminate in the introduction of a range of powerful novel MIMO detectors, such as for example Markov Chain assisted Minimum Bit-Error Rate (MC-MBER) detectors, which are capable of reliably operating in the challenging high-importance rank-deficient scenarios, where there are more transmitters than receivers and hence the resultant channel-matrix becomes non-invertible. As a result, conventional detectors would exhibit a high residual error floor. We then invoke the Soft-Input Soft-Output (SISO) MIMO detectors for creating turbo-detected two- or three-stage concatenated SDM schemes and investigate their attainable performance in the light of their computational complexity. Finally, we introduce the powerful design tools of EXtrinsic Information Transfer (EXIT)-charts and characterize the achievable performance of the diverse near- capacity SISO detectors with the aid of EXIT charts
Digital signal processing techniques for peak-to-average power ratio mitigation in MIMO–OFDM systems
The focus of this thesis is to mitigate the very large peak-to-average
transmit power ratios (PAPRs) inherent to conventional orthogonal
frequency division multiplexing (OFDM) systems, particularly in the
context of transmission over multi-input multi-output (MIMO) wireless
broadband channels. This problem is important as a large PAPR
generally needs an expensive radio frequency (RF) power amplifier at
the transmitter due to the requirement for linear operation over a wide
amplitude range and such a cost would be compounded when multiple
transmit antennas are used. Advanced signal processing techniques
which can reduce PAPR whilst retain the integrity of digital transmission
therefore have considerable potential for application in emergent
MIMO–OFDM wireless systems and form the technical contributions
of this study. [Continues.
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