Partner und Internationale Organisationen
(Englisch)
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AT, BE, BG, HR, CY, CZ, DK, FI, FR, DE, EL, HU, IE, IT, NL, NO, PL, PT, CS, SK, SI, ES, SE, CH, UK
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Abstract
(Englisch)
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The increase of the spectral efficiency in short range radio is one of the prerequisites to achieve the specified transmission rates in broadband wireless systems. Waterfilling is known to maximize the channel capacity. However, real-world systems employ certain coding schemes and adpative schemes have to be found which minimize the bit-error rate rather than maximize the channel capacity. The project has addressed adaptive modulation (AM) and coding (AC) schemes to be used in systems with orthogonal frequency-division multiplexing (OFDM) in combination with bit-interleaved coded modulation (BICM). These properties are part of the IEEE 802.11a and the European HIPERLAN/2 wireless local area network (WLAN) standards. Furthermore, impairments such as non-linear amplifiers or imperfect frequency synchronization have been considered to quantify the loss to be expected in real-world systems.The AM and AC schemes designed in the physical layer (PHY) for single-input single-output (SISO) and multiple-input single-output (MISO) systems in the first part of the project have been extended to the case of multiple-input multiple-output (MIMO) transceivers. As before, the required channel state information (CSI) for adaptation at the transmitter side has to be acquired either by feedback in the return link or by exploiting the channel reciprocity in a time-division duplex system. It turns out that the achievable gain in terms of signal-to-noise improvement decreases for an increasing number of antennas in the MIMO system. The achieved results have been used for an adaptive and scalable physical layer in a wireless personal area network (WPAN) developed in the OFDM cluster with time-division multiple access (TDMA) of the integrated project “My personal Adaptive Global NET” (MAGNET) of the European Union in the 6th framework programme. It is furthermore foreseen to extend the adaptive schemes to the case of multicarrier transmission with frequency-domain spectrum spreading in a follow-up project. The adaptive schemes have been combined with scheduling schemes in the medium access control layer of WPANs. A number of papers have been published on both the PHY and the PHY-MAC approaches. A PhD thesis has been finalized and further papers are foreseen or accepted for publication. Real-world impairments have been considered for both SISO and MIMO systems. The bit-error rate has been calculated analytically using an approximately Gaussian distributed decision variable based on the central limit theorem. Another PhD thesis has been finalized addressing these impairments in OFDM systems
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