Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. We propose space-time block coded OFD...
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Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. We propose space-time block coded OFDM systems that use training symbols coded by STBC. We use two training symbols at the beginning of each of two OFDM frames that are simultaneously transmitted from two corresponding transmit antennas. Based on the orthogonality of space-time block codes, we perform channel estimation by using training symbols, and compare to EM-based channel estimation methods. From the simulation results, we observe that our space-time block coding technique offers a good approach to channel estimation and better signal quality than the EM-based method.
A new system enhancement method is proposed for the EIA/TIA-136 system offering both channel operational range extension and improved performance within the current operational range. The research presented investigat...
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A new system enhancement method is proposed for the EIA/TIA-136 system offering both channel operational range extension and improved performance within the current operational range. The research presented investigates the application of the narrowband adaptive multi-rate (NB-AMR) speech codec and the wideband AMR (WB-AMR) codec, both originally designed for the 200 kHz GSM channel, in the TDMA (TIA/EIA-136) 30 kHz system. In particular, we investigate adaptively allocating bits between NB/WB speech coding and error control within the limited channel bandwidth. Four modes out of seventeen have been carefully chosen for the new TDMA/AMR system. Switching between codec rates as channel conditions change produces range extension below a C/I of 15 dB while also improving performance in the existing operational range above 15 dB. Time slot formats are unchanged so that the method is completely compatible with existing 136 systems.
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