Abstract
Full-rate is very important in any data transmission coding. For transmitting data at low bit rate than full-rate code, higher modulation scheme is required. But it is impossible to design full rate orthogonal designs with complex constellation for more than two transmit antennas. Only Alamouti code provides full-rate for two transmit antennas. In this paper, Bit Error Rate (BER) is calculated for Quasi-Orthogonal Space-time Block Coding (QOSTBC). Here we work with Rayleigh fading channel. We consider the codes which decodes pairs of symbols instead of simple separate decoding like Orthogonal Space-Time Block Coding. In Quasi-Orthogonal Space-time Block Code full-rate is achieved but full-diversity is sacrificed. Diversity is the most important techniques for providing reliable communication over fading channels. One of the diversity techniques that uses multiple transmit and/or receive antennas is space diversity. Multiple antenna technique provides a space diversity to struggle with the fading without necessarily sacrificing bandwidth resources, so the excellent solutions of removing the fading of the channel for broadband wireless communications is using space diversity. Then, with the constellation rotation of the symbol, rotated version of Quasi-Orthogonal Space-Time Block Code is generated. It provides full diversity. We simulate BER for QOSTBC, rotated QOSTBC, orthogonal STBC and for uncoded system. The simulation result shows that QOSTBC and rotated QOSTBC perform better than other systems. It shows that QOSTBC provides a full transmission rate but that rotated QOSTBC provides the full rate with the full diversity.
Highlights
The transmission path in the wireless communication is air or free space for transmitting the electromagnetic signal to the destination
We review the space-time block codes which provide maximum possible diversity for multiple transmit antennas in wireless communications
For complex signal constellations full-rate OSTBCs exist only for two transmit antenna and this code is provided by Alamouti
Summary
The transmission path in the wireless communication is air or free space for transmitting the electromagnetic signal to the destination. The transmitted signal may reach the receiver directly (Line-of-Sight) or through multiple reflections on local objects. The Rayleigh distribution [1] is commonly used to describe the statistical time varying nature of the received fading signal. The fading can be removed by using diversity and space diversity [2] is one of the diversity techniques that use multiple transmit and/or receive antennas. The possibility of deep fading over all paths’ signals is greatly reduced by space diversity creating many independent propagation paths from transmitter to receiver. Data transmission in an ST system is carried out in two dimensions, the space dimension and the time dimension, as the acronym ST suggests. Rotated QOSTBC [3] offers full-diversity. We simulate the BER and make a comparison for QOSTBC and rotated QOSTBC with OSTBC
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