טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMeiri Dror
SubjectWide Band Multitone Version of BLAST
DepartmentDepartment of Electrical Engineering
Supervisor Mr. Yitzhak Kalet


Abstract

The V-BLAST (Vertical Bell Laboratories Layered Space-Time) architecture realizes very high spectral efficiencies over wireless indoor channel in an independent flat fading Rayleigh scattering environment. In this work we develop and analyze a system that uses the V-BLAST architecture in a frequency selective fading environment. By using multicarrier modulation a V-BLAST receiver can be used for decoding the signal arriving in each sub-channel. Motivated by water-pouring solutions and multitone techniques commonly used in SISO systems, our research aims to take advantage of these methods and to improve the performance of the V-BLAST system. We analyze the channel capacity achieved by the water-pouring solution for the MIMO system in frequency selective and non-selective fading channels. In a similar manner to the multitone technique, we derive the Multi-Antenna (MA) and the Multi-Tone-Multi-Antenna (MTMA) techniques for achieving maximum bit rate in MIMO frequency non-selective and frequency selective channels respectively that use V-BLAST architecture. Finally we develop an optimal power and bit loading algorithm which attempts to optimize the system performance by enhancing either the data rate or the power margin, while keeping the other constant. In both methods, a power constraint exists. Simulation results of the proposed system and algorithm show that adaptive loading enables efficient and reliable communication in low SNRs. It also shows significant improvement as compared to a basic OFDM V-BLAST system, which has no a-priori knowledge of the channel characteristics. For example, a system with four transmitters and receivers that uses a 256 multitone symbol doubles the nominal bit rate at SNR of 33dB (for maximum bit rate) and achieves a margin gain of 19dB at BER of (for maximum margin).