טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentCamus Noam
SubjectCoding of Wide Band Multi-Tone (OFDM)Version of BLAST
DepartmentDepartment of Electrical Engineering
Supervisor Mr. Yitzhak Kalet


Abstract

Multiple-Input-Multiple-Output (MIMO) antenna arrays, using spatial diversity, are used to achieve high spectral efficiency over Rayleigh fading wireless channels. The Vertical-BLAST (V-BLAST) architecture is an example of an MIMO system which achieves a bit rate that grows linearly with the number of antennas at transmitter. This architecture originally was designed to work over flat fading channel characteristics. 


The V-BLAST concept can also be used for frequency-selective fading channels. The use of Orthogonal Frequency Division Multiplexing (OFDM) enables the utilization of the V-BLAST technique even in this hostile environment. In the OFDM version of V-BLAST, each of the sub-channels can be viewed as flat narrowband channel and hence a V-BLAST receiver can be used for detecting the signal on each sub-channel.


In order to improve Quality of Service (QoS), i.e., the bit error rate (BER), adaptive loading of multi-tone techniques, used in SISO system, may also be applied to an OFDM-MIMO system. The system may be viewed as havingdegrees of freedom in choosing the transmission parameters (M equals number of transmit antennas and L, number of sub-carriers).

  

This research investigated the use of coding, with and without adaptive loading, in OFDM-MIMO systems. The code used was a turbo-code, combined with bit interleaving coded modulation (BICM). The addition of the BICM turbo-code improved the BER performance of the OFDM-MIMO system. The advantage of this system is that it is relatively simple to implement, because there is no iterative decoding between the MIMO antenna array and the outer turbo code.