By:

Ahmad El-Banna Basem El-Halawany

E-JUST- ECE- ADDC- F11 1

� Intro.

� V-BLAST theory

� Matlab Code

� Simulation Results

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� MIMO system has proved to achieve high capacity compared to SISO, MISO, and SIMO systems.

� Many algorithms have been proposed to reduce the interference in the received signals caused by other transmitters in the system.

� Also, they aim achieve closer values to the Shannon capacity limit.

� D-BLAST (Diagonal Bell Labs Layered Space Time) and V-BLAST (Vertical Bell Labs Layered Space Time) are such schemes used for detection and suppression of the interference in MIMO systems.

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� D-Blast, which was proposed by Gerard J.

Foschini, applies a diagonal space time coding

on the data.

� By applying this algorithm, it could achieve 90%

of Shannon capacity rates as well as high

spectral efficiency.

� However, due to complexity of implementing

the algorithm, V-Blast algorithm was proposed.

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� Objective: How can we get a good tradeoff between performance and complexity for MIMO signal detection

� It divides the data stream into substreams and transmits them through multiple transmitters at the same time and frequency.

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� V-Blast is a single user scheme which has multiple transmitters.

� This results in receiving the data at the receiver

at the same time and frequency. � By implementing VBLAST algorithm, the

diversity gain is increased and the bit error rate (BER) performance is improved.

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� System model of the output signal is:

y= Hx + n

� Detection process consists of three operations: 1. interference suppression

(nulling)

2. interference cancellation (subtraction)

3. Optimal ordering.

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� There are two disadvantages in V-BLAST

algorithms. :

1. The first one is that the error propagates

during symbol detection.

2. The other one is that the number of receive

antennas must be greater than or equal to

the number of transmit antennas to satisfy

the interference nulling process.

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� Since the amount of interference cancelled in each step becomes smaller, a new algorithm was proposed .

� C is a constant. � When the value of C becomes 1,

the algorithm becomes the same as the original V-BLAST detection.

� When C becomes 0, on the other hand, the algorithm becomes minimum mean square error (MMSE) and zero forcing (ZF) detection

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Matlab Code :

Notes: 1. 2 x 2 MIMO system with BPSK modulation is used.

2. The algorithm of V-BLAST is implemented.

3. After that, weight vector is produced using

MMSE,ZF,and ML detectors.

4. Finally, the BER performance is plotted using :

� SNR from 1 :45 dB

� Block size N=10^6

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� Ali Abdullah Al-Saihati , “BER Performance of VBLAST Detection

Schemes over MIMO Channels “, King Fahd University of Petroleum &

Minerals.

� Nirmalend. B and Rabindranath B. “Capacity and V-BLAST Techniques

for MIMO Wireless Channel”. Journal of Theoretical and Applied

Information Technology, 2005- 2010.

� P. W. Wolniansky. G. J. Foschini. G. D. Golden and R. A. Valenzuela “V-

BLAST: An Architecture for Realizing Very High Data Rates Over the

Rich-Scattering Wireless Channel”. Bell Laboratories.

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