Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Zero Forcing


Reliable of High Data Rate Using Spatial Multiplexing and Convolution Code

Eman A. Farhan; Raad H; Mahmood F. Mosleh

Engineering and Technology Journal, 2015, Volume 33, Issue 5, Pages 1189-1201

Spatial Multiplexing (SM) can be achieved higher transmission rate without allocating higher bandwidth or increasing transmit power, so it is wildly used recently to serve the extremely demand of mobile communications. But multipath fading is major bottleneck in increasing the data rate and reliability of transfer of information over wireless channel. SM suffers from significant degradation in term of Bit Error Rate (BER) in such environments. In this research it has been tested a SM system with three types of detection. The first results show the Maximum Likelihood (ML) is the better one, but the complexity is increased dramatically with increasing of data rate or the level modulation order in addition of delay time. On the other hand, Zero Forcing (ZF) is very simple related to ML and it suitable for real time communications, but the problem is the Bit Error Rate (BER) is very high related to the performance of ML. So that this research proposed to adopt ZF decoder, and to support its performance, Convolutional Codes (CC) is added to this system to overcome this problem. The results show the proposed scheme gives a gain of about 10 dB of Signal to Noise Ratio (SNR) at BER of 10-4 for code rate of ½ of CC. To reduce the redundancy informations of CC, 2/3 code rate is proposed instead of ½. The results illustrates such system gives significant gain at high SNR, but the problem is the BER in increased up to system with code at low SNR. Also the results confirm that this problem decreases with high number of antennas. So that MIMO system is suitable for high data rate.

A Modified Grouped Linear ZF Algorithm Using Different Modulation Schemes for MIMO Systems

Ahmed Gh. Wadday; Saod A. Alseyab; Abdulkareem S. bdullah

Engineering and Technology Journal, 2012, Volume 30, Issue 1, Pages 13-23

A new algorithm for a group iterative linear Zero-Forcing (ZF) receiver for
multiple-input multiple-output (MIMO) systems is proposed in this paper. The
proposed algorithm merges between the group linear ZF receiver and V-Blast
algorithms, where the signals in every group are detected by linear ZF method and
then successive interference cancellation detection is applied between the different
groups. Three types of modulation schemes are adopted for testing this algorithm
namely; BPSK, QPSK, and 16 QAM. Simulation results show that the proposed
algorithm achieves a performance improvement over the ZF algorithm and the
grouped linear ZF algorithm at modulations (BPSK, QPSK). The proposed scheme
offers better performance gain for BPSK modulation of about 7dB and 2dB compared
with ZF and MMSE schemes respectively at BER of 10-3. On the other hand, the
proposed scheme offer better performance gain of about 3dB and 1dB compared with
ZF and minimum mean square error schemes for QPSK modulation at BER 10-3.
However, at using modulation of (16QAM), the performance of the proposed
algorithm is almost the same as that of the aforementioned algorithms. A little
increase of computational complexity is noticed with this proposed algorithm
compared with both the ZF, MMSE and the grouped linear ZF algorithms.