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Adaptive radio-frequency resource management for MIMO MC-CDMA on antenna selection Jingxu Han and Mqhele E Dlodlo Department of Electrical Engineering University of Cape Town What is MIMO? MIMO (Multiple Input Multiple Output) is a new wireless technology conceived in the mid 90’s Greatly improves the reliability, range and robustness of existing wireless communication systems Can provide high data rate (channel capacity) high QoS (low bit error rate) Selected for many standards, such as W-CDMA UCT-COE Seminar 000 Page 2 May 24, 2017 Introduction of MC CDMA Multi-carriers CDMA (MC CDMA) is a multiple access technology used in wireless communication systems based on OFDM a strong candidate as an access technique for downlink of broadband cellular systems Obtains benefits from both MC and CDMA techniques: high spectral efficiency, robustness in frequency selective channels UCT-COE Seminar 000 Page 3 May 24, 2017 Combination of MIMO MC-CDMA systems A promising technology for 4G wireless communication since: 1 high date rate 2 high Qos 3 multiple users communication 4 high spectral efficiency UCT-COE Seminar 000 Page 4 May 24, 2017 Why antenna selection? An inherent drawback for multiple antenna system is the increased hardware complexity due to the requirement for radio-frequency chain. Corresponding to power amplifiers, mixers analog to digital converter ect. An ideal approach to reduce the complexity of a multiple antennas system while maintaining the advantages UCT-COE Seminar 000 Page 5 May 24, 2017 Ideas behind antenna selection Choose a subset of best performance antennas either in transmission and/ or reception to feed to the RF chain for signal processing Existing algorithms: 1) maximum signal to noise ratio 2) maximum channel mean 3) minimum instantaneous probability of error UCT-COE Seminar 000 Page 6 May 24, 2017 Proposing algorithm An improved low complexity algorithm proposed based on maximum ratio method the method is simplified to choose the best performance antenna from all the possible antennas, then choose the best performance antenna from the rest possible antennas instead of calculate Frobenius norm for all the possible antennas UCT-COE Seminar 000 Page 7 May 24, 2017 Complexity comparison For instance: selecting 2 antennas out of 10 antennas Old algorithm calculation complexity is 45 Correspondingly the novel one is 19 UCT-COE Seminar 000 Page 8 May 24, 2017 Adaptive RF management Aim to flexibly manage RF resource for MIMO MC-CDMA systems based on antenna selection 1) Set target bit error rate 2) find out minimum number of antennas to feed RF need 3) adaptive increasing the number of antennas on increment of users or interferences UCT-COE Seminar 000 Page 9 May 24, 2017 Simulation results performance of a 2by1 MIMO MC-CDMA system on antenna selection 0 10 -1 10 -2 SER 10 -3 10 32 users 32 users 16 users 16 users 1 user 1 user -4 10 -5 10 0 1 2 3 4 5 SNR 6 7 8 9 10 UCT-COE Seminar 000 Page 10 May 24, 2017 performance of different selected number of transmitters -1 10 2 3 4 5 6 7 -2 BER 10 out out out out out out 7 7 7 7 7 7 -3 10 -4 10 -5 10 0 1 2 3 4 5 SNR 6 7 8 9 10 UCT-COE Seminar 000 Page 11 May 24, 2017 Impact on various number of users -1 10 -2 BER 10 -3 10 2 out 3 out 4 out 5 out 6 out 7 out -4 10 7 7 7 7 7 7 -5 10 0 5 10 15 20 the number of users 25 30 35 UCT-COE Seminar 000 Page 12 May 24, 2017 performance of the proposed adaptive system with target BER to 1% -1 10 BER adaptive -2 10 -3 10 0 5 10 15 20 the number of users 25 30 35 UCT-COE Seminar 000 Page 13 May 24, 2017 performance of the proposed adaptive system with target BER to 0.1% -2 10 BER adaptive -3 10 -4 10 0 2 4 6 SNR 8 10 12 UCT-COE Seminar 000 Page 14 May 24, 2017 Conclusion A novel transmission adaptive technique for MIMO MC-CDMA system as an aim to flexibly manage radio frequency resource based on antenna selection is presented The simulation results, depending on both numbers of users and signal to noise ratio (SNR) value, show significant gains compared to fixed systems for a predefined target bit error rate (BER) UCT-COE Seminar 000 Page 15 May 24, 2017 Future work Performance investigation for the real MIMO channels are needed Effective feedback path is necessary to insure the system, and performance over fast fading channel is also an interesting topic. UCT-COE Seminar 000 Page 16 May 24, 2017 Thanks Questions?