Improvement of bit error rate performance of MC-CDMA  system by using adaptive digital modulation schemes

In Wireless Communication, the transmission channel suffers due to multipath propagation and channel dispersion due to Inter Symbol Interference (ISI), thereby degrades the system performance greatly. Future communication requires high data rate and effective utilization of bandwidth. Hence, there is a need to improve the Bit Error Rate (BER). The proposed work is Adaptive Modulation (AM), combined with Multi Carrier Code Division Multiple Access (MC-CDMA) based transmission system. It is a promising way to increase the data rate and it uses bandwidth in a efficient manner. The Adaptive Modulation based MC-CDMA systems applied to a wide-area environment, can achieve high data rate up to 100Mbps. In this paper M-ary PSK, M-ary QAM and M-ary CPM modulation techniques are used. The Adap-tive modulation based MC-CDMA systems perform well for around 10 number of users. As a whole, the adaptive MC-CDMA system is found to give the optimum BER performance of given digital modulation schemes for fourth generation environment.

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Comparison the Performance Evaluation of Xgpon-Rof System with Wdm and Scm for Different Modulation Schemes

Al-Qadisiyah Journal for Engineering Sciences ◽

10.30772/qjes.v12i4.640 ◽

2019 ◽

Vol 12 (4) ◽

Author(s):

Muntadhar H. Ismeala ◽

Bashar J. Hamzaa ◽

Wasan Kadhim Saada

Keyword(s):

Quality Factor ◽

Wavelength Division Multiplexing ◽

Bit Error Rate ◽

Error Rate ◽

Network Performance ◽

Input Power ◽

Data Rate ◽

Eye Diagram ◽

High Data ◽

Modulation Schemes

At the present time and as a result to the recent developed technology demand for higher data rate and capacity has been increased. For the wireless networks, the combination of radio over fiber (RoF) with (XGPON) Gigabit-capable PON techniques produce a high data rate at lower cost. Thus, this paper illustrates that the performance of RoF-XGPON optical link has been analyzed for multi-channel through combining two multiplexing techniques, such as; Subcarrier Multiplexing (SCM) and Wavelength Division Multiplexing (WDM). The proposed system utilizes WDM-xGPON and SCM-XGPON architecture combined with RoF technology with 10 Gpbs data rate and (2.4, 5.8, 10 and 15) GHz radio frequency (RF), when change the optical fiber length between (10 to 80) km. The network performance is compared with various digital quadrate amplitude modulation schemes, like ; 4 - QAM, 16 - QAM and 64 - QAM for various input power (-2, 2, and 6) dB. The performance analysis is based on the optical spectrum of transmitted and received signals for 4-channel, constellation diagram, eye diagram, bit error rate (BER), power received, and quality factor. The result explain that the WDM-XGPON-Rof performs better than SCM-XGPON-Rof for different modulation schemes. The bit error rate for WDM-XGPON less than the SCM-XGPON while the power received recorded to the WDM-XGPON greater than SCM-XGPON and the quality factor for SCM-XGPON less than the WDM-XGPON. Therefore The simulation results show that the WDM-XGPON-RoF gives better performance from SCM-XGPON-RoF. The software optisystem version 15 has been used to simulate this system

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