International Journal of Networks and Communications, 2020
The demand for high data rate transmission is increasing daily and services require reliable data... more The demand for high data rate transmission is increasing daily and services require reliable data transmission over harsh environment. However, high data rate transmission resulting in signal overlapping at the receiver due to delay and time variation of the received signal. Orthogonal Frequency Division Multiplexing (OFDM) used to solve this problem is associated with Intercarrier Interference (ICI) that affects system performance. OFDM with ICI self-cancellation (OFDM-SC) is proposed to remove ICI generated in OFDM but suffers from poor bandwidth efficiency at low constellation size of modulation. This paper therefore, evaluate the performance of OFDM-SC with higher constellation using Bit Error Rate (BER) and Spectral Efficiency (SE). Mathematical expression for BER and SE is derived using signal strength of the received signal. The system is simulated using MATLAB R2018a to obtained the BER and SE values at different constellation size. The results obtained revealed that, OFDM-SC with 128QAM shows better performance with higher bandwidth efficiency when compared with lower constellation size such as 16QAM and 32QAM. The investigation shows that, OFDM-SC with higher constellation improve the performance of conventional OFDM.
One astable output is at lower frequency and other one at a higher frequency. Lower frequency mul... more One astable output is at lower frequency and other one at a higher frequency. Lower frequency multivibrator controls the frequency of the other. From the basic, working principle of astable, resistors R3, R4 and capacitor C4determines the frequency, so the frequency can be changed by varying R3. This can be done simply by connecting a NPN transistor (BC 107) in parallel with R3 with a series resistance R5 to limit the current. The Output of 555 is connected to the base of transistor through a current limiting resistor R7. When the output of first astable is high, the transistor BC107 becomes ON which in turn makes R5 parallel to R3. Then the total effective resistance goes below the resistance of lower resistor value, which reduces the time of astable 555. Thus increase frequency is just the opposite process which takes place when the first 555 output is low (OFF). Finally, Output of the second 555 is connected to an IR Led through a current limiting resistor R6. Led glows in accordance with the output frequency which is then detected by the TSOP
In the area of wireless communications, the demand for high data rate transmission is rapidly inc... more In the area of wireless communications, the demand for high data rate transmission is rapidly increasing. Orthogonal frequency division multiplexing (OFDM) is known to be a promising technique for high-rate transmission that can overcome the inter symbol interference (ISI) which results from the time dispersive nature of wireless channels. For OFDM communication systems the orthogonality is lost among the sub-carriers due to frequency offset which results in Inter carrier Interference (ICI). This ICI rapidly degrades the performance of OFDM system. A well known problem of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset introduces intercarrier interference (ICI) in the OFDM symbol. This project investigates a method for combating the effects of ICI: ICI self cancellation (SC) using Rayleigh fading channel. This method is compared in terms of bit error rate performance, bandwidth efficiency, and computational complexity. Through simulations, it is shown that the technique is effective in mitigating the effects of ICI. For high values of the frequency offset and for higher order modulation schemes, higher constellation method performs better than the SC method.
International Journal of Networks and Communications, 2020
The demand for high data rate transmission is increasing daily and services require reliable data... more The demand for high data rate transmission is increasing daily and services require reliable data transmission over harsh environment. However, high data rate transmission resulting in signal overlapping at the receiver due to delay and time variation of the received signal. Orthogonal Frequency Division Multiplexing (OFDM) used to solve this problem is associated with Intercarrier Interference (ICI) that affects system performance. OFDM with ICI self-cancellation (OFDM-SC) is proposed to remove ICI generated in OFDM but suffers from poor bandwidth efficiency at low constellation size of modulation. This paper therefore, evaluate the performance of OFDM-SC with higher constellation using Bit Error Rate (BER) and Spectral Efficiency (SE). Mathematical expression for BER and SE is derived using signal strength of the received signal. The system is simulated using MATLAB R2018a to obtained the BER and SE values at different constellation size. The results obtained revealed that, OFDM-SC with 128QAM shows better performance with higher bandwidth efficiency when compared with lower constellation size such as 16QAM and 32QAM. The investigation shows that, OFDM-SC with higher constellation improve the performance of conventional OFDM.
One astable output is at lower frequency and other one at a higher frequency. Lower frequency mul... more One astable output is at lower frequency and other one at a higher frequency. Lower frequency multivibrator controls the frequency of the other. From the basic, working principle of astable, resistors R3, R4 and capacitor C4determines the frequency, so the frequency can be changed by varying R3. This can be done simply by connecting a NPN transistor (BC 107) in parallel with R3 with a series resistance R5 to limit the current. The Output of 555 is connected to the base of transistor through a current limiting resistor R7. When the output of first astable is high, the transistor BC107 becomes ON which in turn makes R5 parallel to R3. Then the total effective resistance goes below the resistance of lower resistor value, which reduces the time of astable 555. Thus increase frequency is just the opposite process which takes place when the first 555 output is low (OFF). Finally, Output of the second 555 is connected to an IR Led through a current limiting resistor R6. Led glows in accordance with the output frequency which is then detected by the TSOP
In the area of wireless communications, the demand for high data rate transmission is rapidly inc... more In the area of wireless communications, the demand for high data rate transmission is rapidly increasing. Orthogonal frequency division multiplexing (OFDM) is known to be a promising technique for high-rate transmission that can overcome the inter symbol interference (ISI) which results from the time dispersive nature of wireless channels. For OFDM communication systems the orthogonality is lost among the sub-carriers due to frequency offset which results in Inter carrier Interference (ICI). This ICI rapidly degrades the performance of OFDM system. A well known problem of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset introduces intercarrier interference (ICI) in the OFDM symbol. This project investigates a method for combating the effects of ICI: ICI self cancellation (SC) using Rayleigh fading channel. This method is compared in terms of bit error rate performance, bandwidth efficiency, and computational complexity. Through simulations, it is shown that the technique is effective in mitigating the effects of ICI. For high values of the frequency offset and for higher order modulation schemes, higher constellation method performs better than the SC method.
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A well known problem of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset introduces intercarrier interference (ICI) in the OFDM symbol. This project investigates a method for combating the effects of ICI: ICI self cancellation (SC) using Rayleigh fading channel.
This method is compared in terms of bit error rate performance, bandwidth efficiency, and computational complexity. Through simulations, it is shown that the technique is effective in mitigating the effects of ICI. For high values of the frequency offset and for higher order modulation schemes, higher constellation method performs better than the SC method.
A well known problem of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset introduces intercarrier interference (ICI) in the OFDM symbol. This project investigates a method for combating the effects of ICI: ICI self cancellation (SC) using Rayleigh fading channel.
This method is compared in terms of bit error rate performance, bandwidth efficiency, and computational complexity. Through simulations, it is shown that the technique is effective in mitigating the effects of ICI. For high values of the frequency offset and for higher order modulation schemes, higher constellation method performs better than the SC method.