Mahwash Manzoor ¹, Lavish Kansal ¹

Affiliations
1 School of Electronics and Electrical Engineering, Lovely Professional University, Phagwara - 144411, Punjab, IN

Abstract

Diverse modern wireless broadband communication systems are based on what is called Orthogonal Frequency Division Multiplexing (OFDM), which is a basic part of WiMAX. By making use of OFDM, we deal with frequency and time selectivity which are the major concerns when mobile or wireless communication is established between base and subscriber stations. WiMAX cuts the cost because it’s a wireless technology and hence there is little maintenance. Also, it provides higher data rates and has large coverage area compared to its counters parts. In this paper, we make a comparison of various channel coding techniques like convolutional codes, BCH codes, LDPC codes and RS codes over two fading channels namely Rayleigh channel and Rician channel and four modulation orders of PSK. The simulation results show that RS codes and BCH codes perform very well in all conditions whereas convolutional codes lag somewhat in their performance. In addition to this, Rician channel has a better response compared to Rayleigh channel in any modulation order or FEC codes being used in a WiMAX system.

Keywords

BCH, BER, FEC, LDPC, RS, WiMAX.

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Mahwash Manzoor ¹, Lavish Kansal ¹

Affiliations
1 School of Electronics and Electrical Engineering, Lovely Professional University, IN

Abstract

The Wireless Interoperability Microwave Access (WiMAX) system in this paper makes use of various forward error correction codes to improve and hence optimize the performance of the system. Two diverse fading channels have been used to study the response of the WiMAX system based on Forward Error Correction (FEC) encoding and M-ary Phase Shift Keying (M-PSK) modulation. Since WiMAX is used for both Line Of Sight (LOS) and Non Line-Of-Sight (NLOS) communication so, Rayleigh and Rician channels have been used, out of which one has LOS component, and other has no LOS component. The performance of WiMAX system has been studied by analyzing the graphs between Bit Error Rate (BER) and Signal to Noise Ratio (SNR) for all the different cases. It is observed that out of all coding techniques reed Solomon (RS) encoding techniques performs better at lower order modulation schemes by providing the BER of 10-3 at lower values of SNR in comparison to all other FEC encoding techniques. But, at higher order modulation level turbo encoding scheme outperform all other FEC schemes. Also, out of channels rician channel has a better response because of one strong line of sight constituent in comparison to Rayleigh fading channel. Further, modified FEC encoding schemes can be incorporated to enhance the BER performance of the WiMAX system.

Keywords

BER, Fading, FEC, MPSK, WiMAX.

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Mahwash Manzoor ¹, Lavish Kansal ¹

Affiliations
1 School of Electronics and Electrical Engineering, Lovely Professional University, Phagwara - 144411, Punjab, IN

Abstract

WiMAX is the most popular wireless technology these days for it has high data rates and better performance than other wireless and wired broadband technologies. The performance of WiMAX is severely affected by the multipath fading environment. The efficiency of the WiMAX system can be improved using efficient forward error coding schemes. In this paper a comparison of various FEC schemes such as BCH, RS, LDPC and convolution encoding has been done on two different channels namely-Rayleigh and AWGN. The BER performance of the WiMAX system is further analyzed by utilizing diverse modulation levels over both Rayleigh and AWGN channel. The simulation results show that the best performance is achieved by RS codes and BCH codes followed by LDPC codes and then the convolutional codes. Also, as we vary the code rate of the convolution encoder the BER further degrades. The graphical representations show that the improvement can go as high as 4 dB in some cases in terms of SNR required achieving a particular BER value. The use of RS and BCH encoding schemes will result in better performance in existing WiMAX systems.

Keywords

AWGN, BCH, FEC, LDPC, WiMAX.

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Misbah Manzoor ¹, Shekhar Verma ², Tapsi Singh ², Mahwash Manzoor ²

Affiliations
1 Department of Electronics and Communication Engineering, SSM College of Engineering, Srinagar - 191111, Jammu and Kashmir, IN
2 Department of Electronics and Communication Engineering, Lovely Professional University, Phagwara - 144411, Punjab, IN

Abstract

The advent of dynamic logic especially domino logic has made the use of dynamic circuits very wide for the implementation of low power VLSI circuits. Dynamic logic style is becoming the designers' choice these days because it has very fast speed and occupies very small area. In this paper we have used various techniques based on domino logic to overcome noise. Each technique has its merits and demerits. Out of these techniques mentioned below we have taken two widely used techniques in domino logic, conditional keeper technique and diode footed domino. We calculated their noise margins at different values of supply voltage. We have done simulations in 90 nm technology. After calculations we found both techniques show fairly good noise immunity but diode footed domino gave better results.

Keywords

Delay, Diode Footed Domino, Immunity, Leakage Tolerance, Noise, Power Consumption, Subthreshold Voltage, Technology Scaling.

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Mahwash Manzoor ¹, Lavish Kansal ¹

Affiliations
1 School of Electronics and Electrical Engineering, Lovely Professional University, Punjab – 144411, IN

Abstract

WiMAX is the modern era wireless technology which gained popularity because of its efficiency, high coverage, scalability and high data rates in any terrain. WiMAX is a Wireless Metropolitan Area Network (WMAN) being used globally for broadband access. There is always a demand for improvement in systems, which in the case of WiMAX can be achieved by using a better coding scheme with a proper modulation technique. In this paper, a comparison has been made on performances of different forward error correction codes on two channels- AWGN and Rayleigh channel. AWGN channel simply adds white Gaussian noise to the signal transmitted through it whereas Rayleigh channel is a fading multipath channel whose characteristics vary continuously with time. The results show that Turbo codes perform the best amongst all the coding techniques, and AWGN channel response is much better than the response of Rayleigh channel. This is because there is no line of sight component in Rayleigh channel and having obstructions in the path of the signal leads to signal fading. These results are shown in this paper as graphical analysis between BER and SNR.

Keywords

Additive White Gaussian Noise (AWGN), Bit Error Rate (BER), Signal to Noise Ratio (SNR), Wireless Metropolitan Area Network (WMAN), Worldwide Interoperability for Microwave Access (WiMAX).

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