B. Siva Kumar Reddy

Adaptive Modulation and Coding for Mobile-WiMAX using SDR in GNU Radio

The demand for high data rates and low bit error rates has prompted the ascent of developing remote innovations, such as WiMAX. Adaptive Modulation and Coding (AMC) plans when joined into WiMAX helps the framework to alertly respond to the channel varieties giving higher information rates and better BER execution. Switching the modulation and coding rates dependent upon channel state information permits to attain higher throughput and better spectral efficiency. This paper deals with proposal of efficient adaptive modulation coding system which maximizes the throughput while upholding a target bit error rate (BER). Software Defined Radio (SDR) idea has been utilized to do most of the signal processing over a software than in hardware. It proposes to select a specific modulation coding schemes in addition to the relating coding rates dependent upon the threshold given. Hence, a selector block is created in GNU Radio companion using Python script. This block switches to proper modulation and coding rates depends upon the thresholds considered. This paper investigations the Mobile-WiMAX framework regarding BER and throughput by considering SNR and channel attenuation factor as the threshold qualities. Obtained results derived a trade-off between BER and throughput.

Improvement in the Performance of WiMAX with Channel Equalizers and Space Time Block Coding Techniques Using Simulink

AbstractWiMAX is a coming forth broadband wireless technology that considered as one of the most prominent solution to provide high speed data services. This paper addresses the design of WiMAX end to end physical layer (PHY) in Simulink with channel equalization and space time block coding techniques. The authors analyzed the performance of WiMAX PHY with decision feedback equalizers (DFE), linear equalizers and blind equalizers over AWGN and multipath faded channels. Results include MISO channel power spectral density (PSD), antenna amplitude/PSD/phase difference, multipath faded and AWGN channel’s effect on the transmitted signal and the performance of proposed equalizers on the received signals. This paper concluded that the linear equalizers have higher frame error rates (FER) than DFE. However, blind equalizers have higher FERs compared to conventional equalizers with better spectral efficiency as they need no training sequence.

Minimizing PAPR and Synchronization Errors in OFDM for WiMAX Using Software Defined Radio

This paper addresses the reduction of peak-to-average power ratio (PAPR) and synchronization errors of an orthogonal frequency division multiplexing (OFDM) for Mobile-WiMAX physical layer (PHY) standard. In the process, the best achievable PAPR of 0 dB with efficient power amplification is found for the OFDM signal using phase modulation technique, which avoids the nonlinear distortion. Further, the constant modulus algorithm (CMA) and sign kurtosis maximization adaptive algorithm (SKMAA) equalizers are used in the system to reduce the synchronization errors. However, the experimental study is performed on a test platform for a practical proof of the concept. The test platform is based on the Ettus universal software radio peripheral (USRP) N210 hardware and the GNU Radio open source software. Several tests are carried out to observe the effect of equalizers on the system. The performance comparison of bit error rate/symbol error rate (BER/SER) values are tabulated for the system with and without equalization.

Modulation switching in OFDM for WiMAX through Rayleigh fading channel using GNU radio

This paper presents modulation switching in OFDM for WiMAX specifications by considering Raleigh fading channel using GNU Radio companion. WiMAX technology is considered as the most eminent solution able to allow a Broadband wireless Access (BWA) in metropolitan areas with a merer installation and lower cost. OFDM is the fundamental block in WiMAX PHY layer. Modulation switching is performed in WiMAX to amend the network performance in the case of Non-LoS communication. This work proposes a script in Python to build a block which selects the modulation scheme to be used in OFDM. The results show that a selector block automatically adopts the modulation scheme to be used, while an OFDM system is in operation.

Channel estimation and equalization in OFDM receiver for WiMAX with Rayleigh distribution

WiMAX is a broadband wireless access technology supports fixed and mobility services. WiMAX physical layer is based on OFDM/OFDMA technologies. This paper analyzes the Rayleigh fade distribution with various modulating frequencies (fm) by varying number of frequency samples. Least square (LS) and Linear Minimum Mean Square Error (LMMSE) channel estimators are compared in terms of BER, SNR and MSE (Mean Square Error) by varying channel length. Blind Channel equalization is analyzed with CMA (Constant Modulus Algorithm) and LMS (Least Minimum Square) algorithms in terms of convergence rate by varying the smoothening length of the channel. The results proved that without channel estimation BER is almost constant for all modulation schemes.

Adaptive Modulation and Coding with Channel Estimation/Equalization for WiMAX Over Multipath Faded Channels

Adaptive modulation and coding (AMC) technique is integrated with WiMAX to provide higher data rates with error free transmission. AMC schemes employ the channel state information (CSI) to utilize the channel efficiently and maximize the throughput with better spectral efficiency. In this paper, least square error (LSE) and minimum mean square error (MMSE) estimators are suggested and bit error rate (BER) performance has been analyzed. Channel equalization is also integrated with with AMC-OFDM system and presented with constant modulus algorithm (CMA) and least mean square (LMS) algorithms in terms of convergence rates analysis. Simulation results proved that increment in modulation scheme size causes to improvement in throughput along with BER value. There is a trade-off among modulation size, throughput, BER value and spectral efficiency. Results also reported the requirement of channel estimation and equalization in high data rate systems.