In this work, a 5 state left to right HMM-based Bangla Isolated word speech recognizer has been developed. To train and test the recognizer, a small corpus of various sampling frequencies have been developed in noisy as well as the noiseless environment. The number of filter banks is varied during the feature extraction phase for both MFCC and PLP. The effects of 2nd and 3rd differential coefficients have also been observed. Experimental results exhibit that MFCC based feature extraction technique is better in CLASSROOM environment on the contrary PLP based technique performs better not only in a noiseless environment but also in when AC or FAN noise is present. We have also noticed that higher sampling frequency and higher filter order don't always help to improve the performance.
In this paper, the bit error rate (BER) performance of SFBC-OFDM systems for frequency selective fading channels is observed for various antenna orientations and modulation schemes. The objective is to find out a suitable configuration with minimum number of receiving antenna that requires minimum signal power level at the receiver to provide reliable voice and video communication. We have considered both M-ary phase shift keying (MPSK) and M-ary quadrature amplitude modulation (MQAM) in the performance analysis considering both perfect and imperfect channel state information (CSI). The authors have expressed the BER under imperfect channel estimation condition as a function of BER under perfect channel condition in this paper. The finding shows, for a BTS with 4 transmitting antenna and MS with 2 receiving antenna BPSK performs better for both perfect and imperfect CSI. Maximum permissible channel estimation error increases with the usage of more receiving antenna at the expense of increased cost.Index Terms: Space-frequency block coding (SFBC), Orthogonal frequency division multiplexing (OFDM), Rayleigh fading, Bit error rate (BER), Channel state information (CSI).flat subchannels [1]. MIMO offers the benefits of spatial multiplexing and transmits diversity which enhances the function of the OFDM system [2]. Recently, space-frequency coded OFDM are being used to exploit the diversities in space and frequency. Considering the numerical analysis of the systems, SFBC-OFDM has been presented and appraised [3]- [11].The major source of high data rate application includes mainly different forms of video over the wireless communication channels. Throughout the world, 82 percent of traffic will occur by IP video traffic by 2021 [Source: Cisco VNI, 2017]. So, we tried to optimize the performance for video data only. For reliable transmission of high data rate, video traffic bit error rate (BER) criterion is monitored. BER should be lower than 10 -6 for reliable transmission of a video signal [12].In our research, the authors have firstly investigated how the BER performance is affected by various parameters considering both perfect and imperfect CSI. Secondly, the authors have expressed the BER under imperfect channel estimation condition as a function of BER under perfect channel condition. Finally, the value of the signal to noise ratio (SNR) at which the BER value reaches the threshold level of 10 -6 for different antenna configurations and modulation schemes is monitored. For a low-cost receiver design, we need to choose less number of the antenna to get comparable yet compromised performance. Battery's lifetime is an important issue to notice. Lower SNR will certainly increase the lifetime. So, we have tried to choose the techniques with lower SNR. We have simulated the results for both perfect CSI and imperfect CSI. In imperfect CSI, we have also observed how performance is deteriorated when the value of channel estimation error (σ e 2 ) isincreased.
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