Performance Evaluation of Discrete Wavelet Transform Architecture

Discrete wavelet transform has local characteristic of unique time scale, it provides effective tool in various fields such as signal compression and signal analysis. This led to the development of various architectures implementing DWT. Since the original pixels are highly correlated, applying compression algorithms directly does not give effective compression ratios. Therefore, applying DWT is a powerful tool for deleting image pixels. The 2 - D wavelet filter as a separable function is first implemented by row DWT and column DWT which generate four subbands LL, LH, HL and HH at each decomposition level.

Next, we use the MATLAB command wavedec to perform wavelet multilevel decomposition on the signal x1. It performs wavelet decomposition of the signal, decomposes multivalued one-dimensional decomposition, and discrete wavelet transform (DWT) uses pyramid algorithm. The device low pass output passes through a high pass filter and a low pass filter and the process continues based on the programmer's specification, a linear time-invariant filter which is the attenuation below the high pass filter frequency and threshold (The MathWorks 1994-2010). This frequency is called the cutoff frequency, and the attenuation factor is specified by the designer. On the other hand, the low-pass filter uses only the low-frequency signal, contrary to the high-pass filter, and attenuates a signal including a frequency higher than the cutoff frequency.

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WPM is a multi-carrier modulation system such as OFDM using Discrete Wavelet Transform (DWT). DWT is a transformation technique that represents composite signals in the time domain and frequency domain. Therefore, in WPM, the packet structure is divided into the time domain and the frequency domain. Thus, if some interference is achieved in a TDMA or FDMA system, all packets will degrade, but in the case of WPM the packet will be far from interference by providing an appropriate packet structure. Both WPM and OFDM are multicarrier modulation systems, but the difference is that OFDM combines transmissions using FFT. WPM uses DWT and wavelet packet modulation and achieves a much better bit error rate than OFDM. The similarity between these modulation schemes is high peak-to-average power ratio (PAPR). In order to obtain better OFDM performance, single - carrier OFDM (SC - OFDM) with reduced PARP is the main goal. SC - WPM can also be used by using the principle of SC - OFDM.