A wavelet packet transceiver for spectral analysis and dynamic spectrum access is presented. The transceiver consists of a Wavelet Packet Spectral Estimator (WPSE) and a Wavelet Packet Multi-carrier Modulator (WPM). The WPSE senses the radio environment to identify Licensed Users (LU) bands and spectrum holes. This information is then used to shape the time-frequency characteristics of the WPM transmission waveform to evade the LU transmission zones. The shaping is done by vacating those sub-carriers which lie in and around the LU bands. The WPM sub-carriers are orthogonal wavelet packet (WP) bases derived from a bank of 2-channel paraunitary filter pairs. The WPSE uses the same filter bank infrastructure as the one used for data modulation and hence doesn't add to the implementation cost. Through simulation studies the operation and advantages of the proposed system are demonstrated. The performances are also compared with existing systems based on Fast Fourier Transform (FFT) and Orthogonal Frequency Division Multiplexing (OFDM). The studies show that WPSE/WPM performs better than FFT/OFDM in regard to bit-error-rate (BER), bandwidth efficiency and interference to the licensees.