The Technique Of Multicarrier Based On Wavelet Packet Used In Tactical Data Link

In this paper, a new multicarrier system—Wavelet Packet Division Multiplexing (WPDM for short) system is investigated, which is used as an alternative method of modulation/demodulation in the Tactical Data Link (TDL for short) for its outstanding characteristics of system capacity, security and robustness. WPDM system introduces the theory of wavelet into the field of communication, and does modulation/demodulation work in the transform domain of wavelet, so the system is belong to Transform Domain Communication System (TDCS for short).Different from the OFDM system, whose sub-carriers is the traditional sine waves or cosine waves, the WPDM system uses the wavelet packet functions as its sub-carriers; for another perspective, OFDM is based on FFT, but WPDM is based on DWT. The advantage of wavelet packet is because of its two important properties that depend on orthogonality: the scaling function and wavelet are orthogonal over both scale and translation. The orthogonal over scale leads to the avoidance of ICI, while the orthogonal over translation leads to the avoidance of ISI.According to the results of theoretical analysis, a simulation platform of WPDM system is build up, in which there are two WPDM systems with representative frameworks, one simple OFDM system and several channel models. A mass of simulations are completed for the comparisons of BER between OFDM system and WPDM system under different channel conditions. Simulations are also done to observe the influences of different wavelets used in the same WPDM system. The principle of how to choose wavelet is given too. In the process of researching, more frameworks of WPDM are derived from the characteristics of Mallat Algorithm and the data for modulation. Simple discussions on the system performance are made too, including a reason that why some WPDM systems has less ISI avoidance capability than the OFDM system. The exploring analysis that this issue gives about the frameworks of WPDM system has been ignored by many researchers. The results having obtained in this paper provide a good groundwork for optimizing the performance of WPDM system, and offer the strong technical supports to implement the highly efficient and greatly secure TDL.