小波包基多载波系统无线分级图像的传输

研究了一种基于小波包变换的多载波系统无线分级图像传输的新方法．该方法信源采用基于小波变换的SPIHT编码，信道部分采用小波包基多载波调制，并将SPIHT输出码流分成重要性不同的若干层，然后引入一种联合信源信道的自适应子载波、比特和功率的分配算法，实现对不同SPIHT层的不等错误保护，在总发送功率一定并满足各层QoS要求的条件下，使各层的比特速率达到最大．在上述方法中．对重要层加以高级别的信道保护，得到了更好的传输效果．仿真结果表明：在低信噪比下，系统采用上述自适应算法比不采用该算法的峰值信噪比要高出10dB以上；在同等条件下，基于小波包变换的多载波系统的图像传输性能也好于基于傅里叶变换的正交频分复用多载波系统．

Wireless Scalable Image Transmission over Wavelet Packet-Based Multicarrier System

A new method for scalable image transmission over wavelet packet-based multicarrier system was proposed. In this method,SPIHT was used as the image coding,the wavelet packet-based multicarrier modulation was used as channel modulation method, and SPIHT output bit streams was divided into layers with different importance, and then a joint source channel subcarrier, bit and power adaptive allocation algorithm was introduced to give the different SPIHT layers unequal error protection and maximize the layers' bit rates under a total power constraint and their respective quality of service requirements. In above method, further performance gain was obtained by providing the important SPIHT layers with better channel error protection. Simulation results indicate that the scheme with the joint source channel adaptive allocation can outperform that without the adaptive allocation by more than 10 dB in delivered quality at low signal to noise ratio;Under the same conditions,the wavelet packet-based multicarrier system also has better bit error rate performance and delivered quality compared with the orthogonal frequency division multiplexing system based on Fourier transform.