Research On Wavelet Packet-Division Multiplexing System Oriented Graded Multi-Service

Today, with the development of mobile communication, users press for the services of high speed data and multimedia more and more. The new need bring forward challenges for the transmission ability of wireless link and net form, while OFDM is hopeful to become a key technology for next generation mobile communication system because of its high spectrum efficiency and good capability of decreasing multipath interference.In the paper, we introduce a substitution of OFDM——wavelet packet-division multiplexing which abbreviation is WPDM. Firstly, its principle and system structure are presented. Secondly, we discuss its six peculiarities. Lots of simulation results prove its advantages over OFDM, so WPDM is adopted as our MCM scheme.In MCM system we can realize the channel's dynamic allocation. This trait offers a method of raising the spectrum efficiency further for transmission system oriented multimedia service. This paper puts away the traditional coarse service classify according to difference of application, and proposes a new concept of fine grading for video service based on importance. At the same time, a corresponding idea of joint source-channel allocation of resource is provided which is oriented to graded multi-service. Namely, little bits and good channels should be devoted to the high grade service which the QoS requirement is high, while more bits and bad channels to the low grade service which the QoS requirement is low. Therefore, we can obtain the target of utilizing spectrum resource more efficiently at the premise of transmission quality guarantee. The solution of image grading by wavelet transform is included in the paper. Both of transmission schemes of image grading and ungrading are simulated in several typical channel environments. The results testify that there is a great increase of output SNR of image in grading scheme comparing the ungrading. At the same time, an algorithm of nested double-cycle based on PRI is put forward for resource allocation. In the end, we discuss the probability of the system's hardware realization.