Abstract
This paper studies the Hierarchical Modulation, a transmission strategy of the approaching scalable multimedia over frequency-selective fading channel for improving the perceptible quality. An optimization strategy for Hierarchical Modulation and convolutional encoding, which can achieve the target bit error rates with minimum global signal-to-noise ratio in a single-user scenario, is suggested. This strategy allows applications to make a free choice of relationship between Higher Priority (HP) and Lower Priority (LP) stream delivery. The similar optimization can be used in multiuser scenario. An image transport task and a transport task of an H.264/MPEG4 AVC video embedding both QVGA and VGA resolutions are simulated as the implementation example of this optimization strategy, and demonstrate savings in SNR and improvement in Peak Signal-to-Noise Ratio (PSNR) for the particular examples shown.
Highlights
Recent developments in media source coding have evolved from consideration of compression efficiency in terms of rate-distortion curves, and on methods for providing easy-to-use scalability features
To achieve a desired value of Peak Signal-to-Noise Ratio (PSNR) = 30 dB, simulation 1 has to provide an Signal-to-Noise Ratio (SNR) per bit greater than 5.3 dB, and simulation 2 only needs to provide an SNR per bit of 3.8 dB, so that 1.5 dB is saved
This paper proposed an optimized hierarchical modulation strategy directed by cross-layer transport priority information for both single user scenario and two users scenario
Summary
Recent developments in media source coding have evolved from consideration of compression efficiency in terms of rate-distortion curves, and on methods for providing easy-to-use scalability features. One strategy that could be employed is to use timeslicing of data with different priorities; in [5], Cover proved that if a sender wants to send information simultaneously to several receivers, given specific channel conditions, superimposing high-rate information on lowrate information may achieve higher bandwidth efficiency than the time-sharing strategy This has led to the concept of an alternative approach for dealing with different streams of information at the physical layer of a system, namely, hierarchical modulation. Since the base layer packets encoded by a scalable codec can be reused by the enhancement layer packets, the scalable codec is more efficient than the nonscalable codec in providing multiresolution media simultaneously In this case, the source packets contributing to the low resolution are allocated to the base bits of the hierarchical constellation and the packets which only contribute to the high resolution are carried by the refinement bits.
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