1. QUALITY-DIFFERENTIATED VIDEO MULTICAST IN MULTIRATE
WIRELESS NETWORKS
ABSTRACT:
Adaptation of modulation and transmission bit-rates for video multicast in a multirate wireless
network is a challenging problem because of network dynamics, variable video bit-rates, and
heterogeneous clients who may expect differentiated video qualities. Prior work on the leader-
based schemes selects the transmission bit-rate that provides reliable transmission for the node
that experiences the worst channel condition.
However, this may penalize other nodes that can achieve a higher throughput by receiving at a
higher rate. In this work, we investigate a rate-adaptive video multicast scheme that can provide
heterogeneous clients differentiated visual qualities matching their channel conditions. We first
propose a rate scheduling model that selects the optimal transmission bitrate for each video
frame to maximize the total visual quality for a multicast group subject to the m inimum-visual-
quality-guaranteed constraint.
We present a practical and easy-to-implement protocol, called QDM, which constructs a cluster-
based structure to characterize node heterogeneity and adapts the transmission bit-rate to network
dynamics based on video quality perceived by the representative cluster heads. Since QDM
selects the rate by a sample-based technique, it is suitable for real-time streaming even without
any preprocess. We show that QDM can adapt to network dynamics and variable video-bit rates
efficiently, and produce a gain of 2-5 dB in terms of the average video quality as compared to the
leader-based approach.
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