To transmit a mixture of real-time and non-real-time traffic in a broadcastsystem, we impose a basic service rate $r_0$ for real-time traffic and use theexcess rate beyond $r_0$ to transmit non-real-time traffic. Considering thetime-varying nature of wireless channels, the basic service rate is guaranteedwith a service outage constraint, where service outage occurs when the channelcapacity is below the basic service rate. This approach is well suited forproviding growing services like video, real-time TV, etc., in grouptransportation systems such as coach, high-speed train, and airplane. We showthat the optimal power allocation policy depends only on the statistics of theminimum gain of all user channels, and it is a combination of water-filling andchannel inversion. We provide the optimal power allocation policy, whichguarantees that real-time traffic be delivered with quality of service (QoS)for every user. Moreover, we show that the required minimum average power tosatisfy the service outage constraint increases linearly with the number ofusers.
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