Power Allocation for Mixed Traffic Broadcast with Service Outage Constraint

TL;DR

This paper proposes an optimal power allocation strategy for broadcast systems transmitting mixed traffic types, ensuring real-time service quality under outage constraints while considering channel variability.

Contribution

It introduces a power allocation policy based on channel statistics that guarantees real-time traffic QoS and accounts for the number of users and outage constraints.

Findings

Optimal policy depends on minimum channel gain statistics.

Power allocation combines water-filling and channel inversion.

Minimum average power increases linearly with user count.

Abstract

To transmit a mixture of real-time and non-real-time traffic in a broadcast system, we impose a basic service rate $r_0$ for real-time traffic and use the excess rate beyond $r_0$ to transmit non-real-time traffic. Considering the time-varying nature of wireless channels, the basic service rate is guaranteed with a service outage constraint, where service outage occurs when the channel capacity is below the basic service rate. This approach is well suited for providing growing services like video, real-time TV, etc., in group transportation systems such as coach, high-speed train, and airplane. We show that the optimal power allocation policy depends only on the statistics of the minimum gain of all user channels, and it is a combination of water-filling and channel inversion. We provide the optimal power allocation policy, which guarantees that real-time traffic be delivered with quality of service (QoS) for every user. Moreover, we show that the required minimum average power to satisfy the service outage constraint increases linearly with the number of users.