We consider a wireless broadcast network with a base station sending
time-sensitive information to a number of clients through unreliable channels.
The Age of Information (AoI), namely the amount of time that elapsed since the
most recently delivered packet was generated, captures the freshness of the
information. We formulate a discrete-time decision problem to find a
transmission scheduling policy that minimizes the expected weighted sum AoI of
the clients in the network.
We first show that in symmetric networks a Greedy policy, which transmits the
packet with highest current age, is optimal. For general networks, we develop
three low-complexity scheduling policies: a randomized policy, a Max-Weight
policy and a Whittle's Index policy, and derive performance guarantees as a
function of the network configuration. To the best of our knowledge, this is
the first work to derive performance guarantees for scheduling policies that
attempt to minimize AoI in wireless networks with unreliable channels.
Numerical results show that both Max-Weight and Whittle's Index policies
outperform the other scheduling policies in every configuration simulated, and
achieve near optimal performance.

本文研究无线广播网络中时间敏感的信息传输，提出了优化最小化网络客户端信息新鲜度的传输调度策略，并实现性能保证。我们在对称网络中表明了最优传输调度策略，而对于一般网络，我们提出了三种低复杂度的调度策略，并据此得出了性能保证，并提出了 Max-Weight 和 Whittle's Index 策略来优化该问题。实验结果表明这两种策略的性能最优。