Staleness Bounds and Efficient Protocols for Dissemination of Global Channel State Information

This paper considers the problem of achieving global channel knowledge throughout a fully connected packetized wireless network with time-varying channels. While the value of channel state information at the transmitter (CSIT) is now well known, there are many scenarios in which it is helpful to have additional channel knowledge beyond conventional CSIT, e.g., cooperative communication systems. The overhead required for global CSI knowledge can be significant, particularly in time-varying channels where the quality of channel estimates is dominated by the “staleness” of the CSI. Nevertheless, the fundamental limits and feasibility of tracking global CSI throughout a network have not been sufficiently studied. This paper presents a framework for analyzing the staleness of protocols that estimate and disseminate CSI to all nodes in a fully connected network. Fundamental bounds on achievable staleness are derived, and efficient dissemination protocols are developed, which achieve these limits. The results provide engineering guidelines on the feasibility of tracking global CSI as a function of network size, the size and composition of the packets, packet error rate, and channel coherence time.