In this dissertation, we look at designing wireless communication frameworks for interactive applications like drone swarms, and industrial automation that require fast and reliable communication. We focus on designing frameworks that make wireless communication highly reliable while also maintaining the latency requirements of the systems being targeted. This is the missing link needed to leverage the power of wireless communication for the next generation of interactive applications.
One of the key contributions of this thesis is the design of cooperative communication based protocol frameworks that leverage a combination of diversity techniques to achieve the target reliability and latency. The framework uses spatial diversity to combat multipath channel fading and repetitions in time and frequency to shield against unmodeled error events. We analyze these protocols using the communication-theoretic delay-limited-capacity framework and consider their sensitivity to different modeling assumptions.
Another key contribution of this thesis is an in-depth exploration of the dynamics of wireless channels in the context of ultra-reliable low-latency communication (URLLC). We revisit some standard concepts such as coherence time and question whether some of the modeling assumptions made in the context of cellular and WLAN communications make sense in the context of URLLC. We find that our cooperative communication frameworks are robust to the nominal dynamic channel models, especially spatial dependence. However, events such as synchronization mismatch or sudden change in the channels due to shadow- causing objects need to be protected against and therefore we build in frequency and time margins.
The final contribution of this thesis is bringing together the temporal model of channel dynamics and machine learning to build intelligent relay selection strategies. This essentially provides the reliability needed by smartly selecting a small set of relays instead of relying on using every single relay available to combat fading. Finally, we present some preliminary experimental findings that pave the way to making these systems practical.