Adaptive Measurement Strategies for Network Optimization and Control

Sammanfattning: The fifth generation networks is rapidly becoming the new network standardand its new technological capabilities are expected to enable a far widervariety of services compared to the fourth generation networks. To ensurethat these services can co-exist and meet their standardized requirements,the network’s resources must be provisioned, managed and reconfigured ina far more complex manner than before. As such, it is no longer sufficientto select a simple, static scheme for gathering the necessary information totake decisions. Instead, it is necessary to adaptively, with regards to networksystem dynamics, trade-off the cost in terms of power, CPU and bandwidthconsumption of the taken measurements to the value their information brings.Orchestration is a wide field, and the way to quantify the value of a givenmeasurement heavily depends on the problem studied. As such, this thesisaddresses adaptive measurement schemes for a number of well-defined networkoptimization problems. The thesis is presented as a compilation, whereafter an introduction detailing the background, purpose, problem formulation,methodology and contributions of our work, we present each problemseparately through the papers submitted to several conferences.First, we study the problem of optimal spectrum access for low priorityservices. We assume that the network manager has limited opportunitiesto measure the spectrum before assigning one (if any) resource block to thesecondary service for transmission, and this measurement has a known costattached to it. We study this framework through the lens of multi-armedbandits with multiple arm pulls per decision, a framework we call predictivebandits. We analyze such bandits and show a problem specific lower bound ontheir regret, as well as design an algorithm which meets this regret asymptotically,studying both the case where measurements are perfect and the casewhere the measurement has noise of known quantity. Studying a syntheticsimulated problem, we find that it performs considerably better compared toa simple benchmark strategy.Secondly, we study a variation of admission control where the controllermust select one of multiple slices to enter a new service into. The agentdoes not know the resources available in the slices initially, and must insteadmeasure these, subject to noise. Mimicking three commonly used admissioncontrol strategies, we study this as a best arm identification problem, whereone or multiple arms is ”correct” (the arm chose by the strategy if it had fullinformation). Through this framework, we analyze each strategy and devisesample complexity lower bounds, as well as algorithms that meet these lowerbounds. In simulations with synthetic data, we show that our measurementalgorithm can vastly reduce the number of required measurements comparedto uniform sampling strategies.Finally, we study a network monitoring system where the controller mustdetect sudden changes in system behavior such as batch traffic arrivals orhandovers, in order to take future action. We study this through the lensof change point detection but argue that the classical framework is insufficientfor capturing both physical time aspects such as delay as well as measurementcosts independently, and present an alternative framework whichiidecouples these, requiring more sophisticated monitoring agents. We show,both through theory and through simulation with both synthetic data anddata from a 5G testbed, that such adaptive schedules qualitatively and quantitativelyimprove upon classical change point detection schemes in terms ofmeasurment frequency, without losing classical optimality guarantees such asthe one on required measurements post change.