Thirty Years of Machine Learning: The Road to Pareto-Optimal Wireless Networks

Future wireless networks have a substantial potential in terms of supporting a broad range of complex compelling applications both in military and civilian fields, where the users are able to enjoy high-rate, low-latency, low-cost and reliable information services. Achieving this ambitious goal requires new radio techniques for adaptive learning and intelligent decision making because of the complex heterogeneous nature of the network structures and wireless services. Machine learning (ML) algorithms have great success in supporting big data analytics, efficient parameter estimation and interactive decision making. Hence, in this article, we review the thirty-year history of ML by elaborating on supervised learning, unsupervised learning, reinforcement learning and deep learning. Furthermore, we investigate their employment in the compelling applications of wireless networks, including heterogeneous networks (HetNets), cognitive radios (CR), Internet of things (IoT), machine to machine networks (M2M), and so on. This article aims for assisting the readers in clarifying the motivation and methodology of the various ML algorithms, so as to invoke them for hitherto unexplored services as well as scenarios of future wireless networks.Comment: 46 pages, 22 fig

Variable-speed rotor helicopters: Performance comparison between continuously variable and fixed-ratio transmissions

Variable speed rotor studies represent a promising research field for rotorcraft performance improvement and fuel consumption reduction. The problems related to employing a main rotor variable speed are numerous and require an interdisciplinary approach. There are two main variable speed concepts, depending on the type of transmission employed: Fixed Ratio Transmission (FRT) and Continuously Variable Transmission (CVT) rotors. The impact of the two types of transmission upon overall helicopter performance is estimated when both are operating at their optimal speeds. This is done by using an optimization strategy able to find the optimal rotational speeds of main rotor and turboshaft engine for each flight condition. The process makes use of two different simulation tools: a turboshaft engine performance code and a helicopter trim simulation code for steady-state level flight. The first is a gas turbine performance simulator (TSHAFT) developed and validated at the University of Padova. The second is a simple tool used to evaluate the single blade forces and integrate them over the 360 degree-revolution of the main rotor, and thus to predict an average value of the power load required by the engine. The results show that the FRT does not present significant performance differences compared to the CVT for a wide range of advancing speeds. However, close to the two conditions of maximum interest, i.e. hover and cruise forward flight, the discrepancies between the two transmission types become relevant: in fact, engine performance is found to be penalized by FRT, stating that significant fuel reductions can be obtained only by employing the CVT concept. In conclusion, FRT is a good way to reduce fuel consumption at intermediate advancing speeds; CVT advantages become relevant only near hover and high speed cruise condition

Tradeoff analysis of technology needs for public service helicopters

The design requirements for a family or type of Public Service Helicopter (PSH) is examined which will satisfy the needs of municipal and state governments in the following mission areas: Emergency Medical Service--Airborne Rescue Squad; Law Enforcement; Search and Rescue; and Environmental Control (Fire Fighting, Pollution, Resource Management). The report compares both design and performance requirements as specified by the PSH user's group against current technological capabilities, RTOPS and US Army LHX design requirements. The study explores various design trade-offs and options available to the aircraft designer/manufacturer in order to meet the several criteria specified by the PSH user's group. In addition, the report includes a brief assessment of the feasibility of employing certain advanced rotorcraft designs to meet the stringent combination of operational capabilities desired by the Public Service Helicopter Users