Energy-Delay Tradeoffs of Virtual Base Stations With a Computational-Resource-Aware Energy Consumption Model

The next generation (5G) cellular network faces the challenges of efficiency, flexibility, and sustainability to support data traffic in the mobile Internet era. To tackle these challenges, cloud-based cellular architectures have been proposed where virtual base stations (VBSs) play a key role. VBSs bring further energy savings but also demands a new energy consumption model as well as the optimization of computational resources. This paper studies the energy-delay tradeoffs of VBSs with delay tolerant traffic. We propose a computational-resource-aware energy consumption model to capture the total energy consumption of a VBS and reflect the dynamic allocation of computational resources including the number of CPU cores and the CPU speed. Based on the model, we analyze the energy-delay tradeoffs of a VBS considering BS sleeping and state switching cost to minimize the weighted sum of power consumption and average delay. We derive the explicit form of the optimal data transmission rate and find the condition under which the energy optimal rate exists and is unique. Opportunities to reduce the average delay and achieve energy savings simultaneously are observed. We further propose an efficient algorithm to jointly optimize the data rate and the number of CPU cores. Numerical results validate our theoretical analyses and under a typical simulation setting we find more than 60% energy savings can be achieved by VBSs compared with conventional base stations under the EARTH model, which demonstrates the great potential of VBSs in 5G cellular systems.Comment: 5 pages, 3 figures, accepted by ICCS'1

Sveobuhvatno mjerenje i evaluacija sustava visokobrzinskog pogonskog vretena

Reducing the manufacturing time is the trend of high precision manufacturing, and the precision of a work-piece is very important for the manufacturing industry. The high-speed motorized spindle is the most critical part and becoming more widely used in the machine tool at present, and its precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and effects of the spindle’s thermal deformations; hence, how to roundly measure and objectively evaluate a high-speed spindle is an inevitable question. Because the comprehensive dynamic properties and evaluation system of spindles directly affect the cutting ability of the whole machine tool before they are manufactured. This paper presents a comprehensive measurement and evaluation system of a high-speed motorized spindle, which reflect the overall performance of motorized spindle and bases on an international standard.Smanjenje proizvodnog vremena tendencija je u visoko preciznoj proizvodnji, pri čemu je preciznost radnog komada vrlo važna u proizvodnoj industriji. Pri tome je visokobrzinsko pogonsko vreteno jedan od najkritičnijih dijelova koji se naširoko koristi u alatnim strojevima, pa njegova preciznost predstavlja važnog čimbenika u sveukupnoj izvedbi visokobrzinskog rezanja. Mnoge studije o visokobrzinskom rezanju su fokusirane na sile rezanja, vibraciju vretena kao i na efekte toplinske deformacije vretena; stoga, kako propisno mjeriti i objektivno evaluirati visokobrzinsko vreteno jedno je od neizbježnih pitanja. Jer sveobuhvatna dinamička svojstva i evaluacija sustava vretena izravno utječu na rezna svojstva cjelokupnog alatnog stroja, prije no što je proizveden. Ovaj rad prikazuje sveobuhvatno mjerenje i evaluaciju visokobrzinskog pogonskog vretena, koja se odražavaju na sveukupne odlike pogonskog vretena, a koja se bazirana na međunarodnim standardima