Modeling And Performance Analysis Of Energy Efficiency And Traffic In Wireless Networks

The rapidly growing data traffic demand and the continuously rising energyconsumption by infrastructure equipments in cellular networks will not only burden theoperating cost for network providers but also increase the carbon dioxide emissions intothe environment. Thus, to satisfy the traffic demand with energy use that cannot follow thetraffic growth significantly, the need for energy efficiency improvement, or say reductionof energy use per traffic bit that is carried in cellular networks, has become unavoidablyimportant, for both economical and environmental advantages. In this thesis, the issues ofenergy saving in cellular networks have been studied through traffic and energy efficiencymodeling and traffic controlling.Firstly, from an operating perspective, an energy efficiency model for cellularnetworks with Poisson-Voronoi Tessellation (PVT) coverage is proposed consideringspatial distributions of traffic load and power consumption. The spatial distributions oftraffic load and power consumption are derived for a typical PVT cell, and can be directlyextended to the whole PVT cellular network based on the Palm theory. Furthermore, theenergy efficiency of PVT cellular networks is evaluated by taking into account traffic loadcharacteristics, wireless channel effects and interference. Numerical results show that theburstiness of traffic load causes the energy efficiency of PVT cellular networks tofluctuate over a wide range. To optimize energy efficiency, a tradeoff between the fixedand the dynamic BS power consumption in accordance with traffic load variations shouldbe considered.Furthermore, from a life-cycle perspective, the embodied energy–consumed by allprocesses associated with the production of equipment is discussed and evaluated in thisthesis. A new cellular network energy efficiency model with embodied energy is proposed,and optimization between the number of cells and their coverage is investigated. Contraryto previous works, we have found that embodied energy accounts for a significantproportion of total energy consumption that cannot be neglected. The simulation resultsalso confirm an important trade-off between operating and embodied energies. Finally, based on aforementioned evaluations of energy efficiency models, wepropose a novel solution for an energy efficient use of cellular networks through trafficload balancing. By modeling the power consumption for BSs connected to uniformlydistributed users, the relationship between the optimal number of active (or shut down)BSs and the traffic load is then derived through the power ratio, which is the ratio betweendynamic and fixed power part of BS power consumption. Both analytical and simulationresults demonstrate that, in order to achieve significant energy savings, less BSs should beturned on at low traffic load while more BSs turned on at high traffic load.The results in this thesis provide some guidelines for the design of energy-efficientcellular access networks and insights into the energy efficiency optimization in cellularnetworks.