Energy Efficient Spectrum Allocation for Green Radio in Two-tier Cellular Networks Wenchi Cheng, Hailin Zhang, Liqiang Zhao and Yongzhao Li Global Telecommunications Conference, GLOBECOM IEEE Reporter : 李後愷

2 Outline  Introduction  System model  Model for energy consumption in downlink  Spectrum allocation for green radio  Simulation and results  Conclusion

Introduction  Green Radio, which aims to reduce energy consumption of information and communication technologies (ICTs).  Over 80% of the power in mobile communications is consumed in the radio access network, especially cost in base stations.  Actually, there are already a lot of energy efficient strategies in cellular access networks. However, these strategies mainly focus on smart ends with uplink energy constrains. 3

System model 4

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6 The mean number of femtocells per cell site is readily obtained as Users are assumed to be uniformly distributed inside each cell site

System model  Two main different strategies for femtocell access have been proposed so far:  Public Access where all the users can access all the femtocells of a given operator.  Private Access where only the subscriber of the femtocell and a list of invited users can access a given femtocell.  U = Um+NfUf denote the average number of users per cell with Um and Uf referring to the number of outdoor users of per macrocell and indoor users of per femtocell respectively  Green factor: the b/J power efficiency per subchannel. 7

Channel Model and Scheduling Strategy  Three factors have bad effects on signal quality: path loss, shadowing (slow fading), multipath fading (fast fading)  Each BS assigns rate adaptively based on the received SIR per user  We assign: 8

9 Channel Model and Scheduling Strategy

BS & FAP Power Consumption 10

Spectrum allocation for green radio 11  According to recent surveys, over 50 percent of calls and 70 percent of data services will take place indoors in the future.

Spectrum allocation for green radio 12

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Simulation 14

Simulation 15

Conclusion  Maximizing the green factor under spatial spectral efficiency is an effective way to improve energy efficiency 16

每週一句  Have + pp.  Had + pp.  Past tense now 17