1. Energy Efficient Spectrum Allocation for Green Radio in Two-tier Cellular Networks Wenchi Cheng, Hailin Zhang, Liqiang Zhao and Yongzhao Li Global Telecommunications Conference, 2009. GLOBECOM 2010. IEEE Reporter : 李後愷

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

3. 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

4. System model 4

5. 5

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

7. 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

8. 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. 9 Channel Model and Scheduling Strategy

10. BS & FAP Power Consumption 10

11. 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.

12. Spectrum allocation for green radio 12

13. 13

14. Simulation 14

15. Simulation 15

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

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