The 8th International Workshop on Small Cell and HetNet 21 May and diversity antennas for femtocells. Interference mitigation.

Transcription

1 The 8th International Workshop on Small Cell and HetNet 21 May 213 Interference mitigation and diversity antennas for femtocells Yue Gao (Frank)

2 Outline Overview Interference Scenarios in Femtocell networks TV White Space and geolocation database model Cross-tier Interference Mitigation in Suburban Femtocell Deployment Dual-mode diversity antenna for Femtocell base stations Ray tracing channel model for an indoor scenario 2

3 Interference Scenarios in Femtocell networks Index Aggressor Victim Interference Type Transmission Mode 1 Macro UE Femto BS Cross-tier Uplink 2 Macro BS Femto UE Cross-tier Downlink 3 Femto UE Macro BS Cross-tier Uplink 4 Femto BS Macro UE Cross-tier Downlink 5 Femto UE Femto BS Co-tier Uplink 6 Femto BS Femto UE Co-tier Downlink Current solutions: Fractional frequency reuse and resource partition; Power control of HeNBs; Collaborative frequency scheduling; 3

4 TV White Space (TVWS) Digital Switchover (DSO) Location-dependent availability Cognitive access methods Use cases Beacon Spectrum sensing Geo-location database Machine-to-Machine Communications Short Range Wireless Access Network Wireless Regional Access Network 4

5 Motivation Obtaining locally available TVWS information using cognitive access method. Utilizing locally available TVWS for Femtocell networks. Designing appropriate resource allocation schemes based on the available TVWS to reduce the interference in Femtocell networks in different deployment scenarios. 5

6 Geo-location Database Model Adopt power control strategy to dynamically determine the maximum allowable transmit power for CR stations Build up the Geo-location database Model 1) Establishing the DTV Station database 2) Calculation of available TVWS channels 3) Calculation of associated maximum allowable transmit power 6

7 Geo-location Database Model The proposed power-control database model is more efficient in obtaining TVWS information than the keep-away region model, e.g. more available TVWS channels obtained with various maximum allowable transmit power. Available TVWS information in Glasgow (NS595655) by power-control model Channel No Max. EIRP (watts) Available TVWS information in Glasgow (NS595655) by keep-away region model Channel No Max. EIRP (watts)

8 TVWS Geo-location Database Model Mobile Phone Application of Geo-location Database Models Android app can be downloaded from 8

9 Cross-tier Interference Mitigation in Suburban Femtocell Deployment The proposed system architecture The Geo-location database model to obtain locally available TVWS information A novel resource allocation scheme using the locally available TVWS to mitigate the downlink cross-tier interference between Macro UEs and nearby Femtocells. Femtocell Classification Resource Allocation 9

10 Simulation set-up Simulation parameters Parameter Assumption Femtocells per macrocell 5 Femto UEs per femtocell 2 Number of Macro UEs 5 Macrocell Radius 288m Femtocell Radius 12m Wall Penetration Loss 1dB/2dB System Bandwidth 1MHz Total No. of RBs 5 RB Bandwidth 18kHz Total enb Transmit Power 46dBm HeNB Transmit Power 2dBm Thermal Noise -174dBm/Hz SINR Threshold -8dB Available TVWS information results from Geolocation database (Simulated location: Queen Mary, University of London) NGR Number of location: TQ36823 Channel No Maximum Allowable EIRP(watts) Minimum Distance between UE and enb Minimum Separation between UE and HeNB 35m 2cm 1

11 Cross-tier Interference Mitigation in Suburban Femtocell Deployment The proposed scheme reduced the cross-tier interference significantly. 1 Empirical CDF percentile.6 CDF Traditional.1 Proposed DRP MUE Total Interference (dbm) 11

12 Cross-tier Interference Mitigation in Suburban Femtocell Deployment The proposed scheme performed better in the scenarios of more dense Femtocell distribution or smaller Macrocell. F. Peng, N. Wang, Y. Gao, L. Cuthbert and X. Zhang, Geo-location Database based TV White Space for Interference Mitigation in LTE Femtocell Networks, The Fourteenth International Symposium on a World of Wireless, Mobile and Multimedia Networks, IEEE WoWMoM 213, 4-7 June 213, Madrid, Spain. (To be appear) 12

13 Summary for Cross-tier Interference Mitigation in Femtocell networks TVWS in a Geo-location database to address the downlink cross-tier interference in LTE femtocell networks. The proposed scheme can reduce the downlink interference suffered by Macro UEs by more than 3dB and 2.5dB at the 7% percentile of the CDF diagram in comparision with the traditional all-shared scheme and the dynamic resource partitioning scheme, respectively. The proposed scheme had better performance in the scenarios of dense femtocell distribution and small macrocells. 13

14 Dual-mode diversity antenna for Femtocell base stations The diversity antennas were modelled and optimised in CST Microwave studio. Simulated 3D radiation patters Measured and simulated 2D radiation patters Y. Gao, S. Wang, O. Falade, X. Chen, C. G. Parini and L. G. Cuthbert, "Mutual coupling effects on pattern diversity antennas for MIMO femtocells," Hindawi International Journal of Antennas and Propagation, special issue on "Mutual Coupling in Antenna Arrays", DOI:1.1155/21/756848, Volume 21 (21)

15 Fabrication and measurement prototype 16 Radiator Shorting post Ground plane Conical mode SMA feeding (S22) 16 Hybrid ring Z Broadside mode feeding (S11) Y X Broadside mode feeding (S11) Anechoic chambers 15

16 Design S-parameters -5 Measured S12 Simulated S12 Amplitude/dB Measured S11 Simulated S11 Measured S22 Simulated S22 Amplitude/dB Design 2 Amplitude/dB Frequency/GHz Frequency/GHz Port Port 1 with a chip resistor Port Frequency/GHz Port 4 16

17 Ray tracing channel model simulation set-up Material properties used at 2.1 GHz Material Permittivity Conductivity Thickness Concrete (Wall, floor and ceiling) m Wood (Door) m Glass (Window) m Mutual coupling levels of the antennas Antenna Types for FAP Dual ideal dipole antennas Dual dipole antennas (λ/4) Proposed antenna design 1 Proposed antenna design 2 Mutual coupling levels No coupling -8.5dB coupling -12dB coupling -3dB coupling 17

18 Ray tracing channel model simulation set-up RoomA 16 metres RoomB Rx3 Rx1 FAP Rx2 X Rx4 Y Receivers 45 metres FAP Corridor Offices and Labs 18

19 Channel capacity formulaiton A 2 x 2 MIMO system s capacity can be calculated as Pk ρ C( ρ) = log2 det In + HH n where H is the normalized n x n channel matrix, I is the identity matrix and ρ is the SNR. With a narrowband assumption, the channel response H is given by M jθk j2π fτk hij = Pk e e k =, θ τ k and k are the received power, phas and time delay of the k-th ray respectively. M is the total number of rays. So that for a 2 x 2 MIMO case, channel realization the H matrix can be built as H h1,1 h1,2 = h2,1 h 2,2 19

20 Channel capacity for different receivers at Room A and B Rx1 at Room A SI SO Dual i deal di pol e Pr oposed Desi gn 1 Pr oposed Desi gn 2 Rx2 at Room A SI SO Dual i deal di pol e Pr oposed Desi gn 1 Pr oposed Desi gn 2 Prob. x < abscissa Prob. x < abscissa Channel Capacity (bit/sec/hz) Rx3 at Room B Prob. x < abscissa SI SO Dual i deal di pol e Pr oposed Desi gn 1 Pr oposed Desi gn Channel Capacity (bit/sec/hz) Channel Capacity (bit/sec/hz) Rx4 at Room B Prob. x < abscissa SI SO Dual i deal di pol e Pr oposed Desi gn 1 Pr oposed Desi gn Channel Capacity (bit/sec/hz) 2

21 Summary for the diversity antennas Two pattern diversity antennas operating from 1.68GHz to 2.5GHz for femtocell base stations with mutual coupling of -12dB and -3dB, respectively. The channel capacity of the proposed Design 2 with very low mutual coupling (-3dB) is close to that of an ideal dipole array without mutual coupling in most cases. The exception case from the results shows that the channel capacity not only depends on the mutual coupling levels but also on the propagation environment. A mutual coupling of -12dB is a reasonable level to maintain a good channel performance and there is no need to obtain a very low mutual coupling in Design 2 at the expense of the diversity antenna performance, such as impendence bandwidth and compactness. 21

22 Special issue on Base Station Antennas for Small Cell or Large-Scale Multiple-Antenna Systems- 1 International Journal of Antennas and Propagation A comprehensive antenna system with beamforming, gain, polarization, patterns for effective enhancement of performance is required. This call for papers aims to have papers with feasible and great potential antenna designs for the base station in a small cell or large-scale multiple-antenna systems. Potential topics include, but not limited to: Multiband and broadband antennas Reconfigurable antennas Multisystem array antennas High directivity beamforming antennas Flexible compact antennas Bendable reconfigurable array antennas Ultrawideband antennas Smart and semi-smart antenna design Low profile compact antennas Circular polarized and dual polarized antennas Multibeam adaptive base station antennas Low mutual coupling effect array antennas 22

23 Special issue on base station antennas - 2 Lead Guest Editors Yue GAO (Frank), EECS, Queen Mary University of London, UK; Cyril LUXEY, EPIB, University Nice Sophia-Antipolis, France; Zhaobiao LV, China Unicom Research Institute, China. Manuscript Due October 25, 213 First Round of Reviews January 17, 214 Publication Date March 14, 214 Before submission authors should carefully read over the journal's Author Guidelines, which are located at Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at 23