On the impact of interference to the performance of home femtocell

1. On the impact of interference to the performance of home femtocell Zhong Zheng Supervisor: Pro. Jyri Hämäläinen Instructor: Mika Husso, Edward Mutafungwa

2. What is femtocell? • Low manufacturing cost, short radio coverage home base station operates in licensed spectrum • Radio traffic is backhauled by premises broadband connection (DSL) to mobile network • Femtocell CPEs are deployed by subscribers. Uncoordinated cell deployment

3. Radio interface limitation in current 3G network • Macrocell base station covers up to a few hundred square meters area and Signal quality decays along with transmit distance in the form of • Under non-line-of-sight condition, signal is blocked by large shadowing or building wall at 2GHz band

4. Why femtocell? • Technical motivation • Reduced separation distance between transmitter and receiver • Interference is isolated by building structure • Limited number of users • Business motivation • Half of voice calls and a majority of data traffic originate indoor • Operators expand network capacity and coverage without much investments on infrastructure. • Subscribers get better radio service at low price

5. 3GPP standardization • New interface Iuh is created between femto base station and HNB-GW • HNB-GW utilizes standard Iu interface to mobile network • Iuh traffic is tunneled through public Internet • In 3GPP Release 8, femtocell access is granted to Close Subscriber Group (CSG). Handover between femtocells is not allowed.

6. Technical challenge • Co-channel interference from macrocell tier and femtocell tier • Self-establishment and self-configuration • QoS management with unreliable broadband backhaul

7. Building structure: multiple dwelling units • A regular building structure and each apartment/house admits same room layout • Grid layout to simplify the model

8. Simulation parameters

9. Effect of building dimension • As building dimensions decrease, the CDF curves approach interference free case but result in a similar outage rate • Indoor radio propagation is locally restricted by building structure and do not spread far from residing apartment

10. Main interference • Regarding to central apartment, the biggest uplink interference source is mainly distributed in the neighboring apartment

11. Flexible spectrum usage • An exclusive band reduces the average uplink transmit power and CDF curves approach interference free case • Outages are not affected due to dominance of indoor interference Shared band usage Exclusive band usage

12. Flexible spectrum usage cont. • A flexible usage scheme allocates a primary band for femtocell and allows femtocell user to do inter-frequency handover to macrocell band as secondary user • By assumption 10% of femtocell users are allowed to handed over to macrocell band, the outage rates are efficiently reduced.

13. Mobile teletrauma service : a use case • Emergency teletrauma service delivered by 3G femtocell from patient apartment • Offer on-site personnel with videoconferencing and other rich multimedia medical data transfer from remote surgeon • Mobile equipment uses nearby femtocell base station either in own apartment or in neighboring apartment

14. Environment description • The number of femto base stations follows market statistics-femtocell penetration ratio • System level simulations are repeated for high-rise apartment block building and terraced houses

15. Simulation result – high-rise building

16. Simulation result – terraced house

17. Simulation result cont. Service can be delivered given that certain femtocell penetration is attained. At 95th percentile outage rate, penetration ratio 0.43 and 0.8 are needed for high-rise building and terraced houses.

18. Conclusion and future work • Femtocell extends the high-data rate service coverage of UMTS to indoor environment • Higher spectral efficiency due to short range and well isolation • With massive deployment, a solution for ubiquitous mobile broadband access • A range of case studies verify CSG femtocell operation • Interference locally distributed • Flexible spectrum scheme is efficient to reduce uplink outage rate • Mobile teletrauma use case: • With a certain level of femtocell penetration ratio, the service can be delivered with sufficient low outage rate • At least an order of magnitude reduction in service outage rates when femtocells are utilized, compared with macrocell only case • Downlink direction study is also interesting and beneficial to complete the use case study. In the long term, the research direction is LTE femtocell.

19. Reference [1] Vikram Chandrasekhar, Jeffrey G. Andrews, and Alan Gatherer. Femtocell networks: A survey. CoRR, abs/0803.0952, 2008. [2] Harri Holma and Antti Toskala. WCDMA for UMTS: HSPA Evolution and LTE. John Wiley & Sons, Inc., New York, NY, USA, 2007. [3] M. Husso, J. H¨am¨al¨ainen, R. J¨antti, and A.M. Wyglinski. Adaptive antennas and dynamic spectrum management for femtocellular networks: A case study. DySPAN 2008. 3rd IEEE Symposium on, pages 1–5, Oct. 2008. [4] M. Husso, J. Hämäläinen, Jäntti, and et. al. Interference suppression by practical transmit beamforming methods in closed femtocells. EURASIP Journal on Wireless Communications and Networking, 2009. [5] H. Claussen. Performance of macro- and co-channel femtocells in a hierarchical cell structure. PIMRC 2007. IEEE 18th International Symposium on, pages 1–5, Sept. 2007. [6] H. Claussen, L.T.W. Ho, and L.G. Samuel. Self-optimization of coverage for femtocell deployments. WTS 2008, pages 278–285, April 2008. [7] H. Claussen, F. Pivit, and LTW Ho. Femtocell coverage optimization using switched multi-element antennas.ICC 09. [8] 3GPP. 3G Home NodeB Study Item Technical Report. TR 25.820, 3rd Generation Partnership Project (3GPP), September 2008.

20. Question ? Thank you!