Your SlideShare is downloading. ×

cognitive femtocell network by nisha menon k


Published on

cognitive femtocell network by nisha menon k

cognitive femtocell network by nisha menon k

Published in: Technology, Business
  • Be the first to comment

  • Be the first to like this

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

No notes for slide


  • 1. Cognitive Femtocell Networks An Opportunistic SpectrumAccessfor FutureIndoorWireless Coverage Nisha Menon K Roll No: 16 S2 MTECH FISAT 4March2014 1
  • 2. Outline • Introduction • Femtocell deployment challenges • Interference • Interference Mitigation In Cognitive Femtocell • Gale Shapley Algorithm Solution • GSOIA • Conclusion 4March2014 2
  • 3. INTRODUCTION 4March2014 3
  • 4. Femtocells • A femtocell is a small cellular base station designed for use in residential or small business environment. • It connects to the service provider’s network via broadband (such as DSL or cable) and typically supports 2 to 5 mobile phones in a residential setting. • A femtocell allows service providers to extend service coverage inside of your home - especially where access would otherwise be limited or unavailable - without the need for expensive cellular towers. • It also decreases backhaul costs since it routes your mobile phone traffic through the IP network. 4March2014 4
  • 5. Femtocells • As given in the Femto forum “ Femtocells are low-power wireless access points that operate in licensed spectrum to connect standard mobile devices to a mobile operator’s network using residential DSL or cable broadband connections ” • They are (similar to Wi-Fi) hotspots which will connect the subscriber to the cellular network using Broadband connection at subscribers home/office. • A femtocell is sometimes referred to as a “home base station”, “access point base station”, “3G access point”, “small cellular base station” and “personal 2G-3G base station”. 4March2014 5
  • 6. 4March2014 6
  • 7. Cognitive Radio 4March2014 7 enables secondary users to sense which portion of the spectrum are available (spectrum hole), select the best available channel, coordinate spectrum access vacate the channel when a primary user reclaims the spectrum usage.
  • 8. 4March2014 8
  • 9. Femtocell Deployment & Technical Challenges Dedicated channel deployment Partial channel sharing deployment Co-channel deployment 4March2014 9
  • 10. Macro layer coverage holes 4March2014 10
  • 11. Need for cognitive femtocell • Co-channel deployments of closed subscriber group femtocells cause coverage holes in macrocells due to co- channel interference. • Femtocells need licensed spectrum but the available radio resources are limited .The solution is to utilize the available spectrum efficiently. • Cognitive radio (CR) and Femtocell (FC) are both attractive technologies due to their marvelous potential to solve problems in current wireless communication systems. 4March2014 11
  • 12. COGNITIVE FEMTOCELLS • The creative combination of CR and FC, resulting in cognitive femtocell (CFC), will be an essential part of the future wireless communication systems. • In order to meet stringent requirements of the LTE Advanced standard, cognitive radio is integrated with femtocells to eliminate interference. • CR-enabled femtocells can actively sense their environment and exploit the network side information obtained from sensing to adaptively mitigate interference. 4March2014 12
  • 13. COGNITIVE FEMTOCELLS • Main characteristics of cognitive femtocell 4March2014 13 Cognitive Capability Self configuration capability
  • 14. Cognitive radio technology in femtocell 4March2014 14
  • 15. Cognitive Module 4March2014 15 Traffic Estimation MAC statistics Spectrum Sensing
  • 16. Self Configuration Module 4March2014 16 Spectrum mobility • Enables femtocells to smoothly perform handover • Minimizes the performance degradation Spectrum sharing management • Avoids co channel collisions of multiple femtocells Spectrum Configuration module • Ensures that femtocell work in the best available channels
  • 17. Steps in cognitive femtocell The cognitive module first senses the environment and collects specific information of all layers Then the cognitive engine analyzes spectrum characteristics and estimates available resources. The self-configuration module exploits cognitive information in a spectrum state database to optimize parameters of all layers in dynamic surroundings. 4March2014 17
  • 18. Cognitive Interference Mitigation 4March2014 18 Interference mitigation techniques Opportunistic interference avoidance Interference cancellation Interference alignment
  • 19. Opportunistic interference avoidance Information required: time frequency, location, antenna spatiality Interference mitigation: Exploit spectrum holes to avoid interference Interference cancellation Side information required: Channel gains, codebooks, and messages of macrocells Interference Mitigation: sphere decoding Interference alignment Side information required: Global channel state information Align all interference in half of the received signal space, and leave the other half interference-free for the desired signal. 4March2014 19
  • 20. The GSOIA solution • The goal is to opportunistically exploit spectrum holes to improve network spectral utilization 4March2014 20 Gale Shapley Algorithm Opportunistic Interference Avoidance
  • 21. The GSOIA solution 4March2014 21 Key ideas • With the opportunistic interference avoidance approach, CFAPs exploit spectrum holes obtained from sensing to avoid inter-tier interference • Gale Shapley Algorithm: A one-to-one policy to avoid multiuser collisions is utilized to mitigate intra-tier interference.
  • 22. Steps in OIA • CFAP listens to scheduled information from MBS • CFAP periodically senses spectrum to identify nearby MacUE • CFAP compares sensing outcomes with scheduled information to identify spectrum opportunities 4March2014 22
  • 23. Steps in GS Algorithm • Each CFAP first calculates the utility of every channel in a spectrum resource pool. Then the CFAP sets a backoff timer for every channel that is inversely proportional to channel utility. • When a backoff timer expires, the CFAP checks the busy tone of the corresponding channel. If there is no busy tone over this channel, CFAP immediately selects it for communications. Otherwise, CFAP abandons this channel and waits for next backoff timer expiration. • The process continues until each CFAP captures one channel or all channels are allocated. 4March2014 23
  • 24. 4March2014 24
  • 25. 4March2014 25 Gale-Shapley ping process. Utility matrix
  • 26. Performance Analysis 4March2014 26
  • 27. Advantages • Mitigate both inter tier and intra tier interferences • With the opportunistic interference avoidance approach, CFAP interweave their signals with those of macrocells without significantly impacting their communications. • Gale-Shapley spectrum sharing provides a one-to-one matching policy to avoid collisions among multiple femtocells 4March2014 27
  • 28. Summary and conclusion • Since both cognitive radio and femtocell are promising technologies to enable energy efficiency in wireless networks, the interplay between them improves energy efficiency. • CR enabled femtocells have good potential to break the spatial reuse barrier of cellular systems. • GSOIA provides one to one matching policy and avoid collisions among multiple femtocells. 4March2014 28
  • 29. References 4March2014 29 • [1] Li Huang, Guangxizhu and Xiaojiang ,” Cognitive Femtocell Networks:An Opportunistic Spectrum Access for Future Indoor Wireless Coverage” IEEE Wireless Commun., vol. 20, no. 2, 2013, pp. 44–51. • [2] K. Zheng, Y. Wang, W. Wang, “Energy-Efficient Wireless In-Home: the Need for Interference-Controlled Femtocells,” IEEE Wireless Commun., vol. 18, no. 6, 2011, pp. 36–44. • [3] A. Damnjanovic et al., “A Survey on 3GPP Heterogeous Networks,” IEEE Wireless Commun., vol. 18, no. 3, 2011, pp. 10–21. • [4] I. F. Akyildiz et al., “Next Generation/Dynamic Spectrum Access/Cognitive Radio Wireless Networks: A Survey,” Computer Network J., vol. 50, no. 13, 2006, pp. 2127–59. • [5] T. Yucek and H. Arslan, “A Survey of Spectrum Sensing Algorithms for Cognitive Radio Applications,” IEEE Commun.Surveys & Tutorials, vol. 11, no. 1, 2009, pp. 116–30. • [6]D. Lopez-Perez et al., “Interference Avoidance and Dynamic Frequency Planning for WiMAX Femtocells Networks,” Proc. IEEE Int’l. Conf. Commun. Sys., Nov. 2008,
  • 30. THANK YOU 4March2014 30