1. Phantom Cell Realization in LTE and its Performance Evaluation Hatim Lokhandwala, Vanlin Sathya and Dr. Bheemarjuna Reddy Tamma Networked Wireless Systems Laboratory (NEWS Lab) Dept. of Computer Science and Engineering IIT Hyderabad, India Dec 16, 2014

2.  Motivation  Introduction to Phantom Based HetNet.  Major Challenges.  Architecture of Phantom UE, Phantom eNB and Initial Cell Acquisition Procedure.  Performance Evaluation.  Conclusion Hatim LokhandwalaANTS 2014 1 Outline

3. [1] http://www.cisco.com/c/en/us/solutions/collateral/service- provider/visual-networking-index-vni/white paper c11-520862.html [2] V. Chandrasekhar, J. G. Andrews, and A. Gatherer, “Femtocell networks: a survey” Communications Magazine, IEEE, vol. 46, no. 9, pp. 59–67, 2008. [3] H. Ishii, Y. Kishiyama, and H. Takahashi, “A novel architecture for lte-b: C- plane/u-plane split and phantom cell concept,” in GC Wkshps, 2012 IEEE, pp. 624–630, IEEE, 2012. Hatim LokhandwalaANTS 2014 2 References / Related Work

4.  Tremendous increase in cellular traffic due to the availability of wide range of devices : smart phones, net-books, tablets etc.  Mobile Data is expected to register a growth of almost 11 times in the next 4 years, reaching 18 exa-bytes per month by 2018 [1].  Mobile video will account for 69% of all mobile data by 2018, up from about 53% in 2013 [1]. Band width Demand is increasing. Hunger for Higher Data Rates. Motivation Hatim LokhandwalaANTS 2014 3

5.  Existing Approaches for outdoor environment includes deployment of Femto eNBs with Macro eNBs forming Femto based HetNet.  Existing Approaches for indoor environments includes deployment of WiFi networks, Femto cells and Distributed Antenna Systems (DAS).  However there is a need for a solution that works in all environments. Femto based HetNets are an option [2].  However Femto based HetNets incur a lot of handover overheads in case of highly mobile users. Motivation (Contd.) Hatim LokhandwalaANTS 2014 4

6.  Phantom eNBs are small eNBs operating on high frequency band (3 GHz spectrum).  Phantom eNBs are of smaller height as compared to Macro eNBs.  Coverage area under Phantom eNB is called as Phantom cells, while coverage area of Macro eNB is called as Macro cells. Phantom eNB Hatim LokhandwalaANTS 2014 5

7. Existing Cellular Band Higher Frequency Band (> 3GHz) eNB PeNB eNB X3 PeNB Frequency Band and Network Topology Hatim LokhandwalaANTS 2014 6 UE

8.  In a Phantom based HetNet a centralized controller (Macro eNB) controls operation of multiple Phantom eNBs under its coverage area, serving the user base.  Control Plane is supported by a continuous realizable coverage layer at lower frequency band i.e. Macro eNB.  Data Plane is supported by Phantom eNBs at higher frequency band.  Macro and Phantom eNB communicate via X3 interface (point- to-point fiber optic connection) Phantom Based Het Net Hatim LokhandwalaANTS 2014 7

9. PeNB S1-D Control and Data Plane Split Hatim LokhandwalaANTS 2014 8 Core N/W S1-C/D C-Plane D-Plane X-3 eNB

10.  Facilitate communication to Macro and Phantom eNBs simultaneously which are operating at different frequency bands.  A UE has to time synchronize with both the eNBs so as to have proper data transfer.  Segregating and categorizing parts of control and the data plane and to specify a definitive boundary between them is a challenging issue.  Macro eNB has to take care of both control and data plane if UE is not in the vicinity of any Phantom eNB. Challenges Hatim LokhandwalaANTS 2014 9

11.  Demand: Simultaneous Reception and Transmission from the Macro eNB (2.5 GHz spectrum) and the Phantom eNB (3 GHz spectrum).  Addition of an extra radio (i.e. UE Phantom Physical Layer) to the existing UE protocol stack.  Higher Layers maintain the information that whether the UE is in phantom mode or in Macro mode.  In Phantom mode, the data from higher layers would be sent through new radio to Phantom eNB.  Any downlink data from Phantom eNB would go up the existing passing through new radio. Protocol Stack : Phantom UE Hatim LokhandwalaANTS 2014 10

12. Protocol Stack of Phantom UE Hatim LokhandwalaANTS 2014 11 UE_Phantom Physical Layer UE_Macro Physical Layer MAC Layer RLC Layer PDCP Layer RRC Layer NAS IP (Data Traffic) PDCP Control RRC Control MAC Control (Control Traffic) Mode (Macro,Phantom) UE

13.  UE tries to find PSS from both the Macro and Phantom eNBs.  No MIB from Phantom eNB.  MIB from Macro eNB is modified to include the information of downlink bandwidth of Phantom eNB as well.  If signal strength from Macro eNB is higher than a nearby Phantom eNB, then UE would be connected to Macro eNB for both control and data transfer.  Other wise UE would be attached to the Phantom eNB for data transfer and Macro eNB for control transfer. Initial Cell Acquisition Procedure Hatim LokhandwalaANTS 2014 12

14.  Layers in Phantom eNB protocol stack are similar to traditional eNB stack but with modifications in functionality.  Phantom eNB is connected just to P-GW and there is no connectivity with MME (Mobility Management Entity).  Macro eNB would perform UE authentication.  Phantom eNB merely stores information that whether UE is authenticated or not.  Two main mechanisms are performed by Macro eNB on behalf of Phantom eNB. 1. Random Access and RRC Connection Set Up. 2. Paging. Protocol Stack : Phantom eNB Hatim LokhandwalaANTS 2014 13

15.  Macro eNB maintains the information that UE is connected to it just for control or control and data transfer both.  Random Access request arrives at Macro eNB.  If UE is attached to Phantom eNB for data transfer random access request is forwarded to appropriate Phantom eNB.  Phantom eNB then assigns a temporary C-RNTI and also determines the timing advance for UE.  Macro eNB assigns resources to UE for transmitting RRC connection request.  Phantom eNB performs contention resolution. Random Access Mechanism Hatim LokhandwalaANTS 2014 14

16. Random Access Mechanism (Contd.) Hatim LokhandwalaANTS 2014 15 UE PeNB eNB If UE attached to PeNB for data then random access req. forwarded. Random Access RRC Connection Req. eNB reserves resources for UE RRC connection req. Forward Random Access Assigns Temp ID and respond to eNB Random Access Response RRC Connection Req. RRC Connection Response RRC Connection Connection Established

17.  S-GW gets the downlink data which it forwards to MME.  MME informs all Macro eNBs under its tracking area about the paging message.  Macro eNB configures at which sub-frames a UE should wake up and perform paging.  Phantom eNB does not send any of the paging messages as it is not connected to MME.  UE performs a match for P-RNTI in paging message and performs random access as explained previously. Paging Hatim LokhandwalaANTS 2014 16

18. Simulation Parameters Parameters Values Operating Freq. of Macro/Femto eNB0.7 GHz Operating Freq. of Phantom eNB2.1 GHz Building Dimensions4 m X 4 m X 20 m Macro/Femto eNB Height30m Phantom eNB Height5m Macro and Phantom/Femto transmit power46 dbm and 20 dbm UE maximum transmit power0.2W LTE modeFDD System Bandwidth for eNBs5 MHz Simulation Time 100 secs Hatim LokhandwalaANTS 2014 17

19. Experimental Set Up  Configuration A : Macro only Network Macro eNB position : (0,0,0) UE positions : (20,i,0) and (-20,i,0) where i = j * 45 [0≤ j ≤4]. No Phantom eNB are deployed in this scenario.  Configuration B : Phantom based HetNet Macro eNB position : (0,0,0) UE positions : (20,i,0) and (-20,i,0) where i=j*45 [0 ≤ j ≤4]. Phantom eNB positions : (15,i,0) and (-15,i,0) where i=j*45 [0 ≤ j ≤4].  Configuration C : Femto Based HetNet Similar Configuration as B with Phantom eNBs being replaced by Femto eNbs. Hatim LokhandwalaANTS 2014 18

20. Throughput Comparisons : Static Scenario Hatim LokhandwalaANTS 2014 19  TCP flows are installed over each of the UEs to transfer 1 MB of data from each of the UEs to a Remote Host and vice versa.  80% increase in throughput is observed when UEs are attached to Phantom eNB.

21. Delay and Jitter Comparisons : Static Scenario Hatim LokhandwalaANTS 2014 20

22. Throughput Comparisons : Mobility Scenario Hatim LokhandwalaANTS 2014 21 A Mobile UE is introduced moving with velocities 1m/s, 3m/s, 5m/s, 10 m/s for different runs.

23.  Mechanisms to split the control and data plane among Macro and Phantom eNBs are designed.  Architectural changes in the UE protocol stack were made to enable communication at dual bands.  Exchange of information between Phantom and Macro eNB over the X3 interface is facilitated.  In future, we plan to move more of the control messages to the Macro eNB with bare minimum control data to be handled by the Phantom eNB. Summary and Future Work Hatim LokhandwalaANTS 2014 22

24.  This work was funded by Deity, Govt. of India (Grant No. 13(6)/2010CC & BT).  IIT Hyderabad Acknowledgements Hatim LokhandwalaANTS 2014 23