Phantom Cell Realization in LTE and its Performance Evaluation Hatim Lokhandwala, Vanlin Sathya and...

Phantom Cell Realization in LTE and its Performance Evaluation

Hatim Lokhandwala, Vanlin Sathya and Dr. Bheemarjuna Reddy TammaNetworked Wireless Systems Laboratory (NEWS Lab)

Dept. of Computer Science and EngineeringIIT Hyderabad, India

Dec 16, 2014

Motivation

Introduction to Phantom Based HetNet.

Major Challenges.

Architecture of Phantom UE, Phantom eNB and Initial Cell

Acquisition Procedure.

Performance Evaluation.

Conclusion

Hatim Lokhandwala ANTS 2014 1

Outline

[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.


References / Related Work

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


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.)


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


Existing Cellular Band Higher Frequency Band (> 3GHz)

eNB

eNB

eNB

PeNB

PeNB

eNB

X3

PeNB

Frequency Band and Network Topology


UE

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


PeNB

S1-D

Control and Data Plane Split


Core N/W

S1-C/D

C-Plane D-Plane

X-3

eNB

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


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


Protocol Stack of Phantom UE


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

(ControlTraffic)

Mode (Macro,Phantom)

UE

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


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


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


Random Access Mechanism (Contd.)


UE PeNBeNB

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 ResponseRRC Connection

Connection Established

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


Simulation ParametersParameters Values

Operating Freq. of Macro/Femto eNB 0.7 GHz

Operating Freq. of Phantom eNB 2.1 GHz

Building Dimensions 4 m X 4 m X 20 m

Macro/Femto eNB Height 30m

Phantom eNB Height 5m

Macro and Phantom/Femto transmit power 46 dbm and 20 dbm

UE maximum transmit power 0.2W

LTE mode FDD

System Bandwidth for eNBs 5 MHz

Simulation Time 100 secs


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 HetNetMacro 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 HetNetSimilar Configuration as B with Phantom eNBs being replaced by Femto eNbs.


Throughput Comparisons : Static Scenario


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.

Delay and Jitter Comparisons : Static Scenario


Throughput Comparisons : Mobility Scenario


A Mobile UE is introduced moving with velocities 1m/s, 3m/s, 5m/s, 10 m/s for different runs.

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


This work was funded by Deity, Govt. of India (Grant No. 13(6)/2010CC & BT).

IIT Hyderabad

Acknowledgements


Thank You

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Phantom Cell Realization in LTE and its Performance Evaluation Hatim Lokhandwala, Vanlin Sathya and...

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