Energy management issues in lte.pptx
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Transcript of Energy management issues in lte.pptx
Energy Management Issues in LTE
Prepared By : Gaurang RathodResearch ScholarWireless CommunicationIndia
Agenda
Introduction
Energy Usage and Traffic Pattern of Traditional and Emerging Internet Application
Energy Management in LTE and DRX
Power Saving Techniques
Solutions in LTE Advanced Release 11
Future Update Scope in LTE
Conclusion
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Long Term Evolution
LTE is a standard for wireless data communication and evolution of the GSM/UMTS standards.
Redesign and simplification of the network architecture to an IP- based system with significantly high data rate and reduced transfer latency.
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LTE Network Architecture
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[Source:Technical Overview of 3GPP Long Term Evolution (LTE) Hyung G. Myung http://hgmyung.googlepages.com/3gppLTE.pdf ]
E-UTRAN Architecture
5[Source: E-UTRAN Architecture(3GPP TR 25.813 7.1.0)]
User Plane Protocol Stack
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RLC and MAC sub layers perform the following functions - Scheduling- ARQ- HARQ
PDCP - Ciphering- Integrity Protection- Header Compression
[Source: E-UTRAN Architecture(3GPP TR 25.813 7.1.0 )]
Control Plane Protocol Stack
7[Source: E-UTRAN Architecture(3GPP TR 25.813 7.1.0 )]
Continue…
The various functions performed by RRC- Broadcast and Paging- RRC connection management- Mobility functions- UE measurement reporting and control
NAS (Non Access Stratum)performs- Authentication- Idle mode mobility handling- Paging origination- Security control for the signaling between aGW and UE
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Traffic Pattern and Energy Usage
The user equipment (UE) stays in RRC_Connected state during active sessions and moves to RRC_Idle during inactive sessions
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Figure: Traffic characteristics of traditional application
Continue…
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UE often ends up moving between connected and idle states frequently to send mostly short bursts of data
Draining device battery and causing excessive signaling overhead in LTE networks
Figure: Traffic characteristics of emerging internet application
Problems with Emerging Traffic Pattern
Time spend in connected state is more compared to idle state
In connected state, UE listen to the network and receive/transmit data. Thus consumes higher power (i.e. about 1–1.5 W)
Excessive signaling is required due to frequent transition between connected and idle states
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RRC States and Tail Time
Tail Time : Time defined by network during which no packet activity in connected state is done then UE transit to RRC_Idle state
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Inactivity Timer and Signaling Overhead
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As inactivity timer time increases, 1. Signaling overhead is decrease2. Duration of connected state is increase
Traffic Type
Ratio of total data exchanged to total signaling overhead for various inactivity timer values
1 s 5 s 10 s 15 s
Active Session
1000 3000 5000 10000
Background Session
40 100 180 270
Discontinuous Reception (DRX)
DRX cycle optimized for power savings generally leads to potentially increased delay, affecting the user experience for delay-sensitive traffic.
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Power Saving Techniques
1. Always Connected with DRX
2. Fast Transition to Idle
3. Adaptive DRX Switching
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Always Connected with DRX UE stays in connected all the time
Effectively eliminating the signaling overhead
To save power, parameters for DRX mechanism is chosen to be similar to when the UE is in idle state
Example A high value of long DRX cycle and smaller value of
inactivity timer
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Drawbacks of Always Connected with DRX
If the UE moves between cells frequently while creating little traffic activity, it will frequently be performing handovers from one cell to another.
A handover from one cell to another requires transfer of all the UE’s configuration information from one eNB to another and is very signaling-intensive.
When in idle state, the UE does not have to perform handovers.
To maintain connectivity, UE has to perform various operations periodically such as scanning and providing periodic channel quality feedback measurements to the eNB, all of which also consume power.
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Fast Transition to Idle
UE indicates its desire to go to Idle state to the network and network allow UE to switched to idle state without waiting for inactivity timer expire.
Tail time is reduced or eliminated entirely.
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Drawbacks of Fast Transition to Idle
If the UE starts requesting connection releases very frequently. Excessive transitions also increase the battery power consumption.
A prohibit timer can be used to define minimum wait time between successive requests.
The eNB may also impose an upper limit on the number of requests in a predefined time window.
If the UE crosses the limit, it will be prohibited from sending further Fast Transition to Idle requests for the remaining duration of the time window.
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Adaptive DRX Switching
The DRX parameters are switched so as to adapt to ongoing traffic activity to obtain the requisite balance between power savings and performance.
Power Saving : making the DRX long cycle longer (i.e., longer sleep in each cycle) and more frequent (i.e., shorter Inactivity Timer)
Performance(Delay) : making the DRX long cycle shorter and longer Inactivity Timer
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Continue…
UE has the information on remaining battery power, the number and type of applications running on the device.
It is better for the UE to indicate to the network to which DRX configuration to switch.
This technique has a much better balance between low power and low delay vs. using only a single DRX configuration optimized for either power or performance.
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Solution Adopted in 3GPP Release 11
UE assistance mechanism was adopted that enables UE to send its preference to the network.
Power Preference Indication Bit : UE can now send a single bit to indicate its preference for power saving
Future Update Scope
A single bit of PPI may not be sufficient to express UE’s various power preferences
Multiple bits of PPI may need to be incorporated in future 3GPP releases so that UE can better inform the network.
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Conclusion
The traffic profile of emerging mobile Internet applications
differs from the traditional traffic profile as it consists of a
constant stream of random aperiodic traffic comprising very
small amounts of data during Inactive sessions, causing the UE
to frequently transition between Connected and Idle states.
Adaptive DRX is one of the main mechanisms envisioned as a
potential solution. It has been shown that DRX configuration
switching is desirable to adapt the requirements of running
applications and to maintain a trade-off between power saving
and latency requirements.
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References
1. M.Gupta, S. C. Jha, A. T. Koc, and R. Vannithamby,"Energy impact of emerging mobile internet applications on LTE networks: issues and solutions," Communications Magazine, IEEE , vol.51, no.2, pp.90,97, February 2013.
2. C. Bontu and E. Illidge, “DRX Mechanism for Power Saving in LTE,” IEEE Commun. Mag., vol. 47, no. 6, June 2009, pp. 48–55.
3. S. C. Jha, A. T. Koc, and R. Vannithamby, “Optimization of Discontinuous Reception (DRX) for Mobile Internet Applications Over LTE,” Proc. IEEE VTC-Fall ’12, Quebec, Canada, Apr. 2012.
4. “LTE RAN Enhancements for Diverse Data Applications,” 3GPP TR 36.822, V11.0.0, Sept. 2012.
5. www.tutorialspoint.com/lte/lte_quick_guide.htm
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Thanking You