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Department nameRenesas Mobile Corporation
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2012/3/28
LTE on Shared Bands (LEONARD)
Kari Rikkinen
TEKES TRIAL seminar 15.02.2012
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Introduction
LTE on Shared Bands (LEONARD)
RME research project in Tekes Trial programme one of the parallel industry projects related to the CORE
project
duration 1.1.2011-31.12.2011 (an extension project included inTekes Trial programme in 2012)
Project focus
LTE technology applicability to shared band operation
LTE and WLAN technology coexistence in same frequency band
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LTE on Shared Bands - examples
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*) *) ERC Dec 11(06)
IMT possible in 3.4-3.8 GHz
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Possible frequency bands for shared bandoperation with LTE technology
ISM 2.4GHz/ 5GHz Open for use if the regulation requirements are met (example of regulation requirements in Europe in separate
slide)
Unlicensed spectrum also available on frequency band below 1GHz (e.g. 902-928 MHz on ITU-R region 2)
Television White Spaces In general, TVWS spectrum (e.g., within 470-790 MHz band in Europe) can be one of suitable resources to
extend LTE systems operation Currently very diverse spectrum utilization opportunities (e.g. in Europe) Spectrum could be allocated for secondary use in spectrum blocks of N x TV channel bandwidth (N 1)
TV channel bandwidth 6 MHz in US, and 8 MHz in Europe
FCC has defined rules and regulations for operation No secondary system coexistence requirements (yet) Main intention is to protect the incumbent user
OFCOM has decided to make the TVWS license-exempt as long as the primary user is not interfered
Satellite Bands Satellite bands are seemingly an attractive option for shared band operation due to large amount of
spectrum allocated for different satellite systems However the protection of the incumbent users can be difficult in spectrum received for downlink (space-to-
earth) transmission In principle similar problem as with TV WS case (how secondary system would detect the location of
primary system receivers) Secondary operation is not currently allowed in satellite bands ?
New IMT-A Bands WRC-2007 identified new IMT-A bands beyond 3 GHz (3.4-3.6 GHz, 3.6-3.8 GHz) are suitable frequency
bands for local area/femto cell deployments No decision yet how these bands will be allocated to different operators, and thus not clear if there will be
any portion of the spectrum which shared between multiple operators/systems
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LTE on Shared Bands - Motivation
Why LTE technology based solutions for shared bands
Additional capacity to cellular system operation Increased capacity needs and shortage of licensed spectrum Opportunisticuse of additional capacity available on shared (e.g. unlicensed) bands
Using the same technology in licensed band and unlicensed band operationsimplifies system operation
New markets and development opportunities for LTE technology based
radio systems Deployment of LTE local area solutions to shared bands
Wireless broadband internet access, e.g., in rural areas
New applications and communication solutions for LTE modemtechnology
Machine to machine (M2M) communications
Vehicle to vehicle (V2V) or vehicle to infrastucture (V2I) communications
Ad-hoc networking of devices, mesh networks, short range communicationsetc
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Spectrum sharing principles
Spectrum sharing principles can be categorized e.g. as follows 1) :
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Collaborative use of
IMT spectrum
(cellular operators)
Authorized spectrum
access (ASA)
ISM band usage Secondary usage of
TV White Space
spectrum
LEONARD focus
1) Peter Anker Cognitive Radio, the market and regulator, presentation, IEEE DySPAN 2010
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Regulations and specifications for devicesoperating in ISM band (Europe)
Additionally, devices operating in 2.4 GHz ISM band need to meet specifications as described in ETSI EN 300328 (latest spec version is V1.8.0, 2011-07), which defines requirements for data transmission equipmentoperating in the 2.4 GHz ISM band and using wide band modulation techniques EN300 328
wideband modulation based systems (other than frequency hopping based systems) need to provide spectrum sharingcapabilities either by non-continuous transmission (duty cycle requirements) or by some detect and avoid mechanism(separate requirements for listen before talk/non-listen before talk based detect and avoid solutions), or
can operate without any specific functional requirements for spectrum sharing if maximum rf output power level is lessthan 10 dBm
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Regulatory requirements: ERC RECOMMENDATION 70-03 RELATING TO THE USE OF SHORT RANGE DEVICES (SRD), Annex 3: Wideband
Data Transmission systems
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Local area deployment environment on SharedBand (example case)
8
What modifications are needed to LTE to be able to claim that LTE system can
provide adequate spectrum sharing mechanism to facilitate sharing between variousradio access technologies *)
*) ERC RECOMMENDATION 70-03,
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Possible solutions to enable co-existence
A list of considered solutions to provideadditional capability to LTE technologybased system to coexist with other radio
access technologies Listen Before Talk
Sense the channel with LTE radio prior to thetransmission
Brute Force (Greedy) Operate without any coexistence concern
Detect and Avoid Interference detection, other RAT / same RAT
detection
Dynamic Frequency Agility
DFS (Dynamic Frequency Selection), DCS,Bandwidth scaling, extra carriers, etc..
Frequency Hopping LTE hops over a larger bandwidth and avoids
interfering
Hybrid Framing Use WLAN to reserve channel for LTE
Discontinuous Operation (time division) Transmission gaps to allow other technologies to
operate (different approach than LBT, here nosensing is done )
Higher Layer Coordination802.19.1 like approach where the coordination is left
for higher layers and radio changes are kept inminimum
Carrier Aggregation PCC on licensed band and SCC is used
opportunistically on shared band (ISM)
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LTE Coexistence and Operation Features
Listen Before Talk
Brute Force
Detect and Avoid
Dynamic Frequency Agility
Frequency Hopping
Hybrid Framing
Discontinuous Operation (TimeDivision)
Higher Layer Coordination
Carrier Aggregation
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Alternative approaches (1) Higher layer coordination in LTE architecture
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In general, central coexistence
unit (CCU) is necessary tocoordinate the RATs on sharedband.
Depending on the coexistencescenario, the central coexistenceunit can be implemented atnetwork management system(NMS) level, or at LTE core
network level. The central coexistence unit
consists of three elements:database, manager and gateway.
The central coexistence unit canprovide the coordinationdecisions for RATs, or justprovide the tunnels for the
coordination informationexchange at higher layer.
A: CCU can obtain the shared band information from external networks.B: CCU can obtain the shared band information through the spectrum sensing from thenodes/UEs.C: Inter/virtual MME connection for multiple LTE CNs (different operators)D: Virtual X2 connection for HeNBs.E: Interworking connection between LTE CN and other RAT network/AP(such as the Wa/Wnconnection for WLAN)F: Interworking connection between LTE CN and other RAT UE (such as Wu for WLAN)G: Connection to the CCU.
LTE CoreNetwork A
LTE UEA
LTE eNBA/shared
Externalnetworks(Internet)
Sharedbandinformation
Other WirelessNetwork(s) onshared band(Network/AP)
Other Wireless applicationUE
LTE CoreNetwork B
LTE UEB
LTE eNBB
A
B
C
D
E
F
G G
CentralCoexistenceUnit (CCU)
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Alternative approaches (2) Listen Before Talk - LTE
Listen-Before-Talk(LBT)or sometimes called Listen-Before-Transmit(orSpectrum OpportunityDetection)
A technique where atransmitter first senses its
radio environment before itstarts a transmission.
LBT in general can be usedby a radio device to find anetwork the device isallowed to operate on or tofind a free radio channel to
operate on Continuous transmission of
control channels requirespecial arrangements
The main principle of LBT-LTE illustrated in the figure
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Alternative approaches (3) Low Power LTE
In the Low Power LTEscheme the maximumtransmit power is limited to10 dBm No need for anyspecific spectrum sharingmechanisms to fulfillregulatory requirements for
ISM band operation.
Spectrum sensing anddynamic channel selectionmechanism is still beneficialto decide optimum spectrumresources for operation
Examples of spectrum usagewith low power LTE isillustrated in the figure
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Analysis Results Summary
In order to utilize current LTE on sharedbands with very minimal modifications
to the LTE radio protocol stack and airinterface the most suitable way wouldbe to use higher layer coordination.
Higher layer coordination would inpractice mean that LTE access point orthe LTE network is connected to acentral entity which allocates andmanages the spectrum utilization in agiven band.
An example of such central coordinationfunction would be 802.19.1 likefunction.
If such approach was taken the mainresearch questions would most probablybe above the radio layers, in LTE case in
the core network of an operator,possibly requiring multioperatorcooperation (connect the coordinationfunctions of different operators).
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To complement the LTE with minimalchanges approach, new approaches
have been considered allowinguncoordinated operation on sharedbands while still aiming to utilize LTEphysical layer and protocol elements asfar as possible
Potential schemes include LTE with listenbefore talkfunctionality and a low powerLTE version with dynamic channelselection mechanism
Further work will include
Further development of LTE basedschemes for uncoordinated operation inshared bands
Performance analysis to verify and
demonstrate proper functionality of thenew concepts
Additionally, some of the new LBT/LTEprinciples may be able to verify withCWCs WARP platform as part of theCORE project collaboration
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THANKS
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