LTE on Shared Bands (LEONARD)

Transcription

2 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 (an extension project included in Tekes Trial programme in 2012) Project focus LTE technology applicability to shared band operation LTE and WLAN technology coexistence in same frequency band Renesas Mobile Corporation. All rights reserved.

4 Possible frequency bands for shared band operation 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 MHz on ITU-R region 2) Television White Spaces In general, TVWS spectrum (e.g., within 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-toearth) 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 ( GHz, 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 Renesas Mobile Corporation. All rights reserved.

5 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 Opportunistic use of additional capacity available on shared (e.g. unlicensed) bands Using the same technology in licensed band and unlicensed band operation simplifies 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 modem technology Machine to machine (M2M) communications Vehicle to vehicle (V2V) or vehicle to infrastucture (V2I) communications Ad-hoc networking of devices, mesh networks, short range communications etc Renesas Mobile Corporation. All rights reserved.

6 Spectrum sharing principles Spectrum sharing principles can be categorized e.g. as follows 1) : 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 Renesas Mobile Corporation. All rights reserved.

7 Regulations and specifications for devices operating in ISM band (Europe) Regulatory requirements: ERC RECOMMENDATION RELATING TO THE USE OF SHORT RANGE DEVICES (SRD), Annex 3: Wideband Data Transmission systems Additionally, devices operating in 2.4 GHz ISM band need to meet specifications as described in ETSI EN (latest spec version is V1.8.0, ), which defines requirements for data transmission equipment operating in the 2.4 GHz ISM band and using wide band modulation techniques EN wideband modulation based systems (other than frequency hopping based systems) need to provide spectrum sharing capabilities 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 less than 10 dbm Renesas Mobile Corporation. All rights reserved.

8 Local area deployment environment on Shared Band (example case) What modifications are needed to LTE to be able to claim that LTE system can provide adequate spectrum sharing mechanism to facilitate sharing between various radio access technologies *) *) ERC RECOMMENDATION 70-03, 8

9 Possible solutions to enable co-existence A list of considered solutions to provide additional capability to LTE technology based system to coexist with other radio access technologies Listen Before Talk Sense the channel with LTE radio prior to the transmission 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 no sensing is done ) Higher Layer Coordination like approach where the coordination is left for higher layers and radio changes are kept in minimum Carrier Aggregation PCC on licensed band and SCC is used opportunistically on shared band (ISM) LTE Coexistence and Operation Features Listen Before Talk Brute Force Detect and Avoid Dynamic Frequency Agility Frequency Hopping Hybrid Framing Discontinuous Operation (Time Division) Higher Layer Coordination Carrier Aggregation Renesas Mobile Corporation. All rights reserved.

10 Alternative approaches (1) Higher layer coordination in LTE architecture External networks (Internet) Shared band information B A G LTE Core Network A LTE enb A /shared LTE UE A C D Central Coexistence Unit (CCU) LTE Core Network B LTE enb B LTE UE B Other Wireless Network(s) on shared band (Network/AP) Other Wireless application UE A: CCU can obtain the shared band information from external networks. B: CCU can obtain the shared band information through the spectrum sensing from the nodes/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/Wn connection for WLAN) F: Interworking connection between LTE CN and other RAT UE (such as Wu for WLAN) G: Connection to the CCU. E F G In general, central coexistence unit (CCU) is necessary to coordinate the RATs on shared band. Depending on the coexistence scenario, the central coexistence unit can be implemented at network 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 can provide the coordination decisions for RATs, or just provide the tunnels for the coordination information exchange at higher layer Renesas Mobile Corporation. All rights reserved.

11 Alternative approaches (2) Listen Before Talk - LTE Listen-Before-Talk (LBT) or sometimes called Listen- Before-Transmit (or Spectrum Opportunity Detection) A technique where a transmitter first senses its radio environment before it starts a transmission. LBT in general can be used by a radio device to find a network the device is allowed to operate on or to find a free radio channel to operate on Continuous transmission of control channels require special arrangements The main principle of LBT- LTE illustrated in the figure Renesas Mobile Corporation. All rights reserved.

12 Alternative approaches (3) Low Power LTE In the Low Power LTE scheme the maximum transmit power is limited to 10 dbm No need for any specific spectrum sharing mechanisms to fulfill regulatory requirements for ISM band operation. Spectrum sensing and dynamic channel selection mechanism is still beneficial to decide optimum spectrum resources for operation Examples of spectrum usage with low power LTE is illustrated in the figure Renesas Mobile Corporation. All rights reserved.

13 Analysis Results Summary In order to utilize current LTE on shared bands with very minimal modifications to the LTE radio protocol stack and air interface the most suitable way would be to use higher layer coordination. Higher layer coordination would in practice mean that LTE access point or the LTE network is connected to a central entity which allocates and manages the spectrum utilization in a given band. An example of such central coordination function would be like function. If such approach was taken the main research questions would most probably be above the radio layers, in LTE case in the core network of an operator, possibly requiring multioperator cooperation (connect the coordination functions of different operators). To complement the LTE with minimal changes approach, new approaches have been considered allowing uncoordinated operation on shared bands while still aiming to utilize LTE physical layer and protocol elements as far as possible Potential schemes include LTE with listen before talk functionality and a low power LTE version with dynamic channel selection mechanism Further work will include Further development of LTE based schemes for uncoordinated operation in shared bands Performance analysis to verify and demonstrate proper functionality of the new concepts Additionally, some of the new LBT/LTE principles may be able to verify with CWC s WARP platform as part of the CORE project collaboration Renesas Mobile Corporation. All rights reserved.