Mobile Networks - Small Cell Alliance Center

教育部行動寬頻尖端技術人才培育計畫-小細胞基站聯盟中心教育部行動寬頻尖端技術人才培育計畫-小細胞基站聯盟中心「小基站與WiFi之異質性網路存取」課程模組單元1Heterogeneous Networks異質性行動寬頻網路簡介助理教授：吳俊興國立高雄大學資訊工程學系

Outline • Syllabus • Next-Generation Mobile Networks • Review the Development of Mobile Networks • Toward 5G: IMT-2020 and LTE-Advanced Pro • HetNet’s Fundamental Technologies • LTE-CA: Carrier Aggregation • ICIC: Inter-Cell Interference Coordination • CoMP: Coordinated Multi Point • HetNet’s Advanced Technologies • RCLWI: RAN Controlled LTE WLAN Interworking • LWIP: LTE WLAN Radio Level Integration with IPsec Tunnel • LWA: LTE-WLAN Aggregation • LTE-U/LTE-LAA/LTE-LSA: Unlicensed, Licensed Assisted Access, Licensed Shared Access

教學目標 本課程介紹行動寬頻的最新發展技術，探討小細胞基站(Small Cells)如何整合各種無線網路，並支援異質性網路(Heterogeneous Networks)，以做為B4G/5G行動通訊網路的基礎。講授重點包括： • 異質行動網路簡介，包括Licensed同步存取、Licensed與Unlicensed/WiFi整合存取 • HetNet以小基站為基礎之異質行動網路，包括ICIC干擾管理與CoMP多點協調等小基站技術，以及RCLWI/LWIP/LWA/LAA等LTE與WiFi整合技術另外，透過學習建置OAI-LTE平台或ITRI Small Cells-LTE平台並與WiFi無線網路進行整合的系列實驗，來達成以下的目標： • 培養學生利用WiFi進行卸載或負載分享的程式實作能力 • 學習在OAI平台或ITRI Small Cell平台上實作影音串流的卸載與負載分享等相關的實驗技術 • 透過期末的LTE與WiFi整合的影音串流的卸載與負載分享的專題實作，培養學生創意思考與解決問題之能力

課程內容

課程教材 • 參考書 (eBook) • Joydeep Acharya, Long Gao, and Sudhanshu Gaur,Heterogeneous Networks in LTE-Advanced, John Wiley & Sons, Ltd, 2014 • Chris Johnson,Long Term Evolution in Bullets, 2nd Edition, CreateSpace Publishing, 2012 • Harri Holma, Antti Toskala, Jussi Reunanen,LTE Small Cell Optimization - 3GPP Evolution to Release 13,John Wiley & Sons, Ltd, 2015 • Protocols (Specifications) • 3GPP LTE-Advanced Pro • ITU IMT-2020 • Small Cell Forum, LTE-U Forum, NGMN, 5G Americas, 5G PPP • Platforms • Open Air Interface • ITRI

Mobile Networks from GSM to LTE Core of 3GPP’s SAE Project (System Architecture Evolution)

Mobile Networks from GSM to LTE (Cont.) • GSM: developed to carry real time services, in a circuit switched manner • GPRS: the first step towards an IP based packet switched solution • Using the same air interface and access method, TDMA (Time Division Multiple Access) • UMTS: 3G standard based on GSM • Developing UTRAN and WCDMA • EPS (Evolved Packet System): purely IP based • A flat, all-IP architecture with separation of control plane and user plane traffic • Composed with E-UTRAN/LTE and packet-switched EPC (Evolved Packet Core)

Network Structure of UMTS(Universal Mobile Telecommunications System) Mobile Station Access Network Core Network • Emulating a circuit switched connection for real time services and a packet switched connection for datacom services • Incoming datacom services are still relying upon the circuit switched core for paging • An IP address is allocated to the UE when a datacom service is established andreleased when the service is released

EPS (Evolved Packet System) / SAE PDN (Packet Data Network) Gateway Access Network Discovery and Selection Function Serving Gateway Mobility Management Entity EvolvedPacket Data Gateway Radio Access Network (RAN) Core Network (CN) A bearer is from UE to eNodeB to S-GW and finally to P-GW

EPC (Evolved Packet Core) • EPC (Evolved Packet Core): main component of EPS, includes • MME: key control-node for LTE – UE paging; chooses S-GW for UE during attach and handover • Authenticating the user (by interacting with HSS - Home Subscriber Server) • S-GW: manages and stores UE contexts; routes and forwards user data packets • P-GW: provides connectivity from the UE to external packet data networks • ePDG: secures data transmission with UE connected to EPC over untrusted non-3GPP access • ANDSF: provides information to UE to discover available access networks (either 3GPP or not)

Evolved Universal Terrestrial Radio Access(E-UTRA) • e-UTRA is the air interface of 3GPP's Long Term Evolution (LTE) • EUTRAN is a radio access network (RAN) which is referred to under the name EUTRAN standard

Protocol Models of CN and RAN • Two main layers • Upper layer: manipulate information specific to LTE • Lower layer: transport information from one point to another • Three types of protocols • (Control plane) signaling protocols • User plane protocols • Transport protocols: transfer data and signaling messages On the air interfaceBy the fixed network

Protocol Stack to Exchange Control Signaling TS 23.401 Stream Control Transmission Protocol

Bearer Implementation (Using GTP) TS 23.401 GTP (GPRS Tunneling Protocol)

Challenges to Operators • Challenges • Increasing data traffic: network capability using traditional macrocell-based deployments is growing at about 30% less than the demand for data • Decreasing profit margins: the profit margins of most operators have also been decreasing globally • The flat rate pricing policies prevent the mobile data revenues of an operator to scale proportionately with the increased usage of mobile broadband data • The cost incurred as a result of setting up more base stations to provide increased capacity and coverage • Rethink methods of operating their networks • Key principle: deliver higher capacity at a reduced cost

Enhancement of Key Capabilitiesfrom IMT-Advanced to IMT-2020 Source: ITU-R M.2083-0 (Sep 2015)

Ways to Increase Capacity • A 1000× increase in capacity is required to support rising demand in 2020* • High capacity can be achieved by • Improving spectral efficiency • Employing more spectrum • Increasing network density • The major gains are expected throughincreasing network density by deployingan overlay network of small cellsover the macro coverage area Related to link level enhancements(but already at near optimal) *Reference: Mallinson, K. (2012) The 2020 vision for LTE. Available at http://www.3gpp.org/2020-vision-for-LTE (accessed November 2013)

Detailed Timeline & Process for IMT-2020 in ITU-R • Working Party 5D, Study Group 5, ITU-R (Radiocommunication) • FG IMT-2020, Focus Group on IMT-2020, SG 13, ITU-T (Telecommunication)

IMT-2020 Vision –A Unified Network Architecture • A Heterogeneous (Licensed) Network with Large and Small Cells (HetNet) • Carrier Aggregation (R8+) → eCA • Intra-band/inter-band contiguous/non-contiguous allocation • Interference Management • Inter-Cell Interference Coordination (ICIC, R8) → eICIC (R10) → feICIC (R11) • Dynamic Coordination between Neighboring Cells • Coordinated Multi Point (CoMP) • Simultaneous Connectivity across Cells • DualNet (TR36.842 R12) • A Heterogeneous Network Integrating (Unlicensed) WLAN/WiFi • WLAN inter-working (Trusted/Un-trusted) • WiFi Offload and Link Aggregation (LWIP, LWA) • LTE in the unlicensed spectrum • LTE-U, LAA (R13) / eLAA (DualNet R14)

5G Vision – 5G-PPP EU Source: https://5g-ppp.eu/ (5G Vision, Feb 2015) https://www.youtube.com/watch?v=bfNmiYtG9Cg

3GPP Roadmap Phase 1: by Sep 2018/Rel-15 • Address a more urgent subset of commercial needs (Not possible to standardize all in time) • Expected deployments in 2020 Phase 2: by Mar 2020/Rel-16 • Target for IMT 2020 submission • Address all identified use-cases & requirements

3GPP 5G Requirements TR22.891with 70s different user cases of four groups (SA1 finalized June 2016)

3GPP 5G Requirements (Cont.)

Three Main 5G Cases and Examples eMBB (enhanced Mobile Broadband) mMTC (massive Machine Type Communications) URLLC (Ultra-Reliable and Low Latency Communications)

Toward a Heterogeneous Network Finding new macro-sites becomes increasingly difficult and can be expensive • Introduce small cells through the addition of low-power base stations (eNBs, HeNBs or Relay Nodes (RNs)) or Remote Radio Heads (RRH) to existing macro-eNBs • Added to increase capacityin hot spots with high user demand and to fill in areas not covered by the macro network – both outdoors and indoors • They also improve network performance and service quality by offloading from the large macro-cells • The result is a heterogeneous network with large macro-cells in combination with small cells providing increased bitrates per unit area HetNet: a wireless network comprised of different types of base stations and wireless technologies, including macro base stations, small cells, distributed antenna systems (DAS), and even Wi-Fi access points

Deployment Scenarios of Small Cell (TR32.835) • A Heterogeneous Network consists of different types of Base Stations (BSs), supporting cells such as macro, micro and pico cells • These types of BSs will be mixed in an operating network • Heterogeneous networks management should consider cells in a heterogeneous network, including small cells • both with and without macro coverage, • both outdoor and indoor small cell deployments and • both sparse and dense small cell deployments F1 and F2 are the carrier frequency for macro layer and local-node layer, respectively

HetNet - A Heterogeneous Networkwith Large and Small Cells Large cell • High-power eNB • Macro-eNB site can be difficult to find Small cell • Low-power base station or RRH (Remote Radio Head) • Off load for large cell • Small site size • Indoor coverage • Hot-spot coverage • Coverage at cell edge of large cell • Coverage in area not covered by the macro-network In heterogeneous networks the cells of different sizes are referred to as macro-, micro-, pico- and femto-cells; listed in order of decreasing base station power

From Macro to Small Cells • Small cells using 3GPP radio access technologies will • Enhance capacity and per-user throughput • Reduce costs and • Uniquely offer tight cooperation with the macro coverage layer • Enhancements for small cells as a key component of R12 • Dual connectivity: Devices maintain simultaneous connections to both macro and small-cell low-power layers to improve cell-edge throughput • Inter-node radio resource aggregation can use radio resources on a common frequency in more than one eNB • Connections can be anchored to a macro cell on one frequency while boosting data-rates via the small cell on a different frequency • Small cell on/off: Energy-efficient load balancing by turning off the low-power nodes when there is no ongoing demand for data transmission • More eNBs increases air interface interference and network power consumption • Making nodes dormant can match available capacity to network traffic loading • 256 QAM: Close proximity of devices to small cells enables use of higher-order modulation • Beneficial in sparse small-cell implementations with low device mobility

HetNet Dual Connectivity • Simultaneous connection to the macro and low-power layer

Carrier Aggregation • Carrier aggregation is used in LTE-Advanced in order to increase the bandwidth, and thereby increase the bitrate, by aggregating multiple carriers together for simultaneous transmission • The aggregation is based on R8/R9 carriers to keep backward compatibility with R8 and R9 UEs • Carrier aggregation can be used for both FDD and TDD Reference: LTE Carrier Aggregation, http://niviuk.free.fr/lte_ca_band.php

Component Carrier • Each aggregated carrier is referred to as a component carrier, CC • The component carrier can have a bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz and • A maximum of five component carriers can be aggregated • Hence the maximum aggregated bandwidth is 100 MHz • In FDD the number of aggregated carriers can be different in DL and UL • However, the number of UL component carriers is always equal to or lower than the number of DL component carriers • The individual component carriers can also be of different bandwidths • For TDD the number of CCs as well as the bandwidths of each CC will normally be the same for DL and UL

Example of Carrier Aggregation (FDD) • The LTE-Advanced UE can be allocated DL and UL resources on the aggregated resource consisting of two or more Component Carriers (CC) • The R8/R9 UEs can be allocated resources on any ONE of the CCs • The CCs can be of different bandwidths

Band Allocation for Aggregation • Intra-band contiguous allocation • The easiest way to arrange aggregation would be to use contiguous component carriers within the same operating frequency band (as defined for LTE) • This might not always be possible, due to operator frequency allocation scenarios. • Intra-band non-contiguous allocation • The component carriers belong to the same operating frequency band, but have a gap, or gaps, in between • Inter-band non-contiguous allocation • The component carriers belong to different operating frequency bands

Intra-band and Inter-band Aggregation Alternatives • The spacing between the centre frequencies of two contiguous CCs is Nx300 kHz, N=integer • For non-contiguous cases the CCs are separated by one, or more, frequency gap(s)

Definitions and Notations for CA • CA is initially specified for only a few combinations of E-UTRA operating bands and number of CCs • New definitions to specify different CA combinations • Aggregated Transmission Bandwidth Configuration (ATBC): total number of aggregated physical resource blocks (PRB) • CA Bandwidth Class: indicates a combination of maximum ATBC and maximum number of CCs. In R10 and R11 three classes are defined • Class A: ATBC ≤ 100, maximum number of CC = 1 • Class B: ATBC ≤ 100, maximum number of CC = 2 • Class C: 100 < ATBC ≤ 200, maximum number of CC = 2 • CA Configuration: indicates a combination of E-UTRA operating band(s) and CA bandwidth class(es), to exemplify the configuration • CA_1C indicates intra-band contiguous CA on E-UTRA operating band 1 and CA bandwidth class C • CA_1A_1A, indicates intra-band non-contiguous CA on band 1 with a one CC on each side of the intra-band gap • CA_1A_5B indicates inter-band CA, on operating band 1 with bandwidth class A and operating band 5 with bandwidth class B Reference: E-UTRA CA configurations 36.101 (Rel 15 Sept 2017) http://www.3gpp.org/DynaReport/SpecVsWi--36101.htm

Three CA Configurations Defined for R10

CA Configurations Defined for R11 and Beyond • In R11 a large number of additional CA configurations are defined • The maximum aggregated bandwidth is still 40 MHz and maximum number of CC is 2 • For both R10 and R11 any UL CC will have the same bandwidth as the corresponding DL CC • Also for inter-band CA there will only be ONE UL CC, i.e. no UL CA • Check updated table in the “Carrier Aggregation for LTE” document for each release

The Primary Component Carrier (PCC) and Secondary Component Carriers (SCCs) • When carrier aggregation is used there are a number of serving cells, one for each component carrier • Different component carriers can be planned to provide different coverage, i.e. different cell size • The RRC connection is only handled by one cell, the Primary serving cell, served by the Primary Component Carrier (DL and UL PCC) • It is also on the DL PCC that the UE receives NAS information, such as security parameters. • In idle mode the UE listens to system information on the DL PCC • On the UL PCC PUCCH is sent • The other component carriers are all referred to as Secondary Component Carriers(DL and UL SCC), serving the Secondary serving cells • The SCCs are added and removed as required, while the PCC is only changed at handover • The coverage of the serving cells may differ, for example due to that CCs on different frequency bands will experience different path loss • In the case of inter-band carrier aggregation the component carriers will experience different path loss, which increases with increasing frequency • Note that for UEs using the same set of CCs, can have different PCC

Primary and Secondary Serving Cells • Each component carrier corresponds to a serving cell • The different serving cells may have different coverage • Carrier aggregation on three component carriers are used for the black UE • The white UE is not within the coverage area of the red component carrier

Changes to R8/R9 for Carrier Aggregation • Introduction of carrier aggregation influences mainly MAC and the physical layer protocol, but also some new RRC messages are introduced • In order to keep R8/R9 compatibility the protocol changes will be kept to a minimum • Basically each component carrier is treated as an R8 carrier • Some changes are required, such as • new RRC messages in order to handle SCC • MAC must be able to handle scheduling on a number of CCs • Major changes on the physical layer are for example that • Signaling information about scheduling on CCs must be provided DL as well as HARQ ACK/NACK per CC must be delivered UL and DL

Radio Interface to Support Carrier Aggregation

CA Scheduling (FDD): Two Main Alternatives • Either resources are scheduled on the same carrier as the grant is received, or so called cross-carrier scheduling may be used

Support Serving Cells with DifferentTiming Advance (TA) • Serving cells with the same TA belongs to the same TA Group (TAG) • From R11 it will be possible to handle CA with CCs requiring different timing advance (TA), for example combining CC from eNB with CC from RRH • For heterogeneous network planning the use of for example remote radio heads (RRH) is of importance

Inter-Cell Interference Coordination (ICIC) • Originally introduced in R8 for macro-cells • eNBs communicate using ICIC via the X2 interface to mitigate inter-cell interference for UEs at the cell edge • “Load Information” X2AP message • Used by an eNB to inform neighbouring eNBs about • UL interference level per Physical Resource Block (PRB); • UL PRBs that are allocated to cell edge UEs, and hence are sensitive to UL interference; • if DL Tx power is higher or lower than a set threshold value • The receiving eNBs use the received information to optimize scheduling for UEs at cell edges

eICIC to Support Heterogeneous Networks • Enhanced ICIC (eICIC) was introduced in LTE R10 • Better support heterogeneous network deployments • Especially interference control for DL control channels • The major change is the addition of time domain ICIC, realized through use of Almost Blank Subframes (ABS) • Includes only control channels and cell-specific reference signals, no user data • Transmitted with reduced power • eICIC between macro-eNB and eNB in small cells • The macro-eNB will transmit ABS according to a semi-static pattern • During these subframes, UEs at the edge, typically in the Cell Range Expansion (CRE) region of small cells, can receive DL information, both control and user data • The macro-eNB will inform the eNB in the small cell about the ABS pattern

ABS for Cell-edge UEs in Small Cells (eICIC) • Further Enhanced ICIC (feICIC) in R11 • Interference handling by UE through inter-cell interference cancellation for control signals • Enabling even further cell range extension • eICIC and feICIC are especially important when Carrier Aggregation (CA) is not used

CoMP – Coordinated Multi Point • CoMP introduced in LTE R11 • One way to ensure that a UE is using both the best DL and the best UL carrier in a heterogeneous network (used both in DL and UL) • With CoMP • A number of transmission/reception points (i.e. eNBs, RNs or RRHs) can be coordinated to provide service to a UE. For examples, • Data can be transmitted at the same time in the same Physical Resource Blocks (PRB) from more than one transmission point to one UE, or • Data can be received from one transmission point in one subframe and from another transmission point in the next subframe

CoMP in a Heterogeneous Network • CoAP is especially useful in heterogeneous networks • The possibility for a UE in the cell range extension region to utilize the best UL in the small cell and the best DL in the macro-cell • A number of macro-cells and small cells can be involved in data transmission to and from one UE • Requires that • The macro-eNB and the base station in the small cell are synchronized • Most likely it will require a combination of macro-eNB with Remote Radio Heads (RRH) in the small cell

Mobile Networks - Small Cell Alliance Center