單元 6 在 LWA-Small 實驗平台上的卸載 ( Off-loading)

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」課程模組使用ITRI LWA-Small Cell (含WiFi) 實驗平台單元6在LWA-Small實驗平台上的卸載(Off-loading) 助理教授：吳俊興助教：王瑞元國立高雄大學資訊工程學系

Outline • LTE Introduction • WLAN Introduction • Difference • UnlicensedBand Introduction • LTE-ACA,LAA,LTE-U • LTERCLWI • LTELWIP • LTELWA • ITRILWA-Small Cell 之LWA實作 • Summary • References

LTEIntroduction • LTE motivation: Moving 3G/UMTS to 4G • Need to ensure the continuity of competitiveness of the 3G (UMTS) system for the future • Technically • User demand for higher data rates and quality of service • Packet switch optimized system • Low complexity • Economically • Continued demand for cost reduction • CAPEX - Capital Expenditure • OPEX - Operating Expenditure • Avoid unnecessary fragmentation of technologies for paired and unpaired band operation • Design goal for experience of the end users • Higher number of supported users • Broader range of applications

Overall LTE Architecture • EPC (Evolved Packet Core) • The Core Network (CN) • The network architecture also called as SAE (Service Architecture Evolution) • E-UTRAN (Evolved Universal Terrestrial Radio Access Network): • The radio access network to UE • LTE frequently used to denote LTE E-UTRAN • Specifically, the PHY (Physical Layer) and Medium Access Control (MAC) layers • Combination of E-UTRAN and EPC/SAE is also called the Evolved Packet System (EPS) UE (User Equipment)

E-UTRAN • E-UTRAN: The first point of entry for a UE to the LTE network • Responsible for transmission/reception of radio signals to and from a given UE and the associated digital signal processing • The E-UTRAN protocols cover the communication process between the UE and the network over the wireless link • Include the medium access control mechanisms by which multiple UEs share the common wireless channel • Ensure link level reliability, segmentation, and reassembly of higher-layer Protocol Data Units (PDUs) and IP header compression • enhanced Node B (eNodeB or eNB) • The single logical node in the E-UTRAN • To implement the AS (Access Stratum) protocols - responsible for transporting data over the wireless connection and managing radio resources

Evolved Packet Core (EPC) • When a UE powers on, the EPC is responsible for • Authentication and the initial connection establishment needed for all subsequent communication • Allocating IP addresses to the UE and forwarding/storing packet data to and from the UE to the external IP network • In the UMTS and LTE wireless telecom protocol stacks • Access Stratum (AS) is a functional layer between the radio network and UE • Non-Access Stratum (NAS)is a functional layer between the core network and UE • The signaling and protocols between the UE and the EPC • The EPC layer comprises several logical nodes such as • Mobility Management Entity (MME) • Serving Gateway (S-GW) • Public Data Network (PDN) Gateway (P-GW) +- – - – - -+ +- – - – - – -+ | HTTP | | Application | +- – - – - -+ +- – - – - – -+ | TCP | | Transport | +- – - – - -+ +- – - – - – -+ | IP | | Internet | | - - - | | - - - | | NAS | | Network | +- – - – - -+ +- – - – - – -+ | AS | | Link | +- – - – - -+ +- – - – - – -+ | Channels | | Physical | +- – - – - -+ +- – - – - – -+

Network Solutions from GSM to LTE Core of 3GPP’s SAE Project (System Architecture Evolution) • 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 • 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) Access Network Discovery and Selection Function Serving Gateway Mobility Management Entity EvolvedPacket Data Gateway

Detailed LTE Architecture • The Core Network (CN) has a control plane and a user plane • Control: MME for NAS signaling between the UE and the CN • User: P-GW and S-GW • P-GW: default router for UE to an external network • S-GW: packet routing and forwarding; mobility anchor for inter-eNodeB handover A bearer is from UE to eNodeB to S-GW and finally to P-GW

WLANIntroduction • A wireless LAN (WLAN or WiFi) • A data transmission system designed to provide location-independent network access between computing devices by using radio waves • The 802.11 specification [IEEE Std 802.11 (ISO/IEC 8802-11: 1999)] as a standard for wireless LANS • Ratified by the Institute of Electrical and Electronics Engineers (IEEE) in the year 1997 • Provides for 1 Mbps and 2 Mbps data rates and a set of fundamental signaling methods and other services • Focus on the bottom two levels the ISO model, the physical layer and link layer • Any LAN application, network operating system, protocol, including TCP/IP and Novell NetWare, will run on an 802.11-compliant WLAN as easily as they run over Ethernet

IEEE 802.11 and the ISO Model

The Major Motivation and Benefit from Wireless LAN • The major motivation and benefit • Increased mobility • Cost-effective network setup for hard-to-wire locations • Untethered from conventional network connections • Network users can move about almost without restriction and access LANs from nearly anywhere • WLANs liberate users from dependence on hard-wired access to the network backbone • Giving them anytime, anywhere network access • This freedom to roam offers numerous user benefits for a variety of work environments • Immediate bedside access to patient information for doctors and hospital staff • Easy, real-time network access for on-site consultants or auditors • Improved database access for roving supervisors such as production line managers, warehouse auditors, or construction engineers • Simplified network configuration with minimal MIS involvement for temporary setups such as trade shows or conference rooms • Faster access to customer information for service vendors and retailers, resulting in better service and improved customer satisfaction • Location-independent access for network administrators, for easier on-site troubleshooting and support • Real-time access to study group meetings and research links for students

IEEE 802.11 Architecture • The difference between a portable and mobile station • A portable station moves from point to point but is only used at a fixed point • Mobile stations access the LAN during movement • When two or more stations come together to communicate with each other, they form a Basic Service Set (BSS) • The minimum BSS consists of two stations • 802.11 LANs use the BSS as the standard building block • A BSS that stands alone and is not connected to a base is called an Independent Basic Service Set (IBSS) or is referred to as an Ad-Hoc Network • An ad-hoc network • A network where stations communicate only peer to peer • There is no base and no one gives permission to talk • Mostly these networks are spontaneous and can be set up rapidly • Ad-Hoc or IBSS networks are characteristically limited both temporally and spatially

IEEE 802.11 Architecture • When BSS's are interconnected the network becomes one with infrastructure • 802.11 infrastructure has several elements • Two or more BSS's are interconnected using a Distribution System or DS • Increases network coverage • Each BSS becomes a component of an extended, larger network • Entry to the DS is accomplished with the use of Access Points (AP) • An access point is a station • Addressable • Data moves between the BSS and the DS with the help of these access points

Logical Link Control Layer • Creating large and complex networks using BSS's and DS's leads us to the next level of hierarchy • Extended Service Set or ESS • The beauty of the ESS is the entire network looks like an independent basic service • Logical Link Control layer (LLC) • Stations within the ESS can communicate or even move between BSS′s transparently to the LLC

Requirements of IEEE 802.11 • It can be used with existing wired networks • 802.11 solved this challenge with the use of a Portal • A portal is the logical integration between wired LANs and 802.11 • It also can serve as the access point to the DS • All data going to an 802.11 LAN from an 802.X LAN must pass through a portal • It thus functions as bridge between wired and wireless • The implementation of the DS is not specified by 802.11 • A distribution system may be created from existing or new technologies • A point-to-point bridge connecting LANs in two separate buildings could become a DS

Services of WLAN • While the implementation for the DS is not specified, 802.11 does specify the services • The DS must support • Services are divided into two sections • Station Services (SS) • Authentication • Deauthentication • Privacy • MAC Service Data Unit (MSDU) Delivery • Distribution System Services (DSS) • Association • Reassociation • Disassociation • Distribution • Integration

Physical Layer • Three physical layers originally defined in 802.11 • Two spread-spectrum radio techniques and • A diffuse infrared specification • The radio-based standards operate within the 2.4 GHz ISM band • Recognized by international regulatory agencies radio operations • Do not require user licensing or special training

Physical Layer • Spread-spectrum techniques, in addition to satisfying regulatory requirements • Increase reliability • Boost throughput • Allow many unrelated products to share the spectrum without explicit cooperation • Minimal interference • Using the frequency hopping technique, the 2.4 GHz band is divided into 75 1-MHz sub-channels • In contrast, the direct sequence signaling technique divides the 2.4 GHz band into 14 22-MHz channels

Data Link Layer • Logical Link Control (LLC) • 802.11 uses the same 802.2 LLC and 48-bit addressing as other 802 LANs, allowing for very simple bridging from wireless to IEEE wired networks, but the MAC is unique to WLANs

Data Link Layer • Media Access Control (MAC) • The 802.11 MAC is very similar in concept to 802.3, in that it is designed to support multiple users on a shared medium by having the sender sense the medium before accessing it • CRC checksum and packet fragmentation

Difference between LTE and WLAN

Future Plan with Non- 3GPP Tech in 3GPP • 3GPP RAN has approved a requirement for TR38.913 on interworking with non-3GPP • General • 3GPP system shall support procedures for interworking with non 3GPP RATs • Interworking with WLAN • The next generation access network shall support interworking with WLAN • The number of solutions selected should be minimized • Exploring further involvement of IEEE in this work should be initiated by liaison to 3GPP

Access Technique • Wi-Fi : OFDM in both uplink and downlink in all latest 802.11 versions • LTE : OFDMA(downlink), SC-FDMA(uplink)

LTE-A Carrier Aggregation • Carrier aggregation is used in LTE-Advanced in order to increase the bandwidth, and thereby increase the bitrate • Since it is important to keep backward compatibility with R8 and R9 UEs the aggregation is based on R8/R9 carriers • Carrier aggregation can be used for both FDD and TDD

LTE-A Carrier Aggregation • 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

Intra-Band and Inter-Band Aggregation Alternatives • The easiest way to arrange aggregation would be to use contiguous component carriers within the same operating frequency band (as defined for LTE), so called intra-band contiguous • This might not always be possible, due to operator frequency allocation scenarios • For non-contiguous allocation it could either be intra-band, i.e. the component carriers belong to the same operating frequency band, but have a gap, or gaps, in between, or it could be inter-band, in which case the component carriers belong to different operating frequency bands

Licensed-Assisted Access(LAA) • Carrier aggregation with at least one SCell operating in the unlicensed spectrum is referred to as Licensed-Assisted Access (LAA) • In LAA, the configured set of serving cells for a UE therefore always includes at least one SCell operating in the unlicensed spectrum according to Frame structure Type 3, also called LAA SCell • Unless otherwise specified, LAA SCells act as regular SCells

LAA- Channel Access Priority Classes • LAA eNB and UE apply Listen-Before-Talk (LBT) before performing a transmission on LAA Scell • Which LBT type the UE applies • Signalled via uplink grant for uplink PUSCH transmission on LAA Scells • Four Channel Access Priority Classes • Can be used when performing uplink and downlink transmissions in LAA carriers

LAA-Multiplexing of Data • Four Channel Access Priority Classes • If a DL transmission burst with PDSCH is transmitted • Channel access has been obtained using Channel Access Priority Class P (1...4), E-UTRAN shall ensure the following where a DL transmission burst refers to the continuous transmission by E-UTRAN after a successful LBT

LTE-U • Early focus to be on unlicensed operation in 5 GHz. However, the core technology should be as frequency agnostic as possible • While different regional requirements emerged from the discussion, most of the companies prefer 3GPP to focus on the standardization of a global solution that can work across regions • Strong interest to study both indoor and outdoor deployments • Fair coexistence between LTE and other technologies such as Wi-Fi as well as between LTE operators is seen necessary

LTE-U • Initial focus will likely be on Licensed-Assisted Carrier Aggregation operation to aggregate a primary cell, using licensed spectrum, to deliver critical information and guaranteed Quality of Service • A co-located secondary cell, using unlicensed spectrum, to opportunistically boost data rate • Two available options: • (1) Secondary cell on unlicensed spectrum used for supplemental downlink capacity only • (2) Secondary cell on unlicensed spectrum used for both supplemental downlink and uplink capacity • Many companies propose to start working on (1) and then follow with (2)

RCLWI • E-UTRAN supports E-UTRAN controlled bi-directional traffic steering between E-UTRAN and WLAN for UEs in RRC_CONNECTED • RAN Controlled WLAN Interworking (RCLWI) • E-UTRAN may send a steering command to the UE indicating to steer traffic from E-UTRAN to WLAN or from WLAN to E-UTRAN • The upper layers in the UE shall be notified upon reception of such a command • Upper layers determine which traffic is off-loadable to WLAN

RCLWI • Similarly as for LWA, two scenarios are supported depending on the backhaul connection between LTE and WLAN • Non-collocated RCLWI scenario for a non-ideal backhaul • Collocated RCLWI scenario for an ideal/internal backhaul • The overall architecture for the non-collocated RCLWI scenario

RCLWI

Network Interfaces • Similarly as for LWA, in the non-collocated RCLWI scenario, the eNB is connected to one or more WT logical nodes via an Xw interface and in the collocated RCLWI scenario the interface between LTE and WLAN is up to implementation • User Plane Plane • There is no user plane interface defined between the eNB and the WT in RCLWI • Control Plane • In the non-collocated RCLWI scenario, the Xw control plane interface (Xw-C) is defined between the eNB and the WT

RCLWI Mobility • A WLAN mobility set is a set of one or more BSSID/HESSID/SSIDs, within which WLAN mobility mechanisms apply while the UE has moved offloadable traffic to WLAN according to a steering command • The UE may perform mobility between WLAN APs belonging to the mobility set without informing the eNB

LTE/WLAN Radio Level Integration with IPsec Tunnel • A UE in RRC_CONNECTED to be configured by the eNB to utilize WLAN radio resources via IPsec tunnelling • Connectivity between eNB and LWIP-SeGW is provided by the Xw interface

LWIP Protocol Architecture • The end to end protocol stack for the bearer transported over the LWIP tunnel

Bearer over LWIP Tunnel - Protocol Stack

IPsec Tunnel • The IPSec tunnel is established following • Exchange of security information between the eNB and LWIP-SeGW • Using the XwAP LWIP Addition Preparation procedure

LWIP MobilityConcept • The same mobility concept for LWA is also used for LWIP • WT node does not exist in LWIP operation • WT related description and procedures does not apply to LWIP • Mobility Set should be considered as the set of WLAN APs across which UE can perform mobility without informing the eNB • When applying the concept for LWIP operation

LTE-WLAN Aggregation • E-UTRAN supports LTE-WLAN aggregation (LWA) operation whereby a UE in RRC_CONNECTED is configured by the eNB to utilize radio resources of LTE and WLAN • Two scenarios are supported depending on the backhaul connection between LTE and WLAN: • Non-collocated LWA scenario for a non-ideal backhaul • Collocated LWA scenario for an ideal/internal backhaul

LWA Radio Protocol Architecture • The radio protocol architecture that a particular bearer uses depends on the LWA backhaul scenario and how the bearer is set up • Two bearer types exist for LWA: • Split LWA bearer and switched LWA bearer

User Plane • In the non-collocated LWA scenario • The Xw user plane interface (Xw-U) is defined between eNB and WT • The Xw-U interface supports flow control based on feedback from WT

User Plane • The Flow Control function is applied in the downlink when an E-RAB is mapped onto an LWA bearer • The flow control information is provided by the WT to the eNB for the eNB to control the downlink user data flow to the WT for the LWA bearer • The OAM configures the eNB with the information of whether the Xw DL delivery status provided from a connected WT concerns LWAAP PDUs successfully delivered to the UE or successfully transferred toward the UE

Control Plane • Transfer of WLAN metrics (e.g. bss load) from WT to eNB • Support of LWA for UE in ECM-CONNECTED: • Establishment, Modification and Release of a UE context at the WT • Control of user plane tunnels between eNB and WT for a specific UE for LWA bearers • General Xw management and error handling functions: • Error indication • Setting up the Xw • Resetting the Xw • Updating the WT configuration data

單元 6 在 LWA-Small 實驗平台上的卸載 ( Off-loading)