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單元 6 OAI-LTE 使用 WiFi 網路的卸載 (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 「小基站與 WiFi 之異質性網路存取」課程模組. 單元 6 OAI-LTE 使用 WiFi 網路的卸載 (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. OAI-LTE Technologies WLAN Technologies LTE-WLAN Integration LTE-A CA, LAA, LTE-U LTE RCLWI LTE LWIP LTE LWA

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單元 6 OAI-LTE 使用 WiFi 網路的卸載 (Off-loading)

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  1. 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6OAI-LTE使用WiFi網路的卸載(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

  2. Outline • OAI-LTE Technologies • WLAN Technologies • LTE-WLAN Integration • LTE-ACA,LAA,LTE-U • LTERCLWI • LTELWIP • LTELWA • Case Study:An OAI Implementation of LTE WLAN Integration • Summary

  3. Long-Term Evolution (LTE) • 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

  4. 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)

  5. 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 | +- – - – - -+ +- – - – - – -+

  6. 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

  7. 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

  8. OAI Overview • Open-source software-based implementation of 4G LTE (Rel 10) • Spanning the full protocol stack of 3GPP standard • E-UTRAN (eNB, partial UE) • EPC (MME, S+P-GW, HSS) • Realtime RF and scalable emulation platforms • Targets EURECOM and National Instruments HW platforms (others in development) • Objectives • Bring academia closer to complex real-world systems • Open-source tools to ensure a common R&D and prototyping framework for rapid proof-of-concept designs • Other use cases • Interoperability with 3rd party components (UE, eNB, EPC) • Matlab/Octave tools for non real-time experimentation • Real-time channel sounding (EMOS) • 802.11p Modem • Unitary simulations

  9. OAI Platform

  10. Use Case of OAI I • Classical 3GPP setup: • OAI EPC + OAI eNB <--> COTS UE • Commercial/3rd party EPC + OAI eNB <-->COTS UE • OAI EPC + Commercial/3rd party eNB <--> COTS UE

  11. Use Case of OAI II • Non-3GPP setup: • OAI eNB <--> OAI UE

  12. Use Case of OAI III • Simulation/Emulation (oaisim) • OAI eNB <--> OAI UE • OAI EPC + OAI eNB <--> OAI UE • Commercial/3rd party EPC + OAI eNB <--> OAI UE • Unitary simulators • DLSCH simulator dlsim • ULSCH simulator ulsim • PUCCH simulator pucchsim • PRACH simulator prachsim • PDCCH simulator pdcchsim • PBCH simulator pbchsim • eMBMS simulator mbmssim • Other uses • EMOS (real-time channel sounding) • octave (simple experimentation)

  13. OpenAirInterface Features • Implements 4G LTE Rel10 Access Stratum (eNB & UE) and EPC (MME, S+P-GW, HSS) • All the stack (incl. PHY) runs entirely on a PC in real-time operating system (RTAI, Xenomai, low-latency kernel) • Works with ExpressMIMO (Eurecom) and USRP (Ettus/National Instruments)

  14. Key Ingredients • Real-time extensions to Linux OS • Today we rely on the low-latency kernel provided by Ubuntu (since Ubuntu 14.04) • In earlier Ubuntu versions RTAI was used • Real-time data acquisition to/from PC • ExpressMIMO uses DMA to transfer signals in and out of PC memory without hogging CPU -> very efficient • USRP transfers data over USB and therefore requires extra CPU time for (de-)packetization of signals • Highly optimized DSP routines running on Intel GPP • Exploiting vector processing (SIMD) • 64-bit MMX → 128-bit SSE2/3/4 → 256-bit AVX2 • OAI features fastest FFT and Turbo decoder of its kind • Multi-threaded parallel processing

  15. OSA Strategic Areas

  16. USRP B210 • Designed by ETTUS (now part of NI) • Analog Devices AD9361 RFIC Dual Channel Transceiver (70 MHz - 6GHz) • Full duplex, MIMO (2 Tx & 2 Rx) operation with up to 56 MHz of real-time bandwidth (61.44MS/s quadrature) • Slightly less in our experiments • Data acquisition over USB3

  17. OAI Software Architecture

  18. L1/L2 Block • OAI follows 3GPP LTE architecture • Good knowledge of LTE is prerequisite to understand OAI • Each block has its own data structure and functions • Interfaces between most blocks are implemented as function calls • Following interfaces are implemented using the Intertask Interface (ITTI) framework • RRC ↔ PDCP, • RRC ↔ S1AP, • PDCP ↔ S1AP • L1/L2 thread instantiated multiple times • For each TX/RX subframe

  19. Master Thread Architecture (USRP) USRP User Space … lte-softmodem.c L1/L2 thread 0 USB Master eNB thread (synchronization) L1/L2 thread N-1 C API Using real-time Linux extension (RTAI, Xenomai, lowlatency kernel) UHD targets/ARCH/USRP/USERSPACE/LIB

  20. Outline • OAI-LTE Technologies • WLAN Technologies • LTE-WLAN Integration • LTE-ACA,LAA,LTE-U • LTERCLWI • LTELWIP • LTELWA • Case Study:An OAI Implementation of LTE WLAN Integration • Summary

  21. 802.11 WLAN • 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

  22. IEEE 802.11 and the ISO Model

  23. The Major Motivation • 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

  24. Benefits from Wireless LAN • 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

  25. 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

  26. BSS and Access Point (AP) • 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

  27. 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

  28. 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

  29. 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

  30. 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 (5GHz, and more) • Recognized by international regulatory agencies radio operations • Do not require user licensing or special training

  31. 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

  32. Data Link Sublayer - LLC • 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

  33. Data Link Sub-layer - MAC • 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 • Having the sender sense the medium before accessing it • CRC checksum and packet fragmentation

  34. Comparisons of LTE and WLAN

  35. Outline • OAI-LTE Technologies • WLAN Technologies • LTE-WLAN Integration • LTE-ACA,LAA,LTE-U • LTERCLWI • LTELWIP • LTELWA • Case Study:An OAI Implementation of LTE WLAN Integration • Summary

  36. Data Explosion • New applications on the Internet –On-demand video/music, online video conferencing, e/m-commerce, Apps, IoT, etc • Users want to always stay connected by some means • Telecom operators are seeing huge surge in data traffic in cellular networks

  37. Future Plan with Non-3GPP Tech in 3GPP • 3GPP RAN has approved a requirement for TR38.913 on interworking with non-3GPP • 10.5.1 General • 3GPP system shall support procedures for interworking with non 3GPP RATs • 10.5.2 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

  38. Access Techniques • Wi-Fi • OFDM in both uplink and downlink in all latest 802.11 versions • LTE • OFDMA(downlink) • SC-FDMA(uplink)

  39. LTE in the Unlicensed Spectrum • Twoareasto helpoperatorsoffloadtrafficinthe unlicensedspectrum: • WLANviaLTE/WLANInterworking(viaoffloador aggregation) • LTEover unlicensedspectrum WLAN Offload Faster LTE Licensed MoreCapacity Link Aggregation UnifiedNetwork WLAN FairCoexistence Carrier Aggregation LTE Unlicensed Source: Keysight, March 2016

  40. 3GPP Standardization Works Jun 2017 Mar 2016 Rel.10 Rel.11 Rel.12 Rel.13 Rel.14 • Interworking • RAN Controlled LTE-WLAN Interworking (RCLWI) • Link Aggregation • LTE-WLAN Aggregation (LWA) • LTE WLAN Radio Level Integration with IPsec Tunnel (LWIP) • Licensed Assisted Access (LAA) • Unlicensed band using carrier aggregation with a licensed LTE cell (3GPP Rel. 12) WLAN Offload RANAssisted Interworking RAN Controlled Interworking(RCLWI) eLWIP Offload LWIP LTE/WLAN Interworking eLWA LWA LTE-U Aggregation LTEover unlicensed eLAA LAA (LBT) Uplink / Mobility Adaption: Keysight, March 2016

  41. LTE/WLAN Integration Roaming / RCLWI LWIP LWA LAA (LSA) LTE + WLAN

  42. 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

  43. LTE-A Carrier Aggregation • Each aggregated carrier is referred to as a component carrier, CC • Have a bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz and a maximum of five component carriers can be aggregated • Maximum aggregated bandwidth is 100 MHz • In FDD the number of aggregated carriers can be different in DL and UL • 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

  44. 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 • Operator frequency allocation scenarios • 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

  45. Licensed-Assisted Access (LAA) • Carrier aggregation with at least one SCell operating in the unlicensed spectrum • Licensed-Assisted Access (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 • LAA SCell • Unless otherwise specified, LAA SCells act as regular SCells

  46. 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 is 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

  47. LAA-Multiplexing of Data • If a DL transmission burst with PDSCH is transmitted, for which channel access • Channel Access Priority Class P (1...4) • E-UTRAN shall ensure the following where a DL transmission burst refers • The continuous transmission by E-UTRAN after a successful LBT

  48. LTE-U • Early focus to be on unlicensed operation in 5 GHz • 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 • Indoor and outdoor deployments • Fair coexistence between LTE and other technologies such as Wi-Fi as well as between LTE operators is seen necessary

  49. LTE-U Idea • 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

  50. LTE-U Options • 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)

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