單元6 OAI-LTE使用WiFi網路的卸載(Off-loading)

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 Case Study: An OAI Implementation of LTE WLAN Integration Summary

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

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)

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 |

EPS (Evolved Packet System) / SAE
PDN (Packet Data Network) Gateway Serving Gateway Access Network Discovery and Selection Function Mobility Management Entity Evolved Packet Data 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)

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

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

OAI Platform

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

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

Use Case of OAI III Simulation/Emulation (oaisim) Unitary simulators
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)

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)

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

OSA Strategic Areas

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

OAI Software Architecture

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

Master Thread Architecture (USRP)
User Space … lte-softmodem.c USB L1/L2 thread 0 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

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 specification [IEEE Std (ISO/IEC : 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 compliant WLAN as easily as they run over Ethernet

IEEE and the ISO Model

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

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

IEEE 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 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

BSS and Access Point (AP)
When BSS's are interconnected the network becomes one with infrastructure 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 It can be used with existing wired networks solved this challenge with the use of a Portal A portal is the logical integration between wired LANs and It also can serve as the access point to the DS All data going to an 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 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, 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 (5GHz, and more) 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 MHz channels

Data Link Sublayer - LLC
Logical Link Control (LLC) uses the same 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 Sub-layer - MAC
Media Access Control (MAC) The 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

Comparisons of LTE and WLAN
Specifications LTE WLAN Full Form Long Term Evolution Wireless Local Area Network Designation of Network elements eNBs(i.e. Base Stations) and UE(Mobile subscriber) APs(Access Points) and STAs(stations or clients) Distance coverage About 2 to 10 miles About 30 meters(maximum) Channel Bandwidth 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz , 20MHz 20MHz(802.11a), 20MHz & 40MHz (802.11n), 80MHz & 160MHz in ac Applications Both indoor and outdoor with mobility Mainly indoor with little mobility Access technique OFDMA (downlink) SC-FDMA (uplink) OFDM in both uplink and downlink in all latest versions MIMO Supported Frequency of operation Various frequency bands country wide supported 2.4 GHz, 5 GHz Topology Supports TDD and FDD Supports only TDD

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

Future Plan with Non-3GPP Tech in 3GPP
3GPP RAN has approved a requirement for TR 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 Techniques Wi-Fi LTE
OFDM in both uplink and downlink in all latest versions LTE OFDMA(downlink) SC-FDMA(uplink)

LTE in the Unlicensed Spectrum
Two areas to help operators offload traffic in the unlicensed spectrum: WLAN via LTE/WLAN Interworking (via offload or aggregation) LTE over unlicensed spectrum WLAN Offload Faster LTE Licensed More Capacity Link Aggregation WLAN Unified Network Carrier Aggregation Fair Coexistence LTE Unlicensed Source: Keysight, March 2016

3GPP Standardization Works
Rel. 12 Rel. 13 Rel. 14 Rel. 11 Rel. 10 LTE/WLAN Interworking LTE over unlicensed eLAA WLAN Offload RAN Assisted Interworking RAN Controlled Interworking (RCLWI) LAA LTE-U Aggregation LWA LWIP Mar 2016 Jun 2017 eLWIP eLWA Uplink / Mobility (LBT) 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) Adaption: Keysight, March 2016

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

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 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

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

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

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 Channel Access Priority Class ( p) QCI 1 1, 3, 5, 65, 66, 69, 70 2 2, 7 3 4, 6, 8, 9 4 -

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

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

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

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)

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 and collocated RCLWI scenario for an ideal/internal backhaul

RCLWI 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 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 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 Mobility Concept 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

LWIP Flow

LWIP Tunnel for Data Bearer Setup Procedure

LWIP Tunnel Setup and Data Bearer Configuration - Init
1.The eNB configures the UE to perform WLAN measurements for LWIP operation 2.The UE applies the new configuration and replies with RRCConnectionReconfigurationComplete message 3.UE sends WLAN measurements to the eNB 3a.The eNB sends the LWIP Addition Request message to request the LWIP-SeGW to allocate resources for a specific UE, including security material 3b.If the LWIP-SeGW is able to admit the tunnel request, it responds with the LWIP Addition Request Acknowledge message

LWIP Tunnel Setup and Data Bearer Configuration - Associate
4.The eNB sends the RRCConnectionReconfiguration message to the UE including the WLAN mobility set 5.The UE applies the new configuration and replies with RRCConnectionReconfigurationComplete message 6.UE associates with WLAN in consideration of the mobility set, if not already associated

LWIP Tunnel Setup and Data Bearer Configuration - Confirm
7.UE sends confirmation of the WLAN association to the eNB 8.The eNB sends the RRCConnectionReconfiguration message to the UE including the necessary parameters to establish IPSec tunnel over WLAN and may, configure data bearers to utilise the IPsec tunnel 9.The UE applies the new configuration and replies with RRCConnectionReconfigurationComplete message

LWIP Tunnel Setup and Data Bearer Configuration
The UE uses the parameters in the new radio resource configuration to setup the IPsec tunnel with the LWIP-SeGW to complete the establishment of the LWIP tunnel with the eNB over the WLAN access eNB may add or remove data bearers to utilise the LWIP tunnel at any time after the establishment of the LWIP tunnel by sending the RRCConnectionReconfiguration message to the UE

Reconfiguration Procedure to Remove WLAN Resources from a Data Bearer

Reconfiguration to Remove WLAN Resources from Data Bearer
UE and eNB have the LWIP tunnel setup via WLAN 1.The UE is configured to receive data from a data bearer over the LWIP tunnel 2.The eNB determines that it needs to remove the WLAN resources for the data bearer

Reconfiguration to Remove WLAN Resources from Data Bearer
3.The eNB sends the RRCConnectionReconfiguration message to the UE including the necessary parameters to remove WLAN resources for the data bearer 4.The UE applies the new configuration and replies with RRCConnectionReconfigurationComplete message 5.UE stops receiving data for the data bearer over the LWIP tunnel

LWIP Tunnel Release Procedure

The Procedure of eNB Initiated LWIP Tunnel Release
UE and eNB have the LWIP tunnel setup via WLAN 1.The eNB determines that it needs to release the LWIP tunnel and initiates the release of the IPsec tunnel between the UE and LWIP-SeGW 2.The eNB sends the RRCConnectionReconfiguration message to the UE including the indication to release the LWIP tunnel

The Procedure of eNB Initiated LWIP Tunnel Release
3.The UE applies the new configuration and replies with the RRCConnectionReconfigurationComplete message 4.The UE releases the IPsec tunnel and associated data bearer configuration, and terminates the LWIP tunnel 5.The eNB sends the LWIP-SeGW Tunnel Release Request message to release remaining resources at the LWIP-SeGW

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

LWA Mobility A WLAN mobility set is a set of one or more WLAN Access Points (APs) identified by one or more BSSID/HESSID/SSIDs WLAN mobility mechanisms apply while the UE is configured with LWA bearer(s) The UE may perform mobility between WLAN APs belonging to the mobility set without informing the eNB All APs belonging to a mobility set share a common WT which terminates Xw-C and Xw-U The termination endpoints for Xw-C and Xw-U may differ The WLAN identifiers belonging to a mobility set may be a subset of all WLAN identifiers associated to the WT

IITH NeWS Lab The Networked Wireless Systems (NeWS) laboratory in the department of Computer Science and Engineering at Indian Institute of Technology Hyderabad A wide range of experimental and theoretical research in Wireless networks, Next-generation Internet, Pervasive Computing, Network Security and ICT for societal development Networked Wireless Systems (NeWS) Lab IIT Hyderabad,

IITH NeWS Lab’s LWIP A variant of LWIP and made commercial UE (Nexus 5) to readily work with the LWIP The developed LWIP testbed uses OpenAirInterface (OAI) for LTE network and Cisco Access Point/Atheros device with Hostapd as Wi-Fi interface The LWIP performance improvement of using UDP transmission over both LTE and Wi-Fi links The video transmission over LWIP unveils the potential of this link level aggregation

3GPP Proposal of LWIP

Architecture Proposal and Standards
This traffic steering is done above the PDCP layer of LTE and the LLC layer of Wi-Fi in their respective protocol stacks Based on the traffic steering mechanism LWIP is realized by introducing a Link Aggregation Layer (LAL) in the protocol stack of LWIP node LAL does not add any new header to the IP data packets received from EPC via the S1-U interface Packets going through LTE and Wi-Fi interfaces follow regular packet forwarding procedures At their protocol stacks and get delivered directly to IP layer

IITH NeWS Lab’s Implementation

LTE Wi-Fi Interworking at Link Level Components

LTE Wi-Fi Interworking Testbed Setup
LWIP testbed setup consists of OAI-LTE and Cisco AP connected through an Ethernet link EXMIMO2 (SDR) boards are used as radio front end for LTE Connected to a Linux machine using PCI express The Linux machine is in turn connected to the OAI core network (openair-cn) Running on a high-end server through gigabit Ethernet OAI core network comprises of MME, S-GW, P- GW, and HSS UE A commercial android phone (Nexus 5)

Working Procedure Running an Android application (developed in- house) in Nexus 5 Enables both LTE and Wi-Fi interfaces simultaneously to send and receive data through both interfaces at the same time The link-aggregation layer located in LWIP device runs a redirection module Traffic steering between LTE and Wi-Fi interfaces The implementation supports dynamic flow movement across LTE and Wi-Fi interfaces

LTE Wi-Fi Interworking Testbed Setup

Power Level of Wi-Fi and LTE Before Any Transmission

A File Is Simultaneously Downloaded Through Wi-Fi and LTE Interfaces

LWIP Experimental Parameters

Downlink Performance The performance of LTE-Wi-Fi integration is studied using UDP iPerf as a traffic application From a remote server iPerf sends data to the UE (Nexus 5) to check the downlink performance iPerf using UDP – LTE only, Wi-Fi only, LWIP Quality of a video transmission – LTE only, Wi-Fi only, LWIP

Throughput in iPerf Test Using UDP

A Video Streaming Over LWIP
Nexus 5 which is located at the coverage edge and its quality is checked using all three cases LTE only, Wi-Fi only, and LWIP The delay through Wi-Fi and LTE networks are comparable to the delay A locally cached data or a data center next to the Gateway of LTE and Wi-Fi networks The LWIP is making a best utilization of both LTE and Wi-Fi links Able to achieve a higher video quality as compared to standalone LTE and Wi-Fi links

A Video Streaming Over LWIP

Summary LTE fundamentality WLAN fundamentality
IEEE 3GPP integrating technologies Aggregating unlicensed bands : LAA, LTE-U RCLWI IPsec Tunneling : LWIP Link-layer aggregation : LWA

References TS Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 Introduction to Wireless LAN and IEEE , IEEE Architecture, Tight Coupling of LTE WiFi Radio Access Networks – A Testbed Evaluation,

單元6 OAI-LTE使用WiFi網路的卸載(Off-loading)

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