S1.2.slides

Fraunhofer FOKUS Competence Center NGNI

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Marius Corici, Mihai Constatin, Dwianto Dana Satriya, Dragos Vingarzan, Valentin Vlad, Lukas Wöllner Fraunhofer Institute FOKUS, Germany

[email protected]

www.FOKUS.fraunhofer.de/go/ngni www.FUSECO-Playground.org

www.OpenEPC.net

Integrating Off-the-shelf 3GPP Access Networks in the OpenEPC Software Toolkit

- Realizing cost-efficient and complete small-scale-operator testbeds -



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Overview

The Problem – Providing research infrastructure for both the academia and the industry – Cost-effective solutions for NGN test-beds in the mobile domain – Realizing realistic testing environments

The OpenEPC Project

– Short overview

Integrating off-the-shelf 2G/GPRS femto-cells in OpenEPC – Interfaces and protocol stacks – Procedures and implemented functionalities – Lessons learned – Validation

Outlook

– 3G/UMTS progress status – 4G/LTE short overview

Q&A



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The Problem: Access to Mobile Technology

Wireless testbeds

– Most deal with WiFi (e.g. open source WiFi drivers like MADWIFI have spurred the creation of numerous test-beds and incredible innovation)

– Also numerous related to ZigBee or Bluetooth

– Yet for the most used today – GPRS, UMTS, LTE – very few

Blocking issues

– Very complex interfaces and protocol stacks

– Education: how many here have learned about the GPRS protocols during university courses?

– Equipment costs

– Proprietary/Specialized hardware

– Interoperability and vendor-locking

– “Secret” algorithms

– Spectrum license required

Today mobile drives innovation in the telecommunication domain

– Such test-beds are “must-have” for all universities and R&D organizations



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What is the 3GPP Evolved Packet Core

An overlay over the operator core network providing all-IP connectivity

– Over heterogeneous accesses (LTE, 3G, 2G, non-3GPP, femto, …)

– Using the operator transport network

– Towards all IP based applications

IP connectivity services include features for:

– Seamless mobility management

– Mobile device reachability

– QoS and charging control

– Secure access and authorization

– Based on the subscription profile

– Based on the application requirements

– With reduced OPEX for the operator

– Forwarding of IP data packets



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Background: The OpenEPC Project www.openepc.net

OpenEPC includes the main functions of 3GPP Evolved Packet Core (Rel. 8, 9, 10, 11, …)

The principles of standard alignment, configurability and extensibility have been respected in the overall architecture and in the specific components implemented

OpenEPC Rel. 4 enables the establishment of small operator network testbeds including:

Core network mobility support (GTP, PMIP)

Integration with real LTE, 3G, 2G and WiFi

AAA for 3GPP and non-3GPP accesses

Policy and Charging Control

Access network selection

Common mobile equipment support

PLEASE NOTE: OpenEPC does not claim 100%

standard compliance, but allows for early prototyping



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OpenEPC Rel. 4 – Functions and Interfaces



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Open Source IMS Core and OpenEPC test-beds around the world

Americas



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3GPP EPC – 2G/GPRS Architecture with EPC

GPRS/EDGE RAN (GERAN) is connected to the core network through two interfaces:

– A interface

for CS attachment, IDLE mode management, CS service establishment, …

– Gb interface

for PS attachment, IDLE mode management, PS bearer establishment, …

In 2G MSC attachment is mandatory for PS services!



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3GPP EPC – Gb – Signaling Plane



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3GPP EPC – Gb – User-data Plane



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3GPP EPC - Gb – BSS <-> SGSN Communication

Network Service (NS)

BSS GPRS Protocol (BSSGP)



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Network Service

NS provides the services:

– Service Data Unit (SDU) transfer – exchange of upper layer protocol data units

– Network congestion indication

– Status indication



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BSS GPRS Protocol (BSSGP)

Provisioning of parameters between: – BSS - derived from RLC/MAC – SGSN - received from higher layers

Provisioning of functionality to enable two physically distinct nodes to operate management control functions.



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Logical Link Control (LLC)

Provides a reliable link between the MS and SGSN



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Logical Link Control (LLC)

Provides a reliable link between MS and SGSN

Separate channels for GMM, SMS, IP, etc

LLC transmission modes:

– Unacknowledged mode

– Acknowledged mode

Modes of operations:

– Async. Disconnected Mode (ADM)

– Async. Balanced Mode (ABM)

Functions:

– Error detection, recovery, reorder

– Congestion control, window management

– XID negotiation – parameter exchange

– Data cyphering



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3GPP EPC – 2G Integration Signaling Plane – GSM Layer 3

GPRS Mobility Management (GMM)

Session Management (SM)



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GPRS Mobility Management and Session Management

GPRS Mobility Management

– Enables the service continuity while the MS is mobile

– Procedures: Attachment/Detachment

Authentication

Paging (PS and CS)

Location procedures – Routing area updates

Session Management

– Establishes PDP Contexts, which provide the IP data paths

– Management of QoS parameters

Short Message Service

– Delivery (SMS-MT) and reception (SMS-MO) of short messages to/from MS

For future development

– Call Control – enabling CS call management



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UE-SGSN Interface – User-Plane Data

Link Layer Connection (LLC) Protocol

Subnetwork Dependent Convergence Protocol (SNDCP)



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Packet Transmission Protocol Stack

The IP data packets are processed and encapsulated by the SNDCP and LLC

SNDCP:

– Maps IP packets to network characteristics

– Packets are conveyed to Network PDUs (N-PDUs)

– An SNDCP header is added

LLC:

– Provides a reliable MS-SGSN link

– Adds an LL header

RLC or BSSGP:

– Receive the LL PDUs

– Encapsulate them in RLC or BSSGP PDUs



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The ip.access nanoGSM/nanoBTS Picocell (model 165G)



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Working with Off-the-Shelf Devices



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Extensive OpenEPC Laboratory Test-bed

OpenEPC can be deployed on multiple machines realizing a comprehensive small mobile operator



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Personal OpenEPC Test-bed

OpenEPC can be completely virtualized in a single box

– External connections are used for connecting base stations, to the Internet or own components

– Some components can be disabled, if not required

Excellent for development

– Each developer can have his/her own EPC test-bed instance



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Single-box OpenEPC Connectivity Solution

OpenEPC can be minimized and run as separate functions in a single box

– Addressing micro-deployments which require complete or partial functionality

Optimizing data paths and control while maintaining standard alignment

– Can be integrated with radio-access and offering IP connectivity

For reduced areas - e.g. femto/nano-cell, “hotspots”, home

With one or multiple radio (or fixed technologies)

in an enterprise wireless environment

– Especially useful in Professional Mobile Radio application



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1. Demo Scenario CS Attachment



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2. Demo Scenario SMS



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3. Demo Scenario PS Attachment



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4. Demo Scenario Operator Indicated Access Network Selection



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5. Demo Scenario Seamless Handover



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Lessons Learned

2G/GPRS was/is hard to implement!

– Many and very complex protocols

– Lots of testing and learning needed to develop them

– Unfortunately has some “secret” parts

The A3/A8 GSM algorithms with the COMP128 authentication – secret but reverse engineered

Using instead the USIM fallback with public AKA/Milenage transformation

– Or “expensive”/impractical protocols

The A interface should use MTP to transport SCCP

Using vendor proprietary SIG-IP to transport SCCP as pure-IP solution (cell was probably developed before 3G/UMTS brought the M3UA over SCTP standard alternative)



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Lessons Learned

3G/UMTS seems simpler now

– Reusing protocols and interfaces towards the Core Network

– Reusing many state-machines in the SGSN and MSC components

– Fortunately over-IP from day 1

– CS parts mostly optional, but not entirely eliminated as initially scoped

4G/LTE even simpler

– More intelligence in eNodeB less components between the Access Point

and the Core Network

– Much simpler to integrate with a Core Network, yet a different type of complexity

– Finally no PS requires IMS for calls, but that exists already in test-beds



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The ip.access nano3G Picocell Access Points



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Cost-effective Mobile Network Testbeds

OpenEPC enables the establishment of small scale networks

– Reduced number of subscribers, reduced number of base stations

– Re-using standard 3GPP radio equipment designed for micro-deployments

– Including all security, efficiency, subscriber oriented characteristics

Deployment examples besides research test-beds:

– isolated regions, enterprise networks, specialized networks

– Professional Mobile Radio: security, M2M (energy, gas), trains, logistics, military



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2G/GPRS References

3GPP TS 23.060 - General Packet Radio Service (GPRS); Service description; Stage 2

3GPP TS 48.016 - General Packet Radio Service (GPRS); Base Station System (BSS) - Serving GPRS Support Node (SGSN) interface; Network service

3GPP TS 48.018 - General Packet Radio Service (GPRS); Base Station System (BSS) - Serving GPRS Support Node (SGSN); BSS GPRS protocol (BSSGP)

3GPP TS 44.064 - Mobile Station - Serving GPRS Support Node (MS-SGSN); Logical Link Control (LLC) Layer Specification

3GPP TS 44.065 - Mobile Station (MS) - Serving GPRS Support Node (SGSN); Subnetwork Dependent Convergence Protocol (SNDCP)

3GPP TS 24.008 - Mobile radio interface Layer 3 specification; Core network protocols; Stage 3

ITU-T Q.711 - Functional description of the signalling connection control part

ITU-T Q.712 - Definition and function of Signalling connection control part messages

ITU-T Q.714 - Signalling connection control part procedures

ITU-T Q.715 - Signalling connection control part user guide

ITU-T Q.716 - Signalling System No. 7 - Signalling connection control part (SCCP) performance

3GPP TS 48.006 Signalling Transport Mechanism Specification for the Base Station System - Mobile Services Switching Centre (BSS-MSC) Interface

3GPP TS 48.008 - Mobile Switching Centre - Base Station system (MSC-BSS) interface; Layer 3 specification

3GPP TS 29.272 - Evolved Packet System (EPS); Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol



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Acronyms

BSS – Base Station Subsystem

BSSGP – BSS GPRS Protocol

BTS – Base Transceiver Station

CC – Call Control

CS – Circuit Switched

EPC – Evolved Packet Core

GERAN – GSM EDGE RAN

GGSN – Gateway GPRS Support Node

GMM – GPRS Mobility Management

GPRS – General Packet Radio Service

GTP – GPRS Tunneling Protocol

HLR – Home Location Register

HSS – Home Subscriber Server

LLC – Logical Link Control

ME(or MS) – Mobile Equipment (Station)

MSC – Mobile Switching Centre

NS – Network Service

PDP – Packet Data Protocol

PGW – Packet Data Network Gateway

PS – Packet Switched

RAN – Radio Access Network

SGSN – Serving GPRS Support Node

SGW – Serving Gateway

SIM – Subscriber Identity Module

SM – Session Managements

SMS – Short Messaging System

SNDCP – Sub-network Dependent Convergent Protocol

USIM – UMTS SIM



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Backup Slides



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OpenEPC is not a product!

Or at least not yet ;-)

Targeted at test-beds and technology trials Driven by your demand

Implementing 90% of the standards with 10% efforts

– All the required security mechanisms, but unsecure for the real-life deployments – Functionality wins over stability – No high-availability – Basic provisioning but not proper management – Decent performance, without deep acceleration

No 100% compliance

– Yet doing very well on interoperability – Always going for the latest concepts (think 3GPP Rel.10-11, IETF drafts, crazy new ideas

to make-it-work)

But nothing wrong with not-a-product – It takes just days to get a new concept working – Sometimes it’s actually faster and better

This is not a “proper” car either, but it beats the Ferrari



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OpenEPC in Quick Numbers

7700 revisions

– And this is just the internal development tree

– 20+ external/project-specific development trees

8.5 commits / week-day (again just internal tree)

Wharf source code statistics (our platform)

– 120 Mbytes

– 4000 files

– 450K lines of C code

– 64K lines of comments

– 75K lines of PHP (GUI and provisioning)



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Integration of Access Networks

OpenEPC integrates with all 3GPP and non-3GPP access networks:

– LTE – interfaces towards third party eNodeB, common UE (S1-U, S1-MME)

– HSPA/UMTS – interfaces towards third party NodeB/RNC, common UE (Iu-PS)

– EDGE/GPRS – interfaces towards third party BTS/BSC, common UE (A, Gb)

– Trusted non-3GPP – AAA and IP connectivity interface

– Untrusted non-3GPP – AAA, IPsec, and IP overlay connectivity interface

Access Network Integration Use Cases:

– Deployment of realistic testbeds

– Perceiving the effect of the radio communication on applications

– Trustfully evaluations of new features

As backup solution, OpenEPC includes its own emulation of the 3GPP accesses

– Using public spectrum (WiFi)

– Enables replication without RAN equipment



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OpenEPC as an EPC functional reference

OpenEPC enables functional testing

– End-to-end scenarios

Most standard functions implemented

Most reference points exported

Completing the testbed ecosystem by integrating with other technologies:

– RAN, transport, IP, applications, etc.

(From 3GPP TS 23.401)

SGi

S12

S3

S1-MME

PCRF

Gx

S6a

HSS

Operator's IP Services

(e.g. IMS, PSS etc.)

Rx

S10

UE

SGSN

LTE-Uu

E-UTRAN

MME

S11

S5 Serving Gateway

PDN Gateway

S1-U

S4

UTRAN

GERAN



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OpenEPC as an EPC functional reference (cont.)

Validation of standards

– Vendor independent implementation

– All features have been demanded and used

– If it’s not there, chances are that you don’t need it

Identification of weak spots

– E.g. PDN GW handovers not so seamless

– E.g. AAA Server S6b functionality not usable in the current state (TS 29.273)

3GPP TS 23.401 OpenEPC Realization

SGi

S12

S3

S1-MME

PCRF

Gx

S6a

HSS

Operator's IP Services

(e.g. IMS, PSS etc.)

Rx

S10

UE

SGSN

LTE-Uu

E-UTRAN

MME

S11

S5 Serving Gateway

PDN Gateway

S1-U

S4

UTRAN

GERAN



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Education

Today students still do not have enough access to Telco technologies – Never heard of SS7 in school – IMS is slowly making its way in the curriculum – The average Telecommunication graduate might know how to design an antenna, but

rarely how IP routing works – Computer Science/Engineering degrees give you a lot of insight into TCP/IP though

This hurts also the industry NG(M)Ns should be built now for the NGStudents

OpenEPC offers and independent and extensive implementation of a mobile network Empowering students to try their ideas Affordable, comprehensive, trouble-free start-up test-bed EPC-in-a-bottle + University-wide licensing = low cost/student



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Operators and Service Providers

Technology field-trials

Understand & evaluate the new architectures

Early estimations

Fast functionality gap-filling

Trial new service concepts without major investments

– Invest <1% in an independent test-bed

– Major vendors give bigger trials for free, but: There are ulterior motives

You don’t get the sources

Ensure correctness, feasibility and “charging” method

– E.g. can IPv6 be deployed now?

– E.g. can charging support fair split of costs between subscribers, content/service providers, advertisers, etc

Prevent vendor-locking by challenging vendors to export and integrate on standard reference points



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Openness

Open = Source code and full control

– For trying new concepts and ideas

– For implementing missing functionality

Independent, Comprehensive, Flexible

ideas

research

patents

standards

pre-products/prototypes



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Hardware and Software Requirements

OpenEPC is designed to work on COTS hardware – Standard x86 would do, other platforms also feasible – Could be optimized for a specific platform

Running on standard Linux

– Reference setup realized on the most used and most user-friendly distribution today, Ubuntu Linux

– Other Debian-based distros should be usable out of the box – With Rel.4 we are adding Fedora Core and other RedHat-based distros – For the rest, it’s just a matter of extending some installation scripts

Low memory foot-print, easy on CPU usage

– Typically using Intel® Atom™ small-form-factor, inexpensive systems

Scalable multi-process architecture – C-based platform, optional C++ modules

Using standard libraries, tools and enablers

– MySQL, Apache, PHP, BIND9, …



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Just add Radio, Devices and Applications



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Small-to-Medium Size Operator Network Testbeds

OpenEPC enables the establishment of small scale networks

– Reduced number of subscribers, reduced number of base stations

– Re-using standard 3GPP radio equipment designed for micro-deployments

– Including all security, efficiency, subscriber oriented characteristics

Deployment examples:

– Small countries, isolated regions, enterprise networks, specialized networks

– Professional Mobile Radio: security, M2M (energy, gas), trains, logistics, military



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Trialing Radio Technologies

OpenEPC provides the network functionality for various radio technologies

– No need for emulations of core network

– Radio technology developers can concentrate on radio technology

Developing new LTE-A, 3G, and 2G equipment

Carrier Aggregation

Separation of Base Band Units from Radio Heads

…



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Trialing Applications

Realizing real network conditions in which applications can be tested

– Mirroring the look-and-feel of network operator environment

– Reproducible network conditions

– Using multiple access networks

– Can be developed and evaluated over multiple mobile devices

– Effects of wireless communication can be determined



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Telekom Innovation Laboratories established an OpenEPC testbed at their premises for enabling the further research in the area of various access technologies, access and core network energy efficiency, as well as in other innovation areas related to the Operator Infrastructures for the Future Internet.

OpenEPC at Deutsche Telekom



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VoLTE

A cost and effort efficient VoLTE testbed presumes putting together the following functionality:

– A VoLTE mobile device application – e.g. FOKUS RCS Client for Android

– An LTE capable smartphone

– An LTE Radio Access Network

– OpenEPC core network providing default and dedicated bearers

– Open IMS Core

– (Optional) IMS Application Servers, Session Border Nodes, Media Servers, …



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SRVCC

A typical OpenEPC testbed setup including VoLTE features

Integration of CS voice

A new CS-PS handover module for mobile devices

CS-PS voice translation

SRVCC AS + specific interfaces

CS Voice

LTE

UMTS

GPRS

S1-U

S1-MME

S5/S8 SGi

S11

S6a

S6d

Gxx Gx Gy/Gz

Rx Sp

S-GW PDN GW

MME

SGSN

PCRF Charging System

OpenIMSCore

HSS/SPR

eNodeB

RNC NodeB

BSC BTS

MSC Sp A

Gb

Iu-PS

S12

S4

Mobile Phone

CS-PS Control

Mobility Manager

CS Voice Stack

CS-PS Translation

SRVCC AS



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Emulating LTE over Public Spectrum

Emulating LTE-Uu – eNodeB simulation with WiFi

– Spectrum-license free

– Full protocols, but no real radio

– Emulating RRC, PDCP, RLC and MAC

– Mobile Station and eNodeB prototypes

LTE-Uu Emulation

WiFi 802.11

Documents

S1.2.slides