Rnc Whitepaper

WHITE PAPER

HSS Products Enabling RNC Development A White Paper

E-mail: [email protected]

www.hssworld.com

RNC Development

COPYRIGHT INFORMATION © Copyright Hughes Software Systems, 2004 All information included in this document is under a license agreement. This publication and its contents are proprietary to Hughes Software Systems. No part of this publication may be reproduced in any form or by any means without the written permission of Hughes Software Systems Plot 31, Electronic City, Sector 18, Gurgaon 122 015, INDIA Tel: +91-124-2346666, 2455555 Fax: +91-124-2455100, 2455101 Website: www.hssworld.com E-mail: [email protected]

TRADEMARKS All the brand names and other products or services mentioned in this document are identified by the trademarks or service marks of their respective owners.

DISCLAIMER The information in this document is subject to change without notice and should not be construed as commitment by Hughes Software Systems. Hughes Software Systems assumes no responsibility or makes no warranties for any errors that may appear in this document and disclaims any implied warranty of merchantability or fitness for a particular purpose.

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Contents 1. Introduction 2. System Overview

5 6

2.1. RNC Position in WCDMA Network 2.2. RNC Functions RNC Internal View 2.3. RNC Interfaces 2.4. RNC Application 2.5. System Requirements for RNC

3. HSS Offerings 3.1. 3.2. 3.3. 3.4. 3.5.

Interface Software Control Plane Stacks User Plane stacks Features of HSS Control Plane stacks: Features of HSS User Plane stacks:

4. HSS Products Features 4.1. 4.2. 4.3. 4.4. 4.5. 4.6. 4.7.

High Performance Reliability Portable Uniform Management Interface Compatibility and Interoperability Standards Compliance HSS Stacks Performance Analysis – A case study

5. Conclusion

6 6 7 8 9 9

10 10 10 10 10 12

14 14 14 14 14 15 15 16

17

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RNC Development

Figures Figure 1: WCDMA Network Architecture ...................................... 6 Figure 2- RNC Internal View for ATM Transport ............................ 7 Figure 3: RNC Internal View for IP Transport .............................. 8

4

1.

This platform is characterized by high data

Introduction 3G

technology

supports

processing capabilities, which facilitate basic 3G a

wide

range

of

applications with varying quality of service profiles.

services such as high-speed data access and highresolution video.

The emerging role of Internet in the sphere of The Interface software consists of a set of

communications has also contributed to the evolution

Control Plane and User Plane protocol stacks. It

of 3G network. 3G networks are logically divided into a Radio Access Network (RAN) and a Core Network (CN), connected via an open interface. The RAN consists of the physical entities, Radio Network Controller (RNC)

handles the syntax and protocol details specified in various 3GPP, ITU-T, IETF specifications. However, the RNC Application controls the decision-making or Resource Management.

and Node B, which manage the resources of the access network. RAN facilitates and supports the interface between the User and the Core Network. A carrier-grade switching system such as RNC typically consists of the following three components:

The

Application

is

responsible

for

managing the resources and coordinating the various interfaces. As it uses the interface software, it does not have to deal with syntax and protocol details.

¡ A hardware platform ¡ Interface software to implement the various

RNC

This paper presents an overview of the RNC, its interfaces with various network nodes and typical

control/user plane protocols specified by various

system requirements of an RNC. It also includes a

standardization bodies.

brief description of the software components provided

¡ RNC Application

by

HSS

and

their

features.

RNC Application Interface Software Protocol Stacks by 3GPP, ITU-T, IETF etc.

High-end Hardware Platform

The hardware platform typically is a chassis comprising multiple line cards for terminating network interfaces. It also consists of processor cards for hosting the various control/user plane stacks and RNC Application.

5

RNC Development

2.

System Overview This section describes the network positioning,

basic functions and different interfaces of RNC in a Wideband Code Division Multiple Access (WCDMA) network. It also outlines the performance and network deployment requirements of a typical carrier grade RNC. Figure 1 depicts the position of RNC in a typical WCDMA Network Architecture.

Uu

Access Network

Core Network

Node B

B Iub

RNC

Iur

RNC

MSC

Iu_CS

VLR

Gs

Iub

Node B

Iu_PS

SGSN

Uu

Figure 1: WCDMA Network Architecture 2.1. RNC Position in WCDMA Network As depicted in Figure 1, the RNC is connected to Node B via an Iub interface. A single RNC may be connected to multiple Node Bs. Unlike the GSM network, an RNC in the UMTS network is connected to

2.2. RNC Functions A typical RNC performs the following functions: ¡ Admission Control ¡ Handover Control ¡ Load Control

other RNCs via an Iur interface. The RNC is connected

¡ Power Control

to Core Network via an Iu interface. The Iu interface

¡ Transfer of User Data

towards the Packet-Switched (PS) domain of the core

¡ Overall system access control

network is called Iu-PS, and the Iu interface towards

¡ Radio channel ciphering and deciphering

the Circuit-Switched (CS) domain is called Iu-CS.

6

¡ Integrity protection

¡

Functions related to mobility such as Handover

RNC Internal View

and relocation

Figure 2 and Figure 3 below depicts the modular

¡ Radio Resource Management and control

structure of an RNC for ATM transport and IP transport respectively and the interaction of various modules with each other.

Transport Network Control Plane

Iub Control Plane

NBAP

ALCAP

Iub User Plane

Iub FP AAL2

SAAL - UNI AAL5 ATM

Iub

Uu User Plane

P D C P

B M C

Uu Control Plane

RRC

RLC

RLC

MAC

MAC

Iub-FP

Iur User Plane

R N C A P P L I C A T I O N

Iur Control Plane

RNSAP

Iur FP

Transport Network Control Plane

ALCAP

SCCP - B MTP3 – B / M3UA AAL2

SAAL – NNI / SCTP AAL5 / IPOA ATM

Iur

Iu Control Plane Iu User Plane

Transport Network Control Plane

RANAP GTP (# 1)

ALCAP

SCCP - B

Iu UP MTP3 – B / M3UA (# 2) AAL2

IPOA SAAL – NNI / SCTP AAL5 / IPOA

AAL5

Uu

ATM

Iu-CS

#1: GTP will exist in the case of Iu-PS #2: Iu-CS uses MTP3 and SAAL for Signaling Transport Plane Iu-PS can use either MTP3/SAAL or M3UA/SCTP for Signaling Transport Plane

Iu-PS

Figure 2- RNC Internal View for ATM Transport

7

RNC Development

Iur User Plane

Iub User Plane

Transport Network Control Plane

IUB FP

TBD

UDP

Iub Control Plane

DATA LINK

Iub

BMC

Uu Control Plane

RRC

SCCP

RTP/RTCP

NBAP

IP

PDCP

RNSAP IUR FP

SCTP

Uu User Plane

Iur Control Plane

R N C A P P L I C A T I O N

UDP

SCTP IP DATA LINK

Iur Iu User Plane

Iu Control Plane

IU UP RTP/ RTCP

RANAP GTPU

SCCP M3UA

UDP

RLC

SCTP IP

MAC Layer 1

Uu

M3UA

DATA LINK

Iu-CS

Iu-PS

Figure 3: RNC Internal View for IP Transport Note: Transport Network Control Plane has not been frozen in the specifications. procedures for services such as Radio Access Bearer Assignment/Release, Paging, and SRNC Relocation.

2.3. RNC Interfaces

It provides a transparent path for the Network Access

¡ Iu Interface

Server (NAS) signaling messages between the User

The Iu interface provides protocol termination for the interface between RNC and the Serving GPRS Support Node (SGSN) or Mobile Station Controller (MSC). This functionality is for packet switched/circuit switched capabilities. The Iu interface facilitates

8

Equipment (UE) and CN. It also transports User data between CN and RNC. ¡ Iub Interface

The Iub interface provides protocol termination for the interface between RNC and Node B. It provides a set of functions, which includes Cell Configuration

Management,

Management/Supervision, Management

and

Radio

System

Common

Link

Information

Transport

Channel

Management. It also relays User data between RNC and Node B.

RNC may support up to 256 Node Bs. It may support approximately 64K subscribers. International standards define six service usage environments of 3G services. The network planning is accomplished in such a way so as to facilitate an equal distribution of these usage sets. The mean traffic intensity can be statistically estimated as 1.15 Busy Hour Call Attempts (BHCA) per user. Therefore, for an average of 64k subscribers, a typical RNC may

¡ Iur Interface

be required to support 74k BHCA. It should also

The Iur interface provides protocol termination

support peek data rate of 20 Mbps for CS domain and

for the interface between Drift RNC and Serving RNC.

200 Mbps in downlink/700 Mbps in uplink for PS

It facilitates procedures for services such as Radio

domain.

Link

Management/Supervision,

Physical

Channel

Reconfiguration, Paging, and Common Transport Channel Management. It also transports User data between two RNCs.

¡ Compatibility and Inter-operability The RNC should be inter-operable with network nodes and User Equipment compliant with different

¡ Uu Interface

UMTS releases.

The Uu interface provides protocol termination for the interface between UMTS Terrestrial Radio Access Network (UTRAN) and UE. It facilitates procedures for services such as RRC Connection and Radio Bearer Management,

Mobility

Management,

and

Measurements. It also facilitates procedures for Paging, Authentication and Ciphering.

2.4. RNC Application The RNC Application interacts with multiple interfaces for the overall control of the RNC. It is also responsible for all decision making. It also performs various other control functions such as Admission control, Power Control, Mobility Management.

2.5. System Requirements for RNC ¡ Performance Based on market research analysis, it can be concluded that a typical medium sized field deployable

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RNC Development

¡ Iu-UP

3.

HSS Offerings This section describes the HSS 3G offerings,

which can enable the OEMs to reduce time-to-market

¡ Iub-FP ¡ Iur-FP ¡ GTP-U ¡ PDCP

for RNC.

3.1. Interface Software HSS has developed the control plane and user plane stacks required for building an RNC. Stacks for various interfaces of RNC - Iu, Iub, Iur and

3.4. Features of HSS Control Plane stacks: ¡ RANAP Stack Features/Functions: w

Uu interface are available as ready-to-use and platform-independent building blocks.

99 w

These interfaces are divided into various planes, Control Plane and User Plane. A brief description of HSS Stacks for various planes is given below.

Supports Release 5, Release 4 and Release Interacts with both 3G SGSN (PS Domain ) and 3G MSC (CS Domain)

w

Provides Iu Signaling Connection Management, where connections are maintained on a per domain/per UE

3.2. Control Plane Stacks

basis. ¡ Radio Access Network Application Protocol

w

(RANAP) – for Iu Interface ¡ RNSAP – for Iur interface ¡ Node B Application protocol (NBAP)- for

procedures from the CN w

Supports Paging Notification where it also implements Paging Coordination.

Iub Interface ¡ Radio Resource Control (RRC) - for Uu

Facilitates a set of general UTRAN

w

Supports SRNS Relocation in conjunction with the RNC Application.

interface ¡ Signaling Connections Control part (SCCP)

w

Provides SCCP Connection Management

¡ Message Transfer Level Part 3 (MTP3)-B

w

Provides Redundancy Support

/SAAL-NNI for the ATM transport option ¡ M3UA/Simple Control Transmission Protocol (SCTP) for the IP transport option ¡ ALCAP ¡ SAAL-UNI(for ATM transport option) – for Iub Interface

¡ RNSAP Stack Features/Functions: w

99 w

3.3. User Plane stacks

10

Supports RNSAP Common, Dedicated, Mobility, and Global procedures for both

¡ Radio Link Control (RLC), Media Access Control (MAC)- for Uu interface

Supports Release 5, Release 4 and Release

SRNC and DRNC w

Provides SCCP Connection Management

w

Provides Redundancy Support

¡ NBAP Stack Features/Functions: w

Supports Release 5, Release 4 and Release

¡ MAC Stack Features/Functions w

99 w

Supports NBAP Common and Dedicated

99 w

procedures w

Provides Redundancy Support

Supports Release 5, Release 4 and Release Supports mapping logical to transport channels

w

Provides selection of appropriate Transport Format for each Transport Channel (TFCI

¡ RRC Stack Features/Functions: w

Supports Release 4 and Release 99

w

Configures RLC/MAC entities

w

Performs the mobility functions of the RRC

Selection) w

transport channels w

connection w

Performs paging and notification

w

Supports UE measurement reporting and reporting control

w

Controls ciphering configuration of RLC/MAC

w

Performs integrity protection and integrity check of RRC messages

w

sets w

Provides traffic volume monitoring

w

Provides dynamic transport channel type switching

w

Provides Ciphering support for TM Mode RBs

w

For message transactions between the RLC,

Supports parallel execution of multiple

MAC and FP protocol entities, zero buffer copy mechanism is used.

Broadcasts information related to the access stratum and non-access stratum. A separate

¡ SCCP Stack Features/Functions:

SIB Encoder Library, which is used at RNC

w

Class 0, 2 Services

and Node B, supports this function.

w

Segmentation and Re-assembly

w

Redundancy Support

w

Distribution Support

¡ RLC Stack Features/Functions: w

Supports multiplexing / de-multiplexing of higher layer PDUs into / from transport block

transactions between UTRAN and UE w

Supports identification of UEs on common

Supports Release 5, Release 4 and Release 99

¡ MTP3-B Stack Features/Functions:

w

Supports Segmentation and Re-assembly

w

Supports Concatenation and Padding

w

Supports the transfer of User Data in

w

Provides Signaling Link Management

AM/UM/TM mode

w

Supports Load Sharing

Provides Error Correction and In-Sequence

w

Provides Redundancy Support

Delivery

w

Provides Distribution Support

w

w

Provides Flow Control

w

Provides Ciphering support for AM/UM Mode

w

Provides Message routing, discrimination and distribution

¡ M3UA Stack Features/Functions:

RBs

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RNC Development

w

Transport of SS7 MTP 3 user signaling over

w

IP using SCTP

99 w

¡ SCTP Stack Features/Functions: w

Reliable transport of signaling on top of an

¡ SAAL-NNI Stack Features/Functions: w

Supports SAAL connection management

w

Provides Link status and remote processor status mechanisms

w

w

w

Supports signaling link error monitoring

w

w

Establishing and releasing end-to-end ondemand AAL2 connections

w

Signaling conversion for MTP-3

¡ SAAL-UNI Stack Features/Functions: w

Establishment and release of SAAL

w

Signaling link error monitoring

w

Flow control

Supports Release 5, Release 4 and Release 99

w

Supports transport of MAC-C/SH SDUs between SRNC and DRNC every 10ms

w

Supports Flow Control of FACH Data Streams

w

Multiplexes several UEs on one Transport Bearer

w

Provides CRC Check

w

Provides Error Detection (CRC Calculation)

w

Provides transport of UL and DL DCH Data

w

Supports Set of Coordinated DCHs on the same Transport Bearer

¡ Iub FP Stack Features/Functions: w

connections for assured transfer of data w

Rate matching of AMR data

¡ Iur FP Stack Features/Functions:

¡ ALCAP(Q.2630, Q.2150) Stack Features/Functions:

Transport of AMR data streams of various data bit rates

Provides reliable exchange of signaling information

Provides RNC Flow Control, Error Detection or Cyclic Redundancy Check (CRC)

unreliable routing-based packet network such as IP.

Supports Release 5, Release 4 and Release

Supports Release 5, Release 4 and Release 99

w

Node Synchronization

w

Transport Channel Synchronization

w

Transport of TBS across Iub interface in Uplink and Downlink Transport channels

3.5. Features of HSS User Plane stacks:

between Node B- CRNC (for common channels) and between Node B - SRNC

¡ GTP-U Stack Features/Functions: w

Supports Release 5, Release 4 and Release 99

w

Provides user data transmission

w

Provides tunneling of multi-protocol data

within each TTI of 10ms/20ms/40ms/80ms w

Error Detection (CRC Calculation)

w

Transport of UL and DL DCH Data

w

Supports set of Coordinated DCHs on the same Transport Bearer

packets ¡ PDCP Stack Features/Functions: ¡ Iu-UP Stack Features/Functions:

12

w

Supports Release 5, Release 4 and Release 99

w

Compression of redundant network PDU header information

w

Transfer of packet data protocol user data using RLC services

w

Sequence numbers for radio bearers to support ‘loss-less’ SRNS relocation

w

Flexible internal memory allocation (dynamic or static) to minimise memory usage

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RNC Development

4.

4.3. Portable

HSS Products Features HSS stacks are platform-independent (ease of

porting) and characterized by high performance, high throughput and high availability. They also provide high scalability. This has been made possible by modular design and porting library.

HSS stacks use a virtual environment known as the Common Stacks Porting Library (CSPL), which provide a uniform OS service interface for interacting with the Operating System. CSPL shields the HSS stacks from the Operating System function calls and instead

provides

consistent

function

interface,

irrespective of the OS used. CSPL maps these function calls to the OS function calls. Thus, all stack

4.1. High Performance

components become available for a particular OS by

The performance aspect of RNC is related to its

porting the CSPL to the OS.

ability to meet the call/session setup delays, timing

The advantages of using CSPL are:

requirements for providing the required QoS to the

¡ Uniform OS Services interface for all stacks

connected UEs. This requires a high throughput,

¡ Standardizes porting to new operating systems

which has been achieved by implementing the following design principles. ¡ Efficient memory management ¡ Optimized data structures ¡ Efficient search algorithms An

efficient

distribution

framework

is

also

required to facilitate high throughput rates. Traffic must be distributed across multiple instances, thereby increasing the traffic handling capacity of nodes and providing a unified view of the external network and stack users.

¡ Readymade ports for popular operating systems: w

Solaris

w

Linux

w

VxWorks

w

Win32

¡ Facilitates integration of a stack entity with other entities ¡ CSPL also provides the following services to the stacks: w

Memory Management for Contexts and Messages

HSS has established a strategy for the distribution of its protocol stacks, which can be tailored according

w

Scheduling

to customer needs.

w

Timer Management

w

Messaging

4.2. Reliability Carrier

grade

solutions

require

very

high

availability, of the order of five nines. This is achieved by ensuring that there are no single points of failure in the system. HSS has prior experience in developing carrier grade solutions and has a ‘High Availability Framework’, which has been used internally for various HSS products and customer solutions to implement high availability systems. High Availability Platform support has been provided for most of the Application Protocol stacks.

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4.4. Uniform Management Interface HSS protocol stacks provide an interface with a Management Entity. This interface is used for initialization, provisioning of the stacks, managing timers, debug trace levels, error levels and statistics reporting required for the operation, administration and maintenance of protocol stacks. These are explained below in detail.

Statistics can be used by the RNC developer to

4.4.1. Provisioning The protocol stacks are initialized and provisioned through

the

information

Management is

provided

Interface.

to

the

The

stacks

static in

the

provisioning API. Examples of static information are the number of nodes connected and the point codes. Parameters

that

tune

the

provide diagnostic for O&M purposes.

run-time-memory

requirements of the stack are provided along with this information. For example, the number of UE contexts supported by the stack is configured through this API. The operator-specific values for Procedure Retries and Timer Values are also provided.

4.4.2. Debugging and Tracing The stacks provide for multiple trace levels. The tracing support is controlled by a compile time option that excludes/includes tracing facilities. After the tracing facilities are included through the compile time option, the run-time control of tracing is achieved through: ¡ Trace flags which specify the module/functionality/control flow for which the tracing information is required. ¡ Trace levels that specify the details of the tracing information required.

4.4.4. Error Handling This module contains the functions for error processing. Any occurrence of an error results in a call to a function in this module. This code is organized in a separate module to allow porting by the user, to enhance system diagnostics and customize the error handling. Error Handling is a compile time option that can be included or excluded using a compile time flag.

4.5. Compatibility and Interoperability HSS has delivered RNC protocol stacks to various customers, where nodes compliant to different UMTS releases have inter-operated with each other. The RNC protocol stacks have been inter-operated with network nodes of various OEMs and have been tested against the standard test tools. It reduces the risk of inter-operability against other vendor equipment.

4.6. Standards Compliance HSS

products

conform

to

the

international

standards published by 3GPP, ETSI and ITU-T. HSS is

By selecting the right trace levels for various

committed towards the continued conformance of its

trace flags, the operation of the stacks can be

products to these standards as they evolve in the near

debugged effectively. APIs are provided to set the

future.

trace level of any trace flag and to retrieve the current trace level.

4.4.3. Statistics Collection APIs are provided to collect various statistics in the RNC protocol stacks. A message-based interface is provided for the initialization and collection of various statistics for events occurring in the stack layer such as reception of peer messages. This facility can be excluded at compile time. The following statistics classes are collected: ¡ Protocol Statistics ¡ Connection Data Statistics ¡ Error Statistics

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RNC Development

4.7. HSS Stacks Performance Analysis – A case study Performance analysis of HSS control plane stacks was done on a COTS reference platform. The reference platform was PowerPC single-processorbased. It had an: ¡ OC3/STM1 Communications controller, ¡ 400 MHz clock, ¡ 100 MHz system bus ¡ 1 MB L2 (secondary cache) cache and ¡ on-chip D/I cache of 32 KB. The messages used in the calculation covered all the important messages required in a typical call setup scenario. Uu Interface: RRC Messages at Uu interface required for Connection Setup ¡ RRC Connection Request ¡ RRC Connection Setup ¡ RRC Connection Setup Complete ¡ Initial Direct Transfer ¡ RRC Security Mode Connection setup/hr (at 10 % CPU) = 115K Iub Interface: NBAP messages at Iub interface required for Connection Setup ¡ Radio Link Setup Request ¡ Radio Link Setup Complete Connection setup/hr (at 5 % CPU) = 125K Iu Interface: RANAP Messages required for Connection Setup ¡ Initial UE message ¡ Security Mode Command ¡ Direct Transfer ¡ Radio Access Bearer (RAB) Assignment Request ¡ RAB Assignment Response Connection setup/hr (at 10 % CPU) = 130K

16

Considering the connection release time and unsuccessful call attempts, and extrapolating the afore-mentioned connection setup data, BHCA of 150K

(from

the

signaling

message-processing

perspective) can be achieved using HSS stacks on a single processor-based platform. HSS has also done a study of standard Network Processors available. Based on this study

and

extrapolating the results, it can be said that HSS user plane protocol stacks, when ported on Network Processor should be able to meet the data throughput requirements.

5.

It meets all the carrier grade requirements such

Conclusion The

implementation

as of

the

HSS

Interface

software facilitates the development of the RNC Application

and

reduces

the

time-to-market

high

availability,

high

throughput

interoperability. The interface software

and

can help

immensely in the development of a typical RNC within a short span of time.

considerably. The Interface software handles the protocol details, thereby allowing the user to focus on the core functionality of RNC Application.

17

Hughes Software Systems is a key supplier of communication technologies for Voice over Packet, Intelligent Networks and High-speed Mobile Networks, and is fully focussed on the needs of its customers to build Next Generation Networks. The comprehensive set of software building blocks from HSS consists of both protocol stacks and Integrated Interfaces for the 3G/UMTS Network Nodes Integrated Interfaces

Stacks

Uu

RRC,RLC,MAC,FP, PDCP

Iu-PS

RANAP, SIGTRAN

Iu-CS

GTP

Iub

NBAP, SAAL, ALCAP

Iur

RNSAP

Hughes Software Systems Plot 31, Electronic City, Sector 18, Gurgaon 122 015, India Tel: +91-124-2346666, 2455555 Fax: +91-124-2455100, 2455101 HSS USA, East Coast

HSS Europe

Germantown Tel: +1-240-453-2498 Boston Tel: +1-617-547-6377 Dallas Tel: +1-972-517-3345

Milton Keynes, UK Tel: +44-1908-221122 Germany Tel: +49-6155-844-274 Finland Tel: +358 40 8290977

HSS USA, West Coast

HSS India

San Jose Tel: +1-408-436-4604 Los Angeles Tel: +1-323-571-0032; 571-0114

E-mail: [email protected]

Gurgaon Tel: +91-124-2455555; 2346666 Bangalore Tel: +91-80-2286390

www.hssworld.com