01 01 rn33021en20gla0 ran interface and protocols [compatibility mode]

8/10/2019 01 01 RN33021EN20GLA0 RAN Interface and Protocols [Compatibility Mode]

1/41

RAN Interface and Pritocols

RN33021EN20GLA0 1


2/41


RN33021EN20GLA0 3


3/41


RN33021EN20GLA0 4


4/41


RN33021EN20GLA0 5


5/41


WCDMA Radio Access Network (WCDMA RAN)

RN33021EN20GLA0 6

WCDMA RAN consists of one or more Radio Network Subsystem (RNS) where eachRNS is constructed by a Radio Network Controller (RNC) and its controlled Node Bs. The

main function of WCDMA RAN is handling all radio-related functionalities and managingradio resources in a 3G network. In addition, WCDMA RAN also handlestelecommunication management for Circuit-switched and Packet-Switched traffic in a 3Gnetwork.

The standardised interface between RNCs is called Iur, and RNC-Node B interface iscalled Iub.

Core Network

Core Network (CN) is responsible for routing calls, data connections or other definedservices to external network as well as handling user mobility.

RAN interface toward Switching Core Network (SCN) is called Iu-CS. It is implemented

by connecting RNC to MSC Server (MSS) for control plane and to Multimedia Gateway(MGW) for user plane.

RAN interface toward Packet Core Network (PCN) is called Iu-PS, and it is implementedby connecting RNC to Serving GPRS Support Node (SGSN).

RAN interface toward Cell Broadcast Center (CBC), for Cell Broadcast Service (CBS), iscalled Iu-BC.

RAN interface toward Positioning Center (PC), for Location Service (LCS), is called Iu-PC. It is implemented by connecting RNC to Standalone SMLC (SAS).

NSN also provides alternative solution for LCS, which is implemented by connecting RNCdirectly to A-GPS server. For this solution, the position calculation is done by RNC. Theproprietary interface toward A-GPS server is called A-GPS Data Interface (ADIF).


6/41


Operation Support System

RN33021EN20GLA0 7

Operations Support System (OSS) is common for both 2G and 3G networks. The samemanagement system is used for managing both the network and the services provided. In

the NSN 3G solution, NetAct Framework is used for this task. The O&M interface towardOSS, called Network Interface for 3rd Generation Network (NWI3), is a CORBA basedinterface.


7/41


UTRAN interfaces are vertically divided into a control plane and a user plane.

RN33021EN20GLA0 8

In the control plane, signalling messages are carried over the interface using a specificapplication protocol.

In the user plane, different kinds of user data is carried over the interface for instanceencoded speech, IP traffic, or various kinds of multimedia information.

Also, higher layer signalling traffic for instance RRC messages between the RNC anduser equipment are carried in the user plane.


8/41


UTRAN interfaces are horizontally divided into radio network layer and transport

RN33021EN20GLA0 9

.

The radio network layer contains the application protocols in the control plane and datastreams carrying user data in the user plane.

The transport network layer offers various signalling bearers and data bearers for reliabletransport of the radio network layer information. Two options are available for transportnetwork layer used in UTRAN: ATM-based and IP-based transport bearers.


9/41


Bearer is a transport entity with specified capacity and Quality of Service (QoS)

RN33021EN20GLA0 10

. .RAN point of view are Radio Access Bearers (RAB) and Radio Bearers.

The UTRAN transport network layer is concerned with bearer management at the lowestlevel.

Within the User Equipment (UE) consists of Mobile Terminal (MT) and TerminalEquipment (TE). MT supports radio transmission and channel management, while TEprovides functions for the operation of the access protocols. MT and TE may exist on thesame device.


10/41


Asynchronous Transfer Mode (ATM) Technology has been selected as transport

RN33021EN20GLA0 11

ATM provides efficient support for transmission of voice, data, and video.

ATM provides QoS mechanism.

ATM runs on SDH/PDH network, as they are used by GSM transport as well.

Starting in Rel-5 specification, all the UTRAN transport can be replaced with IP. In thiscase even though the data link and physical layers could remain based on ATM (knownas IP over ATM), they need not be. This flexibility is provided to suit the needs of bothnew and existing operators.

There are several motivation to implement IP-based transport:

It is better suited to support the rapidly growing mobile data and multimedia services

It can integrate seamlessly with Internet. It provides a better solution for making different radio technologies transparently to

users, etc.


11/41


AAL2 is an ATM adaptation layer on top of ATM layer. It provides mechanism to multiplex

RN33021EN20GLA0 12

data rate and real-time service such as voice. Data from each source is identified by 8-bit

channel identifier (CID).

AAL2 has no Segmentation and Reassembly (SAR) sublayer, but rather introduces CPSand SSSAR at the convergence sublayer. The maximum payload on the CPS packet(AAL2 mini-packet) is 64 bytes. Therefore, to accommodate larger data from a source, itneeds SSSAR layer to be implemented.

In 3G UMTS, AAL2 is used as adaptation layer for user plane in Iub, Iur and Iu-CS.


12/41


AAL2 channel is semi-permanent connection. It needs to be set-up before use and

RN33021EN20GLA0 13

.used. This is done by AAL2 Signalling Protocol, also known in UMTS as Access Link

Control Application Part (ALCAP).


13/41


AAL5 is designed for the transport of large and non-real-time data. In fact, its largest role

RN33021EN20GLA0 14

.which, again, can be up to 64 kbytes long. The SAR adds no overhead to the message

and merely segments it into 48-byte chunks. AAL5 is used across the UMTS Iu-PSinterface to connect to the PS Core Network for the transport of user traffic. With someaddition service specific layer, the AAL5 is also used for transport of signalling.


14/41


ATM provides additional protocol stacks on top of AAL5 CPCS to support reliable

RN33021EN20GLA0 15

. .

The following key function is performed by SSCOP:

Transfer of user data in-sequence.

Error control.

Flow control.

Keep alive.

Error and status reporting.

The role of the SSCF is to interface the protocols accessing the SAAL to the SSCOPbelow. The SSCF provides the following services to the upper layers:

Unacknowledged data transfer.

Assured data transfer.

Transparent transfer of data.

Establishment and release of signalling connections.


15/41


Internet Protocol (IP) is a transport protocol that responsible to deliver IP packet

RN33021EN20GLA0 16

.

Version - The current version of IP is 4.

IHL (Internet Header Length) - This field gives length of the IP header in 32-bit words.The minimum header length is five 32-bit words.

Type of Service - The source IP can designate special routing information. This fieldrecently has received more attention with the emergence of Quality of Service (QoS)technologies.

Total Length - This field identifies the length, in octets, of the IP datagram (IP headerand the data payload).

Identification - This field is an incrementing sequence number assigned to messageswhen they are too large to fit in one datagram.

Flags - The Flags field indicates fragmentation possibilities. The field indicates whetherfragmentation is allowed or not, and tells the receiver that more fragments are on the waywhen fragmentation is in used.

Fragment Offset - This field is a numeric value assigned to each successive fragment.

Time to Live - This bit field indicates the amount of time in seconds or router hops thatthe datagram can survive before being discarded.

Protocol - Protocol field indicates the protocol that will receive the data payload.Common value are: 1 (ICMP), 6 (TCP) and 17 (UDP).

Header Checksum - Calculated value to verify the validity of the header only.

Source IP Address

Destination IP Address

IP Options - This field supports a number of optional header settings primarily used fortesting, debugging, and security.

Padding - The Padding field provides additional zero bits so that the total header lengthis an exact multiple of 32 bits.


16/41


There are several protocols, standardised by IETF or 3GPP, defined to work together with

RN33021EN20GLA0 17

.They are:

Real-time Transport Protocol (RTP)/ Real-time Transport Control Protocol(RTCP).

The RTP protocol (RFC 1889) provides end-to-end delivery of real-time audio andvideo over an IP network via the UDP. RTP provides payload-type identification,sequence numbering and delivery monitoring. Each payload that is sent using RTPis timestamped to ensure that it can be delivered to the CODEC at the correct rate.

RTCP (also covered in RFC 1889) provides control services for an RTP session.These include QoS feedback (e.g. round trip time, jitter, etc.), session identificationand synchronization information.

Streaming Control Transport Protocol (SCTP).

The SCTP protocol (RFC 3286) is a reliable transport protocol which resides on topof IP and is used by M3UA for transport across the IP network. SCTP delivers

messages on the same stream in sequenced order to an application. Messagesthat are not in the same stream do not need to preserve this message order. Whileone stream of messages can be blocked, due to the loss of a packet, for example,another stream can continue to be delivered to the application. It is different to TCPwhich is simply a sequence of bytes.


17/41


Application protocol in Iu-CS control plane is RANAP. RANAP messages are carried over

RN33021EN20GLA0 18

adaptation layer. Other option, RANAP messages can be mapped to IP over ATM

transport with using SS7 protocols over IP (SCCP and M3UA).

In the user plane, with ATM option, Iu-CS utilises AAL2 for carrying user traffic. As aconsequence, ALCAP is needed in transport network layer. On top of AAL2, the user datais carried within Iu User Plane Protocol (Iu-UP) frames. In Support Mode, the Iu-UP framesize can change during the connection. This feature is useful for transport of AMRencoded speech. In Transparent Mode, Iu-UP does not offer any services.


18/41


Using IP as transport network layer in Iu-CS, ATM is now replaced with Ethernet. In the

RN33021EN20GLA0 19

, . ,is used instead of AAL2. With the absence of AAL2, there is no need transport network

layer control plane.


19/41


Control plane part of Iu-PS is the same as it is on Iu-CS. In the user plane, user data -

RN33021EN20GLA0 20

- - -services. The user data are transported by IP over ATM.


20/41


For IP-based transport network in Iu-PS, ATM is replaced with Ethernet. In the control

RN33021EN20GLA0 21

, - . ,transported by IP over Ethernet.


21/41


The complete list of RANAP functions according to 3GPP TS25.413:

RN33021EN20GLA0 22

Relocating SRNC.

Overall RAB management. Queuing the setup of RAB.

Requesting RAB release.

Release of all Iu connection resources

Requesting the release of all Iu connection resources.

SRNS context forwarding function.

Controlling overload in the Iu interface.

Resetting the Iu.

Sending the UE Common ID

Paging the user.

Controlling the tracing of UE activity.

Transport of NAS information between UE and CN.

Controlling the security mode in UTRAN.

Controlling location reporting.

Location reporting.

Data volume reporting function.

Reporting general error situations.

Location related data.

Information transfer.


22/41


Application protocol in Iur control plane is RNSAP. RNSAP messages are carried over

RN33021EN20GLA0 23

adaptation layer. Other option, RNSAP messages can be mapped to IP over ATM

transport with using SS7 protocols over IP (SCCP and M3UA).

In the user plane, with ATM option, Iur utilises AAL2 for carrying user traffic. As aconsequence, ALCAP is needed in transport network layer. On top of AAL2, the user datais carried within Iur Frame Protocol (FP). There are separate Iur FP for dedicated andcommon channels.


23/41


For IP-based Iur, SS7 over IP protocols are used for the control plane. In the user plane,

RN33021EN20GLA0 24

.


24/41


The complete list of RNSAP functions according to 3GPP TS25.423:

RN33021EN20GLA0 25

Radio Link Management.

Physical Channel Reconfiguration. Radio Link Supervision. This function allows the DRNC to report failures and

restorations of a Radio Link;

Compressed Mode Control [FDD].

Measurements on Dedicated Resources.

DL Power Drifting Correction

DCH Rate Control.

CCCH Signalling Transfer.

Paging.

Common Transport Channel Resources Management.

Relocation Execution. Reporting of General Error Situations.

Measurements on Common Resources.

Information Exchange.

Resetting the Iur.

Tracing.

Direct Information Transfer.


25/41


Application protocol in Iub control plane is NBAP. Different to other interface, Iub does not

RN33021EN20GLA0 26

.ATM transport by ATM signalling adaptation layer. There is no option for IP over ATM in

Iub.

In the user plane, Iub utilises AAL2 for carrying user traffic. As a consequence, ALCAP isneeded in transport network layer. On top of AAL2, the user data is carried within IubFrame Protocol (FP). There are separate FP for dedicated and common channels.


26/41


With IP transport option, NBAP messages are carried by SCTP/IP over Ethernet. User

RN33021EN20GLA0 27

.


27/41


The complete list of NBAP functions according to 3GPP TS25.433:

RN33021EN20GLA0 28

Cell Configuration Management.

Common Transport Channel Management. System Information Management.

Resource Event Management.

Configuration Alignment.

Measurements on Common Resources.

Radio Link Management.

Radio Link Supervision.

Compressed Mode Control.

Measurements on Dedicated Resources.

DL Power Drifting Correction.

Reporting of General Error Situations.

Physical Shared Channel Management.

Information Exchange.

Bearer Rearrangement.


28/41


29/41


RN33021EN20GLA0 30


30/41


The figure shows the UMTS architecture in terms of its entities User Equipment (UE),

RN33021EN20GLA0 31

.(CN-UTRAN interface) are shown.

The figure illustrates furthermore the high-level functional grouping into the AccessStratum (AS) and the Non-Access Stratum (NAS). The AS offers services throughService Access Points (SAP) to the NAS.

Radio Interface is constructed of radio protocols stack to perform functionalities asspecified by OSI Layer-1 (physical), Layer-2 (data link) and Layer 3 (network). Protocolsfor each layer are discussed on the next slide.


31/41


Radio Interface is vertically divided into control plane and user plane. Control plane

RN33021EN20GLA0 32

,transfer CN services being accessed by UE.

L1 consists only physical layer, it is mainly focus on WCDMA protocol.

L2 consists of MAC, RLC, PDCP and BMC protocols.

L3 in AS consist of RRC which provides control to all other protocols as well as radioresources.

Note that, this architecture is a general concept of radio interface protocol. The protocolstermination may exist in different Network Elements (NE) depends on the networkarchitecture and provided services.


32/41


The functions of MAC according 3GPP TS 25.321 include:

RN33021EN20GLA0 33

Mapping between logical channels and transport channels;

Selection of appropriate Transport Format for each Transport Channel depending oninstantaneous source rate;

Priority handling between data flows of one UE;

Priority handling between UEs by means of dynamic scheduling;

Identification of UEs on common transport channels;

Identification of MBMS services on common transport channels;

Multiplexing/demultiplexing of upper layer PDUs into/from transport blocks deliveredto/from the physical layer on common transport channels;

Multiplexing/demultiplexing of upper layer PDUs into/from transport block setsdelivered to/from the physical layer on dedicated transport channels;

Segmentation and reassembly of upper layer PDUs

Traffic volume measurement;

Transport Channel type switching;

Ciphering for transparent mode RLC;

Access Service Class selection for RACH transmission;

Control of HS-DSCH transmission and reception including support of HARQ;

HS-DSCH Provided Bit Rate measurement;

Control of E-DCH transmission and reception including support of HARQ;

Generation of uplink scheduling information to assist with E-DCH resource allocation;

E-DCH Provided Bit-rate measurement.


33/41


Radio Link Control (RLC) has three operation modes:

RN33021EN20GLA0 34

Transparent Mode (TM). In this mode, RLC does not do anything but segmentationand reassembly.

Unacknowledged Mode (UM). RLC adds small RLC header containing SequenceNumber and Length Indicator.

Acknowledged Mode (AM). RLC adds some more fields in header to assistretransmission operation.

Besides segmentation and reassembly, RLC performs ciphering for AM and UM touser data.


34/41


For packet-based communication services, Packet Data Convergence Protocol (PDCP) is

RN33021EN20GLA0 35

. .However, RN4.0 does not support any header compression. The PDCP protocol uses the

services of the RNC in three different modes. Those services are available for PDCPthrough the three different Service Access Points (SAPs) on the RLC. RLC SAPs aredata transfers in acknowledged (RLC-AM-SAP), in unacknowledged (RLC-UM-SAP) (notsupported), and in transparent (RLC-TrM-SAP) mode


35/41


The procedure above is used for broadcasting BMC messages from the network to UEs

RN33021EN20GLA0 36

.messages in the Idle mode and in CELL_PCH and URA_PCH RRC-states of Connected

mode.


36/41


The Radio Resource Control (RRC) is the main control protocol in the radio interface. It

RN33021EN20GLA0 37

. . , , , .

RRC specifies radio bearer parameter to support assigned RAB from the core network,including RLC operation mode, mapping logical channels onto transport channels,transport channel configuration and physical channel configuration.

The RRC is also responsible to carry NAS messages (UE CN) transparently in UTRAN.


37/41


Various layers in the user plane in the radio interface protocol are configured and

RN33021EN20GLA0 38

configuration, transport channel configuration, and radio bearer configuration.

If only the physical layer characteristics are modified, then the RRC layer only has tointeract with the PHY layer. A modification may affect scrambling and modulation. A newchannelisation code may be deployed for the connection, which has no impact to thehigher layers. The PHY layer is for instance responsible for radio measurements, and theRNC can change measurement quantities or threshold values. Again, this has no impacton the higher layers.

If the transport channels are modified, then this has an effect both on the MAC (MediumAccess Control) layer and the PHY layer. The MAC layer is responsible for TransportFormat selection, identification of UEs on the common and shared resources, cipheringand de-ciphering, random access control, etc.

Finally, for any radio bearer modification setup, release and reconfiguration allprotocols including protocol in user plane will be modified.


38/41


In the UMTS, RAN consists of two network elements: i.e. RNC and Node B. For general

RN33021EN20GLA0 39

, ,physical layer are terminated in the RNC. Node B only handles the physical layer part

which related to WCDMA and transport network layer.


39/41


The introduction of High-speed packet access services, HSDPA and E-DCH (also called

RN33021EN20GLA0 40

, . - -for HSDPA and MAC-e entity for E-DCH.


40/41


Nokia Siemens Networks provides Internet HSPA (I-HSPA) often called Direct Tunnel

RN33021EN20GLA0 41

.architecture evolution where the user traffic can be directly tunnelled toward GGSN and

Iu-PS control plane remains on SGSN.

With this solution, almost all radio interface protocols are now implemented in I-HSPANode B. It leaves RRC sit in RNC to carry NAS messages toward SGSN.


41/41


01 01 rn33021en20gla0 ran interface and protocols [compatibility mode]

Documents