Mobile Network Evolution: UMTS

Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) cell phone technologies. Currently, the most common form of UMTS uses W-CDMA as the underlying air interface. It is standardized by the 3GPP, and is the European answer to the ITU IMT-2000 requirements for 3G cellular radio systems.

UMTS is packet-based and it allows transmission of text, digitized voice, video, and multimedia at data rates up to 2 megabits per second (Mbps). UMTS offers a consistent set of services to mobile computer and phone users, no matter where they are located in the world.

1. UMTS Network Architecture

A UMTS network consists of three domains; Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). The main function of the core network is to provide switching, routing and transit for user traffic. Core network also contains the databases and network management functions.

The basic Core Network architecture for UMTS is based on GSM network with GPRS. All equipment has to be modified for UMTS operation and services. The UTRAN provides the air interface access method for User Equipment. Base Station is referred as Node-B and control equipment for Node-B's is called Radio Network Controller (RNC).



2. UMTS Protocol Stacks

Mobile Network Evolution: EDGE

EDGE, Enhanced Data rates for GSM Evolution, is a further step for GSM to migrate to 3G. It uses a new air-interface technology -- 8 Phase Shift Keying Modulation (8-PSK) to offer 48 kbits/s per GSM timeslot. The overall offered data speeds of 384Kbps places EDGE as an early pre-taste of 3G and it is actually labeled as 2.75G by the industry.

EDGE is occasionally referred to as Enhanced GPRS (EGPRS) because it increases the capacity and data throughput of GPRS by three to four times. Like GPRS, EDGE is a packet-based service, which provides customers with a constant data connection.

1. EDGE Network Architecture
On top of the GPRS network, it is only necessary to upgrade the MS and the radio access network RAN (BTS + BSC) to support the EDGE functionalities. The RAN for EDGE is referred as GERAN (GSM/EDGE Radio Access Network).



2. EDGE Network Entities

All EDGE network entities are same as those of GPRS except that the MS and the BTS are upgraded with new physical layers to support the new modulation technology. Some industrial notations also included the migration of BSC to RNC (Radio Node Controller) into the EDGE for the new Iu-cs and Iu-ps interface support.


3. EDGE Interfaces and Protocols

Besides all other interfaces that are common with GPRS, the EDGE specific interfaces are between the BSC/RNC and SGSN. Between these two network entites, both the GPRS Gb and the new Iu-ps interfaces are supported. The protocol stacks of the Iu-ps interface control plane and user plane are as below.

Iu-ps Control Plane Protocol Stacks



Iu-ps User Plane Protocol Stacks




4. EDGE Evolution

EDGE Evolution is an upgraded version of EDGE that completed standardization work in 2007 within Release 7 at 3GPP. EDGE Evolution is also referred to as EDGE II or Evolved EDGE by some industry sources. EDGE Evolution boosts the data speeds by up to 300 percent and significantly improves latency, coverage, and spectrum efficiency of existing GSM/EDGE equipment.

Compared to EDGE, EDGE Evolution is expected to provide:
• A dramatic increase in data rates. The actual amount depends on the version used, but EDGE Evolution is expected to quadruple the throughput rates for EDGE with peak theoretical network speeds of 1184 kbps to 1894 kbps in type 1 or type 2 respectively for the downlink and 473 to 947 kbps for the uplink.
• A 50 percent increase in spectral efficiency and capacity
• Reduced latency for initial access and round trip time, enabling better quality of service (QoS) for Push-to-Talk (PTT) and Voice over IP (VoIP)
• Compatibility with existing frequency plans, thus facilitating rapid deployment in existing networks
• A simple upgrade to existing GSM equipment allowing a more efficient use of scarce existing spectrum
• A better seamless experience for subscribers as they roam from HSPA networks to EDGE networks
• Compatibility with existing frequency plans, thus facilitating rapid deployment in existing networks

Mobile Network Evolution: GPRS

GPRS (General Packet Radio Service) is a packet based upgrade to the GSM networks. It allows GSM networks to be truly compatible with the Internet. GPRS uses a packet-mode technique to transfer bursty traffic in an efficient manner. It promises data rates from 56 up to 114 Kbps and continuous connection to the Internet for mobile phone and computer users. Along the evolution path of the GSM network towards 3G and beyond, GPRS is refered as a 2.5G technology.

1. GPRS Network Architecture



2. GPRS Network Entities

2.1 MS
GPRS enabled MS.

2.2 BTS
Same as the GSM BTS.

2.3 BSC
The GSM BSC enhanced with the Packet Control Unit (PCU) to differentiates whether data is to be routed to the packet switched or circuit switched networks.

The PCU or Packet Control Unit is a hardware router that is added to the BSC. It differentiates data destined for the standard GSM network (circuit switched data) and data destined for the GPRS network (Packet Switched Data). The PCU itself may be a separate physical entity, or more often these days it is incorporated into the base station controller, BSC, thereby saving additional hardware costs.

2.4 SGSN
The SGSN or Serving GPRS Support Node element of the GPRS network provides a number of takes focussed on the IP elements of the overall system. It provides a variety of services to the mobiles:

• Packet routing and transfer
• Mobility management
• Attach/detach
• Logical link management
• Authentication
• Charging data

There is a location register within the SGSN and this stores location information (e.g., current cell, current VLR). It also stores the user profiles (e.g., IMSI, packet addresses used) for all the GPRS users registered with the particular SGSN.

2.5 GGSN
The GGSN, Gateway GPRS Support Node is one of the most important entities within the GPRS network architecture.

The GGSN organises the interworking between the GPRS network and external packet switched networks to which the mobiles may be connected. These may include both Internet and X.25 networks.

The GGSN can be considered to be a combination of a gateway, router and firewall as it hides the internal network to the outside. In operation, when the GGSN receives data addressed to a specific user, it checks if the user is active, then forwarding the data. In the opposite direction, packet data from the mobile is routed to the right destination network by the GGSN.

3. GPRS Interfaces and Protocols



4. GPRS Control and User Planes





5. GPRS Core Protocol -- GTP

GPRS Tunnelling Protocol (GTP) is the core protocol used in GPRS network between the SGSN and the GGSN for GPRS service control and user data delivery. It is is a group of IP-based communications protocols. GTP can be classified into separate protocol subgroups according to their usage, GTP-C, GTP-U and GTP' respectively.

GTP-C is used within the GPRS core network for signaling between the GGSN and the SGSN. GTP-C includes the control procedures that allows the SGSN to activate a session on a user's behalf (PDP context activation), to deactivate the same session, to adjust quality of service parameters, or to update a session for a subscriber who has just arrived from another SGSN.

GTP-U is used for carrying user data within the GPRS Core Network and between the Radio Access Network and the core network. The user data transported can be packets in any of IPv4, IPv6, or PPP formats.

GTP' (GTP prime) uses the same message structure as GTP-C and GTP-U, but has an independent function. It can be used for carrying charging data from the Charging Data Function (CDF) to the Charging Gateway Function (CGF).



6. GPRS User Sessions -- PDP Context
A Packet Data Protocol (PDP) context is a GPRS user session established allowing the MS and the network to exchange IP packets with QoS specifications. A PDP Context has a record of parameters, which consists of all the required information for establishing the end-to-end connection:

• PDP Type
• PDP address type
• QoS profile request (QoS parameters requested by user)
• QoS profile negotiated (QoS parameters negotiated by network)
• Authentication type (PAP or CHAP)
• DNS type (Dynamic DNS or Static DNS)

Mobile Network Evolution: GSM -- The Starting Point

Global System for Mobile Communication (GSM) is a set of ETSI standards specifying the infrastructure for a digital cellular service. As a fully digital system, GSM allows both speech and data services and allows roaming across networks and countries. These features made GSM a very popular system, not only in european countries but also elsewhere in the world.

In the mobile network evolution path shown above, the GSM system is the starting point to be address in this series of articles.

1. GSM Network Architecture



2. GSM Network Entities

2.1 Mobile Station (MS)
The Mobile Station (MS) is the user equipment in GSM, i.e. the cellular phone itself. The MSs in GSM are independent from networks-providers. The identity of the subscriber is obtained from a SIM (Subscriber Identity Module) that has to be inserted into the MS to make it work. The SIM contains the IMSI (International Mobile Subscriber Identity) which uniquely identifies the subscriber to the network. It also contains information necessary to encrypt the connections on the radio interface. The MS itself is identified by an IMEI (International Mobile Equipment Identity), which can be obtained by the network upon request. Without the SIM, calls to and from the mobile station is not allowed, except that the alls to the international emergency number, 112, is allowed without the SIM.

2.2 Base Transciever Station (BTS)
The Base Transciever Station (BTS) is the entity corresponding to one cellular site communicating with the Mobile Stations. Usually, the BTS will have an antenna with several TRXs (radio transcievers) that each communicate on one radio frequency. Speech and data transmissions from the MS is encoded in the BTS from the special encoding used on the radio interface to the standard 64 kbit/s encoding used in telecommunication networks.

2.3 Base Station Controller (BSC)
A Base Station Controller (BSC) controls the magnitude of several hundred BTSs for subscriber registration, location update, call setup and handover control etc. It is the entrance point for an MS to gain access to the overall mobile network services.

2.4 Mobile Switching Centre (MSC)
The Mobile Switching Centre (MSC) is a typical telecom switch with extended functionalities to support mobile services. The basic function of the MSC is to switch speech and data connections between BSCs, with other MSCs or other GSM-networks and external non-mobile-networks. It also takes care of all mobility management tasks.

2.5 Visitors Location Register (VLR)
For each MSC, there is an associated VLR to store the information about all subscribers that are roaming within its service coverage. The subscriber infromation is obtained either through the MS initiated location update procedure when it enters the covered area or through the notification from the subscriber's Home Location Register (HLR). The VLR serves the routing of all service initiated or targeted to the MS.

2.6 Home Location Register (HLR)
The HLR is the home register of a subscriber. It is where the subscriber information, allowed services, authentication information, location information etc. of a subscriber are permanently stored.

2.7 Equipment Identity Register (EIR)
The Equipment Identity Register (EIR) is an optional register. Its purpose is to register IMEIs of mobile stations in use. By implementing the EIR the network provider can implement a widely range of control functions to the served MSs, such as blacklisting malfunctional or stolen mobile stations etc.

2.8 Gateway MSC (GMSC)
A Gateway Mobile Switching Centre (GMSC) provides the edge function within the mobile network. It terminates the PSTN (Public Switched Telephone Network) signalling and traffic formats and converts to protocols employed in mobile networks. For mobile terminated services, it interacts with the HLR (Home Location Register) to perform routing functions.

3. GSM Interfaces and Protocols





4. GSM Air Interface Channel Structure

Mobile Network Evolution: CDMAone to CDMA2000

Code Division Multiple Access (CDMA) is a method for transmitting simultaneous digital signals over a shared portion of the spectrum. As a competing technology to its European GSM peer and its successors, this American technology initiates an alternative cellular system implementation.

1. CDMAone

CDMAone refers to the original ITU IS-95 (CDMA) wireless interface protocol that was first standardized in 1993 and employed to build up the first CDMA cellular network. In the mobile network evolution term, CDMAone is considered as a second-generation (2G) mobile wireless technology.

There are two versions of IS-95, called IS-95A and IS-95B. The IS-95A protocol employs a 1.25-MHz carrier, operates in radio-frequency bands at either 800 MHz or 1.9 GHz, and supports data speeds of up to 14.4 Kbps. IS-95B can support data speeds of up to 115 kbps by bundling up to eight channels.



2. CDMA2000 Overview

CDMA2000 represents a family of standards which includes technologies as listed below. CDMA2000 is also known by its ITU name, IMT-2000 CDMA Multi-Carrier (MC).

i. CDMA 2000 1x
ii. CDMA 2000 1x EV DO
a) CDMA2000 1xEV-DO Release 0
b) CDMA2000 1xEV-DO Revision A (Rev A)
c) CDMA2000 1xEV-DO Revision B(Rev B)
d) CDMA2000 1xEV-DO Revision C(Rev C)
iii. CDMA 2000 1x EVDV
iv. CDMA 2000 3x

The CDMA 2000 standard was divided into two phases 1x and 3x. 1x is used to refer that the standard carrier on the air interface is 1.25 MHz, which is the same as for IS-95A/B. 3X is a multi-carrier approach, and is used to refer 3 times standard carrier of 1.25 MHz i.e. 3.75 MHz.

CDMA 2000 1x utilizes a single carrier of 1.25 MHz of radio spectrum as IS-95. However, it uses a different vocoder and walshcodes, 256/ 128 verses 64, allowing for higher data rates and more voice conversions than are possible over cdmaOne systems. 1x EV-DO means one carrier, which is data only, while 1x EV-DV means one carrier that supports data and voice services. However, when referring to CDMA 2000 3x, the use of 3.75 MHz of the spectrum, or 3x1.25 MHz, is defined with a change in the modulation scheme as well as the vocoders.

3. CDMA2000 1xRTT

CDMA2000 1xRTT is considered as a 2.5G (or 2.75G) technology. CDMA2000 1xRTT is the core CDMA2000 wireless air interface standard and is also known as 1x, 1xRTT, and IS-2000. The designation "1x", meaning "1 times Radio Transmission Technology", indicates the same RF bandwidth as IS-95 (CDMA-One): a duplex pair of 1.25 MHz radio channels. 1xRTT almost doubles the capacity of IS-95 by adding 64 more traffic channels to the forward link, orthogonal to the original set of 64. Although capable of higher data rates, most deployments are limited to a peak of 144 kbit/s. IS-2000 also made changes to the data link layer for the greater use of data services, including medium and link access control protocols and QoS.



4. CDMA2000 EV-DO

CDMA2000 EV-DO (Evolution-Data Optimized or Evolution-Data only) is refered as the CDMA version of 3G technology. It is a broadband access radio technology standardized by 3rd Generation Partnership Project 2 (3GPP2), provides access to mobile devices with air interface speeds of up to 2.4 Mbit/s with Rev. 0, up to 3.1 Mbit/s with Rev. A, upto 14.7 Mbit/s with Rev. B and upto 200 Mbit/s with Rev. C, etc.



CDMA2000 1xEV-DO requires a multi-mode device to be fully backward compatible with 1X and cdmaOne systems to support the all-IP network and the air interface that has been optimized for data.

CDMA2000 1xEV-DO Rev.0 provides a peak data rate of 2.4 Mbps in the forward link and 153 kbps in the reverse link in a 1.25 MHz CDMA carrier. With average throughput of 400-800 kbps in the forward link.

CDMA2000 1xEV-DO Rev A is an enhanced version of Rev.0,represents a major step in the evolution of CDMA2000 standards towards converged communication networks and ubiquitous delivery of voice and data services across fixed and wireless networks. The key features that the Rev.A provides are:
• High-speed data: Delivers a peak data rate of 1.8 Mbps on the reverse link and 3.1 Mbps on the forward link.
• Higher system capacity: Improves sector capacity within the 1.25 MHz channel. It has twice the sector capacity on the down link and is 1.2 times higher on the forward link compared to Release 0.
• Improved Quality of Service (QoS): Lower latency, prioritization of low-latency applications and QoS software enhancements added to Revision A improve performance of delay-sensitive applications such as VoIP, push-to-talk, instant messaging and video telephony.
• VoIP: Is possible because of the high data rate on the reverse link, lower latency and improved QoS.

CDMA 2000 1x Ev-DO Rev-B introduces a 64-QAM modulation scheme and will deliver peak rates of 73.5 Mbps in the forward link and 27 Mbps in the reverse link through the aggregation of 15, 1.25 MHz carriers within 20 MHz of bandwidth. A single 1.25 MHz carrier and an aggregated 5 MHz carrier in the forward link will deliver a peak rate of up to 4.9 Mbps and 14.7 Mbps, respectively.

CDMA 2000 1x Ev-DO Rev-C delivers higher data rates and spectral efficiency along with low latency, making it ideal for enriched multimedia services. Revision C supports flexible and dynamic channel bandwidth scalability from 1.25 MHz up to 20 MHz and are backward-compatible with Revisions A and B. Revision C not only increases the peak rates up to 200 Mbps in the downlink but also provides significant gain in sector throughput.

5. CDMA2000 EV-DV

CDMA2000 EV-DV supports up to 3.1 Mbps forward link throughput. One of the advantageous of EV-DV is its ability to give carriers both voice and broadband data on a single channel, using the same legacy digital voice technology operating over current 1x networks.

EV-DV has been commercially unsuccessful due to lack of carrier interest.



6. CDMA2000 3x

CDMA2000 3x is an ITU-approved third-generation (3G) mobile wireless technology. It is also known as Multi-Carrier or MC.

CDMA2000 3x utilizes a pair of 3.75-MHz radio channels (i.e., 3 X 1.25 MHz) to achieve higher data rates. The 3x version of CDMA2000 has not been deployed and is not under development at present.

CDMA2000 Protocols

1. Overview

CDMA2000, also known as IMT-CDMA Multi-Carrier or IS-2000 is a technology for CDMA operators to advance their cdmaOne/IS-95 to 2.5G and 3G cellular networks. 3GPP2, the standard body behind CDMA2000, defines all the network functionalities, interfaces and operation protocols.

As adopted by a lot of operators, CDMA2000 is normally deployed in several phases. The first phase, CDMA2000 1x, supports an average of 144 kbps packet data in a mobile environment. The second release of 1x, called 1x-EV-DO supports data rates up to 2 Mbits/sec on a dedicated data carrier. Finally, 1x-EV-DV will support even higher peak rates, simultaneous voice and high-speed data, as well as improved Quality of Service mechanisms.

Major CDMA2000 network elements and interfaces are shown in the following figure.

A summary of all CDMA2000 protocols are listed as follows:

- A1: A1 Signaling, SCCP, MTP3, MTP2, MTP1
- A3: A3 Signaling, TCP, IP, AAL5, SSSAR, AAL2
- A7: A7 Signaling, TCP, IP, AAL5
- A8: GRE, IP, PPP
- A9: A9 signaling TCP, UDP, IP
- A10: GRE, IP, PPP
- A11: A11 signaling, UDP, IP, PPP, Mobile IP
- A12: RADIUS, UDP, IP, PPP
- A13: A13 Signaling, TCP/UDP, IP
- A14: A14 Signaling, TCP/UDP, IP
- A15: A15 Signaling, TCP/UDP, IP
- 3GPP2 IOS 3.x and IOS 4.x
- Other Protocols: PPP in HDLC-likeFraming, IPCP, Diameter, IKE

2. A1 Interface

The A1 interface carries signaling information between the Call Control (CC) and Mobility Management (MM) functions of the MSC and the call control component of the BS (BSC). The application signaling protocol used over this interface is the Base Station Application Part (BSAP). BSAP includes two sub-application parts; the BS management application part (BSMAP), and the direct transfer application part (DTAP).

The BS Management Application Part (BSMAP) supports all Radio Resource Management and Facility Management procedures between the MSC and the BS, or to a cell(s) within the BS. BSMAP messages are not passed to the MS, but are used only to perform functions at the MSC or the BS. A BSMAP message (Complete Layer 3 Information) is also used together with a DTAP message to establish a connection for a MS between the BS and the MSC, in response to the first layer 3 air interface message sent by the MS to the BS for each MS system request.

The Direct Transfer Application Part (DTAP) messages are used to transfer call processing and mobility management messages between the MSC and BS. DTAP messages carry information that is primarily used by the MS. The BS maps the DTAP messages going to and coming from the MSC from/into the appropriate air interface signaling protocol.

BSMAP Messages

- Additional Service Notification
- ADDS Page
- ADDS Page Ack
- ADDS Transfer
- ADDS Transfer Ack
- Assignment Complete
- Assignment Failure
- Assignment Request
- Authentication Request
- Authentication Response
- Base Station Challenge
- Base Station Challenge Response
- Block
- Block Acknowledge
- BS Service Request
- BS Service Response
- Clear Command
- Clear Complete
- Clear Request
- Complete Layer 3 Information
- Feature Notification
- Feature Notification Ack
- Handoff Command
- Handoff Commenced
- Handoff Complete
- Handoff Failure
- Handoff Performed
- Handoff Request
- Handoff Request Acknowledge
- Handoff Required
- Handoff Required Reject
- PACA Command
- PACA Command Ack
- PACA Update
- PACA Update Ack
- Paging Request
- Privacy Mode Command
- Privacy Mode Complete
- Radio Measurements for Position Request
- Radio Measurements for Position Response
- Rejection
- Rejection
- Reset Acknowledge
- Reset Circuit
- Reset Circuit Acknowledge
- SSD Update Request
- SSD Update Response
- Status Request
- Status Response
- Transcoder Control Acknowledge
- Transcoder Control Request
- Unblock
- Unblock Acknowledge
- User Zone Reject

DTAP Messages

- Additional Service Request
- ADDS Deliver
- ADDS Deliver Ack
- Alert With Information
- Authentication Request
- Authentication Response
- Base Station Challenge
- Base Station Challenge Response
- CM Service Request
- Connect
- Flash with Information
- Flash with Information Ack
- Location Updating Accept
- Location Updating Reject
- Location Updating Request
- Paging Response
- Parameter Update Confirm
- Parameter Update Request
- Rejection
- Service Release
- Service Release Complete
- SSD Update Request
- SSD Update Response
- Status Request
- Status Response
- User Zone Reject
- User Zone Update
- User Zone Update Request

3. A2 Interface

The A2 interface carries 64/56 kbps PCM information (voice/data) or 64 kbps Unrestricted Digital Information (UDI, for ISDN) between the Switch component of the MSC and one of the following:
- the channel element component of the BS (in the case of an analog air interface), or
- the Selection/Distribution Unit (SDU) function (in the case of a voice call over a digital air interface),

4. A3 Interface

The A3 interface carries coded user information (voice/data) and signaling information between the SDU function and the channel element component of the BS (BTS). This interface is composed of signaling and user traffic sub-channels between two BSCs. It provides the ability to establish and remove A3 traffic connections.

A3 signaling messages are listed as follows:

- A3-Connect
- A3-Connect Ack
- A3-Remove
- A3-Remove Ack
- A3-Drop
- A3-Propagation Delay Measurement Report
- A3-IS-95 FCH Forward
- A3-IS-95 FCH Reverse
- A3-Physical Transition Directive
- A3-Physical Transition Directive Ack
- A3-IS-2000 FCH Forward
- A3-IS-2000 FCH Reverse
- A3-Traffic Channel Status
- A3-IS-2000 DCCH Forward
- A3-IS-2000 DCCH Reverse
- A3-IS 2000 SCH Forward
- A3-IS 2000 SCH Reverese
- A3-FCH Forward Traffic Frame
- A3-DCCH Forward Traffic Frame
- A3-FCH Reverse Traffic Frame
- A3-DCCH Reverse Traffic Frame
- A3-SCH Reverse Traffic Frame

5. A5 Interface

The A5 interface carries a full duplex stream of bytes between the MSC and the SDU function.

6. A7 Interface

The A7 interface provides direct BS to BS signaling for the support of an efficient soft handoff procedure.

A7 signaling messages are:

- A7-Handoff Request
- A7-Handoff Request Ack
- A7-Drop Target
- A7-Drop Target Ack
- A7-Target Removal Request
- A7-Target Removal Response
- A7-Source Transfer Performed
- A7-Reset
- A7-Reset Acknowledge
- A7-Paging Channel Message Transfer
- A7-Paging Channel Message Transfer Ack
- A7-Access Channel Message Transfer
- A7-Access Channel Message Transfer Ack
- A7-Burst Request
- A7-Burst Response
- A7-Burst Commit
- A7-Burst Release

7. A8 Interface

The A8 interface carries user traffic between the BS and the PCF. The A8 interface uses the Generic Routing Encapsulation (GRE) protocol to provide a mechanism for encapsulating arbitrary packets within an arbitrary transport protocol for traffic delivery between BSC and PCF.

8. A9 Interface

The A9 interface carries signaling information between the BS and the PCF. The A8/A9 interfaces support mobility between BSCs under the same PCF.

The A9 interface signaling messages are listed below:

- A9-Setup A8
- A9-Connect A8
- A9-Disconnect A8
- A9-Release A8
- A9-Release A8 Complete
- A9-BS Service Request
- A9-BS Service Response
- A9-AL Connected
- A9-AL Connected Ack
- A9-AL Disconnected
- A9-AL Disconnected Ack
- A9-Short Data Delivery
- A9-Short Data Ack
- A9-Update-A8
- A9-Update-A8-Ack
- A9-Version Info
- A9-Version Info Ack

9. A10 Interface

The A10 interface carries user traffic between the PCF and the PDSN. The A10 interface uses the Generic Routing Encapsulation (GRE) protocol to provide a mechanism for encapsulating arbitrary packets within an arbitrary transport protocol for traffic delivery between PCF and PDSN.


10. A11 Interface

The A11 interface carries signaling information between the PCF and the PDSN for packet data services and provides a signaling connection between a PCF and PDSN pair (A11). A11 signaling messages are also used for passing accounting related and other information from the PCF to the PDSN. The A10/A11 interfaces support mobility between PCFs under the same PDSN.

The A11 signaling messages are

- Registration Request
- Registration Reply
- Registration Update
- Registration Acknowledgment

11. A12 Interface

The A12 interface uses RADIUS protocol for authentication purposes.

12. A13 Interface

The A13 protocol is responsible for information exchange between the source and target AN. The protocol is divided up into information from the target to source direction, and information from the source to the target direction. Signaling over the A13 interface requires a reliable transport protocol and appropriate addressing and routing mechanisms to deliver messages from the target to source destination.

All A13 messages are listed below

- A13-Session Information Request
- A13-Session Information Confirm
- A13-Session Information Reject
- A13-Session Information Response

13. A14 Interface

The A14 interface between the AN and the SC/MM function of the PCF is used for performing HRPD Session and HRPD mobility related operations. Procedures included in A14 interface functions are

• UATI assignment procedure.
• General updating procedure.
• Terminal authentication.
• Session release.
• Session information updating procedure.
• Paging procedure.

For supporting above procedures, the A14 interfaces uses the following messages:

- General Update
- General Update Complete
- Authentication Command
- Authentication Request
- Authentication Response
- Authentication Completed
- Authentication Completed Ack
- UATI Request
- UATI Assignment
- UATI Complete
- UATI Complete Ack
- UATI Assignment Failure
- Session Release
- Session Release Complete
- Paging Request
- Paging Request Ack
- Paging Response
- Paging Response Ack
- Session Information Update
- Session Information Update Ack
- Session Release Command
- Authentication Failure
- Authentication Failure Ack
- Keep Alive Request
- Keep Alive Request Ack

14. A15 Interface

The A15 interface is used for sending paging request messages from the AN that manages the registered sector to the ANs that send paging messages over the air. This interface is used for inter AN paging.

All messages used in A15 signaling are as follows:

- Paging Request
- Paging Response
- Paging Response Ack