Test Set Packet Data Network Emulation

Last updated: October 28, 2004

This section is only applicable to the lab application.

Packet Data Service Overview

The packet data services in cdma200 system primarily identified with service option 33 (SO33) allow you to exchange data between the wireless devices and a remote server over an IP data network. Packet data service options provide a means of establishing and maintaining traffic channels for packet data service. SO33 is used to request packet data service through a packet data serving node (PDSN) supporting an internet standard Point-to-Point Protocol (PPP) interface to network layer protocols.

When a packet data connection is established, a wireless device can send or receive data through the test set's front panel RF connector, and the test set will route data through the rear panel LAN port to or from a packet data network.

Network Reference Model

In cdma2000 system, for all calls supporting packet data services, a Packet Data Serving Node (PDSN) exists that interfaces between the transmission of the data in the packet data network and the transmission of the data (via the Radio Access Network (RAN)) over the air interface. The PDSN interfaces to the base station (BS) through a Packet Control Function (PCF), which may or may not be co-located with the BS. See Network Reference Model for Packet Data Service .

When an SO33 packet data session is open, the test set will emulate the Base Station (BS), Base Station Controller (BSC), Mobile Switching Center (MSC), as well as the relevant functions of the following two entities ( Packet Control Function (PCF) and Packet Data Serving Node (PDSN) ) which are specified in 3GPP2 A.S0001-A Version 2.0, 3GPP2 Access Network Interfaces Interoperability Specification:

Network Reference Model for Packet Data Service

Packet Control Function (PCF)

One network entity that is emulated by the test set is the PCF which is to manage the relay of packets between the PDSN (see Packet Data Serving Node (PDSN) ) and the BS.

When an SO33 call is initiated, a physical traffic channel is assigned to the call, following normal service negotiation procedures. After the call transitions to the connected state, the PCF initiates the setting up of signaling and traffic connections between the PCF and the PDSN.

If the connection between the PCF and the PDSN was successful, a PPP (Point to Point Protocol) link layer connection between the wireless device and the PDSN is opened.

Packet Data Serving Node (PDSN)

Another network entity that is emulated by the test set is the PDSN. The PDSN is a specialized router that functions as an interface to the fixed networks (like the Internet). The PDSN establishes, maintains, and terminates link layer sessions and routes packet data between a wireless device and the network it is communicating with.

When an SO33 call is first connected, a PPP (Point to Point Protocol) link layer connection between a wireless device and the PDSN is opened. A physical traffic channel assignment allocates bandwidth to this connection, supporting data exchange between the wireless device and the BS.

The test set's internal PDSN emulation only supports simple IP protocol (see What is Simple IP and Mobile IP? ). The test set supports mobile IP protocol by working together with an external Mobile IP Simulator (MOB-IP-SIM) provided by the Software Concepts, Inc. (see Simple IP and Mobile IP ).

Packet Data Service Protocol Stacks

Service Option 33 Interface Protocols shows a simplified SO33 packet data service protocol stacks in the test set. The Radio Link Protocol (RLP) Type 3 and SO33 Physical Channel are explained here. For other communication protocols on the links between the mobile station and the PDSN via a base station/packet control function (BS/PCF), see the 3GPP2 C.S0017-0-2 standard.

Service Option 33 Interface Protocols

Radio Link Protocol (RLP) Type 3

Radio Link Protocol Type 3 (RLP) is a protocol that specifies how data is delivered over the RF link between the wireless device and the base station.

RLP provides an octet stream transport service over forward and reverse traffic channels. It operates on a featureless octet stream, delivering the octets in the order received. RLP is unaware of higher layer framing. That is, it does not concern itself with the framework of the data packets formed in IP and PPP.

When transferring data, RLP is a pure Negative AcKnowledge based (NAK-based) protocol. That is, the receiver does not acknowledge received data frames; it only requests the retransmission of data frames that were not received. When a frame is missing RLP responds by sending a NAK frame requesting retransmission. When a new or retransmitted frame is received it is placed in a storage buffer that manages sequential delivery of RLP frames to the upper layers.

There are three general types of frames sent by RLP:

Control (SYNC, SYNC/ACK, NAK) frames: The control frames are used to synchronize RLP data transfer between the wireless device and the base station. Once synchronized, RLP data frames can be transferred.
Data (New, Retransmitted) frames: The new data frames indicate the data frames being sent for the first time. The retransmitted data frames indicates the data frames being resent in response to received NAK control frames.
Fill and Idle frames: When RLP frames are carried as primary traffic and no RLP frames in the above listed types are available, an idle frame or a fill frame shall be generated and supplied if a Fundicated RLP frame is needed, and a Blank RLP frame shall be supplied if a Supplemental RLP frame is needed.

The test set keeps a running count of data and maintains a set of RLP frame counters. See Data Counters .

SO33 Physical Channel

The RLP specifies that RLP frames are carried on either the F/R FCH (Forward/Reverse Fundamental Channel), the F/R SCH (Forward/Reverse Supplemental Channel), or the F/R DCCH (Forward/Reverse Dedicated Control Channel). The test set does not support the F/R DCCH.

High speed operation uses a Supplemental Channel to increase the traffic channel's bandwidth. Forward high speed operation uses a Forward Supplemental Channel. Reverse high speed operation uses a Reverse Supplemental Channel. The mobile station requests reverse high speed operation and reports changes in the number of the Preferred Reverse Supplemental Channel Rate by sending a Supplemental Channel Request Message (SCRM) or a Supplemental Channel Request Mini Message (SCRMM). The base station controls both forward and reverse high speed operation by allocating Supplemental Channels for some time period via an Extended Supplemental Channel Assignment Message (ESCAM), or a Universal Handoff Direction Message (UHDM), or a Forward Supplemental Channel Assignment Mini Message (FSCAMM). The channels for the packet data service that can be assigned by the test set depends upon the packet data service option configuration. See Packet Data Service Options for details.

The SO33 relay layer protocol specifies that RLP can be carried as either primary traffic or secondary traffic. The test set configures the Mux Sublayer to carry RLP as primary traffic only. The test set supports the multiplex options including 0x1, 0x2, 0x3, 0x905, 0x909, 0x911, 0x921 for the SO33.

How Does Packet Data Service Work?

When a wireless device attempts to access or transfer data, for instance when a selection is made from a web browser on a mobile station, the mobile station must request an SO33 connection. If the test set is configured to one of the available packet data service options (see Packet Data Service Options ), that service option will be automatically connected if the service negotiation between the wireless device and the test set was successful.

When an SO33 packet data call is connected, a PPP (Point to Point Protocol) link layer connection between a wireless device and the PDSN is opened. A physical traffic channel assignment allocates bandwidth to this connection, supporting packet data exchange between the LAN port on the test set and the wireless device.

The data link layer connection is kept open by the wireless device and the PDSN (see Packet Data Serving Node (PDSN) ) only as long as is determined by PPP. Occurrences such as link quality failure, expiration of an idle-period timer, or administrative closing of the link (such as exiting the browser on the wireless device) will cause the data link layer connection to be closed. See also Packet Data Connection Processing States .

Standards References

For Service Option 33: Data Service Options for Spread Spectrum Systems: cdma2000 High Speed Packet Data Service Option 33, 3GPP2 C.S0017-0-2.12

For RLP: Data Service Options for Spread Spectrum Systems: Radio Link Protocol Type 3, 3GPP2 C.S0017-0-2.10