Packet Data Network Emulation in the Test Set
This section is only applicable to the lab application.
Network Reference Model
In addition to testing wireless devices with TAP in a factory/laboratory environment (see C.S0029 Test Application Specification Description (TAP/ETAP) ), the lab application can emulate a real-world access network to provide packet data connection between an access terminal (AT) and a packet data network (such as the Internet). This is achieved by emulating the relevant behaviors of the Access Network (AN) using the Default Packet Application protocol (see Session Application Type ), the Packet Control Function (PCF) as well as the Packet Data Service Node (PDSN) as shown in the figure below.
- The AN supporting Default Packet Application protocols provide a means of establishing and maintaining traffic channels for packet data transmission over the air interface.
- The PCF is used to manage the relay of packets between the PDSN and the AN.
- The PDSN is used to establish, maintain, and terminate link layer sessions (such as PPP session) and route packet data between an AT and the packet data network (such as the Internet).
When a packet data connection is established (that is, both the physical traffic channel and PPP connection are open between the AT and the test set), the AT 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 (see How Does Test Set Support Simple IP Packet Data Connection? ).
There are several applications of the Data Channel. See Data Channel Applications .
For the signaling procedures during packet data connection establishment, see Packet Data Connection Call Flow .
For the state transitions during a packet data connection establishment, see Packet Data Connection Processing States Lifecycle .
Protocol Reference Model
The figure below shows a simplified protocol reference model for packet data service. The Default Packet Application Description (DPA) protocols are briefly explained here. For other communication protocols, refer to the Standard References .
Default Packet Application Description
The Default Packet Application (DPA) is an application layer protocol defined in the 3GPP2 C.S0024 Section 3 . It provides an octet stream used for transporting user data. The applications used and the streams upon which they operate are negotiated as part of session negotiation. The DPA protocol consists of the following protocols:
- Radio Link Protocol (RLP): provides retransmission and duplicate detection for an octet aligned data stream. The RLP carries an octet stream from the upper layer and is unaware of higher layer framing. It operates on a featureless octet stream and uses a Negative AcKnowledge based (NAK-based) retransmissions. That is, the receiver does not acknowledge received data frames and only requests the retransmission of data frames that were not received. When a frame is missing RLP responds by sending a NAK message to request the 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.
- Location Update Protocol (LUP): provides mobility management between data service networks.
- Flow Control Protocol (FCP): provides flow control of data traffic such as enabling or disabling the data flow.