7.30 Test method for UL Data Compression (UDC)

36.523-33GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC)Part 3: Test suitesRelease 17TSUser Equipment (UE) conformance specification

7.30.1 General

UDC testing uses the PDCP test model (Non ROHC) specified in subclause 4.2.1.3.2. The PDCP is configured in transparent mode. ROHC is not configured. Data sent in DL is not compressed, data sent in UL may be compressed. This is indicated in the UL Data PDUs.

UDC works on the condition that the compression buffer and decompression buffer are synchronized. The SS shall support a decompressor and a decompression buffer, which are accessed and controlled by TTCN via a set of external functions.

7.30.2 Initialization

When the PDCP DRB is configured, a predefined dictionary can be provided to the UE. This dictionary will be used by the UE’s compression function. If no dictionary is provided then the compression buffer will be initialized with all 0s.

At the SS side, the external function fx_UDC_Initialise is used to initialize the decompression buffer consistently with the setting of the UE’s compression buffer. If the compression buffer is reset at the UE side, then the same needs to be done at the SS side. This is normally achieved by passing the reset flag FR, received in the Data PDU, to the decompressor.

7.30.3 Compression and decompression

With each PDCP Data PDU the UE provides information if the contained SDU is compressed, if the compression buffer has been reset, as well as the Checksum calculated during compression.

This information allows the TTCN to request the SS to decompress the data using external function fx_UDC_Decompress. The compressed SDU, as well as the information if the compression was reset or not before compression, are passed. If decompression succeeds then the decompressed SDU, the calculated Checksum, as well as a success indication are returned. The TTCN can then compare the Checksum received in the PDU to the Checksum returned by fx_UDC_Decompress. If decompression does not succeed failure is reported.