26.1323GPPRelease 18Speech and video telephony terminal acoustic test specificationTS
This Annex provides packet delay and loss profiles to be inserted on the IP packets in the test system when testing the UE delay and speech quality for MTSI-based speech with LTE access in jitter and error conditions. The profiles are based on the assumption that one IP packet corresponds to 20ms of the speech sequence. In order to preserve the synchronization of the elements in the profile and the timing of the speech sequence (e.g. the RTP time stamp) when the speech codec does not produce one packet every 20ms, e.g. during speech codec DTX operation, the profiles needs to be sub-sampled in accordance with the rate of production of the packets containg the speech frames.
The variation in the packet arrival time and the loss rate of the speech packets experienced by the receiving UE in an LTE connection will vary depending on several parameters and operating conditions of the LTE network. Standardized characteristics with respect to Packet Delay Budget (PDB) and Packet Error Loss Rate (PELR) for different QoS Class Identifiers (QCI) for an LTE access network are defined in 3GPP TS 23.203 :
– The PDB of a QCI defines an upper bound for the time that a packet may be delayed between the UE and the PCEF. For a certain QCI the value of the PDB is the same in uplink and downlink. The purpose of the PDB is to support the configuration of scheduling and link layer functions (e.g. the setting of scheduling priority weights and HARQ target operating points). The PDB shall be interpreted as a maximum delay with a confidence level of 98 percent.
– The PELR of a QCI defines an upper bound for the rate of SDUs (e.g. IP packets) that have been processed by the sender of a link layer protocol (e.g. RLC in E‑UTRAN) but that are not successfully delivered by the corresponding receiver to the upper layer (e.g. PDCP in E‑UTRAN). Thus, the PELR defines an upper bound for a rate of non congestion related packet losses. The purpose of the PELR is to allow for appropriate link layer protocol configurations (e.g. RLC and HARQ in E‑UTRAN). For a certain QCI the value of the PELR is the same in uplink and downlink.
The stipulated PDB and PELR as defined in 3GPP TS 23.203 for QCI1 intended for Conversational Voice services results in that on each link 99 percent of the packets will be successfully delivered over an LTE air interface with a maximum delay of less than 80ms with a confidence level of 98 percent.