B.4 Streaming

26.3463GPPMultimedia Broadcast/Multicast Service (MBMS)Protocols and codecsRelease 17TS

B.4.1 Void

B.4.2 Void

B.4.3 Void

B.4.4 Example parameters

B.4.4.1 Parameter derivation algorithm

This clause provides recommendations for the derivation of the transport parameter T. This recommendation is based on the following input parameters:

– B the maximum source block size, in bytes

– P the maximum repair packet payload size, in bytes, which is a multiple of Al

– Al the symbol alignment factor, in bytes

– KMAX the maximum number of source symbols per source block.

– KMIN a minimum target on the number of symbols per source block

– GMAX a maximum target number of symbols per repair packet

A requirement on these inputs is that ceil(B/P) ≤ KMAX. Based on the above inputs, the transport parameter T is calculated as follows:

Let,

G = min{ceil(P·KMIN/B), P/Al, GMAX} – the approximate number of symbols per packet

T = floor(P/(Al·G))·Al

The value of T derived above should be considered as a guide to the actual value of T used. It may be advantageous to ensure that T divides into P, or it may be advantageous to set the value of T smaller to minimize wastage when full size repair symbols are used to recover partial source symbols at the end of lost source packets (as long as the maximum number of source symbols in a source block does not exceed KMAX). Furthermore, the choice of T may depend on the source packet size distribution, e.g., if all source packets are the same size then it is advantageous to choose T so that the actual payload size of a repair packet P’, where P’ is a multiple of T, is equal to (or as few bytes as possible larger than) the number of bytes each source packet occupies in the source block.

Recommended settings for the input parameters, Al, KMIN and GMAX are as follows:

Al = 4 KMIN = 1024 GMAX = 10

B.4.4.2 Examples

The above algorithm leads to transport parameters as shown in Table B.4.4.2-1 below, assuming the recommended values for Al, KMIN and GMAX and P = 512:

Table B.4.4.2-1

Max source block size B

G

Symbol size T

G∙T

40 KB

10

48

480

160 KB

4

128

512

640 KB

1

512

512