12.21 Starting Frame Number Description

3GPP44.060General Packet Radio Service (GPRS)Mobile Station (MS) - Base Station System (BSS) interfaceRadio Link Control / Medium Access Control (RLC/MAC) protocolRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

There are two types of encoding for this IE : Relative Frame Number or Absolute Frame Number.

Table 12.21.1: Starting Frame Number Description information element

< Starting Frame Number Description IE > ::=

{ 0 < Absolute Frame Number Encoding >

| 1 < Relative Frame Number Encoding > } ;

If the mobile station is in packet transfer mode during the block immediately before the starting time and the lowest numbered PDCH assigned to the MS is different immediately before and after the starting time then the mobile station shall be ready to receive or transmit no later than one radio block from the starting time (see 3GPP TS 45.002).

12.21.1 Absolute Frame Number Encoding

In this case, the field is encoded as the 16-bit Starting Time IE defined in 3GPP TS 44.018, and the value of the Starting FN is obtained directly.

If the Starting FN is not aligned to the start of a block period and the mobile station is in packet transfer mode during the TDMA immediately before the Starting FN, then the mobile station shall align the starting time to the next block boundary and continue to use the currently assigned allocation upto the next block boundary.

12.21.2 Relative Frame Number Encoding

In this case, the field indicates the delay, relative to the first TDMA frame (N) of the RLC/MAC block containing the Starting Time field, before the assigned or requested resource becomes valid.

The value of this field is the 13 bit binary representation of the integer k, from which the offset to be applied to N can be derived.

The value of the Starting Frame Number is calculated as follows:

For (k mod 3) equal to:	The value of the Starting Frame Number is:
0 or 1	N + 4 + 4 k + (k div3), N + 5 + 4k + (k div3) (NOTE 1)
2	N + 5 + 4 k + (k div3)
0 £ k £ 8191

EXAMPLE: Starting Frame Number Description (13-bit field):
k = 1 0000000000001 block with first TDMA frame number = N+8 or N+9
k = 2 0000000000010 block with first TDMA frame number = N+13
k = 3 0000000000011 block with first TDMA frame number = N+17 or N+18

NOTE 1: In these cases, only one of the frame numbers N+4+4k+kdiv3 or N+5+4k+kdiv3 is valid, because the other corresponds to an idle frame, depending on the position of the block in the multi-frame.

NOTE 2: The value of (k+1) gives the number of relative blocks. The maximum number of relative blocks is therefore 8 192; this value was chosen according to the interval of time encoded by the Starting Time IE in 3GPP TS 44.018 (32 024 frames).

NOTE 3: The value (k=0) should not be used, so as to leave time for the MS to analyse the message and get ready to receive or transmit.