GSM Cordless Telephony System Broadcast Channel (CTSBCH)
Timeslot Assignment

Finding even the most basic information for telecommunications standards can sometimes be a real challenge, even with a good search engine, so here is information on CTSBCH Timeslot Assignment pulled from Table 1 (subclause 6.3.3): TNSi,j of the Digital Cellular Telecommunications System (Phase 2+); Multiplexing and multiple access on the radio path (3GPP TS 45.002 version 6.12.0 Release 6) document. Caveat: If you are performing critical work, be sure to obtain the latest version of the specification an confirm all data presented here, since these things can change without notice. See abbreviation definitions at bottom of page.

"For the CTSBCH, a procedure of timeslot shifting from one 52-multiframe to another is defined. The usage of this procedure is mandatory in CTS idle mode and optional in CTS dedicated mode. When the shifting procedure is not applied, the CTSBCH timeslot number shall be equal to the TNC broadcast in the current 52-multiframe CTSBCH-SB.

The following parameters are required for the timeslot shifting procedure.

Parameters broadcast in the CTSBCH-SB:

a) TNI: initial timeslot number (0 to 7, 3 bits), defined by the three LSBs (BN3, BN2, BN1) of the FPBI (specified in 3GPP TS 23.003)

b) TNSCN: timeslot number series couple number (0 to 31, 5 bits), defined by the 5 bits (BN8, ..., BN4) of the FPBI. Defines the couple of timeslot number circular series (TNSTNSCN,0, TNSTNSCN,1) to be used to form the timeslot shifting sequence."

TNSCNTNSTNSCN,0TNSTNSCN,1
0( 0, 1, 2, 4, 7, 5, 6, 3 )( 0, 3, 5, 7, 6, 2, 1, 4 )
1( 0, 1, 2, 5, 3, 6, 7, 4 )( 0, 4, 1, 5, 7, 6, 3, 2 )
2( 0, 1, 2, 6, 5, 3, 7, 4 )( 0, 3, 6, 7, 5, 2, 4, 1 )
3( 0, 1, 2, 6, 7, 5, 4, 3 )( 0, 3, 7, 4, 6, 2, 5, 1 )
4( 0, 1, 3, 2, 5, 6, 7, 4 )( 0, 4, 7, 6, 2, 1, 5, 3 )
5( 0, 1, 3, 6, 7, 5, 2, 4 )( 0, 3, 7, 4, 2, 6, 5, 1 )
6( 0, 1, 4, 2, 5, 6, 7, 3 )( 0, 2, 6, 3, 7, 5, 4, 1 )
7( 0, 1, 4, 2, 5, 7, 6, 3 )( 0, 4, 7, 3, 5, 6, 2, 1 )
8( 0, 1, 4, 2, 6, 5, 7, 3 )( 0, 2, 1, 5, 3, 6, 7, 4 )
9( 0, 1, 4, 5, 7, 3, 6, 2 )( 0, 3, 7, 6, 5, 2, 4, 1 )
10( 0, 1, 4, 6, 5, 7, 3, 2 )( 0, 4, 7, 5, 1, 2, 6, 3 )
11( 0, 1, 4, 7, 3, 5, 6, 2 )( 0, 4, 2, 1, 5, 7, 6, 3 )
12( 0, 1, 4, 7, 6, 3, 5, 2 )( 0, 4, 2, 1, 5, 6, 7, 3 )
13( 0, 1, 5, 2, 4, 7, 6, 3 )( 0, 3, 7, 5, 1, 4, 6, 2 )
14( 0, 1, 5, 2, 6, 4, 7, 3 )( 0, 3, 4, 5, 7, 6, 2, 1 )
15( 0, 1, 5, 6, 2, 4, 7, 3 )( 0, 3, 7, 6, 4, 5, 2, 1 )
16( 0, 1, 5, 6, 7, 4, 3, 2 )( 0, 4, 7, 6, 2, 5, 1, 3 )
17( 0, 2, 1, 3, 6, 7, 5, 4 )( 0, 3, 7, 4, 1, 5, 6, 2 )
18( 0, 2, 1, 5, 6, 7, 4, 3 )( 0, 4, 7, 5, 1, 3, 6, 2 )
19( 0, 2, 3, 4, 7, 6, 5, 1 )( 0, 3, 1, 5, 2, 6, 7, 4 )
20( 0, 2, 3, 6, 7, 5, 1, 4 )( 0, 4, 7, 6, 3, 5, 2, 1 )
21( 0, 2, 3, 7, 5, 6, 4, 1 )( 0, 3, 6, 2, 1, 5, 7, 4 )
22( 0, 2, 4, 7, 3, 6, 5, 1 )( 0, 3, 5, 6, 7, 4, 1, 2 )
23( 0, 2, 5, 3, 6, 7, 4, 1 )( 0, 3, 7, 6, 5, 1, 2, 4 )
24( 0, 2, 5, 3, 7, 6, 4, 1 )( 0, 3, 5, 1, 2, 6, 7, 4 )
25( 0, 2, 6, 3, 1, 5, 7, 4 )( 0, 3, 4, 7, 6, 5, 1, 2 )
26( 0, 2, 6, 5, 1, 4, 7, 3 )( 0, 4, 5, 7, 6, 3, 1, 2 )
27( 0, 2, 6, 5, 3, 7, 4, 1 )( 0, 3, 6, 7, 5, 1, 2, 4 )
28( 0, 3, 5, 1, 2, 6, 7, 4 )( 0, 4, 7, 6, 5, 2, 3, 1 )
29( 0, 3, 5, 2, 6, 7, 4, 1 )( 0, 4, 7, 3, 6, 5, 1, 2 )
30( 0, 3, 6, 7, 4, 2, 5, 1 )( 0, 4, 1, 2, 6, 5, 7, 3 )
31( 0, 3, 7, 5, 6, 2, 4, 1 )( 0, 4, 7, 6, 3, 5, 1, 2 )


a) TNSCO : TNS couple order (1 bit), defines together with TNSCN the ordered couple (TNS1, TNS2).
if TNSCO = 0 then (TNS1, TNS2) = (TNSTNSCN,0, TNSTNSCN,1)
if TNSCO = 1 then (TNS1, TNS2) = (TNSTNSCN,1, TNSTNSCN,0)

b) parameters to be used to form the timeslot shifting sequence.
x0 : 0 to 7, 3 bits
x1 : 0 to 7, 3 bits
x2 : 0 to 7, 3 bits
x3 : 0 to 7, 3 bits