9.1.36 System information type 4

3GPP44.018GSM/EDGE Radio Resource Control (RRC) protocolMobile radio interface Layer 3 specificationRelease 17TS

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

This message is sent on the BCCH by the network giving information on control of the RACH, the location area identification and various other information about the cell. See table 9.1.36.1. Special requirements for the transmission of this message apply, see 3GPP TS 45.002. The L2 pseudo length of this message is the sum of lengths of all information elements present in the message except the SI 4 Rest Octets and L2 Pseudo Length information elements.

Message type: SYSTEM INFORMATION TYPE 4

Significance: dual

Direction: network to mobile station

Table 9.1.36.1: SYSTEM INFORMATION TYPE 4 message content

IEI	Information element	Type / Reference	Presence	Format	length
	L2 Pseudo Length	L2 Pseudo Length 10.5.2.19	M	V	1
	RR management Protocol Discriminator	Protocol Discriminator 10.2	M	V	1/2
	Skip Indicator	Skip Indicator 10.3.1	M	V	1/2
	System Information Type 4 Message Type	Message Type 10.4	M	V	1
	Location Area Identification	Location Area Identification 10.5.1.3	M	V	5
	Cell Selection Parameters	Cell Selection Parameters 10.5.2.4	M	V	2
	RACH Control Parameters	RACH Control Parameters 10.5.2.29	M	V	3
64	CBCH Channel Description	Channel description 10.5.2.5	O	TV	4
72	CBCH Mobile Allocation	Mobile Allocation 10.5.2.21	C	TLV	3-6
	SI 4 Rest Octets	SI 4 Rest Octets 10.5.2.35	M	V	0-10

9.1.36.1 CBCH Channel description

This information element is present if SMSCB is active in the cell and indicates (together with the CBCH Mobile Allocation IE) where to find the CBCH.

9.1.36.2 CBCH Mobile Allocation

If the CBCH Channel Description Information Element indicates frequency hopping, the CBCH Mobile Allocation IE shall be present. If the CBCH Channel Description does not indicate frequency hopping, the CBCH Mobile Allocation IE shall be considered as an unnecessary IE in the message.

9.1.36.3 SI 4 Rest Octets

The sum of the length of this IE and the L2 pseudo length of the message equals 22.