3GPP TSG-CN WG1 	Tdoc 3GPP N1-99 571
Sophia Antipolis, FRANCE
1 – 4 June 1999

Source:	[TSG-N1 ] Vodafone
To:	TSG-S1, SMG 1, TSG-S2, SMG 12, SMG 2 WP A
 
Draft Liaison Statement on class B mobiles
The TSG-N1 have discussed the LS from SMG 12 in N1-99-550 (SMG12 C-99-479) (which answers an earlier LS from SMG 2) which relates to the behaviour of GPRS mobiles using the class B mode of operation. TSG N1 would like to offer the following thoughts and information to SMG 1.

TSG-N1 believe that there are two issues which need to be tackled independently:

a)	what are the requirements on mobiles using class B mode of operation to receive MSC originated Page messages?; and 
b)	when a mobile in class B mode of operation receives a page message from the MSC, what should it do?

TSG-N1 believe that the first issue is a matter for SMG 1 (SA 1) and SMG 2 to resolve. However, TSG-N1 note that the requirements may vary according to the presence/absence of the Gs interface. When the Gs interface is present all page messages should arrive in the mobile.

TSG-N1 believe that the second issue is more of a matter between SMG 1 (SA 1) and TSG-CN1 (SMG 3 WP A).

The attached text in N1-99-572 is an example of how some of the issues might be clarified within GSM 03.60.

Within TSG-N1, the main point of contention was whether or not a mobile in class B mode of operation had to respond to MSC based paging, or, could delay the page response, or, could leave the implementation to choose whether to respond or ignore the page.

Operators expressed their opinion that the introduction of GPRS should not lead to a degradation of the voice QoS. Failure to respond to paging will lead to a degradation in the success rate of MT calls. Additionally, this degradation will be impossible for the operator to influence or control. 

Delaying the page response will be detrimental to the call set up time observed by the A party and will slightly increase MT call failures. However a delay of up to [1] second might not be intolerable to the overall system. Longer delays are likely to result in system problems caused by the retransmission of paging messages by various nodes and the expiry of MSC based timers. 

Some manufacturers noted that users who wished to ensure that packet had higher priority than circuit could temporarily detach from Circuit Switched and configure their mobiles to operate in class C mode of operation.