LAU reject with cause no suitable cells in Location Area
In this scenario is when network will send message to the mobile station(MS) mentioning LAU reject with cause as no suitable cells in Location Area.
This reject cause is transmitted by network to the MS with the intension of MS to be camped on the same PLMN. But with different LA or with different RAT (Radio Access Technology). This cause is sent by network (either HPLMN or VPLMN) to Mobile Subscriber(MS).
When Mobile receives this message, it will not search for another PLMN but it will search for another location area(LA) of the same PLMN. It is like network saying MS that "I will not be able to provide services on this LA, please try another LA in this PLMN".
Figure depicts two networks viz. gsm network and WCDMA network. WCDMA network will have LA5 and LA6 regions providing 3G service. All other location areas are LA1,LA2,LA3 and LA5 provides 2G service. As mentioned both the 2G and 3G service regions are overlapping. Suppose if subscriber-Z has subscribed for only 2G services and not 3G services. Let us assume that subscriber-Z moves to the overlapping region where both the services are available and tries to access 3G service then network will send the above reject cause i.e. "no suitable cells are found in this location area".
This reject cause from network indicates to MS that you may register with LA3 providing 2G services and not with LA5/LA6 providing 3G services. Hence mobile will register with LA3. Please note that network sends this message only when other LAs are available to provide service to the mobile station.