The sms queue will attempt to send one SMS per subscriber
to fill all the available slots. It will handle the case
where paging has not started, timed out or if there was
any kind of other failure. It is also retransmitting SMS
in case of failures.
The SMSqueue will be responsible of sending to the user. It will
do so in a loop and will also try not to overload the BTS. This
means the throughput of SMS will be limited.