A method for controlling access of wireless devices to a wireless communication network, comprising: defining an access class with which a wireless device may be associated, the access class having associated with it: i) access class barring information determining under what conditions a wireless device associated with the access class is allowed to access the network; and ii) at least one characteristic of a signal to be transmitted by a wireless device, associated with the access class to access the network; assigning a wireless device to the access class; the network notifying said wireless device of the access class barring information associated with its access class; said wireless device determining whether it is allowed to access the network based on the access class barring information; and if said wireless device is allowed to access the network, said wireless device transmitting the signal with at least one of said characteristics, wherein the signal transmitted by said wireless device to access the network is a random access preamble, and the at least one characteristic of the signal includes a set of one or more preambles allocated to the access class, characterised in that: the defining further comprises assigning pre-arranged meanings to specific preambles or subsets of preambles from the set of one or more preambles allocated to the access class, said wireless device transmitting the signal by selecting a preamble from the set of one or more preambles allocated to the access class and signifying additional information to the network by its selection of preamble, said additional information including at least one of: an acceptable waiting time before random access is allowed or before the network allocates uplink resources for access to the network; a request for said wireless device to change its access class; and a notification that said wireless device is changing its access class. defining an access class with which a wireless device may be associated, the access class having associated with it: i) access class barring information determining under what conditions a wireless device associated with the access class is allowed to access the network; and ii) at least one characteristic of a signal to be transmitted by a wireless device, associated with the access class to access the network; assigning a wireless device to the access class; the network notifying said wireless device of the access class barring information associated with its access class; said wireless device determining whether it is allowed to access the network based on the access class barring information; and if said wireless device is allowed to access the network, said wireless device transmitting the signal with at least one of said characteristics, wherein the signal transmitted by said wireless device to access the network is a random access preamble, and the at least one characteristic of the signal includes a set of one or more preambles allocated to the access class, characterised in that: the defining further comprises assigning pre-arranged meanings to specific preambles or subsets of preambles from the set of one or more preambles allocated to the access class, said wireless device transmitting the signal by selecting a preamble from the set of one or more preambles allocated to the access class and signifying additional information to the network by its selection of preamble, said additional information including at least one of: an acceptable waiting time before random access is allowed or before the network allocates uplink resources for access to the network; a request for said wireless device to change its access class; and a notification that said wireless device is changing its access class. the defining further comprises assigning pre-arranged meanings to specific preambles or subsets of preambles from the set of one or more preambles allocated to the access class, said wireless device transmitting the signal by selecting a preamble from the set of one or more preambles allocated to the access class and signifying additional information to the network by its selection of preamble, said additional information including at least one of: an acceptable waiting time before random access is allowed or before the network allocates uplink resources for access to the network; a request for said wireless device to change its access class; and a notification that said wireless device is changing its access class. an acceptable waiting time before random access is allowed or before the network allocates uplink resources for access to the network; a request for said wireless device to change its access class; and a notification that said wireless device is changing its access class.