Network attachment is a key process by which the terminal registers to the network, so as to allow the subscriber to initiate or accept incoming communication sessions. Until this step is successfully completed, the user has no access to the network, except in case of emergency.
The network attachment is generally performed when the terminal is switched on, and relies on many different mechanisms within the network and the terminal, which are further described in this section.
Broadcast of system information is an operation performed by the network. It is not specific to E-UTRAN networks, as similar processes exist, e.g. for UMTS, GSM and North-American CDMA systems, as well as IEEE Wireless Ethernet technologies. It is essential for terminals to understand which kind of network is present in terms of available technology, operators, and which channels and parameters shall be used to connect to the network in order to attempt a registration procedure.
Lots of different information can be broadcasted by the network so as to ease terminal life. However, the amount of broadcasted information shall not compromise the radio capacity. This trade-off has always been a subject of concern in standard committees, looking for solutions which allow the transmission of many parameters in the most efficient way.
Looking back to 2G/GSM, the broadcast channel was quite limited in terms of capacity (a few hundreds of bits per second) ...