Page 80 - From GMS to LTE

66 From GSM to LTE-Advanced Pro and 5G

Instruction Figure 1.53 Structure of the SELECT
(SELECT) Length of the data field command APDU.

A0 A4 00 00 02 6F 02

File ID, e.g. 0x6F02 for EF IMSI

Table 1.9 Some fields of the response APDU for a SELECT command.

Byte Description Length

3–4 File size 2
5–6 File ID 2
7 Type of file (transparent, linear fixed, cyclic) 1
9–11 Access rights 3
12 File status 1

To physically communicate with the SIM card, there are eight contact areas on the top
side of the SIM card. Only five of those contacts are required:
C1: power supply;
●
C2: reset;
●
C3: clock;
●
C5: ground;
●
C7: input/output.
●
As only a single line is used for the input and output of command and status APDUs,
the data are transferred in half‐duplex mode only. The clock speed for the transmission
has been defined as C3/327. At a clock speed of 5 MHz on C3, the transmission speed is
thus 13,440 bit/s.

1.11 The Intelligent Network Subsystem and CAMEL

All components that have been described in this chapter are mandatory elements for
the operation of a mobile network in which billing records are collected and invoices
sent once a month. To offer prepaid services for which subscribers have to be billed in
real‐time, additional logic and databases are necessary. These are referred to as the
Intelligent Network (IN) and implemented on a Service Control Point (SCP) as described
in Section 1.4. Prepaid services have become very popular in many countries since their
introduction in the mid‐1990s. Instead of receiving a bill once a month, a prepaid sub-
scriber has an account with the network operator, which is funded in advance with a
certain amount of money determined by the subscriber. The amount on the account
can then be used for phone calls, SMS and data services. During every call or event,