# Exercise 3.2: GSM Services

List of GSM services

Any  "Public Land Mobile Network"  $\rm (PLMN)$  must provide the fixed network infrastructure and so-called  "interworking functions"  $\rm (IWF)$.  This is the only way to provide the desired services at the user interface.

GSM services are divided into three categories:

• Bearer services,
• Tele services,
• Supplementary services.

Basis for data transmission are the  bearer services,  where the maximum data rate is  $\text{9.6 kbits/s}$.

Tele services  are end-to-end services.  The most important of these are:

1. the telephone service,
2. the fax service,
3. the short message service  $\rm (SMS)$.

Various  supplementary services  belong to each phase of GSM development:

1. "call display",  "call forwarding"  and  "caller ID"  in phase 1,
2. "call waiting",  "hold"  and  "conference call"  in phase 2,
3. "GPRS",  "HSCSD",  "EDGE"  in phase 2+.

Hint:  The exercise belongs to the chapter  "General Description of GSM".

### Questions

1

Which of the GSM services are the basis for data transmission?

 bearer services, teleservices, supplementary services.

2

What is the maximum data rate for GSM data transmission?

 $2.4 \ \rm kbit/s$. $7.8 \ \rm kbit/s$. $9.6 \ \rm kbit/s$.

3

Which statements are true for teleservices?

 Tele services are end-to-end services. A distinction is made between synchronous and asynchronous tele services. Examples are the telephone, fax and SMS services.

4

Which supplementary services originate from GSM phase 2?

 "Call Forwarding", "Call Waiting", "General Packet Radio Service"  $\rm (GPRS)$, "Conference Call"  $\rm (CONF)$.

5

What technology is used in  "High Speed Circuit-Switched Data"  $\rm (HSCSD)$?

 Packet switching, circuit switching.

### Solution

#### Solution

(1)  Correct is the  proposed solution 1:

• Bearer services form the basis for data transmission.
• They provide the technical means to transport data in a secured manner.

(2)  Correct is the  proposed solution 3:

• The maximum data rate for GSM data transmission is  $9.6 \rm kbit/s$.
• There are synchronous and asynchronous as well as circuit-switched and packet-switched data transmission.

(3)  Correct are the  proposed solutions 1 and 3:

• Proposition 2 is incorrect:
• The terms  "synchronous"  and  "asynchronous"  play a role only in connection with bearer services.

(4)  Correct are the  proposed solutions 2 and 4:

• In contrast,  "call forwarding"  belongs to GSM phase 1 and  "General Packet Radio Service"  $\rm (GPRS)$  to phase 2+.

(5)  Correct is the  proposed solution 2:

• "High Speed Circuit-Switched Data"  $\rm (HSCSD)$  was introduced as a circuit-switched transmission technology.
• In contrast,  "General Packet Radio Service"  $\rm (GPRS)$  operates as packet-switched and  "Enhanced Data Rate for GSM Evolution"  $\rm (EDGE)$  can be described as circuit-switched data service.