Exercise 3.5Z: GSM Network Components

From LNTwww

Base Station Subsystem of GSM

For the mobile phone standard  "Global System for Mobile Communications"  - abbreviated  $\rm GSM$ - the network infrastructure includes the following subsystems:

  • "Base Station Subsystem"   $\rm (BSS)$,
  • "Switching & Management Subsystem"   $\rm (SMSS)$,
  • "Operation & Maintenance Subsystem"   $\rm (OMSS)$.

The  "Base Station Subsystem"  is mainly responsible for the GSM radio network (see diagram), while the  "Switching & Management Subsystem"  represents the switching network and the  "Operation & Maintenance Subsystem"  is responsible for operation and maintenance.

The following terms will continue to be used in the questions on these exercise:

  • "Authentication Center"   $\rm (AUC)$,
  • "Base Station Controller"   $\rm (BSC)$,
  • "Base Transceiver Station"   $\rm (BTS)$,
  • "Gateway Mobile Switching Center"   $\rm (GMSC)$,
  • "Home Location Register"   $\rm (HLR)$,
  • "Mobile Switching Center"   $\rm (MSC)$,
  • "Operation and Maintenance Center"   $\rm (OMC)$,
  • "Visitor Location Register"   $\rm (VLR)$.

Notes:     This exercise belongs to the chapter  Characteristics of GSM.



With which of the three subsystems does the mobile station communicate?

With the BSS,
with the SMSS,
with the OMSS.


Which statements apply to a base transceiver station  (BTS)?

It includes the base station's transmitting and receiving devices.
The task of the BTS is to switch calls.
In most cases, several BTS are subordinate to a common base station controller  (BSC).


How many links can a BTS with multiple antennas support if each antenna covers a sector of  $120^\circ$ ?

$N_{\rm max}\ = \ $


Which of the following components are part of the OMSS?

The MSC.
The OMC.


Which of the following components are databases?

The AUC.
The HLR.
The VLR.


(1)  Each mobile station  (MS)  is in communication with a base transceiver station  (BTS).  This is part of the base station subsystem  (BSS)   ⇒   solution 1.

(2)  Correct are the statements 1 and 3.

  • In contrast, the base transceiver station is not responsible for switching tasks,
  • but this is rather the task of a mobile switching center  (MSC), which is part of the switching and management subsystem  (SMSS).

(3) If, as is usually the case with GSM, the individual antennas cover $120^\circ$ sectors, a BTS can provide up to three connection paths   ⇒   $N_{\rm max} \hspace{0.15cm}\underline{= 3}$.

(4)  Only the operation and management center (OMC) belongs to the OMSS   ⇒   Proposal 3 .

  • In contrast, MSC and GMSC are components of the mobile switching network  (SMSS).
  • With regard to OMC, a distinction is made between OMC-B (for BSS monitoring) and OMC-S (for SMSS monitoring).

(5)  Solutions 1, 3 und 4 are correct:

  • The gateway mobile switching center  (GMSC) is a hardware unit that is responsible for switching between the fixed network and the mobile network.
  • The other three terms given describe databases of the switching & management subsystem  (SMSS).
  • The authentication center  (AUC)  is responsible for the storage of confidential data and keys.
  • The home location register  (HLR) is a central register for the entire Public Land Mobile Network (PLMN) for managing unencrypted subscriber data, subscribed services and routing for calls from a mobile operator's own subscribers.
  • Contrary, the  visitors' location register  (VLR) contains information about the current visitors of other operators who are located in the current PLMN.