CDMA cellular mobile communication system

Base station subsystem (BSS)

Base station subsystem is the general term for the wireless devices and wireless channel control devices that serve one or several cells. Generally, a BSS contains one more base station controllers (BSC) and base transmitter stations (BTS).

 Mobile switch center (MSC)   

MSC is a functional entity that performs control and switching to the mobile stations within the area that it serves, and an automatic connecting device for the subscriber traffic between the CDMA network and other public networks or other MSCs. MSC is the kernel of the CDMA cellular mobile communication system, and it is different from a wired switch in that an MSC must consider the allocation of the wireless resources and the mobility of subscribers, and at least it must implement the follows processing activities:

1. Location Registration processing;

2. Handoff.

   Gateway MSC (GMSC)

When a non-CDMA subscriber calls a CDMA subscriber, the call will first be routed to an MSC, which will inquires the corresponding HLR and further route the call to the called party’s MSC. This kind of MSC is called Gateway MSC (GMSC). It is up to the network operator to select which MSCs as GMSCs.

  Visitor location register (VLR)

VLR is responsible for the storage and updating of the subscriber data of mobile stations that roamed to the service area of this VLR. The VLR is generally configured together with the MSC. When the mobile station enters a new location area, the MSC will notice the VLR, which will initiate registration processing to the HLR to update the subscriber location information. The VLR also stores necessary information for the establishment of calls in the database for the MSC to search. One VLR can cover one or more MSC areas. Specifically, the following information is included:

Service profile information (PROFILE)

Mobile identification number/international mobile subscriber identity (MIN/IMSI)

Shared secret data                       SSD

Electronic serial number (ESN)

Mobile station authentication data (AUTHEN)

Mobile station authorization data (AUTHOR)

Mobile station temporary local directory number (TLDN)

Mobile station location area information (LAI)

  Home location register (HLR)

The HLR provides subscriber information storage and management functions for the mobile network, including mobile subscriber subscription and cancellation and service authorization and cancellation. At the same time, it helps in the implementation of subscriber’s call and service operations. A CDMA can contain one or more HLRs based on the number of subscribers, equipment capacity and network organization mode, with multi-HLR mode realized in the form of virtual HLRs. The subscriber information stored in the HLR includes the following two types in information:

1. Subscription information

Some location information that enables the realization of call routing and accounting, such as VLR address, MSC address and local mobile station identity.

2. Subscriber-related information stored in the HLR

Mainly including:

Service profile information (PROFILE)

Mobile identification number/international mobile subscriber identity (MIN/IMSI)

Shared secret data SSD

Electronic serial number (ESN)

Mobile directory number (MDN)

IMSI/MIN and MDN are often used as key for access to the mobile subscriber database.

The HLR also contains the following mobile subscriber information:

Telecom services

Data services

IN services

Short message service data

Service restriction (such as roaming restriction)

Supplementary service parameters

  Authentication center (AUC)

Authentication center is a function entity for the management of authentication information related to the mobile station. It implement mobile subscriber authentication, stores the mobile subscriber authentication parameters, and is able to generate and transmit the corresponding authentication parameters based on the request from MSC/VLR. The authentication parameters in the AUC can be stored in the encrypted form. The authentication center is generally configured together with the HLR. The authentication parameter stored in the AUC include:

1. Authentication key (A_KEY);

2. Share secret data  (SSD);

3. Mobile identification number/international mobile subscriber identity (MIN/IMSI);

4. Authentication algorithm (AAV);

5. Accounting (COUNT).

   Short message center (MC or SC)

As an independent entity in the CDMA cellular mobile communication system, the short message center works in coordination with other entities such as MSC, HLR to implement the reception, storing and transfer of the short messages from CDMA cellular mobile communication system subscribers, and store subscriber-related short message data. 

  Short message entity (SME)

SME is a function entity for synthesis and analysis of short messages.