Showing posts with label Functions. Show all posts
Showing posts with label Functions. Show all posts

Function of MSC

MSC full form Mobile Switching Center is the centerpiece of an NSS full form network switching subsystem. 

MSC most commonly used with a communications switching function, such as call set-up, release, and routing. 

MSC is a telephone exchange that makes the connection between mobile users within the network, from mobile users to the public switched telephone network and also from mobile users to other mobile networks.

Function of BSC

BSC full form is Base Station Controller reserve radio frequency for communication and manages handovers between BTS. BCS connected to a single MSC. 

Some function of BSC are following below :

  • To control BTS.
  • Radio resource management. 
  • Handoff management and control.
  • It handles radio channel set up and frequency hopping. 
  • The BSC is physically connected through leased lines or microwave links to the MSC. 

Function of OMC

OMC full form is operations and maintenance center used in the switching system in GSM network architecture is connected to all equipment in the switching system and to the BSC. 


The implementation of ( operations and maintenance centers) OMC is called the operation and support system.

Now we can also check the function of OMC :

  • Used in security management. 
  • Used in maintenance tasks.
  • Used in network configuration, operation and performance management. 
  • Used in administration and commercial operations like subscriptions and terminals charging and in statistics. 

TCH in GSM

TCH stands for a traffic channel in GSM.
This article describes the GSM traffic channel. Traffic channel carries digitally encoded user data or user speech on the forward and reverse link.
TCH support two types of information rates, they are
  • Full rate ( TCH/F )
  • Half rate ( TCH/H )
TCH is a group of 26 consecutive TDMA frame, called multi-frame of the 26 TDMA frames, 24 are used as TCH frames, one frame (thirteen ) is for SACCH and 26th is the unused or idle frame.
TCH data transmitted in 26 consecutive frames

1. Full rate TCH  (TCH/F)

Full rate speech channel  (TCH/FS) - At 13 Kbps the full rate speech channel is digitized. After channel coding, full rate speech channel carries 22.8 Kbps.

Full rate data channel (TCH/F9.6), Full rate data channel (TCH/F4.8), Full rate data channel (TCH/F2.4) channel carries the data at the speed of 9.6 Kbps, 4.8Kbps, 2.4Kbps respectively.

After channel coding is applied is converted to data transferred rate at up to 22.8 Kbps.

2. Half rate TCH (TCH/H)


Half rate speech channel (TCH/HS) - At 6.5 Kbps the half rate speech channel is digitized. After channel coding, half rate speech channel carries up to 11.4 Kbps.

Hull rate data channel ( TCH/H4.8), Full rate data channel (TCH/H2.4) channels carry the data at the speed of 4.8 Kbps, 2.4 Kbps respectively.

After channel coding is applied is converted to data transferred rate at up to 11.4 Kbps.
Explore more information:

  1. CCCH in GSM
  2. BCCH in GSM
  3. AGCH in GSM
  4. FCCH in GSM
  5. RACH in GSM
  6. DCCH in GSM
  7. SACCH in GSM
  8. SDCCH in GSM
  9. FACCH in GSM

CCCH in GSM

CCCH stands for the common control channel in GSM.

GSM  common control channel ( CCCH ) is used for conveying from network to the mobile subscriber and provide access to the mobile subscriber,

There are three types of different channels  : (I) PCH, (II) AGCH, (III) RACH

Refer the following link to know details of the PCH, AGCH, RACH channel, and their processing.
  • GSM Paging channel ( PCH )
  • GSM Access grant channel ( AGCH )
  • GSM Random access channel ( RACH )

Explore more information:

BCCH in GSM

BCCH stands for the broadcast control channel. This article learns to GSM broadcast control channel.

The BCCH  is a forward channel and also is a unidirectional base to mobile channel that provides information about the network, the cell in which the mobile is currently located and adjacent cells. BCCH is transmitted in 51 frames multi frame structure in a frame next to SCH on TS0. It broadcast a list of the channel that is currently in use within the cell.

The BCCH includes two channels, they are : (I) FCCH  (II) SCH

Refer the following link to know details of the PCH, AGCH, RACH channel, and their processing. 
  • Frequency correction channel ( FCCH )
  • Synchronization Channel ( SCH )

AGCH in GSM

AGCH stands for Access grant channel in GSM. 

The AACH is used by the base station to provide forward link communication to the mobile. It carries data that instructs the mobile to operate in a specific channel with a particular dedicated control channel.

It is the message sent by the base station before a subscriber is moved off the control channel.

The AGCH is used by the base station to respond to RACH sent by the mobile station in the earlier CCCH frame. 

RACH in GSM

RACH stands for Random access channel in GSM.

It is a reverse link channel. With the help of RACH, the mobile station originates a call, send signaling message when not on call, acknowledges message.

It uses a slotted ALOHA access method. All mobile must access or respond to a PCH alert within TS0 of a GSM frame.

At the BTS each frame will accept the RACH transmissions from the mobiles during TS0. The base station responds to the RACH transmission by allocating a channel and a stand-alone dedicated control channel for signaling in the presence of a call. The connection is confirmed by the BS full form ( base station ) over the access grant channel.

Random access burst

DCCH channel in GSM

DCCHs stands for dedicated control channels in GSM. 

The dedicated control channel comes into the picture after a call is established. The dedicated control channels are bidirectional. They have the same formats and function in the forward and the reverse links.

Refer the following link to know details of the PCH, AGCH, RACH channel, and their processing.
  • GSM Fast associated control channel ( FACCH )
  • GSM Slow associated control channel ( SACCH )
  • GSM Stand dedicated control channel ( SDCCH )

SACCH in GSM

SACCH stands for Slow associated control channel GSM. 

It is related to the traffic channel or SDCCH.

On the forward link, it is used to send regularly changing information like: 
  • Transmit power channel 
  • Broadcast messages
  • Specific timing advance instruction for each user
On the reverse link, it carries information about 
  • Received signal strength 
  • Quality of TCH and BCH
  • Measurement results from neighboring cells
  • It is used to inform the base of power measurements made by the mobile of signal strength in the adjacent cells
  • It is transmitted during the total 13th frame of every dedicated control channel multi-frame
  • SACCH exchanges control information between the base station and mobile station a call or call set up

SDCCH in GSM

The full form of SDCCH is Stand-Alone Dedicated Control Channel GSM. 

The Standalone dedicated control channel is allocated for every mobile station.

It contains the signaling data that follows the connection of the mobile with the base station, prior to the allocation of TCH by the base station ( BS ) to the MS.

It guarantees that the mobile station, as well as the base station, will remain connected. The base station and mobile switching center will verify the subscriber unit and assign the needed resources to the mobile.

This channel that accepts the newly completed call from the BCH. It holds the traffic while waiting for the base station to assign a TCH channel.

The SDCCH is also used to transmit authentication and alert messages as the mobile synchronize itself with the frame structure and wait for TCH.

SDCCH can be assigned its own physical channel. Also, they can occupy the TS0 slot of the BCH if there is a low demand for BCH or CCCH traffic. 

FACCH in GSM

FACCH full form is Fast associated control channel.

 FACCH carries important messages. It is used for the exchange of time-critical information between the mobile and the base station during the process of the cell.

 The FACCH  is assigned whenever SDCCH is not dedicated to a user and there is an urgent message like a handoff request.

 The FACCH was transmitted control information by stealing capacity from the associated traffic channel. It is done by setting two special bits called stealing bits. In the TCH forward channel burst.

 If a stealing bit is set, the time slot contains FACCH data for that frame.
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