This document describes radio transmission techniques and channels in GSM networks. It discusses Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA) and defines physical and logical channels. It provides details on different control channels like Broadcast Control Channel (BCCH), Common Control Channel (CCCH), and Dedicated Control Channel (DCCH). It also describes traffic channels and various burst types used in GSM frames.

1. Radio Transmission Techniques
FDMA
TDMA
CDMA
Channels
Physical channels
Logical channels

2. Frequency
Channel
Time

3. Frequency Time Slot
Channel
Time
0 1 2 3 4 5 6 7

4. Frequency
Code
Time
Code 1
Code 2
Code 3

5. Channels
Physical Channels
Associated with frequency bands, time slots, codes
Physical channels transfer bits from one network
element to another
Logical Channels
Distinguished by the nature of carried information and
the way to assemble bits into data units
Three types
 one-to-one: traffic channels between a BTS and a MS
 one-to-many: synchronization signals from BTS to MSs in a cell
 many-to-one: from MSs to the same BTS

6. Air Interface Layers
Layer 3
Messages Messages
Messages
Logical Layer 2 Logical
Channels Packets Channels
Radio Layer 1 Radio
Transmission Bits Transmission
Terminal Base
Station

7. GSM Frame Structure
Superframe ... 51 Multiframe
6.12 sec
120 msec ... 26 Frames
4.615 msec 0 7 8 Multiframe
Coded data Midamble
0.57692 msec
3 57 1 26 1 57 3 8.25
156.25 bits
Tail bit Stealing Flag Guard period

8. Frame Types
• There are two types of multiframe
– 26 TDMA-frame multiframe is used to carry
TCH, SACCH and FACCH
– 51 TDMA-frame multiframe is used to carry
BCCH, CCH, SDCCH and SACCH

9. Burst and Frames
• The information contained in one time slot
on the TDMA frame is call a burst.
• Five types of burst
– Normal Burst (NB)
– Frequency Correction Burst (FB)
– Synchronization Burst (SB)
– Access Burst (AB)
– Dummy Burst

10. Traffic TCH/F: Full-rate Traffic Channel Two-way
channels TCH/H: Half-rate Traffic Channel
(TCH)
FCCH: Frequency correction
BCH SCH: Synchronization
BCCH: Broadcast control
Base-to-
Signaling PCH: Paging mobile
CCCH
channel AGCH: Access grant
RACH: Random access
SDCCH: Stand-alone dedicated control
DCCH
SACCH: Slow associated control
Two-way
FACCH: Fast associated control

11. Logical Channels
• Control Channels
– Broadcast Channels (BCH)
– Common Control Channels (CCCH)
– Dedicated Control Channels (DCCH)
• Traffic Channels (TCH)
– Full Rate (TCH/F)
– Half Rate (TCH/H)

12. UP / Down-Link
Down-link: the transmission path from Base Station
to Mobile Station
Up-link: the transmission path from Mobile Station
to Base Station

13. Control Channels
• Broadcast Channels (BCH)
– Frequency Correction Channel (FCCH)
– Synchronization Channel (SCH)
– Broadcast Control Channel (BCCH)
• Common Control Channels (CCCH)
– Paging Channel (PCH)
– Random Access Channel (RACH)
– Access Grant Channel (AGCH)
• Dedicated Control Channels (DCCH)
– Stand alone Dedicated Control Channel (SDCCH)
– Cell Broadcast Channel (CBCH)
– Slow Associated Control Channel (SACCH)
– Fast Associated Control Channel (FACCH)

14. Broadcast Channels (BCH)
To help the MH (Mobile Handset)
to turn to a BTS
to listen for the cell information
 to start roaming, waiting for calls to arrive, making calls
Because BTSs are not synchronized with each other,
every time a MH decides to camp to another cell, its
FCCH, SCH, and BCCH must be read.

15. Frequency Correction Channel
(FCCH)
• Provide MH with the frequency reference of
the system
– To enable the Mobile Handset (MH) to
synchronize with the frequency
• Transmission properties
– Transmit on the down-link
– Point to multi-point.

16. Synchronization Channel (SCH)
• MH synchronize with the structure within the
locative cell
– MH can receive information from the proper time slots
on the TDMA structure
• To ensure a GSM BTS is chose
– The Base Station Identity Code (BSIC) can only be
decoded by a GSM BTS
• Transmission properties
– Transmit on down-link
– Point to multi-point.

17. Broadcast Control Channel
(BCCH)
• BTS broadcast cell information to MH
– LAI ( Location Area Identity), to start roaming,
waiting for calls to arrive, making calls
– maximum output power allowed in the cell
– information about BCCH carriers for the
neighboring cells
• MH will perform measurement to BTS
• Transmission properties
– Transmit on down-link
– Point to multi-point

18. Common Control Channels (CCCH)
CCCH support the establishment of a dedicated
communication path (dedicated channel) between
the MH and the BTS
Three types of CCCH
Paging Channel (PCH)
Random Access Channel (RACH)
Access Grant Channel (AGCH)

19. Paging Channel (PCH)
• Used by BTS to page particular MH in the cell
– MH actively listen to PCH to check contact info
within certain time
– Contact could be incoming call or short message
• Contact info on PCH include
– IMSI (MH’s identity number), or
– TMSI (temporary number)
• Transmission properties
– Transmit on down-link
– point to point

20. Random Access Channel
(RACH)
• Used by MH to request a dedicated channel
for call setup
– Shared by any MH attempts to access the
network
– Channel request message contains the reason
for the access attempt
• Transmission properties
– Transmit on up-link
– Point to pint.

21. Access Grant Channel (AGCH)
• The network assigns a signaling channel via
AGCH
– A Stand alone Dedicated Control Channel
(SDCCH) is assigned
• Transmission properties
– Transmit on down-link
– Point to point

22. Dedicated Control Channels
(DCCH)
DCCH are used for transferring nonuser
information between the network and the MH
Messages on DCCH Including
 channel maintenance
 mobility management
 radio resource management
Four kinds of DCCH
Stand alone Dedicated Control Channel (SDCCH)
Cell Broadcast Channel (CBCH)
Slow Associated Control Channel (SACCH)
Fast Associated Control Channel (FACCH)

23. Stand alone Dedicated Control
Channel (SDCCH)
• Transfer signaling information between the
BTS and the MH
• Typically used for location updating prior
to use of a traffic channel
• Transmission properties
– Bidirectional channel, transmit on both up and
down-link
– Point to point.

24. Cell Broadcast Channel (CBCH)
• To carry Short Message Service Cell
Broadcast (SMSCB)
• Use the same physical channel as SDCCH
• Transmission properties
– Transmit on down-link
– Point to multi-point

25. Slow Associated Control
Channel (SACCH)
• Carries control and measurement parameters along
with routine data necessary to maintain a radio
link between the MH and the BTS
– On the uplink, MS sends averaged measurements
(signal strength and quality) of current and neighboring
BCCH
– On downlink, MS receives information about
transmitting power to use and an instruction with time
advance/retard
• Transmission properties
– Bidirection channel, transmit on both up and down link
– Point to point

26. Fast Associated Control Channel
(FACCH)
• An FACCH is used over a TCH where it
steals time slots from a TCH
– a 20 ms segment of speech is stolen to carry
handover signaling information
• Appears on demand

27. Traffic Channels (TCH)
• TCH transport user information (speech/data)
• TCH are bidirectional dedicated channels
between the network and the MH

28. Burstinformation contained in one time slot is a
The
burst
Five types of burst
Normal Burst (NB)
 To carry information on traffic and control channels
Frequency Correction Burst (FB)
 To synchronize the frequency of the mobile
Synchronization Burst (SB)
 To synchronize the frames of the mobile
Access Burst (AB)
 For random and handover access
Dummy Burst
 For padding the frame