Tutorial 6

Mobile Communication Networks

Mohamed Esam

Air InterfaceAir Interface

Base Stations

GSM channels• Physical channel:

• Certain time slot at certain frequency

• Logical channel:• Types of Data in the physical

channel

Logical Channels

Traffic Channel (TCH) Control Channel (CCH)

Full rate(/F)

Half Rate(/H)

One Eight (/8)

Broadcast Channel (BCH)

Common Control Channel

(CCCH) Dedicated Control Channel (DCCH)

Cell Broadcast Channel (CBCH)

Frequency Correction

channel )FCCH(

Synchronization Channel (SCH)

Broadcast Control

Channel (BCCH)

Standalone Dedicated

Control Channel (SDCCH)

Slow Associated Control Channel

(SACCH)

Fast Associated Control Channel (FACCH)

Paging Channel

(PCH)

Random Access Channel (RACH)

Access Grant Channel (AGCH)

Traffic Channels• Traffic means voice transmission.

• Full Rate:• 22.8Kbps, and speech coding 13Kbps.

• Half Rate:• 11.4Kbps, and speech coding 6.5Kbps.

• One Eight:• For signaling or SMS’s.

Control Channels• To control the network performance.• You can note the sequence to establish a call.• BCH:

• FCCH:• Carrier signal to inform the MS with carrier

frequency.• SCH:

• Define the frame number of the cell and Base Station Identification Code (BSIC)

• BCCH:• Send information about the cell.• Send Location Area Identity (LAI) of the

neighbor MSC’s.• Send Max. allowed power of the MS.• Carrier frequencies of the neighbor cells.

•Downlink

•Point to Multipoint

•@TS0

• CCCH:• PCH: (downlink)

• MS listen to the paging channel to know if the paging message is for it or not. If yes it means that there is a call or SMS for it. It uses in IMSI (International Mobile Subscriber Identity)

• RACH: (uplink)• To reply on PCH• Send request for dedicated

channel (SDCCH)

• AGCH: (downlink)• Reply for the request of SDCCH

with the time slot No.

Point to Point

• DCCH:• SDCCH: (Downlink)

• For call signaling setup. Operates at TCH/8 or TCH/4.

• SACCH:• Downlink to inform the MS power level.• Uplink to inform the BS with the MS power level.

• FACCH:• For handover by stealing 20 ms from the speech.

• CBCH: (Downlink)• Each cell sends a short message to all MS’s every 2

ms to broadcast the users with information from a service center to mobile stations.

Burst

• Each logical channel is backed into something called Burst and each logical channel has a one type of the burst types.

• The Burst is sent via physical channel (time slot @ certain frequency(.

Burst (logical Channel)

Time Slot X of Carrier Y Period = 0.577 mSec

GSM Frames

Burst Types• Normal

• Frequency Correction

• Synchronization

• Access

• Dummy

o

6

13

57

2

4

Omni Cell planning

6

13

57

2

4

120 Sectorization

63

57

2

41

60 Sectorization

o

810

1

7

2

3

4

9

6

12

5

11

Tricell planning: (Most (Most Common)Common)

No. of cells in the cluster can be divided by 3

Tricell planning

D1 D2D3

C3 C2C1

A3 A2A1

B3 B2B1 D1 D2

D3

C3 C2C1

A3 A2A1

B3 B2B1

D1 D2D3

C3 C2C1

A3 A2A1

B3 B2B1 D1 D2

D3

C3 C2C1

A3 A2A1

B3 B2B1

D1 D2D3

C3 C2C1

A3 A2A1

B3 B2B1

D1 D2D3

C3 C2C1

A3 A2A1

B3 B2B1

D1 D2D3

C3 C2C1

A3 A2A1

B3 B2B1

D1 D2D3

C3 C2C1

A3 A2A1

B3 B2B1

))/(3

1log(10/ RDIC

Thanks