Slide 1Bursts
History of GSM Story
CEPT decided to develop unique mobile standard in 1982 and 6 study group established
Results converged to the comprehensive characteristics defined in 1987 and a tender announced
Equipment delivery started in March 1991 and first BTS operated in June 91
Since 1995 area-wide operation started
8000 pages of 13 series recommendation adopted by ETSI
Cellular Mobile Course
TRAU: Transcoding rate and adaptation unit
IWF: Inter Working Functions
HLR: Home location register
VLR: Visitor location register
EIR: Equipment identity register
Smart card
Except emergency calls, MS can only operate if SIM card has first been activated
Type of SIM card
SIM card serial number
Location information
List of carrier frequencies
Speech code/decode and data-rate
Comprises of BTS and BSC
BTS includes TRXs and TRAU
BSC controls radio resource, handover and is transparent for connection-related signaling from/to MSC
Cellular Mobile Course
MSC is responsible for:
Connection to/from ISDN, PSTN, PDN
Handling supplementary services
HLR includes quasi permanent static data of subscriber and current location area (LA) of MS
VLR managing sub.s who are currently roaming
VLR stores information transmitted by HLR and updates it once LA changed
Cellular Mobile Course
OSS comprises of OMC, AuC and EIR
OMC functions
Administration of subscribers and equipment (TMN)
Billing and generation of network state and resources allocation (capacity and frequency)
AuC contains encryption codes and information to protect sub.s identity
EIR is a database including sub.s number and IMEI (white, gray and black lists)
89372
00005
00011
67838
005
Uplink
890
915
935
960
124
1
2
3
Channels:
Downlink
time
7 0 1 2 3 4 5 6 7 0 1 2
7 0 1 2 3 4 5 6 7 0 1 2
7 0 1 2 3 4 5 6 7 0 1 2
Fn+1
Logical channel: one burst period (0.577 ms) per TDMA frame
Example: relationship between logical and physical channels
Physical channel with data rate 4a
K1
K1
K1
K2
K1
K1
K1
K2
K1
K1
K1
K2
K1
K1
K1
K2
K1
K1
K1
K2
K1
- Access Burst: for call set up
- Dummy Burst: idle slots
3
TB
57
Frequency Hopping (FH)
Changing of TRX frequency after transmission of each TDMA frame (burst) (slow frequency hopping)
There are different methods under research
Reducing defect of multipath reception and co-channel interference
Equalize the quality of transmission channels
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
C0
C1
C2
Uplink
5
0
1
2
3
4
5
6
7
0
1
2
3
4
0
1
2
3
4
5
6
7
C0
C1
C2
Downlink
D0
E0
Downlink
RACH: Random Access Channel (capacity request)
AGCH: Access Grant Channel (in response to RACH)
SDCCH: Stand-alone Dedicated Control Channel (preparation of connection before TCH assignment)
SACCH: Slow Associated dedicated Control Channel (signal strength measurement report and NT inf.)
FACCH: Fast Associated dedicated Control Channel (when TCH exist and for handover controlling)
Traffic
channels
Control
channels
Logical
channels
TCH
CCH
Bm
Doubled channel number
For signaling and control and is not passed to sub.s. following ISDN, referred as Dm
Broadcast
P-to-MP
BCCH: point to multipoint, information about network identification, availability of such options such as FH and Voice Activity Detection (VAD) and identification of frequencies being used by the BS and neighboring BS
PCH: for the selective addressing of a called mobile terminal during a connect request from the network
RACH: requesting of channel capacity from the BS to establish a connection using an S-ALOHA access protocol
AGCH: in response to the RACH the mobile terminal is allocated a SDCCH or a TCH over the AGCH that only exist on the downlink
SDCCH: low rate, 782 bps, control channel for preparation of connection before TCH assignment including registration, authentication, location area updating, ciphering commands and data for call set up
SACCH: always allocated parallel to TCH or an SDCCH to transmit at a data rate 383bps system information from BS to MS and measurement data of signal strength from MS to BS
FACCH: short term 4600bps or 9200bps when TCH exist and uses TCH time slots for handover handling and sending necessary control data.
Cellular Mobile Course
period = 6.12 s
Hyperframe
2,048 superframes, 2 715 648 / period = 3 h 28 min 53 s 750 ms
TDMA-frame, 120/26 ms
burst, 15/26 ms