Giuseppe Bianchi
Frequency [MHz]
960
DOWNLINK
BS MS
Use top & bottom as additional guard
935
#
915
890.2
“guard band”
890
Giuseppe Bianchi
&' ( "
1 2 3 4 5 6 7 8
890.4
UPLINK
MS BS
$
! "
% &
Fuplink (n ) = [890.2 + 0.2(n − 1)] MHz
Fdwlink (n ) = [935.2 + 0.2(n − 1)] MHz
60dB
35dB
Specification: 9dB
In practice, due to power control and shadowing, adjacent channels
Cannot be used within the same cell…
Giuseppe Bianchi
!
"
#$ % &
& )& ( "
* + ', !!! ( "
&
'( )
&' "
) & . / +&'0 µ
time
slot
0
-
time
slot
7
577 µs
1 frame = 60/13 ms = 4.615 ms
26 frames = 120 ms (this is the key number)
Giuseppe Bianchi
time
! "
frequency
#$
% $
&
'
(
Total n. of channels: 992
200 KHz
200 KHz
200 KHz
200 KHz
200 KHz
slot
200 KHz
200 KHz
200 KHz
200 KHz
577us 577us
577us 577us 577us
time
Giuseppe Bianchi
577us
577us 577us
$) *+,,
$
"
1 2 34 51 +
*
"
1710-1785 MHz uplink; 1805-1880 MHz downlink
#6 78 9
"
.
1740-1785 MHz uplink; 1835-1880 MHz downlink
%&
$%
+
,
A total of 374 carriers (versus124 in GSM)
-%
: . .
+
.
First and second operators @ 900 MHz; Third etc @1800 MHz
DCS 1800 deployment (1996+):
» 15 MHz (=75 carriers) to Wind; 7.5 (=37 carriers) to first and second
operator (plus existing 27 GSM 900 carriers)
Giuseppe Bianchi
.
"
$% /.0$% 1
2
( , , $0
;
( 0 $0 &
2
3
* ' $ +'& < & ' $ &+'& ; ,
* +, ', $ , & < , , ', $ 0 & ; 0
* , $ 0
< 0! $ 00
-
Giuseppe Bianchi
$
. /
- MS uses SAME slot number on uplink and downlink
- Uplink and downlink carriers always have a 45 MHz separation
-I.e. if uplink carrier is 894.2 downlink is 919.2
-3 slot delay shift!!
0
1
2
3
UPLINK
0
4
1
5
6
7
DOWNLINK
2
3
4
5
MS: no need to transmit and receive in the same time
on two different frequencies!
Giuseppe Bianchi
6
7
0# (
/
0
1
f7
f6
f5
f4
f3
f2
f1
Hopping sequence (example):
… f1 f2 f5 f6
f3
f7
f4
f1…
Slow = on a per-frame basis
- 1 hop per frame (4.615 ms) = 217 hops/second
.
;
=
*
>
!
Giuseppe Bianchi
""
-
$
Normal burst
TB
3
DATA
57
Training
sequence
26
S
1
S
1
Data
57
TB GP
3 8.25
148 bit burst
156.25 bit (15/26 ms = 0.577 ms)
% &&
3
4
"
?
?
@"
@
"
$
*
<
"
A
&
.
*
. -
22.8 kbps gross rate
13 kbps net rate!
%3
5
7
B
"
Giuseppe Bianchi
%
C7: :
"
*
" -
2
/"
6' 7
7
8 A
7
.
.
A
D
(
;
E
"
.
"
"
5 8
*, 6
.
F
.
;
>
:
. $ ) ;
( ;
A
" -
Because channel estimate reliable ONLY when the radio channel
“sounding” is taken!
Multipath fading rapidly changes the channel impulse response…
Giuseppe Bianchi
/
(
Different codes used in adjacent cells! Avoids training sequence
Disruption because of co-channel interference.
Giuseppe Bianchi
0
3
4
7.6 bits
4.9 bits
156.75 bits; 162.2 bits
Giuseppe Bianchi
5
d
&
G6
G6
2,
,
,
&
.
A
.
A
+
" 5
&3
.
.
.
.
BTS downlink tx
)
!H )
!H )
5
Giuseppe Bianchi
MS downlink rx
1
2
1
3
2
4
3
4
MS uplink rx
9 BTS uplink rx
1
1
1
Expected RX time!
6 /
…
dwlink slot 1
dwlink slot 1
MS time
…
…
…
dwlink slot 4
dwlink slot 4
uplink slot 1
BTS time
uplink slot 1
Maximum cell radius:
GTbits 2d
=
Crate
c
c ⋅ GTbits 300000 ⋅ 8.25
→ d=
≈
≈ 4.5 Km
2Crate
2 ⋅ 270833
Is there something wrong? (GSM says that cells go up to 35 km)
Giuseppe Bianchi
#
6
TA (transmitted in the SACCH)
& 5
*
5 .
G6
& " / $&!
/
1
.
"
A
dwlink slot 4
.
67"
6 7/
dwlink slot 4
BTS time
A
I.e. transmit after 468.75 bits
after downlink slot
6 7/ &!
Transmit after 405.75 bits time
Giuseppe Bianchi
TA
uplink slot 1
uplink slot 1
uplink slot 1
TA avoids collision!
MS time
/
1
"
:+ + 5
3
)
;+ :+ + 5
3
)
;+ :
"
3
) $6 7
,
67/ )
& &
, + ,
"
3
31.5 [bits ]
TA
d=
⋅c =
⋅ 300000 [km / s ] = 34.89 [km]
2
270833 [bits / s ]
8.25 bits Guard time additionally available for imperfect sync (+/- error)
Giuseppe Bianchi
0
7
5
0
8
Solution: USE A DIFFERENT BURST FORMAT
Access Burst: much longer Guard Period available
drawback: much less space for useful information
Access burst
TB
8
Training
sequence
41
Data
36
TB
3
GP
68.25
88 bit burst
156.25 bit (0.577 ms)
No collision with subsequent slot for distances up to 37.8 km
Giuseppe Bianchi
-
"
,
,
B .
7
*
G
G
C >
:
G
G
. .
G
Giuseppe Bianchi
# (
)
5
Frequency Correction Burst
TB
3
,
Fixed bit pattern (all 0s)
142
/ 6' <
$ % &
; A
H & )
=
>
TB GP
3 8.25
1
3
(
*&+'+ , ! (
E
"
,
%
:
, 8
Giuseppe Bianchi
+
"
-
9
#)5 0
1
? 8
)
:
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:"
&
.
.
>
.
E.g. Fc + Pi/2
% /
3 7
Fc – Pi/2
& &% ,
.
>
.
A
.
.
51
* >
A
/
A
1 = vary phase of Pi/2 in 1 bit symbol
0 = vary phase of –Pi/2 in 1 bit symbol
5
A
A
Giuseppe Bianchi
" #B 6 7B 6 7B 1 4 2
. I
>
9
#)5 0
3 7
1
$ % /$
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7
G
A
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@ >
A
J
Giuseppe Bianchi
:"
51
"
9
#)5 0
1
3 7
:"
Advantage: continuous phase modulation = lower spectrum occupancy
Disadvantage: ISI
Giuseppe Bianchi
$
5
Dummy Burst
TB
3
;
$
Fixed bit pattern
58
,
&
#.
%;
Giuseppe Bianchi
Training
sequence
26
Fixed bit pattern
58
*
+"
TB GP
3 8.25
6--!
6--!
G: :
6
5
Synchronization Burst
TB
3
Training
sequence
64
Sync data
39
5
5
#
Sync data
39
TB GP
3 8.25
8
"
.
I
>
,
3
:
.
.
i.e. synchronize frame counter
:
G #: *G
#
:
%&"
-
3 bits network code (operator)
» Important at international boundary, where same frequencies
can be shared by different operators
3 bits color code
To avoid listening a signal from another cell, thinking it
comes from the actual one!
Giuseppe Bianchi
5
Giuseppe Bianchi
; /
1
Logical channels
(traffic channels, signalling (=control) channels)
Physical channels
(FDMA/TDMA)
6 .
#
K
>
.
%
%
5
G
#
A
;
>
%.
>
%
.
Giuseppe Bianchi
" ;
G
%
; /
/
Physical Channel: data rate r, time slot i
frequency
#
$
%
frequency
Frame 8
Frame 9
Frame 10
Frame 11
Frame 12
Logical channel A: data rate r/3, time slot i, frame 3k
Logical channel B: data rate 2r/3, time slot i, frame 3k+1, 3k+2
Giuseppe Bianchi
/
Traffic channel (TCH)
Broadcast channel
TCH/F
6:
TCH/H
6:
BCCH
G
FCCH
C >
3
Dedicated Control channel (DCCH)
MS
BSS
:
BSS MS
BSS MS
RACH
3
. 7
MS BSS
AGCH
7
J
BSS MS
PCH
5
BSS MS
SDCCH
SACCH
$
;
FACCH C
Additional logical channels available for special purposes
(SMS, group calls, …)
Giuseppe Bianchi
BSS
BSS MS
SCH
Common Control channel (CCCH)
MS
MS
BSS
MS
BSS
MS
BSS
.
1 1 /
/
/
Setup for an incoming call (call
arriving from fixed network part MS responds to a call)
Steps:
- paging for MS
- MS responds on RACH
- MS granted an SDCCH
- authentication & ciphering on SDCCH
- MS granted a TS (TCH/FACCH)
- connection completed on FACCH
- Data transmitted on TCH
Giuseppe Bianchi
7
,
,
5
Giuseppe Bianchi
5
)!<#
Periodic pattern of 26 frames (120 ms = 15/26 ms/TS * 8 TS/frame* 26 frame)
1
2
3
4 5
6
7
8 9 10 11 12
13 14 15 16 17 18 19 20 21 22 23 24
24 TCH frames over 26
Same TS in every frame
01234567012345670123456701234567
Theoretical rate: 1/8 channel rate: r=33.85 kbps
2 signalling frames: r
31.25 kbps
Burst overhead (114 bits over 156.25):
r 22.8 kbps
Giuseppe Bianchi
TB
3
DATA
57
S Training S
1 Seq. (26) 1
Data
57
148 bit burst
156.25 bit (0.577 ms)
TB GP
3 8.25
/
Analog
voice
A/D conversion
8000 samples/s
13 bit/sample
160 voice
samples
(20 ms)
(2080 bits)
Speech CODER
(8:1 compression)
Giuseppe Bianchi
Digital voice
104 kbps
260 bits block
13 kbps
$
%+
D
6
&+ &
"
L
A
A
A
@
*
/@
1
.
*, . -
listening
talking
talking
time
A
B
A "
.<
&
.
3
C
*
3
A
: .
7
59
.
;
A
* , . -
Giuseppe Bianchi
.
? .
" 6M
@
.
* # /
-
)
)
/
Coding: needed to move from 10-1 to 10-3 radio channel native BER
down to acceptable range (10-5 to 10-6) BER
260 bits
182 bits
78 bits
Parity bits
Tail bits(0000)
50 bits 3
132 bits
260 bits block divided into
-Class I: important bits (182)
-Class Ia: Most important 50
-Class Ib: Less important 132
-Class II: low importance bits (78)
4
Convolutional coding, r=1/2
378 bits
78 bits
456 bits
First step: block coding for error detection in class Ia (error discard frame)
Second step: convolutional coding for error correction
Giuseppe Bianchi
5
3
1 /
8
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
57
448 449 450 451 452 453 454 455
B1 B2 B3 B4 B5 B6 B7 B8
8 blocks, each with 57 bits
Giuseppe Bianchi
$ /
1 /
Block n
Block n-1
B1 B2 B3 B4 B5 B6 B7 B8
B5n −1 / B1n
…
B1 B2 B3 B4 B5 B6 B7 B8
…
B8n −1 / B4n B5n / B1n +1
Block n+1
B1 B2 B3 B4 B5 B6 B7 B8
…
…
PRICE TO PAY: delay!! (block spreaded over 8 bursts
%"
= Bxn −1
TB
3
Giuseppe Bianchi
B8n / B4n +1
37 ms)
1 /
= Bxn− 4
Training
S
S
sequence
1
1
26
TB GP
3 8.25
5
#
A
3
C .
.
"
B
, &
<
&
A
B
.
&
A GC#
If this happens, receiver muted
Giuseppe Bianchi
+
0
)
4
.
6 .
TCH/F(0…7)
1
2
3
4 5
6
)
7
TCH/F(0…7)
8 9 10 11 12
13 14 15 16 17 18 19 20 21 22 23 24
SACCH(0…7)
SACCH-0 SACCH-1 SACCH-2 SACCH-3 SACCH-4 SACCH-5 SACCH-6 SACCH-7
1 SACCH burst (per TCH) every 26 frames (120 ms)
Giuseppe Bianchi
IDLE frame
))! "
5
3
5
Block coding adds 40 bits (=224)
4 tail (zero) bits (=228)
1/2 Convolutional encoding (=456 bits)
B
, "
* 53
(
+" <
B1 B2 B3 B4 B5 B6 B7 B8
A "
7: : "
"
/
% --!
3
, " ) , . / !, !'! " )
Giuseppe Bianchi
(I
104 frames = 480 ms
Odd/even
interleaving
))!
' 7
0
"
*
& 5 *
&
:8
&
* &
A
% %
E
*
Giuseppe Bianchi
1
free
+
,
+
5&
,
+
I
3
free
2
3
4
5
6
7
Power level
Timing advance
(21 bytes – datalink layer)
Includes measurement reports
0
Maximum power
(defined by class)
2 dB steps;
%
+"
2
)
;
& &
.
. .
6
&
+ :+ " &
6 %
,
:
%*
5 ;
A A
$
+ *
(
:
% --!
0 = 43 dBm (20 W)
15 = 13 dBm (20 mW)
5
Minimum power
(13 dBm for GSM)
(0 dBm for DCS 1800)
Giuseppe Bianchi
+"
"
&3 &
G :
,
++
:
+
,
1
CD .@
5 ;
5
CDE;
A
H
RX signal
level
"
From
To
(dBm) (dBm)
-
G 1
3
* ;-
Bit error
Ratio
From
(%)
To
(%)
RXQUAL_0
-
0.2
RXLEV_0
-
-110
RXQUAL_1
0.2
0.4
RXLEV_1
-110
-109
RXLEV_2
-109
-108
RXQUAL_2
0.4
0.8
RXLEV_3
-108
-107
RXQUAL_3
0.8
1.6
…
…
…
RXQUAL_4
1.6
3.2
…
…
…
RXQUAL_5
3.2
6.4
RXLEV_62
-49
-48
RXQUAL_6
6.4
12.8
RXLEV_63
-48
-
RXQUAL_7
12.8
-
Averaged over 1 SACCH block (480ms = 104 frames)
Giuseppe Bianchi
#
)
? --!3
2
;
5
5
A
5
.
)
"
.
Call setup
Handover
? --!
:'
&
B
*
*
:
, "
C +
*
:/
& 1
D
"
D
" (* & & ? --!
, N&)
O" ). P / 0 ' ( " *A !, ! "
Giuseppe Bianchi
-!
7: : I-
# ))!
)!
Via Stealing bits
- upper bit = odd bits stolen
- lower bit = even bits stolen
- both bits = all burst stolen
Figure: shows example of 2 FACCH blocks
stealing a TCH (note begin and end behavior
due to interleaving)
time
Giuseppe Bianchi
!
%
)!<!
% ++
,
%+ ,
"
(: + *
FF
:
.
. A
95 bits class I
» + 3 parity + 6 tail + convolutional coding 104/211
17 bits class 2
B
* 53
A
*"
"
53
.
G
? &
TCH/H 0…7
[subchannel 0]
1
TCH/H 8…15
[subchannel 1]
2
3
4
( H
H
) A
-
SACCH 0…7
5
Giuseppe Bianchi
6
7
SACCH 8…15
8
9
10
11
12
-!
G
4
,
,
0 '& ( " *
%
Q ' < ', < 0 '&<
5
* ,
,
A
;
G
#
.
A
-
Giuseppe Bianchi
' <
"
*
/ 0 *III"
A
3
"
*
(
6
-
Giuseppe Bianchi
5
)
/
6
, &
* (
! '!, .
*A
. % 0
: "
, &
; C >
:
:
*C: : #. .
;
"
:
* : !" !#" 3
2
, &
R
R %!% % G: :
3 .
5
*5: - ) 7
J
*7J : - O/ 57J : P
51 frame structure - downlink
C
GGGG5555C
55555555C
10 frame sub-block
Giuseppe Bianchi
55555555C
55555555C
55555555
5))!
2
"
:
:
(
3
. 7
:
51 frame structure - uplink
333333333333333333333333333333333333333333333333333
2
, 8
;% 6.
2
&
Provided that:
+
& %
&
/
H
• All empty slots are filled with DUMMY bursts
• Downlink power control must be disabled
Giuseppe Bianchi
1
-!
0
/
First operation when MS turned ON: spectrum analysis
(either on list of up to 32 Radio Frequency Channel Numbers of current network)
(or on whole 124 carriers spectrum)
Giuseppe Bianchi
/
%
5
,
+
" * /?--!1
"
:
C
B&&
C
3
"
,
" %-!
*& "
>
-
25 bits (+ 10 parity + 4 tail + ½ convolutional coding = 78
bits)
6 bits: BSIC
19 bits: Frame Number (reduced)
?
< %
Giuseppe Bianchi
6--!
%
/
8 TS, 4.615 ms
0
1
2
3
4
1 multiframe = 26 TDMA frames (120 ms)
TTTTTTTTTTTTS TTTTTTTTTTTT
6
7
1 multiframe = 51 TDMA frames (235.38 ms)
C
GGGG5555C
55555555C
………
…
Multiframe 1
Multiframe 0 Multiframe 1 Multiframe 2
Multiframe 0
5
55555555C
55555555C
55555555
Multiframe 49 Multiframe 50
Multiframe 25
1 superframe = 51 x 26-multiframe or 26 x 51-multiframe (1326 TDMA frames, 6.12 s)
superframe 0
superframe 1
superframe 2
superframe 2046 superframe 2047
1 hyperframe = 2048 superframe (2715648 TDMA frames, 3h28m53s.76)
Giuseppe Bianchi
9
" 7
Superframe #
FN =
? &
Multiframe #
frame #
H
.
, &
.
H
; G: :
I.e. which specific information transmitted on BCCH during a
given multiframe
% + , &
2
H
Giuseppe Bianchi
.
"
.
5))!
:
&"
.
"
7: :
A
G: :
184 bits / (51*8*15/26 ms) ~ 782 bps
B, &
5
+ *
.
"
Random access backoff values
Maximum power an MS may access (MS_TXPWR_MAX_CCCH)
Minimum received power at MS (RXLEV_ACCESS_MIN)
Is cell allowed? (CELL_BAR_ACCESS)
Etc.
8
Needed if frequency hopping is applied
8
G: :
Giuseppe Bianchi
G #:
"
1
/
6
51 frame structure – small capacity cell
DOWN
UP
C
GGGG5555C
33
55555555C
C
C
33333333333333333333333
33
Integrates SDCCH in same channel as other control information
Leaves additional TS all available for TCH
51 frame structure – large capacity cell
DOWN
UP
GGGG5555
55555555
55555555
55555555
55555555
333333333333333333333333333333333333333333333333333
Used in TS 2 (and, eventually, 4 and 6) of beacon carrier
Provides additional paging and RACH channels
Giuseppe Bianchi
9
=>
?*7
Last frame (idle) in TCH multiframe (Frame #25) used as “search frame”!
TTTTTTTTTTTT S TTTTTTTTTTTT
- An active call transmits/receive in 25 frames, except the last one.
- in this last frame, it can monitor the BCCH of this (and neighbor) cell
- this particular numbering allows to scan all BCCH slots during a superframe
- important slots while call is active: frequency correction FCCH and sync SCH!
- needed for handover
-Worst case: at most every 11 TCH multiframes (1.32 s), there will be
a frequency correction burst of a neighboring cell
Giuseppe Bianchi
5 5<C
Giuseppe Bianchi
&
5
<
5
9
:
/ /
.
only upon explicit request from MS
5
needed to “wake-up” MS from IDLE state when incoming call
arrives to MS
37:
(
Generally SDCCH (but immediate TCH assignment is possible)
1) paging
MS
BSS/MSC
2) Random access
3) Channel assignment
Paging channel:
PCH
Access Grant Channel:
AGCH
Random Access Channel: RACH
Giuseppe Bianchi
PAGCH
CCCH
Common Control
CHannel
/ /
5 5&
E
A
,
5
.
5
.
5 5
.
%,6%-
S
List of cells where paging should be performed
Identity of paged user (IMSI or TMSI)
5 5&
5
*
,
.
)
A
5 5, &
% &
8 + 5 5&
5
Giuseppe Bianchi
*
7: : * ,
G
&"
-
$
$ @
%
&
*
" A
< -! *
!
#
A
"$
"
2
+5 5
0
#
Switches off otherwise
-!
0
6--!
2
0 "$
+
&&
51 frame BCCH structure - downlink
C
GGGG5555C
55555555C
Giuseppe Bianchi
55555555C
55555555C
55555555
"
#
E
E
*
%
*
.
"
;
.
"
6
7
"
,
"
C -!
T > - !&
*
"
+6 parity; + 4 tail; + ½ convolutional coding
TB
8
Training
Seq. (41)
100: response to radio call
101: emergency call
110: new establishment of call
111: supplementary service (SMS, etc)
…
000: other case
Access burst
Data
TB
36
3
GP
68.25
Channel_req message
$
%
&
'
#
Random discriminator: (0…31) value randomly generated by MS
Giuseppe Bianchi
)!
MS-C
A,B
C,B
MS-A
C
A,B
A
B
MS-B
Multiple Access Technique for simultaneous access
Collision resolution based on
- random retrial period
Same thing..!
- “permission” probability
(SLOTTED ALOHA protocol)
Giuseppe Bianchi
)!
I
.
&
3
%
A
*
+
idle :
success :
collision :
"
% A
+
)
3
(1 − p )
N −1
Np(1 − p )
N
N
k =2
N k
N −k
(
)
p 1− p
k
Maximum efficiency: when p=1/N
Giuseppe Bianchi
+
)!
6--!
G (
.
uniform distribution; max value: 3 to 50
. .
. "
.
.
Never greater than 7
+
.
37:
A
,3
*
/
-
MSs divided into 10 groups, depending on SIM-related
information
BTS may block selected groups
Allows to reduce RACH load down to as low as 10%
» Emergency calls bypass this rule…
Giuseppe Bianchi
/
MS
BTS
Channel_request
/% *
BSC
Channel_required
rnd number
rnd&frame number,
Delay (TA estimate)
Channel_activation
Ch_activation_ack
Immediate_assignment
rnd&frame number, channel description,
Initial TA, initial max power
Giuseppe Bianchi
MSC
/
+5 5
#' ' 7J :
.
/
.
– name PAGCH is perhaps better…
%
=
+
>
37:
.
.
I.e. which message to send in case of many messages, and on
which paging slot (4 bursts)
.
"
3M
To monitor PAGCH for Immediate Assignment message
detection
B&&
Giuseppe Bianchi
5 &
G
+
7
"
% &
8 (
A
&
"
2
4
::
*
%;
&
&
&
"
&
, &
/
,
* *
+
MS1
MS2
1
%
ID1
ID2
ID1
leave
continues
Giuseppe Bianchi
,
BTS
/
MS
…
…
BTS
…
…
/% =
BSC
MSC
Immediate_assignment
Initial_message
MS ID (IMSI or TMSI), MS capabilities
(=classmark), establishment cause
Initial_message_ack (UA)
Establishment_indication
Copy of Initial message (including MS ID)
Further signaling: MSC to MS
Giuseppe Bianchi
%
$
)
)
% $))!
%
"
!
-
% --!
53
,
+
,
% --!
&"
A "
, & 5/% --!) 1
: : *H , 7: : *
:: .
$.
.
SDCCH/4 for small
cells – SDCCH shares
%6 BCCH+PAGCH channel
- see before 184 bits / (51*8*15/26 ms) = 598/765 kbps ~ 782 bit/s
7: :
A
.
.
!!!!
7777777777777777
&&&&++++
!!!!
!!!!
7777777777777777
&&&&++++
&&&&++++
Giuseppe Bianchi