Frequency [MHz] 960 DOWNLINK BS MS 935 915 UPLINK MS BS 890 890.4 890.2 guard band Use top & bottom as additional guard! " # $ %& &'( " 1 2 3 4 5 6 7 8 F F uplink dwlink ( n) = [ 890.2 + 0.2( n 1) ] ( n) = 935.2 + 0.2( n 1) MHz [ ]MHz
60dB 35dB Specification: 9dB In practice, due to power control and shadowing, adjacent channels Cannot be used within the same cell
!"#$% & &)&( " *+',!!!( " - &'() &'" )&. / +&'0 µ time slot 0 time slot 7 time 577 µs 1 frame = 60/13 ms = 4.615 ms 26 frames = 120 ms (this is the key number)
! "#$ %$ & '( frequency Total n. of channels: 992 200 KHz 200 KHz 200 KHz 200 KHz 200 KHz 200 KHz 200 KHz 200 KHz 200 KHz slot 577us 577us 577us 577us 577us 577us 577us 577us time
$)*+,, $"* 1 2 34 51 +" 1710-1785 MHz uplink; 1805-1880 MHz downlink #6 78 9 ". 1740-1785 MHz uplink; 1835-1880 MHz downlink %&$%+, 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)
- ".$%/.0$%1 2 (,, $0 ; ( 0 $0 & 23 *'$+'&<&'$&+'& ; -, *+, ', $, &<,, ', $0 & ; - 0 *, $0 <0!$0 0 -
$./ - 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 4 5 6 7 DOWNLINK UPLINK 0 1 2 3 4 5 6 7 MS: no need to transmit and receive in the same time on two different frequencies!
0#( / 01 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. ; = * > -! ""
$ TB 3 DATA 57 S 1 Normal burst 148 bit burst Training sequence 26 %&& 34 " "? @ " * $ < -? @ " A &. *. - 22.8 kbps gross rate 13 kbps net rate! %35 7 % " B " C7: : * " - S 1 Data 57 156.25 bit (15/26 ms = 0.577 ms) TB 3 GP 8.25
2/" 6'7 7. 8 A. A ". ;. $) ; 7 D " ( ; (58 ; " *, 6 > : A " -. E. F Because channel estimate reliable ONLY when the radio channel sounding is taken! Multipath fading rapidly changes the channel impulse response
/( Different codes used in adjacent cells! Avoids training sequence Disruption because of co-channel interference.
0345 7.6 bits 4.9 bits 156.75 bits; 162.2 bits
d &,"5 &&3 G6.. A. )..!H ) G6 A.!H ) BTS downlink tx 1 2 3 4 MS downlink rx 1 2 3 4 MS uplink rx 1 2,,+59 BTS uplink rx 1 1 Expected RX time!
6/ dwlink slot 1 dwlink slot 4 dwlink slot 1 dwlink slot 4 MS time uplink slot 1 BTS time uplink slot 1 Maximum cell radius: GT C 2d c d c GT 2C bits bits = = 4. 5 rate rate 300000 8.25 2 270833 Is there something wrong? (GSM says that cells go up to 35 km) Km
# 6 TA (transmitted in the SACCH) &5*/1 5.. " G6 A &" / $&!. 6 7" 6 7/ A I.e. transmit after 468.75 bits after downlink slot 6 7/ &! Transmit after 405.75 bits time BTS time TA dwlink slot 4 dwlink slot 4 uplink slot 1 uplink slot 1 uplink slot 1 TA avoids collision! MS time
/1 ":++53 ) ;+:++53 ) ;+:"3 )$6 7," 6 7/ ) &&,+,3 [ bits] [ bits / s] TA 31.5 d = c = 300000 89 2 270833 [ km / s] = 34. [ km] 8.25 bits Guard time additionally available for imperfect sync (+/- error)
07 508 Solution: USE A DIFFERENT BURST FORMAT Access Burst: much longer Guard Period available drawback: much less space for useful information Access burst TB 8 Training sequence 41 Data 36 TB 3 GP 68.25 88 bit burst 156.25 bit (0.577 ms) No collision with subsequent slot for distances up to 37.8 km
-",,* B. G 7G C> : G G.. G
#( )5 Frequency Correction Burst TB 3 Fixed bit pattern (all 0s) 142 TB 3 GP 8.25 /6'<1,$% &3 ; A H &)( *&+'+,!( - => E "%:+",,8
9 #)503 037 1 :"?8& ).. > :. E.g. Fc + Pi/2 Fc Pi/2 % /&&%, 51. >. *> A / A - ).. A 1 = vary phase of Pi/2 in 1 bit symbol 0 = vary phase of Pi/2 in 1 bit symbol 5 A " #B 6 7B 6 7B 1 4 2 > A. I
9 #)503 037 1 :" $% /$ &&%, 51 7 G A "?. @ > A J
9 #)503 037 1 :" Advantage: continuous phase modulation = lower spectrum occupancy Disadvantage: ISI
$ 5 Dummy Burst TB 3 Fixed bit pattern 58 Training sequence 26 Fixed bit pattern 58 TB 3 GP 8.25 ;,*6--! $&+"6--! #. %; G: :
TB 3 65 Sync data 39 558 # ". 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! Synchronization Burst Training sequence 64 Sync data 39 TB 3 GP 8.25
5
;/1 1 Logical channels (traffic channels, signalling (=control) channels) Physical channels (FDMA/TDMA) 6. K A > #. % %. > % %> % 5 G #;. " ; G
;/ / frequency Physical Channel: data rate r, time slot i # $ % 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
/ Traffic channel (TCH) TCH/F 6 : MS BSS TCH/H 6 : 3 MS BSS Broadcast channel BCCH G BSSMS FCCH C> : BSSMS SCH BSSMS Common Control channel (CCCH) RACH 3. 7 MSBSS AGCH 7J BSSMS PCH 5 BSSMS Dedicated Control channel (DCCH) SDCCH $ MS BSS SACCH ; MS BSS FACCH C MS BSS Additional logical channels available for special purposes (SMS, group calls, )
. 11/// 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
7,, 55
)!<# 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 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 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 TB 3 DATA 57 S 1 Training Seq. (26) S 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 Digital voice 104 kbps 160 voice samples (20 ms) (2080 bits) Speech CODER (8:1 compression) 260 bits block 13 kbps
$ %+&+&@*/@1 D A " L. 6 A A *,. - talking listening talking time A B.<& A ". 3 C*359 A. ;?. @ :. A " 6 M 7 *,. -.. *#/ -
))/ 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 4 260 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) Convolutional coding, r=1/2 378 bits 78 bits First step: block coding for error detection in class Ia (errordiscard frame) Second step: convolutional coding for error correction 456 bits
531/ 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................................................................ 448 449 450 451 452 453 454 455 57 B1 B2 B3 B4 B5 B6 B7 B8 8 blocks, each with 57 bits
B1 $/1/ Block n-1 Block n Block n+1 B2 B3 B4 B5 B6 B7 B8 B1 B2 B3 B4 B5 B6 B7 B8 B1 B2 B3 B4 B5 B6 B7 B8 n 1 n B5 / B1 n n 1 B B n 1 n n 1 B8 / B / n+ 4 B5 B1 / + 8 4 PRICE TO PAY: delay!! (block spreaded over 8 bursts37 ms) %" "1/ 1 = B n x = n Bx 4 TB 3 S 1 Training sequence 26 S 1 TB 3 GP 8.25
5# A 3 C.. " B<&+,& A B. & A GC# If this happens, receiver muted
0)) 4. 6. TCH/F(0 7) TCH/F(0 7) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 SACCH(0 7) IDLE frame 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)
))!"3 55 Block coding adds 40 bits (=224) 4 tail (zero) bits (=228) 1/2 Convolutional encoding (=456 bits) B*53, " ( +" < A " " / 7: : " ( I %--!3, " ),. /!,!'!" ) B1 B2 B3 B4 B5 B6 B7 B8 Odd/even interleaving 104 frames = 480 ms
))! '7 "* &5* &+, :8 &+, *&5& 0 1 2 3 4 5 6 7 free free Power level Timing advance (21 bytes datalink layer) Includes measurement reports A *+3 %% E I
0 Maximum power (defined by class) 2 db steps; Minimum power (13 dbm for GSM) (0 dbm for DCS 1800) %) +" 2 ;... &&6+*( & +:+"&: 6%,:%*%--! 5 ; A A $ 0 = 43 dbm (20 W) 15 = 13 dbm (20 mw) 5&3&, +, G: +"++ ":
1 CD.@ 5 ; A 5 H " - CDE; G1 3 * ; - Bit error From To RX signal level From (dbm) To (dbm) Ratio RXQUAL_0 (%) - (%) 0.2 RXLEV_0 - -110 RXQUAL_1 0.2 0.4 RXLEV_1 RXLEV_2 RXLEV_3-110 -109-108 -109-108 -107 RXQUAL_2 RXQUAL_3 RXQUAL_4 0.4 0.8 1.6 0.8 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)
#))?--!3555 2 ; A. ". Call setup Handover?--!:' & B**:, " C+*:/&1-! D " D " ( *- &&?--!, N&)O" ). P/ 0 '( " *A!,!" 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
!%)!<! %++, (:+* %+,FF : ".. A 95 bits class I» + 3 parity + 6 tail + convolutional coding 104/211 17 bits class 2 B*53. A *" ( H H )A - G "?&53 TCH/H 0 7 [subchannel 0] TCH/H 8 15 [subchannel 1] SACCH 0 7 SACCH 8 15 1 2 3 4 5 6 7 8 9 10 11 12
- -! G 0 '&( " * % - 4 Q '<', <0 '&<'<,,5 *- G,,"*3 # A ; / 0 *III-. " A " *( A -
6- -
5) /6,&*(!'!,. *A. - %0:",& ; C> : : *C: : - #.. ; " : *: - 2,&! "! # " 3 R R %!%%G: : 3. 5 *5: -)7J *7J : -O/ 57J : P 51 frame structure - downlink C G G G G 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 10 frame sub-block
5))! 2": : ( 3. 7: 51 frame structure - uplink 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 2,8+ /1 ;%6.&%H 2 && -! Provided that: All empty slots are filled with DUMMY bursts Downlink power control must be disabled
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)
/ %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)?<%6--!
%/ 8 TS, 4.615 ms 0 1 2 3 4 5 6 7 1 multiframe = 26 TDMA frames (120 ms) 1 multiframe = 51 TDMA frames (235.38 ms) T T T T T T T T T T T T S T T T T T T T T T T T T C G G G G 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 Multiframe 0 Multiframe 1 Multiframe 2 Multiframe 49 Multiframe 50 Multiframe 0 Multiframe 1 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)
9 "7 FN = Superframe # Multiframe # frame #?&H.,& H. ; G: : I.e. which specific information transmitted on BCCH during a given multiframe %+,& H 2. ".
5))! : &" ". A 7: : 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: : G#: "
1 /6 51 frame structure small capacity cell DOWN C G G G G 5 5 5 5 C 5 5 5 5 5 5 5 5 C C C UP 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Integrates SDCCH in same channel as other control information Leaves additional TS all available for TCH 51 frame structure large capacity cell DOWN G G G G 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 UP 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Used in TS 2 (and, eventually, 4 and 6) of beacon carrier Provides additional paging and RACH channels
9 =>?*7 Last frame (idle) in TCH multiframe (Frame #25) used as search frame! T T T T T T T T T T T T S T T T T T T T T T T T T - 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
55<C&< 55
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 2) Random access 3) Channel assignment BSS/MSC Paging channel: PCH Access Grant Channel: AGCH Random Access Channel: RACH PAGCH CCCH Common Control CHannel
// 55&55%- E A.,,6%- 5. S 5. List of cells where paging should be performed Identity of paged user (IMSI or TMSI) 55&5* *,. ) A 7: : *, &" - 55,&%&G 8+55&5
$$@ %&+55 *<-!*0 " A "! ## 2 A " $ Switches off otherwise -!0+&& 6--! 2 0 " $ 51 frame BCCH structure - downlink C G G G G 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5 C 5 5 5 5 5 5 5 5
"*% # *. - E ". E ; " 6C-! 7", " * T > -!& " +6 parity; + 4 tail; + ½ convolutional coding TB 8 Training Seq. (41) Access burst Data 36 TB 3 GP 68.25 100: response to radio call 101: emergency call 110: new establishment of call 111: supplementary service (SMS, etc) 000: other case Channel_req message $ % & ' # Random discriminator: (0 31) value randomly generated by MS
)! MS-C A,B C,B C A,B A B MS-A MS-B Multiple Access Technique for simultaneous access Collision resolution based on - random retrial period - permission probability Same thing..! (SLOTTED ALOHA protocol)
)! I.&"++ 3% A %A ) *+3 idle : success : collision : ( 1 p) Np N k = 2 ( 1 p) N k N p N 1 k ( 1 p) Maximum efficiency: when p=1/n N k
)! 6--! G (. uniform distribution; max value: 3 to 50... ".. Never greater than 7 +,3. A * / - 37: 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
// //%* MS BTS BSC MSC Channel_request 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
// +55 #''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&&5&G+
7 "%&*&&& 8 ( A %; " &&,& 2"/,1 **+%, 4 : : MS1 MS2 BTS ID1 ID2 leave ID1 continues
// //%= 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
% $ $) ) ) )% $))! $))! % "!%--! -53%--!, &" A " +,&5/%--!)1, : : *H, 7: : - * %6 - : :. $.. 184 bits / (51*8*15/26 ms) = 598/765 kbps ~ 782 bit/s 7: : A..!!!! & & & & + + + + 7 7 7 7! 7 7 7 7! 7 7 7 7! 7 7 7 7!!!!! & & & & + + + + 7 7 7 & 7 + 7 7 7 & 7 + 7 7 7 & 7 + 7 7 7 & 7 + SDCCH/4 for small cells SDCCH shares BCCH+PAGCH channel - see before -