GSM AIR INTERFACE AND PHYSICAL LAYER INTRODUCTION€¦ · · 2017-09-03GSM AIR INTERFACE AND...

GSM AIR INTERFACE AND

PHYSICAL LAYER INTRODUCTION

An d r ea s Ber g s t r ö m Er ic sso n Resea r c h , Lin k ö pin g

Lec t u r e FOR

TSKS05 Ko m m u n ik at io n ssy s t em CDIO 2013-09-10

AND YES, THESE SLIDES

ARE AVAILABLE AT COURSE HOM EPAGE....

http://www.commsys.isy.liu.se/sv/student/kurser/TSKS05

... So y o u n e e d n o T t a k e a n y n o t e s .



Ericsson Internal | 2012-09-09 |

Ag e n d a ›Ab o u t m e ›GSM BASICS ›RADIO NETWORK DEPLOYMENT ›GSM RADIO INTERFACE (UM) ›GPRS/EDGE – Pa c k e t d a t a in g s m ›GSM PHYSICAL LAYER ›Re c e n t /Fu t u r e GSM De v e l o p m e n t ›QUESTIONS? COMMENTS?


› Currently at Ericsson Research Linköping since Oct 2011:

– LTE/LTE-Advanced and beyond… – WiFi (802.11x MAC stuff and Lte+WiFI integration) – HetNet SON (Self-Optimizing Networks) – Simulations, Simulator Development etc. – …

› Previously at GSM Systems department at Ericsson 2005-2011:

– Research, Analysis, Simulations, Simulator development and Standardization.

– Main topics: GSM Packet Data specifics: EGPRS/EDGE, EDGE Evolution, M2M, smartphone enhancements etc…

– ….

› Education: – M.Sc. in Applied Physics & E.E. (Y) (1999-2005) – Thesis work at E/// Research HT04-VT05 (HSDPA Iub Flow control) – …

› Personal:

– From Sundsvall, now live in Västerlösa, Linköping – Married to Gunilla with kids Kerstin 3.5years and Oskar 0.5years – …

› Hobbies

– Triathlon – 3rd place in Swedish national championships 2013 at the Olympic distance in my age group and 2nd place in the total Swedish Triathlon Cup of 2013.

– …

ABOUT ME An d r e a s Be r g s t r Öm

GSM BASICS GERAN Net w o r k Ov er v iew FREQUENCY BANDS GSM LOGICAL CHANNELS PROTOCOL STACK GM M STATE M ACHINE RRC STATE M ACHINE


GERAN n e t w o r k o v e r v ie w (SIMPLIFIED PICTURE)

BTS

BSC SGSN GGSN

MSC/VLR HLR/AUC

PSTN

”Internet”

Radio network (GERAN)

Core Network

Radio interface (Um)


GSM FREQUENCY BANDS


GSM LOGICAL CHANNELS

GSM (E)GPRS

+

NOTE: Many of the s.k. P-Channels ((E)GPRS specific ones) are now deprecated from the 3GPP specs....


PROTOCOL STACK (1/2) PACKET SWITCHED

USER PLANE:

CONTROL PLANE:


PROTOCOL STACK (2/2) CIRCUIT SWITCHED

USER PLANE:

CONTROL PLANE:


GMM STATE MACHINE GMM =GPRS MOBILITY MANAGEMENT

MS Unreachable

MS Reachable Location updates on routing area level

Location updates on cell level


RRC STATE MACHINE RRC=RADIO RESOURCE CONTROL

UTRAN E-UTRAN GERAN

RADIO NETWORK DEPLOYM ENT

- DIVIDING THE RESOURCES - Fr eq u en c y r eu se CONCEPTS - Fr eq u en c y r eu se PATTERNS - FREQUENCY HOPPING - POWER CONTROL


DIVIDING THE RESOURCESES

› Among operators – Done by dividing the spectrum.

› Duplex communication – Half/Full Duplex, TDD/FDD

› Multiple access – FDMA, TDMA, CDMA, SDMA, …

› Cellular planning – Neighbouring cells can not use the same resources. Or can they?


FREQUENCY r e u s e CONCEPTS

Frequency reuse = Using same frequencies in different cells separated by “sufficient” distance to cause minimal interference with each other. The frequency reuse possible is dependent on many factors such as real world propagation environment, technology etc. Frequency plan= Assignment of radio frequencies to radio transmission sites (cell sites) that are located within a defined geographic area. The frequency plan may use ratios that are different dependent on the number of transmitting sites to the number of antennas (sectors) on each site.


FRECUENCY REUSE PATTERNS (1/3)

Example of looser reuse Example of tighter reuse

›In GSM typically k = 3, 7 or 12.


FRECUENCY REUSE PATTERNS (2/3) › In the GSM 900-band (2x25MHz wide), we can have 124 carriers á

200kHz. › Diving these into groups of 12 frequencies gives 10 such groups where

one cell can thus be covered by 10 carriers where each carrier can have 8 TDMA timeslots. Hence in total 80 Timeslots = e.g. 80 FR CS calls.

› These resources need to be shared between operators on this band.


FRECUENCY REUSE PATTERNS (3/3)

Loose (4x3) Frequency Reuse Pattern for BCCH (giving less interference and capacity)

Tighter (3x3) Frequency Reuse Pattern for TCH (giving more interference and capacity)

<Cluster Size> x <Sectors per Site>


FREQUENCY HOPPING SPREAD SPECTRUM (FHSS)

› Purpose: Increase the channel diversity (in the frequency domain)

› NOTE: Never hop on BCH.

› Base Band Hopping

› Synthesized Hopping


POWER CONTROL › Mainly on TCH (CS),

since (most often) fixed code rates there

› PS typically adjusts code rate instead of power

› No power control on BCH

GSM RADIO INTERFACE (UM )

TDM A Fr a m e St r u c t u r e AND Bu r s t Ty pes M APPING OF LOGICAL TO PHYSICAL CHANNELS RADIO INTERFACE STRUCTURE RADIO INTERFACE ex a m pl e


TDMA FRAME STRUCTURE AND BURST TYPES


MAPPING OF LOGICAL TO PHYSICAL CHANNELS

26-TDMA Multiframe Example (TCH+SACCH)

51-TDMA Multiframe Example (CCCH)


Ra d io in t e r f a c e s t r u c t u r e Mu l t ip l e a c c e s s : TDMA+FDMA Du p l e x : FDD (+TDD)

Time

frequency

880

915

925

960

TDMA frame

downlink

uplink

...

...

...

...

...

...

200 kHz carrier


Ra d io in t e r f a c e e x a m p l e Sp e e c h c h a n n e l (n o t e TDD s t r u c t u r e )

Time

frequency

880

915

925

960

TDMA frame

downlink

uplink

...

...

...

...

...

...

200 kHz carrier

(E)GPRS/EDGE PACKET DATA IN GSM

M o d u l a t io n a n d CODING SCHEM ES RADIO INTERFACE EXAM PLE EGPRS LINK QUALITY CONTROL GM SK AND 8PSK POWER


MODULATION AND CODING SCHEMES › The radio block is the basic unit

of transmission › Channel coding/interleaving over

one radio block › Nine modulation/coding schemes

(MCS) defined

TDMA frame (~4.6 ms)

Time axis

120 ms


Ra d io in t e r f a c e EXAMPLE (1/3) Pa c k e t d a t a c h a n n e l (5+1)

Time

frequency

880

915

925

960

TDMA frame

downlink

uplink

...

...

...

...

...

...

200 kHz carrier


Ra d io in t e r f a c e EXAMPLE (2/3) Pa c k e t d a t a c h a n n e l (2+3)

Time

frequency

880

915

925

960

TDMA frame

downlink

uplink

...

...

...

...

...

...

200 kHz carrier


Ra d io in t e r f a c e EXAMPLE (3/3) Pa c k e t d a t a c h a n n e l (8 +8 )

Time

frequency

880

915

925

960

TDMA frame

downlink

uplink

...

...

...

...

...

...

200 kHz carrier


EGPRS LINK QUALITY CONTROl › Link Adaptation (LA)

– Extensive set of modulation and coding schemes

› Incremental Redundancy (IR) – Code combining of transmission

attempts (chase+soft) › LA and IR can be combined


GMSK a n d 8 PSK p o w e r

P0

GMSK 8PSK

0 dB

-2 dB

-4 dB

-6 dB

Average power

reduction

P1

P2

P3

P0,P1 P2

P3

-3.3 dB

Peaks up to 3.3 dB

higher

GSM PHYSICAL LAYER

Tr a n sm iss io n a n d r ec ept io n (TX/RX CHAIN) Ch a n n el c o d in g AND INTERLEAVING M o d u l a t io n Dem o d u l a t io n Dein t er l ea v in g Ch a n n el d ec o d in g


Tr a n s m is s io n a n d r e c e p t io n (TX/RX CHAIN)

Modulator Burst

Mapping

Insertion of TS

Tx pulse shaping

Radio transmitter

Radio channel

Radio receiver

Rx filter

t

t

t

Eq./Demod

analog digital

RF

Interleaver Data+Header

Channel Encoder

Channel Decoder

De-Interleaver

Binary data for

Transmission

Received Binary data

From Higher Protocols

To Higher Protocols

0 1 0 … 0 0 1 1 0 0.. 0 1 1 0..

0 0

1

1010

1100

z1 + w1i, z2 + w2i, ….

20.34, -15.65, -34.32, …

20.34,9.54

20.34,-15.65

20.34, 9.54, …

0 1 0 …

Ch. Est

x1 + y1i, x2 + y2i, ….

Ciphering

De-cipheri

ng


Ch a n n e l c o d in g Ch. Enc Int Mod

Ch. Dec Deint Dem

› Uncoded bits are coded in the channel encoder. › In EGPRS a 1/3 convolutional code is used (EGPRS2 DL uses a

Turbo Encoder). 0 1 0 0 0 1 0 0 1 1 1 0 0 1 0 1

› To reach the desired code rate of the MCS used, the code word is punctured

0 1 0 0 1 1 1 0 0 1 0 1

1 0 1 1 1 1 1 0 1 1 1 0

0 0 0 1 1 1 0 1 0

R=4/9

Example for full-rate speech:


INTERLEAVING Ch. Enc Int Mod

Ch. Dec Deint Dem

› The punctured code word is interleaved to avoid bursty errors at the receiver.

0 0 0 1 1 1 0 1 0 0 1 2 3 4 5 6 7 8

mod(3k,9) 0 0 1 0 0 0 1 1 1

0 2 4 6 8 1 3 5 7


CIPHERING Ch. Enc Int Mod

Ch. Dec Deint Dem

The GSM ciphering algorithm is called A5. There are four variants of A5 in GSM, only first three of which are widely deployed: A5/0—no ciphering at all • A5/1: strong(er) ciphering, intended for use in North America and Europe • A5/2: weak ciphering, intended for use in other parts of the world, but now deprecated by the

GSMA • A5/3: even stronger ciphering with open design


Mo d u l a t io n (1/2) Ch. Enc Int Mod

Ch. Dec Deint Dem

› The modulation consists of – Modulating the bits onto symbols – Modulating the symbols onto a transmit pulse

0 0 1 0 0 0 1 1 1

› Possible modulations: – For GSM/GPRS: GMSK – For EGPRS/EDGE: GMSK and 8PSK – For EGPRS2: GMSK, QPSK, 8PSK, 16QAM, 32QAM (see later slide)

Mod.

I

Q

000

001 011

010

110

111 101

100

s1 = I1+Q1j s2 = I2+Q2j s3 = I3+Q3j s1 s2 s3


MODULATION (2/2) Ch. Enc Int Mod

Ch. Dec Deint Dem

› Pulse modulation – To transmit the information over the air

interface and keep it within the carrier spectrum mask, a transmit pulse is needed.

s1

s2

s3

*

*

*

+

+

Ts

|s|

Burst sample (4xoversampling)


AIR INTERFACE (UM) Ch. Enc Int Mod

Ch. Dec Deint Dem

› See earlier slides....


De m o d u l a t io n Ch. Enc Int Mod

Ch. Dec Deint Dem

› The demodulation consist of two major tasks: 1. Channel estimation 2. Signal demodulation

r

Ch. est

Dem.

The channel estimator uses the known training sequence code (TSC) to estimate the channel.

TSC Tail

Tail + Intf./Noise

s

-5,-1, 1 …

The demodulator returns soft bit values. The larger absolut value, the larger confident from the demodulator.


d e in t e r l e a v in g › The deinterleaver performs the reverse operation of the

interleaver. The quality of the code word is spread out

Ch. Enc Int Mod

Ch. Dec Deint Dem

mod(3k,9)-1

0 0 1 0 0 0 1 1 1

0 2 4 6 8 1 3 5 7

-5 -1 1 2 -50 73 62 100 88

Bin Soft value sign

0 -

1 +

Qua

lity

(Transmitted

Int. bit pos

Soft val.

0 0 1 0 0 0 1 1 1)

0 1 2 3 4 5 6 7 8

-5 73 -1 62 1 100 2 88 -50

Qua

lity


Ch a n n e l d e c o d in g › The soft bits are depunctured with the same puncturing

scheme used in the transmitter. › A Viterbi decoder is used in the decoding.

Ch. Enc Int Mod

Ch. Dec Deint Dem

-5 0 73 -1 62 1 100 0 2 88 -50 0

1 0 1 1 1 1 1 0 1 1 1 0

0s (= no confidence on whether it’s a 0 or 1) is inserted in the punctured bit positions as soft value

Viterbi dec.

0 1 0 0

› In case Incremental Redundancy, IR, is used, the soft values are combined before Viterbi decoding

-5 0 73 -1 62 1 100 0 2 88 -50 0

-5 10 0 0 12 10 1 -30 5 28 -23 58 +

Prev. Trans.

Curr. Trans. Viterbi dec.

0 1 0 0

RECENT/FUt u r e GSM d ev el o pm en t

- EDGE EVOLUTION - VAM OS - OTHER 3GPP a c t iv it ies


EDGE Ev o l u t io n (1/7)

Dual carrier DL 1.0 Mbps with 32QAM & 10 TS

10 ms TTI 80 ms e2e latency

Higher symbol rate UL/DL +20% bitrate per carrier/timeslot

16/32-QAM & Turbo codes DL & 100 kbps per timeslot

32-QAM UL 100 kbps per timeslot &

Dual-antenna terminals 3 - 8 dB link improvement

16-QAM UL & 80 kbps per timeslot

Fast Ack/Nack


EDGE Ev o l u t io n (2/7) EGPRS2 Co d in g s c h e m e s u p l in k

Uplink Level A MCS Modulation Bitrate (kbps) Symbol Rate

UAS-11 16QAM 76.8

NSR

UAS-10 16QAM 67.2

UAS-9 16QAM 59.2

UAS-8 16QAM 51.2

UAS-7 16QAM 44.8

MCS-6 8PSK 29.6

MCS-5 8PSK 22.4

MCS-4 GMSK 17.6

MCS-3 GMSK 14.8

MCS-2 GMSK 11.2

MCS-1 GMSK 8.8

MCS Modulation Bitrate (kbps) Symbol Rate

UBS-12 32QAM 118.4

HSR

UBS-11 32QAM 108.8

UBS-10 32QAM 88.8

UBS-9 16QAM 67.2

UBS-8 16QAM 59.2

UBS-7 16QAM 44.8

UBS-6 QPSK 29.6

UBS-5 QPSK 22.4

MCS-4 GMSK 17.6

NSR MCS-3 GMSK 14.8

MCS-2 GMSK 11.2

MCS-1 GMSK 8.8

Uplink Level B

› Level A: Adding 16QAM › Level B: Adding 16QAM+32QAM+Higher symbol rate


Downlink Level A MCS Modulation Bitrate (kbps) Symbol Rate

DAS-12 32QAM 98.4

NSR

DAS-11 32QAM 81.6

DAS-10 32QAM 65.6

DAS-9 16QAM 54.4

DAS-8 16QAM 44.8

DAS-7 8PSK 32.8

DAS-6 8PSK 27.2

DAS-5 8PSK 22.4

MCS-4 GMSK 17.6

MCS-3 GMSK 14.8

MCS-2 GMSK 11.2

MCS-1 GMSK 8.8

MCS Modulation Bitrate (kbps) Symbol Rate

DBS-12 32QAM 118.4

HSR

DBS-11 32QAM 108.8

DBS-10 32QAM 88.8

DBS-9 16QAM 67.2

DBS-8 16QAM 59.2

DBS-7 16QAM 44.8

DBS-6 QPSK 29.6

DBS-5 QPSK 22.4

MCS-4 GMSK 17.6

NSR MCS-3 GMSK 14.8

MCS-2 GMSK 11.2

MCS-1 GMSK 8.8

Downlink Level B

Level A: Adding 16QAM+32QAM+turbo codes Level B: Adding QPSK+16QAM+32QAM+turbo

codes+Higher symbol rate

EDGE Ev o l u t io n (3/7) EGPRS2 Co d in g s c h e m e s Do w n l in k


EDGE Ev o l u t io n (4 /7) EGPRS2 Lin k p e r f o r m a n c e Do w n l in k t h r o u g h p u t p e r t im e s l o t (n o IRC/MSRD)

Downlink, no IRC

0

20

40

60

80

100

120

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46

C/I

Rad

io L

ink

Bitr

ate

(kbp

s)

EGPRSEGPRS2-AEGPRS2-B


EDGE Ev o l u t io n (5/7) EGPRS2 Lin k p e r f o r m a n c e Do w n l in k t h r o u g h p u t p e r t im e s l o t (w it h IRC/MSRD)

Downlink, with IRC

0

20

40

60

80

100

120

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46

C/I

Rad

io L

ink

Bitr

ate

(kbp

s)



EDGE Ev o l u t io n (6 /7) EGPRS2 Lin k p e r f o r m a n c e Up l in k t h r o u g h p u t p e r t im e s l o t (n o IRC)

Uplink, no IRC

0

20

40

60

80

100

120

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46

C/I

Rad

io L

ink

Bitr

ate

(kbp

s)



EDGE Ev o l u t io n (7/7) EGPRS2 Lin k p e r f o r m a n c e Up l in k t h r o u g h p u t p e r t im e s l o t (w it h IRC)

Uplink with IRC

0

20

40

60

80

100

120

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46

C/I

Rad

io L

ink

Bitr

ate

(kbp

s)



VAMOS (Vo ic e s e r v ic e s o v e r Ad a p t iv e Mu l t i-u s e r CHa n n e l s o n On e Sl o t )

Full rate (FR), half rate (HR), VAMOS FR (VFR) and VAMOS HR (VHR) allocations on a single time slot

One Timeslot

VAMOS downlink air interface. The RBS is transmitting a single AQPSK modulated signal to a pair of VAMOS mobiles

Two examples of the AQPSK constellation. The subchannel power distribution is illustrated by the length of the colored vectors

VAMOS uplink air interface. Two mobiles simultaneously transmit GMSK modulated signals on the same carrier frequency

Cell capacity as a function of the number of TCH TRXs


OTHER 3GPP a c t iv it ie s (AFFECTING THE GSM UM)

› M2M/Smartphone improvements: – Handle more users with smaller transactions per user.

› Introdution of OFDM in GSM – A.k.a SPEED – Single Precoded Enhanched EGPRS Downlink)

› Multi-Carrier Downlink – Up to 4 carriers i DL to one UE

› MIMO for GSM › ...

AGAIN, THESE SLIDES

SHOULD BEAVAILABLE AT COURSE HOM EPAGE




GOOD LUCK!

GSM AIR INTERFACE AND PHYSICAL LAYER INTRODUCTION€¦ · · 2017-09-03GSM AIR INTERFACE AND...

Documents

Transcript of GSM AIR INTERFACE AND PHYSICAL LAYER INTRODUCTION€¦ · · 2017-09-03GSM AIR INTERFACE AND...