lecture2 utran overview

8/3/2019 Lecture2 Utran Overview

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n ro uc on o o e e u ar e wor s

Part II: RAN / UTRAN

.

Video and Multimedia Transmissions over Cellular Networks

12.10.2009

(http://www.nt.tuwien.ac.at/teaching/courses/winter-term/389134)



Repetition of the last lecture

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Video and Multimedia Transmissions over Cellular Networks 389.134




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Outline of this lecture

•– TDMA

–

– Channels

• Radio Link UMTS

– WCDMA

– Slot format– Channels

• Upgrade to HSDPA (high level point of view)

5




Outline of this lecture

•– Site: http://www.3gpp.org

– 00 – 11

•

– 41 – 55

• UMTS R99

– 21 – 37

• Today:

– TS 25.401 "UTRAN overall description",– TS 25.301 "Radio Interface Protocol Architecture“

• Lecture slides

6


– http://www.nt.tuwien.ac.at/teaching/courses/winter-term/389134



Accessing a Share Media

•– How to share the media between different users

–

– GPRS: Time (TDMA)

– UMTS: Codes ((W)CDMA)

TDMA Time Division Multiple Access

7


CDMA Co e D v s on Mu t p e Access



Physical and Logical Channels – The Difference

RLC Radio Link ControlMAC Media Access Contr.

• Physical channels

–

– Each channel is identified through its physical parameters

• Transport channels

– Provide bearers for information exchange MAC/physical

– Transport channels are unidirectional

•

– Provide bearers for information exchange between MAC and RLC

– Logical channels can be bi-directional

8


– Two types: traffic channels, control channels



GSM Radio Link: TDMA

•– Random Access: ALOHA + collision detection

–

• Each user is assigned one or more time slots

• Signaling overhead

• –…

– Orthogonal frequency bands (GSM 900: 880-915/ 925-960 MHz)

• 124 Channels with 200kHz each

Down

Up

9




GSM Radio Link: Physical Channels

•– Random Access: ALOHA + collision detection

–

– Each user is assigned one or more time slots

• Frame structure of GSM

– The basic TDMA frame

TDMA Time Division Multiple Access

GSM Global System for Mobile

Communications

1 2 3 4 5 6 7 8

4,615ms

T T

G u

G u

i l i l r d

r d

577s

10




GSM Radio Link: Logical Channels

•– Full/Half rate channels (TCH/F or H)

• 13kbit/s of audio information ma to 22.8kbit/s encoded bit rate

• Broadcast Channels (BCHs)

• Downlink only, beacon signals

– Frequency Correction Channel (FCCH)

• MS frequency tuning (frequency only – frame timing is missing!)

–

• Frame timing + BSIC

– Broadcast Control Channel (BCCH)

• Cell specific information (LAI, permitted power, neighboring cells …)

• Common Control Channels (CCCHs)

LAI Local Area Information

BSIC Base Station Info Code

11




GSM Radio Link: Logical Channels

• • Start up phase of information exchange between MS and BS

– Pa in Channel PCH

• Paging a MS due to a call from landline

• Downlink only, may be (miss) used for traffic and commercials – an om ccess anne

• Allows the MS to request for resources in the cell

• U link onl

– Access Grant Channel (AGCH)• Grants access to a stand alone Control Channel in the cell (after RACH)

– e ca e on ro anne s s

– Dedicated to one MS, bi-directional

• Standalone Dedicated Control Channel (SDCCH)• Slow Associated Control Channel (SACCH)

• Fast Associated Control Channel (FACCH)

12




GSM Radio Link: The frame structure

•– Avoid excessive signaling

–

– Allow low data rate bearers on the logical link layer

• Frames of GSM– Hyper frame

• ncryp on

– Super frame

• Cell broadcast

– Multi frame

• Signalling

– TDMA frame• 8 Timeslots (users)

– Timeslot

•

13




GSM Radio Link: Physical Channels

•– Permanent on connection

–

– Slot 13 and 26 over up to 4 multi frames

– 950bit/s (in bursts!)

• Fast Associated Contr CH (FACCH)

–

– No normal TCH channel

– Steals bit between Midamble and Data

– 456 bit in 8 consecutive TDMA frames

• an om ccess

– Uplink slot for access burst

–

14




A real example: KPI analysis

•– What mobile generate the most signals (faulty terminals)

per second

– Wh ?

• More detailed analysis show

– Same mobile has different patterns throughout the day

• Why?• Any Ideas….

– Consider the picture!

– Mobility is the key

•

15




A real example: KPI analysis II

•– A certain cell shows periodic massive register rejects?

–

• Cell was not loaded All mobiles in IDLE get active

• Ideas?

– Hints:

-

• GMM• Train

BCCH Resources

– Handover of all idle terminals cause overload in the BCCH!

– Next cells impacted by the mobiles rejected to change LAC

depleted!

16




GSM Radio Link: Summary

• – Slot based physical channels

– –

• 8 users per cell

– One ower am lifier

• Signaling hidden in super-frames

– Data transfer in bursts

– Allows for different data rate channels

• Cells may be signaling limited

– Information of the physical layer is important to understand

17




From GSM to GPRS

• – Core network elements

–

• More than one slot per user and TDMA multi frame

– U to 8 slots classes of mobiles

– Allows higher data rate

• Up / Down link not symmetric

– Packet oriented traffic• Different coding sets (data protection)

– CS 1 - 4

• Mobility management

– A ow p ysica i e an ogica active at t e same time

– Different to audio dataCS Code Set

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19




UMTS Radio Link: Welcome to the UTRAN

• – Contains: RNC, NodeB, MS

–

– RNC fully meshed

• Protocols, Interfaces– Iub, Iur, Uu

– RANAPRNC Radio Network Controller

SRNC Serving RNC

• Operation modesDRNC Drift RNC

20




UMTS RAN: The Protocol Architecture

RRC Radio Resource Control

PDCP Packet Data Conv. Proto.

roa cas essa e on r.

RLC Radio Link Control

MAC Media Access Control

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• – PS data header compression

–

– Optional implementation (not used)

• Radio Link Control Protocol

– Two modes of operation

• Transparent, Non-Transparent

• Ack / NonAck

– Functions

• Mapping

• Ciphering

• rror correct on

• Flow control, segmentation

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• – Cell broadcast messages

–

• Radio Resource Control Protocol RRC– Routing Function Entity

• Route CM and MM to/from RNC

– Broa cast Contro Function Entity

– Paging / Notification Ctrl Func Ent

–

– Transfer Mode Entity

– All UTRAN to UE control functions

23




UMTS Radio Link: WCDMA

• – TDD + TDMA + CMDA (UTRA TDD)

– + –

• Wideband compared to cdmaOne

• Problem: Qualcom owns key patents in UTRA FDD (and pushed them to

• WCDMA key numbers

–

– Higher bit rate – less spreading

– Frequency reuse one (different cell planning)

– Near-far effect - power control is important

• Courses on modulation and spreading:

– 389.063: Mobile Communications

24


– 389.051: Introduction to Telecommunications



UMTS Radio Link: Logical Channels

•

– distributes information that allows UEs to attach to network

• information about radio environment:

, ..

• Common Control Channel (CCCH)

– for exchange of first messages with attaching UE• no specific (dedicated) control channel has been assigned yet

• Dedicated Control Channel (DCCH)

–

• e.g. power control

• Paging Control Channel (PCCH)

– for paging UEs

• Common Transport Channel (CTCH)

–• for broadcasting information to all, or a group of UEs

• Dedicated Transport Channel (DTCH)

25


– exc ange o user ata



UMTS Radio Link: Transport Channels

• Provide specific service quality, e.g.

• Bit rate, error protection, power level, access method

• Data packets that are transmitted over Transport Channels are called

„Transport Blocks“

– “„

• Each Transport Channel is described by a set of „Transport Formats“ it

can provide, i.e.

– Transport Block Size, Transport Block Set Size, Transmission time interval

• How long does it take to transmit a Transport Block Set

– Type of error protection (Channel Coding and Cyclic Redundancy Check)

• Channel Coding: redundant transmission of information

– Efficiency of Channel Coding

,is chosen from the Transport Format Set

26




UMTS Radio Link: Transport Channels (some)

– downlink, fixed bit rate, high power level (needs to be audible to all)

– used for BCCH

• Random Access Channel (RACH)

– uplink, random access

– mostly used by CCCH and DCCH (also DTCH)

• Dedicated Channel (DCH)

– uplink and downlink, dedicated to a particular UE

–

• Downlink Shared Channel (DSCH)– dedicated user traffic but shared by several users

– very mpor an or a a ra c no e ca e an w or one user

– optional to implement

• Note there is no Uplink Shared Channel

– At the time of standardization no use was anticipated

27




UMTS Radio Link: Physical Channels

• ommon o anne– a signaling sequence known to network and UE is spread with the

code used in the P-CCPCH in which further information is available

• Primary Common Control Physical Channel (P-CCPCH)– used by BCCH / BCH

– uses a code broadcasted on CPICH

–

• Dedicated Physical Data Channel (DPDCH)

– physical channel dedicated to a user

-– P-SCH sends known, invariant signaling sequence of 256 chips

– allows UE to s nchronize

28




UMTS Radio Link: Mapping of the Channels

• as one p ys ca c anne• UMTS has several physical channels

– app n s more comp ex

29




UMTS Radio Link: Packetization on the Link

– We need packetization for

• Error control

• Synchronization

• Start/End of Transmission

• UMTS R99 packetization example

30


UMTS R di Li k T i i DPDCH



UMTS Radio Link: Transmission on DPDCH

•

31


UMTS R di Li k S



UMTS Radio Link: Summary

• n• Max data rate DCH: 384kbit/s

• eren a a ra e c anne s ava a e

• Higher complexity in the RAN– es e

– Soft Handover

– Errors will show time patterns

•

– Two different operation modes

– Used codes will introduce patterns (Turbo Code!)• Again – understand physical layer to understand

measurements on Gn

32


F UMTS R99 t HSDPA



From UMTS R99 to HSDPA

• e goa s– Reduce RTT

– -

• New elements

– The MAC-hs

– Hybrid – ARQ

– Adaptive Modulation and Coding (AMC)

• MAC-hs

RTT Round Trip Time

AMC Adaptive Modulation

and Coding

33






• y r– Error correction methods:

•

– Add information to protect payload, e.g. CRC

• Automatic Repeat reQuest (ARQ) –

• Hybrid ARQ combines FEC and ARQ

• Adaptive Modulation and Coding (AMC)– UMTS R99

• Fixe mo u ation

• Variable Spreading Factor (SF)

– HSDPA• Fixed SF (16)

• Adaptive modulation and coding (AMC)

34


HSDPA: The new Channels



HSDPA: The new Channels

• c anne s– HSDPA needs major changes to UMTS links

– – -

– High Speed – Shared Control Channel (HS-SCCH)

– High Speed – Dedicated Physical Control Channel (HS-DPCCH)

35


LTE Whatever it may be



LTE Whatever it may be

• – Revolutionary step to update the core network

– ,

– Put everything into the NodeB

mp emen a on

36


Summary of this lecture




•

– TDMA based technology

–

– Fixed time patterns

• GPRS– Inherited most elements from GSM

• One receiver, one sender (up/downlink link correlated!)

– RAN is not mes e

• UMTS

–

– Packetization still present!

– RNCs are meshed• Soft handover

• Low RTT possible

37


– ys ca ayer met o s e co ng w e v s e at g er ayers





•

– Real packet switched channels

–

• Lower RTT (80ms)

• Hard handover only• Data transmission on IP depends on

– Physical link technology (slots, frames, time stamps, error

, …

– Logical Channels (frame sizes, …)– Transport Channels (data rate, residual errors, delay, …)

• Next sto : IP transmission over UMTS link– Error patterns

– Optimization headroom

38




Thank you for your attention

uest ons

[email protected]

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