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8/3/2019 Lecture2 Utran Overview
http://slidepdf.com/reader/full/lecture2-utran-overview 1/39
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)
8/3/2019 Lecture2 Utran Overview
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Repetition of the last lecture
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X
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Repetition of the last lecture
•
SGSN GGSNGn INTERNETGi
XX
X X
RNC SGSN GGSNIu-ps Gn
X XX
HLRSGSN
X
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Repetition of the last lecture
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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)
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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
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– http://www.nt.tuwien.ac.at/teaching/courses/winter-term/389134
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Accessing a Share Media
•– How to share the media between different users
–
– GPRS: Time (TDMA)
– UMTS: Codes ((W)CDMA)
TDMA Time Division Multiple Access
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CDMA Co e D v s on Mu t p e Access
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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
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Video and Multimedia Transmissions over Cellular Networks 389.134
– Two types: traffic channels, control channels
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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
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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
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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
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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)
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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
•
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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
–
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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
•
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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!
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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
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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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Repetition of the last lecture
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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
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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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UMTS RAN: The Protocol Architecture
• – 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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UMTS RAN: The Protocol Architecture
• – 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
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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
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– 389.051: Introduction to Telecommunications
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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)
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– exc ange o user ata
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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
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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
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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
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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
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UMTS Radio Link: Packetization on the Link
– We need packetization for
• Error control
• Synchronization
• Start/End of Transmission
• UMTS R99 packetization example
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UMTS R di Li k T i i DPDCH
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UMTS Radio Link: Transmission on DPDCH
•
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UMTS R di Li k S
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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
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F UMTS R99 t HSDPA
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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
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Video and Multimedia Transmissions over Cellular Networks 389.134
From UMTS R99 to HSDPA
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From UMTS R99 to HSDPA
• 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)
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HSDPA: The new Channels
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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)
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LTE Whatever it may be
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LTE Whatever it may be
• – Revolutionary step to update the core network
– ,
– Put everything into the NodeB
mp emen a on
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Video and Multimedia Transmissions over Cellular Networks 389.134
Summary of this lecture
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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
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Video and Multimedia Transmissions over Cellular Networks 389.134
– ys ca ayer met o s e co ng w e v s e at g er ayers
Summary of this lecture
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Summary of this lecture
•
– 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
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Thank you for your attention
uest ons