192620010 Mobile & Wireless Networking - Universiteit Twenteheijenkgj/mwn/slides/... ·...
Transcript of 192620010 Mobile & Wireless Networking - Universiteit Twenteheijenkgj/mwn/slides/... ·...
Mobile and Wireless Networking 2013 / 2014
192620010
Mobile & Wireless Networking
Lecture 6: Cellular Systems (UMTS / LTE) (2/2)
& Other systems
[Reader, Part 5] [Optional: Schiller, Section 4.2, 4.3, 5, 6]
Geert Heijenk
Mobile and Wireless Networking 2013 / 2014
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Outline of Lecture 6
q Cellular Systems (UMTS / LTE) (2/2) q UMTS High Speed Downlink Packet Access (HSDPA) q UMTS High Speed Uplink Packet Access (HSUPA) q Long Term Evolution (LTE)
q Other systems
q DECT q TETRA q Satellite Systems
Mobile and Wireless Networking 2013 / 2014
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HSDPA (The downlink) Main improvements:
q MAC-layer: from RNC to base station q Improved radio: higher order modulation
initially 16-QAM, newer releases 64 QAM Techniques used:
q Fast Adaptive Modulation & Coding q Fast Channel-Dependent Scheduling q Fast Hybrid ARQ
Result: q increases throughput (→14.4 Mbps) q reduces latency q increases data capacity q newer releases promise throughputs up to 86.4 Mbps
(with MIMO, 64-QAM, and multiple carriers (dual-cell)) Introduction:
q 2006 (in NL, max 28.8 Mbps (2012))
Mobile and Wireless Networking 2013 / 2014
Fast Channel-Dependent Scheduling
Schedule a packet for transmission to a certain user when it has a “good” channel
• Increases throughput • May decrease fairness between users à trade-off
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Example of Fast Channel-Dependent Scheduling
Proportional Fair Scheduling: Rm(n): achievable data rate of user m in the nth slot / subframe Tm(n): average data rate of user m in the the last tc slots / subframes base station will transmit to user m* in the nth slot / subframe: average data rate is updated after each slot / subframe:
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m*(n) = arg maxm=1,2,...,M
Rm (n)Tm (n)
Tm (n+1) =(1! 1
tc)Tm (n)+ (
1tc)Rm (n) m =m*(n)
(1! 1tc)Tm (n) m "m*(n)
#
$
%%
&
%%
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HSUPA (the enhanced uplink)
Main improvements: q MAC-layer: from RNC to base station (as HSDPA)
l no higher order modulation
Techniques used: q Fast Channel-Dependent Scheduling q Fast Hybrid ARQ
Result: q increases throughput (→5.76 Mbps) q reduces latency q increases data capacity q newer releases promise throughputs up to 23 Mbps
(with higher order modulation, and multiple carriers (dual-cell)) Introduction:
q 2008 (in NL, max 5.76 Mbps (2012))
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Outline of Lecture 6
q Cellular Systems (UMTS / LTE) (2/2) q UMTS High Speed Downlink Packet Access (HSDPA) q UMTS High Speed Uplink Packet Access (HSUPA) q Long Term Evolution (LTE)
q Other systems
q DECT q TETRA q Satellite Systems
Mobile and Wireless Networking 2013 / 2014
Long Term Evolution: Background
• Evolution of 3G UMTS radio access technology • Supporting (only) (IP) packet-based services • Targets:
• Increased data rates (ê100 Mbit/s, é50 Mbit/s) • Increased capacity (3 – 4 x Rel. 6 (HSDPA)) • Improved spectrum efficiency (x3) • Reduced latency: <5 ms RTT, <100ms channel setup, • Reduced cost • Spectrum flexibility
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LTE Characteristics
• Flexible channel bandwidth: • 1.4, 3, 5, 10, 15, 20 MHz
• Duplexing: • FDD, TDD, and combined FDD/TDD (half duplex)
• Downlink: • OFDMA
• Uplink: • Single Carrier FDMA (OFDMA with extra Discrete Fourier Transform)
• MIMO: • up to 4x4 in downlink, or multi-user MIMO (down-/uplink)
• Hybrid ARQ: • multiple parallel stop-and-wait, with soft combining / incremental
redundancy • Max Data Rates:
• 75 Mbit/s (uplink), 300 Mbit/s (downlink, with MIMO) • New core network:
• Evolved Packet Core (EPC) / Evolved Packet System (EPS)
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LTE Resource Blocks
• Resource Blocks (RB) is the smallest resource unit that can be assigned to a mobile (2 at a time) • RB lasts 0.5 ms (6 or 7 OFDM symbols) • RB spans over a 180 kHz sub-channel (containing 12 15 kHz subcarriers) • Number of sub-channels depends on channel bandwidth
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Source: Capozzi, Piro, Grieco, Boggia & Camarda: Downlink Packet Scheduling in LTE Cellular Networks In: IEEE Communications Surveys & Tutorials, Early Access Article, IEEE Xplore, 2012, pp. 1 - 8."
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Trade-off: • efficiency • fairness / QoS Constraints: • uplink: contiguous sub-channels • control overhead for signaling RB allocation • resolution of channel info • energy consumption
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Source: Capozzi, Piro, Grieco, Boggia & Camarda: Downlink Packet Scheduling in LTE Cellular Networks In: IEEE Communications Surveys & Tutorials, Early Access Article, IEEE Xplore, 2012, pp. 1 - 8."
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LTE Network Architecture: Evolved Packet System
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UE: User Equipment eNodeB: evolved Node B MME: Mobility Management Entity HSS: Home Subscriber Server SGW: Serving GateWay PGW: Packet data network GateWay
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EPS user-plane protocols
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EPS control-plane protocols
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Outline of Lecture 6
q Cellular Systems (UMTS / LTE) (2/2) q UMTS High Speed Downlink Packet Access (HSDPA) q UMTS High Speed Uplink Packet Access (HSUPA) q Long Term Evolution (LTE)
q Other systems
q DECT q TETRA q Satellite Systems
Mobile and Wireless Networking 2013 / 2014
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Digital Enhanced Cordless Telecommunication (DECT)
q DECT (Digital European Cordless Telephone) standardized by ETSI for cordless telephones, renamed for international marketing reasons into „Digital Enhanced Cordless Telecommunication“
q standard describes air interface between base-station and mobile phone
q Characteristics q frequency: 1880-1990 MHz q channels: 120 full duplex q duplex mechanism: TDD (Time Division Duplex) with 10 ms frame
length q multiplexing scheme: FDMA with 10 carrier frequencies,
TDMA with 2x 12 slots q modulation: digital, Gaußian Minimum Shift Key (GMSK) q power: 10 mW average (max. 250 mW) q range: approx. 50 m in buildings, 300 m open space
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DECT Dynamic Channel Allocation
q periodically (< 30s) measure RSSI on all frequency/timeslot combinations
q keep list of combinations with least RSSI for setting up new channels
q listen to channels with high RSSI to see what is strongest base-station
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Outline of Lecture 6
q Cellular Systems (UMTS / LTE) (2/2) q UMTS High Speed Downlink Packet Access (HSDPA) q UMTS High Speed Uplink Packet Access (HSUPA) q Long Term Evolution (LTE)
q Other systems
q DECT q TETRA q Satellite Systems
Mobile and Wireless Networking 2013 / 2014
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Trunked Radio Systems
q many different radio carriers q assign single carrier for a short period to one user/group of
users q police, ambulance, rescue teams, taxi service, fleet
management q interfaces to public networks, voice and data services q very reliable, fast call setup, local operation
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TETRA - Terrestrial Trunked Radio
q ETSI standard q formerly: Trans European Trunked Radio q offers Voice+Data and Packet Data Optimized service q point-to-point and point-to-multipoint q ad-hoc and infrastructure networks q several frequencies: 380-400 MHz, 410-430 MHz q FDD, DQPSK q group call, broadcast, discrete listening q Netherlands: C2000 project
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Outline of Lecture 6
q Cellular Systems (UMTS / LTE) (2/2) q UMTS High Speed Downlink Packet Access (HSDPA) q UMTS High Speed Uplink Packet Access (HSUPA) q Long Term Evolution (LTE)
q Other systems
q DECT q TETRA q Satellite Systems
Mobile and Wireless Networking 2013 / 2014
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Satellite Basics
q elliptical or circular orbits q complete rotation time depends on distance satellite-earth q inclination: angle between orbit and equator q elevation: angle between satellite and horizon q LOS (Line of Sight) to the satellite necessary for connection
è high elevation needed, less absorption due to e.g. buildings q Uplink: connection base station - satellite q Downlink: connection satellite - base station q typically separated frequencies for uplink and downlink
q transponder used for sending/receiving and shifting of frequencies q transparent transponder: only shift of frequencies q regenerative transponder: additionally signal regeneration
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Four different types of satellite orbits can be identified depending on the shape and diameter of the orbit:
q GEO: geostationary orbit, ca. 36000 km above earth surface
q LEO (Low Earth Orbit): ca. 500 - 1500 km q MEO (Medium Earth Orbit) or ICO (Intermediate Circular
Orbit): ca. 6000 - 20000 km q HEO (Highly Elliptical Orbit) elliptical orbits
Orbits I
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Orbits II
earth
km 35768
10000
1000
LEO (Globalstar,
Irdium)
HEO
inner and outer Van Allen belts
MEO (ICO)
GEO (Inmarsat)
Van-Allen-Belts: ionized particles 2000 - 6000 km and 15000 - 30000 km above earth surface
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Geostationary satellites
q Orbit 35,786 km distance to earth surface, orbit in equatorial plane (inclination 0°)
è complete rotation exactly one day, satellite is synchronous to earth rotation
q fix antenna positions, no adjusting necessary q satellites typically have a large footprint (up to 34% of earth
surface!), therefore difficult to reuse frequencies q bad elevations in areas with latitude above 60° due to fixed position
above the equator q high transmit power needed q high latency due to long distance (ca. 275 ms)
è not useful for global coverage for small mobile phones and data
transmission, typically used for radio and TV transmission
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LEO systems
Orbit ca. 500 - 1500 km above earth surface q visibility of a satellite ca. 10 - 40 minutes q global radio coverage possible q latency comparable with terrestrial long distance
connections, ca. 5 - 10 ms q smaller footprints, better frequency reuse q but now handover necessary from one satellite to another q many satellites necessary for global coverage q more complex systems due to moving satellites Examples: q Iridium (start 1998, 66 satellites, FDMA/TDMA-based,
uses inter-satellite links) q Bankruptcy in 1999, deal with US DoD (free use, saving from “deorbiting”)
q Globalstar (start 1999, 48 satellites, CDMA-based, no inter-satellite links è no service when no gateway station in view) q Bankruptcy in 2002, assets sold to new company.
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MEO systems
q Orbit ca. 5000 - 12000 km above earth surface q comparison with LEO systems:
q slower moving satellites q less satellites needed q simpler system design q for many connections no hand-over needed q higher latency, ca. 70 - 80 ms q higher sending power needed q special antennas for small footprints needed
Example: q GPS (Global Positioning System)