192620010 Mobile & Wireless Networking Lecture 6: Cellular ...

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

Outline of Lecture 6 q 

Cellular Systems (UMTS / LTE) (2/2) q  q  q 

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UMTS High Speed Downlink Packet Access (HSDPA) UMTS High Speed Uplink Packet Access (HSUPA) Long Term Evolution (LTE)

Other systems q  q  q 

DECT TETRA Satellite Systems

2 Mobile and Wireless Networking 2013 / 2014

HSDPA (The downlink) Main improvements: q  q 

MAC-layer: from RNC to base station Improved radio: higher order modulation initially 16-QAM, newer releases 64 QAM

Techniques used: q  q  q 

Fast Adaptive Modulation & Coding Fast Channel-Dependent Scheduling Fast Hybrid ARQ

Result: q  q  q  q 

increases throughput (→14.4 Mbps) reduces latency increases data capacity 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)) 3 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


Example of Fast Channel-Dependent Scheduling Proportional Fair Scheduling: Rm(n): Tm(n):

achievable data rate of user m in the nth slot / subframe 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: Rm (n) m=1,2,...,M T (n) m

m* (n) = arg max

average data rate is updated after each slot / subframe: # 1 1 % (1! )Tm (n) + ( )Rm (n) m = m* (n) tc tc % Tm (n +1) = $ 1 % (1! )Tm (n) m " m* (n) % tc & 5 Mobile and Wireless Networking 2013 / 2014

HSUPA (the enhanced uplink) Main improvements: q 

MAC-layer: from RNC to base station (as HSDPA) l 

no higher order modulation

Techniques used: q  q 

Fast Channel-Dependent Scheduling Fast Hybrid ARQ

Result: q  q  q  q 

increases throughput (→5.76 Mbps) reduces latency increases data capacity 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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Long Term Evolution: Background

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Evolution of 3G UMTS radio access technology Supporting (only) (IP) packet-based services

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Targets:

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•  •  •  •  •  • 

Increased data rates (ê100 Mbit/s, é50 Mbit/s) Increased capacity (3 – 4 x Rel. 6 (HSDPA)) Improved spectrum efficiency (x3) Reduced latency: ?J: Early Access Article, IEEE Xplore, 2012, pp. 1 - 8." 11 Mobile and Wireless Networking 2013 / 2014

LTE Network Architecture: Evolved Packet System

UE: User Equipment eNodeB: evolved Node B MME: Mobility Management Entity HSS: Home Subscriber Server SGW: Serving GateWay PGW: Packet data network GateWay 12 Mobile and Wireless Networking 2013 / 2014

EPS user-plane protocols


EPS control-plane protocols




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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“

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standard describes air interface between base-station and mobile phone Characteristics

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frequency: 1880-1990 MHz channels: 120 full duplex duplex mechanism: TDD (Time Division Duplex) with 10 ms frame length multiplexing scheme: FDMA with 10 carrier frequencies, TDMA with 2x 12 slots modulation: digital, Gaußian Minimum Shift Key (GMSK) power: 10 mW average (max. 250 mW) range: approx. 50 m in buildings, 300 m open space 16 Mobile and Wireless Networking 2013 / 2014

DECT Dynamic Channel Allocation q  q  q 

periodically (< 30s) measure RSSI on all frequency/timeslot combinations keep list of combinations with least RSSI for setting up new channels listen to channels with high RSSI to see what is strongest basestation




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Trunked Radio Systems q  q  q  q  q 

many different radio carriers assign single carrier for a short period to one user/group of users police, ambulance, rescue teams, taxi service, fleet management interfaces to public networks, voice and data services very reliable, fast call setup, local operation


TETRA - Terrestrial Trunked Radio q  q  q  q  q  q  q  q  q 

ETSI standard formerly: Trans European Trunked Radio offers Voice+Data and Packet Data Optimized service point-to-point and point-to-multipoint ad-hoc and infrastructure networks several frequencies: 380-400 MHz, 410-430 MHz FDD, DQPSK group call, broadcast, discrete listening Netherlands: C2000 project




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Satellite Basics q  q  q  q  q 

elliptical or circular orbits complete rotation time depends on distance satellite-earth inclination: angle between orbit and equator elevation: angle between satellite and horizon LOS (Line of Sight) to the satellite necessary for connection è high elevation needed, less absorption due to e.g. buildings

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Uplink: connection base station - satellite Downlink: connection satellite - base station typically separated frequencies for uplink and downlink q  q  q 

transponder used for sending/receiving and shifting of frequencies transparent transponder: only shift of frequencies regenerative transponder: additionally signal regeneration


Orbits I 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 II GEO (Inmarsat) HEO

MEO (ICO)

LEO (Globalstar, Irdium)

inner and outer Van Allen belts earth 1000 10000

Van-Allen-Belts: ionized particles 2000 - 6000 km and 15000 - 30000 km above earth surface

35768 km


Geostationary satellites q  è 

Orbit 35,786 km distance to earth surface, orbit in equatorial plane (inclination 0°) complete rotation exactly one day, satellite is synchronous to earth rotation q  q  q  q  q 

fix antenna positions, no adjusting necessary satellites typically have a large footprint (up to 34% of earth surface!), therefore difficult to reuse frequencies bad elevations in areas with latitude above 60° due to fixed position above the equator high transmit power needed 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 25 Mobile and Wireless Networking 2013 / 2014

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 

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Bankruptcy in 1999, deal with US DoD (free use, saving from “deorbiting”)

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.


MEO systems q  q 

Orbit ca. 5000 - 12000 km above earth surface comparison with LEO systems: q  q  q  q  q  q  q 

slower moving satellites less satellites needed simpler system design for many connections no hand-over needed higher latency, ca. 70 - 80 ms higher sending power needed special antennas for small footprints needed

Example: q  GPS (Global Positioning System)
