Block 3: Lecture 1!Wireless networks!Part 3: lecture 3!

Mobile networks!!

Last time?!•  WiFi!

–  Speed and ranges and channels!–  Specifications!–  DCF mechanisms!!

•  WiMax!

Ingredients 1: Mobile Phones, PDAs & Co.!

Ingredients 2: Antennas!

Ingredients 3: Infrastructure 1!

Ingredients 3: Infrastructure 2!

Switching units!

Data bases!Management!

Monitoring!

Ingredient 4: frequencies!

Test!

Mobile traffic!

Some facts (I)!1.  Global mobile data traffic grew 81 percent in 2013.!

–  From 820 petabytes/month in Dec 2012 to 1.5 exabytes/month in Dec. 2013!

!2.  Mobile traffic in 2013 was 18 times the traffic of the whole

Internet in 2000!–  In 2000 traffic in the Internet was 1 exabyte!

3.  Over half a billion (526 million) mobile devices and connections were added in 2013!–  The total number of mobile devices is now 7 billions!!

Some facts (II)!4.  In 2013 3% of the mobile connections are 4G. They generate

30% of the mobile traffic.!

5.  Mobile video traffic exceeds 50 percent of the total traffic.!–  It is expected that in 2018 video will represent 2/3 of the mobile

traffic.!!

6.  45 percent of total mobile data traffic was offloaded onto the fixed network through Wi-Fi or femtocell in 2013!

!

Access methods!

Access schemes!

OFDMA!

The access and multiplexing technique adopted in WiMaX and LTE-Advanced to achieve higher data rates:!

"1gpbs to non-mobile users and 100mbps to mobile users.!

.!

Cellular networks!

Cellular networks architectures!

Mobile Switching

Center

Public telephone network

Mobile Switching

Center

•  connects cells to wired tel. net.!•  manages call setup!

MSC •  covers geographical region!•  base station (BS) analogous

to 802.11 AP!•  mobile users attach to

network through BS!•  air-interface: physical and

link layer protocol between mobile and BS!

cell

wired network

2G (voice)!

BSC BTS

Base transceiver station (BTS)

Base station controller (BSC)

Mobile Switching Center (MSC)

Mobile subscribers

Base station system (BSS) MSC

Public telephone network

Gateway MSC

G

3G (voice + data)!

radio network controller

MSC

SGSN

Public telephone network

Gateway MSC

G

Serving GPRS Support Node (SGSN)

Gateway GPRS Support Node (GGSN)

Public Internet

GGSN

G Key insight: new cellular data!network operates in parallel !(except at edge) with existing !cellular voice network!v  voice network unchanged in core!v  data network operates in parallel!

radio network controller

MSC

SGSN

Public telephone network

Gateway MSC

G

Public Internet

GGSN

G

radio access network Universal Terrestrial Radio Access Network (UTRAN)

core network General Packet Radio Service

(GPRS) Core Network

public Internet

radio interface (WCDMA, HSPA)

3G architecture!

GSM!

GSM!Formerly: Groupe Spéciale Mobile (founded 1982)!Now: Global System for Mobile Communication!!Pan-European standard, today many providers all over the world use GSM (>220 countries in Asia, Africa, Europe, Australia, America)!–  more than 4,2 billion subscribers in more than 700 networks!–  more than 75% of all digital mobile phones use GSM! !

NL coverage!

KPN GSM coverage!

.!

Source: http://maps.mobileworldlive.com/ !

.!

Vodafone GSM coverage!

.!

GSM Components and Subsystems!

•  MS (mobile station)!•  BS (base station)!•  MSC (mobile switching center)!•  LR (location register)!

•  RSS (radio subsystem): covers all radio aspects!•  NSS (network and switching subsystem): call forwarding,

handover, switching!•  OSS (operation subsystem): management of the network!

Overview!

fixed network

BSC

BSC

MSC MSC

GMSC

OMC, EIR, AUC

VLR

HLR NSS with OSS

RSS

VLR

Slide from: Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2013

Elements and interfaces!

NSS

MS MS

BTS

BSC

GMSC

IWF

OMC

BTS

BSC

MSC MSC

Abis

Um

EIR

HLR

VLR VLR

A

BSS

PDN

ISDN, PSTN

RSS

radio cell

radio cell

MS

AUC OSS

signaling

O

Slide from: Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2013

possible radio coverage of the cell

idealized shape of the cell cell

GSM cellular network!

•  use of several carrier frequencies!•  not the same frequency in adjoining cells!•  cell sizes vary from some 100 m up to 35 km depending on user density,

geography, transceiver power etc.!•  hexagonal shape of cells is idealized (cells overlap, shapes depend on

geography)!•  if a mobile user changes cells handover of the connection to the neighbor cell!

Slide from: Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2013

Mobility in cellular nets!

Handling mobility in cellular networks!

•  home network: network of cellular provider you subscribe to!–  home location register (HLR): database in home network

containing permanent cell phone #, profile information (services, preferences, billing), information about current location (could be in another network)!

•  visited network: network in which mobile currently resides!–  visitor location register (VLR): database with entry for each user

currently in network!–  could be home network!

Handover decision!receive level

BTSold receive level

BTSnew

MS MS

HO_MARGIN

BTSold BTSnew

Slide from: Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2013

Public switched telephone network

mobile user

home Mobile

Switching Center

HLR home network

visited network

correspondent

Mobile Switching

Center

VLR

1 call routed !to home network!

2

home MSC consults HLR,!gets roaming number of!mobile in visited network!

3

home MSC sets up 2nd leg of call!to MSC in visited network!

4

MSC in visited network completes!call through base station to mobile!

GSM: indirect routing to mobile!

Mobile Switching

Center

VLR

old BSS new BSS

old routing

new routing

GSM: handoff with common MSC!•  handoff goal: route call via new base

station (without interruption)!!•  reasons for handoff:!

–  stronger signal to/from new BSS (continuing connectivity, less battery drain)!

–  load balance: free up channel in current BSS!

–  GSM doesn’t mandate why to perform handoff (policy), only how (mechanism)!

•  handoff initiated by old BSS!

Mobile Switching

Center

VLR

old BSS

1

3

2 4

5 6

7 8

new BSS

1. old BSS informs MSC of impending handoff, provides list of 1+ new BSSs !

2. MSC sets up path (allocates resources) to new BSS!

3. new BSS allocates radio channel for use by mobile!

4. new BSS signals MSC, old BSS: ready !5. old BSS tells mobile: perform handoff to new BSS!6. mobile, new BSS signal to activate new channel!7. mobile signals via new BSS to MSC: handoff

complete. MSC reroutes call!8 MSC-old-BSS resources released!!

GSM: handoff with common MSC!

Handover procedure!

HO access

BTSold BSCnew measurement result

BSCold

Link establishment

MSC MS measurement report

HO decision HO required

BTSnew

HO request

resource allocation ch. activation

ch. activation ack HO request ack HO command HO command HO command

HO complete HO complete clear command clear command

clear complete clear complete

Hard handover

Slide from: Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2013

home network

Home MSC

PSTN

correspondent

MSC anchor MSC

MSC MSC

(a) before handoff

•  anchor MSC: first MSC visited during call!

–  call remains routed through anchor MSC!

•  new MSCs add on to end of MSC chain as mobile moves to new MSC!

•  optional path minimization step to shorten multi-MSC chain!

GSM: handoff between MSC!

home network

Home MSC

PSTN

correspondent

MSC anchor MSC

MSC MSC

(b) after handoff

GSM: handoff between MSC!

•  anchor MSC: first MSC visited during call!

–  call remains routed through anchor MSC!

•  new MSCs add on to end of MSC chain as mobile moves to new MSC!

•  optional path minimization step to shorten multi-MSC chain!

Mobility summary!GSM element ! Comment on GSM element ! Mobile IP element!

Home system! Network to which mobile user’s permanent phone number belongs!

Home network!

Gateway Mobile Switching Center, or “home MSC”. Home Location Register (HLR)!

Home MSC: point of contact to obtain routable address of mobile user. HLR: database in home system containing permanent phone number, profile information, current location of mobile user, subscription information!

Home agent!

Visited System! Network other than home system where mobile user is currently residing!

Visited network!

Visited Mobile services Switching Center.!Visitor Location Record (VLR)!

Visited MSC: responsible for setting up calls to/from mobile nodes in cells associated with MSC. VLR: temporary database entry in visited system, containing subscription information for each visiting mobile user!

Foreign agent!

Mobile Station Roaming Number (MSRN), or “roaming number”!

Routable address for telephone call segment between home MSC and visited MSC, visible to neither the mobile nor the correspondent.!

Care-of-address!

Pause!

LTE!

Long Term Evolution!Initiated in 2004 by NTT DoCoMo, focus on enhancing the Universal Terrestrial Radio Access (UTRA) and optimizing 3GPP’s radio access architecture!•  LTE is not 4G – sometimes called 3.9G!

–  Does not fulfill all requirements for IMT advanced!!!•  Simplified network architecture: flat IP-based network replacing the

GPRS core, optimized for the IP-Multimedia Subsystem (IMS), no more circuit switching!

•  Much higher data throughput supported by multiple antennas!•  Much higher flexibility in terms of spectrum, bandwidth, data rates!•  Much lower RTT – good for interactive traffic and gaming!!

LTE advanced!•  Worldwide functionality & roaming •  Interworking with other radio access systems •  Enhanced peak data rates to support advanced services

and applications (100 Mbit/s for high and 1 Gbit/s for low mobility)

•  Relay Nodes to increase coverage •  100 MHz bandwidth (5x LTE with 20 MHz)

All IP core !•  The EPC - Evolved Packet Core!

•  Allows for subscriber tracking, mobility management, and session management in the network.!

EPC architecture!

SGW/PDNGW!The gateways (Serving GW and PDN GW) deal with the user plane. !!They transport the IP data traffic between the User Equipment (UE) and the external networks.!!SGW: point of interconnect between the radio side and the EPC!PDNGW: point of interconnect between the EPC and the external IP networks!

Offloading!

Offloading!Motivation: to reduce the load on the cellular network data can be offloaded to:!•  WiFi!•  Femtocells!

With the observation that:!29% of calls placed at home.!57% of mobile usage at home or at work.!

.!

WiFi offloading!Transparently move all user traffic to WiFi when they are in WiFi range!!1.  Network bypass!2.  Managed network bypass!3.  Integrated data offload!

Remember 802.11u?!

Cell sizes!Type Range Output power (W) Usage

Macro-cell 1km-70lm 20-60 Rural, highway Micro-cell 0.1km-1.0km 5-10 Urban, street Pico-cell In building 0.1-0.5 Enterprise

Femto-cell In room 0.02-0.1 Indoor, very high-rate coverage

The cell sizes decreases as the throughput demand and usage increase. !

.!

Support 2/6 users.!Price comparable to Wifi Access!

.!

LTE in action!

SURFnet!

Pilot project at the UU.

Literature!

Chapter 6 - Wireless and mobile networks!

Few slides were adapted from: Computer Networking: A Top Down Approach , 5th edition. Jim Kurose, Keith Ross Addison-Wesley, April 2009

Chapter 10 - Cellular Wireless Networks!

Chapter 4 - Telecommunication systems!

The end…. Or nearly.!

Fiber Day!•  Agenda and details to be found online:!•  https://www.os3.nl/2013-2014/courses/an/fiber_day_2014 "!

•  Be there at 10.30! Jaap van Ginkel will be accompanying you.!

Part1 summary!!Workings of TCP and UDP work, namely how congestion control work. Differences and effects of different TCP implementations, their scalability and performance.!UDP aggressive behavior needs to be ‘controlled’.!!Make your own TCP implementation.!!Improvement of switching speeds with cut-through switching techniques.!!Queuing mechanisms to aid QoS.!

Part2 summary!•  Traffic Engineering and MPLS.!

•  Physical layer and fiber optics workings, architecture and installation of an optical networks. This could be extended upon.!

•  Multiplexing techniques, advantages and disadvantages.!

•  Concept of routing will ‘fade’, moving down to Layer3 to Layer1/2.!

•  Circuits and packets. When to use what when. Know the traffic patters.!

•  Importance of reducing delays.!

•  Software Defined Networking.!

Part3 summary!•  Emergence of WiFi as the technology of choice for mobile

connections.!

•  MobileIP architecture shows the weakness of the current TCP model.!

•  Mobile demand increase requires understanding of handover, roaming and seamless transitions within networks.!

•  LTE offloading.!

Preparation for the exam!

The material page on the Wiki is the reference for the material.!!Exam is open book.!2.5 hours.!!See you Tuesday 27th.!10.30-13.00!!

@12.30 today!