mobile basics

7/28/2019 Mobile Basics

1/54

Mobile Communication Systems


2/54

Course Outline

Introduction Mobile communication systems issues, system

structure, safety

Wireless communication fundamentals

Propagation, Modulation and Coding, Frequencyreuse.

Intersystem Operation + Mobility Management

Location tracking and Paging, Handoff, Trunkingtheory.

Second Generation Cellular (2G) :

GSM


3/54

Outline

2.5G Cellular: Wireless Data Services

GPRS (General Packet Radio Service)

EDGE (Enhanced Data GSM Evolution)

3G Cellular: Structure, protocols and advance services

UMTS (Universal Mobile Telecom.Services)

Cdma 2000 1x EV-DO (Evolved DataOptimized)

Location Based Systems/Services


4/54

Mobile vs. Wireless Wireless Communication System:

Any electrical communication system that uses anaturally occurring communication channel, such as air,water, earth.

Mobile wireless communication systems focus

Communicate over the air via radio-waves

Support some form of user mobility


5/54

Wireless Issues

Wireless link implications

communications channelis the air

poor quality: fading, shadowing, weather, etc.

data rate and coverage vary

regulatedby governments

frequency allocated, licensing, etc.limited bandwidth

low bit rate, frequency planning and reuse, interference

power issues

Power levels regulated (safety issue), conserve mobile

terminal battery lifesecurity issues

wireless channel is a broadcastmedium!


6/54

Mobility Issues

Mobility Types

User mobility : user can access network while mobile

must handoff calls/connections in progress as user moves

track users as they move so they can receive info/calls

Service mobility: users services follow them

Need to have authentication and services follow user Degree of Mobility

Geographic range

ranges from a house/apartment to worldwide

Speed

ranges from stationary to bullet train cordless phone vs. cell phone

Mobility portable device


7/54

Device Issues

Mobile Device Issues

Portability

Device and accessories size and weight

Usability

User characteristics (size, dexterity, knowledge, etc.)

Environment characteristics (Temperature, degree of mobility,etc)

Device Characteristics

startup time

data integrity and security

cpu speed and memory size power supply

user interface (keypad, voice, etc.)

Functionality (standalone, network dependent)

Connectability (always, partial, never)


8/54

Mobile devices


9/54

Wireless Networks

Wireless Wide Area Networks (WWANs)

Cellular Networks :

GSM, cdmaone (IS-95), UMTS, cdma2000 EVDO

Satellite Networks:

Iridium, Globalstar, GPS, etc.

Wireless Metro Area Networks (WMANs)

IEEE 802.16 WiMAX

Wireless Local Area Networks (WLANs)

IEEE 802.11, a, b, g, etc. (infrastructure, ad hoc, sensor)

Wireless Personal Area Networks (WPANs)

IEEE 802.15 (Bluetooth), IrDa, Zigbee, etc.


10/54

Wireless Networks


11/54

Licensed vs. Unlicensed

Licensed Spectrum

need to buy right to use spectrum allocation in aspecific geographic location from the government

(e.g., AM/FM radio)

Prevents interference licensee can control signalquality

Unlicensed spectrum

Anyone can operate in the spectrum (e.g. ISM

band for WLANs) but must maintain proper behaviorin spectrum (max power level and frequencyleakage, etc.)

Can have interference problems


12/54

Mobile Phone Systems

Mobile phone systems

Support communication to mobile users via wirelessradio channel

Variety of systems and standards:

Analog 1G : NMT, AMPS, TACS

Digital 2G: GSM, IS-95b (cdmaone),

3G: UMTS, cdma 2000

Scope of services and coverage areas growing

SMS, MMS, laptop data, etc.

Focus now on wireless data and location awareservices


13/54

Trends in cellular systems

2G(second generation) is the current generation ofmobile phones, and includes such standards as GSM,TDMA and CDMA, which primarily transmit voice

over a circuit switched network. Data service is possiblesuch as SMS in GSM

2.5Gis a bridge between 2G and 3G. The term 2.5G(second and a half generation) describes systems thatprovide faster services than 2G, but not quite as fast or

advanced as newer 3G systems. 2.5G provides some ofthe benefits of 3G (i.e. it is packet-switched) and usessome of the existing 2G infrastructure.

GPRS is an example of a 2.5G cellular standard.


14/54


3G is the next (third) generation of mobile

telephony that will require a different

infrastructure than 2G. It is packet-switched(faster and more efficient) rather than circuit-

switched (slower and less efficient), and can

transmit both voice (telephone calls) and non-

voice data (such as email, video, and otherlarge files).


15/54


CDMA2000: CDMA2000 is an upgrade to the originalCDMA (Code Division Multiple Access) network and isan evolving standard with several phased

implementations. CDMA2000 1xhas the capability ofusing up to three separate 1.25 MHz channels for datatransmission.

EDGE (Enhanced Data Rates for GSM Evolution): EDGEuses the same TDMA (Time Division Multiple Access)

frame structure, logic channel and 200 kHz carrierbandwidth as todays GSM networks, which allowsexisting cell plans to remain intact. EDGE provides ashort-term upgrade path for GSM operators anddirectly competes with CDMA2000.


16/54

Migration to 3G3G2.75G

MultimediaIntermediateMultimedia2.5G

Packet Data2GDigital Voice1G

Analog VoiceGPRS W-CDMA

GSM(UMTS)EDGE

115 Kbps

NMT 9.6 Kbps 384 Kbps Up to 2 Mbps

GSM/TD-SCDMA

GPRSTDMA

(Overlay)2 Mbps?TACS 115 Kbps

9.6 Kbps

iDEN iDEN9.6 Kbps PDC (Overlay)

9.6 Kbps

AMPS cdma2000CDMA 1xRTTCDMA 1X-EV-DV

PHS14.4 Kbps Over 2.4 Mbps

(IP-Based) 144 Kbps/ 64 Kbps

64 KbpsPHS 2003 - 2004+2003+

2001+ Source: U.S. Bancorp Piper Jaffray1992 - 2000+1984 - 1996+


17/54

Future Generations

Other Tradeoffs:Rate Rate vs. Coverage

Rate vs. Delay4G

Rate vs. Cost802.11b WLAN 3G Rate vs. Energy

2G

2G Cellular

Mobility

Fundamental Design Breakthroughs Needed


18/54

Spectrum Regulation

PTA regulates the spectrum allocation inpaksitan

PTA auctions spectral blocks for set applications.

Some spectrum set aside for universal use

Worldwide spectrum controlled by ITU-R


19/54

Standards

Interacting systems require standardization

Companies want their systems adopted as

standard- Alternatively try for de-facto standards

Standards determined by TIA/CTIA in US -

IEEE standards often adopted- Process fraught with inefficiencies and conflicts

Worldwide standards determined by ITU-T

- In Europe, ETSI is equivalent of IEEE


20/54

Main Points

The wireless vision encompasses many exciting systemsand applications

Technical challenges transcend across all layers of thesystem design.

Cross-layer design emerging as a key theme in wireless.

Existing and emerging systems provide excellent qualityfor certain applications but poor interoperability.

Standards and spectral allocation heavily impact theevolution of wireless technology


21/54

Future Wireless Networks

Ubiquitous Communication Among People and DevicesWireless Internet access

Nth generation CellularWireless Ad Hoc Networks

Sensor NetworksWireless EntertainmentSmart Homes/SpacesAutomated HighwaysAll this and more

Hard Delay Constraints

Hard Energy Constraints


22/54

First-Generation Analog

Advanced Mobile Phone Service (AMPS)

In North America, two 25-MHz bands allocated to

AMPS

One for transmission from base to mobile unit

One for transmission from mobile unit to base

Each band split in two to encourage competition

Frequency reuse exploited


23/54

Frequency Division Multiple Access

Definition - FDMA is a multiple access

method in which users are assigned

specific frequency bands. The user hassole right of using the frequency band

for the entire call duration. (Qualcomm, 1997)


24/54

FDMA

Frequency Division Multiple Access

F

requency

Time

Chan A

Chan B

Chan C

Chan D


25/54

Differences Between First and

Second Generation Systems Digital traffic channelsfirst-generation systems are

almost purely analog; second-generation systems aredigital

Encryption

all second generation systems provideencryption to prevent eavesdropping

Error detection and correctionsecond-generationdigital traffic allows for detection and correction,

giving clear voice reception Channel accesssecond-generation systems allow

channels to be dynamically shared by a number ofusers


26/54

Time Division Multiple Access

Definition - TDMA is an assigned frequency

band shared among a few users. However,

each user is allowed to transmit in

predetermined time slots. Hence,channelization of users in the same band is

achieved through separation in time.(Qualcomm, 1997)


27/54

TDMA

Time Division Multiple Access

F

requency

Time

Chan A

Chan B


28/54

Mobile Wireless TDMA Design

Considerations Number of logical channels (number of time slots in

TDMA frame): 8

Maximum cell radius (R): 35 km

Frequency: region around 900 MHz Maximum vehicle speed (V

m):250 km/hr

Bandwidth: Not to exceed 200 kHz (25 kHz perchannel)


29/54

Paging & SMS

Evolution of Paging

Tone Boy, early 1960s

Tone-Voice, late 1960s

Digital Pagers, 1970s

Numeric Paging Systems

Alpha/Numeric Paging Systems


30/54

Paging

Larger coverage area in each site

Signal, Numeric, Alpha-numeric

Marketed by coverage area. Features--Web messaging, modem

messaging


31/54

Paging

Current Applications

Fax Forwarding

E-Mail Forwarding

Voice Mail Notification

Automated Problem Notification

Two-way Paging


32/54

Wireless Local Loop

Wired technologies responding to need for reliable,high-speed access by residential, business, andgovernment subscribers

ISDN, xDSL, cable modems

Increasing interest shown in competing wirelesstechnologies for subscriber access

Wireless local loop (WLL)

Narrowband

offers a replacement for existing telephonyservices

Broadbandprovides high-speed two-way voice and dataservice


33/54

WLL Configuration


34/54

Advantages of WLL over Wired

Approach Costwireless systems are less expensive due to cost

of cable installation thats avoided

Installation timeWLL systems can be installed in a

small fraction of the time required for a new wiredsystem

Selective installationradio units installed for

subscribers who want service at a given time

With a wired system, cable is laid out in anticipation of

serving every subscriber in a given area


35/54

Propagation Considerations for

WLL Most high-speed WLL schemes use millimeter wave

frequencies (10 GHz to about 300 GHz)

There are wide unused frequency bands available above 25

GHz At these high frequencies, wide channel bandwidths can be

used, providing high data rates

Small size transceivers and adaptive antenna arrays can be

used


36/54

Propagation Considerations for

WLL Millimeter wave systems have some

undesirable propagation characteristics

Free space loss increases with the square of the

frequency; losses are much higher in millimeterwave range

Above 10 GHz, attenuation effects due to rainfalland atmospheric or gaseous absorption are large

Multipath losses can be quite high


37/54

Atmospheric Absorption

Radio waves at frequencies above 10 GHz are

subject to molecular absorption

Peak of water vapor absorption at 22 GHz

Peak of oxygen absorption near 60 GHz

Favorable windows for communication:

From 28 GHz to 42 GHz

From 75 GHz to 95 GHz


38/54

Effect of Rain

Attenuation due to rain

Presence of raindrops can severely degrade the reliabilityand performance of communication links

The effect of rain depends on drop shape, drop size, rain

rate, and frequency

Estimated attenuation due to rain:

A = attenuation (dB/km)

R = rain rate (mm/hr)

a and b depend on drop sizes and frequency

baRA


39/54

Effects of Vegetation

Trees near subscriber sites can lead to multipath

fading

Multipath effects from the tree canopy are diffraction

and scattering Multipath effects highly variable due to wind


40/54

Multipoint Distribution Service

(MDS) Multichannel multipoint distribution service (MMDS)

Also referred to as wireless cable

Used mainly by residential subscribers and small

businesses Local multipoint distribution service (LMDS)

Appeals to larger companies with greater bandwidth

demands


41/54

Advantages of MMDS

MMDS signals have larger wavelengths andcan travel farther without losing significantpower

Equipment at lower frequencies is lessexpensive

MMDS signals don't get blocked as easily by

objects and are less susceptible to rainabsorption


42/54


43/54

802.16 Standards Development

Use wireless links with microwave or millimeter

wave radios

Use licensed spectrum

Are metropolitan in scale

Provide public network service to fee-paying

customers

Use point-to-multipoint architecture with stationaryrooftop or tower-mounted antennas


44/54

802.16 Standards Development

Provide efficient transport of heterogeneous traffic

supporting quality of service (QoS)

Use wireless links with microwave or millimeter

wave radios Are capable of broadband transmissions (>2 Mbps)


45/54

IEEE 802.16.1 Services

Digital audio/video multicast

Digital telephony

ATM

Internet protocol

Bridged LAN

Back-haul Frame relay


46/54

IEEE 802.16.3 Services

Voice transport

Data transport

Bridged LAN


47/54

LAN Extension

Wireless LAN linked into a wired LAN onsame premises

Wired LAN

Backbone Support servers and stationary workstations

Wireless LAN

Stations in large open areas

Manufacturing plants, stock exchange trading floors,and warehouses


48/54

Wireless LAN Applications

LAN Extension

Cross-building interconnect

Nomadic Access

Ad hoc networking


49/54

Ad Hoc Networking

Temporary peer-to-peer network set up to meet

immediate need

Example:

Group of employees with laptops convene for a

meeting; employees link computers in a temporary

network for duration of meeting


50/54

Wireless LAN Requirements

Throughput

Number of nodes

Connection to backbone LAN

Service area Battery power consumption

Transmission robustness and security

Collocated network operation

License-free operation

Handoff/roaming

Dynamic configuration


51/54

Sensor Networks

Specialized wireless networks to gather data from a specific system,usually no mobility of sensor nodes

APPLICATIONS:

Military, Environmental, Health, Home, Space Exploration,Chemical Processing

SENSOR TYPES:

Seismic, Low Sampling Rate Magnetic, Thermal, Visual,

Infrared, Acoustic, Radar

SENSOR TASKS:

Temperature, Humidity, Vehicular Movement, LightningCondition, Pressure, Soil Makeup, Noise Levels, Presence or

Absence of Certain Types of Objects, Mechanical StressLevels on Attached Objects, Current Characteristics (Speed,Direction, Size) of an Object .


52/54

Example Sensor Network


53/54


54/54

Applications of WPAN

mobile basics

Documents