what is pcs personal communication services2 what is pcs personal communication services a wide...
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What is PCS
Personal Communication Services
A wide variety of network services that includes
wireless access and personal mobility services
Provided through a small terminal
Enables communication at any time, at any place,
and in any form.
The market for such services is tremendously
big
Think of cell-phone market
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Several PCS systems
High-tier Systems
GSM: Global System for Mobile Communications
The mobile telephony system that we are using
IS-136
USA digital cellular mobile telephony system
TDMA based multiple access
Personal Digital Cellular
IS-95 cdmaOne System
CDMA based multiple access
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Several PCS systems
Low-tier systems
Residential, business and public cordless access
applications and systems
Cordless Telephone 2 (CT2)
Digital Enhanced Cordless Telephone (DECT)
Personal Access Communication Systems (PACS)
Personal Handy Telephone System (PHS)
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Several PCS systems
Wideband wireless systems
For Internet access and multimedia transfer
Cdma2000
W-CDMA, proposed by Europe
SCDMA, proposed by Chine/Europe
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Several PCS systems
Other PCS Systems
Special data systems
CDPD: Cellular Digital Packet Data
RAM Mobile Data
Advanced Radio Data Information System (ARDIS)
Paging Systems
Mobile Satellite Systems
LEO, MEO, HEO satellites for data/voice
ISM band systems: Bluetooth, 802.11, etc.
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PCS Problems
How to integrate mobile and wireless users to
the Public Switched Telephone Network
(PSTN) (Voice Network) Cellular mobile telephony system
How to integrate mobile and wireless users to
the Internet (Data Network) Mobile IP, DHCP, Cellular IP
How to integrate all of them together and also
add multimedia services (3G Systems)
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Internet PSTN
(Telephone Network)
Looking to PCS from different
Angles
Mobile Users
-Cell phone users
-Cordless phone users
Mobile Users
-Laptop users
-Pocket PC users
-Mobile IP, DHCP enabled
computers
Wireless Access
Telecom People View Data Networking People View
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Telecom and Data Networking
-Radio Propagation
-Link Characteristics
-Error Models
-Wireless Medium
Access (MAC)
- Error Control
-Data Transmission
-Mobile IP (integrating
mobile hosts to
internet)
-Ad-hoc Networks
-TCP over Wireless
-Service Discovery
- Voice Transmission
- Frequency Reuse
- Handoff
Management
-Location Tracking
-Roaming
-QoS
-GSM, CDMA,
Cordless Phones,
-GPRS, EDGE
Telecom Interest Data Networking Interest
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Very Basic Cellular/PCS Architecture
Base Station
(BS) Mobile Station
Base Station
Controller
Mobility
Database
Mobile
Switching
Center
(MSC)
Radio Network
Public Switched
Telephone Network
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Wireless System Definitions
Mobile Station A station in the cellular radio service intended for use while
in motion at unspecified locations. They can be either hand-
held personal units (portables) or installed on vehicles
(mobiles)
Base station A fixed station in a mobile radio system used for radio
communication with the mobile stations. Base stations are
located at the center or edge of a coverage region. They
consists of radio channels and transmitter and receiver
antennas mounted on top of a tower.
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Wireless System Definitions
Mobile Switching Center Switching center which coordinates the routing of calls in a
large service area. In a cellular radio system, the MSC
connections the cellular base stations and the mobiles to
the PSTN (telephone network). It is also called Mobile
Telephone Switching Office (MTSO)
Subscriber A user who pays subscription charges for using a mobile
communication system
Transceiver A device capable of simultaneously transmitting and
receiving radio signals
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Wireless System Definitions
Control Channel Radio channel used for transmission of call setup, call
request, call initiation and other beacon and control
purposes.
Forward Channel Radio channel used for transmission of information from
the base station to the mobile
Reverse Channel Radio channel used for transmission of information from
mobile to base station
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Wireless System Definitions
Simplex Systems Communication systems which provide only one-way
communication
Half Duplex Systems Communication Systems which allow two-way
communication by using the same radio channel for both
transmission and reception. At any given time, the user can
either transmit or receive information.
Full Duplex Systems Communication systems which allow simultaneous two-way
communication. Transmission and reception is typically on
two different channels (FDD).
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Wireless System Definitions
Handoff The process of transferring a mobile station from one
channel or base station to an other.
Roamer A mobile station which operates in a service area (market)
other than that from which service has been subscribed.
Page A brief message which is broadcast over the entire service
area, usually in simulcast fashion by many base stations at
the same time.
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PCS Systems Classification
Cordless Telephones
Cellular Telephony (High-tier)
Wide Area Wireless Data Systems (High-tier)
High Speed Local and Personal Area Networks
Paging Messaging Systems
Satellite Based Mobile Systems
3G Systems
…
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Major Mobile Radio Standards - USA
Standard Type Year
Intro
Multiple
Access
Frequency
Band
(MHz)
Modulation Channel
BW
(KHz)
AMPS Cellular 1983 FDMA 824-894 FM 30
USDC Cellular 1991 TDMA 824-894 DQPSK 30
CDPD Cellular 1993 FH/Packet 824-894 GMSK 30
IS-95 Cellular/PCS 1993 CDMA 824-894
1800-2000
QPSK/BPSK 1250
FLEX Paging 1993 Simplex Several 4-FSK 15
DCS-1900
(GSM)
PCS 1994 TDMA 1850-1990 GMSK 200
PACS Cordless/PCS 1994 TDMA/FDMA 1850-1990 DQPSK 300
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Major Mobile Radio Standards - Europe
Standard Type Year
Intro
Multiple
Access
Frequency
Band
(MHz)
Modulation Channel
BW
(KHz)
ETACS Cellular 1985 FDMA 900 FM 25
NMT-900 Cellular 1986 FDMA 890-960 FM 12.5
GSM Cellular/PCS 1990 TDMA 890-960 GMSK 200KHz
C-450 Cellular 1985 FDMA 450-465 FM 20-10
ERMES Paging 1993 FDMA4 Several 4-FSK 25
CT2 Cordless 1989 FDMA 864-868 GFSK 100
DECT Cordless 1993 TDMA 1880-1900 GFSK 1728
DCS-1800 Cordless/PCS 1993 TDMA 1710-1880 GMSK 200
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Cordless Telephones
Characterized by Low mobility (in terms of range and speed)
Low power consumption
Two-way tetherless (wireless) voice communication
High circuit quality
Low cost equipment, small form factor and long talk-time
No handoffs between base units
Appeared as analog devices
Digital devices appeared later with CT2, DECT standards in Europe and ISM band technologies in USA
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Cordless Telephones
Usage
At homes
At public places where cordless phone base units are available
Design Choices
Few users per MHz
Few users per base unit Many base units are connected to only one handset
Large number of base units per usage area
Short transmission range
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Cordless Phone
Some more features
32 Kb/s adaptive differential pulse code
modulation (ADPCM) digital speech encoding
Tx power <= 10 mW
Low-complexity radio signal processing No forward error correction (FEC) or whatsoever.
Low transmission delay < 50ms
Simple Frequency Shift Modulation (FSK)
Time Division Duplex (TDD)
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Cellular Telephony
Characterized by
High mobility provision
Wide-range
Two-way tetherless voice communication
Handoff and roaming support
Integrated with sophisticated public switched
telephone network (PSTN)
High transmit power requires at the handsets
(~2W)
Wired connection
A Cellular Network
Public
Switched
Telephone
Network
(PSTN)
Mobile
Telephone
Switching
Center
(MTSC)
Base Transceiver Station (BTS) Mobile User
Cell 1
Cell 2
Cordless connection
HLR VLR
HLR = Home Location Register
VLR = Visitor Location Register
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Cellular System
Handoffs (typically 30 mseconds):
1. At any time, mobile station (MS) is in one cell and under the control of
a BS
2. When a MS leaves a cell, BS notices weak signal
3. BS asks surrounding BSs if they are getting a stronger signal
4. BS transfers ownership to one with strongest signal
5. MTSO assigns new channel to the MS and notifies MS of new boss
Public
Switched
Telephone
Network
(PSTN)
Mobile
Telephone
Switching
Center
(MTSC)
Cell 1
Cell 2
HLR VLR
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Cellular Telephony Systems
Mobile users and handsets
Very complex circuitry and design
Base stations
Provides gateway functionality between wireless
and wireline links
~1 million dollar
Mobile switching centers
Connect cellular system to the terrestrial
telephone network
Frequency Reuse
The concept of frequency reuse is based on
assigning to each cell a group of radio
channels used within a small geographic area Cells are assigned a group of channels that is completely different
from neighbouring cells
The coverage area of cells is called the footprint and is limited by a
boundary so that the same group of channels can be used in cells
that are far enough apart
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Frequency Reuse using 7
frequencies allocations
f4
f3 f2
f1 f6
f7
f5 f4
f3 f2
f1 f6
f7
f5
f4
f3 f2
f1 f6
f7
f5
f4
f3 f2
f1 f6
f7
f5
f4
f3 f2
f1 f6
f7
f5
Each cell is generally 4 to 8 miles (6 to 16 KM) in diameter with
a lower limit around 2 miles.
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Cellular Networks
First Generation Analog Systems
Analog Modulation, mostly FM
AMPS
Voice Traffic
FDMA/FDD multiple access
Second Generation (2G) Digital Systems
Digital Modulation
Voice Traffic
TDMA/FDD and CDMA/FDD multiple access
2.5G Digital Systems
Voice + Low-datarate Data
Third Generation Digital
Voice + High-datarate Data
Multimedia Transmission also
Cellular networks: From 1G to 3G
1G: First generation wireless cellular: Early 1980s Analog transmission, primarily speech: AMPS (Advanced
Mobile Phone Systems) and others
2G: Second generation wireless cellular: Late 1980s Digital transmission
Primarily speech and low bit-rate data (9.6 Kbps)
High-tier: GSM, IS-95 (CDMA), etc
Low-tier (PCS): Low-cost, low-power, low-mobility e.g. PACS
2.5G: 2G evolved to medium rate (< 100kbps) data
3G: future Broadband multimedia 144 kbps - 384 kbps for high-mobility, high coverage
2 Mbps for low-mobility and low coverage
Beyond 3G: research in 4G
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1G
(<1Kbps)
1 Kbps
10 Kbps
100 Kbps
2 Mbps
1 Mbps
Data Rates
1980 1990 2000 2010
2G
(9.6Kbps)
2.5G
(10-150Kbps)
3G
(144Kbps to 2Mbps)
Years
40
Wireless Network Evolution to 3rd Generation
Enabling Technologies
AMPS
GSM
IS-95
GPRS
CDMA-2000
1XRTT
EDGE
CDMA2000
3XRTT
(UMTS)
2.5G
3G
2G
2 Mbps
500 kbps
150 Kbps
100 Kbps
50 Kbps
10 Kbps
1999 2000 2001 2002 2003
TDMA Migration
1G-2G Migration
CDMA Migration
1980
1G
1 Kbps
W-CDMA
(UMTS)
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2G Technologies cdmaOne (IS-95) GSM, DCS-1900 IS-54/IS-136
PDC
Uplink Frequencies
(MHz)
824-849 (Cellular)
1850-1910 (US PCS)
890-915 MHz (Eurpe)
1850-1910 (US PCS)
800 MHz, 1500 Mhz
(Japan)
1850-1910 (US PCS)
Downlink Frequencies 869-894 MHz (US
Cellular)
1930-1990 MHz (US
PCS)
935-960 (Europa)
1930-1990 (US PCS)
869-894 MHz (Cellular)
1930-1990 (US PCS)
800 MHz, 1500 MHz
(Japan)
Deplexing FDD FDD FDD
Multiple Access CDMA TDMA TDMA
Modulation BPSK with Quadrature
Spreading
GMSK with BT=0.3 p/4 DQPSK
Carrier Seperation 1.25 MHz 200 KHz 30 KHz (IS-136)
(25 KHz PDC)
Channel Data Rate 1.2288 Mchips/sec 270.833 Kbps 48.6 Kbps (IS-136)
42 Kbps (PDC)
Voice Channels per
carrier
64 8 3
Speech Coding CELP at 13Kbps
EVRC at 8Kbps
RPE-LTP at 13 Kbps VSELP at 7.95 Kbps
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2G and Data
2G is developed for voice communications
You can send data over 2G channels by
using modem
Provides adat rates in the order of ~9.6 Kbps
Increased data rates are requires for internet
application
This requires evolution towards new systems:
2.5 G
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2.5 Technologies
Evolution of TDMA Systems
HSCSD for 2.5G GSM Up to 57.6 Kbps data-rate
GPRS for GSM and IS-136 Up to 171.2 Kbps data-rate
EDGE for 2.5G GSM and IS-136 Up to 384 Kbps data-rate
Evolution of CDMA Systems
IS-95B Up to 64 Kbps
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3G Systems
Goals
Voice and Data Transmission
Simultanous voice and data access
Multi-megabit Internet access
Interactive web sessions
Voice-activated calls
Multimedia Content
Live music
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3G Systems (Con’t)
Evolution of Systems CDMA sysystem evaolved to CDMA2000
CDMA2000-1xRTT: Upto 307 Kbps
CDMA2000-1xEV:
CDMA2000-1xEVDO: upto 2.4 Mbps
CDMA2000-1xEVDV: 144 Kbps datarate
GSM, IS-136 and PDC evolved to W-CDMA (Wideband CDMA) (also called UMTS)
Up to 2.048 Mbps data-rates
Future systems 8Mbps
Expected to be fully deployed by 2010-2015
New spectrum is allocated for these technologies
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Interest to 3G Applications
Western Eastern USA
Europe Europe
Emails 4.5 4.7 4.3
City maps/directions 4.3 4.2 4.2
Latest news 4.0 4.4 4.0
Authorize/enable payment 3.4 3.8 3.0
Banking/trading online 3.5 3.4 3.2
Downloading music 3.1 3.4 3.2
Shopping/reservation 3.0 3.1 2.9
Animated images 2.4 2.7 2.6
Chat rooms, forums 2.3 2.9 2.2
Interactive games 2.0 2.2 2.4
Games for money 1.8 1.8 1.8
(Means based upon a six-point interest scale, where 6 indicates high interest and 1 indicates low interest.)
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Upgrade Paths for 2G Technologies
IS-136
PDC GSM IS-95
IS-95B HSCSD
GPRS
EDGE
W-CDMA EDGE
TD-SCDMA
cdma200-1xRTT
cdma2000-1xEV,DV,DO
cdma200-3xRTT
2G
2.5G
3G
GSM Protocol Architecture
BSSMAP = BSS Mobile Application part
BTSM = BTS management
CM = Connection Management
LAPD = Link Access Protocol, D Channel
Base Transceiver
Station
Mobile
Station
Radio
LAPDm
RRM
Radio
LAPDm
RRM
MM
CM
64 Kbps
LAPD
BTSM
64 Kbps
MTP
SCCP
Base Station
Controller
64 Kbps
LAPD
BTSM
BSSMA
P
64Kbp
s
MTP
SCCP
MM
CM
BSSMA
P
Mobile Service
Switching Center
MM = Mobility Management
MTP = Message Transfer Part
RRM = Radio Resources Management
SCCP = Signal Connection Control Point
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Alternatives to 3G Cellular
Major technical undertaking with many organizational and marketing overtones.
Questions about the need for the additional investment for 3G (happy with 2.5G)
Wireless LAN in public places such as shopping malls and airports offer options
Other high-speed wireless-data solutions compete with 3G
Mobitex low data rates (nominally 8 Kbps), it uses a narrowband (2.5KHz) as compared to 30 KHz (GSM) and 5 MHz (3G).
Ricochet: 40 -128 kbps data rates. Bankruptcy
Flash-OFDM: 1.5 Mbps (upto 3 Mbps)
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4G Systems
Wireless networks with cellular data rates of 20
Mbits/second and beyond.
AT&T has began a two-phase upgrade of its wireless
network on the way to 4G Access.
Nortel developing developing features for Internet
protocol-based 4G networks
Alcatel, Ericsson, Nokia and Siemens found a new
Wireless World Research Forum (WWRF) for
research on wireless communications beyond 3G.
Many new technologies and techniques (multiplexing,
intelligent antennas, digital signal processing)
Industry response is mixed (some very critical)
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Engineering Issues
Steps in MTSO controlled call
TDMA design
CDMA design
Handoff
Power control
Traffic engineering
55
Steps in an MTSO Controlled
Call between Mobile Users Mobile unit initialization
Mobile-originated call
Paging
Call accepted
Ongoing call
Handoff
Call blocking
Call termination
Call drop
Calls to/from fixed and remote mobile subscriber
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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 (Vm):250 km/hr
Maximum coding delay: approx. 20 ms
Maximum delay spread (m): 10 s
Bandwidth: Not to exceed 200 kHz (25 kHz per channel)
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Mobile Wireless CDMA Design
Considerations
Soft Handoff – mobile station temporarily connected to more than one base station simultaneously
RAKE receiver – when multiple versions of a signal arrive more than one chip interval apart, RAKE receiver attempts to recover signals from multiple paths and combine them This method achieves better performance than simply
recovering dominant signal and treating remaining signals as noise
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What is WiMax?
Worldwide Interoperability for Microwave
Access
Last mile wireless broadband access
Alternative to cable and DSL
Deliver data, voice, video
Support hundreds to thousands of
homes/business
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Defined by IEEE as 802.16
Typical target environment:
Targets fixed, portable, and mobile
stations
Environments with and without line of
sight
Cell radius of 3-10 kilometers
Capacities of up to 40 Mbps per channel
Mobile network deployments of up to 15
Mbps, 3 km radius
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Builds on and
Extends WiFi Technology
Advantages of WiFi are:
Easy to deploy, unlicensed spectrum, low
cost
Supports (limited) mobility
But WiMax needs to address the
following:
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WiFi limitations Susceptible to interference
802.11 targets short-range indoor
operation (mostly)
Security is a concern
Limited level of mobility
WiMax is intended to complement WiFi
WiMax Forum: promotes WiMax and looks
after interoperability
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