Wireless Overview
76
JFS 10/11/00 JFS May, 2001 Wireless Overview John Skeffington, Sun Microsystems National Wireless Engineering Conference October 31, 2000 Cellular
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Here is an overview of Cellular Communications I gave back in 2001. It is slightly out of date, but has good info.
Transcript of Wireless Overview
JFS 10/11/00JFS May, 2001
Wireless Overview
John Skeffington, Sun Microsystems
National Wireless Engineering ConferenceOctober 31, 2000
Cellular
JFS 10/11/00JFS May, 2001
Agenda
• Historical Perspective • Building a Cellular System• Current Landscape• Future Landscape
JFS 10/11/00JFS May, 2001
Historical Perspective (US)
• Evolved from Two-way Radio Systems• Mobile Phone System (MTS)
– Operator Interaction Required– 15 - 25 Simultaneous Users on System
• Improved Mobile Phone System (IMTS)– Incorporated Direct Dial – Still in Service until Early 1990’s
• Advanced Mobile Phone Service (AMPS)– 1st Commercial Phone Call Placed in 1983
JFS 10/11/00JFS May, 2001
Definitions
• Wireless - Large coverage area, high mobility (pedestrian and automotive) usage.
• Cellular - A communications system where a small number of radio frequencies are carefully managed and re-used in a geographic area. – Full duplex, two frequencies used for each conversation
• PCS - Personal Communications System - A spectrum of frequencies allocated by the FCC for newer cellular type technologies.
JFS 10/11/00JFS May, 2001
Agenda
• Historical Perspective • Building a Cellular System• Current Landscape• Future Landscape
JFS 10/11/00JFS May, 2001
Pre Cellular ServicePre-Cellular Scenario - Metropolitan area using seven channels (14 frequencies): seven simultaneous calls
JFS 10/11/00JFS May, 2001
Basic Components
• Mobile Switch• Central Switching Office Building• Base Stations• Leased locations for Base Stations• Connections to Landline• Antennas, Cable, Towers, etc.• Mobile Phones• Customers
JFS 10/11/00JFS May, 2001
Basic Analog Cellular System
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
BillingSystem
JFS 10/11/00JFS May, 2001
Assumptions for “My Mobile”
• Mobile Switching Center in place• Base Station (BTS) equipment cost $250,000• Base Station Construction cost $200,000• BTS rental $1000 per month• One T1 line required per BTS, $1200 per month• Subscriber usage is 50 minutes per month• 5% of subscribers use system at any given time• BTS upgrade is $100,000 • Very simplistic financial estimating
JFS 10/11/00JFS May, 2001
My Mobile Service
3 BTS $3600/mon3 T1 $3000/mon21 simultaneous calls420 subscribers$0.31 per minute
3 BTS $ 750,000
BTS const $ 600,000
Total Capital $1,350,000
Three Cell System
JFS 10/11/00JFS May, 2001
Handoffs• Handoff: Major enabling technology that creates
mobile communications, transfer of call from one cell to another– First generation handoffs (AMPS)
– MSC initiated, mobile had “passive” role– MSC would query neighboring cells to determine when to
handoff based on received power getting lower.– “Intelligence” of handoffs contained to MSC
– Hard Handoff: “break before make” connection – Second generation handoff
– Mobile initiated, mobile has active role– Database assisted
– Soft Handoff: “make before break” connection
JFS 10/11/00JFS May, 2001
Basic Hard Handoff
A
B
C
• Caller is active in cell A
• Caller is driving on “blue” road
• System detects lower signal level in cell A as caller moves to edge
• System checks other cells to determine which has stronger signal
• Cell B is determined to be stronger signal
• System directs mobile to tune to Cell B frequency
JFS 10/11/00JFS May, 2001
Basic Hard Handoff
A
B
C
• Mobile tunes to cell B while still on call
• Call is now established in cell B
• System detects lower signal level in cell B as caller moves to edge
• System checks other cells to determine which has stronger signal
• Cell C is determined to be stronger signal
• System directs mobile to tune to Cell C frequency
JFS 10/11/00JFS May, 2001
Basic Hard Handoff
A
B
C
• Mobile tunes to cell C while still on call
• Call is now established in cell C
• System detects lower signal level in cell C as caller moves to edge
• System checks other cells to determine which has stronger signal
• Cell A is determined to be stronger signal
• System directs mobile to tune to Cell A frequency
JFS 10/11/00JFS May, 2001
My Mobile Service
1 MSC8 BTS $9600/mon8 T1 $8000/mon56 simultaneous calls1120 subscribers$0.31 per minute
5 BTS $1,250,000BTS const $1,000,000Total Capital $2,250,000
Eight Cell System
JFS 10/11/00JFS May, 2001
Definitions• Down Link, Forward Link - Radio connection from base
station to mobile• Up Link, Reverse Link - Radio connection from mobile
to base station• Channel: A physical (or logical) radio frequency(s)
– Traffic (voice) channel - A channel dedicated to voice usage– Control (overhead) channel - A channel dedicated to control
functions– Access Channel - Channel used for mobile to gain access to system (reverse
link)– Paging Channel - Channel used for messaging from system to mobiles
(forward link)
JFS 10/11/00JFS May, 2001
Forward / Reverse Links
Up Link
Down Link
Up Link
Down Link
0.6 watt portable3 watt portable
JFS 10/11/00JFS May, 2001
Power Control●System works best when all mobiles appear to be same power at base station●Mobility of mobiles requires power control to be dynamic●Base station tells mobiles whether to power up or down●Revisions made to original AMPS specs to allow additional (lower) power levels●CDMA power control happens every 20 msec
JFS 10/11/00JFS May, 2001
Why is Power Control Needed?●Many Mobiles, many Distances●Power Level Inversely Proportional to Square of Distance
● Mobile at One Mile = One Watt● Same Mobile at Two Miles = 1/4 Watt● Same Mobile at Three Miles = 1/9 Watt
1 2 3 4 5 6 7 8 9 100
0.5
1
1.5
2
2.5
3
3.5
4
4.5
distance
power
JFS 10/11/00JFS May, 2001
Where do I Place Sites?●Site Location Factors●Link Budget
● Method of estimating power levels anywhere within coverage
●Technical● Terrain and Clutter● Equally spaced “cell centers”
●Business● Lease cost● Acquisition and Construction cost
JFS 10/11/00JFS May, 2001
System Design Tools• Tools predict propagation
of radio signal based on link budget
• Creates many different output formats
Ideal Cell Locations
Predicted Signal Levels
JFS 10/11/00JFS May, 2001
System Manangement
JFS 10/11/00JFS May, 2001
28 Cell Cellular System1 MSC28 BTS $33600/mon28 T1 $28000/mon196 simultaneous calls3920 subscribers$0.31 per minute
20 BTS $5,000,000BTS const $4,000,000Total Capital $9,000,000
JFS 10/11/00JFS May, 2001
1
2
3
4
5
6
7 1
2
3
5
7
2
37
4
1
2
37
1
4
56
7
7
5
Frequency Re-useMetropolitan area using seven channels: 28 simultaneous calls. Seven cell re-use pattern, same frequency never closer than two cell radii.
6
Numbers represent frequency being usedHexagons represent cell coverage areasShading represents frequency grouping
JFS 10/11/00JFS May, 2001
High Usage Cells
1 MSC28 BTS $33600/mon28 T1 $28000/mon196 simultaneous calls3920 subscribers$0.31 per minute
High Usage Cells (hot spot) develops based on statistics from system
JFS 10/11/00JFS May, 2001
Increasing Capacity
●Omni-directional cell transmit equal power in all directions●Cells can be split into sectors using directional antennas●Requires additional BTS equipment●Very similar to multiple cells in same location●Careful frequency planning required●Most common is three sector, but six sectors have been implemented in many cities●Sectorizing and adding “voice channels” very profitable to equipment provider
Omni-directional cell
Sectorized cell
JFS 10/11/00JFS May, 2001
Capacity Increased1 MSC28 BTS $33600/mon34 T1 $34000/mon238 simultaneous calls4760 subscribers$0.28 per minute
3 BTS upgrades $300,000
JFS 10/11/00JFS May, 2001
System Monitoring
●28 base stations in service 24 x 7●System reports statistics every 10 minutes
● 40 items each base station ● 6,720 per hour, 161,280 per day
● Each T1 status reported● 168 per hour, 4,032 per day
●Lots of data to look at !
JFS 10/11/00JFS May, 2001
Additional Hot Spot1 MSC28 BTS $33600/mon34 T1 $34000/mon238 simultaneous calls4760 subscribers$0.28 per minute
JFS 10/11/00JFS May, 2001
More Capacity Needed1 MSC28 BTS $33600/mon40 T1 $40000/mon280 simultaneous calls5600 subscribers$0.26 per minute
3 BTS upgrades $300,000
JFS 10/11/00JFS May, 2001
Additional Capacity Added
1 MSC28 BTS $33,600/mon49 T1 $49,000/mon343 simultaneous calls6860 subscribers$0.24 per minute
3 BTS upgrades $300,000
JFS 10/11/00JFS May, 2001
Entire System Sectorized1 MSC28 BTS $33,600/mon93T1 $93,000/mon651 simultaneous calls13020 subscribers$0.19 per minute
22 BTS upgrades $2,200,000
JFS 10/11/00JFS May, 2001
Analog Cellular System
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiverSystem
Subscriber
Data Base
PSTN
BillingSystem
Voice MailSystem
Customer CareSystem
ProvisioningSystem
Connection to other networks
JFS 10/11/00JFS May, 2001
Network Sizing
MobileSwitching
CenterBase
TransceiverSystem
BaseTransceiver
System
BaseTransceiverSystem
Subscriber
Data Base
PSTN
BillingSystem
Voice MailSystem
Customer CareSystem
ProvisioningSystem
Connection to other networks
• Public Switched Telephone Network is at Center of Mobile Network
• Interconnect Between devices needs to be sized properly
JFS 10/11/00JFS May, 2001
Network Sizing
●Most networks sized for 2% blocking●Unit of measure for telco sizing
● Erlang● Equivalent to one phone call for 60 minutes● Used to size a path through the network● One Erlang:
– 1 - 1 hour call– 2 - 30 minute calls– 4 - 15 minute calls– 60 - 1 minute calls
JFS 10/11/00JFS May, 2001
First Generation Cellular●Advanced Mobile Phone System (AMPS)
● American Standard, 824 MHz – 894 MHz● Initially 666, Later Expanded to 832 Channels
● Split Between Two Carriers● A Carrier (non- wireline carrier)● B Carrier (wireline provider)
● 42 Control Channels (21 for each carrier)● First Commercial Cellular Phone Call Made in 1983● Designed as "Higher Power" (3 watt) Car Based System● Proprietary System for Infrastructure Vendors
JFS 10/11/00JFS May, 2001
Other First Generation
●Nine Incompatible Standards used in Europe ● Total Access Communication System (TACS) – UK● Nordic Mobile Telephone (NMT)
●Japanese Total Area Cellular System JTACS●Proprietary System for Infrastructure Vendors
JFS 10/11/00JFS May, 2001
Capacity Increases in 1 G Networks●Increase Spectrum
●Cell Splitting (requires careful frequency planning)
● Three Sector● Six Sector● Add Additional Cells
●Move to Digital Standard● Significant Improvement with similar Infrastructure
Investment
JFS 10/11/00JFS May, 2001
Generic Digital System
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
System
Subscriber
Data Base
PSTN
Internet
IWF
Base Station
Controller
Voice MailSystem
Customer CareSystem
ProvisioningSystem
Connection to other networks
JFS 10/11/00JFS May, 2001
Second Generation Systems●GSM – Global System for Mobile
● Channelized, 6 Time Slots / Channel● Time Division Multiple Access (TDMA) Based ● Most Widely Deployed, Most Predicted Growth● Common Digital Standard Across Europe, Africa, Middle East, US● SIM cards widely used● Defined Interfaces Between Infrastructure Elements
● Multiple Vendors Used in Same Network● First Commercial Service in 1991● Frequency Planning Crucial● Major Vendors: Ericcson, Nokia, Nortel, Motorola, Lucent
JFS 10/11/00JFS May, 2001
Second Generation Systems
●Time Division Multiple Access (TDMA)● Channelized, 3 Time Slots/Channel ● Primarily Deployed in US
● AT&T Wireless (Dual Band, Dual Mode Phones, IS-154)● SBC (Cellular One in Chicago, IS-54)● Some Markets Will be Transitioned to TDMA from CDMA due to mergers
● Frequency Planning Crucial● First Commercial Service in 1990● Typically One Infrastructure Vendor per Market● Major Vendors: Ericsson, Lucent
JFS 10/11/00JFS May, 2001
Second Generation Systems
●Code Division Multiple Access (CDMA)● Spread Spectrum Coded Transmission, Non Channelized● One Frequency for Entire System● Primarily Used in US, Canada, Australia, Korea and parts of
China● SprintPCS, Verizon, PrimeCo
● Typically One Infrastructure Vendor per Market (not per Carrier)
● Complex Power Control● First Commercial Service in Late 1995● Major Vendors: Nortel, Lucent, Motorola, Ericsson, Nokia
JFS 10/11/00JFS May, 2001
Mobile Call Origination FlowRegistration
Control and System Parameters
Dialed Digits
Traffic Channel Information
Access Request
Access Confirmation
Call Setup Information
Call Setup Information
Call Termination
Release Resources
Mobile Communication
System
Mobile Communication
s Device
Phone Call
JFS 10/11/00JFS May, 2001
Mobile Call Origination
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile to Land Call Flow Example
Mobile User Initiates Call
JFS 10/11/00JFS May, 2001
Mobile Call Origination
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile to Land Call Flow Example
JFS 10/11/00JFS May, 2001
Mobile Call Origination
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile to Land Call Flow Example
Validate Subscriber
JFS 10/11/00JFS May, 2001
Mobile Call Origination
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile to Land Call Flow Example
Valid Subscriber
JFS 10/11/00JFS May, 2001
Mobile Call Origination
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile to Land Call Flow Example
Phone Rings
JFS 10/11/00JFS May, 2001
Mobile Call Origination
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile to Land Call Flow Example
Phone Answered
JFS 10/11/00JFS May, 2001
Mobile Call Origination
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile to Land Call Flow Example
Call Established
JFS 10/11/00JFS May, 2001
Mobile Call Termination FlowRegistration
Control and System Parameters
Page Response
Page for Mobile
Call Setup Information
Call Setup Information
Call Termination
Release Resources
Mobile Communication
System
Phone Call
Mobile Communication
s Device
JFS 10/11/00JFS May, 2001
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile Call TerminationLand to Mobile Call
Flow Example
Land Line User Initiates Call
JFS 10/11/00JFS May, 2001
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile Call TerminationLand to Mobile Call
Flow Example
Validate Subscriber
JFS 10/11/00JFS May, 2001
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile Call TerminationLand to Mobile Call
Flow Example
Valid Subscriber
JFS 10/11/00JFS May, 2001
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile Call TerminationLand to Mobile Call
Flow Example
Page Mobile
JFS 10/11/00JFS May, 2001
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile Call TerminationLand to Mobile Call
Flow Example
Page Response
JFS 10/11/00JFS May, 2001
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile Call TerminationLand to Mobile Call
Flow Example
Page Response
Update SubscriberDatabase
JFS 10/11/00JFS May, 2001
MobileSwitching
Center
BaseTransceiver
System
BaseTransceiver
System
BaseTransceiver
SystemSubscriber
Data Base
PSTN
Mobile Call TerminationLand to Mobile Call
Flow Example
Page ResponseCall Established
JFS 10/11/00JFS May, 2001
Spectrum ComparisonAMPS
TDMA
GSM
CDMA
no time slots
3 time slots
8 time slots (6 voice, 2 control)
180 kHz
180 kHz
200 kHz
1.23 MHz
30 kHz
30 kHz
JFS 10/11/00JFS May, 2001
Comparison of Current Systems
AMPS GSM TDMA CDMA
Physical Channelsper Carrier 1 8 3 Variable
Channel Spacing(kHz) 30 200 30 1,230
Cellular Efficiency(conversations
/cell/MHz)2.3 5.0 – 6.6 7.0 12.1 – 45.1
CapacityCompared to
AMPS- 2.1 – 2.8 3 5.2 – 19.6
CapacityCompared to GSM - - 1 - 1.4 1.8 – 6.8
CapacityCompared to
TDMA- - - 1.7 – 6.4
Reference David J. Goodman, Wireless Personal Communications Systems, 1997 Addison Wesley Longman, Inc.
JFS 10/11/00JFS May, 2001
Agenda
• Historical Perspective
• Cellular Overview
• Current Landscape
• Future Landscape
JFS 10/11/00JFS May, 2001
Chicago Wireless Market
• Seven Carriers now in service– Cingular - TDMA (AMPS & IS-54)– Verizon - CDMA(AMPS, IS-95A/B, Jstd-8)– Nextel - TDMA based – PrimeCo - CDMA(Jstd-8)– Sprint PCS - CDMA (Jstd-8)– AT&T Wireless - TDMA(IS-136)– VoiceStream -GSM
JFS 10/11/00JFS May, 2001
Issues Facing Today’s Carriers• Network Sizing
– Coverage vs. Capacity– Quality of Service
• Hot Spots– Concentrated areas of usage– Special Events, Sporting Events, Trade Shows – Emergency Requirements
• E911
JFS 10/11/00JFS May, 2001
Network Sizing (14.4 kbps Terminals)
MobileSwitching
Center
BaseTransceiver
SystemBase
TransceiverSystem
BaseTransceiver
System
Subscriber
Data Base
PSTN
Internet
IWF
Base Station
Controller
2-3 Voice Channels per DS0
(64/3=21DS0)
64 Voice Channels
One T1 per 64Channel Base
Station
14.4 kbps
JFS 10/11/00JFS May, 2001
Current Situation
• Short Message Service (SMS)– Currently Deployed Across All Standards – 180 - 240 Characters per Message
• Wireless Internet Access– Wireless Application Protocol (WAP)– In Service now– Designed for Low Bandwidth– Compatibility Problems
JFS 10/11/00JFS May, 2001
Agenda
• Historical Perspective
• Cellular Overview
• Current Landscape
• Future Landscape
JFS 10/11/00JFS May, 2001
JFS 10/11/00JFS May, 2001
3G Challenges• Network Capacity
– Current Networks Sized to Provide 9.6 - 14.4 kbps– Future Networks to Provide 1+ Mbps– Capacity Planning (Where will it be needed?)– Ubiquitous Coverage (in-building, in-residence)– Cell Site Development Costs (alternatives to traditional cells?)
• Is 3G Viable - Auction Costs• What is 3G?
– Current Standards Define Technical Aspects– Is There a “Killer App”?
– Video (one and two way)?– Instant Messaging?
JFS 10/11/00JFS May, 2001
Evolving Wireless Standards
2G(up to 14.4 kbps)
2G+(up to 384 kbps)
3G(up to 2 mbps)
GSM
TDMA
CDMA
GPRS EDGE W-CDMA
IS-136+(64 kbps)
IS-95B(64 kbps)
IS-136HS
CDMA-2000
?
No Clear Winner - Yet!
1X-EV
JFS 10/11/00JFS May, 2001
A
Basic Soft/Softer Handoff
B
C
• Caller is driving on “blue” road• Caller is active in cell A sector 1
and cell B sector 3• Phone is constantly checking for
neighbor cells• Phone communicates with network
and adds sectors as they exceed power threshold
• Phone detects lower signal level in cell A S1 as caller moves to edge
• Cell A S1 is dropped from call• Cell B S2 is added to call
12
3
12
3
12
3
B
C
JFS 10/11/00JFS May, 2001
Basic Soft/Softer Handoff
C
• Caller is active in cell B sector 3 and cell B sector 2
• Phone is constantly checking for neighbor cells
• Phone detects cell C S1 as exceeding threshold, adds to call
• Phone detects lower signal level in cell B S3 as caller moves to edge
• Cell B S3 is dropped from call
12
3
12
3
12
3
A
B
C
JFS 10/11/00JFS May, 2001
Basic Soft/Softer Handoff
C
12
3
12
3
12
3
A
B
C
• Caller is active in cell B sector 2 and cell C sector 1
• Phone is constantly checking for neighbor cells
• Phone detects cell C sector 2 as exceeding threshold, adds to call
• Phone detects lower signal level in cell B sector 2 as caller moves to edge, cell B sector 3 is dropped from call
• Phone detects cell C sector 3 as exceeding threshold, adds to call
JFS 10/11/00JFS May, 2001
B
C
• Caller is active in cell C sectors 1, 2 and 3 - softer handoff
• Phone is constantly checking for neighbor cells
• Phone detects lower signal level in cell C sector 1 as caller moves to edge, cell C sector 1 is dropped from call
• Phone detects cell A sector 2 as exceeding threshold, adds to call
• Phone detects lower signal level in cell C sector 2,cell C sector 2 is dropped from call
Basic Soft/Softer Handoff
12
3
12
3
12
3
A
B
C
JFS 10/11/00JFS May, 2001
B
C
12
3
12
3
12
3
A
B
C
• Caller is active in cell C sector 3 and cell A sector 2
• Phone is constantly checking for neighbor cells
• Phone detects lower signal level in cell C sector 3 as caller moves to edge, cell C sector 3 is dropped from call
• Phone detects cell A sector 3 as exceeding threshold, adds to call
• Phone detects cell A sector 1 as exceeding threshold, adds to call
Basic Soft/Softer Handoff
JFS 10/11/00JFS May, 2001
B
C
12
3
12
3
12
3
A
B
C
• Caller is active in cell A sectors 1, 2 and 3 - softer handoff
• Phone is constantly checking for neighbor cells
• Phone detects lower signal level in cell A sector 2 as caller moves to edge, cell A sector 2 is dropped from call
Basic Soft/Softer Handoff
JFS 10/11/00JFS May, 2001
B
C
12
3
12
3
12
3
A
B
C
Basic Soft/Softer Handoff• Caller is active in cell A sectors 1
and 3 - softer handoff• Phone is constantly checking for
neighbor cell
