Transcript Reverse Channel 1

Cellular Networks
Lecture 6
Paul Flynn
Cellular Telephony Architecture
Radio tower
PSTN
Telephone
Network
Mobile Switching
Center
Very Basic Cellular/PCS
Architecture
Public Switched
Telephone Network
Mobility
Database
Base Station
Controller
Mobile
Switching
Center
(MSC)
Radio Network
Base Station
(BS)
Mobile Station
Duplex Communication - FDD
• FDD: Frequency Division Duplex
Mobile
Terminal
M
Forward Channel
Reverse Channel
Base Station
B
Forward Channel and Reverse Channel use different frequency
bands
Access Methods
Frequency
Frequency
FDMA
Time
Time
Frequency
TDMA
CDMA
Time
Clusters
• A cluster is a group of cells
– No channels are reused within a cluster
A seven Cell Cluster
Example - Frequency Spectrum
Allocation in U.S. Cellular Radio
Service Forward Channel
Reverse Channel
991 992
…
1023
1
…
2
799
824-849 MHz
991 992
…
1023
1
2
…
799
869-894 MHz
Channel Number
Reverse Channel 1 <=N <= 799
991 <= N <= 1023
Center Frequency (MHz)
0.030N + 825.0
0.030(N-1023) + 825.0
Forward Channel 1 <=N <= 799
0.030N + 870.0
991 <= N <= 1023
0.030(N-1023) + 870.0
(Channels 800-990 are unused)
Channel bandwidth is 45 MHz
Frequency Reuse
• Only a small number of radio channel
frequencies were available for mobile
systems
– Therefore engineers had to find a way to reuse
radio channels to carry more than one
conversation at a time
– The solution the industry adopted was called
frequency reuse. Implemented by restructuring the
mobile telephone system architecture into the
cellular concept
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
Frequency Reuse
• Cells with the
same number
have the same
set of
frequencies
Frequency Reuse
Frequency Reuse using 7
frequencies allocations
f2
f7
f3
f7
f1
f6
f4
f6
f5
f2
f2
f7
f3
f7
f3
f1
f1
f6
f4
f6
f4
f5
f5
f2
f3
f1
f4
f5
f2
f7
f3
f1
f6
f4
f5
Each cell is generally 4 to 8 miles in diameter with a lower limit
around 2 miles.
Cell Splitting
• Allows urban centres to be split into as many
areas as necessary for acceptable service levels
in heavy-traffic regions, while larger, less
expensive cells can be used to cover remote
rural regions
Cellular Concept with Sectors
frequency re-use
base station
Hand-off
• The final obstacle
in the development
of the cellular
network involved
the problem
created when a
mobile subscriber
moved from one
cell to another
during a call
Looking to PCS from different
Angles
PSTN
(Telephone Network)
Internet
Wireless Access
Mobile Users
-Cell phone users
-Cordless phone users
Telecom People View
Mobile Users
-Laptop users
-Pocket PC users
-Mobile IP, DHCP enabled
computers
Data Networking People View
Telecom and Data Networking
Telecom Interest
- Voice Transmission
- Frequency Reuse
- Handoff
Management
-Location Tracking
-Roaming
-QoS
-GSM, CDMA,
Cordless Phones,
-GPRS, EDGE
Data Networking Interest
-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
Major Mobile Radio Standards
USA
Standard
Type
Year
Intro
Multiple
Access
Frequency
Band
(MHz)
Modulation
Channe
l
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
1994
TDMA
1850-1990
GMSK
200
1994
TDMA/FDMA
1850-1990
DQPSK
300
DCS-1900 PCS
(GSM)
PACS
Cordless/PC
S
Major Mobile Radio Standards Europe
Standard
Type
Year
Intro
Multiple
Access
Frequency
Band
(MHz)
Modulation
Channe
l
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
1993
TDMA
1710-1880
GMSK
200
DCS-1800 Cordless/PC
S
Example - Frequency Spectrum
Allocation in U.S. Cellular Radio
Service Forward Channel
Reverse Channel
991 992
…
1023
1
…
2
799
824-849 MHz
991 992
…
1023
1
2
…
799
869-894 MHz
Channel Number
Reverse Channel 1 <=N <= 799
991 <= N <= 1023
Center Frequency (MHz)
0.030N + 825.0
0.030(N-1023) + 825.0
Forward Channel 1 <=N <= 799
0.030N + 870.0
991 <= N <= 1023
0.030(N-1023) + 870.0
(Channels 800-990 are unused)
Channel bandwidth is 45 MHz
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
GSM Speech Signal Processing
GSM and CDMA Coverage Map
Worldwide
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
• 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
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:
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
WiMax Deployment