Wireless and Mobile Communication
FCS, KNR, AJ, ZZA, MJH
CHAPTER 1
INTRODUCTION TO CELLULAR SYSTEMS
Contents
•
•
•
•
•
Evolution of Mobile Radio Communication
Mobile Radio Systems Around the World
Examples of Wireless Communication Systems
Modern Wireless Communication Systems
Wireless LAN, MAN, PAN
Wireless communication system
Why Wireless?
• Freedom from wire
• No Bunch of wire running
• No cost of installation of wire
• Global Coverage
• Stay connected
• Roaming allows flexibility to stay connected
anywhere and anytime
• Rapidly growing market attests to public to need for
mobility and uninterrupted access
• Flexibility
• Connect to multiple device simultaneously
• Services can be reaches you whenever you go
(mobility)
Advantages and disadvantages of
Wireless Communication
The electronics boom
Figure 1.1 The growth of mobile telephony as compared with other popular inventions of the 20th century.
Examples of Mobile Radio Systems
● Paging Systems
● CordlessTelephones
● Cellular Telephony
● Ad hoc Network
● Sensor Network
● Wireless PAN, LAN, MAN
● Satellite Based Mobile Systems
Paging System
Cordless Telephone System
Cellular System
Ad hoc Network
A local network with wireless or temporary plug-in connection, in
which mobile or portable devices are part of the network only while
they are in close proximity.
Sensor Network
A large number of tiny immobile sensors are planted on an ad hoc basis to sense and
transmit some physical characteristics of the environment.
Wireless PAN, LAN, MAN
Satellite Based Mobile Systems
Evolution of Mobile Radio Communication
• 1897: Marconi initiated wireless telegraph.
• Wireless Communication can be classified into three eras:
•
•
•
Pioneer Era (Till 1920)
Pre Cellular Era (1920-1979)
Cellular Era (beyond 1979)
• 1946: First commercial mobile telephone system was
launched by BELL in St. Louis, USA.
• Few lucky customers got the services. Early mobile systems
used single high power transmitters with analog FM
techniques to give coverage up to about 50 miles and hence
only limited customers could get the service due to this
severe constraints of bandwidth.
Cellular Era (1979 onwards)
• To overcome the constraints of bandwidth scarcity and to
give coverage to larger sections, BELL lab introduced the
principle of Cellular concept.
• By frequency reuse technique this method delivered better
coverage, better utility of available frequency spectrum and
reduced transmitter power.
• But the established calls are to be handed over between
base stations while the phones are on move.
• Even though the US based BELL lab introduced the cellular
principle, the Nordic countries were the first to introduce
cellular services for commercial use with the introduction of
the Nordic Mobile Telephone (NMT) in 1981.
• NTT (Nippon Telephone & Telegraph) introduces the first
cellular system in Japan in 1979.
• AMPS (advanced mobile phone service) introduced by AT&T
in North America in 1984.
Traditional mobile telephone
system
◼
A base station provides coverage (communication
capabilities) to users on mobile phones within its coverage
area.
◼
Users outside the coverage area receive/transmit signals
with too low amplitude for reliable communications.
◼
Users within the coverage area transmit and receive signals
from the base station.
◼
The base station itself is connected to the wired
telephone network.
First Mobile Telephone
System
One and only one
high power base
station with which all
users communicate.
Normal
Telephone
System
Entire Coverage
Area
Wired connection
Circular Coverage Areas
◼
Original cellular system was developed assuming
base station antennas are omnidirectional, i.e., they
transmit in all directions equally.
Users located outside
some distance to the
base station receive
weak signals.
Result: base station has
circular coverage
area.
Problem with Original Design
◼
Original mobile telephone system could only support a
handful of users at a time…over an entire city!
◼
With only one high power base station (BS), users
phones also needed to be able to transmit at high
powers (to reliably transmit signals to the distant base
station).
◼
Car phones were therefore much more feasible than
handheld phones, e.g., police car phones.
Improved Design (Cellular)
◼
Over the next few decades, researchers at AT&T
Bell Labs developed the core ideas for today’s
cellular systems.
◼
Although these core ideas existed since the 60’s, it
was not until the 80’s that electronic equipment
became available to realize a cellular system.
◼
In the mid 80’s the first generation of cellular
systems was developed and deployed.
Cellular Concept
◼
Why not a large radio tower and large service area?
–
Number of simultaneous users would be very
limited
(to total number of traffic channels T)
–
Mobile handset would have greater power
requirement
Cellular Concept
◼
Cellular concept - small cells with frequency reuse
– Advantages
• lower power handsets
• Increases system capacity with frequency reuse
– Drawbacks:
• Cost of cells
• Handoffs between cells must be supported
• Need to track user to route incoming call/message
Cellular Concept
◼
Offers very high capacity in a limited spectrum allocation
◼
Replace a single high power tx (larger cell) to many low
power tx (small cells)
◼
Neighbouring base stations are assigned different
groups of channel so that the interference between base
stations is minimised
◼
Provide additional radio capacity with no additional
increase in radio spectrum
Cellular system infrastructure
Reverse Link
Forward Link
Terminology
● Mobile Station (MS)
●
●
A station in the cellular radio service intended for use while in motion.
●
Can be either hand-held personal units (portables) or installed on vehicles (mobiles).
Base Transceiver System (BTS) / (BS)
●
A fixed station in a mobile radio system used for radio communication with the MS.
●
Located at the center or edge of a coverage region.
●
Consists of radio channels and transmitter and receiver antennas on top of tower.
●
Both tower and antenna are a part of the BTS, while all associated
electronics are contained in the Base Station Controller (BSC).
●
Mobile Switching Center (MSC)
●
Coordinates the routing of calls in a large service area.
●
Connects the cellular base stations and the mobiles to the PSTN.
●
Also called Mobile Telephone Switching Office (MTSO)
• Home location register (HLR) and visitor location
register (VLR)
•
•
•
two sets of pointers that support mobility and enable the use of
the same telephone numbers worldwide.
HLR is located at the MSC where the MS is registered and where
the initial home location for billing and access information is
maintained.
• any incoming call, based on the called number, is directed
to HLR of the home MSC and then HLR redirects the call to
the MSC (and the BS) where the MS is currently located.
VLR basically contains information about all visiting MSs in that
particular MSC area.
Simplex channels between BS and MS
• Four simplex channels are needed to exchange
synchronization and data between BS and MS.
• The control links are used to exchange control
messages (such as authentication, subscriber
information, call parameter negotiations)
between the BS and MS
• Traffic (or information) channels are used to
transfer actual data between the two.
• The channels from BS to MS are known as
forward channels (or downlinks),
• Reverse channels (uplinks) is used for
communication from MS to BS.
• Control information needs to be exchanged
before actual data information transfer can
take place.
Handshake steps for call setup using
control channels
• Control channels are used for a short
duration for exchanging control
information between BS and each MS
needing any service.
• Therefore, all MSs use just a few
control channels to achieve this and
hence have to compete for such access
in shared mode.
• On the other hand, traffic channels are
exclusively allocated to each MS by the BS,
and a large number of channels are used
for the traffic.
• Therefore, handing of control and traffic
channels must be considered in different
ways.
Example 1
1. State problems of the traditional mobile telephony
system?
2. How cellular concept solves the problem of capacity
in the traditional mobile telephone system?
3. Give advantages and disadvantages of cellular
concept?
4. What is reverse channel and forward channel?
5. Draw the architecture of cellular telephony system?
Evolutions of Mobile Communication
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
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
Major Mobile Radio Standards – Japan
Evolution of Mobile Technologies
48
Comparison
www.gsmarena.com
Modern Wireless Communication
System
https://www.internetadvisor.com/smartphone-statistics