Advance Computer Networks
Wireless Communication
Why Wireless Communication?
Question: Why do we need a new technology
when we have such a developed public
telephone network.
Answer: Mobility.
Confinement Versus Freedom
2
Challenges of Mobility
Challenges of using a radio channel:
 The use of radio channels necessitates methods of sharing them – channel
access. (FDMA, TDMA, CDMA)
 The wireless channel – poses a more challenging problem than with wires.
Bandwidth: it is possible to add wires but not bandwidth. So it is important to
develop technologies that provide for spectrum reuse.
Privacy and security - a more difficult issue than with wired phone.
Others: low energy (battery), hand off, roaming, etc.
3
First Generation Systems
 Cellular concept emerges in early 1970s.
 Cellular technology allows frequencyreuse. With this we need to have Handoff
(handover)
 In 1G we had analog voice but Control
Link was digital
4
Examples of First Generation
Cellular Systems (FDMA based)
1)
Advanced Mobile Phone System (AMPS)
2)
Narrowband AMPS (NAMPS)
3)
Nordic Mobile Telephone (NAMPS)
4)
European Total Access System (ETACS)
5)
Japanese TACS (JTACS)
6)
Nippon Telephone and Telegram (NTT)
7)
Cordless Telephone 2 (CT2)
5
First Generation – AMPS and
European Total Access Cellular
System (ETACS)
Parameter
AMPS
ETACS
Multiple Access
FDMA
FDMA
Duplexing
FDD
FDD
Channel Bandwidth
30kHz
25kHz
Traffic Channel per RF Channel
1
1
Reverse Channel Frequency
824 – 849 MHz
890 – 915 MHz
Forward Channel Frequency
869 – 894 MHz
935 – 960 MHz
Voice Modulation
FM
FM
Peak Deviation: Voice Channels
Control/Wideband Data
± 12 kHz
± 8 kHz
± 10 kHz
± 6.4 kHz
Channel Coding for Data
Transmission
BCH(40,28) on FC/BCH(48,36) on
RC
BCH(40,28) on FC/BCH(48,36) on
RC
Data Rate on Control channel
10kbps
8kbps
Spectral Efficiency
0.33 bps/Hz
0.33 bps/Hz
Number of Channels
832
1000
6
Digital Communication: Transmitter
From Other
Channels
1010010
Analog
input
Analog to
Digital
Converter
Bits
10110
Source
Encode
01101
Multiplex
Encrypt
Encoded
Bits
Encrypted
Data
01101
Multiplexe
01010
d Data
10101
Digital Bandpass
waveform
Pulse
modulated
waveform
Bandpass
modulate
Bit to Sym.
& Pulse
Modulate
Channel
Encoded
Data
Scrambled
data
Channel
Encode
100110
1
Scrambler
10001
7
Digital Communication:
Receiver
Digital
Bandpass
waveform
Digital
Baseband
waveform
De-modulate
Bits
Equalizer,
Timing
and Sym.
to Bits
Channel
Decode
Channel
Decoded
Data
01101
Descramble
Descrambled
10001
Bits
Source
Decoded
Bits
Analog
output
D/A
101001
0
Demultiplexe
d Bits
Decrypted
Bits
Source
Decode
Decrypt
10110
DeMultiplex
To other
Channels
8
Performance Metrics
• Analog Communication Systems
^ m(t)m(t)
– Metric is fidelity: want
– SNR typically used as performance metric
• Digital Communication Systems
^ are data rate (R bps) and probability of
– Metrics
bit error (Pb=p(bb))
– Symbols already known at the receiver
– Without noise/distortion/sync. problem, we
will never make bit errors
9
Second Generation Cellular
Systems (TDMA and CDMA
based)
1)
GSM (Global System for Mobile)
2)
PDC (Personal Digital Cellular)
3)
PHS (Personal Handy System)
4)
DAMPS (Digital AMPS)
5)
CDMAone (IS-95)
6)
Personal Communication System (PCS)-1900 (IS-136)
10
Second Generation –
IS136/CDMA/GSM
Parameter
IS-136
IS-95
GSM
Multiple Access
TDMA/FDD
CDMA/FDD
TDMA/FDD
Modulation
π/4 DQPSK
BPSK
GMSK
Channel Bandwidth
30 kHz
1.25 MHz
200 kHz
Reverse Channel
Frequency Band
824 – 849 MHz
1.85 – 1.99 GHz
824 – 849 MHz
1.85 – 1.99 GHz
890 – 915 MHz
1.85 – 1.99 GHz
Forward Channel
Frequency Band
869 – 894 MHz
1.85 – 1.99 GHz
869 – 894 MHz
1.85 – 1.99 GHz
935 – 960 MHz
1.85 – 1.99 GHz
Channel Data Rate
48.6 kbps
1.2288 Mcps
270.83 kbps
Carrier Spacing
30 kHz
1.25 MHz
200 KHz
Speech Coding
VSELP(Vector Sum
excited linear prediction)
CELP
RPE-LTP
Users per carrier
3
variable
8
11
Second Generation –Benefits
Higher Capacity, Mobility
Easy frequency planning
-Dynamic Channel Allocation
(GSM)
-Single Frequency Band
(CDMA)
Better performance
-Low dropped call rate
-Faster switching
MAHO (Soft Handoff in CDMA)
Error correction
-FEC
-Interleaving
Value-added Services
-SMS
-Limited data transmission
capabilities
12
Second Generation - Success
Four operational digital cellular technology: Dec’ 2000
Source: EMC Database
13
Evolution to 2.5G Mobile Radio
Networks (data-centric)
1. High speed circuit switched data (HSCSD): GSM
2.
GPRS for 2.5G GSM and IS-136
3.
EDGE for 2.5G GSM and IS-136
4.
IS95B and CDMA2000 1x
14
General Packet Radio Service (GPRS)
15
Enhanced Data for Global Evolution (EDGE)
• EDGE uses 8PSK as opposed to GMSK as a
modulation scheme. Essentially squeezing in more
data in the available bandwidth.
• Data rates closer to 3G. Intended to be used by
operators who don’t have a 3G license but wish to
deliver higher data rates.
• Requires all the radio cards in the existing
GSM/GPRS network to be replaced.
• Expensive solution to obtain similar data rates to
the lowest expected 3G performance.
• Raw data rate using one GSM carrier can go up to
547.2 kbps (practical 384 kbps)
16
IS 95 B and CDMA2000 1x
•
•
•
•
•
The 2.5 G Evolution of IS95 A.
Uses extra codes for increased data rates
Data Rates upto 115.2 kbps
Easy upgrade to CDMA2000
Intermediate steps to 3G:
– CDMA2000 1x, Release 0: Data rates of up to
153.6kbps
– CDMA2000 1x, Release A: Data rates of up to
307.2 kbps
17
IMT-2000 (3G)
• The International Telecommunications Union (ITU)
defined the key requirements for International
Mobile Telecommunications 2000 (IMT-2000) services.
• These requirements were that the system should support
data rates of:
• 2 Mbps in fixed or in-building environments
• 384 kbps in pedestrian or urban environments
•144 kbps in wide area mobile environments
• IMT-2000 is more commonly known as… 3G.
18
Migration Path
2000
Japa
n
PDC
Europe
GSM
2001
2002
2003
W-CDMA
GPRS
EDGE
HSCSD
Americ
a
AMPS/D-AMPS
IS-95A
2G
System
3G
System
D-AMPS
IS-95B
CDMA2000
Easy upgrade
Upgrade requiring new modulation
Upgrade requiring entire new radio system
19
Universal Frequency Reuse
Frequency
Reuse Factor = 7 for AMPS
CDMA Universal
Frequency Reuse
CC
BB
C
B
GG
A
G
DD
AA
D
EE
FF
E
C
F
B
D
A
G
A
E
F
Frequency Reuse Factor = 4
for TDMA systems
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
20
CDMA2000
• Evolution of 1x RTT concept
• High data rate service which is compatible
to IS 95
• 1x EVDO: Evolution of the 1x system data
optimized
• As in 1x-RTT technology utilizes 1.25 MHz
of band
• System requires a separate carrier for the
data
• 2.4 Mbps forward link, 153.3 kbps reverse
link
• Rev. A: Support for VoIP: 3.1 Mbps FL, 1.8
Mbps RL
• New revisions: B and other enhancement
21
3G W-CDMA (UMTS)
• High-Speed Downlink Packet Access (HSDPA)
• HSUPA and HSPA, HSPA+ Phase 1 and 2
22
TD-SCDMA
23
Timeline: For UMTS and
CDMA2000
24
5) Wireless Local Loop
25
WIRELESS LOCAL LOOP
• Definition: A telephone system where subscribers are
connected to the public switched telephone network
using radio signals rather than copper wire for part or all
of the communication between the subscriber and the
switch.
• Countries with available elaborate telecommunication
infrastructure used it to increase competition
• Countries without available elaborate
telecommunication infrastructure use it for efficient and
feasible method of broadband delivery
26
Some Countries using CDMA for
WLL
Algeria, Azerbaijan, Bermuda, Brazil,
Cambodia, China, Columbia, Dem. Rep. of
Congo,Dominican Republic, Egypt,
Ethiopia, Fiji, Guatemala, Haiti, India,
Indonesia
Kenya, Kuwait, Laos, Malaysia, Mauritius,
Mexico, Moldova, Nepal, Nigeria,
Pakistan, Poland, Puerto Rico, Romania,
Russia, Uganda, Ukraine,Vietnam,Yemen
27
6) Other Systems
28
WIRELESS LOCAL AREA NETWORKS
(WLANs)
• Network- group of two or more computer
systems linked together. Local area networks
are usually confined to one building.
• Wireless Fidelity (Wi-Fi)
– 802.11a (DS-SS) became standard (2Mpbs).
– 802.11b is common (11Mbps) 2.4 GHz. Also has the
FH-SS extension.
– 802.11g also uses the 2.4 GHz band. Data Rate: 54
Mbps. Uses OFDM
– 802.11n: Uses OFDM and MIMO
29
Other Standards
• Long Term Evolution
– Initial Deployment in the 700 MHz Frequency Band
– Data Rate of tens of Mbps
– Uses OFDM and MIMO
• Worldwide Interoperability for Microwave Access
(WiMax)
– Operate in the 2.5, 3.5, or 5.8 GHz bands.
– Data Rates of tens of Mbps.
– Versions: IEEE 802.16d and e with amendments like:
802.16f, g, h, i, j and k
– Uses OFDM and MIMO
• Variants of both are candidates for IMT-Advanced (4G)
30
7) IMT-Advanced(4G)
31
IMT-Advanced (4G)
• The min requirements for peak spectral efficiencies
– Downlink peak spectral efficiency is 15 bit/s/Hz
– Uplink peak spectral efficiency is 6.75 bit/s/Hz.
• Six Proposals are under review
• Some are based on WiMax 802.16m and some on LTE
• Both uses OFDM and MIMO
• Final Decision by October 2010
32
IMT-Advanced (4G): Time-Line
WP 5D
meetings
2008
No.1
(0)
No.2
2009
No.3
No.4
2010
No.5
No.6
No.7
No.8
2011
No.9
No.10
Step1 and 2
(20 months)
Step 3
(8 months)
(1)
Step 4
(16 months)
Steps 5,6 and 7
(20 months)
(2)
(3)
Steps 8
(12 months)
(4)
Steps in radio interface development process:
Step 1: Issuance of the circular letter
Step 2: Development of candidate RITs and SRITs
Step 3: Submission/Reception of the RIT and SRIT proposals
and acknowledgement of receipt
Step 4: Evaluation of candidate RITs and SRITs
by evaluation groups
Step 5: Review and coordination of outside evaluation activities
Step 6: Review to assess compliance with minimum requirements
Step 7: Consideration of evaluation results, consensus building
and decision
Step 8: Development of radio interface Recommendation(s)
Critical milestones in radio interface development process:
(0): Issue an invitation to propose RITs
(1): ITU proposed cut off for submission
of candidate RIT and SRIT proposals
March 2008
October 2009
(2): Cut off for evaluation report to ITU
June 2010
(3): WP 5D decides framework and key
October 2010
characteristics of IMT-Advanced RITs and SRITs
(4): WP 5D completes development of radio
February 2011
interface specification Recommendations
IMT-Advanced A2-01
Cellular Technology Roadmap
34
8) Wireless Operators in Pakistan
35
Cellular Operators in Pakistan
1) Mobilink
Technology: GSM, GPRS, EDGE (WiMAx deployment:
Infinity)
2) Ufone
Technology: GSM, GPRS, EDGE
3) China Mobile Pakistan (CMPak, Paktel): Zong
Technology: EGSM, GPRS, EDGE
4) Warid
Technology: GSM, GPRS, EDGE (Associated company
Wateen: WiMax)
5) Telenor
Technology: GSM, GPRS, EDGE
36
WLL Operators
1) V-PTCLWirless
Technology: CDMA2000, EVDO Rev. A
2) TeleCard
Technology: CDMA2000
3) WorldCall
Technology: CDMA2000, EVDO Rev. A
4) Diallog (negotiation going on with World Call)
Technology: CDMA2000 1x, EVDO
5) SCO
Technology: CDMA2000 1x, EVDO (?)
37
Latest News (Pakistan)
•
•
•
•
Auction of 3G spectrum????????
Only Mobile operators are eligible to bid ??
Three licenses to be issued??
Possible (UMTS FDD Band I):
– 1920 to 1980 MHz (Up link)
– 2110 to 2170 MHz (Down link)
• WiMax has been deployed
38
Issues with widespread usage of wireless
data

Why are new services/mobile content required?
 Tough competition
 Low ARPU
 No differentiation in Service Offerings

Problem:
 What services will differentiate one operator from the other?
 How would these services be delivered?
39
Technologies

2G: Mainly Voice & SMS

2.5G: Limited Data Capability

3G and Beyond: High Speed Data coupled with data
centric applications and services
40
Services Evolution With Enriched User Experiences
Mobile TV
Voice
Wallpaper
2D Gaming
Location Based
Services
Mobile
Commerce
3D Gaming
Services Evolution
Text
Paul,
Messaging
How
did
the
meeti
ng
go?
Send
Option
s
Ringtones
MMS
Music & Video
on Demand
Blogging
Social Networking
RSS Feeds
& Tagging
41