Wireless Networks
Lecture 25
1st Review
Dr. Ghalib A. Shah

1


Last Lecture






Cdma2000 introduction
New MAC and Physical layer features
Physical layer of cdma2000
Reverse Physical channels
New Network elements in cdma2000
► Packet Control Function (PCF)
► Packet Data Serving Node (PDSN)

 Mobility Management
 Handoff
► Intera-PCF
► Inter-PCF/Intra-PDSN
► Inter-PDSN
2

Lecture 1 - Introduction Part I
I.
II.
III.
IV.
V.

The Wireless vision
Radio Waves
Channel Capacity
Signal-to-Noise Ratio
EM Spectrum

3


Lecture 1 - Introduction Part II
 Wireless Transmission
► Baseband signal, carrier frequency, fundamental
frequency
► antenna size must correspond to signal’s
wavelength
• 1 MHz signal  few 100 m-s high antenna;
• 1 GHz signal  few cm-s high antenna

 Encoding/Modulation
 Noises
► Thermal, Intermodulation, Crosstalk, Impulse

 Losses/Gain


4


Lecture 3 – Introduction Part III
 Multiplexing
 Transmission Mediums
► Guided, Unguided

 Propagation modes
► Ground wave, Sky wave, LOS

 Multi-path propagation
► Reflection, Diffraction, Scattering

 Fading

5


Lecture 4 – Error part I





Transmission Errors
Parity Check
Cyclic Redundancy Check
Block Error Code


6


Lecture 5 – Error part II
 Block Codes
► Hamming
► BCH (Generalization of Hamming)
► Reed Solmon (Subclass of non-binary BCH)

 ARQ
► Sliding window
► Go-back-N

7


Lecture 6 – Multiple Access (Part I)





FDMA
TDMA
CDMA
Random Access
► ALOHA
► Slotted ALOHA
► Reservation-based ALOHA


8


Lecture 7 – Multiple Access (Part II)
 CSMA
► Versions of CSMA
► CSMA/CA

 Spread Spectrum
► Frequency Hoping
► Direct Sequence

9


Lecture 8 – Evolution Part I
 1G wireless cellular networks
► NMT
► AMPS
► TACS

 2G cellular systems
►
►
►
►

GSM
IS-136

PDC
IS-95

10


Lecture 9 – Evolution Part II
 2.5G
►
►
►
►

HSCSD
GPRS
EDGE
IS-95B

 3G
► UMTS/W-CDMA
► CDMA2000

11


Specifications of 2.5G and 3G standards
Technology

Channel 
BW


Duplex

Infrastructure Changes

New 
Spectrum

New handsets

HSCSD

200 KHz

FDD

Software upgrade at BS

No

Yes, New headsets provide 
57.6 kbps on HSCSD and
 9.6 kbps on GSM

GPRS

200 KHz

FDD


New packet overlay at routers 
and gateways

No

Yes, new GPRS sets work at
 171.2 kbps, 9.6 kbps on
 GSM, dual­mode.

EDGE

200 KHz

FDD

New TX/Rx at BS, software 
upgrade at BS, controller

No

Yes, new set work at 384 
kbps on EDGE, GPRS at 
144 kbps and GSM at 9.6 
kbps, tri­mode

W­CDMA

5 MHz

FDD


Completely new BS

Yes

Yes, new handsets work at 2
 Mbps in WCDMA and rest 
as above

IS­95B

1.25 MHz

FDD

New software at BS

No

Yes, IS­95B at 64kbps, IS­
95A at 14.4 kbps and IS­95 
at 9.6 kbps

Cdma2000
1xRTT

1.25 MHz

FDD


New software at backbone, new 
channel cards at BS, new packet
 service node

No

1xRTT at 144 kbps and rest 
as above. Older sets will 
work.

Cdma2000 
1xEV(DO/DV)

1.25 MHz

FDD

New software and cards upgrade
 to 1xRTT

No

1xEV at 2.4 Mbps and as 
above

Cdma2000
3xRTT

3.75 MHz


FDD

Backbone modifications and
 channel cards at BS

May be

3xRTT at 2 Mbps and rest
 as above

12


Lecture 10 Evolution III
 Limitation of 3G
 4G
►
►
►
►
►
►

Objectives
Issues
QoS
Security
Multimedia Service
Applications


 Convergence of Cellular and WLAN
 Billing Issue
13


Quality of Service (QoS)
 Traffic generated by the different services will
not only increase traffic loads on the networks,
but will also require different quality of service
(QoS) requirements (e.g., cell loss rate, delay,
and jitter) for different streams (e.g., video,
voice, data).
 Providing QoS guarantees in 4G networks is a
non-trivial issue where both QoS signaling
across different networks and service
differentiation between mobile flows will have to
be addressed.
14


Security
 Security in wireless networks mainly involves
authentication, confidentiality, integrity, and
authorization for the access of network connectivity and
QoS resources for the mobile nodes flow.
 The heterogeneity of wireless networks complicates the
security issue.
 Dynamic reconfigurable, adaptive, and lightweight
security mechanisms should be developed.
 AAA (Authentication Authorization Auditing) protocols

provide a framework for such suffered especially for
control plane functions and installing security policies in
the mobile node such as encryption, decryption and
filtering.
15


Lecture 11 – Cell Conept part I
 Cellular Concept
 Frequency Reuse
 Locating co-channel cells

16


Lecture 12 – Cell Concept Part II
 Channel Assignment Strategies
 Handoff Strategies
► When to handoff
► 1G, BS based
► 2G or todays, Mobile-Assisted

 Prioritizing Handoff
► Guard channels concept
► Queuing handoff requests

 Practical handoff considerations
► Umbrella cell
► Cell dragging
17



Lecture 13 – Cell Concept Part III
 Interference and system capacity
► Co-channel interference and capacity
► Adjacent channel interference and capacity

 Channel Planning for Wireless System

18


Lacture 14 – Cell Concept Part IV
 Trunking and Grade of Service
► Measuring Traffic Intensity
► Trunked Systems
• Blocked Calls Cleared
• Blocked Calls Delayed

► Erlang Charts

 Improving Coverage and Capacity
►
►
►
►

Cell Splitting
Sectoring
Repeaters for Range Extension

Microcell Zone Concept
19


Lecture 15 - AMPS







AMPS introduction
System Overview
Call handling
Air interface
Supervisory signals
N-AMPS

20


Lecture 16 GSM








GSM Introduction
GSM System Architecture
GSM Network Areas
Specifications
Subscriber Services
Mobility

21


Lecture 17 – GPRS (part I)






Introduction to GPRS
GPRS Architecture
Registration and Session Management
Routing Scenario in GPRS
Channels Classification

22


PDP Context Activation
MS

SGSN


GGSN

Activate PDP Context Request
PDP type,PDP Address
QoS Requested,Access Point,…
Security Functions
Create PDP Context Request
PDP type,PDP Address
QoS Negotiated,Access Point,…
Activate PDP Context Accept
PDP type,PDP Address
QoS Negotiated,…

Create PDP Context Response
PDP type,QoS Negotiated,…

23


Lecture 18 – GPRS part II
 GPRS Protocol Architecture
►
►
►
►








MS – BSS
BSS – SGSN
SGSN – GGSN
GGSN – PDN

GPRS Air Interface
Data Routing and Mobility
Uplink Data Transfer
Downlink Data Transfer
QoS in GPRS
24


Lecture 19 - IS-95




IS-136
CDMA/IS-95
Advantages
►
►



Drawbacks

►



Self-jamming, near-far problem,

IS-95 Forward Channels
►
►
►
►



Higher capacity, Improves voice quality (new coder), Less power
consumption (6-7 mW)
Privacy, graceful degradation

Pilot Channel
Sync Channel
Paging
Traffic

IS-95 Reverse Channels

25