1. ELECTRONIC COMMUNICATIONS A SYSTEMS APPROACH CHAPTER Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Electronic Communications: A Systems Approach Beasley | Hymer | Miller Wireless Communications Systems Mobile and Cellular Data Systems 10

2. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Mobile and Cellular Date Networks Third-Generation Systems (3G)  Deployment tied to market conditions and availability of spectrum. See Table 10-7: Basic Characteristics of the Paths to 3G in the Textbook Also on the next slide

3. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Table 10-7 Basic Characteristics of the Paths to 3G

4. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Mobile and Cellular Date Networks Third-Generation Systems (3G)  WCDMA Universal Mobile Telecommunications Service (UMTS); based on direct- sequence spread spectrum (DSSS). Fourth-Generation Systems (4G)  Not fully defined as yet. True 4G will peak at 1Gb/s  Systems that are now called 4G are: More accurately called 3.9G not 4G 20-40Mb/s

5. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Mobile and Cellular Date Networks Wireless Application Protocol (WAP)  World standard to bridge gaps between mobile communications, Internet, corporate intranets;  Address delivery problems with wireless data networks Bandwidth, latency, connection stability, availability.

6. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Wireless Security Five aspects to consider when securing a communication link:  Confidentiality (privacy)  Integrity  Authentication  Nonrepudiation  Availability of network

7. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Wireless Security Attacks on a wireless network:  Passive  Active  External Perpetrated by someone without network access They can listen or transmit interference  Internal The more subtle and dangerous attacks

8. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Wireless Security Countermeasures use cryptography to protect transmitted data from eavesdropping.  Data Encryption Standard (DES) 56 bit key – 2 56 combinations Brute force attack with today’s PCs can overcome this in less than a day Triple DES and AES are replacements  Cipher text (encrypted message)

9. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Wireless Security  Cipher text (weak encrypted message)

10. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Figure 10-20 An example of cipher text (an encrypted message).

11. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Cipher Text  Cipher text (weak encrypted message) The encrypted message on the previous slide has a slightly different distribution of characters than un encrypted text Characters in this example found by: Shifting up alphabet by four characters

12. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Table 10-8 The Predicted Character Shift for Cipher-text Message Shown in Figure 10-20

13. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Two-Way and Trucked Radio Systems Regulatory designation  Specialized land-mobile radio (SMR); may be analog or digital.  Repeaters (transceivers) provide wide- area coverage.  Different standards for the US and Europe US - Project 25 Europe - TETRA

14. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Figure 10-23 Block diagram of a basic trunked radio system.

15. Electronic Communications: A Systems Approach Beasley | Hymer | Miller Copyright © 2014 by Pearson Education, Inc. All Rights Reserved Two-Way and Trucked Radio Systems Regulatory designation  High-elevation repeater serving number of remote units dispersed over wide geographic area.  Trunking systems rely on frequency- division multiple-access (FDMA) methods of multiple-user access.