1. Wireless Computer Networking Melanie Hanson May 6, 2002

2. Outline Types of Networks Layers of a network Data transfer techniques Frequency Hopping Direct Sequence Spread Spectrum Infrared Orthogonal Frequency Division Multiplexing

3. Network Types Cellular Controlled by a base station Ad Hoc No base station No specific structure

4. Network Layers 7 layers in the traditional network Physical layer contains hardware Applications layer is user software

5. Types of Data Transfer Spread Spectrum Frequency Hopping Direct Sequence Spread Spectrum Infrared Orthogonal Frequency Division Multiplexing

6. Spread Spectrum Allows multiple access Little interference due to other systems Uses ISM band Industrial 902MHz to 928MHz Scientific 2.4GHz to 2.4853Ghz Medical 5.727GHz to 5.85GHz

7. Frequency Hopping Frequency is periodically changed Generates narrow band signals

8. Direct Sequence Spread Spectrum Carrier is modulated following a specific sequence of bits For ‘0’ the chip sequence is used For ‘1’ the inverse chip sequence is used

9. Infrared Intensity Modulation with Direct Detection (IM/DD) Signal is modulated onto the instantaneous power of the carrier signal Direct detection aspect describes the process of a photodetector

10. Orthogonal Frequency Division Multiplexing Break signal into small orthogonal parts Transmit steps Serial to parallel conversion Modulation Inverse Fourier transform Parallel to serial conversion Digital to analog conversion

11. Which is best? Depends on situation and environment