Friday, July 3, 2015

MOBILE AND PERVASIVE COMPUTING

1. Cellular Wireless Networks:

Importance of Wireless

 Freedom of movement

 No loss of connectivity

 Increase in productivity

Cellular Network Organization

 Use multiple low-power transmitters (100 W or less)

 Areas divided into cells

 Each served by its own antenna

 Served by base station consisting of transmitter, receiver, and

control unit

 Band of frequencies allocated

 Cells set up such that antennas of all neighbors are equidistant
(hexagonal pattern)

Frequency Reuse

 Adjacent cells assigned different frequencies to avoid interference or  crosstalk

 Objective is to reuse frequency in nearby cells

 10 to 50 frequencies assigned to each cell

 Transmission power controlled to limit power at that frequency  escaping to adjacent cells

 The issue is to determine how many cells must intervene between  two cells using the same frequency

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