14-CellularWirelessNetworks eighth

14-CellularWirelessNetworks eighth - William Stallings Data...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
William Stallings Data and Computer Communications 8 th Edition Chapter 14 Cellular Wireless Networks
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Key Points Use multiple, low-power transmitters Major technical problem is fading …time variation of received  signals caused by changes in transmission medium First generation:  analog . . Used FDM Second generation:  digital  most commonly uses CDMA (Code Division Multiple Access) Objective of third generation is to provide fairly high speed  communications to support multimedia
Background image of page 2
Principles of Cellular Networks Underlying technology for mobile phones,  personal communication systems, wireless  networking etc. Developed for mobile radio telephone Replace high power transmitter/receiver systems Typical support for 25 channels over 80km Use lower power, shorter range, more transmitters
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Cellular Network Organization Multiple low power transmitters 100w or less Area divided into cells Each with own antenna Each with own range of frequencies Served by base station Transmitter, receiver, control unit Adjacent cells on different frequencies to avoid  crosstalk
Background image of page 4
Shape of Cells Square Width  d  cell has four neighbors at distance  d  and four at  distance       d Better if all adjacent antennas equidistant Simplifies choosing and switching to new antenna Hexagon Provides equidistant antennas Radius defined as radius of circumscribing circle Distance from center to vertex equals length of side Distance between centers of cells radius  is       R Not always precise hexagons Topographical limitations Local signal propagation conditions Location of antennas 2 3
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Cellular Geometries
Background image of page 6
Frequency Reuse Power of base transceiver controlled Allow communications within cell on given frequency Limit escaping power to adjacent cells Allow re-use of frequencies in nearby cells Use same frequency for multiple conversations 10 – 50 frequencies per cell E.g.  cells all using same number of frequencies K   total number of frequencies used in systems Each cell has  K/N   frequencies Advanced Mobile Phone Service (AMPS)  K =395,  N =7 giving 57  frequencies per cell on average
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Frequency Reuse Patterns
Background image of page 8
Increasing Capacity (1) Add new channels Not all channels used to start with Frequency borrowing Taken from adjacent cells by congested cells Or assign frequencies dynamically Cell splitting Non-uniform distribution of topography and traffic Smaller cells in high use areas Original cells 6.5 – 13 km 1.5 km limit in general More frequent handoff More base stations
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 45

14-CellularWirelessNetworks eighth - William Stallings Data...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online