Cellular Systems
Mobile Communications
Cellular Systems
Wen-Shen Wuen
Trans. Wireless Technology Laboratory
National Chiao Tung University
Vincent W.-S. Wuen
Mobile Communications
1
Outline
Cellular Systems
Outline
1 Cellular System Fundamentals
2 Frequency Reuse
3
Interference and System Capacity
4 Trunking and Grade of Services
5
Improving Coverage and Capacity in Cellular Systems
6 Channel Assignment Strategies
7 Handoff Strategies
Vincent W.-S. Wuen
Mobile Communications
2
Cellular System Fundamentals
Cellular Systems
Introdcution
Early mobile radio systems:
Cover a large area by using a single, high powered transmitter
with an antenna mounted on a tall tower.
No frequency reuse, no interference
Limited user capacity
Cellular concept:
Based on power fall off with distance of signal propagation and
reuse the same channel frequency at spatially separated
locations
Sovling problem of spectral congestion and user capacity
Replacing a single, high power transmitter (large cell) with
many low power transmitters (small cells)
Available channels can be reused as many times as necessary
so long as the co-channel interference is kept below acceptable
levels
Vincent W.-S. Wuen
Mobile Communications
4
Cellular System Fundamentals
Cellular Systems
Cellular System
Each cell is assigned to a unique channel set, Cn
Adjacent cells: cells assigned to a different channel sets
Co-channel cells: cells using the same channel sets
Vincent W.-S. Wuen
Mobile Communications
5
Cellular System Fundamentals
Cellular Systems
Tesselating Cell Shapes
To approximate the contours of constant received power
around the base station
Hexagonal cells:
Having largest area for a given distance between the center of a
polygon and its farthest perimeter points
Approximating a circular radiation pattern for an omnidirectional
base station antenna and free space propagation
Diamond cells: better approximating contours of constant
power in modern urban microcells
Vincent W.-S. Wuen
Mobile Communications
6
Frequency Reuse
Cellular Systems
Frequency Reuse