HF Multi-hop Network for Emergency Communication. There are Maximum Useful Frequency (MUF) and lower Absorption Frequency (ALF) bounds for communication between tow terminals. HF communication is dependent on: 1- Frequency 2- Range or path length 3- Antenna elevation angle
There are Maximum Useful Frequency (MUF) and lower Absorption Frequency (ALF) bounds for communication between tow terminals.
HF communication is dependent on:
2- Range or path length
3- Antenna elevation angle
4- Height of the ionosphere
5- density of ionization of the layer
Region between maximum ground-wave distance(30~50km) and closest point where HF are returned from the ionosphere.
Critical frequency :
= the maximum electron density in a given ionized layer
Maximum Usable Frequency (MUF) :
D= the distance between the station h= height of the reflection point
Optimal work Frequency (OWF) :
The Relationship between angle and frequency
F1 layer at 12:00
E layer at 12:00
The Relationship between frequency and distance
E layer at 12.00
F1 layer at 12.00
F at 22.00
Frequency and distance
Angle and frequency
Receive the internationally broadcasted radio in HF band.Experiment
DSP Receiver NRD-545
(T2FD): Terminated Tilted Folded Dipole
We analyze the model when data packet is transmitted using direct broadcasting.
The packet will be forwarded by HF multi hop in same frequency that have been received.
The purpose of our proposal system
To assure the data we transmitted can be received by all stations
Situation1：Recover the connection
Situation2：skip zone access
In said A station skip zone
Stations in the skip zone can be reached by successfully usage of theGround wave and reflection on the ionosphere by HF band.
HF coverage distance :
Stations: 1-fixed 2-moving (by car)
Elevation angle:height elevation angle
The distance of HFcoverage area and signal strength