Reference Manual

Frequency Hopping
25 Frequency Hopping
"Frequency hopping" means that the radio frequency channel of a BPC
may change on a per TDMA frame basis. Frequency hopping improves
the quality of the transmission on the air interface.
The Frequency hopping function is used to increase the efficiency of the
channel coding and interleaving in the following situations:
•
Multipath (or Rayleigh) fading
−
Is often frequency-dependent. In case of a dip, changing
of frequencies reduces this problem.
• Interference problems
− Without frequency hopping, a connection may experience
high interference for a long time. With frequency
hopping this time is shortened. However, frequency
hopping does not reduce the overall system interference
level, but averages it.
There are two types of frequency hopping available:
•
Baseband hopping
•
Synthesizer hopping
25.1 References
/GSM 08.58/ GSM 08.58 (phase 2) version: 4.2.0
/GSM 05.02/ GSM 05.02 (phase 2) version: 4.3.0
Whenever a reference is made to a function described in another chapter,
please refer to the table of contents to find the appropriate chapter.
25.2 Concepts
Baseband Hopping Each transmitter will always transmit on
the same frequency. The physical channel
data will be sent from different
transmitters with every burst.
Synthesizer Hopping The physical channel data will be sent
from the same transmitter all the time.
But the transmitter will use a new
frequency with every burst.
25.3 Function
Frequency hopping is provided on a slot-by-slot basis according to /
GSM:05.02.6.2/.
Supported channel combinations /GSM:05.02:6.4/:
• (i) TCH/F+FACCH/F+SACCH/TF
• (ii) TCH/H(0,1) + FACCH/H(0,1) + SACCH/TH(0,1)
• (vii) SDCCH/8 [0..7]+SACCH/C8 [0..7]
EN/LZT 720 0008 R1A
2001-06-26
227 (421)
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