Codan Radio MT-4E Paging - Manual (Page 50)

USER GUIDE | MT-4E PAGING SYSTEMS
Chapter 5: Technical Information Page 42
NARROWBAND PAGING COVERAGE
Codan MT-4E paging systems support wideband (25 KHz) and narrowband (12.5 KHz) paging. The
coverage area of the wideband / narrowband paging system is affected by two factors, the deviation of
the transmitter and the IF bandwidth of the receiver.
When transitioning to a narrowband system from a wideband system, the transmitter deviation level
is reduced and the receiver IF bandwidth will also be reduced. This may cause a minor reduction in
coverage area. If the paging system is required to do both narrowband and wideband paging (or an
older wideband receiver is still being used in a narrowband system), the wideband receiver will have
reduced coverage when receiving narrowband pages.
The coverage area needed may be defi ned by different parameters called Channel Performance
Criterion (CPC), and different values of those parameters. Depending on who is designing the system,
the CPC may be SINAD or Bit Error Rate or another metric.
In analog systems there tends to be about a 2-3 dB difference in signal level required in narrowband
vs. wideband when using 12 dB SINAD as the CPC. The coverage loss is determined by the distance
required to make up that 2-3 dB signal level difference. However, if using 20 dB SINAD (dBS) or 25 dBS
then the difference is as high as 6 dB.
These numbers depend on the receiver used in the fi eld and have nothing to do with the transmitter, if
the same type of transmitter is used in the entire system. If different transmitters are used in the system,
the coverage could change based on the Signal-to-Noise (S/N) performance of each transmitter.
The TIA (Telecommunications Industry Association) standard TSB-88.1-C provides a recommended
best practice reference for developers and suppliers of land mobile communications system design,
modeling, simulation and spectrum management software, and automated tools. The following numbers
are from TSB-88.1-C and show the Carrier to Noise level required to meet the specifi ed CPC (either
SINAD or BER). Unfortunately, no paging modulation types are listed.
Analog FM ± 5kHz (25 kHz)
Wideband
Analog FM ± 2.5kHz (12.5 kHz)
Narrowband
Wideband –
Narrowband
Difference
CPC (dB SINAD) Carrier to Noise CPC (dB SINAD) Carrier to Noise
12 dBS 4 dB 12 dBS 7 dB 3 dB
20 dBS 20 dB 20 dBS 26 dB 6 dB
25 dBS 27 dB 25 dBS 33 dB 6 dB
Difference of 3 dB for 12 dBS CPC and 6 dB for 20 & 25 dBS CPC.
EDACS® Digital (25 kHz)
Wideband
EDACS® Digital (12.5 kHz)
Narrowband
Wideband –
Narrowband
Difference
CPC (BER) Carrier to Noise CPC (BER) Carrier to Noise
5% 5.3 dB 5% 7.3 dB 2 dB
2% 15.7 dB 2% 17.7 dB 2 dB
1% 19.2 dB 1% 21.2 dB 2 dB
Difference of 2 dB for 5%, 2%, and 1 % BER.