Chapter
5
5.1
PDH
The
main Transmission Backbone of MTT is based on PDH protocol. For
that they used “DMR 2000 Radio ”, which is a product of NOKIA.
And because of the low traffic capacity most of the links in the
low traffic area are consisting of the above radios.
Fig
5.1 – MTT’s PDH Network (NOKIA DMR 2000)
PDH network consist of mainly
two types of radios
- Nokia DMR 2000 Radio
- Ericsson MINI – LINK E Radio
5.2
MTT’s MINI – LINK E Network
are:
Mulleriyawa to CCOM – 8*2
Mulleriyawa to SITA (WTC) – 8*2
Mulleriyawa to Suntel
Mulleriyawa to Hutchission Telecom
(Walpola)
Mulleriyawa to Aluth Mawatha –
8*2
Hunnasgiriya to Hanthana – 8*2
5.3 Nokia DMR2000 radio
Fig 5.2 Nokia DMR 2000 Radio
Basic Concept
The Radio Relay Equipment DMR 2000 is a member of the
Nokia Telecommunications’ Digital Radio Relay Equipment Family.
It operates in the 1.7 …… 2.7 GHz frequency band. The DMR 2000
can transmit two, four, eight or sixteen 2 Mbit/s G.703 signals or
one 34 Mbit/s signal. An 8 Mbit/s interface can be implemented by
using an external multiplexer (Second order Multiplex Equipment DM
8 = one E2 – size plug – in – unit).
The
good system value of Radio Relay Equipment DMR 2000 and O – QPSK
(Offset Quadrature Phase Shift Keying) modulation method enable
the implementation of long radio hops and produce good interface
immunity.
The
main channel capacity variants are
2
* 2 Mbit/s
4
* 2 Mbit/s
8
* 2 Mbit/s
16
* 2 Mbit/s
34
* 1 Mbit/s
There
are two transmitter power options: 20 dBm and 30 dBm. This
corresponds to an output power of
0.1 W and 1 W, respectively. In addition to this, the
output power could be adjusted either manually or automatically by
means of the ALCQ
feature (Adaptive Level Control with Quality Measure) within a
wide range (15 dB) to optimize the route.
All
commissioning and transmission management functions of the DMR
2000(software settings, controls, measurements, fault locations)
may be performed either locally with a handheld Server Terminal or
remotely by the TMS.
Fig 5.3 - Basic
Units of the DMR 2000 Radio
Basically
DMR 2000 consists of only four main units as shown in the Fig 5.3
- A Base Band Unit
- A
Tx/Rx unit
- A Power Supply Unit
- Antenna Branching Unit
One
of the important features of the DMR 2000 Radio Relay Equipment is
the Adaptive Level Control with Quality Measure. That is adjusting
the transmitted output power according to information from the far
end receiver and this feature guarantees good performance in a
difficult propagation environment. Specially, where fading or even
single errors are expected or where radio hops are very long. ALCQ
also minimizes the interference caused from and to adjacent radio
connections.
The
transmitter output power can also be adjusted or switched off
manually if required using the Service Terminal or the TMS.
Fig 5.4
– Antenna Filter and the Loop Mixture
Above
Fig 5.4 shows the
next important parts of the radio system. RF cable to the antenna
is connected to the ‘Loop Mixture’, and when the system is
connected with a space diversity antenna, it is also connected to
another interface of the Loop Mixture. ‘Filter’ will also work
as a duplexer in the Tx/Rx operation.
All
the operations with the radio system can be monitored and
maintained by the TMS (Transmission Management System) and also
with the ‘Service Terminal’.
5.4
Key functionality of the Service terminal
The Service Terminal provides the user interface to the built-in
facilities of Nokia Q1 managed equipment. The Service Terminal can
be used for various purposes such as review of alarm status in the
equipment, setting operation modes, extensive measurements
including signal quality statistics, internal voltages etc., and
programming of internal parameters of the equipment. All these
operation are performed by connecting the Service Terminal to the
management interface of the equipment involved and issuing the
proper commands using the Service Terminal keyboard. The results
are shown in alphanumeric form on the display.
Key
benefits:
- Review of
alarm status
- Extensive
measurements possible
- Setting of
operation modes
5.5
Training experiences with the DMR 2000 Radio System
Because
of the presence of a ‘Test
Setup’ prepared to test the DMR Radios in MTT’s Control Centre
I was fortunate to get more experience in these Radios.
Chapter
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