32(48)
Date
Rev
Documentnumber
Prepared
Doc respons/Approved
Checked
Reference
1999-07-15
A
1531-BDV BS 101 05 Uen
INSTALLATION INSTRUCTION
Subject responsible
7.4
Base Station (
KRCNB 201 03/_
and
KRCNB 301 03/_
)
The Base Station (BS) enables radio communication between the Integrated Cordless system and the portable
telephones. The communication via two 2B+D interfaces requires two twisted pair cables. Both interfaces provide in
total eight 32 kbit/s speech paths between a BS and IC-CU2, enabling a BS to handle eight simultaneous calls. The
BS is connected to the IC-CU2 via two wire pairs called serial communication wires (SC0 & SC1) carrying up to 8
simultaneous digital voice connections and the central power feeding. Apart from data communication these two twisted
pairs are also used to distribute power to the BSs. Two additional pairs can be wired to provide a greater powering
range. There are three methods to power BSs:
1.
centrally via backplane (with or without EPP)
2.
centrally via external input (with / w.o EPP)
3.
via local power supply (optional).
With the first and second methods power is distributed via the IC-CU2 to the BS. The cable length between BS and
IC-CU2 depends on the number of wires used for power feeding, the type of cable and environmental noise. In the
third case (local feeding), BSs are powered by an AC-adapter or another power source which is not routed via the
cabinet.
The number of BSs used in a system depends on the area to be covered and the traffic density. Typical in-house
coverage is a radius of up to 30 meters. In practice the cell size may vary between 10 meters indoors in worst case
situations, up to 300 meters outdoor in free space.
The BS has two main functions:
•
to modulate a carrier with the digital encoded information (TDMA frame directed to portable)
•
to demodulate a modulated carrier (TDMA frame received from portable).
A special cover (KRY NB 101 01) is available to mount the BS (KRCNB 201 03) outdoors providing splash proof
housing and water tight sealings for the wiring.
7.4.1
Base Station Planning
The major task when providing a wireless service is to estimate the number of BSs and to find their most suitable
location. A number of factors tend to limit the range of a BS like the materials the wall is composed of or the location
and size of machines, furniture, air-conditioning systems, elevators etc. This results in unexpected reflections or
absorption of radio waves. Generally BSs should not be located on outer walls, except if the outdoor area has to be
covered as well, as this reduces the area actually covered. All of these unpredictable influencing factors make it
extremely difficult to define rules for how to cover an area with a suitable number of BSs. In difficult environments the
use of a site survey tool (LTT NB 101 01/_) is recommended.
Establish a Base Station plan for the installation site to determine the best location for the BSs.
Base Station aerial range
•
In an office environment located in a steel concrete building up to 30 m in diameter can be covered,
including, in normal conditions, the neighbouring floors as well.
•
Production halls up to 200 m in diameter are covered but ranges can be smaller if bulky machines, cranes
etc. are part of the interior.
•
Outdoor ranges can be up to 300m.
When installing a BS, position it, then walk around to determine cell coverage area either by listening to the speech
quality - whether mutes or crackling sounds are heard in the portable - or measure the RQI indicator using the portables
Service Display facility (see