<li><ahref="#basestation">Setup of a base station</a>
</ul>
<pclass="toppic">
<aname="history"></a>
History
</p>
<p>
B-Netz was the second mobile telephone network in Germany.
It was the successor of the A-Netz.
It existed between 1972 and 1994.
Using digital technology and later microprocessors, the phone were still as big as a suitcase.
It used full duplex radio link.
The call was placed by atomatic dialing in both direction, so no requirement for an operator.
After full deployment in 1986, there were 158 base stations.
Early devices used up to 38 voice channels. Later units used up to 75 voice channels.
A maximum of about 27,000 subscribers were counted 1986.
The basic charge in the beginning was 270 German Marks.
Calls were charged like regular calls.
The network was congested in 1979, so there was a stop for new subscribers.
Due to congestion, in 1980, the German Federal Post Office lowered the basic charge down to 180 German Marks, but added an extra charge of about 1 German Marks per minute, no matter what direction the call was made.
<li>Funkwahl ohne Gebührenübermittlung: dialing without metering support
<li>Funkwahl mit Gebührenübermittlung: dialing with metering support
<li>Wahlziffer: dialing digits
<li>Funkwahlende: end of dialing
<li>Schlußsignal: hangup signal
</ul>
</p>
<p>
Digits used by base station:
</p>
<p>
<ul>
<li>Gruppenfreisignal: idle pattern
<li>Wahlziffer: dialing digits
<li>Kanalbefehl: channel assignment
<li>Trennsignal: clear signal
</ul>
</p>
<br>
<p>
Idle base station:
</p>
<p>
When a base station transceiver is idle, it repeatingly sends one idle pattern ("Gruppenfreisignal") on downlink.
This signal can be used by the mobile subscriber to select a particular base stations to lower call fees or to select the base station that a car is driving close to.
If no pattern is selected, the mobile station selects any base station on mobile originated call.
If a pattern 1..9 is selected, the mobile station selects only the base stations which sends that idle pattern.
</p>
<p>
There is a special idle pattern that is used for reduced TX power.
This is used in areas with many base station that are close together.
The idle signal 19 is used.
The mobile station will reduce TX power when selecting this base station for outgoing call.
</p>
<br>
<p>
Call from mobile station:
</p>
<p>
The mobile station starts scanning all traffic channels one time.
If there is a signal on the channel, the mobile station tries to decode it for 400 ms max.
If there is no signal or if there is no idle pattern or if the idle pattern does not match the selected one, the mobile station continues with the next channel.
If no channel is found, a busy signal is indicated to the mobile subscriber.
</p>
<p>
If a free and suitable channel was found, the mobile station sends channel allocation signal ("Kanalbelegung") on uplink channel and waits for dial request signal ("Wahlabruf") from the base station.
</p>
<p>
When the base station receives the channel allocation signal, it stops idle pattern and transmits dial request signal.
</p>
<p>
If no dial request signal is received within *TBD* seconds, the mobile station will *TBD*.
</p>
<p>
When the mobile station receives the dial request signal, it seamlessly transmits a dial string.
The string consist of a start signal ("Funkwahl"), 5 digits ("Wahlziffern") of mobile identity, dialed digits (without 0 at the beginning) and the stop signal ("Funkwahlende"):
</p>
<p>
<ul>
<li>Funkwahl
<li>Wahlziffer 5 (Example of mobile identity: 50993)
<li>Wahlziffer 0
<li>Wahlziffer 9
<li>Wahlziffer 9
<li>Wahlziffer 3
<li>Wahlziffer 3 (Example of dialing: 0310, no first digit)
<li>Wahlziffer 1
<li>Wahlziffer 0
<li>Funkwahlende
</ul>
</p>
<p>
The mobile station can send two different start signals.
One indicates to the base station to send metering pulses.
If metering is selected, the bandwidth is reduced from 3000 Hz down to 2700 Hz.
The metering pulse is then sent as a 2900 Hz tone.
The duration is *TBD* ms and the frequency deviation *TBD* KHz.
</p>
<p>
While dialing is received by the base station, it repeats the 5 digits of mobile identy.
This takes place after *TBD*.
</p>
<p>
The mobile station compares the repeated identiy and *TBD* if it mismatches.
</p>
<p>
The dial string is repeated once again by the mobile station.
Afterwards the mobile station connects the speech path and conversation takes place.
</p>
<p>
If the dial string is received correctly once again by the base station, it connectes the speech path and conversation takes place.
</p>
<p>
If the base station receives different repeated dialing or different mobile identity, it sends clear signal ("Trennsignal") for 12 seconds and returns to idle state.
</p>
<p>
If the mobile stations receives clear signal during dialing, it indicates busy signal to the subscriber and returns to idle state.
</p>
<br>
<p>
Call to mobile station:
</p>
<p>
The calling party dials the prefix of the city where the base station is located, followed by "05", followed by the 5 digits mobile station id.
(E.g. base station on Stollberg Hill: +49-4671-05-50993)
</p>
<p>
The transceiver of the base station switches to channel 19 and sends a paging sequence that consists of 5 digits ("Wahlziffern") mobile identity and the channel assignment digit ("Kanalbefehl"):
</p>
<p>
<ul>
<li>Wahlziffer 5 (Example of mobile identity: 50993)
<li>Wahlziffer 0
<li>Wahlziffer 9
<li>Wahlziffer 9
<li>Wahlziffer 3
<li>Kanalbefehl 1 (Example of channel: 1)
</ul>
</p>
<p>
Then the base station returns to the ordered channel and waits 2 seconds for the mobile station to send the call acknowledge signal ("Rufbestätigung").
If it is not received, the base station repeats the paging sequence again.
If there is still no call acknowledge signal, it returns to idle state and indicates announcenemnt to the calling party that the mobile station is (currently) not available.
If the mobile station does not receive the call hold signal within 640 ms, it returns to idle state.
</p>
<p>
When the called mobile subscriber answers, the mobile station sends the answer signal ("Beginnsignal").
</p>
<p>
When the base station receives the answer signal, it stops sending call hold signal and connects the speech path and conversation takes place.
</p>
<p>
When the mobile station detects that the call hold signal is gone, it connects the speech path and conversation takes place.
</p>
<p>
If the mobile subscriber does not answer within 60 seconds, the base station sends clear signal ("Trennsignal") for 12 seconds and returns to idle state.
</p>
<p>
When the mobile station receives clear signal, it stops ringing tone and returns to idle state.
</p>
<br>
<p>
Release by the mobile station:
</p>
<p>
When the mobile subscriber hangs up, the mobile station sends 4 times the hangup signal ("Schlußsignal") and returns to idle state.
</p>
<p>
When the base station receives the hangup signal, it releases the call and returns to idle state.
</p>
<br>
<p>
Release by the base station:
</p>
<p>
When the party on the fixed network hangs up, base station sends the clear signal ("Trennsignal") for 12 seconds and returns to idle state.
</p>
<p>
When the mobile station receives the clear signal, it returns to idle
state.
</p>
<br>
<p>
Signal loss:
</p>
<p>
When the signal gets lost for more than 9,6 seconds, the mobile station will return to idle and indicates busy signal to the mobile subscriber.
The base station will *TBD*, clears the call and returns to idle state.