Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1997-05-21
2004-11-30
Olms, Douglas (Department: 2661)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S337000, C455S557000
Reexamination Certificate
active
06826170
ABSTRACT:
The object of the invention is a method for forming a data transfer connection between a data transfer system and a subscriber device, terminal equipment and a data transfer system wherein at least two subscriber devices are connected to one subscriber connection of the data transfer system. The invention can be preferably applied, for example, in Wireless Local Loop networks, i.e. WLL networks.
WLL systems are a preferable way to extend the public switched telephone network to new subscribers since the extension can be carried out without having to provide cabling for each subscriber separately. In wireless local loop networks, i.e. WLL networks, the terminal equipment which are in use comprise a telephone or some other subscriber station which is suitable for connecting to the public switched telephone network and a tranceiver unit connected to it. The adaptation between the subscriber station and the tranceiver unit is executed by a line adapter. The tranceiver unit is usually connected by radio to a cellular service, which could be, for example, to a GSM system. It is often desirable to use one subscriber connection both for speech transmission and for transmission of character based data, such as telefaxes. There are, however, problems associated with this, especially in WLL systems, and they will be described more closely in the following.
In the following, the prior art is presented by describing first in some detail WLL terminal equipment according to the prior art and its connection to the data transfer system and by describing subsequently a solution according to the prior art for connecting two subscriber stations to the WLL data transfer system.
FIG. 1
shows a prior known solution for the implementation of a WLL terminal equipment. The WLL terminal equipment
100
is connected to a cellular system which comprises base stations
151
for transferring data by radio via an antenna
150
to terminal equipment. The base stations are connected to base station controllers
152
which are further connected to a switching center
153
. The switching center
153
is linked to the public switched telephone network PSTN. Also a home location register HLR is connected to the switching center. The data concerning the subscribers of the system is stored to this register.
Terminal equipment
100
comprises an antenna
104
for transmitting and receiving a radio frequency signal. The received signal is amplified and demodulated into a baseband signal in an RF part
113
and the baseband signal is processed in a signal processing block
114
of the baseband part
110
. Similarly, the transmitted baseband signal is processed for transmission according to specifications of the cellular system in block
114
and modulated into an RF frequency and amplified in the RF part
113
to be fed to the antenna
104
.
The signal processing and the RF part are controlled by a processor
111
to which a memory
112
is connected for storing programs and parameters. A regulator
115
forms the supply voltages for the baseband part and for the RF part.
A line adapter part
130
comprises an audio part
134
for adapting the audio signal of the baseband part
110
and the audio signal of the telephone set to each other. A DTMF detector
133
detects dialling signals which are transferred in the audio line and transmits them to the processor
131
of the line adapter part. A HOOK detector
135
detects the state of the hook switch of the telephone device and transmits the status mode data to the processor
131
and to a tone generator
136
. The tone generator
136
forms audio signals to the telephone on the basis of the status mode data of the connection which have been transmitted by the cellular system. A ringing generator
137
forms a high voltage ringing signal (for example, 45 V AC) for the ringing function of the telephone set. Voltage between lines/loop current (for example, 40 V DC) is formed in a DC regulator
138
to meet the specifications of the telephone set from the high voltage formed by a DC/DC converter block. The processor
131
controls the blocks of the line adapter and it is connected to the processor
111
of the mobile station part
110
, for example, through serial bus. The program of the processor and the parameters connected to the functions of the line adapter and the status mode data of the connection are stored into a memory
132
connected to the processor
131
.
The above presented solution according to the prior art has been described in more detail in the patent specification U.S. Pat. No. 5,117,450 (WO 9014729). Other WLL systems according to the prior art have been described, for example, in the patent specifications U.S. Pat. Nos. 4,658,096, 4,775,997 and 4,922,517.
It is often desirable to use one subscriber connection of the telephone both for speech transmission and for the transmission of character based data, such as telefaxes. The simplest method in this case is to connect in parallel a telephone set and, for example, a telefax to the same subscriber line. However, with respect to this arrangement the problem arises in the context of an incoming connection, since one does not know whether it is a phone call or a telefax transmission. In this case, one has to answer the phone and if it is concluded from the audio signals that it is a telefax transmission, the telephone receiver is set on-hook and the receiving function of the telefax is switched on. However, this demands that there is someone next to the telephone set monitoring all incoming connections. If the person is not present, the telefax has to be connected to an auto answer mode and thus only telefaxes can be transmitted to the subscriber connection. In this case, it is not possible to use, for example, a telephone answering machine parallel with the telefax. The telefax can also be used in an auto answer mode constantly but then, as an ordinary call is coming to the subscriber connection, the telefax feeds a disturbing audio signal to the line until the receiver notices that it is not a telefax transmission and receives the call by using the telephone.
To solve the above mentioned problem, two separate subscriber connections are often used, one for the telephone and the other for the telefax.
FIG. 2
shows a prior known solution like this. A telephone
201
has been connected to the first WLL connection and a telefax
202
has been connected to the second WLL connection. For each connection there is a separate connection device
210
,
220
which comprises an antenna
214
,
224
, an RF part
213
,
223
, a baseband part (BB)
212
,
222
, a line adapter (LA1, LA2)
211
,
221
and an interface for connecting the subscriber station (INTERFACE
1
, INTERFACE
2
). However, the disadvantage of this solution is that the acquiring and upkeep of several subscriber connections leads to considerable costs.
The above mentioned disadvantages can be reduced by a prior known incoming call type recognition. The device answers the call automatically and receives the signal from the line for a maximum predetermined time. If it is a telefax transmission, the device detects the audio signal of a transmitting telefax and connects the line to the telefax. If, instead, during the predetermined time the device does not detect the audio signal of a telefax, it connects the line to the telephone. The problem with this kind of combination device is, however, that in the context of an ordinary call the device answers the incoming connection even though there is no one present to answer the call. In this case, connecting the line uses unnecessarily the capacity of the data transfer network and causes unnecessary costs to the caller. This is a special problem with the WLL connection since the capability of the WLL network to transmit connections in the communications channel is usually lower than the number of connections in the network in which case the forming of unnecessary connections may cause a network overload.
With the WLL network, there are also disadvantages associated with solutions according to the prior art
Nokia Mobile Phones Ltd.
Olms Douglas
Perman & Green LLP
Phunkulh Bob A.
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