Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1998-11-16
2001-10-02
Cumming, William (Department: 2681)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
Reexamination Certificate
active
06298246
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of Great Britain Application No. 9724612.8 filed Nov. 20, 1997.
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to wireless telecommunications systems, and more particularly to subscriber terminals for wireless telecommunications systems.
BACKGROUND OF THE INVENTION
A wireless telecommunications system has been proposed in which a geographical area is divided into cells, each cell having one or more central terminals (CTs) for communicating over wireless links with a number of subscriber terminals (STs) in the cell. These wireless links are established over predetermined frequency channels, a frequency channel typically consisting of one frequency for uplink signals from a subscriber terminal to the central terminal, and another frequency for downlink signals from the central terminal to the subscriber terminal.
The system finds a wide variety of possible applications, for example in rural, remote, or sparsely populated areas where the cost of laying permanent wire or optical networks would be too expensive, in heavily built-up areas where conventional wired systems are at full capacity or the cost of laying such systems would involve too much interruption to the existing infrastructure or be too expensive, and so on.
In one embodiment, the central terminal may be connected to a telephone network and exists to relay messages from subscriber terminals in the cell controlled by the central terminal to the telephone network, and vice versa. By this approach, an item of telecommunications equipment connected to a subscriber terminal may make an outgoing call to the telephone network, and may receive incoming calls from the telephone network.
However, such a wireless telecommunications system is not restricted to use with telephone signals, but could instead handle any other appropriate type of telecommunications signal, such as video signals, or data signals such as those used for transmitting data over the Internet, and in order to support new technologies such as broadband and video-on-demand technologies.
FIG. 1
illustrates an example of a typical prior art configuration for a subscriber terminal for such a wireless telecommunications system.
FIG. 1
includes a schematic representation of customer premises
22
. A customer radio unit (CRU)
24
would typically be mounted on the customer's premises and may include a flat panel antenna or the like
23
. The customer radio unit is mounted at a location on the customer's premises, or on a mast, etc, and in an orientation such that the flat panel antenna
23
within the customer radio unit
24
faces in the direction
26
of the central terminal for the service area in which the customer radio unit
24
is located.
The customer radio unit
24
is typically connected via a drop line
28
to a power supply unit (PSU)
30
within the customer's premises. The power supply unit
30
is connected to the local power supply for providing power to the customer radio unit
24
and to a network terminal unit (NTU)
32
. The customer radio unit is also connected via the power supply unit
30
to the network terminal unit
32
, which in turn is connected to telecommunications equipment in the customer's premises, for example to one or more telephones
34
, facsimile machines
36
and computers
38
. The telecommunications equipment is represented as being within a single customer's premises. However, this need not be the case, as the subscriber terminal
20
may support more than one line, so that a number of items of subscriber telecommunications equipment could be supported by a single subscriber terminal
20
. The subscriber terminal
20
can also be arranged to support analog and digital communications, for example analog communications at
16
,
32
or 64 Kbits/sec or digital communications in accordance with the ISDN BRA standard.
The CRU
24
typically includes all of the necessary processing circuitry to convert incoming wireless telecommunications signals into signals recognisable by the items of telecommunications equipment, and also to convert such signals from those items of telecommunications equipment into wireless telecommunications signals for transmission from the antenna
23
.
A significant problem with this approach is that the CRU
24
is an expensive item of equipment to replace. Since this is generally located on the outside of the customer's premises, it is prone to theft. In addition, all of the components within the CRU
24
have to be able to withstand the exposure to varying climatic conditions that arise as a result of the CRU
24
being mounted externally. For example, the components must be able to withstand significant variations in temperature, and variations in humidity.
However, one reason why the CRU
24
has previously included all of the necessary processing circuitry to convert incoming wireless telecommunications signals into signals recognizable by the items of telecommunications equipment is that it reduces the technical complexity of the subscriber terminal to have all of the processing circuitry in one housing.
Further, problems with attenuation of the wireless signals transmitted between the central terminal and the subscriber terminal, and vice versa, have previously dictated that the processing circuits of the subscriber terminal should be located physically close to the antenna
23
. To illustrate this, it will be appreciated that a signal transmitted from the central terminal at a predetermined power level will be attenuated as it is propagated to the antenna
23
of the subscriber terminal
20
.
Once the signal has been received by the antenna
23
, there will also be further attenuation within the subscriber terminal as the signal is passed from the antenna to the processing circuits within the subscriber terminal.
Clearly, the further away those processing circuits are from the antenna, then the greater the attenuation is likely to be. A signal strength threshold will be determined below which a signal cannot be processed by the processing circuits within the subscriber terminal
20
. Hence, in order to improve the range of the wireless telecommunications system, it has been considered advisable to minimise the distance between the antenna
23
and the processing circuitry of the subscriber terminal provided to process that received signal.
The above requirements have led to the development of subscriber terminals such as those illustrated in
FIG. 1
, in which an expensive customer radio unit
24
engineered to withstand exposure to varying climatic conditions has been mounted on the exterior of a subscriber's premises.
SUMMARY OF THE INVENTION
Viewed from a first aspect, the present invention provides a subscriber terminal for communicating over a wireless link with a central terminal of a wireless telecommunications system, the subscriber terminal comprising: a first signal processing unit associated with an antenna to transmit and receive signals over the wireless link at first frequencies within an operating frequency band, the first signal processing unit comprising a frequency converter for converting signals between said first frequencies and a second frequency; a second signal processing unit remote from the first signal processing unit and associated with an item of telecommunications equipment to pass signals between said item of telecommunications equipment and the first signal processing unit, the second signal processing unit being formed from signal processing circuitry which is independent of the operating frequency band, the signals being passed between the first signal processing unit and the second signal processing unit at the second frequency via a connection medium connecting the first and second signal processing units.
In accordance with the present invention, the subscriber terminal comprises two distinct signal processing units, the first signal processing unit being associated with an antenna of the subscriber terminal, and t
Cooper Ian L.
Gohlar Tarlochan S.
Lysejko Martin
Airspan Networks Inc.
Baker & Botts L.L.P.
Cumming William
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