Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Reexamination Certificate
2002-10-08
2004-02-10
Maung, Nay (Department: 2684)
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
C455S101000, C455S133000, C455S562100
Reexamination Certificate
active
06690927
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to digital message communication according to the DECT standard and, in particular, to a transmit-receive terminal provided for a connection-oriented communication system according to the DECT standard or according to a derivative thereof, as well as to a method for communicating between a transmit-receive terminal and a base station by means of which the communications connection can be improved.
The ETSI DECT standard (DECT=Digital Enhanced Cordless Telecommunications) provides for digital transmission of voice signals as well as for digital transmission of data. This standard (ETS 300 175, parts 2-3) describes both the physical layer, which is also referred to as PHL, and the medium access control layer, which is also referred to as MAC, of a digital communication system. The DECT concept operates as a centrally controlled system in the case of which mobile units synchronize themselves with one or a plurality of base stations.
In the following, a survey of the overall structure of a communications connection between a first mobile unit
32
and a second mobile unit
34
will be described making reference to FIG.
3
. It is assumed that the mobile unit
32
is held by a first subscriber and the mobile unit
34
by a second subscriber, and that both subscribers want to communicate via a DECT system at the first subscriber's premises, i.e. the mobile unit
32
, as well as at the second subscriber's premises, i.e. the mobile unit
34
.
Larger telephone installations consist e.g. of DECT systems in an office building, which are implemented such that persons who stay in the building possess a cordless DECT mobile unit
32
and
34
, respectively. If e.g. several persons possessing a DECT mobile unit are accommodated in one office, this office will also be equipped with a base station
30
a-
30
d so that the radio signals received by a DECT mobile unit or sent to a DECT mobile unit only have to be transmitted over the comparatively short distance, in relation to the total connection, between a respective mobile unit and the base station arranged within radio reach, whereupon they are fed into a permanently wired line
12
via respective converters in the base station.
All the DECT base stations
30
a
-
30
d
, which are accommodated e.g. in individual offices, or in the individual storeys of a multis-torey office building, are permanently wired to a respective central DECT exchange
10
. The exchange
10
is therefore the interface between the DECT system of the office building and the “outside world”, i.e. the public ISDN telecommunications network, the public analog network, a current distribution network or some other network through which data are transmitted. This other network may e.g. also be the internet. The “outside world” or rather the network in question is generally referred to as channel
38
in FIG.
3
.
FIG. 3
therefore shows the situation in which both parties participating in a telephone conversation hold a DECT mobile unit in their hands. It goes without saying that one party may have a DECT mobile unit on one side, whereas on the other side there may be a party participating in the conversation who has some other terminal device.
In the following, a description will be given of the communication taking place between the DECT mobile unit
34
and the base station
30
c
when it is assumed that the DECT mobile unit
34
is arranged in the vicinity of the base station
30
c
and is intended to communicate with this very base station
30
c
according to the protocol.
In the ETSI DECT standard (ETS 300 175) it is specified that a base station is provided with a first transmit-receive antenna
31
a
and that a base station may additionally have a second receive antenna
31
b
so as to achieve an antenna diversity in the communication between the base station and the mobile unit
34
. The antenna diversity with two antennas in the base station
30
c
serves to improve the transmission reliability between the base station
30
c
and the mobile unit
34
. Analogously, also the base station
30
a
may comprise a first transmit-receive antenna
31
c
and a second transmit-receive antenna
31
d
so as to achieve an antenna diversity also in the communication with the mobile unit
32
.
The concept described in the ETSI DECT standard is disadvantageous insofar as, in spite of the diversity possibility provided in the base station in order to improve the transmission quality, the transmission qualities achieved are still not always satisfactory.
DECT mobile units may also be self-sufficient mobile units without any subscriber, such as sensors for various purposes, operating units, printers, monitoring devices and the like. Certain self-sufficient mobile units, and in particular special sensors, may be fixedly installed. If the quality of the communications connection between the mobile unit and the base station is here poor, the so-called “human control loop” does not exist.
When telephones are considered, a telephone subscriber will, in the case of a poor communications connection, almost intuitively change position in the sense of the “human control loop” so as to obtain a better transmission quality. This possibility does, however, not exist in the case of self-sufficient mobile units having no operator.
Fixedly installed mobile units additionally entail the problem that they are fixedly installed once and for all and that they must then communicate at this fixed position. When the mobile unit is being installed, the directional characteristic of the mobile unit with respect to the base station is not necessarily taken into account. It may therefore happen that the mobile unit is installed at a position which is so unfavourable that its antenna lobe is positioned very badly with respect to the base station with which the mobile unit is intended to communicate. In this case and also in the case of a mobile self-sufficient unit, the antenna diversity of the base station will remedy the problems in question only to a very limited extent.
It is the object of the present invention to improve the transmission quality between a base station and a mobile unit in a system operating according to the DECT standard or according to a derivative of the DECT standard.
In accordance with a first aspect of the present invention, this object is achieved by a transmit-receive terminal for a connection-oriented communication system operating according to the DECT standard or according to a derivative thereof, said transmit-receive terminal being implemented for communicating with a base station provided with a plurality of transmit-receive antennas, comprising: a plurality of transmit-receive antennas for communicating with a base station; a device for determining the quality of a communications connection between the transmit-receive terminal and the base station; and a switch for switching over from one transmit-receive antenna to another transmit-receive antenna, said switch being effective for switching over if the quality of the communications connection is below a pre-determined threshold, said switch being arranged for switching over from one transmit-receive antenna to the other transmit-receive antenna with a time constant which differs from a time constant with which a change from one transmit-receive antenna of the base station to another transmit-receive antenna of the base station is effected in the base station.
In accordance with a second aspect of the present invention, this object is achieved by a method for communicating between a transmit-receive terminal including at least two transmit-receive antennas and provided for a connection-oriented communication system, which operates according to the DECT standard or according to a derivative thereof, and a base station provided with a plurality of transmit-receive antennas, comprising the following steps: transmitting/receiving by means of the transmit-receive terminal making use of a transmit-receive antenna; determining in said transmit-receive terminal the
Gerhaeuser Heinz
Heuberger Albert
Hupp Juergen
Kleinhenz Thomas
Noether Frank
Fraunhofer-Gessellschaft Zur Foerderung der Angewandten Forschun
Lee John J
Maung Nay
Vedder Price Kaufman & Kammholz P.C.
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