Note: Descriptions are shown in the official language in which they were submitted.
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Translation of PCT/EP04/003251
Method and tester for determining an error rate of a
mobile-telephone device with variable block assignment
The invention relates to a method and a tester for
determining an error rate of a mobile-telephone device in
the case of a data transfer with variable block
assignment.
The basic structure of a known GSM mobile-telephone
system, for example, as described in "Digital Mobile
Telephone Systems", Dr.-Ing. Klaus David and Dr.-Ing.
Thorsten Benkner, B. G. Teubner Stuttgart 1996, pages 326
to 341, is shown in much simplified form in Figure 5. In
a mobile-telephone system of this kind structured
according to the GSM standard, a mobile-telephone device,
which is disposed, for example, in the motor vehicle 1
illustrated in Figure 5, communicates with a base station
2.
In order to transmit information between the base station
2 and the mobile-telephone device, a downlink signal 3 is
transmitted from the base station 2 to the mobile-
telephone device, and an uplink signal 4 is transmitted
back from the mobile-telephone device to the base station
2. To keep the downlink signal 3 and the uplink signal 4
separate from one another, both signals are transmitted
with different carrier frequencies (FDD, Frequency
Division Duplex).
The transmission of information in the downlink signal 3
and in the uplink signal 4 does not take place in a
continuous manner, but in so-called bursts, wherein,
eight such bursts of a respective downlink signal 3 or
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uplink signal 4 together form a frame. In Figure 5, a
downlink frame of this kind is indicated by the reference
number 5, and the corresponding uplink frame is indicated
by the reference number 6, wherein each burst is
transmitted in a timeslot of a frame. The timeslots are
numbered continuously from 0 to 7. The downlink frame 5
is transmitted with a first carrier frequency flDL. and
the uplink frame 6 is transmitted with a corresponding
carrier frequency floL~
The information is transmitted only in individual bursts
of the respective downlink signal 3 or uplink signal 4.
For this purpose, one or more given timeslots 0 to 7 of
the frame are assigned by the base station 2 to the
mobile-telephone device of the motor vehicle 1. Each
timeslot 0 to 7 of successive downlink frames~5 and
uplink frames 6 forms a transmission channel for the
exchange of information between the base station 2 and
the mobile-telephone device of the motor vehicle 1. For
the first carrier frequency flpL and the corresponding
carrier frequency fiur. of the uplink signal 4, there are
therefore eight transmission channels, so that eight
mobile-telephone devices can exchange information with
the base station 2 independently from one another on this
pair of carrier frequencies.
In addition to the first carrier frequency flDL and the
corresponding carrier frequency fiuL for the uplink signal
4, further carrier frequencies are provided for the
downlink signal 3, and carrier frequencies corresponding
to these are provided for the uplink signal 4. As a
result of the TDMA structure with its eight timeslots 0
to 7 in one frame, there are therefore eight transmission
channels for each of the 7.24 carrier-frequency pairs in
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the context of GSM 900 as illustrated in Figure 5,
wherein all transmission channels are independent of one
another. The eight transmission channels for each carrier
frequency pair, together with the 124 independent carrier
frequency pairs, therefore provide a total of 992
transmission channels.
The use of one transmission channel simultaneously for
several mobile-telephone devices to achieve an improved
exploitation of the transmission capacity of a mobile
telephone system of this kind is already known. Within a
transmission channel, the mobile telephones are addressed
by a base station, thereby specifying which of the
several mobile-telephone devices receives data from the
base station in which timeslots.
Corresponding timeslots of four successive frames of the
downlink signal 3, or respectively the uplink signal 4,
together form a transmission block of the respective
transmission channel. For one respective transmission
block, which is transmitted from the base station, it can
be specified using an address signal ADR, to which of the
mobile-telephone devices communicating with the base
station in the same transmission channel the transmission
block is transmitted from the base station.
Once again, in a much simplified form, Figure 6
illustrates a system of this kind. A total of eight
mobile-telephone devices 7, which jointly use one
transmission channel in order to communicate with the
base station 2, are shown. This means that a given
timeslot of the downlink frame 5 and the uplink frame 6
is used for the transmission of information between the
mobile-telephone devices 7 and the base station 2. In
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order to transmit data in a transmission block from the
base station 2 to a given mobile-telephone device 8, an
address signal ADR, which respectively addresses a given
mobile-telephone device 8, is transmitted in each
transmission block of the downlink signal 9. By
evaluating the address signals ADR, the mobile-telephone
device 8 recognises that the information contained in the
transmission block is transmitted to this mobile-
telephone device. The other mobile-telephone devices 7 do
not recognise the address signal ADR as their own and
reject the information of the transmission block. The
base station 2 communicates to each mobile-telephone
device 7, for example, at the time of establishing the
connection, in which of the transmission blocks the
mobile-telephone devices 7 actually evaluate an address
signal ADR.
In this context, mobile telephones are all subscriber
devices, which communicate with the base station 2. The
correctness of the data of a transmission block received
by the mobile-telephone device 8 is checked, for example,
using a checksum. For each of the received transmission
blocks, which were addressed to the mobile-telephone
device 8, the base station 2 is notified on request,
which transmission blocks were received and evaluated
correctly. At the request of the base station 2, the
mobile-telephone device 8 therefore transmits
confirmation signals, for example, for each correctly-
evaluated transmission block, a first marking "ack"
(acknowledged), and for each incorrectly-evaluated
transmission block, a second marking "nack" (not
acknowledged). To achieve a correct communication of the
complete information to the mobile-telephone device 8,
each transmission block, for which the base station 2 has
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received, for example, a second confirmation signal
"nack", is re-transmitted.
In developing mobile-telephone devices and in testing
5 devices in production, it is necessary to determine the
number of transmission blocks received and evaluated
incorrectly and to compare these with the number of
transmission blocks transmitted and/or addressed as a
whole to this mobile-telephone device. With a given level
and given propagation conditions, a permitted maximum
threshold of ten per cent (10~) is provided in the
specification, for example, for an EGPRS, for an error
rate (BLEB, Block Error Rate) determined in this manner.
The invention is based upon the object of providing a
method and a tester for determining an error rate, with
which the error rate for various requirements of the
mobile-telephone device can be determined.
The object is achieved by the method according to the
invention as specified in claim 1 and the tester
according to the invention as specified in claim 9.
To determine an error rate of a mobile-telephone device
according to the invention, transmission blocks are
transmitted to the mobile-telephone device in order to
determine whether the mobile-telephone device has
received and evaluated these transmission blocks
correctly. The number of incorrectly-evaluated
transmission blocks, which addressed the mobile-telephone
device under test, is determined from the marking "ack"
or "nack" transmitted back respectively, and the error
rate of the mobile-telephone device is determined from
this number.
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In evaluating the data contained in a transmission block,
the mobile-telephone device is subjected to a
particularly large stress, if all of the transmission
blocks transmitted contain an address signal ADR, which
addresses the mobile-telephone device under test. The
number of transmission blocks of a multiblock, which
address the mobile-telephone device under test, is
therefore specified according to the invention. In this
context, a multiblock consists of a fixed number of
successive transmission blocks of a transmission channel.
As a result of this variable specification of the number
of transmission blocks with an address signal ADR, which
addresses the mobile-telephone device under test, the
stress on the mobile-telephone device under test can be
influenced in a targeted manner. For example, evaluations
regarding an increase in the error rate with increasing
stress are therefore also possible.
The dependent claims relate to advantageous further
developments of the method according to the invention and
the tester according to the invention.
The invention is described in detail in the description
below with reference to the drawings. The drawings are as
follows:
Figure 1 shows a schematic presentation of a signal
transmitted from a base station to a mobile-
telephone device,
Figure 2 shows a schematic presentation of several
transmission blocks respectively in one
transmission channel,
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Figure 3 shows a simplified schematic presentation of a
tester according to the invention,
Figure 4 shows examples for the addressing of a
different number of transmission blocks of one
multiblock in each case to the mobile-
telephone device under test and their
different arrangement,
Figure 5 shows a schematic presentation of the
transmission of information in a mobile
telephone system according to the GSM
standard, and
Figure 6 shows a schematic presentation of the
transmission of information between a base
station and several mobile-telephone devices
in one transmission channel.
Figure 1 again illustrates the structure of a downlink
signal by way of example. The entire signal consists of a
concatenation of individual frames, wherein eight frames
9.1 to 9.8 are shown and wherein each frame 9.1 to 9.8 is
further subdivided. The frames 9.1 to 9.8 are subdivided
into timeslots, wherein eight respective timeslots
together form one frame. The individual timeslots are
numbered continuously from 0 to 7.
The smallest unit of information, which can be
transmitted between the base station 2 and a mobile-
telephone device, is formed by one transmission block. A
transmission block of this kind consists respectively of
one given timeslot in four successive frames. By way of
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example, Figure 1 shows three examples of transmission
blocks of this kind for the first four frames 9.1 to 9.4.
A first transmission block 11.0 (BOo) is formed, for
example, from the timeslots numbered 0 of the four frames
9.1 to 9.4.
A second transmission block 12.0 (BO1) is formed
correspondingly by the timeslots with the number 1 in the
same frames 9.1 to 9.4, while the third transmission
block 13.0 (BOz) shown in the diagram is formed by the
timeslots with the number 2 in the frames 9.1 to 9.4.
Correspondingly, the three further transmission blocks
Blo, B11 and B1z are formed by the frames 9.5, 9.6, 9.7
and 9.8 with the timeslots numbered 0, 1 and 2. As
already explained in the introduction, corresponding
timeslots of mutually successive frames 9,1 to 9.8 form a
transmission channel, in which a mobile-telephone device
communicates with a base station. Accordingly, the
illustrated example shows two respective, mutually-
successive transmission blocks, 11.0 (BOo) and 11.1 (Blo)
for a first transmission channel, 12.0 (BO1) and 12.1
(B11) for a second transmission channel and 13.0 (B02) and
13.1 (B12) for a third transmission channel.
zs
The communication between a mobile-telephone device and
the base station 2 is therefore not restricted to a
single transmission channel of this kind. On the
contrary, in order to increase the quantity of data
transmissible between the mobile-telephone device and the
base station 2, any number of timeslots 0 to 7 of the
frames 9.1 to 9.8 can be used for communication between
the mobile-telephone device and the base station 2. The
number of timeslots 0 to 7, in which a mobile-telephone
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device communicates with the base station 2 can therefore
vary between one and all of the eight timeslots 0 to 7 of
a frame.
For example, all three transmission channels illustrated
in Figure 1 with the transmission blocks 11.0 and 11.1 of
the first transmission channel, the transmission blocks
12.0 and 12.1 of the second transmission channel and the
transmission blocks 13.0 and 13.1 of the third
transmission channel can be used for data transmission
between the base station 2 and the mobile-telephone
device.
The further time course is shown schematically in Figure
2, wherein, by way of explanation, the three transmission
channels, described with reference to Figure 1, are shown
again as the first transmission channel 14, the second
transmission channel 15 and the third transmission
channel 16. The individual transmission blocks BOo to Bllo
of the first transmission channel 14 are indicated by the
reference numbers 14.0, 14.1 etc. up to 14.11.
Correspondingly, the individual transmission blocks BO1 to
B111 of the second transmission channel 15 are indicated
by the reference numbers 15.0 to 15.11, and the
transmission blocks BOz to Bllz of the third transmission
channel 16 are indicated with the reference numbers 16.0
to 16.11.
For each transmission channel 14, 15 and 16, the
illustrated twelve successive transmission blocks 14.0 to
14.11, 15.0 to 15.11 and 16.0 to 16.11 respectively form
a multiblock of the corresponding transmission channel
14, 15 and l6. Each of the illustrated transmission
blocks BO1 to 8111 is assigned to a given one of the
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mobile-telephone devices 7 by means of an address signal
ADR, which is transmitted in a header of the respective
transmission block of the transmission blocks of the
downlink signal 9 from the base station 2.
To provide a measure for the quality of the data
evaluation of a mobile-telephone device, the number of
transmission blocks of the downlink signal incorrectly
evaluated by the mobile-telephone device is determined.
For this purpose, the corresponding markings, which are
transmitted back to the base station by the mobile
telephone device on request from the base station, are
evaluated.
1S For example, with regard to transmission channel 14, the
number of transmission blocks 14.0 to 14.11, in which the
base station 2 transmits to the mobile-telephone device
under test is specified according to the invention in a
variable manner between only one of the transmission
blocks 14.0 to 14.11 and a maximum of all twelve
transmission blocks 14.0 to 14.11 of a multiblock of the
transmission channel 14. Accordingly, the stress, to
which the mobile-telephone device under test is
subjected, can be influenced in a targeted manner.
while only a slight stress to the mobile-telephone device
under test is caused by isolated transmission blocks
addressing the mobile-telephone device under test,
because there is a considerable time interval between the
individual evaluation algorithms to be implemented by the
mobile-telephone device under test, the maximum stress is
caused in the evaluation of the transmission blocks 14.0
to 14.11, when determining the error rate, for example,
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of the first transmission channel 14, with the maximum of
twelve transmission blocks 14.0 to 14.11.
By preference, the error rate is determined not only
through the evaluation of the number of transmission
blocks transmitted in the first transmission channel 14
to the mobile-telephone device under test, but
additionally with the use of several timeslots, that is
to say, for example, by the additional use of the second
transmission channel 15 and the third transmission
channel 16 and by also transmitting transmission blocks
addressed to the mobile-telephone device under test in
these transmission channels, According to one preferred
embodiment of the method according to the invention, the
number of transmission channels used can also be adjusted
in a variable manner between only one transmission
channel and all of the transmission channels determined
by the timeslots of the frame. In the example of a mobile
telephone system provided in the introduction, there are
eight transmission channels for the respective eight
timeslots 0 to 7 of the frame.
In this context, the number of transmission blocks, which
address the mobile-telephone device under test, can be
specified separately for the individual transmission
channels used. The specification of the transmission
channels, in which a communication takes place between
the base station 2 and the mobile-telephone device 8, is
preferably implemented at the time of establishing the
connection. For example, if more transmission blocks are
used for the transmission of data from the base station 2
to the mobile-telephone device 8 in order to increase the
data rate,-a new agreement regarding the transmission
channels is made between the mobile-telephone device 8
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and the base station 2, which then applies until further
instructions.
By way of example, Figure 4 shows a mobile-telephone
device, for which the error rate is to be determined, in
communication with a base station 2 or respectively with
a tester emulating a base station, in four transmission
channels, which are represented respectively by a
multiblock 20, 21, 22 and 23. The schematic structure of
a tester of this kind according to the invention is
described below with reference to Figure 3. While, in the
first two transmission channels 20 and 21, which are
marked with the index "0" and respectively "1" in the
individual transmission blocks BO1 to BO11, four
transmission blocks respectively are transmitted to the
mobile-telephone device under test 8, in other words,
these transmission blocks contain a corresponding address
signal ADR in the header, the transmission channels with
the index "2" and respectively "3" contain three or
respectively five transmission blocks, which address the
mobile-telephone device under test. The transmission
blocks, in which data are transmitted from the base
station 2 to the mobile-telephone device under test, are
indicated with an arrow.
The other transmission blocks can preferably contain
dummy data, for example, a predetermined data record
without information content. In this context, the
association of four timeslots to form one transmission
block can also be cancelled. For the transmission blocks,
which do not address the mobile-telephone device under
test, any measures are permissible in principle, provided
it can be ensured that these transmission blocks do not
transmit any information to the mobile-telephone device
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under test. For example, it is also possible to transmit
to another mobile-telephone device or to reduce the
level.
Figure 4 also illustrates the possibility of using
identical or different patterns for the arrangement of
the transmission blocks addressed respectively to the
mobile-telephone device under test in different
transmission channels, also with an identical number of
transmission blocks transmitted to the mobile-telephone
device. For example, a uniform arrangement of the four
transmission blocks transmitted to the mobile-telephone
device under test can take place via the transmission
blocks of a multiblock, as illustrated for the multiblock
indicated with reference number 20.
However, the transmission blocks BO1 to 8111 of a second
multiblock 21, which are transmitted to the mobile-
telephone device, are distributed in an irregular manner.
The arrangement within a multiblock can, for example, be
purely random, thereby providing a statistical
distribution, which reduces the probability of the
occurrence of a systematic error in the implementation of
the measurement.
For a third multiblock 22, a uniform distribution of the
transmission blocks transmitted to the mobile-telephone
device under test is once again illustrated, wherein the
number of transmission blocks addressing the mobile-
telephone device under test is reduced by comparison with
the two multiblocks 20 and 21.
Similarly, the number and the arrangement of the
transmission blocks in the multiblock of the individual
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transmission channels can be selected to be the same for
all multiblocks and transmission channels.
In particular, a different arrangement and mutually
different numbers of transmission blocks, which address
the mobile-telephone device under test, can also be
specified for multiblocks of the same transmission
channel disposed in time succession relative to one
another. This is especially advantageous, if the
determination of the error rate is to be defined for
variable conditions of the mobile-telephone device.
A tester 25 according to the invention and an arrangement
with a mobile-telephone device under test 1 are shown in
a much simplified form in Figure 3. The tester 25
according to the invention comprises a
transmitterlreceiver device 26, which comprises a
transmitter device 26.1 for the transmission of a
downlink signal and a receiver device 26.2 for receiving
an uplink signal transmitted by the mobile-telephone
device under test 31 via its antenna 32. Data are
transmitted between the mobile-telephone device 31 and
the tester 25 either via the antennae 30, 32 or via a
connecting cable.
Message signals, that is to say, including the
confirmation signals "ack" and respectively "nack", which
are transmitted by the mobile-telephone device under test
31, are received by the receiver device 26.2. The
receiver device 26.2 is connected to an evaluation unit
27, which registers the number of correctly-evaluated or
incorrectly-evaluated transmission blocks of the downlink
signal. If only the number of correctly-evaluated
transmission blocks is determined, the corresponding
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number of incorrectly-evaluated transmission blocks can
be calculated.
The evaluation unit 27 also comprises a computer unit,
5 which is suitable for determining an error rate for the
mobile-telephone device 31 from the number of
incorrectly-evaluated transmission blocks.
The error rate determined in the evaluation unit 27 is
10 then displayed on a display device 29. The display on
this display device 29 can be provided either by
displaying a numerical value or via a corresponding
graphic display. Instead of the integrated display device
29, as shown by way of example in Figure 3, the output
15 may, of course, also be provided on a screen, for
example, of a connected computer system.
In order to specify the transmission blocks addressing
the mobile-telephone device under test 31, a selection
device 28 is also disposed in the tester 25 according to
the invention. On the basis of the specifications set by
an operator of the tester 25 according to the invention,
the selection device 28 defines which transmission blocks
of the downlink signal are transmitted via the antenna 30
of the tester 25 or the connecting cable with an address
signal ADR addressing the mobile-telephone device under
test. In this context, it has already been explained with
reference to Figure 4, that, for different transmission
channels and/or for multiblocks transmitted successively,
a different number of transmission blocks addressing the
mobile-telephone device 31 under test, which can,
moreover, be arranged differently within a multiblock,
can be transmitted in each case.
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The selection device 28 therefore comprises means 28.1,
with which a respectively variable stress on the mobile-
telephone device 31 can be generated. In the simplest
case, a memory is provided for this purpose, in which a
profile for the successively transmitted multiblocks is
stored for each of the transmission channels used, which
specifies the number and distribution of the transmission
blocks, which are transmitted to the mobile-telephone
device under test. In order to determine the number and
the distribution of transmission blocks transmitted to
the mobile-telephone device under test 31, the number and
distribution of address signals ADR addressing the
mobile-telephone device for the subsequent multiblocks
could also conceivably be calculated from the preceding
multiblocks by means of a routine in the selection device
2$.
During the implementation of the method according to the
invention for determining the error rate, it is also
possible for the base station 2 or respectively the
tester 25 used for the implementation and the mobile-
telephone device under test to communicate with one
another via a sudden-frequency-change process. In this
case, the term "transmission channel" relates to the
connection between the base station 2 and the mobile-
telephone device under test including the sudden-
frequency change. This means that the transmission
channel is then continued with the new carrier frequency,
and the specification of the number of transmission
blocks, which addresses the mobile-telephone device under
test, does not take the respective sudden-frequency
change into consideration.
