Concept for combining coded data packets
Description
The present invention relates to a concept for transmitting payload data (useful data,
Nutzdaten) in the form of a plurality of coded data packets that may be combined, at the
receiving end, such that they are adapted to a transmission quality, so as to adapt a coding
gain to the transmission quality and/or to a transmission situation. Embodiments of the
present invention may be employed, in particular, in unidirectional multipoint-to-point
transmission systems.
For transmitting small payload data quantities as arise, e.g., with measuring devices, such
as heating, electricity or water meters, for example, two different transmission modes may
be employed, in principle. For one thing, sensor and/or payload data may be transmitted
from a transmitter associated with the measuring device in question to a central receiver by
means of unidirectional transmission (multipoint-to-point transmission). With such
unidirectional transmission, the transmitter cyclically transmits its transmitter identification
and a current sensor value at specific transmission times, which in most cases are selected
randomly. Time lags between the transmission times are mostly adapted to a battery
characteristic and selected such that a battery life becomes maximal. In this context, the
transmitter will receive no confirmation whatsoever from the central receiver concerning
the receipt of the sensor value, i.e. it has no knowledge of whether or not a transmission
packet containing the sensor value has arrived at the receiver and/or has been able to be
decoded. If, however, such an acknowledgement of receipt (ACK/NAK) is desired, one
may fall back on bidirectional transmission.
In bidirectional transmission, a transceiver is provided at the sensor end. The transceiver
transmits its sensor data and/or data packets only when asked to do so by a remote-side
sensing device (central receiver). To this end, the sensor-end transceiver must constantly
listen in to a radio channel to find out whether or not there is a transmission request
directed at it.
For sensor and/or payload data transmission, so-called (wireless) sensor networks are also
being used more and more frequently, wherein information about individual subscribers or
nodes of the network are relayed until they eventually arrive at the desired information
receiver. In this manner, data may be routed over a long distance if sensor nodes exist
accordingly.
For sensor and/or payload data transmission, simple low-cost telemetry transceivers
comprising amplitude (ASK) or frequency modulation (FSK) are mostly employed in the
above-mentioned system approaches. In this context, reception is often not coherent, and in
most cases no channel coding is utilized.
In contrast, in more complex digital wireless communication systems, transmission modes
are used nowadays which transmit information and/or payload data such that they are
distributed to different data packets that are sent out in a temporally and/or spatially offset
manner, and such that they have different redundancy information, i.e. are channel-coded
differently. Given high signal quality, i.e. a high signal-to-noise ratio (SNR), the coded
data packets may be received and decoded individually. If the SNR at the receiver
decreases, a code gain or coding gain may be realized by combining two or more data
packets received. In coding theory, the code gain describes a difference of a required bit
energy in relation to a noise power spectral density between an uncoded and a coded
message in order to achieve an identical bit error rate. The uncoded message represents the
reference with which the message coded by means of channel coding is compared. Such
transmission modes, which are also referred to as code-combining and/or incrementalredundancy
transmission modes, have been frequently applied, in the prior art, with socalled
packet-oriented automatic repeat request protocols (ARQ protocols). If an error
arises, at the receiving end, in decoding a data packet, a further data packet with
redundancy, i.e. a further coded data packet, is requested at the transmitter via a return
channel.
ARQ protocols are used in communication networks to guarantee reliable data
transmission by means of repeat transmissions. By means of a possibility of error
recognition, a receiver may ascertain any transmission errors that have occurred in data
packets. Via the return channel, said receiver may communicate the result of the error
recognition to the transmitter of the data packet. This is usually effected by transmitting socalled
ACK/NAK signals (acknowledgement or negative acknowledgement, i.e. correct
receipt confirmed, or request for repetition). If need be, a disturbed message is
retransmitted until such time as it has reached the receiver without any errors.
So-called hybrid ARQ protocols (HARQ) represent an extended variant of the ARQ
protocol, which comprises combining ARQ mechanisms, such as check sum formation,
block confirmation and/or block repetition, with error-correcting coding. In this context,
payload data may be channel-coded with an error-correcting block code or an errorcorrecting
convolution code. I.e., unlike ARQ methods, wherein only error-recognizing
redundancy information (e.g. CRC) is transmitted in addition to the payload data in a data
packet, HARQ methods additionally comprise transmission of error-correcting redundancy
information in the data packet in accordance with forward error correction methods (FEC
methods). One may basically distinguish between three different types of HARQ methods:
The simplest version, type I HARQ, adds both error-recognizing and error-correcting
redundancy information to the payload data prior to each transmission so as to obtain a
coded data packet. When the coded data packet is received, the receiver first of all decodes
the error-correcting channel code. Given sufficient transmission quality, all of the
transmission errors should be correctable, and the receiver should thus be able to obtain the
correct payload data. If the transmission quality is poor, and if, consequently, not all of the
transmission errors can be corrected, the receiver may ascertain this by means of the errorrecognizing
code. In this case, the coded data packet received is discarded, and repeat
transmission is requested via a return channel. Thus, type I HARQ designates transmission
with perfectly identical repetition of the data sent in the initial transmission. Upon renewed
reception of the data, information that was generated in the previous reception of said data
may be reused. A possible principle for this is known from IEEE Transactions on
Communications, Vol. COM-33, No. 5, May 1985, D. Chase, "Code Combining - A
Maximum-Likelihood Decoding Approach for Combining an Arbitrary Number of Noisy
Packets". In this context, payload data is transmitted in data packets that are coded with a
code having a relatively high code rate R and that are repeated to achieve reliable
communication if the redundancy of the code is not sufficient to overcome, e.g., channel
interference problems. The receiver combines received noisy data packets to obtain a
combined data packet having a code rate R' < R small enough to ensure reliable
combination even with transmission channels that cause extremely high error rates. In this
context, one tries to reduce the delay (caused by packet repetitions) to a minimum by
combining a minimum number of data packets while realizing a sufficiently good and high
code rate in order to reliably decode the payload data transmitted.
In accordance with a further conventional method, logarithmic likelihood ratios (LLR - log
likelihood ratios) for payload data of the previously transmitted data packet, said payload
data having to be decoded, are determined during a decoding attempt of a previously
transmitted data packet. If a decoding attempt fails, renewed transmission of the
corresponding data packet is effected. For decoding the payload data of the newly sent data
packet, the LLRs determined during the previous decoding attempt are utilized as a-priori
information in a forward-moving procedure, similar to the known turbo-code principle.
With type II HARQ, a repeat transmission does not involve repeating precisely the data of
the initial transmission, but involves transmitting additional redundancy that would not be
decodable on its own without the data of the initial transmission (non-self-decodable).
Such type II HARQ methods are typically also referred to as incremental-redundancy
HARQ methods. In this context, the payload data and error-recognizing bits (CRC) are
initially coded at the transmitter end, for example by means of a systematic "parent" code.
This results in a code word consisting of systematic bits and so-called parity bits. In the
first data packet sent, the systematic portion of the code word and a specific number, i.e.
not all, of the parity bits which together form a code word of a parent code are sent. Said
code word is coded at the receiver end. If this is not possible and if repeat transmission is
requested, the transmitter will transmit, in a subsequent data packet, additional parity bits
of possibly different powers and/or at altered channel conditions. Upon reception of the
subsequent data packet, a new decoding attempt is made, which involves combining the
additional parity bits with the ones previously received. This process can be repeated until
such time as all of the parity bits of the parent code have been transmitted.
As was already described at the outset, there are simple digital wireless communication
systems comprising only unidirectional transmission from the transmitter to the receiver,
i.e. without any return channel. Such unidirectional multipoint-to-point communication
systems are particularly suitable for low-cost transmission of small quantities of payload
data as arise, e.g., with measuring devices, for example heating, electricity or water meters.
However, with such communication systems, wherein a multitude of transmitters
communicate with one receiver (multipoint-to-point), there is the problem that substantial
interference may result at the receiver, depending on the number of transmitters and their
random transmission times. Due to random transmission times of the transmitters and their
number, which is often not predictable either, the interference or reception quality achieved
at the receiver is not predictable. Nevertheless, it is to be ensured that transmitter-specific
payload data can be decoded fast, efficiently and reliably at the central receiver even under
most diverse receiving conditions.
The object of the present invention thus is to provide a concept with which payload data
may be decoded as fast, efficiently and reliably as possible under diverse receiving
conditions in a unidirectional multipoint-to-point communication system.
This object is achieved by a transmitter having the features of claim 1, a receiver having
the features of claim 10, and a method as claimed in claims 17 and 18.
Embodiments of the present invention additionally include computer programs for
performing the inventive methods.
The finding of the present invention consists in achieving the above object by using code
combining and/or incremental redundancy in a wireless, unidirectional multipoint-to-point
transmission system without return channel from the central receiver to the individual
transmitters. In an inventive multipoint-to-point transmission system, a plurality of
subscribers, or transmitters, transmit their respective payload data in the form of coded
data packets to a central receiver at a random or pseudorandom transmission time in each
case. Transmission of the coded data packet associated with a payload data packet takes up
a specific transmission time interval T in each case. Given a large number of transmitters
M, many data packets from different transmitters will arrive at the central receiver at the
same time, which leads to increased interference at the receiver and, thus, to aggravated
receiving conditions. In accordance with an embodiment of the present invention, the
transmitters transmit their respective payload data within their transmission time interval T
by means of N coded data packets, which may comprise different redundancy information
and/or are coded differently. Depending on the transmission quality, in the receiver, a
channel-coded data packet may then be decoded by itself, or several channel-coded receive
packets of a subscriber may be combined so as to obtain an overall higher redundancy
and/or a higher code gain on account of the combination. The generator polynomials for
the convolution encoder and puncturing schemes for differently coding the payload data
into N coded data packets are selected such that at the receiver, a coded data packet may be
decoded by itself, but also several data packets may be decoded together.
In a non-synchronous multipoint-to-point transmission system without return channel, the
receiver may possibly have to sort a large number of receive packets (M · N per
transmission time interval T) so as to combine the proper data packets. Since the
transmission times of the coded data packets are random or pseudorandom, the receiver
will not be readily able to recognize which receive packets belong together. This will be
the case, in particular, if the receiver and/or the transmitters are mobile. It would take up
too much computing time to try out all of the possible combinations of data packets, and it
would not be possible, or require a large amount of computing expenditure, to operate the
system in real time.
The inventive approach may also be advantageously employed for increasing the effective
range of the transmission system. In addition, for example the receiver and/or at least some
(or all) of the transmitters of the transmission system may be mobile, and, thus, the
distances between transmitter and receiver may change, so that different receptionthreshold
SNRs may arise due to the different distances. In accordance with the invention,
in the receiver, a coded data packet of the transmitter may be decoded by itself, or several
data packets of the transmitter may be decoded together. Given a small distance between
transmitter and receiver, for example a coded data packet by itself or only a combination of
few data packets is sufficient to be able to decode the original payload data. In addition, it
is also possible to combine several data packets sent out by a transmitter having an
increased distance from the receiver so as to achieve a reduction in the reception-threshold
SNR, so that the effective range, i.e. for fixed reception, may be realized by a receiver-end
combination of several data packets of the respective transmitter. This approach is
advantageous particularly when poor transmission conditions arise for transmissions over
long distances.
In accordance with embodiments of the present invention, specific information about a
transmitted data packet is accommodated in a core area of the data packet, said core area
having improved protection. Said core area is protected by a code of relatively high
redundancy which still enables error-free decoding of the core area even with a small
signal-to-noise power ratio or signal-to-interference ratio.
Embodiments of the present invention include a transmitter for transmitting payload data to
a receiver via a communication channel within the transmission time interval T. The
transmitter comprises a means for generating a plurality of channel-coded data from the
payload data, each of the channel-coded data packets comprising packet core data having a
packet identifications that are different for each data packet, and the packet core data being
coded with a channel code of higher redundancy than the payload data. The higher
redundancy of the coded packet core data relates to the respective redundancy, associated
with the payload data, of a data packet. That is, the packet core data redundancy per coded
data packet is higher than the payload data redundancy of the coded data packet. Moreover,
the transmitter comprises a means for transmitting the plurality of channel-coded data
packets to the receiver within the transmission time interval.
In accordance with an embodiment, the redundancy of the channel code for the packet core
data is selected such that a threshold of the decodability of the packet core data is at least
as good as a threshold achieved when combining all of the possible N data packets. In
other words, a code gain of the channel code used for the packet core data is at least as
high as a code gain with regard to the coded payload data, the latter code gain being
achieved by combining all of the channel-coded data packets of the transmission time
interval T. Therefore, for example, a code rate of the channel code used for the packet core
data is equal to or lower than a code rate of the coded payload data, the latter code rate
being achieved by combining all of the channel-coded data packets of the transmission
time interval T.
In accordance with a preferred embodiment, wherein the transmitter is employed in a
multipoint-to-point transmission system, the means for generating the channel-coded data
packets is configured to provide each of the channel-coded data packets with packet core
data corresponding to the packet identification of the respective channel-coded data packet,
and to at least a portion of a transmitter identification of the transmitter. That is, in the
packet core data domain, a transmitter ID or a transmitter sub ID and a number n (n = 1,
2,..., N) of the associated data packet may be stored so as to ensure, at the receiver end, that
only different data packets of a transmitter are combined with one another.
Since an inventive transmitter may preferably be employed in a low-cost unidirectional
transmission system, the means for transmitting is configured, in accordance with
embodiments, to transmit the plurality of channel-coded data packets from the receiver to
the transmitter within the transmission time interval T in a manner that is independent of a
return channel with regard to content and transmission times. I.e., transmission of the
plurality of channel-coded data packets is effected independently of reception of the
plurality of channel-coded data packets and/or of success or failure of decoding the
payload data.
Embodiments of the present invention further include a receiver for receiving the payload
data transmitted from an inventive transmitter to the receiver via a communication channel
within a time interval T by means of a plurality of channel-coded data packets. Each of the
channel-coded data packets comprises packet core data having a packet identification of
the respective channel-coded data packet, the packet core data being coded with a channel
code of higher redundancy than the payload data. The receiver comprises a means for
receiving the plurality of channel-coded data packets within the time interval T, and a
decoder adapted to decode packet core data of a first received channel-coded data packet of
the time interval, and, in the event of failure of error-free decoding of the first channelcoded
data packet, to decode packet core data of at least one second received channelcoded
data packet of the time interval T so as to determine a suitable further channel-coded
data packet of the time interval for combination with the first channel-coded data packet so
as to obtain, on account of the combination, an increased code gain for decoding of the
payload data.
Combining of received channel-coded data packets will only take place, therefore, if the
redundancy information, or the error-corrected redundancy information, of a first received
channel-coded data packet is not already sufficient for error-free decoding of the payload
data. This is the case, for example, in the event of poor receiving conditions (e.g. low
SNR). To this end, the receiver is configured, in accordance with preferred embodiments,
to combine the channel-coded first data packet with a further second data packet into a new
(longer) data packet, i.e. to reverse the puncturing in accordance with the scheme in the
transmitter and to decode said combined longer data packet so as to obtain the increased
code gain.
Since, in accordance with embodiments, the receiver is a central receiver in a
unidirectional multipoint-to-point transmission system, the receiver does not have, in
accordance with a preferred embodiment, any return channel that would lead to any
transmitter, so that the transmitter cannot be caused to repeatedly transmit a channel-coded
data packet in the event that decoding of the payload data has failed.
At least one transmitter and one receiver in accordance with embodiments of the present
invention may be combined into a system for transmitting payload data from the at least
one transmitter to the receiver within a time interval. The system then comprises a means
for generating a plurality of channel-coded data packets from the payload data, each of the
channel-coded data packets comprising packet core data corresponding to a packet
identification of the respective channel-coded data packet, and the packet core data being
coded with a channel code of higher redundancy than the payload data. In addition, a
transmitter is provided for transmitting the plurality of channel-coded data packets within
the time interval. The system also includes a receiver for receiving the plurality of channelcoded
data packets within the time interval. Said receiver is coupled to a decoder adapted
to decode packet core data of a first received channel-coded data packet of the time
interval, and, in the event of failure of error-free decoding of the first channel-coded data
packet, to decode packet core data of at least one second received channel-coded data
packet of the time interval so as to determine a suitable further channel-coded data packet
of the time interval for combination with the first coded data packet so as to obtain, on
account of the combination, an increased code gain for decoding of the payload data.
Thus, embodiments of the present invention enable effective utilization of incremental
redundancy and/or code combining even for unidirectional transmission modes without
return channel, in particular in multipoint-to-point transmission systems wherein many
subscribers transmit data to a central receiving point. As a result, a larger transmission
range may be achieved than in the prior art by reducing a necessary signal-to-noise ratio at
the receiver. Alternatively, it is also possible to reduce the transmitting power required
while maintaining the transmission range. In addition, higher transmission reliability also
results in the case of time-variant transmission channels as arise, for example, on account
of mobile transmitters and/or receivers. I.e., the present invention enables incremental
redundancy and/or code combining at the receiver without using a return channel from the
receiver to a transmitter for this purpose.
Preferred further developments of an inventive transmitter/receiver are the subject matter
of the respective dependent claims.
Preferred embodiments of the present invention will be explained in more detail below
with reference to the accompanying figures, wherein:
shows a schematic representation of a unidirectional multipoint-to-point
communication system comprising a plurality of transmitters and a central
receiver in accordance with embodiments of the present invention;
shows a schematic representation of the generation of a plurality of channelcoded
data packets from a payload data packet in accordance with an
embodiment of the present invention;
shows a schematic representation of a plurality of generated coded data packets
in a time interval in accordance with an embodiment of the present invention;
shows a schematic representation of a unidirectional transmission of incremental
redundancy by means of a plurality of coded data packets in accordance with a
further embodiment of the present invention;
shows a schematic structure of a data packet in accordance with an embodiment
of the present invention; and
shows a schematic representation of a transmitter-specific frequency offset
relative to a nominal transmitting frequency.
Fig. 1 schematically shows a multi-subscriber communication system 100 wherein a
plurality of transmitters 110-m (m = 1, 2, M) unidirectionally transmit their payload
data 112-m to a central receiver 120 in each case, i.e. there is no return channel from the
receiver 120 to any of the transmitters 110-m (m = 1, 2, M).
Each of the transmitters 110-m (m = 1, 2, M) comprises a means ENC for generating a
plurality of channel-coded data packets from the payload data 112-m (m = 1, 2, M).
This may be interpreted to mean that the payload data 112-m (m = 1, 2, M), which is to
be transmitted within a transmission time interval in each case, has the plurality of
channel-coded data packets associated with it. In addition, each transmitter 110-m (m = 1,
2, M) comprises a means TX for transmitting the plurality of channel-coded data
packets to the receiver 120 within the time interval.
One of the transmitters 110-m (m = 1, 2, M) and/or the means ENC for generating the
plurality of channel-coded data packets is to be explained in more detail by means of Figs.
2-5. For clarity's sake, the subscriber index m (m = 1, 2, M) shall be omitted in most
cases below.
Fig. 2 illustrates that the means ENC is configured to form a plurality of channel-coded
data packets 210-n (n = 1, 2, N) from the payload data 112, each of the channel-coded
data packets 210-n (n - 1, 2, N) comprising packet core data 212-n (n = 1, 2, N)
corresponding to a packet identification P-Idn (n = 1, 2, N) that is different for each data
packet, and the packet core data 212-n (n = 1, 2, N) being coded with a channel code of
higher redundancy than the payload data 112. This means that for each data packet 210-n
(n = 1, 2, N), more redundancy information with regard to the packet core data 212-n (n
= 1, 2, N) is transmitted than is redundancy information with regard to the payload data.
The payload data 112 and/or redundancy information derived therefrom, such as errorrecognizing
redundancy information and/or error-correcting redundancy information, is
transmitted in the data packets 210-n (n = 1, 2, N) in corresponding data fields 214-n (n
= 1, 2, N). In accordance with embodiments, the payload data 112 is transmitted in an
undivided manner. Rather, all of the payload data 112 is transmitted in a state where it is
coded differently in each of the channel-coded data packets 210-n (n = 1, 2, N), or the
payload data 112 is transmitted in a state where it is coded only in a first one 210-1 of the
data packets, whereupon only additional redundancy information is subsequently
transmitted in the further data packets 210-n (n = 2, 3, N).
Since the channel-coded data packets 210-n generally comprise the coded payload data
and/or the coded payload data word together with the redundancy information (data fields
214-n), the coded data field 214-n will frequently also be represented as "payload data with
redundancy" in the context of the description which follows. It shall be noted that, in
accordance with the above explanations referring to Fig. 2, the data fields 214-n may
comprise either the coded payload data with the redundancy information derived from the
associated payload data 112, or may comprise only redundancy information derived from
the associated payload data 112.
The data packets 210-n (n = 1, 2 N) associated with a payload data packet 112 are
transmitted from the transmitter 110 to the receiver 120 within a transmission time interval
T. In this context, in accordance with an embodiment, the transmitter 110 and/or the means
TX for transmitting is configured to transmit a first one of the plurality of channel-coded
data packets 210-1 at a random time t l and to subsequently transmit any remaining data
packets 210-n (n = 2, 3, N) of the plurality of channel-coded data packets within the
transmission time interval T. Thus, the time interval T forms, as it were, a transmission
time frame for the channel-coded data packets 210-n (n = 1, 2, N) associated with a
payload data word and/or packet 112. Even though within said transmission time frame T
the individual data packets 210-n (n = 1, 2, N) may be transmitted at random or
pseudorandom transmission times t (n = 1, 2, N), time lags t = (tn+1 - t ) of
consecutive data packets 210-n, 210-(n+l) (n = 1, 2, n-1) are determined or
predetermined, in accordance with another embodiment, similar to time division multiple
access (TDMA). I.e., the means TX for transmitting is configured, in accordance with an
embodiment, to transmit the plurality of channel-coded data packets 210-n to the receiver
120 within the time interval T in accordance with time division multiple access.
As was already set forth above, the packet core data 212-n (n = 1, 2, N) include a packet
identification, or packet number P-Idn (n = 1, 2, N) that is different for each data packet
210-n (n = 1, 2, N). In a multi-subscriber system having a plurality of transmitters 110,
it is advantageous - although not compulsory - to provide, in the core data domain 212-n
of a data packet 210-n (n = 1, 2, N), at least a portion of a transmitter identification SId
m (m = 1, 2, M) of the respective transmitter 110-m in addition to P-Id (n = 1, 2,
N) so as to be able to associate the respective data packet 210-n (n = 1, 2, N) with the
correct transmitter 110-m (m = 1, 2, M) at the receiver end. This enables the receiver
120 of a non-synchronous multipoint-to-point transmission system without return channel
to sort the possibly large number of receive packets (M · N per time interval T) and to
combine the proper data packets with one another. Instead of the transmitter identification,
it would also be possible to provide time information indicating the time lag to the next
data packet transmitted. In this manner, it would also be possible to recognize any packets
that belong together.
The receiver 120 receives the transmitter-specific payload data 112-m (m = 1, 2, M)
that is transmitted from one of the transmitters 110-m (m = 1, 2, M) to the receiver 120
via a communication channel within the time interval T by means of the plurality of
channel-coded data packets. Each of the channel-coded data packets 210-n (n = 1, 2, N)
comprises packet core data 212-n (n = 1, 2, N) at least corresponding to a packet
identification of the respective channel-coded data packet 210-n (n = 1, 2, N), the
packet core data 212-n (n = 1, 2, N) being coded with a channel code of higher
redundancy than the transmitter-specific payload data 112-m (m = 1, 2, M). The
receiver 120 comprises a means RX for receiving the plurality of channel-coded data
packets 210-n (n = 1, 2, N) within the time interval T, like an antenna having a
downstream analog front end and a digital receiver stage, for example. In addition, the
receiver 120 comprises a decoder DEC adapted to decode packet core data 212-n (n = 1, 2,
N) of a first received channel-coded data packet, e.g. 210-1, of the time interval T and,
if error-free decoding of the first channel-coded data packet 210-1 fails (to obtain the
transmitter-specific payload data 112-m), to decode packet core data of at least one further
received channel-coded data packet 210-n (n = 2, 3, N) of the time interval T so as to
determine a suitable further channel-coded data packet of the time interval T for combining
with the first channel-coded data packet 210-1 so as to obtain, on account of the
combination, an increased code gain for decoding of the transmitter-specific payload data
12-m (m = 1, 2, M).
In this context, the receiver 120 comprises no return channel that would lead to any of the
transmitters 110-m (m = 1, 2, M) so as to cause it to repeatedly transmit a channelcoded
data packet in the event that decoding of the payload data 112 has failed.
In accordance with embodiments, the decoder DEC is configured to utilize any information
about redundancy and/or payload data, said information having been obtained by decoding
the first channel-coded data packet 210-1, as redundancy information for decoding the at
least second channel-coded data packet 210-n (n = 2, 3, N) so as to obtain the increased
code gain.
Since at least the transmission time i of the first data packet 210-1 for each transmitter
110-m is pseudorandom, the receiver 120 will not readily recognize which receive packets
belong together. This is the case particularly if the receiver 120 and/or the transmitters
110-m are mobile. It would take up too much computing time and/or too many hardware
resources to try out all of the possible attempts to combine data packets, and it would not
be possible, or would be possible only with a large amount of computing expenditure, to
operate the transmission system 100 in real time. For this reason, specific information
(packet core data) about the transmission packet 210-n (n = 1, 2, N) is accommodated in
the core area 212-n (n = 1, 2, N) of the data packet 210-n (n = 1, 2, N), said core area
having improved protection. Said information is at least the packet identification P-Idn (n =
1, 2, N) and preferably also the transmitter identification S-Idm (m - 1, 2, M) and/or
any information of the respective transmitter, said information being derived from said
identification. The core area and/or the packet core data 212-n (n = 1, 2, N) are
protected with a code of higher redundancy in each case than the data field 214-n (n = 1, 2,
N). It is therefore possible to decode the packet core data 212-n (n = 1, 2, N) even
with a low signal-to-noise or signal-to-interference ratio at the receiver 120 and to thus
obtain the packet identification P-Idn (n = 1, 2, N) and, if it exists, also the transmitter
identification S-Idm (m = 1, 2, M). The threshold of decodability of the packet core data
212-n (n = 1, 2, N) thus is at least as good as the threshold achieved when combining all
of the possible N data packets 210-n (n = 1, 2, N) of the transmission time frame T.
Applied differently, the code gain associated with the core area 212-n (n = 1, 2, N)
corresponds at least to the code gain resulting from the combination of all of the N data
packets 210-n (n = 1, 2, N) and/or their coded payload data fields 214-n (n = 1, 2,
N).
As was already described at the outset, there are basically different possibilities of
combining the received channel-coded data packets 210-n (n = 1, 2, N) or a portion of
same so as to obtain a higher code gain as a result of said combination.
Fig. 3a shows a transmission frame 300 of a transmitter 110. Within the transmission time
interval T, N channel-coded data packets 210-n are sent out by the transmitter 110 at
pseudorandom times tn (n = 1, 2, N). In accordance with an embodiment, each data
packet 210-n (n = 1, 2, N) in the data field 214-n (n = 1, 2, N) contains the coded
payload data, which is coded differently, and, therefore, the redundancy information differs
from data packet to data packet. I.e., in accordance with an embodiment, the means ENC
for generating is configured, for example, to generate the channel-coded data packets 210-
n (n = 1, 2, N) with respectively different redundancy information with regard to the
payload data packet 112.
An inventive approach to generating the channel-coded data packets 210-n having
respectively different coded payload data and associated redundancy information with
regard to the associated original payload data packet 112 is represented by way of example
by means of Fig. 3b. As is depicted in Fig. 3b, the payload data 12 of the length L is
supplied to the coder ENC, e.g. a convolution encoder, at the code rate R' < R N, which
generates a coded long data packet 210 of the length L/R' from the payload data 112. With
regard to the overview shown in Fig. 3b, it shall be noted that in said overview only the
coded payload data with the redundancy information (data fields 214-n) derived from the
payload data are depicted in the data packets 210-n without explicitly indicating the
associated core data 212-n, which may be associated, for example, with the associated data
fields 214-n prior to the transmission operation.
In accordance with the invention, a so-called puncturing scheme is performed, at the
convolution encoder ENC, on the long code word 210 obtained, puncturing comprising
omitting and/or taking out ("puncturing") specific positions of the long code word
obtained. In this manner, the resulting code rate may be increased, for example. In
addition, the code word lengths may be specifically designed for a certain frame length for
subsequent data transmission and/or data storage processes, for example.
As is shown by way of example in Fig. 3b, a puncturing scheme is used wherein the coded
starting data packet 210 is split up into two equal parts (i.e. N=2), so that two punctured
transmission packets 1 and 2 result that may be transmitted, as a coded data packet 210-1,
210-2 in each case, in the form of the coded payload and redundancy data 214-1, 214-2
with the associated core data 212-1, 212-2. The coded data packets 1 and 2 may now both
comprise the same code rate Ln (R = 2) or different code rates (R ¹R2), for example.
If, for example, the punctured transmission packets 1 and 2 have the same code rate Ri=R2,
a lower combined code rate R'=Rn/2 will result in the event of a receiver-end combination
of the first data packet 210-1 and the second data packet 210-2. If a further received
channel-coded data packet 210-3 having the code rate R R1- R2 (not shown in Fig. 3b)
were utilized, at the receiver end, for decoding and combining, the combined code rate in
this case would decrease to R -R„/3 if the data was sent in such a manner that it was coded
differently 3 times accordingly. This sequence may be continued for as long as one likes.
For the above explanations it was assumed that the code rate Rn (with Ri=R2=...=Rn) is the
same in each case for the data packets 210-n used for combining and decoding.
In accordance with further embodiments of the present invention it is also possible for the
code rates Rn (n = 1, 2, N) with which the payload data 112 in the associated coded data
packets 210-n (e.g. with the punctured transmission packets) is coded to differ from data
packet to data packet. Also, it is possible that predefined groups of data packets 210-n (e.g.
with n = 1, 3, ... "odd-numbered" and/or n = 2, 4 ... "even-numbered") may have mutually
different code rates. The respective group may include any selection (e.g. individual data
packets, several consecutive data packets, etc.) of the data packets 210-n that are based on
an associated payload data packet 112. Said association of different code rates may be
effected, for example, in that the punctured data packets 210-n have different sizes, so that
R ¹ R2 results with regard to the code rates (e.g. with ¾=½ and R2= 3 , etc.). For example,
in a first data packet 210-1, a channel code of the rate may result from this, whereas in a
second data packet 210-2, the coded payload data is transmitted in such a manner that it is
coded with a channel code of the rate R2, etc.
If, at the receiver end, decoding of the first data packet 210-1 and/or of the data field 214-1
fails on account of an SNR at the receiver 120 being too low, an effective code rate of R' =
1/(1 Ri + 1/R2) = 1/(2+3) = 1/5 might be achieved by combining the first coded data packet
210-1 with the second coded data packet 210-2, which increases the likelihood of
successful decoding of the payload data 112. The fact that the proper packets are combined
with one another is ensured by previously decoding the packet core data 212-n.
In accordance with embodiments of the present invention, the encoder ENC may be
configured to generate at least one predefined group or all of the coded data packets 210-n
such that they are decodable by themselves with at the decoder end given a (sufficiently
correct) transmission, so as to obtain the associated payload data 112. Moreover, the
encoder ENC may be configured such that, additionally, also a predefined selection of the
coded further data packets 210-n (n = 2, 3, N) are combinable and decodable, for
example by reversing (feeding back) the puncturing. For example, the plurality of channelcoded
data packets 210-n may be generated from an individual, relatively long channelcoded
data packet 210 by means of suitable puncturing, for example, the convolution code
and the puncturing being selected such that each of the plurality of channel-coded data
packets is decodable by itself and/or that all of the possible combinations of the data
packets 210-n (2, 3, N data packets) are decodable by reversing the puncturing.
Said properties may be obtained, for example, by means of the selection of the generator
polynomials for the convolution encoder ENC and the puncturing patterns (puncturing
scheme). In addition, the generator polynomials for the convolution encoder ENC and the
puncturing patterns (puncturing scheme) may be adapted to the specific data rate, coding
rate and detection threshold SNR of the transmitter-receiver system. In this context, in
particular, performance properties, which are predefined by the coded transmission packets
210-n, for the decoding may be obtained or set. For example, the generator polynomials for
the convolution encoder ENC and the puncturing patterns may be selected such that a
desired performance is achieved at the decoder end, for example irrespective of which of
the coded data packets 210-n or which of the predefined groups of coded data packets are
combined and decoded at the receiver end.
In addition, such embodiments are also feasible wherein, in a later data packet, the data of
the first data packet 210-1 (coded payload data + redundancy) is not accurately repeated,
but only additional redundancy information is transmitted that would not be decodable by
itself without the data of the first data packet 210-1. I.e., in such a case, both the payload
data 112 and associated redundancy information for error recognition and correction would
be transmitted in the first data packet 210-1 only. In subsequent data packets 210-2, 210-3,
210-N, additional redundancy information would then be transmitted only in an
incremental manner. This shall be explained in more detail with reference to Fig. 4.
At the transmitter end, the payload data 112 and error-recognizing bits (CRC) are initially
coded by means of a systematic "parent" code, for example. This results in a code word
410 of systematic bits 412 and parity bits 414. In a first data field 214-1 transmitted at a
time tj, the systematic portion 412 of the code word and a specific number, i.e. not all, of
parity bits 414-1, which together form a code word 420 of a parent code, are transmitted to
the receiver 120. At a further time t2, the transmitter 110 transmits, in a data field 214-2 of
a subsequent coded data packet 210-2, additional parity bits 414-2 with possibly different
powers or by means of different channel conditions. At a further time t3, the transmitter
110 transmits additional parity bits 414-3 in a further data packet 214-3 , etc.
At the receiver end, one initially attempts to decode the code word 420. If error-free
decoding is not possible, a new decoding attempt is made, which includes combining the
additional parity bits 414-2 of the data packet 210-2 with the previously received parity
bits 414-1 of the data packet 210-1. This process may be repeated until such time as
decoding of the payload data 112 is successful.
Due to the incrementally transmitted redundancy information, the effective code rate R'
resulting from the combination may be adapted to the channel and/or transmission
properties. In the normal case, i.e. given a good channel and/or little interference between
the subscribers, only the punctured code of the first data packet 210-1 is used initially, and
it is only as the channel quality decreases that the punctured locations contained in the
subsequent data packets 210-2, 210-3, 210-N are utilized in order to increase
correctability.
In each of the different cases, the number of data packets 210-n (n = 1, 2, N) eventually
combined for error-free decoding is inversely proportional to the receiver-end SNR. I.e.,
the poorer the receiving conditions, the larger the number of data packets to be combined.
Fig. 5 once again illustrates a possible structure of a data packet 210-n (n = 1, 2, N).
The core area 212-n (n = 1, 2, N), enjoying improved protection, of the data packet 210-
n (n = 1, 2, N) contains the packet core data in the form of an optional transmitter
identification number or a portion thereof (ID/Sub ID) as well as the number of the
transmission packet (packet No.). Provision of the transmitter identification number or the
portion thereof is advantageous, particularly in case of large subscriber numbers M.
As has already been mentioned, the core area 212-n (n = 1, 2, N) is protected better than
the payload data domain 214-n (n = 1, 2, N) so that it may also be decoded under
extremely poor channel conditions (worst case). Such poor transmission conditions occur
in case of maximum temporal interference of the received data packets at the receiver 120,
i.e. if all of the M subscribers accidentally transmit at the same time. Such poor
transmission conditions also occur in the event of transmissions being effected over long
distances.
The decoding threshold of the packet core data 212-n (n = 1, 2, N) should in this context
be at least equal to or even better than the decoding threshold of the (payload) data fields
214-n (n = 1, 2, N) when combining all of the N data packets 210-n. I.e., the core area
212-n (n = 1, 2, N) should comprise, relative to its source information 512-n (n = 1, 2,
N), an at least equal or higher amount of redundancy information 5 13-n (n = 1, 2, N)
as/than the sum of the redundancy information 515-n (n = 1, 2, N) of all N data packets
210-n (n = 1, 2, N) of a transmission time interval T. For example, the core area 212-n
(n = 1, 2, N) might be protected with a convolution code of the rate ¼, whereas the
payload data 112 is protected with an effective convolution code of the rate ½. If one were
to split up the coded payload data 214-n to N = 2 payload data packets, each data packet by
itself would have the rate 1 and, therefore, no additional redundancy. When combining the
two blocks in the receiver 120, e.g. the information of the second packet 210-2 might be
used as redundancy information of the first packet 210-1.
If the payload data is coded by a convolution code of the rate 1/2, the amount (number) of
coded payload data is double the amount of the non-coded payload data. If double the
amount of coded payload data is transferred into data packets, the length of a data packet
will be equal to the length of the uncoded payload data. If one considers the code rate
between the uncoded payload data and the coded payload data of a data packet, the code
rate 1 will result. Partitioning of the data to both data packets may be performed such that
each data packet is decodable by itself, and that the code rate 1/2 results when the two data
packets are combined in the receiver. Thus, the coded payload data is split up into two data
packets that are sent out by the transmitter at different times.
In addition to the higher redundancy in the core area 212-n (n = 1, 2, N), it is also
advantageous to provide, in the core area, one synchronization word 516-n (n = 1, 2, N)
in each case, with help of which the receiver 120 may synchronize itself as fast as possible.
Said synchronization, or the synchronization word 516-n (n = 1, 2, N), is used in each
data packet 210-n (n = 1, 2, N) since in a multi-subscriber system, each transmitter
comprises its own reference clock source (oscillator) having different tolerances. In
accordance with a further embodiment, the means ENC for generating is also configured to
further provide the packet core data 212-n (n = 1, 2, N) of a channel-coded data packet
210-n (n = 1, 2, N) with synchronization data 516-n (n = 1, 2, N) so as to enable the
receiver 120 to detect the channel-coded data packet 210-n (n = 1, 2, N) from the
transmitter 110-m (m = 1, 2, M). For example, the synchronization data 516-n (n = 1, 2,
N) might be a so-called Manchester code. The Manchester code is a line code which
obtains the clock signal during coding. In this context, a bit sequence modulates the
phasing of a clock signal in a binary manner. The detection threshold, i.e. the SNR, at
which the receiver 120 must recognize an individual receive packet 210-n (n = 1, 2, N)
is dependent on an overall sensitivity of the receiver 120, which results when all of the
receive packets 210-1, 210-2, 210-N are combined. I.e., the more data packets 210-n are
combinable, the more the reception threshold will decrease, and the higher the
requirements placed upon the synchronization of the receiver 120 will be.
The transmitters send out their data packets 210-n (n = 1, 2, N) at pseudorandom times
that are initially not known to the receiver 120. If, additionally, the receiver 120 is also
mobile rather than stationary, the transmitters located in the reception range of the receiver
120 will constantly change. If a transmitter 110-m additionally sends out, in accordance
with the invention, redundant data packets for code combining, the receiver 120 should be
able to associate the data packets with a transmitter so that the proper data packets may be
combined. Association of the receive packets with a transmitter will become difficult when
the packet core data of an individual data packet cannot be unambiguously decoded due to
the interference in the transmission channel. Precisely in this case, the decodability of the
payload data 112-m is to be improved by combining several redundant data packets. If,
therefore, in a disturbed transmission channel, many receive packets were received from
several transmitters in an incomplete manner and have to be combined with one another,
this may be effected, for example, by trying all of the combination possibilities. In the case
mentioned here, incomplete reception makes itself felt, for example, in that the data
packets cannot be unambiguously associated with a transmitter since, e.g., the ID was
received incorrectly.
In the event of there being a small number of transmitters, this may still be practicable.
However, if the number of receive packets increases, e.g. because a very large number of
transmitters are located in the reception range of the receiver, the computing power
required for different combination possibilities increases exponentially as a result. In
accordance with embodiments of the present invention, however, said combination
possibilities in the receiver 120 may be restricted in a targeted manner, whereby the
processing speed of the receiver 120 may be increased.
The increased protection of the transmitter and packet identification in the core area 212-n
(n = 1, 2, N) may ensure, even in case of poor reception, that each receive packet 210-n
(n = 1, 2, N) may be unambiguously associated. Thus, data packets of identical
transmitters may be combined in the receiver 120, and computing expenditure for miscombinations
that would arise by randomly combining any data packets can be avoided.
With regard to the term "mis-combinations" it shall be noted that said term does not relate
to missing combinations but to combinations that do not lead to payload data transmitted,
i.e. to combinations yielding a wrong result. In the case of very long transmitter
identifications, which may lie at about 48 bits and more, a large amount of redundancy
information would be transmitted in the core area 212-n (n = 1, 2, N) when using the
entire transmitter identification, which may lead to increased energy consumption and,
thus, shortened battery life of the corresponding transmitter 110-m. To avoid this, it is also
possible, in accordance with an embodiment, to transmit only a portion of the transmitter
identification (sub ID) in the core area 212-n (n = 1, 2, N) or only a relatively small
MAC (message authentication code) address. Consequently, unambiguous association of
data packets 210-n (n = 1, 2, N) with a transmitter 110-m is no longer possible,
however, since several transmitters can use the same partial identification in the core area
212-n (n = 1, 2, N), so that this again may result in mis-combinations. However, their
number is far smaller than in a unidirectional multi-subscriber system without any
transmitter identification in the protected core area 212-n (n = 1, 2, N).
In accordance with further embodiments of the present invention, the number of possible
packet combinations may be limited by exploiting time information. Typically, the data
packets 210-n (n = 1, 2, N) are transmitted by the transmitter 110-m in a random
manner, but only within a certain transmission time window T. While exploiting this time
information, the receiver 120 may further limit the number of possible data packet
combinations. I.e., in accordance with embodiments, the decoder DEC is configured, at the
receiver end, to utilize information about the transmission time interval T for decoding the
packet core data 212-n (n = 2, 3, N) of the at least second channel-coded data packet
210-n (n = 2, 3, N) from the transmitter 110-m, such that starting from the first channelcoded
data packet 210-1, the at least second channel-coded data packet 210-n (n = 2, 3,
N) was received one time period, which corresponds to the time interval T, earlier or later
at a maximum.
A further approach to reducing possible data packet combinations results from different
frequency offsets of the individual transmitters 110-m with regard to a nominal
transmitting frequency fc .n om- This transmitter-specific frequency offset is typically - this is
different from transmitter to transmitter - in a range of up to ±100 ppm (parts per million),
so that the individual transmitters have slightly different transmitting frequencies fc m (m =
1, 2, M) around the nominal transmitting frequency fcnom (see Fig. 6). As a matter of
principle, the frequency offset A m (m = 1, 2, M) per transmitter intermittently lies in a
range of less than ±10 ppm, however. A frequency offset of a transmitter relative to the
nominal transmitting frequency may arise, for example, due to manufacturing tolerances of
the quartz crystal oscillator. Said frequency offset exists over a long period of time. In
addition, a frequency offset may be caused by aging of components. Said frequency offset,
too, only changes slowly over time. An intermittent change in the frequency offset may be
caused by a rapid temperature change in the electronic circuit, for example.
If the receiver is additionally configured to perform a frequency estimation of the received
signal, said information may be used for correctly combining data packets. In accordance
with embodiments, the receiver 120 may detect, for example, a frequency offset which
amounts to fm (m = 1, 2, M) and lies within the range of less than 10 ppm around f m
(m = 1, 2, M). The receiver may detect the offset of the transmitting frequency f ,m,
being possible for said frequency offset to have a fluctuation of Afm . The frequency offset
of a data packet may be used as association with a transmitter. Said frequency offset should
be in the range Afm around fc m so that the data packet is associated with the correct
transmitter. This can be used for further limiting the number of possible data packet
combinations, since only such receive packets are combined whose frequency offset A m
lies within a certain limit. I.e., the decoder DEC of the receiver 120 is configured, in
accordance with some embodiments, to determine and utilize information about a
transmitter-specific deviation Afm (m = 1, 2, M) of an actual transmitting frequency fC ,
(m = 1, 2, M) of the transmitter 110-m from a nominal transmitting frequency f .n 0m for
decoding the at least second channel-coded data packet 210-n (n = 2, 3, N) of the
transmitter 110-m and of the time interval T, such that channel-coded data packets received
with the transmitter-specific deviation may be associated with the transmitter 110-m. The
parameter fm characterizes the frequency range around f m in which a data packet may be
associated with another data packet. For example, if A m is at 10 Hz with f 1 = 6000 Hz,
and if, for example, a data packet is received at a frequency of 6004 Hz, said data packet
may be associated with a data packet having 6002 Hz.
Embodiments of the present invention may be employed, e.g., for realizing a system for
transmitting relatively small data quantities, for example sensor data of, e.g., heating,
electricity or water meters. In this context, a measuring means comprising a radio
transmitter in accordance with an embodiment of the present invention may be mounted on
the meters/sensors, said radio transmitter wirelessly transmitting the sensor data and/or
payload data to a central receiver 120 in the above-described manner. Accordingly,
embodiments of the present invention also include a communication system comprising at
least one transmitter 110 and one receiver 120 in accordance with the embodiments
described herein. Such a communication system exhibits no return channel from the
receiver 120 to any transmitter 110-m (m = 1, 2, M), and each transmitter transmits its
data packets 210-n (n = 1, 2, N) at a random or pseudorandom time tn (n = 1, 2, N)
not known to the receiver 120. Thus, the receiver 120 receives a large number of transmit
signals of different meters and/or sensors.
Even though some aspects of the present invention were described in connection with
transmit/receive devices, it shall be understood that said aspects also represent a
description of corresponding transmit/receive methods, so that a block or a component of a
transmit/receive device should also be understood as a corresponding method step or as a
feature of a method step. By analogy thereto, aspects described in connection with or as a
method step also represent a description of a corresponding block or detail or feature of a
corresponding device.
Depending on specific implementation requirements, embodiments of the invention may
be implemented in hardware or in software. Implementation may be performed using a
digital storage medium, for example a floppy disc, a DVD, a Blu-ray disc, a CD, a ROM, a
PROM, an EPROM, an EEPROM, or a flash memory, a hard disc or any other magnetic or
optical memory which has electronically readable control signals stored thereon that may
cooperate, or indeed do cooperate, with a programmable computer system such that the
respective transmission/reception method is performed. This is why the digital storage
medium may be computer-readable. Some embodiments in accordance with the invention
thus include a data carrier having electronically readable control signals that are capable of
cooperating with a programmable computer system or a digital signal processor such that
any of the methods described herein is performed.
In some embodiments, a programmable logic device (e.g. a field-programmable gate array,
an FPGA) may be used for performing some or all of the functionalities of the methods
described herein. In some embodiments, a field-programmable gate array may cooperate
with a microprocessor to perform any of the methods described herein. In some
embodiments, the methods are generally performed by any hardware device. The latter
may be a universally employable hardware such as a computer processor (CPU) or a
hardware specific to the method, such as an ASIC, for example.
The above-described embodiments merely represent an illustration of the principles of the
present invention. It is to be understood that modifications and variations of the
arrangements and details described herein will be appreciated by other persons skilled in
the art. This is why it is intended that the invention be limited only by the scope of the
following claims rather than by the specific details that were presented herein by means of
the description and the explanation of the embodiments.
Claims
1. Transmitter ( 110-m) for transmitting payload data ( 112-m) to a receiver (120) via a
communication channel within a time interval (T), comprising
a means (ENC) for generating a plurality of channel-coded data packets (210-n)
from the payload data ( 1 12-m), each of the channel-coded data packets comprising
packet core data (212-n) corresponding to a packet identification which is different
for each data packet, and the packet core data (212-n) being coded with a channel
code of a higher redundancy than the payload data ( 112-m); and
a means (TX) for transmitting the plurality of channel-coded data packets (210-n)
to the receiver (120) within the time interval (T).
2. Transmitter as claimed in claim 1, wherein the means (TX) for transmitting is
configured to transmit the plurality of channel-coded data packets (210-n) from the
receiver (120) to the transmitter (110-m) within the time interval (T) in a manner
that is independent of a return channel with regard to content and transmission
times.
3. Transmitter as claimed in any of the previous claims, wherein the means (TX) for
transmitting is configured to transmit a first one of the plurality of channel-coded
data packets (210-1) at a random time and to subsequently transmit any remaining
data packets of the plurality of channel-coded data packets within the time interval.
4. Transmitter as claimed in claim 3, wherein the means (TX) for transmitting is
configured to transmit the plurality of channel-coded data packets (210-n) at
predetermined time lags (At) within the time interval (T) after the random point in
time.
5. Transmitter as claimed in any of the previous claims, wherein the means (TX) for
transmitting is configured to transmit the plurality of channel-coded data packets
(210-n) within the time interval (T) in accordance with time division multiple
access.
6. Transmitter as claimed in any of the previous claims, wherein the means (ENC) for
generating is configured to provide each of the channel-coded data packets (210-n)
with packet core data (212-n) corresponding to the packet identification of the
respective channel-coded data packet and to at least a portion of a transmitter
identification of the transmitter.
7. Transmitter as claimed in any of the previous claims, wherein the means (ENC) for
generating is configured to generate the channel-coded data packets (210-n) with
items of redundancy information (515-n) that are different, respectively, with
regard to the payload data ( 112-m).
8. Transmitter as claimed in any of the previous claims, wherein the means (ENC) for
generating is configured to further provide the packet core data (212-n) of a
channel-coded data packet (210-n) with synchronization data so as to enable the
receiver (120) to detect the channel-coded data packet (210-n) from the transmitter
( 1 10-m).
9. Transmitter as claimed in any of the previous claims, coupled to a measuring
device, in particular a heating, electricity or water meter, so that the payload data
(112-m) is provided to the transmitter (110-m) in the form of measurement data
from the measuring device.
10. Transmitter as claimed in any of the previous claims, wherein the means (ENC) for
generating is configured to generate the channel-coded data packets (210-n) from
the payload data packet ( 112) by means of a convolution code and a puncturing
scheme, so that each channel-coded data packet (210-n) of a predefined group of
channel-coded data packets (210-n) based on an associated payload data packet
( 112) is decodable independently of the other channel-coded data packets (210-n)
of the group.
11. Transmitter as claimed in claim 10, wherein the means (ENC) for generating is
further configured such that at least a predefined selection of combinations of the
channel-coded data packets (210-n) based on the associated payload data packet
( 112-n) are decodable.
12. Receiver (120) for receiving payload data ( 112-m) transmitted from a transmitter
( 110-m) to the receiver (120) via a communication channel within a time interval T
by means of a plurality of channel-coded data packets (210-n), each of the channelcoded
data packets (210-n) comprising packet core data (212-n) corresponding to a
packet identification of the respective channel-coded data packet, and the packet
core data (212-n) being coded with a channel code of higher redundancy than the
payload data ( 112-m), comprising:
a means (RX) for receiving the plurality of channel-coded data packets (210-n)
within the time interval (T); and
a decoder (DEC) adapted to decode packet core data (212-1) of a first received
channel-coded data packet (210-1) of the time interval (T), and, in the event of
failure of error-free decoding of the first channel-coded data packet (210-1), to
decode packet core data (212-2) of at least one second received channel-coded data
packet (210-2) of the time interval (T) so as to determine a suitable further channelcoded
data packet (210-2) of the time interval for combination with the first
channel-coded data packet (210-1) so as to obtain, on account of the combination,
an increased code gain for decoding of the payload data ( 112-m).
13. Receiver as claimed in claim 12, comprising no return channel that would lead to
the transmitter ( 110-m) for causing the transmitter to repeatedly transmit a channelcoded
data packet (210-2) in the event that decoding of the payload data has failed.
1 . Receiver as claimed in claims 12 or 13, wherein the decoder (DEC) is configured to
utilize any information obtained by decoding the first channel-coded data packet
(210-1) as redundancy information for decoding the second or a further channelcoded
data packet (210-2), or vice versa, so as to obtain the increased code gain.
15. Receiver as claimed in any of claims 12 to 14, wherein the decoder (DEC) is
configured to utilize information about the time interval (T) for decoding the packet
core data (212-2) of the at least second channel-coded data packet (210-2) from the
transmitter (110-m) and of the time interval (T), such that starting from the first
channel-coded data packet (210-1), the at least second channel-coded data packet
(210-2) was received one time period, which corresponds to the time interval,
earlier or later at a maximum.
16. Receiver as claimed in any of claims 12 to 15, wherein the decoder (DEC) is
configured to determine and utilize information about a transmitter-specific
deviation ( | fc ,nom - fc ,m l ) of an actual transmitting frequency of the transmitter
( 110-m) from a nominal transmitting frequency (fc .nom) for decoding the packet core
data (212-2) of the at least second channel-coded data packet (210-2) of the
transmitter ( 110-m) and of the time interval (T), such that channel-coded data
packets received with the transmitter-specific deviation ( f ,nom - fe , l ) may be
associated with the transmitter ( 110-m).
Receiver as claimed in any of claims 12 to 16, wherein the decoder (DEC) is
configured to decode a channel-coded data packet (210-n) of a predefined group of
channel-coded data packets (210-n), which are based on an associated payload data
packet (112), independently of the other channel-coded data packets (210-n) of the
group.
Receiver as claimed in claim 17, wherein the decoder (DEC) is configured to
decode at least a predefined selection of combinations of the channel-coded data
packets (210-n) based on the associated payload data packet ( 1 12-n).
System for transmitting payload data ( 112-m) from a transmitter ( 110-m) to a
receiver (120) via a communication channel within a time interval (T), comprising:
a means (ENC) for generating a plurality of channel-coded data packets (210-n)
from the payload data ( 112-m), each of the channel-coded data packets comprising
packet core data (212-n) corresponding to a packet identification of the respective
channel-coded data packet, and the packet core data being coded with a channel
code of a higher redundancy than the payload data ( 112-m);
a transmitter (TX; 110-m) for transmitting the plurality of channel-coded data
packets (210-n) within the time interval (T);
a receiver (RX; 120) for receiving the plurality of channel-coded data packets (210-
n) within the time interval (T); and
a decoder (DEC) adapted to decode packet core data (212-1) of a first received
channel-coded data packet (210-1) of the time interval (T), and, if error-free
decoding of the first channel-coded data packet (210-1) so as to obtain the payload
data ( 112-m) fails, to decode packet core data (212-2) of at least one second
received channel-coded data packet (210-2) of the time interval (T) so as to
determine a suitable further channel-coded data packet of the time interval for
combination with the first channel-coded data packet so as to obtain, on account of
the combination, an increased code gain for decoding of the payload data.
System as claimed in claim 19, wherein no return channel is provided between the
receiver (120) and the transmitter ( 110-m) for causing the transmitter to repeatedly
transmit a channel-coded data packet in the event that decoding of the payload data
has failed.
Method of transmitting payload data ( 112-m) to a receiver (120) via a
communication channel within a time interval (T), comprising:
a generating a plurality of channel-coded data packets (210-n) from the payload
data ( 112-m), each of the channel-coded data packets comprising packet core data
(212-n) corresponding to a packet identification which is different for each data
packet, and the packet core data being coded with a channel code of a higher
redundancy than the payload data; and
transmitting the plurality of channel-coded data packets (210-n) to the receiver
(120) within the time interval (T).
Method as claimed in claim 21, in accordance with which a plurality of transmitters
(110-m) transmit transmitter-specific payload data packets (112-m) to the receiver
(120), each transmitter ( 110-m) generating a plurality of channel-coded,
transmitter-specific data packets (210-n) from the transmitter-specific payload data
packet, and each of the channel-coded, transmitter-specific data packets comprising
channel-coded, transmitter-specific packet core data (212-n) corresponding to a
packet identification of the respective channel-coded data packet and to at least a
portion of the transmitter identification of the transmitter ( 1 10-m), the transmitterspecific
packet core data being coded with a channel code of higher redundancy
than the transmitter-specific payload data packet.
Method as claimed in claims 2 1 or 22, wherein transmission of the plurality of
channel-coded data packets (210-n) within the time interval (T) is performed
independently of reception of the plurality of channel-coded data packets and/or of
success or failure of decoding of the payload data.
Method as claimed in any of claims 2 1 to 23, wherein the channel-coded data
packets (210-n) are generated from the payload data packet ( 112) by means of a
convolution code and a puncturing scheme, so that each channel-coded data packet
(210-n) of a predefined group of channel-coded data packets (210-n) based on an
associated payload data packet ( 112) is decodable independently of the other
channel-coded data packets (210-n) of the group.
Method as claimed in claim 24, wherein the channel-coded data packets (210-n) are
generated from the payload data packet ( 112) by means of the convolution code and
the puncturing scheme, so that at least a predefined selection of combinations of the
channel-coded data packets (210-n) based on the associated payload data packet
( 112-n) are decodable.
Method of receiving payload data ( 112-m) transmitted from a transmitter ( 110-m)
to a receiver (120) via a noisy communication channel within a time interval (T) by
means of a plurality of channel-coded data packets (210-n), each of the channelcoded
data packets comprising packet core data (212-n) corresponding to a packet
identification which is different for each data packet, and the packet core data (212-
n) being coded with a channel code of higher redundancy than the payload data
( 112-m), comprising:
receiving the plurality of channel-coded data packets (210-n) within the time
interval (T);
decoding packet core data (212-1) of a first channel-coded data packet (210-1) of
the time interval (T); and
in the event of failure of decoding of the first channel-coded data packet (210-1),
decoding packet core data (212-2) of at least one second channel-coded data packet
(210-2) of the time interval (T) so as to determine a suitable further channel-coded
data packet of the time interval for combination with the first channel-coded data
packet so as to obtain, on account of the combination, an increased code gain for
decoding of the payload data.
Method of receiving payload data as claimed in claim 26, wherein a channel-coded
data packet (210-n) of a predefined group of channel-coded data packets (210-n)
based on an associated payload data packet ( 112) is decoded independently of the
other channel-coded data packets (210-n) of the group.
Method of receiving payload data as claimed in claim 27, wherein a predefined
selection of combinations of the channel-coded data packets (210-n) based on the
associated payload data packet ( 12-n) are decoded.
Computer program for performing a method as claimed in any of claims 2 1
when the computer program runs on a computer or microcontroller.