Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
  • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
  • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
  • H04B7/0842—Weighted combining
  • H04B7/0848—Joint weighting
  • H04B7/0857—Joint weighting using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/0202—Channel estimation
  • H04L25/0204—Channel estimation of multiple channels
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/0202—Channel estimation
  • H04L25/0224—Channel estimation using sounding signals
  • H04L25/0226—Channel estimation using sounding signals sounding signals per se
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
  • H04L25/03006—Arrangements for removing intersymbol interference
  • H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
  • H04L2025/03426—Arrangements for removing intersymbol interference characterised by the type of transmission transmission using multiple-input and multiple-output channels

Definitions

• Mobile radio system method for transmitting a user datastream and for detecting a transmission mode in a mobile radio system and mobile station
• the invention relates to devices and methods for the transmission of a user datastream in a mobile radio system with a transmitter with a first transmitting antenna and with a second transmitting antenna, which is spatially separated from the first transmitting antenna, to a receiver with a first receiving antenna and with a second receiving antenna, which is spatially separated from the first receiving antenna.
• Mobile radio systems with a plurality of antennas, in particular at the base station end are known from e.g. so-called "transmission diversity" systems, in which a plurality of antennas at the transmitting end and/or the receiving end are used to achieve improved transmission reliability by exploiting spatial diversity.
• Mobile stations with a plurality of antennas are also being developed, however, in the course of the development of existing mobile radio systems, such as GSM and the associated EGPRS Standard in connection with the so-called 3GPP-GERAJSf Project ("Feasibility study for evolved GSM/EDGE Radio Access Network
• MIMO Multiple Input Multiple Output
• a spatial selectivity is used here for the common transmission of a plurality of datastreams via a common physical medium, in particular the air interface.
• An object of the invention is further to improve mobile radio systems of the above-mentioned kind.
• the data transmission rates or error susceptibility of new mobile stations is to be improved without extensive interventions into existing mobile radio systems becoming necessary for this purpose .
• the object is achieved by means of a mobile radio system, a method for transmitting a user datastream and a mobile station according to claims 1, 6 and 10.
• the object is likewise achieved by means of a mobile radio system and a method for detecting a transmission mode of a receiver according to claims 3 and 9, which enable, in particular, the integration of the transmission method according to the invention into existing mobile radio systems, wherein existing network equipment and mobile telephones may continue to be used in the conventional manner.
• assigned to a training sequence used for encoding a first partial transmit datastream is an associated partner training sequence, which is matched to the training sequence in respect of its correlation properties and which is used for encoding a second partial datastream.
• the encoding may thereby be undertaken either jointly with or independently of a modulation used.
• First and second modulated transmit signals generated in this manner are transmitted via a first and a second transmitting antenna from a transmitter to a receiver.
• the receiver comprises a first and a second receiving antenna and a decoder unit, and is set up to decode a first receive signal from the first receiving antenna and a second receive signal from the second receiving antenna jointly using the training sequence and the associated partner training sequence in a first and a second partial receive datastream, and to combine these to form a user receiver datastream.
• the data transmission in MIMO systems can be improved.
• the mobile radio system comprises a further transmission mode in addition to the transmission mode described above.
• the further transmission mode may be either e.g. a conventional transmission mode with just one partial datastream or a future transmission mode.
• the receiver attempts to decode part of the first modulated receive signal in a first direction and another part of the receive signal in a second modulation direction. Since in the case of e.g. GSM systems, it is known from the GSM Standard which training sequence a transmitter has used in encoding the transmit signal, the modulation direction used by the transmitter is derived by correlation of the decoded receive datastreams with the known training sequence. The modulation direction can here be used to detect one of two operating modes .
• the user transmit datastream is apportioned without overlap to the first and second partial transmit datastreams. In this manner, it is achieved that the first and second partial transmit datastreams are free from redundancies, so the transmission rate is maximised.
• At least parts of the user transmit datastream are apportioned by e.g. timing-based and/or spatial channel encoding to both the first and the second partial transmit datastream so that redundant information is contained in the transmitted transmit signals .
• this redundant information can be used for error correction.
• Fig. 1 shows a mobile radio system according to an embodiment of the invention.
• Fig. 2 shows a first quantity of training sequences for a first transmission mode and a second quantity of training sequences for a second transmission mode.
• Fig. 3 shows autocorrelation functions of partner training sequences used according to the invention.
• Fig. 4 shows cumulative distribution functions of the simulated SNIR degradations.
• Fig. 5 shows probability density functions of the cross-correlation of training sequences and partner training sequences .
• Fig. 6 is a schematic representation of a method for transmitting a user datastream.
• Fig. 7 is a flowchart for a method for the detection of a transmission mode of a receiver.
• Fig. 1 shows a mobile radio system 100 according to one embodiment of the invention.
• the mobile radio system 100 comprises a transmitter 101 and a receiver 102 in a mobile radio network 106, such as a GSM network.
• the transmitter 101 may be a base station
• the receiver 102 may be a mobile station, wherein the transmitter 101 transmits data to the receiver 102 in what is known as the downlink direction.
• the uplink i.e. from a mobile station to a base station, is also possible.
• the transmitter 101 contains an encoding unit 103 and two transmitting antennas 104a and 104b.
• the encoding unit 103 is connected to a data input 105 via which a user transmit datastream is prepared for encoding by the encoding unit 103 and subsequent transmission via the transmitting antennas 104a and 104b.
• the two transmitting antennas are spatially separated from one another. For example, they may be two rod or dipole antennas arranged in parallel or orthogonally relative to one another. An individual plane antenna with two polarisation directions, orthogonal relative to one another, can, however, also act as the first and second transmitting antennas 104a and 104b.
• the encoding unit 103 comprises a distributing device 107 and two modulation devices 108a and 108b, which are connected to the first transmitting antenna 104a and the second transmitting antenna 104b respectively.
• the distributing device 107 may be e.g. a multiplexer, which passes information units received via the data input 105, such as data packets with voice, video or other data, either to the first modulation device 108a or the second modulation device 108b.
• the distributing device 107 passes at least part of the data both to the first modulation device 108a and the second modulation device 108b in order to generate a controlled redundancy between the modulated transmit signals generated by the modulation devices 108a and 108b.
• the encoding unit 103 also contains a memory 109, in which are stored at least one training sequence, also known as a "Training Sequence Code", TSC, and one partner training sequence PTSC assigned to the training sequence TSC.
• TSC Training Sequence Code
• the training sequence TSC and the partner training sequence PTSC do not have to be stored locally in the encoding unit 103, but may, for example, be provided via a SIM card integral to a mobile station or via a data network connected to a base station.
• the training sequence TSC and the associated partner training sequence PTSC have predetermined, matched correlation properties.
• the training sequence TSC is used by the first modulation device 108a to generate a first transmit signal based on a first partial transmit datastream generated by the distributing device 107.
• the associated partner training sequence PTSC is used by the second modulation device 108b to generate a second transmit signal based on a second partial transmit datastream generated by the distributing device 107.
• the receiver 102 contains a first receiving antenna 110a, a second receiving antenna 110b and a decoding unit 111.
• the decoding unit 111 is set up to receive a first receive signal from the first receiving antenna 110a and a second receive signal from the second receiving antenna 110b, to decode them jointly and to make available via a data output 112 a user datastream generated therefrom.
• the decoding unit 111 comprises a first demodulation device 113a, a second demodulation device 113b and a combining device 114.
• the decoding unit 111 comprises a memory 115 in which both the training sequence TSC and the partner training sequence PTSC assigned thereto are stored.
• the first demodulation device 113a and the second demodulation device 113b will be components of a common demodulator 116.
• the improved decoding of the first and second receive signals can be achieved.
• the combining device 114 combines the two partial datastreams generated by the first and second decoding devices 113a and 113b to form a user receive datastream, which is made available via the data output 112 of the receiver 102. If redundant information has been introduced by means of channel encoding into the two partial datastreams by the transmitter 101, it is removed by the combining device 114 by appropriate channel decoding.
• Fig. 2 shows a first quantity 200 of training sequences TSC, which are used in a first transmission mode 204, also referred to below as dual-stream mode.
• the first quantity 200 contains elements 201, which each contain a set comprising a training sequence TSC and an associated partner training sequence PTSC.
• a second quantity 202 of training sequences TSC contains elements 203, which each contain just one individual training sequence TSC.
• the second quantity 202 is used in a second transmission mode 205, known as the single-stream mode.
• Fig. 2 also shows identifiers 206, to each of which an element 201 of the first quantity 200 and an element
• both the first quantity 200 and the second quantity 202 each comprise eight elements 201 and 203 respectively.
• the training sequences TSC of the first quantity 200 are the same training sequences TSC contained in the associated elements 203.
• the associated partner training sequences PTSC are, however, contained only in the elements 201 of the first quantity 200.
• Partner training sequences PTSC which possess especially good correlation properties in respect of their assigned training sequences TSC, may, for example, be generated by a method described in the German patent application with application number 10 2006 017 296.5.
• new partner training sequences PTSC having the same autocorrelation properties as the training sequences TSC are generated.
• they have especially low cross-correlation properties relative to the standard-conformal training sequences TSC on which they are based, so they can be used jointly with these training sequences TSC.
• partner training sequences PTSC can also be obtained by searching through all possible 16- bit sequences by selecting the 16-bit sequences that fulfil the following properties as well as possible:
• the SNIR degradation between two possible 16-bit sequences constitutes a measure of the interference to a datastream encoded with the first bit sequence from a datastream encoded with the second bit sequence as the interference source . It provides a measure of the degradation of the transmission channel in dB in the event of joint channel detection for a transmission channel of order L.
• the following Table contains the bit sequences of eight partner training sequences PTSC, which are assigned to the eight training sequences TSC according to the GSM Standard for GMSK (Gaussian Minimum Shift Keying) modulation and which are used in the embodiment example of the present invention: Identif Partner training sequence (PTSC) bits ier
• the following Table contains the eight symbol sequences of partner training sequences PTSC, which are assigned to the eight training sequences TSC according to the GSM Standard for 8-PSK (8 Phase Shift Keying) modulation and which are used in the embodiment example of the present invention:
• the standardised autocorrelation properties of the eight partner training sequences PTSC are shown in Fig. 3.
• Fig. 4 shows the cumulative distribution functions of the simulated SNIR degradation for different channel orders .
• the SNIR degradation indicates the degradation of the Signal to Noise plus Interference Ratio (SNIR) whilst the channel order indicates the degree of multipath propagation or degree of delay dispersion of the transmission channel, expressed in symbol duration.
• SNIR Signal to Noise plus Interference Ratio
• the SNIR degradation increases both with the use of a multiplicity of possible pairs of training sequences TSC and partner training sequences PTSC, and with increasing channel order. Nevertheless, it can be recognised that the SNIR degradation for any given channel order lies within a comparable order of magnitude.
• the inter-channel interference dominates over other types of interference.
• EGPRS data transmission mode in particular, data transmission frequently takes place in a range with high SNIR values . The reason is that this transmission takes place preferentially on the frequency of the Broadcast Control Channels (BCCH) , which is transmitted at full power and also exhibits a low level of re-use in adjacent cells.
• BCCH Broadcast Control Channels
• This range and this operating mode are therefore especially suited to the dual-stream transmission mode. For example, in a first time slot of the BCCH channel, signalling data for the configuration of a cell of a mobile radio network can be transmitted, and in subsequent time slots, further data can be transmitted in EGPRS mode with full transmission power.
• Fig. 5 shows the probability density distribution of the cross-correlation of training sequences and partner training sequences . It shows that the interference between the training sequences TSC according to the GSM Standard (broken line) is on average higher than that between the training sequences TSC and the partner training sequences PTSC
• partner training sequences PTSC are just one possible example, since different 16-bit sequences can be selected in the manner described above .
• Fig. 6 shows a schematic representation of a method 600 for transmitting a user datastream in a mobile radio system 100.
• a user transmit datastream 601 e.g. digitalised voice, sound or image data
• a distributing device 107 divides a first partial transmit datastream 602a and a second partial transmit datastream 602b.
• This division may take place symmetrically or asymmetrically, e.g. as a function of a previously defined transmission quality or anticipated transmission rate of a physical transmission channel assigned to the partial datastreams .
• Information units such as individual symbols or entire data packets of the user transmit datastream 601, may here be assigned to either one or other of the partial transmit datastreams 602a or 602b, in order to allow maximum data transmission rates.
• the first partial transmit datastream 602a is encoded and modulated, using a training sequence TSC, by a first modulation device 108a.
• a resultant first transmit signal 603a is then emitted via a first transmitting antenna 104b.
• the second partial transmit datastream 602b is encoded and modulated, using a partner training sequence PTSC assigned to the training sequence TSC, by a second modulation device 108b.
• a resultant second transmit signal 603b is then emitted via a second transmitting antenna 104a.
• the two transmit signals 603a and 603b are transmitted via the same transmission medium, in particular an air interface .
• the interference arising as a result between the first transmit signal 603a and the second transmit signal is represented by the connection 604 and the mixers 605a and 605b.
• the two data transmission channels are affected by further interference signals 606a and 606b, e.g. transmit signals 603 from other transmitters 101 in the mobile radio system, or other electromagnetic interference sources .
• a first receive signal 607a is received via a first receiving antenna 110a and fed to a first demodulation device 113a.
• a second receive signal 607b is also fed via a second receiving antenna 110b to a second demodulation device 113b.
• the first and the second demodulation devices 113a and 113b are part of a common demodulator 116, and exchange data via an interface 608 during the decoding of the first and second receive signals 607a and 607b. This may be e.g. probability information relating to symbols to be decoded.
• the receiver 102 receives modulated receive signals 607a and 607b via two spatially separated receiving antennas 110a and 110b, it is rather improbable that interference in the medium will affect both transmission paths in the same manner.
• the manner in which one of the propagation paths is subject to interference will differ in the case of the other transmission path. For example, through Maximum Ratio Combining (MRC) , decoding is undertaken in a manner such that the overall error probability is minimised.
• the first receive signal 607a is demodulated and decoded into a first partial receive datastream 609a using the training sequence TSC.
• the second receive signal 607b is demodulated and decoded into a second partial receive datastream 609b using the partner training sequence PTSC.
• the two partial receive datastreams 609a and 609b are directed to a combining device 114.
• the combining device 114 generates a user receiver datastream 610 from the information from the two partial receive datastreams 609a and 609b.
• the user receiver datastream 610 is identical with the user transmit datastream 601. Transmission errors arising from e.g. a channel decoding undertaken by the combining device can be eliminated.
• user transmit and user receiver datastreams 601 and 610 may, however, differ from one another, which can be compensated either from the application level by error-correction or error-masking devices, which are not shown in Fig. 6, or by repeat transmission of the data transmitted unsuccessfully.
• a signalling operation is performed, according to a further embodiment of the present invention, on the basis of the applied modulation itself.
• Fig. 7 shows a flowchart for a method 700 for the detection of a transmission mode of a receiver 102.
• a training sequence TSC is selected by the receiver 102.
• the GSM Standard defines which training sequences may be used by a transmitter 101.
• the training sequence TSC used for a specific data transmission is here selected by a base station and, using appropriate control information, signalled to a mobile station, e.g. by transmitting an associated identifier 206, so the receiver 102 can select the training sequence TSC from the quantity of training sequences contained in the Standard.
• assigned to an identifier 206 in the first transmission mode 204 is a set of training sequences TSC and associated partner training sequences PTSC, and assigned to an identifier 206 in the second transmission mode 205, is only a training sequence TSC. In all cases, therefore, only one identifier has to be transmitted, so that existing signalling means can be used unmodified in the two modes .
• the receiver 102 receives a modulated receive signal from a receiving antenna 110. At this point, the receiver 102 does not know whether a transmitter 101 is being operated currently in the first transmission mode 204 or the second transmission mode 205.
• the receiver 102 decodes at least a first part of the modulated receive signal in a first modulation direction and a second part of the receive signal in a second modulation direction. This gives rise to a first part of a decoded receive datastream and a second part of a decoded receive datastream.
• steps 703 and 704 may be undertaken simultaneously by different demodulation devices, e.g. the first demodulation device 113a and the second demodulation device 113b.
• the two demodulated parts may be identical.
• a first conformity of the first part of the receive datastream with the selected training sequence TSC is determined and a second conformity of the second part of the receive datastream with the selected training sequence TSC is determined. Since the modulated receive signal contains a training sequence TSC both in the first transmission mode 204 and in the second transmission mode 205, a relatively great conformity must exist, at least in one of the two modulation directions, between the selected training sequence TSC and the first/second parts of the receive datastream, which enables a differential recognition of the modulation direction used.
• a step 707 the conformities of the first and second receive datastreams determined in steps 705 and 706 respectively are compared with the selected training sequence TSC.
• step 708 It is determined in step 708, on the basis of the comparison from step 707, which transmission mode has been used by the transmitter 101. If the first conformity is greater than the second conformity, i.e. the modulated receive signal has been modulated by the transmitter 101 in the first modulation direction, the receiver 102 is switched into the first transmission mode 204. If, conversely, the second conformity is greater than the first conformity, the receiver 102 is switched into the second transmission mode 205.
• a decoding of further data may then be undertaken by the receiver 102, either in the first transmission mode 204 or in the second transmission mode 205.
• further data bits from a so-called burst which also contains the training sequence TSC, may be decoded. It is unimportant whether this subsequent decoding is undertaken in the first or the second modulation direction.
• the conventional, single- stream mode i.e. the second transmission mode
• the standard-conformal modulation direction i.e. the forwards direction.
• the modulation direction for the first transmit signal modulated by the transmitter 101 may be reversed.
• phase-modulation processes normal in GSM systems this corresponds with the reversal of phase shifting, which is expressed by a negative preceding sign in the mathematical formulae that form the basis.
• phase shifting which is expressed by a negative preceding sign in the mathematical formulae that form the basis.
• other symmetrical modifications of the modulation e.g. the shifting of a phase by a predetermined amount, are also possible.
• GMSK modulation comprises the following steps: Step 1: Differential encoding
• Every data bit di [0,1] is differentially encoded.
• the modulating data value ax which is supplied to the modulator, is then:
• Step 2 Filtration and output phase
• the modulating data value ax in a Dirac impulse representation activates a linear filter with an impulse response gr(fc) defined in the GSM Standard, so the output phase of the modulated signal is as follows:
• the modulation index h has a value of 1/2, which corresponds to a maximum phase change of ⁇ /2 per symbol interval .
• Step 3 Modulation
• the modulated high-frequency carrier signal looks as follows:
• Ec corresponds to the energy per modulated bit, f0 to the carrier frequency and ⁇ O to a random phase shift, unchanged during the transmission interval .
• the output phase is modified as follows in Step 2, at least for the first partial datastream, using the training sequence TSC:
• the method 700 for detection of a transmission mode of a receiver 102 is here used to select between a single-stream mode and a dual-stream mode, a detection of this kind may also be used for signalling other operating modes and parameters orcontrol information.
• the application of the method 700 is not restricted to MIMO systems, i.e. transmitter 101 and receiver 102 with a plurality of transmitting antennas 104 and receiving antennas 110 respectively.
• a transmitter 101 with more than four transmitting antennas 104 may use two antennas per user datastream.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Power Engineering (AREA)
• Mobile Radio Communication Systems (AREA)
• Radio Transmission System (AREA)

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• 2006
  • 2006-08-16 DE DE200610038142 patent/DE102006038142A1/de not_active Ceased
• 2007
  • 2007-08-15 WO PCT/IB2007/003159 patent/WO2008020320A2/en not_active Ceased
  • 2007-08-15 EP EP07825455A patent/EP2074775A2/de not_active Withdrawn

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