Title of Invention

METHOD AND TRANSMITTING DEVICE FOR TRANSMITTING DATA SYMBOLS FROM SUBSCRIBER SIGNALS VIA A RADIO INTERFACE OF A MOBILE COMMUNICATIONS SYSTEM

Abstract Method and transmitting device for transmitting data symbols from subscriber signals via a radio interface of a mobile communications system In the case of the method according to the invention, N data symbols of a subscriber signal form a block In a first method step, the block is divided into a plurality of partial blocks having Ns data symbols. The Ns data symbols are then allocated to sub-carriers and are modulated in parallel onto these various sub-carriers, the modulation being carried out for each of the sub-carriers with at least one individual code symbol. The sub-carriers are heterodyned to form a broadband carrier, so that the Ns data symbols are transmitted simultaneously. The transmission then takes place in N/Ns successive partial blocks via the radio interface.
Full Text Description
Method and transmitting device for transmitting data symbols from subscriber signals via a radio interface of a mobile communications system
The invention relates to a method and a transmitting device for transmitting data symbols from subscriber signals via a radio interface of a mobile communications system, for example for base stations or mobile stations in mobile radio networks.
CDMA radio systems with a plurality of carriers are known from G.Fettweis, A.S.Bahai, K.Anvari, "On multi-carrier code division multiple access (MC=CDMA) modem design", Proceedings of the IEEE 44th Vehicular Technology Conference VTC'94, Stockholm, 1994, pages 1670-1674. When such systems are used for mobile communication, there is a radio interface between fixed-position base stations and moving mobile stations. The transmission path from a base station to a mobile station is called the downlink, and the transmission path from a mobile station to a base station is called the uplink.
However,,, the CDMA radio system with a plurality of carriers according to the prior art is difficult to implement in mobile communications systems since the production of the transmitted signals at the trans- " mission end, which transmitted signals contain data symbols allocated to subscriber signals, cannot be adequately marched to the transmission conditions of the radio interface.
In consequence, the invention is based on the
object of specifying an improved method and an improved
transmitting device for the transmission of data. This
object is achieved by the method and the transmitting
device having the features of the invention.



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Developments of the invention can be found in the dependent claims.
In the case of the method according to the invention for transmitting data symbols which originate from one or more subscriber signals, a radio interface of a mobile communications system is presupposed which uses subscriber separation, for example in accordance" with the CDMA method. In this case, N data symbols of a subscriber signal form a block. Such a block is, for example, a radio block as is transmitted within one timeslot in TDMA systems (time division multiple access} .
In a first method step, the block is divided into a plurality of partial blocks with Ns data symbols. The Ns data symbols are then allocated to sub-carriers and are modulated in parallel onto these "various sub-carriers, the modulation for each of the sub-carriers being carried out with at least one individual code symbol. The sub-carriers are heterodyned to form a broadband carrier, so that the Ns data symbols are transmitted simultaneously. The transmission is then carried out in N/Ns successive partial blocks via the radio interface.
The described transmission method has an equivalent at the receiver end. This results in the radio interface having a system structure which is highly resistant to interference as a result of the advantages of the CDMA subscriber separation (with modulation/spreading of data symbols using different code symbols), for example frequency diversity and interference diversity, and which, by using the multi carrier method with the aid of a plurality of sub-carriers', allows flexible allocation of frequency resources. The method according to the invention allows multiple subscriber interference and inter-symbol interference to be taken into account and compensated for in an appropriate manner.

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The method according to the invention makes it easier to achieve cost-effective implementation of flexible CDMA mobile communications systems. The signal production for the subscriber separation with DS (direct sequence) CDMA and by means of multiple-carrier methods is combined according to the invention. 'The transmission of data symbols can use the specific advantages of both methods flexibly and with a large number of degrees of freedom.
According to an advantageous development of the invention, the sub-carriers are heterodyned linearly to form a broadband carrier. The complexity of signal production and of detection after transmission is thus kept low.
According to a refinement of the invention, one data symbol is transmitted on a plurality of sub-carriers. This ensures frequency diversity for this data symbol, making the transmission more interference-resistant. In addition, it is advantageous to arrange unused frequency bands between the sub-carriers for the data symbol or groups of sub-carriers. Such interleaving of the frequency bands for different data symbols or subscriber signals results in transmission errors being scattered, and the capability to compensate for them more easily at the receiver end.
If, for a given range of allocated frequencies, sub-carriers are allocated to a partial block or to a data symbol in such a way as to maximize the interval between the centre frequencies of the sub-carriers, this results in the best-possible frequency diversity.
The flexibility of the method according to the invention is advantageously used, in particular, if the number of data symbols in a partial block can be varied depending on the transmission conditions of the radio interface. In this way, the bit rate can also be adapted, depending on the requirements or the maximum permissible values in the transmission conditions.

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It is likewise advantageous to be able to vary* the number Q of sub-carriers allocated to one - data symbol, depending on the transmission conditions of the radio interface. This makes it possible to match the interference immunity to the transmission conditions and at the same time to manage the frequency resources _ economically.
According to a further refinement of the invention, a period which is intended for transmission-of a data symbol can be varied depending on the transmission conditions of the radio interface by varying the number of simultaneously transmitted data symbols in a partial block. This allows the advantages of the multi-carrier or of the code multiplex method to be used depending on the length of the period and/or the number of simultaneously transmitted data symbols. This can be done for a constant data rate; the radio interface parameters are set individually, depending on the specific transmission conditions.
If a guard time without any information transmission is provided within a period which is intended for transmission of a data symbol, then particularly simple and economic receivers can be used at the receiver end. This option is feasible when the periods set for a data symbol are relatively long.
According to the invention, it is possible to select the data symbols without any limitations from the set of complex numbers since, owing to the sub-carrier-related modulation, a large number of individual modulation types and a large and easily variable range of combinations of data symbols and code symbols can be selected.
In addition to CDMA subscriber separation, the method according to the invention can also provide subscriber separation in accordance with a TDMA and/or FDMA method, so that it can easily be implemented in existing mobile radio networks.

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The modulation is prepared in a sub-carrier-related manner by using a memory device for storing values of individual codes in matrix form, these values including any required linear transformation of data symbols to form modulated data symbols and/or pulse shaping of the data to be transmitted, by means "of weighting.
The control means advantageously allow symbol related individual processing of the data symbols to be carried out by allocating a different number of sub-carriers to at least two data symbols in a block, or by dividing a block into at least two partial blocks with a different number of data symbols. The data symbols in a block may have different importance. Thus, for example, interference with signalling symbols is normally more serious than with symbols for voice transmission. The method according to the invention can take account of this in an excellent manner, since the symbols or the partial blocks are dealt with individually.
The interference immunity can be described by the product of the bandwidth of the sub-carriers and the transmission duration for a symbol so that "appropriate allocation of resources (number of sub-carriers and symbol duration) of the radio interface "within a block defines an individual interference immunity.
A control means in the transmitting device is advantageously designed in such a manner that the symbol-related individual processing of the data symbols is switched over in accordance with the stipulations of a device for radio resource management depending on the transmission conditions and/or the load level of a radio cell. This ensures the flexibility to satisfy the requirements, even during operation.

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According to the invention, it is possible to use existing frequency bands of a GSM mobile radio network or of another mobile radio network, for example PDC, IS-54/136, PHS, DECT or IS-95, for one or more frequency bands of a sub-carrier, and/or to arrange these frequency bands between sub-carriers.
The transmitting device may be used in base stations or mobile stations. A major advantage of the transmission method according to the invention is that conventional detection methods can be used for the corresponding receiving devices, and it is thus possible to match the specific capabilities of the communication partner by simple parameter setting in the transmitting device.
The subject matter of the invention is explained in more detail in the following text using exemplary embodiments and with reference to accompanying drawing illustrations, in which: FIG 1 shows a block diagram of a mobile radio
network, FIG 2 shows a schematic illustration of the frequency
resources of the radio interface, FIG 3 shows a schematic illustration of the structure
of a radio block, FIGS 4a, b show schematic illustrations of the
allocation of the data to sub-carriers,and FIG 5 shows a block diagram of a transmitting device.
The structure of the mobile communications system illustrated in FIG 1 corresponds to that of a known GSM mobile radio network which comprises a plurality of mobile switching centres MSC which are networked with one another and produce access to a landline network PSTN. Furthermore, these mobile' switching centres MSC are connected to in each case at least one base station controller BSC. Each base station controller BSC in turn allows a link to at least one base station BS. Such a base station BS is a

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radio station which can set up an information link to mobile stations MS via a radio interface. By way of example, FIG 1 shows three radio links between three mobile stations MS and one base station BS. An operation and maintenance centre OMC carries out monitoring and maintenance functions for the mobile radio network, or for parts of it. The operation and maintenance centre OMC and the base station controller BSC carry out the functions of setting and adaptation of the allocation of radio resources within the radio cells of the base stations BS. The functionality of the mobile communications system can also be transferred to other radio communications systems, and if required to fixed-position mobile stations MS as well. The method according to the invention can also be used in such radio communications systems.
The communications links between the base station BS and the mobile stations MS are subject to multi-path propagation, which is caused by reflections, for example on buildings or vegetation, in addition to the direct propagation path. If one assumes that the mobile stations MS are moving, then multi-path propagation together with other interference leads to the signal components of the various propagation paths of a subscriber signal being superimposed as a function of time at the receiving base station BS. It is furthermore assumed that the subscriber signals of different mobile stations MS are superimposed at the reception point to form a received signal since, according to the exemplary embodiment, subscriber separation is carried out using a CDMA method- The method indicated in the following text is intended to be matched to the continuously changing transmission conditions.
The task of the transmitting base station BS is to prepare for transmission data d contained in the subscriber signals and to transmit such data to the

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Individual mobile stations MS in subscriber-specific communications links .
FIG 2 shows the frequency allocation within the mobile communications system. A network operator has 12 frequency bands 0..11 available in the radio cell of. the base station BS which, in Fig. 1, is linked to three mobile stations MS. Of these, three frequency bands are already allocated to an existing GSM mobile radio network, and will also continue to be used. Furthermore, nine sub-carriers 1,2,..9 are available. According to FIG 2, a constant bandwidth is assumed for all the frequency bands. However, this is not a precondition for a mobile communications system in the sense of the invention.
For a transmitting device as explained in more detail in FIG 5, all that is required is the capability to combine a plurality of such frequency bands to form a broadband radio interface. The transmitting device can in this case be used in parallel with a transmitting device for the GSM mode, or can carry out its functions by suitable parameter setting.
FIG 3 shows the structure of a radio block of a subscriber signal. Such a radio block is transmitted in one time slot of a TDMA frame structure. Each frame contains at least one time slot for one or more subscriber signals.
The duration of the radio blocks is designated Tbu. The radio block comprises two blocks, each having N data symbols d, the length of each block being Tb1. The two blocks are separated by a training sequence tseq with a duration of Tseq. The radio block is terminated by a guard time Tg, which is intended to compensate for delay time differences arising from the different distances between the mobile stations MS and the base station BS.
FIG 3 also shows how an individual data symbol d can be transmitted in accordance with a pure CDMA

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method on the left - or in accordance with a pure multi-carrier method - on the right. In the case of the CDMA method, each data symbol d is spread over the bandwidth Bu with Q code symbols. In the case of the multi-carrier method, each data symbol d is modulated onto Q sub-carriers, the sum of the bandwidths of the sub-carriers giving the bandwidth Bu. In both cases, the time to transmit a data symbol is the symbol duration Ts.
The invention now deviates from the rigid scheme of the two methods and prepares for a transmission in accordance with FIGS 4a, 4b.
FIG " 4a shows the case of transmission of a partial block with a spread by a code symbol c per data symbol d.
The block with N data symbols d is divided in partial blocks with Ns = 3 data symbols d(1), d(2) and d(3). The data symbol d(1) is allocated the sub-carriers 1, 4 and 7, the data symbol d(2) the sub-carriers 2, 5 and 8, and, finally, the data symbol d(3) the sub-carriers 3, 6 and 9. The procedure for the other partial blocks in the block is equivalent. The allocation strategy is in this case intended to maximize the interval between the centre frequencies of the sub-carriers for a data symbol, for example d(1), in order to allow as much frequency diversity as possible to be used for the transmission.
In the allocation according to FIG 4a, the individual data symbols d(1), d(2) and d(3) in a partial block are dealt with equivalently in this respect. If the individual data symbols have different weightings, an individual data symbol d(1) may also be given-preference by allocation of a greater number of sub-carriers .
Each of these symbols is spread during the symbol duration Ts with an individual code symbol c(1)-c(2), C(3). The number of code symbols per data symbol d

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is in this case reduced to Q=l, as a result of which, provided the other parameters are suitably chosen, receiving stations MS without CDMA reception can also be supplied.
Particularly in this case, it is possible to provide a guard time as well within a symbol duration Ts, to make it easier to use cheap receivers without equalization. This allows simple and cost-effective mobile stations MS to be used.
Furthermore, the invention makes it possible to lengthen the symbol duration Ts without reducing the data rate by increasing the number of simultaneously transmitted data symbols, that is to say the length Ns of a partial block. A longer symbol duration Ts is advantageous, particularly within hierarchical cell structures of a mobile communications network using pico cells or microcells.
FIG 4b shows the case of transmission of partial blocks of a plurality of subscriber signals with a spread by codes c per data symbol d.
The blocks of the K subscriber signals with N data symbols d are divided into partial blocks with Ns = 3 data symbols d(1)(k) , d(2)(k) and d(3)(k), where k=l..K. The data symbol d(1) (k) is allocated the sub-carriers 1, 4 and 7, the data symbol d(2)(k) the sub carriers 2, 5 and 8, and, finally, the data symbol ri(3)(k) the sub-carriers 3, 6 and 9. The procedure for the other partial blocks in the block is equivalent.
Each of these data symbols d(1)(k), d(2)(K) and d(3)(k) is spread during the symbol duration Ts with a subscriber-specific code c(k) (q), k=1..K, q=l..Q. K is the number of subscribers in the same frequency channel and time slot, and Q is the number of code symbols per data symbol d. This subscriber-specific code c(k) (q) allows the data symbols d(1)(k), d(2)(k) and d(3)(k) of the various subscriber signals to be separated again at the receiver end, for example using a so-called JD (Joint

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Detection) CDMA method. In addition, it is possible to
provide for individual data symbols, d(1)(k}, d(2)(K) and
d(3)(k) to be spread among the different sub-carriers with different sub-carrier-related codes, thus using three different codes for the data symbols d(1) (k), d(2) (K) and d(3) (K) .
A transmitting device for carrying out the method is shown in FIG 5. The transmitting device contains control means SE with a memory device SP. modulation means MOD and a transmission device HF.
The data symbols d of the subscriber signals arrive in the transmitting device at the network end and are fed to the modulation means MOD, Data modulation, for example error protection, interleaving
etc., are caried-out in one part of the modulation
means MOD. In addition, the data symbols d in a block are divrded by the control means SE into partial blocks with Ms data symbols d.
The length Ns and the position of the partial blocks are stored in the memory device SP. In addition, values zeta are stored in matrix form which, when read By the modulation means MOD, cause the spreading of the data symbols d.
These values zeta are, for example, in the form:

where k=l..K, and Ns = l. .Ns, 8 designating the elements for inverse discrete Fourier transformation (IDFT) or some other linear transformation.
In addition, the values zeta include factors for pulse shaping:

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zeta(k,ns)=ax.zeta, where x=1..9 (since there are nine sub-carriers according to FIG 4),
in such a manner that, in this way, individual sub-carriers and the subsequent broadband transmitted signal are given a form which can be predetermined and which produces a narrow spectrum, for example a GMSK form or a form based on an inverted cosine function.
This type of spreading to produce transmitted signals s in the form:
3(K) = zeta(k)-d(k), where k=l..K, results in signals which, after digital/analogue conversion and low-pass filtering in the transmission means HF, and appropriate amplification, are transmitted via the radio interface to the* receiving mobile stations MS.
The following text describes the allocation and modulation strategy which make it possible for the transmitting device, controlled by the control means SE, to carry out flexible transmission methods by setting of the parameters Ns, Ts, Q and the sub-carriers per data symbol d.
The choice of the parameters takes account of the transmission conditions (severe noise and interference} and the load level of the radio resources (time slots, frequencies, codes) in the radio cell {a large number of subscribers). These conditions are signalled to the control means SE by the base station controller BSC and/or by the operation and maintenance centre OMC. The control means SE then select a parameter set for each link.
At the same time, it is possible to comply with the requirements of the individual mobile stations MS who are requesting special transmission conditions (no CDMA or a multi-carrier method only within a specific bandwidth) and special data rates. The data set to be

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selected for the values zeta is also determined in this way.
The method according to the invention can carry out the following settings in a flexible manner:
A large number of sub-carriers per data symbol d and/or a long symbol duration Ts improves the transmission quality.
A large number of data symbols d per partial block increase the data rate for a constant symbol duration Ts.
The transmission quality can be set specifically for data symbols d or partial blocks .
The pulse shaping and transformation may be variable.
Frequency diversity can be achieved by allocating a large number of sub-carriers for one data symbol d or by means of a plurality of code symbols per data symbol d.
The method according to the invention is thus suitable in particular for use in future mobile communications systems, such as UMTS (Universal Mobile Communications System) or FPLMTS (Future Public Land Mobile Telecommunications System).

14 -
1. Method for transmitting data symbols (d) from
subscriber signals via a radio interface of a mobile
communications system,
N data symbols (d) of a subscriber signal forming a
block,
with the following method steps:
- division of the block into a plurality of partial blocks with Ns data symbols (d),
- allocation of the Ns data symbols (d) to sub-carriers,
- parallel modulation of the Ns data symbols (d) onto in each case at least one sub-carrier for simultaneous transmission, the modulation for each of the sub-carriers being carried out using at least one individual code symbol (c),
- heterodyning of the sub-carriers to form a broadband carrier, and
- transmission of the partial blocks via the radio interface.

2. Method according to Claim 1, using linear heterodyning of the sub-carriers to form a broadband carrier.
3. Method according to Claim 1 or 2, in which a data symbol (d) is transmitted on a plurality of sub-carriers .
4. Method according to one of the preceding claims, in which unused frequency bands are arranged between the sub-carriers or groups of sub-carriers for the data symbol (d) .
5. Method according to Claim 4, with allocation of sub-carriers to a partial block, which allocation maximizes the interval between the centre frequencies of the sub-carriers.
6. Method according to Claim 4, with allocation of sub-carriers to a data symbol (d), which allocation
2.
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maximizes the interval between the centre frequencies of the sub-carriers. ' 7. Method according to one of Claims 4 to 6, in which other subscriber signals are transmitted in frequency bands between the sub-carriers or groups of sub-carriers with data symbols (d) of a partial block.
8. Method according to one of the preceding claims, in which the number of data symbols (d) in a partial block can be varied depending on the transmission conditions of the radio interface.
9. Method according to one of the preceding claims, in which the number Q of sub-carriers allocated to one data symbol (d) is variable depending on the transmission conditions of the radio interface.
10. Method according to one of the preceding claims, in which a period which is intended for transmission of a data symbol (d) is variable depending on the transmission conditions of the radio interface, by varying the number of simultaneously transmitted data symbols (d) in a partial block.
11. Method according to one of the preceding claims, in which a guard time without any information transmission is provided within a period which is intended for transmission of a data symbol (d).
12. Method according to one of the preceding claims, in which the data symbols (d) are chosen from the set of complex numbers.
13. Transmitting device for transmitting data symbols (d) from subscriber signals via a radio interface of a mobile communications system,
N data symbols (d) of a subscriber signal forming a block,
- having control means (SE) for dividing the block into a plurality of partial blocks with Ns data symbols (d),
- having modulation means (MOD) for modulating the Ns data symbols (d) onto in each case at least one sub-
-
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carrier for simultaneous transmission, the modulation
for each of the sub-carriers being carried out with
at least one individual code symbol (c) , and for
heterodyning of the sub-carriers to form a broadband
carrier, and
having transmission means (HF) for transmitting the
partial blocks via the radio interface.
14 . Transmitting device according to Claim 13 having separation means for additional subscriber separation in

accordance with a TDMA and/or FDMA method.
15. Transmitting device according to one of Claims
13 or 14, having a memory device (SP) for storing
values (zeta) of individual codes (c) related to the
sub-carriers in the form of a matrix, the values being
read by the modulation means (MOD).
16. Transmitting device according to Claim 15, in which the values (zeta) result in linear transformation of the data symbols (d) to form modulated data symbols.
17. Transmitting device according to Claim 15 or
16, in which a factor_for pulse shaping of the data (d)
to be transmitted is included in the values (zeta) by
means of sub -carrier related weighting.
18. Transmitting device according to one of Claims 13 to 17, in which symbol-related individual processing of the data symbols (d) is carried out by the control means (SE) by assigning a different number of sub carriers to at least two data symbols (d) in a block:
19. Transmitting device according to one of Claims 13 to 18, in which symbol-related individual processing of the data symbols (d) is carried out by the control means (SE) by a block being divided into at least two partial blocks having a different number Ns of data symbols (d) .
20. Transmitting device according to one of Claims 13 to 19, in which symbol-related individual processing of the data symbols (d) is carried out by the control means (SE) by allocating a different product of the
18.
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"bandwidth of the sub-carriers and the transmission duration for a symbol to at least two data symbols (d) or two partial blocks of a block.
21. Transmitting device according to one of Claims 17 to 19, in which the control means (SE) switch over the symbol-related individual processing of the data symbols (d) in accordance with the stipulations of a device (BSC, OMC) for radio resource management, depending on the transmission conditions and/or the load level of a radio cell.
22. Transmitting device according to one of Claims 13 to 21, in which existing frequency bands in a GSM mobile radio network or another mobile radio network are used as at least one frequency band of a sub-carrier.
23. Transmitting device according to one of Claims 13 to 22, which is designed as part of a base station (BS) of a mobile communications system.
24. Transmitting device according to one of Claims 13 to 22, which is designed as part of a mobile station (MS) of a mobile communications system.
Dated this 24th day of MARCH 1998.
Method and transmitting device for transmitting data symbols from subscriber signals via a radio interface of a mobile communications system
In the case of the method according to the invention, N data symbols of a subscriber signal form a block In a first method step, the block is divided into a plurality of partial blocks having Ns data symbols. The Ns data symbols are then allocated to sub-carriers and are modulated in parallel onto these various sub-carriers, the modulation being carried out for each of the sub-carriers with at least one individual code symbol. The sub-carriers are heterodyned to form a broadband carrier, so that the Ns data symbols are transmitted simultaneously. The transmission then takes place in N/Ns successive partial blocks via the radio interface.

Documents:

00491-cal-1998-abstract.pdf

00491-cal-1998-claims.pdf

00491-cal-1998-correspondence.pdf

00491-cal-1998-description(complete).pdf

00491-cal-1998-drawings.pdf

00491-cal-1998-form-1.pdf

00491-cal-1998-form-2.pdf

00491-cal-1998-form-3.pdf

00491-cal-1998-gpa.pdf

491-CAL-1998-(15-10-2012)-FORM-27-1.1.pdf

491-CAL-1998-(15-10-2012)-FORM-27.pdf

491-CAL-1998-CORRESPONDENCE 1.1.pdf

491-CAL-1998-FORM-27.pdf

491-cal-1998-granted-abstract.pdf

491-cal-1998-granted-claims.pdf

491-cal-1998-granted-correspondence.pdf

491-cal-1998-granted-description (complete).pdf

491-cal-1998-granted-drawings.pdf

491-cal-1998-granted-form 1.pdf

491-cal-1998-granted-form 2.pdf

491-cal-1998-granted-form 3.pdf

491-cal-1998-granted-gpa.pdf

491-cal-1998-granted-letter patent.pdf

491-cal-1998-granted-reply to examination report.pdf

491-cal-1998-granted-specification.pdf

491-CAL-1998-PA.pdf


Patent Number 195148
Indian Patent Application Number 491/CAL/1998
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date 21-Oct-2005
Date of Filing 24-Mar-1998
Name of Patentee SIEMENS AKTIENGESELLSCHAFT
Applicant Address WITTELSBACHERPLATZ 2, 80333 MUENCHEN
Inventors:
# Inventor's Name Inventor's Address
1 PETER JUNG IM RABENTAL 28, 67697 OTTERBERG
2 JORG PLECHINGER KURT-SCHUMACHER-STR.70,67663 KAISERS-IAUTERN
3 FRIEDBERT BERENS KELTENWEG 67,67663 KAISERSLAUTERN
4 PAUL WALTER BAIER BURGUNDERSTR.6,67661 KAISERSLAUTERN
PCT International Classification Number H04B 7/216
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA