WO2000002321A2

WO2000002321A2 - Method for transmitting data

Info

Publication number: WO2000002321A2
Application number: PCT/DE1999/001984
Authority: WO
Inventors: Kurt Aretz; Edgar Bolinth; Michael Franzen; Erich Kamperschroer; Theo Kreul; Lutz Jarbot; Uwe Schwark; Markus Nasshan
Original assignee: Siemens Aktiengesellschaft
Priority date: 1998-07-03
Filing date: 1999-07-01
Publication date: 2000-01-13
Also published as: AU5847399A; WO2000002321A3; CN1308793A; EP1095471A2; DE19829818A1

Abstract

The invention relates to a method for transmitting data in a communication system with a given number of communication links that can be activated to and/or from available communication connections via which signals can be simultaneously transmitted in a common frequency band, especially for the transmission of data in a UTMS communication system in a TDD operating mode. According to the inventive method, the signals have a data component and a training component (m), especially a midamble, between which known symbols specified in advance by the receiver and transmitter can be transmitted as part of the training component. The aim of the invention is to optimize utilization of available transmission capacity. This is achieved by adjusting the length of the training component (m) according to the number of communication links that can be activated.

Description

description

Data transmission method

The invention relates to a method for transmitting data in a communication system with a given number of activatable communication connections to and / or from existing communication connections, via which signals can be transmitted simultaneously in a common frequency band, in particular for transmitting data in a UMTS communication system m TDD mode, wherein the signals have a data part and a training part, in particular a midamble, and m symbols which are known to the training part and have previously been incorporated between the respective transmitter and receiver of the signals can be transmitted. The signals can be transmitted by radio and / or by fixed lines.

In communication systems, messages (for example voice, picture information or other data) are transmitted via transmission channels. In radio communication systems, this is done with the help of electromagnetic waves via an air or radio interface. Carrier frequencies are used which lie in the frequency band intended for the respective system. With GSM (Global System for Mobile Communication), the carrier frequencies are in the range of 900 MHz. For future radio communication systems, for example the UMTS (Universal Mobile Telecommunication System) or other 3rd generation systems, frequencies in the frequency band around 2,000 MHz are planned.

A method of the type mentioned at the outset for radio transmission of digital signals from a transmitter side to a reception side is known from EP 0 767 543 A2. In the known method, so-called bursts are transmitted together with the data training sequences, which enable the receiver to determine the discrete-time impulse responses of the active transmission evaluate channels (channel impulse responses) to determine the received data.

The mobile radio system considered in EP 0 767 543 A2 is a joint detection code division multiple access (JD-CDMA) mobile radio system, in which a combination of the known multiple access methods frequency division multiple access (FDMA), time division multiple access (TDMA) and CDMA is used. In the technically more difficult to handle upward direction of the mobile radio system, d. H. in the direction from the terminals to a base station, a plurality of the subscribers are active simultaneously in the same frequency band. A subscriber-specific CDMA code is assigned to the signals of the individual subscribers. The data is transmitted in bursts consisting of a training sequence in the form of a midamble and two data blocks that are sent before and after the midamble. The midambles contain subscriber-specific test signals that are known to the receiver in the base station and enable channel estimation there. The midamble code to be sent by a specific subscriber consists of a sequence of elements which is divided into information units (chips). The midamble code has a predetermined number of chips. The data blocks of the bursts are encoded with the subscriber-specific CDMA code before they are transmitted.

The sum of all signals of the active participants arrives at the receiver. Since the signals of the participants are at least in part ^¬ example transmitted in a common frequency band at the same time, the receiver must the sum signal among the Verwen- fertil Mittambelinformation into the individual signals and decode disassemble. The relevant midamble information of the individual participants serves this purpose. The sum of the midamble information is, for example, partly overlaid with the received data information, namely the part of the midamble information received first and last due to different transit times of the bursts transmitted simultaneously. The middle part of the received midamble information can be free be evaluated by overlay, using knowledge of the received symbols.

In the known method, the midamble for each subscriber or for each communication connection must have a section with a length which is sufficiently large to be able to contain information of the channel impulse response which can be estimated for the communication connection. If the evaluable part of the midamble is shorter than the sum of these individual lengths, not every channel impulse response can

Communication connections are estimated. Under certain circumstances, none of the channel impulse responses can be estimated.

One way to ensure that all channel impulse responses can be estimated is to do the maximum possible

Specify the number of communication connections over which signals can be transmitted simultaneously in the common frequency band. The length of the midamble or training sequence is then selected according to the maximum possible number. This solution is known, for example, from private CDMA radio telephone systems in which individual handsets can be connected to one or more base stations via radio connections. For example, a base station can simultaneously communicate with four handsets over a common frequency band. In this case, the evaluable part of the midamble or the training part is set to four times the estimated length of information of the channel impulse response that can be estimated for one of the possible communication connections. In many cases, but not all four possible handsets are registered at the base station, that is, for example, a maximum of two handsets ben via the base station Betrie ^¬. The midamble is therefore designed to be unnecessarily long so that the available frequency band cannot be used to the greatest possible extent for data transmission or for other purposes. The object of the present invention is to provide a method for data transmission of the type mentioned at the outset, which enables the optimum use of the available transmission capacity when signals from several communication connections are transmitted simultaneously over a common frequency band.

The object is achieved by a method having the features of claim 1. Further training is the subject of the dependent claims.

According to a core concept of the present invention, the length of the traim part is set depending on the number of communication connections that can be activated. Activatable communication connections are understood to mean communication connections that can be built up to existing communication connections. In private CDMA radio telephone systems, for example, these are possible communication connections to and / or from hand-held devices and / or other devices that are registered or logged into the system. In particular, however, it is possible to change the number of activatable communication connections during the operation of the communication system, for example by setting up further activatable communication connections to existing communication connections and / or by setting up further communication connections. The invention is particularly applicable to UMTS communication systems m TDD (Time Division Duplex) mode and / or FDD (Frequency Division Duplex) mode.

An essential advantage of the method according to the invention is that the length of the training part is adapted to the number of communication connections that can be activated, so that the training part does not take up any unnecessary part of the transmission capacity. For example, in the case of multiple access methods that work according to the TDMA-CDMA principle, the maximum possible bandwidth in each time slot can be fully used for data transmission.

In systems in which an estimation of time-discrete channel impulse responses of the communication connections from communication connections to a common base station, or vice versa, takes place on the receiver side, according to a further development, the section of the training part that can be evaluated when estimating the channel impulse responses has a length

Ta = ∑ Te (k)

where Te ^(k) , with k = 1 ... K, is the estimation length of information of the channel impulse response that can be estimated for the k-th activatable communication connection and where K is the number of activatable communication connections. In particular, the estimation lengths Te ^{! K)} are the same for all channel impulse responses. However, the estimation lengths are preferably of different sizes.

In the case of further training, the training part, in particular the midamble, is composed of the section that can be evaluated and a section that cannot be evaluated in every operating situation due to the system when estimating the channel impulse responses, or not. The training part is divided into information units (chips). Its non-evaluable section has a length in particular

Tr = (W-l) * Tc, (2)

where W is the respective or average number of chips per estimation length Te ^(k) and where Tc is the length of a chip. The reason why a section of the training part cannot be evaluated when estimating the channel impulse responses is is, in particular, that, as is known from EP 0 767 543 A2, the first and the last section of the midamble are received with data blocks superimposed due to the coding with a connection-specific code.

The invention will now be explained by way of example with regard to further advantages and features with reference to the accompanying figures. However, it is not limited to these examples. The individual figures show: FIG. 1 a block diagram of a mobile radio network,

2 shows a schematic representation of the frame structure of a radio interface, FIG. 3 shows a schematic representation of the structure of a radio block, FIG. 4 shows a block diagram of a private CDMA radio telephone system, FIG. 5 shows the structure of a midamble in a first state of the in FIG. 4 shows the private radio telephone system shown in FIG. 4 and FIG. 6 shows the structure of the midamble in a second state of the private radio telephone system shown in FIG. 4. In Fig. 1 illustrated radio communication system corresponds in structure to a known GSM mobile network, which consists of a plurality of mobile switching centers MSC, which are interconnected and provide access to ei ^¬ nem landline PSTN. Furthermore, these mobile switching centers MSC are each connected to at least one base station controller BSC. Each base station controller BSC in turn enables a connection to at least one base station BS. Such a base station BS is a radio station which can establish radio connections to mobile stations MS via a radio interface.

1 shows, by way of example, radio connections for the transmission of user information ni and signaling information si between three mobile stations MS and a base station BS shown, wherein a mobile station MS two data channels DK1 and DK2 and the other mobile stations MS are each assigned a data channel DK3 and DK4. An operation and maintenance center OMC implements control and maintenance functions for the cellular network or for parts of it. The functionality of this structure is used by the radio communication system according to the invention. However, it can also be transferred to other radio communication systems in which the invention can be used.

The base station BS is connected to an antenna device which, for. B. consists of three individual emitters. Each of the individual radiators radiates in a sector of the radio cell supplied by the base station BS. However, a larger number of individual radiators can alternatively be used, so that spatial subscriber separation using an SDMA method (Space Division Multiple Access) can also be used.

The base station BS provides the mobile stations MS with organizational information about the location area and about the radio cell. The organizational information is emitted simultaneously via all individual radiators of the antenna device.

The communication links over which the useful information ni and the signaling information si are transmitted between the base station BS and the mobile stations MS are subject to a multipath propagation, which is caused by reflections, for example, on buildings in addition to the direct propagation path.

If one assumes a movement of the mobile stations MS, the multipath propagation together with further interference leads to the signal components of the different propagation paths of a subscriber signal being superimposed on one another in the received mobile station MS. Furthermore, Assume that the subscriber signals of different base stations BS overlap at the receiving location to form a receiving signal in a frequency channel. The task of a receiving mobile station MS is to select data symbols d of the useful information ni transmitted in the subscriber signals, the signaling information si and data of the organizational information.

The frame structure of the radio interface can be seen from FIG. 2. According to a TDMA component, a division of a broadband frequency range, for example the bandwidth B = 1.6 MHz, into a plurality of time slots ts, for example eight time slots ts1 to ts8, is provided. Each time slot ts within the frequency range forms a frequency channel. Within the frequency channels, which are provided for the transmission of user data, information from several communication connections is transmitted simultaneously in radio blocks. According to an FDMA (Frequency Division Multiple Access) component, the radio communication system is assigned several frequency ranges.

According to FIG. 3, these radio blocks for the transmission of useful data consist of data parts with data symbols d, in which sections with middle messages m known at the receiving end are embedded. The data symbols d are connection-specific with a

Fine structure, a spreading code (CDMA code), spread so that, for example, K data channels DK1, DK2, DK3,... DKK can be separated at the receiving end by this CDMA component. Each of these data channels DK1, DK2, DK3, ... DKK is assigned a specific energy E per symbol on the transmission side.

The spreading of individual symbols of the data symbols d, each with a number Q of chips, means that Q subsections of the duration Tc are transmitted within the symbol duration Ts. The Q chips form the individual CDMA code. The midamble consists of a number L of chips, also of the duration Tc. It is still within the time slot A protection time guard of duration Tg is provided to compensate for different signal propagation times of the communication connections of successive time slots ts. The two data parts of the radio block shown in FIG. 3, which are transmitted before and after the midamble m, each have N data symbols d each with the symbol duration Ts, so that the data parts each have a duration of Ts * N.

The four data channels DK1, DK2, DK3 and DK4 shown in FIG. 1 are assigned to the same time slot tsl, for example. The four active data channels DK1, DK2, DK3 and DK4, each of which represents a communication link, jointly use the middle am m of their data block (see FIG. 3). In order to be able to optimally use the time slot tsl for the transmission of data symbols d and for the transmission of the organizational information, the length or duration of the midamble m is set precisely to the number four of data channels DK1, DK2, DK3 and DK4. The section of the midamble m that can be evaluated when estimating the channel impulse responses has a duration of

4 Ta = ∑ Te ^(k) , k = ι

where Te ^(k) , k = 1 ... 4, is the estimation length of information of the channel impulse response that can be estimated for the respective data channel DK1, DK2, DK3 or DK4. As yet the execution ^¬ based embodiment according to FIG. 4 to FIG. 6 will be explained, the midamble can be m a system-related, in the estimation of the channel impulse responses can not be evaluated section have, so that the duration of the midamble m by the inequality

L * Tc> Ta

is described. If the number of data channels changes, the duration of the midamble is adjusted accordingly that the greatest possible number of data symbols d can always be transmitted in the radio block (see FIG. 3).

Within the broadband frequency range of bandwidth B, the successive time slots ts are combined to form a frame and are used repeatedly by a group of communication connections. Additional frequency channels, for example for frequency or time synchronization of the mobile stations MS, are not introduced in every frame, but at predetermined times within a multi-frame.

The parameters of the radio interface, such as the duration of a radio block, number L of chips per midamble m, protection time (guard) Tg, number N of data symbols per data part, symbol duration Ts, number Q of chips per symbol, number W of the estimated length of a value that can be estimated for a communication connection Information and chip duration Tc can be set differently in the upward direction (MS → BS) and in the downward direction (BS - »MS). In particular, a different number of communication connections can each be assigned to a common radio block in the upward and downward direction.

Depending on the transmission conditions via the radio interface, it may also be necessary to vary the number W of chips per length Te. A reduction of activated communication links per time slot ts can therefore advertising also used to increase the estimated length of the so that in contrast to the prior art, the increase in the estimated length Te to Ver ^¬ ringerung the number N of each data portion transmitted data symbols d does not necessarily .

In a variant of the radio communication system shown, a maximum number of communication connections per time slot ts can be specified in order to ensure effective data transmission. to ensure wear. In contrast to the prior art, the length or duration of the middle am m is only set to this maximum number if the maximum number of communication connections is actually activated or can be activated, ie if the corresponding number of communication connections (mobile stations) for the base station BS is registered.

FIG. 4 shows a private radio telephone system, whereby private means that all existing communication connections are owned by the same person or the same organization. The telephone system can therefore also be a business system used, for example, by a company. The radio telephone system shown in FIG. 4 is connected to an Integrated Services Digital Network (ISDN). Two base stations BS1 and BS2 of the radio telephone system are connected to a network termination NA. Radio connections (represented by double arrows) to mobile hand stations HS1, HS2 and HS3 are established from the base stations BS1 and BS2. The user data are in each case one or more communication connections to or from one of the base stations BS1 and BS2 CDMA-coded and transmitted simultaneously in radio blocks in a common frequency band. The structure of the radio blocks is essentially the same as the structure shown in FIG. 3. The operation of the radio telephone system is now described in more detail below.

In a first state of the radio telephone system of FIG. 4 there are communication connections between the hand station HS1 and the hand station HS2 each with the base station BS1 and between the hand station HS3 and the base station BS2. The communication link between the hand station HS2 and the base station BS1 is designated VI. The radio blocks sent via the communication link VI cannot spread directly between the antennas of the base station BS1 and the hand station HS2, since obstacles W (for example walls made of reinforced concrete) interfere with the transmission. other. However, the radio blocks are reflected and reach the receiver at least with limited transmission quality.

In the first state of the radio telephone system, the midamble m of the radio blocks transmitted between the base station BS2 and the hand station HS3 has the structure shown in FIG. 5. Only a communication link to the base station BS2 can be activated. The midamble m consists of a number L of complex chips, of which, however, only a number of W <L are evaluated when estimating the channel impulse responses due to the system. These W chips are sufficient to estimate the channel impulse response of a communication link. The unevaluated part of the midamble comprises a number of W - 1 chips.

Starting from the first state of the telephone system described above, a further communication link V2 is now opened, namely between the hand station HS2 and the base station BS2. The disturbed communication link VI can be maintained or interrupted. In accordance with the newly established communication link V2, the structure of the radio blocks that are received or sent by the base station BS2 is now changed. The midamble m is extended in accordance with an additional number W of complex chips in order to be able to estimate the channel impulse responses of two signals transmitted simultaneously in the common frequency band. The midamble information sent to or from the hand stations HS2 and HS3 is derived from a basic midcode code of length 2 * W, where W corresponds to the expected number of channel coefficients to be estimated for the individual channel impulse responses. The midamble m is derived by a rotation to the right of the basic midamble code and a periodic stretching up to L = (K + 1) * W - 1 chips. K is the number of activatable ones

Communication connections over which signals can be transmitted simultaneously in the common frequency band, here K = 2. Consequently, the midamble m in the second state of the radio telephone system has a number of L = 2 * W + W - 1 chips.

In order to be able to activate the communication link V2 between the hand station HS2 and the base station BS2, the hand station HS2 is registered with the base station BS2, as a result of which the number of communication connections maintained via the base station BS2 increases from 1 to 2. For example, a maximum number of four hand stations can be registered at each of the two base stations BS1 and BS2, between which and a communication link can be activated between them and the base station BS1 or BS2. The maximum possible number of hand stations is therefore between four and eight, depending on whether the individual

Hand stations are registered with only one or both of the base stations BS1 and BS2.

Claims

claims

1. Method for the transmission of data in a communication system with a given number of activatable communication connections to and / or from existing communication connections, via which signals can be transmitted simultaneously in a common frequency band, in particular for the transmission of data in a UMTS communication system in TDD - Operating mode, wherein the signals have a data part and a training part (m), in particular a midamble, and wherein in the training part (m) known symbols, which were previously agreed between the respective transmitter and receiver of the signals, can be transmitted, characterized in that the length of the Training part (m) is set depending on the number of communication connections that can be activated.

2. The method according to claim 1, wherein an estimation of time-discrete channel impulse responses of the communication connections from communication connections to a common base station or vice versa, takes place on the receiver side, respectively, so that the portion of the training part (m) that can be evaluated in the estimation of the channel impulse responses is a length

Ta ∑ Te ⁽ k = l

has, where Te ^lk) , k = 1 ... K, is the estimation length of information of the channel impulse response which can be estimated for the kth activatable communication connection and where K is the number of activatable communication connections.

3. The method according to claim 2, characterized in that the estimated lengths Te ^(k) are the same for all channel impulse responses.

4. The method of claim 2 or 3, d a d u r c h g e k e n n z e i c h n e t that the training part (m) is subdivided into information units (chips) and has a length with a length that is system-specific and cannot be evaluated in the estimation of the channel impulse responses and / or not in every operating state

Tr = (W-l) * Tc,

where W is the respective or average number of chips per estimation length Te ^(k> and where Tc is the length of a chip.

5. The method according to any one of claims 1 to 4, so that the length of the training part (m) is set when the number of communication connections which can be activated, in particular when registering an additional handset at a private cell phone base station, is changed.