WO2000016575A1

WO2000016575A1 - Method and radio communication system for providing a control channel

Info

Publication number: WO2000016575A1
Application number: PCT/DE1999/002893
Authority: WO
Inventors: Meik Kottkamp; Michael Färber; Volker Sommer; Michael Benz; Anja Klein; Armin Sitte; Thomas Ulrich
Original assignee: Siemens Aktiengesellschaft
Priority date: 1998-09-10
Filing date: 1999-09-10
Publication date: 2000-03-23
Also published as: DE19841464A1; AU1149700A; DE19841464C2; EP1112667A1

Abstract

According to the invention one or more channels which form a control channel are assigned to a base station for the transmission of control information. This makes it possible to vary the bit rate of the control channel. At least one synchronization sequence is transmitted by the base station and the channel(s) of the control channel correspond to the selection of one or more synchronization sequences and/or a succession of several synchronization sequences. A subscriber station receives the at least one synchronization sequence and determines the configuration of the control channel on the basis of the synchronization sequence recognized and/or the succession of synchronization sequences recognized, which indicate the channel(s). Many variants of a single synchronization sequence and/or the order in which different synchronization sequences are transmitted can, for example, be used to indicate the configuration of the control channel. In this way the presence of a scalable control channel can be indicated already in the synchronization phase and with little additional effort.

Description

description

Method and radio communication system for providing an organizational channel

The invention relates to a method and a radio communication system for providing an organizational channel, in particular within a mobile radio system with broadband channels and TDD or FDD transmission mode.

In radio communication systems, messages (for example voice, image information or other data) are transmitted with the aid of electromagnetic waves via a radio interface. The radio interface relates to a connection between a base station and subscriber stations, it being possible for the subscriber stations to be mobile stations or fixed radio stations. The electromagnetic waves are emitted at carrier frequencies that lie in the frequency band provided for the respective system. For future radio communication systems, for example the UMTS (Universal Mobile Telecommunication System) or other 3rd generation systems, frequencies in the frequency band of approx. 2000 MHz are provided.

Two modes are provided for the third mobile radio generation, one mode being FDD operation (frequency division duplex), see ETSI STC SMG2 UMTS-Ll, Tdoc SMG2 UMTS-Ll 221/98, dated August 25, 1998, and the other mode a TDD operation (time division duplex), see DE 198 27 700. The operating modes are used in different frequency bands and use both time slots.

From ETSI STC SMG2 UMTS-Ll, Tdoc SMG2 UMTS-Ll 221/98, dated 25.8.1998, chapters 2.3.3.2.3 and 6.3 describe a synchronization procedure for FDD operation that uses synchronization sequences in each time slot (slot) are sent. This is a synchronization of the possible at the beginning of the time slot. The sequence of transmissions of a second synchronization sequence signals which code group (scrambling code) is used by the base station. The beginning of the frame can also be derived from this.

A method for providing an organizational channel is known from the GSM mobile radio system (global system for mobile communications), which method defines a channel in a predetermined frequency band for transmitting the organizational information. Only a limited amount of organizational information can be transmitted via this one channel, which is sufficient for signaling to the voice services in the GSM mobile radio system.

The invention has for its object to provide a method and a radio communication system with which greater flexibility in the provision of an organizational channel is achieved. This object is achieved by the method with the features of claim 1 and the radio communication system with the features of claim 14. Advantageous further developments can be found in the subclaims.

According to the invention, a channel or a plurality of channels are assigned to a base station for the transmission of organizational information, which form the organizational channel. This allows the data rate of the organizational channel to be varied. At least one synchronization sequence is transmitted by the base station, the channel or channels of the organization channel corresponding to the selection of one or more synchronization sequences and / or the sequence of several synchronization sequences. A subscriber station receives the at least one synchronization sequence and determines the configuration of the organization channel on the basis of the recognized synchronization sequence denoting the channel or channels and / or the recognized sequence of several synchronization sequences. For example, many variants of a single synchronization sequence and / or the sequence in which different synchronization sequences are transmitted can be used to signal the configuration of the organization channel. It is thus possible to indicate a scalable organizational channel in the synchronization phase with little additional effort.

The organization channel can be adapted to the individual needs of the individual radio cells and also over time according to the services offered. The flexibility of providing organizational information via the organizational channel is therefore much greater.

The configuration of the organization channel in TDD mode is advantageously designated by the number, the time slots used within a frame structure and / or the spread codes used for the channels. In FDD mode, this is a combination of scrambling code and the channelization code. This information can be complete or refer to parameters that are already known throughout the system. Depending on the current needs of a radio cell, the capacity of the organizational channel can be adapted to the subscriber stations, e.g. Additional spreading codes are assigned to an already assigned time slot and / or additional time slots with a spreading code as channels within the organization channel and the assignment is signaled with the aid of the synchronization sequences. If the required capacity is reduced, the assignment r is canceled, as a result of which the capacity is expanded with the channels which have become free for the user data transmission.

A high coding gain is achieved if the coding of the configuration of the organizational channel is determined by the choice and / or the sequence of the synchronization sequences extends over several time slots or several frames. For example, 17 variants of the second synchronization sequence are used and the sequence of eight transmissions of the second

Q Synchronization sequence evaluated, there are 17 options available. Only a small part of it has to be used.

The synchronization sequences are advantageously unmodulated orthogonal gold codes. So the synchronization procedure of FDD operation hardly needs to be modified. The synchronization method is particularly suitable for radio communication systems in which the time slots are part of a TDD transmission scheme with broadband channels. Here, several time slots per frame can be used to signal the configuration of the organization channel. Use in FDD mode is also possible. For multimode subscriber stations, parts of the detection device can thus be used for both modes.

In order to use as little system resources as possible for "broadcast" purposes in TDD mode, the synchronization sequences are sent in m time slots, with which additional organizational information of the organization channel is transmitted. This means that only a small number of time slots have to be waited (from the base station to the The degree of freedom of the asymmetry of both transmission directions is hardly restricted. In order to keep the interference on the other channels caused by the synchronization sequences low, these are transmitted with other transmissions of the base station, for example the organizational information of lower power this disadvantage is easily compensated for.

As in the FDD operation described above, two synchronization sequences are advantageously in one time slot Posted. The first synchronization sequence is used to Be ^¬ mood of the reception timing and Grobsynchroni- tion. The sequence of the second synchronization sequences over several transmissions encodes the organization channel and possibly further information such as a time offset of the transmission within the time slot. According to an advantageous embodiment of the invention, a time interval between the two synchronization sequences is specified in a time slot. This makes it possible to use a single, switchable filter to detect both synchronization sequences. The second synchronization sequence can also be sent before the first, so the time interval is negative. Further information can be encoded in the temporal ratio of the first to the second synchronization sequence. If two different filters are used, the two sequences can also be sent simultaneously. With two synchronization sequences separated in time, the interfering interferences are better distributed over time, so that fewer burst-like interferences arise.

It is also advantageous sationssequenzen by a choice of Synchroni ^¬ and / or to transmit more information whose sequence. This enables a faster operational readiness of the subscriber stations. The further information relates to a frame synchronization as well as midambles and spreading codes used by the base station in TDD mode or in FDD mode the code group used by the base station (scrambling code).

Embodiments of the invention are explained in more detail with reference to the accompanying drawings.

1 shows a radio communication system, 2 shows a schematic representation of a TDD radio interface between base station and subscriber stations,

3 shows a scheme for sending synchronization sequences,

Fig. 4 differently designed organizational channels, unt

5 shows a flowchart for the synchronization and the determination of the configuration of the organizational channel.

The mobile radio system shown in FIG. 1 as an example of a radio communication system consists of a large number of mobile switching centers MSC which are networked with one another or which provide access to a fixed network PSTN. Furthermore, these mobile switching centers MSC are each provided with at least one device RNC for controlling the base stations BS and for allocating radio resources, i.e. a radio resource manager. Each of these devices RNC in turn enables a connection to at least one base station BS. Such a base station BS can connect via a radio interface to a subscriber station, e.g. Build mobile stations MS or other mobile and stationary devices. The subscriber stations MS contain synchronization means SYNC for synchronization and evaluation means AUS for detection and evaluation of the signals received by the base station BS. At least one radio cell is formed by each base station BS.

1 shows connections VI, V2, V3 for the transmission of useful information and signaling information between mobile stations MS and a base station BS and an organization channel BCCH as a point-to-multipoint connection. Organizational information oi is transmitted in the organization channel BCCH and can be evaluated for all subscriber stations MS and contains information about the services offered in the radio cell and about the configuration of the channel of the radio interface. An operations and maintenance center OMC implements control and maintenance functions for the mobile radio system or for parts thereof. The functionality of this structure can be transferred to other radio communication systems in which the invention can be used, in particular for subscriber access networks with a wireless subscriber line.

The frame structure of a TDD radio transmission (time division duplex) is shown in FIG. 2. According to a TDMA component (time division multiple access), a division of a broadband frequency range, for example the bandwidth B = 5 MHz m, into a plurality of time slots ts of the same duration, for example 16 time slots tsO to tsl5. A frequency band extends over a frequency range B. Some of the time slots are used in the downward direction DL and some of the time slots are used in the upward direction UL. An asymmetry ratio of 3: 1 in favor of the downward direction DL is shown as an example.

In this TDD transmission method, the frequency band for the upward direction UL corresponds to the frequency band for the downward direction DL. The same is repeated for other carrier frequencies. Due to the variable allocation of the time slots ts for upward or downward direction UL, DL, diverse asymmetrical resource allocations can be made.

Information of several connections is transmitted in radio blocks within the time slots ts. The data d are spread individually for each connection with a fine structure, a spreading code c, so that, for example, n connections can be separated at the receiving end by this CDMA component (code division multiple access). The spreading of individual symbols of the data d causes Tsym Q chips of the duration T _c ιp to be transmitted within the symbol duration. The Q chips form the connection-specific spreading code c. A channel K1, K2, K3, K4 is designated within a frequency band B by a time slot ts, a spreading code c and thus implicitly a spreading factor. The dimension of the time slot ts is missing in the FDD mode.

Within a broadband frequency range B, the successive time slots ts are structured according to a frame structure. So 16 time slots ts are combined into a frame for.

The parameters of the radio interface used are advantageous ^¬ way legally:

Chip rate: 4,096 Mcps

Frame duration: 10 ms Number of time slots: 16

Duration of a time slot: 625 μs spreading factor: 16

Modulation type: QPSK

Bandwidth: 5 MHz Repeat rate: 1

These parameters enable the best possible harmonization with an FDD mode (frequency division duplex) for the 3rd generation of mobile communications. Not only in TDD mode but also in an FDD mode, signaling to the organization channel BCCH can be carried out with the aid of the synchronization sequences described below.

In the downward direction according to FIG. 3, two time slots ts0, ts8 are used for synchronization, for example. For example, two synchronization sequences cp are sent in a time slot ts8, separated by a time interval tgap. The separation of the two synchronization sequences cp, it has the advantage of reduced interference, since the interference power of both sequences is better distributed over time. The first synchronization sequence cp is the same in every time slot tsO, ts8. The second synchronization sequence it can be re-selected from time slot tsO to time slot tsδ.

The choice and sequence of the second synchronization sequence corresponds to a time offset toff with which the transmission of the first synchronization sequence cp is delayed with respect to the start of the time slot ts8. By receiving and evaluating the synchronization sequences, the receiving subscriber station MS can determine the time offset toff and take it into account in the synchronization.

Neighboring base stations BS are frame-synchronized in TDD mode. According to the invention, neighboring base stations BS are assigned a different time offset toff for the transmission of the synchronization sequences. For example

32 different time offsets toff are used, so that cell groupings (clusters) can be formed and when the time offset toff changes for a base station BS, the entire grouping does not have to be changed.

The choice and sequence of the second synchronization sequences over, for example, 4 frames fr and two time slots tsO, ts8 per frame fr result in the use of 17 different unmodulated orthogonal cold codes

Q with 256 chip length 17 different options with which additional information is transmitted in addition to the time offset toff. Because of the many possibilities, the coding gain is large, so that the synchronization sequences cp can be sent with low power.

The further information relates to the frame synchronization, midambles used by the base station, spreading codes (the midambles and spreading codes are assigned independently of one another) and information on the configuration of an organization channel BCCH. In the case of two time slots ts per frame fr used for the synchronization, the frame start after detection of the synchronization is m one time slot ts still inaccurate by a factor of two. The frame synchronization is consequently easily brought about by a certain sequence of second synchronization sequences. In addition, the later detection of information from the organization channel BCCH is accelerated if middle messages, spreading codes and configuration information are already transmitted during the synchronization.

In particular, there is the possibility of introducing a scalable organizational channel BCCH, which is announced independently of the use of the time offset toff by the sequence of the synchronization sequences. 4, e.g. Organizational information is transmitted in one, two or four channels. Through the signaling with the synchronization sequences cp, any channels K1, K2, K3, K4 denoted by spreading code c and time slot ts can also be signaled beyond the number four. In the case of transmission methods without a TDMA component or without a CDMA component, the information about the time slots ts or the spreading codes c is superfluous. Possibly. According to the selected transmission method, other parameters for channels K1, K2, K3, K4 of the organizational channel BCCH must be signaled.

This means that the data rate of the BCCH organizational channel can be adapted to the cell-specific requirements in accordance with the services offered there. This will enable future modifications to the BCCH organizational channel. The parameters (number of channels, time slots and spreading codes) of the Organi ^¬ sationskanals BCCH must therefore not be pre-set system-wide fixed, but the synchronization can be communicated while.

In addition to the variants in FIG. 4, it is also possible to refer to additional channels with organizational information by means of the further information from the synchronization. In this way, organizational information can also be temporarily sent in m additional channels. The organizational channel BCCH is sent in parallel to other user data connections, but with a larger error protection coding if necessary.

The transmissions of the organization channel BCCH and the synchronization sequences cp are preferably located in the same time slot ts, as a result of which only two time slots tsO, ts8 have to be reserved continuously for the downlink DL. The adjustability of the asymmetry is only slightly restricted.

If the asymmetry ratios in the system are such that more than two time slots ts0, ts8 are used for the downward direction DL, organizational information can also be transmitted in the remaining time slots ts assigned to the downward direction DL. It is then also possible to transmit the organizational information only in time slots ts in which the synchronization sequences cp, es are not sent. This further reduces the interference on the user data connections. The flexibility of the BCCH organizational channel offers additional advantages, e.g. a distribution over several time slots makes the transmission more robust against interference.

The use of a multicode transmission in the organization channel BCCH (several spreading codes c per time slot ts) within a time slot ts enables an adaptive increase in the data rate of the organization channel BCCH. The same can also be achieved by reducing the spreading factor, which is also communicated by the choice and sequence of the synchronization sequences. The choice of the time slots ts for transmitting the organizational information can be made by a higher-level entity, e.g. a radio resource manager RNC, for several base stations BS are coordinated.

The assignment made in a control device, for example the radio resource manager RNC of a base station system of time slots tsO, ts8 for the synchronization, of channels K1, K2, K3, K4 of the organization channel and of different time offsets toff with respect to the beginning of the time slot tsO, ts8 for sending the synchronization sequences cp, the synchronization is preceded by the first step 1 . In a second step 2, a plurality of base stations BS send the synchronization sequences cp, it in the predetermined order, which is individual for each base station BS and corresponds to the time offset toff.

In a third step 3, a subscriber station MS receives the synchronization sequences cp, and carries out a rough synchronization on the basis of the first synchronization sequence cp. By evaluating the second synchronization sequences in a fourth step 4, the time slot synchronization to the beginning of the time slot ts is possible, whereupon the frame synchronization is also carried out in a fifth step 5 by evaluating the further information. Steps 3 to 5 are carried out by synchronization means SYNC assigned to the subscriber station, which, for example, represent a signal processing processor and correlators formed by signal-adapted filters.

In a sixth step 6, the configuration of the organization channel BCCH is determined on the basis of the further information in the evaluation means AUS formed by a signal processor, and the preparation for the reception of the organization channel BCCH is initiated.

Claims

claims

1. A method for providing an organizational channel (BCCH) in a radio communication system, in which a base station (BS) is assigned one or more channels (K1, K2, K3, K4) for transmitting organizational information (oi) that represent the organizational channel (BCCH) form, the base station (BS) sends at least one synchronization sequence (cp, es), the channel or channels

(K1, K2, K3, K4) correspond to the choice of one or more synchronization sequences (cp, es) and / or the sequence of several synchronization sequences (cp, es), a subscriber station (MS) which has at least one synchronization sequence (cp, es ), the subscriber station (MS) receives the configuration of the organization channel on the basis of the recognized synchronization sequence (cp, es) and / or the channels (K1, K2, K3, K4) and / or the recognized sequence of multiple synchronization sequences (cp, es) (BCCH) determined.

2. The method according to claim 1, in which the configuration of the organization channel (BCCH) is a variable number of channels (Kl, K2) denoted by time slots (ts) and / or spreading codes (c) or a combination of scrambling code and the channel , K3, K4).

3. The method according to claim 1, wherein the configuration of the organization channel (BCCH) relates to a variable number of channels (Kl, K2, K3, K4) designated by a combination of scrambling code and the channel designating code.

4. The method according to any one of the preceding claims, in which a coding of the configuration of the organizational channel (BCCH) by choice and / or sequence of the synchronization sequences (cp, es) extends over several time slots (ts).

5. The method according to any one of the preceding claims, in which the synchronization sequences (cp, es) are sent in time slots (ts) in which the channels (Kl, K2, K3, K4) of the organization channel (BCCH) are arranged.

6. The method according to any one of the preceding claims, wherein the synchronization sequences (cp, es) are sent with less power than the organizational information (oi).

7. The method according to any one of the preceding claims, wherein the synchronization sequences (cp, es) are unmodulated orthogonal gold codes.

8. The method according to any one of the preceding claims, in which the synchronization sequences (cp, es) and organizational information are transmitted in time slots (ts) which are part of a TDD transmission scheme with broadband channels, one or more time slots (ts) per Frame (fr) can be used for synchronization.

9. The method as claimed in one of the preceding claims, in which a plurality of base stations (BS) is synchronously assigned a time slot (ts) for transmitting the at least one synchronization sequence (cp, es), adjacent base stations (BS) having a different time offset (toff) with regard to the beginning of the time slot (ts) for sending the synchronization sequence (cp, es), and the time offset (toff) with the choice of one or more synchronization sequences (cp, es) and / or the sequence of several synchronization sequences (cp, es ) corresponds.

10. The method according to any one of the preceding claims, in which two synchronization sequences (cp, es) are sent in a time slot (ts).

11. The method according to claim 10, wherein a time interval (tgap) between the two synchronization sequences (cp, es) is specified in a time slot (ts).

12. The method according to any one of the preceding claims, in which the base station (BS) transmits further information by a choice of the synchronization sequences (cp, es) and / or their sequence.

13. The method as claimed in claim 12, in which the further information relates to a frame synchronization and / or middle messages and / or spreading codes (c) and / or a scrambling code used by the base station (BS).

14. Radio communication system for providing an organizational channel (BCCH) with at least one base station (BS) for sending organizational information (oi) and at least one synchronization sequence (cp, es), with a control device (RNC) that the base station (BS) assigns one or more channels (Kl, K2, K3, K4) for transmitting the organizational information (oi) that form the organizational channel (BCCH), the channel or channels (Kl, K2, K3, K4) with the Choice of one or more synchronization sequences (cp, es) and / or the sequence of several synchronization sequences (cp, es) correspond with a subscriber station (MS) for receiving and evaluating the at least one synchronization sequence (cp, es), with evaluation means assigned to the subscriber station ( OFF), the recognized synchronization sequence (cp, es) and / or the channel or channels (Kl, K2, K3, K) designating determine the sequence of multiple synchronization sequences (cp, es) the configuration of the organizational channel (BCCH).