WO1999022475A2

WO1999022475A2 - Radiocommunications system and control device

Info

Publication number: WO1999022475A2
Application number: PCT/DE1998/003147
Authority: WO
Inventors: Stefan Bahrenburg; Jürgen Mayer; Johannes Schlee; Paul Walter Baier; Dieter Emmer; Tobias Weber
Original assignee: Siemens Aktiengesellschaft
Priority date: 1997-10-27
Filing date: 1998-10-27
Publication date: 1999-05-06
Also published as: WO1999022475A3; EP1027815A2; AU1748199A; CN1278395A; JP2001522163A; CN1135881C; KR20010031496A

Abstract

The invention relates to a radiocommunications system constructed by radio cells in which realized data channels are distinguishable in a radio cell by expansion codes assigned to said data channels. A set of expansion codes is assigned to specific combined radio cells, whereby the set of expansion codes differentiates (code-reuse) itself from the sets of expansion codes which are utilized by adjacent combined radio cells. The radiocommunications system is especially suited for use in third generation TD/CDMA mobile radio networks.

Description

description

Radio communication system and control device

The invention relates to a radio communication system constructed from radio cells, in particular a mobile radio network and a control device.

The term “transmission” encompasses the processes during transmission and / or reception in the form of point-to-point and / or in the form of point-to-multipoint communication. Transmitting, receiving and / or processing devices are usually used for the transmission.

In communication systems, messages (for example voice, image information or other data) are transmitted via transmission channels, in radio communication systems this is done with the aid of electromagnetic waves via a radio interface. The electromagnetic waves are emitted at carrier frequencies that lie in the frequency range provided 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 range of approx. 2000 MHz are provided.

The emitted electromagnetic waves are attenuated due to losses due to reflection, diffraction and radiation due to the curvature of the earth and the like. As a result, the reception power that is available at the receiving radio station decreases. This damping is location-dependent and also time-dependent for moving radio stations.

There is a radio interface between a transmitting and a receiving radio station, via which the electronic tromagnetic waves a data transmission takes place. From DE 195 49 158 a radio communication system is known which uses CDMA subscriber separation (CDMA code division multiple access), the radio interface additionally having a time division multiplex subscriber separation (TDMA time division multiple access). On the receiving side, a JD (Joint Detection) method is used in order to perform an improved detection of the transmitted data with knowledge of spreading codes of several participants. It is known that at least two data channels can be allocated to a connection via the radio interface, each data channel being distinguishable by an individual spreading code. The data channel is also understood to mean logical channels via which user data can be transmitted.

It is known from the GSM mobile radio network that data is transmitted as a radio block (burst), middle messages with known symbols being transmitted within a radio block. These midambles can be used in the sense of training sequences for tuning the radio station on the reception side.

The receiving radio station uses the midambles to estimate the channel impulse responses for different transmission channels. It is also known from the GSM mobile radio network to combine adjacent radio cells into a cluster and to transmit m to the different radio cells m different frequency bands within this cluster.

Spread codes can be assigned to CDMA channels in two different ways:

Random generation of spreading codes: this has the disadvantage that the spreading codes cannot be optimized with regard to their separability;

A set of fixed spreading codes: this has the disadvantage that the CDMA channels to which the same spreading code is assigned are difficult to separate under certain circumstances. The invention is therefore based on the object of specifying a radio communication system and a control device for data transmission with which the capacity utilization of the radio communication system is improved.

This object is achieved by a radio communication system with the features of claim 1 and a control device with features according to claim 8. Advantageous further developments can be found in the subclaims.

The invention is therefore based on the idea of carrying out a spreading code planning in such a way that radio cells within which transmission is carried out in the same frequency bands form a subset, and the same spreading codes are not used simultaneously in the radio cells locally adjacent to this subset. So it is possible that a limited number of easily separable spreading codes can be used efficiently.

A further development of the invention also provides for corresponding midamble code planning. The result of this is that a limited number of midambles can be allocated efficiently.

One embodiment of the invention provides that at least one frequency cluster contains only one radio cell. In such a radio communication system, which is constructed from radio cells, data sequences which are not disjoint in time and frequency and which are transmitted in a radio cell can be distinguished by spread codes assigned to them, each radio cell is assigned a set of spread codes, and a plurality of radio cells are combined to form a code cluster , and the sets of spreading codes assigned simultaneously to the radio cells within a code cluster are different.

Another advantageous embodiment provides that the radio interface additionally contains a TDMA component. As a result, the transmission resources and the code resources can be used even more efficiently and flexibly.

By incorporating the invention into the system concept of 3rd generation TD / CDMA mobile radio networks, there are considerable advantages with regard to the use of the JD method (joint detection), in which the signals are detected with the knowledge of spreading codes of several subscribers the separability of the subscriber signals and thus the capacity utilization.

The invention is described in more detail below on the basis of preferred exemplary embodiments. The figures listed below serve to explain the embodiments of the invention.

Show

1 shows a block diagram of a mobile radio network,

2 shows a schematic representation of the frame structure of the radio interface,

3 shows a schematic illustration of the structure of a radio block,

4 shows a schematic representation of code clusters consisting of radio cells

5 shows a schematic representation of code clusters consisting of frequency clusters

The structure of the radio communication system shown in FIG. 1 corresponds to a known GSM mobile radio network which consists of a large number of mobile switching centers MSC which are networked with one another and which provide access to a fixed network PSTN. Furthermore, these mobile switching each MSC 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 a radio connection to mobile radio stations, the mobile stations MS, via a radio interface. A radio cell FZ is essentially defined by the range of the base station. The allocation of resources such as codes and frequency bands to radio cells and thus to the transmitted data sequences can be controlled by control devices such as the base station controller BSC.

1 shows three radio connections for transmitting useful information ni and signaling information si between three mobile stations MS and a base station BS, one mobile station MS for increasing the data rate two data channels DK1 and DK2 and the other mobile stations MS each a data channel DK3 or DK4 are allocated. 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 e.g. 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 (according to adaptive antennas) 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 (LA location area) and via the radio cell (radio cell identifier). The organizational information is emitted simultaneously via all individual radiators of the antenna device.

The connections with the user information ni and signaling information si between the base station BS and the mobile stations MS are subject to multipath propagation, which is caused by reflections, for example, on buildings in addition to the direct propagation path. Directional radiation by certain individual radiators of the antenna device AE results in a greater antenna gain in comparison to the omnidirectional radiation. The quality of the connections is improved by the directional radiation.

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 receiving mobile station MS. Furthermore, it is assumed that the subscriber signals of different base stations BS are superimposed on a frequency channel at the receiving location to form a received signal rx m. The task of a receiving mobile station MS is to detect data symbols d of the useful information ni, signaling information si and data of the organizational information transmitted in the subscriber signals.

The frame structure of the radio interface can be seen from FIG. 2. According to a TDMA component, the time range is divided into time slots ts, a sequence of, for example, 8 time slots ts1 to tsδ being combined to form a TDMA frame.

The entire frequency range available to a radio communication system is divided into two sub-ranges, one of which is used for the uplmk connections, the which is reserved for downlmk associations. A down-lmk connection, together with the corresponding uplink connection, forms a duplex radio connection, with the same or different data rates being able to be transmitted in the up- and downlmk. According to an FDMA component, the sub-areas are divided into m frequency bands, for example the bandwidth B = 1.6 MHz.

A sequence of time slots of the same time slot number over the TDMA frames of a frequency band and optionally a frequency hopping function form a physical channel.

A digital data stream to be transmitted via this physical channel is first modulated. The resulting data symbols are combined into data parts dt consisting of data sequences. According to a CDMA component, the data parts are spread by a spreading code, the CDMA code, i.e. A certain broadband signal form is modulated onto a data sequence. The resulting chip sequences are combined with a midamble and form a radio block

(burst). The midamble is different for each connection, at least in the uplink.

These radio blocks are transmitted within the corresponding physical channels. In order to be able to transmit several radio blocks within a physical channel, the data sequences of different radio blocks within a physical channel are spread individually with different storage codes, whereby they can be separated in the receiver. A specific physical channel forms a CDMA channel CC together with a specific spreading code.

Logical channels, such as data channels DK or control channels, are assigned to these CDMA channels according to a certain scheme.

3 shows such a radio trestle for the transmission of user data from data parts dt with data symbols d, which m cuts are embedded with midambles known at the reception. The data parts dt are spread so that, for example, K data channels DK1, DK2, DK3,... DKK can be separated on the receiving side 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 d with Q chips has the effect that Q sub-sections of the duration Tc are transmitted within the symbol duration Ts. The Q chips form the individual CDMA code. The midamble m consists of L chips, also of the duration Tc. For each connection, an individual midamble m consisting of L complex chips is used, at least in the uplink. The necessary M different midambles are derived from a basic midamble code of length M * W, where M is the maximum number of subscribers (connections) and W is the expected maximum number of channel coefficients of the channel impulse response. The connection-specific midamble m is derived by rotating to the right of a basic midamble code by W * m chips and periodically stretching to L> (M + 1) * W - 1 chips.

By using a common midamble m for several data channels DK1 and DK2 of a connection VI, V2, V3, it is possible to transmit a larger number of data channels DK1 and DK2 in one time slot ts.

Furthermore, a protection time guard of the duration Tg is provided within the time slot ts to compensate for different signal tents of the connections of successive time slots ts.

Control 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 are, for example, as follows:

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 These parameters enable the best possible harmonization of a TDD (Time Division Duplex) mode with an FDD (Frequency Division Duplex) mode for the 3rd generation of mobile communications.

The parameters can also be set differently in the upward (MS -> BS) (uplink) and downward direction (BS -> MS) (downlink).

As described above, different data channels within a physical channel are based on different spreading codes. It turned out that, depending on what type of spreading codes are used, how these spreading codes are generated and how the spreading codes are allocated or how the receiving devices are informed, the situation can arise that an infinite number of well separable ones cannot be created Spreading codes are available.

FIG. 4 shows how a limited number of spreading codes can be efficiently allocated in a cellular mobile radio system by code planning. For example, seven adjacent radio cells FZ represented by hexagons are always combined to form a so-called code cluster KC (in this case, a frequency cluster FC is represented by a radio cell). Within a code cluster, a different set of C1-C7 spreading codes is used in each radio cell. In one embodiment variant, these spreading codes are only used again in radio cells of neighboring code clusters (code reuse).

FIG. 5 also shows how a limited number of code codes can be used in a cellular mobile radio system

Spreading codes can be allocated efficiently. For example, seven adjacent radio cells FZ represented by hexagons are always combined to form a so-called frequency cluster FC. Within a frequency cluster, a different set of frequency bands F1-F7 is used in each radio cell. Furthermore, for example, seven adjacent frequency clusters FC are always combined to form a code cluster KC. Within a code cluster, a different set of C1-C7 spreading codes is used in each frequency cluster. In one embodiment variant, these spreading codes are only used again in radio cells of adjacent code clusters (code reuse).

In this radio communication system constructed from radio cells FZ, radio blocks that are not disjunct in time and frequency and transmitted in a first radio cell can be distinguished by different spreading codes assigned to them and / or at least partially by different middle messages assigned by them. These spreading codes and / or midambles are not used simultaneously in second radio cells in which transmission takes place within the same frequency bands as in the first radio cell and which are located in the vicinity of the first radio cell.

In one embodiment variant, the spreading codes used in the first radio cell are also used in neighboring radio cells in which transmission takes place within different frequency bands than in the first radio cell.

In a further embodiment variant, the spreading codes used in the first radio cell are also used in non-adjacent barten radio cells used in which is transmitted within the same frequency bands as in the first radio cell.

In one embodiment, the allocation of sets of midambles is carried out according to the above-described scheme for the allocation of sets of spreading codes. The formation of the code clusters relating to the midambles can, however, take place independently of the formation of the code clusters relating to the spreading codes, the code clusters not necessarily referring to identical frequency clusters.

The sets of spreading codes or middle notes can be generated from a basic code in the radio stations MS, BS or in the control devices BSC, to which the radio stations are assigned. Central control devices OMC and / or decentralized control devices BSC can be used to assign the sets of spreading codes or middle messages to the individual radio cells. Decentralized control units BSC can also be used to allocate the sets of spreading codes or midambles and of frequency and time resources to data channels.

In another embodiment variant, the sets of spreading codes or middle messages are queried from memory devices which can be located in the control devices BSC.

In a further embodiment, the allocation of the sets of spreading codes or midambles is performed dynamically by central control devices OMC. Furthermore, it is possible for the sets of spreading codes or middle notes to be predetermined when setting up or expanding the mobile radio system.

Furthermore, an embodiment variant can be implemented in which no spread code planning, but only midamble code planning takes place. Another embodiment of the invention provides that only one frequency band is assigned to at least one radio cell FZ.

When the invention is used in 3rd generation mobile radio networks, there are considerable advantages with regard to the separability of the subscriber signals and thus the use of the JD method (joint detection), in which the signals are detected with the knowledge of spreading codes of several subscribers Capacity utilization. In this embodiment, the radio stations MS, BS are provided with joint detection receiving devices, the joint detection method being implemented essentially by digital signal processors.

The mobile radio network presented in the exemplary embodiments with a combination of FDMA, TDMA and CDMA is suitable for requirements on 3rd generation systems. In particular, it is suitable for an implementation in existing GSM mobile radio networks, for which only a small amount of change is required.

Claims

claims

1. Radio communication system, which is constructed from radio cells (FZ), in which a) each radio cell (FZ) is assigned a set (F) of frequency bands for data transmission, b) several radio cells (FZ) to form a frequency cluster (FC ) are summarized, c) the sets (F1-F7) of frequency bands assigned to the radio cells (FZ) within a frequency cluster are different, d) data sequences transmitted in a radio cell (FZ) that are not disjoint in time and frequency are assigned by them Spreading codes are distinguishable, e) a set (C) of spreading codes is assigned to each frequency cluster, f) several frequency clusters (FC) are combined to form a code cluster (KC), and g) the frequency clusters (FC ) within a code cluster (KC) simultaneously assigned sets (C1-C7) of

Spreading codes are different.

2. Radio communication system according to claim 1, in which a) transmitted in a radio cell (FZ) via the radio interface, in which time and frequency non-disjoint radio blocks are at least partially assigned different middle signals (m), b) each frequency cluster (FC) a set of midambles is assigned, c) several frequency clusters (FC) are combined to form a code cluster (KC), and d) assigned to the frequency clusters (FC) within a code cluster (KC) Sets of midambles are different.

3. Radio communication system according to one of the preceding claims, in which at least one frequency cluster (FC) contains only one radio cell (FZ).

4. Radio communication system which is built up from radio cells (FZ), in which a) data sequences transmitted in a radio cell (FZ) that are not disjoint in time and frequency can be distinguished by spread codes assigned to them, b) each radio cell (FZ) a set (C) of spreading codes is assigned, c) a plurality of radio cells (FZ) are combined to form a code cluster (KC), and d) which are assigned to the radio cells (FZ) within a code cluster (KC) at the same time Sets (C1-C7) of spreading codes are different.

5. Radio communication system according to claim 4, in which a) in a radio cell (FZ) transmitted via the radio interface, in which the time and frequency are not disjoint radio blocks are at least partially assigned different middle messages (m), b) each radio cell (FZ ) a set of midambles is assigned, c) several radio cells (FZ) are combined to form a code cluster (KC), and d) the sets of midambles simultaneously assigned to the radio cells (FZ) within a code cluster (KC) are different.

6. Radio communication system according to one of the preceding claims, in which adjacent frequency clusters (FC) or radio cells (FZ) are combined to form a code cluster (KC).

7. Radio communication system according to one of the preceding claims, in which the formation of the code clusters (KC) relating to the midambles and the code clusters (KC) relating to the spreading codes takes place independently of one another.

8. Radio communication system according to one of the preceding claims, in which the radio interface additionally contains a TDMA component.

9. Radio communication system according to one of the preceding claims, wherein the radio stations (MS, BS) detect the received signals according to the joint detection method.

10. Control device (BSC) which assigns frequency bands and spreading codes used for data transmission to radio cells (FZ), so that a) each radio cell (FZ) is assigned a set of frequency bands for data transmission, b) several radio cells (FZ) to a frequency Clusters (FC) are combined, c) the sets of frequency bands assigned to the radio cells (FZ) within a frequency cluster (FC) are different, d) data sequences that are not disjoint in time and frequency are transmitted in a radio cell (FZ) assigned to them

Spreading codes are distinguishable, e) a set of spreading codes is assigned to each frequency cluster (FC), f) several frequency clusters (FC) are combined to form a code cluster (KC), and g) the frequency clusters (FC ) within a code cluster (KC) sets of spreading codes assigned simultaneously are different.

11. Control device (BSC) according to claim 10, the frequency bands used for data transmission, midambles and spreading codes assigned to radio cells (FZ), so that a) in a radio cell (FZ) transmitted via the radio interface, in which time and frequency non-disjoint radio blocks are at least partially assigned different midambles, b) a set of midambles is assigned to each frequency cluster (FC), c) several frequency clusters (FC) are combined to form a code cluster (KC), and d) the sets of midambles assigned to the frequency clusters (FC) within a code cluster (KC) are different.

12. Control device (BSC) according to one of claims 10 to 11, the middle messages and spread codes used for data assignment to radio cells (FZ), so that at least one frequency cluster (FC) contains only one radio cell (FZ).

13. Control device (BSC) which assigns spreading codes used for data transmission to radio cells (FZ), so that a) in a radio cell (FZ) transmitted in time and frequency non-disjoint data sequences can be distinguished by spreading codes assigned to them, b) each radio cell (FZ) a set (C) of spreading codes is assigned, c) several radio cells (FZ) are combined to form a code cluster (KC), and d) which are assigned to the radio cells (FZ) within a code cluster (KC) at the same time Sets (C1-C7) of spreading codes are different.

14. Control device (BSC) according to claim 13, which assigns midambles and spreading codes used for data transmission to radio cells (FZ), so that a) in a radio cell (FZ) transmitted via the radio interface, at least in time and frequency not disjoint radio blocks some different middle names are assigned, b) a set of middle names is assigned to each radio cell (FZ), c) several radio cells (FZ) are combined to form a code cluster (KC), and d) the radio cells (FZ) within a code cluster (KC) simultaneously assigned sets of midambles are different.

15. Control device (BSC) according to one of claims 10 to 14, the frequency bands used for data transmission, midambles and spreading codes assigned to radio cells (FZ), so that adjacent frequency clusters (FC) or radio cells (FZ) to a code cluster (KC) are summarized.

16. Control device (BSC) according to one of claims 10 to

15, which assigns the frequency bands, midambles and spreading codes used for data transmission to radio cells (FZ) so that the code clusters (KC) and the code clusters (KC) relating to the midambles are formed independently of one another.

17. Control device (BSC) according to one of claims 10 to

16, which allocates frequency bands, midambles, spreading codes and time slots (ts) used for data transmission to radio cells (FZ), so that the radio interface additionally contains a TDMA component.