WO1999060727A1

WO1999060727A1 - Tdma radiocommunications system with several radio concentrators

Info

Publication number: WO1999060727A1
Application number: PCT/DE1999/001311
Authority: WO
Inventors: Gerhard Ritter; Karl Kammerlander
Original assignee: Siemens Aktiengesellschaft
Priority date: 1998-05-20
Filing date: 1999-05-03
Publication date: 1999-11-25
Also published as: AU4767999A

Abstract

The inventive radiocommunications system contains several radio concentrators to which mobile terminals can be connected with radio connections. The radio connection is organised according to a TDMA subscriber separation. Transmitting/receiving devices which accommodate radio connections to the mobile terminals in first time slots and radio connections to adjacent radio concentrators in second time slots are arranged in the radio concentrators. The connection can then be established without using any other network-end components of the radiocommunications system. The concentrators are organised and installed in the manner of a radio network so that radio coverage is provided.

Description

description

TDMA RADIO COMMUNICATION SYSTEM WITH SEVERAL RADIO NODE STATIONS

The invention relates to a radio communication system with a TDMA subscriber separation to mobile devices.

Radio communication systems, such as the GSM (global system for mobile communications) mobile radio system or system of the third generation of mobile radio, have so far been organized centrally in licensed frequency ranges. A mobile terminal sets up a connection to the nearest base station, whereupon fixed lines are used to establish a connection to the next mobile switching center, where the further connection sequence to the second subscriber is conveyed. This means that there is considerable switching effort even for subscribers in neighboring radio cells.

A radio telephone network is known from R. Tichy, "Crack in the Network", the week of April 9, 1998, in which the connections are to be switched without infrastructure, i.e. between the terminals. However, the uncoordinated installation of such terminals cannot guarantee a nationwide radio coverage.

Furthermore, with the DECT cordless telephony system (digital enhanced cordless telephony), a radio communication system is known which allows base stations to be set up anywhere in a non-licensed frequency range, but which in turn are connected to the fixed network. The connection for the connections takes place in the fixed network.

Frequency division multiplexing (FDMA), time slot multiplexing (TDMA) or a method known as code division multiplexing (CDMA) are used for subscriber separation in radio transmission. The GSM mobile radio system and the DECT cordless telephony system use a combination of FDMA and TDMA. The invention is based on the object of specifying a radio communication system which, in a self-organizing manner, reduces the switching effort and ensures a nationwide radio coverage. This object is achieved by the radio communication system with the features of patent claim 1. Advantageous developments of the invention can be found in the subclaims.

The radio communication system contains several radio node stations to which mobile devices can be connected via radio connections. In addition, stationary terminals can be connected via leased lines. The radio link is organized according to a TDMA subscriber separation, which minimizes the interference between the links. Transmitter / receiver devices are arranged in the radio node stations and maintain the radio connections to the mobile terminals in first time slots and radio connections to neighboring radio node stations in second time slots. The connection can thus be established while avoiding further network-side components of the radio communication system. Since the radio node stations are planned and installed in the sense of a radio network, the radio coverage is also covered. The TDMA subscriber separation minimizes the mutual interference, whereby the radio resources can be freely divided between the supply of the mobile devices and switching functions for further radio node stations.

The interference is further reduced if synchronization devices arranged in the radio node stations bring about a synchronization of the radio connections at least between radio node stations of a partial area. The synchronization advantageously relates to the frames of the TDMA transmission. According to various embodiments of the invention, the synchronicity is determined by evaluating radio signals from neighboring radio node stations, by evaluating signals from a GPS receiver and / or by achieved signals from a synchronization point in the radio communication system. These methods can also be combined with one another. A radio node station can assume the role of a central point for several stations, at which the other radio node stations are oriented with regard to synchronization. This saves, for example, GPS receivers at other radio node stations.

According to an advantageous development of the invention, a CDMA subscriber separation is additionally carried out for the radio connection. This means that the radio resources can be better used in broadband frequency channels and individual codes for connections to mobile devices or other radio node stations can also be separated within a time slot. At least one code is advantageously reserved for signaling purposes between the radio node stations.

It is within the scope of the invention that switching devices arranged in the radio node stations create a list of node radio stations via which a connection is to be established. In the event of failure of a radio node station via which the connection was made, an alternative route is advantageously determined immediately, so that there is no termination of the connection. To the radio technology

According to an advantageous embodiment of the invention, to better utilize resources, a connection is triggered if no data transmission for this connection has taken place during a predefinable period of time.

A signaling device provided in the radio node stations advantageously assigns an index for shortened signaling to the neighboring radio node stations. The signaling messages for the exchange between the radio node stations thus become shorter and consume fewer resources. According to a further embodiment of the invention, a subset of the radio node stations forms so-called access node stations that are connected to a fixed network. The radio connection is either routed directly to the desired subscriber or to the next access node station. The first variant is selected if the subscriber is not far away in a radio cell, during which a connection is preferably routed via the access node stations and the fixed network if this is not the case. The delay times are shorter in the fixed network and the radio load is then not as high.

The switching tasks are facilitated if storage devices arranged in the radio node stations record an image of at least parts of the radio communication system and thus assume decentralized switching functions for these parts of the radio communication system. A subset of the radio node stations, e.g. coincides with the access node stations, can be designed as information node stations in whose storage device the image of the radio communication system is stored and can be called up by the other radio node stations. This means that switching through a radio node station is also possible beyond parts of the system.

According to advantageous developments of the invention, assignment devices are arranged in the radio node stations, which assign time slots to the connections according to the principle of the least disturbed time slots. In terms of an ODMA (opportunity driven multiple access) system, the cheapest channels for the next connection are selected. This leads to good quality connections. This selection is facilitated, for example, by channel measurement sequences transmitted in the time slots with constant power. The best channel can be selected on the basis of the evaluated channel measurement sequences and the detection can subsequently be improved by a corresponding equalization. The following description of several exemplary embodiments of the radio communication system according to the invention has only an exemplary character. The features described are not absolutely necessary in the manner shown to achieve the desired success.

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

Show

1 shows a radio communication system with networked radio node stations, FIG. 2 shows a radio communication system with networked radio node stations and connected mobile and stationary terminals,

3 shows a radio communication system with a fixed network as a backbone network, FIG. 4 shows a block diagram of a radio node station,

5 shows a frame structure of the radio transmission, and

6 shows a division of codes for signaling and for user data transmission.

The radio communication system according to Fig. 1 consists of a larger number of radio node stations KN which, similar to base stations, cover a certain radio range, i.e. a cell to supply with radio resources. There are also radio connections between the radio node stations KN, via which signaling and user data transmission is carried out. The individual radio node stations KN have radio contact to a maximum of 3 to 4 neighboring stations. The radio node stations KN of the entire radio communication system are thus networked with one another.

In Fig. 2 it is also shown that to the radio node stations KN mobile devices via radio connections, so-called mobile Stations MS, and stationary devices FS are connected via leased lines. Individual radio node stations KN are also connected to a public fixed network, a packet data network or the Internet PSTN.

The radio connections between the radio node stations KN and between a radio node station KN and a mobile station MS are carried out according to a common protocol. The transmission method explained in more detail in FIG. 5 with TDMA subscriber separation provides that the radio connection to the mobile stations MS is maintained in first time slots and the radio connections to neighboring radio node stations KN in second time slots. The radio communication system according to the invention allows the connection between mobile stations MS of a radio cell without the need for further network-side components in addition to the radio node station KN of the radio cell concerned.

The radio node stations KN are frame-synchronized with one another, at least in partial areas of the radio communication system. The frames with several time slots begin at approximately the same time in these radio node stations KN. The synchronization can be carried out by evaluating radio signals from neighboring radio node stations KN. Such a method is known from EP 98 107 763. Alternatively, the synchronization can be carried out by evaluating signals from a synchronization point SY in the radio communication system. Further explanations can be found in DE 198 18 325. For example, a so-called reflection measurement method is used. A third possibility is to use GPS receivers GPS, at least for some radio node stations KN. Like the synchronization point SY, these can also be the basis for a synchronization of neighboring radio node stations KN by means of radio connections. 3 shows such arrangements for synchronization, it being possible for these three measures to be combined with one another. 3 that part of the radio node stations KN as access node stations ZKN are connected to a sufficiently broadband fixed network BB which functions as a backbone network. The connection via the fixed network BB is preferred for longer transmission links, ie connections from a mobile station MS or a stationary terminal FS are possibly made via radio connections to the next access node stations ZKN and from there via the fixed network BB. Since each terminal MS, FS can be assigned to a radio node station KN, the radio communication system can have a nationwide effect.

To establish a connection between two participants, the sequence of the radio node stations KN for the connection to be set up is first determined. Images of at least parts of the radio communication system stored in the radio node stations KN serve this purpose. By means of signaling messages, neighboring radio node stations KN exchange information, i.e. Possibilities of connection to further radio node stations KN and to the fixed network BB, as well as to the time slots and codes used, and via terminal devices MS, FS in the radio cell. In order to be able to communicate across sub-areas of the radio communication system, more complete images of the network are stored in a number of radio node stations KN, which are designed as information node stations IKN. This information can be called up by the other radio control stations KN.

Each radio node station KN, which a request for

Receives connection establishment from a neighboring station, passes this request on to the next radio node station KN. Since the radio node stations KN maintain a list of the current connection data, which indicate the assignment of the connections to the time slot and code for the transmission and for the reception case, the connection options can be estimated quickly. As long as a connection is active, ie Information is transmitted, all information received from a radio node station KN is transmitted to the selected neighboring radio node station KN according to the assignment.

If one of the transmission links is blocked and therefore not available, this status is reported back and the connection is not established. The entries in the connection lists of the radio node stations KN are deleted when the blocking message is received and the blocking message is forwarded. In this case, it is possible that an alternative route is immediately determined in the radio node station KN which first detects the blockage or in another radio node station KN. This alternative route represents a detour to the next radio node station KN in the list, which is not affected by the blocking. The blocking is only reported back if no such alternative route is established.

Every connection that has been set up is triggered at the end of the connection by a connection being closed. The entries in the lists of the connection data of all radio node stations KN involved are deleted. The connection is also triggered if no information is transmitted over a certain period of time. To monitor the

The duration of a timer of a switching device VM of the radio node station KN is provided. This can happen if the connection is blocked. The automatic release prevents radio resources from being tied up unnecessarily.

For the signaling between the radio node stations KN, a short description by means of an index 0 to n is provided, where n represents the maximum number of neighboring stations. This enables short signaling messages between the radio node stations KN. This signaling allows other radio node stations KN with regard to their Query neighboring stations and their index assignment. With the aid of the signaling, each radio node station KN can query its neighboring stations and make an image of at least parts of the radio communication system. If an image of the entire radio communication system is available as a result of such signaling in the radio node stations KN or at least in the information node stations IKN, it can be conveyed by specifying the target node station KN. In a sub-area of the radio communication system, a replacement is provided for an information node station IKN, which can take over these functions if the information node stations IKN fail.

The frame structure of the radio transmission can be seen from FIG. 5. According to a TDMA component, a division of a broadband frequency range, for example the bandwidth B = 5 MHz, into a plurality of time slots ts of the same duration, for example 16 time slots ts0 to tsl5, is provided. The frequency range B forms a frequency channel. Part of the time slots ts0 to ts9 is used in the downward direction DL and part of the time slots ts10 to tsl5 is used in the upward direction UL. In between is a switch point SP. In this TDD transmission method, the frequency channel for the upward direction UL corresponds to the frequency channel for the downward direction DL.

Information from several connections to mobile stations MS or neighboring radio node stations KN is transmitted within time slots ts. This further information consists of sections with data d, in which channel measurement sequences known at the receiving end, so-called training sequences, tseql to tseqn are embedded. The data d are spread individually for each connection with a fine structure, a code c, so that, for example, n connections can be separated at the receiving end by this CDMA component. The training sequences tseql to tseqn are sent with constant power, so that the measurement results can be averaged and the allocation of connections to time slots ts is supported according to the principle of the least disturbed time slots.

The spreading of individual symbols of the data d has the effect that within the symbol duration T _S ym Q chips of the duration T _C i _{p are} transmitted which result in a specific signal form. The Q chips form the connection-specific code c. Furthermore, a protection time gp is provided within the time slot ts to compensate for different signal delays of the connections.

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. From the point of view of a radio node station KN, first and second time slots are reserved both in the upward UL and in the downward direction, which are provided for connections to mobile stations MS or neighboring radio node stations KN. The radio node stations can be distinguished on the basis of their code c, see FIG. 6 for this purpose. The code 0 is used for signaling, during which the codes 1 to n designate and distinguish adjacent radio node stations KN. In addition, it is possible to allow the connection to both in a single time slot ts. The distinction between mobile station MS and radio node station KN is then made only on the basis of code c.

5 also shows the possibility of determining before lead times TA. The transmitted signals are measured between the radio node stations KN and the transmission time is set with the aid of the specific lead times TA such that the signals arrive at the receiving radio node station KN exactly in the time grid. Since the position of the radio node stations KN does not change, a one-time setting of the connection path by sending a shortened synchronization block and feedback is sufficient the lead time TA when installing or setting up a radio node station KN.

4 shows a radio node station KN in a highly simplified representation. A transmission / reception device TRX is connected to an antenna and processes transmission and reception signals. In the transmitting / receiving device TRX, the transmission signals to be radiated are converted digitally / analogously, converted from the baseband to the frequency range of the radiation, and the transmission signals are modulated, amplified and radiated via an antenna. A synchronization device SYNC has previously provided frame synchronization between the radio node stations KN and setting the lead time TA.

An allocation device ZE sets the transmission signals in

Radio blocks together and assigns them to the corresponding frequency band and time slot. A signaling device SE, which manages the indices for the neighboring radio node stations KN, controls the assignment device ZE in this regard. A signal processing device in the transmitting / receiving device TRX evaluates received signals and carries out channel estimation and data detection.

The connections to the fixed network BB or neighboring radio node stations KN are switched in a switching device VM and the routes are defined for this. Lists stored in a storage device SP with the data on the mobile stations MS and an image of at least a partial area of the radio communication system are used for this purpose.

Claims

claims

1. A radio communication system with a plurality of radio node stations (KN) can be connected to the mobile terminals (MS) via radio connections, the radio connection being organized according to a TDMA subscriber separation, with transmit / arranged in the radio node stations (KN). Receiving devices (TRX) which maintain the radio connections to the mobile terminals (MS) in first time slots (ts) and radio connections to neighboring radio node stations (KN) in second time slots (ts).

2. Radio communication system according to claim 1, with synchronization devices (SYNC) arranged in the radio node stations (KN) for synchronizing the radio connections at least between radio node stations (KN) of a partial area. ^■

3. Radio communication system according to claim 2, wherein the synchronization devices (SYNC) are designed such that the synchronicity is achieved by evaluating radio signals from neighboring radio node stations (KN).

4. Radio communication system according to claim 2, the synchronization devices (SYNC) are designed such that the synchronicity is achieved by evaluating signals from a GPS receiver (GPS).

5. Radio communication system according to claim 2, the synchronization devices (SYNC) are designed such that the synchronism is achieved by evaluating signals from a synchronization point (SY) in the radio communication system.

6. Radio communication system according to one of the preceding claims, in which the transceivers (TRX) are designed such that a CDMA subscriber separation is additionally carried out for the radio connection.

7. Radio communication system according to claim 6, in which at least one code is reserved for signaling purposes between the radio node stations (KN).

8. Radio communication system according to one of the preceding claims, with switching devices (VM) arranged in the radio node stations (KN) for creating a list of node radio stations (KN) via which a connection is established.

9. Radio communication system according to claim 8, in which the switching devices (VM) are designed such that an alternative route is determined in the event of failure of a node radio station (KN) via which the connection was made.

10. Radio communication system according to claim 8, wherein the switching devices (VM) are designed such that a connection is triggered if no data transmission for this connection has taken place during a predeterminable period of time.

11. Radio communication system according to one of the preceding claims, with a signaling device (SE) arranged in the radio node stations (KN), which in each case assigns an index (i) for a shortened signaling to the neighboring radio node stations (KN).

12. Radio communication system according to one of the preceding claims, in which a subset of the radio node stations

(KN) are connected to a fixed network (BB) and thus form access node stations (ZKN).

13. Radio communication system according to claim 12, in which a connection is preferably conducted via the access node stations (ZKN) and the fixed network (BB).

14. Radio communication system according to one of the preceding claims, with storage devices (SP) arranged in the radio node stations (KN), in which an image of at least parts of the radio communication system is stored.

15. Radio communication system according to claim 14, in which a subset of the radio node stations (KN) is designed as information node stations (IKN), in whose storage device (SP) the image of the radio communication system is stored and of the other radio node stations (KN) is available.

16. Radio communication system according to one of the preceding claims, with in the radio node stations (KN) arranged allocation devices (ZE), which assign the connections time slots (ts) according to the principle of the least disturbed time slots.

17. Radio communication system according to one of the preceding claims, in which the transceivers (TRX) are designed in such a way that channel measurement sequences with constant power are transmitted in the time slots (ts).