WO1999022531A2

WO1999022531A2 - Base station and receiver for a mobile communication system with tdma components

Info

Publication number: WO1999022531A2
Application number: PCT/DE1998/003039
Authority: WO
Inventors: Gerhard Ritter
Original assignee: Siemens Aktiengesellschaft
Priority date: 1997-10-27
Filing date: 1998-10-16
Publication date: 1999-05-06
Also published as: WO1999022531A3; EP1027812A2; AU1660499A

Abstract

The inventive base station for a mobile communication system with TDMA components contains a signal processing device (SP) to prepare useful information (ni) and organisational information (oi) for transmission via a radio interface. The signal processing device (SP) is controlled by a control device (SE) in such a way that the useful information (ni) is prepared for transmission in a frequency channel (FK1) of a first high frequency carrier (TRI) with TDMA components and the organisational information (oi) is prepared independently from the useful information (ni) for transmission in a frequency channel (FK2) of a second high frequency carrier (TR2) with TDMA components. The frequency channel of the first high frequency carrier has a larger band width than the frequency channel of the second high frequency channel. Separate transmission devices (UE1, UE2) modulate a transmission signal (tx2) for high frequency transmission of the organisational information using the second high frequency carrier and a transmission signal (tx1) for high frequency emission of useful information using the first high frequency carrier.

Description

description

Base station and receiving device for a mobile communication system with a TDMA component

The invention relates to a base station and a receiving device for a mobile communication system with a TDMA component for transmitting information of several connections between mobile stations and the base station via a radio interface, the receiving device being used particularly in mobile stations.

The construction of digital radio networks is in J.Oudelaar, "Evolution towards UMTS", PIMRC 94, 5th IEEE International Symp. On Personal, Indoor and Mobile Radio Communications, The Hague, NL, September 18-22, 1994, p.852 -856, and M.Lenti, H. Hageman, "Paging in UMTS", RACE Mobile Telecommunications Workshop, Vol. 1, Amsterdam, NL, 17th-19th May 1994, pp.405-410.

The known mobile radio system according to the GSM standard (Global System for Mobile Communication) is a mobile communication system with a TDMA component as a multiple access method (time division multiple access) for subscriber separation. According to a frame structure (TDMA frame), information from several subscriber connections is transmitted in time slots. The information is transmitted block by block in radio blocks (bursts). A distinction can be made between transmission channels for useful information - such as voice, data or signaling - and transmission channels for organizational information - such as information on the location area, the radio cell, the channel structure and options that are supported within the cell. The transmission channels for user information relate to connections between the mobile stations and a base station (point-to-point

Connections) in the downlink (downlink) as in the uplink (uplink). The transmission channels (e.g. BCCH, broad cast control channel; FCCH, frequency correction channel; SCH, synchronization channel) for the organizational information, on the other hand, relate to connections from one base station to several mobile stations (point-to-multipoint connections) only in the downward direction.

From the older patent application DE 197 13 667.2 a mobile communication system is known which uses a TDMA subscriber separation for the block-wise transmission of user information in time slots and prepares organizational information for a permanent wave transmission independent of the time slots. In addition, a CDMA component is provided as a code division multiple access method for simultaneous connections in a time slot. The useful information of several connections contained in the time slot formed as a transmission channel can be differentiated by spreading codes. The base station is connected to an antenna device, which consists of a number of individual radiators, each of which radiates in a sector of the radio cell supplied by the base station (principle of the adaptive antennas). The user information and organizational information are emitted at high frequencies with approximately the same power.

The invention is based on the object of specifying a transmission of useful information and organizational information for a mobile communication system with a TDMA component which enables the most economical and effective use of the radio resources. This object is achieved by the base station with the features of patent claim 1 and the receiving device with the features of patent claim 11. Advantageous further developments can be found in the subclaims.

A base station according to the invention for a mobile communication system with a TDMA component contains a signal processing device for preparing useful information and of organizational information for transmission via a radio interface. The signal processing device is controlled by a control device in such a way that the useful information for transmission in a frequency channel of a first high-frequency carrier with a TDMA component and the organizational information for transmission in a frequency channel of a second high-frequency carrier with TDMA component are prepared independently of the useful information. The frequency channel of the first high-frequency carrier is chosen to be broadband compared to the frequency channel of the second high-frequency carrier. Separate transmission devices modulate a transmission signal for high-frequency radiation of the organizational information using the second high-frequency carrier and a transmission signal for high-frequency radiation of the useful information using the first high-frequency carrier.

According to the invention, a separate high-frequency carrier with a TDMA component is used to transmit the organizational information regardless of the transmission of the useful information. The organization channel - the frequency channel for the organization information - can thus be used with a constant output for control information, for example handover information, synchronization information and information about the possibilities and configuration of the mobile communication system, on a large number of mobile stations. By separating the transmission of the organizational information from the useful information, an independent power control is also possible, which permits optimized cell planning for the frequency channels of the useful information. The radio resources are better used for the useful information, since the separation results in an increase in capacity for the useful information. The organizational information is always available through its own high-frequency carrier. A synchronization of base stations with each other is not necessary. In particular for next generation mobile communication systems (UMTS), provided that they are based on an evolution of a system with a TDMA component, the subject matter of the invention is advantageous since it uses adaptive antennas (SDMA, space division multiple access) Directed radiation of the useful information results in an increase in capacity with the same bandwidth - supported. Sectorized radio cells as well as "switched beam" solutions - in which the base station specifically directs the transmission of information to a group of mobile stations with a large number of connections - are used to improve the utilization of radio resources by the inventive solution of the separation of the organizational channel and the traffic channel (traffic channel ) supported with appropriate high-frequency carriers.

According to a further development of the invention, it is particularly advantageous to additionally use a CDMA component in the mobile communication system with frequency channels formed by time slots, in which the useful information of several connections is transmitted simultaneously. The useful information of different connections can be distinguished according to a connection-specific fine structure. This preferably consists of individual spreading codes and associated spreading factors with which the useful information of multinational connections is spread in a time slot.

The useful information is thus transmitted over a broad band, for example in a 1.6 or 2.0 MHz frequency band, in comparison to the organizational information. Correct power control is particularly important in such mobile communication systems - for example with TDMA / CDMA components - since several subscriber signals are transmitted simultaneously in one frequency channel. Fluctuations in performance of the received information are largely compensated for by exact power regulation - possible through the various high-frequency carriers for organizational and usage information. A JD method (joint detection) is advantageously used in the detection of the useful information. This allows the interference of other subscriber signals to be taken into account when detecting a subscriber signal.

The greater process gain for the organizational information is advantageously achieved in that its data rate does not have to correlate with the data rate of the useful information, e.g. a much lower data rate, for example less than or equal to 1 kbit / s, is used. The organizational information is therefore limited to the most essential information, which can, however, be transmitted in a very interference-resistant manner.

The separate treatment of useful information and organizational information is particularly advantageous if directed radiation (see above) is possible with an antenna device assigned to the base station. The useful information is directed and the organizational information is broadcast omnidirectionally or sectorally, with less antenna gain than for directed radiation. The directional effect of the antennas can be used to achieve greater ranges for the useful information.

The separation has also increased the reach for the organizational information. If the useful information and the organizational information are emitted independently of one another, this results in a simplified structure of the transmission devices, with power regulation adapted to the conditions in each case for setting the range for the organizational information.

The invention is explained in more detail below with reference to an exemplary embodiment with reference to drawings. Show

1 shows the block diagram of a mobile communication system,

2 shows a schematic illustration of the TDMA / CDMA components or the TDMA component for transmitting the information on the radio interface,

3 shows a schematic representation of the devices in a base station, and

4 shows a schematic representation of the devices in a mobile station.

The structure of the mobile communication system shown in FIG. 1 corresponds to a known GSM system which has a plurality of mobile switching centers MSC, base station controls BSC, base stations BS and mobile stations MS and at least one operations and maintenance center OMC. The mobile switching centers MSC are networked with one another or provide access to another communication network, for example a fixed network 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, break down and maintain one or more radio connections to mobile stations MS via a radio interface. The operation and maintenance center OMC, for example connected to a base station controller BSC, implements control and maintenance functions for the mobile radio network and for its network devices. The functionality of this structure is not limited to the GSM system shown, but can also be transferred to other mobile communication systems, so that the invention can also be used there. 1 shows, by way of example, a plurality of radio connections for the transmission of useful information ni, for example voice or data information or signaling information, between two mobile stations 1 and 2 and a base station BS and of organizational information oi between three mobile stations 1, 2 and 3 and the base station BS. The user information ni is transmitted on point-to-point connections in the downward direction as in the upward direction, while the transmission of the organizational information oi on point-to-multipoint connections is initiated only in the downward direction. The base station BS is connected to an antenna device AE which has, for example, four individual radiators for directional radiation into radio areas formed by sectors SEC. In principle, a larger number of individual steel workers - which can be used as adaptive antennas - are also possible, which generate radiation lobes which are matched to the spatial position of the mobile stations MS. The antenna device AE is therefore controlled by the base station BS in such a way that the useful information ni prepared by it is sent to the mobile stations 1 and 3 in a directed manner. A gain in capacity - adaptive antenna gain - can be achieved by a higher number of point-to-point connections with the same bandwidth. The radio resources are better used.

The organizational information oi made available by the base station BS to all mobile stations MS on point-to-multipoint connections - possibly continuously - includes, for example, basic information for identifying the network, the location area (LA) and the radio area, but also information over the available frequency channels of the base station BS and over the frequencies of the neighboring radio areas. The organizational information oi is usually stored in logical transmission channels -

Control channels - such as the broadcast channel (BCCH, broadcast control channel) with frequency channel (FCCH, frequency control Channel) and synchronization channel (SCH, synchronization channel) or the general control channel (CCCH, common control channel) in the downward direction. An omnidirectional or sectoral radiation of the organizational information oi takes place via the antenna device AE by means of its own “beacon” BEA, but in a frequency channel of another high-frequency carrier with a TDMA component independently of the useful information ni. The useful information ni is also in a frequency channel of an associated high-frequency carrier sent with TDMA component, which differs from the radio frequency carrier for the radiation of the organizational information oi and is used exclusively for the transmission of useful information The frequency channel of the first radio frequency carrier for the transmission of information is chosen to be broadband compared to the second radio frequency carrier for the transmission of organizational information for example in an advantageous manner by additionally including a CDMA component for spreading the simultaneous Te containing the useful information of several connections Subscriber signals can be reached in one time slot. Spreading of the signals containing the organizational information in a time slot of the independent TDMA component is possible in principle, but is omitted because of the unnecessary differentiation of the signals.

FIG. 2 shows the transmission of the useful information ni with the TDMA / CDMA component separately from the transmission of the organizational information oi with the TDMA component via the radio interface parts. The bandwidth B for the useful information transmission in a frequency channel FKl of the high-frequency carrier TRl is, for example, B = 2 MHz. The bandwidth for the organizational information transmission in a frequency channel FK2 of the high-frequency carrier TR2 is chosen to be significantly smaller, for example in the KHz range. Several frequency channels - not shown - can be provided for the mobile communication system. A time axis is t divided into a time grid consisting of a plurality of time slots ts, for example eight per time frame, in order to send and receive the useful information ni block by block in radio blocks. The subscriber signals for several mobile stations MS are transmitted simultaneously in the same frequency channel FK1. The subscriber separation per radio block takes place with the aid of spreading codes, for example eight codes cl to c8, with associated stimulus factors. A uniform spreading method is used for data, voice and signaling in the user information ni.

The useful information ni is transmitted block by block in the time slots ts according to the TDMA / CDMA method, while the organizational information oi is inserted independently of this into one or more time slots ts of another high-frequency carrier according to the TDMA method. Preferably, in the narrowband frequency channel FK2, a carrier of the known mobile communication system according to the GSM standard is used as a high-frequency carrier TR2 with a TDMA component. The organizational information oi can include basic information with information about the configuration of the mobile communication system, about the available frequency channels in the radio area managed by the base station or about the frequencies of the neighboring radio areas, as well as information about establishing a connection and forwarding an existing connection ( mobile assisted handover) included.

An optimized power control is possible for the useful information ni, which can be set separately and independently of the organizational information for the respective mobile stations MS from the base station BS on the basis of measured and signaled reception powers. The same applies to the organizational information oi, which can be subjected to optimized performance control separately and independently of the useful information. The data rate of the organizational information oi can therefore also be significant can be set lower, for example 200 bit / s, than that of the Nu zInformation, which can be 16 Kbit / s in the case of a voice transmission.

3 shows devices in the base station which are provided for controlling the transmission of information in accordance with the invention. The antenna device AE has the individual beams, the number of which - indicated by dashed lines - can be variable. They carry out the directed emission of transmission signals txl into the sectors SEC and the omnidirectional emission of transmission signals tx2 with the aid of the "beacon" BEA. Separate transmission devices UE1 and UE2 are connected to the antenna device AE, one transmission device UE2 of which the respective Transmitted signal tx2 for the high-frequency radiation of the organizational information oi is modulated by means of the independent high-frequency carrier and the other transmission device UE1 modulates the transmitted signal txl for the high-frequency radiation of the useful information ni by means of the other high-frequency carrier Amplification of the useful information ni or organizational information oi prepared by a digital signal processing device SP. The signal processing device SP, for example a digital signal process, is controlled essor, from a control unit SE, wherein programs for performing the control are in memory MEM.

In the signal processing device SP, the subscriber signals from eight communication connections of a time slot are assigned to a time slot in a multiplex device. The spreading of the information ni in the signal processing device SP with the assigned spreading codes results in signals which in the combination device result in a common broadband signal in the

Frequency channel of the associated high-frequency carrier are superimposed. Then in the transmission device UE1 Implementation in the analog high-frequency signal txl instead. An analog procedure without spreading with time slot according to the TDMA component for the information oi takes place separately on another high-frequency carrier, the transmission device UE2 causing and executing the conversion into the analog high-frequency signal tx2.

A receiving device which is used in mobile stations MS is shown in FIG. Received signals rxl and rx2 received by an antenna device, which correlate with the transmission signals txl and tx 2 according to FIG. 3, are amplified into the baseband in separate high-frequency devices HF1 and HF2, which correspond to the transmission devices UE1 and UE2 of the base station according to FIG implemented and demodulated. The separation according to different radio frequency carriers for useful information transmission and organizational information transmission is thus guaranteed. In an analog / digital converter ADC, the respective received signals are converted into symbols with a discrete set of values, for example digitized. A coupling device KE connects the analog / digital converter ADC to a signal processing device SP, which as a digital signal processor has a JD processor JD-P for jointly detecting the useful information ni according to the JD-CDMA method (joint detection) and a RAKE receiver Detecting the organizational information oi.

The detection is carried out in parallel, the signal processing device SP correlating the received data of the useful information ni with the spreading codes known in the receiver, so that the bandwidth of the received signals is reduced and the distance from signal level to noise level is increased. This enables data detection even in the event of strong interference from interferers or between the symbols.

In mobile stations MS, the RAKE receiver RAKE measures the reception power for the organizational information oi and uses it as a reference for decisions to switch to other radio cells and for power control regardless of the useful information.

Claims

claims

1. base station (BS) for a mobile communication system with TDMA component for transmitting information of several connections between mobile stations (MS) and the base station (BS) via a radio interface,

with a signal processing device (SP) for preparing useful information (ni) and organizational information (oi) for transmission via the radio interface,

- With a control device (SE) for controlling the signal processing device (SP) such that the useful information (ni) for transmission in a frequency channel (FKl) of a first high-frequency carrier (TRl) with TDMA component and the organizational information (oi) for the transmission be prepared in a frequency channel (FK2) of a second high-frequency carrier (TR2) with a TDMA component independently of the useful information (ni), the frequency channel (FKl) of the first high-frequency carrier (TRl) compared to the frequency channel (FK) of the second high-frequency carrier (TR2 ) broadband is selected,

- With separate transmission devices (UE1, UE2), of which one transmission device (UE2) modulates a transmission signal (tx2) for high-frequency radiation of the organizational information (oi) with the aid of the second high-frequency carrier and the other transmission device (UE1) modulates a transmission signal ( txl) for a high-frequency radiation of the useful information (ni) modulated with the aid of the first high-frequency carrier.

2. Base station according to claim 1, in which the mobile communication system additionally has a CDMA component, with frequency channels formed by time slots (ts), in which the useful information (ni) of several connections is transmitted simultaneously, the useful information (ni ) according to different connections a connection-specific fine structure can be distinguished.

3. Base station according to claim 2, in which the useful information (ni) of simultaneous connections in a time slot (ts) is provided with individual spreading codes (cl to c8) and associated spreading factors.

4. Base station according to one of the preceding claims, in which a high-frequency carrier (TR2) with TDMA component of the known mobile communication system according to the GSM standard is used to transmit the organizational information (oi) in the narrowband frequency channel.

5. Base station according to one of the preceding claims, in which the radio-frequency carrier (TR2) with the TDMA component is used for omnidirectional radiation of the organizational information (oi) to the mobile stations (MS).

6. Base station according to one of the preceding claims, in which basic information required by the mobile station (MS) for communication with the base station (BS), or information for frequency correction or for synchronization is transmitted as organizational information (oi).

7. Base station according to claim 6, in which the basic information contains information about the configuration of the mobile communication system, about the available frequency channels in the radio area supervised by the base station (BS) or about the frequencies of the neighboring radio areas.

8. Base station according to one of the preceding claims, in which information for establishing a connection and for forwarding an existing connection is transmitted as organizational information (oi).

9. Base station according to one of the preceding claims, with an assigned antenna device (AE) for a directional radiation of the useful information (ni) with the aid of the first high-frequency carrier and an omnidirectional or sectoral radiation of the organizational information (oi) with the aid of the second high-frequency carrier.

10. Base station according to one of the preceding claims, in which the transmission rate of the organizational information (oi) is adjustable independently of the transmission rate of the useful information (ni).

11. receiving device for a radio station (MS) of a mobile communication system with a TDMA component for the transmission of information of several connections between mobile stations (MS) and the base station (BS) via a radio interface,

- With separate high-frequency devices (HF1, HF2) for demodulating received signals (rxl, rx2), - With a coupling device (KE) for connecting the high-frequency devices (HF1, HF2) with a signal processing device (SP), which according to the TDMA component with the help processed useful information (ni) transmitted by a first high-frequency carrier and organizational information (oi) transmitted independently of the useful information (ni) in accordance with the TDMA component of a second high-frequency carrier.

12. Receiving device according to claim 11, in which the signal processing device (SP) is a JD-CDMA (Joint detection) processing unit (JD-P) for the output of the user information (ni) of a plurality of connections which are transmitted simultaneously according to a CDMA component in a time slot and has a RAKE receiver (RAKE) for the output of the organizational information (oi).

13. Mobile station (MS) with a receiving device according to claim 11 or 12.