DE19913371A1 - Initial transmit power setting for the downward direction of W-CDMA radio communication systems - Google Patents

Abstract

The invention relates to a method for regulating the transmission power in a radio communication system, in which base stations and subscriber stations are connected by a radio interface. A subscriber station receives transmissions from a base station and determines a measured value therefrom for regulating the transmission power. According to the invention, the subscriber station links a service-dependent transmission power value to the measured value to obtain a regulating value and transmits said regulating value to the base station. The base station uses the regulating value to regulate the transmission power. The invention is characterised in that a reference to the desired service is immediately established, thus allowing the base station to calculate and regulate the necessary transmission power for the subsequent transmissions without further requests.

Description

The invention relates to a method and a subscriber station tion used to set the transmission power for a base station are trained. The invention particularly relates to initial transmission power setting of the base station for a Connection to the subscriber station within a W-CDMA radio Communication system.

In radio communication systems, messages (for example wise language, image information or other data) as signals with the help of electromagnetic waves over a radio interface transferred. The radio interface relates on a connection between a base station and subscriber merstations, the subscriber stations being mobile stations or can be fixed radio stations. The blasting of the Electromagnetic waves occur with carrier frequencies zen that in the Fre foreseen for the respective system quenzband lie. For future radio communication systems, for example UMTS (Universal Mobile Telecommunication System) or other 3rd generation systems are frequencies provided in the frequency band of approx. 2000 MHz.

The 3rd generation radio communication systems should be one Participant known as CDMA (Code Division Multiple Access) Use the separation process. Is that frequency used band broadband, so is the radio interface as W-CDMA (wideband CDMA) radio interface organized. At all Radio communication systems, but especially in such with CDMA radio interface, is a transmission power position necessary to keep the interference low and To compensate for fading effects in the reception performance. A fast and accurate transmission power setting is desirable  worth, but presupposes that the transmission power control has already settled in.

From ARIB Specification: "Specification of Air-Interface for 3G Mobile System ", Vol. 3, dated January 14, 1999, p. 94, it is known that after the subscriber station has received power from Base station transmissions within the established ver has received a transmission power control in one closed loop. Depending on the quality of the Measurement of the reception power regulates the closed loop more or less quickly to the setpoint of the transmission power the base station.

About the initial transmission power, i.e. before the closed one Loop in the connection regulates the transmission power ARIB Specification: "Specification of Air-Interface for 3 G Mobile System ", Vol. 3, dated January 14, 1999, no information taken become. The problems caused by too high an initial Transmit power, unnecessary interference, or by one too result in low transmission power, reduced transmission quality were neglected.

The invention is therefore based on the object, a Ver drive and specify a subscriber station that is responsible for the An initial phase of a connection of an improved transmission power attitude result. The task is performed using the procedure the features of claim 1 and the subscriber station with solved the features of claim 10. Advantageous Next Formations of the invention can be found in the dependent claims men.

In the procedure for setting the transmission power in a radio Communication systems are base stations and subscriber stations tions connected to each other via a radio interface. A subscriber station receives broadcasts from a base station and uses this to determine a measured value for the transmission power setting. According to the part linked  subscriber station with a service-dependent transmission power value the measured value to a control value and transmits this control value to the base station, which is the control value for the transmission power position used. Because immediately a reference to the desired service is established, the base station can be used without further requests the necessary transmission power for the next Calculate and set broadcasts to the subscriber station.

The transmission power setting is particularly quick when the The control value is transmitted in an RACH channel. The RACH channel (Random Access Channel) is used to establish a connection construction and the transmission of short packet data in upward direction tung. This can be used for the first, the initial off transmission of a connection the correct transmission power value be put.

Further advantageous developments of the invention provide that measurement and transmission power values on reception power or are related to signal-to-noise ratios. These values are easily ascertainable in the subscriber station and give one Reference that allows the transmission power of the connection relative to the transmission power in an organizational channel, the previously measured by the subscriber station, correct adjust.

Is the radio interface after a CDMA transmission ver drive organized, creating a flexible capacity distribution is possible by setting a spreading factor, so the control value advantageously also takes into account a ratio of spreading factors between the received measured mailings and the desired service. The Relationship can be through separate information or a previously indicated or specified spreading factor for the Service.

According to advantageous embodiments of the invention Control value on a difference in the transmission powers or Sig  nal / noise ratios of the base station in an organization tion channel and a channel for the desired service In this case, the base station can from the control value and Z. B. the previously used transmission power in the organization channel quickly calculate the required transmission power itself. Alternatively, the subscriber station can perform the calculation men if the transmission power is known in the organizational channel is, so that the control value directly on the transmission power of the Base station is related to the desired service.

In a further development of the invention it is provided that the Control value is related to a value that includes the measured value compares to a minimum value. The minimum value is for example the minimum required reception power or the minimum required signal / noise ratio for a service. By the reference to a minimum value reduces the value range of the control value, so that the coding of the control value is possible with just a few bits. This binds less transmission capacity.

An embodiment of the invention is based on the enclosed ing drawings explained in more detail.

Show

Fig. 1, a radio communication system,

Fig. 2 shows a process flow for transmitter power setting of a base station, and

Fig. 3 shows a schematic structure of a subscriber station.

The mobile radio system shown in Fig. 1 as an example of a radio communication system consists of a plurality of mobile switching centers MSC, which are networked with each other or provide access to a fixed network PSTN. Furthermore, these mobile switching centers MSG are each connected to at least one device RNC for controlling the base stations BS and for allocating radio resources, ie a radio resource manager. Each of these facilities RNC in turn enables a connection to at least one base station BS. Such a base station BS can interface via a radio link to a subscriber station, e.g. B. mobile stations MS or other mobile and statio nary end devices. At least one radio cell is formed by each base station BS. According to DE 198 34 210, the radio interface is designed as a broadband radio interface, B = 5 MHz, with CDMA subscriber separation (Code Division Multiple Access).

In figure. 1 are examples of connections V1, V2, V3 for transfer transmission of user information ni and signaling information tion as point-to-point connections between Mobilsta tion MS and a base station BS and an organizational card BCCH as a point-to-multipoint connection from the base station BS to the subscriber stations MS shown.

An operation and maintenance center OMC realizes control and maintenance functions for the mobile radio system or for parts from that. The functionality of this structure is different Radio communication systems transferable, in which the Erfin can be used, especially for participants access networks with wireless subscriber connection.

Referring to FIG. 2 send the base station BS in the organization channel BCCH at a constant and known transmit power. The subscriber station MS receives the transmissions from the base stations BS and in each case determines a measured value mw. For establishing a connection, the base station BS is selected for which the best transmission conditions are present (e.g. lowest attenuation or best signal / noise ratio) .

In a memory device SP, see FIG. 3, the subscriber station MS also stores a service-dependent transmission power value sw, which is linked by the subscriber station MS to the measured value mw. The service-dependent transmission power value sw is different for a voice service or for certain parcel data services and takes into account individual quality of service.

A control value delta is determined from both values mw, sw telt in a channel with random access RACH, RACH channel (Random Access Channel), to the base station BS via will wear. This transmission also includes, for example a resource allocation request or short data pa packet data transmission.

The base station BS receives the control value delta, determined the transmission power P desired by the subscriber station MS and will provide it for the next broadcast this subscriber station MS in a channel FACH (Forward Access Channel) of the connection.

For the measurement, transmission power and control values mw, sw, delta different variants are possible:

Measured value mw:

• - Receiving power R _{MS, BCCH of} the transmissions of the base station BS in the BCCH at the subscriber station MS
• - Signal / noise ratio SIR _{MS, BCCH of} the transmissions of the base station BS in the BCCH at the subscriber station MS

Transmitting power value sw:

• - Receiving power R _MS required for the desired service _{, service of} the transmissions of the base station BS at the subscriber station MS
• - For the desired service (service) required signal / noise ratio SIR _{MS, service of} the transmissions of the base station BS at the subscriber station MS

The values are connected to each other using the following equation:

P _{BS, BCCH} is the transmission power of the base station BS in the organizational channel BCCH and P _{BS, service is} the desired transmission power of the base station BS for the service.

This results in different forms of representation for the control value delta to be transmitted, z. B .:

• 1. delta = P _{BS, service}
• 2. delta = Δ
• 3. delta = SIR _{MS, BCCH}
• 4. delta = SIR, _MSBCCH - SIR _{MS, BCCHmin}

The final calculation of the transmission power of the base station BS is carried out at 2) to 4) by the base station BS. At 1 ) the calculation has already been carried out by the subscriber station MS.

If reference is made to the signal-to-noise ratio SIR, the selected spreading factors SF in the organization channel BCCH and in the channel FACH of the connection must be taken into account. The spreading factor SF _BCCH is fixed and known. The spreading factor SF _{service to be selected} for the transmission from the base station BS to the subscriber station MS of the service can either be set permanently, during the establishment of the connection context, or can be signaled in the transmission of the subscriber station MS to the base station BS in the RACH channel. When using the signal-to-noise ratio SIR, a correction term is therefore used

considered.

Variant 4) offers particular advantages, since the received signal / noise ratio SIR _{MS, BCCH is compared} with a minimum value mwmin, which relates to a minimum signal / noise ratio SIR _{MS, BCCH of} the organization channel BCCH for the service. Particularly high-rate data services can only be received in a radio cell at a short distance from the base station BS, since otherwise the transmission power of the base station BS would have to be too high. The minimum value therefore specifies a service-dependent threshold value for reception. The difference according to 4) can be encoded with just a few bits, since the range of values is much smaller than when the received signal / noise ratio SIR _{MS, BCCH is signaled} .

An example of the calculation according to the above equation results in a measured signal / noise ratio in the BCCH SIR _{MS, BCCH} of -3 dB, a desired signal / noise ratio of the service SIR _{MS, service} of 0.7 db (speech in the downward direction at vehicle speeds) and spreading factors SF = 128 for the service and SF = 256 in the BCCH a transmission power of the base station BS, which should be 6.7 dB above the transmission power in the BCCH.

A subscriber station MS according to FIG. 3 receives the transmissions from the base station BS of the organization channel BCCH as received signals via an antenna device AE. The received signals are amplified in an HF part HF-T, filtered and fed to a receiving device RXE, in which digitization and further signal evaluation take place.

An evaluation device AU determines a measured value mw Transmission power setting from the base transmissions station BS and performs a calculation of the control value delta through, whereby the service-dependent transmission power value sw be is taken into account. The service-dependent transmission power value sw is stored in a storage device SP and can from can be called up by the evaluation device AU. Furthermore ver the evaluation device AU initiates the transmission of the rule value delta via a transmitter TXE and the antennas device AE to the base station BS.

Claims (10)

1. Method for setting the transmission power in a radio communication system, in which

• Base stations (BS) and subscriber stations (MS) are connected to one another via a radio interface,
• - A subscriber station (MS) receives transmissions from a base station (BS) and uses this to determine a measured value (mw) for the transmission power setting, and
• the measured value (mw) influences later transmission power settings of the base station (BS),

characterized by

• that the subscriber station (MS) links a service-dependent transmission power value (sw) with the measured value (mw) to form a control value (delta),
• - This control value (delta) to the base station (BS) transmits, and
• - The control value (delta) is used for setting the transmission power of the base station (BS).

2. The method according to claim 1, characterized in that that the transmission of the control value (delta) in a RACH Channel takes place. 3. The method according to any one of the preceding claims, characterized characterized in that the transmission power setting of the Ba sisstation (BS) already for the initial transmissions of a Connection to the subscriber station (MS) is established. 4. The method according to any one of the preceding claims, characterized characterized that measurement and transmission power values (sw, mw) are related to reception services. 5. The method according to any one of claims 1 to 3, characterized characterized that measurement and transmission power values (sw, mw) are related to signal-to-noise ratios.   6. The method according to claim 5, characterized in that the radio interface after a CDMA transmission ver driving is organized and the control value (delta) additionally a ratio of spreading factors (SF) between the received NEN broadcasts of the base station (BS) and the desired one Service taken into account. 7. The method according to any one of the preceding claims, characterized characterized in that the control value (delta) is based on a difference limit of the transmission powers or the signal / noise ratios the base station (BS) in an organizational channel (BCCH) and a channel (FACH) related to the desired service. 8. The method according to any one of claims 1 to 6, characterized characterized in that the control value (delta) on the send Performance of the base station (BS) for the desired service is related. 9. The method according to any one of the preceding claims, characterized characterized that the control value (delta) to a value related to the measured value (mw) with a minimum value (mwmin) for the measured value (mw). 10. subscriber station (MS) for a radio communication system which is connected to a base station (BS) via a radio interface,
with a receiving device (RXE) for receiving transmissions from the base station (BS),
with a storage device (SP) for storing a service-dependent transmission power value (sw),
with an evaluation device (AU) for determining a measured value (mw) from the transmissions of the base station (BS) and for linking the service-dependent transmit power value (sw) with the measured value (mw) to form a control value (delta) for setting the transmit power,
with a transmitter (TXE) for transmitting the control value (delta) to the base station (BS).