The invention relates to a method for transmitting payload information in a radio communication system having at least one radio network controller, at least one base station and at least one subscriber station.
The invention also relates to a radio communication system.
Communication systems are becoming increasingly important. Significant efforts are being made to link cable-based communication systems to radio communication systems. The resulting hybrid communication systems generate an increase in the number of available services, but also allow greater flexibility in terms of communication. At the same time, devices are being developed which can use various systems (multi-homing).
Considerable importance is attached to the radio communication systems due to the subscriber mobility which is made possible.
In radio communication systems, information (e.g. voice, image information, video information, SMS [Short Message Service] or other data) is transmitted with the aid of electromagnetic waves via a radio interface between sending and receiving station (base station or subscriber station). In this case, the emission of the electromagnetic waves takes place using carrier frequencies which lie in the frequency band which is provided for the relevant system.
Frequencies of 900, 1800 and 1900 MHz are used for the GSM (Global System for Mobile Communication) mobile radio system that has been implemented. These systems essentially transfer voice, fax and SMS (Short Message Service) short messages, as well as digital data.
Frequencies in the frequency band of approx. 2000 MHz are provided for future mobile radio systems using CDMA or TD/CDMA transmission methods, e.g. UMTS (Universal Mobile Telecommunication System) or other third-generation systems. These third-generation systems are developed with the aims of worldwide radio coverage, a large offering of services for data transmission and, most importantly, flexible management of the capacity of the radio interface, which is the interface with the fewest resources in radio communication systems. In the context of these radio communication systems, the flexible management of the radio interface should primarily allow a subscriber station to send and/or receive a large amount of data at high data speed as required.
The access of stations to the shared radio resources of the transmission medium, e.g. time, frequency, throughput or space, is governed by multiple access (MA) methods in these radio communication systems.
In the case of time division multiple access (TDMA) methods, each send and receive frequency band is divided into time slots, wherein one or more cyclically repeated time slots are assigned to the stations. Using TDMA, the radio resource of time is separated in a station-specific manner.
In the case of frequency division multiple access (FDMA) methods, the whole frequency band is divided into narrow-band portions, wherein one or more narrow-band frequency bands are assigned to the stations. Using FDMA, the radio resource of frequency is separated in a station-specific manner.
In the case of code division multiple access (CDMA) methods, the throughput/information which has to be transmitted is encoded in a station-specific manner by a scrambling code which includes of a multiplicity of individual so-called chips, whereby the throughput which must be transmitted is scrambled randomly over a wide frequency range in accordance with a code. The scrambling codes which are used by different stations within a cell/base station are mutually orthogonal or essentially orthogonal in each case, whereby a receiver recognizes the signal throughput which is intended for the receiver and suppresses other signals. Using CDMA, the radio resource of throughput is separated in a station-specific manner by scrambling codes.
In the case of orthogonal frequency multiple access methods (OFDM), the data is transferred in a broadband manner, wherein the frequency band is divided into equidistant orthogonal subcarriers, such that the simultaneous phase shifting of the subcarriers covers a two-dimensional data flow in the time-frequency range. Using OFDM, the radio resource of frequency is separated in a station-specific manner by orthogonal subcarriers. The combined data symbols which are transferred on the orthogonal subcarriers during a time unit are called OFDM symbols.
The multiple access methods can be combined. In this way, a multiplicity of radio communication systems use a combination of the TDMA and FDMA methods, wherein each narrow-band frequency band is divided into time slots.
For the purpose of the aforementioned UMTS mobile radio system, a distinction is made between a so-called FDD (frequency division duplex) mode and a TDD (time division duplex) mode. In particular, the TDD mode is characterized in that a shared frequency band is used for the signal transmission in both uplink (UL) direction and in downlink (DL) direction, while the FDD mode uses a different frequency band for the two transmission directions in each case.
In radio communication connections of the second and/or third generation, information can be transmitted in a circuit-switched (CS) or packet-switched (PS) manner.
The connection between the base station, of which there is at least one, and the subscriber station, of which there is at least one, takes place via a radio communication interface. The base station can support a plurality of radio cells in this case.
The base station, of which there is at least one, and a radio network controller (RNC) are usually components of a base station subsystem (RNS radio network subsystem). A radio communication system normally includes a plurality of base station subsystems which are connected to a core network (CN). The radio network controller of the base station subsystem is connected to an access facility (SGSN Serving GPRS Support Node) of the core network in this case.
In addition to individual items of payload information, radio communication systems transmit data which is made available to a plurality of users. Such items of payload information include, for example, video streams or other items of broadcast and/or multicast information. The services for transmitting items of payload information which are not merely intended individually for a single subscriber, but are made available to a plurality of subscribers, are grouped under the term MBMS (Multimedia Broadcast/Multicast Service). Different MBMS (Multimedia Broadcast/Multicast Service) services are usually provided as separate data streams by the core network.
WO 02/19741 A2 discloses a communication system in which an IP multicast is sent to a plurality of devices in an IP network. In order to ensure that, on the network side, there is information about which end devices wish to receive which IP multicast, an “end device membership query” is periodically sent to the end devices from the network side. Upon receipt of a membership query, an end device sends a membership report as a reply to a local router and, in the membership report, identifies those multicast groups which this end device wishes to receive.
3GPP (3rd Generation Partnership Project) TS 22.146 V5.2.0 Release 5 describes the requirements which must be supported by a 3GPP system (UTRAN [Universal Terrestrial Radio Access Network] and GERAN [GSM EDGE Radio Access Network]), in order to provide broadcast and multicast services (EDGE: Enhanced Data rates for GSM Evolution).
Before the items of payload information are made available as a service to a plurality of subscribers, a notification takes place in relation to the subscriber stations of those subscribers who want to use the service, before the actual transmission of the items of payload information of the service. This notification of the subscriber stations is necessary so that the receivers can be configured. Depending on the mode of the subscriber stations (e.g. “connected mode” or “idle mode”), they are notified by a “notification” or “paging”, for example. Group-specific mechanisms are normally used for notification, wherein a plurality of subscriber stations are addressed simultaneously.
The transmission of items of broadcast/multicast information as services should take place advantageously. In particular, any avoidable utilization of radio resources should be avoided whenever possible.