The present invention relates to channel setup in a wireless communications network, and particularly but not exclusively to channel state transitions and radio bearer reconfigurations.
In current wireless communications networks, a number of radio resource (RRC) messages are utilised for different channel state transitions and radio bearer reconfigurations. For example, a cell update confirm message is used to move a user equipment from a paging channel state (Cell/URA_PCH) to a forward access channel state (Cell_FACH). A radio bearer reconfiguration message is used to move a user equipment (UE) from a forward access channel state to a dedicated channel state (Cell_DCH). A radio bearer reconfiguration message is also used to reconfigure radio bearers when in the dedicated channel state.
Many applications need to transmit data when the user equipment is in the forward access state or paging channel state. The transition time to a dedicated channel state which allows transmission of the data is often one of the major factors that influences user performance. This is particularly evident for higher data rates, where the transmission time of the data is decreased but the transition time to the dedicated channel state remains the same. Also, even if the user equipment is in the dedicated channel state, the data rate may need to be changed and this requires radio resource control (RRC) signalling, which is time consuming.
It is one aim of the present of the present invention to reduce the time for RRC state transitions and to reconfigure radio bearers. Another aim is to improve the reliability of RRC signalling.
According to one aspect of the present invention there is provided a method of setting up channels in a wireless communications network comprising the steps of: receiving at a user terminal a broadcast message including at least one predefined radio configuration; receiving at the user terminal a configuration message from a network controller, said configuration message comprising an indication to configure the user terminal to adopt the at least one predefined radio configuration for a new transmission channel; and indicating to the controller that the user terminal is configured to transmit data according to the predefined radio configuration.
A further aspect of the invention provides a user terminal for use in a wireless communications network comprising: means for receiving a broadcast message including at least one predefined radio configuration; a store for storing said at least one predefined radio configuration; means for receiving a configuration message from a network controller, said configuration message comprising an indication to configure the user terminal to adopt the at least one predefined radio configuration for a new transmission channel; and means for accessing said at least one predefined radio configuration from the store and configuring a new transmission channel in accordance with the predefined radio configuration.
Another aspect provides a network entity for use in a wireless communications network, the network entity comprising: means for transmitting to a plurality of user terminals in the network a broadcast message including at least one predefined radio configuration; and means for transmitting a configuration message comprising an indication to configure one of said user terminals to adopt the at least one predefined radio configuration for a new transmission channel.
By arranging for at least one predefined radio configuration to be transmitted in a broadcast message, the message size of the configuration message can be reduced so that it can be carried over the air interface more quickly and more reliably. In the described embodiment, the configuration message is a radio resource control (RRC) message, for example in accordance with release 6 or the 3GPP specification for the UMTS (Universal Mobile Telecommunication Service) terrestrial radio access (UTRA).
For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made by way of example to the accompanying drawings.
As illustrated in FIG. in 1, in step 1 the user equipment sends a cell update message over a radio access channel to indicate that it has uplink data available to transmit. In step 2, the radio network controller responds by transmitting a cell update confirm message which acknowledges the cell update message and instructs the user equipment to enter a Cell_FACH state, where data transmission is possible. In step 3, the user equipment transmits a UTRAN (Universal Telecommunications Radio Access Network) mobility information confirm message (UMI CONFIRM) to acknowledge the cell update confirm message. It is now possible for the user equipment to transmit data on the radio access channel, that is it is in the Cell_FACH state. If the available amount of data (traffic volume) is above a configured threshold, the user equipment transmits a measurement report to inform the radio network controller (RNC) about the available amount of data as indicated in step 4. When the radio network controller receives a measurement report it can decide to move the user equipment over to a dedicated channel, Cell_DCH state, since the radio access channel has very limited performance. The radio network controller sends a radio bearer reconfiguration message in step 5 which instructs the user equipment to move to a dedicated channel. The user equipment responds with a radio bearer reconfiguration confirm message in step 6 which acknowledges the received message and indicates that the user equipment has entered the Cell_DCH state and is ready to transmit data on the dedicated channel.
The messages exchanged between the user equipment and the radio network controller to achieve the changes in channel state discussed above are referred to herein as radio resource control (RRC) messages. RRC signalling (the exchange of RRC messages) represents a significant part of the time required to set up a call. RRC messages comprise information elements containing generally applicable information (common to all dedicated channels is a cell or network, and specific information, specific to a particular channel.
According to the described embodiment of the invention, the information elements lEs representing common network information is broadcast to users in a particular cell from the Node-B for that cell, rather than being conveyed in each of the RRC messages during an RRC signalling exchange. This information already exists in system information block 16 (SIB 16). This information could be broadcast in an extension to SIB 16, or in a new SIB. The extended SIB or new SIB would broadcast predefined configurations for the most common radio bearers used in the network. Whenever the radio network controller (RNC) wished to establish a new dedicated channel to a user equipment, all general information elements are deleted and an indicator identifying one of the predefined configurations indicated by the SIB would be included. Information elements that are not general remain in the RRC message itself. An example structure of an existing SIB is given in 3GPP TS 25.331 Chapter 13.7.
Predefined or default configurations which are broadcast to the user equipment (UE) are stored at the user equipment in a memory so that they are ready for use when instructed by an RRC message. According to the described embodiment of the present invention, predefined or default configurations are defined for the cell update confirm message and the radio bearer reconfiguration message.
The above described embodiment of the present invention provides a number of advantages. The cell update confirm message can be used to move the user equipment directly from the paging state to the dedicated channel stage (
Where a radio bearer reconfiguration message is used to move the user equipment from the forward access channel state to the dedicated channel state, or to reconfigure the radio bearers in the dedicated channel state, use of the above described compressed RRC message reduces the time to take the new configuration into use. This is because the time taken to transmit the truncated RRC message (
The invention can also be implemented in a voiceover internet protocol (VoIP) call where at RAB setup, the RAB data rate is configured to accommodate the transmission of RTP (Transport Protocol for Real-time Applications) packets with uncompressed headers. This RAB rate is used in the initial phase until ROHC (Robust Header Compensation) can compress the headers. At that point, the RAB data rate is reconfigured to a rate suitable for transmission of RTP packets with compressed headers. In the case uncompressed headers need to be transmitted, the RAB data rate is again reconfigured and adapted to the transmission of uncompressed headers.
As an alternative to transmitting predefined radio configuration using an SIB, a default configuration could be hard coded into the mobile terminal. In that case, the RRC message could include an indication that the default configuration is to be utilised for the channel.
This application claims priority of U.S. Provisional Patent Application Ser. No. 60/567,772, filed May 4, 2004. The subject matter of the earlier filed application is hereby incorporated by reference.
Number | Date | Country | |
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60567772 | May 2004 | US |