Communication system

A Home NodeB (HNB) is provided that can be triggered to dynamically change its operating radio parameters, such as its transmission frequency or its primary scrambling code without having to be rebooted and which communicates the changed operating parameters to the mobile user devices served thereby. In this way a seamless changeover of the operating parameters can be provided that is transparent to users. The HNB may be triggered to change operating parameters by the mobile operating network or by an internal procedure.

TECHNICAL FIELD

The present invention relates to mobile telecommunication networks, particularly but not exclusively networks operating according to the 3GPP standards or equivalents or derivatives thereof. The invention has particular although not exclusive relevance to the operation of a home base station and user equipment (UE) associated with the home base station.

BACKGROUND ART

Under the 3GPP standards, a NodeB (or an eNB in LTE) is the base station via which mobile devices connect to the core network. Recently the 3GPP standards body has adopted an official architecture and started work on a new standard for home base stations (HNB). Where the home base station is operating in accordance with the LTE standard, the HNB is sometimes referred to as a HeNB. A similar architecture will also be applied in the WiMAX network. In this case, the home base station is commonly referred to as a femto cell. For simplicity, the present application will use the term HNB to refer to any such home base station. The HNB will provide radio coverage (3G/4G/WiMAX) within the home and will connect to the core network via a suitable public network (for example via an ADSL link to the Internet) and in the case of the 3GPP standards, via an optional HNB gateway (HNB-GW).

An HNB will operate on the same or on a different frequency to the macro cell(s) within which it is located and on the same or a different frequency to other HNBs operating in its vicinity. Under current proposals, the operating radio parameters (such as its frequency and/or its primary scrambling code (PSC)) of the HNB are either acquired from the core network operator when the HNB is powered up or are acquired through a self configuration routine that involves learning the surrounding environment, and the only way that these parameters can be changed is by resetting or rebooting the HNB. It is expected that HNBs will be widely deployed. For example, provision has been given in 3GPP TS 22.011 to address 125 million HNBs within a PLMN (Public Land Mobile Network). The inventors have realized that with such a wide spread deployment, radio conditions around the HNB may change regularly resulting in varying levels of interference.

DISCLOSURE OF INVENTION

The inventors have concluded, therefore, that it would be beneficial if the HNB can change its operating radio parameters after power on, during its normal operational state, based on new radio conditions and communicate its new parameters to the UEs being served by the HNB.

Although for efficiency of understanding for those of skill in the art, the invention will be described in detail in the context of a 3G system, the principles of the invention can be applied to other systems (such as WiMAX) in which mobile devices or User Equipment (UE) communicate with one of several base stations with the corresponding elements of the system changed as required.

According to one aspect, the present invention provides a home base station comprising: transceiver circuitry operable to transmit wireless signals to and to receive wireless signals from a user device in accordance with current operating radio parameters; and a parameter control module operable, in response to a trigger, to obtain new operating radio parameters (such as a new transmission frequency or a new Primary Scrambling Code (PSC) or equivalent) and to reconfigure the transceiver circuitry with the new operating radio parameters. The reconfiguration can be performed dynamically while the home base station is serving one or more mobile telephones and without having to power down or reset the home base station. The new operating parameters may be obtained either by receiving them from the Mobile Network Operator via any node which is higher or at the same level in the hierarchy within the operator network or by determining them following a consideration of the surrounding environment. A communications control module is provided that communicates with the user device to inform the user device of the new operating radio parameters

In a preferred embodiment, the communications control module communicates with the user device to inform the user device of the new operating radio parameters prior to the parameter control module reconfiguring the transceiver circuitry. The communications control module may inform user devices operating in a Connected mode of the change but not user devices operating in an Idle mode or it may try to inform all user devices regardless of their operating mode. The communications control module may inform user devices using a dedicated control channel, a broadcast control channel or some other channel such as an MBMS service. The user devices may be informed by updating a Neighbour Cell List, to include the home base station as a neighbour with the new configuration. The communications control module may inform user devices operating in different modes using different control channels. Regardless of the way in which the different user devices are informed of the change, they are preferably given timing information that defines when the reconfiguration will take place.

According to another aspect, the present invention provides a mobile user device comprising: transceiver circuitry for transmitting signals to and for receiving signals from a home base station in accordance with current operating radio parameters of a home base station; and a parameter control module operable to obtain data identifying new operating radio parameters of the home base station and to reconfigure said transceiver circuitry with the new operating radio parameters. Typically the mobile device will receive the new operating radio parameters from the home base station.

The mobile device may have a first mode of operation and a second mode of operation and the communications control module may be arranged to receive the new operating radio parameters over a dedicated control channel when the user device is operating in the first mode of operation and to receive the new operating radio parameters over a broadcast channel when the user device is operating in the second mode of operation. The first mode of operation may be a Connected mode of operation and the second mode of operation may be an Idle mode of operation.

The mobile device may be informed of the change via a broadcast control channel or via a dedicated control channel. The information received by the mobile device preferably includes timing information identifying when the changeover will take place. Between the time that the mobile device is informed of the change and the time of the changeover, the mobile device preferably continues to communicate with the home base station using the current operating parameters.

The present invention also provides a communications control signal for use in reconfiguring operating parameters of a transceiver circuit, the signal including a first portion for signalling a change of frequency or a change in primary scrambling code and a second portion for signalling timing information indicating when the transceiver circuit should be reconfigured.

The invention provides, for all methods disclosed, corresponding computer programs or computer program products for execution on corresponding equipment, the equipment itself (user equipment, nodes or components thereof) and methods of updating the equipment. The computer programs may be provided on a recording medium such as a CD-ROM or the like.

BEST MODE FOR CARRYING OUT THE INVENTION

Overview

FIG. 1schematically illustrates a mobile (cellular) telecommunication system1in which a user of a mobile telephone (MT)3can communicate with other users (not shown) via a macro cell of a 3G Radio Access Network (RAN) base station5, a Radio Network Controller7and a core telephone network8when the user is away from home9; and which can communicate with other users (not shown) via the cell of a home base station (HNB)11, a public data network (in this case the Internet13), a home base station gateway (HNB-GW)15and the core telephone network7when the user is at home9. The HNB11will typically connect to the HNB-GW15via a suitable residential Internet connection such as an ADSL or cable connection16and is programmed with the IP address of the HNB-GW15so that all uplink communications are transmitted to the HNB-GW15. The HNB11is configured by the mobile telephone network operator (forming part of the core network8) by sending appropriate control signals to the HNB11via the Internet13. As those skilled in the art will appreciate, the HNB11can communicate with a number of different mobile telephones3.

Mobile Telephone

FIG. 2schematically illustrates the main components of the mobile telephone3shown inFIG. 1. As shown, the mobile telephone3includes transceiver circuitry23which is operable to transmit signals to and to receive signals from the RAN base station5or the HNB11via one or more antennae25. As shown, the mobile telephone3also includes a controller27which controls the operation of the mobile telephone3and which is connected to the transceiver circuit23and to a loudspeaker29, a microphone31, a display33, and a keypad35. The controller27operates in accordance with software instructions stored within memory37. As shown, these software instructions include, among other things, an operating system39, a parameter control module40and a communications control module41. In this embodiment, the parameter control module40controls parameter values used by the transceiver circuit23in its communications with the HNB11; and the communications control module41controls the communications with the HNB11and selects the home base station11when the mobile telephone3is within range of their HNB11. The selection may be automatic or manually controlled by the user. During initial registration with the HNB11, the parameter control module40will acquire the operating radio parameters for the HNB11and will use them to configure the transceiver circuitry23for subsequent communications with the HNB11.

Home Base Station

FIG. 3is a block diagram illustrating the main components of the home base station (HNB)11shown inFIG. 1. As shown, the HNB11includes transceiver circuitry51which is operable to transmit signals to, and to receive signals from, the mobile telephone3via one or more antennae53and which is operable to transmit signals to and to receive signals from the HNB-GW15via a HNB-GW interface55. The operation of the transceiver circuitry51is controlled by a controller57in accordance with software stored in memory59. The software includes, among other things, an operating system61, a communications control module63and a parameter control module65. The communications control module63is operable to control communications between the HNB11and the mobile telephone3and the HNB-GW15. The parameter control module65is operable to receive operating parameters from the mobile operator via the Internet13and to configure the transceiver circuitry51in accordance with those parameters. As will be described in more detail below, the parameter control module65is operable to change the operating parameters of the transceiver circuitry51. It does this when triggered by a radio resource management (RRM) entity within the mobile operator network or by some internally generated trigger generated, for example, by a mobile network operator policy function. In this embodiment, prior to the reconfiguration, the communications control module63informs registered mobile telephones3with the changed operating radio parameters.

In the above description, the mobile telephone3and the home base station11are described for ease of understanding as having a number of discrete modules (such as the communications control and the parameter control modules). Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the invention, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities.

Operation

In operation, the parameter control module65is operable, when triggered, to change the operating radio parameters of the HNB11. The trigger may be supplied by a radio resource management (RRM) entity of the PLMN or by some internal trigger generating mechanism. The trigger may be generated based on a management policy of the mobile operator or based on sensed interference conditions. For example, the mobile operator may implement a policy that at certain times of the day, one group of HNBs11will be configured to operate with different operating parameters than those normally used by those HNBs. This may be done, for example, to reduce interference caused to another group of HNBs. Alternatively, the HNB11may be programmed to change its operating parameters if it detects interference above a certain threshold.

When the HNB11is triggered to change its operating parameters, the parameter control module65will obtain the new operating parameters and the communications control module63will initiate a procedure that provides an organised transition between the old and new operating parameters. To provide a seamless change over, registered mobile telephones3that are in connected modes Cell-DCH and Cell-FACH (ie those actively transmitting or receiving data from the HNB11) have to be informed of the new operating parameters in advance of the changeover and have to be informed of when the changeover will occur. Mobile telephones3that are in the IDLE mode or in the CELL-PCH or URA-PCH connected modes are not transmitting or receiving data at the current time and informing them of the new radio parameters is less important (and indeed can be omitted) for providing users with a seamless transition.

A number of different options for informing registered mobile telephones3of the change will now be described.

Option 1—Cell-DCH and Cell-FACH

When the mobile telephone3is in either the Cell-DCH or Cell-FACH mode, various techniques can be used to inform the mobile telephone3of the new radio parameters. However, one of the simplest techniques is to reuse the existing inter frequency handover RRC procedure illustrated inFIG. 4(which is used when the mobile telephone3moves between cells or RAN base stations5). As shown, at step s1, the HNB11is serving a mobile telephone3in the Cell-DCH mode. At step s3the HNB11decides to change its operating radio parameters and in step s5the HNB11sends an RRC reconfiguration message to the mobile telephone3with an activation time, over a control channel dedicated to the mobile telephone3. A change in the frequency can be indicated using the existing “frequency Info” Information Element (IE); and a change in the PSC can be indicated using the existing “Primary CPICH Info” Information Element. The activation time effectively defines a delay before the changeover will take place and can be defined by a Connection Frame number (CFN). The CFN is a counter maintained by both the HNB11and the mobile telephone3that counts from 0 to 255 and is incremented every 10 ms. Therefore specifying a CFN value identifies to the mobile telephone3a time point when the changeover will take place. At step s7the HNB11and the mobile telephone3change the radio parameters (in this case the frequency from f1to f2) at the activation time. Once the mobile telephone3has completed the reconfiguration, it sends, in step s9, an RRC reconfiguration message confirming that the change has been completed.

Another option is to include the new operating radio parameters in the System Information Block (SIB) type3, using three new Information Elements (IEs), which is broadcast over the broadcast control channel (BCCH). The three new IEs would provide the new Frequency Information; Primary CPICH Information; and a Margin time. The procedure for synchronising the changeover in this case is illustrated inFIG. 5. In step s11, the HNB11decides to change the operating radio parameters of the cell based on the trigger. In step s13, the HNB11sends the mobile telephone3a system information change indication (BCCH Modification Info) and the SIB3including the new parameters over the broadcast control channel (BCCH). The BCCH Modification Info tells the mobile telephone3what information to look at in the SIB3. Typically the HNB11will repeat the transmission of the BCCH Modification Info and the SIB3a number of times to ensure that the mobile telephone3is able to receive the modification information before the changeover. In step s15the mobile telephone3reads the new operating parameters from the SIB when it is received or after an optional Modification time defined by the SIB. In step s17the mobile telephone3and the HNB11change the operating radio parameters at a Margin time defined in the SIB. The defined Margin time will be chosen to give sufficient time for the synthesiser that forms part of the transceiver circuitry23, to change the operating frequency and to start operating on the new frequency after expiry of the Margin time. The HNB11will then stop broadcasting, in step s19, the new parameters after expiry of Margin time.

The Margin time therefore provides a synchronised way of changing the operating parameters. The Margin time may be specified using a System Frame Number (SFN). The SFN is a counter that is maintained by both the HNB11and the mobile telephone3and that is also incremented every 10 ms. However, the SFN counter counts between 0 and 4095. The SFN is used to define the Margin time due to the longer time required to perform the procedure illustrated inFIG. 5. Where the HNB11uses both options 1 and 2 to inform mobile telephones of the change, it will set the Activation time and the Margin time in order to ensure that the mobile telephones3operating in the different modes perform the switchover at the same time.

Another way that the HNB11can inform mobile telephones3of the new operating parameters, is to change the Neighbour Cell List (NCL). More specifically, one of the routine tasks performed by the HNB11is to inform mobile telephones3that it is serving of neighbouring cells. It does this so that the mobile telephone3can handover to one of those neighbouring cells when, for example, the mobile telephone3moves out of range of the HNB11. This information is transmitted in SIB11or SIB12over the Broadcast Control Channel (BCCH). Thus, when a PSC and/or frequency change is triggered, the HNB11includes in the broadcast neighbour cell list (SIB11/12) itself as a neighbour with the new configuration (it can also configure the Cell Individual Offset (CIO) parameter so that the ranking of the cells in the NCL that will be performed by the mobile telephone3will favour the new cell over the other neighbours). Depending on the change to the operating radio parameters, this may involve changing the Intra frequency measurement system information IE and/or the Inter-frequency measurement system information IE in Measurement control system information of SIB type11or12. For example, if the HNB11is changing frequency, then it would change the Inter-frequency measurement system information IE, but if it is keeping the same frequency and changing only its primary scrambling code (PSC), then the HNB11would change the Intra-frequency measurement system information IE.

The mobile telephone3maintains a list of neighbouring cells and upon receiving the information about the new cell, it adds it to the stored list. When the reconfiguration of the HNB11is performed, the mobile telephone3will lose contact with the HNB11and will start the reselection procedure to find a new cell. This reselection procedure uses the Neighbour Cell List and the CIO parameters for the cells in the NCL to identify a new cell with which to register. As a result of the changes made to the NCL by the HNB11immediately prior to its reconfiguration, the mobile telephone3should quickly reselect the HNB11on its new configuration.

Advantages

The embodiments described above offer a number of important advantages over existing HNBs, which can only be reconfigured at power up and hence would require a reboot if changes were desired. The advantages include:The end user will not notice any change in the operating parameters of the HNB and can expect reliable and seamless service even when normal service is ongoing. This will also mean that the user will remain connected to the HNB and will not switch cell to another cell where less favourable rates may apply.In the prior art, the HNB would always be reset or rebooted to change its operating parameters, which leads to disruption of ongoing services in connected mode which in turn leads to a bad user experience.There is no need to send a service engineer to perform the change during the night, as is currently done for macro cells.
Modifications and Alternatives

A detailed embodiment has been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above embodiment whilst still benefiting from the inventions embodied therein.

In the above embodiment, a mobile telephone based telecommunications system was described. As those skilled in the art will appreciate, the signalling techniques described in the present application can be employed in other communications system. Other communications nodes or devices may include user devices such as, for example, personal digital assistants, laptop computers, web browsers, etc.

In the embodiment described above, the mobile telephone and the HNB each include transceiver circuitry. Typically this circuitry will be formed by dedicated hardware circuits. However, in some embodiments, part of the transceiver circuitry may be implemented as software run by the corresponding controller.

In the above embodiments, a number of software modules were described. As those skilled in the art will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied to the HNB or to the mobile telephone as a signal over a computer network, or on a recording medium. Further, the functionality performed by part or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of base station5and the mobile telephones3in order to update their functionalities.

This application is based upon and claims the benefit or priority from United Kingdom Patent Application No. 0902628.7, filed on Feb. 17, 2009, the disclosure of which is incorporated herein in its entirety by reference.