WO2011110566A1

WO2011110566A1 - A method of switching between a data exchange mode and a measurement mode in a communications system

Info

Publication number: WO2011110566A1
Application number: PCT/EP2011/053477
Authority: WO
Inventors: Perttu Aukusti Mella
Original assignee: Nokia Siemens Networks Oy
Priority date: 2010-03-10
Filing date: 2011-03-08
Publication date: 2011-09-15

Abstract

A method of switching between a data exchange mode and a measurement mode in a communications system includes sending a control message to a mobile station, receiving the control message at the mobile station, and switching from the data exchange mode to the measurement mode upon receiving the control message if it is required to start a measurement and switching from the measurement mode to the data exchange mode upon receiving the control message if it is required to stop the measurement.

Description

A METHOD OF SWITCHING BETWEEN A DATA EXCHANGE MODE AND A MEASUREMENT MODE IN A COMMUNICATIONS SYSTEM

FIELD OF THE INVENTION

The invention generally relates to a method of switching between a data exchange mode and a measurement mode in a communications system. More particularly, the invention relates to activation of a compressed mode for providing a transmission gap in the uplink and the downlink to allow a mobile station to take measurements.

BACKGROUND OF THE INVENTION

A mobile station or user equipment (UE) is required to make many inter-frequency and inter-system measurements during uplink and downlink transmission when it is in a CELL DCH RRC state. However, the UE cannot perform measurements while transmission or exchange of data is taking place. Therefore a so-called compressed mode is required in order to provide a transmission gap in the uplink and downlink so that the UE can take measurements (apart from in the rare case of dual receiver 3G UEs, which can measure without using a compressed mode in the downlink direction, or in both uplink and downlink such a UE informs its capability to the network and the radio network controller (RNC) activates the compressed mode only if needed) .

The current method for activating the compressed (measurement) mode requires that it is activated in both the UE and the Node B using synchronized RRC (radio resource control) and NBAP/RNSAP (Node B application part/ radio network subsystem application part) procedures. These procedures are required so that activated compressed mode transmission gaps are synchronized at both the transmitting and receiving ends when data exchange is taking place between the UE and BTS.

A disadvantage of using such a synchronized procedure is that it causes a 400-700 millisecond transmission delay in a situation where time is critical.

Thus there is a need for a method of activating a measurement mode that does not cause unwanted delays.

SUMMARY OF THE INVENTION

Accordingly, the invention provides a method of switching between a data exchange mode and a measurement mode in a communications system. The method includes sending a control message to a mobile station, receiving the control message at the mobile station and switching from the data exchange mode to the measurement mode upon receiving the control message if it is required to start a measurement and switching from the measurement mode to the data exchange mode upon receiving the control message if it is required to stop the measurement.

In this way, the measurement mode can be activated in an unsynchroni zed manner, without the need for RRC and NBAP/RNSAP synchronization procedures. Nothing is required to be signalled to any network node, e.g., a NodeB or eNodeB. Therefore unwanted delays caused by having to synchronize at both the transmitting and receiving ends are eliminated. Furthermore, this procedure is simpler to implement in a network than conventional methods .

Preferably, the measurement mode is a compressed mode. The compressed mode allows for a transmission gap in the uplink and downlink in which measurement by the mobile station can take place.

In an advantageous embodiment, the method further comprises synchronizing a transmission gap between the mobile station and a network node. The step of synchronizing can comprise pre-configuring a transmission gap pattern sequence in the mobile station and the network node. The transmission gap pattern sequence (s) can be pre-configured to the mobile station and network node, e.g. Node B. Pre-configuration of transmission gap pattern sequences may take place in the radio link setup phase, for example (and can be reconfigured later if needed) . Switching may then take place at the beginning of a next transmission gap in the pre-configured transmission gap pattern sequence.

The step of switching can include activating or deactivating the measurement mode in the network node. A compressed mode (e.g. for the RRC connection) can be activated or deactivated so that inter-system and inter-frequency neighbour cell measurements can be performed when the mobile station is in a CELL_DCH RRC state. The compressed mode provides a transmission gap in the uplink and downlink so that the mobile station can take such measurements.

Preferably, the switching is performed by the mobile station. When the mobile station receives the control message, it activates or deactivates the measurement mode in the network node depending on whether it is required to start or finish a measurement. The switching may then further include the mobile station activating its own measurement mode. When the mobile station receives the control message it may activate or deactivate the measurement mode in itself, in addition to activating or deactivating the measurement mode in the network node.

Alternatively, the switching may be performed by the network node. Instead of activation or deactivation of the measurement mode being performed by the mobile station, this may also take place in the network node. In this case, the network node may also activate the measurement mode in the mobile station.

The control message can be sent from a network control node, for example a base station controller, a radio network controller (RNC) or RNC functionality in an eNodeB. When the RNC decides that inter-system or inter-frequency measurement should be activated, it can activate the measurement or compressed mode by sending only a RRC : Measurement control message to the mobile station. This procedure is unsynchroni zed and can contain information about neighbouring cells to be measured and about the measured target system. The control message may also include information about measurement attributes. The network node, e.g. NodeB or eNodeB, does not need to be informed by the RNC using NBAP protocol in this phase. In this way, the RNC has control of activating or deactivating the measurement/compressed mode. This is especially useful when inter-system and inter- frequency measurements are triggered by the RNC, e.g. in service, load and capability based handovers (and certain quality and coverage handovers - there are several of these but only DL Tx power and uplink quality are triggered by the RNC) . Inter-system and Inter-frequency neighbour cells for inter-system and inter-frequency handover measurement can be signaled to the mobile station in the control message. Alternatively, inter-system and inter-frequency neighbour cells for inter-system and inter-frequency handover measurement can be signaled to the mobile station in a system information block.

The invention also provides a mobile station. The mobile station includes a receiver adapted to receive a control message from a control node of a communications network. A processor is also provided in the mobile station. The processor is configured to switch from a data exchange mode to a measurement mode when the control message is received at the receiver if it is required to start a measurement and to switch from the measurement mode to the data exchange mode when the control message is received at the receiver if it is required to stop the measurement. The mobile station receives a control message; e.g. a RRC control message from a RNC in the communications network. When it receives the control message, the mobile station either activates or deactivates the measurement mode, for example a compressed mode, depending on whether the mobile station is required to respectively start or stop taking measurements (e.g. inter-system and/or inter frequency neighbour cell measurements) .

The control message can signal inter-system and inter- frequency neighbour cells for inter-system and inter-frequency handover measurement to the mobile station.

Alternatively, a system information block (SIB) can signal inter-system and inter-frequency neighbour cells for inter- system and inter-frequency handover measurement to the mobile station . A node of the network may control the processor to switch from the data exchange mode to the measurement mode. Instead of the mobile station switching itself to activate or deactivate the measurement mode, the network node, for example a NodeB or eNodeB may control the processor of the mobile station to activate or deactivate the measurement mode upon receiving the control message.

The processor can be further configured to activate or deactivate the measurement mode in a node of the communications network. Alternatively or in addition to switching the mobile station from the data exchange mode to the measurement mode, and vice versa, the processor can switch the network node between the data exchange and measurement modes .

The invention further provides a communications network. The communications network includes a control node adapted to send a control message to a network node in communication with the network. The control node (e.g. a radio network controller (RNC) ) is adapted to control the network node (e.g. mobile station or base station) to switch from a data exchange mode to a measurement mode if it is required to start a measurement and to switch from the measurement mode to the data exchange mode if it is required to stop the measurement. Sending a control message from the control node to the network node is an unsynchronized procedure. In this way, unwanted delays are avoided, since no synchronization is required between the mobile station and another node in the communications network.

In an advantageous embodiment, the network node (for example a mobile station or Node B) is configured to activate or deactivate the measurement mode in a further node of the network (for example a Node B or mobile station, respectively) In other words, the control node sends a message to the network node, which activates or deactivates the measurement mode in the network node. That network node then respectively activates or deactivates the measurement node in another node of the network.

Preferably, the control node is further adapted to pre- configure a transmission gap pattern sequence in the network node and in a further node of the network. A transmission gap between the two network nodes (for example a mobile station and a Node B) can be pre-configured, for example by the control node in the radio link set-up phase between the network node (mobile station) and the communications network. The transmission gap pattern sequence (s) can be pre-configured to both the network node, e.g., mobile station and further network node, e.g. a Node B. Switching (activating the measurement mode or compressed mode) may then take place at the beginning of a next transmission gap in the pre-configured transmission gap pattern sequence. In other words, a compressed mode can be activated and deactivated after a LI or L2 indication is received from the mobile station.

The invention will now be described, by way of example only, with reference to specific embodiments, and to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a simplified schematic block diagram of a communications network according to an embodiment of the invention; and Figure 2 is a flowchart illustrating a method of switching between a data exchange mode and a measurement mode in the communications network according to an embodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Figure 1 schematically shows a wireless communications network having a base station NB, which is a network node. The base station NB may be a base transceiver station (BTS) , Node B or eNodeB. The base station NB is interfaced to a radio network controller RNC over an interface Iub (of course many additional base stations in the network may be interfaced to the radio network controller RNC but they are not shown here for simplicity) . A user equipment or mobile station UE may be in communication with the network via the base station NB over an interface Uu . The mobile station UE has a transmit/receive unit TR and a processor P.

The radio network controller RNC has in fact two functionalities of a serving RNC SRNC and a drift RNC DRNC interfaced with each other over an interface Iur. The serving RNC and drift RNC may be in physically the same RNC or two different RNCs; however, logically they are described here as one network controller RNC.

The method according to an embodiment of the invention will now be described with reference to the flow chart in Figure 2.

When the mobile station UE is required to take a measurement, e.g. an inter-system or inter-frequency measurement, in a CELL_DCH RRC state, the radio network controller RNC sends a RRC: Measurement Control message to the mobile station UE in step SI. In step S2 the mobile station receives the RRC : Measurement Control message from the network controller RNC at the transmit receive unit TR. Upon receiving the RRC: Measurement Control message from the RNC, the processor P in the mobile station UE controls the mobile station to activate a compressed mode in itself in step S3. In step S4, the mobile station UE then also activates the compressed mode in the base station NB by using signalling over the LI or L2 physical layers. The mobile station UE then sends an RRC: Measurement Report message to the network controller RNC in step S5. Then, when the mobile station UE is required to stop measuring, the network controller RNC sends a further RRC: Measurement Control message to the mobile station UE in step S6, which instructs the mobile station UE to stop the measurement. In step S7, the mobile station UE receives the RRC: Measurement Control message from the radio network controller RNC at the transmit/receive unit TR and in step S8 the processor P controls the mobile station UE to deactivate both its own compressed mode and that in the base station NB.

In a preferred embodiment of the invention, the RNC pre- configures required transmission gap sequences to the base station NB and the mobile station UE during the radio link setup phase and the compressed mode for the RRC connection is activated during the pre-configured transmission gaps. Firstly the transmission gap pattern sequence is loaded in the serving RNC part of the radio network controller SRNC. Then, using synchronised NBAP/RNSAP procedures, a radio link is set up by the radio network controller RNC by sending a Radio Link Reconfiguration Prepare message to the base station NB. The transmission gap pattern sequence is preconfigured to the base station NB and the mobile station UE during this radio link setup to the mobile station UE using an RRC procedure and the pattern can be reconfigured later if needed. The RRC procedure used in preconfiguration and reconfiguration can be, for example, an RRC: Physical channel reconfiguration procedure. This phase loading of transmission gap sequences does not cause any delay to the compressed mode activation procedure. The preconfigured pattern contains also synchronization information, TGCFN, signaled to both the mobile station UE and the network node NB, to be used when CM is activated using LI or L2 signalling.

When the radio network controller RNC decides that inter- system or inter-frequency measurements are required, the radio network controller RNC activates the compressed mode by sending an RRC: Measurement Control message only to the UE . This message contains information about neighbouring cells to be measured and the measured target system (WCDMA (inter- frequency) or GSM (inter-system) or LTE or any such system) , as well as the relevant measurement attributes. The base station NB does not need to be informed by the network controller RNC using the NBAP protocol when the RNC activates the compressed mode.

When the mobile station UE receives the RRC: Measurement Control message, it activates the compressed mode in the base station NB by signalling to the base station NB using physical layer LI or L2 signalling in the next pre-configured transmission gap (TGCFN to be used) after indication of activation of the compressed mode is received in the LI or L2 signalling from the mobile station UE . The mobile station UE also activates its own compressed mode. The compressed mode gap synchronization between the mobile station UE and the base station NB is then based on information in the pre-configured transmission gap pattern sequences in the mobile station UE and the base station NB loaded during the radio link set-up phase. Compressed mode gap synchronization in the transmitting and receiving directions is based on the pre- configured compressed mode synchronization information so that no synchronization is required upon activation of the compressed mode.

In an alternative embodiment, inter-system and inter- frequency neighbour cells broadcasted in system information blocks (SIBs) can be used when the mobile station UE is in the CELL_DCH RRC state . If neighbour cells are signaled in SIBs then a reduced amount of data must be signaled using RRC signaling, for example, when the compressed mode is started. Signalling of neighbouring cells using RRC in pre-configured manner would require reconfiguration of the neighbour cell set when soft handover occurs because all active set cells have dedicated neighbour cell sets. If the mobile station UE is in soft handover and several cells are in an active set, the mobile station UE can select from neighbour cells received in SIBs only those which fit to the maximum allowed cell amount using a selection algorithm.

In a further embodiment, the radio network controller RNC sends the RRC: Measurement Control message to mobile station UE to start the measurement, as in the embodiments described above. However, the compressed mode is activated by the radio network controller RNC sending a message (s) to the base station NB and/or additional base stations in the network. After receiving the message from the network controller RNC, the base station (s) NB activates compressed mode in the mobile station UE .

Although the invention has been described hereinabove with reference to specific embodiments, it is not limited to these embodiments, and no doubt further alternatives will occur to the skilled person, which lie within the scope of the invention as claimed.

Claims

1. A method of switching between a data exchange mode and a measurement mode in a communications system, the method comprising :

sending a control message to a mobile station;

receiving the control message at the mobile station; and switching from the data exchange mode to the measurement mode upon receiving the control message if it is required to start a measurement and switching from the measurement mode to the data exchange mode upon receiving the control message if it is required to stop the measurement.

2. The method according to claim 1, wherein the measurement mode is a compressed mode.

3. The method according to claim 1 or claim 2, further comprising synchronizing a transmission gap between the mobile station and a network node.

4. The method according to claim 3, wherein the step of synchronizing comprises pre-configuring a transmission gap pattern sequence in the mobile station and the network node.

5. The method according to claim 4, wherein the step of switching takes place at the beginning of a next transmission gap in the pre-configured transmission gap pattern sequence.

6. The method according to any of claims 1 to 5, wherein the step of switching comprises activating or deactivating the measurement mode in the network node.

7. The method according to any of claims 1 to 6, wherein said switching is performed by the mobile station.

8. The method according to any of claims 1 to 7, wherein switching further comprises the mobile station activating its own measurement mode.

9. The method according to any of claims 1 to 6, wherein the switching is performed by the network node.

10. The method according to claim 9, wherein the network node activates the measurement mode in the mobile station.

11. The method according to any of claims 1 to 10, wherein the control message is sent from a network control node.

12. The method according to any of claims 1 to 11, wherein the control message comprises information about measurement attributes .

13. The method according to any of claims 1 to 12, wherein inter-system and inter-frequency neighbour cells for inter- system and inter-frequency handover measurement are signaled to the mobile station in the control message.

14. The method according to any of claims 1 to 13, wherein inter-system and inter-frequency neighbour cells for inter- system and inter-frequency handover measurement are signaled to the mobile station in a system information block.

15. A mobile station, comprising:

a receiver adapted to receive a control message from a control node of a communications network; and

a processor configured to switch from a data exchange mode to a measurement mode when the control message is received at the receiver if it is required to start a measurement and to switch from the measurement mode to the data exchange mode when the control message is received at the receiver if it is required to stop the measurement.

16. The mobile station according to claim 15, wherein a node of the network controls the processor to switch from the data exchange mode to the measurement mode.

17. The mobile station according to claim 15, wherein the processor is further configured to activate or deactivate the measurement mode in a node of the communications network.

18. A communications network, comprising a control node adapted to send a control message to a network node in communication with the network for controlling the network node to switch from a data exchange mode to a measurement mode if it is required to start a measurement and to switch from the measurement mode to the data exchange mode if it is required to stop the measurement.

19. The network according to claim 18, wherein the said network node is configured to activate or deactivate the measurement mode in a further node of the network.

20. The network according to claim 19, wherein the control node is further adapted to pre-configure a transmission gap pattern sequence in the said network node and in said further node of the network.