Inter base station handover method, radio communication system, drx control method, base station, and communication terminal

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SPANISH OFFICE OF

PATENTS AND TRADEMARKS

SPAIN

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© Int. Cl .:

H04W 76/28

H04W 36/00

H04W 36/08

H04W 52/02 (2008.01) (2009.01) (2009.01) (2009.01)

TRANSLATION OF EUROPEAN PATENT

T3 © Date of submission and number of the European application: 01.02.2008 E 15171829 (3) © Date and publication number of the European concession: 27.03.2019 EP 2947917 © Title: Method of transfer between base stations, radio communication system, DRX control method, base station and communication terminal

<td>© Priority:</td><td>© Owner / s:</td>

<td>05.02.2007 JP 2007025873</td><td>NEC CORPORATION (100.0%) 7-1, Shiba 5-chome Minato-ku</td>

<td>© Date of publication and mention in BOPI of the patent translation:</td><td>Tokyo 108-8001, JP © lnventor / es:</td>

<td> 27.11.2019</td><td>FUTAKI, HISASHI and LEE, JINSOCK © Agent / Representative: ELZABURU, SLP</td>

ES 2 733 007 T3

Notice: Within nine months from the date of publication in the European Patent Bulletin, of the mention of granting the European patent, any person may object to the European Patent Office to the granted patent. The opposition must be in writing and be motivated; It will only be considered as formulated once payment of the opposition fee has been made (art. 99.1 of the

Convention on the Granting of European Patents).

ES 2 733 007 T3

DESCRIPTION

Transfer method between base stations, radio communication system, DRX control method, base station and communication terminal

The present invention relates to a radio communication system, and more particularly to a radio communication system and method that transfers between base stations from a home base station or a destination base station.

In Long Term Evolution (LTE) of 3GPP (Cooperation Project 3^to Generation), a study is being conducted in which the following information (RAN Context Data (Radio Access Network)), which is the information concerning a mobile station that transfers between base stations, is transferred from a base station from origin (source eNB) to a destination base station (destination eNB), when the mobile station performs a handover (abbreviated "HO") between base stations. (For example, see Non-Patent Document 1).

one. QoS Profiles (QoS Profiles of SAE carriers (System Architecture Evolution))

two. AS configuration (RLC Window Size (Radio Link Control), etc.)

In addition, when the originating base station is transmitting downlink data, the originating base station performs a data forwarding that transfers data not sent to the destination base station.

The mobile station that has moved to the destination cell accesses the destination base station through the Random Access Channel (RACH), which is an uplink channel, to acquire a Timing Advance (TA), provided to uplink synchronization, and uplink programming information from the destination base station. After that, the mobile station adjusts the transmission timing according to the acquired TA and transmits a "HO Confirmation", which is a control signal to notify that the mobile station has made the transfer to the destination base station, in the assigned time and frequency.

In LTE, a study is also being conducted on DRX control (Discontinuous Reception: intermittent reception) of a mobile station in RRC (Radio Resource Control) _Connected state (see Non-Patent Document 1).

A base station performs a DRX control of the entire mobile stations in a cell that manages the base station, and a mobile station performs a discontinuous reception at a periodic interval (also called “DRX cycle” or “DRX period”) specified by the base station. A DRX cycle (DRX period) includes a reception period during which data is continuously received and a period of non-reception during which data is not received, as shown in FIGURE 18.

Non-Patent Document 1:

TS 36.300 v0.3.1 (Section 10.1, etc.) of 3GPP

Non-Patent Document 2:

3GPP RAN WG2 [R2-070088 Summary of email discussion on DRX in LTE_ACTIVE], &lt;Internet URL http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_56bis/Documents/R2-070088.zip&gt;

The following gives an analysis of the technology related to the present invention.

Today, a study has just begun on how to combine HO control between base stations proposed by the LTE and DRX control. And so, a small study has been done on a practical method to save energy in a mobile station when these controls are combined.

The US document US 2006/068789 A1 describes a radio configuration selection system with a power supply control at the base station to control the transmission power or select the communication method (modulation type). In particular, this known system establishes information on the side of the base station. In addition, when a destination base station receives a transfer request from a terminal, the destination base station selects a radio configuration upon accepting the terminal and transmits the selected radio configuration to a source base station, that is the configuration of radio is transmitted from the destination base station to the originating base station.

Therefore, in view of the problems described above, it is an object of the present invention to provide a method, system, base station, and communication terminal for saving power of a mobile station when a handover control and a hand control are combined. DRX It is another object of the present invention to provide a method, system, base station, and communication terminal to allow the suppression of an increase or reduction in a load on one side of the network involved in the handover control. These objects are achieved with the characteristics of the claims.

ES 2 733 007 T3

To solve one or more of the problems described above, the invention described by this application provides a handover method (HO) between base stations and a radio communication system, which implements the method, which have the following general configuration.

In a handover method between base stations and a radiocommunication system of the present invention, a home base station (origin eNB) forwards a Latency Context to a destination base station (destination eNB) during a handover to optimize the continuation of DRX control before and after handover.

After a mobile station has completed a handover, the destination base station (destination eNB) uses the Latency Context to perform DRX control of the mobile station.

If the mobile station (User Equipment: UE) has remained in a long DRX cycle in the source cell, the destination base station (destination eNB) can also use the Latency Context also for processing to move the status of the mobile station (UE) to LTE_Idle.

In the present invention, at least one of the following is included in the Latency Context.

a DRX (Discontinuous Receive) level at the current time (when an HO request is generated), a time during which a mobile station has remained at the current DRX level, an average DRX level during management by the station home base, a maximum DRX level during management by the home base station, a minimum DRX level during management by the home base station, a storage size or temporary transmission memory in the HO preparation period, and a programming time at the home base station / status time RRC_Connected at the home base station

A home base station and a destination base station in the present invention can be base stations not only in the same communication system but also in different systems.

EFFECT OF THE INVENTION

According to the present invention, it is possible to optimize the continuation of DRX control before and after a handover. For example, the present invention allows a low activity mobile station to initiate a DRX control more quickly. As a result, the reduction of the power consumption of the mobile station can be achieved.

The present invention also allows a low activity mobile station to transit to an Inactive state more quickly. As a result, the reduction of the power consumption of the mobile station can be achieved. Furthermore, in the present invention, it is possible to avoid an HO between base stations that is not really necessary, thus avoiding an increase in the load of a network.

To describe the present invention in more detail, exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGURE 1 is a diagram for explaining a transfer flow between base stations in an exemplary embodiment of the present invention.

FIGURE 2 is a diagram to explain a handover between base stations in an exemplary embodiment of the present invention.

FIGURE 3 is a diagram for explaining a control of the activity level of a mobile station after a handover between base stations in an exemplary embodiment of the present invention.

FIGURES 4A and 4B are diagrams to explain a control of the activity level of a mobile station after a handover between base stations in an exemplary embodiment of the present invention.

FIGURES 5A and 5B are diagrams for explaining a control of the level of activity of a mobile station after a handover between base stations in an exemplary embodiment of the present invention.

FIGURE 6 is a diagram for explaining a control of the level of activity of a mobile station in a first exemplary embodiment of the present invention.

FIGURE 7 is a diagram for explaining the energy saving effect of a mobile station in a first exemplary embodiment of the present invention.

FIGURE 8 is a diagram for explaining a control of the level of activity of a mobile station in a second exemplary embodiment of the present invention.

FIGURE 9 is a diagram to explain the effect of energy saving of a mobile station and the effect of reducing the load of a NW in the second exemplary embodiment of the present invention.

FIGURE 10 is a diagram for explaining a control of the level of activity of a mobile station in an exemplary embodiment of the present invention.

FIGURE 11 is a diagram to explain a transfer flow between base stations.

FIGURE 12 is a diagram to explain a control of the activity level of a mobile station in an example.

FIGURE 13 is a diagram to explain an operation of a mobile station in an example.

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FIGURE 14 is a diagram showing an example of the configuration of a base station in an example of the present invention.

FIGURE 15 is a diagram showing an example of the configuration of a mobile station in an example of the present invention.

FIGURE 16 is a diagram showing an example of the configuration of a mobile station in another example of the present invention.

FIGURES 17A and 17B are diagrams to explain an HO in another example of the present invention.

FIGURE 18 is a diagram to explain a DRX cycle.

FIGURE 19 is a diagram for explaining a transfer flow between base stations in a modification of an exemplary embodiment of the present invention.

In the exemplary embodiment below, an example is used in which the present invention is applied to a system proposed by the 3GPP LTE although it is not limited thereto.

As an example of DRX control (Discontinuous Reception) in handover (abbreviated “HO”), a base station changes the parameters (see FIGURE 18) related to a DRX cycle, such as the period of non-reception, depending on the state of transmission / reception of data (called “Activity”) of a mobile station. Although a base station changes the parameters in the description below because an example of 3GPP LTE is used, the network side, for example, a 3GPP base station control apparatus (RNC: Radio Network Controller) , you can change the parameters. As an indicator that indicates an Activity rate (grade), the indicator such as an "Activity level" can be used. Depending on this level of activity, the time ratio (Ts), during which data is stored in the storage or temporary transmission memory, can be used at a predetermined period (T) ((Ts / T) x 100 (%) when represented in%). Note that, in the present invention, the Activity level is not limited to (Ts / T) x 100 (%) but that other value (conversion value) that correlates with (Ts / T) can also be used. .

Although a practical example of "Activity" and "Activity level" was described above, the definition of "Activity" and "Activity level" in this specification is of course not limited to the above but should be understood as the state of General data transmission / reception and its frequency.

A base station and a mobile station may use an indicator called "DRX level", acquired based on the Activity level, according to the signal used for DRX control. An Activity level value can be used directly as a DRX level, or a value acquired by converting an Activity level value (preferably a value that has a high correlation with an Activity level value), can be used as a DRX level A DRX level can be represented as a percentage (%). In this case, although a discrete value (for example, an integer value) is normally used as a value in the range of 0-100%, a continuous value such as a decimal number can of course be used. Alternatively, several discrete core values ​​can be used as DRX levels.

First, as an example of the operation proposed by the LTE in which the HO is combined between base stations (between eNB) and the DRX control, the following describes the DRX control of a mobile station in the HO preparation period during which performs a sequence of the following operations.

- The mobile station transmits the Measurement Report to the home base station.

- The source base station checks the Measurement Report to determine which base station is a candidate for the destination base station, and the origin base station and the destination base station exchange information related to the handover indicating whether the base station of Destination may or may not accept the transfer.

For example, a method is known in which a mobile station, for which a long period of non-reception is configured by the DRX control, ignores the currently configured DRX control and transits to the Active operation (the state in which the mobile station can continuously receive the downlink signal) and that a mobile station, for which a short period of non-reception is configured, performs a HO, while remaining in the state in which the short period of non-reception is configured (for example, see Non-Patent Document 2). However, a practical method to implement the described method is not shown. The following describes a practical implementation method.

The HO procedure between base stations in a mobile station under DRX control will be described with reference to FIGURE 11.

The uplink programming information (UL assignment) is transmitted from the home base station to the mobile station. The mobile station that will conduct an HO between base stations transmits a Measurement Report in cells adjacent to the source cell, in which the mobile station resides, to the home base station.

ES 2 733 007 T3

The originating base station transmits a signal (DRX Control Signaling), which instructs the mobile station to move from the DRX (Discontinuous Receive) operation to the continuous reception (or to reduce the period of non-reception of the DRX cycle), to the mobile station and stops the DRX control of the mobile station. It should be noted that, although the base station receiving the Measurement Report outputs the DRX control stop signal to the mobile station in the example sequence operation in FIGURE 11, the base station receiving the Measurement Report does not You need to always take the DRX control stop signal to the mobile station. For example, a rule can be predetermined to allow the mobile station to stop the DRX operation itself.

The originating base station transfers the RAN Context Data (QoS Profile, AS configuration) in the mobile station to the destination base station.

After receiving the notification (Context Confirmation), which indicates that the HO can be accepted, from the destination base station, the originating base station transmits the HO start permission command (HO Command) to the mobile station .

After receiving the HO start command (HO Command) from the originating base station, the mobile station that has moved to the destination cell transmits an uplink synchronization request (UL Synchronization) via a RACH which is an uplink channel, and acquires the transmission timing adjustment value (Timing Advance: TA) and uplink programming information (UL assignment) from the destination base station.

After that, the mobile station transmits an HO Confirmation at the assigned time and frequency, adjusting the transmission timing according to the transmission timing adjustment (TA) value received from the destination base station, to inform the base station of destination that the mobile station has made the transfer.

The destination base station, which has received the HO Confirmation from the mobile station, transmits a control signal (HO Completed) to the home base station to inform that the handover has been completed, notifies the MME (Management Entity) of Mobility) / UPE (User Plan Entity) that the mobile station performed the HO between stations to move to the cell that is managed by the destination base station (update from UE (User Equipment) to the MME / UPE) , and complete the HO operation between base stations. Point out that, at this point in time, the mobile station is still in the Active operation.

If the mobile station that performed the handover does not transmit or receive data for a predetermined period (determined by the timer included on the side of the destination base station) after the handover, the destination base station restarts the DRX control for the mobile station

The uplink programming information (UL allocation: time and frequency allocation information) is transmitted from the destination base station to the mobile station to allow the mobile station to transmit data (UL data transmission), if it is necessary.

As described above, the mobile station is controlled by combining HO and DRX.

FIGURE 12 is a diagram to explain the calculation of the time that the UE remains in DRX shown in FIGURE 13, and FIGURE 12 shows an example of changes in the DRX level when a mobile station in DRX control operation performs the HO between base stations. It is assumed that a mobile station moves through the center of each cell and moves the distance equal to the diameter.

In the example in FIGURE 12, the state is called as follows.

"Active" when the DRX level is 100%, and "DRX" when the DRX level is 20%.

An inactive state in which the DRX level is 0% is the RRC_Idle (LTE_Idle) state.

In the description below, a model proposed by the 3GPP LTE is used as an example where 100% of the DRX level is 100% of the Activity Level. When a frame includes 10 TTI (Transmission Time Intervals), a mobile station whose DRX level is 100% (ie Active operation) monitors the downlink signal (DL) (demodulates a control channel) on each TTI. On the other hand, a mobile station whose DRX level is 20% monitors the DL signal only in the two continuous TTIs of the 10 TTIs but not in the remaining eight TTIs that are periods of non-reception. It is of course possible to define a DRX level value smaller than 100%, for example, 90% or 95%, as "Active".

In the example in FIGURE 12, cell 1 is managed by the base station 1, and cells 2, 3, and 4 are managed respectively by the base stations 2, 3, and 4. We also assume that the mobile station performs the

EN 2 733 007 T3 data transmission / reception only for HO operation in cells 2, 3, and 4. The change in the DRX level is indicated by the bold line.

In FIGURE 12, the symbol X indicates the time during which the mobile station is active during an HO procedure and the symbol Y indicates the time during which the mobile station is under the control of DRX (DRX stay).

Now, we assume that the mobile station is in cell 1 and is under the control of DRX. When an HO is performed between base stations to move to cell 2, the mobile station becomes Active and performs the HO operation. Because, in cell 2, the mobile station does not perform data transmission / reception immediately after HO, base station 2 changes the state of the mobile station from the Active to the DRX after a time limit of one timer, which corresponds to the active transition time to DRX. After that, the mobile station performs an HO from cell 2 to cell 3, to cell 4, and then to cell 5, one after the other, and, in that case, the operation is performed in the same way that when the mobile station performs an HO from cell 1 to cell 2.

Assume that the transition time of the mobile station from Active to DRX in HO is one minute (X in FIGURE 12 is one minute) and that the mobile station intermittently transmits / receives data for 30 minutes. Under this assumption, FIGURE 13 shows in table form an example of the time of stay of DRX in 30 minutes when the parameters are varied, such as the speed of movement and the diameter of the cell.

In this example, the time required for an HO, which will be several 10 milliseconds, is so much shorter than the cell stay time that this time is ignored in the calculation.

In FIGURE 13, it is assumed that the frequency of data transmission / reception of the mobile station is not so high that the mobile station can remain in DRX (the mobile station does not need to be kept Active). In FIGURE 12 and FIGURE 13, a model is assumed in which cells 1 to 5 are adjacent to each other and the mobile station moves in a straight line at a constant speed along the diameters of the multiple cells.

FIGURE 13 shows that when the movement speed of the mobile station is 120 km / h (2 km / minute) and the radius of the cell is 6 km (cell diameter = 12 km), the time that the mobile station Resides in each cell is 12 km / 2 km = 6 minutes (X + Y = 6 minutes in FIGURE 12), and the HO is done 4 times.

Therefore, in 30 minutes, the mobile station moves through 5 (= 4 + 1) cells and resides in the DRX cycle for 5 (= 6-1) minutes in each cell (i.e., X = 1 minute and Y = 5 minutes in FIGURE 12).

As a result, in 30 minutes, the mobile station remains in DRX for 5x5 = 25 minutes.

On the other hand, when the movement speed is 60 km / h and the cell diameter is 1 km, the residence time in each cell and the transition time from Active to DRX are both 1 minute and, therefore, the station Mobile does not travel to DRX for 30 minutes.

That is, in FIGURE 12, Y = 0 minutes because X = 1 minute and X + Y = 1 minute, which means that the next HO operation starts without starting DRX control in a destination cell and As a result, while the mobile station from cell 1 to cell 5, an HO is performed four times without performing DRX control.

As described above, when the residence time of a low activity mobile station in a cell is shorter than the transition time to DRX (this time is managed, for example, by a timer on the side of the base station) , the mobile station cannot make a transition to DRX in the cell and, as a result, consumes extra power.

Similarly, when the time spent in a cell is shorter than the transition time to the RRC_Idle state, the mobile station cannot transition to the RRC_Idle state and, as a result, consumes extra power. In this case, a mobile station, whose Activity is low enough to move the mobile station to the RRC_Idle state, repeats an unnecessary HO. Such wasteful HO will cause a higher network load (base station, UPE / MME) than it is supposed to be, and therefore there is room for improvement.

An exemplary embodiment in another aspect of the present invention is that the DRX control of a mobile station, which is performed in a destination cell after an HO between base stations, is started at the same time that the HO is completed. In doing so, the exemplary embodiment prevents the mobile station from consuming extra power in the destination cell and prevents the repetition of an unnecessary HO, thereby reducing the network load. In the exemplary embodiment described below, also, an example is described in which the present invention is applied to a system, proposed by the 3GPP LTE, although it is not limited thereto.

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FIGURE 1 and FIGURE 2 are diagrams showing the flow (sequence diagram) of HO between base stations of a mobile station, for which the DRX operation is performed in this exemplary embodiment, and the concept of system configuration .

An origin base station (101) transmits uplink programming information (UL assignment) to a mobile station (103) and, before performing an HO between base stations, the mobile station (103) first transmits a Measurement Report in the cells adjacent to the source cell, where the mobile station (103) is now located, to the home base station (101).

The originating base station (101) transmits the signal (DRX Control Signaling) to the mobile station (103) to instruct the mobile station (103) to transit from the DRX to Active, and for the DRX control of the mobile station (103).

The originating base station (101) transfers a Latency Context as well as a QoS Profile and AS Configuration of the mobile station (103) to a destination base station (102).

After receiving the notification signal (Context Confirmation), which indicates that the destination base station (102) is ready to accept the HO, from the destination base station (102), the origin base station (101) transmits the HO start permission signal (HO command) to the mobile station (103).

After receiving the control signal (HO command) from the home base station (101), the mobile station (103), access the destination base station (102) through the RACH (Random Access Channel), which is an uplink channel, to acquire the transmission timing adjustment value (Timing Advance: TA) and uplink programming information (UL Assignment) from the destination base station (102).

The mobile station (103) adjusts the transmission timing according to the transmission timing adjustment value (TA) and transmits the signal (HO confirmation) to the destination base station (102) at the time and frequency assigned to notify the destination base station (102) that the mobile station (103) has performed a handover.

The destination base station (102) transmits the control signal (HO Completed) to the home base station (101) and notifies an MME / UPE (104) that the mobile station (103), which performed the HO between stations base, has been moved to the cell managed by the destination base station (102) (update of the UE to the MME / UPE) and, after that, completes the HO operation between base stations.

After the HO operation is completed, the destination base station (102) uses at least one Latency Context, which is one of the following that includes information on the mobile station in the source cell and that has been transferred from the home base station (101),

QoS Profile;

AS configuration;

Latency Context;

Number of packages arrived from the UPE (User Plan Entity); and

Internal Information that has the destination base station (102);

to perform the DRX control of the mobile station (103) and transmits the signal (Early DRX Control Signaling) that causes the mobile station to transit to a suitable DRX state.

Any of the following can be used as an element for the Latency Context.

(A) Current DRX level;

(B) Time of stay at the current DRX level (C) Average DRX level in the source cell (D) Maximum DRX level in the source cell (E) Minimum DRX level in the source cell (F ) Storage size or temporary transmission memory in the HO preparation period (G) Programming time in the source cell / residence time RRC_Connected in the source cell

Although the DRX cycle (DRX period) is defined according to a DRX level in this exemplary embodiment, the length of the DRX cycle can be determined according to a DRX level each time the base station performs the DRX control operation. Alternatively, a table containing the correspondence between the

EN 2 733 007 T3 DRX levels and DRX cycles (DRX periods) at a base station or a mobile station to determine the DRX cycle (DRX period) by referencing the correspondence table. It is desirable that, for a higher DRX level, the length of the non-reception period in the DRX cycle be less than the length of the reception period in the DRX cycle. This correspondence is assumed in the description of the exemplary embodiment below but the exemplary embodiment is not limited to this adjustment.

The present invention provides the following methods for performing DRX control.

(I) Set the DRX cycle (DRX period) and adjust the relationship between the reception period and the non-reception period.

(II) Set the reception period, and adjust the non-reception period. At the same time, vary the length of the DRX cycle (DRX period).

(III) Set the relationship between the reception period and the non-reception period, and adjust the DRX cycle (DRX period).

For each element for the Latency Context, the following describes how to determine what is the DRX level of a mobile station in the destination cell after the HO between base stations is performed.

(A) When the current DRX level (in the source cell in the requested HO) (= Old) is used as the Latency Context, New is determined from the expression (1) (see FIGURE 3).

New = Old + M (I) where M is the predefined margin that is a fixed value. In the example shown in FIGURE 3, M = 25% and, because Lviejo is 25%, New = 50%.

(B) When the current DRX residence time T and the current DRX level are used as the Latency Context, New is determined from the expressions (2) and (3) (see FIGURES 4A and 4B).

New = Old + M_T

- (2) (7 ^ r₀)

M2 (T &lt;7₀)

- (3) where M1 and M2 are predefined margins and M1 &lt;M2. T0 is a threshold to select one of the predefined margins.

If the current DRX residence time T is greater than or equal to the threshold time T0, the margin MT is set to M1; if T is less than Το, Μγ is set to M2. New is the value generated by adding Μγ to Old · (C) When the average DRX level (= Lmed) in the source cell is used as the Latency Context, New is determined from the expression (4).

New = Lmed + Mmed

-(4)

In this case, if an integer value is used as the DRX level, Lmed is an integer greater than or equal to (or less than or equal to)

<img file="ES2733007T3_D0003.tif" />

-(5)

ES 2 733 007 T3 and is closer to that value, and Mave is the predefined fixed margin.

(D) When the maximum DRX level (= Lmax) in the source cell is used as Latency Context, New is determined from the expression (6).

New = Lmax + Mmax

- (6) where Mmax is a predefined margin that is fixed.

(E) When the minimum DRX level (= Lmin) in the source cell is used as Latency Context, New is determined from the expression (7).

New = Lmin + Mmin where Mmin is a predefined margin that is fixed.

(F) When the storage size or temporary transmission memory (Salm) of the originating base station in the HO preparation period in the origin cell is used as Latency Context, New is determined based on the relationship between K thresholds and K-1 levels of DRX defined in advance as shown in expression (8) (see FIGURES 5A and 5B).

-(8)

In the example in FIGURE 5A, because the size of the storage or temporary transmission memory Salm of the home base station in the HO preparation period in the source cell is S1 &lt;Salm &lt;S2, when Lviejo is the 25%, we have

New ⁼ 50% from the correspondence table between the thresholds of the storage or temporary memory and New shown in FIGURE 5B. The correspondence table between the thresholds of the store or temporary memory and New is maintained in a memory (for example, a rewritable nonvolatile memory) that can be referenced by the controller at the base station.

(G) When the programming time in the source cell / residence time RRC_Connected in the source cell (RORI) is used as Latency Context, New is determined based on the relationship between K thresholds and K-1 levels of DRX defined in advance as shown in expression (9).

L NEW - *

<img file="ES2733007T3_D0004.tif" />

- (9) (H) When two or more elements (J) described above are used as Latency Context, New is determined from the expression (10).

ES 2 733 007 T3

<img file="ES2733007T3_D0005.tif" />

... (10) where wj is the weight in New, J, determined from the Latency Context of order j, and satisfies the following relationship.

...(11)

The following describes some examples.

«First exemplary embodiment&gt;

FIGURE 6 and FIGURE 7 are diagrams showing a first exemplary embodiment of the present invention. In the first exemplary embodiment, the current DRX cycle is used as the Latency Context, and the DRX level of the mobile station in the HO termination period in the destination cell is determined by the use of the expression (12) shown below (the same as the expression (1) shown above).

New = Old + M

...(12)

In this example, M = 0, that is, the DRX level in the destination cell in the HO termination period is set to the same state as that of the DRX level in the source cell immediately before the start of the HO operation.

In this example, the DRX level of the mobile station is called as follows.

"Active" when the DRX level is 100% "DRX Short" when the DRX level is 60% "Long DRX" when the DRX level is 20% "Inactive" when the DRX level is 0%

As described above, a DRX level of less than 100%, for example 90%, can be defined as “Active”. For example, the ratio of the non-reception period of the “Short DRX” in the DRX cycle is set shorter than the non-reception period of the “Long DRX”.

Suppose there are four cells, 1, 2, 3, and 4, and that the cells and base stations are related in such a way that cells 1, 2, 3, and 4 are managed respectively by the base stations 1, 2, 3, and 4.

Also suppose that the mobile station performs an HO in cells, 1, 2, 3, and 4 in this order and that, in cells 2, 3, and 4, the mobile station performs a data transmission / reception only for the HO operation.

Assume that the change in the DRX level in the present invention is as shown in FIGURE 6 when the mobile station, which is under the control of the DRX operation, performs an HO between base stations.

In the initial state, suppose that the mobile station that is moving fast resides in cell 1 and that the DRX level is DRX Long. When an HO is performed between base stations to cell 2, this base station becomes Active and performs the HO operation.

Because the DRX level of the mobile station in the destination cell in the HO termination period is set equal to the DRX level in the source cell in this example, the DRX level of the mobile station in the cell 2 in the HO termination period is determined DRX Long which is the same level of DRX as that in cell 1.

In the HO termination period, base station 2 transmits a signal (Early DRX Control Signaling), which instructs the mobile station to transit Long DRX, to the mobile station and initiates the station's DRX control mobile immediately after completion of the HO.

The mobile station performs an HO from cell 2 to cell 3 and from cell 3 to cell 4. In this case, as in the HO from cell 1 to cell 2, each base station immediately instructs the station mobile for

ES 2 733 007 T3 transits to DRX Long in the period of termination of HO and starts the control of DRX. This reduces the extra power consumption of the mobile station in the cell after HO.

FIGURE 7 shows the DRX residence time of a mobile station for 30 minutes on the assumption that the transition time from Active to DRX is one minute and the mobile station transmits and receives data intermittently during the 30 minutes. Because the time required for the HO, several 10 milliseconds, is so much shorter than the cell stay time that this time is ignored in the calculation.

It is assumed that the frequency of data transmission / reception of the mobile station is not so high in the HO destination that the mobile station can remain in the DRX (the mobile station does not need to remain Active). It is also assumed that, in each cell, the mobile station moves through the center of the cell and moves the distance equal to the diameter of the cell. A model is assumed in which the cells are adjacent to each other and the mobile station moves in a straight line at a uniform speed along the diameters of the multiple cells.

In the case where the present invention is used, the DRX level of the mobile station is changed to a DRX level equal to that at the origin level, immediately after the termination of the HO (for example, in several milliseconds) .

For example, when the movement speed of the mobile station is 120 km / h and the diameter of the cell is 12 km in FIGURE 7, the time that the mobile station resides in each cell is 6 minutes, an HO is performed 4 times , and the mobile station resides through 5 cells.

In the example shown in FIGURE 13, the transition from Active to DRX is triggered by the time limit in the timer that the base station has, as described above, and therefore the 30-minute DRX residence time is 25 (= (6-1) x 5) minutes.

On the contrary, because the mobile station can transit to the DRX in the HO termination period in this example, the residence time of DRX for 30 minutes is 29 minutes, which is the sum of 5 (= 6-1 ) minutes during which the mobile station resides in the first cell and 24 (= 4x6) minutes during which the mobile station resides in the cells after HO.

As a result, the DRX stay period of the present invention is four minutes longer than that (25 minutes) in the exemplary embodiment shown in FIGURE 13. And, the power consumption of the mobile station can be decreased in proportion to an increase in the period of stay of DRX.

On the other hand, when the movement speed is 60 km / h and the diameter of the cell is 1 km, the mobile station resides in each cell for one minute, the HO is done 29 times, and the mobile station resides through 30 cells.

Because both the residence time in each cell and the transition time from Active to DRX are one minute in the example shown in FIGURE 13, the mobile station does not travel to DRX for 30 minutes. That is, the mobile station remains Active for 30 minutes.

On the contrary, the mobile station may transit to DRX (for example Long DRX), immediately after the termination of the HO in this example and, in each cell, the mobile station may remain in DRX after the HO. For this reason, for 30 minutes, the mobile station can reside in DRX for a maximum of 29 minutes which is the sum of 0 (= 1-1) minutes during which the mobile station resides in the first cell and 29 (= 1 x 29) minutes during which the mobile station resides in the cells after HO.

As a result, the period of stay of DRX according to the present invention is 29 minutes longer than that in the case shown in FIGURE 13, thus also reducing the power consumption of the mobile station.

&lt;Second Exemplary Embodiment&gt;

FIGURE 8 and FIGURE 9 are diagrams showing a second exemplary embodiment of the present invention. As the second exemplary embodiment of the present invention, the following describes a case in which the current DRX level Lviejo and the residence time at the current DRX level T are used as Latency Context to determine the DRX level of the mobile station in the period of termination of HO in the destination cell by using the expressions (13) and (14) (the same as the expressions (2) and (3)).

New = Lviejo + Mt

...(13)

ES 2 733 007 T3

ME

M2 (T &lt;7₀)

- (14) where Το is a predefined threshold, and Μγ is a margin. Assume that M1 = -40% and M2 = 0% and that the value of the DRX level, if negative, is replaced by 0.

In this example, the DRX level of the mobile station is called as follows:

“Active” when the DRX level is 100%;

“DRX Cuts” when the DRX level is 60%;

“Long DRX” when the DRX level is 20%; and “Inactive” when the DRX level is 0%

As described above, a DRX level of less than 100%, for example 90%, can be defined as “Active”. For example, the ratio of the non-reception period of the “Short DRX” in the DRX cycle is set shorter than the non-reception period of the “Long DRX”.

Assume that the cells and base stations are related in such a way that cells 1,2, 3, and 4 are managed respectively by base stations 1,2, 3, and 4 and that, in cells 2, 3, and 4, the mobile station performs a data transmission / reception only for the HO.

Assume that the change in DRX level in this example is as shown in FIGURE 8 when the mobile station performs an HO between base stations.

In the initial state, suppose that the mobile station that is moving fast resides in cell 1 and its DRX level is Long DRX. Let's also assume that the time Ti, during which the mobile station remains in Long DRX in cell 1, is greater than or equal to To.

When an HO is performed between base stations to cell 2, this mobile station transits to Activa and performs the HO.

In this example, the DRX level of the mobile station in the destination cell in the HO termination period is the value generated by adding the margin to the DRX level in the source cell. Therefore, the level of DRX Lnew, 2 of the mobile station in cell 2 in the HO termination period is calculated by adding the margin Mt = Mi = -40% to the Lviejo level, i = 20% in cell 1 . This calculation gives 0% (the actual value is -20%, and the negative value is replaced by 0) and determines that the mobile station will transit to the Inactive state.

In the HO termination period, base station 2 transmits a signal (Early DRX Control Signaling) to the mobile station to instruct it to transit to the Inactive state.

The transition from the mobile station to the Inactive state eliminates the need for the mobile station to sequentially perform an HO from cell 2 to cell 3 and from cell 3 to cell 4, thereby reducing the extra power consumption of the station mobile.

Another advantage is that the network (NW) can avoid an increase in the load that will be caused by an unnecessary repeated HO of the mobile station.

FIGURE 9 shows the number of times the mobile station repeats an HO until the mobile station transits to Inactive in the event that the transition time from Active to Long DRX is one minute and the transition time from Long to Inactive DRX It's five minutes.

The time required for the HO, several 10 milliseconds, is much shorter than the time spent in the cell that is neglected in the calculation.

It is assumed that, in the initial state, the DRX level is Long DRX in a cell where the mobile station resides first, the mobile station definitely performs the HO to the next cell, and the observation time is 30 minutes.

It is also assumed that the mobile station moves through the center of each cell and moves the distance equal to the diameter. When the present invention is applied, the DRX level is determined to be the value, generated by adding the margin to the DRX level equal to that in the source cell, immediately after the termination of the HO (for example, several milliseconds).

ES 2 733 007 T3

In this example, if the maximum DRX stay time is less than five minutes, the mobile station remains in Long DRX and, if the maximum DRX stay time is greater than or equal to five minutes, a negative margin is added to make to the mobile station, go to the Inactive state (RRC_Idle).

In FIGURE 9, when the movement speed of the mobile station is 120 km / h and the cell diameter is 12 km, the time that the mobile station resides in each cell is six minutes. The mobile station performs an HO once only for the first time and thus the mobile station resides through two cells.

In the related technique, the transition from Active to Long DRX or from Long to Inactive DRX is triggered when the base station timer has timed out. Therefore, the mobile station transits to DRX Larga in one minute in the second cell and, after that, transits to Inactive in five minutes.

In the present invention, because the mobile station transits to DRX Long in the period of termination of HO and, after that, transits to Inactive in five minutes, the HO is performed once as in the related technique.

It takes a minute for the mobile station to travel to DRX Larga in the example shown in FIGURE 13, while the mobile station in this example transits to DRX Long without waiting a minute but as short as several milliseconds. This reduces the power consumption of the mobile station.

Then, when the movement speed is 60 km / h and the diameter of the cell is 1 km, the time spent in each cell is one minute.

Because the next HO is performed before the mobile station transits to DRX Long in the example shown in FIGURE 13, the mobile station repeats the HO for 30 minutes of the observation time, with the result that the HO is repeated 29 times

On the contrary, because the mobile station is allowed to transit Long DRX immediately after the first HO (for example, in several milliseconds) in this example, the Long DRX stay time is added, even if the HO is repeated . After the HO is repeated five times, the mobile station transits from Long to Inactive DRX.

As a result, the present invention reduces the number of HO operations by 24 compared to the example shown in FIGURE 13, reduces the power consumption of the mobile station, and reduces the network load (NW).

As described above, the present invention avoids extra power consumption in the HO between base stations of a mobile station performing the DRX operation and an increase in the NW load.

In addition to those described above, the maximum storage time or temporary transmission memory of the originating base station, the storage size or average temporary memory of the base station of the originating cell, and so on can be used as the Context of Latency The storage size or average temporary memory of the base station of the source cell and so on are calculated either from the result of the monitoring of the storage size or temporary transmission memory obtained through a periodic polling or at from a result of recording the storage size or temporary transmission memory based on the generation of an event in the time data that is accumulated in the storage or temporary memory of transmission.

The method described below can be used to perform DRX control in the target cell after HO (see FIGURE 10).

When a mobile station and a base station have established the RRC connection (RRC_Connected state) but the mobile station does not perform a data transmission / reception for a predetermined time TD, the DRX level of the mobile station is decreased as shown by the expression (15).

Lnew = Lviejo - Δ L

...(15)

On the contrary, when a mobile station continues the transmission / reception of data for a predetermined time TU, the DRX level of the mobile station is increased as shown by the expression (16).

ES 2 733 007 T3

New = Old + Δ L

...(16)

To implement this DRX control, one of the following two methods can be used.

- The base station determines the NEW and informs the mobile station of the New.

- The base station informs the mobile station of the DL, TU, and TD, and the base station and the mobile station each determine the New.

This DRX control method is applicable not only to a mobile station that has performed an HO but also to mobile stations that reside in a cell.

Although the transition time from Active to Long DRX is assumed to take a minute in the previous example, the effect of the present invention becomes more remarkable since the transition time from Active to Long DRX becomes longer. In the present invention, if a mobile station initiates a continuous reception on the downlink but no data is transmitted during a predetermined period, there is a case in which the mobile station does not enter DRX (discontinuous reception), but transits to the state RRC_IDLE

FIGURE 14 is a diagram schematically showing an example of the configuration of a base station in the example shown in FIGURE 1 and FIGURE 2. Because the origin base station (101) and the destination base station (102 ) in FIGURE 1 and FIGURE 2 have the same configuration, FIGURE 14 shows the configuration of the home base station only. With reference to FIGURE 14, the home base station comprises a radio (RF) unit 105 having a transmission unit and a receiving unit not shown, a baseband unit 106 which performs a baseband processing, a encoding / decoding unit (CODEC) 107 which encodes transmission data and decodes reception data, a control unit 108, a transmission / reception unit 109 that communicates with a destination base station via a wired line, a DRX controller 110 that derives a DRX level, a storage unit or temporary memory 111, an encoding / decoding unit 112 which encodes a control signal to be transmitted and decodes a received control signal.

The control unit 108 comprises a programmer 108-1 that controls the operation of the encoding / decoding unit (CODEC) 107 and the DRX controller 110 and a controller 108-2 that controls the transmission / reception unit 109. The storage or temporary memory unit 111 comprises a storage or transmission memory (not shown) in which the transmission data is accumulated and a temporary storage or reception memory (not shown) in which the reception data is accumulated. The DRX controller 110 monitors the accumulated data in the storage or temporary storage memory of the storage unit or temporary memory 111, derives the Activity level of a mobile station and, as described above, derives a DRX level that has the correlation with the level of Activity itself or with the level of Activity obtained from the operation for the level of Activity. Programmer 108-1 notifies the DRX 110 controller when to monitor the storage or temporary transmission memory.

When a DRX level is acquired from the DRX 110 controller, the 108-2 controller performs the DRX to transmit the signal (DRX Control Signaling) to the mobile station. The control signal of the control unit 108 is encoded by the encoding / decoding unit 112 to generate a control signal corresponding to the DRX Control Signaling and, after the baseband processing is performed, the signal Control is transmitted by radio to the mobile station from the radio unit 105. Controller 108-2 transmits not only a Latency Context that includes the level of DRX received from the DRX 110 controller but also Context Data that includes the QoS Profile and AS Configuration to the destination base station through the transmission / reception unit 109. In addition, when a signal (Confirm Context, Completed HO, etc.) is received from the destination base station through the transmission / reception unit 109, controller 108-2 informs programmer 108-1 of the received signal and , when the corresponding event is generated, programmer 108-1 schedules the next processing.

In the present invention, a portable 3GPP LTE terminal can be used as a mobile station. As described above, either the side of the base station can detect the Activity level of a mobile station and derive the DRX level or the side of the mobile station detects the Activity level of the mobile station and informs the station base of the level of activity detected. FIGURE 15 is a diagram showing an example of the configuration of a mobile station in an example of a communication terminal of the present invention. With reference to FIGURE 15, an Activity level controller (Activity Level CTRL) 126 of the mobile station (communication terminal) 103 monitors the accumulator status of the storage or temporary transmission memory of a storage unit or memory Temporal 124 and calculate the Activity level. A control unit 125, comprising a programming unit not shown, controls the monitoring of the accumulation state of the storage or temporary transmission memory of the storage unit or temporary memory

ES 2 733 007 T3

124. The Activity level can be transmitted to the base station, for example, as the control signal to allow the base station to derive the DRX level based on the Activity level, received from the mobile station, and to perform the control of DRX In the period of non-reception of the DRX cycle, the mobile station 103 inactivates the RF receiving unit (not shown) of an RF unit 121. The description of a baseband unit 122, CODEC units 123 and 127, etc., is omitted.

FIGURE 16 is a diagram showing an example of the configuration of a mobile station in another example of a communication terminal of the present invention. The mobile station (communication terminal) in this example comprises a DRX level controller (DRX Level CTRL) 128 instead of the Activity level controller shown in FIGURE 15. The DRX level controller 128 monitors the accumulation status of the storage or temporary transmission memory (not shown) of the storage unit or temporary memory 124 to calculate the Activity level and derives the DRX level according to the Activity level. The mobile station autonomously performs DRX control according to the level of acquired DRX. When it is transferred to the DRX control, the mobile station transmits a control signal to the base station to inform it about the DRX level and the start of the DRX control, and the base station records and manages the start of the DRX control.

Next, as another example of the present invention, the following describes an example of a mobile station compatible with the dual LTE operation of 3GPP and WCDMA (Multiple Broadband Code Division Access). FIGURES 17A and 17B are diagrams schematically showing another example of the present invention. FIGURE 17B is a diagram showing the latency control unit configuration of a base station control station (RNC: also called "Radio Network Controller") 4 shown in FIGURE 17A. At least one Latency Context is transferred from a first LTE 1 base station to a second LTE 2 base station to allow the second LTE 2 base station to immediately perform DRX control according to the level of DRX that has been used by the first base station of LTE 1. When a transfer is made from the second LTE 2 base station to a WCDMA 5 base station, at least one Latency Context is transferred from the second LTE base station 2 to the base station control station (RNC) 4 and the DRX level is transmitted from the base station control station 4 to the base station 5 to allow the WCDMA 5 base station to perform the DRX control of a mobile station 3 according to the activity status of the mobile station of that mobile LTE station of the 3GPP before handover. As shown in FIGURE 17B, the base station control station 4 comprises a Latency Control relay unit 44 that receives the Latency Context from the LTE base station through a transmission / reception interface 41 and transmits to the WCDMA 5 base station, which is under the base station control station 4, through a transmit / receive interface 42.

It is possible, as a matter of course, to apply the present invention to a handover between WLAN access points (APs) and a handover between WiMAX base stations (Wireless Microwave Access Interoperability).

The present invention is also applicable to the control of the discontinuous reception of a first node when a transition from a state occurs, in which the first node and the second node that can perform radio communication with each other are relatively mobile and the second node manages the first node, to a state in which the first node and a third node that can perform radio communication with each other (the third node can communicate with the second node) are relatively mobile and the third node manages the first node.

FIGURE 19 is a diagram showing a transfer flow between base stations in a modification of an exemplary embodiment of the present invention. In the exemplary embodiment shown in FIGURE 1, the destination base station 102 transmits the handover termination signal (HO Completed) to the originating base station 101 and, after that, transmits the start control instruction signal of DRX (Early DRX Control Signaling) to mobile station 103. Instead of transmitting this signal (Early DRX Control Signaling), it is also possible to transmit DRX control information to mobile station 103, as shown in FIGURE 19, including DRX control information (for example, contents equivalent to the contents of the Early DRX Control Signaling such as the DRX level or the DRX cycle) in a signal (Context Confirmation), transmitted from the destination base station 102 to the home base station 101, and in a command (HO command) transmitted from the home base station 101 to the mobile station 103. That is, when the Context Data is received from the source base station 101 in FIGURE 19, the destination base station 102 executes DRX selection processing (DRX Selection) based on the Latency Context included in the Data. Context and transmits the selected DRX control information (New DRX control information) to the originating base station 101 through the signal (Confirm Context). The source base station 101 transmits the DRX control information (New DRX control information) to the mobile station 103 via a command (HO command). The mobile station 103, which has received the signal (HO command) transmits a signal (HO confirmation) to the destination base station 102 and, immediately after the response indicating that a signal is correctly received (HO confirmation) is returned from the destination base station 102, starts the DRX.

To allow adequate consumption of the mobile station battery, the DRX in E-UTRAN (Evolved UTRAN) has the following features.

ES 2 733 007 T3

There is no sub-state of RRC and MAC (Media Access Control) to distinguish between different levels of DRX.

The DRX values ​​that can be used are controlled by the network (NW) and are present for x seconds from the non-DRX state. The x value may be the same as the paging DRX used in LTE_IDLE (the actual values ​​will be studied in the future and not defined in this specification).

The measurement request and the reporting criteria may vary depending on the length of the DRX period. That is, a longer DRX period may correspond to a more abandoned request.

When the radio service quality (service cell) (the precise definition of radio quality will be studied in the future) is greater than a threshold, the network (NW) can transmit the threshold to the mobile station (UE) to indicate that no there is a need for the measurement of adjoining cells.

Regardless of the DRX cycle, a mobile station (UE) can use a first available RACH opportunity to transmit a measurement report (UL measurement report). Immediately after transmitting the measurement result, the mobile station (UE) can change its own DRX operation (whether the method is predefined or not by the eNB will be studied in the future).

HARQ processing with respect to uplink data transmission is independent of DRX processing. It will be studied in the future whether HARQ DL data processing is independent or not of DRX processing.

During a handover, a source eNB transfers the Latency Context to a destination eNB to optimize the continuation of the DRX control before and after the handover. The Latency Context includes at least the last DRX level and a medium / maximum / minimum DRX level in the source cell. If the UE has been at a low DRX level in the source cell, the destination eNB can also use the Latency Context also for processing to shift the status of the UE to LTE_IDLE.

In the present invention, during a handover procedure, a home base station forwards information, which represents a state of transmission and / or reception activity of a mobile station, to a destination base station directly or through a control apparatus base station that controls the destination base station; and after termination of the handover, the destination base station can perform a DRX control of the mobile station or perform a state control to make the mobile station transit to an Inactive state, while reflecting the activity status of the mobile mobile station when the mobile station was under the control of the home base station, based on the activity status information on the mobile station received from the home base station.

In the present invention, when a transfer is made between base stations, a mobile station transmits a Measurement Report to a home base station;

the originating base station transmits a signal to the mobile station to stop the DRX control of the mobile station, the signal that instructs the mobile station to transit from a DRX (Discontinuous Reception) to continuous reception or a period of no reduced reception of a DRX cycle;

the originating base station forwards a Latency Context to a destination base station, the Latency Context which is information to control the DRX of the mobile station;

the originating base station transmits a handover command (HO command), which allows a handover to the mobile station to be initiated, after receiving a notification from the destination base station indicating that handover is acceptable;

the mobile station transmits a Transfer Confirmation (HO Confirmation) to the destination base station after receiving the transfer command (HO command) from the originating base station;

the destination base station transmits a Transfer Termination (HO Completed) to the home base station; and the destination base station transmits a signal (Early DRX Control Signaling) to the mobile station after a handover termination, based on the Latency Context forwarded from the home base station, the signal indicating a start of control DRX of the mobile station.

In the present invention, by using a DRX level, which is an indicator of a reception period and a period of non-reception of a DRX cycle in a transfer request time, such as the Latency Context, the station target base can calculate a new DRX level by adding a predetermined margin to a level of

ES 2 733 007 T3

DRX on the side of the home base station, which is transferred from the home base station, and, based on the newly calculated DRX level and perform DRX control of the mobile station.

In the present invention, by using a DRX residence time, during which the mobile station has remained at the DRX level in a transfer request time, such as the Latency Context, the destination base station can calculate a new level of DRX, adding a first margin or a second margin (the second margin is larger than the first margin) to the time of stay of DRX, depending on whether the DRX stay time is equal to or longer or is shorter than a predetermined time, and perform DRX control of the mobile station, based on the newly calculated DRX level.

In the present invention, by using an average DRX level on the side of the originating base station, such as the Latency Context, the destination base station can calculate a new DRX level by adding a predetermined margin to the DRX level medium and, based on the newly calculated DRX level and perform DRX control of the mobile station.

In the present invention, by using a maximum DRX level on the side of the originating base station, such as the Latency Context, the destination base station can calculate a new DRX level by adding a predetermined margin to the DRX level maximum and perform DRX control of the mobile station based on the newly calculated DRX level.

In the present invention, by using a minimum DRX level on the side of the originating base station, such as the Latency Context, the destination base station can calculate a new DRX level by adding a predetermined margin to the DRX level minimum and perform DRX control of the mobile station, based on the newly calculated DRX level.

In the present invention, through the use of a storage size or temporary transmission memory in a period of preparation of the transfer on the side of the originating base station, such as the Latency Context, the destination base station that determines a new DRX level that corresponds to the size of the storage or temporary memory from a relationship between K, where K is an integer greater than or equal to 2, thresholds and K-1 default DRX levels for the storage size or temporary transmission memory and perform DRX control of the mobile station, based on the newly determined DRX level.

While the present invention has been described with reference to the previous examples, it is to be understood that the present invention is not limited to the configuration of the preceding examples and that those modifications that can be made by those skilled in the art are included within of the scope of the present invention.

Exemplary embodiments and examples can be changed and adjusted within the scope of all descriptions (including claims) of the present invention and is based on the basic technological concept thereof. Within the scope of the claims of the present invention, several elements described can be combined and selected in a variety of ways.

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