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

ES 2 553 333 T3

DESCRIPTION

Handover method from base station to base station, wireless 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 performs a handover between base stations from a source base station or a destination base station.

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

1. QoS Profiles (SAE Carrier QoS Profiles (System Architecture Evolution))

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

Also, when the source base station is transmitting downlink data, the source base station performs data forwarding that transfers unsent data 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 scheduling information from the destination base station. After that, the mobile station adjusts the transmission timing according to the acquired TA and transmits an "HO Confirmation", which is a control signal to notify that the mobile station has made the handover to the destination base station, at the assigned time and frequency.

In LTE, a study is also being carried out 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 DRX control of entire mobile stations in a cell managed by the base station, and a mobile station performs discontinuous reception at a specified periodic interval (also called "DRX cycle" or "DRX period"). by the base station. A DRX cycle (DRX period) includes a receive period during which data is continuously received and a non-receive period during which no data is 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], <Internet URL http://www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_56bis/Documents/R2-070088.zip>

Document WO 2006/018670 A1 describes a method to support handover of a mobile station from a first radio access unit of a wireless communication network to a second radio access unit of a wireless communication network, wherein the mobile station transmits information about its activity status to the second radio access unit when it is to be handed over to the second radio access unit to improve a context handover in the event of a handover of the mobile station.

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

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

Therefore, in view of the problems described above, it is an object of the present invention to provide a communication method, system, base station, and terminal for saving power of a mobile station when handover control and handover control are combined. DRX.

It is another object of the present invention to provide a communication method, system, base station, and terminal to allow the suppression of an increase or decrease in a load on one side of the network involved in the control of

ES 2 553 333 T3 handover.

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, having the following general configuration.

Specifically, the present invention provides a mobile station as defined by claim 1 and a method as defined by claim 3.

In a handover method between base stations and a radio communication system of the present invention, a source base station (source eNB) forwards a Latency Context to a destination base station (destination eNB) during a handover to optimize performance. 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 a DRX check of the mobile station.

If the mobile station (User Equipment: UE) has stayed in a long DRX cycle in the source cell, the destination base station (destination eNB) can use Latency Context also for processing to move the state 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 level (Discontinuous Reception) 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 source base, a maximum DRX level during management by the source base station, a minimum DRX level during management by the source base station, a buffer size or transmit buffer in the HO setup period, and a scheduling time at the source base station / RRC_Connected status time at the source base station

A source base station and a destination base station in the present invention may 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 check more quickly. As a result, the reduction of the power consumption of the mobile station can be achieved.

The present invention also enables a low activity mobile station to transition to an Idle 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 on 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 handover flow between base stations in an exemplary embodiment of the present invention.

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

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

FIGURES 4A and 4B are diagrams 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 5A and 5B are diagrams 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.

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

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

FIGURE 10 is a diagram for explaining a control of the activity level of a mobile station in a

ES 2 553 333 T3 exemplary embodiment of the present invention.

FIGURE 11 is a diagram for explaining a handover flow between base stations.

FIGURE 12 is a diagram for explaining an activity level control of a mobile station in an example.

FIGURE 13 is a diagram for explaining an operation of a mobile station in an example.

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 for explaining an HO in another example of the present invention.

FIGURE 18 is a diagram to explain a XRD cycle.

FIGURE 19 is a diagram for explaining a handover 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 but is not limited thereto.

As an example of DRX (Discontinuous Receive) control on handover (abbreviated "HO"), a base station changes the parameters (see FIGURE 18) related to a DRX cycle, such as the period of no reception, depending on the status 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 indicating a rate (degree) of Activity, the indicator such as an "Activity level" can be used. According to this level of activity, the ratio of the time (Ts), during which data is accumulated in the buffer or transmission buffer, to a predetermined period (T) ((Ts / T) x 100 (%) can be used 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 has a correlation 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 can 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 XRD 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 XRD level. A XRD level can be represented as a percentage (%). In this case, although a discrete value (eg, 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 center values ​​can be used as XRD levels.

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

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

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

For example, a method is known in which a mobile station, for which a long period of no reception is configured by DRX control, ignores the currently configured DRX control and transitions to 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 no reception is configured, performs an HO, while remaining in the state in which the short no-reception period is configured (for example, see Non-Patent Document 2). However, a practical method for implementing 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.

ES 2 553 333 T3

The uplink scheduling information (UL assignment) is transmitted from the home base station to the mobile station. The mobile station that will perform an HO between base stations transmits a Measurement Report in adjoining cells of the originating cell, in which the mobile station resides, to the originating base station.

The originating base station transmits a signal (DRX Control Signaling), which instructs the mobile station to move from DRX (Discontinuous Reception) operation to 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 sequence operation example in FIGURE 11, the base station receiving the Measurement Report does not You need to always output 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 source 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), indicating 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) through a RACH which is an uplink channel, and acquires the transmission timing adjustment value (Timing Advance: TA) and the uplink scheduling 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 value (TA) received from the destination base station, to inform the base station destination that the mobile station has performed the handover

The destination base station, which has received the HO Confirmation from the mobile station, transmits a control signal (HO Completed) to the origin base station to inform that the handover has been completed, notifies the MME (Management Entity of Mobility) / UPE (User Plane 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 MME / UPE) , and completes the HO operation between base stations. Note that, at this point in time, the mobile station is still in Active operation.

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

The uplink scheduling information (UL assignment: time and frequency assignment information) is transmitted from the destination base station to the mobile station to enable the mobile station to transmit data (UL data transmission), if required. 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 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. A mobile station is supposed to move through the center of each cell and move 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 idle state where the DRX level is 0% is the RRC_Idle (LTE_Idle) state.

In the description below, a model proposed by 3GPP LTE is used as an example where 100% of the DRX level is 100% of the Activity Level. When a frame includes 10 TTIs (Transmission Time Slots), a mobile station whose DRX level is 100% (i.e. Active operation) monitors the downlink (DL) signal (demodulates a control channel) on each TTI. On the other hand, a mobile station whose level

ES 2 553 333 T3 of DRX is 20% monitors the DL signal only in the two continuous TTIs of the 10 TTIs but not in the remaining eight TTIs which are periods of no reception. It is of course possible to define a XRD level value smaller than 100%, eg 90% or 95%, as "Active".

In the example in FIGURE 12, cell 1 is managed by base station 1, and cells 2, 3, and 4 are managed respectively by base stations 2, 3, and 4. We also assume that the mobile station performs the data transmission / reception only for HO operation in cells 2, 3, and 4. The change in 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 transmit / receive data immediately after the HO, the base station 2 changes the state of the mobile station from Active to DRX after a timeout of one hour occurs. timer, which corresponds to the Active to DRX transition time. After that, the mobile station performs an HO from cell 2 to cell 3, to cell 4, and then to cell 5, one after another, and in that case, the operation is performed in the same way than when the mobile station performs an HO from cell 1 to cell 2.

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

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

In FIGURE 13, it is assumed that the mobile station's data transmission / reception frequency is not so high that the mobile station can stay in DRX (the mobile station need not stay 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 moving speed of the mobile station is 120 km / h (2 km / minute) and the cell radius 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 performed 4 times.

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

As a result, in 30 minutes, the mobile station stays 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 dwell time in each cell and the transition time from Active to XRD are both 1 minute and therefore the station mobile does not transit 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 on a target 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 time of stay 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 is unable to transition to DRX in the cell and consumes extra power as a result.

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 transition the mobile station to the RRC_Idle state, repeats an unnecessary HO. Such wasteful HO will lead to higher network load (base station, UPE / MME) than it is supposed to be, and thus there is room for improvement.

An exemplary embodiment in another aspect of the present invention is that the DRX control of a mobile station,

ES 2 553 333 T3 that is performed in a destination cell after an HO between base stations, starts at the same time that the HO is completed. By doing so, the exemplary embodiment prevents the mobile station from consuming extra power in the destination cell and avoids the repetition of an unnecessary HO, thereby reducing the load on the network. 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, but not limited thereto.

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 the system configuration .

An originating base station (101) transmits uplink scheduling information (UL assignment) to a mobile station (103) and, before conducting an HO between base stations, the mobile station (103) first transmits a Measurement Report in the adjoining cells of the home 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 source base station (101) transfers a Latency Context as well as a QoS Profile and AS Configuration from 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 source 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 source base station (101), the mobile station (103), accesses the destination base station (102) through the RACH (Random Access Channel), which is an uplink channel, to acquire the transmission timing setting value (Timing Advance: TA) and the uplink scheduling 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 assigned time and frequency 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 origin base station (101) and notifies an MME / UPE (104) that the mobile station (103), which performed the HO between stations base, it has been moved to the cell managed by the destination base station 102 (update from UE to MME / UPE) and after that completes 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 at the mobile station in the source cell and has been transferred from the home base station (101),

QoS profile;

AS configuration;

Latency Context;

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

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

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

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

(A) Current XRD level;

(B) Time spent at current DRX level (C) Average DRX level in source cell (D) Maximum DRX level in source cell (E) Minimum DRX level in source cell (F ) Buffer size or transmission buffer in HO preparation period (G) Programming time in source cell / RRC_Connected dwell time in source cell

Although the XRD cycle (XRD period) is defined according to a XRD level in this exemplary embodiment, the length

ES 2 553 333 T3 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 DRX levels and the DRX cycles (DRX periods) in a base station or mobile station can be provided to determine the DRX cycle (DRX period) by referencing the correspondence table. . It is desirable that, for a higher XRD level, the length of the non-reception period in the DRX cycle is less than the length of the reception period in the XRD cycle. This correspondence is assumed in the description of the exemplary embodiment below but the exemplary embodiment is not limited to this setting.

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

(I) Set the XRD cycle (XRD 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 XRD cycle (XRD period).

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

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

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

Lnew = Lold + M

... (1) where M is the predefined margin which is a fixed value. In the example shown in FIGURE 3, M = 25% and, since Lold is 25%, Lnew⁼ 50%.

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

Lnew = Lold + M_T

- (2) 'Ml

M2 (T &lt;7₀)

... (3) where M1 and M2 are predefined margins and MKM2. To 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 To, the margin Mt is set to M1; if T is less than To, Mt is set to M2. Lnew is the value generated by adding Mt to Lold- (C) When the mean XRD level (= Lmed) in the source cell is used as the Latency Context, Lnew is determined from expression (4).

Lnew = 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)

ΕςΜ / ς ^

... (5) and is closer to that value, and MAVE is the predefined fixed margin.

ES 2 553 333 T3 (D) When the maximum XRD level (= I_max) in the source cell is used as Latency Context, Lnew is determined from expression (6).

Lnew = Lmax + Mmax

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

(E) When the minimum XRD level (= I_min) in the source cell is used as Latency Context, Lnew is determined from expression (7).

Lnew = Lmin + Mmin

.. (7) where Mmin is a predefined margin that is fixed.

(F) When the transmit buffer size (Salm) of the originating base station in the HO preparation period in the originating cell is used as Latency Context, Lnew is determined based on the relationship between K thresholds and K-1 levels of XRD defined in advance as shown in expression (8) (see FIGURE 5A and 5B).

L EGG

<td>TO-</td><td></td>

<td></td><td> (0&lt;</td>

<td> . 4.</td><td>(χ., = θ)</td>

...(8)

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

Lnew ⁼ 50% from the table of correspondence between buffer thresholds and Lnew shown in FIGURE 5B. The mapping table between buffer thresholds and Lnew is maintained in a memory (eg, rewritable non-volatile memory) that can be referenced by the controller at the base station.

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

(^ 1 &lt;^ ori - ^ 2) (0 &lt;R_{or /} &lt;2? I)

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

^L NEW = * ^L NEW, J + M

...(10)

TO.

ES 2 553 333 T3 where Wj is the weight in Lnew, j, determined from the Latency Context of order j, and satisfies the following relation.

<img file="ES2553333T3_D0001.tif" />

The following describes some examples.

<First Exemplary Realization>

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 using expression (12) shown below. (the same as expression (1) shown above).

Lnuevo - Lviejo + 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 initiation. HO operation.

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

"Active" when the DRX level is 100% "Short DRX" 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 XRD level less than 100%, eg 90%, can be defined as "Active". For example, the ratio of the “Short DRX” non-reception period in the DRX cycle is set shorter than the “Long DRX” non-reception period.

Suppose that 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 base stations 1, 2, 3, and 4.

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

Suppose 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 the fast moving mobile station resides in cell 1 and 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 Long DRX which is the same DRX level 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 transition to Long DRX, to the mobile station and initiates DRX control of the station. mobile immediately after the termination 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 gives instructions to the station mobile to transition to Long DRX in the HO termination period and initiates DRX control. This reduces the extra power consumption of the mobile station in the cell after HO.

FIGURE 7 shows the DRX dwell time of a mobile station for 30 minutes assuming the transition time from Active to DRX is one minute and the mobile station transmits and receives data

ES 2 553 333 T3 intermittently during the 30 minutes. Because the time required for HO, several 10 milliseconds, is so much shorter than the cell dwell time that this time is ignored in the calculation.

It is assumed that the data transmission / reception frequency of the mobile station is not so high at the HO destination that the mobile station can stay in the DRX (the mobile station does not need to stay in the 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 source level, immediately after the termination of the HO (for example, in several milliseconds) .

For example, when the speed of movement 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 across 5 cells.

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

In contrast, because the mobile station can transit to the DRX in the HO termination period in this example, the DRX stay time 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 XRD 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 XRD.

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

Because both the stay 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 transit to DRX, for 30 minutes. That is, the mobile station remains Active for 30 minutes.

On the contrary, the mobile station can transit to DRX (eg Long DRX), immediately after the termination of the HO in this example and, in each cell, the mobile station can remain in DRX after the HO. For this reason, for 30 minutes, the mobile station can reside in DRX for the 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 the HO.

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

<Second Exemplary Realization>

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 where the current DRX level Lviejo and the dwell time at the current DRX level T are used as Latency Context to determine the DRX level of the mobile station in the HO termination period in the destination cell using expressions (13) and (14) (the same as expressions (2) and (3)).

Lnuevo - Lviejo + M_T

... (13) # 2 (T &lt;T₀)

<img file="ES2553333T3_D0002.tif" />

...(14)

ES 2 553 333 T3 where To is a predefined threshold, and Mt is a margin. Suppose that M1 = -40% and M2 = 0% and that the value of the XRD level, if negative, is replaced by 0.

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

“Active” when the XRD level is 100%;

“Short XRD” when the XRD level is 60%;

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

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

Suppose that 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.

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

In the initial state, suppose the fast moving mobile station resides in cell 1 and its DRX level is DRX Long. Also suppose that the time T1, during which the mobile station remains in Long DRX in cell 1, is greater than or equal to T0.

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

In this example, the mobile station's DRX level 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 DRX level Lnew, 2 of the mobile station in cell 2 in the HO termination period is calculated by adding the margin Mt = M1 = -40% to the level Lold, 1 = 20% in cell 1 . This calculation returns 0% (the actual value is -20%, and the negative value is replaced by 0) and determines that the mobile station will transition to the Idle state.

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

The transition of the mobile station to the Idle 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 load that will be caused by repeated unnecessary HO from the mobile station.

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

The time required for HO, several 10 milliseconds, is so 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 applying the present invention, the XRD level is determined to be the value, generated by adding the margin to the XRD level equal to that in the source cell, immediately after the termination of the HO (eg, several milliseconds).

In this example, if the maximum DRX stay time is less than five minutes, the mobile station stays 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 the mobile station transiting to the Idle state (RRC_Idle).

In FIGURE 9, when the speed of movement 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

ES 2 553 333 T3 only the first time and thus the mobile station resides through two cells.

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

In the present invention, because the mobile station transitions to Long DRX in the HO termination period and thereafter transitions to Idle in five minutes, the HO is performed once as in the related art.

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

Then, when the speed of movement 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 transitions to Long DRX 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 repeats 29 times.

On the contrary, because the mobile station is allowed to transit to 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 repeats . After the HO repeats five times, the mobile station transits from DRX Long to Idle.

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 HO between base stations of a mobile station performing DRX operation and an increase in NW load.

In addition to those described above, the maximum transmit buffer size of the source base station, the average buffer size of the source cell base station, and so on can be used as Latency The average buffer or buffer size of the source cell's base station and so on are calculated either from the transmission buffer or buffer size monitoring result obtained through periodic polling or from starting from a record result of the transmission buffer size or buffer size based on the generation of an event in the time data that accumulates in the buffer buffer or transmission buffer size. transmission.

The method described below can be used to perform XRD control on 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 lowered as shown by the expression (15).

Lnew = Lold - Δ L

...(15)

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

Lnew = Lold + Δ L. (16)

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

- The base station determines the Lnew and informs the mobile station of the Lnew.

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

This DRX control method is applicable not only to a mobile station that has performed an HO but

ES 2 553 333 T3 also to mobile stations residing in a cell.

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

FIGURE 14 is a diagram showing schematically an example of the configuration of a base station in the example shown in FIGURE 1 and FIGURE 2. Because the source 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 source base station only. With reference to FIGURE 14, the originating base station comprises a radio (RF) unit 105 having a transmitting unit and a receiving unit not shown, a baseband unit 106 that performs baseband processing, a encoding / decoding unit (CODEC) 107 which encodes transmission data and decodes reception data, a control unit 108, a transmit / receive unit 109 that communicates with a target base station over a wired line, a DRX controller 110 that derives a DRX level, a buffer or buffer unit 111, an encode / decode 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 transmitting / receiving unit 109. The buffer or buffer unit 111 comprises a transmitting buffer or buffer (not shown) in which transmission data is accumulated and a receiving buffer or buffer (not shown) in which reception data is accumulated. The DRX controller 110 monitors the data accumulated in the buffer or transmit buffer of the buffer unit 111, derives the Activity level of a mobile station, and, as described above, derives a DRX level having the correlation with the Activity level itself or with the Activity level obtained from the operation for the Activity level. The programmer 108-1 notifies the DRX controller 110 when to monitor the transmit buffer.

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

In the present invention, a 3GPP LTE portable terminal can be used as a mobile station. As described above, either the base station side can detect the Activity level of a mobile station and derive the DRX level or the mobile station side detects the Activity level of the mobile station and informs the station base of detected Activity level. 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 accumulation status of the transmission buffer or buffer of a buffer or memory unit. time 124 and calculates the Activity level. A control unit 125, comprising a programming unit not shown, controls the monitoring of the accumulation status of the transmit buffer or buffer unit 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 DRX control. In the non-reception period of the DRX cycle, the mobile station 103 inactivates the RF reception unit (not shown) of an RF unit 121. The description of a baseband unit 122, the 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 transmit buffer or buffer (not shown) of the buffer unit 124 to calculate the Activity level and derives the DRX level based on the Activity level. The mobile station performs

ES 2 553 333 T3 autonomously controls the DRX according to the level of DRX acquired. When transitioning to DRX control, the mobile station transmits a control signal to the base station to inform it of the DRX level and the start of DRX control, and the base station records and manages the start of DRX control.

Next, as another example of the present invention, the following describes an example of a mobile station that supports dual LTE operation of 3GPP and WCDMA (Broadband Code Division Multiple 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 base station 1 to a second LTE base station 2 to allow the second LTE base station 2 to immediately perform DRX control based on the dRx level that has been used by the first LTE base station 1. When handover from the second LTE base station 2 to a WCDMA base station 5, 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 allowing the WCDMA base station 5 to perform DRX control of a mobile station 3 according to the activity status of the mobile station of that 3GPP LTE mobile station 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 transmit / receive interface 41 and transmits to the WCDMA base station 5, 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 (Wireless Local Area Network) access points (AP) and a handover between WiMAX (Wireless Microwave Access interoperability) base stations.

The present invention is also applicable to the control of the discontinuous reception of a first node when a transition occurs from a state, in which the first node and the second node that can carry out 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 handover 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 completion signal (HO Completed) to the source base station 101 and thereafter transmits the control start command signal. DRX (Early DRX Control Signaling) to mobile station 103. Instead of transmitting this signal (Early DRX Control Signaling), it is also possible to transmit the DRX control information to the mobile station 103, as shown in FIGURE 19, including DRX control information (e.g. contents equivalent to the contents of Early XRD Control Signaling such as XRD level or XRD cycle) in a signal (Context Confirmation), transmitted from the destination base station 102 to the origin base station 101, and in a command (HO Command) transmitted from the origin 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 the DRX selection processing (DRX Selection) based on the Latency Context included in the Data. and transmits the selected DRX control information (New DRX control information) to the originating base station 101 via the (Confirm Context) signal. The originating base station 101 transmits the DRX control information (New DRX control information) to the mobile station 103 through 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) returned from destination base station 102, initiates DRX.

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

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

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

Measurement request and 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.

ES 2 553 333 T3

When the radio quality of service (serving 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 it does not there is a need for measurement of neighboring cells.

Regardless of the DRX cycle, a mobile station (UE) can use a first available opportunity from RACH in order 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 or not the method is predefined by the eNB will be studied in the future).

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

During a handover, a source eNB passes Latency Context to a destination eNB to optimize continuation of DRX control before and after handover. The Latency Context includes at least the latest DRX level and a mean / 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 use Latency Context also for processing to shift the UE state to LTE_IDLE.

In the present invention, during a handover procedure, an originating base station forwards information, representing a state of transmission and / or reception activity from a mobile station, to a destination base station directly or through a control apparatus. base station that controls the destination base station; and after a handover completion, the destination base station may perform a DRX check of the mobile station or perform a status check to make the mobile station transition to an Idle state, while reflecting the activity state of the mobile station. mobile station when the mobile station was under the control of the home base station, based on the activity status information at the mobile station received from the home base station.

In the present invention, when handover is performed between base stations, a mobile station transmits a Measurement Report to an originating 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 transition from a DRX (Discontinuous Reception) to a continuous reception or a period of no reduced reception of a XRD cycle;

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

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

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

the destination base station transmits a Handover Termination (HO Completed) to the origin base station; ^Y 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 originating base station, the signal indicating a start of control of DRX of the mobile station.

In the present invention, using a DRX level, which is an indicator of a reception period and a non-reception period of a DRX cycle in a handover request time, as the Latency Context, the target base station You can calculate a new DRX level by adding a predetermined margin to a DRX level on the side of the originating base station, which is transferred from the originating base station, and, based on the newly calculated DRX level and perform the DRX check of the mobile station.

In the present invention, using a DRX dwell time, during which the mobile station has remained at the DRX level in a handover request time, such as 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 DRX dwell time, depending on whether the DRX stay time is equal to or longer or shorter than a predetermined time, and perform the DRX control of the mobile station, based on the newly calculated DRX level.

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

In the present invention, using a maximum XRD level on the home base station side, such as the

ES 2 553 333 T3

Latency context, the target base station can calculate a new DRX level by adding a predetermined margin to the maximum DRX level and perform the DRX control of the mobile station based on the newly calculated DRX level.

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

In the present invention, using a transmission buffer size in a handover preparation period on the source base station side, such as Latency Context, the destination base station determines a new DRX level which corresponds to the size of the buffer or temporary memory from a relation between K, where K is an integer greater than or equal to 2, thresholds and K-1 predetermined DRX levels for the transmit buffer size 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 foregoing examples, it is to be understood that the present invention is not limited to the configuration of the foregoing examples and that those modifications that may be made by those skilled in the art are included within within the scope of the present invention.

Exemplary embodiments and examples may 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, various elements described can be combined and selected in a variety of ways.