JP4489966B2 - Adaptive location registration level - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to telecommunications systems, and in particular to paging techniques in mobile communication systems.
[0002]
[Prior art]
A mobile communication system is composed of cell areas where mobile terminals enter and exit geographically defined “cells”. Therefore, some mobile terminals may move in the cell area at a higher speed than other terminals. In other words, when used at a high speed, the cell boundary may be crossed on the order of several minutes. In addition, there may be a terminal that moves at a high speed at a certain time (such as a normal commuting time zone), but becomes less mobile after one hour.
[0003]
Mobile communication networks are designed to communicate with mobile terminals by broadcast within the cell area. That is, in this embodiment, one base station serves one cell in a geographical area, and the mobile switching center serves a base station in a predetermined area. Here, the geographical area served by the base station is determined according to the transmission distance and the characteristics of the base station in the cell. Similarly, the location registration area served by the mobile switching center is determined geographically based on the optimum traffic characteristics between the mobile switching center and the location registration area.
[0004]
The mobile switching center provides two important functions for the mobile terminal. One is that the mobile switching center records the position of the mobile terminal in the cellular area almost accurately, which makes it possible to find the mobile terminal when a call is received by the mobile terminal. One way to update location information is for the mobile terminal to periodically communicate its location to the network. Depending on the location information update interval, it is possible to determine the location of the mobile terminal almost accurately using this method, but it requires a lot of transmissions to update the location information and places a burden on system resources. Become. From this point of view, many methods have been developed for optimizing trade-offs such as improving the accuracy of location information and minimizing the location information update load.
[0005]
Another important function provided by the mobile switching center is paging. When a mobile terminal receives an incoming call, the mobile switching center transmits a page message to the mobile terminal. This process is already widely known. A paging message to a specific mobile terminal is transmitted to a location registration area defined as a plurality of cells in the vicinity of the cell in which the mobile terminal previously existed. That is, the location registration area is defined as a cell group (one or more) that can move freely without telling the network that it has moved to a new location. Therefore, the minimum area that can be recognized by the network when a certain mobile terminal is present in a certain area is the location registration area. Grouping a plurality of cells to form a location registration area for paging purposes is a known technique.
[0006]
U.S. Pat. No. 5,289,527 describes a paging technique in which all cells advertise their geographical location, and location registration of the mobile terminal is effective in an area within a certain radius from the cell location. According to this, when the mobile terminal moves to a new cell whose distance from the previously registered cell is a certain distance or more, new location registration is performed.
[0007]
In a system in which a location registration area (which may be a predetermined area or a dynamically determined area) is the smallest area where a mobile terminal can exist, The paging message is transmitted on the page channel for all cells in the location registration area. Although the page message is sent to all cells in the location registration area, the mobile terminal sends only one of these messages (one message sent to one cell where the mobile terminal actually exists). Many page messages on the paging channel are wasted because they are received. That is, since a mobile terminal exists only in one cell at a certain point, even if the network transmits a page message to all cells in the location registration area, the mobile terminal receives one page message from the network. It becomes only. All page messages transmitted to a cell in which no mobile terminal exists to page the mobile terminal is an unnecessary load on the page control channel.
[0008]
Of course, if the location registration load is increased, the paging load can be reduced. That is, if the mobile terminal frequently updates the location information, the system can grasp the exact location of the mobile terminal in units of cells, so that the paging load on unnecessary cells can be reduced. In order to transmit the paging message only to the area where the mobile terminal exists, the mobile terminal must frequently update the location information, for example, every time the mobile terminal moves to a new cell. However, a large location registration load is applied to the system. Such tradeoff between location registration cost / load and paging cost / load is described in detail in "Location Management Methods for Third-Generation Mobile Systems", IEEE Communication Magazine, August 1997. Although it is necessary to consider the trade-off between the location registration load and the paging load, in the conventional technology, in order to reduce one load (location registration load or paging load), the other load must be increased. turn into.
[0009]
However, considering the mobility of various mobile terminals, paging can be performed in a form suitable for the nature of the mobile terminal, that is, the mobility rate of the mobile terminal. From such a viewpoint, in the present invention, paging to the mobile terminal is performed at either the location registration area level or the cell area level based on the mobility rate of the mobile terminal. Although several techniques for determining the mobility rate of a mobile terminal are known, the present invention is not limited to these specific techniques. This is a technique using either paging at the location registration area level or paging at the cell level according to the mobility of a certain mobile terminal.
[0010]
Other objects and advantages of the present invention will be more fully understood from the following detailed description of the preferred embodiments and the accompanying drawings.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the present invention, it is determined how to perform paging in consideration of the mobility of various mobile terminals. Since the mobility of the mobile terminal is variable and varies from terminal to terminal, the mobility rate of each mobile terminal is first determined. The mobility rate can be easily determined by the location registration frequency performed by the mobile terminal. A mobile terminal with a high mobility rate frequently performs location registration, while a location registration frequency of a mobile terminal with a low mobility rate is low. That is, it can be determined that a mobile terminal that frequently performs location registration is moving at high speed. On the other hand, a mobile terminal that stays in the same cell for a long time and hardly performs location registration can be determined to be almost stationary.
[0012]
In the preferred embodiment of the present invention, at least two location registration levels are utilized. Location registration area level and cell area level. In the conventional location registration system, various location registration area signals are used. In the present invention, in addition to this, a cell level registration signal is used. This is a technique for selectively using paging in the location registration area and paging in the cell area depending on the mobility pattern of the mobile terminal.
[0013]
In the conventional system, both the network and the mobile terminal grasp the position of the mobile terminal. In addition to this, the preferred embodiment of the present invention uses flag information and timer information of the mobile terminal. Here, the flag is set when the mobile terminal moves to a new cell without performing location registration. That is, the mobile terminal moves to a new cell in the previously registered location registration area. The flag is reset when location registration is performed, and is performed when the mobile terminal moves to a new location registration area. On the other hand, the timer of the mobile terminal is reset when position registration is performed, and operates until a predetermined time elapses or position registration is performed. Here, the predetermined time may be provided from the network, or may be preinstalled in the mobile terminal. In addition, the network can use a regular registration timer at predetermined time intervals.
[0014]
FIG. 1 shows a general environment to which the present invention can be applied. The mobile terminal MS located in the location registration area 1 can receive various cells in the location registration area 1, namely cell 1, cell 2. . . Move cell 5. In the conventional registration system, as long as the mobile terminal stays in the location registration area 1, no location information registration is performed even if the cell in the location registration area 1 is moved. Therefore, when there is an incoming call to the mobile terminal, a page message is transmitted on the page channel to all the cells in the location registration area 1, and to the mobile terminal MS existing in any cell in the area 1 To reach. There are various methods for determining the location registration area (overlapping area, non-overlapping area, wide area, narrow area, etc.), but the smallest possible area of the mobile terminal that the network knows about Generally, it is set so that.
[0015]
When the mobile terminal moves from one location registration area to another area (for example, when the mobile terminal moves from the location registration area 1 to the location registration area 2 or from the location registration area 2 to the location registration area 3), the mobile terminal performs location update processing. I do. As a result, the network can know that the mobile terminal has moved into the new location registration area.
[0016]
FIG. 2 is a diagram illustrating a preferred embodiment of the present invention from the viewpoint of various processes executed by the mobile terminal under various circumstances. Box 10 and box 11 indicate the previous location registration level of a certain mobile terminal. Box 10 indicates a mobile terminal (terminal with high mobility) whose location information was previously registered at the location registration area level, and box 11 indicates a mobile terminal (terminal with low mobility) whose location information was previously registered at the cell level. Show. The header shown in the upper part of FIG. 2 indicates a situation detected by the mobile terminal. The header 12 indicates that the mobile terminal has moved to a new cell in the previous location registration area, as in the case of moving from cell 1 in the same location registration area 1 to cell 2 in FIG. The header 15 indicates that although the mobile terminal stayed in the same cell, the network assigned the cell to a new location registration area. That is, in FIG. 1, although the mobile terminal stayed in the cell 5, the cell 5 allocated to the location registration area 1 at the time t = t ₀ is the position at the later time t = t _1. This is the case when it is assigned to the registration area 3. The header 18 indicates that the mobile terminal has moved to a new cell in the new location registration area, as in the case of moving from the cell 4 in the location registration area 1 to the cell 7 in the location registration area 2 in FIG. Show. Finally, the header 21 indicates that a certain time has elapsed since the mobile terminal did not move to a new cell or a new location registration area.
[0017]
In FIG. 2, boxes 13, 14, 16, 17, 19, 20, 22, 23 move under various header situations 12, 15, 18, 21 depending on the previous location registration level 10, 11 of the mobile terminal. It is the table | surface which showed the process which a terminal performs. That is, the mobile terminal 10 previously registered at the location registration area level executes the following process.
[0018]
1) When the mobile terminal moves to a new cell in the location registration area so far, the mobile terminal does not perform processing (13). This is the case (12) where the mobile terminal (10) that performed the previous update at the location registration area level did not move to the new location registration area.
[0019]
2) If the mobile terminal stays in the previous cell but the cell is assigned to a new location registration area (15), the mobile terminal performs location information update processing (16). This is because, in the mobile terminal 10 that has performed the previous update at the location registration area level, the cell that has existed until now is located in the new location registration area because the network has reassigned the geographical area. This is the case. That is, this is a case where cell rearrangement is executed. Of course, such rearrangement processing is not performed every day, but is generally performed in the process of expanding the network scale.
[0020]
3) When the mobile terminal moves to a new cell in a new location registration area, a location information update process is performed (19). This is the case where the mobile terminal 10 that performed the previous update in the location registration area moves to a new location registration area (18).
[0021]
4) If the mobile terminal does not move to a new cell or a new location registration area and a certain period of time has elapsed (21), the mobile terminal looks at the flag and checks the flag status. Here, the flag is set when moving to a new cell without performing position information update processing (when moving to a cell in the current position registration area). If the flag is not set in box 22, the mobile terminal updates location registration area information at the cell level. If the flag is set, no processing is performed.
[0022]
When the mobile terminal has updated the previous location information at the cell level as shown in box 11, the following processing is executed according to the header statuses 12, 15, 18, and 21.
[0023]
1) When the mobile terminal moves to a new cell in the current location registration area (12), the mobile terminal performs a location information update process (14). This is a case where the mobile terminal starts moving and mobility becomes high.
[0024]
2) Although the mobile terminal remains in the cell so far, if the cell is assigned to a new location registration area (15), no processing is performed (17). This is the case (15) in the mobile terminal 11 that has performed the previous update at the cell level, although the network has relocated the mobile terminal to a new location registration area, but continues to exist in the previous cell. .
[0025]
3) If the mobile terminal has moved to a new cell in the new location registration area 18, a location information update process is performed (20). When the mobile terminal 11 that performed the previous update in the cell area moves to a new location registration area (18), a location information update process (20) is required.
[0026]
4) If a certain period has elapsed (21), no processing is performed. Therefore, the location information update process of the mobile terminal differs depending on the previous registration level (cell level or location registration area level) and the new situation. In addition, the position information update of the boxes 14, 16, 19, and 20 is performed at the position registration area level.
[0027]
In another preferred embodiment, a periodic registration timer is used rather than a timer inside the mobile terminal or a timer provided by the network. In this case, the processing in the box 22 is different. When the flag is set in the box 22, the mobile terminal performs the location information update process at the location registration area level. If the flag is not set in box 22, the mobile terminal performs a location information update process at the cell level. Also. In the case of a regular registration timer, the box 23 is position information update processing at the cell level.
[0028]
3 and 4 show a flowchart of the preferred embodiment. Following the power-on of step 30, the mobile terminal checks the previous location registration level in step 31. The previous location registration level is either the cell level or the location registration area level. If the previous registration level is the location registration area level (32), it is checked whether the location is in the same location registration area (34). In this case (36), the mobile terminal resets the flag (42). If they are not in the same location registration area (37), location registration area update processing is performed (40), and the flag is reset (42).
[0029]
On the other hand, if the registration level of the mobile terminal is the cell level (33), it is checked whether it is located in the same cell as before (35). If it is in the same cell (38), the flag is reset (42). If it is located in a different cell (39), position information update processing is performed at the position registration area level in step 41, and the flag is reset in step 42.
[0030]
Following step 42 (flag reset), the mobile terminal starts a timer at step 43 to see if the situation shown by the headers 12, 15, 18, 21 in FIG. 2 occurs. The mobile terminal status change test is performed in step 44, and a step 45 (corresponding to the box 12 in FIG. 2) for recognizing that the mobile terminal has moved to a new cell in the current location registration area, Step 46 for recognizing that the cell has moved to a new cell (corresponding to box 18 in FIG. 2), Step 47 for recognizing that the cell has been assigned to a new location registration area (box in FIG. 2) 15), the process proceeds to point A in FIG. 3 (see FIG. 4) for recognizing that a certain period of time corresponding to the box 21 in FIG. 2 has elapsed. In step 45, if the mobile terminal has moved to a new cell in the previous location registration area, it is checked in step 48 whether the previous location registration level is the cell level or the location registration area level. If it is determined in step 49 that the previous registration level is the cell level, the mobile terminal performs location information registration processing at the location registration area level in step 51 (corresponding to box 14 in FIG. 2). In step 52, the timer is reset, and in step 53, the flag is reset.
[0031]
On the other hand, if it is determined in step 50 that the previous registration level is the position registration area level, the situation corresponding to box 13 in FIG. 2 is reached, and no processing other than setting the flag in step 54 is performed.
[0032]
When the mobile terminal recognizes that it has moved to a new cell in the new location registration area in step 46 (corresponding to box 18 in FIG. 2), as shown in boxes 19 and 20 in FIG. Regardless of whether the previous registration level is the location registration area level (box 10) or the cell level (box 11), the location information update process is performed at the location registration area level. That is, following step 46 in FIG. 3, the mobile terminal executes a location information update process at the location registration area level at step 55, resets the timer at step 56, and resets the flag at step 57.
[0033]
In step 47 (corresponding to box 15 in FIG. 2), when the mobile terminal recognizes that the cell in which the mobile terminal exists is the same but the cell has been reassigned to a new location registration area, the previous registration level is Whether it is the position registration area level or the cell level is confirmed in step 58. If it is determined in step 59 (corresponding to box 16 in FIG. 2) that the previous registration level is the location registration area level, the mobile terminal executes location information update processing at the location registration area level in step 61; In step 62, the timer is reset, and in step 63, the flag is reset. On the other hand, if it is determined in step 60 (corresponding to box 17 in FIG. 2) that the previous registration level is the cell level, the mobile terminal performs no processing. In this case, since the mobile terminal has not moved to a new cell, the process of resetting the flag is not performed following step 60.
[0034]
The point A in FIG. 4 indicates that the process proceeds from the point A in FIG. 3, and the flowcharts in FIGS. 3 and 4 form one flowchart. FIG. 4 is a flowchart showing processing in a situation where a certain period has elapsed (corresponding to box 21 in FIG. 2). That is, following step 44, when the mobile terminal recognizes that a certain period of time has passed before moving to a new cell or new location registration area, the process proceeds to point A in FIGS. Here, when it is recognized in step 65 that the power is turned off, the process ends in step 66. If it is recognized in step 64 that a certain period has elapsed, the processing of box 22 or 23 is performed according to the previous registration level 10 or 11 as shown in FIG. That is, the position information update process is executed or no process is performed. That is, in step 67, the mobile terminal checks whether the previous registration level is the location registration area level (box 10 in FIG. 2) or the cell level (box 11 in FIG. 2). If it is determined in step 68 that the previous registration level is the position registration area level, the process of box 22 in FIG. 2 is executed, and it is determined whether or not the flag is set when a certain period of time has passed. Confirm with 70. If it is determined in step 71 that the flag is set, the timer is reset in step 73, and the flag is reset in step 74. On the other hand, if it is determined in step 72 that the flag has not been set when a certain period of time has elapsed, position information update processing at the cell level is performed in step 75, and the timer is reset in step 76. Following steps 74 and 76, processing proceeds to point B in FIG. The point B in FIG. 4 corresponds to the point B in FIG. 3, and the process proceeds to the next situation change test in step 44.
[0035]
In step 69, when the mobile terminal determines that the previous registration level is the cell level when a certain period of time has elapsed, the timer is reset in step 77. Then, the process proceeds to point B in FIG.
[0036]
The timer and flag processing can be incorporated in a processor circuit mounted on a conventional mobile terminal. Therefore, by adding a timer function, a flag function, and a mechanism for processing the embodiment shown in FIGS. 2 to 4 to the conventional processor circuit software, the present invention can be implemented in various types of mobile terminals. .
[0037]
The present invention is also applied to another embodiment having a registration level of 2 or more. For mobile terminals with low mobility, other registrations between the location registration area level and the cell level, such as the registration at the geographical level located between the wide location registration area level and the narrow cell level, are made. Levels can also be provided. According to this, in a situation where mobility is low, the mobile terminal registers at the cell level, the registration level increases as the mobility increases, and eventually reaches the location registration area level, depending on the degree of mobility. Will raise or lower the registration level. In this alternative embodiment, there is an advantage obtained by increasing the number of registration levels, but it also increases the complexity of the system, so it cannot always be said to be a desirable method.
[0038]
According to the present invention, location information update processing and network location management processing are determined by the past mobility rate of the mobile terminal. As a result, it is possible to avoid an unnecessary paging load on a geographically large area and to realize an optimal environment that avoids an unnecessary load that requires frequent location registration.
[0039]
In the description of step 61, it has been stated that the mobile terminal that has performed registration at the location registration area level performs registration at the location registration area level when the location registration area of the cell is changed. Although there is no problem in registering at the location registration area level, there may be an approach to register at the cell level. This is because, when the paging load of a cell is high, there is an advantage that the number of paging messages transmitted to neighboring cells can be reduced by having all mobile terminals in the cell register at the cell level. This method is suitable for cases where the paging load is temporarily high.
[0040]
Although the present invention has been described as the most practical and presently preferred embodiment, the present invention is not limited to the illustrated embodiment. On the contrary, various modifications and equivalent configurations within the scope and spirit of the claims are included.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a cellular configuration.
FIG. 2 is a table showing location information registration processing corresponding to the embodiment of the present invention.
FIG. 3 is a flowchart corresponding to an embodiment of the present invention.
FIG. 4 is a flowchart corresponding to an embodiment of the present invention.

Claims (19)

A location registration update method for a mobile terminal existing in a geographically defined cell and a geographically defined location registration area,
a) determining a mobility factor (31) of the mobile terminal;
b) setting a timer (43);
c) if the mobile terminal leaves the geographically defined cell without leaving the geographically defined location registration area, setting a flag (54);
d ) If the mobility factor indicates that the mobility of the mobile terminal is relatively low (33),
1) If the mobile terminal leaves the geographically defined cell (39), perform location registration update (41),
2) Although the mobile terminal remains in the geographically defined cell (33), the geographical location registration area is newly reassigned and the new geographically defined location registration area When it comes to be included in the process of not performing location registration update,
e ) If the mobility factor indicates that the mobility of the mobile terminal is relatively high (34),
1) If the mobile terminal leaves the geographically defined location registration area (37), update location registration (40),
2) The mobile terminal leaves the geographically defined cell and moves to a new geographically defined cell, but continues to exist in the same geographically defined location registration area. (36) includes a step of not performing location registration update;
3) If the timer exceeds a predetermined time (64), check the flag (70),
i) if the flag is not set (72) performing location registration update at the geographically defined cell area level (75);
A location registration update method comprising: The method of claim 1 , further comprising the step of resetting the flag after step d1 ). The method of claim 1 , further comprising the step of resetting the flag after step e1 ). The method of claim 1 , further comprising the step of resetting the timer after step e3i ).   The method according to claim 1, wherein the step b) comprises a step of transmitting a predetermined time to the mobile terminal. p ) if mobility is determined to be relatively low (33/49) if the mobile terminal moves to a new geographically defined cell (45/46), or
q ) resetting the timer when the mobility is determined to be relatively high (32/59) and the mobile terminal moves to a new geographically defined location registration area (46/47); The method of claim 1, further comprising: The step e3 )
ii ) if the flag is set (71) further resetting the timer (73) and clearing the flag (74) ;
The method of claim 1 , wherein in step e3i), the timer is reset (76) along with the location registration update (75) . The method of claim 6 , further comprising the step of resetting the timer after step d1 ). The method of claim 6 , further comprising the step of resetting the flag after step e1 ). After step e )
s) When the mobile terminal leaves the geographically defined location registration area (46/47),
t) If the mobile terminal leaves the geographically defined cell (45/46),
u) or when any of the above timers has elapsed (64) (44)
The method according to any one of claims 1 to 9 , further comprising: f ) repeating steps a) to e ). The location registration update in the steps d 1), d 2), e 1), e 2) is performed based on the geographically defined location registration area (40/41). The method according to 1. The method of claim 1, wherein the location registration update in step e3 ) is performed based on the geographically defined cells (75). Transmission / reception processing means for checking category information (31) indicating mobility of the mobile terminal and performing location registration update on the mobile communication network,
A timer (43) for measuring the passage of a predetermined time;
A mobile terminal comprising a flag (42) that is set when the mobile terminal leaves a previously geographically defined cell without leaving the geographically defined location registration area. And
When it is determined that the mobility of the mobile terminal is relatively low according to the category information, the location registration is updated at the location registration area level every time the mobile terminal moves to a new geographically defined cell. (51/55),
If it is determined from the category information that the mobility of the mobile terminal is relatively high, the location registration is updated at the location registration area level every time the mobile terminal moves to a new location registration area (55/61). )
A mobile terminal characterized in that location registration is updated (75) at a cell level when the timer elapses for a certain time (64) and the flag is not set (72). If the mobile terminal determined to have relatively low mobility according to the category information is assigned to a new location registration area without moving to a new cell (60), no location registration update is performed. The mobile terminal according to claim 13 . If the mobile terminal determined to have relatively high mobility based on the category information has moved to a new cell but has not moved to a new location registration area (50), location registration update is not performed. The mobile terminal according to claim 13 . A location registration update method for a mobile terminal existing in a geographically defined cell and a geographically defined location registration area,
a) determining a mobility factor of the mobile terminal (31);
b) setting a timer (43);
c) If the mobility factor indicates that the mobility of the mobile terminal is relatively low:
1) When the mobile terminal leaves the geographically defined cell (45/46), it performs location registration update based on the location registration area (51/55),
2) Although the mobile terminal remains in the geographically defined cell (47), a new geographical location registration area is reassigned and included in the new geographically defined location registration area. In the case of being able to do so, the step (60) of not performing the location registration update,
d) If the mobility factor indicates that the mobility of the mobile terminal is relatively high,
1) When the mobile terminal leaves the geographically defined location registration area and the geographically defined cell (46), it performs location registration update based on the location registration area (55),
2) If the mobile terminal has moved in the geographically defined location registration area but remains in the geographically defined cell (47), it updates the location registration based on the location registration area. Done (61),
3) The mobile terminal leaves the geographically defined cell and moves to a new geographically defined cell, but continues to exist in the same geographically defined location registration area ( 45) includes a step (50) of not performing location registration update;
4) A location registration update method comprising a step (22) of performing location registration update based on the geographically defined cell when the timer has elapsed (21) .   The method of claim 1, wherein step b) includes obtaining a timer value from a periodic registration timer. The mobile terminal according to claim 13 , wherein the timer is a periodic registration timer. The method of claim 16 , wherein step b) includes obtaining a timer value from a periodic registration timer.

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