JPH04287430A - Radio zone discrimination system - Google Patents

Abstract

PURPOSE:To reduce a power supply battery of a mobile equipment by changing a radio zone discrimination period depending whether or not other radio zone is, overlapped on a radio zone in which a mobile station is resident. CONSTITUTION:Suppose that frequencies f1,f2 are assigned to macro cells 1, 2 and f11, f12, f13 are assigned to micro cells 1,2,3 respectively as control channels. A mobile station scans a reception level of all control channels f1-fn of a radio zone to select a control channel whose level is a prescribed level or over. A means displaying whether or not other radio zone of a base station is overlapped on one radio zone is provided to the control channel sent from each base station to the mobile station and the mobile station receiving the display representing the overlapped radio zone executes the radio zone movement discrimination for a short period while the mobile station is resident in the radio zone.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for determining a wireless zone in a mobile communication system, and particularly to a method for determining a wireless zone in a mobile communication system, and in particular, a wireless zone is arranged so that part or all of the wireless zone is overlapped with a wireless zone formed by other base stations. It relates to a wireless zone determination method in a mobile communication system.

0002

2. Description of the Related Art FIG. 1 shows an example of a system configuration of a mobile communication system in which a part or all of a wireless zone is arranged so as to be overlapped with another wireless zone. In this example, the wireless zone can be roughly divided into two types of zones. One is a macro cell 1 and the other is a micro cell 2. A plurality of microcells 2 are arranged within a macrocell 1, and the microcells are superimposed on the macrocell. The mobile station selects a wireless zone in which it is located while moving within a service area 3 consisting of a plurality of wireless zones, and makes a call with a base station in the wireless zone.

In the example of FIG. 1 where the wireless zone is composed of macro cell 1 and micro cell 2, in the area where the micro cells overlap (the dotted area in the figure), the mobile station uses the wireless Select the microcell as a zone. However, in an area where there are no microcells and only macrocells (shaded area in the figure), the mobile station selects the macrocell as the wireless zone for communication. Furthermore, there are macrocells that do not include microcells, such as macrocell 4 in FIG. 1.

[0004] Next, a method for selecting a radio zone in which a mobile station will make a call will be explained. Control channels fl to fn are assigned to each wireless zone, and the mobile station measures the reception level of the control channels fl to fn in each wireless zone and selects a control channel with a certain level or higher to determine whether the mobile station Zones can be selected. In the case of a system in which a microcell is superimposed on a macrocell, as in the example in Figure 1, the reception levels of the macrocell control channel and the microcell control channel are above a certain level in the superimposed area, and the mobile station is Select the microcell as a zone. In the non-overlapping area, only the reception level of the control channel of the macro cell is above a certain level, and the mobile station selects the macro cell as the zone in which it is located.

[0005] The above-mentioned measurement of the reception level of the control channel in the wireless zone must be carried out periodically at a certain period. This is because, as the mobile station is moving, the wireless zone in which it is located changes. When all the control channels of a wireless zone are fl to fn, the period (scanning period) for measuring the reception levels of fl to fn depends on the shape of the wireless zone. For example, in the case of a circular wireless zone, the scan period depends on the radius of the wireless zone. If the wireless zone radius is large, the period may be long, but if the wireless zone radius is small, the period must be shortened. This is because if scanning is performed at a long period when the zone radius is small, even if the mobile station moves and the radio zone in which it is located changes, it may not be possible to detect the change in the radio zone in which it is located due to the movement. Therefore, when the zone radius is small, the scan period must be shortened according to the radius.

[0006]

Next, a conventional method for determining a scan period when a part or all of a wireless zone overlaps with another wireless zone will be described. Figure 2
If the mobile station is located in the macro cell 1 indicated by the numeral 1a on which no micro cells are superimposed, such as point C, there is no problem even if the mobile station scans at a long period. However, like points A and B, microcells 1 to 3 (numbers 2a to 3)
If the mobile station is located in macro cell 2 (indicated by numeral 1b) on which macro cell 2 (indicated by 2c) is superimposed, the mobile station selects the micro cell while moving, so the radius of the micro cell In addition, it is necessary to scan at short intervals. In other words, the required scan period differs depending on the location where the mobile station is located.

[0007] However, in the conventional system, since the scan period was constant, it was necessary to set the scan period to the shortest period among the scan periods that differ depending on the location where the mobile station is located. In other words, in this method, in the case of non-overlapping macrocells, there is no need to scan at a short cycle that matches the microcell radius, but it is necessary to scan at a short cycle that matches the microcell radius. In other words, a shorter scan period means more scans per unit time, which means more time to measure the reception level, which consumes more power and has a drawback in terms of battery saving. there were. Furthermore, if a call arrives while scanning, there is a problem in that there is a possibility that the call cannot be received.

[0008] The present invention provides a method for determining a reception level of a control channel in determining a radio zone in a mobile communication system including a zone configuration in which a part or all of a radio zone is arranged so as to be superimposed on another radio zone. is constant, so even when the mobile station is in a location where it does not need to scan in short cycles, it scans in short cycles, which solves the problem of increased battery power consumption. The purpose is to provide a zone determination method.

[0009]

According to the present invention, the above-mentioned problems are solved by the means set forth in the claims. In other words, the invention of claim 1 provides a mobile device in which a service area is composed of a plurality of wireless zones, and a portion or all of at least one wireless zone within the service area is arranged so that it overlaps with another wireless zone. In the communication method, means is provided on a control channel transmitted from each base station to a mobile station to display whether or not another wireless zone is superimposed on the wireless zone of the base station. The wireless zone determination method is characterized in that a mobile station that has received an indication indicating superimposition performs a wireless zone movement determination in a short period while it is located in the wireless zone, and the invention according to claim 2 is As a method of transmitting information related to the superimposition of wireless zones according to the above invention, the control information signal on the control channel accompanying the communication channel at the end of communication indicates that the wireless zone in which the mobile station is located is different from other wireless zones. It is designed to display and send out whether or not the images are superimposed.

[0010] Furthermore, the invention as claimed in claim 3 is such that the service area is composed of a plurality of wireless zones, and at least one wireless zone within the service area is arranged so that part or all of it overlaps with other wireless zones. In a mobile communication system that has been developed, a means for displaying whether or not another wireless zone is superimposed on the wireless zone of the base station on a control channel transmitted from each base station to a mobile station; If the radio zone is superimposed with another radio zone, the radio base station is equipped with means for displaying and transmitting search information for the control channel of the superimposed zone, displaying the superimposition and searching for the control channel of the superimposed zone. The mobile station that has received the information uses a wireless zone determination method that shortens the observation period of the control channel of the superimposed zone and performs zone movement determination in a short period, and the invention of claim 4 is the invention of claim 3. Sends an indication of whether or not the wireless zone in which the mobile station is located overlaps with another wireless zone, and displays and sends control channel search information for the overlapping zone, along with the communication channel at the end of communication. The system is configured such that control information signals on a control channel are used.

[0011]

[Operation] In wireless zone determination in a mobile communication system in which a part or all of a wireless zone is arranged so as to be superimposed on another wireless zone, the present invention adjusts the wireless zone determination period to the wireless The most important feature is that the zone is changed depending on whether or not another wireless zone is superimposed on the zone. This technology differs from the conventional technology in that the wireless zone determination cycle is not constant, but changes depending on the location of the mobile station. Hereinafter, the effects of the present invention will be explained in detail based on examples.

0012

[Example] FIG. 1 described earlier regarding an example of the present invention
Explain using. That is, FIG. 1 shows a configuration in which a part or all of a wireless zone is arranged so as to be overlapped with another wireless zone. The wireless zone determination method under this configuration can also be performed by measuring the reception level, interference amount, etc. of the control channels fl to fn assigned to each wireless zone, as in the conventional method.

[0013] The specific procedure for wireless zone determination will be explained below using FIG. 2. FIG. 2 shows a system configuration in which microcells are superimposed on macrocells, and it is assumed that each macrocell and microcell has a name as shown in the figure. Control channels are assigned to each cell, and in this case, macrocell 1 and macrocell 2 have f1 and f2, respectively, and microcell 1, microcell 2, and microcell 3 have f11, f12, and f13. Assume that it is assigned as a control channel. The mobile station selects a control channel having a certain level or higher by scanning the reception levels of all control channels fl to fn in the wireless zone. For example, A
The point is an area where microcell 1 overlaps macrocell 2, so by measuring the reception level of the control channel, f
11 and f2 become above a certain level, and the mobile station selects the micro cell 1 as the wireless zone in which to make a call.

[0014] Also, at point B, no microcells overlap and the area is only macrocell 2, so only f2 is above a certain level, and the mobile station selects macrocell 2 as the radio zone for making a call. By measuring the reception level in this manner, it is possible to determine the wireless zone where the reception level is above a certain level as the wireless zone in which the user is located, and to select the wireless zone in which the call is to be made. In the above explanation using FIG. 2, it was shown that in the overlapping area, the two control channels are at a certain level or higher, but the mobile station can determine whether these two control channels are the control channels of the macro cell or not. , it must be possible to determine whether it is a control channel of a microcell.

Also, as in the present invention, control channels fl to f
In order to make it possible to change the period for scanning the reception level of n depending on whether or not each wireless zone is superimposed with another wireless zone, the content of the downlink control channel includes information as shown in FIG. is necessary. As shown in the figure, the downlink control channel includes an information bit A (indicated by the number 5) that identifies whether the control channel is associated with a macro cell or a micro cell. ) and an information bit B (indicated by the number 6) indicating whether another wireless zone is superimposed on the wireless zone of the control channel. By looking at information A, the mobile station can identify whether the wireless zone is a macro cell or a micro cell, and if micro cells overlap, it is possible to select a micro cell as the wireless zone for making a call. becomes.

Next, control channels fl to f of each wireless zone
The method of the present invention for determining the cycle (scan cycle) for measuring n will be explained using the flowchart of FIG. 4 (S101 to S105 in the figure each represent a step). First, the mobile station selects the control channel of the macro cell from among the control channels whose reception level is above a certain level, and acquires the control channel (step 101).
. Next, the content of the control channel is read, and it is determined based on the value of information bit B whether a microcell is superimposed on the macrocell (step 102). If the determination results are superimposed, the scan period is set to S, and if they are not superimposed, the scan period is set to L (steps 103 and 104).
). However, the value of S here is smaller than the value of L, and if they overlap, the scan period will be shortened. Then, control channels fl to fn are scanned in this scan period (step 105), and when the control channel of the macro cell changes due to movement of the mobile station, step 101
Return to

[0017] The method of determining the scan period in wireless zone determination described above is based on whether or not the macro cells in which the mobile station is located overlap, and the scan period is changed accordingly. In the conventional method, the scanning period was constant, so it was necessary to scan at a short period matching the microcell radius regardless of the conditions of the location where the mobile station was located. When a microcell is located in a macrocell that does not overlap, scanning can be performed at a long period matching the radius of the macrocell. As a result, when a mobile station is located in a macro cell where a micro cell does not overlap, by reducing the number of scans, the time required to measure the reception level can be reduced, thereby reducing power consumption. This makes it possible to greatly increase the effect of battery saving. Furthermore, since the scanning time can be reduced, there is also the advantage that if an incoming call is received during scanning, the possibility of missing the incoming call can be reduced.

Next, with reference to FIG. 5, the advantages of the method of the present invention for determining a scan period by determining a wireless zone will be quantitatively illustrated in comparison with the conventional method. As shown in the figure, the diameters of macrocells 7a and 7b are R = 5km, and the diameter of microcell 8 is r = 0.5km. Macrocell A has overlapping microcells, and macrocell B has overlapping microcells. Make it not exist. In the conventional method, the scan period is constant regardless of whether macro cells overlap or not, so scanning is performed at a scan period that matches the micro cell diameter r=0.5 km. Mobile station moving speed 20km/h
Then, the time to cross the microcell is 1.5 minutes. Taking this into consideration, the scan period should be set to 1.5 minutes/2=0
．． It will be 75 minutes. All control channels to be scanned are 20
If we assume that each channel requires a measurement time of 1 second, the time required for one scan is 20 seconds, and the scan period is 0.75 minutes, so 20/45=
This means that 44% of the time is spent scanning. On the other hand, in the method of the present invention, a mobile station located in macro cell A can determine the scan period according to the macro cell diameter because no micro cell overlaps with macro cell A.

Assuming that the mobile station moves at a speed of 20 km/h, it takes 7.5 minutes to cross the macro cell, and with the method of the present invention, it is only necessary to scan for 20/450=4.4% of the time. When the mobile station is on standby, in addition to the scanning time described above, the time to receive incoming calls is the time it uses power. If it is divided,
The time ratio for receiving incoming calls is 2%, and the time ratio for using power during mobile station standby is 4% in the conventional system.
4+2=46%, 4.4+2=6.4 in the method of the present invention
%. As described above, the method of the present invention can save power and improve the battery saving effect compared to the conventional method.

Here, the fact that the time ratio for receiving incoming calls is 2% will be explained based on the control channel configuration diagram shown in FIG. The control channel 9 is composed of a broadcast channel 9a, an incoming channel 9b, and a cell individual signaling channel 9c, and the number of information bytes for each is 25,500,72.
It is assumed to be 5 bytes. Since the incoming channels are divided into 20 groups, each group has 25 bytes, and the ratio of the incoming channels in one group to the total control channels is 2%. Therefore, the time ratio at which the mobile station receives an incoming call is calculated to be 2%.

Next, using FIG. 7, the hardware configuration of a mobile station that implements the present invention will be shown. As shown in the figure, the mobile station receiving section includes a CPU 11, a receiving section 12, a demodulating section 13,
It is composed of a level measuring circuit 14, a synthesizer 15, and a timer 16. In wireless zone determination, it is necessary to monitor the content of the control channel, which is done by the demodulator 1.
can be obtained by output 2 from 3. It is also necessary to scan and measure the reception levels of the control channels fl to fn, which can be done by controlling the synthesizer 15 according to instructions from the CPU 11 and obtaining an output from the level measuring circuit 14. The scan cycle can be set by the CPU 11 instructing the timer 16 about the scan cycle, and the timer 16 interrupting the CPU 11.

In the first embodiment, the method of scanning all the control channels fl to fn, which is the sum of the microcell control channel and the macrocell control channel, has been described above. It has been assumed that the control channel of the microcell and the control channel of the macrocell may be the same channel. However, in the second embodiment described below, the same channel is not assigned to the control channel for the macro cell and the control channel for the micro cell, and f11 to f1n are the control channels for the macro cell, and f2 to f2m are the control channels for the micro cell. Consider the case where it is assigned to

[0023] In this case, the mobile station first scans the control channels of the macro cell f1l to f1n at a long cycle matching the macro cell radius, selects the control channel of the macro cell whose reception level is above a certain level, and starts reception. . If the microcells overlap, the control channels f2l to f2m of the microcells are scanned at a short cycle matching the microcell radius, and if they are not overlapped, f2l to f2m are not scanned. By continuing to scan the control channels f1l to f1n of the macro cell at long intervals, the power consumption of the mobile station can be reduced compared to the conventional method, as described in the first embodiment. In other words, non-overlapping macro cells can perform scanning at a longer cycle than overlapping macro cells, which has an advantage in terms of battery saving.

[0024] As a third embodiment, a method may also be considered in which, among the control channels of each radio zone, a display indicating superimposition and search information for the control channel of the microcell, which is the superimposed zone, is displayed. Here, the search information is FDMA
In the case of a system, it means a carrier frequency, in the case of a TDMA system, it means a carrier frequency and slot number, and in the case of a CDMA system, it means a carrier frequency and a spreading code. In this embodiment, when a mobile station is located in an overlapping macro cell,
Only the control channel of the microcell notified via the control channel needs to be scanned at a short cycle that matches the microcell radius, making it possible to shorten the total scanning time, reducing mobile station power consumption and improving the reception of incoming call information. From the point of view,
It's even more effective.

In the first to third embodiments described above, a control channel containing only control signals, such as a common control channel, has been assumed as the control channel, but the control channel may also include a communication channel attached to a communication channel. Ancillary control channels also exist. When a mobile station performs communication such as voice communication, it may move to another wireless zone during communication. In this case, at the end of communication, information regarding the superimposition of the wireless zone in which the mobile station is located is displayed on the control channel attached to the communication channel, and depending on whether or not there is superimposition, the wireless The scan period for zone selection can be changed. In this way, by displaying whether or not the wireless zone in which the mobile station is located overlaps with the control channel attached to the communication channel, it is possible to read the control channel containing only control signals after a call. It has the advantage that there is no need to determine the scan period, and the scan period can be determined immediately after the call.

[0026] In the above embodiments, as an example of a mobile communication system in which a part or all of a wireless zone is arranged so as to be overlapped with another wireless zone, a system consisting of macro cells and micro cells will be described. However, if a micro cell is overlaid with a pico cell smaller than a micro cell, or even if an even smaller cell is overlapping, the mobile station described above is located in the wireless zone. A method of changing the scan period depending on whether or not other wireless zones overlap can be applied. Furthermore, as shown in FIG. 8, even when another wireless zone 23 is superimposed across a plurality of wireless zones 21 and 22, the same method as in the above embodiment can be applied.

[0027]

As explained above, in the present invention, whether or not the wireless zones in which a mobile station is located overlaps is notified through a control channel, and depending on whether or not the wireless zones overlap, the wireless zone The scan period for selection is changed. Therefore, if the wireless zone in which the mobile station is located does not overlap with other wireless zones, the time taken to measure the reception level can be reduced by lengthening the scan cycle compared to the case where they overlap. Because you can
Power consumption can be reduced. Furthermore, since the time spent scanning other control channels is short, it also has the effect of reducing the probability of missing an incoming signal.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example in which wireless zones are arranged so as to overlap with other wireless zones.

FIG. 2 is a diagram showing an example in which a micro cell overlaps a macro cell.

FIG. 3 is a diagram showing information included in a downlink control channel in the present invention.

FIG. 4 is a flowchart showing an example of control for determining a scan period according to the present invention.

FIG. 5 is a diagram illustrating cell size and scan period.

FIG. 6 is a diagram showing an example of the configuration of a control channel.

FIG. 7 is a diagram showing an example of the configuration of a mobile station implementing the present invention.

FIG. 8 is a diagram illustrating an example in which another wireless zone overlaps across a plurality of wireless zones.

[Explanation of symbols]

1, 4 Macrocell 1a, 1b Macrocell 1, Macrocell 22
Microcells 2a to 2c Microcells 1 to Microcells 33
Service area 5 Information A 6 Information B 7a, 7b Macro cell A, Macro cell B8
Micro cell 9 Control channel 9a Broadcast channel 9b Incoming channel 9c Individual cell signaling channel 11
CPU 12 Receiving section 13 Demodulating section 14 Level measuring circuit 15 Synthesizer 16 Timers 21 to 23 Wireless zone

Claims (4)

[Claims] 1. A mobile communication system in which a service area is composed of a plurality of wireless zones, and a portion or all of at least one wireless zone within the service area is arranged so as to overlap with another wireless zone, A control channel transmitted from each base station to a mobile station is provided with means for displaying whether or not another radio zone is superimposed on the radio zone of the base station, and a display indicating the superimposition of the radio zone. A wireless zone determination method characterized in that a mobile station that has received a mobile station executes a wireless zone transition determination at short intervals while the mobile station is located in the wireless zone. [Claim 2] At the end of communication, the control information signal on the control channel accompanying the communication channel is sent with an indication of whether or not the wireless zone in which the mobile station is located overlaps with another wireless zone. The wireless base station is equipped with a means to
The wireless zone determination method according to claim 1. 3. A mobile communication system in which a service area is composed of a plurality of wireless zones, and a portion or all of at least one wireless zone within the service area is arranged so as to overlap with another wireless zone, means for displaying, on a control channel transmitted from each base station to a mobile station, whether or not the radio zone of the base station is superimposed on another radio zone; If so, the radio base station is equipped with a means for displaying and transmitting the control channel search information of the superimposed zone, and the mobile station that receives the display indicating the superimposition and the search information of the control channel of the superimposed zone , a wireless zone determination method characterized by shortening the observation period of a control channel in a superimposed zone to perform zone transition determination in a short period. [Claim 4] At the end of communication, a control information signal on a control channel attached to a communication channel is sent with an indication of whether or not the radio zone in which the mobile station is located overlaps with another radio zone. 4. The wireless zone determination system according to claim 3, wherein the wireless base station is equipped with means for displaying and transmitting search information for control channels in the superimposed zone.