JP2697885B2 - Channel selection specification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a multi-channel communication system in which a communication channel is selected from a plurality of channels between a base station and a mobile station. The present invention relates to a channel selection designation method in a mobile radio communication system for performing channel access.

(Prior Art) Generally, in the field of mobile radio communication, in order to effectively use radio channels, mobile stations are configured to be able to use all radio channels, and select and use an empty channel for each communication. Is controlled. A method of selecting and using a channel for communication between a base station and a mobile station from a plurality of channels in this manner is called a multi-channel access method. There are two ways.

Fixedly assign a radio channel to be used for each base station,
The vacant channel is managed on the base station side, and the channel is designated from the base station to the mobile station during communication.

The base station and the mobile station can use all the radio channels, and the base station or the mobile station searches for an empty channel from all the channels and designates the channel to the partner station.

Is a method used in a so-called cellular radio system such as a car telephone. Is a method used in cordless telephones and the like, and is a category of dynamic channel assignment.

In order to perform the dynamic channel assignment, it is necessary for the base station or the mobile station to always search for an available channel and prepare for communication. Conventionally, this search for an empty channel has been performed in the base station. The reason is that the base station has more power capacity than the mobile station in terms of power capacity and does not need to operate intermittently.Moreover, the base station is superior in processing capacity to the mobile station and has a complicated control. Easy execution.

(Problem to be Solved by the Invention) However, as a method of searching for an empty channel in the base station, a method of checking for the presence or absence of an uplink signal from the mobile station is usually employed. In this case, the condition for determining an empty channel is that the signal level (interference wave level when the channel is used) received on the channel is equal to or less than a certain value. As described above, when an idle channel is selected under the condition that the interference wave level is equal to or less than a certain value, the interference wave level is guaranteed to be equal to or lower than a predetermined value for the idle channel selected by the base station. The desired signal level cannot be known by the base station until the connection is established, and the ratio of the desired signal reception level to the interference signal reception level, which determines the communication quality, may not satisfy the required value in some cases.

In order not to fall into such a situation, it is necessary to lower the determination threshold of the interference wave reception level, which is the vacancy determination condition when selecting the vacant channel. However, lowering the determination threshold decreases the number of channels that can be used as idle channels, which hinders effective use of the channels. If the ratio of the desired wave reception level to the interference wave reception level can be known in advance when an empty channel is selected, more effective channel use becomes possible.

Further, the above problem is also a problem that occurs when a mobile station detects an empty channel only from the detection of an interference wave level.

Therefore, an object of the present invention is to provide a channel selection designating method capable of improving a reduction in channel utilization efficiency, which is a problem of a method of selecting a vacant channel only from determination of an interference wave level, which is a conventional technique. is there.

[Configuration of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a mobile radio using a communication channel between a mobile station and a base station as a partner station by multi-channel access. A channel selection designation method in a communication system, wherein a mobile station that is waiting is a control signal that the base station transmits to any mobile station that is located in the wireless zone or a base station that is performing another communication in the wireless zone. Receiving the signal of the channel to be transmitted to the mobile station, detecting the reception level thereof, obtaining the average reception level D, and selecting at least the base station from the channels usable for other communication in the wireless zone. , A signal level received in a channel not used for communication is detected, an average reception level U is obtained, and a ratio between the reception level U and the reception level D is calculated. Hazuki, the base station selects a channel usable for communication among the channels not used for communication, channel selection designation method which is characterized in that the channel designated for the base station prior to the communication.

Is the gist.

(Operation) While the mobile station is on standby, the nearest base station receives a signal to be transmitted to another mobile station or a signal to be transmitted for zone selection or incoming call, and sets the reception level D to a desired wave level. The reception level U, that is, the interference wave level is detected from the signal received when the base station searches for a channel not used for communication in the wireless zone, and the desired wave reception level D and the interference wave reception level U are detected. Based on the ratio, a channel not used by the base station for communication is selected, and a channel is designated from the mobile station to the base station prior to communication. Thus, based on the signal transmitted by the base station which is the communication partner station,
Conventionally, the mobile station measures the ratio between the desired wave reception level D and the interference wave reception level U, selects a channel not used by the base station for communication, and designates a channel to the base station. As in the technique, it is possible to greatly improve the reduction in channel utilization efficiency caused by selecting a channel not used by the base station for communication based only on the determination of the interference wave reception level U.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS.

In a normal mobile radio communication system, the base station has a fixed period for the purpose of supporting selection of a zone in which the mobile station is located, and the like.
Alternatively, it always transmits a notification signal. In general, there are a plurality of mobile stations around one base station,
From the stand-by mobile station, it is possible to receive a signal transmitted by the base station for communication with another mobile station in addition to the broadcast signal.

In this embodiment, the reception level of the signal from the base station that the mobile station can receive is measured during standby, and that level is set as the desired wave reception level. The mobile station performs channel selection / designation by focusing on the fact that the ratio of the desired wave reception level to the interference wave reception level can be obtained during standby by setting the wave reception level.

The mobile radio communication system to which this embodiment can be applied may be any system as long as it is a system for performing multi-channel access. Hereinafter, a system using one carrier in a time-division manner will be described as an example. The time division multiplexing, that is, the TDMA method, can receive the above-mentioned broadcast signal and the signal transmitted from the base station to other mobile stations as a continuous signal at a time, and can be said to be a channel configuration particularly suitable for this embodiment.

When this TDMA technology is applied to mobile communication, as a method of realizing the dynamic channel assignment described in the related art, a plurality of base stations and mobile stations can freely access each time-divided channel (time slot). A method has been proposed (Swedish PTT, “Digital Cordle
ss Telephones ", Specification 8211-A130) In this embodiment, a description will be given on the assumption that a dynamic channel assignment is performed in such a TDMA channel configuration.

FIG. 1 shows a minimum configuration of a base station and a mobile station necessary for realizing this embodiment. FIG. 1A shows the basic configuration of a base station. In the figure, 1 is a transmitter, 2 is a receiver, 3 is a baseband unit, 4 is a control unit, 5 is a storage unit, and 6 is a transmitting and receiving antenna.

The signal of the TDMA configuration is configured by the baseband unit 3 under the control of the control unit 4 and transmitted to the mobile station via the transmitter 1. Further, a signal from the mobile station is guided to the baseband unit 3 via the receiver 1. The base station does not transmit during the time period when transmission is not necessary in the TDMA signal, or when it is determined that transmission will cause interference to nearby stations (that is, the own station will receive interference). The signal transmitted from is burst-like. Also, the signal transmitted from the mobile station is a burst signal because it is transmitted only on the channel selected by the mobile station.

FIG. 1 (b) shows the basic configuration of the mobile station. In the figure, 7
Is a transmitter, 8 is a receiver, 9 is a baseband unit, 10 is a control unit, 11 is a storage unit, and 12 is a transmitting and receiving antenna.

The signal transmitted from the base station is received by the receiver 8 and guided to the baseband unit 9. During standby, the receiver 8 is started up at a constant period to receive a signal transmitted from the base station. The reason for performing the reception at a constant cycle is for battery saving. At this time, the reception level is set to the receiver 8
From the controller 10 and the data is transmitted to each channel (TDMA
(Slot) is stored in the storage unit 11 correspondingly. The mobile station always keeps the received data up to date during standby. Also, considering that the level changes due to fading, the stored data will need to be subjected to an averaging process by the control unit 10. In that case, data obtained by performing averaging processing based on the received data received several times may be stored in the storage unit 11. Further, since a signal received during standby generally includes a code for identifying a base station indicating a transmission source, a mobile station can easily receive a signal by performing signal decoding processing. It is possible to determine whether the obtained signal is a signal from the nearest base station.

Next, FIG. 2 shows an example of the TDMA channel configuration and a base station transmission signal (hereinafter referred to as a downlink signal) described on the left. FIG. 1A shows an example of the arrangement of base stations, in which 13 is a mobile station, 14 to 17 are base stations, and 18 is a boundary of a wireless zone.
FIG. 2B shows a reception example of each downlink signal received at the point of the mobile station 13. In the figure, 19 is a broadcast signal transmitted by the base station 14, 20 is a broadcast signal transmitted by the base station 15,
Reference numeral 21 denotes a channel used by the base station 15 for communication, 22 denotes a channel used by the base station 14 for communication, 23 denotes a broadcast signal transmitted by the base station 16, and a broken-line channel receives a signal. It does not. Here, base station 14
17 each hold one free channel in advance and use that channel as a control channel for transmitting control information from the base station. In this control channel,
A notification signal is transmitted at all times, and usually notifies the mobile station of area information necessary for performing a zone determination. When making an incoming call, an incoming signal can be transmitted using this channel.

This embodiment can be executed even if the broadcast signal is not always transmitted. However, such a broadcast signal is basically necessary when configuring a mobile communication system having a small zone configuration. This embodiment is more effective when the notification signal is being transmitted.

Here, it is assumed that the mobile station 13 has selected the base station 14 as the nearest base station and has registered the location in advance. At this time, the mobile station
Reference numeral 13 measures the reception level of the broadcast signal 19 from the base station 14 and the signal 22 transmitted by the base station 14 for communication with another mobile station as a desired wave reception level. The mobile station 13 measures the reception level of the signal in the other time division time zone as the interference wave reception level. In the example of FIG. 2, the mobile station 13 stores a channel in which the ratio between the desired wave reception level and the interference wave reception level satisfies a required value from among the channels indicated by broken lines in the figure, and starts communication. In this case, a channel is specified to the base station 14 so that a communication channel is set to the stored channel.

At this time, if the broadcast signal is not transmitted, the base station
The signal transmitted by 14 to another mobile station may be measured as a desired wave level. In addition, when the base station 14 is not performing communication, the channel selection function itself does not stop by using the conventional method of selecting a free channel only from the interference wave reception level.

Next, FIG. 3 shows a timing at which the mobile station receives a downlink signal. FIG. 3 shows an example in which one frame of TDMA is composed of six channels starting from the broadcast signal 24 as shown in FIG. In FIG. 3, 25 is an empty channel,
26 is the channel being used for communication, 27 is TDMA1 frame length, 2
8 indicates a receiver ON time length, and 29 indicates a receiver OFF time length. (B) and (C) of FIG. 3 show the TDMA frame sequence and the timing at which the mobile station intermittently receives. That is, in the case of the TDMA channel configuration, one frame length is usually 27
Is several msec to several tens of msec, and the time 28 during which the mobile station turns on the receiver is several tens msec to several hundred msec. No, that is, channel selection is possible without impairing the effect of battery saving.

Next, a method of specifying a channel from a mobile station will be described. FIG. 4 and FIG. 5 show a channel designation control sequence in the case of outgoing and incoming calls.

FIG. 4 shows the transmission signal 33 transmitted on the channel selected by the mobile station 31. Since the base station 32 always receives all the channels, it responds with the channel that this mobile station 31 has called.
You just have to return 35. At this time, the base station 32 needs to confirm the channel 34 before returning the response 35. That is, since the downlink signal and the uplink signal returned by the mobile station 31 are separated in the frequency band or the time zone, the level fluctuation due to fading may be independent. The method of the channel confirmation 34 performed by the base station 32 includes, for example, the interference wave level in the channel that has been measured in advance (this measurement can be performed in the same manner as the interference wave measurement in the mobile station described above) and the calling. A method of confirming that the ratio of the signal reception levels satisfies a required value may be used.

In FIG. 4, the base station 32 checks the channel for the first time.
This shows a case where the mobile station 31 again specifies a different channel 36 after notifying the mobile station 31 that the result of 34 does not satisfy the required value. In order to cope with such a case, it is necessary for the mobile station to select a plurality of channels in advance.

FIG. 5 shows a channel designation control sequence when an incoming call is made from the base station 32. In this case, the base station 32
Does not select a vacant channel, and returns the incoming call signal 37 using the downlink control channel transmitting the broadcast signal. The mobile station 31 sends a response signal to the
What is necessary is just to perform channel designation 38 for 32. This response signal can be returned to the base station 32 by the channel selected by the mobile station 31 in the same manner as in the above-mentioned example of the calling. Further, in the method not using the broadcast signal, the base station 32 tentatively selects a channel (that is, the base station selects an empty channel immediately before returning the incoming call signal), transmits the incoming call signal on that channel, and thereafter, The mobile station 31 can negotiate whether to use the channel selected.

The above embodiment is based on the premise that multi-access of a wireless channel is performed based on the principle of TDMA.
Even when the channel has the FDMA configuration or the FDMA / TDMA configuration, it is possible to perform channel selection and designation according to the above embodiment by adding an operation of switching the reception frequency at the time of channel search.

[Effects of the Invention] As described above, according to the present invention, it is possible to perform channel selection based on a desired wave level to interference wave level ratio at a mobile station without making a significant change in a normal standby state of the mobile station. Is possible, and the frequency utilization rate can be improved as compared with the related art. In addition, the functions mounted on the base station are reduced by decentralizing the functions of the base station, so that the base station can be made more economical.

[Brief description of the drawings]

FIGS. 1 to 5 are diagrams for realizing an embodiment of a selection / designation method according to the present invention. FIG. 1 is a block diagram showing a configuration example of a base station and a mobile station, and FIG. FIG. 3 is a diagram showing an example of a station arrangement and an example of a base station transmission signal, FIG. 3 is a diagram showing a configuration example of a base station downlink signal and its reception timing, and FIG. 4 is an example of a channel designation control sequence in the case of calling. Figure,
FIG. 5 is a diagram showing an example of a channel designation control sequence for an incoming call. 13: mobile station, 14-17: base station.

Claims (1)

(57) [Claims] 1. A channel selection and designation method in a mobile radio communication system using a communication channel between a mobile station and a base station as a partner station by multi-channel access. The base station receives a control signal transmitted to any mobile station located in the wireless zone or a signal of a channel transmitted by the base station to another communicating mobile station in the wireless zone, and detects its reception level. The average reception level D is obtained, and a signal level received at least in a channel not used by the base station for communication in the wireless zone is detected from channels available for other communication, and the average level is detected. A reception level U is obtained, and based on a ratio between the reception level U and the reception level D, the base station is used for communication from channels not used for communication. A method for selecting a possible channel, and specifying a channel to the base station prior to communication.