JPH05206927A - Transmission power control system for mobile communication system - Google Patents

Abstract

PURPOSE:To enlarge transmission power so as to reduce a compulsory cut rate to a call which is newly generated only when a desired wave level is low, and to a hand-off when the desired wave level is low and the power ratio of a desired wave to an interference wave is low. CONSTITUTION:At the time of allocating a call channel to the newly generated call, a base station 310 and a mobile station 320 measure the reception power levels Dup and Ddown of the desired wave, and enlarge transmission power Uup and Udown only when between the levels and a controlled variable is smaller than a necessary desired wave level Dreq. The base station 310 and the mobile station 320 measure the reception power of the desired wave and the reception power of the interference wave, and enlarge transmission power not only when the desired wave level is low but also when the ratio of the desired wave to interference wave power is less than a prescribed value CIRreq as to the hand- off. Thus, a probability that the channel which can be allocated to the hand-off does not exist is low, and the compulsory cut rate can be suppressed low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a base station provided in each of a plurality of cells and selecting a call channel from a plurality of call channels in response to a call request. A cellular system that assigns a call channel when the interference wave power of the call channel is less than a certain value and the desired wave-to-interference wave power ratio in the call channel is more than a required value due to the transmission power. The present invention relates to a transmission power control method for mobile communication systems.

[0002]

2. Description of the Related Art In a mobile communication system such as a cordless telephone system, a channel is not fixedly assigned to a base station, but a base station carries out a carrier sense for each communication and selects a channel which is determined to be free and uses it dynamically. Assign channels. In a system that performs such dynamic channel allocation, communication that is determined to be available may interfere with other communication. For this reason, it is necessary to switch channels during communication (hereinafter referred to as handoff). At this time, if there is no free channel, it is forcibly disconnected. The forced disconnection rate, which is this probability, must be kept sufficiently lower than the call loss rate in terms of service.

As a countermeasure against this, there is a method of reducing forced disconnection by dedicating a part of all channels to outgoing calls and dedicating them to handoff.

When there is no channel that can be assigned by the base station in communication, if there is a channel that can be assigned to another adjacent base station, there is also a method of switching to that channel to reduce forced disconnection.

[0005]

However, the method of dedicating a part of the channels to the handoff only has a problem in that the utilization efficiency of the channels dedicated to the handoff becomes low, so that the number of calls carried at the same call loss rate becomes small.

On the other hand, in the method of switching to the channel of another adjacent base station to reduce the forced disconnection, not only the control in cooperation with the other base station is required, but also the connection with the base station of the adjacent zone is established. As a result, the transmission power is often increased, which raises the problem that the surrounding interference wave level increases and the frequency utilization efficiency decreases.

An object of the present invention is to solve the above-mentioned problems, to secure a channel dedicated to handoff, to control a handoff to surrounding base stations, and to reduce the frequency utilization efficiency due to an increase in transmission power. An object is to provide a suppressed transmission power control method for a mobile communication system.

[0008]

According to a first aspect of the invention, a base station provided in each of a plurality of cells responds to a call request.
A call channel is selected from a plurality of call channels, the base station and the mobile station can select a plurality of transmission powers, the interference wave power of the call channel is a certain value or less, and the desired wave pair in the call channel is selected. A transmission power control method of a cellular mobile communication system for allocating the call channel when the interference wave power ratio is a required value or more, and when allocating the call channel to a newly generated call, The station and the mobile station measure the received power of the desired wave, select the smallest transmission power at which the received power of the desired wave is a certain value or more, respectively, when switching the call channel during a call, the base station and the mobile station, The received power of the desired wave and the received power of the interference wave of the channel selected as the switching destination are measured, and the received power of the desired wave is equal to or higher than the predetermined value, and Wherein the desired wave-to-interference wave power ratio respectively select the smallest transmission power equal to or greater than the required value.

In a second aspect of the present invention, a base station provided in each of a plurality of cells selects a call channel from a plurality of call channels in response to a call request, and the base station and the mobile station select a plurality of transmission powers. Is possible and the interference wave power of the communication channel is below a certain value, and the desired mobile-to-interference wave power ratio in the communication channel is more than a required value In the transmission power control method of the system, when a call channel is allocated to a newly generated call, the base station and the mobile station measure the reception power of the desired wave, and the reception power of the desired wave is a constant value. When each of the above-mentioned smallest transmission powers is selected and the communication channel is switched during a call, the base station and the mobile station measure the reception power of the desired wave and receive the reception power of the desired wave. , The minimum transmission power that exceeds a certain value is selected, and if there is no usable communication channel, the base station and the mobile station receive the reception power of the desired wave and the interference wave of the channel selected as the switching destination. The power is measured, and the smallest transmission power at which the reception power of the desired wave is equal to or higher than the predetermined value and the power ratio of the desired wave to the interference wave is equal to or higher than the required value is selected.

[0010]

According to the first aspect of the present invention, for a newly generated call, the transmission power is increased only when the desired wave level is small, and the transmission power is increased when the desired wave to interference wave power ratio is small. Never. Therefore, the average transmission power becomes low and the interference wave level becomes low as a whole. For handoff, the transmission power is increased if the desired wave-to-interference wave power ratio is low, but the forced disconnection rate can be suppressed to a low level because the interference wave level is low and the probability that there is no empty channel is low.

According to the second aspect of the present invention, after checking that there is no channel that can be used without increasing the transmission power for handoff, the transmission power is increased and the usable channel is selected and assigned. Therefore, the channel is not used with high transmission power, the interference wave level can be further reduced, and the forced disconnection rate can be further reduced.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 3 shows an example of the configuration of a mobile communication system in which the transmission power control system of the present invention is used. This mobile communication system includes base stations 310 and 311 and a mobile station 32.
0, 321, and a control device 330. Also, D
up, Uup, Ddown, and Udown are the upstream desired wave level at the base station 310, the upstream interference wave level at the base station 310, the downstream desired wave level at the mobile station 320, and the downstream interference wave level at the mobile station 320, respectively.

The transmission power changes the control amount for each communication. Here, description will be made taking as an example the case where the control is performed in one step, that is, the control amount is 0 or the constant value A is set. If the transmission power when the control amount is 0 is P, the transmission power when the control amount is A is P-A
Becomes In the transmission power control method of the present invention, a method of selecting transmission power differs between a call channel assigned to a newly generated call and a call channel assigned to handoff.

FIG. 1 shows a transmission power selection algorithm which is an embodiment of the transmission power control system of the first invention.

When a channel allocation request is issued to the mobile station 320 close to the base station 310 (step 101), if this channel allocation request is for a newly generated call (steps 102, 103), an arbitrary algorithm is used. To select the communication channel i (step 104), and the base station 310 measures the uplink interference wave level Up and the downlink interference wave level Udown at the mobile station 320, and these channels are both below a certain carrier sense level C. Is determined to be an empty channel (step 105). Next, the upstream desired wave level Dup is measured, and if the ratio (Dup-A) between this and the control amount is greater than or equal to the required desired wave level Dreq, the upstream transmission power Pup is set to P-A, and otherwise P is set (step S 106, 107, 108). Similarly for downlink, the downlink desired wave level Ddown is measured, and if the ratio of this and the control amount (Ddown-A) is equal to or higher than the required desired wave level, the downlink transmission power Pdown is set to P-A, and otherwise is set to P ( Steps 109, 110, 111). Then, the uplink desired wave-to-interference wave power ratio (CIRup = Dup− (P−Pup) −) in the base station 310 after the transmission power control is further performed.
Up) and the downlink desired wave-to-interference wave power ratio (CIRdown = Ddown− (P−Pdown) in the mobile station 320.
If (n) -Udown) is greater than or equal to the required value CIRreq (step 112), it is allocated and used (step 128). If it is determined in step 105 that the channel is not an empty channel and if the desired wave-to-interference wave power ratio is not greater than or equal to the required value in step 112, the parameter i is set to 1 until all channels are selected (step 113). (Step 114) and channel selection (step 10)
Repeat from 4). After selecting all channels, the call is lost (step 115).

If the channel allocation request in step 101 is for handoff (step 103), the speech channel i is selected by an arbitrary algorithm (step 1).
16), the base station 310 measures the uplink interference wave level Uup and the downlink interference wave level Udown in the mobile station 320, respectively, and determines that a channel having a constant carrier sense level C or less is an empty channel (step 117). ). Next, the upstream desired wave level Dup is measured, and the ratio of this to the control amount (Dup-A) determines the desired desired wave level Dre.
If q or more and the ratio of the desired wave-to-interference wave power ratio and the control amount (Dup-A-Up) is not less than the required value CIRreq of the desired wave-to-interference wave power ratio, the upstream transmission power Pup is P-
A and P otherwise (steps 118 and 11)
9, 120). Similarly for down link, desired down wave level Ddow
n is measured, the ratio of this to the control amount (Ddown-A) is equal to or higher than the required desired wave level Dreq, and the ratio of the desired wave-to-interference wave power ratio and the control amount (Ddown-A-Udown).
Is equal to or higher than the required value CIRreq of the desired wave-to-interference wave power ratio, the downlink transmission power Pdown is set to P-A, and otherwise P is set (steps 121, 122, 123). Then, the uplink desired wave-to-interference wave power ratio (CIRup = Dup− (P−Pu) in the base station 310 after the transmission power control is further performed.
p) -Uup) and downlink desired wave-to-interference wave power ratio (CIRdown = Ddown- (PP) in the mobile station 320.
If (down) -Udown) is greater than or equal to the required value CIRreq (step 124), it is allocated and used (step 128). If it is determined in step 117 that the channel is not an empty channel and if the desired wave-to-interference wave power ratio is not greater than or equal to the required value in step 124, the parameter i is selected until all channels are selected (step 125).
Is incremented by 1 (step 126) and channel selection (step 116) is repeated. After selecting all the channels, forced disconnection is performed (step 127).

FIG. 2 shows a transmission power selection algorithm which is an embodiment of the transmission power control system of the second invention.

When a channel allocation request is issued to the mobile station 320 near the base station 310 (step 201), the call channel i is selected by an arbitrary algorithm (step 2).
02, 203), and the base station 310 detects the uplink interference wave level Uu.
p and the downlink interference wave level Udow at the mobile station 320
Each of n is measured, and a channel whose carrier sense level C is equal to or lower than a certain level is determined to be an empty channel (step 204). Next, the upstream desired wave level Dup is measured, and if the ratio of this to the control amount (Dup-A) is not less than the required desired wave level Dreq, the upstream transmission power Pup is P-A.
And P otherwise (steps 205, 206,
207). Similarly, for the downlink, the downlink desired wave level Ddown is measured, and if the ratio of the downlink desired wave level Ddown (Ddown-A) is equal to or higher than the required desired wave level, the downlink transmission power Pdown is set to P-.
A and P otherwise (steps 208, 20)
9, 210). And the base station 3 after the transmission power control
Uplink desired wave-to-interference wave power ratio (CIRup =
Dup- (P-Pup) -Uup) and downlink desired wave-to-interference wave power ratio (CIRdown = D) in the mobile station 320.
If down- (P-Pdown) -Udown) is greater than or equal to the required value CIRreq (step 211), it is assigned and used (step 229). Step 20
If it is determined in step 4 that the channel is not an empty channel, and if the desired wave-to-interference wave power ratio is not greater than or equal to the required value in step 211, parameter i is set to 1 until all channels are selected (step 212). Addition (step 213) and channel selection (step 203) are repeated. After selecting all the channels, if the channel allocation request in step 201 is for a newly generated call (step 21
4) The call is lost (step 215).

If the channel allocation request in step 201 is for handoff (step 214), the speech channel i is selected by an arbitrary algorithm (step 2).
17), the base station 310 determines that a channel in which both the uplink interference wave level Uup and the downlink interference wave level Udown in the mobile station 320 are equal to or lower than a constant carrier sense level C is an empty channel (step 218). Next, the ratio (Dup-A) of the upstream desired wave level Dup to the control amount is equal to or higher than the required desired wave level Dreq, and the ratio of the desired wave-to-interference wave power ratio and the controlled variable (Dup-A-Up) is the desired wave. If it is equal to or higher than the required value CIRreq for the interference wave power ratio, the upstream transmission power Pup is set to P-A, and otherwise P is set (steps 219, 220, and 221). Similarly in the downlink, the ratio (Ddown-A) of the downlink desired wave level Ddown and the control amount is equal to or higher than the required desired wave level Dreq, and the ratio of the desired wave-to-interference wave power ratio and the control amount (Ddown-A-Udown).
Is the required value CIRreq of the desired wave to interference wave power ratio or more, the downlink transmission power Pdown is set to P-A, and otherwise P is set (steps 222, 223, and 224). Then, the uplink desired wave-to-interference wave power ratio (CIRup = Dup− (P−Pu) in the base station 310 after the transmission power control is further performed.
p) -Uup) and downlink desired wave-to-interference wave power ratio (CIRdown = Ddown- (PP) in the mobile station 320.
If (down) -Udown) is greater than or equal to the required value CIRreq (step 225), it is assigned and used (step 229). If it is determined in step 218 that the channel is not an empty channel and if the desired wave-to-interference wave power ratio is not greater than or equal to the required value in step 225, 1 is set to parameter i until all channels are selected (step 226). The process is repeated from addition (step 227) and channel selection (step 217). After all channels are selected, forced disconnection is performed (step 228).

As described above, the transmission power for the newly generated call is increased only when the desired wave level is low, and the transmission power is increased for the handoff even when the desired wave-to-interference wave power ratio is low. Therefore, it is possible to suppress the probability that channels are not allocated and reduce the forced disconnection rate.

[0022]

As described in detail above, according to the first invention, the probability that there is no channel that can be allocated for handoff is low, and the forced disconnection rate can be reduced. Further, according to the second invention, the forced cutting rate can be further reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a control algorithm of a transmission power control system of the first invention.

FIG. 2 is a diagram showing an embodiment of a control algorithm of the transmission power control method of the second invention.

FIG. 3 is a diagram illustrating a configuration example of a mobile communication system.

[Explanation of symbols]

102, 202, 216 Initialization of channel selection parameters 103, 214 Branch depending on the type of channel allocation request 104, 116, 203, 217 Channel selection 105, 117, 204, 218 Carrier sense 106-111, 118-123, 205- 210, 2
19 to 224 Transmission power selection 112, 124, 211, 225 Desired wave to interference wave power ratio condition determination 113, 125, 212, 226 All channel selection condition determination 114, 126, 213, 227 Channel selection parameter update 310 , 311 Base station 320, 321 Mobile station 330 Control device

Claims (2)

[Claims] 1. A base station provided in each of a plurality of cells selects a call channel from a plurality of call channels in response to a call request, and a base station and a mobile station can select a plurality of transmission powers. The transmission power of the cellular mobile communication system that allocates the speech channel when the interference wave power of the speech channel is below a certain value and the desired wave-to-interference power ratio in the speech channel is above a required value. In the control method, when allocating a communication channel to a newly generated call, the base station and the mobile station measure the received power of the desired wave, and the received power of the desired wave becomes a certain value or more. When selecting a small transmission power and switching the call channel during a call, the base station and mobile station receive the desired signal and select the channel to switch to. Mobile communication characterized by measuring the received power of a wave and selecting the smallest transmission power at which the received power of the desired wave is equal to or more than the predetermined value and the power ratio of the desired wave to the interference wave is equal to or more than a required value. System transmission power control method. 2. A base station provided in each of a plurality of cells selects a call channel from a plurality of call channels in response to a call request, and the base station and the mobile station can select a plurality of transmission powers. The transmission power of the cellular mobile communication system that allocates the speech channel when the interference wave power of the speech channel is below a certain value and the desired wave-to-interference power ratio in the speech channel is above a required value. In the control method, when allocating a communication channel to a newly generated call, the base station and the mobile station measure the received power of the desired wave, and the received power of the desired wave becomes a certain value or more. When selecting a small transmission power and switching the communication channel during a call, the base station and mobile station measure the reception power of the desired wave, and the reception power of the desired wave is below a certain value. If the available transmission channel does not exist, the base station and mobile station measure the reception power of the desired wave and the reception power of the interference wave of the channel selected as the switching destination. A transmission power control method for a mobile communication system, characterized in that the smallest transmission power at which the reception power of the desired wave is equal to or higher than the predetermined value and the power ratio of the desired wave to the interference wave is equal to or higher than a required value is selected.