JPH07203519A - Radio channel allocating method - Google Patents

Abstract

PURPOSE:To make the probability of acquisition of each base station by a mobile station approximately equal. CONSTITUTION:This method estimates the phase (timing) phi3 of the control channel 21 of a base station which newly starts transmission and the reception level L3 of the terminal of its service area so as to receive the control channels 16 and 17 of peripheral base stations by the base station to detect their levels L1 and L2 and their phases phi1 and phi2. The probability P1 of acquiring the channel 16 is obtained by phi21/(2pi)g(L1).phi31/(2pi)(1--g(L<3>)).phi32(2pi)(1-g(L2)) and subsequently the probability P2 and P3 of respectively acquiring the channels 17 and 21 are obtained similarly so as to obtain phi3 making the distribution of P1 to P3 minimum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention communicates using the time division multiple access (TDMA) on the same frequency, and the base station performs autonomous distributed control, transmits a control channel at a timing that does not give interference, and moves. The present invention relates to a method of allocating a control channel to a base station so as to minimize a traffic deviation between the base stations in a mobile communication system for transmitting a signal to the station.

[0002]

2. Description of the Related Art Conventionally, when a base station is newly provided and operated for the first time, or when the main power is supplied to start the base station, the control signal is transmitted from the base station before the control signal is transmitted. After confirming that the control channel (timing) to be transmitted is not being transmitted by another base station, or even if it is transmitting, it is lower than the level that causes interference, then control signal is sent on that control channel (timing). Was being sent.

[0003]

When a mobile station searches for a control channel and first captures a control signal of a prescribed level or higher, a control signal is sent and received between the mobile station and the base station according to the control signal of the base station. In the mobile communication system that performs
, When the mobile station 11 is between the cell 12 and the cell 13, that is, the base station 14 of the cell 12 and the cell 13
When it is possible to communicate with any of the base stations 15 of
The mobile station 11 controls the control signal (control channel) 1 of the base station 14.
If the probability of capturing 6 is equal to the probability of capturing the control signal (control channel) 17 of the base station 15, the base station 14
There is no bias in the traffic between and.

However, the cell 1 partially overlaps with the cell 12
8 is provided and a new control signal is transmitted from the base station 19 of the cell 18, the base station 14,
When a control signal is transmitted by selecting a channel that does not interfere with each of the 15 control channels 16 and 17, a control channel (timing) transmitted by the base station 19 as shown in FIG.
21 may be in a state slightly before the control channel (timing) 16 transmitted by the base station 14, and in such a case, the mobile station 11 causes the control channels 16 and 21 of the base station 14 and the base station 19 to be different from each other. In a state in which the mobile station can receive the control channel 21, the mobile station captures the control channel 21 of the base station 19 when the channel search is started from immediately after the control channel 16 to immediately before the control channel 21. The control channel 16 of the station 14 is acquired when the channel search is started from immediately after the control channel 21 to immediately before the control channel 16, and this probability becomes extremely small. Therefore, the traffic of the base station 19 increases, and the call loss rate increases even though the traffic accommodated by the base station 14 has a margin.

[0005]

According to the first aspect of the present invention, the phase of the control channel of another base station is detected, and the control channel signal is transmitted at a phase that is as far as possible from that phase. The phase of the control channel of another base station is detected so that its reception level is equal to or higher than a predetermined value. According to the invention of claim 2, the reception level of the control channel of the other base station is measured, and the signal of the control channel is transmitted at a phase that is 180 degrees out of phase with the maximum phase thereof.

According to the third aspect of the invention, one TDMA cycle is used.
The level of the control signal transmitted from the other base station is measured over the above, the phase difference between the signals of the adjacent phases is detected by using the measured one signal as the phase reference, and the control channel is now set. Predetermine the reception level that will be received at the zone edge that communicates with the mobile station made by the base station that is trying to allocate, assuming the phase φ of the control channel to be allocated now, and that phase φ, Phase difference with the adjacent phase of the measured signal, each phase difference, the measured reception level, the probability of capturing each base station of the mobile station near the zone edge from the predetermined reception level, the The phase φ that minimizes the variance of the probability is obtained, and the control channel signal is transmitted at that phase φ.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the processing after the phase detection is performed for a reception level equal to or higher than a threshold value.

[0008]

FIG. 1 shows an embodiment of the invention of claim 1. The base station 19 which is going to newly transmit the signal of the control channel receives the control signal from the peripheral base station for one cycle or more of TDMA, and measures the phase difference (time difference) of the sequentially received signals. To do. At that time, signals with a reception level below the threshold that does not cause interference are ignored. For example, as shown in FIG. 1A, control channel signal 1 from base station 14
6 and the control channel signal 17 from the base station 15 and the control channel signal 23 from another base station are received, but the reception level of the control channel signal 23 is below the threshold value. Therefore, the phase difference φ ₁₂ between the control channel signal 16 and the next control channel signal 17, and the control channel signal 17
And detecting each a phase difference phi ₂₁ to the next control channel signal 16, assigns the maximum phase difference, the control channel 21 of the base station 19 to the phase of the middle of phi ₂₁ in this example as shown in FIG. 1B . In this way, the control channel 2 has a phase separated as far as possible from the phase of the control channel of each receiving base station.
1 can be assigned.

Next, an embodiment of the invention of claim 2 will be described with reference to FIG. The control channel signals of the peripheral base stations are received one by one, the reception level thereof is measured, and it is checked whether or not the reception level is higher than the reception level of the control channel signal previously received and stored (S ₁ ). If the level of the received signal is higher, the control channel signal BS _m and phase φ
_M and _m are stored instead of the previous memory (S ₂ ), it is checked whether the reception level has been measured for all control channels, and if not completed for all channels, the process returns to step 1 (S ₃ ). If the level of the signal received at step S ₁ is lower than the stored reception level, the process immediately proceeds to step S ₃ . When the reception level measurement for all control channels is completed in step S ₃ , the stored phase φ
The control channel of the base station is transmitted with a phase (timing) φ _n that is opposite to _m , that is, shifted by π (S ₄ ).

For example, as shown in FIG. 1C, a control channel signal 1
6 and 17 are sequentially received, and the one with the highest received level is left. In this example, the control channel signal 1 from the base station 14
6 is received first, its reception level is stored, then
Since the control channel signal 17 from the base station 15 is received and its reception level is smaller than the control channel signal 16,
The reception level of the control channel signal 16 is kept stored, and the next reception is the control channel signal 16 from the base station 14 again. Therefore, the control channel signal of the maximum reception level is 16, which is shown in FIG. 1D. As shown, the control channel signal 21 is transmitted from the base station 19 in a phase shifted by 180 degrees with respect to the phase of the control channel signal 16.

Next, an embodiment of the invention of claim 3 will be described with reference to FIG. In this case, the base station 19 which is going to transmit the control channel signal 21 receives the control channel signal from another base station for one cycle or more of TDMA, measures the reception level, and controls the one The phase of another reception control channel signal is detected using the channel signal as a phase reference. For example, as shown in FIG. 3A, the control channel signal 16 from the base station 14 is received with the phase φ ₁ and the level L ₁ , and the control signal 17 from the base station 15 is received with the phase φ ₂ and the level L ₂ and received. It is assumed that these are only these two control channel signals. On the other hand, the base station 1 which the mobile station will receive at the edge of the communication zone with the mobile station created by the base station 19
The reception level of the control channel signal 21 from 9 is previously set to L ₃
Assume

In the mobile communication, the level fluctuation is large depending on the state of the propagation path, and the level L _j for judging that the mobile station is within the communication range with the base station according to the reception level L _r ,
The probability P that the reception level L _r exceeds is calculated as g (L _r ). Therefore, assuming the control channel signal 21 to be transmitted between the adjacent reception control channel signals, the phase difference between the adjacent control channel signals within one TDMA cycle including this control channel signal is obtained, respectively, and these phase differences,
From each measured reception level and the expected reception level, obtain the probability that the mobile station captures the control channel signal of each base station, and make each probability as equal as possible, that is, minimize the variance of these probabilities. Control channel signal 21
Find the phase of.

In the example of FIG. 3, as shown in FIG.
Transmission phase φ of channel signal 21₃Is φ ₁Greater than φ₂Than
If small, move control channel signal 16 of base station 14
Probability that a station will capture P₁Can be expressed by the following equation. P₁= (Φ_{twenty one}/ 2π) g (L₁) × (φ₁₃/ 2π) (1
-G (L₃)) × (φ ₃₂/ 2π) (1-g (L₂)) Φ_{twenty one}Is from control channel signal 17 to control channel signal 16
Phase difference up to φ₁₃Control channel signal 16 to control channel
Phase difference up to channel signal 21, φ₃₂Is the control channel signal
It is the phase difference from 21 to the control channel signal 17.
(Φ_{twenty one}/ 2π) g (L₁) Is φ_{twenty one}The mobile station during the search
Is the probability of starting and capturing the control channel signal 16.
, (Φ₁₃/ 2π) (1-g (L₃)) Is the mobile station φ₁₃
To start the search to capture the control channel signal 21
There is no probability, (φ₃₂/ 2π) (1-g (L₂)) Is
Mobile station is φ₃₂Control channel signal 1
Probability of not capturing 7.

Similarly, the control channel signal of the base station 15
The probability P that the mobile station captures 17₂Can be expressed by the following equation. P₂= (Φ₃₂/ 2π) g (L₂) × (φ_{twenty one}/ 2π) (1
-G (L₁)) × (φ ₁₃/ 2π) (1-g (L)) The mobile station captures the control channel signal 21 of the base station 21.
Probability P₃Can be expressed by the following equation.

P₃= (Φ₁₃/ 2π) g (L₃) × (φ_{twenty one}
/ 2π) (1-g (L₁)) × (φ ₃₂/ 2π) (1-g
(L₂)) Furthermore, as shown in FIG. 3B, φ₃Is φ₂Greater than φ₁Less than
In this case, the mobile station sends control channel signals 16, 17, 21
Probability of capturing each P₁, P₂, P₃Are respectively
Given in.

P ₁ = (φ ₃₁ / 2π) g (L ₁ ) × (φ ₁₂
/ 2π) (1-g (L ₂ )) × (φ ₂₃ / 2π) (1-g
(L ₃ )) P ₂ = (φ ₁₂ / 2π) g (L ₂ ) × (φ ₂₃ / 2π) (1
−g (L ₃ )) × (φ ₃₁ / 2π) (1-g (L ₁ )) P ₃ = (φ ₂₃ / 2π) g (L ₃ ) × (φ ₃₁ / 2π) (1
-G (L ₁ )) × (φ ₁₂ / 2π) (1-g (L ₂ )) The above probabilities P _{1 to} P ₃ should be as equal as possible, that is, the variance of P _{1 to} P ₃ should be minimized. Φ ₃ is determined so that

In the embodiment shown in FIG. 3, the calculation amount can be reduced by executing the above-mentioned processing for the reception level equal to or higher than the threshold value.

[0018]

As described above, according to the present invention, the control channel of the base station to be newly transmitted is determined in consideration of the transmission timing (phase) of the control channel signals of the peripheral base stations, and each base station , The probability of being captured by the mobile station becomes almost equal, and the traffic is not biased to a specific base station,
It is possible to provide high-quality services with a low call loss rate.

[Brief description of drawings]

FIG. 1 is a diagram showing an arrangement of control channel signals for explaining an embodiment of each invention of claims 1 and 2;

FIG. 2 is a flow chart showing an embodiment of the invention of claim 2;

FIG. 3 is a diagram showing an arrangement of control channel signals for explaining an embodiment of the invention of claim 3;

FIG. 4 is a diagram showing a configuration example of a mobile communication system.

FIG. 5 is a diagram showing an arrangement of control channels for explaining problems of a conventional wireless channel allocation method.

Claims (4)

[Claims] 1. Two-way communication between two or more wireless base stations (hereinafter referred to as base stations) and the base stations and wireless mobile stations (hereinafter referred to as mobile stations) in a TDMA (time division multiple access) system. In mobile radio communication for performing the control channel allocation, the control channel allocated to one frequency is used as a plurality of control channels in a time-division manner in a plurality of base stations to continuously transmit control signals at that time. In the method, the phase of a control signal transmitted from another base station is detected over one or more of the TDMA cycles, and the control channel signal is transmitted at a phase that is as far as possible from the detected phase. Radio channel allocation method. 2. Two-way communication between two or more radio base stations (hereinafter referred to as base stations) and the base stations and radio mobile stations (hereinafter referred to as mobile stations) in a TDMA (time division multiple access) system. In mobile radio communication for performing a method, a control channel allocated to one frequency is used as a plurality of control channels in a time division manner by a plurality of base stations, and a control signal is continuously transmitted periodically.
In the method of allocating the control channel at that time, the level of the control signal transmitted from another base station over one or more of the TDMA cycle and the phase within the cycle are detected, and the highest level among the detected levels is detected. The level of the signal with the highest level is detected, and the detected phase with the highest level is 18
A radio channel allocation method, characterized in that a control channel signal is transmitted in a phase shifted by 0 degree. 3. Mobile radio communication in which two or more radio base stations (hereinafter referred to as base stations) and two-way communication between the base stations and radio mobile stations (hereinafter referred to as mobile stations) are performed by the TDMA method. A method of allocating a control channel at that time in a method of continuously transmitting control signals as a plurality of control channels by using a control channel allocated to one frequency in a time division manner in a plurality of base stations, The levels of all control signals transmitted from other base stations and receivable over one or more of the TDMA periods are measured, and one signal measured in the above measurement is used as a phase reference, and each of the adjacent measured above is measured. Detect the phase difference between the phase signals and set in advance the reception level that will be received at the zone edge that communicates with the mobile station created by the base station that is about to allocate the control channel. Assuming the phase φ of the control channel, and the phase φ, the phase difference between the adjacent phase of the measured signal and the phase difference of each adjacent phase signal, the measured reception level and the predetermined From the reception level, the probability that the mobile station captures each base station near the zone edge is obtained, the phase φ that minimizes the variance of the above probabilities is obtained, and the control channel signal is transmitted at that phase φ. Radio channel allocation method. 4. The phase difference detection, the probability determination, and the dispersion minimum phase determination for the measured signal having a measurement level equal to or higher than a threshold value in the measured signal. Wireless channel allocation method.