JP2003259442A - Cdma (code division multiple access) base station apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CDMA base station apparatus capable of insuring communication quality of a user during communication and communicating with reduction in interference signals by using an array antenna. <P>SOLUTION: The CDMA base station apparatus comprises a control channel receiving part for receiving assignment request signals for new communication channels; a prediction part for predicting information on each incoming wave from mobile stations in communication and new mobile stations, by using signals received at the array antenna; and an assignment control part for communication channel for deciding the pros and cons of assigning new communication channels by information on communication quality based on the signals received at the array antenna, the assignment request signal for new communication channels, and information on the predicted each incoming wave. When new mobile stations communicate by using the new communication channels, if at least one of new mobile stations and one of each mobile station in communication determine that it is impossible to perform communication satisfying the predicted quality, the apparatus refuses an assignment of the new communication channels. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA base station apparatus used in a CDMA (Code Division Multiple Access) cellular mobile radio communication system using an array antenna. This is to determine whether or not a new user can assign a new communication channel to a mobile station of a new user in consideration of the influence on the communication quality of an existing mobile station during communication.

[0002]

2. Description of the Related Art W-CDMA (W
ide band-Code Division MultipleAccess)
High-speed, wide-band communication is expected for not only voice but also moving images. Furthermore, recently, studies have begun on the 4th generation mobile communication system aiming at high-speed and wideband transmission, which is about 10 times higher than the 3rd generation system. In order to provide high-speed services with limited frequency resources, it is necessary to make more efficient use of frequencies, and using adaptive array antennas for base stations is being considered as one of the countermeasures. In a CDMA communication system, by using different spreading codes, many users can communicate at the same time in the same frequency band. However, when the number of simultaneous communication users increases, intersymbol interference cannot be ignored. Therefore, if an adaptive array antenna is used as the base station antenna, it is possible to reduce interference signals.

However, when a new communication channel allocation request is received when a new call (outgoing call, incoming call) for which communication is newly requested occurs, the directional characteristic of the adaptive array antenna is changed, and the movement during communication is performed. The communication quality of the station may be significantly deteriorated and communication may not be continued.
FIG. 7 is an explanatory diagram showing an example of a CDMA mobile communication system using an adaptive array antenna. In FIG. 7A, 21 is a mobile station of user 1, 22 is a mobile station of user 2, 24 is a base station, 25 is an adaptive array antenna of the base station, and 25a and 25b are antenna elements thereof. The number of elements is arbitrary. By controlling the antenna weight that multiplies the output signal of each antenna element during reception, the reception beam pattern can be freely controlled.
Reference numeral 26 is a cover area (cell) of the base station 24. In the uplink in which the transmission waves from the mobile stations 21 and 22 are received by the base station 24, the mobile station 21 of the user 1 receives the beam with the beam pattern shown as the user 1 directivity 31. User 1 directivity 31 has a main lobe in the direction of mobile station 21 of user 1 and a beam null in the direction of mobile station 22 of user 2. The same applies to the user 2 directivity 32 with respect to the mobile station 22 of the user 2.
However, the number of beam nulls that can be controlled by the adaptive array antenna is (number of array antenna elements-1).
It depends on the degree of freedom. However, in a CDMA communication system, usually, simultaneous communication is performed with users who exceed the number of elements of the array antenna.

In FIG. 7B, the mobile station 23 of the user 3 newly performs communication in a state where two users whose number is equal to the number of antenna elements are simultaneously communicating as shown in FIG. 7A. The case of obtaining is shown. There are cases where the mobile station 23 of the user 3 makes a call and cases where the mobile station 23 of the user 3 makes a call to the mobile station 23 of the user 3 located inside and outside the cover area 26 via the base station 24. . If the mobile station 2 of user 3
If 3 newly starts communication, the number of users in communication exceeds the number of antenna elements, so that the beam null cannot be directed to another station. In addition, when the angular difference of each user approaches the resolution or more, including the case where the number of users is less than the number of antenna elements, the directivity of one user approaches the direction of the beam null with respect to other users. However, there is also a problem that the gain decreases and the amount of interference increases.
As described above, the amount of interference greatly varies depending on the angular relationship including the mobile station 23 of the new user 3, the mobile station 21 of the user 1 and the mobile station 22 of the user 2 in communication. Furthermore, this interference has a great influence on the communication quality of the mobile station 21 of the user 1 and the mobile station 22 of the user 2 which are already in communication.

Therefore, even when the mobile station 23 of the new user 3 requests allocation of a new communication channel for a new call, the mobile station 2 of another user (user 1, user 2).
In some cases, the communication quality of 1 and 22 already in communication exceeds the required quality and there is no influence, but depending on the position of the mobile station 23 of the new user 3, the mobile station 23 of the new user 3 may be present.
Not only the communication quality of the
The communication quality of the mobile station 22 may also deteriorate, and communication may be disabled during communication. Therefore, in the adaptive array antenna, new communication channel allocation control for determining whether or not to accept a new communication channel allocation request for a new call (outgoing call, incoming call) for which communication is newly requested is very important. However, in the case of applying the adaptive array antenna to the CDMA system, almost no study has been made on a new communication channel allocation control method in which users far exceeding the number of antenna elements perform simultaneous communication.

Considering the case where a normal omni antenna or a sector antenna is used in the CDMA system without using an adaptive array antenna, the interference level in the same cell is determined by the transmission power control (or the number of mobile stations in communication). When one mobile station can use a plurality of communication channels, it can be regarded that it is almost proportional to the number of communication channels in communication). Therefore, when a new call occurs, the number of all mobile stations currently in communication ( (Or the total number of communication channels), the transmission rate of each mobile station, and the total number of mobile stations (or the total number of communication channels) that can be accommodated in the base station, which is preset in consideration of the amount of interference from neighboring cells. By comparing with, it is possible to easily determine whether or not a new communication channel can be assigned. However, when the adaptive array antenna is applied, the directivity pattern of the adaptive array antenna changes depending on the number of users in communication and the positions thereof, so that the method of determining whether or not to allocate the new communication channel becomes complicated.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a user who is in communication even when a new communication channel allocation request signal is accepted when a new user makes or receives a call. A CDMA base station device that guarantees the communication quality of the wireless communication system and enables communication with reduced interference signals by using an array antenna without having to worry about the communication quality fluctuation due to the traffic fluctuation in the wireless zone during communication. It is intended to be provided.

[0008]

According to a first aspect of the present invention, a CDMA base for communicating with a plurality of mobile stations in a wireless zone by code division multiple access using an array antenna. Control station receiving means for receiving a new communication channel allocation request signal from the array antenna using a control channel from a new mobile station requesting allocation of a new communication channel among the plurality of mobile stations An estimating means for estimating information about individual arriving waves from the mobile station in communication and the new mobile station among the plurality of mobile stations by using a received signal of the array antenna; and the control channel receiving means. When the new communication channel allocation request signal is received, the received signal of the array antenna, the new communication channel allocation request signal, and the estimation signal are received. The communication channel allocation control means for determining whether or not to allocate a new communication channel to the new mobile station based on communication quality information based on the information about the individual incoming waves estimated by the means. The control means, when the new mobile station communicates using the communication channel, at least one mobile station of the new mobile station and each of the mobile stations in communication satisfies the communication quality specified in advance. When it is determined that communication cannot be performed, the new communication channel allocation to the new mobile station is rejected.
Therefore, if a new communication channel allocation request is temporarily accepted when a new user makes or receives a call, and if at least one mobile station cannot carry out communication that satisfies the communication quality specified in advance, then a new communication channel for the new mobile station is obtained. By rejecting the allocation of the communication, once the communication channel is allocated, the communication quality of the user who is communicating is guaranteed, and is not affected by the fluctuation of the call origination volume during communication or the number of communication channels of the base station equipment. Therefore, the system design in which the array antenna is introduced becomes easy, and the performance of the array antenna is utilized to enable communication with reduced interference signals.

According to a second aspect of the present invention, in the CDMA base station apparatus according to the first aspect, the radio zone is angle-divided into a plurality of sectors, and the array antenna is arranged for each sector. Code division multiple access is performed for each sector, and the estimating means estimates information regarding the individual incoming waves for each sector in which the mobile station in communication and the new mobile station are located, and assigns the communication channel. The control means, when the control channel receiving means receives the new communication channel allocation request signal,
The received signal of the array antenna and the new communication channel allocation request signal, and the individual from the communicating mobile station and the new mobile station located in all the sectors in the radio zone estimated by the estimating means. Whether or not to allocate the new communication channel to the new mobile station is determined based on the information on the communication quality based on the information on the incoming wave. Therefore, whether or not to allocate a new communication channel is determined by also taking into account information about individual arriving waves from a mobile station in communication and a new mobile station located in another sector in the same radio zone that is easily affected by interference. Therefore, the communication quality can be accurately predicted. In addition, a plurality of sectors in the same wireless zone usually share the base station equipment at the same place, so that the incoming wave information can be easily managed in a unified manner, which can be easily realized.

[0010]

1 is a flow chart for explaining an embodiment of a CDMA base station apparatus of the present invention. FIG. 2 is an explanatory diagram showing an example of a communication channel management table and information of mobile stations in communication used in the embodiment of the present invention. FIG. 2A is a communication channel management table, and FIG. 2B is an explanatory diagram showing information on mobile stations in communication. Although not shown in the figure, the configuration of the embodiment of the CDMA base station apparatus of the present invention is such that, from among a plurality of mobile stations, a new mobile station requesting allocation of a new communication channel uses a control channel to perform new communication. A control channel receiving unit that receives a channel allocation request signal from an array antenna, and information about individual arriving waves from the mobile station in communication and the new mobile station among the plurality of mobile stations, using the reception signal of the array antenna. When estimating the estimation unit and the control channel receiving unit receives a new communication channel allocation request signal, the received signal of the array antenna and the new communication channel allocation request signal and information about the individual arriving waves estimated by the estimating unit, Based on communication quality information based on
The communication channel allocation control unit determines whether or not to allocate a new communication channel to a new mobile station.

With reference to FIGS. 1 and 2, a description will be given of a new communication channel allocation control operation for deciding whether or not a new communication channel can be allocated when a new call (calling or receiving call) to a mobile station of a new user occurs. To do. Here, in particular, only when the number of communication channels requested by a new user is less than or equal to the number of unused communication channels and the estimated communication quality of all mobile stations satisfies the required communication quality of each, a new communication channel for a new call is provided. The case of performing allocation will be taken up as an example. In the flowchart of FIG. 1, reading and writing required data from the communication channel management table shown in FIG.
Also, the estimation of the incoming wave information regarding the incoming wave from the mobile station in communication is described separately from the flow of the new communication channel allocation control operation. That is, the communication channel management table shown in FIG. 2A manages the state of the communication channel currently in use, and is updated at any time depending on whether the communication channel is secured or released, separately from the flow of FIG. this is,
This is for distinguishing a communication channel in use and an unused communication channel, and for making a call loss when there is a new communication channel allocation request exceeding the number of unused communication channels. Let Nc be the total number of communication channels of the base station, K be the total number of users in communication, and k ₁ to k _K be mobile station numbers that specify each user k (k = _{1 to K} ).

In this table, communication channel numbers 1 to Nc
Corresponding to, the mobile station numbers k _{1 to} k _K , which are information for identifying the user using each communication channel, are written. For example, if the user 2 uses two communication channels with communication channel numbers 1 and 2, the mobile station number k ₂ is written corresponding to each of the communication channel numbers 1 and ₂ . For a communication channel that is not used, information indicating "empty" is written corresponding to the communication channel number. The total number of users K in communication and the total number of channels N used by all users can be calculated from the information in the above-mentioned table, but may be directly written in this communication channel management table. If it is premised that each user uses only one channel, the number of used channels N = the number of users K. Figure 2
The information on the in-communication mobile station shown in (b) is information on the mobile station necessary for communication quality at the time of new communication channel allocation control.
The information of the mobile station during communication is information that needs to be managed separately from the flow of FIG.

First, an example of the contents of the mobile station information collected will be described with reference to FIG. Individual mobile station information during communication relating to users (k = 1 to K) in communication is
Estimated direction of arrival θ _k , estimated received power P _k , assignable communication channel CINR (Carrier to Interference plus Noise Rati)
o) such as γ ^(k) req. The estimated arrival direction θ _k is the direction of the mobile station of the user k seen from the base station, and the estimated received power P _k is the received power of the incoming wave from this mobile station. If the array propagation vector v _k is used, the estimated arrival direction θ _k is unnecessary. The estimation unit described above receives the estimated arrival direction θ _k (or the array propagation vector v _k ) and the estimated reception power P _k as the arrival wave information regarding the arrival wave from each mobile station in communication, and receives the received signal from the array antenna. The signal (the array input signal of each element of this array antenna) is used for estimation at any time. The arrival wave is estimated by the well-known MUSIC (M
Ultiple SIgnal Classification) and ESPRIT (Estimatio
n of Signal Parametersvia Rotational Invariance Te
chniques) or beamformer
It can be done by law. CINR is a parameter of communication quality in the carrier band. The communication quality parameters used for the new communication channel allocation control may be those that can be mutually converted into CINR. For example, SINR (Signal to Interference plus Noise R in the baseband band
ratio) and BER (Bit Error Rate). Since these pieces of information are necessary when it is necessary to estimate the above-mentioned communication quality, they need to be managed and stored as a table like the communication channel management table shown in FIG. There is no. However, in order to speed up the process of communication quality estimation, it may be stored as one piece of information in the communication channel management table.

In FIG. 1, a new mobile station (new user
When there is a new communication channel allocation request at the time of calling from k = K + 1), the number of requested communication channels is Nreq. When the transmission rate from the mobile station is high, one user uses a plurality of communication channels and transmits using a spreading code assigned to each communication channel. First, the total number N of communication channels used by all users in communication is read from the communication channel management table shown in FIG. In S1, it is determined whether or not the value obtained by adding Nreq to N is equal to or less than the total number of communication channels Nc held by the base station.
If it is Nc or less, the process proceeds to S2. If it exceeds Nc, the communication channel has no margin, so that the acceptance of the new communication channel allocation request is rejected. As a result, new calls will be rejected. In S2, new user (k = K + 1)
The arrival wave of the received signal from the mobile station of the new user is estimated based on the new communication channel allocation request signal at the time of calling received from the mobile station. Here, the in-communication mobile station information of each in-communication user k (k = 1 to K) shown in FIG. 2B is collected. That is, estimated arrival direction θ _k , estimated received power P _k ,
Collect γ ^(k) req, which is the CINR threshold for assigning communication channels. New user k = K + 1 communication channel allocatable CIN
Γ ^{(K + 1)} req, which is the R threshold value, is determined according to the number of channels Nreq requested by the new user, or is collected if determined in advance.

In S3, the optimum weight w _k is calculated when it is assumed that a new communication channel allocation request at the time of calling of a new user (k = K + 1) is accepted and communication is performed. Here, k = 1 to K + 1, and this is performed for the mobile station of each user in communication and the mobile station of the new user. Next, S
In 4, first, k = 1 is set, and the process proceeds to S5. In S5, it is determined whether or not k is K + 1 or less. If K + 1 or less, the process proceeds to S6, and if it exceeds K + 1, the process proceeds to S7. In S6, the CINR ^(k) of the kth user, assuming that a new user has been accepted, is predicted. A specific method of calculating CINR ^(k) will be described later, and the description thereof will be omitted here. In S8, it is determined whether or not this CINR ^(k) is greater than or equal to the required CINR of the kth user, γ ^(k) req, and γ
If it is ^(k) req or more, the process proceeds to S9, and if it is less than γ ^(k) req, the acceptance of the new call is rejected by rejecting the acceptance of the new communication channel allocation request of the new call. . Therefore, if the user k whose received CINR ^(k) does not satisfy γ ^(k) req is detected, the prediction calculation of the received CINR ^(k) for the mobile stations of the remaining users is not performed, and at that time, a new call The acceptance of the new communication channel allocation request is rejected, and as a result, the new call is also rejected, and the generated new call is lost. The value of γ ^(k) req, which is the above-mentioned CINR threshold for assigning communication channels, is for determining whether or not new communication channels can be assigned, and therefore any value with which the mobile station can perform communication can be used. You can specify the value. Normally, the value matches the required CINR value when communicating using the communication channel, but it does not necessarily have to match the required CINR value. Further, the threshold value may be changed depending on the traffic situation and the like. S
In step 9, the value of k is incremented by 1, and the user of the next number is allowed to repeat steps S5 and below.

On the other hand, the process proceeds from S5 to S7.
CINR for all users including new call users
^(k)Is γ^(k)This is the case when the condition that is req or more is satisfied.
All communications used by all communicating users in S7
Number of channels N, number of communication channels requested by new user Nreq
Is added to update the value of N, weight update and new call
By assigning communication channels to
To the process of accepting. At that time, as shown in FIG.
New user (k = K + 1) in the communication channel management table
And the number of the assigned communication channel.
Mobile station number k of new user_{K + 1}Write.
Here, the weight update is calculated in S3,
New communication channel allocation when a new user (k = K + 1) makes a call
Optimal weight w when request is accepted _k(K = 1
~ K + 1), each user k (k
= 1 to K + 1) Set the weight for the mobile station
Means

As a whole, the above-mentioned flow corresponds to the function of the communication channel allocation control unit described above.
However, the step of S2 is a function executed by the estimation unit that estimates the information about the individual arriving waves described above with respect to the mobile station of the new user. In S6, the communication channel allocation control unit notifies the new mobile station of the communication quality information based on the received signal from the array antenna, the new communication channel allocation request signal, and the information about the individual arriving waves estimated by the estimation means. Whether to assign a new communication channel is determined. Particularly, when a new mobile station communicates using a communication channel, at least one mobile station among the new mobile station and each mobile station in communication cannot perform communication satisfying the communication quality specified in advance. If it is determined that the new communication channel is denied to the new mobile station.

In the above-described flow, the determination process in S1, that is, the determination as to whether or not there are free communication channels equal to or larger than the requested communication channel number Nreq can be omitted. It can be omitted when the number of communication channels Nc is set sufficiently in the base station. If, as a result of omitting this determination, the number of simultaneously connected communication channels becomes too large, it can be seen that the reception CINR has deteriorated in S7, and therefore the acceptance of the new call will be rejected. The optimum weight calculation in S3 does not necessarily have to be calculated for all mobile stations of k = 1 to K + 1. For example, a mobile station whose reception CINR is estimated to be sufficiently large or to be sufficiently smaller than γ (k) req without the need to perform weight calculation based on the magnitude of the received power is omitted. It is also possible. In the latter case, the processing of S4 to S9 can be skipped and the new call acceptance rejected immediately.

FIG. 3 shows an embodiment of the present invention.
It is an explanatory view showing how a new communication channel allocation request at the time of calling from a plurality of users is processed. Here, the CINR threshold γ ^(k) req at which communication channels can be assigned is taken as the required CINR value. In the figure, the calling event is a white circle,
The final call event is a black circle, the call loss is x, and the CINR prediction calculation is △.
, And each of the users 1 to K is explained with the time series as the horizontal axis. The CINR prediction calculation means the processing by steps S2 to S9 in FIG. In FIG. 1, the request communication channel determination is performed, but in FIG. 3, the case where the request communication channel determination is not performed or the request communication channel determination result is always OK will be described.

At time point 1, the user 1 makes a new communication channel allocation request at the time of making a call in the absence of a user in communication. The determination result of whether or not the predicted CINR of the user 1 satisfies the required CINR is OK. As a result, the new communication channel allocation request for the new call of user 1 is accepted. Time point
In 2, user 2 requests a new communication channel allocation at the time of calling and performs CINR prediction calculation of users 1 and 2. A user
Regarding the predicted CINRs of 1 and 2, the determination result of whether or not the required CINR is satisfied is OK. As a result, the new communication channel allocation request for the new call of the user 2 is also accepted. At time point 3, user 3 requests a new communication channel allocation at the time of calling, and performs CINR prediction calculation for users 1, 2, and 3. User 1,
The determination result of whether or not the desired CINR is satisfied for at least one of the two or three predicted CINRs is NG. As a result, the user
The new communication channel allocation request for the new call of 2 is rejected and a call loss occurs. At time point 4, the user 2 finishes the communication and terminates the call, and a free communication channel is generated.

At time point 5, the user 3 again makes a communication channel allocation request at the time of calling, and performs CINR prediction calculation of the users 1 and 3. Regarding the predicted CINRs of the users 1 and 3, the determination result of whether or not the desired CINR is satisfied is OK. As a result, this time, the new communication channel allocation request for the new call of the user 3 is accepted. At time point 6, user K requests a new communication channel allocation at the time of calling, and performs CINR prediction calculation for users 1, 3, and K. The determination result of whether or not the desired CINR is satisfied for at least one of the predicted CINRs of the users 1, 3, and K is NG. As a result, the new communication channel allocation request for the new call of the user K is rejected and a call loss occurs. At time point 7, user 3 terminates the communication and ends the call. At time point 8, user K requests a new communication channel allocation at the time of calling and performs CINR prediction calculation for users 1 and K. Regarding the predicted CINR of users 1 and K, the judgment result of whether or not the desired CINR is satisfied is
OK. As a result, the new communication channel allocation request for the new call of user K is accepted this time. At time point 9, user 1 terminates the call, and at time point 10, user K terminates the call.

In the above description, the CINR prediction calculation for the mobile station of the communicating user is necessary when the new user makes a call. Therefore, the arrival wave estimation and the optimum weight calculation necessary for predicting the CINR may be performed at the time when the call is made. However, since it takes time to calculate, the arrival wave estimation for the mobile station of the user during communication is performed at any time during communication, for example, at a predetermined time interval, regardless of whether or not there is a new call. At the time of occurrence of, the immediately preceding estimated value or measured value may be used. The optimum weight calculation for the mobile station in communication is necessary for the directivity control of the adaptive array antenna in communication. This optimum weight also changes due to a change in the position of the user's mobile station or the occurrence of a call termination. Therefore, in order to further improve the communication quality, it may be performed during the communication, for example, at a predetermined time interval and / or when a call termination event occurs.

In the above description, the case where the new communication channel allocation request for the new call is the new communication channel allocation request when the mobile station of the new user in the cell makes a call. On the other hand, the same can be done when the new communication channel allocation request for a new call is a new communication channel allocation request when a new user in a cell arrives at a mobile station. For example, this new communication channel allocation request at the time of an incoming call is made as a response signal from the mobile station to an incoming request signal from the base station to the mobile station. In this case, the number of requested communication channels is known first on the base station side, and therefore step S1 is executed. Here, if the acceptance of the new communication channel allocation request for the new incoming call is not rejected, then an incoming request signal is transmitted from the base station to the new user, and then a response is sent from the mobile station of this new user. The signal is received using the control channel. Based on this response signal, the arrival direction and the received power of the new user mobile station are estimated in S2, the steps following S3 are executed, and similarly, the wait request is updated and the channel request of the new incoming call is accepted, or the new request is received. Deny acceptance of new communication channel allocation request for incoming call.

Here, an example of the arrival wave estimation regarding the received signal from the mobile station of the new user K + 1, the optimum weight w _k calculation when the new user is accepted, and the CINR prediction will be supplementarily described. The mobile station of the new user K + 1 transmits a new communication channel allocation request signal for a new call using the uplink common control channel (random access channel), and requests the new communication channel allocation from the base station. To do. That is, the establishment of a communication link is requested.
The new communication channel allocation request signal at the time of calling from the mobile station of the new user K + 1 is received by the base station, and the pilot signal included in this received signal is used to transmit the new communication channel allocation request signal at the time of calling. Estimate the direction of arrival θ _{K + 1} . Since these processes are performed at very short time intervals, the arrival direction estimated at this time hardly changes even when the user data is transmitted to the base station using the dedicated communication channel. Direction of arrival θ during communication
It can be considered as _{K + 1} .

On the other hand, the received power P _{K + 1} of the incoming wave at the stage when the user data is transmitted from the mobile station K + 1 of the new user using the communication channel is, for example, at the transmission rate (mobile station transmission rate). I can decide. In the case of DS-CDMA, if the same modulation method is used, transmission power proportional to the transmission rate is required. This transmission rate information is usually the number of requested communication channels.
Since it has a correspondence relationship with Nreq, it can also serve as the required communication channel number Nreq. If the transmission rate information is included in the new communication channel allocation request signal, the required communication channel number Nreq can also be known. Further, the requested communication channel number Nreq may be included in the new communication channel allocation request signal together with the transmission rate information. For the received power P _{K + 1} ,
The received power P _{K + 1} when received using the communication channel may be estimated based on the received power of the new communication channel allocation request signal received using the control channel.

Based on the arrival direction θ _{K + 1} of the incoming wave from the mobile station of the new user _{K + 1} and the received power P _{K + 1} ,
Received signal of the array antenna only by the incoming wave from the mobile station of new user K + 1 (array input signal of each element)
Is calculated. The received signal of the array antenna in the current state during communication with the mobile station k (k = 1 to K), plus the received signal of the array antenna based on only the arriving wave from the mobile station of the new user K + 1. Is the received signal of the array antenna when it is assumed that the new user K + 1 is included. Depending on the received signal of the array antenna, the optimum weight w _k (hereinafter, referred to as w _k ′) of the mobile station k (k = 1 to K + 1) at the time of accepting a new user is, for example, the least squares error method. Calculated based on (MMSE).

Next, a supplementary explanation of CINR will be given.
Nobuyoshi Kikuma, "Adaptive Signal Processing by Array Antenna," Science and Technology Publications (1998-11), p.26, 27, describes SINR (Signal to Interference plus Noise) for the output of array antenna.
Ratio) (corresponding to the value obtained by normalizing the CINR in this specification with the spreading gain PG). C for a user k
INR ^(k) is the array antenna of the interference wave including the thermal noise of the array antenna output power (C) of the desired wave contained in the output signal of the array antenna despread with the spreading code of the target user k. It is defined as the ratio of output power (I + N).

The array antenna output power (C) of the desired wave of a certain user k is received by the array antenna at each antenna element of the incoming wave (estimated arrival direction θ _k , estimated received power P _k ) from the mobile station of the user k. Optimal weight w after assuming that a signal has been assigned a communication channel to a new user
It is calculated as the power when combined output is performed using _k '. More specifically, it is _obtained by the autocorrelation matrix calculated from the estimated arrival direction θ _k and the estimated received power P _k and the above-mentioned optimum weight w _k ′. On the other hand, the array antenna output power (I + N) of the interference wave including the thermal noise is the received signal of the array antenna when it is assumed that the new user K + 1 is included, which is the optimum weight w _k ′ described above. From the power when synthesized and output using
It is calculated as a value obtained by subtracting the array antenna output power (C) of the desired wave of. In order to estimate the communication quality CINR ^(k) of a certain user k, it suffices to know the optimum weight w _k ′, the estimated arrival direction θ _k , and the estimated received power P _k , and it is not necessary to know the other users. . Therefore, step S3 in FIG. 1 may be executed between step S5 and step S6. Therefore, in the calculation of the optimum weight w _k ', the received CINR ^(k) is γ as in the CINR ^{(k) in} S6.
^(k) If the user k that does not satisfy req is detected, the calculation for the mobile stations of the remaining users can be omitted.

In estimating the communication quality CINR ^(k) described above, it is not necessary to directly estimate the information of the arrival direction θ _k . Instead of theta _k, the arrangement of the array, the frequency, the array propagation vector v _k direct estimation obtained by the arrival direction theta _k, the correlation matrix is calculated using this may estimate the communication quality. For the array propagation vector, refer to the above-mentioned, Adaptive Signal Processing by Array Antenna, P.28-31. Note that the interference wave is not generated only by other users who are performing communication using the communication channel. The CDMA communication system uses the control channel for allocating the communication channel and the control channel for registering the position of the mobile station, which are already described, and the code spread signal is transmitted even when the communication channel is not used. I am sending. Therefore, in the interference wave described above, a signal transmitted during non-communication that does not use these communication channels other than interference from other users who are communicating using the communication channel, and further other wireless zones ( Interference due to radio waves coming from neighboring cells) is also included.

In the above-mentioned CDMA communication system, as shown in FIG. 7, the coverage area (cell) of the base station 24 is an isotropic omni-cell. On the other hand, in order to improve the frequency utilization efficiency, the omni-cell cover area may be angularly divided into a plurality of sectors, as illustrated in FIG. 5 described later. Cellular mobile communication systems have been designed by replacing these individual sectors with omnicells. In a CDMA cellular mobile radio communication system using such a sector, an array antenna is arranged for each sector, and code division multiple access is performed for each sector.

The communication channel allocation control as to whether or not to accept the new communication channel allocation request signal of the new call (call origination or call reception) shown in FIG. 1 is performed for each sector. The communication channel management table shown in FIG. 2 is also managed for each sector. Estimating means for estimating information about each incoming wave is
Estimate for each sector where the mobile station in communication and the new mobile station are located. Mobile station information regarding a mobile station that is communicating using the communication channel is collected for each sector in which the mobile station that is communicating is located. However, if each sector is operated within the allowable CINR limit, interference from other sectors will have an effect. Therefore, the above-mentioned communication channel allocation control unit, when the control channel receiving unit receives the new communication channel allocation request signal, the received signal of the array antenna and the new communication channel allocation request signal and within the wireless zone estimated by the estimating means. Whether or not to allocate the new communication channel to the new mobile station is determined based on the communication quality information based on the information about the individual arriving waves from the communicating mobile station and the new mobile station located in all sectors of To do.

FIG. 4 shows an embodiment of the present invention.
FIG. 6 is an explanatory diagram showing how a new communication channel request at the time of calling from a plurality of users is processed in the sectorized system. The symbols in the figure are the same as those in FIG. The sector to which each user belongs
It is shown by the subscript of the user number. At time point 1,
The user 1 ₁ carries a new communication channel assignment request during a call while the user is not in communication. Prediction CINR of the user 1 ₁ meets a desired CINR whether the determination result is OK.
As a result, the new communication channel assignment request of the new call of the user 1 ₁ is accepted. At time 2, the user 1 ₂ of the second sector performs new communication channel assignment request during a call,
Performs user 1 _1, 1 ₂ of the CINR prediction calculation. Regarding the predicted CINRs of the users 1 ₁ and 12 ₂ , it is determined whether or not the desired CINR is satisfied.
OK. As a result, the new communication channel assignment request of the new call of the user 1 ₂ is also accepted. Third at time point 3
User 1 ₃ sector performs new communication channel assignment request during a call, performs user 1 _1, 1 _2, 1 ₃ of the CINR predictive calculation. Prediction CINR of the user 1 _1, 1 _2, 1 _3, meets the desired CINR whether the determination result is OK. As a result, the new communication channel assignment request from a user 1 ₃ is also accepted. At time 4, the user 21 of the first sector performs a new communication channel assignment request during a call, performs user 1 _1, 2 _1, 1 _2, 1 ₃ of the CINR predictive calculation. With respect to the predicted CINRs of the users 1 ₁ , 2 ₁ , 1 ₂ , and 1 ₃ , the determination result of whether or not the desired CINR is satisfied is OK. As a result, the new communication channel assignment request from a user 2 ₁ is also accepted.

At time point 5, user 3 _{1 of} the first sector
Makes a request for new communication channel allocation when calling and the user
CINR prediction calculation of 1 ₁ , 2 ₁ , 3 ₁ , 1 ₂ and 1 ₃ is performed. User 1 ₁ ,
For at least one of the predicted CINRs of 2 ₁ , 3 ₁ , 1 ₂ and 1 ₃ ,
The result of the determination as to whether or not the desired CINR is satisfied is NG. As a result, the new communication channel allocation request from the user 3 ₁ is rejected and a call loss occurs. User 1 ₃ at time 6, time 7
User 1 _2, a termination call to end the communication in. Time point
In 8, the user 3 ₁ again requests a new communication channel allocation at the time of calling, and performs CINR prediction calculation of the users 1 ₁ , 2 ₁ , 3 ₁ . For the predicted CINR of users 1 ₁ , 2 ₁ , 3 ₁ , the desired CINR
The determination result of whether or not the condition is satisfied is OK. As a result, the new communication channel allocation request from the user 3 ₁ is accepted this time. User 3 ₁ at time 9 and user 2 at time 10
_1, user 1 ₁ at time 12, a termination call to end the communication. When there are a plurality of cells, it is desirable to consider the interference given to neighboring cells when a new communication channel is assigned. The CINR threshold γ ^(k) req that can be assigned to the communication channel of each base station can be set to a large threshold with a margin in advance, so that interference to neighboring cells can be considered. .

FIG. 5 is an explanatory diagram of a sectorized cell. FIG. 5A is an explanatory diagram of the cell model.
(B) is an explanatory view showing an example of a directivity pattern of an adaptive array antenna in a sectorized cell. In FIG. 5A, 11 is a sectorized hexagonal cell in which an omni cell is divided into 3 sectors. 12 is an array antenna provided in each sector,
Reference numeral 13 shows individual directional characteristics of the antenna elements forming each array antenna. In FIG. 5B, 14, 15,
16 is a mobile station of users 1-3. The case where a mobile station of one user is located in one sector is shown. The number of elements of the array antenna of each sector is 8,
Reference numerals 17 (solid line), 18 (broken line), and 19 (dotted line) indicate the directional characteristics. The main lobe is directed toward the target user and the beam null is directed toward the other users.

A simulation was performed using the cell model with eight antenna elements shown in FIG. The total number of antenna elements is 8 × 3 = 2 because it has 3 sectors.
It becomes 4. The mobile station is an isolated cell with no interference from neighboring cells, and mobile stations are uniformly distributed in the cell. The new communication channel allocation request signal at the time of call origination follows Poisson occurrence of the average generation interval Ta within one sector. The number of communication channels required by the mobile station shall be one. It is assumed that the transmission power from each mobile station is adjusted so as to compensate for the distance variation to the base station. The required CINR for satisfying the communication quality required by each communication channel is fixed γreq = 10 dB for all users, and it is assumed that all users communicate at the same speed. Since there is no perfect orthogonality between spreading codes in the uplink, the spreading factor (processing gain with spreading codes)
With PG, the interference amount is 1 / PG. Here, PG = 20dB
Shows the simulation result. Assuming that the arrival directions and received powers of all mobile stations can be accurately estimated, the optimum weights of the adaptive array antenna are obtained for each user and the received CINR is estimated. The user who has received the new communication channel allocation request is disconnected after using the communication channel for the hold time ts seconds. The average holding time Ts (= ρTa) is 120
It was decided to have an exponential distribution of seconds.

FIG. 6 is a graph showing the simulation results of the embodiment of the present invention and the prior art. Figure 6
(A) is a graph which shows the cumulative probability of CINR which is a parameter of communication quality. The cumulative probability on the vertical axis indicates the probability that the CINR value will be less than or equal to the value on the horizontal axis. It generates a call volume of ρ = 25 erlangs per sector. The required value of CINR γreq was set to 10 dB for all users. The number of base station communication channels was not limited. The solid line indicates the simulation result when the new communication channel allocation control is performed, and the broken line indicates the simulation result when the new communication channel allocation control is not performed. If the new communication channel allocation control is not performed, the cumulative probability that the CINR will be the required value of 10 dB or less is about 1%. This value means the CINR deterioration rate during communication. On the other hand, when the new communication channel allocation control is performed, a call loss that is almost equal to the CINR deterioration rate occurs. However, once the communication channel is assigned, the CINR does not fall below 10 dB during communication, so it can be seen that call control works effectively.

FIG. 6 (b) is a graph showing the characteristics of the call loss rate with respect to the call origination volume in the case where call control is performed.
FIG. 6C is a graph showing the characteristics of the call loss rate with respect to the call origination volume in the case without call control. In all cases, the number of communication channels (number of equipment) assigned to each sector of the base station is set to 20 to 50 channels, the solid line indicates the call loss rate,
The broken line shows the CINR deterioration rate. The same scale is used for the blocking rate and the CINR deterioration rate. In addition, CINR in 20ch of Fig. 6 (c)
The deterioration rate is below the range shown in the figure, so it is not shown in the figure.

As can be seen from FIG. 6 (b), when the above-mentioned new communication channel allocation control is performed, the received CINR (communication quality) does not deteriorate regardless of the number of communication channels and the call origination amount. On the other hand, as can be seen from FIG. 6 (b), when the new communication channel allocation control is not performed, the deterioration rate of the received CINR greatly changes depending on the number of communication channels and the call origination amount. Therefore, in order to suppress the deterioration to a predetermined value or less without call control, the number of communication channels and the call origination amount are 2
Since it is necessary to limit one parameter in advance, control becomes complicated. Therefore, the performance of the adaptive array antenna cannot be fully utilized. In this way, by performing the above-mentioned new communication channel allocation control, the communication quality does not deteriorate even if the call origination amount or the number of communication channels changes, so apply the adaptive array antenna without worrying about the communication quality at all. You can

In the above description, the call control method is to pay attention to the communication quality of the uplink and determine whether or not to accept the new communication channel allocation request when a new call occurs. The downlink communication quality was not considered because it is difficult to evaluate. However, if the downlink communication quality is also evaluated, it is desirable to determine whether or not to accept the communication channel allocation request in consideration of this evaluation.

[0040]

As is clear from the above description, according to the present invention, when performing code division multiple access with a plurality of mobile stations in a cell using an array antenna, the Guarantees the communication quality, without worrying about the communication quality fluctuation due to the traffic fluctuation in the cell during communication,
There is an effect that it is possible to perform communication with reduced interference signals by using the array antenna.

[Brief description of drawings]

FIG. 1 is a flowchart for explaining an embodiment of a CDMA base station device of the present invention.

FIG. 2 is an explanatory diagram showing an example of a communication channel management table used in the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing how a new communication channel allocation request at the time of calling from a plurality of users is processed in the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing how a new communication channel allocation request at the time of calling from a plurality of users is processed in the sectorized system according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of a sectorized cell.

FIG. 6 is a graph showing simulation results of an embodiment of the present invention and a conventional technique.

FIG. 7 is an explanatory diagram showing an example of a CDMA mobile communication system using an adaptive array antenna.

[Explanation of symbols]

21 ... User 1 mobile station, 22 ... User 2 mobile station, 23
... mobile station of user 3, 24 ... base station, 31 ... user 1 directivity, 32 ... user 2 directivity, 25 ... adaptive array antenna, 25a ... antenna element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI theme code (reference) H04Q 7/28 H04J 13/00 D 7/36 F term (reference) 5K022 EE01 EE11 EE31 5K067 AA03 BB04 CC10 DD23 EE02 EE10 EE55 KK02

Claims (2)

[Claims] 1. A CDMA base station apparatus for communicating with a plurality of mobile stations in a wireless zone by code division multiple access using an array antenna, wherein a new communication channel of the plurality of mobile stations is used. Control channel receiving means for receiving a new communication channel allocation request signal from the array antenna using a control channel from a new mobile station requesting allocation, a mobile station in communication among the plurality of mobile stations, and the new mobile station. Estimating means for estimating information about individual arriving waves from a mobile station by using the received signal of the array antenna, and when the control channel receiving means receives the new communication channel allocation request signal, the received signal of the array antenna And information on the individual incoming waves estimated by the new communication channel allocation request signal and the estimating means, Communication channel allocation control means for deciding whether or not to allocate a new communication channel to the new mobile station based on the communication quality information based on the communication quality information, wherein the communication channel allocation control means uses the communication channel for the new mobile station. When it is determined that at least one mobile station of the new mobile station and each of the mobile stations in communication cannot perform communication that satisfies the communication quality specified in advance, A CDMA base station device characterized by rejecting a new communication channel allocation to a new mobile station. 2. The wireless zone is angle-divided into a plurality of sectors, the array antenna is arranged for each sector, the code division multiple access is performed for each sector, and the estimation means is for each of the individual sectors. Information about the arriving wave is estimated for each sector in which the mobile station in communication and the new mobile station are located, and the communication channel allocation control means receives the new communication channel allocation request signal by the control channel receiving means. At this time, the received signals of the array antenna, the new communication channel allocation request signal, and the new mobile channel from the communicating mobile station and the new mobile station located in all the sectors in the radio zone estimated by the estimating means. The new communication to the new mobile station based on the information on the communication quality based on the information about each incoming wave. Determining the assignment executability of Yaneru, CDMA base station apparatus according to claim 1, characterized in that.