JP2007060086A - Wireless resource allocation method and base station in multibeam wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless resource allocation method for effectively utilizing wireless resources and a base station for performing the wireless resource allocation method in a multibeam wireless communication system. <P>SOLUTION: The wireless resource allocation method calculates wireless resources assigned to a wireless terminal for newly requesting a wireless resource and a wireless terminal to which a wireless resource has already been allocated in order to attain a requested transmission rate of each wireless terminal on the basis of a power density of each beam, calculates an equivalent transmission rate obtained when the calculated wireless resource is assigned to a reference terminal in common in the system, for each wireless terminal, calculates the sum of the equivalent transmission rates of the wireless terminals belonging to each beam, and calculates the wireless resource assigned to each beam on the basis of the sum of the equivalent transmission rates, repeats the calculations above for a plurality of number of times, and shares the wireless resources calculated finally to the wireless terminals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to radio resource allocation to radio terminals in a multi-beam radio communication system, and more particularly, to radio resource allocation in consideration of characteristics of radio terminals for the purpose of effectively using radio resources. .

  In the multi-beam wireless communication system, inter-beam interference occurs because the frequency is repeatedly used. FIG. 9 is a diagram for explaining the inter-beam interference. In FIG. 9, the frequencies f1, f2, and f3 are repeatedly used. For example, a beam around a beam using the frequency f1 uses the frequency f2 or f3, and none uses the frequency f1, but a beam skipped by one uses the frequency f1. Exists. Since the beam to a certain region or area leaks into the surrounding region or area, the beams become interference sources with each other, and inter-beam interference occurs.

  Since inter-beam interference causes a reduction in system capacity, a technique for adjusting the amount of radio resources such as the power and frequency band for each beam so that the inter-beam interference is reduced has been proposed (for example, non-patent). Reference 1).

FIG. 10 is a flowchart of a conventional radio resource allocation method. In the prior art, transmission methods such as a modulation method and a coding method are determined in advance.
(S101) First, an error rate BER (Bit Error Ratio) requested by the wireless terminal and a transmission rate are acquired.
(S102) The necessary frequency band W is calculated from the transmission method and the transmission rate requested by the wireless terminal.
(S103) Necessary C / (N + I) is calculated from the transmission method and the error rate BER required by the wireless terminal. Here, C / (N + I) is the ratio of the interference power I and the noise power N to the carrier power C.
(S104) The power C required to achieve the calculated C / (N + I) is calculated from the G / T of the wireless terminal, the interference amount I and the beam gain Gγ at the current position of the wireless terminal. Here, G / T is the ratio of the noise temperature to the antenna gain of the wireless terminal, and is an indicator of the reception performance of the wireless terminal.
(S105) The calculated frequency band W and power C are allocated to the radio terminal, and communication is performed with the radio terminal using the allocated frequency band W and power C beams. Note that the frequency band and power of an entire beam are the sum of the frequency band and power allocated to the wireless terminals in the beam.

  In S <b> 104, the interference amount I is calculated on the assumption that the power of other beams leaks into the frequency band W on average. Since the amount of interference I varies depending on the position of the wireless terminal in the beam, even if the error rate BER and transmission rate required by the wireless terminal are the same, the power used for communication varies depending on the position of the wireless terminal in the beam. It becomes. FIG. 11 is a diagram illustrating an example of the relationship between the position in the beam and the necessary power.

  Changing the power used for communication depending on the position of the wireless terminal in the beam means that the amount of interference with other beams changes. FIG. 12 shows C / (N + I) of each wireless terminal calculated by arranging frequencies in a certain pattern. The circles in FIG. 12 are C / (N + I) values that are necessary to prevent quality degradation. For example, C / (N + I) of a wireless terminal using the frequency band 1 of the beam 1 in FIG. 12 satisfies a value necessary to prevent quality degradation, but the frequency band within the same beam C / (N + I) of a wireless terminal using 2 does not satisfy a value necessary for preventing quality degradation.

  Further, a technique has been proposed for allocating radio resources to each beam according to the number of radio terminals in the beam and the desired transmission rate in the total number of radio terminals in the beam for effective use of radio resources (for example, (See Patent Documents 1, 2, and 3.)

  FIG. 13 is a diagram illustrating another example of radio resource allocation according to the related art. FIG. 13A shows the sum of the required transmission rates of the wireless terminals belonging to each of the beam A, the beam B, and the beam C. The sum of the required transmission rates decreases in the order of the beam C, the beam B, and the beam A. ing. FIG. 13B shows radio resources allocated to the beams A to C based on the total required transmission rate shown in FIG. Many radio resources are allocated in descending order of the total required transmission rate. Finally, in each beam, radio resources are allocated to each radio terminal. This is shown in FIG. In FIG. 13C, the radio terminals A1 and A2 exist in the beam A, the radio terminals B1 and B2 exist in the beam B, and the radio terminals C1 and C2 exist in the beam C. Since the required transmission rates of the wireless terminals in each beam are the same, the wireless resources are evenly distributed.

JP 2005-33338 A JP 2003-258806 A JP 2003-179966 A Y. Kishi, S .; Konishi, S .; Nomoto, “Optimum Radio Channel Allocation Taking Account of Both Frequency and Power Constraints for Wide-Area Wireless Access Systems”, IEICE. Commun. Vol. E87-B, NO. 12, pp. 3722-3733, December 2004

  Since the G / T of each wireless terminal, the required error rate BER, and the interference amount I depending on the position differ from wireless terminal to wireless terminal, surplus or shortage of the wireless resource occurs in the above-described wireless resource allocation. For example, in FIG. 13, the G / T of the wireless terminal A2 is inferior to the G / T of the wireless terminal A1, and the wireless terminal A1 achieves the required transmission rate with the assigned wireless resources. In this case, in order to achieve the required transmission rate, the radio terminal A2 needs radio resources indicated by dotted lines, and the allocated radio resources are insufficient. In FIG. 13, the amount of interference of the wireless terminal B2 is smaller than the amount of interference of the wireless terminal B1, and the wireless terminal B2 achieves the requested transmission rate with the assigned wireless resources. In this case, in order to achieve the required transmission rate, the radio terminal B1 may be a radio resource indicated by a dotted line, and the allocated radio resource is redundant. Further, in FIG. 13, it is assumed that the required error rate BER of the wireless terminal C1 is stricter than the required error rate BER of the wireless terminal C2, and the wireless terminal C2 achieves the required transmission rate with the allocated radio resources. In this case, the radio terminal C1 requires radio resources indicated by dotted lines in order to achieve the required transmission rate, and the allocated radio resources are insufficient.

  Accordingly, an object of the present invention is to provide a radio resource allocation method that effectively uses radio resources and a base station that executes the radio resource allocation method.

According to the wireless lease allocation method of the present invention,
A radio resource allocation method in a base station in a multi-beam radio communication system, which is based on the power density of each beam for a radio terminal newly requesting radio resources and a radio terminal to which radio resources have already been assigned. A first step of calculating a radio resource to be allocated to each radio terminal in order to achieve a required transmission rate of each radio terminal, and an equivalent obtained when the calculated radio resource is allocated to a common reference terminal in the system A second step of calculating a transmission rate for each wireless terminal, a third step of calculating, for each beam, an equivalent transmission rate sum of wireless terminals belonging to the beam, and assigning to each beam based on the equivalent transmission rate sum The fourth step of calculating the radio resource is repeated a plurality of times, and the radio resource calculated in the last first step is Characterized by allocating to the wireless terminal.

According to another embodiment of the wireless lease allocation method of the present invention,
The conditions unique to each wireless terminal include at least one of reception performance of the wireless terminal, interference amount at the current position of the wireless terminal, beam gain at the current position of the wireless terminal, and quality required by the wireless terminal. Is also preferable.

According to another embodiment of the wireless lease distribution method of the present invention,
The radio resource allocated to each beam calculated in the fourth step is also preferably a radio resource necessary to achieve the equivalent transmission rate sum with one reference terminal.

Furthermore, according to another embodiment of the wireless lease allocation method of the present invention,
The radio resources allocated to each beam calculated in the fourth step are also preferably those in which the radio resources of the entire system are allocated according to the ratio of the equivalent transmission rate sum of each beam.

Furthermore, according to another embodiment of the wireless lease allocation method of the present invention,
Of the radio resources allocated to each beam calculated in the fourth step, the frequency band and power are preferably determined based on the amount of inter-beam interference determined according to the distribution.

Furthermore, according to another embodiment of the wireless lease allocation method of the present invention,
The interference amount of the reference terminal is also preferably an average value of the interference amount in the beam.

Furthermore, according to another embodiment of the wireless lease allocation method of the present invention,
The first to fourth steps are repeated until the difference between the radio resource allocated to each beam calculated in the fourth step and the radio resource calculated in the previous fourth step is within a predetermined value. It is also preferable to do this.

Furthermore, according to another embodiment of the wireless lease allocation method of the present invention,
Based on the power density of the beam to which the radio terminal that newly requested the radio resource belongs, the radio resource to be assigned to the radio terminal is calculated in order to achieve the required transmission rate of the radio terminal, and assigned to the beam to which the radio terminal belongs. It is also preferable to determine whether or not the calculated radio resource can be allocated from the existing radio resources, and to start the first step when the allocation is impossible.

According to the base station in the present invention,
Based on the power density of each beam and the conditions specific to each radio terminal for a radio terminal newly requesting radio resources and a radio terminal to which radio resources have already been assigned, which are base stations in a multi-beam radio communication system In order to achieve the required transmission rate of each radio terminal, the radio resource allocated to each radio terminal is calculated, and the equivalent transmission rate obtained when the calculated radio resource is allocated to a common reference terminal in the system is calculated for each radio terminal. Conversion means for calculating the terminal, beam resource distribution means for calculating the equivalent transmission rate sum of the wireless terminals belonging to each beam, and calculating radio resources allocated to each beam based on the equivalent transmission rate sum, and processing in the conversion means A repetition control means for controlling the repetition of processing in the beam resource distribution means, and a repetition by the repetition control means. After completion, the radio resources of each radio terminal conversion means has calculated, and having a terminal resource allocation means for allocating to each wireless terminal.

  By calculating the radio resources allocated to each radio terminal in order to achieve the required transmission rate of each radio terminal, and by allocating radio resources by converting to an equivalent transmission rate using a common reference terminal in the system, It is possible to allocate radio resources in consideration of terminal performance, location, and required quality. As a result, it is possible to eliminate allocation of surplus resources and realize efficient radio resource allocation.

  The best mode for carrying out the present invention will be described in detail below with reference to the drawings. In the following description, a transmission method means a method for transmission specified by a combination of a modulation method, a coding method, and a coding rate, and a radio resource means a frequency band, power, and transmission method. It shall mean any or a combination thereof.

  FIG. 1 is a configuration diagram of a radio communication system to which a radio resource allocation method according to the present invention is applied. According to FIG. 1, the base station 1 transmits a beam 20, a beam 30, and a beam 40, and wireless terminals 2-1 to 2 -N (N is an integer equal to or greater than 1) exist in the beam 20. −1 to 3−M (M is an integer of 1 or more) exists in the beam 30, and wireless terminals 4-1 to 4 -K (K is an integer of 1 or more) exist in the beam 40. Note that the number of wireless terminals in each beam is not uniform. Generally, the greater the number of wireless terminals, the greater the amount of information transmitted and received. Therefore, the greater the number of wireless terminals, the higher the required transmission rate for the entire beam. Further, the configuration of FIG. 1 may be a mode in which the base station 1 transmits a beam via a communication satellite.

  FIG. 2 is a flowchart of a radio resource allocation method according to the present invention. In the following description, it is assumed that the radio terminal 2-1 in the beam 20 requests radio resources from the base station 1 in order to start communication. Also, wireless terminals 2-2 to 2-n (n is an integer equal to or smaller than N) in the beam 20, wireless terminals 3-1 to 3-m (m is an integer equal to or smaller than M) and the beam 40 in the beam 30. It is assumed that the wireless terminals 4-1 to 4-k (k is an integer equal to or smaller than K) are already assigned wireless resources.

First, for the wireless terminal 2-1 that requested the wireless resource, the conditions specific to the wireless terminal 2-1, that is, the G / T of the wireless terminal 2-1, the interference amount I at the current position of the wireless terminal 2-1, and Based on the beam gain Gγ and the BER required by the radio terminal 2-1, the terminal resource calculation is performed, and the transmission method T2-1, which is a radio resource necessary to achieve the transmission rate required by the radio terminal _2-1. And the frequency band _W2-1 are determined (S201).

The terminal resource calculation will be described with reference to FIG. First, the power density _P 20 _{/ W 20} from the power _{P 20} and the frequency band _{W 20} radio terminal 2-1 is currently assigned to belong beam 20, i.e., determine the power per unit frequency, the power density _P 20 / W ₂₀ , the reception C / (N + I) of the wireless terminal 2-1 is calculated from the G / T of the wireless terminal 2-1 and the amount of interference I and the beam gain Gγ at the current position of the wireless terminal 2-1 (S31). ). Subsequently, the reception of the calculated radio terminal 2-1 C / (N + I) , the radio terminal 2-1 from the error rate BER to request, determines the transmission method _{T 2-1} to be used (S32). Finally, the transmission system T _2-1 was determined from the transmission rate radio terminal 2-1 requests, determines the frequency band W _2-1 required to achieve a transmission speed requested.

Returning to FIG. 2, whether or not the frequency band W _2-1 required to satisfy the transmission rate and error rate BER required by the wireless terminal 2-1 calculated in S 201 can be allocated from the beam 20. judge. In other words, in the beam 20, the wireless terminal is set to W _2-2 + W _2-3 +... + W _2-n that is the sum of the frequency bands already allocated to the wireless terminals _{2-2 to 2-n.} the value obtained by adding the frequency band _{W 2-1} to 2-1, it is determined whether the frequency band _{W 20} below, which is allocated to the beam 20 (S202). If it is equal to or less than the frequency band W ₂₀ allocated to the beam 20, the allocation is possible, and the frequency band W _2-1 calculated in S201 is allocated to the radio terminal 21, and the radio resource allocation ends (S203).

  When allocation is impossible, the radio terminal 2-1, the radio terminal 2-2 to which the radio resource is already allocated, the radio terminal 2-n, the radio terminal 3-1 to the radio terminal 3-m, and the radio terminal 4-1 to radio Radio resources are redistributed to the terminal 4-k (hereinafter referred to as all radio terminals) (S205 to S207).

  First, the terminal resource calculation shown in FIG. 3 is performed for each of all wireless terminals based on the conditions specific to each wireless terminal, and the transmission method and frequency band to be allocated are calculated (S205). Subsequently, an equivalent transmission rate, which is a transmission rate obtained when the transmission scheme and frequency band calculated in S205 are assigned to a predetermined reference terminal in the system, is calculated for each wireless terminal (S206). The reference terminal is a virtual wireless terminal serving as a system reference, and is defined as having a predetermined G / T and a predetermined required BER, and existing at a position where the interference amount I is an average in the beam.

Subsequently, the sum of the equivalent transmission rates of the radio terminals 2-1 to 2-n in the beam 20, the sum of the equivalent transmission rates of the radio terminals 3-1 to 3-m in the beam 30, and the beam 40 The sum of the equivalent transmission speeds of the wireless terminals 4-1 to 4-k is calculated. Finally, the frequency band W _sys and power P _sys that can be used in the entire system are allocated to each beam based on the total equivalent transmission speed of the wireless terminals in each beam (S207).

  In S207, the change in the frequency band and power of each beam means that the power density of each beam has been changed, and the power density of each beam is a precondition for the terminal resource calculation shown in FIG. Therefore, it eventually affects the calculation results of S205 to S207. Accordingly, S205 to S207 are repeatedly calculated L times to converge the frequency band and power allocated to each beam. (S208, S209).

  FIG. 5 shows how the average of C / (N + I) of each wireless terminal in the beam converges by repeating S205 to S207. According to FIG. 5, it can be seen that convergence is achieved at about L = 5.

  The repetition may be repeated a predetermined number of times, or may be repeated until the difference between the value of the radio resource allocated to each beam and the value of the radio resource calculated last time is within a predetermined value. Is possible.

  After repeated calculations, if the equivalent transmission rate sum of the radio terminals of each beam can be achieved by the frequency band and power allocated to each beam (S210), the transmission scheme calculated in S205 is transmitted to all radio terminals. And a frequency band are allocated (S211). On the other hand, if it cannot be achieved, the allocation of radio resources to the radio terminal 2-1 is impossible and the process ends (S212).

  In S207 and S210, the radio resource allocated to each beam may be a radio resource necessary to achieve the equivalent transmission rate sum of each beam by one reference terminal in the beam. It is also possible to use radio resources that are allocated according to the ratio of the equivalent transmission rate sum of each beam. The former case is a guaranteed service that guarantees the transmission rate required by the wireless terminal, and the latter case is a best effort type service.

  In addition, the beam resource allocation in S207 will be described in which reduction of inter-beam interference is effective for increasing the transmission rate of the entire system and inter-beam interference is minimized.

  In a multi-beam wireless communication system, the interference with surrounding beams increases as the beam power increases. If the amount of power is reduced in order to reduce the amount of interference, the frequency band to be used must be widened in order to achieve the desired transmission rate, and as a result, the frequency band that can be used by the peripheral beam is narrowed. The power to achieve the desired transmission rate with the peripheral beam increases and interference increases. Therefore, in order to reduce interference, it is necessary to distribute the power and frequency band of each beam in a balanced manner.

  Specifically, an optimization method for obtaining the minimum value of the inter-beam interference is applied by using the inter-beam interference as a function of the power and the frequency band. As a simple application method, a method of using the power and frequency band for each beam as a parameter to be optimized can be considered. However, if there are many optimization parameters, there may be a case where a minimal solution is obtained.

  Therefore, the constraint condition is added to reduce the parameter to be optimized. In a multi-beam wireless communication system, what can be a constraint condition is a condition in which inter-beam interference is reduced as a whole system. For example, the sum of the frequency bands allocated to the plurality of beams constituting the frequency cluster may always be the upper limit frequency band of the system, or the frequency bands of the beams may be equal among all the clusters.

  As a distribution method, an optimization method for a nonlinear model such as sequential quadratic programming is applied. In other words, the beam transmission rate is the sum of the equivalent transmission rates of the wireless terminals in the beam, and the constrained sequential quadratic programming method is used so that the inter-beam interference is minimized in the entire system. By solving the amount of the frequency band, the power and the frequency band assigned to each beam are obtained. This method is called an inter-beam interference minimum resource allocation method. Table 1 shows a comparison of transmission rates when the optimization is performed using the inter-beam interference minimum resource allocation method and when the optimization is not performed.

続いて、等価伝送速度についてより詳細に説明する。図６のモデム特性から理解できる様に、伝送速度は、周波数帯域Ｗと、受信電力Ｃ（送信電力とビーム利得の積）と、熱雑音Ｎと、干渉量Ｉと、誤り率ＢＥＲと、伝送方式Ｔとから求めることができる。

Subsequently, the equivalent transmission rate will be described in more detail. As can be understood from the modem characteristics of FIG. 6, the transmission speed includes the frequency band W, the received power C (product of transmission power and beam gain), thermal noise N, interference amount I, error rate BER, and transmission. It can be obtained from method T.

For example, BER in the ^{10 -5,} the thermal noise is constant irrespective of the frequency, the power density was allocated to a certain beam _P / W = P _r, the wireless terminal the reception C / (N + I) of the vertical axis of FIG. 6 7 and rewriting FIG. 6, the graph of FIG. 7A can be obtained. Next, FIG. 7B with the frequency band as a parameter can be obtained from the graph of FIG.

  The transmission rate at the point of intersection with the reference terminal G / T in the graph passing through the point of intersection of the vertical axis as the transmission rate required by the wireless terminal and the point of the horizontal axis as G / T of the wireless terminal is equivalent. It becomes the transmission speed. In other words, it is the transmission rate when the wireless resource necessary to achieve the transmission rate required by the terminal is given to the reference terminal, and by using the equivalent transmission rate, the characteristics of the wireless terminal, the required quality, and the location of the wireless terminal It is possible to allocate radio resources in consideration of the amount of interference due to.

  In the conversion from the required transmission rate of the wireless terminal to the equivalent transmission rate, the position and error rate of the wireless terminal may be used instead of G / T of the wireless terminal. Furthermore, any combination of G / T, position, and error rate BER of the wireless terminal may be used. For example, as the position of the wireless terminal is the center of the beam, the beam gain Gγ increases and the amount of interference I decreases, so the reception C / (N + I) of the wireless terminal increases. Conversely, the closer the wireless terminal is to the end of the beam, the lower the reception C / (N + I) of the wireless terminal. Therefore, the transmission rate required by the wireless terminal can be converted into an equivalent transmission rate using the relationship between the position of the wireless terminal in the beam and the reception C / (N + I) of the wireless terminal. In this case, the horizontal axis of the graph corresponding to FIG. 7B is the position in the beam. For example, the position that is the average value of the amount of interference in the beam is converted to the equivalent transmission speed with the position of the reference terminal as the position.

  Similarly, when the error rate BER is used, the transmission rate required by the terminal can be converted into an equivalent transmission rate for a predetermined BER.

  In a time division multiple access system, time slots are also subject to allocation as radio resources.

  FIG. 4 is a block diagram of the base station 1 according to the present invention. According to FIG. 4, the base station 1 includes a modem 10 for transmitting / receiving a beam to / from each wireless terminal, a terminal resource distribution unit 11, a beam resource distribution unit 12, a conversion unit 13, a terminal characteristic database 14, a beam resource. An optimization unit 15, a traffic measurement unit 16, and a repetition control unit 17 are provided.

  The conversion unit 13 acquires information such as the G / T of the wireless terminal, the request BER, and the interference amount I at the current position of the wireless terminal from the terminal characteristic database 14, and sets the transmission rate required by the wireless terminal to the equivalent of the reference terminal. Convert to transmission speed.

  The beam resource allocation unit 12 allocates power and frequency band so as to achieve the equivalent transmission rate sum of the wireless terminals in the beam. Alternatively, the power and frequency of the entire system are allocated according to the ratio of the equivalent transmission speed sum of each beam.

  The beam resource optimization unit 15 adjusts the power and frequency to be allocated using the above-described inter-beam interference minimum resource allocation method, and the repetition control unit 17 repeats calculation of equivalent transmission rate and beam resource allocation, That is, the repetition of S205 to S207 in FIG. 2 is controlled.

  The terminal resource allocation unit 11 allocates the frequency band and power to the radio terminal from the frequency band and power allocated to the beam.

  The traffic measurement unit 16 measures the traffic of the wireless terminal. The transmission rate measured by the traffic measurement unit 16 can be used as a substitute for the transmission rate required by the wireless terminal.

  The maximum number of terminals that can be accommodated for each beam is compared with the radio resource allocation method according to the present invention and the methods described in Non-Patent Document 1 and Patent Document 1. For all 19 multi-beams, each beam is either a uniform beam distributed uniformly by wireless terminals or a non-uniformly distributed non-uniform beam. Table 2 shows the combinations of uniform and non-uniform beams. Three types of patterns 1 to 3 shown are provided, and comparison is made for each. In the non-uniform beam, X% of all radio terminals in the beam are concentrated at a position where C / (N + I) is the lowest in the beam, and the remaining radio terminals are uniformly distributed in the beam. Note that x = X / 100 is called a terminal concentration rate.

図８は、端末集中率に対するビーム内の収容端末数の比較結果である。特許文献１による方法は、ビーム間干渉低減の効果により、非特許文献１に記載の方法よりも収容端末数が増加する。しかし、ビーム内に無線端末が均一分布すると想定して各ビームへ無線リソースの配分を行うため、端末集中率が増加するほど想定と異なる分布となる。このため、特許文献１に記載の方法は、端末集中率の増加に対して均一ビームの収容端末数は一定であるが、不均一ビームの収容端末数が大きく低下する。

FIG. 8 is a comparison result of the number of accommodated terminals in the beam with respect to the terminal concentration rate. The method according to Patent Literature 1 increases the number of accommodated terminals as compared with the method described in Non-Patent Literature 1 due to the effect of reducing inter-beam interference. However, since wireless resources are allocated to each beam assuming that wireless terminals are uniformly distributed in the beam, the distribution differs from the assumption as the terminal concentration rate increases. For this reason, in the method described in Patent Document 1, the number of terminals accommodated with a uniform beam is constant as the terminal concentration rate increases, but the number of terminals accommodated with a non-uniform beam greatly decreases.

  On the other hand, in the method according to the present invention, radio resources are allocated to each beam according to the position of the radio terminal in the beam. Therefore, the uniform beam and the non-uniform beam have the same number of accommodated terminals in all terminal concentration rates. Compared with the prior art, the terminal accommodation number of non-uniform beams is increased by up to about 1.3 times. Here, the number of accommodated terminals was evaluated, but when the number of wireless terminals actually communicating is smaller than the number of accommodated terminals, the surplus wireless resources are added to the communicating wireless terminals for transmission. Speed can also be improved.

  As described above, radio resources are effectively used by allocating radio resources to each beam and each radio terminal so as to increase the transmission capacity of the system while considering the characteristics of the radio terminal.

1 is a configuration diagram of a radio communication system to which a radio resource allocation method according to the present invention is applied. FIG. 6 is a flowchart of a radio resource allocation method according to the present invention. It is a flowchart of terminal resource calculation. FIG. 4 is a block diagram of a base station according to the present invention. It is a figure which shows a mode that the average of C / (N + I) of each radio | wireless terminal in a beam converges. It is a figure which shows a modem characteristic. It is a figure explaining conversion of an equivalent transmission rate. It is a figure which shows the comparison result of the accommodation radio | wireless terminal number by this invention and a prior art. It is a figure explaining interference between beams. It is a flowchart of the radio | wireless resource allocation method by a prior art. It is a figure which shows the relationship between the position in a beam, and required electric power. It is a figure which shows the example of a relationship of the frequency band for every beam, and C / (N + I). It is a figure which shows the other example of radio | wireless resource allocation by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base station 10 Modem 11 Terminal resource allocation part 12 Beam resource allocation part 13 Conversion part 14 Terminal characteristic database 15 Beam resource optimization part 16 Traffic measurement part 17 Repeat control part 2-1 to 2-N, 3-1 to 3 -M, 4-1 to 4-K radio terminal 20, 30, 40 beams

Claims (9)

A method of allocating radio resources at a base station in a multi-beam radio communication system,
For a wireless terminal that has newly requested a wireless resource and a wireless terminal that has already been assigned a wireless resource,
A first step of calculating a radio resource allocated to each radio terminal to achieve a required transmission rate of each radio terminal based on a power density of each beam and a condition specific to each radio terminal;
A second step of calculating, for each wireless terminal, an equivalent transmission rate obtained when the calculated wireless resource is allocated to a common reference terminal in the system;
A third step of calculating, for each beam, an equivalent transmission rate sum of wireless terminals belonging to the beam;
A fourth step of calculating a radio resource allocated to each beam based on the equivalent transmission rate sum;
Is repeated a plurality of times, and the radio resource calculated in the last first step is allocated to each radio terminal.   The conditions unique to each wireless terminal include at least one of reception performance of the wireless terminal, interference amount at the current position of the wireless terminal, beam gain at the current position of the wireless terminal, and quality required by the wireless terminal. The method of claim 1, wherein:   The method according to claim 1 or 2, wherein the radio resource allocated to each beam calculated in the fourth step is a radio resource required to achieve an equivalent transmission rate sum with one reference terminal. .   The radio resource allocated to each beam calculated in the fourth step is obtained by allocating radio resources of the entire system in accordance with a ratio of the equivalent transmission rate sum of each beam. The method described.   The frequency band and power among the radio resources allocated to each beam calculated in the fourth step are determined based on an inter-beam interference amount determined according to the distribution. The method according to item.   The method according to claim 1, wherein the interference amount of the reference terminal is an average value of interference amounts in the beam.   The first to fourth steps are repeated until the difference between the radio resource allocated to each beam calculated in the fourth step and the radio resource calculated in the previous fourth step is within a predetermined value. The method according to claim 1, wherein the method is performed. Based on the power density of the beam to which the wireless terminal that newly requested the wireless resource belongs, calculate the wireless resource allocated to the wireless terminal in order to achieve the requested transmission rate of the wireless terminal;
From the radio resources allocated to the beam to which the radio terminal belongs, determine whether the calculated radio resources can be allocated,
8. A method according to any one of claims 1 to 7, characterized in that the first step is started if assignment is not possible. A base station in a multi-beam wireless communication system,
To achieve the required transmission rate of each radio terminal based on the power density of each beam and the conditions specific to each radio terminal for a radio terminal newly requesting radio resources and a radio terminal to which radio resources have already been allocated Calculating a radio resource to be assigned to each radio terminal, a conversion means for calculating for each radio terminal an equivalent transmission rate obtained when the calculated radio resource is assigned to a common reference terminal in the system,
Beam resource distribution means for calculating an equivalent transmission rate sum of radio terminals belonging to each beam, and calculating radio resources allocated to each beam based on the equivalent transmission rate sum;
Repetitive control means for controlling the processing in the conversion means and the repetition of the processing in the beam resource distribution means;
Terminal resource distribution means for allocating the radio resources of each wireless terminal calculated by the conversion means to each wireless terminal after the repetition by the repetition control means;
A base station characterized by comprising:

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