JP2003324376A - Mobile communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase communication traffic in a mobile communication system. <P>SOLUTION: When a maximum communication speed R in each mobile station determined in accordance with a received SINR is smaller than a threshold R<SB>min</SB>, a communication request from the mobile station is rejected. A requested communication traffic is grasped from a queue length Q of a communication request, and the threshold R<SB>min</SB>is changed in accordance with the requested communication traffic. The threshold R<SB>min</SB>is basically reduced (S150) to expand coverage when the queue length Q is smaller than a predetermined lower limit value Q<SB>low</SB>(S140), and meanwhile, the threshold R<SB>min</SB>is basically increased (S165) to reduce the coverage when the queue length Q is equal to or greater than a predetermined higher limit value Q<SB>high</SB>(S155). Since providing communication traffic increases by increasing the threshold R<SB>min</SB>, the queue length Q quickly reduces and the threshold R<SB>min</SB>in also reduces. The providing communication traffic temporally averaged in accordance with the fluctuation of the threshold R<SB>min</SB>becomes a value larger than that of when the threshold R<SB>min</SB>is fixed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system adopting an adaptive modulation method.

[0002]

2. Description of the Related Art In a cellular mobile communication system, a plurality of base stations are arranged two-dimensionally or three-dimensionally, and a target area is divided into service areas (cells) for each base station. The base station is basically located at the center of each cell, and the base station accepts a communication request from a mobile station in each cell, thereby realizing communication in the entire target area. Here, since the same transmission band is used in each cell or in a combination of some cells, communication in one cell is regarded as an interfering wave (interference wave) with respect to communication in other cells. Become. The frequency utilization efficiency that can be represented by the maximum number of bits that can be transmitted per unit frequency (1 Hz) depends on the position of the mobile station, that is, the desired signal-to-interference signal strength (SINR) at the reception point. The adaptive modulation method is
Maximize the communication speed with the mobile station by monitoring the SINR of each mobile station and selecting the optimum modulation multilevel number or symbol rate according to the SINR and using it for communication with the mobile station. Therefore, the communication amount (overall throughput) of the entire mobile communication system can be improved.

Generally, a mobile station located near the base station is S
In an environment with a high INR, it is possible to receive / transmit a large amount of communication. On the other hand, the mobile station located at the cell edge (that is, near the midpoint between two base stations using the same transmission band) has a low SINR, and it is difficult to realize a large communication amount. That is, if the coverage (applicable range) of each base station is set small, the amount of communication that can be provided can be increased, and conversely, if the coverage is large, the amount of communication that can be provided is reduced. That is, in the system using the adaptive modulation method, the communication amount that can be provided by the base station and the coverage of the base station have a trade-off relationship.

Mobile communication systems that already exist, for example,
In the HDR system proposed by Qualcomm in the United States and the Infostations system proposed by Rutgers University in the United States, the system design determines at which point of this trade-off the system operates. Specifically, the coverage of each base station is a fixed size according to the size of the cell of the base station.

[0005]

However, the amount of communication to be improved by the adaptive modulation method in the conventional mobile communication system is under "static" control, and even "dynamic" control is performed. Was not considered.
Therefore, there has been a problem that the communication volume obtained by the conventional mobile communication system does not always utilize the performance of the base station sufficiently.

The present invention has been made to solve the above-mentioned problems, and provides a mobile communication system in which "dynamic" control is added to an adaptive modulation system to further improve the communication amount. With the goal.

[0007]

A mobile communication system according to the present invention includes environment detecting means for detecting a radio communication environment of each of a plurality of mobile stations with a base station, and the radio communication of each mobile station. An adaptive control means for realizing an adaptive modulation method for changing the modulation method of wireless communication for the mobile station according to the environment, wherein the adaptive control means changes the communication request amount from the plurality of mobile stations to the base station. Based on the allowable level determining means for setting and changing the allowable level related to the wireless communication environment based on the wireless communication environment of each mobile station and the allowable level, the wireless communication environment is lower than the allowable level. Communication request permission / denial means for rejecting a communication request from the station to the base station.

According to the adaptive modulation method, a mobile station having a good radio communication environment with the base station (here, the environment means a transmission path state) is higher than a mobile station having a poor radio communication environment. A modulation method that gives the communication speed is applied. According to the present invention, basically, when the communication request amount is large, the allowable level is raised and the mobile stations that can receive the communication service are limited to those having a good wireless communication environment. As a result, the average communication speed of the mobile stations provided with the communication service is improved, and the communication request from the mobile station having a good wireless communication environment is processed promptly, and thus the communication request amount can be promptly reduced. it can. During that time, the communication service is temporarily suspended for mobile stations with poor wireless communication environment, but if the allowable level is lowered due to the reduction of the communication request amount, communication will be performed even for mobile stations with poor wireless communication environment. Services are provided. The process of dynamically applying the adaptive modulation method by varying the permissible level as described above is compared with the process of always treating the communication request from the target mobile station by the base station equally.
It is possible to improve the average communication speed and increase the amount of communication processed. Considering that the wireless communication environment generally deteriorates with distance from the base station, and that the closer to the base station, the better, the fluctuation of the allowable level in the present invention corresponds to the fluctuation of coverage.

[0009] In a preferred aspect of the present invention, the mobile communication system is a cellular system, and the environment detection means uses the radio communication environment as a strength ratio (SINR) between a desired signal and an interference signal in the mobile station. To detect.

[0010] In another preferred aspect, a control buffer for storing a queue of packets requested to be transmitted to the base station is provided, and the allowable level determining means has the packet stored in the control buffer. The communication request amount is grasped on the basis of the queue length.

In still another preferred embodiment,
The permissible level determining means raises the permissible level when the queue length exceeds a predetermined upper limit length, and lowers the permissible level when the queue length falls below a predetermined lower limit length.

In the mobile communication system according to another aspect of the present invention, the adaptive control means is less than the allowable level when the allowable level is an upper limit that can be set and the queue length exceeds a predetermined upper limit length. It has a queue organizing means for removing the packet from the mobile station in the wireless communication environment from the queue.

According to the present invention, by removing a packet transmitted at a low communication rate from the packet queue, the processing of the communication request when the allowable level is raised is performed more quickly and the allowable level is lowered. The average amount of communication, including the case where it occurs, is further improved.

In a preferred aspect of the present invention, the queue organizing means adds to the queue the packet newly requested to be transmitted by the mobile station in the radio communication environment of the allowable level or higher, Removing from the queue the packets from the mobile station in the wireless communication environment below the acceptable level.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1] FIG. 1 is a schematic diagram showing a schematic configuration of a cellular mobile communication system according to an embodiment of the present invention, in which a plurality of base stations 2 are two-dimensionally arranged and communication services are provided. The target area is divided into cells 4 for each base station 2. The base station 2 is basically located at the center of each cell 4, and when the base station 2 receives a communication request from the mobile station 6 in each cell 4, communication in the entire target area is realized. The center 8 monitors the amount of communication provided by each base station 2 and gives a guideline for packet allocation to each base station 2. Each of the base stations 2 receives a packet from the mobile station 6, a transmission unit 12 that provides transmission resources, a communication request processing unit 14 that allocates the transmission resources of the transmission unit 12 to a communication-requested packet, and a packet allocation. It is configured to include a buffer 16.

FIG. 2 is a schematic functional block diagram of the communication request processing unit of the base station. The communication request processing unit 14 includes a packet allocation control function 20 and a packet allocation buffer control function 2.
2. It has a resource control function 24 and a communication amount control function 26.

When the receiving unit 10 receives a packet from the mobile station 6, the receiving unit 10 stores the received packet in the receiving buffer,
A transmission packet allocation request is issued to the packet allocation control function 20. When there is a transmission packet allocation request, the packet allocation control function 20 determines whether or not to allow the transmission packet allocation for the request based on the priority of the request and the packet allocation control guideline at that time.
Factors that determine the “request priority” include, for example, the service class, the requested communication speed, the total communication request amount, and the past request count. When the transmission packet allocation is impossible, the packet allocation control function 20 issues a command to discard the packet corresponding to the request from the reception buffer. As a result, the packet once stored in the reception buffer is discarded, and the packet allocation buffer 16
Not transferred to. On the other hand, when the transmission packet can be allocated, the reception packet is transferred from the reception buffer to the packet allocation buffer 16.

One or a plurality of packet allocation buffers 16 are provided. The plurality of packet allocation buffers 16 are
For example, it is necessary when handling services of different service classes.

The packet allocation buffer control function 22 controls the packet allocation buffer 16. As the packet allocation buffer control function 22, the resource control function 2
4 information of each message in the packet allocation buffer 16 (position in the buffer, service class, total requested communication amount, etc.), packet order in the buffer is exchanged, and packets in the buffer are deleted as necessary. There are things.

When the packet allocation buffer control function 22 determines the transmission timing of a packet, the packet is transmitted by the resource control function 24. That is, the resource control function 24 allocates the transmission resource of the transmission unit 12 to the packet whose transmission timing has been determined, and the packet is transmitted from the base station 2 using this transmission resource. Incidentally, examples of the category regarding the transmission resource include transmission power, transmission time, the number and type of codes in the code division system, and the length and number of slots in the time division system.

The traffic control function 26 controls each control method in the packet allocation control function 20, the packet allocation buffer control function 22 and the resource control function 24. In this system, the communication amount control function 26 adaptively changes the control of these other functions according to the requested communication amount, as described later. Further, the control itself of the communication amount control function 26 can be changed based on the packet allocation guideline input from the outside such as the center 8. By the way, the center 8 monitors the provided communication amount which the communication amount control function 26 grasps based on the information from other functions, and determines the packet allocation guideline to each base station 2. Further, the communication amount control function 26 is a parameter indicating a control state in the packet allocation control function 20, the packet allocation buffer control function 22, and the resource control function 24 (a requested communication amount in a cell, a provided communication amount, and a communication amount that is not provided). , Etc.), and by transmitting the collected data to the base station 2 of another cell via the center 8 or the network, it can be reflected in the control of the packet allocation guideline of the communication amount control function 26 of the other cell. is there.

This system uses the conventional adaptive modulation system.
Communication with multiple modulation methods with different communication speeds, similar to the system
Can provide services. As the specifications of the system
The lower limit communication speed given by R_low, Upper limit communication speed is R
_highExpress. At the same timing, S of each mobile station 6
Services are provided at different communication speeds according to INR
It For example, a digital modulation method that gives different communication speeds
As BPSK (communication speed 1 bps / Hz), QPSK (communication
Communication speed 2 bps / Hz), 8PSK (communication speed 3 bps / Hz), 1
6QAM (communication speed 4 bps / Hz) can be mentioned. Well
When this system provides communication services,
The minimum value of the credit rate is R_min, The highest value is R_maxThen, the basic
R_maxIs the fastest modulation method available for the system.
Trust rate R_{hig h}Which is similar to conventional adaptive modulation schemes
Is. On the other hand, R_minIs not fixed, but the communication request processing unit
It is changed according to the requested communication volume based on the control in 14.
This is a major feature that differs from conventional systems. Figure 3
Is a communication request processing unit 1 that performs characteristic control of this system.
It is a flowchart which shows the processing algorithm of No. 4. This figure
In the following, the communication volume control function 26 according to the communication request volume
Processing contents of communication request processing unit 14 including adaptive control by
Will be explained.

When the base station 2 receives a new packet allocation request from the mobile station 6 (S100), the received packet is temporarily stored in the receiving buffer of the receiving unit 10. The packet allocation control function 20 obtains the value of the SINR at the point of the mobile station 6 as the transmission source, which is transmitted by the received packet. The maximum communication speed with the mobile station 6 is SIN.
A modulation method that depends on R and generally has a higher communication speed as the SINR is larger can be adopted. Based on the predetermined relationship between the SINR and the maximum communication speed, the packet allocation control function 20 determines the maximum communication speed R for the mobile station 6 concerned.
Is determined (S105).

If R is equal to or higher than the minimum speed R _min provided by the system at that time (S110), the packet length required to transmit the requested communication is obtained (S11).
5) Then, the time required for transmitting the packet is calculated (S120). Then, the packet is put into the packet allocation buffer 16 (S125).

On the other hand, if R is smaller than R _min at that time (S110), packet allocation for the request becomes impossible and the request is rejected.

The packet allocation buffer control function 22 monitors the queue length Q of the packet allocation buffer 16, grasps the requested communication amount using the Q, and performs adaptive control according to the requested communication amount. First, it is determined whether or not Q = 0 (S130), and if Q = 0, that is, if the communication channel is not used at all, even if R is a low request, it is determined by the system. If it is within the specifications,
Since there is no need to reject it, the lower limit communication speed R _low of the system is set as R _min (S135). Note that steps S130 and S135 are executed only when the packet request is rejected in step S110. This is because when the packet request is not rejected in step S110, the packet is put into the packet allocation buffer 16 and Q cannot be 0.

If it is determined in step S130 that Q ≠ 0, and if it is determined in step S110 that R ≧ R _min and the packet is input to the packet allocation buffer 16, the queue length Q is set in advance. Lower bound matrix length Q
_When it is outside the range specified by _low and the upper limit matrix length Q _high , R _min is basically changed (S140 to S140).
165). That is, when the requested communication amount is small (Q <Q
If it is _low (S140), unless R _min is the lower limit value R _low of the system (S145), R _min is gradually decreased (S150). As a result, the service can be provided even to the mobile station 6 having a poorer communication environment. On the other hand, when the requested communication amount is large (when Q ≧ Q _high ) (S155), R _min is the system upper limit value R.
Unless it is _high (S160), R _min is increased stepwise (S165). As a result, the service to the mobile station 6 having a poor communication environment is suppressed.

As described above, in the present system, the point at which the system operates in the trade-off relationship between the communication amount that the base station can provide and the coverage of the base station depends on the system. It is changed according to the required communication volume. That is, when the requested communication amount is small, transmission packets are assigned to all requests (that is, to requests from the mobile station 6 located at any point in the cell), and services are provided. It On the other hand, when the requested communication amount increases, the coverage is limited. When the coverage is limited, the mobile station 6 that has a low SINR like the mobile station 6 located near the cell edge and thus has difficulty in high-speed communication
Service is temporarily stopped, but the SINR is large like the mobile station 6 located in the vicinity of the base station 2, and thus the service is provided to the mobile station 6 capable of high-speed communication, so that the base station 2 increases the amount of communication that can be provided. Therefore, temporarily reduce the coverage to quickly reduce the required communication volume, and then expand the coverage,
The service is also provided to the mobile station 6 located at a location where the communication environment is poor.

FIG. 4 is a graph showing the relationship between the required communication amount and the provided communication amount in this system, obtained by simulation. In FIG. 4, the horizontal axis represents the normalized required communication amount that is averaged in consideration of the assumed distribution of mobile stations 6 in the cell and the above-described temporal variation of R _min , and the vertical axis corresponds to it. It is the amount of normalized communication provided.
In the figure, the black circles are the measurement points based on the simulation, and the solid line 200 connecting them represents the tendency of the change in the provided communication amount with respect to the required communication amount. A horizontal dotted line 210 represents the upper limit of the provided communication amount realized in the conventional system, that is, the system in which the entire cell is always included in the coverage. In the conventional system, the provided communication amount does not increase beyond the dotted line 210 even if the requested communication amount increases, but in the present system, the provided communication amount exceeds the conventional upper limit in accordance with the increase in the requested communication amount. To do.

FIG. 5 is a graph showing a cumulative probability distribution curve showing the distribution of the positions of mobile stations to which communication is assigned in this system, where the normalized required communication amount is changed as a parameter. In the figure, the horizontal axis is the normalized position from the base station, 0 corresponds to the center of the cell, and 1 corresponds to the middle point (cell edge) of the distance to the adjacent cell. The dotted line is a curve that accumulates the distribution of the mobile stations 6 regardless of whether or not communication is assigned. As the required amount increases, the distribution probability near the center (near the horizontal axis 0) becomes higher, indicating that the communication provided by the base station is biased toward the central portion, that is, the coverage is reduced. Also, this figure
The limitation of the service area in this system due to the increase in requested traffic is not to completely reject the request of mobile stations outside a certain range, but to reduce the packet allocation rate gradually. It is understood that there is.

[Embodiment 2] A cellular type mobile communication system according to a second embodiment of the present invention has the same basic configuration and control as the system of the first embodiment. Therefore, regarding the present embodiment, the differences from the first embodiment will be described below with reference to FIGS. 1 to 3 and the description thereof.

Although the present system is based on the control method of the system of the first embodiment, it is a system in which the trade-off between the provided communication amount and the coverage is dynamically used. Specifically, when the communication request α satisfies the condition of step S110 and is input to the packet allocation buffer 16, if the queue length Q exceeds a predetermined upper limit value Q _high , the packet is already transmitted at that time. Among the communication requests input to the allocation buffer 16, the communication request β having the minimum communication speed R and the communication request α are compared with each other. And
When the communication speed of the communication request β is lower, the communication request β is removed from the buffer, and the communication request α is put at the end of the buffer.

FIG. 6 is a graph showing the relationship between the requested communication amount and the provided communication amount in the present system, obtained by simulation, and corresponds to FIG. 4 of the first embodiment. In the figure, the solid line 300 represents the characteristics of this system. FIG. 6 shows the increase rate of the communication traffic of the present system in the portion exceeding the upper limit of the communication traffic of the conventional system of about 0.5 bps / Hz (level of the dotted line 210 in FIG. 4) of the first embodiment. It is shown to be able to provide a larger amount of traffic than that of the system.

FIG. 7 is a graph showing a cumulative probability distribution curve showing the distribution of the positions of mobile stations to which communication is assigned in the present system, and corresponds to FIG. 5 of the first embodiment. Comparing FIG. 7 with FIG. 5, the limitation of coverage by this system is stricter than that of the system of the first embodiment, and when the required communication amount becomes large, the mobile station 6 distant from the base station 2 by a certain distance or more is Almost no communication is assigned.

[0036]

According to the mobile communication system of the present invention, the communication amount can be further improved by adding "dynamic" control to the adaptive modulation method according to the required communication amount.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of a cellular mobile communication system according to an embodiment of the present invention.

FIG. 2 is a schematic functional block diagram of a communication request processing unit of a base station.

FIG. 3 is a flowchart showing a processing algorithm of a communication request processing unit.

FIG. 4 is a graph showing the relationship between the required communication volume and the provided communication volume in the cellular mobile communication system of the first embodiment, obtained by simulation.

FIG. 5 is a graph showing a cumulative probability distribution curve showing the distribution of the positions of mobile stations to which communication is assigned in the system of the first embodiment.

FIG. 6 is a graph showing the relationship between the required communication volume and the provided communication volume in the cellular mobile communication system of the second embodiment, obtained by simulation.

FIG. 7 is a graph showing a cumulative probability distribution curve showing a distribution of positions of mobile stations to which communication is assigned in the system of the second embodiment.

[Explanation of symbols]

2 base stations, 4 cells, 6 mobile stations, 8 centers, 14
Communication request processing unit, 16 packet allocation buffer, 20
Packet allocation control function, 22 packet allocation buffer control function, 24 resource control function, 26 traffic control function.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Makoto Iwai             2-3-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo KDDI             Within the corporation (72) Inventor Jay Paget             New Jersey, United States             07748 Middletown Merrick Court             Two F term (reference) 5K067 AA12 BB04 BB21 CC10 DD04                       EE02 EE10 EE65 JJ02 JJ22                       JJ43 KK13 KK15

Claims (6)

[Claims] 1. An environment detecting unit for detecting a wireless communication environment of each of a plurality of mobile stations with a base station, and a modulation method of wireless communication for the mobile station according to the wireless communication environment of each mobile station. In the mobile communication system having adaptive control means for realizing an adaptive modulation method for changing the wireless communication environment, the adaptive control means sets an allowable level related to the wireless communication environment based on communication request amounts from the plurality of mobile stations to the base station. And an acceptable level determining means for making a change, comparing the wireless communication environment of each mobile station and the acceptable level, and rejecting a communication request from the mobile station whose wireless communication environment is inferior to the acceptable level to the base station. A mobile communication system, comprising: 2. The mobile communication system according to claim 1, wherein the mobile communication system is a cellular system, and the environment detecting means has a strength ratio between a desired signal and an interference signal in the mobile station as the wireless communication environment. A mobile communication system characterized by: 3. The mobile communication system according to claim 1, further comprising a control buffer that stores a queue of packets requested to be transmitted to the base station, and the allowable level determining unit includes the control unit. A mobile communication system, comprising: grasping the communication request amount based on a queue length of the packet stored in a buffer. 4. The mobile communication system according to claim 3, wherein the permissible level determining means raises the permissible level when the queue length exceeds a predetermined upper limit length, and the queue length falls below a predetermined lower limit length. In that case, the mobile communication system is characterized in that the allowable level is lowered. 5. The mobile communication system according to claim 3, wherein the adaptive control means sets the allowable level to an upper limit that can be set, and the queue length exceeds a predetermined upper limit length.
A mobile communication system comprising: queue organizing means for removing from the queue the packets from the mobile station in the wireless communication environment below the allowable level. 6. The mobile communication system according to claim 5, wherein the queue organizing unit places in the queue the packet newly requested to be transmitted by the mobile station in the wireless communication environment of the allowable level or higher. A mobile communication system comprising: adding and removing from the queue the packet from the mobile station in the wireless communication environment that is less than the allowable level.