JP2006254511A - Communication method and base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a communication method capable of always achieving advanced communication quality, even under a multimedia communication environment. <P>SOLUTION: According to the communication method, when there is a request for a communication allowance from a user's terminal of low-speed transmission (low-speed communication user), a highest transmission speed is notified to the low-speed communication user, whereas, in the case of there being a request for a communication allowance from a user's terminal of high-speed packet transmission (high-speed communication user), the traffic control of a frame unit is performed for the high-speed communication user, and the traffic is held within a predetermined reference range. That is, the traffic control of a frame unit is performed for a high-speed communication user; whereas, the traffic control of a frame unit will not be performed for the low-speed communication user. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a base station of a wireless communication system that employs a CDMA (Code Division Multiple Access) method as a communication method, and particularly to a communication method including traffic control corresponding to a multimedia communication environment.

  Hereinafter, conventional traffic control will be described. With the recent increase in demand for mobile communication, there is a demand for the construction of a wireless communication system that can accommodate many users. In the CDMA system currently commercialized as third generation mobile communication, a large number of users' signals are multiplexed using a plurality of spreading codes to accommodate a large number of users in one base station. In this case, each user transmits a signal using a different spread signal, and the receiving station performs correlation reception using the spread code of each user. Thereby, good communication quality is obtained.

  However, since communication signals have weak interference with each other, and the influence of this mutual interference increases as the number of accommodated users increases, the number of users that can be accommodated by one base station is limited. If many communications are accommodated exceeding the limit, the communication quality deteriorates and becomes less than the allowable level. In order to avoid such a state, the base station determines whether or not to give communication permission to a new communication applicant. This series of control for determining the communication permission is called “radio source control” or “traffic control”.

Here, an example of conventional traffic control in the CDMA system will be described (see Non-Patent Document 1). Non-Patent Document 1 deals with CDMA uplink, and the base station performs traffic control in a range where the received power is below a reference level. Specifically, communication permission is given within a range where the following conditional expression (1) is satisfied.
KE _b / SF + N ₀ + I _other ≦ I _max (1)
Note that I _max represents the maximum allowable interference power, I _other represents interference power from other cells, K represents the number of communication users, E _b represents power per bit, and N ₀ represents noise power. SF represents spreading gain. The allowable interference noise ratio I _max / N ₀ is set to about 6 to 10 [dB] according to the cell design.

The left side of the above equation (1) corresponds to the received signal power at the base station. That is, the base station accommodates communication within a range where the received signal falls within the reference level I _max . In the prior art, an appropriate power threshold value T _block is set, and communication is permitted for a new user when the current received power I _c is smaller than the threshold value T _block .

When applying a specific configuration of the traffic control, for example, the base station measures the received power I _c by reception power measurement unit, receives a communication request from a new user at the request signal receiving unit. Then, the traffic control unit compares the measured received power I _c with the power threshold T _block to determine whether a new user can be accommodated. For example, when “I _c <T _block ” is satisfied Permits new communications, otherwise it does not grant communications. Thereafter, the traffic control result notifying unit notifies the new user whether communication is possible or not.

  As described above, in the traffic control in the CDMA system, the interference that affects each communication increases in proportion to the received signal power. Therefore, by setting an upper limit on the received signal power, the influence of the interference on the communication is reduced. ing. Thereby, access permission can be given to a new user within a range in which a certain communication quality can be ensured. This control method is simple and effective for low-speed transmission communication found in voice communication.

  Next, another general traffic control will be described. In this traffic control, for example, it is assumed that a predetermined time frame is transmitted as one unit. The base station uses this frame to give only a communication permission regarding the maximum transmission rate to the user. That is, each user notifies the base station of the desired maximum transmission rate, and the base station determines whether or not a request can be made according to a request from the user. Therefore, each user can perform communication by selecting an arbitrary transmission rate within the maximum transmission rate permitted from the base station, and further freely change the transmission rate for each frame within the maximum transmission rate. You can also. At this time, the user whose maximum transmission rate is insufficient notifies the base station of a change request for the maximum transmission rate, and based on this, the base station determines whether or not to grant the change.

  As described above, in the general traffic control, the user autonomously changes the transmission rate of each frame within the given maximum transmission rate. In other words, traffic control in units of frames is not performed. In this case, the received power fluctuates in the base station. However, in an environment where many low-speed transmission users communicate simultaneously, the received power can be stabilized by the statistical multiplexing effect.

  Next, transmission power control will be described as one of main technologies supporting the CDMA system. In the CDMA system, transmission power control and traffic control are independent techniques, but since both are related to each other in the embodiments described later, conventional transmission power control will also be described here.

  In the CDMA system, transmission power control is performed so that a signal transmitted from each terminal has a predetermined reception level at the base station. In conventional transmission power control, control is performed such that a signal to interference plus noise ratio (SINR) of each signal is equal to a required SINR. That is, in the base station, after receiving a signal from each user, the SINR of the signal is measured, and when the SINR is lower than the required SINR, transmission power control (TPC: Transmitter Power Control) for increasing power to the user. On the other hand, if it is higher than the required SINR, a TPC command for power reduction is transmitted to the user.

Y. Ishikawa and N. Umeda, “Capacity design and performance of call admission control in cellular CDMA systems” IEEE J. Select. Areas Commun., Vol.15, no.8, pp. 1627--1635, Oct. 1997.

  However, the above-described conventional traffic control has the following problems.

  The conventional traffic control is constructed assuming voice-centric communication, that is, each user performs low-speed transmission (12.2 kbps, etc.) at the voice communication level, and other new users are subscribed. It was assumed that it would not have a significant impact on other communication users. On the other hand, in recent years, there is also a great demand for high-speed transmission (384 kbps, etc.) centering on data communication, and for example, a system construction corresponding to multimedia communication is required in consideration of transmission of images or large-capacity mail. Yes.

  However, in the multimedia communication environment, it is necessary for a new user to cope with various required transmission rates. In this case, if the traffic control is uniformly performed by the received power as in the conventional case, the influence on other users varies depending on the transmission speed of the new user. In particular, when a high-speed transmission user who performs communication using a large amount of power is suddenly accommodated, there arises a problem that the communication quality of other users greatly deteriorates at the beginning of the frame.

  On the other hand, in the above conventional transmission power control, the user's transmission power is controlled by transmitting a TPC command once in one slot (0.667 ms), so that high-speed transmission users who communicate using large power are suddenly accommodated. Then, control over a plurality of slots is required, and a certain amount of time is required for convergence of received power. As a result, even if the above equation (1) is satisfied, the interference power increases rapidly due to the increase in traffic, and transmission power control cannot follow at the head of the frame, and the communication quality greatly deteriorates at the head of the frame. There was a problem.

  The present invention has been made in view of the above, and is always sophisticated even in a multimedia communication environment, that is, even when a high-speed transmission user who performs communication using large power is accommodated. An object is to obtain a communication method capable of realizing communication quality.

  In order to solve the above-described problems and achieve the object, in the communication method according to the present invention, for example, high-speed packet transmission is performed as a process for giving a communication permission to a communication requesting user who satisfies a certain standard. A traffic control step for performing traffic control in units of frames for the high-speed communication user when a request for communication permission is received from a user terminal (high-speed communication user) and accommodating the traffic within a predetermined reference range. It is characterized by that.

  According to the present invention, for high-speed communication users, the traffic control is performed in units of frames. On the other hand, for low-speed communication users, the maximum transmission rate is notified by the same control as in the prior art. The user autonomously determines the transmission rate for each frame. That is, traffic control in units of frames is not performed for low-speed communication users.

  According to the present invention, for high-speed communication users, frame-based traffic control is performed, while for low-speed communication users, the maximum transmission rate is determined by the same control as in the past, and each user within that range is determined. Autonomously determines the transmission rate for each frame. That is, traffic control in units of frames is not performed for low-speed communication users. As a result, the transmission load of the entire system can be kept small, and the reception power can be stabilized even in a multimedia communication environment. In addition, there is an effect that a gradual system transition to high-speed packet communication is possible while effectively using conventional resources. In addition, a sudden increase in interference power is avoided, and the interference power is increased step by step in units of frames. Thereby, even in a multimedia communication environment, there is an effect that it is possible to always realize high communication quality while avoiding deterioration of reception quality at the head of a frame.

  Embodiments of a communication method (traffic control, transmission power control) according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
In the first embodiment, traffic control in the CDMA uplink will be described. In this embodiment, low-speed communication users (voices, etc.) are accommodated in the same manner as in the prior art, and traffic control for each new high-speed communication user (data such as images or large-capacity mail) is performed. Do. By managing the transmission speed of high-speed communication users on a frame-by-frame basis, it avoids a sudden increase in traffic and ensures high communication quality even in a multimedia communication environment.

  FIG. 1 is a diagram showing a configuration of a communication system and a base station for realizing traffic control according to the present invention. This communication system includes a base station 1, a terminal (high-speed communication terminal) 2 owned by a high-speed packet transmission user, and a terminal 3 owned by a low-speed line communication user. The base station 1 also includes a request signal receiving unit 11 for packets that receives a request signal from a user (high-speed communication user) that performs high-speed packet transmission, and a line that receives a request signal from a line communication user that performs low-speed communication. A request signal receiving unit 12 for communication, a traffic control unit 13 (including a traffic control unit 15 for packet communication and a traffic control unit 16 for line communication), and a communication permission notification unit 14 are configured.

  Here, the traffic control of the present embodiment will be described. In the multimedia communication environment, the high-speed communication terminal 2 notifies the base station 1 of the requested transmission rate via an uplink when data to be transmitted is generated. As a method of notifying this transmission rate, a method of notifying the transmission rate requested by the user for each frame, a method of notifying the base station of the amount of information to be transmitted at the same time, and a method of notifying the allowable delay time, etc. Various methods are conceivable.

  2 and 3 are diagrams illustrating an example of a request signal format from a user who performs high-speed packet transmission. In FIG. 2, the transmission rate requested by the user is notified for each frame. Here, each terminal notifies its own user ID and the requested transmission rate to the base station 1. In FIG. 3, the amount of information desired to be transmitted is notified. Here, each terminal collectively notifies the base station 1 of the information amount necessary for information transmission and the allowable delay amount.

  In the base station 1, the request signal receiving unit 11 for packets confirms the user ID and the requested transmission rate based on the received request signal. Next, the traffic control unit 15 grants communication permission in the next frame to the high-speed communication user as far as possible. At this time, various algorithms can be considered as a method for determining whether or not to give communication permission to the high-speed communication user. For example, there are various methods such as traffic control considering allowable delay, traffic control capable of maintaining communication quality of low-speed communication users, and traffic control considering propagation characteristics of each user.

  Next, the communication permission notifying unit 7 converts the communication permission in the next frame determined by the above determination into a transmission signal and notifies the high-speed communication terminal 3 on the downlink. FIG. 4 is a diagram illustrating an example of a transmission format of traffic control information notified from the base station to the terminal in the downlink. Here, the ID of each user and the permitted transmission rate are transmitted for each frame as a communication permission notification. The high-speed communication terminal 3 recognizes the transmission rate to be used in the next frame by receiving the communication permission notification from the base station 1. Further, the base station 1 transmits a pilot signal in the downlink. Each terminal performs packet transmission on the uplink with reference to the timing of this pilot signal. As a result, each terminal can perform packet transmission at substantially the same time timing.

  FIG. 5 is a diagram illustrating a configuration of the terminal 3 that performs high-speed packet transmission, and includes a pilot signal reception unit 20, a traffic control information reception unit 21, a packet transmission unit 22, a transmission rate determination unit 23, and transmission information. The storage unit 24 is configured.

  In terminal 3, pilot signal receiving section 20 establishes timing synchronization based on the received pilot signal. Next, the traffic control information receiving unit 21 receives traffic control information given as a communication permission notification (receives a user ID and a permitted transmission rate for each frame). Then, the transmission rate determination unit 23 determines the packet transmission rate in the next frame based on the allowable transmission rate described in the traffic control information. Finally, the packet transmission unit 22 converts the information stored in the transmission information storage unit 24 into a transmission signal in packet format, and transmits the converted signal on the uplink.

  As described above, the communication system according to the present embodiment performs traffic control in units of frames for high-speed communication users, while determining the maximum transmission rate for low-speed communication users by the same control as before. In this range, each user autonomously determines the transmission rate for each frame. That is, traffic control in units of frames is not performed for low-speed communication users.

  FIG. 6 is a diagram showing the properties of each communication traffic. Usually, for low-speed transmission of voice or the like, the number of users increases, but the received power is stabilized by the statistical multiplexing effect without performing traffic control in units of frames. In addition, when traffic control is performed on a frame basis, frequent request signals in the uplink and an increase in traffic control information in the downlink may be considered, which may lead to a decrease in system efficiency. On the other hand, in high-speed packet transmission with a small number of users, a sufficient statistical multiplexing effect cannot be obtained, resulting in a large variation in received power. Further, since the power per communication is large, other users are greatly affected when the communication is accommodated. In addition, since the number of users is small, even when frame-based traffic control is performed, the request signal in the uplink and the traffic control information in the downlink are small, and the control load on the system can be kept small. .

  As described above, in the present embodiment, in consideration of the above-described properties, for high-speed communication users, traffic control is performed in units of frames, while for low-speed communication users, the same control as in the past is performed. The maximum transmission rate is determined, and each user autonomously determines the transmission rate for each frame within the range. That is, traffic control in units of frames is not performed for low-speed communication users. As a result, the transmission load of the entire system can be kept small, and the received power can be stabilized even in a multimedia communication environment. Further, for traffic control for low-speed transmission users, the conventional transmission method can be used as it is, so that no extra cost is generated. In addition, the system can be gradually shifted to high-speed packet communication while effectively using conventional resources.

Embodiment 2. FIG.
In the second embodiment, in the uplink of the CDMA system, the traffic of the high-speed communication user is not suddenly accommodated in one frame, but the power is gradually increased in units of frames, so that the fluctuation of the received power is predetermined. Keep within range. By such traffic control, it is possible to avoid the sudden deterioration of the reception quality at the beginning of the frame and to stabilize the reception quality. Note that this embodiment is not defined as a condition in which a low-speed communication user and a high-speed communication user exist at the same time. For example, the present embodiment can also be applied to a case where traffic control is performed on a frame basis for all users. .

  FIG. 7 is a diagram showing a configuration of a base station for realizing traffic control according to the present invention. The base station of this embodiment includes a received power measuring unit 31, an allowable maximum traffic parameter determining unit 32, a request signal receiving unit 33, a traffic control unit 34, and a communication permission notifying unit 35. In addition, since apparatuses other than the base station 1a constituting the communication system are the same as those in FIG. 1 described above, the same reference numerals are given and description thereof is omitted.

Here, the traffic control of the present embodiment will be described. In the base station 1a, first, the received power measuring unit 31 measures the received power I _c of the current frame. On the other hand, the request signal receiving unit 33 receives a request signal from the user. Next, the allowable maximum traffic parameter determination unit 32 determines a maximum traffic parameter described later that is allowed in the next frame based on the measured value. Thereafter, the traffic control unit 34 performs traffic control in consideration of both the request signal from the user and the maximum traffic allowed in the next frame. Finally, the communication permission notification unit 35 converts the traffic allocated by this control into a transmission format of traffic control information, and transmits the converted signal on the downlink.

  FIG. 8 is a diagram illustrating an example of an accommodation state of high-speed transmission users when the traffic control according to the present embodiment is applied. High-speed communication user traffic is accommodated in stages over multiple frames. By increasing the traffic step by step in units of frames, a sudden change in received power at the beginning of the frame is suppressed.

FIG. 9 is a diagram illustrating a traffic control flowchart according to the present embodiment. First, the received power measuring unit 31 measures the received power I _c (before despreading) using the current frame (step S1). Next, the allowable maximum traffic parameter determination unit 32 _sets the smaller one of the received power I _c × 10 ^{D / 10} and I _{0, max} as the power threshold T (corresponding to the maximum traffic parameter) (step S2). Note that D [dB] represents the power increase rate allowed between frames, and I _{0, max} represents the maximum allowable received power in the base station. Finally, the traffic control unit 34 performs traffic control (resource allocation) so that the received power after transmission power control does not exceed the threshold T in the next frame (step S3).

  As described above, in this embodiment, a sudden increase in interference power is avoided, and the interference power is increased step by step in units of frames. Thereby, even in a multimedia communication environment, it is possible to always realize high communication quality while avoiding deterioration of reception quality at the head of a frame (deterioration of reception SINR). Also, although the amount of power increase per frame is small, the received power can be greatly increased using a plurality of frames. For example, when D = 2 [dB], an increase of 10 [dB] is possible in 5 frames.

  Note that the power increase rate D [dB] allowed between frames can be various values depending on the environment. For example, when D [dB] is small, fluctuations in received power between frames can be suppressed, but it takes time to accommodate high-speed transmission packets. On the other hand, when D [dB] is large, the variation in received power increases, but high-speed transmission packets can be accommodated in a short time. In an actual environment, considering both of these characteristics, an appropriate D that can smoothly accommodate a user is set while minimizing deterioration in reception quality.

As an example, there are 20 users performing low-speed voice communication (spreading factor SF = 64, required SINR: γ = 1.0 dB) of 12.2 kbps in the traffic CDMA uplink, and 384 × 2 kbps for the next frame Assume a situation where a new request for high-speed packet transmission occurs. Based on the resource control of the present embodiment, the base station determines the type of transmission packet in the next frame and its required SINR: γ _k and spreading gain SF _k , and notifies the user of the resulting resource control information . The new user determines the transmission rate according to the notified resource control information and starts packet transmission.

  FIG. 10 is a diagram showing the relationship among packet transmission rate, spreading gain (SF), and required SINR (γ). FIG. 11 is a diagram showing the allowable transmission rate of a new user when resource control according to the present embodiment is used with D = 1, 2, ∞. As shown in the figure, depending on D, the packet transmission rate for each frame is increased stepwise. When D = 1, it takes time to accommodate high-speed transmission packets. Further, when D = ∞, high-speed transmission packets can be accommodated immediately, but other communication packets are adversely affected. In the case of D = 2, degradation of reception quality in other communication packets can be reduced while accommodating high-speed transmission packets in a short time. In this way, by setting an appropriate D, it is possible to accommodate a smooth user.

Embodiment 3 FIG.
In the third embodiment, the algorithm in step S3 of the traffic control in the second embodiment described above, that is, the algorithm for performing the traffic control so that the received power does not exceed the threshold value T (of the traffic control unit 34). Process).

  First, the received power of the base station in the SINR reference transmission power control state normally used in the CDMA system will be theoretically described.

  Normally, in the CDMA system, transmission power control is performed so that the received signal of each user matches the required SINR. If there are K users in the cell in the current frame and SINR-based transmission power control is ideally performed, the relationship of the following equation (2) is established.

Where SF _k represents the spreading gain of user k, γ _k represents the required SINR of user k, P _k represents the received power of the signal of user k, and P _IN is the sum of interference from other cells and noise power. Represents. Further, when Expression (2) is expressed as a determinant, it can be expressed as Expression (3).

  When subtraction between the k-th row and the other rows of the matrix A is performed, the received power of the signal of the user k can be derived by the following equation (4).

  However, φ (K) <1 because of the accommodation capability of the CDMA system. At this time, the total received power at the base station is expressed by the following equation (5).

  Thus, the received power in the SINR reference transmission power control state can be expressed in a theoretically simple form.

  Next, a method for determining the traffic increase amount (a new user that can be accommodated) so that the received power does not exceed the threshold T based on the above theoretical relationship (processing of the traffic control unit 34) will be described. Here, the theoretical formula regarding the derived received power is further developed to derive the capacity of traffic that can be accommodated when the variation of the received power is limited.

When the number of users changes from K to K + ΔK, the condition of Expression (6) is necessary to suppress the change in received power of Expression (5) within E = ₁₀ log ₁₀ (T / I _c ) [dB]. Is done.
1 / (1-φ (K + ΔK)) ≦ 10 ^{E / 10} / (1-φ (K + ΔK))
(6)

  When this relationship is modified, the following equation (7) is obtained.

  Further, when considering the user who ends the signal in the current frame, it can be expressed as the following equation (8).

  Here, k = 1,..., K represents a user in communication, k = K + 1,..., K + K1 represents a new user, and k = K + K1 + 1,.

  Equation (8) gives a theoretical condition regarding the traffic that can be accommodated under the constraint that the change in received power is kept within E [dB]. In the process of deriving this theoretical condition, no approximation is used, and if the above theoretical formula (8) is used, the traffic volume that can be accommodated can be determined clearly within a range where the received power does not exceed the threshold value T.

  In the actual environment, each user notifies the required transmission rate, and various combinations of traffic satisfying Expression (8) can be considered. For example, in determining a traffic combination, it is possible to apply scheduling in consideration of QoS and propagation characteristics. Further, in equation (8), since the required SINR and spreading gain of the new user are taken into consideration, traffic control according to the transmission rate of the new user is possible. That is, according to the transmission rate of the new user, it is possible to distinguish between terminals that can be accommodated immediately and terminals that are accommodated in stages. The theoretical formula (8) can be used even when there is interference power from other cells.

  As described above, in the present embodiment, the traffic control unit 34 performs traffic control in consideration of the user's requested SINR and spreading gain. Thereby, the change of received power can be reliably suppressed within a certain range.

Embodiment 4 FIG.
In the fourth embodiment, the algorithm of step S3 of the traffic control in the second embodiment described above, that is, the algorithm for performing the traffic control so that the received power does not exceed the threshold value T (of the traffic control unit 34). Process). Here, an algorithm that further simplifies the traffic control described in the third embodiment will be described.

  As traffic control, control as simple as practical is required. Therefore, in the present embodiment, the following equation (9) is used as the traffic increase condition.

Expression (9) is a condition almost equal to Expression (8) when SF _k / γ _k is large.

In addition, there is a method of accommodating users within the range of Expression (10) using various weighting parameters w _k for each user.

However, the parameter w _k is an arbitrary parameter that is determined in consideration of, for example, the priority of packet transmission for each user, and includes elements other than restrictions on power fluctuations. Thus, in this embodiment, traffic control is performed while suppressing fluctuations in transmission power under various conditions.

  Thus, in the present embodiment, new packet transmission that can be accommodated is performed using equations (9) and (10), that is, using the required SINR and spreading gain of each user managed by the base station. decide. In addition, when there are many packet transmission candidates and the expressions (8), (9), and (10) cannot be satisfied in one frame, processing for reducing the transmission rate and increasing the spreading gain, or required The transmission rate is reduced by processing such as lowering the SINR to reduce the coding rate, etc., and accommodate users in stages. Thereby, the change of received power can be reliably suppressed within a certain range.

Embodiment 5. FIG.
In the fifth embodiment, transmission power control considering the influence of traffic control in the CDMA uplink will be described. In the present embodiment, when the traffic increases, a transmission power increase command is notified to each user in advance, thereby avoiding degradation of received signal quality.

  FIG. 12 is a diagram showing a configuration of a communication system, a base station, and a terminal for realizing transmission power control according to the present invention. The base station 41 of the present embodiment includes a traffic control unit 51 and a transmission power control (TPC) command value determination unit 52, and the terminal 42 includes a TPC command reception unit 53, a transmission power determination unit 54, The signal transmission unit 55 is configured. The terminal 42 has the same configuration as a conventional transmission power control device (terminal).

  Here, transmission power control according to the present embodiment will be described. For example, even if the traffic control described in the first to fourth embodiments described above is used, a small fluctuation in interference power may remain at the beginning of the frame. This is because the interference power increases as the traffic increases. In order to eliminate this phenomenon, in this embodiment, transmission power control is performed simultaneously with traffic control.

  In the base station 41, first, the traffic control unit 51 performs, for example, the traffic control of the first to fourth embodiments described above. Based on the result of the traffic control, the TPC command value determination unit 52 determines the TPC command value. Then, the determined TPC command is notified to each user on the downlink.

  Next, in the terminal 42 owned by each user, the transmission power determination unit 54 determines the transmission power value in the next slot based on the TPC command received by the TPC command reception unit 53. Then, the signal transmission unit 55 transmits the signal of the next slot using the determined transmission power.

  FIG. 13 is a flowchart showing a TPC command determination method in the base station. In the base station 41, the traffic control unit 51 performs resource control for the next frame (step S11). Next, when traffic increases due to traffic control (Yes in step S12), the TPC command value determining unit 52 notifies all users of a transmission power increase command in the last slot of the current frame (step S13). FIG. 14 is a diagram illustrating the notification timing of the TPC command. FIG. 15 is a diagram illustrating a TPC command notification method when transmission power control is performed in a frame. However, if the traffic does not increase (No at Step S12), a normal TPC command is transmitted (Step S14).

With this control, since the transmission power step of each user starts at a level higher by one step at the start stage of the next frame, the increase in interference power can be absorbed. Although various setting methods are possible as the transmission power step, Δ _TPC [dB] is used as the transmission power step here.

As described above, in the present embodiment, traffic control is performed, and transmission power control is performed in order to absorb fluctuations in interference power at the head of a frame accompanying an increase in traffic. Thereby, for example, when the power control step Δ _TPC [dB] is larger than the power increase amount D [dB], it is possible to completely avoid the deterioration of the reception quality at the head of the next frame.

  In the present embodiment, the processing when the traffic control and the transmission power control of the first to fourth embodiments described above are combined has been described. However, the present invention is not limited to this, and for example, the first to fourth embodiments. Even when the transmission power control of the present embodiment is applied to traffic control other than the above, the same effect as described above can be obtained. That is, the transmission power control according to the present embodiment may be applied to normal traffic control in which no restriction is imposed on fluctuations in reception power.

Embodiment 6 FIG.
In the sixth embodiment, a transmission power changing method different from the transmission power control of the fifth embodiment described above will be described. Here, various commands for increasing the transmission power are notified to each user. The operations other than the transmission power changing method are the same as those in the fifth embodiment.

  FIG. 16 is a diagram showing a configuration of a communication system, a base station, and a terminal for realizing transmission power control according to the present invention. The base station 61 of the present embodiment includes a traffic control unit 71, a transmission power and power step determination unit 72, and the terminal 62 includes a transmission power and power step reception unit 73, a transmission power determination unit 74, The signal transmission unit 75 is configured.

Here, transmission power control according to the present embodiment will be described. In the transmission power control according to the present embodiment, the power step for increasing the power is set to a variable value Δ _TPC ′ [dB].

In the base station 61, the traffic control unit 71 performs traffic control for the next frame as in the fifth embodiment. Next, the transmission power and power step determination unit 72 determines a transmission power increase step in the next frame based on the traffic control result, and notifies each user of the result. FIG. 17 is a diagram illustrating an example of signal formats of transmission power control information and traffic control information notified from the base station 61 to the user. Each information is notified according to a format determined in advance between the base station and the user. FIG. 18 is a diagram illustrating an example of a relationship between a transmission power step notifying unit and a power step in the signal format. Here, the value Δ _TPC ′ = 0 [dB] (no increase in transmission power) when “00”, the value Δ _TPC ′ = 1 [dB] when “01”, and the value Δ when “10”. _{In the case of TPC} ′ = 2 [dB] and “11”, the power step of the value Δ _TPC ′ = 3 [dB] is used. That is, the transmission power can be increased by various values by notifying the power step from the base station 61.

  Next, a method for determining the power step will be described. In the present embodiment, the power step is determined according to the traffic increase amount in the next frame. That is, as the amount of increase in traffic increases, more interference power is generated, so the power step is set to be larger.

  The transmission power and power step determination unit 72 determines the power step using the following equation (11).

  Expression (11) is a modification of Expression (8). From this relationship, the relationship between the traffic amount in the next frame and the increase rate E [dB] of the reception power after transmission power control can be understood. From this equation (11), if the transmission power step is set to E [dB] or more, the desired signal power increase rate becomes larger than the interference power increase rate, and the degradation of the received signal at the beginning of the frame can be almost eliminated.

FIG. 19 is a diagram showing received SINR levels in each slot of the next frame of a low-speed communication user (see (a)) and a high-speed communication user (see (b)). Here, it is assumed that there are 20 users of 12.2 kbps low-speed voice communication in the W-CDM uplink, and a new high-speed packet communication of 768 kbps is newly accommodated from the next frame. Each user performs closed-loop transmission power control for each slot. Also, here, the received SINR level up to the previous frame, the received SINR when normal transmission power control is performed, and the power step Δ _TPC ′ = 1, 2, 3, 4 [dB] are used in the transmission power control. The received SINR is shown. As can be seen from the figure, as the power step Δ _TPC ′ is increased, the degradation of the received SINR at the beginning of the frame is eliminated.

  Thus, in the present embodiment, when the traffic is greatly increased by the traffic control in the base station, a large value is notified to the user as the transmission power step. On the other hand, when the increase in traffic is small, a small value is notified as the transmission power step. That is, the transmission power step is made variable in consideration of traffic fluctuation in the next frame. As a result, it is possible to avoid degradation of reception quality under various traffic environments.

Embodiment 7 FIG.
In Embodiment 7, a case will be described in which the methods of Embodiments 5 and 6 described above are applied to the downlink.

  FIG. 20 is a diagram showing a configuration of a communication system and a base station for realizing traffic control and transmission power control according to the present invention. This communication system includes a base station 81, a terminal (high-speed communication terminal) 82 owned by a high-speed packet transmission user, and a terminal 83 owned by a low-speed line communication user. The base station 81 includes a propagation information receiving unit 91, a traffic control unit 92, a transmission power determining unit 93, and a signal transmission unit 94. FIG. 21 is a diagram showing the amount of traffic from the base station to each user in the cell.

  First, the situation regarding the downlink of the CDMA system up to now will be described. Regarding the CDMA downlink, the basic configuration of the packet communication scheme is being studied by the International Standards Organization 3GPP and the like. With regard to the basic system configuration of packet communication, much consideration has been given in the downlink rather than the uplink. This is because the standardization organization 3GPP has prioritized the construction of a downlink system with a large amount of traffic.

  In the basic system configuration up to now, the base station transmits a pilot signal in the downlink, and each user receives the pilot signal to measure the received SINR. The received SINR is notified to the base station through the uplink control channel, and the base station performs packet transmission in the next frame based on the information.

  Here, processing of each device constituting the communication system of the present embodiment will be described. In the base station 81, the propagation information receiving unit 91 first receives propagation path information from the user. Next, the traffic control unit 92 performs traffic control for the next frame based on the propagation path information. In this embodiment, the amount of high-speed transmission traffic is increased step by step. Further, the transmission power determination unit 93 increases the transmission power amount to the user according to the traffic increase amount, and the signal transmission unit 94 generates a transmission signal to each user.

  In this process, the traffic control unit 92 suppresses a rapid increase in interference by increasing the traffic amount to the high-speed transmission user step by step. This technique stabilizes the reception quality of users in the cell and can also avoid sudden changes in interference power given to users in other cells.

  Also, in CDMA downlink, signal transmission is performed so that the amount of mutual interference between users is reduced, but the mutual interference power is not completely eliminated. Therefore, when the amount of transmission traffic from the base station increases, the reception quality of each user may deteriorate. Therefore, in the present embodiment, the transmission power determination unit 93 increases the transmission power to each user according to the increase in traffic volume. As a result, it is possible to prevent degradation of reception quality.

  Thus, in this Embodiment, the transmission power to each user is adjusted according to the traffic amount in the next frame. Thereby, it is possible to stabilize the reception quality even in the downlink. In the downlink, unlike the uplink, there is no need to notify using a TPC command or the like, and the base station directly changes the transmission power from the traffic control result.

  In the present embodiment, a case has been described in which the process of increasing the traffic volume in stages and the process of determining the transmission power to each user according to the traffic volume are combined. It may be configured to execute one of the processes.

Embodiment 8 FIG.
The eighth embodiment accommodates high-speed transmission users by a method different from the first to seventh embodiments. Note that the processing of this embodiment can be applied to both uplink and downlink of the CDMA scheme.

  FIG. 22 is a diagram showing a transmission format when accommodating high-speed transmission users. Here, the transmission power of a signal transmitted in one frame is changed with time. For example, when the base station accommodates a high-speed transmission user by traffic control, the terminal of the high-speed transmission user transmits a signal with a small transmission power for the first slot of the frame. Thereafter, the transmission power is gradually increased in time within the frame. Also, other users' terminals gradually increase the transmission power by the transmission power control for each slot. Thereby, it is possible to avoid a rapid deterioration of the reception quality.

  Further, the terminal of the high-speed transmission user increases the transmission power step by step within the frame, and finally transmits a signal with a large transmission power. Also, the base station determines the format of the high-speed transmission packet in advance as shown in FIG. 22, and performs transmission power control based on the format. This makes it possible to construct a simple system.

  As a signal configuration method for increasing the transmission power of a high-speed transmission user over time, for example, a method of improving only the transmission power while using the same symbol rate and chip rate, or spreading used in the middle A method of increasing the signal transmission rate by increasing the number of codes and multiplexing transmission of a plurality of spread signals is conceivable. Another possible method is to increase the symbol transmission rate by transmitting one symbol of a signal with high power in a short time by reducing the spreading factor of the spreading code from the middle.

  As described above, the communication method and the base station according to the present invention are useful for a radio communication system that adopts a CDMA method as a communication method, and in particular, a communication method and a base station including traffic control corresponding to a multimedia communication environment. Suitable as

It is a figure which shows the structure of the communication system and base station for implement | achieving the traffic control concerning this invention. It is a figure which shows an example of the request signal format from the user who performs high-speed packet transmission. It is a figure which shows an example of the request signal format from the user who performs high-speed packet transmission. It is a figure which shows an example of the transmission format of traffic control information. It is a figure which shows the structure of a terminal. It is a figure which shows the property which communication traffic has. It is a figure which shows the structure of the base station for implement | achieving the traffic control concerning this invention. It is a figure which shows an example of the accommodation state of the high-speed transmission user at the time of applying the traffic control of Embodiment 2. FIG. FIG. 10 is a diagram illustrating a flowchart of traffic control according to the second embodiment. It is a figure which shows the relationship between the transmission rate of a packet, spreading | diffusion gain (SF), and required SINR ((gamma)). It is a figure which shows the allowable transmission rate of a new user at the time of using the resource control of this Embodiment as D = 1,2, ∞. It is a figure which shows the structure of the communication system, base station, and terminal for implement | achieving transmission power control concerning this invention. It is a flowchart which shows the TPC command determination method. It is a figure which shows the notification timing of a TPC command. It is a figure which shows the notification method of the TPC command in the case of implementing transmission power control within a flame | frame. It is a figure which shows the structure of the communication system, base station, and terminal for implement | achieving transmission power control concerning this invention. It is a figure which shows an example of the signal format of transmission power control information and traffic control information. It is a figure which shows an example of the relationship between the transmission power step notification part in a signal format, and a power step. It is a figure which shows the reception SINR level in each slot of the next frame of a low-speed communication user and a high-speed communication user. It is a figure which shows the structure of the communication system and base station for implement | achieving the traffic control and transmission power control concerning this invention. It is a figure which shows the traffic amount to each user in a cell from a base station. It is a figure which shows the transmission format at the time of a high-speed transmission user accommodation.

Explanation of symbols

1, 1a, 41, 61, 81 Base station 2, 3, 42, 62, 82, 83 Terminal 11, 12 Request signal reception unit 13 Traffic control unit 14 Communication permission notification unit 15, 16 Traffic control unit 20 Pilot signal reception unit DESCRIPTION OF SYMBOLS 21 Traffic control information receiving part 22 Packet transmission part 23 Transmission rate determination part 24 Transmission information preservation | save part 31 Received power measurement part 32 Allowable maximum traffic parameter determination part 33 Request signal reception part 34 Traffic control part 35 Communication permission notification part 51 Traffic control Unit 52 transmission power control (TPC) command value determination unit 53 TPC command reception unit 54 transmission power determination unit 55 signal transmission unit 71 traffic control unit 72 transmission power and power step determination unit 73 transmission power and power step reception unit 74 transmission power determination Part 75 Signal transmission part 91 Propagation information reception Part 92 traffic control unit 93 transmission power determination unit 94 a signal transmission unit

Claims (24)

In a communication method for giving communication permission to a communication requesting user who satisfies a certain standard,
When there is a communication permission request from a user terminal (high-speed communication user) that performs high-speed packet transmission, traffic control is performed for each high-speed communication user in units of frames and the traffic is accommodated within a predetermined reference range. Control step,
A communication method comprising:   When there is a request for communication permission from a user terminal (low-speed communication user) that performs low-speed transmission, the low-speed communication user is notified autonomously within the speed range. The communication method according to claim 1, wherein a transmission rate for each frame is determined. In the traffic control step,
3. The communication method according to claim 1, wherein the amount of traffic to be accommodated is increased step by step in units of frames. In the traffic control step,
4. The communication method according to claim 3, wherein the next traffic amount is determined according to the received power. In the traffic control step,
A received power measurement step for measuring the received power of the current frame;
A threshold value determining step for determining a threshold value of received power of the next frame based on the measurement result;
A traffic control step for high-speed users that accommodates traffic in stages by performing traffic control so that the received power of the next frame does not exceed the threshold value;
The communication method according to claim 3 or 4, characterized by comprising: In the traffic control step for high-speed users,
6. The communication method according to claim 5, wherein the amount of traffic that can be accommodated is clearly determined by using the required SINR (signal to interference noise power ratio) and spreading gain of a new high-speed communication user. Further, when accommodating the traffic of the high-speed communication user, an uplink transmission power control step of notifying each user currently transmitting to predetermined information for increasing the transmission power to the base station,
The communication method according to any one of claims 1 to 6, further comprising: In a communication method for giving communication permission to a communication requesting user who satisfies a certain standard,
An uplink transmission power control step of notifying predetermined information for increasing the transmission power to the base station to each user currently transmitting when newly accommodating traffic of a high-speed communication user;
A communication method comprising: In the uplink transmission power control step,
The base station notifies each user of a transmission power control (TPC) command for increasing the transmission power to one level higher as the predetermined information. Communication method. In the uplink transmission power control step,
The base station adaptively determines the transmission power increase rate according to the traffic increase amount in the next frame, and sets a variable transmission power width corresponding to the increase rate as the predetermined information for each user. The communication method according to claim 7 or 8, wherein notification is performed. In the uplink transmission power control step,
The communication method according to claim 10, wherein an increase rate of transmission power is determined using a required SINR and a spreading factor of traffic in a next frame. Furthermore, when accommodating the traffic of the high-speed communication user, the base station, a downlink transmission power control step of increasing the transmission power to each user according to the traffic increase amount in the next frame,
The communication method according to claim 1, further comprising: When there is a request for communication permission from a user who performs high-speed packet transmission (high-speed communication user) and the high-speed transmission user is accommodated by traffic control, transmission power control in slot units is performed on the signal of the high-speed communication user, A transmission power control process for high-speed users that gradually increases transmission power,
A communication method comprising: In a base station that grants communication permission to users who want to communicate that meet certain criteria,
When there is a request for communication permission from a user terminal that performs low-speed transmission (low-speed communication user), the user terminal that performs high-speed packet transmission (high-speed communication) is notified to the low-speed communication user. A traffic control means for performing traffic control in units of frames for the high-speed communication user when receiving a communication permission request from a user) and accommodating the traffic within a predetermined reference range;
A base station comprising: In a base station that grants communication permission to users who want to communicate that meet certain criteria,
When there is a request for communication permission from a user terminal that performs high-speed packet transmission, traffic control means that performs traffic control in units of frames for the high-speed communication user and accommodates traffic within a predetermined reference range;
A received power measuring means for measuring the received power of the current frame;
With
The traffic control means includes
A base station that performs traffic control based on received power of a next frame. In a base station that grants communication permission to users who want to communicate that meet certain criteria,
When there is a request for communication permission from a user terminal that performs low-speed transmission (low-speed communication user), the user terminal that performs high-speed packet transmission (high-speed communication) is notified to the low-speed communication user. A traffic control means for performing traffic control in units of frames for the high-speed communication user when a request for communication permission is received from a user) and accommodating the traffic within a predetermined reference range;
A received power measuring means for measuring the received power of the current frame;
Threshold value determining means for determining a threshold value of received power of the next frame based on the measurement result;
With
The traffic control means includes
A base station characterized by gradually increasing the amount of traffic to be accommodated in units of frames by performing traffic control so that received power of a next frame does not exceed the threshold value. The traffic control means includes
The base station according to claim 16, wherein the amount of traffic that can be accommodated is specifically determined by using a required SINR (signal to interference noise power ratio) and spreading gain of a new high-speed communication user. Further, when accommodating the traffic of the high-speed communication user, information notifying means for notifying each user currently transmitting, of predetermined information for increasing transmission power,
The base station according to claim 14, further comprising: In a base station that grants communication permission to users who want to communicate that meet certain criteria,
Information notification means for notifying predetermined information for increasing transmission power to the base station to each user currently transmitting when newly accommodating traffic of high-speed communication users,
A base station comprising: The information notification means includes
The base station according to claim 18 or 19, wherein a transmission power control (TPC) command for increasing transmission power to one level higher is notified to each user as the predetermined information. The information notification means includes
The transmission power increase rate is adaptively determined according to the traffic increase amount in the next frame, and the variable transmission power width corresponding to the increase rate is notified to each user as the predetermined information. The base station according to claim 18 or 19, characterized in that The information notification means includes
The base station according to claim 21, wherein an increase rate of transmission power is determined using a required SINR and a spreading factor of traffic in a next frame. Further, when accommodating the traffic of the high-speed communication user, downlink transmission power control means for increasing the transmission power to each user according to the amount of traffic increase in the next frame,
The base station according to any one of claims 14 to 22, comprising: When there is a request for communication permission from a user who performs high-speed packet transmission (high-speed communication user) and the high-speed transmission user is accommodated by traffic control, transmission power control is performed in units of slots for the signal of the high-speed communication user. , Transmission power control means for gradually increasing the transmission power,
A base station comprising:

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