JP3648377B2 - ATM cell transmission method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In accordance with the ATM (Asynchronous Transfer Mode) system, an ATM cell input / output by an ATM switch or an ATM terminal is transmitted between a base node device and one or more communication modules. For example, the present invention relates to an ATM cell transmission method transmitted via a wireless line.
[0002]
[Prior art]
A wireless ATM system is promising as one of the methods for realizing next-generation broadband multimedia personal communication. In the wireless ATM system, communication on a radio line between a radio base station and a radio module is also performed according to the ATM system. In the ATM system, communication information is transferred in a fixed-length packet (53 bytes; that is, a header part of 5 bytes and a payload part of 48 bytes) called a cell.
[0003]
FIG. 11 shows a basic configuration example of the wireless ATM system. In FIG. 11, 11-1 to 11-n are ATM terminals, 12-1 to 12-n are radio modules, 1300 is a radio base station, 14 is an ATM switch, and 110-1 to 110-n are Transmission paths of communication information sent from the ATM terminal to the wireless module, 111-1 to 111-n are transmission paths of communication information sent from the wireless module to the ATM terminal, and 121-1 to 121-n are Transmission path of communication information sent from the radio module to the radio base station, 120-1 to 120-n are transmission paths of communication information sent from the radio base station to the radio module, and 130 is from the radio base station A transmission path 131 of communication information sent to the ATM exchange, 131 is a transmission path of communication information sent from the ATM exchange to the radio base station. The ATM terminal and the wireless module, and the wireless base station and the ATM switch are connected by wired lines (110-1 to 110-n, 111-1 to 111-n, 130, 131), and the wireless module and the wireless base station are connected. Are connected by wireless lines (120-1 to 120-n, 121-1 to 121-n). FIG. 11 shows an example in which an ATM terminal is connected to the wireless module, but a configuration example of a wireless ATM system in which an ATM switch is connected to the wireless module instead of the ATM terminal can be considered.
[0004]
FIG. 12 shows a configuration example of the U plane (user plane) protocol in the wireless ATM system shown in FIG. As shown in FIG. 12, the application data transmitted from the ATM terminal arrives at the wireless module after being processed in the AAL layer (ATM adaptation layer), ATM layer, and PHY layer (physical layer). The wireless module performs processing at the ATM layer on the received data, and then performs WAL layer (wireless access layer; for example, MAC (Medium Access Control) protocol over wireless media) processing via a wireless line. To the radio base station. The wireless base station that has received the data from the wireless line performs ATM processing on the data and then transmits it to the ATM switch. As shown in FIG. 12, in a wireless ATM system, a relay node (a radio module, a radio base station, an ATM switch) performs received data exchange processing via an ATM layer, and then passes through a PHY layer or a WAL layer. Data is transmitted to the stage node (or destination terminal).
[0005]
One of the processes performed in the WAL layer is a TDMA (Time Division Multiple Access) method, FDMA (Frequency Division Multiple) as a method for accessing a wireless channel when performing communication between the wireless module and the wireless base station. (Access) system and CDMA (Code Division Multiple Access) system exist, but in order to enable high-speed wideband communication and dynamic band allocation necessary for providing ATM communication even on a wireless line. Therefore, it is considered most suitable to use a TDMA system that allows flexible adjustment of the wireless channel speed. In the TDMA scheme, data signals are transmitted so that multiple radio modules have the same carrier frequency and do not overlap in time with one radio base station. A fixed-length TDMA frame (hereinafter, simply referred to as a frame) serving as a basic period of data signal transmission / reception is determined, and communication is performed using a time slot allocated in the frame. FIG. 13 shows a structural example of a frame used in the TDMA system. In FIG. 13, the frame is time-divided into an uplink (for transmission from the radio module to the radio base station) and a downlink (for transmission from the radio base station to the radio module) (TDMA / TDD (Time Division Duplex)). method).
[0006]
By the way, in communication using the ATM system, in order to meet various communication qualities required by multimedia applications, several QoS (service quality) requirements such as cell loss and cell delay can be met. A service class is defined. One of these service classes is an ABR (Available Bit Rate) service class. FIG. 14 shows an overview of the ABR service. In the ABR service, in addition to a cell (data cell) containing communication information, an RM cell (Resource Management cell) is sent to the receiving terminal (22) at regular intervals from the transmitting terminal (21). (Forward RM cell), the receiving terminal transmits the received RM cell back to the transmitting terminal (backward RM cell). At this time, the congestion state in the ATM network is overwritten on the RM cell by the ATM switch (24) in the passing ATM network (23) and the receiving terminal to be turned back, and these information is finally backed up. It is transmitted to the transmitting terminal that receives the word RM cell, and the transmitting terminal changes the cell transmission rate according to the congestion state in the ATM network. In FIG. 14, the RM cell is shown by a shaded block.
[0007]
In the ATM switch and the receiving terminal, in order to prevent the occurrence and continuation of congestion, the cell transmission rate is controlled to the transmitting terminal by updating the following information in the RM cell.
ER (Explicit Cell Rate): 2-byte information
Explicit cell speed. The cell speed that can be sent is described. The transmitting terminal is not allowed to transmit cells at a rate exceeding this value.
CI (Congestion Indication): 1-bit information
Congestion indication bit. When this bit value is set, the transmitting terminal must reduce the cell transmission rate.
-NI (No Increase): 1-bit information
Speed increase prohibition bit. When this bit value is set, the transmitting terminal must not increase the cell transmission rate.
[0008]
When the ABR service is provided in the wireless ATM system shown in FIG. 11, the ATM terminal that is the data transmission source that has received the backward RM cell returned from the transmission destination receives the ER described in the RM cell. Based on the value, the CI bit, and the NI bit, the cell transfer rate of the subsequent ATM cell is calculated, and the ATM cell is transferred within a range not exceeding this rate. At this time, in the wired line portion (between the transmission source ATM terminal and the wireless module, ahead of the wireless base station), it is not necessary to execute the bandwidth reassignment of the virtual connection accompanying the change of the cell transfer rate. In the radio channel portion with the radio base station, it is necessary to change the data transfer rate explicitly by changing the number of time slots in one frame as the cell transfer rate is changed. However, it is difficult to recognize the cell transfer rate newly calculated by the ATM terminal in the wireless line portion that changes the number of time slots, and therefore it is very difficult to change the number of time slots based on this rate. there were.
[0009]
[Problems to be solved by the invention]
As described above, when the ABR service is provided in the conventional wireless ATM system, it is necessary to perform the band reallocation of the radio line part in accordance with the change of the cell transfer rate of the ATM terminal as the transmission source. It is difficult for a radio base station or a radio module that manages and executes the band reallocation to recognize the change in the cell transfer rate at the ATM terminal described above. This is a problem common to all ATM systems realized through a transmission medium that needs to ensure a line capacity when transferring ATM cells regardless of the wireless ATM system.
[0010]
The present invention has been made in consideration of the above circumstances, and when bidirectionally transmitting ATM cells between a base node device and a plurality of communication modules via a transmission medium that needs to ensure line capacity explicitly. Another object of the present invention is to provide an ATM cell transmission method that enables reallocation of line capacity according to the cell transfer rate of each virtual connection or each communication module.
[0011]
[Means for Solving the Problems]
The present invention is an ATM cell transmission method in a base node device (for example, a radio base station) for bidirectionally transmitting an ATM cell to a plurality of communication modules via a common transmission medium, For each communication module and for each cell transfer direction between the communication module and the own device, corresponding to the data string of the ATM cell transmitted / received to / from the same communication module, the ATM cell transmitting device is directed to the receiving device. Alternatively, when a resource management cell (for example, an RM cell) transmitted from the ATM cell receiving device to the transmitting device is received, the communication module refers to the resource management cell and transmits and receives the ATM cell. A cell transfer rate to be provided in a corresponding cell transfer direction on the transmission medium is obtained, and the communication module is set in the corresponding cell transfer direction on the common transmission medium. If at least the bandwidth to be reserved for providing the cell transfer rate is provided to the network, and the bandwidth can be secured, the bandwidth is set to the cell transfer direction corresponding to the common transmission medium. It is characterized by assigning it again.
Preferably, the cell transfer rate is an ATM node or a reception of the ATM cell through which a virtual connection to which the ATM cell belongs is described in a resource management cell transmitted to the transmitting device from the ATM cell receiving device. You may make it equal to the allowable cell transfer rate (for example, ER value) overwritten in the apparatus.
Preferably, the cell transfer rate is a current cell transfer rate (for example, a CCR value) in the ATM cell transmitting device described in a resource management cell transmitted from the ATM cell transmitting device to the receiving device. ).
Preferably, the cell transfer rate is an ATM node or a reception of the ATM cell through which a virtual connection to which the ATM cell belongs is described in a resource management cell transmitted to the transmitting device from the ATM cell receiving device. With reference to allowable cell transfer rate (eg, ER value) and bit information (eg, CI bit information, NI bit information, or both bit information) for conveying information related to congestion, which is overwritten in the device When the bit information is set to a value indicating that there is congestion with respect to the cell transfer rate provided on the common transmission medium in the virtual connection to which the ATM cell currently belongs ( For example, when the CI bit information is set to 1, a value obtained by reducing the cell transfer rate is set as the cell transfer rate. Therefore, when the bit information is set to a value indicating that there is no congestion and an increase in cell transmission rate is not prohibited (for example, both CI bit information and NI bit information are set to 0) If the cell transfer rate exceeds the allowable cell transfer rate (for example, ER value), the value obtained by increasing the cell transfer rate is obtained as the cell transfer rate. It may be replaced with an allowable cell transfer rate.
The present invention is also an ATM cell transmission method in a base node device (for example, a radio base station) for bidirectional transmission of ATM cells with a plurality of communication modules via a common transmission medium. In response to a data string of the ATM cells belonging to the same virtual connection, a resource management cell (for example, transmitted from the ATM cell transmitter to the receiver or from the ATM cell receiver to the transmitter) , RM cell), a step of obtaining a cell transfer rate to be provided on the common transmission medium in the virtual connection to which the ATM cell belongs with reference to the resource management cell; On the transmission medium for the virtual connection so that at least the cell transfer rate is provided in the transfer of ATM cells If the bandwidth to be secured is obtained and the bandwidth can be secured, the bandwidth is newly assigned to the virtual connection. The cell transfer rate is determined by the ATM cell receiver. Allowable cell transfer rate (for example, ER value) written in the resource management cell transmitted to the transmitting device and overwritten in the ATM node through which the virtual connection to which the ATM cell belongs or the receiving device of the ATM cell It is equal to.
The present invention is also an ATM cell transmission method in a base node device (for example, a radio base station) for bidirectional transmission of ATM cells with a plurality of communication modules via a common transmission medium. In response to a data string of the ATM cells belonging to the same virtual connection, a resource management cell (for example, transmitted from the ATM cell transmitter to the receiver or from the ATM cell receiver to the transmitter) , RM cell), a step of obtaining a cell transfer rate to be provided on the common transmission medium in the virtual connection to which the ATM cell belongs with reference to the resource management cell; On the transmission medium for the virtual connection so that at least the cell transfer rate is provided in the transfer of ATM cells If the bandwidth to be secured is obtained and the bandwidth can be secured, the bandwidth is newly assigned to the virtual connection. The cell transfer rate is determined by the ATM cell receiver. Allowable cell transfer rate (for example, ER value) written in the resource management cell transmitted to the transmitting device and overwritten in the ATM node through which the virtual connection to which the ATM cell belongs or the receiving device of the ATM cell And bit information for conveying information related to congestion, and for the cell transfer rate currently provided on the common transmission medium in the virtual connection to which the ATM cell belongs, When the bit information is set to a value indicating that there is congestion, a value obtained by reducing the cell transfer rate is set to the cell transfer rate. And when the bit information is set to a value indicating that there is no congestion and an increase in cell transmission rate is not prohibited, a value obtained by increasing the cell transfer rate is set as the cell transfer rate. When the cell transfer rate exceeds the allowable cell transfer rate, the cell transfer rate is replaced with the allowable cell transfer rate.
Preferably, when it is impossible to secure the bandwidth necessary for providing the determined cell transfer rate in the virtual connection on the common transmission medium, only the bandwidth that can be secured is allocated to the virtual connection. And a second cell transfer rate that can be provided in the virtual connection by allocating a band that can be secured (in this case, the cell transfer rate in each of claims 1 to 6 is the first cell transfer rate) ) And an allowable cell transfer rate (for example, ER value) described in a resource management cell transmitted from the receiving device of the received ATM cell to the transmitting device exceeds the second cell transfer rate. In this case, the second cell transfer rate may be overwritten as the allowable cell transfer rate in the resource management cell.
The present invention is also an ATM cell transmission method in a base node device (for example, a radio base station) for bidirectional transmission of ATM cells with a plurality of communication modules via a common transmission medium. Then, for each virtual connection, a first cell transfer rate transmitted over the virtual connection is calculated, and based on the first cell transfer rate and a bandwidth that can be used on the common transmission medium, A bandwidth to be secured on the common transmission medium is newly obtained for the virtual connection, and when the resource management cell (for example, RM cell) corresponding to the virtual connection is received, the obtained bandwidth is secured. The second cell transfer rate that can be provided by the second cell transfer rate and the allowable cell transfer rate (for example, ER value) described in the resource management cell are compared, and the second cell transfer rate is compared. If the transmission rate exceeds the allowable cell transfer rate, the second cell transfer rate is corrected so that the difference from the allowable cell transfer rate does not increase, and the second cell transfer rate is adjusted based on the corrected second cell transfer rate. Thus, a bandwidth to be secured on the common transmission medium is newly allocated to the virtual connection.
Preferably, the transmission medium may be a wireless line.
[0017]
Preferably, when it is impossible to secure the bandwidth necessary for providing the determined cell transfer rate in the virtual connection on the common transmission medium, only the bandwidth that can be secured is allocated to the virtual connection. And a second cell transfer rate that can be provided in the virtual connection by allocating a band that can be secured (in this case, the cell transfer rate in each of claims 1 to 6 is the first cell transfer rate) ) And an allowable cell transfer rate (for example, ER value) described in a resource management cell transmitted from the receiving device of the received ATM cell to the transmitting device exceeds the second cell transfer rate. In this case, the second cell transfer rate may be overwritten as an allowable cell transfer rate (for example, ER value) in the resource management cell.
[0019]
According to the present invention (Claim 8), ATM cell transmission in a base node apparatus (for example, a radio base station) for bidirectional transmission of ATM cells with a plurality of communication modules via a common transmission medium. A method for calculating, for each virtual connection, a first cell transfer rate transmitted over the virtual connection, and based on the first cell transfer rate and a bandwidth available on the common transmission medium. Then, the bandwidth to be secured on the common transmission medium is newly obtained for the virtual connection, and when the resource management cell (for example, RM cell) corresponding to the virtual connection is received, the obtained bandwidth is By comparing the second cell transfer rate that can be provided by ensuring and the allowable cell transfer rate (for example, ER value) described in the resource management cell, the second cell transfer rate is compared. When the cell transfer rate exceeds the allowable cell transfer rate (for example, ER value), the second cell transfer rate is corrected so that the difference from the allowable cell transfer rate (for example, ER value) does not increase. The bandwidth to be secured on the common transmission medium may be newly allocated to the virtual connection based on the modified second cell transfer rate.
[0022]
The present invention relating to the apparatus is also established as an invention relating to a method, and the present invention relating to a method is also established as an invention relating to an apparatus.
Further, the present invention relating to an apparatus or a method has a function for causing a computer to execute a procedure corresponding to the invention (or for causing a computer to function as a means corresponding to the invention, or for a computer to have a function corresponding to the invention. It can also be realized as a computer-readable recording medium on which a program (for realizing) is recorded.
[0023]
According to the present invention, in a communication system in which ATM cells are bidirectionally transmitted via a common transmission medium between one base node device such as a wireless ATM system and one or more communication modules, the base node device is provided. In (radio base station), information described in a resource management cell (for example, RM cell) is collected and provided to a virtual connection in which the resource management cell performs resource management based on this information The cell transfer rate is dynamically changed as in the ABR service by calculating the power cell transfer rate and reallocating the channel capacity (for example, radio channel capacity) in the common transmission medium based on this value. The line capacity can be allocated to the ATM service after recognizing the change in the cell transfer rate in the transmission device of the virtual connection. It is possible to prevent the deterioration of service quality due to insufficient amount, also can prevent the allocation of redundant bandwidth.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the invention will be described with reference to the drawings.
In this embodiment, an embodiment of the invention in a wireless ATM system using a radio line as a transmission medium will be described, a base node will be described as a radio base station, and a communication module will be described as a radio module.
[0025]
FIG. 1 is a configuration example of a radio base station according to an embodiment of the present invention. The radio base station in FIG. 1 corresponds to a configuration example of the radio base station 13 in FIG. 11 when the present invention is applied to the wireless ATM system in FIG.
[0026]
As shown in FIG. 1, the radio base station according to the present embodiment includes an ATM processing unit 31, a radio frame processing unit 32, and a frame scheduler 33.
The ATM processing unit 31 processes the ATM cell received from the wired line or the ATM cell extracted from the wireless frame processing unit 32, and transfers the ATM cell to the wireless frame processing unit 32 or sends it over the wired line. In addition to processing, cell traffic information (number of accumulated cells, cell arrival speed, etc.) for each virtual connection (VC) and information in the RM cell are transferred to the frame scheduler 33.
[0027]
In the radio frame processing unit 32, the ATM cell delivered from the ATM processing unit 31 is incorporated into a radio frame based on the slot allocation obtained by the frame scheduler 33, and is sent out on the radio channel; The ATM cell is extracted from the received radio frame and delivered to the ATM processing unit 31.
[0028]
The frame scheduler 33 performs slot allocation of a radio frame based on various parameters obtained at the time of connection setting, cell traffic information for each VC delivered from the ATM processing unit 31, and information in the RM cell, and this slot allocation information is transmitted to the radio. A process of notifying the frame processing unit 32 is performed.
[0029]
The ATM processing unit 31 extracts the RM cell information for the RM cell among the received ATM cells and transfers it to the frame scheduler 33, and corrects the RM cell information according to the instruction of the frame scheduler 33 as necessary. RM cell processing units 311 and 312 may be provided. Note that the RM cell processing unit 311 performs processing of the RM cell received from the wired line, and the RM cell processing unit 312 performs processing of the RM cell received from the wireless line. In addition, the ATM processing unit 31 cell traffic information for each VC relating to cells arriving from the wired line and cell traffic for each VC relating to cells arriving from the wireless line and delivered from the radio frame processing unit as necessary. Information is collected and delivered to the frame scheduler 33.
[0030]
The radio frame processing unit 32 generates a radio frame by inserting the cell delivered from the ATM processing unit 31 into the corresponding slot position based on the slot allocation method in the radio frame obtained by the frame scheduler 33. A frame generation unit 321 for sending the frame to the wireless line later, an ATM cell extraction unit 322 for extracting a cell from the received radio frame and delivering the cell to the ATM cell processing unit 31 are provided.
[0031]
FIG. 2 shows an example of a radio slot allocation method performed by the frame scheduler (33 in FIG. 1) for a service class defined in ATM.
For the CBR (Constant Bit Rate) service, radio slots are fixedly allocated so that cell transfer at the PCR (peak cell rate), which is a parameter obtained at the time of connection setting, is possible.
[0032]
For VBR (Variable Bit Rate) service, both real-time VBR service and non-real-time VBR service, cell transfer according to parameters, PCR, SCR (average cell rate), MBS (maximum burst size), which are obtained at the time of connection setup Wireless slots are allocated so as to be possible. At that time, in the frame scheduler, radio slots are fixedly allocated in advance so that the minimum cell transfer according to these parameters is possible, and in addition, according to the degree of burst of cell traffic during service, VBR services are provided by dynamically allocating radio slots.
[0033]
A radio slot is dynamically allocated to an ABR (Available Bit Rate) service and a UBR (Unspecified Bit Rate) service based on the characteristics of cell traffic to be transmitted.
[0034]
As described above, for the CBR service and the VBR service, it is necessary to provide a cell transfer rate to be guaranteed in each service by performing fixed allocation of radio slots based on various parameters. Therefore, the radio channel capacity that can be used by the ABR service and UBR service in which dynamic radio slot allocation is performed is based on the radio channel capacity provided between the radio base station and the radio module, and the CBR service and VBR service are used. It is equal to the radio channel capacity obtained by subtracting the radio channel capacity fixedly secured for the virtual connection to be provided, and the radio slot is allocated to the virtual connection providing the ABR service and the UBR service within a range not exceeding this capacity. Will be done.
[0035]
In the following, some examples of the method of assigning radio slots for ABR services performed in the frame scheduler when the present invention is implemented will be described in detail.
The frame scheduler (33 in FIG. 1) dynamically determines the number of radio slots allocated to the ABR service based on information in the RM cell delivered from the RM cell processing unit (311 and 312 in FIG. 1). At this time, the information in the RM cell used is as follows.
ER value in backward RM cell (Procedure 1 described later)
-CCR value in forward RM cell (procedure 2 described later)
CI bit and NI bit in backward RM cell (Procedure 3 described later)
Hereinafter, a method for changing a radio slot allocated to the ABR service by using the above-described RM cell information will be described.
[0036]
FIG. 3 shows the relationship of the information referred to for the reassignment of the radio slot for the ABR VC transferred in the uplink performed in the radio base station. The description of each parameter used in the following description is as follows.
Rr: Cell transfer rate obtained from the RM cell
・ RL: Upper limit of cell transfer rate required by radio line capacity limit
Rm: Current cell transfer rate measurement
・ Rs: Cell transfer rate currently secured on the radio line
・ ERnew: New ER value
・ Rsnew: Cell transfer rate newly secured on the radio line
Now, the procedure (1) will be described as a first example.
[0037]
This procedure (1) is to change the slot assignment of the radio frame based on the ER value in the backward RM cell.
In the ABR service, the ER value in the backward RM cell is overwritten with the cell transfer rate at which the cell (or destination terminal) through which the RM cell has passed can be transferred without causing congestion. In this radio base station, by examining the ER value in the backward RM cell, the radio frame allocation slot for the ABR connection in which this RM cell performs resource management (that is, for the radio module in which this connection is set) The necessity of increasing / decreasing the number is determined, and the number of slots is reassigned based on the result.
[0038]
FIG. 4 shows an example of a radio slot reassignment procedure in the frame scheduler 33 based on the ER value of the backward RM cell.
When the RM cell is received by the RM cell processing units 311 and 312 in the radio base station and the information in the RM cell is received by the frame scheduler (step S11), the DIR bit of the RM cell is checked, and the RM cell It is determined whether it is a backward RM cell (whether DIR = 1) (step S12). If this is a backward RM cell, the ER value of this RM cell is extracted (step S13), and the ER value is set as the Rr value (step S14). Then, the minimum value of the cell transfer rate RL value and the Rr value obtained by the upper limit of the usable bandwidth in the radio channel is set as the cell transfer rate Rsnew value newly secured on the radio channel (step S15). ), The minimum value of the Rsnew value and the ER value is set as the ERnew value and overwritten as the ER value in the backward RM cell (step S16). Finally, the radio frame slot is reassigned so that cell transfer at the Rsnew value can be provided to the virtual connection on the radio line (step S17), and the operation of the frame scheduler is terminated (step S18). ).
[0039]
The radio slot allocated to the ABR virtual connection in the uplink direction is based on the backward RM cell received by the RM cell processing unit 311, and the radio slot allocated to the ABR virtual connection in the downlink direction is RM. Based on the backward RM cell received by the cell processing unit 312, reallocation according to the procedure shown in FIG. 4 is performed.
[0040]
By executing this procedure (1), the radio base station refers to the ER value in the backward RM cell for the upper limit value of the cell transfer rate of the ABR virtual connection that communicates with the radio module. Therefore, it is not possible to allocate more than necessary wireless channel capacity to the virtual connection on the wireless channel.
[0041]
Next, procedure (2) will be described as a second example.
This procedure (2) is to change the slot assignment of the radio frame based on the CCR value in the forward RM cell.
[0042]
In the ABR service, the CCR value in the forward RM cell is overwritten with the current cell transmission rate on the ABR connection in the transmitting terminal. The radio base station determines the necessity of increase / decrease in the number of radio frame allocation slots for the ABR connection (that is, for the radio module to which the connection is set) by examining the CCR value in the forward RM cell. Based on the result, the number of slots is reallocated.
[0043]
FIG. 5 shows an example of a radio slot reassignment procedure in the frame scheduler 33 based on the CCR value of the forward RM cell.
When the RM cell is received by the RM cell processing units 311 and 312 in the radio base station and the information in the RM cell is received by the frame scheduler (step S21), the DIR bit of the RM cell is checked, and the RM cell It is determined whether the cell is a forward RM cell (whether DIR = 0) (step S22). If this is a forward RM cell, the CCR value of this RM cell is extracted (step S23), and a value obtained by multiplying the CCR value by a constant α is set as the Rr value (step S24). Then, the minimum value of the cell transfer rate RL value and the Rr value obtained by the upper limit of the usable bandwidth in the radio channel is set as the cell transfer rate Rsnew value newly secured on the radio channel (step S25). ), The minimum value of the Rsnew value and the ER value is set as the ERnew value and overwritten as the ER value in the backward RM cell (step S26). Finally, the radio frame slot is reassigned so that cell transfer at the Rsnew value can be provided to the virtual connection on the radio line (step S27), and the operation of the frame scheduler is terminated (step S27). S28).
[0044]
Note that the radio slot allocated to the ABR virtual connection in the uplink direction is based on the forward RM cell received by the RM cell processing unit 312, and the radio slot allocated to the ABR virtual connection in the downlink direction is RM. Based on the forward RM cell received by the cell processing unit 311, reallocation according to the procedure shown in FIG. 5 is performed.
[0045]
In step S24, a value obtained by multiplying the CCR value by the constant α is set as the Rr value. At this time, if the CCR value which is the current cell transfer rate is set as it is as the Rr value, in the backward RM cell in step S26. The CCR value is overwritten as it is, but this does not allow cell transmission at a rate exceeding the current cell transfer rate (CCR value) at the transmitting terminal that has received this RM cell. . Therefore, a value obtained by multiplying the CCR value by a constant α exceeding 1 is set as the Rr value.
[0046]
By executing this procedure (2), the radio base station refers to the current cell transfer rate value of the ABR virtual connection for communication with the radio module by referring to the CCR value in the forward RM cell. Therefore, it is not necessary to allocate more than necessary wireless channel capacity to the virtual connection on the wireless channel.
[0047]
Next, procedure (3) will be described.
This procedure (3) changes the slot assignment of the radio frame based on the CI bit information and the NI bit information in the backward RM cell.
[0048]
In the ABR service, the CI bit and NI bit in the backward RM cell are overwritten with information indicating whether or not the node (or destination terminal) through which the RM cell has passed is congested. In this radio base station, by checking the CI bit and NI bit in the backward RM cell, the radio frame for the ABR connection in which the RM cell performs resource management (that is, for the radio module in which this connection is set) The necessity of increasing / decreasing the number of assigned slots is determined, and the number of slots is reassigned based on the result.
[0049]
FIG. 6 shows an example of a radio slot reassignment procedure in the frame scheduler 33 based on the CI bit and NI bit of the backward RM cell.
When the RM cell is received by the RM cell processing units 311 and 312 in the radio base station and the information in the RM cell is received by the frame scheduler (step S31), the DIR bit of the RM cell is checked, and the RM cell It is determined whether it is a backward RM cell (whether DIR = 1) (step S32). If this is a backward RM cell, the CI bit, NI bit, and ER value of this RM cell are extracted (step S33), and the Rr value is calculated based on these values (step S34). Then, the minimum value of the cell transfer rate RL value and the Rr value obtained by the upper limit of the usable bandwidth in the radio channel is set as the cell transfer rate Rsnew value newly secured on the radio channel (step S35). ), The minimum value of the Rsnew value and the ER value is set as the ERnew value and overwritten as the ER value in the backward RM cell (step S36). Finally, the radio frame slot is reassigned so that cell transfer at the Rsnew value can be provided to the virtual connection on the radio line (step S37), and the operation of the frame scheduler is terminated (step S37). S38).
[0050]
The radio slot allocated to the ABR virtual connection in the uplink direction is based on the backward RM cell received by the RM cell processing unit 311, and the radio slot allocated to the ABR virtual connection in the downlink direction is RM. Based on the backward RM cell received by the cell processing unit 312, reallocation according to the procedure shown in FIG. 6 is performed.
[0051]
FIG. 7 shows an example of the Rr value recalculation procedure performed in step S34 of FIG.
After extracting the CI bit, NI bit, and ER value of the backward RM cell, recalculation of the Rr value is started. As an initial value, the speed Rs value currently secured on the wireless line is set as the Rr value (step S41). If the CI bit is 1 (step S42), it indicates that congestion has occurred prior to this radio base station, so the Rr value is reduced (step S43). As a reduction method, for example, according to the formula defined in the Source Behavior of the ABR service,
Rr = Rr−Rr × RDF
A means for calculating by the above can be considered. RDF is a rate reduction factor (constant) when the cell transfer rate is reduced (for example, 1/16).
[0052]
Next, if the extracted CI bit is 0 and the NI bit is 0 (step S44), it indicates that congestion has not occurred before this radio base station. This is performed (step S45). As an increase method, for example, according to the formula defined in the Source Behavior of the ABR service,
Rr = Rr + RIF × PCR
A means for calculating by the above can be considered. RIF is a rate increase factor (constant) when the cell transfer rate is increased (for example, 1/16). PCR is the maximum cell transfer rate that can be provided in the ABR service, and is a parameter defined when setting up an ABR connection.
[0053]
The Rr value calculated in step S43 or step S45 is compared with the ER value (step S46). If the Rr value exceeds the ER value, the cell transfer rate (ER value) that can be provided in this virtual connection is determined. Since it indicates that an excess Rr value is to be secured on the radio line, the Rr value is replaced with an ER value, and Rr is reduced (step S47). If the Rr value is lower than the ER value, it is found that the bottleneck of the virtual connection is the wireless channel section, and the ER value in the backward RM cell is replaced with the Rr value (step S48).
[0054]
The Rr value obtained by the above procedure becomes the new Rr value calculated in step S34 (step S49).
By executing this procedure (3), the radio base station changes how the cell transfer rate value of the ABR virtual connection that communicates with the radio module changes by receiving the backward RM cell. Can be known by referring to the CI bit information, NI bit information, and ER value in the backward RM cell, the radio channel capacity necessary to provide the cell transfer rate after the change is It can be assigned immediately to this virtual connection. In addition, the virtual connection transmitting terminal is notified of the upper limit value of the cell transfer rate in this wireless channel section by overwriting the Rr value calculated in this procedure (3) as the ER value of the backward RM as necessary. The cell transfer rate can be set so as not to exceed the upper limit.
[0055]
By the way, both of the procedure (1) and the procedure (3) reassign slots in the radio frame based on the received information in the backward RM cell. For example, in the procedure (1), the radio channel capacity is allocated so as to be equal to the ER value in the backward RM cell. This is an effective procedure when means for correcting the ER value is adopted. In the procedure (3), the radio channel capacity is allocated based on the CI bit information, NI bit information, and ER value in the backward RM cell. This is the congestion notification means in the ATM switch node through which the virtual connection passes. This is an effective procedure when means for correcting the CI bit and NI bit in the backward RM cell is employed. In general, since it is impossible for the radio base station to know which congestion notification means is performed in the ATM switch node through which the virtual connection passes, in the radio base station, when the backward RM cell is received, the procedure (1) and ( It is desirable to execute 3) in parallel and use a smaller capacity of the obtained wireless channel capacity as a wireless channel capacity to be allocated to the virtual connection, and reallocate slots in the radio frame based on this capacity. Note that the procedure (2) is a procedure for reallocating slots in the radio frame based on the received information in the forward RM, and is a procedure executed independently of the procedures (1) and (3). is there.
[0056]
In the above procedures (1) to (3), the radio frame slot is reassigned based on the information (ER value, CCR value, CI bit, NI bit) in the RM cell received by the radio base station. The means has been described. In addition, a means for reassigning radio frame slots based on the arrival process of ATM cells in the radio base station can be considered (procedure (4)).
[0057]
Hereinafter, the procedure (4) will be described.
In this procedure (4), the arrival process of the ATM cell in the radio base station is monitored, and the slot allocation of the radio frame is changed based on the arrival speed obtained thereby.
[0058]
In a virtual connection that provides ABR service (as well as UBR service), the bandwidth required for cell transfer is not always secured (for ABR service, cell transfer at the minimum cell transfer rate to be guaranteed is provided) Therefore, there is a case where a certain amount of bandwidth is always secured), and if there is a usable bandwidth, cell transfer is performed using that bandwidth. In this procedure, the transfer rate of the cells arriving at the radio base station is constantly monitored, and the radio channel capacity is reassigned based on this rate value.
[0059]
FIG. 8 shows an example of a radio slot reassignment procedure by the frame scheduler 33 based on the cell arrival rate obtained by monitoring at the radio base station.
Each time a predetermined time elapses or a predetermined number of cells arrives (step S61), the cell arrival rate (Rm) for each virtual connection is determined by the arrival cell information obtained in the ATM processing unit 31. Measurement is performed (step S62). Then, the cell transfer rate Rsnew that newly secures the minimum value of the cell transfer rate RL value obtained by the upper limit of the usable bandwidth in the radio channel and the value obtained by multiplying the Rm value by the constant α on the radio channel. (Step S63), the Rsnew value and the minimum value of the ER value in the backward RM cell received thereafter are set as the ERnew value (step S64), and this value is newly set in the backward RM cell. Overwrite as a valid ER value. Finally, reassignment of slots in the radio frame is performed so that cell transfer with the calculated Rsnew value is possible (step S65).
[0060]
Note that when the Rsnew value is calculated in step S63, the value obtained by multiplying the Rm value by the constant α is compared with the RL value. At this time, when the comparison is performed using the Rm value as it is, the backward RM is determined in step S64. The Rm value is overwritten as the ER value in the cell as it is, but this does not allow cell transmission at a rate exceeding the current cell transfer rate (Rm value) at the transmitting terminal that has received this RM cell. It becomes. In order to prevent this, a value obtained by multiplying the Rm value by a constant α exceeding 1 is compared with the RL value.
[0061]
As described above, procedures (1) and (3) for reassigning slots in radio frames based on information in backward RM cells, and procedures for reassigning slots in radio frames based on information in forward RM cells. Examples of four procedures that can be performed independently have been shown, such as (2) and the procedure (4) for reassigning the slot in the radio frame based on the arrival process of the ATM cell in the radio base station. ), Procedure (2) and procedure (3) can be carried out in combination of any two or three, and in these combinations including procedure (2), procedure (2) is replaced with procedure (4). Other forms are also possible. When the above two or more procedures are combined and executed, for example, each procedure is executed in parallel, and each procedure executed in parallel changes the slot assignment of the radio frame independently.
[0062]
As described above, the sum of the radio channel capacities allocated to the virtual connections that provide the ABR service and the UBR service provides the CBR service and the VBR service based on the radio channel capacity between the radio base station and the radio module. It is necessary not to exceed the wireless line capacity obtained by subtracting the fixed wireless line capacity for the virtual connection.
[0063]
For example, as shown in FIG. 9, the wireless base station allocates the wireless channel capacity by holding a correspondence table between the virtual connection requesting the ABR service and the UBR service and the wireless channel capacity allocated to the connection in the wireless base station. Manage. Corresponding to the identifier (41) of the virtual connection requesting the ABR service and UBR service managed in this radio base station, the cell transfer rate (42) obtained by monitoring the cell traffic and the reassignment of slots in the radio frame The obtained cell transfer rate (43) is at least described. The sum of the current cell transfer rates in the virtual connection described in this table (44), and the radio channel capacity that can be provided for the ABR service and UBR service are also described (45).
[0064]
As a method of reallocating slots in a radio frame for a virtual connection that provides an ABR service and a UBR service, for example, it is possible to obtain a radio channel capacity compared to the current cell transfer rate (cell transfer rate obtained by monitoring) in each virtual connection. It is possible to do this. In the example of FIG. 9, since the ratio of the current cell transfer rate in the virtual connections # 1, # 2, and # 3 is 2: 4: 3, the cell transfer rate on the wireless line is equal to this ratio. Assigned.
[0065]
In the above description, the cell transfer rate monitoring for each virtual connection and the allocation of the radio channel capacity have been described. It may be assigned. In that case, in FIG. 9, each value is described corresponding to the wireless module.
[0066]
Means for allocating slots for each virtual connection as means for allocating slots in a radio frame based on the radio channel capacity calculated by the above-described procedures (1) to (4) or a combination thereof; and a radio module A means for performing slot allocation every time can be considered.
[0067]
When slot allocation is performed for each wireless module, for example, first, slot allocation is performed for each virtual connection by the above-described method, and the following result is collected for each wireless module.
[0068]
FIG. 10 shows an example of slot allocation according to each means. (A) is an example which allocates a slot for every virtual connection, (b) is an example which allocates a slot for every wireless module.
[0069]
In order to realize efficient use of the radio channel capacity, it is preferable to employ means for allocating slots for each radio module. This is because, in this radio base station, a radio line capacity is fixedly assigned to a virtual connection requesting the CBR service and VBR service regardless of the presence or absence of a cell to be transmitted. When the allocation is performed, the radio frame slot allocated to the virtual connection requesting the CBR service and the VBR service where there is no cell to be transmitted is transmitted in an unused state. On the other hand, when slot assignment is performed for each wireless module, if a virtual connection as described above exists, it becomes possible to insert a cell belonging to a virtual connection requesting another service in the wireless module. As a result, more efficient use than a wireless line is possible.
[0070]
The above functions can also be realized as software.
Further, in the present embodiment, a computer-readable program having recorded thereon a program for causing a computer to execute a predetermined procedure (or for causing a computer to function as a predetermined means or for causing a computer to realize a predetermined function) It can also be implemented as a recording medium.
The present invention is not limited to the above-described embodiment, and can be implemented with various modifications within the technical scope thereof.
[0071]
【The invention's effect】
According to the present invention, in the base node device, the information described in the resource management cell is collected, and the cell to be provided to the virtual connection that the resource management cell performs resource management based on this information By calculating the transfer rate and reallocating the line capacity in the common transmission medium based on this value, the allocation of the line capacity to the ATM service whose cell transfer rate is dynamically changed is transmitted to the virtual connection. Since it can be performed after recognizing a change in the cell transfer rate in the apparatus, it is possible to prevent deterioration of service quality due to insufficient line capacity, and it is possible to prevent allocation of redundant line capacity.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a radio base station according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining a policy at the time of radio slot allocation for various services in ATM;
FIG. 3 is a diagram for explaining a system concept of radio slot allocation based on in-RM cell information;
FIG. 4 is a flowchart showing an example of a slot number reallocation procedure.
FIG. 5 is a flowchart showing another example of the slot number reallocation procedure;
FIG. 6 is a flowchart showing still another example of the slot number reallocation procedure.
FIG. 7 is a flowchart illustrating an example of an Rr value calculation procedure.
FIG. 8 is a flowchart showing still another example of the slot number reallocation procedure.
FIG. 9 is a diagram showing a correspondence between a virtual connection, a current cell transfer rate, and a cell transfer rate assigned on a wireless line.
FIG. 10 is a diagram showing an example of slot allocation in a radio frame
FIG. 11 is a diagram showing a basic configuration example of a wireless ATM system.
FIG. 12 is a diagram illustrating a configuration example of a U-plane protocol of a wireless ATM system.
FIG. 13 is a diagram showing a configuration example of a radio frame used in the TDMA scheme.
FIG. 14 is a diagram for explaining the outline of the ABR service;
[Explanation of symbols]
11-1 to 11-n ... ATM terminal
12-1 to 12-n ... wireless module
13 ... Radio base station
14 ... ATM switch
31 ... ATM processor
32 ... Radio frame processing section
33 ... Frame scheduler
311, 312 ... RM cell processing unit
321 ... Frame generation unit
322 ... ATM cell extraction unit

Claims (9)

An ATM cell transmission method in a base node apparatus for bidirectionally transmitting an ATM cell to a plurality of communication modules via a common transmission medium,
For each communication module and for each cell transfer direction between the communication module and the own device, corresponding to the data string of the ATM cell transmitted / received to / from the same communication module, the ATM cell transmitting device is directed to the receiving device. Alternatively, when a resource management cell transmitted from the ATM cell receiving device to the transmitting device is received, the communication module that transmits and receives the ATM cell is referred to the resource management cell and corresponds to the common transmission medium. Find the cell transfer rate to be provided in the cell transfer direction,
A bandwidth to be secured to provide at least the cell transfer rate to the communication module in a corresponding cell transfer direction of the common transmission medium is obtained, and when the bandwidth can be secured, An ATM cell transmission method characterized in that the band is newly assigned to a corresponding cell transfer direction of a transmission medium.   The cell transfer rate is overwritten in the ATM node or the ATM cell receiving device through which the virtual connection to which the ATM cell belongs is described in the resource management cell transmitted from the ATM cell receiving device to the transmitting device. The ATM cell transmission method according to claim 1, wherein the ATM cell transmission rate is equal to an allowable cell transfer rate.   The cell transfer rate is equal to a current cell transfer rate in the ATM cell transmitter described in a resource management cell transmitted from the ATM cell transmitter to the receiver. The ATM cell transmission method according to claim 1.   The cell transfer rate is overwritten in the ATM node or the ATM cell receiving device through which the virtual connection to which the ATM cell belongs is described in the resource management cell transmitted to the transmitting device from the ATM cell receiving device. Obtained by referring to the permissible cell transfer rate and bit information for conveying information related to congestion, and currently provided on the common transmission medium in the virtual connection to which the ATM cell belongs. When the bit information is set to a value indicating that there is congestion with respect to the cell transfer rate, a value obtained by reducing the cell transfer rate is obtained as the cell transfer rate, and the bit information is free of congestion. And the cell transfer rate is increased if it is set to a value indicating that the increase in cell transmission rate is not prohibited. The ATM cell according to claim 1, wherein a value is obtained as the cell transfer rate, and when the cell transfer rate exceeds the allowable cell transfer rate, the cell transfer rate is replaced with the allowable cell transfer rate. Transmission method. An ATM cell transmission method in a base node apparatus for bidirectionally transmitting an ATM cell to a plurality of communication modules via a common transmission medium,
Corresponding to the data string of the ATM cells belonging to the same virtual connection, when a resource management cell transmitted from the ATM cell transmitting device to the receiving device or from the ATM cell receiving device to the transmitting device is received. Determining a cell transfer rate to be provided on the common transmission medium in the virtual connection to which the ATM cell belongs with reference to the resource management cell;
A bandwidth to be secured on the transmission medium is obtained for the virtual connection so that at least the cell transfer speed is provided in the transfer of ATM cells on the virtual connection, and the bandwidth can be secured. And reallocating the bandwidth to the virtual connection.
The cell transfer rate is overwritten in the ATM node or the ATM cell receiving device through which the virtual connection to which the ATM cell belongs is described in the resource management cell transmitted to the transmitting device from the ATM cell receiving device. An ATM cell transmission method, characterized in that the ATM cell transmission rate is equal to an allowable cell transfer rate. An ATM cell transmission method in a base node apparatus for bidirectionally transmitting an ATM cell to a plurality of communication modules via a common transmission medium,
Corresponding to the data string of the ATM cells belonging to the same virtual connection, when a resource management cell transmitted from the ATM cell transmitting device to the receiving device or from the ATM cell receiving device to the transmitting device is received. Determining a cell transfer rate to be provided on the common transmission medium in the virtual connection to which the ATM cell belongs with reference to the resource management cell;
A bandwidth to be secured on the transmission medium is obtained for the virtual connection so that at least the cell transfer speed is provided in the transfer of ATM cells on the virtual connection, and the bandwidth can be secured. And reallocating the bandwidth to the virtual connection.
The cell transfer rate is overwritten in the ATM node or the ATM cell receiving device through which the virtual connection to which the ATM cell belongs is described in the resource management cell transmitted to the transmitting device from the ATM cell receiving device. Obtained by referring to the permissible cell transfer rate and bit information for conveying information related to congestion, and currently provided on the common transmission medium in the virtual connection to which the ATM cell belongs. When the bit information is set to a value indicating that there is congestion with respect to the cell transfer rate, a value obtained by reducing the cell transfer rate is obtained as the cell transfer rate, and the bit information is free of congestion. And the cell transfer rate is increased if it is set to a value indicating that the increase in cell transmission rate is not prohibited. Calculated values as the cell transmission rate, when the cell transmission rate exceeds the allowable cell transmission rate, ATM cell transmission method characterized by replacing the cell transmission rate to the allowable cell rate.   If it is not possible on the common transmission medium to secure the bandwidth necessary for providing the determined cell transfer rate in the virtual connection, only the bandwidth that can be secured is allocated to the virtual connection, A second cell transfer rate that can be provided in the virtual connection is determined by allocating a band that can be secured, and is described in a resource management cell that is transmitted from the receiving device of the received ATM cell to the transmitting device. When the allowed cell transfer rate is higher than the second cell transfer rate, the second cell transfer rate is overwritten as the allowable cell transfer rate in the resource management cell. 7. The ATM cell transmission method according to any one of 1 to 6. An ATM cell transmission method in a base node apparatus for bidirectionally transmitting an ATM cell to a plurality of communication modules via a common transmission medium,
For each virtual connection, a first cell transfer rate transmitted over the virtual connection is calculated, and the virtual connection is determined based on the first cell transfer rate and a bandwidth available on the common transmission medium. Again, obtain the bandwidth to be secured on the common transmission medium,
When a resource management cell corresponding to the virtual connection is received, a second cell transfer rate that can be provided by securing the obtained bandwidth, and an allowable cell transfer rate described in the resource management cell When the second cell transfer rate exceeds the allowable cell transfer rate, the second cell transfer rate is corrected so that the difference from the allowable cell transfer rate does not increase. An ATM cell transmission method, wherein a bandwidth to be secured on the common transmission medium is newly allocated to the virtual connection based on the modified second cell transfer rate. Claim 1, 5, ATM cell transfer method according to 6 or 8, wherein the transmission medium is a wireless channel.

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