Radio transmitter

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a technique for realizing efficient data transmission in wireless communication using a fixed-length data transmission slot (data communication channel). For example, wireless communication stations use the TDMA / TDD method (time division multiple access /). It is a suitable technology for subscriber wireless access systems that perform wireless communication by time division multiple access), and holds the transmission data to be transmitted to the wireless section as an element string of the wireless transmission queue, which is the transmission queue. The present invention relates to a technique for reducing retention in the wireless transmission queue and the delay time caused by the retention.

【0002】

[Conventional technology]

For example, a subscriber wireless access system using wireless communication called WLL (wireless local loop) or FWA (Fixed wireless access) is known. As shown in Fig. 1, for example, the subscriber wireless access system includes a base station (BS) 1 fixedly installed by a telecommunications carrier and a subscriber station (CS) 2 fixedly installed on the home side of a plurality of users. And are connected by communication in the TDMA / TDD system wireless section, and data communication is performed between LAN3 connected to different subscriber stations 2 by wireless communication between base station 1 and subscriber station 2. In addition, data communication with other subscriber LANs is possible via a backbone network 4 such as a public communication network or LAN connected to the base station 1. The base station 1 accommodates a large number of subscriber stations 2, and such one-to-multipoint radio equipment is also called a P-MP (Point-Multi Point) system.

【0003】

A channel (data transmission time slot) is assigned to such wireless communication between the base station 1 and the subscriber station 2, and the data transmission channel is used as a base under the allocation control by the base station 1. Shared by multiple subscriber stations 2 under station 1. For example, when the base station 1 and the backbone network 4 or the subscriber station 2 and the LAN 3 are connected by the wired LAN interface of Ethernet (registered trademark) and IEEE802.3, it is addressed to each subscriber terminal accommodated in the subscriber LAN3. Unicast data having individual addresses and broadcast data having addresses assigned to a plurality of subscriber terminals are transmitted and received by wireless communication between base station 1 and subscriber station 2, and a large amount of data is frequently wirelessly transmitted. Be communicated.

【0004】

Here, for example, in a wireless communication system that employs a TDMA / TDD wireless connection system, each subscriber station 2 transmits and receives transmission data (frames) only on a specific data transmission channel assigned and controlled by the base station 1. The data transmission channel (data communication slot) assigned to the subscriber station 2 has a fixed length due to the nature of the TDMA / TDD system. Normally, the length of this data transmission channel is set to a size that can store the maximum frame defined by Ethernet (registered trademark) and IEEE802.3.

【0005】

[Problems to be Solved by the Invention]

However, the Ethernet (registered trademark) and IEEE802.3 data frames that are actually transmitted and received using the data transmission slot have variable lengths, and since data frames of various sizes are transmitted and received, the data assigned to a fixed length is used. Since many capacities of the transmission slots were unused, efficient data transmission could not be performed, and as a result, the wireless transmission medium could not be effectively used.

【0006】

More specifically, in a wireless transmission device that transmits data in a wireless section using a fixed size data transmission slot, for example, in a wireless transmission device that uses the TDMA / TDD method as the wireless line control method, data A fixed-size time slot for transmission (hereinafter also referred to as Dch (abbreviation of Datachame1)) is assigned to the radio section at regular intervals, and transmission data is placed on this to transmit the radio section. Among the wireless transmission devices, for example, in a wireless transmission device in which the data transmitted in the wireless section is a LAN frame and the LAN frame is transmitted (bridged) without being decomposed, the Dch size is the maximum size LAN frame. In order to be able to transmit (1518 bytes), it will be taken to a size of at least 1518 x 8 bit time.

【0007】

However, the actual size of the LAN frame can be any size in the range of 64 bytes to 1518 bytes, so as shown in Fig. 11, only one LAN frame is stored and transmitted for one Dch. In many cases, free space will be created in Dch, and the Dch usage rate (ratio of transmitted data in Dch) will not be so high on average. Here, if a plurality of LAN frames can be concatenated and stored for one Dch and the free area can be made as small as possible, the Dch usage rate, and eventually the transmission speed (transmission throughput) of the LAN frame in the wireless section. It becomes possible to raise.

【0008】

For example, assuming a wireless transmission device with a Dch size of 1518 x 8 bit time and a Dch transmission speed of 500 slots per second in the wireless section, a LAN frame with a size of 64 bytes from the LAN side is assigned to this device. The following is a comparison of unconnected transmission and connected transmission when continuously input. In the following explanation, it is assumed that the connection processing by the CPU is sufficiently fast and the connection processing for 22 frames is in time within each Dch transmission cycle.

【0009】

(1) When transmitting a wireless section without connecting LAN frames: In this case, the Dch usage rate is (64/15 18) x 100 = 4.2%. In addition, since one LAN frame is stored in one Dch and transmitted wirelessly, the LAN frame transmission speed in the wireless section is equal to the transmission speed (radio band) of the Dch, and the maximum transmission capacity is about 500 pps. Will have.

【0010】

(2) When transmitting by concatenating multiple LAN frames in the wireless section: An identification data area (including the head identifier indicating the boundary of the LAN frame, LAN frame size, etc.) is required to identify each LAN frame at the time of concatenation. Therefore, if we take 4 bytes and add it to the beginning of each LAN frame to be connected, the number of LAN frames that can be connected is 1518 / (64 + 4) = 22 frames. In this case, the Dch usage rate is (64 × 22) / 1518 × 100 = 93%. The maximum LAN frame transmission speed in the wireless section is Dch transmission speed (= 500) x number of connections (= 22) = 11000 pps, and the transmission capacity increases by the number of connections. That is, it has 22 times the transmission capacity of the unconnected transmission in (1).

【0011】

Next, the necessity of concatenated transmission of wireless sections will be described from the viewpoint of actual traffic flowing on the LAN. In the following description, the maximum size LAN frame that cannot be connected is referred to as a long frame, and the LAN frames of a size that can be connected multiple times within the same Dch are collectively referred to as a short frame.

【0012】

When data is transferred by a file transfer protocol typified by FTP (Fi1e Transfer Protoco1) on a LAN, long frames of the maximum size (1518 bytes) are continuously generated. When transmitting a long frame in a wireless section, each LAN frame cannot be connected, so the transmission speed is fixed to the Dch transmission speed (wireless band). However, in almost all protocols including FTP, acknowledgment packets are generated at regular intervals during execution.

【0013】

Normally, on a LAN, a large number of communications using a plurality of protocols are executed at the same time, so that there are a large number of short frames as a whole. Therefore, in order to smoothly execute a large number of these communications, it is considered indispensable to connect and transmit short frames in the radio zone. Furthermore, in the Internet telephone (VoIP: Voice Over IP) that uses the Internet infrastructure as a telephone network, communication is executed using a short frame of about 64 bytes.

【0014】

In the case of VoIP, the bandwidth used per channel is about 5Kbps to 64Kbps (the bandwidth used depends on the voice coding method), but when considering multi-channel use, short-frame traffic increases by the number of channels. Will be done. Internet telephones (VoIP) are expected to become widespread in the future, and short-frame traffic in LANs is expected to increase. Therefore, high transmission throughput performance for short frames is required even in wireless sections. come. Therefore, it can be said that it is indispensable to connect and transmit short frames in the wireless section and realize high transmission throughput performance for the short frames.

【0015】

Here, when performing linked transmission of frames in a wireless section, it is required to reduce the delay time required for transmission in order to ensure communication quality. For example, in VoIP, the total allowable delay time for data transmission is considered to be about 200 milliseconds in order to ensure telephone quality. Therefore, it is required to keep the delay time generated in the wireless transmission device as small as possible. Further, even in communication that does not require real-time performance such as file transfer, for example, in communication by TCP (Transmission Control Protoco1), a data transmission waiting time waiting for an acknowledgment occurs every time a certain amount of data is transmitted. Since the confirmation response waiting time is determined by the delay time, it is known that in different transmission systems having the same bandwidth, the larger the delay time, the lower the effective throughput during communication. For this reason as well, it is required to keep the delay time generated in the wireless transmission device as small as possible.

【0016】

Here, in general, if enqueues (inputs of queue elements) and dequeues (outputs of queue elements) occur randomly in a single queue (queue), according to statistical mathematics, these occurrences are Poisson. Follow the distribution. According to queuing theory, under this premise, the "number of queues" is ρ²/ (1-ρ) It is known that Therefore, the "delay time caused by retention" at this time is ρ²/ (1-ρ) × (1 / dequeue speed) ... (A) Given in. Here, it is a traffic intensity defined by ρ = (enqueue speed) / (decue speed), and the unit is sometimes called "erlang".

【0017】

Then, from the above equation (A), it can be seen that the delay time generated by the retention of the queue element in the queue has a profile as shown in FIG. 12 with respect to the enqueue amount (LAN input load) (enqueue speed). The delay time becomes infinite as it approaches) = (dequeue speed). The queuing theory considers the range of "ρ <1", that is, "enqueue speed <dequeue speed".

【0018】

In reality, the queue has a finite depth (the upper limit of the number of elements that can be accommodated in the queue), so the profile is as shown in FIG. From FIG. 13, the delay time due to residence is sufficiently small in the range where ρ <1, that is, the dequeue speed is larger than the enqueue speed, and becomes maximum after ρ approaches 1 and exceeds a certain point. The delay time (13.1) is reached. The point at which this maximum delay time is reached determines the maximum transmission throughput point of the device (the upper limit that can be transferred with zero packet loss), and in the area beyond that, the so-called congestion state (13.2) that exceeds the processing upper limit of the device. )to go into.

【0019】

Here, regarding a wireless transmission device that wirelessly connects two or more LAN segments, for example, a wireless LAN system or an FWA system, consider the configuration of a queue inside the device. This is generally as shown in Fig. 14, and the queue on the side that transmits to the wireless section on the Dch is shown as the wireless transmission queue (14.1), and the queue on the side that receives from the Dch in the wireless section is shown as the wireless reception queue (14.2). is there.

【0020】

Comparing the LAN band and the wireless section band, Fast Ethernet (registered trademark) (standardized by IEEE802.3u), which provides a data transmission speed of up to 100 Mbps, is currently becoming the mainstream for the LAN band. On the other hand, the maximum data transmission speed of the wireless section band is 11 Mbps in the wireless LAN system based on the IEEE802.11b HighRate standard, for example. In general, it can be considered that the LAN band is larger than the radio section band, and in the radio receive queue (14.2), the WRXQout (14.5) speed (that is, the dequeue speed from the radio receive queue) is WRXQin. (14.6) It can be considered that it is larger than the speed (that is, the enqueue speed to the wireless reception queue), there is almost no retention in the wireless reception queue (14.2), and there is almost no delay time caused by this.

【0021】

On the other hand, in the wireless transmission queue (14.1), the input traffic from the LAN may exceed the transmission processing capacity of the wireless section, and at this time, the maximum number of stagnation occurs in the wireless transmission queue, causing a large delay time. Let me. In this way, the state where there is input traffic from the LAN that exceeds the upper limit of the transmission performance of the device means that the device is in a congested state, and in principle, the delay that occurs in this state cannot be avoided. Can not.

【0022】

However, in reality, when connecting LAN frames and enqueue processing to the wireless transmission queue by software processing, if the method is not devised, it is considerably lower than the maximum throughput point of the device "a certain range". Even with the input load of, the maximum number of stagnation may occur inside the wireless transmission queue, causing a large delay time. That is, as shown in FIG. 17, the delay becomes large even in a certain LAN input load range II (17.2), which is quite low, and the delay in this range is the delay that occurs within the range in which the device guarantees data transmission. Therefore, it must be kept as small as possible.

【0023】

Here, the delay caused by the retention inside the queue occurs on the wireless transmission queue (14.1) side as described above. Therefore, as shown in FIG. 15 again, the wireless transmission queue is set to (15.1). The processing configuration by general software will be described as follows. That is, the wireless transmission queue (15.1) stores the data portion (Dch data (15.2)) on the Dch in the wireless section as a queue element, and the Dch data (15.2) usually contains a plurality of LAN frames (15.3). It is connected.

【0024】

Here, Lin (15.4) represents the input of the LAN frame. Win (15.5) represents an enqueue to the wireless transmit queue. Wout (15.6) represents a dequeue from the wireless transmit queue.

【0025】

The concatenation / enqueue task (15.7) is a task that concatenates and stores multiple LAN frames input to the device in one Dch data and wins (15.5) in the wireless transmission queue (15.1) (hereinafter, also simply a task). Describe). The task is started periodically as shown in Fig. 16, and LAN frames that are Lin (15.4) within that cycle are concatenated into one Dch data (15.2), and when the enqueue condition is satisfied, Win ( 15.5)

【0026】

Enqueue Win (15.5) The conditions are the following two. The free area of Dch data (that is, the free area of the transmission slot) is too small to concatenate and store newly Lin (15.4) LAN frames in the same Dch. There is no new Lin (15.4) LAN frame. In addition, the task wins (15.5) the current Dch data to the wireless transmission queue when the above conditions are met or the number of input LAN frames reaches the (preset) upper limit. End the process.

【0027】

FIG. 16 shows the processing cycle of the wireless transmission device. Here, T_Lin (16.1) represents the average input period of the LAN frame. T_Win (16.2) represents the average enqueue period to the wireless transmit queue. T_Wout (16.3) represents the average dequeue period from the wireless transmit queue. T_Task (16.4) represents the average activation cycle of concatenated / enqueue tasks.

【0028】

Therefore, in general, the task cycle (T_Task (16.4)) tends to increase as the LAN frame input load increases. When the LAN frame input load is sufficiently small, the task cycle (T_Task (16.4)) is smaller than the Wout cycle (T_Wout (16.3)), but after the LAN frame input load exceeds a certain level, the task cycle (T_Task) On the contrary, (16.4)) can be considered to be larger than the Wout period (T_Wout (16.3)).

【0029】

The wireless transmission driver (15.8) has the role of taking out the Dch data (queue element) stored in the wireless transmission queue (15.1) and placing it on the Dch (Wout (15.6)). Since the wireless transmission driver (15.8) creates a Dch according to the periodically occurring Wout (15.6), it is an interrupt process that is activated in the Wout cycle (T_Wout (16.3)). That is, the Wout cycle (T_Wout) is also the activation cycle of the wireless transmission driver.

【0030】

The conditions for generating each region I to IV shown in FIG. 17 are as follows. (1) T_Wout <T_Link (ie Wout velocity> Lin velocity); region of I (17.1). In this region, as shown in FIG. 18, since the LAN input load is smaller than the wireless band (Wout speed), the retention of the wireless transmission queue is sufficiently small and almost no delay occurs.

【0031】

(2) T_Wout> T_Lin (that is, Wout speed <Lin speed); (2) -1; Number of connections in 1 task processing (T_Task / T_Lin) <Maximum number of connections (joint_max); (2)-1.1; T_Wout <T_Task; II area (17.2). At this time, as shown in FIG. 19, Wout speed <Win speed, the maximum number of stays in the wireless transmission queue occurs, and the maximum delay time occurs. (2)-1.2; T_Wout <T_Task; III area (17.3). At this time, as shown in FIG. 20, Wout speed <Win speed, the retention of the wireless transmission queue is sufficiently small, and almost no delay occurs. (2) -2.1; Number of concatenations in task processing (T_Task / T_Lin)> Maximum number of concatenations; Region of IV (17.4). From this point onward, as shown in Fig. 21, "Wout speed <Win speed" is always set, the maximum number of stays occurs in the wireless transmission queue, and the maximum delay time occurs (in a congested state where the transmission processing upper limit of the device is exceeded). enter).

【0032】

The problem here is that the maximum delay time occurs in region II (17.2). In this area II (17.2), the task cycle T_Task is shorter than the dequeue cycle T_Wout, so if you win each time the task process ends, the Win speed exceeds the Wout speed, and as a result, the maximum number stays in the wireless transmission queue. Will occur, causing a large delay time.

【0033】

The present invention has been made in view of the above-mentioned conventional circumstances, and enables wireless transmission by storing a plurality of transmission data frames in a fixed-length data transmission channel (slot) and in a wireless transmission queue. The purpose is to reduce the stagnation of data and the delay caused by it, and to realize effective utilization of wireless transmission media by efficient data transmission. A further object of the present invention is apparent in the following description.

【0034】

[Means for solving problems]

In order to suppress the occurrence of delay in the above area II (17.2), it can be said that the concatenated task must not win unconditionally at the end of processing. To explain concretely with reference to Fig. 22, assuming that the elapsed time since the task was last enqueued Win is ΔT (22.1), the number of LAN frames connected to the task becomes the maximum number of connections at the end of processing. If it has not been reached, Win must not be performed while the condition of T <T_Wout is satisfied. This is because if Win is established when this condition is not satisfied, T_Win <T_Wout, is satisfied, and (Win speed exceeds Wout speed, maximum retention occurs in the wireless transmission queue, and a large delay time occurs. Therefore, one of the basic concepts of the present invention is to give appropriate control to the enqueue process (Win) to the wireless transmission queue and adjust the timing of enqueue (Win) so as not to cause stagnation. Area II (17.2) It is to suppress the occurrence of delays in other areas.

【0035】

The present invention is a wireless transmission device that periodically allocates a fixed size data transmission slot to a wireless section to transmit data in the wireless section, and uses an element string of a wireless transmission queue that is a transmission queue for transmission data. A connecting means for connecting a memory to be held and a plurality of transmission data which are elements of a wireless transmission queue, a wireless transmission means for mounting a wireless transmission queue element output from the memory in a data transmission slot, and a wireless transmission from the memory. In response to the output of the queue element, the control means for controlling the memory to hold the next queue element for wireless transmission is provided. Therefore, in order to control the timing of enqueuing (Win) the wireless transmission queue element in response to the dequeue (Wout) of the wireless transmission queue element, a plurality of transmission data are concatenated and stored in the data transmission slot. It is possible to suppress the occurrence of delay in concatenated storage while realizing effective use of slot (channel) capacity by wireless transmission.

【0036】

More specifically, in the wireless transmission device of the present invention, the control means monitors the number of wireless transmission queue elements held in the memory, and the wireless transmission queue without or has a wireless transmission queue element. When the number of elements decreases from the previous memory output, the memory is controlled to hold the next wireless transmission queue element. More specifically, in the wireless transmission device of the present invention, the control means controls the memory to hold the next wireless transmission queue element in synchronization with the output of the wireless transmission queue element from the memory. I do.

【0037】

Further, the present invention is a wireless transmission device that periodically allocates a fixed size data transmission slot to a wireless section to transmit data in the wireless section, and is an element of a wireless transmission queue that is a transmission queue for transmission data. A data transmission slot that stores a memory that holds columns, a concatenation means that sequentially concatenates and stores multiple transmission data for the elements of the wireless transmission queue held in the memory, and a wireless transmission queue element that is output from the memory. When the wireless transmission means to be mounted on the device and the wireless transmission queue element to be concatenated and stored are output from the memory, or when the next transmission data is stored in the wireless transmission cue element to be concatenated and stored, the size of the data transmission slot is exceeded. In the case of such a case, the control means for shifting the processing target of the concatenated means to the concatenated storage of the transmission data for the next wireless transmission queue element held in the memory is provided. Therefore, by directly performing the transmission data concatenation processing on the elements of the wireless transmission queue held in the memory, the retention in the queue is reduced, and the queue elements to be concatenated are migrated at an appropriate timing. Can be made to.

【0038】

More specifically, in the wireless transmission device of the present invention, the above memory and the control means are connected by an internal bus to form a module to reduce the burden on software processing, and the module is provided with. A bus interface is provided to output the wireless transmission queue element output from the memory to the wireless transmission means, and the control means determines the free size of the wireless transmission queue element to be concatenated and stored and the size of the transmission data to be concatenated and stored next. Is compared, and the concatenated storage processing target is transferred to the next wireless transmission queue element.

【0039】

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, the present invention takes as an example a P-MP (Point to Mu1ti Point) type system in which a plurality of CS (subscriber stations) 2 are wirelessly connected to one BS (base station) 1. Will be specifically described. Although BS1 and CS2 correspond to the wireless transmission device according to the present invention, respectively, BS1 will be mainly described in the following description.

【0040】

Each CS2 has a function to transmit the LAN frame (transmission data) input from the LAN3 side of its own device to BS1 through the wireless section, and also the LAN frame from the Dch (data transmission slot) received from BS1 through the wireless section. It has a function to take out and transfer it to the LAN3 side of its own device. BS1 has a function to transmit the LAN frame input from the LAN4 side of the own device to a specific CS2 through the wireless section, and also takes out the LAN frame from the Dch received from CS2 through the wireless section and uses this as the own device. It has a function to transfer to the LAN4 side.

【0041】

Wireless transmission from BS to CS is called downlink transmission, and conversely, wireless transmission from CS to BS is called uplink transmission. In this example, the connection process during uplink transmission is for delay suppression, which will be described later. Since it is the same as the concatenation process at the time of downlink transmission except that it does not have the control process of, the process at the time of downlink transmission will be described below. That is, the processing performed by BS1 when transmitting data to the wireless section will be described.

【0042】

BS1 transmits this to all CS2 when the LAN frame input from the LAN4 side is a multicast frame, and which CS2 is transmitted when the LAN frame input from the LAN4 side is a unicast frame. After deciding, transmit this to the CS2. As shown in FIG. 2, BS1 has a CAM (Content Address Memory) (2.1) inside the device, and the destination CS1 is determined by referring to the CAM (2.1). CAM (2.1) is a device that can record multiple "MAC address and CS number" pairs internally, and by inputting the MAC address as an input value, the corresponding CS number is output as an output value. It is an associative storage memory device that can be used.

【0043】

When the destination MAC address of the LAN frame is input to CAM (2.1) during downlink transmission, CAM (2.1) outputs the CS number if there is a CS number corresponding to that MAC address. If the corresponding MAC address does not exist, CAM (2.1) outputs a value indicating that there is no corresponding MAC address. Therefore, in order for CAM (2.1) to output a valid CS number, it must first be recorded in CAM.

【0044】

Here, the wireless reception driver and the wireless reception task function in BS1 during uplink transmission, although not shown in FIG. The wireless reception driver has the function of receiving the uplink transmission request from each CS2, allocating the bandwidth (Dch) for uplink transmission to each CS2, and actually receiving the Dch, and the wireless reception task is the Dch from the wireless reception driver. It has a function to receive the Dch data transmitted from CS on the PC and the CS number of the sender, take out the LAN frame stored inside the Dch data, and transfer it to the LAN4 side.

【0045】

In the wireless reception task, when the LAN frame is extracted from the Dch data, the set of the source MAC address and the source CS number is recorded in CAM (2.1). In the wireless reception task, it is possible to realize return transmission between two different CSs by searching for CAM (2.1) by the destination MAC address of the extracted LAN frame. Therefore, for a LAN frame that has been transmitted upstream once, when a LAN frame in the opposite direction is input to BS1, it is possible to determine the destination CS2 from CAM (2.1).

【0046】

Note that BS1 cannot determine to which CS2 a LAN frame in the opposite direction is sent for a LAN frame that has never been transmitted upstream. In this case, (1) Send to all CSs, ( 2) Either of the two methods of discarding the received LAN frame will be taken. A normal bridge performs the operation (flooding) of (1) for a LAN frame whose destination is unknown, but in the case of a wireless transmission device, in order to effectively use the wireless band shared by all devices, (2) The option of taking the method is also conceivable. In actual communication via LAN, multicast always occurs at the very beginning of communication, and unicast occurs in response to it (the unicast frame does not occur from the beginning in the downlink direction). , (2) does not seem to cause any problems.

【0047】

Based on the above processing, the connection processing for each destination CS2 is executed in the connection / enqueue task (2.2) of BS1 at the time of downlink transmission. The flow of connection processing in BS1 when multiple CS2s are wirelessly connected to BS1 is as follows.

【0048】

(1) When BS1 receives a unicast LAN frame from its own LAN4 side, the concatenation / enqueue task (2.2) searches for CAM (2.1) using the CAM search function (2.3) and determines its destination. (2) Multiple concatenated work areas (2.4) are allocated to the memory of BS1 for each CS2, and after the destination CS2 is determined, the LAN received in the concatenated work area (2.4) for the CS2. The frame is transferred. (3) If LAN frames addressed to the same CS are continuously received, they are transferred to the same connection work area (2.4) and connected.

【0049】

The transfer connection processing for each connection work area (2.4) of each CS is performed as follows. First, the first transmission data (LAN frame) is stored in the concatenated work area (2.4), then the size of the second LAN frame and the data transmission slot (Dch) when the first LAN frame is stored. Compare with the free size left in, and if there is free size that can store this second frame, insert a delimiter bit between the first and second frames to make the second frame Is stored in the same concatenated work area (2.4) as the first frame.

【0050】

Furthermore, the size of the third frame is compared with the free size left in the data transmission slot when the first and second frames are stored, and when there is a free size that can store the third frame. Inserts a delimiter bit between the second and third frames to store the third frame in the same concatenated workspace (2.4) as the first and second frames. If there is a free size to store the next frame in the fixed-length data transmission slot in this way, the process of storing this in the same data transmission slot is performed, and the same connection work area (2.4) is used. Store multiple frames addressed to CS. When receiving a multicast LAN frame or flooding a unicast LAN frame whose destination cannot be determined, these LAN frames must be transferred / concatenated to all CS concatenation work areas (2.4). become.

【0051】

(4) If the free space required for the connection work area (2.4) for a certain CS is exhausted and the LAN frame addressed to the same CS that was continuously received cannot be connected anymore, the connection data of that area is transferred to the wireless for the CS. Enqueue to the send queue (2.5). The received LAN frame is transferred to another connection work area (2.4) for the same CS. (5) The data (queue element) enqueued in the wireless transmission queue (2.5) is placed on the Dch (data transmission slot) assigned to the wireless section for each CS by the wireless transmission driver (2.6). It is transmitted to the CS. (6) When the number of received LAN frames is exhausted or the upper limit of the number of LAN frames to be processed is reached, the processing of the concatenation / enqueue task (2.2) ends.

【0052】

Then, in the enqueue and dequeue processing to the wireless transmission queue (2.5) described above, in BS1 of this example, any control processing for suppressing retention as shown in the following methods 1 to 4 is performed.

【0053】

First, the method 1 will be described. In this method 1, the method by queue monitoring is implemented as shown in FIG. Since the number of queue elements in the wireless transmission queue is decremented by 1 each time it is dequeued (Wout), the interval at which the number of queue elements is -1 is T_Wout. Therefore, in task (2.2), if there is data waiting for Win that has not reached the maximum number of concatenated data at the end of processing (step S1), refer to the current number of queue elements Q (N) and the current number of queue elements. Is 0 (step S2), or the current number of queue elements Q (N) is compared with the number of queue elements Q (N-1) saved at the end of the previous task processing (current queue). When the condition of (number of elements) <(number of previous queue elements) is satisfied (step S3), the next queue element is enqueued (Win) to the wireless transmission queue (step S4), and the current number of queue elements is saved. And end the task processing.

【0054】

On the other hand, if the above conditions (steps S1 and S3) are not satisfied, the task saves the current number of queue elements without winning, ends the task processing (step S5), and transitions to the execution waiting state. .. As described above, if there is an input LAN frame at the time of the next task processing, the connection processing is added to the current connection data. In this way, task (2.2) self-controls the number of queue elements in the wireless transmission queue or changes in the number of queue elements, and as a result, the next queue is added to the wireless transmission queue according to the dequeue of the queue elements. The queue element is enqueued, which prevents the queue element from staying in the wireless transmission queue, especially in the area II (17.2), and avoids the occurrence of delay.

【0055】

Next, a method 2 different from the above method will be described. In this method 2, the enqueue process (Win) is executed by the interrupt process as shown in FIG. The configuration for implementing this method 2 is divided into a concatenation task (4.1) that performs concatenation processing and an enqueue driver (4.2) that enqueues (Win) to the wireless transmission queue (4.3).

【0056】

The concatenation task (4.1) is a periodic start task, and in each task process, the LAN frame is concatenated. Then, the concatenation task (4.1) executes Win only when the current concatenation process reaches the maximum number of concatenations, and does not win other than that. The enqueue driver (4.2) is an interrupt process that is activated in the T_Wout cycle, and in each process that is interrupt-activated in synchronization with the dequeue, the concatenated task (4.1) wins the concatenated data and ends the process. To do. The enqueue driver (4.2) uses a flag that can be referenced in common with the concatenation task (4.1) to notify the concatenation task (4.1) that the Wout of the concatenation data has been executed, and the concatenation task. (4.1) acknowledges the end of the consolidation process with this notification.

【0057】

In this way, the enqueue driver (4.2) is self-controlled to enqueue the next queue element into the wireless transmit queue in synchronization with the dequeue, which is more than T_Wout, especially in region II (17.2). It is possible to prevent Win in a short cycle, prevent the queue element from staying in the wireless transmission queue, and avoid the occurrence of delay.

【0058】

Next, a method 3 different from the above method will be described. In this method 3, as shown in FIG. 5, the concatenation task (5.2) performs the concatenation process in the area (5.1) of each queue element of the wireless transmission queue (5.3). Directly to. The concatenation task (5.2) moves to the area of the next queue element if the current (first) queue element is dequeued (Wout) or if it can no longer be concatenated to the area of the current queue element. Carry out consolidation.

【0059】

The area (5.1) of each queue element has a flag that can be referred to in common with the dedicated concatenation task, and the wireless transmission driver (not shown) uses this flag when executing Wout. The concatenation task (5.2) is notified that the queue element has been Wouted, and the concatenation task recognizes the end of the concatenation process for the queue element with this notification. By performing the processing by the concatenated task (5.2) by self-control in this way, the concatenated task continues the concatenated processing for one queue element area (5.1) within the T_Wout time. It is possible to obtain the same effect as preventing Win in a shorter cycle than T_Wout, prevent the queue element from staying in the wireless transmission queue, and avoid the occurrence of delay.

【0060】

Next, the method 4 will be described. As shown in FIG. 6, this method 4 directly concatenates and stores each element of the wireless transmission queue in the above method 3 in one hardware module (concatenated FIFO module). ). The connected FIFO module 6 has a bus interface (6.3) that interfaces the external bus (6.1) accessible from the control unit (CPU) of the wireless transmission device with the internal bus (6.2) inside the connected FIFO module, and an external bus. It has a concatenated FIFO section (6.6) with a write buffer memory (6.4) for writing LAN frames through (6.1) and multiple FIFO element memories (6.5).

【0061】

The concatenated FIFO module 6 is further stored in the free space size register (6.7) that stores the free space size in the FIFO element memory (6.5) that is continuing to execute the concatenation process, and in the write buffer memory (6.4). The write buffer data size register (6.8) that stores the LAN frame size and the FIFO read size that stores the read size when reading the concatenated data stored in the concatenated FIFO (6.6) through the external bus (6.1) ( It has a readsize) register (6.9) internally, compares the free space size register (6.7) with the write buffer data size register (6.8), and determines the received LAN frame in the write buffer memory (6.4) as the FIFO element memory. It is equipped with a connected FIFO control unit (6.10) that transfers data to the appropriate location in (6.5).

【0062】

In this concatenated FIFO module 6, when a LAN frame is written through the external bus (6.1), it is first written to the write buffer memory (6.4), and at this time, the concatenated FIFO control unit (6.10) sends the write buffer memory (6.4). Set the LAN frame size in the write buffer data size register (6.8). Next, the concatenated FIFO control unit (6.10) compares the values of the write buffer data size register (6.8) and the free area size register (6.7), and performs either of the following processes (1) or (2). To execute.

【0063】

(1) If the receive LAN frame size free area size, the LAN frame stored in the write buffer memory (6.4) is added with necessary header information, etc., and then the FIFO that is currently concatenated is being processed. Transfer to the element memory (6.5), concatenate additionally, and update the free area size register (6.7). (2) If the receive LAN frame size> free space size, find the next unused FIFO element memory (6.5) and store it in the light header memory (6.4). The LAN frame is transferred after adding the necessary header information, and the free area size register (6.7) is updated. The LAN frames written after this are added to the following FIFO element memory described above and concatenated.

【0064】

The concatenated FIFO control unit (6.10) sets the FIFO element memory (6.5) to be read next to be read through the external bus (6.1), and at the same time, reads the concatenated data size in this FIFO element memory (6.5). Set to size register (6.9) to make it readable via external bus (6.1). Then, when the concatenated data is read from the external bus (6.1), the concatenated FIFO control unit (6.10) returns the read FIFO element memory (6.5) to an unused state, and at the same time, the next The FIFO element memory (6.5) to be read is set to be read through the external bus, and the concatenated data size in the FIFO element memory is set in the FIFO read size register (6.9).

【0065】

Since the connection processing is performed by the connection FIFO module 6 as described above, processing by software (connection task) is not required, and the operation and effect of the above method 3 can be obtained. For example, as shown in Fig. 7, the connected FIFO module 6 cooperates with the LAN reception driver (7.1) and the wireless transmission driver (7.2), which consist of software modules, to connect the received LAN frames to the wireless section. The LAN reception driver (7.1) transfers the LAN frame to the concatenated FIFO module 6 for each LAN frame reception, and the wireless transmission driver (7.2) extracts the concatenated data from the concatenated FIFO module 6 after executing a series of transmission processes. And put it on Dch to execute transmission to the radio section.

【0066】

Here, the above example targets a wireless transmission device based on the TDMA / TDD method, but the present invention is not particularly limited to this, and the upper layer connects a plurality of PDUs (Protocol Data Units) into a lower layer. On the other hand, even in a general wireless transmission device having a method of enqueuing in a transmission queue as one SDU (Service Data Unit), the delay time generated inside the queue is reduced by performing the same control as in the above example. The effect can be obtained.

【0067】

[Example]

The effect of the present invention is shown with the result of actual measurement using a wireless transmission device. The wireless transmission device used in this example transmits data in the wireless section by the TDMA / TDD method. The depth of the wireless transmission queue is 128 (128 concatenated data can be stored). In this wireless transmission device, the delay time is measured in each of the two cases: (1) enqueue processing is performed asynchronously to the dequeue, and (2) enqueue control is performed by the "queue monitoring method" shown in method 1 above. do it.

【0068】

The configuration of the device for which the delay was measured is as shown in Fig. 8. The wireless transmission device A connected to the wired (LAN) transmission section A and the wireless transmission device B connected to the wired (LAN) transmission section B are connected. The LAN frame (transmission data) generated in the wired (LAN) transmission section B is transmitted to the wired (LAN) transmission section A through the delay measuring device 8, and the LAN frame is wirelessly transmitted from the wireless transmission device A to the wireless transmission device B. It is to be sent. The measurement was performed by generating only a 64-byte LAN frame using a method similar to RFC1242 / RFC25442.

【0069】

As a result, the delay time characteristic as shown in FIG. 9 is obtained in the case of (1) when the enqueue is not controlled, and the delay time as shown in FIG. 10 is obtained in the case of (2) when the enqueue is controlled. The characteristics were obtained. From these results, in Fig. 9, a delay time exceeding 100 milliseconds occurs between 0.9 and 1.7% of the input load from the LAN, but in Fig. 21, the delay that occurred in the same section of Fig. 9 occurs. It can be seen that the delay time is completely suppressed (delay time is 5 milliseconds or less, about 1/20 of that without Win control). That is, it was confirmed that the present invention has a remarkable effect of suppressing delay.

【0070】

[Effect of the invention]

As described above, according to the present invention, when the transmission data is concatenated and placed in the data transmission slot of the radio section for wireless transmission, the process of enqueuing the concatenated data to the wireless transmission queue waiting for transmission is performed. Since the control is performed in response to the dequeue from the transmission queue, the retention in the wireless transmission queue and the delay caused by it are reduced, and the effective utilization of the wireless transmission medium by efficient data transmission is realized. be able to.

[Simple explanation of drawings]

[Figure 1]

It is a figure which shows an example of the wireless transmission system to which this invention is applied.

[Figure 2]

It is a figure which shows an example of the structure which concerns on this invention.

[Fig. 3]

It is a flowchart explaining method 1 which concerns on this invention.

[Fig. 4]

It is a figure explaining the method 2 which concerns on this invention.

[Fig. 5]

It is a figure explaining the method 3 which concerns on this invention.

[Fig. 6]

It is a figure explaining the method 4 which concerns on this invention.

[Fig. 7]

It is a figure explaining the method 5 which concerns on this invention.

[Fig. 8]

It is a figure explaining the equipment structure of the delay measurement in the Example of this invention.

[Fig. 9]

It is a figure which shows the measurement result at the time of not performing the enqueue control in the Example of this invention.

[Fig. 10]

It is a figure which shows the measurement result at the time of performing the enqueue control in the Example of this invention.

[Fig. 11]

It is a figure explaining the free space generated in Dch.

[Fig. 12]

It is a figure which shows the profile of the delay time which occurs in a queue in queuing theory.

[Fig. 13]

It is a figure which shows the profile of the delay time which occurs in an actual queue.

[Fig. 14]

It is a figure explaining the queue in a wireless transmission apparatus.

[Fig. 15]

It is a figure explaining the connection process of a LAN frame and the enqueue process to a queue for wireless transmission.

[Fig. 16]

It is a figure explaining each processing cycle in a wireless transmission apparatus.

[Fig. 17]

It is a figure which shows the profile of the delay time | hearing which occurs in the queue in a wireless transmission device.

[Fig. 18]

It is a figure explaining the processing state in the state of (17.1) of FIG.

[Fig. 19]

It is a figure explaining the processing state in the state of (17.2) of FIG.

[Fig. 20]

It is a figure explaining the processing state in the state of (17.3) of FIG.

[Fig. 21]

It is a figure explaining the processing state in the state of (17.4) of FIG.

[Fig. 22]

It is a figure explaining the condition for suppressing the delay which occurs in the state of (17.2) of FIG.

[Explanation of symbols]

1: Base station (BS), 2: Subscriber station (CS), 3: LAN, 4: Backbone network (LAN), (2.2): Concatenated enqueue task, (2.4): Concatenated work area, (2.5): Wireless Send queue, (2.6): Wireless send driver,