JP2003092590A - Radio transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the effective utilization of a radio transmission medium by efficient data transmission by storing a plurality of transmission data frames in a slot for data transmission of a fixed length for radio transmission and reducing retention in a queue for radio transmission and delay caused thereby. SOLUTION: The element strings of a queue for radio transmission (2.5) being the transmission waiting string of transmission data are held and a connection en-queue task (2.2) successively connect a plurality of pieces of transmission data to the element of the queue for radio transmission. A radio driver (2.6) transmits the outputted element of the queue for radio transmission mounted on a data transmission slot. In the case that the element of the queue for radio transmission of the object of combination storing is outputted or the case of exceeding the size of the slot for data transmission when storing next transmission data, control for moving a processing object to the combination storing of transmission data to the element of the queue for next radio transmission is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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, the wireless communication stations are TDMA / TDD. A wireless transmission queue, which is a technology suitable for use in a subscriber wireless access system that performs wireless communication by a system (time-division multiple access / time-division duplex), and which is a transmission queue for transmission data to be transmitted in a wireless section. The present invention relates to a technique for holding the same in the wireless transmission queue and reducing the delay time resulting from the retention.

[0002]

2. Description of the Related Art For example, WLL (wireless local loo)
p) or FWA (Fixed wireless access) is known as a subscriber wireless access system using wireless communication. Subscriber wireless access system,
For example, as shown in FIG. 1, a base station (BS) 1 fixedly installed by a telecommunications carrier and a subscriber station (CS) 2 fixedly installed at a plurality of users' premises are provided in a TDMA / TDD wireless system. The base station 1 and the subscriber station 2 wirelessly communicate with each other in order to perform data communication between the LANs 3 connected to different subscriber stations 2,
Further, another subscriber L is connected via the backbone network 4 such as a public communication network or LAN connected to the base station 1.
Data communication with the AN is possible. The base station 1 accommodates a large number of subscriber stations 2, and such one-to-multidirectional wireless equipment is also called a P-MP (Point-Multi Point) system.

A channel (data transmission time slot) is assigned for data transmission in such wireless communication between the base station 1 and the subscriber station 2. Under the assignment control by the base station 1, this data transmission channel is assigned. The channel is shared by a plurality of subscriber stations 2 under the base station 1. For example, base station 1 and backbone network 4, or subscriber station 2 and LAN
3 and Ethernet (registered trademark) and IEEE80
When connected by the wired LAN interface of 2.3, unicast data having an individual address addressed to each subscriber terminal accommodated in the subscriber LAN 3 and broadcast data having addresses assigned to a plurality of subscriber terminals are provided. , The base station 1 and the subscriber station 2 are wirelessly transmitted and received, and a large amount of data is frequently wirelessly communicated.

Here, in a wireless communication system that adopts a wireless connection system such as the TDMA / TDD system, each subscriber station 2 transmits data (frames) only through a specific data transmission channel allocated and controlled by the base station 1. The data transmission channel (data communication slot) assigned to the subscriber station 2 can be transmitted and received by TD.
It has a fixed length due to the nature of the MA / TDD system. The length of this data transmission channel is usually Eth.
It is set to a size capable of storing the maximum frame defined by Internet (registered trademark) and IEEE802.3.

[0005]

However, the Ether that is actually transmitted / received using the data transmission slot is used.
Since the data frames of net (registered trademark) and IEEE802.3 have variable lengths and transmit / receive data frames of various sizes, many capacities of data transmission slots assigned to fixed lengths are unused and efficient. However, it was impossible to effectively use the wireless transmission medium.

More specifically, a wireless transmission device for performing data transmission in a wireless section by using a fixed size data transmission slot, for example, T as a wireless line control system.
In a wireless transmission device using the DMA / TDD system,
Fixed size time slot for data transmission (hereinafter Dc
h (also referred to as Datachame1) is assigned to a wireless section at a fixed cycle, and transmission data is placed on this and transmitted in the wireless section. Among the wireless transmission devices, for example, in a wireless transmission device in which data transmitted in a wireless section is a LAN frame and the LAN frame is transmitted without being decomposed (bridged), the Dch size is the maximum size LAN frame. (1518 bytes) to be transmitted, at least 1518 ×
The size of 8 bit time is taken.

However, since the actual size of the LAN frame can be any size within the range of 64 bytes to 1518 bytes, as shown in FIG.
When only one LAN frame is stored for h and transmitted, an empty area is created in Dch in many cases, and the Dch usage rate (ratio of transmission data in Dch) does not become so high on average. . here,
If a plurality of LAN frames can be concatenated and stored for one Dch and the empty area can be made as small as possible, the Dch usage rate, and eventually the LAN in the wireless section.
It is possible to increase the frame transmission rate (transmission throughput).

For example, the Dch size is 1518 × 8 bit time, and the Dch transmission rate in the wireless section is 50 per second.
Assuming a wireless transmission device with 0 slots, LA device with a size of 64 bytes is connected to this device from the LAN side.
The comparison between non-concatenated transmission and concatenated transmission when N frames are continuously input is as follows. In addition,
In the following description, 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.

(1) When transmitting in a wireless section without connecting LAN frames: In this case, the Dch usage rate is (6
4/1518) × 100 = 4.2%. Also, 1
Since one LAN frame is stored in one Dch and wirelessly transmitted, the LAN frame transmission rate in the wireless section is
It becomes equal to the transmission speed (wireless band) of Dch, and the maximum is 50
It has a transmission capacity of about 0 pps.

(2) When a plurality of LAN frames are connected in a wireless section and transmitted: An identification data area for identifying each LAN frame at the time of connection (a head identifier indicating a boundary of LAN frames, a LAN frame size, etc. are entered. ) Is required, and considering that it is added to the beginning of each LAN frame to be concatenated with 4 bytes, the number of concatenable LAN frames is 1518 / (64 + 4).
= 22 frames. In this case, the Dch usage rate is
(64 × 22) / 1518 × 100 = 93%. The maximum LAN frame transmission rate in the wireless section is Dch transmission rate (= 500) × number of connections (= 22) =
The transmission capacity is 11000 pps, and the transmission capacity is increased by the number corresponding to the number of connections. That is, the transmission capacity is 22 times as high as that of the unconnected transmission of (1).

Next, the necessity of connecting and transmitting 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 a long frame,
LAN frames of a size capable of being connected in the same Dch are collectively referred to as a short frame.

On a LAN, FTP (Fi1e Transfer Proto
When data transfer is performed by the file transfer protocol represented by co1), long frames of the maximum size (1518 bytes) occur consecutively. When transmitting long frames in the wireless section, each LAN frame cannot be linked, so the transmission speed is Dch transmission speed (wireless band)
Will be fixed to. However, in almost all protocols including the above-mentioned FTP, the acknowledgment packet is generated at a constant interval when the protocol is executed.

[0013] Normally, on a LAN, a large number of short frames exist as a whole, because a large number of communications by a plurality of protocols are simultaneously executed.
Therefore, in order to smoothly execute these many communications, it is considered that it is indispensable to connect and transmit the short frames in the wireless section. Furthermore, in an 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.

In the case of VoIP, the bandwidth used per channel is about 5 Kbps to 64 Kbps (the bandwidth used varies depending on the voice coding method), but when considering use in multiple channels, short-frame traffic is channel It will increase by a few minutes. It is predicted that Internet telephony (VoIP) will be widely used in the future, and since short-frame traffic in LAN is expected to increase, high transmission throughput performance for short frames is required even in a wireless section. come. For this reason, 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, in the case of performing frame-to-frame transmission in a wireless section, it is required to reduce a delay time required for transmission in order to secure communication quality. For example, in VoIp, in order to ensure telephone quality,
It is considered that the allowable total delay time of data transmission is about 200 milliseconds. For this reason, it is required to minimize the delay time generated in the wireless transmission device. Also,
Even in communication that does not require real-time processing such as file transfer, for example, TCP (Transmission Control Pro
In the communication by toco1), a data transmission waiting time waiting for an acknowledgment occurs every time a certain amount of data is transmitted. And
Since this 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 also, it is required to minimize the delay time generated in the wireless transmission device.

Here, in general, a single queue
If enqueues (inputs of queue elements) and dequeues (outputs of queue elements) occur randomly, according to statistical mathematics, these occurrences follow a Poisson distribution. According to the queuing theory, it is known that the “number of queued queues” is ρ ² / (1−ρ) under this assumption. Therefore, the "delay time generated by staying" at this time is given by ρ ² / (1−ρ) × (1 / dequeue rate) (A). Here, ρ = traffic density defined by (enqueue speed) / (dequeue speed), and the unit may be referred to as “erlang”.

From the above equation (A), it is understood that the delay time caused by the retention of queue elements 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 when approaching = (dequeue speed). The queuing theory considers the range of “ρ <1”, that is, “enqueue speed <dequeue speed”.

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 retention is sufficiently small in the range where ρ <1, that is, the dequeuing speed is larger than the enqueuing speed, and when ρ approaches 1 and exceeds a certain point, the delay time increases rapidly and reaches the maximum. 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 at which packet loss can be transferred), and in the area beyond that, the so-called congestion state (13 Enter 2).

Here, a wireless transmission device for wirelessly connecting two or more LAN segments, for example, a wireless L
Regarding the AN system and the FWA system, consider the configuration of the queue inside the device. This is generally as shown in FIG. 14, in which the queue on the side of loading on the Dch and transmitting to the wireless section is the wireless transmission queue (14.1), and the queue on the side received from Dch of the wireless section is the wireless reception queue (14.2). ).

Here, comparing the LAN band and the band of the wireless section, the LAN band is currently 100 Mbps at maximum.
Fast Ethernet (registered trademark) (standardized by IEEE802.3u), which provides the above data transmission speed, is becoming mainstream. On the other hand, the band of the wireless section is, for example, IEEE802.11bHig.
In the wireless LAN system based on the hRate standard, the maximum data transmission rate is 11 Mbps. In general, it can be considered that the bandwidth of the LAN is larger than the bandwidth of the wireless section, and the WRXQout (1
4.5) The rate (ie dequeuing rate from the radio receive queue) is equal to the WRXQin (14.6) rate (ie
It can be considered that it is larger than the enqueuing speed to the wireless reception queue), that there is almost no stay in the wireless reception queue (14.2), and there is almost no delay time caused thereby.

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 stays occurs in the wireless transmission queue, It causes a large delay time. In this way, a LAN that exceeds the upper limit of the transmission performance of the device
The condition that there is input traffic from the device means that the device is in a congestion condition, and the delay that occurs in this condition cannot be avoided in principle.

However, in reality, when the LAN frames are concatenated by the software process and the enqueue process to the wireless transmission queue is carried out, if the method is not devised, the value is "certain constant" which is considerably lower than the maximum throughput point of the device. Even with an input load of "range", the maximum number of stays may occur inside the wireless transmission queue, resulting in a large delay time. That is, as shown in FIG. 17, a certain LAN input load range II which is considerably low.
Even with (17.2), the delay becomes large, and the delay in this range must be kept as small as possible because it is the delay that occurs within the range in which the device guarantees data transmission.

Here, the delay caused by staying in the queue is caused by the radio transmission queue (14.1) as described above.
Since it occurs on the side, the wireless transmission queue is represented again as (15.1) as shown in FIG. 15, and the processing configuration by general software will be described. That is, in the wireless transmission queue (15.1), the data portion (Dch data (15.
2)) is stored as a queue element, and Dch data (1
In 5.2), there are usually multiple LAN frames (15.3).
Are connected.

Here, Lin (15.4) represents the input of a LAN frame. Win (15.5) represents the enqueue to the wireless transmission queue. Wout (15.
6) represents dequeuing from the wireless transmission queue.

The connection / enqueue task (15.7) is
One Dch for multiple LAN frames input to the device
This is a task of connecting and storing the data and Win (15.5) in the wireless transmission queue (15.1) (hereinafter, also simply referred to as a task). The task is periodically activated as shown in FIG. 16, and the LAN frame which is Lin (15.4) in the period is connected to one Dch data (15.2), and the enqueue condition is satisfied. Sometimes Win (1
5.5)

The enqueue Win (15.5) conditions are the following two. The size of the empty area of the Dch data (that is, the empty area of the transmission slot) is small, and a new Lin (15.
4) The stored LAN frames cannot be concatenated and stored in the same Dch. There is no newly Lin (15.4) LAN frame. When the above conditions are met or the number of input LAN frames reaches the upper limit (preset), the task sends the current Dch data to the wireless transmission queue by W.
in (15.5), and the process ends.

FIG. 16 shows a processing cycle of the wireless transmission device. Here, T_Lin (16.1) represents the average input cycle 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) is
Shows the average activation cycle of concatenation / enqueue tasks.

Therefore, in general, the task period (T_T
ask (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 the Wout period (T_Wout (1
6.3)), but after the LAN frame input load exceeds a certain level, the task cycle (T_Task)
(16.4)), on the contrary, the Wout cycle (T_Wout
It may be considered that the value becomes larger than (16.3)).

The wireless transmission driver (15.8) extracts the Dch data (queue element) stored in the wireless transmission queue (15.1) and puts it on Dch (W).
out (15.6)). The wireless transmission driver (15.8) uses the periodically generated Wout
Since Dch is created according to (15.6), Wou
The interrupt process is activated in t cycles (T_Wout (16.3)). That is, the Wout cycle (T_Wou
t) is also the activation period of the wireless transmission driver.

The conditions for generation of the areas I to IV shown in FIG. 17 are as follows. (1) T_Wout <T_Link (that is, Wou
t speed> Lin speed); region of I (17.1). In this area, as shown in FIG. 18, since the LAN input load is smaller than the wireless band (Wout speed), the stay in the wireless transmission queue is sufficiently small and delay hardly occurs.

(2) T_Wout> T_Lin (that is, Wout speed <Lin speed); (2) -1; Number of connections in one task process (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.
“Wout speed <Win speed” is established, the maximum number of stays occurs in the wireless transmission queue, and the maximum delay time occurs. (2) -1.2; T_Wout <T_Task; II
Region of I (17.3). At this time, as shown in FIG. 20, “Wout rate <Win rate” is established, and the stay in the wireless transmission queue is sufficiently small, and the delay hardly occurs. (2) -2.1; number of connections in task processing (T_Tas
k / T_Lin)> maximum number of connections; IV region (17.
4). From this point onward, as shown in FIG. 21, it is always “Wo
The ut speed becomes less than the Win speed, and the maximum number of stays occurs in the wireless transmission queue, and the maximum delay time occurs (the congestion state exceeds the transmission processing upper limit of the device).

The problem here is that the region of II (1
The maximum delay time occurs in 7.2).
In this II area (17.2), the task cycle T_Ta
Since sk is in a state shorter than the dequeue period T_Wout, when Win is performed each time task processing is completed, the Win speed exceeds the Wout speed, and as a result, the maximum number of stays occurs in the wireless transmission queue, causing a large delay time. I will end up.

The present invention has been made in view of the above-mentioned conventional circumstances, and makes it possible to store a plurality of transmission data frames in a fixed-length data transmission channel (slot) and wirelessly transmit the same, and also to perform wireless transmission. An object of the present invention is to reduce the stay in the credit queue and the delay caused thereby, and to effectively utilize the wireless transmission medium by efficient data transmission. A further object of the present invention will be apparent from the following description.

[0034]

[Means for Solving the Problems] Area II (17.
In order to suppress the occurrence of delay in 2), it can be said that the linked task must not unconditionally win at the end of processing. Figure 2
More specifically, referring to FIG. 2, assuming that the elapsed time from the last enqueue Win of the task is ΔT (22.1), the task has the maximum number of connected LAN frames at the end of processing. ΔT <T_Wou if not reached
Win must not be performed while the conditions of t and t are satisfied. Because if this condition is Win when not satisfied,
This is because T_Win <T_Wout is satisfied, and (the Win speed exceeds the Wout speed, the maximum stay occurs in the wireless transmission queue, and a large delay time occurs. Therefore, the basic concept of the present invention is One is to give appropriate control to the enqueuing process (Win) to the wireless transmission queue, adjust the timing of enqueuing (Win) so as not to cause stagnation, and further to the area II (17.2) and other This is to suppress the occurrence of delay in the area.

The present invention is a radio transmission apparatus for periodically allocating a fixed size data transmission slot to a radio section to perform data transmission in the radio section, and of a radio transmission queue which is a transmission queue of transmission data. A memory for holding a sequence of elements, a connecting means for connecting a plurality of transmission data to be elements of a wireless transmission queue, a wireless transmission means for mounting the wireless transmission queue element output from the memory in a data transmission slot, and a memory Control means for controlling the memory to hold the next wireless transmission queue element in response to the output of the wireless transmission queue element. Therefore, in order to control the timing of enqueuing (Win) the wireless transmission queue element in response to the wireless transmission queue element being dequeued (Wout), a plurality of transmission data are concatenated and stored in the data transmission slot. It is possible to suppress the occurrence of delay in linked storage while realizing effective use of slot (channel) capacity by wirelessly transmitting data by wireless transmission.

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 element does not have or is held by the wireless transmission queue element. When the number of transmission queue elements has decreased from the previous memory output, control is performed to cause the memory to hold the next wireless transmission queue element. Further, more specifically, in the wireless transmission device of the present invention, the control means synchronizes with the output of the wireless transmission queue element from the memory,
The memory is controlled to hold the next wireless transmission queue element.

Further, the present invention is a radio transmission apparatus for periodically allocating fixed-size data transmission slots to a radio section for data transmission in the radio section, which is a transmission queue for transmission data. A memory for holding a queue element array, a connecting means for sequentially connecting and storing a plurality of transmission data to the elements of the wireless transmission queue held in the memory, and a wireless transmission queue element output from the memory. The size of the data transmission slot when the wireless transmission means to be placed in the data transmission slot and the wireless transmission queue element to be stored concatenated are output from the memory or the next transmission data is stored in the wireless transmission queue element to be stored concatenated. If it exceeds the limit, the processing target of the connection means is moved to the connection storage of the transmission data for the next wireless transmission queue element held in the memory. It comprises a control means, a to. Therefore, by directly connecting the transmission data to the elements of the wireless transmission queue held in the memory, the retention in the queue is reduced, and the queue elements to be connected are transferred at an appropriate timing. Can be made.

More specifically, in the wireless transmission device of the present invention, the above-mentioned memory and control means are connected by an internal bus to form a module to reduce the load on software processing. Is provided with a bus interface for outputting the wireless transmission queue element output from the memory to the wireless transmission means, and the control means controls the empty size of the wireless transmission queue element to be stored concatenated and the transmission data to be stored next. The size of the linked storage processing is moved to the next wireless transmission queue element.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG.
The present invention will be described in detail with reference to a P-MP (Point to Mu1ti Point) type system in which a plurality of CS (subscriber stations) 2 are wirelessly connected to a (base station) 1. In addition, BS
1 and CS2 respectively correspond to the wireless transmission device according to the present invention, but in the following description, BS1 will be mainly described.

Each CS2 has a function of transmitting a LAN frame (transmission data) input from the LAN3 side of its own device to the BS1 through the wireless section, and also Dch (data transmission slot) received from the BS1 through the wireless section. It has a function of taking out a LAN frame from the device and transferring it to the LAN 3 side of the own device. BS1
It has a function of transmitting a LAN frame input from the LAN4 side of its own device to a specific CS2 through a wireless section, and Dch received from CS2 through the wireless section.
Take out the LAN frame from the
It has the function of transferring to the N4 side.

Radio transmission from the BS to the CS is called downlink transmission, and radio transmission from the CS to the BS is called uplink transmission. In the present example, the linking process at the time of the uplink transmission is a delay described later. Since the processing is the same as the concatenation processing at the time of downlink transmission except that the control processing for suppressing is not provided, the processing at the time of downlink transmission will be described below. That is, the processing performed by the BS 1 when transmitting data to the wireless section will be described.

BS1 is an LA input from the LAN4 side.
If N frames are multicast frames, all C
If this is transmitted to S2 and the LAN frame input from the LAN4 side is a unicast frame, which C
After deciding whether to transmit to S2, this is transmitted to the CS2. As shown in FIG. 2, BS1 has a CAM inside the device.
(Content Address Memory) (2.1)
CS as a destination by referring to CAM (2.1)
Determine one. CAM (2.1) is a device capable of internally recording a plurality of sets of "MAC address and CS number", and by inputting a MAC address as an input value, the corresponding CS number as an output value. Is an associative memory device capable of outputting

During downlink transmission, the destination MA of the LAN frame
If the C address is input to CAM (2.1), the MA
If the CS number corresponding to the C address exists, CAM
(2.1) outputs the CS number. 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 to output a valid CS number to the CAM (2.1), it is necessary to record to the CAM first.

Here, at the time of uplink transmission, at BS1,
Although not shown in FIG. 2, the wireless reception driver and the wireless reception task function. The wireless reception driver has a function of receiving an upstream transmission request from each CS2, allocating a band (Dch) for upstream transmission to each CS2, and actually receiving Dch. The wireless reception task performs Dch from the wireless reception driver. Receives the Dch data transmitted from the CS and the CS number of the transmission source, extracts the LAN frame stored in the Dch data, and extracts the LAN
It has a function to transfer to the 4 side.

In the radio reception task, Dch data to L
MAC of the sender when the AN frame is retrieved
The combination of the address and the CS number of the sender is CAM (2.1)
To record. In the wireless reception task, the extracted L
According to the destination MAC address of the AN frame, the CAM (2.
By searching 1), it is possible to realize loopback transmission between two different CSs. Therefore, with respect to a LAN frame that has undergone upstream transmission once, when a LAN frame in the opposite direction is input to BS1, it becomes possible to determine the destination CS2 from CAM (2.1).

Since BS1 cannot determine to which CS2 the LAN frame in the reverse direction is to be sent for the LAN frame for which upstream transmission has never been performed, in this case, (1) it is sent to all CSs. Or (2) discarding the received LAn frame. An ordinary bridge does not know the destination L
Operation (1) for AN frame (flooding)
However, in the case of a wireless transmission device, the option (2) may be adopted in order to effectively use the wireless band shared by all devices. In the actual communication performed through the LAN, the multicast always occurs at the very first stage of the communication, and the unicast occurs in response to it (the unicast frame does not occur in the downward direction from the beginning). It is considered that the method (2) does not cause any problems.

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

(1) When the BS1 receives a unicast LAN frame from its own LAN4 side, the concatenation / enqueue task (2.2) searches the CAM (2.1) by the CAM search function (2.3). And determine its destination. (2) In the memory of BS1, a plurality of linked work areas (2.4) are allocated for each CS2, and the CS of the destination is
After 2 is determined, the connection work area (2.
The LAN frame received in 4) is transferred. (3) When a LAN frame addressed to the same CS is subsequently received, the LAN frame is transferred to the same concatenation work area (2.4) and concatenated.

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 concatenation work area (2.4), then the size of the second LAN frame and the data transmission slot ( Dch) is compared with the free size left, and if there is a free size that can store this second frame, a delimiter bit is inserted between the first frame and the second frame, and the second frame is inserted. Frame is the same connected work area as the first frame (2.4)
To store.

Further, the size of the third frame is compared with the empty size left in the data transmission slot when the first and second frames are stored, and the empty size that can store the third frame is determined. In some cases, a delimiter bit is inserted between the second frame and the third frame, and the third frame is stored in the same concatenated work area (2.4) as the first and second frames. . In this way, if there is a free size for storing the next frame in the fixed length data transmission slot, it is stored in the same data transmission slot, and it is stored in the same concatenation work area (2.4). A plurality of frames addressed to the same CS are stored. Note that when a multicast LAN frame is received, or a unicast LA whose destination cannot be determined
If flooding N frames, these LA
The N frame is a concatenated work area for all CSs (2.4).
Will be transferred and linked to.

(4) A connection work area for a certain CS (2.
If there is no free space required in 4) and the LAN frame destined for the same CS that cannot be further concatenated, the concatenated data in that region is enqueued in the wireless transmission queue (2.5) for that CS. . The received LAN frame is transferred to another concatenated work area (2.4) for the same CS. (5) The data (queue element) enqueued in the wireless transmission queue (2.5) is the wireless transmission driver (2.6).
Dch assigned to the radio section for each CS
It is placed in the (data transmission slot) and transmitted to the CS. (6) When there are no received LAN frames, or when the maximum number of LAN frames to process has been reached, concatenation /
The processing of the enqueue task (2.2) ends.

Then, the above-mentioned radio transmission queue (2.5)
In the enqueuing and dequeuing to the BS of this example
In No. 1, one of the control processes for suppressing the retention as shown in the following methods 1 to 4 is performed.

First, the method 1 will be described. In the method 1, as shown in FIG. 3, a method by queue monitoring is carried out. In the wireless transmission queue, the number of queue elements decreases by 1 each time it is dequeued (Wout), so the number of queue elements is -1.
The time interval is T_Wout. Therefore, the task (2.2) refers to the current queue element number Q (N) when there is data waiting for Win that has not reached the maximum number of connections at the end of processing (step S1), and refers to the current queue. The number of 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, and (currently When the condition of (the number of queue elements in the queue) <(the number of previous queue elements) is satisfied (step S3), the next queue element is enqueued (Win) in the wireless transmission queue (step S3).
4) The current number of queue elements is saved and the task processing ends.

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 Win, ends the task processing (step S5), and waits for execution. Transition to. As described above, when there is an input LAN frame at the time of the next task processing, the concatenation processing is added to the current concatenated data. In this way, the task (2.2) monitors the number of queue elements of the wireless transmission queue or the change in the number of queue elements by self-control, and as a result, the wireless transmission queue is changed in response to the dequeuing of the queue element. By enqueuing the next queue element, this prevents the queue element from staying in the wireless transmission queue, especially in the area II (17.2), and avoids the occurrence of delay. There is.

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 carrying out this method 2 has a connection task (4.
1) and an enqueue (W to the wireless transmission queue (4.3))
in) which is separated into an enqueue driver (4.2).

The concatenated task (4.1) is a periodical activation task, and concatenates LAN frames in each task processing. The concatenation task (4.1) executes Win only when the current concatenation process reaches the maximum number of concatenations,
It won't win other than that. The enqueue driver (4.2) is an interrupt process activated in the T_Wout cycle, and in each process interrupt-activated in synchronization with the dequeue, the concatenated task (4.1) wins the concatenated data which is concatenated. Ends the process. The enqueue driver (4.2) uses a flag which can be referenced in common with the linked task (4.1), and uses the linked task (4.1).
Is notified that the Wout of the connection data has been executed, and the connection task (4.1) recognizes the end of the connection processing by this notification.

In this way, the enqueue driver (4.
2) self-controls so as to enqueue the next queue element in the radio transmission queue in synchronization with the dequeue, so that the Win element is Winned in a cycle shorter than T_Wout, particularly in the area II (17.2). This prevents the queue element from staying in the wireless transmission queue and avoids the occurrence of delay.

Next, a method 3 different from the above method will be described. In the method 3, as shown in FIG. 5, the concatenation task (5.2) performs the concatenation process on the wireless transmission queue (5.2.
Directly for the area (5.1) of each cue element in 3). If the current (top) queue element is dequeued (Wout), or if it is not possible to connect to the current queue element area any more, the link task (5.2) moves to the next queue element area. Transfer and perform ligation.

The area (5.1) of each queue element is provided with a flag which can be referred to in common with the dedicated concatenated task, and the wireless transmission driver (not shown) uses Wou.
This flag is used when executing
The fact that it is out is notified to the linked task (5.2), and the linked task recognizes the end of the linked processing for the queue element by this notification. In this way, the linked task (5.2) performs processing by self-control,
The concatenation task will continue the concatenation process for one queue element area (5.1) within the time T_Wout, which is substantially equivalent to preventing Win from being cycled in a shorter period than T_Wout. It is possible to obtain an effect, prevent a situation where queue elements are accumulated in the wireless transmission queue, and avoid occurrence of delay.

Next, the method 4 will be described. In the method 4, as shown in FIG. 6, a process of directly connecting and storing each element of the wireless transmission queue in the method 3 is performed.
Hardware module (concatenated FIFO module)
It was realized in. This connection FIFO module 6
Is a bus interface (6.3) for interfacing the external bus (6.1) accessible from the control unit (CPU) of the wireless transmission device with the internal bus (6.2) inside the connection FIFO module; A write buffer (write) for writing a LAN frame through the bus (6.1)
It has a concatenated FIFO section (6.6) with a buffer memory (6.4) and a plurality of FIFO element memories (6.5).

The concatenated FIFO module 6 further includes a free area size register (6.7) for storing the free area size in the FIFO element memory (6.5) in which the concatenated process is continuously executed, and a write buffer memory. A write buffer data size register (6.) for storing the LAN frame size currently stored in (6.4).
8) and a connection FIFO through the external bus (6.1)
FIFO read size (rea that stores the read size when reading the concatenated data stored in (6.6))
It has a dsize) register (6.9) inside, and compares the free area size register (6.7) with the write buffer data size register (6.8) to find that the write buffer memory (6.4) There is a concatenated FIFO controller (6.10) for transferring the received LAN frame of the above to the appropriate location of the FIFO element memory (6.5).

In this concatenated FIFO module 6, when a LAN frame is written through the external bus (6.1), it is first written in the write buffer memory (6.4), and at this time, the concatenated FIFO control section (6.10). )But,
The LAN frame size in the write buffer memory (6.4) is set to the write buffer data size register (6.8)
Set to. Next, the concatenated FIFO control unit (6.10)
Is the write buffer data size register (6.8)
And the value of the free area size register (6.7) are compared with each other, and either the following processing (1) or (2) is executed.

(1) When the received LAN frame size ≦ the free area size, the write buffer memory (6.
After adding the necessary header information to the LAN frame stored in 4), the FIFO that is currently continuing the concatenation process.
The data is transferred to the element memory (6.5) and additionally connected, and the free area size register (6.7) is updated. (2) If the received LAN frame size> free area size, the next unused FIFO element memory (6.5) that is currently unused is newly found, and in response to this, the write buffers memory (6. The LAN frame stored in 4) is transferred after adding necessary header information, and the free space size register (6.7) is updated. Note that the LAN frame written after this is the next FIFO above.
O element memory is additionally connected.

The concatenated FIFO control unit (6.10) sets the FIFO element memory (6.5) to be read next so that it is read through the external bus (6.1), and at the same time, this FIFO element memory (6) is read. .. 5) sets the concatenated data size in the FIFO read size register (6.9) so that it can be read via the external bus (6.1).
When the concatenated data is read from the external bus (6.1), the concatenated FIFO controller (6.10)
The read FIFO element memory (6.5) is returned to the unused state and at the same time, the FIFO to be read next.
The O element memory (6.5) 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).

Since the concatenation process is performed by the concatenation FIFO module 6 as described above, the process (concatenation task) by software is not required, and the action and effect of the above method 3 can be obtained. Note that, for example, as shown in FIG.
The FO module 6 is an L consisting of software modules.
AN reception driver (7.1) and wireless transmission driver (7.
In cooperation with 2), a series of processes for connecting the received LAN frames and transmitting them to the wireless section is executed, and the LAN reception driver (7.1) concatenates the FIFOs each time the LAN frame is received.
The LAN frame is transferred to the module 6, and the wireless transmission driver (7.2) takes out the concatenated data from the concatenated FIFO module 6, puts it on Dch, and executes the transmission to the wireless section.

Here, the above example is directed to the wireless transmission apparatus of the TDMA / TDD system, but the present invention is not particularly limited to this, and the upper layer has a plurality of PDUs (Protocols).
Data Unit), and one SD for the lower layer
Even in a general wireless transmission device having a method of enqueuing a transmission queue as a U (Service Data Unit), it is possible to obtain the effect of reducing the delay time generated inside the queue by performing the same control as the above example. You can

[0067]

The effects of the present invention are shown by the results of actual measurement using a wireless transmission device. The wireless transmission device used in this example performs data transmission in a wireless section by the TDMA / TDD system. The depth of the wireless transmission queue is 12
8 (128 concatenated data can be stored). In this wireless transmission device, the delay time is measured in each of two cases: (1) enqueue processing is performed asynchronously with dequeue, and (2) enqueue control by the "queue monitoring method" shown in method 1 above is performed. do it.

The configuration of the device for which the delay measurement is performed is as shown in FIG. 8, and the wireless transmission device A connected to the wired (LAN) transmission section A and the wireless transmission device connected to the wired (LAN) transmission section B. A 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 using B and L.
The AN frame is wirelessly transmitted from the wireless transmission device A to the wireless transmission device B. In addition, RFC1242 / RFC
According to the 25442 standard, only a LAN frame of 64 bytes was generated and measured.

As a result, the delay time characteristic as shown in FIG. 9 is obtained in the case of not controlling enqueue (1), and in the case of controlling the enqueue (2), FIG.
The delay time characteristics as shown in (3) were obtained. From these, in FIG. 9, the input load from the LAN is 0.9 to 1.7.
%, A delay time exceeding 100 milliseconds occurs, but in FIG. 21, the delay occurring in the same section in FIG. 9 is completely suppressed (the delay time is 5 milliseconds or less, Win control It is about 1/20 of that without). That is, it was confirmed that the present invention provides a remarkable effect of delay suppression.

[0070]

As described above, according to the present invention,
Controls the process of enqueuing the concatenated data to the wireless transmission queue waiting to be transmitted in response to the dequeuing from the wireless transmission queue when the transmission data is concatenated and placed in the data transmission slot in the wireless section and wirelessly transmitted. By doing so, it is possible to reduce the stay in the wireless transmission queue and the delay that occurs due to this, and to effectively utilize the wireless transmission medium by efficient data transmission.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a wireless transmission system to which the present invention is applied.

FIG. 2 is a diagram showing an example of a configuration according to the present invention.

FIG. 3 is a flowchart illustrating a method 1 according to the present invention.

FIG. 4 is a diagram illustrating a method 2 according to the present invention.

FIG. 5 is a diagram illustrating a method 3 according to the present invention.

FIG. 6 is a diagram illustrating a method 4 according to the present invention.

FIG. 7 is a diagram illustrating method 5 according to the present invention.

FIG. 8 is a diagram illustrating a device configuration for delay measurement according to an embodiment of the present invention.

FIG. 9 is a diagram showing a measurement result when enqueue control is not performed in the example of the present invention.

FIG. 10 is a diagram showing a measurement result when enqueue control is performed in the example of the present invention.

FIG. 11 is a diagram illustrating an empty area that occurs in Dch.

FIG. 12 is a diagram showing a profile of delay time occurring in a queue in queuing theory.

FIG. 13 is a diagram showing a profile of delay time generated in an actual queue.

FIG. 14 is a diagram illustrating a queue in a wireless transmission device.

FIG. 15 is a diagram illustrating a LAN frame concatenation process and an enqueue process for a wireless transmission queue.

FIG. 16 is a diagram illustrating each processing cycle in the wireless transmission device.

FIG. 17 is a diagram showing a profile of a delay time which occurs in a queue in the wireless transmission device.

FIG. 18 is a diagram illustrating a processing state in the state (17.1) of FIG. 17;

FIG. 19 is a diagram illustrating a processing state in the state (17.2) of FIG.

20 is a diagram illustrating a processing state in the state (17.3) of FIG.

FIG. 21 is a diagram illustrating a processing state in the state (17.4) of FIG.

22 is a diagram illustrating a condition for suppressing a delay that occurs in the state of the state (17.2) in FIG.

[Explanation of symbols]

1: base station (BS), 2: subscriber station (CS), 3: L
AN, 4: Backbone network (LAN),
(2.2): Concatenated enqueue task, (2.4): Concatenated work area, (2.5): Wireless transmission queue, (2.
6): Wireless transmission driver,

Claims (5)

[Claims] 1. A wireless transmission apparatus for allocating a fixed-size data transmission slot to a wireless section periodically to perform data transmission in the wireless section, holding an element sequence of a wireless transmission queue which is a transmission queue of transmission data. Memory, a connection means for connecting a plurality of transmission data which is an element of the wireless transmission queue, a wireless transmission means for placing the wireless transmission queue element output from the memory in the data transmission slot, and a wireless transmission queue from the memory A wireless transmission device, comprising: a control unit that controls the memory to hold the next wireless transmission queue element in response to the output of the element. 2. The wireless transmission device according to claim 1, wherein the control unit monitors the number of wireless transmission queue elements held in the memory, and the wireless transmission apparatus has no wireless transmission queue element or holds the wireless transmission queue element. A wireless transmission device, characterized in that, when the number of credit queue elements is smaller than that at the time of the previous memory output, control is performed to hold the next wireless transmission queue element in the memory. 3. The wireless transmission device according to claim 1, wherein 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. A wireless transmission device characterized by performing. 4. A wireless transmission apparatus for allocating fixed-size data transmission slots periodically to a wireless section to perform data transmission in the wireless section, holding an element sequence of a wireless transmission queue which is a transmission queue of transmission data. Memory, a connection means for sequentially connecting and storing a plurality of transmission data to the elements of the wireless transmission queue held in the memory, and a wireless device for mounting the wireless transmission queue element output from the memory in the data transmission slot. When the transmitting means and the wireless transmission queue element to be linked and stored are output from the memory, or when the next transmission data is stored in the wireless transmission queue element to be linked and stored, it exceeds the size of the data transmission slot. , A control means for shifting the processing target of the connection means to the connection storage of the transmission data for the next wireless transmission queue element held in the memory Wireless transmission apparatus comprising the and. 5. The wireless transmission device according to claim 4, wherein the memory and the control means are connected by an internal bus to form a module, and the module further includes a wireless transmission queue element output from the memory. Is provided to the wireless transmission means, and the control means compares the empty size of the wireless transmission queue element to be concatenated and stored with the size of the transmission data to be concatenated and stored next for wireless transmission. A wireless transmission device, characterized in that a connection storage processing target is transferred to a queue element.