JP3709376B2 - Data transmission device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a communication frame such as a radio frame that repeats a randomly generated data packet (hereinafter referred to as a packet) between a single base station and a plurality of subscriber stations at a constant period. The present invention relates to a data transmission apparatus for bidirectional transmission.
[0002]
[Prior art]
Randomly generated data such as variable-length data frames (simply referred to as frames) used in communication systems such as Ethernet (registered trademark) is divided into fixed-length packets and a single base is used in time slots. When transmitting between a station and a plurality of subscriber stations, a data transmission apparatus is used in which a plurality of subscriber stations share a band and efficiently use the band by utilizing the statistical multiplexing effect on bursty data traffic. ing.
[0003]
In this data transmission apparatus, the number of packets stored in the base station and each subscriber station is periodically measured, and the base station allocates time slots based on the measurement results.
[0004]
FIG. 13 uses a time division duplex (TDD) / time division multi-channel access (TDD) system in which randomly generated packets are transmitted between a single base station and a plurality of subscriber stations. 2 shows a format of one radio frame in a P-MP (point to multi-point) radio access system. Note that the frame of one radio frame is different from a frame such as an ether frame.
[0005]
One radio frame includes a downlink composed of a downlink header region TS11 and a downlink data region TS12, an uplink composed of a DMF (delay measurement frame) region TS13, a slot request region TS14, and an uplink data region TS15, and a guard time TS16. It is composed of
[0006]
The downlink header region TS11 is a time zone for notifying each subscriber station of instructions and monitoring control information regarding a time schedule such as time slot allocation determined by the base station according to the downlink and uplink traffic volume.
[0007]
The downlink data area TS12 is a time zone for transmitting data to the subscriber station in the downlink by dividing it into time slots corresponding to packets.
[0008]
The DMF region TS13 is a time zone for measuring the propagation delay between the base station and each subscriber station. The radio data from each subscriber station is adjusted by adjusting the transmission timing of the radio data from each subscriber station. It is provided to prevent collisions at the base station.
[0009]
The slot request area TS14 is an area for each subscriber station to request the number of time slots for packet transmission from the base station. Usually, a plurality of time slots are prepared so as to respond to time slot allocation requests for transmitting packets from a plurality of subscriber stations.
[0010]
In practice, transmission of an uplink slot request from each subscriber station is performed based on a schedule instruction specified in the downlink header region TS11.
[0011]
The guard time TS16 is a parameter that is set in advance at the boundary between the uplink and the downlink, and is fixed in advance.
[0012]
As shown in an enlarged manner in FIG. 13, the downlink header area TS11 is composed of five areas TS17 to TS21.
[0013]
The preamble region TS17 is used for a training signal that enables each subscriber station to normally receive a burst wave from the base station.
[0014]
The base station number area TS18 indicates the number of the base station that is the transmission source of the packet transmitted in the downlink data area TS12.
[0015]
A frame position designation area TS19 indicates the start position of each of the areas TS11 to TS15.
[0016]
The command area TS20 is a frame for controlling the subscriber station and is composed of a subscriber station number to be controlled and a control command.
[0017]
The slot allocation area TS21 includes a slot number for allocation of each of the slot request area TS14 and the uplink data area TS15, and a subscriber station number allocated to the slot number.
[0018]
[Problems to be solved by the invention]
The inventor of this application has found the following problems in bidirectional communication between a single base station and a plurality of subscriber stations using one radio frame configured as described above.
[0019]
In general, in a base station, there is a calculation time for making a schedule, that is, a time difference between the time when the number of packets accumulated for a certain subscriber station is measured and the time when a time slot is actually allocated. There is a possibility that some or all of the accumulated packets are transmitted. In this case, a time slot is assigned to a packet that has already been transmitted, and so-called time slot is wasted.
[0020]
Also, at the subscriber station, the slot allocation unit of the base station issues a slot use permission based on the time when the number of packets accumulated in the subscriber station is measured and the information on the measured number of packets, and each subscriber There is a time difference between the time points notified to the station, and there is a possibility that some or all of the packets accumulated during that time are transmitted. In this case as well, so-called time slot is wasted.
[0021]
In particular, in the TDD scheme, the number of time slots allocated to the uplink data area TS15 in the uplink direction and the number of time slots allocated to the downlink data area TS12 in the downlink direction are increased in the traffic amount in order to improve the bandwidth utilization efficiency. When a dynamic slot allocation method that dynamically changes in response to this is adopted, information on the number of packets stored in the transmission buffer of the subscriber station is also required for the allocation of the downlink data area TS12 in the downlink direction. We found that a time lag occurred on the same principle.
[0022]
The present invention has been made in consideration of such problems, and an object of the present invention is to provide a data transmission apparatus that makes it possible not to assign a time slot to an already sent packet.
[0023]
Another object of the present invention is to provide a data transmission apparatus that can avoid wasting time slots.
[0024]
Further, according to the present invention, although the total capacity of the downstream area data amount and the upstream area data amount is constant, the ratio of each data amount is dynamically changed for each communication frame (one wireless frame or one wired frame). It is an object of the present invention to provide a data transmission apparatus that can avoid wasting time slots by allocating time slots to already transmitted packets in the dynamic slot allocation method.
[0025]
[Means for Solving the Problems]
According to the data transmission apparatus of the present invention, a communication frame having a fixed length including a downlink data area divided into a plurality of time slots is repeated at a fixed period, and a packet read from a transmission buffer of a single base station is added to a plurality of subscriptions. In the data transmission apparatus for transmitting to the user station in the time slot of the downlink data area, the base station determines the number of packets addressed to the subscriber station in the transmission buffer. Every communication frame cycle A packet number measurement unit that periodically measures; a slot assignment unit that assigns time slots based on the measured number of packets; and a slot assignment storage unit that stores time slot assignments, the slot assignment unit comprising: When allocating the time slot, the time slot is allocated based on a value obtained by subtracting the number of already allocated packets stored in the slot allocation storage unit from the number of measured packets (claim 1). invention).
[0026]
According to the present invention, the base station is provided with a time slot allocation storage unit that stores time slot allocation. When the slot allocation unit of the base station allocates the time slot based on the number of measurement packets, Since the number of already allocated packets stored in the allocation storage unit is subtracted and allocated, it is possible to prevent a time slot from being allocated to an already transmitted packet. It can be avoided.
[0027]
As the communication frame, a wireless frame or a wired frame such as an optical fiber line can be used.
[0028]
In this case, when the data transmission apparatus is a time division multiplexing data transmission apparatus, when the slot allocation unit allocates a time slot in the current communication frame, it is based on a value obtained by subtracting the number of packets allocated in the previous communication frame. Thus, it is possible to prevent retransmission of already sent packets (the invention according to claim 2).
[0029]
In the data transmission apparatus of the present invention, an uplink is transmitted from a plurality of subscriber stations to a single base station, and transmission is performed from the single base station to the plurality of subscriber stations. There is a communication frame of a certain length that is repeated at a certain period including a downlink, and the uplink includes a slot request area for requesting a time slot from the plurality of subscriber stations to the single base station, An uplink data area divided into a plurality of time slots for transmitting packets from the plurality of subscriber stations to the single base station is included, and the downlink is assigned slot allocation from the base station. In the data transmission apparatus including a slot allocation area to be notified to the subscriber station, each of the plurality of subscriber stations includes a transmission buffer and a packet number measuring unit for measuring the number of packets in the transmission buffer. And, Every communication frame cycle The number of packets in the transmission buffer is periodically measured, and the measured value is transmitted as the number of time slot requests in the slot request region. The base station determines the time in the uplink data region based on the received number of time slot requests. A slot allocation unit for allocating a slot; and a slot allocation storage unit for storing the allocation of a time slot. The slot allocation unit is already allocated from the number of time slot requests stored in the slot allocation storage unit. The time slot of the upstream data area is assigned based on a value obtained by subtracting the number of time slots.
[0030]
According to the present invention, the slot allocation unit of the base station allocates the time slot already allocated and stored in the slot allocation storage unit from the number of time slot requests from the subscriber station when allocating the time slot in the uplink data area. Since the allocation is based on the value obtained by subtracting the number of slots, it is possible to avoid allocating a time slot to a transmitted packet, and a time slot generated by allocating a time slot to a transmitted packet. Is wasted.
[0031]
In this case, when the data transmission apparatus is a time division multiple access data transmission apparatus, when the slot allocation unit allocates a time slot in the current communication frame, it is allocated in the previous and previous communication frames from the number of time slot requests. By assigning based on the value obtained by subtracting the current time slot, it is possible to avoid assigning the time slot to the already sent packet, and waste of the time slot caused by assigning the time slot to the already sent packet. Is avoided in advance (the invention according to claim 4).
[0032]
A data transmission apparatus according to the present invention includes an uplink for transmission from a plurality of subscriber stations to a single base station, and a downlink for transmission from the single base station to the plurality of subscriber stations. A communication frame of a fixed length that repeats at a fixed cycle including: a slot request area for requesting a time slot from the plurality of subscriber stations to the single base station on the uplink; An uplink data area divided into a plurality of time slots for transmitting packets from one subscriber station to the single base station, and the downlink is assigned slot assignments from the base station. In a data transmission apparatus including a slot allocation area to be notified to a user station, and a downlink data area divided into a plurality of time slots for transmitting packets from the base station to the plurality of subscriber stations, The number of subscriber station has a respective transmit buffer, the packet counting unit for counting the number of packets in the transmission buffer , Zhou Periodically measure the number of packets in the transmission buffer, and transmit the measured value as the number of time slot requests in the slot request area. The base station counts the number of packets addressed to the subscriber station in its transmission buffer. Around A packet number measurement unit that periodically measures, and a slot allocation unit that allocates the time slot of the downlink data area based on the measured number of packets and allocates the time slot of the uplink data area based on the received number of time slot requests; A slot allocation storage unit for storing time slot allocation, wherein the slot allocation unit allocates the time slot of the downlink data area based on the number of measurement packets and the uplink data based on the number of time slot requests region Are allocated based on the value obtained by subtracting the number of timeslots already allocated stored in the slot allocation storage unit from the number of measurement packets and the number of timeslot requests. Ruko (Invention of claim 5)
[0033]
According to the present invention, in the dynamic slot allocation method, the base station is provided with the slot allocation storage unit, and the time slot is allocated with reference to the stored contents. Therefore, the time slot can be allocated to the transmitted packet. This avoids wasting time slots.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the drawings referred to below, the same reference numerals are given to the components corresponding to those shown in FIG. 13 and the detailed description thereof is omitted. Moreover, in order to avoid complexity, it demonstrates with reference to the said FIG. 13 as needed.
[0035]
FIG. 1 shows the overall configuration of a communication system 10 to which an embodiment of the present invention is applied.
[0036]
The communication system 10 is used as a P-MP (point to multi-point) type that provides a fixed wireless access service to a plurality of subscribers.
[0037]
The communication system 10 is basically capable of bidirectional communication with a base station 11 fixed to a building or a power pole, etc., and a fixed base station 11 via a wireless line. It is composed of a plurality of subscriber stations 21 (1) to (3) (also referred to as subscriber stations 21 as representative) that are arranged in a company or at home.
[0038]
In practice, the wireless line is established through wireless communication between the antenna 12 of the base station 11 and the antennas 22 (1) to (3) (also referred to as antennas 22) of the plurality of subscriber stations 21.
[0039]
The subscriber station 21 is connected to terminals 20 (1) to (3) (also referred to as terminals 20) such as personal computers by wire or wirelessly. Each terminal 20 and each subscriber station 21 can be integrated. On the other hand, the base station 11 is connected to the network 13 mainly by wire.
[0040]
Accordingly, each subscriber station 21 can access the network 13 via the wireless line and the base station 11. As the network 13, an IP (internet protocol) network or the like can be used.
[0041]
For communication between the base station 11 and the plurality of subscriber stations 21, bidirectional communication employing a TDD (time division duplex) / TDMA (time division multiple access) scheme is possible. In this case, a common radio frequency, for example, a 26 [GHz] band is assigned between the base station 11 and the plurality of subscriber stations 21, and efficient communication is possible due to a difference in time slots to be used.
[0042]
For communication between the base station 11 and the plurality of subscriber stations 21, an FDD (frequency division duplex) / TDMA method, which will be described later, can be adopted instead of the TDD / TDMA method. In either case of the TDD / TDMA scheme or the FDD / TDMA scheme, the downlink direction is a TDM (time division multiplex) scheme, and the uplink direction is a TDMA scheme.
[0043]
FIG. 13 described above shows a configuration of a radio frame (one radio frame) based on the TDD scheme for performing communication between the plurality of subscriber stations 21 and the base station 11. As a period of one radio frame, a fixed period, for example, 2 [ms] or the like is selected from about 1 to 10 [ms]. Of course, a shorter period or a longer period can be selected as the period of one radio frame in relation to hardware or the like. Note that a frame of one radio frame having a fixed period and a frame such as a variable-length ether frame are different.
[0044]
As described above, one radio frame is composed of the downlink composed of the downlink header region TS11 and the downlink data region TS12, the uplink composed of the DMF region TS13, the slot request region TS14, and the uplink data region TS15, and the guard time TS16. Composed.
[0045]
FIG. 2 shows a detailed configuration of the downlink data area TS12 in FIG.
[0046]
The downlink data area TS12 is divided into a plurality of time slots, and a fixed downlink packet (also simply referred to as a packet) Pd is assigned to each. Each downlink fixed-length packet Pd includes a subscriber station number Pd1, recombination information Pd2 including adjacent packet presence / absence information X, etc., fixed-length data Pd3 that is actual data, and an error detection code Pd4.
[0047]
FIG. 3 shows an example of 2-bit adjacent packet presence / absence information X {X = (a, b)} indicating the relationship of the packet to the adjacent packet in the recombination information Pd2. The adjacent packet presence / absence information X = (a, b) indicates that the packet is a frame (for example, an Ether frame; hereinafter, when describing the recombination information Pd2, the frame is an Ether frame in order to avoid confusion with one radio frame. And an information bit indicating whether or not the packet is the first packet in the data frame (simply referred to as information) a (a = 1 is the first, a = 0 is not the first), and the packet is the last in the Ethernet frame. It consists of information bits (simply referred to as information) b (b = 1 at the end, b = 0 at the end, not the end) indicating whether it is a packet.
[0048]
In this case, the adjacent packet presence / absence information X = (a, b) = (1, 1) means that one complete ether frame is accommodated in the packet. In other words, it means that one Ethernet frame has a data length equal to or shorter than a fixed-length packet. The adjacent packet presence / absence information X = (a, b) = (1, 0) means that the packet is the head packet of the Ether frame and there is a subsequent packet. The adjacent packet presence / absence information X = (a, b) = (0, 0) means that the packet is an intermediate packet in which a subsequent packet exists after the previous packet (also referred to as a predecessor packet). The adjacent packet presence / absence information X = (a, b) = (0, 1) means that the packet follows the previous packet and is the final packet of the frame. At this time, it is assumed that the order of the packets is not changed in the transmission path.
[0049]
FIG. 4 shows a detailed configuration of the upstream data area TS15 in FIG.
[0050]
The uplink data area TS15 is divided into a plurality of time slots, and an uplink fixed length packet (also simply referred to as a packet) Pu is allocated to each. Each uplink fixed-length packet Pu includes guard time Pu1, preamble Pu2, subscriber station number Pu3, recombination information Pu4 including adjacent packet presence / absence information X, fixed-length data Pu5 that is actual data, and error detection code Pu6 It is composed of
[0051]
Note that in the case of a communication system in which data transmission of packets by time slots is performed only in the downlink, the uplink data region TS15 is not required in one radio frame. Further, in the case of a communication system in which data transmission of packets using time slots is performed only on the uplink, the downlink data area is not required in one radio frame.
[0052]
Upper and lower data areas TS12 (FIG. 2), TS15 (FIG. 4 ) Is common to the TDD / TDMA system and the FDD / TDMA system.
[0053]
The data length of one downlink fixed length packet Pd or one uplink fixed length packet Pu can be selected to be 64 bytes or 128 bytes, for example.
[0054]
FIG. 5 shows the configuration of each subscriber station 21 as an example. The subscriber station 21 basically includes an antenna 22, a high frequency circuit 32, and a communication control circuit 33 connected to the high frequency circuit 32 and the terminal 20.
[0055]
The high-frequency circuit 32 includes a receiver 41, a transmitter 42, and a one-circuit / two-contact switch 43 disposed between the transceivers 41 and 42 and the antenna 22.
[0056]
The transmitter 42 of the high frequency circuit 32 converts the intermediate frequency signal supplied from the communication control circuit 33 into a radio frequency signal by a built-in mixer and converts the radio frequency high frequency signal with a built-in power amplifier. The power is amplified and supplied to the antenna 22 via the switch 43.
[0057]
The receiver 41 of the high frequency circuit 32 inputs a radio frequency high frequency signal received by the antenna 22 via the switch 43, amplifies it with a built-in low noise amplifier, and then uses the built-in mixer to set the frequency to an intermediate frequency. The data is converted and supplied to the modulation / demodulation circuit 51 of the communication control circuit 33.
[0058]
The communication control circuit 33 includes a modulation / demodulation circuit 51, a TDD-TDM / TDMA (simply referred to as TDD / TDMA) control circuit 52, a communication interface circuit 53 connected to the terminal 20, a downlink reception buffer 61, and an uplink transmission buffer 62. The packet number measuring unit 63 is provided.
[0059]
The packet number measuring unit 63 periodically measures the number of packets stored in the uplink transmission buffer 62 for each period of one radio frame, and uses this as information of a slot request (also referred to as the number of slot requests) 71 as TDD / TDMA. This is transmitted to the control circuit 52. Information on the slot request 71 is notified from the TDD / TDMA control circuit 52 to the base station 11 through the modulation / demodulation circuit 51, the transmitter 42, the switch 43 and the antenna 22 in the time zone of the slot request area TS14 of one radio frame in FIG. The
[0060]
FIG. 6 shows a configuration of the base station 11 as an example. The base station 11 basically includes an antenna 12, a high frequency circuit 132, and a communication control circuit 34 connected to the high frequency circuit 132 and the network 13.
[0061]
The configuration and operation of the high-frequency circuit 132 are the same as those of the high-frequency circuit 32 of the subscriber station 21 shown in FIG.
[0062]
The communication control circuit 34 includes a modulation / demodulation circuit 151, a TDD-TDM / TDMA (simply referred to as TDD / TDMA) control circuit 152, a communication interface circuit 153 connected to the network 13, a slot allocation unit 54, and reception for each uplink subscriber station. A buffer 64, a downlink subscriber station transmission buffer 65, a packet number measuring unit 66, and a slot allocation storage unit 67 are provided.
[0063]
The packet number measurement unit 66 periodically measures the number of packets for each subscriber station 21 stored in the transmission buffer 65 for each downlink subscriber station for each period of one radio frame, and transmits this to the slot allocation unit 54. . The TDD / TDMA control circuit 152 13 The information of the slot request 71 of each subscriber station 21 notified in the time zone of the slot request area TS14 of one radio frame is extracted and transmitted to the slot allocation unit 54.
[0064]
The slot allocation unit 54 relates to the allocation of time slots constituting the upper and lower data areas TS12 and TS15 of the downlink and uplink based on the number of packets (number of stored packets) for each subscriber station 21 and the information of the slot request 71. A so-called schedule calculation is performed to determine which time slot is assigned to which radio frame to which subscriber station 21, information on the slot assignment 72 is determined, and the TDD / TDMA control circuit 152 is notified.
[0065]
The allocation of the time slot to the uplink data area TS15 in the uplink direction for each subscriber station 21 is notified in the time slot of the slot allocation area TS21 in one radio frame in FIG.
[0066]
The communication interface circuits 53 and 153, the TDD / TDMA control circuits 52 and 152, the packet number measuring units 63 and 66, and the slot allocating unit 54 of each subscriber station 21 and the base station 11 are respectively a CPU (central processing unit). ) Including a microcomputer, various programs are installed in a ROM (read only memory) and executed by the CPU, and when configured as hardware, an ASIC (application specific) integrated circuit) and a predetermined function is executed.
[0067]
For example, the functions of the communication interface circuits 53 and 153 will be described. Variable length data such as an Ethernet (registered trademark) frame supplied from the terminal 20 to the subscriber station 21 is stored in the subscriber station 21. The communication interface circuit 53 divides the packet into uplink fixed length packets Pu. At this time, the communication interface circuit 53 further adds recombination information Pu4 including adjacent packet presence / absence information X to each uplink fixed-length packet Pu.
[0068]
Each uplink fixed length packet Pu is assigned a slot according to the contents of the slot assignment area TS21 from the base station 11, and is transmitted from each subscriber station 21 functioning as a transmission side device through a wireless line.
[0069]
Each uplink fixed-length packet Pu received at the base station 11 functioning as a receiving side device is recombined by the communication interface circuit 153 based on the recombination information Pu4 and the like, and the presence or absence of a packet is detected. If there is no missing packet, the recombined ether frame is output as data to the network 13 side.
[0070]
The same applies to data supplied from the network 13 to the base station 11. In this case, the data is divided into downlink fixed-length packets Pd by the communication interface circuit 153 of the base station 11 that functions as a transmission side device. The recombination information Pd2 including the adjacent packet presence / absence information X is added to the downlink fixed-length packet Pd, and is transmitted to the subscriber station 21 functioning as a receiving-side apparatus through a wireless line.
[0071]
The downlink fixed-length packet Pd received by the communication interface circuit 53 of the corresponding subscriber station 21 is recombined based on the recombination information Pd2, the presence / absence of a packet loss is detected, and there is no packet loss Is transmitted to the terminal 20.
[0072]
A communication system 10 to which an embodiment of the present invention is applied is basically configured and operates as described above.
[0073]
Next, slot allocation processing by schedule calculation in the slot allocation unit 54 will be described in the following order.
[0074]
(1) Description of slot allocation processing to the downlink data area TS12 for transmitting data from the base station 11 to each subscriber station 21.
[0075]
(2) After the base station 11 receives the information of the slot request 71 from each subscriber station 21, the slot allocation processing to the uplink data area TS15 for transmitting data from each subscriber station 21 to the base station 11 Description.
[0076]
(3) Description of dynamic slot allocation processing that dynamically changes the ratio of the data amounts of the upper and lower data areas TS15 and TS12, including the processes (1) and (2) above, for each radio frame.
[0077]
First, (1) time slot allocation in the downlink data area TS12 for transmitting data from the base station 11 to each subscriber station 21 will be described with reference to the time chart of FIG.
[0078]
In this case, the number of stored packets (referred to as P) addressed to each subscriber station 21 stored in the transmission buffer 65 for each downlink subscriber station is, for example, at the boundary of one radio frame as shown in FIG. It is measured and updated by the packet number measuring unit 66 every radio frame period, and notified to the slot allocating unit 54. The slot allocation unit 54 performs schedule calculation over a time corresponding to about one radio frame period based on the notified number of stored packets addressed to each subscriber station 21, and performs slot calculation in the downlink data area TS12 of the next frame. Shall be executed.
[0079]
Here, in order to avoid the complexity of the explanation and give priority to the ease of understanding, an explanation will be given by taking an example of assignment to one subscriber station 21, but the same applies to a plurality of subscriber stations 21 as well. can do.
[0080]
Therefore, first, at the time t0 at the beginning of the radio frame N-2, the number P of accumulated packets of a certain subscriber station 21 is measured by the packet number measuring unit 66, and the measured value (here, P1) is obtained. It is assumed that it has been transmitted to the slot allocation unit 54.
[0081]
With this measured value P1, the slot allocation unit 54 starts schedule calculation at substantially the same time t0.
[0082]
Next, it is assumed that the accumulated packet number P is measured and the packet number P is updated to P = P2 at the time t1 at the beginning of the radio frame N-1.
[0083]
At that time t1, the schedule calculation of the number of stored packets P = P1 in the radio frame N-2 is completed.
[0084]
Based on this schedule calculation result, the slot allocation number for the subscriber station 21 is R1, and the slot allocation storage unit 67 stores that the slot allocation number R1 is allocated to the radio frame N-1. Note that the slot allocation number R1 is the same as the measured value P1 of the number of stored packets if there is a margin in the time slot, but it is not always the same. If the sum of the number of packets stored in all subscriber stations 21 exceeds the total number of time slots, a restriction occurs. Therefore, a variable different from the stored packet number P is given to the slot allocation number R.
[0085]
At this time t1, the slot allocation unit 54 starts a new schedule calculation based on the new accumulated packet number P = P2-R1.
[0086]
Next, at time t2, the number of stored packets equal to the number of slot allocations R1 (also referred to as the number of allocated packets) P = R1 is transferred to the subscriber in the downlink data area TS12 of the radio frame N-1. It is transmitted to the station 21. That is, in the base station 11, R1 data out of the stored packet number P2 is read from the transmission buffer 65 for each downlink subscriber station by the TDD / TDMA control circuit 152, and the modulation / demodulation circuit 151, the transmitter 142, the switch 143 And transmitted through the antenna 12.
[0087]
This transmission data is received by the receiver 41 through the wireless line, the antenna 22 of the subscriber station 21, and the switch 43.
[0088]
Received data is stored in the downlink reception buffer 61 via the modem circuit 51 and the TDD / TDMA control circuit 52.
[0089]
Next, it is assumed that the number of stored packets P has been updated to P = P3 in the measurement at the start time t3 of the radio frame N. At this time point t3, since the slot allocation number R1 is transmitted to the subscriber station 21 in the downlink data area TS12 at the time point t3, it is deleted from the transmission buffer 65 for each downlink subscriber station.
[0090]
Next, at the time t3, the schedule calculation of the number of stored packets P = P2-R1 of the radio frame N-1 ends.
[0091]
Assume that the number of slot allocations by this schedule calculation is R2. The slot allocation number R2 is used for allocation of the downlink data area TS12 of the radio frame N and is stored in the slot allocation storage unit 67.
[0092]
At this time t3, the slot allocation unit 54 starts a new schedule calculation based on the new accumulated packet number P = P3-R2.
[0093]
The data of the slot allocation number R2 is transmitted to the subscriber station 21 in the downlink data area TS12 of the radio frame N at time t4 according to the schedule. Thereafter, similar processing is repeated after time t3.
[0094]
On the other hand, in the subscriber station 21, the communication interface circuit 53 refers to the recombination information Pdu of the data packet stored in the downlink reception buffer 61, recombines the Ethernet frame, etc., and transmits the recombined information to the terminal 20. .
[0095]
As described above, according to this embodiment, one radio frame having a certain length including the downlink data region TS12 and the uplink data region TS15 divided into a plurality of time slots is repeated at a certain period, and The packet from the downlink subscriber station transmission buffer 65 is transmitted to the plurality of subscriber stations 21 in the time slot of the downlink data area TS12. Then, the packet number measuring unit 66 of the base station 11 measures the number of stored packets for each subscriber station 21 in the downlink subscriber station transmission buffer 65 at a period of one radio frame. When allocating a time slot, the slot allocation unit 54 allocates a time slot based on a value (P−R) obtained by subtracting the already allocated packet number R stored in the slot allocation storage unit 67 from the accumulated packet number P.
[0096]
As described above, the time slot allocation storage unit stores the time slot allocation in the base station 11. 6 7 and the slot allocation unit 54 assigns the number of packets already allocated in the slot allocation storage unit 67 by subtraction correction when allocating time slots based on the number of measured packets. During the calculation (from the time when the number of packets is measured until the slot is assigned), the time slot is not duplicated and assigned to the already transmitted data already transmitted to the subscriber station 21 in the downlink data area TS12. It is possible to avoid wasting time slots.
[0097]
In practice, in this embodiment, when the slot allocation unit 54 allocates a time slot in the current one radio frame N, based on a value obtained by subtracting the slot allocation number R1 allocated in the previous radio frame N-1. By assigning, it is possible to prevent a time slot from being assigned to a previously sent packet.
[0098]
Next, (2) after the base station 11 receives the information of the slot request 71 from each subscriber station 21, the uplink data area TS15 for transmitting data from each subscriber station 21 to the base station 11 on the uplink The slot allocation process will be described with reference to the time chart of FIG.
[0099]
Here, in order to avoid the complexity of the explanation and give priority to the ease of understanding, an explanation will be given by taking an example of assignment to one subscriber station 21, but the same applies to a plurality of subscriber stations 21 as well. can do.
[0100]
In this case, the number of packets stored for each subscriber station 21 stored in the uplink transmission buffer 62 of the subscriber station 21 (referred to as Q to distinguish from the above P) is, for example, one radio frame in FIG. Is measured and updated by the packet number measurement unit 63 every one radio frame period at the boundary.
[0101]
The number Q of stored packets is the slot request 71 information (referred to as the slot request number) in the slot request area TS14 of the uplink, and the TDD / TDMA control circuit 52, the modem circuit 51, and the transmitter 42 of each subscriber station 21. The signal is transmitted through the switch 43 and the antenna 22, and is received by the receiver 141 through the antenna 12 and the switch 143 of the base station 11 through the wireless line. The received information is notified to the slot allocation unit 54 through the modem circuit 151 and the TDD / TDMA control circuit 152 as information of the slot request 71 (number of slot requests).
[0102]
The slot allocation unit 54 performs schedule calculation over a time corresponding to about one radio frame period based on the notified number of slot requests addressed to each subscriber station 21, and until the slot allocation area TS21 of the next frame is reached. The schedule calculation is terminated and slot allocation processing is executed. The slot allocation number allocated in this allocation process is referred to as U.
[0103]
Therefore, first, it is assumed that the measured value of the number Q of stored packets of a certain subscriber station 21 is measured as Q1 by the packet number measuring unit 63 at the start time t10 of the radio frame N-4. At this time t10, the slot allocation unit 54 of the base station 11 starts the schedule calculation. However, since the slot request 71 information (number of slot requests) is not actually received, as described later, Nothing is assigned.
[0104]
Next, in the uplink slot request region TS14 of the radio frame N-4 at time t11, the measured value Q1 of the accumulated packet number Q measured at the subscriber station 21 at time t10 is the slot request number (equal value). Q1.) Is transmitted from the subscriber station 21 and supplied to the slot allocation unit 54 of the base station 11.
[0105]
Next, in the measurement at the beginning time t14 of the radio frame N-3, the number Q of packets stored in the uplink transmission buffer 62 is updated to Q = Q2.
[0106]
At this time t14, the slot allocation unit 54 of the base station 11 confirms the number of slot requests at the present time, and since the value is Q1, the schedule calculation based on the number of slot requests Q1 is started.
[0107]
Next, in the slot request area TS14 at time t15, the accumulated packet number Q2 measured by the packet number measurement unit 63 of the subscriber station 21 at time t14 is supplied to the slot allocation unit 54 of the base station 11 as the slot request number Q2. Is done.
[0108]
Further, the stored packet count Q of the subscriber station 21 is measured as Q = Q3 at the start time t16 of the radio frame N-2.
[0109]
Further, at time t16, the schedule calculation started from time t14 ends, and a slot is allocated. The number of assigned slots is U1. The slot allocation number U1 is stored in the slot allocation storage unit 67.
[0110]
Further, at time t16, the slot allocation unit 54 confirms the slot request number Q2, and schedule calculation based on a value Q2-U1 obtained by subtracting the slot allocation number U1 from the slot request number Q2 is started.
[0111]
Next, at time t17, the uplink data area TS15 of the radio frame N-2 is scheduled to transmit the same number of stored packets as the slot allocation number U1, and the schedule for the downlink of the radio frame N-2 is set. The subscriber station 21 is notified in the slot allocation area TS21.
[0112]
Next, at time t18, the stored packet count Q3 of the subscriber station 21 is notified to the slot allocation unit 54 of the base station 11 as the slot request count Q3.
[0113]
Next, in the subscriber station 21, according to the schedule, data of the slot allocation number U1 is read from the uplink transmission buffer 62 by the TDD / TDMA control circuit 52 at time t19. Then, the read data is transmitted from the subscriber station 21 to the base station 11 via the radio line in the uplink data area TS15 of the radio frame N-2 at the time t19, and the uplink of the base station 11 is transmitted. It is stored in the reception buffer 64 for each subscriber station.
[0114]
At time t19, since the data of the slot allocation number U1 is read from the uplink transmission buffer 62 of the subscriber station 21, the number of stored packets is decreased by U1.
[0115]
Next, at the start time t20 of the radio frame N-1, the number Q of stored packets in the subscriber station 21 is measured as Q = Q4.
[0116]
At this time t20, the schedule calculation started from the time t16 is completed, and a slot is allocated. The number of assigned slots is U2. The slot allocation number U2 is stored in the slot allocation storage unit 67.
[0117]
Furthermore, at this time t20, the slot allocation number 54 is confirmed by the slot allocation unit 54, and schedule calculation based on the value Q3- (U2 + U1) obtained by subtracting the slot allocation number U2 + U1 from the slot request number Q3 is started.
[0118]
Next, at time t21, the uplink data area TS15 of the radio frame N-1 is scheduled to transmit the same number of stored packets as the slot allocation number U2, and the schedule for the downlink of the radio frame N-1 is set. The subscriber station 21 is notified in the slot allocation area TS21.
[0119]
Next, at time t22, the stored packet count Q4 of the subscriber station 21 is notified to the slot allocation unit 54 of the base station 11 as the slot request count Q4.
[0120]
Next, in the subscriber station 21, according to the schedule, data of the slot allocation number U2 is read from the uplink transmission buffer 62 by the TDD / TDMA control circuit 52 at time t23. Then, the read data is transmitted from the subscriber station 21 to the base station 11 via the radio line in the uplink data area TS15 of the radio frame N-1 at the time t23, and the uplink of the base station 11 is transmitted. It is stored in the reception buffer 64 for each subscriber station.
[0121]
At time t23, since the data of the slot allocation number U2 is read from the uplink transmission buffer 62 of the subscriber station 21, the number of stored packets is decreased by U2.
[0122]
Next, at the start time t24 of the radio frame N, the number Q of stored packets in the subscriber station 21 is measured as Q = Q5.
[0123]
At this time point t24, the schedule calculation started from the time point t20 is completed, and a slot is assigned. The number of assigned slots is U3. The slot allocation number U3 is stored in the slot allocation storage unit 67.
[0124]
Further, at time t24, the slot allocation unit 54 confirms the slot request number Q4, and schedule calculation based on a value Q4- (U3 + U2) obtained by subtracting the slot allocation number U3 + U2 from the slot request number Q4 is started.
[0125]
Next, at time t25, the uplink data area TS15 of the radio frame N is scheduled to transmit the same number of stored packets as the slot allocation number U3, and the downlink slot allocation area TS21 of the radio frame N is transmitted. Then, the subscriber station 21 is notified.
[0126]
The data of the accumulated packet number U3 is transmitted and stored in the uplink data area TS15 of the radio frame N from the subscriber station 21 to the uplink subscriber station reception buffer 64 of the base station 11 according to the schedule. Thereafter, the same processing as that after time t24 is repeated.
[0127]
On the other hand, the communication interface circuit 153 of the base station 11 refers to the data recombination information Pdu stored in the reception buffer 64 for each upstream subscriber station 21, recombines the Ethernet frame, etc., and transmits it to the network 13. Is done.
[0128]
According to the above-described embodiment, an uplink in which transmission from a plurality of subscriber stations 21 to a single base station 11 is performed, and a downlink in which transmission from the base station 11 to a plurality of subscriber stations 21 is performed. There is one radio frame of a certain length that is repeated at a certain period including: a slot request area TS14 for requesting time slots from a plurality of subscriber stations 21 to the base station 11 and a plurality of subscribers on the uplink In order to send a packet from the station 21 to the base station 11, an uplink data region TS15 divided into a plurality of time slots is included, and information on the slot allocation 72 from the base station 11 is transmitted to the plurality of subscriber stations 21 in the downlink. And a downlink data area TS12 divided into a plurality of time slots in order to send packets from the base station 11 to the plurality of subscriber stations 21.
[0129]
Each subscriber station 21 measures the number Q of stored packets stored in the uplink transmission buffer 62 with a constant period equal to the period of one radio frame by the packet number measuring unit 63. The measurement value Q is transmitted as the slot request number Q in the slot request area TS14.
[0130]
The base station 11 allocates the time slot of the uplink data area TS15 by the slot allocation unit 54 based on the slot request number Q.
[0131]
Further, the slot allocation unit 54 stores the time slot allocation in the slot allocation storage unit 67.
[0132]
Then, when allocating the time slot of the uplink data area TS15 based on the slot request number Q, the slot allocation unit 54 allocates based on the value obtained by subtracting the number of time slots already allocated to the slot allocation storage unit 67.
[0133]
As described above, when assigning the time slot of the uplink data area TS15, the slot assignment unit 54 of the base station 11 is already assigned from the slot request number Q from the subscriber station 21 and stored in the slot assignment storage unit 67. Since the number of assigned time slots is subtracted and assigned, reassignment of time slots to already transmitted packets is prevented, and waste of time slots can be avoided in advance.
[0134]
In this case, since the data transmission apparatus is a TDMA transmission apparatus, a procedure for transmitting the packet count Q measured by the subscriber station 21 as the slot request count Q is required. For this reason, when transmitting data in the uplink direction, when the slot allocation unit 54 allocates a time slot in the current radio frame N, the radio frames N-1 and N-2 to which the previous and previous time slots are allocated. By assigning based on the value {for example, Q4− (S3 + S2)} obtained by subtracting the time slot assigned in step 1, reassignment of the time slot to the already transmitted packet is prevented, and waste of the time slot is avoided in advance. .
[0135]
Note that this uplink slot allocation requires transmission and reception in the slot request area TS14 from the subscriber station 21 having the slot request number Q as compared with the downlink slot allocation. Allocation is increased by one radio frame.
[0136]
When the time for schedule calculation is not a time of one radio frame but a time of two radio frames, for example, when assigning a time slot in the radio frame N, the radio to which the previous and previous time slots were assigned is assigned. The frames may be N-2, N-3, and N-4.
[0137]
Next, (3) dynamic slot allocation that dynamically changes the ratio of the respective data amounts of the upper and lower data areas TS15 and TS12 in one radio frame, including the processes (1) and (2) above. The processing will be described with reference to the flowchart of FIG. For ease of understanding, description will be made with reference to the time charts of FIGS.
[0138]
In this case, the slot allocation unit 54 performs, for example, the schedule calculation for the downlink time slot allocation shown in FIG. 7 and the allocation of the uplink time slot shown in FIG. Schedule calculations are simultaneously performed in parallel, and based on the allocation result, time slots are dynamically allocated to the downlink data area TS12 and the uplink data area TS15 in the same radio frame. That is, the total number of time slots allocated to the downlink data area TS12, the uplink data area, and TS15 in one radio frame is constant, but when this total number is S, for example, the number of slot allocations to the downlink data area TS12 However, if it is Sd, a large number of slots corresponding to the number of remaining S-Sd is allocated to the upstream data area TS15. By controlling in this way, time slots can be used effectively, and there is a high possibility that data can be transmitted from the base station 11 to the subscriber station 21 or from the subscriber station 21 to the base station 11 in a short time.
[0139]
Each process shown in the flowchart of FIG. 9 is executed by the slot allocation unit 54 of the base station 11.
[0140]
In steps A1 to A3 in the flowchart, the data transmission amount between the base station 11 and the subscriber station 21 is determined. Here, the process of steps B1 to B6 showing the details of the process of step A1 is the part for performing the correction calculation described above.
[0141]
In this case, in the processing of Steps B1 to B4, in order to perform the time slot allocation processing of the uplink data region TS15 in the radio frame N, the allocation processing performed in the radio frame N-2 and the radio frame N-1 is considered, respectively. Perform subtraction correction processing. This subtraction correction process is a slot allocation process that is performed at time t20 in FIG. 8, and the result of the schedule calculation based on it is performed at time t25.
[0142]
Further, in the processing of steps B5 and B6, in order to perform the time slot allocation processing of the downlink data region TS12 in the radio frame N, subtraction correction processing is performed in consideration of the allocation processing performed in the radio frame N-1. This subtraction correction process is a slot allocation process performed at time t1 in FIG. 7, and the result of the schedule calculation based on the subtraction correction process is performed at time t3. As described above, the correction calculation here does not need to receive the notification of the number of slot requests from the subscriber station 21, and therefore does not need to consider the correction of the radio frame N-2.
[0143]
In step A1, therefore, the packet number measurement unit 63 of the subscriber station 21 and the packet number measurement unit 66 of each base station 11 measure the number of packets and the slot allocation unit 54 of the base station 11 assigns slots. The number of packets is corrected based on the time difference between.
[0144]
In the process of step B1 that constitutes step A1, correction calculation is necessary for the subscriber station 21 to which the allocation has been performed, so the allocation process of the radio frame N-2 is confirmed (the above-mentioned slot allocation number U1).
[0145]
In the process of step B2, correction calculation is performed to subtract the slot allocation number U1 allocated in the allocation process of the radio frame N-2 from the slot request count Q3 of the radio frame N-2 (Q3-U1).
[0146]
Next, in the process of step B3, since correction calculation is required for the subscriber station 21 to which the allocation has been performed, the allocation process of the radio frame N-1 is confirmed (the above-described slot allocation number U2).
[0147]
In the process of step B4, correction calculation is performed to subtract the slot allocation number U2 allocated in the allocation process of the radio frame N-1 from the slot request count Q3 of the radio frame N (Q3-U2).
[0148]
Next, in the process of step B5, since correction calculation is required for the subscriber station 21 to which the allocation has been performed, the allocation process of the radio frame N-1 is confirmed (the above-mentioned slot allocation number R1).
[0149]
In the process of step B6, a correction calculation is performed to subtract the slot allocation number R1 allocated in the allocation process of the radio frame N-1 from the accumulated packet number P2 of the base station 11 {described above (P2-R1)}.
[0150]
Next, in step A2, the distribution amount of the number of time slots in the upper and lower data areas TS12 and TS15 in the radio frame N is determined from the number of packets after subtraction correction.
[0151]
In practice, when determining this distribution, if the number of time slots is equal to or less than the total number of time slots in the upper and lower data areas TS12 and TS15 of one radio frame, What is necessary is just to allocate a slot allocation number. In this way, data of the number of packets corresponding to the number of time slots allocated in one radio frame can be transmitted in one radio frame, and the transmission time is shortened.
[0152]
Of course, the time slot may not be allocated in one frame. In this case, if the time slot is distributed to the upper and lower data areas TS12 and TS15 so that the number of radio frames to be used is minimized at this time. Good.
[0153]
Next, in step A3, since there are actually a plurality of subscriber stations 21, slot allocation is performed in the upper and lower data areas TS12 and TS15 so that the data transfer rates to the plurality of subscriber stations 21 are equal, that is, fair. The subscriber station number for notifying the user or the subscriber station number for transferring data is determined.
[0154]
In addition, the base station 11 determines the subscriber station number that permits the notification of the packet measurement value to the subscriber station 21, that is, the notification of the number of slot requests, so that the data transfer rate is equal, that is, fair.
[0155]
The slot allocation numbers satisfying these are determined as the slot allocation numbers R2 and U3 in step A3.
[0156]
As described above, according to the embodiment described above, an uplink in which transmission from the plurality of subscriber stations 21 to the base station 11 is performed, and a downlink in which transmission from the base station 11 to the plurality of subscriber stations 21 is performed. And a radio frame having a fixed length that repeats at a fixed cycle, and a slot request region TS14 for requesting time slots from the plurality of subscriber stations 21 to the base station 11 and a plurality of subscriber stations on the uplink An uplink data area TS15 divided into a plurality of time slots for transmitting packets from the base station 11 to the base station 11 is included, and a slot for notifying the plurality of subscriber stations 21 of slot allocation from the base station 11 is included in the downlink. An allocation area TS21 and a downlink data area TS12 divided into a plurality of time slots for transmitting packets from the base station 11 to the plurality of subscriber stations 21 are included.
[0157]
Each of the plurality of subscriber stations 21 includes an upstream transmission buffer 62 and a packet number measuring unit 63 that measures the number of packets in the upstream transmission buffer 62, and the upstream transmission buffer 62 at a constant cycle that is the same cycle as one radio frame. The number of packets inside is measured, and this measured value is transmitted as the number of time slot requests in the slot request area TS14.
[0158]
The base station 11 measures the number of packets addressed to each subscriber station in the transmission buffer 65 for each downlink subscriber station by the packet number measuring unit 66 at a constant period of the same period as one radio frame.
[0159]
Then, the slot allocation unit 54 allocates time slots in the downlink data area TS12 based on the measured number of packets, and allocates time slots in the uplink data area TS15 based on the number of time slot requests.
[0160]
Further, the assigned time slot assignment is stored in the slot assignment storage unit 67.
[0161]
In this case, the slot allocation unit 54 allocates the time slot of the downlink data region TS12 based on the number of measurement packets and allocates the time slot of the uplink data region TS15 based on the number of time slot requests. The number is assigned based on a value obtained by subtracting the number of timeslots already assigned and stored in the slot assignment storage unit 67, and the distribution amount of the upper and lower data areas is determined and assigned.
[0162]
In this way, since slot allocation within one radio frame can be dynamically performed, packet retransmission can be prevented to avoid wasting time slots, and high-speed packet transfer is possible. .
[0163]
Next, FIG. 10 shows a configuration example of the FDD subscriber station 21A. FIG. 11 shows a configuration example of the FDD-type base station 11A. FIG. 12 shows the structure of an FDD radio frame.
[0164]
10 of the FDD system and the subscriber station 21 of FIG. 5 of the TDD system, the base station 11A of FIG. 11 of the FDD system, the base station 11 of FIG. 6 of the TDD system, and the FDD system. In the radio frame of FIG. 12 and the radio frame of FIGS. 13, 2, and 3 of the TDD system described above, the same reference numerals are assigned to corresponding elements, and detailed description thereof is omitted.
[0165]
Since the FDD scheme is frequency multiplexing, different radio frequencies are used in the uplink direction and the downlink direction. Therefore, the switches 43 and 143 constituting the TDD type high frequency circuits 32 and 132 are replaced with diplexers 44 and 144 in the FDD type as shown in FIGS. As is well known, the diplexers 44 and 144 are composed of a bandpass filter for reception frequency and a bandpass filter for transmission frequency, respectively, and lead output signals from the transmitters 42 and 142 to the antennas 12 and 22 side, respectively. The signal transmitted and received by the antennas 12 and 22 is guided to the receivers 41 and 141 side.
[0166]
On the other hand, as is clear from FIG. 13 and FIG. 12, one radio frame is divided in series in the downlink and the uplink in the TDD scheme, whereas in the FDD scheme, the radio frame is divided. The downlink radio frame and the uplink radio frame are configured in parallel.
[0167]
The downlink data area TS12 in the downlink radio frame shown in FIG. 12 has the same configuration as the downlink fixed length packet Pd shown in the downlink data area TS12 of FIG.
[0168]
Similarly, the uplink data area TS15 in the uplink radio frame shown in FIG. 12 has the same configuration as the uplink fixed length packet Pu shown in the uplink data area TS15 in FIG.
[0169]
The slot allocation unit 54 shown in FIG. 11 can perform correction calculation using the algorithm shown in FIG. 9 as in the TDD scheme. In the FDD scheme, the dynamic slot allocation scheme cannot be adopted in the scheme.
[0170]
The present invention is not limited to the above-described embodiment, and may be applied to, for example, a bidirectional optical line in which a base station and a subscriber station are connected by an optical fiber instead of a wireless line as a transmission line. Of course, various configurations can be adopted without departing from the gist of the present invention.
[0171]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent time slots from being allocated to already transmitted data (packets) by considering the allocation of existing slots.
[0172]
Further, the present invention can avoid wasting time slots.
[0173]
Further, according to the present invention, although the total capacity of the downstream area data amount and the upstream area data amount is constant, the ratio of each data amount is dynamically changed for each communication frame (one wireless frame or one wired frame). In the dynamic slot allocation method, it is possible to avoid wasting time slots by allocating time slots to already transmitted packets.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a communication system to which an embodiment of the present invention is applied.
FIG. 2 is a structural diagram of a downlink data area and a downlink fixed-length packet.
FIG. 3 is an explanatory diagram of adjacent packet presence / absence information.
FIG. 4 is a structural diagram of an uplink data area and an uplink fixed length packet.
FIG. 5 is a block diagram showing a configuration of a TDD subscriber station.
FIG. 6 is a block diagram showing a configuration of a TDD base station.
FIG. 7 is a time chart used for explaining slot allocation processing in a downlink data area.
FIG. 8 is a time chart used for explaining slot allocation processing in an uplink data area.
FIG. 9 is a flowchart for explaining dynamic slot allocation processing;
FIG. 10 is a block diagram showing a configuration of an FDD subscriber station.
FIG. 11 is a block diagram showing a configuration of an FDD base station.
FIG. 12 is a configuration diagram of an FDD radio frame.
FIG. 13 is a configuration diagram of a TDD radio frame.
[Explanation of symbols]
10: Communication system 11, 11A: Base station
13 ... Network 20 ... Terminal
21, 21A ... subscriber station 54 ... slot allocation unit
62: Upstream transmission buffer 63, 66: Number of packets measuring unit
65 ... Transmission buffer for each downlink subscriber station 67 ... Slot allocation storage unit
71 ... Slot request 72 ... Slot allocation

Claims (5)

A communication frame having a certain length including a downlink data area divided into a plurality of time slots is repeated at a certain period, and packets read from a transmission buffer of a single base station are transmitted to a plurality of subscriber stations in the downlink data area. In a data transmission device that transmits in time slots,
The base station
A packet number measuring unit that periodically measures the number of packets addressed to the subscriber station in the transmission buffer for each period of one communication frame;
A slot allocation unit that allocates time slots based on the measured number of packets;
A slot assignment storage unit for storing time slot assignments;
The slot allocation unit allocates the time slot based on a value obtained by subtracting the number of already allocated packets stored in the slot allocation storage unit from the number of measured packets. Transmission equipment. The data transmission apparatus according to claim 1, wherein
When the data transmission device is a time division multiplexing data transmission device,
The data transmission device according to claim 1, wherein when the slot allocation unit allocates a time slot in the current communication frame, the slot allocation unit allocates the time slot based on a value obtained by subtracting the number of packets allocated in the previous communication frame. Repeated at a constant cycle including an uplink in which transmission from a plurality of subscriber stations to a single base station and a downlink in which transmission from the single base station to the plurality of subscriber stations is performed There is a communication frame of a certain length,
The uplink includes a slot request area for requesting a time slot from the plurality of subscriber stations to the single base station, and a plurality of slots for transmitting packets from the plurality of subscriber stations to the single base station. The upstream data area divided into the time slots of
In the data transmission apparatus, the downlink includes a slot allocation area for notifying the plurality of subscriber stations of slot allocation from the base station,
Each of the plurality of subscriber stations has a transmission buffer and a packet number measurement unit that measures the number of packets in the transmission buffer, and periodically measures the number of packets in the transmission buffer for each period of one communication frame. Then, this measured value is transmitted as the number of time slot requests in the slot request area,
The base station has a slot allocation unit that allocates the time slot of the uplink data area based on the received number of time slot requests, and a slot allocation storage unit that stores the allocation of the time slot,
The slot allocating unit allocates the time slot of the uplink data area based on a value obtained by subtracting the number of already allocated time slots stored in the slot allocation storing unit from the number of time slot requests. Data transmission equipment. The data transmission apparatus according to claim 3, wherein
When the data transmission device is a time division multiple access data transmission device,
When the slot allocation unit allocates a time slot in the current communication frame, the slot allocation unit allocates based on a value obtained by subtracting the time slot allocated in the previous and previous communication frames from the number of time slot requests. . Repeated at a constant cycle including an uplink in which transmission from a plurality of subscriber stations to a single base station and a downlink in which transmission from the single base station to the plurality of subscriber stations is performed There is a communication frame of a certain length,
The uplink includes a slot request area for requesting a time slot from the plurality of subscriber stations to the single base station, and a plurality of slots for transmitting packets from the plurality of subscriber stations to the single base station. The upstream data area divided into the time slots of
The downlink is divided into a slot allocation area for notifying the plurality of subscriber stations of slot allocation from the base station, and a plurality of time slots for transmitting packets from the base station to the plurality of subscriber stations. In a data transmission apparatus including a downstream data area,
Said plurality of subscriber stations, respectively, and the transmission buffer has packet counting unit for counting the number of packets in the transmission buffer, and measuring the number of packets of periodic manner wherein in the transmit buffer, the measured value In the slot request area as the number of time slot requests,
The base station
A packet counting unit for counting the number of packets per addressed subscriber station in the transmission buffer of itself, periodic manner,
A slot allocation unit that allocates the time slot of the downlink data area based on the measured number of packets and allocates the time slot of the uplink data area based on the received number of time slot requests;
A slot assignment storage unit for storing time slot assignments;
The slot allocation unit allocates the time slot of the downlink data area based on the number of measurement packets and allocates the time slot of the uplink data area based on the number of time slot requests. from the request number, to allocate, based on the respective values of the number of time slots were subtract already assigned is stored in the slot assignment storage unit
Data transmission device comprising a call.

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