JP2008028430A - Transmitter apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure a transmission band by preferentially transmitting packets of data such as AV data needing real time performance. <P>SOLUTION: A transmitter apparatus used in a transmission network where a minimum packet transmission interval is prescribed is provided with: packet generating part for generating a packet from input data; a packet transmitting part for transmitting the packet to the transmission network; and a packet transmission control part, wherein the packet transmission control part controls the transmission of the packet transmitting part such that the packet transmitting part transmits the packets at a packet transmission interval shorter than the minimum packet transmission interval. Thus, even if any interfering terminals get into the system, since the transmitter apparatus can preferentially transmit the AV packets (AV data) and the transmission band of wireless packets for AV services can be ensured, the AV transmission services with high quality can be provided, where the real time performance of the video data and the audio data is ensured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmission apparatus that transmits data via a transmission network.

  Conventionally, systems for distributing video data, audio data (hereinafter referred to as AV data), etc. via a network (transmission network) have been put into practical use. In particular, in recent years, the use of wireless for network transmission lines is increasing because of the labor saving of wiring and the fact that a network can be used anywhere without worrying about the location. As a specific example, a system for wirelessly transmitting a program such as a video to a terminal of each user in a closed space such as a moving body such as an aircraft or a hall has been developed.

  FIG. 11 is a schematic diagram of an AV data distribution system by wireless transmission. In FIG. 11, 1100 is a video server, 1101 is a wireless access point (hereinafter referred to as AP), and 1102 to 1109 are wireless terminals (hereinafter referred to as AV terminals) for viewing AV data. AV data output from the video server 1100 is distributed wirelessly from the AP 1101 to AV terminals (1102 to 1109).

  Any wireless may be used in the AV data distribution system. As an example, there is a wireless transmission method defined in IEEE 802.11 that is used in a wireless LAN. For the details of IEEE802.11, many technical books have been issued. For example, "802.11 high-speed wireless LAN textbook" (issued by IDG Japan Co., Ltd.) is detailed. Hereinafter, description will be given by taking IEEE 802.11 as an example.

  In IEEE 802.11, CSMA / CA (Carrier Sense Multiple Access with Collision Avidance) is adopted to avoid collision of radio transmission packets from each radio terminal. Each wireless terminal transmits (accesses) a packet after confirming that the transmission path is not used continuously for a certain period of time. That is, packet transmission is performed with a predetermined packet transmission interval. As a method for confirming that the transmission line is not used continuously for a certain period of time, the wireless terminal constantly monitors the radio wave (carrier), and if the radio carrier is not detected, the radio of the channel is not used. Judge.

  In the description of this application, generally, in wireless transmission, a transmission unit below the second layer (data link layer) of the OSI reference model is conventionally called a frame, and a transmission unit above the third layer (network layer) is a packet. However, in the present application, the term “transmission unit” is unified to a packet.

  FIG. 9 is a timing chart for explaining wireless access (transmission) by IEEE 802.11 CSMA / CA. FIG. 10 shows parameters related to the packet transmission interval used in the wireless access by CSMA / CA. In CSMA / CA, a waiting time before each terminal transmits a radio packet is defined. An individual value is defined for the waiting time depending on the type of wireless packet to be transmitted. This waiting time is the transmission interval between packets.

  The waiting time in transmitting general data (also applicable to AV data) is a fixed waiting time DIFS (Distributed Inter Frame Space) plus a random waiting time Backoff. Backoff, which is a random value, prevents a situation where a plurality of terminals simultaneously transmit packets after a predetermined time from the end of the previous packet transmission and radio packets collide. The transmitting terminal can transmit the data packet 901 after the time of DIFS (911) and Backoff (912) from the end timing 920 of the wireless carrier 900 detected in the wireless transmission network. Here, DIFS is the time that must be waited when sending a general data packet as described above. Backoff is a multiple of a fixed time (slot time) and is a random value. This random value is generated within the contention window (CW) range. That is, the transmission waiting time is obtained by multiplying the slot time and the random value. The value of CW increases from the first transmission every time the number of retransmissions increases. Since Backoff is determined by a random number, a transmission terminal (terminal with the shortest Backoff) that first acquires a transmission right in the wireless system can transmit a packet. That is, each wireless terminal is given a fair transmission opportunity. The DIFS time, slot time and CW size are shown in FIG.

  Confirmation that data is actually transmitted correctly to the receiving terminal is determined by whether or not an ACK (Acknowledge) signal from the receiving terminal arrives. If there is no ACK signal, it is determined that there is a communication failure and data is retransmitted. To do. That is, the transmitting terminal transmits a data packet to the receiving terminal and receives an ACK from the receiving terminal, thereby completing a series of data communication. If ACK cannot be received within a certain period of time, retransmission is performed a predetermined number of times until ACK is received. The transmission confirmation ACK (902) is transmitted after the SIFS 913 interval after the transmission of the data packet 901 (921). This SIFS (Short Interframe Space) is a fixed value, and is the shortest transmission waiting time (minimum packet transmission interval) in the IEEE802.11 standard. This is because ACK is transmission confirmation, and therefore it is necessary to notify the transmission side with priority over other packets.

  As described above, in IEEE802.11 (CSMA / CA), by defining the waiting time until wireless packet transmission, wireless packets are transmitted simultaneously from wireless terminals and collided as wireless radio waves. It has a mechanism that eliminates as much as possible the risk that the waveform is disturbed and the packet is discarded as a result.

  Here, problems that may occur when an AV data distribution system is realized by CSMA / CA will be described. As described above, since each wireless terminal is given a fair transmission opportunity, as shown by 1110 and 1111 in FIG. 11, even when a wireless terminal such as a personal computer is brought into the system, a fair packet transmission opportunity is provided. Therefore, for the AV data distribution system, the packet cannot be transmitted at the transmission timing necessary for the system, and the terminal becomes an obstacle. As a specific example, when a video is distributed by the AV data wiring system in the above-mentioned aircraft, a personal computer brought in by a passenger may have a wireless communication function, which interferes with the system.

  In FIG. 11, since the personal computer 1110 accesses the AP 1101 and transmits data to the personal computer 1111 via the AP 1101 or directly transfers data from the personal computer 1110 to the personal computer 1111 in the ad hoc mode, the AV data is consumed. The wireless band that can be used by the distribution system is under pressure. Since the AV data is required to be transmitted in real time, if the AV data cannot be transmitted at a necessary timing, the real time cannot be secured, and the quality of video / audio deteriorates. Hereinafter, terminals such as personal computers 1110 and 1111 that interfere with the AV data distribution system are referred to as disturbing terminals.

  The above problem is caused by the fact that a transmission opportunity is impartially given by DIFS and random Backoff when transmitting a data packet. From another point of view, it is possible to change the packet priority by changing the waiting time until packet transmission. As such an example, there is Patent Document 1 (Japanese Patent Laid-Open No. 11-220497).

Patent Document 1 discloses a method in which a large amount of data is input as transmission data from a circuit-switched service by performing higher priority control and circuit control than ACK using a frame interval shorter than ACK, and packet-switched service such as radio When the transmission cannot be performed by one transmission within the accessible time of, that is, when a fragment is generated, the remaining packet of the fragment is transmitted adjacently.
JP-A-11-220497 802.11 high-speed wireless LAN textbook (issued by IDG Japan)

  However, the above conventional method has the following problems. As described also in FIG. 3 of Patent Document 1, the terminal 3 transmits data (acquires transmission right) immediately after the packet A is transmitted from the terminal 2. Since the first packet until the fragment occurs waits for a random period in addition to DIFS, there is a problem that the transmission priority of the first packet is not necessarily included even when the fragment does not occur. In other words, each terminal basically has a transmission priority right and does not exclude the influence of an interfering terminal.

  The method of Patent Document 1 is a method that does not return an ACK for the first packet of a fragment, but returns an ACK after all fragmented packets have arrived. In other words, ACK is not returned for each packet in the CSMA / CA environment. For example, even if an error occurred in the middle of a fragment packet, an error occurred unless the remaining packets were transmitted. Since we do not know, transmission is inefficient. The inefficiency of transmission will be specifically described. For example, assume that data P is input from a circuit-switched service, fragmented in a packet-switched service, and transmitted in packets P1, P2, and P3. At this time, even if the packet of P1 or P2 is not transmitted / received normally and an error occurs, an ACK to P1 and P2 is not returned, so the transmitting terminal continues until transmission of P3. After that, an ACK for all of P1, P2, and P3 is returned, and since an error is known for the first time, retransmission is performed. In addition, since all of P1, P2, and P3, that is, all of P must be retransmitted, the transmission band is consumed correspondingly, resulting in very inefficient transmission. This problem is due to the fact that ACK is not performed for packet units (in the above, individual packets of P1, P2, and P3) in the packet switching service.

  As shown in FIG. 1 of Patent Document 1, since SIFS, which is an original ACK transmission waiting time, is used for a fragment packet and 2 SIFS is used for the original ACK, only the ACK transmission waiting time is increased. It is. Accordingly, since it takes time until ACK transmission, the usable bandwidth as a whole is reduced.

  In order to solve the above-described problems, the present invention provides a packet generation unit that generates a packet from input data in a transmission network in which a minimum packet transmission interval is defined, and a packet transmission unit that transmits the packet to the transmission network. And packet transmission control means for performing transmission control of the packet transmission means so as to transmit the packet at a transmission interval shorter than the minimum packet transmission interval.

  Thus, even when a disturbing terminal enters the AV data distribution system wirelessly, it is possible to always transmit a priority packet such as an AV packet with priority, and a transmission device that guarantees a band for AV data transmission. It can be provided.

  According to the transmission apparatus of the present invention, even when an interfering terminal enters the system, AV packets (AV data) can be preferentially transmitted and the transmission band of the AV service wireless packet is guaranteed. It is possible to provide a high-quality AV transmission service that guarantees real-time performance such as audio data.

  The above effect is effective regardless of the data rate of AV data.

  Further, since the waiting time at the time of priority packet transmission is short, the overall usable bandwidth is improved, and the transmission bandwidth of the transmission network can be effectively utilized.

  The present invention can be applied not only during unicast transmission but also during multicast transmission.

  In addition, since ACK at the time of unicast is not transmitted in units of fragments, but is returned in units of wireless packets, retransmission is performed in units of packets in which errors occur even when packet errors are retransmitted. It is possible to provide a system with high transmission efficiency without retransmitting received packets. .

  In addition, the priority packet according to the present invention is preferentially transmitted when a fragment is generated as in Patent Document 1, and transmission of the priority packet is given priority in any case, and an effect peculiar to the present invention is obtained. It is possible.

  In addition, the present invention can be easily modified in various ways by changing the means for controlling packet transmission, and it is possible to construct various systems that guarantee the transmission bandwidth of priority data packets with a simple configuration. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiment of the present invention, a wireless transmission network conforming to IEEE802.11a will be described as an example of a data link layer transmission method. The transmission data to be transmitted may be any data, but as an example, it is assumed that data (AV data) such as video and audio that requires real-time transmission. A packet composed of AV data is referred to as an AV packet, and the AV packet is referred to as a priority data packet in distinction from a normal data packet because the transmission band must be guaranteed to maintain real-time characteristics. Packets other than priority data packets are called normal data packets.

  In this embodiment, as shown in FIG. 11, a wireless infrastructure mode for distributing AV data from an access point to each terminal will be described as an example of an AV data distribution system.

(Embodiment 1)
In the present embodiment, a case where priority data packets are transmitted by unicast will be described. Unicast is a one-to-one communication from a transmitting terminal to one receiving terminal. FIG. 1 is a schematic diagram illustrating a configuration of a transmission apparatus according to the present application. In FIG. 1, reference numeral 100 denotes a transmission apparatus according to the present application, which corresponds to the AP 1101 in FIG. Reference numeral 101 denotes packet generation means, 102 denotes packet transmission means, 103 denotes packet transmission control means, 104 denotes carrier sensing means, and 105 denotes a transmission / reception antenna.

  FIG. 8 is a schematic diagram of a packet format in the MAC layer that is a data link layer of IEEE802.11a. In FIG. 8, 800 indicates the entire MAC packet. Reference numeral 801 denotes a MAC header, which defines 30 octets. However, in infrastructure mode, 24 octets are used because part of the MAC address definition is not used. Reference numeral 802 denotes a packet (frame) body, which is a place for storing data to be transmitted. In the case of this embodiment, AV data is stored. A frame check sequence (FCS) 803 stores a code for checking whether or not there is an error in the transmitted wireless packet. In IEEE802.11a, a necessary header or the like (not shown in FIG. 8) such as a physical layer preamble is added to the MAC layer radio packet shown in FIG. 8 and transmitted in the physical layer. Hereinafter, the operation of the transmission apparatus 100 will be described in detail with reference to FIGS. 1 and 8.

  As for the AV data 110, a MAC packet 800 is generated by the packet generation unit 101. Here, a series of AV data is divided into data as appropriate and stored in the packet body 802 of each packet. Further, a MAC header 801 and an FSC 803 are added.

  The packet transmission means 102 inputs the MAC packet at 111, performs wireless physical layer processing such as preamble addition and modulation, and outputs the packet to be transmitted from the antenna 105 as a wireless transmission packet at 112.

  The packet transmission control means 103 controls the transmission timing of the packet transmission means 102 at 115. Further, the packet transmission control means 103 is notified from the packet transmission means 102 at 116 whether or not a packet to be transmitted is ready. The carrier sensing means 104 receives the radio reception signal 113 from the antenna 105 and constantly monitors the current radio wave (carrier) status. That is, the packet sensing state is grasped by sensing the carrier in the wireless transmission network by the carrier sensing means 104. This radio wave (carrier) status is transmitted to the packet transmission control means 103 at 114.

  A feature of the present invention resides in a packet transmission control algorithm of the packet transmission control means 103, which transmits a packet (priority packet) to be preferentially transmitted with a waiting time shorter than the transmission waiting time defined by IEEE802.11a. Thus, the transmission apparatus 100 can transmit the priority packet at the intended timing to secure the transmission band of the priority packet. Hereinafter, further detailed description will be made with reference to the drawings.

  FIG. 2 is a timing chart when a priority data packet is transmitted by unicast. At the time of transmission of the packet 200, the carrier sensing means 104 detects the wireless carrier, and the packet transmission control means 103 causes the packet transmission means 102 to wait for packet transmission.

  When the wireless carrier of the packet 200 is no longer detected at the timing 220, the next packet can be transmitted. For comparison with the feature of the present invention, first, what happens when the present invention is not applied will be described. To do.

  In IEEE802.11a, as already described with reference to FIG. 9, in the AP 1101 in FIG. 11 and all wireless terminals, when there is a packet to be transmitted, it is confirmed that a carrier is not detected for a certain period of time. Packets can be transmitted. In IEEE802.11a, the waiting time at this time is a timing 922 when DIFS and Backoff have elapsed from 920, which is the end time 900 in FIG. As shown in FIG. 10, DIFS is 34 uS, and Backoff is the time obtained by multiplying the slot time 9 uS by the CW size that is randomly determined at each terminal for transmission. In wireless transmission, only ACK, which is a confirmation of communication, may be detected from another terminal due to a hidden terminal problem. The waiting time at this time is 16 uS of SIFS. This SIFS is the minimum waiting time for transmitting a radio packet. In the environment of FIG. 11, since there are interfering terminals 1110 and 1111, transmission of the AV packet from the AP 1101 to the AV terminals 1102 to 1109 is performed at the same time as the above waiting time, and the transmission timing is obtained fairly. Therefore, for example, when a large amount of data is transmitted from the interfering terminal 1110 to 1111 in the ad hoc mode, the interfering terminal 1110 acquires the transmission right and consumes a large transmission band. As a result, the real-time property of AV transmission cannot be guaranteed.

  On the other hand, in the present invention, the packet transmission control means 103 transmits the priority data packet at the VSIFS interval shorter than the SIFS from the timing 220. For example, VSIFS may be 15 uS, which is shorter than SIFS (16 uS). In the configuration of FIG. 1, the packet transmission control unit 103 detects the timing 220 based on the signal 114 from the carrier sensing unit 104, and waits for a time corresponding to only the VSIFS 210 from the timing 220 to transmit the priority data packet 201 to the packet transmission unit 102. Let

In this embodiment, the case where transmission is performed by unicast is taken as an example, so that the priority data packet 201 is transmitted to one AV terminal. In this embodiment, the case of transmission to AV terminal 1102 is taken as an example. When the transmission of the priority data packet 201 is completed from the AP 1101 to the AV terminal 1102, the AV terminal 1102 returns an ACK confirming the reception to the AP 1101. The waiting time from timing 221 is SSIFS 211. Since the SSIFS 211 that is the waiting time of the ACK 202 must be transmitted with priority over all data packets including the priority data packet, if the period is shorter than the VSIFS 212 (15 uS in this embodiment), for example, 14 uS. Good. That means
SSIFS <VSIFS <SIFS
It is.

  However, in unicast, since the ACK for the priority data packet 201 is not returned except for the AV terminal 1102, whether the packet transmission control means 103 detects the carrier in the carrier sensing means 104 next to the priority data packet 201 or not. Regardless of the case, the SSIFS does not necessarily have to be shorter than the VSIFS, and the SSIFS may be the same as the normal SIFS, the same as the VSIF, or the like if the ACK continues to be waited and the hidden terminal problem does not occur.

  After the transmission end timing 222 of the ACK 202, the packet transmission control unit 103 similarly transmits the priority data packet 203 after the VSIFS 212, and the ACK 204 is transmitted after the SSIFS 213 from the timing 223. In this embodiment, since the priority data packets are continuously transmitted from the packet transmitting means 102, the interfering terminal does not acquire the packet transmission right and consume the radio band.

  As described above, before a disturbing terminal compliant with IEEE802.11a becomes in a transmittable state, the wireless band is secured first by transmitting a packet, and as a result, the disturbing terminal is prevented from transmitting a packet. It is possible to secure the bandwidth required by the priority data packet without causing the terminal to consume the wireless transmission bandwidth.

  In this case, since the priority data packet is continuously transmitted after waiting for the VSIFS, it is not always necessary to detect the wireless carrier. Therefore, in FIG. 1, the carrier sensing means 104 can be realized without being mounted.

(Embodiment 2)
In the present embodiment, a case will be described in which transmission of normal data packets is performed while priority is given to transmission of priority data packets by unicast. Specifically, a case where transmission of a normal data packet is permitted when there is no priority data packet to be transmitted next when an ACK is returned from the receiving terminal after transmitting the priority data packet will be described. The configuration of the transmission apparatus is the same as in FIG. 1 described in the first embodiment, and the control method in the packet transmission control means 103 is different.

FIG. 3 is a timing chart in the case of performing transmission of normal data packets while giving priority to transmission of priority data packets in unicast. The packet transmission control shown in FIG. 3 is performed by the packet transmission control means 103. In FIG. 3, the process up to the timing 322 is the same as that described in FIG. That is, 300 corresponds to 200, VSIFS 310 is the same as VSIFS 210, priority data packet 301 is the same as priority data packet 201, SSIFS 311 is the same as SSIFS 211, and ACK 302 is the same as ACK 202. That is, until the timing 322, the control timing from the packet transmission control means 103 to the packet transmission means 102 is the same as the processing up to the timing 222 in FIG. (Timing 220 = Timing 320, Timing 221 = Timing 321)
If there is a priority data packet to be transmitted at the packet transmission means 102 at the timing 322, the packet is preferentially transmitted. However, for example, when the data rate of the AV data 110 is lower than the data rate that can be transmitted by IEEE802.11a, a case where a priority packet to be transmitted to the packet transmission unit 102 is not generated may occur. In such a case, transmission of a normal data packet that is not a priority data packet from the AP 1101, AV terminal, or interfering terminal is permitted. In this embodiment, as an example, a case where ad hoc communication (direct communication) from the disturbing terminal 1110 to the disturbing terminal 1111 is permitted is taken as an example.

  The normal data packet 303 is transmitted from the timing 322 after waiting for the period of DIFS 312 and Backoff 313 according to the IEEE802.11a transmission method according to the conventional method described in FIG. At this time, if a priority data packet to be transmitted to the packet transmission means 102 is prepared in the period 330, the priority data packet is transmitted first, but in FIG. 3, no priority data packet is prepared in this period. Indicates the state.

  During communication of the normal data packet 303, the carrier sensing unit 104 detects a radio carrier, and therefore the priority data packet cannot be transmitted from the packet transmission unit 102 during this period. When a priority data packet to be transmitted to the packet transmission unit 102 is generated during transmission of the normal data packet 303, the packet transmission unit waits for the period of VSIFS 314 from the timing 323 after the transmission of the normal data packet 303 is finished. A priority data packet 304 is transmitted from 102. The packet transmission control at this time is performed by the packet transmission control means 103. Thereafter, after waiting for the period of SSIFS 315, ACK 305 is transmitted from the AV terminal.

  In the example of the present embodiment, priority is given to the transmission of the priority data packet, so that the bandwidth of the priority packet can be secured, and at the same time, general data communication can be performed in the free time.

  In this embodiment, general data communication is exemplified by communication between interfering terminals. However, communication from an AV terminal to the AP 1101 may be used. In this case, for example, AV to be requested from the AV terminal to the video server 1100 is required. Channel selection can be performed. Further, a normal data packet may be transmitted from the AP 1101 to the AV terminal.

(Embodiment 3)
In this embodiment, priority is given to transmission of priority data packets in unicast, and even when there is no priority data packet to be transmitted, a transmission right is always secured without giving a transmission opportunity to other terminals. Give an explanation. Specifically, when an ACK is returned from a receiving terminal after transmitting a priority data packet, there is no priority data packet to be transmitted next so that it can be transmitted as soon as possible when the priority data packet is prepared. A transmitting apparatus to be described will be described. The configuration of the transmission apparatus is the same as that of FIG. 1 described in the first embodiment.

FIG. 4 is a timing diagram in the case of transmitting a dummy packet when there is no priority data packet to be transmitted while giving priority to transmission of the priority data packet in unicast. The transmission control shown in FIG. 4 is performed by the packet transmission control means 103. In FIG. 4, the processing up to timing 422 is the same as that described in FIG. That is, 400 corresponds to 200, VSIFS 410 is the same as VSIFS 210, priority data packet 401 is the same as priority data packet 201, SSIFS 411 is the same as SSIFS 211, and ACK 402 is the same as ACK 202. That is, until the timing 422, the control timing from the packet transmission control means 103 to the packet transmission means 102 is the same as the processing up to the timing 222 in FIG. (Timing 220 = Timing 420, Timing 221 = Timing 421)

When there is a priority data packet to be transmitted at the timing 422 in the packet transmission means 102, the priority transmission packet is to be transmitted to the packet transmission means 102 as described in the second embodiment. Occurs when is not generated. At this time, in the method described in the second embodiment, transmission of normal data packets is permitted. However, in this embodiment, transmission of dummy packets from the transmission device 100 allows transmission to other wireless devices. Always keep the transmission right.

  If the priority data packet is not prepared in the packet transmission unit 102 at 423 after the VSIFS 412 from the timing 422, the packet transmission control unit 103 controls to transmit the dummy packet 403 from the packet transmission unit 102. For example, the dummy packet 403 includes only the MAC header of FIG. 8 (in this case, 24 octets) and 4 octets of FCS, and the packet body is set to 0 octets or the like, so that the wireless packet can be transmitted in the shortest time. Good. The transmission destination of the dummy packet may be transmitted to a terminal that does not exist in the system of FIG. As a result, other terminals do not perform reception processing, and thus no additional devices are added to the system.

  After timing 424, similarly, after the dummy packet transmission ends, the VSIFS interval is waited. If there is no priority data packet to be transmitted at that time in the packet transmission means 102, the dummy packet is transmitted. FIG. 4 illustrates a case where there is no priority data packet at timing 425 after VSIFS 413 and a dummy packet 404 is transmitted. At the timing 427 after waiting for the VSIFS 414 interval from the timing 426 which is the transmission end time of the dummy packet 404, the priority data packet to be transmitted is generated in the packet transmission means 102. Therefore, the priority data packet 405 is transmitted. The AV terminal to which 405 is transmitted waits for SSIFS 415 and then transmits ACK 406.

  According to the method of the present embodiment, if there is a priority data packet to be transmitted, transmission is performed with priority over the disturbing terminal, and if there is no priority data packet to be transmitted, VSIFS and a dummy packet as short as possible are transmitted. The priority of the priority data packet can be increased by preventing the disturbing terminal from transmitting the packet and enabling transmission as soon as possible when the next priority data packet is generated. As a result, even when the data rate of AV data is low, high-quality transmission with a transmission band secured is possible.

  The VSIFS (412, 413 in FIG. 4) used as the waiting time until the dummy data is transmitted has been described as the same value as the waiting time until the priority data packet is transmitted. Not limited to this, any length may be used as long as it is shorter than the transmission waiting time of the disturbing terminal.

  In this embodiment, since the priority data packet or the dummy packet is continuously transmitted from the transmission device, it is not always necessary to detect the wireless carrier. Therefore, in FIG. 1, the carrier sensing means 104 can be realized without being mounted.

(Embodiment 4)
In this embodiment, a case where priority data packets are transmitted by multicast will be described. The configuration of the transmission apparatus is the same as that of FIG. 1 described in the first embodiment. Multicast is a transmission method in which a transmitting apparatus transmits a packet to one or a plurality of terminals, and an ACK for confirmation of reception from each receiving terminal is not returned. In multicast, it is possible to transmit AV packets to a large number of AV terminals all at once. In the example of FIG. 11, AV packets are simultaneously transmitted to a plurality of AV terminals 1102 to 1109 using the AP 1101 as a transmission device. Can be sent. A combination of a plurality of AV terminals that receive one multicast packet is arbitrary, and naturally, the multicast may be transmitted to one AV terminal.

  FIG. 5 is a timing chart when priority data packets are transmitted by multicast. Even in multicast, the transmission waiting time is set to VSIFS shorter than SIFS, so that packets are transmitted with priority over interfering terminals. The transmission control shown in FIG. 5 is performed by the packet transmission control means 103.

  Only the VSIFS 510 waits for transmission from 520, which is the transmission completion timing of 500, and the priority data packet 501 is transmitted from the packet transmission means 102. Next, it waits for VSIFS 511 from the transmission completion timing 521 of the priority data packet 501 and transmits the priority data packet 502 (transmission completion timing 522). Thereafter, similarly, the priority data packet 503 is transmitted after waiting for the VSIFS 512 (transmission completion timing 523), and the priority data packet 504 is transmitted after waiting for the VSIFS 513. By repeating these operations, the packet transmission from the disturbing terminal is prevented and the priority data packet transmission is given priority.

  In this embodiment, since the priority data packets are continuously transmitted from the packet transmitting means 102, the interfering terminal does not acquire the packet transmission right and consume the radio band.

  In this case, since the priority data packet is continuously transmitted after waiting for the VSIFS, it is not always necessary to detect the wireless carrier. Therefore, in FIG. 1, the carrier sensing means 104 can be realized without being mounted.

(Embodiment 5)
In the present embodiment, a case will be described in which normal data packets are transmitted while priority is given to transmission of priority data packets by multicast. The configuration of the transmission apparatus is the same as in FIG. 1 described in the first embodiment, and the control method of the packet transmission control means 103 is different. In this embodiment, a case will be described in which transmission of a normal data packet is permitted when a priority data packet to be transmitted next is not generated even after transmission of a priority data packet and waiting for transmission for a VSIFS period. .

  FIG. 6 is a timing chart in the case of transmitting normal data packets while giving priority to transmission of priority data packets in multicast. In FIG. 6, the process up to timing 621 is the same as that described in FIG. That is, 600 corresponds to 500, timing 620 corresponds to 520, VSIFS 610 is the same as VSIFS 510, and priority data packet 601 is the same as priority data packet 501.

  When there is a priority data packet to be transmitted at the timing 621 in the packet transmission unit 102, the packet is transmitted with priority. However, as described in the second embodiment, there is a priority packet to be transmitted to the packet transmission unit 102. If it has not been generated. In such a case, transmission of a normal data packet that is not a priority data packet from the AP 1101, AV terminal, or interfering terminal is permitted. In this embodiment, as an example, a case where ad hoc communication (direct communication) from the disturbing terminal 1110 to the disturbing terminal 1111 is permitted is taken as an example.

  The normal data packet 602 is transmitted from the timing 621 after waiting for a period of DIFS 611 and Backoff 612 according to the IEEE 802.11a transmission method according to the conventional method described with reference to FIG. At this time, if a priority data packet to be transmitted to the packet transmission means 102 is prepared in the period 630, the priority data packet is transmitted first. In FIG. 6, the priority data packet is prepared in this period. Indicates no state. During the communication of the normal data packet 602, the carrier sensing means 104 detects the radio carrier, and therefore the priority data packet cannot be transmitted during this period. However, the priority data packet 603 generated by the packet transmission unit 102 during transmission of the normal data packet 602 (631) and during the period of VSIFS 613 waited for the period of VSIFS 613 from the timing of 623 after the end of transmission of the normal data packet 602. Later, it is transmitted from the packet transmission means 102. Transmission control of the priority data packet from the packet transmission unit 102 is performed by the packet transmission control unit 103.

  In FIG. 6, ACK 615 is transmitted after SIFS 614, which is a normal waiting time of ACK in IEEE 802.11a from timing 624. This ACK 615 corresponds to the normal data packet 602 and is transmitted from the disturbing terminal 1111 to the disturbing terminal 1110 for confirmation of reception. If a priority data packet is generated in the packet transmission unit 102 from timing 624 to a timing after VSIFS (not shown, but before timing 625), the priority data packet has priority. Needless to say, it is sent from.

  In the example of the present embodiment, general data communication can be performed at the same time as securing the priority packet bandwidth.

  In this embodiment, general data communication is exemplified by communication between disturbing terminals, but communication from the AV terminal to the AP 1101 may be used. In this case, for example, the AV to be requested from the AV terminal to the video server 1100 may be used. Channel selection etc. can be performed. Further, a normal data packet may be transmitted from the AP 1101 to the AV terminal.

  Although the case where the normal data packet is transmitted by unicast is taken as an example, it goes without saying that the present invention is effective even if the normal data packet is a multicast packet. In this case, the ACK for the normal data packet is not returned.

(Embodiment 6)
In this embodiment, priority is given to transmission of priority data packets by multicast, and even when there is no priority data packet to be transmitted, a case where transmission rights are always secured without giving a transmission opportunity to other terminals will be described. Do. The configuration of the transmission apparatus is the same as that of FIG. 1 described in the first embodiment. In the present embodiment, even after waiting for VSIFS after transmitting a priority data packet, there is no priority data packet to be transmitted next, and a transmission apparatus that enables transmission as soon as possible when a priority data packet is prepared Will be described.

  FIG. 7 is a timing diagram in the case of transmitting a dummy packet when there is no priority data packet to be transmitted while giving priority to transmission of the priority data packet in multicast. In FIG. 7, the processing up to timing 721 is the same as that described in FIG. That is, 700 corresponds to 500, timing 720 corresponds to 520, VSIFS 710 is the same as VSIFS 510, and priority data packet 701 is the same as priority data packet 501. That is, until the timing 721, the control timing from the packet transmission control means 103 to the packet transmission means 102 is the same as the processing up to the timing 521 in FIG.

  At timing 721, there is a case where a priority packet to be transmitted to the packet transmission unit 102 is not generated as described in the second embodiment. At this time, in the method described in the fifth embodiment, the transmission of the normal data packet is permitted. However, in this method, the normal data packet communication is performed when the priority data packet is generated during or immediately after the normal data packet transmission. Immediately after that, a priority data packet can be transmitted. The present embodiment provides a transmission apparatus that can transmit priority data packets as quickly as possible without allowing transmission of normal data packets.

  If a priority data packet is not prepared at 722 after VSIFS 711 from timing 721, a dummy packet 702 is transmitted. For example, as described in the third embodiment, the dummy packet 702 includes only the MAC header (in this case, 24 octets) and 4 octets of FCS in FIG. In this way, the wireless packet is completely transmitted. As a transmission destination, transmission may be made to a terminal that does not exist in the system of FIG. Similarly, after the dummy packet transmission is completed, the VSIFS interval is waited. If there is no priority data packet to be transmitted at that time, the dummy packet is transmitted. In FIG. 7, there is no priority data packet to be transmitted at timing 724 after VSIFS 712 from timing 723, and there is no priority data packet to be transmitted at timing 726 after VSIFS 713 after transmission 725 after transmission of dummy packet 703. A case where a dummy packet 704 is transmitted is illustrated. At timing 728 after VSIFS 714 from timing 727, a priority data packet 705 to be transmitted is generated in the packet transmission unit 102 and transmitted from the packet transmission unit 102. If there is a priority data packet to be transmitted at timing 730 after VSIFS 715 from the end of transmission of the priority data packet 729, transmission is performed, but FIG. 7 illustrates a case where there is no priority data packet to be transmitted and a dummy packet 706 is transmitted. (Transmission end timing 731). During this time, transmission control of the priority data packet from the packet transmission means 102 is performed by the packet transmission control means 103.

  According to the method of this embodiment, if there is a priority data packet to be transmitted, transmission is performed with priority over the disturbing terminal, and if there is no priority data packet to be transmitted, VSIFS and a dummy packet with the minimum length are transmitted. By preventing the disturbing terminal from transmitting the packet, the priority of the priority data packet can be further increased by enabling transmission as soon as possible when the next priority data packet is generated. It becomes possible. As a result, even when the data rate of AV data is low, high-quality transmission with a transmission band secured is possible.

  The VSIFS (711, 712, and 713 in FIG. 4) used as the waiting time until the dummy data is transmitted has been described as the same value as the waiting time until the priority data packet is transmitted. However, the length is not limited to this, and may be any length as long as it is shorter than the transmission waiting time of the disturbing terminal.

  In this embodiment, since the priority data packet or the dummy packet is continuously transmitted from the transmission device, it is not always necessary to detect the wireless carrier. Therefore, in FIG. 1, the carrier sensing means 104 can be realized without being mounted.

  As specifically described in the above embodiments, the present invention is realized.

  In the embodiment of the present application, IEEE802.11a has been described as an example of wireless transmission. However, the present invention is not limited to IEEE802.11a, and may be IEEE802.11b or IEEE802.11g. Further, this is effective not only for IEEE802.11 but also for all transmission systems that determine the packet transmission priority by using the difference in waiting time until packet transmission. Needless to say, the present invention is effective not only for wireless communication but also for priority. Therefore, such a case is not excluded from the scope of the present invention.

  In the embodiment of the present application, the configuration of FIG. 1 has been described. However, the configuration of the present application can be easily realized using software, and even in such a case, it is not excluded from the scope of the present invention. Absent.

  Further, in the embodiment of the present application, the infrastructure mode transmitted from the AP to the terminal has been described as an example. However, the present application can also be applied to the ad hoc mode, and even when applied to the ad hoc mode, it is excluded from the scope of the present invention. Not what you want.

  In the embodiment of the present application, the case where an AV packet is transmitted from an AP to an AV terminal has been described as an example. Therefore, a case where a priority data packet and a normal data packet are transmitted from the configuration of FIG. 1 will be described. However, it goes without saying that a receiving terminal that returns an ACK can also be realized with the configuration of FIG.

  Further, in the embodiment of the present application, the condition for transmitting the normal data packet between transmissions of the priority data packet is set as the case where the generation of the priority data packet is not completed even when the priority data packet can be transmitted. Although explained as an example, not limited to this, create a normal data packet transmission opportunity to the extent that it does not interfere with the bandwidth guarantee of the priority data packet, such as creating a normal data packet transmission opportunity once in several times Also good.

  In the present application, the case of various transmission modes has been described in many embodiments. However, various modifications or combinations can be made based on the method described in the embodiments of the present application depending on the system configuration. Such a case is not excluded from the scope of the present invention.

  In the embodiment of the present application, SIFS, DIFS, and Backoff have been described as examples of transmission waiting times. However, in IEEE802.11, other waiting times such as PIFS (Point Interface Space) are also defined. However, if the priority data packet is transmitted in a shorter time than the other waiting times, the effect of the present invention can be obtained. Therefore, the waiting time until the priority data packet is transmitted is Various modifications are possible, and even such a case is not excluded from the scope of the present invention. Needless to say, this is the same for protocols other than IEEE 802.11.

  In the embodiment of the present application, an example in which a normal data packet is transmitted by an interfering terminal is taken as an example. However, even when an access point transmits a normal data packet, it is not excluded from the scope of the present invention.

  In the embodiment of the present application, the case where the SSIFS is 15 uS has been described as an example, but it goes without saying that a wider transmission band can be secured as the SSIFS value is shorter. Therefore, such a case is not excluded from the scope of the present invention.

  Further, in the present application, specific examples have been described in the first to sixth embodiments. However, particularly in wireless communication, a hidden terminal problem, access point and terminal arrangement, or wireless channel selection of each system Etc., or a combination of multicast and unicast, etc., the arrival ranges and detection ranges of various packets change. Therefore, the waiting time for preferential transmission of the priority data packet can be changed according to the situation of the system. Accordingly, the present invention is not excluded from the scope of the present invention as long as it has the feature of the present invention that the priority data packet is transmitted with a short waiting time. Depending on the situation in which the system is placed, ACK is a reception confirmation. Therefore, in consideration of the fact that a packet that should be acknowledged is not transmitted unless it is received, it has the same value as the specified minimum transmission interval of packets. Even when a priority data packet is transmitted, the present invention may be realized.

  The transmission device according to the present invention can preferentially transmit AV packets (AV data) even when an interfering terminal enters the system, and the transmission band of the AV service radio packet is guaranteed. It is useful when transmitting data that must be transmitted with a guaranteed transmission band such as video and audio.

Schematic diagram showing the configuration of the transmitter according to the present application Timing chart when priority data packet is transmitted by unicast Timing diagram when transmission of normal data packets is performed while giving priority to transmission of priority data packets by unicast Timing diagram when sending a dummy packet when there is no priority data packet to be transmitted while giving priority to the transmission of the priority data packet by unicast Timing diagram for sending priority data packets by multicast Timing chart when priority data packet transmission is prioritized and normal data packet transmission is also performed Timing diagram when sending a dummy packet when there is no priority data packet to be transmitted while giving priority to transmission of the priority data packet by multicast Schematic diagram of packet format in the MAC layer of IEEE 802.11 Timing diagram for explaining wireless access by CSMA / CA of IEEE 802.11 The figure which shows the parameter regarding the packet transmission interval used by the radio | wireless access by CSMA / CA. Schematic diagram of AV data distribution system by wireless transmission

Explanation of symbols

101 packet generation means 102 packet transmission means 103 packet transmission control means 104 carrier sensing means

Claims (6)

In a transmission network where the minimum packet transmission interval is specified,
Packet generating means for generating a packet from input data;
Packet transmission means for transmitting the packet to the transmission network;
Packet transmission control means for performing transmission control of the packet transmission means to transmit the packet at a transmission interval shorter than the minimum packet transmission interval;
A transmission device comprising: 2. The transmission apparatus according to claim 1, wherein the packet transmission control means grasps a packet transmission status in the transmission network by sensing a carrier in the transmission network by a carrier sensing means. The transmission apparatus according to claim 1 or 2, wherein the packet transmission control means performs transmission control of the packet transmission means so as to continuously transmit priority data packets. 4. The transmission apparatus according to claim 1, wherein the packet transmission control unit transmits a dummy packet when there is no priority data packet to be transmitted to the packet transmission unit. 5. The transmission apparatus according to claim 1, wherein the transmission network is a transmission network conforming to IEEE 802.11. 6. The transmission apparatus according to claim 1, wherein the minimum packet transmission interval is SIFS (Short Interframe Space).

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