JP2007267182A - Communication device and memory region management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make proper a memory region managing the reception status of a packet and/or a divided packet. <P>SOLUTION: In a communication system, a base station and a radio communication device 200 are connected by a wireless LAN. Each of equipment continuously transmits/receives a packet or divides and transmits/receives the packet. In the radio communication device 200, a communication section 250 receives the packet and/or the divided packet and a storage section 255 stores reception status information indicating a reception status thereof. In accordance with the state of a transmission line, a storage region proper section 275 narrows down the region of the storage section 255 to be equal to or more than a maximum value Fn for the number of divided packets that can be transmitted in a divided manner, based on latency 1a and a minimum transmission time Tf for one divided packet, less than the number of bits obtained by multiplying a maximum value Pmax for the number of packets that can be continuously transmitted, by a maximum value Fmax for the number of divided packets that can be generated by dividing one packet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a communication device and a memory area management method that allow packets to be transmitted / received continuously or to be transmitted / received by dividing the packets. In particular, the present invention relates to optimization of the size of a memory area that stores information on whether or not a packet and / or a divided packet has been correctly received.

  2. Description of the Related Art Conventionally, when wireless devices wirelessly communicate with each other via a wireless LAN, a method for continuously transmitting information to be transmitted as packets has been known. In this method, various retransmission schemes have been developed to increase the likelihood that packets will be transmitted correctly during transmission. One of them is a radio link protocol.

  Based on this wireless link protocol, when a packet is transmitted from a transmitting device to a receiving device, the receiving device detects, for example, an error using CRC checksum information or detects the strength of a radio wave. Whether or not the packet has been correctly received is determined by the error detection method. When the packet is correctly received, the receiving device transmits “ACK”, which is a message notifying that the packet has been transmitted correctly, to the transmitting device.

  On the other hand, if the packet is not correctly received, the receiving side device transmits “NAK”, which is a message notifying that the packet has not been correctly transmitted, to the transmitting side device. On the other hand, the transmitting device retransmits the corresponding packet under a certain condition. At the same time, determination information (reception status information) as to whether or not the packet has been correctly received is stored in an acknowledgment bitmap (ACK MAP) corresponding to each packet, thereby managing the reception status of each packet. (For example, see Patent Document 1).

  This acknowledgment bitmap only needs to have a memory area that can store reception status information for the maximum number of packets that must be managed. For example, when the maximum value of the number of packets that can be transmitted continuously is “64”, the acknowledgment bitmap only needs to have a 64-bit storage area to manage 64 packets.

International Publication No. WO2003 / 005631 Pamphlet

  However, in the case of a communication system that allows a packet to be transmitted as a smaller unit divided packet (fragmented packet) by dividing the packet, the acknowledgment bitmap is the number of packets that can be transmitted continuously. The reception status information of the number calculated by the maximum value of the number of divided packets (number of fragments) that can be generated by dividing the maximum value × 1 packet must be stored. For example, when the maximum value of the number of packets that can be continuously transmitted is “64” and the maximum value of the number of divided packets that can be generated by dividing one packet is “16”, the acknowledgment bitmap is 1024 (= 64 × 16) It is necessary to have a storage area of 1024 bits in order to manage packets and / or divided packets.

  On the other hand, normally, a segment packet belonging to a previously transmitted packet is preferentially transmitted so that a segment packet belonging to a previously transmitted packet is received earlier than a segment packet belonging to a later transmitted packet. . This is because the user of the receiving side device can see the information contained in the packet by assembling the divided packets when all the divided packets are aligned.

  On the other hand, in general, it is unlikely that packets with the maximum number of packets will be transmitted continuously. Due to the nature at the time of packet transmission, it is calculated by the maximum value of the number of packets that can be generated by dividing the maximum number of packets that can be transmitted continuously × 1 packet prepared in the acknowledgment bitmap. It is very unlikely that all storage areas with a certain number of bits will be used. Therefore, it is not a good idea to hold the storage area having the number of bits of the maximum number of packets that can be transmitted continuously × the maximum value of the number of divided packets that can be generated because it wastes memory space.

  In order to solve the above problem, in the present invention, a communication device for optimizing a memory area for managing the reception status in communication that allows packets to be transmitted / received continuously or allows the packets to be transmitted / received in a divided manner And a memory area management method for managing the reception status.

  That is, in order to solve the above-described problem, according to an aspect of the present invention, there is provided a communication device that continuously transmits / receives packets, or allows the packet to be transmitted / received separately. In accordance with the state of the communication unit that receives the fragmented packet, the storage unit that stores the reception status information indicating the reception status of the packet and / or the divided packet, and the state of the transmission path that transmits the packet and / or the divided packet. Thus, an area smaller than the number of bits obtained by multiplying the maximum value Pmax of a given number of packets that can be continuously transmitted by the maximum value Fmax of a given number of divided packets that can be generated by dividing one packet is described above. There is provided a communication device including a storage area optimizing unit that automatically narrows the area of the storage unit.

  According to this, the memory area secured by the storage unit is the number of bits obtained by multiplying the maximum value Pmax of the number of packets that can be continuously transmitted and the maximum value Fmax of the number of divided packets that can be generated in accordance with the state of the transmission path. It is optimized for areas with fewer bits. Thereby, useless consumption of the memory space provided in the communication device can be avoided. In particular, in a mobile electronic device such as a mobile phone, the device itself is small and the capacity of a volatile memory (RAM) that can be used is limited. Therefore, the present invention capable of managing the reception status of packets and / or divided packets while minimizing the consumption of memory space is particularly useful for mobile electronic devices.

  The storage area optimizing unit obtains a maximum value Fn of the number of divided packets that can be divided and transmitted based on a predetermined latency la and a minimum time Tf required to transmit one divided packet, The number of bits is equal to or greater than the maximum value Fn of the number of divided packets that can be transmitted, and is smaller than the number of bits obtained by multiplying the maximum value Pmax of the number of continuously transmittable packets by the maximum value Fmax of the number of divided packets that can be generated. You may make it optimize the area | region of the said memory | storage part to the number of bits.

  One index indicating the state of a transmission path for transmitting a packet is latency la. Latency la is a delay time taken from the reception of a transmission request to the completion of data transmission. If the data transmission is not completed within the latency la after receiving the transmission request, the packet is discarded.

  From the latency la value, a predetermined upper limit can be found in the maximum value of the number of divided packets that can be actually divided and transmitted from the state of the transmission path. From this upper limit value, the area of the storage unit can be optimized.

  In addition, the storage area optimizing unit may manage the storage area in a fixed manner or dynamically depending on the state of the transmission path. The communication device may be a device that communicates wirelessly with another device.

  In order to solve the above-described problem, according to another aspect of the present invention, packets are continuously transmitted / received, or the packets are allowed to be transmitted / received separately. Or a memory area management method for a communication device that stores reception status information indicating a reception status of a fragmented packet in a storage unit, which takes in the latency la and determines one packet based on information about the transmission time of the packet and / or the fragmented packet. The minimum time Tf required to transmit a divided packet is calculated, and the number of divided packets that can be divided and transmitted based on the acquired latency la and the calculated minimum time Tf required to transmit one divided packet is calculated. It can be generated by finding the maximum value Fn and dividing the maximum value Pmax of a given number of packets that can be transmitted continuously and one packet. The area of the storage unit is automatically set in an area having a bit number that is less than the number of bits multiplied by the maximum value Fmax of the given number of divided packets and equal to or greater than the maximum value Fn of the number of divided packets that can be divided and transmitted. A memory area management method that narrows the size of the memory is provided.

  In this memory area management method, the latency la is acquired, and the minimum time Tf necessary for transmitting one divided packet is calculated based on the information on the transmission time of the packet and / or the divided packet. Based on the acquired latency la and the calculated minimum time Tf required to transmit one divided packet, a maximum value Fn of the number of divided packets that can be divided and transmitted is obtained. The maximum value Fn of the number of divided packets that can be divided and transmitted is less than the number of bits obtained by multiplying the maximum value Pmax of a given number of packets that can be continuously transmitted by the maximum value Fmax of the given number of divided packets that can be generated. The area of the storage unit is automatically narrowed to the area of the above number of bits.

  According to this, the memory area secured by the storage unit is smaller than the maximum value Pmax of a given number of packets that can be continuously transmitted × the maximum number Fmax of a given number of divided packets that can be generated, and can be divided and transmitted. It is optimized to an area having a bit number equal to or larger than the maximum value Fn of the number of divided packets. Thereby, useless consumption of the memory space provided in the communication device can be avoided.

  In addition, as information regarding the transmission time of the packet and / or the divided packet, when a burst mode (Burst Mode) in which packets are continuously transmitted is used, the interval between each packet (IFS: Inter Frame Space) shown in FIG. ), When transmitting one divided packet, PHY Header indicating the modulation rate of the divided packet, minimum time required for transmitting the divided packet, and the like.

  As described above, according to the present invention, a communication device that optimizes a memory area for managing a reception status in communication that allows packets to be transmitted / received continuously or to be transmitted / received by dividing the packets. And a memory area management method for managing the reception status.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, components having the same configuration and function are denoted by the same reference numerals, and redundant description is omitted.

(Communications system)
First, a communication system according to an embodiment of the present invention will be described with reference to FIG. The communication system 10 includes a base station 100 as an access point and a PC (Personal Computer) 200a and a TV 200b having a wireless LAN card. The PC 200a and the TV 200b are examples of the wireless communication device 200. The base station 100 and the wireless communication device 200 are connected by a wireless LAN, thereby transmitting and receiving packets continuously, or transmitting and receiving divided packets. The base station 100 can communicate with an electronic device (not shown) via the HUB 400 via the wired LAN 500.

  There are standards (protocols) such as IEEE802.11a and IEEE802.11e for wireless LAN, and its access control system (MAC (Medium Access Control) system) is based on, for example, MBOA (MultiBand OFDM Alliance). It has been standardized in detail. According to this, in a burst mode in which a plurality of packets can be transmitted continuously, when a packet is transmitted from a transmitting device to a receiving device, the receiving device detects an error using, for example, CRC checksum information. Thus, it is determined whether or not the packet is correctly received. When the packet is correctly received, the receiving side device notifies the transmitting side device that the packet has been correctly received by transmitting “ACK” to the transmitting side device.

  On the other hand, if the packet is not correctly received, the receiving side device transmits “NAK” to the transmitting side device to notify the transmitting side device that the packet has not been correctly transmitted. As a result, the transmission side device retransmits the packet under certain conditions.

  In such an access control method, when the base station 100 in FIG. 1 is a transmitting device, the PC 200a and the TV 200b are receiving devices, and when the PC 200a and the TV 200b are transmitting devices, the base station 100 is connected to the receiving device. However, hereinafter, the base station 100 will be described as a transmission-side device, and the wireless communication apparatus 200 indicated by the PC 200a and the TV 200b will be described as a reception-side device.

(Base station 100)
The base station 100, which is a transmission side device, divides the packet into smaller units of fragments (fragmentation) according to the state of the transmission path, and the fragmented packet (also referred to as a divided packet) is the wireless communication device 200. Transmit to. For example, a case will be described in which the base station 100 continuously transmits packets based on the Block ACK (BA) system defined by IEEE 802.11e. In the BA system, the transmission side device can continuously transmit packets. On the other hand, the receiving side device does not need to respond to each packet of continuously transmitted packets (that is, transmission of ACK or NAK), but can respond once to a plurality of continuously transmitted packets. Good.

  Specifically, as shown in FIG. 2, in the BA system defined by IEEE802.11e, a maximum of 64 packets (Seq. # 1 packet, Seq. #) To which a unique sequence number is assigned. 2 packets,..., Seq. # 64 packets) can be transmitted continuously. Furthermore, the divided packets (Frag. # 1 packet, Frag. # 2 packet,..., Frag. # 16 packet) obtained by dividing each packet into a maximum of 16 small units can be divided and transmitted. It is.

  That is, the maximum number of packets that can be transmitted continuously determined by the protocol is “64” in the case of IEEE802.11e, and can be generated by dividing one packet determined by the protocol. The maximum number of packets is “16” in the case of IEEE 802.11e.

  In addition, the hardware configuration of the base station 100 is the same as the hardware configuration of the wireless communication apparatus 200 described below, and thus the description thereof is omitted.

(Configuration and function of wireless communication device)
First, the configuration and function of the wireless communication apparatus 200 that is the receiving side device will be described with reference to the hardware configuration diagram of FIG. 3A and the functional configuration diagram of FIG.

  As shown in FIG. 3A, the wireless communication device 200 includes a ROM 205, a CPU 210, a RAM 215, a wireless communication circuit 220, and a bus 225.

  The ROM 205 stores a basic program for operating the wireless communication apparatus 200, a program that starts when the wireless communication apparatus 200 is abnormal, and the like. The CPU 210 controls the entire wireless communication device 200. The RAM 215 stores various data necessary for operating the wireless communication device 200. The RAM 215 stores reception status information for managing the reception status of packets and / or divided packets transmitted from the base station 100.

  The wireless communication circuit 220 is an interface for packet communication with the base station 100 via the wireless LAN 300 by a wireless communication method defined in a protocol such as IEEE802.11e. The bus 225 is a path for exchanging information among the devices of the ROM 205, the CPU 210, the RAM 215, and the wireless communication circuit 220. The RAM 215 is an example of a storage device, and may be a storage device such as an optical disk, a magneto-optical disk, or a hard disk.

  Next, the functional configuration of the wireless communication apparatus 200 will be described with reference to FIG. The wireless communication apparatus 200 has the functions indicated by the functional blocks of the communication unit 250, the storage unit 255, the reception status determination unit 260, the message creation unit 265, the packet assembly unit 270, and the storage area optimization unit 275. .

  The communication unit 250 transmits and receives a packet or a divided packet (fragmented packet).

  The storage unit 255 stores the reception status (that is, reception status information) of packets and / or divided packets transmitted from the base station 100. The acknowledgment bitmap storing the reception status of the packet and / or the divided packet in this way is hereinafter referred to as ACK Map 255a.

  As shown on the left side of FIG. 4, the ACK Map 255a is a bitmap indicating the number of packets that can be continuously transmitted on the vertical axis and the number of divided packets that can be generated (divided) from one packet on the horizontal axis. In the case of IEEE 802.11e, as described above, the maximum value of the number of packets that can be continuously transmitted is “64”, and the maximum value of the number of divided packets that can be generated by dividing one packet is “16”. Therefore, conventionally, the ACK Map 255a has a fixed memory area of 64 bits in the vertical direction, 16 bits in the horizontal direction, and a total of 1024 (= 64 × 16) bits.

  For example, in the case of VoIP (Voice over IP), since image data and audio data can be transmitted from the base station 100, the storage unit 255 of the wireless communication apparatus 200 has a 1024-bit memory area for managing the image data reception status. In addition, a 1024-bit memory area is consumed to manage the voice data reception status. Therefore, a total memory area of 2048 bits is required for the ACK Map 255a.

  However, a memory area management method that suppresses memory consumption as much as possible is desired for devices such as mobile electronic devices such as mobile phones that are small in size and limited in the capacity of volatile memory (RAM) that can be accommodated. . From such a background, in the present embodiment, the memory area secured as the ACK Map 255a is optimized so as to be smaller than the conventional one, which will be described later.

  The reception status determination unit 260 determines whether or not the packet has been correctly received by an error detection method such as detecting an error using the CRC checksum information or detecting the strength of the radio wave. When the message creation unit 265 correctly receives the packet, the message creation unit 265 outputs “ACK” as a message notifying that the packet has been correctly transmitted. On the other hand, if the packet creation unit 265 does not receive the packet correctly, it outputs “NAK” as a message notifying that the packet has not been transmitted correctly.

  When a plurality of divided packets belonging to the same packet are correctly received among the received divided packets, the packet assembling unit 270 assembles the divided packets and reconstructs one packet. Further, when the packet assembly unit 270 correctly receives packets necessary for assembly, the packet assembly unit 270 reassembles the data by assembling the packets.

  The storage area optimizing unit 275 determines the maximum number of packets that can be transmitted continuously and one packet determined in advance by the protocol according to the transmission path for transmitting the packet and / or the divided packet. The area of ACK Map 255a is narrowed to an area smaller than the number of bits obtained by multiplying the maximum number of divided packets that can be generated by dividing.

  Note that each function of the wireless communication device 200 described above is actually executed by the CPU executing a program describing a processing procedure for realizing these functions, or for realizing any of the functions. This is achieved by controlling the IC or the like. For example, the functions of the reception status determination unit 260, message creation unit 265, packet assembly unit 270, and storage area optimization unit 275 of the wireless communication apparatus 200 shown in FIG. 3B are processing procedures for realizing these functions. 3 is stored in the ROM 205 of FIG. 3A, and the CPU 210 executes the program stored in this manner. Further, for example, the function of the communication unit 250 is achieved by an IC chip provided in the wireless LAN card.

(Packet division and transmission path status)
Next, the relationship between packet division and transmission path status will be described. When the state of the transmission path is good, the packet is transmitted from the base station 100 to the wireless communication apparatus 200 without being divided. In this case, the condition of the transmission path is good, so even if a packet of the original size is transmitted, it collides with other packets on the transmission path, or the packet deteriorates and the packet is received correctly. This is because there is a low probability of not being performed. Also, if the packet is divided and transmitted, the overhead increases, so it is better not to divide the packet as much as possible.

  Therefore, the packet is not divided when the state of the transmission path is good. Therefore, in the ACK Map 255a, the range indicated by R in FIG. 5, that is, the 64-bit region with the fragment number “1” and the sequence numbers “1” to “64” is the maximum range to be used. .

  For example, as shown in FIG. 6, when six undivided packets (Seq.No # 1, Seq. # 2,... Seq. # 6) are transmitted from the base station 100, FIG. As for the memory area of 5 ACK Map 255a, since each packet is not divided, only the area “1” is used on the horizontal axis. Since six packets are transmitted, the vertical axis uses the area “1” to “6”. Therefore, in this case, the use area is only 6 (= 1 × 6) bits in the memory area of the ACK Map 255a. Note that the size of each packet in FIG. 6 is equal to or less than the maximum transfer unit (MSDU: MAC Service Data Unit) in the MAC system.

  At this time, as shown in FIG. Packets # 1, # 4, and # 6 are received in error, and Seq. When the packets # 2, # 3, and # 5 are correctly received, the reception status determination unit 260, based on these determinations, sets “x” to the bit position (1, 1) of the ACK Map 255a, the bit position (1, 2) “◯”, bit position (1, 3) “◯”, bit position (1, 4) “×”, bit position (1, 5) “◯”, bit position (1, 6) “○” is stored in. These pieces of information are reception status information indicating the reception status of packets and / or divided packets.

  For a packet corresponding to the bit position in which “x” is stored, “NAK” is transmitted to the base station 100, and the packet is retransmitted from the base station 100 under certain conditions. When all the six packets are correctly received, the packets are assembled and provided to the user as data, and at the bit position (1, 1) to bit position (1, 6) of ACK Map 255a. The stored reception status information is deleted by the reception status determination unit 260.

  On the other hand, when the state of the transmission path is inferior, one packet is divided into a maximum of 16 divided packets, and is transmitted from the base station 100 to the wireless communication apparatus 200 for each divided packet. In this case, since the state of the transmission path is bad, when a packet of the original size is transmitted, there is a high probability that the packet will collide with other packets or the packet will deteriorate and the packet will not be received correctly. Therefore, for example, when four packets are transmitted, as shown in FIG. 7, only the area of sequence numbers “1” to “4” is used in the memory area of ACK Map 255a. That is, only the 64 (= 16 × 4) bit area indicated by S is used at most among the memory areas of the ACK Map 255a.

  For example, as shown in FIG. 8, a plurality of divided packets (Seq. # 1 + Frag. # 1, Seq. # 1 + Frag. # 2,...) Generated by dividing the packet are transmitted from the base station 100. In the case of the ACK Map 255a in FIG. 7, since the first packet and the third packet are divided into four divided packets, the horizontal axis indicates the fragment No. regions “1” to “4”. used. Further, since three packets are transmitted, the area of sequence No. “1” to “3” is used on the vertical axis. Therefore, in this case, the used area is only 12 (= 4 × 3) bits in the memory area of the ACK Map 255a.

  At this time, as shown in FIG. # 1 packet is divided into four divided packets, and Seq. # 1 + Frag. The # 1 and # 3 divided packets are received in error, and the same Seq. Frag. When the divided packets # 2 and # 4 are correctly received, the reception status determination unit 260, based on these determinations, as shown in FIG. 7, the bit position (1, 1) and the bit position of the ACK Map 255a “X” is stored in (3, 1), and “◯” is stored in bit position (2, 1) and bit position (4, 1).

  Next, Seq. Since the packet # 2 is transmitted without being divided and is correctly received, “◯” is stored in the bit position (1, 2) of the ACK Map 255a in FIG. Bit positions (2, 2) to (4, 2) are not used.

  Furthermore, Seq. The packet of # 3 is divided into four divided packets, and Seq. # 3 Frag. The # 1 and # 4 divided packets are received in error, and the same Seq. Frag. When the divided packets # 2 and # 3 are correctly received, the reception status determination unit 260, based on these determinations, as shown in FIG. 7, the bit position (1, 3) and the bit position of the ACK Map 255a “X” is stored in (4, 3), and “◯” is stored in bit position (2, 3) and bit position (3, 3).

  “NAK” is transmitted to the base station 100 for the divided packet managed by the bit in which “x” is stored, whereby the divided packet is retransmitted from the base station 100. Further, when all the divided packets are correctly received, the divided packets are assembled and provided to the user. For example, Frag. # 1-Frag. After the # 4 divided packet is correctly received and the information is provided to the user, the reception status information stored in the bit positions (1, 1) to (4, 1) of the ACK Map 255a is the reception status. It is erased by the determination unit 260.

(Operation of Wireless Communication Device 200)
Next, the operation of the wireless communication apparatus 200 will be described with reference to the flowchart showing the memory area optimization processing in FIG.

  Here, a wireless LAN system 802.11a using the 5 GHz band will be described as an example. Further, VoIP will be described as one of applications using 802.11a. The allowable latency of this VoIP is generally considered to be 30 (msec). In 802.11a, the maximum value Pmax “64” of the number of packets that can be continuously transmitted and the maximum value Fmax “16” of the number of divided packets that can be generated from one packet are stored in the RAM 215 in advance. Has been.

  First, the memory area optimizing process is started from step 900, and the process proceeds to step 905. The storage area optimizing unit 275 acquires the value “30” of the latency la from the RAM 215, proceeds to step 910, and can transmit continuously. The value “64” of the maximum value Pmax of the correct number of packets is acquired, and the process proceeds to step 915 to acquire the value “16” of the maximum value Fmax of the number of divided packets that can be generated. Next, the storage area optimizing unit 275 proceeds to step 920 and calculates the minimum time Tf necessary for transmitting one divided packet.

  When the burst mode (Burst Mode) for continuously transmitting packets defined in 802.11a is used, as shown in FIG. 10, the interval between each packet (IFS: Inter Frame Space) is set to SIFS. = 16 (usec) must be maintained. Furthermore, when one fragment packet (fragment) is transmitted, a PHY Header indicating the modulation rate of the fragment packet must be added before each fragment packet. The transmission time of this PHY Header is 20 (usec). Thereafter, the actual fragmented packets (fragments # 1 and # 2 in FIG. 10) are transmitted. At this time, regardless of the size (number of bytes) of the divided packet, the minimum unit of packet transmission defined by 802.11a, that is, 4 (usec) is required as the minimum transmission time. As a result, the minimum time Tf required to transmit one divided packet is 40 (= 16 + 20 + 4) (usec). In this way, the minimum time Tf necessary for transmitting the divided packet is calculated in step 920.

  Next, the storage area optimizing unit 275 proceeds to step 925 to obtain the maximum value Fn of the number of divided packets that can be divided and transmitted. As described above, generally, the maximum allowable latency when using VoIP is considered to be about 30 (msec). For this reason, if the data transmission is not completed within 30 (msec) after receiving the transmission request, the packet is discarded.

Considering this, since the minimum time Tf required to transmit one fragmented packet is 40 (usec), the maximum value Fn of the number of fragmented packets that can be sent at one time without requesting Block ACK is as follows: Calculated.
Fn = 30 (msec) / 40 (usec) = 750 (fragment)
As a result, it can be seen that it is not necessary to manage the reception status of packets and / or fragmented packets with Fn = 750 (fragment) or more.

  Therefore, the storage area optimizing unit 275 proceeds to step 930, and the number of divided packets that are smaller than the maximum value Pmax of the number of packets that can be continuously transmitted × the maximum value Fmax of the number of divided packets that can be generated and that can be divided and transmitted. An area having a number of bits larger than the maximum value Fn is secured as a memory area of the ACK Map 255a. When this is expressed visually, as shown in FIG. 11, the R area has 64 bits, so the S area must secure an area satisfying (686 + n) / 16 ≦ n. As a result, n becomes “46”. In this way, the areas indicated by R and S are secured as memory areas. As a result, it can be seen that the 274 (= 1024-750) bits in the hatched portion Q are not used for managing the reception status of the packet and / or the divided packet.

  In this way, the storage area optimizing unit 275 is smaller than the maximum value Pmax of the number of packets that can be continuously transmitted P × the maximum value Fmax bits of the number of divided packets that can be generated and the maximum value of the number of divided packets that can be divided and transmitted. An area of Fn bits or more is secured as a memory area of ACK Map 255a, and the process proceeds to step 995 to end the present process.

  As described above, when the maximum value Pmax of the number of packets that can be continuously transmitted is “64” and the maximum value Fmax of the number of divided packets that can be generated is “16”, conventionally, as described above, the maximum value is “1024”. The 1024-bit memory area is reserved for grasping the reception status so that the reception status information of the packet and / or the divided packet can be stored in the ACK Map 255a.

When all the maximum “1024” packets and / or fragmented packets are transmitted in burst mode, it takes from the first packet and / or fragmented packet to the end of transmitting the last packet and / or fragmented packet. the time is,
1024 (fragment) x 40 (minimum time required for transmission of 1-segment packet)
= 40960 (usec)
It becomes.

  However, considering the state of the transmission path for transmitting packets and / or divided packets, such as latency, for example, as described above, there is a predetermined upper limit on the number of packets and / or divided packets that can be transmitted at one time. The inventors have found.

  Therefore, the wireless communication apparatus 200 according to the present embodiment automatically narrows the memory area for storing the reception status information of the packet and / or the divided packet according to the state of the transmission path that transmits the packet and / or the divided packet. . Thereby, useless consumption of the memory space provided in the device can be suppressed. In particular, in mobile electronic devices such as mobile phones, the devices themselves are small, and the capacity of volatile memory (RAM) that can be used is limited. Therefore, the communication apparatus according to the present embodiment that can manage the reception status of packets and / or divided packets while minimizing memory consumption is particularly useful for mobile electronic devices.

  The storage area optimizing unit 275 may fix and manage the memory area of the ACK Map 255a without further optimization after automatically reducing the memory area of the ACK Map 255a according to the state of the transmission path as described above. However, it may be managed dynamically according to the state of the transmission path. Examples of the dynamic management according to the state of the transmission path include the following methods.

  That is, the storage area optimizing unit 275 determines whether a packet and / or a divided packet that has been correctly received and a packet and / or a divided packet that have not been correctly received among a transmitted packet and / or a divided packet for a certain period of time or A certain fixed number is accumulated, and the accumulated number of packets and / or the number of divided packets are compared. As a result, the storage area optimizing unit 275 further increases the packet when the ratio of the correctly received packet and / or the divided packet and / or the divided packet exceeds a certain threshold value. Is divided into a larger number of divided packets, a memory area larger than the current memory area is allocated to the ACK Map 255a. According to this, an optimal area that is smaller than Pmax × Fmax bits and dynamically adapted to the state of the transmission path can be allocated to the memory area.

  The communication system 10 is an example of a system that transmits packets by wireless communication. The base station 100 is an example of a communication device and may be any electronic device having wireless communication means such as a server capable of wireless communication. The wireless communication device 200 is an example of a communication device, and is not limited to the PC 200a or the TV 200b. For example, the wireless communication device 200 has all wireless communication means such as a mobile device such as a mobile phone, a notebook PC, and a PDA (Personal Digital Assistant). Any electronic device may be used.

  The communication system 10 may be a system in which a plurality of electronic devices (PC, PDA, mobile phone, etc.) capable of wireless communication are connected via an ad hoc network without requiring an access point such as a wireless LAN. . In an ad hoc network, not only IEEE802.11e but also a technology in which a large number of terminals are connected to each other without an access point while using technologies such as IEEE802.11x and Bluetooth widely used for wireless connection of computers and the like (multiple Hop communication).

  In the above embodiment, the operations of the respective units are related to each other, and can be replaced as a series of operations in consideration of the relationship between each other. And by replacing in this way, the embodiment of the invention of the communication device can be made the embodiment of the invention of the communication method.

  Further, by replacing the operation of each unit with the processing of each unit, a program embodiment can be obtained. Also, by storing the program in a computer-readable recording medium, the embodiment of the program can be made an embodiment of a computer-readable recording medium recorded in the program.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, the ACK Map 255a is composed of a bit map indicating the number of divided packets that can be generated (divided) on the horizontal axis and the number of packets that can be continuously transmitted on the vertical axis. However, in the present invention, any method may be used for recording the reception status information as long as the necessary minimum memory space is secured.

1 is an overall view of a communication system according to an embodiment of the present invention. It is a figure for demonstrating the packet concerning the same embodiment and a division | segmentation packet. FIG. 3A according to the embodiment is a hardware configuration diagram of the wireless communication apparatus according to the embodiment, and FIG. 3B is a functional configuration diagram of the wireless communication apparatus according to the embodiment. It is the figure which showed the memory area of ACK Map concerning the embodiment. It is the figure which showed an example of the memory utilization area | region of ACK Map concerning the embodiment. It is the figure which showed an example of the packet reception condition concerning the embodiment. It is the figure which showed an example of the memory utilization area | region of ACK Map concerning the embodiment. It is the figure which showed an example of the packet reception condition concerning the embodiment. 5 is a flowchart showing a memory area optimization processing routine executed by the wireless communication apparatus in the embodiment. It is the figure which showed an example of the packet transmission required time concerning the embodiment. It is the figure which showed optimization of the memory area of ACK Map concerning the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Communication system 100 Base station 200 Wireless communication apparatus 205 ROM
210 CPU
215 RAM
220 wireless communication circuit 200a PC
200b TV
225 Bus 250 Communication unit 255 Storage unit 255a ACK Map
260 reception status determination unit 265 message creation unit 270 packet assembly unit 275 storage area optimization unit 300 wireless LAN

Claims (6)

A communication device that allows continuous transmission / reception of packets or allows transmission / reception of divided packets,
A communication unit for receiving the packet and / or the divided packet;
A storage unit for storing reception status information indicating a reception status of the packet and / or the divided packet;
The maximum value Pmax of the given number of packets that can be continuously transmitted and the given number of divided packets that can be generated by dividing one packet in accordance with the state of the transmission path for transmitting the packet and / or the divided packet. And a storage area optimizing unit that automatically narrows the area of the storage unit to an area that is smaller than the number of bits multiplied by the maximum value Fmax. The storage area optimizing unit
A maximum value Fn of the number of divided packets that can be divided and transmitted is determined based on a predetermined latency la and a minimum time Tf required to transmit one divided packet, and the maximum number of divided packets that can be divided and transmitted is determined. The number of bits equal to or greater than the value Fn and less than the number of bits obtained by multiplying the maximum value Pmax of the number of packets that can be continuously transmitted and the maximum value Fmax of the number of divided packets that can be generated The communication device according to claim 1, wherein the communication device is optimized. The storage area optimizing unit
The communication apparatus according to claim 1, wherein the area of the storage unit is fixed and managed according to a state of a transmission path. The storage area optimizing unit
The communication apparatus according to claim 1, wherein the storage unit area is dynamically managed in accordance with a state of a transmission path.   The communication device according to claim 1, wherein the communication device wirelessly communicates with another device. A communication device that continuously transmits / receives packets, or allows the packet to be transmitted / received in a divided manner, and stores reception status information indicating reception status of received packets and / or divided packets in a storage unit. A memory area management method,
Capture latency la,
Calculating a minimum time Tf required to transmit one fragmented packet based on the information on the transmission time of the packet and / or the fragmented packet;
A maximum value Fn of the number of divided packets that can be divided and transmitted is determined based on the acquired latency la and the calculated minimum time Tf required to transmit one divided packet,
The maximum number Pmax of a given number of packets that can be transmitted continuously and the maximum value Fmax of a given number of divided packets that can be generated by dividing one packet are less than the number of bits, and are obtained as described above. A memory area management method for automatically narrowing the storage area to an area having a number of bits equal to or greater than the maximum number Fn of divided packets that can be divided and transmitted.

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