WIRELESS COMMUNICATION DEVICE AND WIRELESS COMMUNICATION METHOD

Abstract

A wireless communication device that performs packet transmission in accordance with a packet transmission system that performs wireless bandwidth allocation by virtual carrier sensing has a time-point management section that manages the time-point and outputs current time-point information, and a parameter management section that manages a parameter relating to packet transmission right acquisition priority. The parameter management section includes: a parameter holding section that holds, in association with a time-point, a parameter relating to packet transmission right acquisition priority that changes with a different distribution between wireless communication devices located in the same wireless LAN area, in a prescribed period; and a parameter alteration section that reads, from the parameter holding section, the parameter associated with current time-point information and dynamically alters a current parameter relating to packet transmission right acquisition priority in accordance with the parameter thus read.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a layout diagram of a wireless LAN network according to an embodiment of the present invention.

FIG. 2 is a hardware layout diagram of a wireless communication device.

FIG. 3 is a function block layout diagram of a wireless communication device.

FIG. 4 is a flow chart showing packet transmission processing performed according to the present invention.

FIG. 5 is a time chart showing the transmission right acquisition condition of each VoIP terminal when transmission right acquisition priority times are set at different time-points for each of the VoIP terminals in accordance with the packet generation period.

FIG. 6 is a time chart showing the transmission right acquisition condition of each VoIP terminal when the transmission right acquisition priority times of each VoIP terminal are allocated no more than the calculated channel occupation time if transmission and reception are performed with the maximum transmission rate.

FIG. 7 is a time chart showing the transmission right acquisition condition of each VoIP terminal when the transmission right acquisition priority times are allocated such that no overlapping of the VoIP terminals takes place.

FIG. 8 is a time chart showing the transmission right acquisition condition of each VoIP terminal when the transmission right acquisition priority times of each VoIP terminal are allocated such that there is partial overlap with the transmission right acquisition priority times of other VoIP terminals.

FIG. 9 is a time chart showing the transmission right acquisition condition of each VoIP terminal when the maximum value of the distribution function of packet transmission right acquisition priority time is after an intermediate time-point.

FIG. 10 is a time chart showing the transmission right acquisition condition of each VoIP terminal when the maximum value of the distribution function of packet transmission right acquisition priority time is before the intermediate time-point.

FIG. 11 is a time chart showing the transmission right acquisition condition of each VoIP terminal when the packet transmission right acquisition priority time of a given terminal is set to the last in the case where another VoIP terminal becomes unable to acquire a transmission right within the packet transmission right acquisition priority time.

FIG. 12 is a table showing the values of IFS and CWmin for VoIP terminals A to C and a data terminal D respectively.

FIG. 13 is a table showing the values of IFS and CWmin for VoIP terminals A to C respectively in the case where the transmission waiting time parameter that is once set to a small value is held for a prescribed period.

FIG. 14 is a table showing the values of IFS and CWmin of a VoIP terminal A in a period in the case where a ramp function is employed in the distribution of priority time.

FIG. 15 is a table showing the values of IFS and CWmin of a VoIP terminal A in the case where the transmission rate of the VoIP terminal A drops and another VoIP terminal becomes unable to acquire a transmission right within the transmission right acquisition priority period.

Claims

1. A wireless communication device that performs packet transmission in accordance with a packet transmission system that performs wireless bandwidth allocation by virtual carrier sensing, comprising: time-point management module that manages a time-point and outputs current time-point information; andparameter management module that manages a parameter relating to packet transmission right acquisition priority,wherein said parameter management module comprises:parameter holding module that holds, in association with a time-point, a parameter relating to packet transmission right acquisition priority that changes with a different distribution between wireless communication devices located in the same wireless LAN area, in a prescribed period; andparameter alteration module that reads, from said parameter holding module, said parameter associated with current time-point information that is output by said time-point management module and dynamically alters a current parameter relating to packet transmission right acquisition priority in accordance with the parameter thus read.

2. The wireless communication device according to claim 1 further comprising: transmission rate control module that manages the transmission rate used by this wireless communication device itself and outputs maximum transfer rate information; andchannel occupation time calculation module that calculates the channel occupation time corresponding to the time required for packet transmission and reception, based on the maximum transmission rate information that is output by said transmission rate control module and transmission packet size,wherein said parameter management module is configured to set a packet transmission right acquisition priority time of this wireless communication device itself to a value longer than the channel occupation time calculated by said channel occupation time calculation module.

3. The wireless communication device according to claim 1, wherein said parameter management module is configured to set the packet transmission right acquisition priority time of this wireless communication device itself such that the packet transmission right acquisition priority time of this wireless communication device itself partially overlaps with a packet transmission right acquisition priority time of another wireless communication device in the same wireless LAN area.

4. The wireless communication device according to claim 1, wherein said parameter management module is configured to manage said parameter by employing, as a distribution function of packet transmission right acquisition priority in the packet transmission right acquisition priority time, a function in which the maximum value of the packet transmission right acquisition priority occurs subsequent to an intermediate time-point of the packet transmission right acquisition priority time and before a termination time-point thereof.

5. The wireless communication device according to claim 1, wherein said parameter management module is configured to manage said parameter by employing a step function as a distribution function of packet transmission right acquisition priority in the packet transmission right acquisition priority time.

6. The wireless communication device according to claim 1 further comprising: failure management module that manages and outputs at least one of a transmission failure probability based on a transmission failure history in the packet transmission right acquisition priority time and a transmission right acquisition failure probability based on a transmission right acquisition failure history,wherein, when at least one of the transmission failure probability and transmission right acquisition failure probability output by said failure management module is a prescribed threshold value or more, said parameter management module is configured to increase the value of the packet transmission right acquisition priority in the packet transmission right acquisition priority time or a variance of this value.

7. The wireless communication device according to claim 1, wherein said parameter management module is configured to use a Contention Window in accordance with a prescribed distribution function in the packet transmission right acquisition priority time, not only on an initial transmission, but also on re-transmitting, so long as this is within the packet transmission right acquisition priority time.

8. The wireless communication device according to claim 1, wherein said parameter management module is configured to set the packet transmission right acquisition priority time such that the packet transmission right acquisition priority time of a wireless communication device whose channel occupation time has been increased to such an extent as to impede transmission right acquisition by another wireless communication device among a plurality of wireless communication devices located within the same wireless LAN area, is last in terms of time among packet transmission right acquisition priority times of said plurality of wireless communication devices.

9. A wireless communication method in a wireless communication device provided with parameter holding module that holds, in association with a time-point, a parameter relating to packet transmission right acquisition priority that changes with a different distribution between wireless communication devices located in the same wireless LAN area, in a prescribed period, the wireless communication method being a method for performing packet transmission in accordance with a packet transmission system that performs wireless bandwidth allocation by virtual carrier sensing,the wireless communication method comprising:a time-point ascertaining step of ascertaining a current time-point;a parameter reading step of reading the parameter relating to packet transmission right acquisition priority associated with current time-point information, from said parameter holding module; anda parameter alteration step of dynamically altering the current parameter relating to packet transmission right acquisition priority, in accordance with the parameter thus read.