Master station of communication system and access control method

• US 7,957,342 B2
• Filed: 12/04/2007
• Issued: 06/07/2011
• Est. Priority Date: 08/06/2003
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Yamaguchi, Tsuyoshi, Yoshizawa, Kensuke, Ohmi, Shinichiro
• Primary Examiner(s): Pham; Chi H.
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US11/987,762
• Publication Number:
  US 20080117882A1
• Time in Patent Office: 1,281 Days
• Field of Search: 455/507
• US Class Current: 370/328
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/188 Time-out mechanisms
• CPC Class Codes: H04W 12/08 Access security
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

A communication bandwidth is divided into a beacon period in which all master stations compete for transmission of a beacon packet, a first carrier sense multiple access (CSMA) period in which only authorized specific stations are allowed to compete for access, and a second CSMA period in which all stations are allowed to compete for access. The master stations exchange information with each other about a communication bandwidth being used in the first CSMA period, thereby calculating a communication bandwidth which can be used by each communication system in the first CSMA period, based on the information.

Claims

1. A master station which manages a communication system, the master station comprising:

a receiver to receive a beacon packet from another master station which manages another communication system which shares a same channel with the communication system, the other master station periodically setting a beacon period in the other communication system to the channel, the beacon packet being transmitted from the other master station during the beacon period, a start time of transmission of the beacon packet being different from a start time of the beacon period, the beacon packet including information indicating an offset which is a period from the start time of the beacon period to the start time of the transmission of the beacon packet; and

a bandwidth manager to synchronize a beacon period in the communication system with the beacon period in the other communication system on the basis of the information indicating the offset, a beacon packet being transmitted from the master station during the beacon period in the communication system.

2. The master station according to claim 1, wherein the bandwidth manager synchronizes the communication system with the other communication system by repeating a process of:

obtaining a beacon packet transmission time, which is a timer value of the other master station, at a time point when the other master station starts the transmission of the beacon packet on the basis of the information indicating the offset;

obtaining a timer value of the master station at a time point when the master station receives the beacon packet from the other master station; and

correcting the timer value of the master station to an intermediate value between the beacon packet transmission time and the timer value of the master station.

3. A method performed by a master station which manages a communication system, the method comprising the steps of:

receiving a beacon packet from another master station which manages another communication system which shares a same channel with the communication system, the other master station periodically setting a beacon period in the other communication system to the channel, the beacon packet being transmitted from the other master station during the beacon period, a start time of transmission of the beacon packet being different from a start time of the beacon period, the beacon packet including information indicating an offset which is a period from the start time of the beacon period to the start time of the transmission of the beacon packet; and

synchronizing a beacon period in the communication system with the beacon period in the other communication system on the basis of the information indicating the offset, a beacon packet being transmitted from the master station during the beacon period in the communication system.

4. The method according to claim 3, wherein, at the synchronizing step, the communication system is synchronized with the other communication system by repeating a process of:

obtaining a beacon packet transmission time, which is a timer value of the other master station, at a time point when the other master station starts the transmission of the beacon packet on the basis of the information indicating the offset;

obtaining a timer value of the master station at a time point when the master station receives the beacon packet from the other master station; and

correcting the timer value of the master station to an intermediate value between the beacon packet transmission time and the timer value of the master station.