Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1998-08-25
2002-08-06
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S337000, C370S445000
Reexamination Certificate
active
06430172
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio communication system, a transmitting apparatus, a radio communication control apparatus, a receiving apparatus, and a radio communication method suited to transfer asynchronous data and isochronous data among a plurality of terminals.
2. Description of the Related Art
As computers have become highly functional, it has been frequently performed that a plurality of computers are connected to form a local area network (LAN) in order to share files and data and to transfer data and electronic mail. In a conventional LAN, computers are connected by wire with the use of optical fibers, coaxial cables, or twisted pair cables.
In such a wired LAN, since connection work is required, it is difficult to form a LAN easily. In addition, cable wiring is troublesome in a wired LAN. Therefore, a radio LAN has drawn attention as a system which releases the user from wiring required for the conventional wired LAN. In this system, data collision is avoided by the use of carrier sense multiple access (CSMA) or polling when asynchronous data is transferred.
FIGS. 1A and 1B
and
FIGS. 2A
to
2
C roughly show radio data communication methods with the conventional technology.
FIGS. 1A and 1B
illustrate CSMA communication. Each communication apparatus formed of a personal computer and a communication unit senses whether a carrier signal is on a transfer path prior to communication. When there is no signal, the apparatus can start transmission. A communication apparatus “A” starts data transfer since there is not a carrier signal on the transfer path. On the other hand, since a communication apparatus “B” senses the carrier signal sent from the communication apparatus “A” on the transfer path, it does not transmit data. After a time “t” generated by a certain random number elapses, the communication apparatus “B” again senses a carrier signal. When there is no carrier signal on the path, the apparatus can transmit data. In CSMA, data may collide with each other on a transfer path. Therefore, each communication apparatus monitors a transfer path after data transfer, and if collision occurs, the data is again transmitted after a certain time period. A control station for controlling communication is not required in CSMA.
FIGS. 2A
to
2
C illustrate polling communication. In this method, a control station for controlling communication is provided to control communication by each communication apparatus constituting a system. The control station sequentially inquires of each communication apparatus whether it has data to be transmitted. In
FIGS. 2A
to
2
C, a communication apparatus “a” is inquired of first. When the communication apparatus “a” has data to be transmitted, it transmits the data. After this transmission, the communication apparatus “b” is then inquired next. When it has data to be transmitted, it transmits the data. In this method, data does not collide with each other on a transfer path.
In recent years, it has been required that data, such as sound, music, and a motion picture, be transferred through such a radio LAN. Such data is usually large in size and needs to maintain continuity in time. When such data is to be transferred in the above conventional system, a data transfer rate may increase or decrease according to the increase or decrease of traffic in a transfer path.
When other data transfer is not performed and traffic is light on a transfer path, the specified transfer rate is ensured and transfer can be performed without any problems. If the traffic is heavy on the transfer path, however, a data delay becomes large and the transfer rate decreases. Therefore, to eliminate this delay, the receiving side needs to have a very large buffer. In some cases, data becomes intermittent. This means that reproduction of a motion picture or sound is paused.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a radio communication system, a transmitting apparatus, a radio communication control apparatus, a receiving apparatus, and a radio communication method which suppress a delay time to a low level and ensure a constant transfer rate without being affected by an increase or decrease of communication traffic.
The foregoing object is achieved in one aspect of the present invention through the provision of a radio communication system including a plurality of radio communication terminals and a radio communication control terminal for controlling radio communication, including: radio communication means having transmitting means and receiving means; and radio communication control means having controlling means, transmitting means, and receiving means for controlling communication performed by the radio communication means, wherein asynchronous data and isochronous data is transferred through a radio communication path for communication among a plurality of the radio communication means.
The foregoing object is achieved in another aspect of the present invention through the provision of a radio communication method used between a plurality of radio communication terminals and a radio communication control terminal for controlling radio communication, wherein, when communication is performed among the plurality of radio communication terminals through a radio communication path, asynchronous data and isochronous data is transferred through the radio communication path.
As described above, asynchronous data and isochronous data can be transferred through a radio communication path with which communication is performed among a plurality of radio communication terminals.
The foregoing object is achieved in still another aspect of the present invention through the provision of a transmitting apparatus for transmitting information data in units of frames, including: means for requesting information-data transmission and for transmitting information related to the information data in a first time region of a frame; means for receiving information indicating whether communication according to the request is allowed and if the communication is allowed, for receiving information related to a second time region, in which communication is allowed, in the frame; and means for transmitting the information data in the second time region according to the information.
The foregoing object is achieved in yet another aspect of the present invention through the provision of a transmitting method for transmitting information data in units of frames, including the steps of: requesting information-data transmission and transmitting information related to the information data in a first time region of a frame; receiving information indicating whether communication according to the request is allowed and if the communication is allowed, receiving information related to a second time region, in which communication is allowed, in the frame; and transmitting the information data in the second time region according to the information.
As described above, since data is transferred in units of frames, a transmitting apparatus transmits a transmission request and information related to information data in a first region in a frame, and the transmitting apparatus transmits the information data in a second time region, in which communication is allowed, in the frame, the information data is transmitted at a constant transfer rate without being affected by an increase and decrease of traffic during communication.
The foregoing object is achieved in a further aspect of the present invention through the provision of a radio communication control apparatus for controlling information-data communication performed in units of frames among a plurality of radio communication terminals, including: means for receiving a transmission request of information data and for receiving information related to the information data in a first time region in a frame; determination means for determining whether transmission of the information data is allowed in a second time region in the frame, according to the
Hiraiwa Hisaki
Sugita Takehiro
Usui Takashi
Cangialosi Salvatore
Maioli Jay H.
Sony Corporation
Vanderpuye Ken
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