Communication system, control terminal and communication terminal

1 . A communication system comprising:

a control terminal and a communication terminal connected to the control terminal by way of a wireless channel;

the control terminal comprising:

a control terminal side control unit for instructing to generate a first frame including information necessary for connecting the communication terminal to the control terminal per se at every predetermined time interval and instructing to generate at least one or more of second frames each including information by which the communication terminal can identify the control terminal per se and having a data amount smaller than a data amount of the first frame within the first frame interval;

a wireless controller for generating the first frame and the second frame in accordance with an instruction of generating the frames from the control terminal side control unit; and

a transmitting unit for transmitting the first frame and the second frame generated by the wireless controller to the wireless channel by using a frequency previously allocated to the control terminal per se; and

the communication terminal comprises:

a receiving unit for receiving the frame from the wireless channel at the instructed frequency;

a wireless module for determining whether the frame received by the receiving unit is the first frame or the second frame; and

a communication terminal side control unit for instructing the frequency to be searched and confirming presence of the control terminal based on the first frame or the second frame determined by the wireless module.

2 . The communication system according to claim 1 , wherein the second frame is transmitted at a transmission rate higher than a transmission rate of the first frame.

3 . The communication system according to claim 1 , wherein the control terminal generates the second frame including a portion of the information for connecting the communication terminal to the control terminal per se.

4 . The communication system according to claim 1 , wherein the control terminal generates the second frame including a number of sets of the communication terminals at least controlled by the control terminal per se, or a state of using a medium.

5 . The communication system according to claim 1 , wherein when the control terminal per se cannot add a new one of the communication terminal to control, the control terminal generates the second frame including that the control terminal per se cannot add the new one of the communication terminal to control.

6 . The communication system according to claim 1 , wherein when the control terminal per cannot add a new one of the communication terminal to control, the control terminal does not generate the second frame.

7 . The communication system according to claim 1 , wherein there are present a plurality of the control terminals; and

wherein when the communication terminal receives predetermined numbers of the first frames and the second frames in searching a certain frequency, the frequency is switched to search other frequency.

8 . The communication system according to claim 7 , wherein when the frequency to be searched is switched at each time of receiving a predetermined number of the frames, the communication terminal counts the predetermined number such that at least one of the first frame is present in the predetermined number of the frames.

9 . The communication system according to claim 7 , wherein the communication terminal includes a memory for storing a frame content of the first frame when the first frame is received; and

wherein the communication terminal utilizes information of the memory in a case in which the first frame or the second frame is a frame from the same control terminal stored to the memory when the first frame or the second frame is received.

10 . The communication system according to claim 7 , wherein the control terminals are communicated with each other and the control terminals generate and transmit the first frames at the same time.

11 . The communication system according to claim 10 , wherein the control terminals generate the second frames at the same time.

12 . The communication system according to claim 7 , wherein the communication terminal measures a receiving intensity when the first frame or the second frame is received; and

wherein the communication terminal selects the control terminal to be selected based on information of the receiving intensity from the control terminals presence of which is confirmed based on the received first frame and received the second frame.

13 . A control terminal which informs presence of the control terminal per se by way of a wireless channel by using a previously determined frequency, and is select by a communication terminal and connected to the communication terminal, the control terminal comprising:

a control terminal side control unit for outputting to instruct to generate a first frame including information necessary for connecting the communication terminal to the control terminal per se at every predetermined time interval, and outputting to instruct to generate at least one or more of second frames each including information by which the communication terminal can identify the control terminal per se and having a data amount smaller than a data amount of the first frame within the interval of the first frame;

a wireless controller for generating the first frame or the second frame in accordance with an instruction of generating the frame from the control terminal side control unit; and

a transmitting unit for transmitting the first frame or the second frame generated by the wireless controller to the wireless channel by using a frequency previously allocated to the control terminal per se.

14 . The control terminal according to claim 13 , wherein the second frame is transmitted by a transmission rate higher than a transmission rate of the first frame.

15 . The control terminal according to claim 13 , wherein the control terminal generates the second frame including a portion of the information for connecting the communication terminal to the control terminal per se.

16 . The control terminal according to claim 13 , wherein the control terminal generates the second frame including a number of sets of the communication terminals controlled at least by the control terminal per se, or a state of using a medium.

17 . The control terminal according to claim 13 , wherein when the control terminal per se cannot add a new one of the communication terminal to control, the control terminal generates the second frame including that the control terminal per se cannot add the new one of the communication terminal to control.

18 . The control terminal according to claim 13 , wherein when the control terminal per se cannot add a new one of the communication terminal to control, the second frame is not generated.

19 . A communication terminal for carrying out a wireless communication with a control terminal for outputting a first frame including information necessary for connecting the communication terminal to the control terminal per se at every predetermined time interval and outputting at least one or more of second frames each including information by which the communication terminal can identify the control terminal per se and having a data amount smaller than a data amount of the first frame within the first frame interval by using a previously determined frequency, the communication terminal comprising:

a receiving unit for receiving the frame from a wireless channel at the instructed frequency;

a wireless module for determining whether the frame received by the receiving unit is the first frame or the second frame; and

a communication terminal side control unit for instructing the frequency to be searched and confirming presence of the control terminal based on the first frame or the second frame determined by the wireless module.

20 . The communication terminal according to claim 19 , wherein there are a plurality of the control terminals; and

wherein when predetermined numbers of the first frames and the second frames are received in searching a certain frequency, the frequency is switched to search other frequency.

21 . The communication terminal according to claim 20 , wherein when the frequency to be searched is switched at every time of receiving the predetermined number of the frames, the communication terminal counts the predetermined number such that at least one of the first frame is present in the predetermined numbers of the frames.

22 . The communication terminal according to claim 20 , wherein the communication terminal includes a memory for storing a frame content of the first frame when the first frame is received; and

wherein information of the memory is utilized in a case in which the first frame or the second frame is a frame from the same control terminal stored to the memory when the first frame or the second frame is received.

23 . The communication terminal according to claim 20 , wherein a receiving intensity is measured when the first frame or the second frame is received; and

wherein the control terminal to be connected is selected based on information of the receiving intensity from the control terminal presence of which is confirmed based on the received first frame or the received second frame.