[0052] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.
[0053] The application principle of the present invention will be described in detail below with reference to the accompanying drawings.
[0054] The present invention provides a method for establishing a control channel in a cognitive radio network, which takes into account the problem of competition between multiple unlicensed users for the frequency band during the establishment of the control channel. In this method, the control channel and the data transmission channel may be different channels After the control channel is established, unlicensed users select the appropriate data transmission channel through the exchange of control information and channel density information, which solves the uneven distribution of unlicensed users and the control channel and data in the existing control channel establishment method. The transmission channel is a problem faced by the same channel; in addition, the unlicensed user in the present invention adopts the real-time monitoring mode, which avoids the control channel establishment failure problem caused by the unlicensed user being both the sender and the receiver, such as figure 1 As shown, it specifically includes the following steps:
[0055] (1) Unlicensed users access the available channels, specifically including the following steps:
[0056] (1.1) Perceive the authorized channel to obtain the channel set available to unlicensed users and the density information of the available channels; among them, the method of obtaining channel density information is: unlicensed users monitor the information of unlicensed users within their communication range Communication, obtain the channels accessed by unlicensed users within its communication range, count the number of unlicensed users in each channel, and obtain the density of unlicensed users in each available channel;
[0057] The density of the channel is represented by the number of unlicensed users on the unit frequency band, namely ρ C =M C /B C; Where: ρ C Represents the density of channel C, M C Represents the number of unauthorized users on channel C, B C Represents the bandwidth of channel C; it is usually assumed that the frequency band in the cognitive radio network is divided into N channels of equal bandwidth, so the bandwidth of each channel is equal, namely: B C =B/N, where B is the total bandwidth of the frequency band in the cognitive radio network.
[0058] (1.2) Generate channel hopping sequence according to the available channel set and channel hopping method;
[0059] (1.3) At the beginning of each time slot, if the unlicensed user does not transmit data, it will access the corresponding channel according to its channel hopping sequence. The generation process of the channel hopping sequence is in the prior art, so I won’t repeat it here. . Before accessing the channel, the unlicensed user first perceives the channel in real time, and perceives whether there is an authorized user using this frequency band. If authorized users are using this frequency band, unlicensed users will skip this channel and try to access the next channel in their channel hopping sequence.
[0060] Such as figure 2 As shown, the time of each time slot can be divided into time used for channel switching, time used for channel sensing, time used for channel competition, and time used for data transmission;
[0061] The channel switching includes two modes: channel switching mode 1 and channel switching mode 2; channel switching mode 1 refers to unlicensed users performing hopping channel switching according to their channel hopping sequence; channel switching mode 2 refers to unlicensed users following control information The data transmission channel determined during the exchange process is switched.
[0062] The channel sensing refers to that unlicensed users perform channel sensing before accessing the channel, and sense whether the channel is occupied by authorized users;
[0063] The channel competition refers to the competition between unlicensed users for the right to use the channel to send RTS data packet frames in an attempt to establish a control channel with the intended unlicensed user;
[0064] (2) The exchange of control information between the unauthorized user and the destination unauthorized user includes:
[0065] (2.1) When an unlicensed user has data to transmit, it will compete for the right to use the channel; preferably, the unlicensed user uses the carrier sense multiple access/conflict detection method based on the distributed coordination function to compete for the channel. Right to use; the competition process is an existing technology, so I won’t go into too much detail in this application;
[0066] (2.2) After the unlicensed user successfully competes for the right to use the channel, the unlicensed user will encapsulate the set of available channels and the density information of the available channels that he perceives in the RTS data packet frame and transmit it to the intended unlicensed user ; Its purpose: After successfully receiving the RTS data packet frame, the unauthorized user will obtain the available channels and the density information of each channel perceived by the unauthorized user sending the RTS data packet frame;
[0067] (2.3) When the unauthorized user has no data to transmit or is in the process of backoff reduction, the unauthorized user performs real-time monitoring; when the unauthorized user listens to the RTS packet frame, the target user is himself, then the CTS is sent to the RTS data The sender of the packet frame is used to inform the sender of the received RTS data packet frame that it has successfully established communication with the destination unauthorized user and the determined data transmission channel;
[0068] (2.4) When the unauthorized user who sends the RTS data packet frame receives the CTS data packet frame, it will jump to the determined data transmission channel contained in the CTS data packet frame for data transmission; when sending the RTS data packet frame When the unauthorized user does not receive the CTS packet frame, there will be a RTS packet frame conflict or the unauthorized user and the target unauthorized user do not access the same channel, the unauthorized user will perform the RTS packet frame retransmission process until it is received Its purpose is that the CTS data packet frame sent by the unauthorized user or the remaining time of the current time slot is not enough for the sending of RTS data packet frame and the reception of CTS data packet frame;
[0069] Among them: such as image 3 As shown, the RTS data packet frame includes: address information, duration information of unlicensed users and their intended unlicensed users, the available channel set of the unlicensed user, and the channel density information of the available channel set; where, The time length of the duration information is sufficient to transmit a short inter-frame interval SIFS;
[0070] Such as Figure 4 As shown, the CTS data packet frame includes: address information, duration information, and determined data transmission channel information of the unlicensed user and the purpose of the unlicensed user; wherein the duration of the information is long enough to complete one CTS data packet frame and SIFS transmission time between a short frame interval.
[0071] (3) Establish a data transmission channel to realize data transmission; in the present invention, when the unlicensed user and the target unlicensed user access the same available channel at the same time, the data transmission channel can be established according to the control information exchange process, the specific implementation method for:
[0072] Purpose Unlicensed users obtain the set of available channels perceived by the sender of the RTS packet frame from the RTS packet And the channel density set of each available channel Where |C t | Is the number of available channels perceived by the sender of the RTS packet frame, C ti And ρ ti Is the available channel set C t The i-th usable channel and its corresponding channel density; then the purpose of unauthorized users will be C t And the set of available channels Comparing to get the public available channel set Where |C r |and|C C |respectively the number of available channels perceived by the destination unauthorized user and the number of publicly available channels between the destination unauthorized user and the sender of the RTS packet frame, C Ci Is C C The i-th common control channel in the middle. Then according to ρ t And ρ r Calculate C C The average density of the channels in and the ascending order of the average density value obtained to obtain the density set of publicly available channels Where ρ r It is the set of channel density perceived by unlicensed users for the purpose. Choose the channel density as ρ C1' The corresponding channel is used as the data transmission channel between the destination unauthorized user and the sender of the RTS data packet frame. among them, ρ Cx' Is C C The average density of the x'th channel in, ρ tx' With ρ rx' They are the density of the x'th channel perceived by the sender of the RTS packet and the destination unauthorized user.
[0073] In summary:
[0074] The invention discloses a method for establishing a control channel in a cognitive radio network, which includes available channel access; control information exchange; and data transmission channel establishment. Before establishing a control channel, an unlicensed user first perceives the available frequency band and frequency band density information; then accesses the available channel according to its channel hopping sequence; when it has data to transmit, it turns on the channel competition mode; After the competition is successful, send the RTS data packet frame with the available channel and channel density information. When the destination node receives the RTS data packet frame, it determines the difference between the two based on the public available channels and density information of the two. Data transmission channel. The invention effectively solves the problem of low-efficiency frequency band utilization caused by the uneven distribution of unlicensed users in each frequency band in the traditional cognitive radio network. In addition, the separation of the control channel and the data transmission channel in the method of the present invention can increase the chance of attempting to establish the control channel. In addition, the method in the present invention fully considers the characteristics of the cognitive radio network, shortens the length of the duration contained in the control information, and reduces the control channel caused by the unlicensed user and the target unlicensed user not in the same frequency band. Establish a delay problem.
[0075] The basic principles and main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the foregoing embodiments. The foregoing embodiments and descriptions only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have Various changes and improvements, these changes and improvements fall within the scope of the claimed invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.
