CN106027118B - A kind of channel of cognitive radio networks crosses method and system - Google Patents

Abstract

It crosses method the invention discloses a kind of channel of cognition wireless network, including：The corresponding non-slotted channel sequence that crosses of each user in cognition wireless network is generated, and section independently starts the channel channel of user in different times using same CH algorithms；When crossing there are two subscriber channels, the corresponding new non-slotted channel sequence of two users is generated, and using new non-slotted channel sequence as the non-slotted channel sequence that crosses using recent minimum channel access algorithm；It is crossed using the corresponding non-slotted channel sequence that crosses of each user；Crossing the time for user can be shortened, and then improve the speed that crosses of channel hopping；It crosses system the present invention also provides a kind of channel of cognition wireless network, crossing the time for user can be shortened, and then improve the speed that crosses of channel hopping.

Description

A channel crossover method and system for a cognitive radio network

technical field

The present invention relates to the technical field of channel crossover, in particular to a channel crossover method and system for a cognitive wireless network.

Background technique

Currently, due to the exponential growth of various wireless devices and fixed spectrum allocation rules, some spectrums are already overcrowded, while most spectrums are unused or not utilized at a high rate. In order to alleviate the unbalanced utilization of spectrum resources, cognitive radio technology is proposed to enable secondary users to effectively utilize the scarce and valuable spectrum resources.

In cognitive radio networks (CRNS), secondary users may not know each other's existence in advance, thus, before they exchange information, they detect each other's presence to establish a communication link. Channel rendezvous is a basic process in which two or more radios of a secondary user intersect and establish a link on a commonly used channel, among which channel hopping (Channel Hopping, CH) is one of the most representative techniques of blind rendezvous . Using CH technology, each secondary user of CRN selects a set of channels and frequency hopping sequences in the channels to meet with potential neighbors.

In the existing channel crossover method, each user independently uses the same frequency hopping algorithm to generate its own channel frequency hopping sequence, and they can communicate directly when they exist on the same frequency hopping channel in a certain time slot. And, when two users rendezvous, they will exchange each other's frequency hopping sequences in the next few time slots, and then frequency hop in their own way. For example, as shown in Figure 1, there are three users u ₁ , u ₂ , and u ₃ , and these three users have 6 common channels. When u ₂ and u ₃ meet for the first time in time slot 1 of channel 4, they will Continuous frequency hopping (skipping channel 3 time slot 3 and channel 5 time slot 4) until u ₁ and u ₂ meet at channel 4 time slot 9, at this time, since u ₁ can get the next time slot of u ₃ through u ₂ ( time slot 10), u ₁ can switch to the channel of u ₃ in time slot 10, therefore, the rendezvous time (TTR) of these three users is 11 time slots; thus it can be understood that such frequency hopping extends all The rendezvous time of the user affects the rendezvous speed of the channel frequency hopping. Therefore, how to shorten the rendezvous time of the user, and further increase the rendezvous speed of the channel frequency hopping, is a technical problem to be solved by those skilled in the art.

Contents of the invention

In view of this, the present invention provides a method and system for channel rendezvous in a cognitive wireless network, so as to shorten the rendezvous time of users and increase the rendezvous speed of channel frequency hopping.

In order to solve the above technical problems, the present invention provides a channel convergence method for a cognitive wireless network, including:

Use the same CH algorithm to generate the corresponding intersection time slot channel sequence for each user in the cognitive wireless network, and independently start the user's channel channel in different time periods;

When there are two user channel intersections, use the least recent channel access algorithm to generate new time slot channel sequences corresponding to the two users, and use the new time slot channel sequence as the intersection time slot channel sequence;

The rendezvous is performed by using the rendezvous time slot channel sequence corresponding to each user.

Wherein, when there are two user channel intersections, the new time slot channel sequence corresponding to the two users is generated by using the least recent channel access algorithm, and the new time slot channel sequence is used as the intersection time slot channel sequence, including:

Determine the value of a message length;

When two user channels converge, the least recent channel access algorithm is used to generate a new time slot channel sequence corresponding to an information length for each of the two users, and the new time slot channel sequence is used as a crossover time slot channel sequence.

Among them, using the least recent channel access algorithm to generate a new time slot channel sequence corresponding to an information length for two users, including:

Comparing the crossover time slot channel sequences of two users with channel crossover, determining the crossover time slot that the two users will cross over on the same channel within one message length;

Determining the user with more available channels among the two users as the target user;

The number of visits of each available and non-overlapping channel of the target user is counted, and the channel with the least number of visits is selected as the access channel of the crossover time slot.

Wherein, determining the user with more available channels among the two users as the target user includes:

respectively counting the number of available channels of the two users;

selecting users with a large number of said users as target users;

If the numbers of available channels of the two users are the same, one user is randomly selected as the target user.

Wherein, selecting the channel with the least number of visits as the access channel of the rendezvous time slot includes:

Selecting the channel with the least number of visits as the access channel of the rendezvous time slot;

If there are a plurality of channels with the least number of visits, a channel is randomly selected from the plurality of channels with the least number of visits as the access channel of the rendezvous time slot.

The present invention also provides a channel convergence system of a cognitive wireless network, including:

The CH algorithm module is used to use the same CH algorithm to generate the corresponding intersection time slot channel sequence of each user in the cognitive wireless network, and independently start the user's channel channel in different time periods;

The least recent channel access algorithm module is used to generate the new time slot channel sequence corresponding to the two users by using the least recent channel access algorithm when there are two user channel intersections, and use the new time slot channel sequence as the intersection time slot channel sequence;

The rendezvous module is configured to use the rendezvous time slot channel sequence corresponding to each user to perform rendezvous.

Wherein, the least recent channel access algorithm module includes:

an information length determining unit, configured to determine a value of an information length;

The least recent channel access algorithm unit is used to generate a new time-slot channel sequence corresponding to an information length for each of the two users by using the least-recent channel access algorithm when there are two user channel intersections, and convert the new time-slot channel sequence as a cross-slot channel sequence.

Wherein, the least recent channel access algorithm unit includes:

The rendezvous time slot subunit is used to compare the rendezvous time slot channel sequences of two users with channel rendezvous, and determine the rendezvous time slot that the two users will rendezvous on the same channel within one message length;

a target user subunit, configured to determine the user with more available channels among the two users as the target user;

The channel changing subunit is configured to count the number of visits of each available and non-overlapping channel of the target user, and select the channel with the least number of visits as the access channel of the rendezvous time slot.

Wherein, the target user subunit is specifically used to separately count the number of available channels of the two users; select the user with the largest number as the target user; if the number of available channels of the two users is the same, randomly Select a user as a child of the target user.

Wherein, the channel changing subunit is specifically configured to select the channel with the least number of visits as the access channel of the intersection time slot; if there are multiple channels with the least number of visits, randomly select one of the channels with the least number of visits The channel serves as the access channel of the rendezvous time slot.

The above-mentioned method for channel crossing in a cognitive wireless network provided by the present invention includes: using the same CH algorithm to generate a crossover time slot channel sequence corresponding to each user in the cognitive wireless network, and independently starting the channels of the users in different time periods channel; when there are two user channel intersections, use the least recent channel access algorithm to generate a new time slot channel sequence corresponding to the two users, and use the new time slot channel sequence as the intersection time slot channel sequence; use each user's corresponding The crossover time slot channel sequence of the crossover is performed;

It can be seen that this method uses the least recent channel access algorithm to change the channel sequence of rendezvous time slots of users who have rendezvous to prevent them from rendezvous, so as to increase the speed of rendezvous between them and other channels, thereby shortening the rendezvous time of users, thereby improving channel efficiency. Convergence speed of frequency hopping; the present invention also provides a channel converging system of a cognitive wireless network, which has the above-mentioned beneficial effects, and will not be repeated here.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

FIG. 1 is a schematic diagram of a channel rendezvous process provided by the prior art;

FIG. 2 is a flowchart of a channel rendezvous method for a cognitive wireless network provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of an improved channel rendezvous process provided by an embodiment of the present invention;

Fig. 4 is the experimental diagram of the channel rendezvous process after L=20 improvement under the symmetrical situation that the embodiment of the present invention provides;

Fig. 5 is the experimental diagram of the channel rendezvous process after N=10 improvement under the symmetrical situation provided by the embodiment of the present invention;

FIG. 6 is an experimental diagram of the channel rendezvous process after L=20 improvement under the asymmetrical condition provided by the embodiment of the present invention;

FIG. 7 is an experimental diagram of the channel rendezvous process after N=10 improvement provided by the embodiment of the present invention under the asymmetrical condition;

FIG. 8 is a schematic structural block diagram of a channel crossover system of a cognitive wireless network provided by an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The core of the present invention is to provide a channel convergence method and system for a cognitive wireless network, so as to shorten the convergence time of users and increase the convergence speed of channel frequency hopping.

In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

It is assumed that a CRN is composed of N (N≥2) secondary users, and they can be represented by a set N={u ₁ , . . . , u _N }. It is assumed that the system is slotted and that all time slots have the same and fixed length. The licensed spectrum is divided into M (M≧1) non-overlapping channels denoted by M={c ₁ , . . . , c _M }. It is assumed that all secondary users in the network know all these channels, and each user is equipped with a single cognitive radio. Considering the heterogeneity of the spectrum, set Indicates the available channels of group u _I.

If user i and user j hop on the same channel in the same time slot, then they merge. The acceleration algorithm is a collection of converging users, each of which acts as a radio entity. Therefore, they can try to merge with other users to form a group. Its working principle is shown in FIG. 2: Referring to FIG. 2, FIG. 2 shows a flow chart of a channel rendezvous method for a cognitive wireless network provided by an embodiment of the present invention. The method may specifically include the following steps:

S100. Using the same CH algorithm to generate a channel sequence of converging time slots corresponding to each user in the cognitive wireless network, and independently start the channel channels of the users in different time periods;

Among them, the purpose of this step is that all users use the same CH algorithm to generate their cross-slot channel sequences, for example, users u ₁ , u ₂ , u ₃ shown in Figure 1 in each of the 16 time slots The channels corresponding to the slots form a channel sequence of intersecting time slots; each user starts the channel independently from different time periods. For example, the users u ₁ , u ₂ , and u ₃ shown in FIG. 1 independently activate the channels of the users in three different time periods.

S110. When there is channel intersection of two users, use the least recent channel access algorithm to generate a new time slot channel sequence corresponding to the two users, and use the new time slot channel sequence as the intersection time slot channel sequence;

Wherein, each user communicates by using the intersecting time slot channel sequence generated by the CH algorithm, and if there are two users in the same channel in the same time slot, the two users are intersecting. Since they will share each other's FM sequence information in the next time slot after rendezvous, that is, the two users no longer need to rendezvous; therefore, in order to shorten the rendezvous time of each user in the cognitive wireless network, it is necessary to prevent the The users who have merged are merged again; therefore, the method uses the least recent channel access algorithm to generate a new time slot channel sequence corresponding to the two users, and uses the new time slot channel sequence as the merged time slot channel sequence. In this way, when each channel performs rendezvous, not all of them use the default frequency hopping sequence generated by the CH algorithm to try rendezvous.

The specific process of step S110 may be:

Determine the value of a message length;

When two user channels converge, the least recent channel access algorithm is used to generate a new time slot channel sequence corresponding to an information length for each of the two users, and the new time slot channel sequence is used as a crossover time slot channel sequence.

Wherein, it is not necessary to modify the channels corresponding to all the subsequent time slots of the merged users, and only need to modify within one message length; here, the value of one message length can be set as the length used by all users for rendezvous.

That is, when any two users converge, they will share each other's frequency hopping sequence information from the next time slot. Define a message length as L, and then they use the least recent channel access algorithm to generate a new channel sequence of L next slots, and notify the contact method, that is, the change of the channel sequence of crossing slots, in this time slot.

Among them, using the least recent channel access algorithm to generate a new time slot channel sequence corresponding to an information length for two users, including:

Comparing the crossover time slot channel sequences of two users with channel crossover, determining the crossover time slot that the two users will cross over on the same channel within one message length;

Determining the user with more available channels among the two users as the target user;

The number of visits of each available and non-overlapping channel of the target user is counted, and the channel with the least number of visits is selected as the access channel of the crossover time slot.

Wherein, if the number of available channels of the two users is the same, a user is randomly selected as the target user; if there are multiple channels with the least number of visits, a channel is randomly selected from the multiple channels with the least number of visits as the target user. access channel for the above-mentioned crossover slot.

That is, when any two users meet in a certain time slot, they will share frequency hopping sequence information in the next time slot. Use the least recent channel access algorithm to reduce repeated rendezvous to speed up rendezvous with other users. In this algorithm, only the channels of those time slots where the users are about to rejoin are changed. The basic requirement is that they do not hop to the same channel during these timeslots. Its working principle can be as follows:

Comparing two crossover time slot channel sequences to find out the time slot where two users are about to cross over on the same channel;

Users with more channels available will be chosen to change their sequence, which will make the sequence more flexible. They can be randomly selected if they have the same number of available channels.

The access channel is retuned during these selected time slots. The specific method is to calculate the number of visits of each available and non-overlapping channel of the user in the first L time slots of the time slot to be adjusted, and then select the channel with the least number of visits as the access time of the time slot channel. If there are multiple channels with the least access times, one of the channels is randomly selected.

S120. Perform rendezvous by using the rendezvous timeslot channel sequence corresponding to each user.

Wherein, when the new sequence is completed, each user uses its corresponding default frequency hopping sequence to try to rendezvous.

Please refer to Figure 1 and Figure 3 and use a simple example to illustrate the principle of the algorithm and the process of accelerating convergence:

As shown in Figure 1, there are three users u ₁ , u ₂ , and u ₃ , and these three users have 6 common channels. When u ₂ and u ₃ meet for the first time in channel 4 time slot 1, they will continue to hop frequency (skip channel 3 time slot 3 and channel 5 time slot 4) until u ₁ and u ₂ intersect in channel 4 time slot 9, at this time, since u ₁ can get the next time slot of u ₃ through u ₂ (time slot 10), u ₁ can switch to the channel of u ₃ in time slot 10, therefore, the rendezvous time (TTR) of these three users is 11 time slots;

Using the method of this embodiment, i.e. under accelerated conditions, once u ₂ and u ₃ meet for the first time in channel 4 slot 1, they will change their frequency hopping sequence to ensure that they will not be in any slot time hopping onto the same channel. For example, u ₂ changes the channel sequence of time slot 3, time slot 4 and time slot 5, then, when u ₁ and u ₂ intersect in channel 2 time slot 4, since u ₁ can get u ₃ next through u ₂ For the channel of time slot (slot 5), u ₁ can switch to the channel of u ₃ in time slot 5. All their rendezvous times are reduced from 11 to 6.

The performance of the above method can be evaluated using a simulator written in C++, in which a random algorithm effective both in symmetric and asymmetric cases is chosen as the sequence generation algorithm. Please refer to Figure 4 to Figure 7 for the experimental results;

Wherein, Fig. 4 shows the total time and the number of users (L=20) in the symmetrical case, that is, in the symmetrical case, the intersection time increases with the increase of users with L=20, and all users have 6 common available channels. However, recent least channel access algorithms greatly reduce the time required for rendezvous. Fig. 5 shows the time ratio and the intersection message length (N=10) in the symmetrical case, that is, in the symmetrical case, the intersection time ratio between the random algorithm and the least recent channel access algorithm is low. When L is small, the ratio decreases with the increase of L, and when L reaches a constant value, the ratio will also obtain a dynamic stable value.

Figure 6 shows the total time and the number of users (L=20) under the asymmetrical situation, that is, under the asymmetrical situation, the time of convergence increases with the increase of users with L=20, and all users have at least 3 a common channel. However, recent least channel access algorithms greatly reduce the time required for rendezvous. Fig. 7 shows the time ratio and the intersection message length (N=10) in the case of asymmetry, that is, in the case of asymmetry, the time ratio of the intersection between the random algorithm and the least recent channel access algorithm is low. When L is small, the ratio decreases with the increase of L, and when L reaches a constant value, the ratio will also obtain a dynamic stable value.

Based on the above technical solution, the channel rendezvous method of the cognitive wireless network proposed in the embodiment of the present invention uses the least recent channel access algorithm to change the rendezvous time slot channel sequence of the users who have rendezvous to prevent them from rendezvous, so as to improve their communication with other channels. The speed of rendezvous can shorten the rendezvous time of users, thereby increasing the rendezvous speed of channel frequency hopping;

Based on the above-mentioned channel crossover method for a cognitive wireless network provided by the embodiment of the present invention, an embodiment of the present invention also provides a channel crossover system for a cognitive wireless network, which can refer to FIG. 8 for mutual correspondence, and the system can include the following content:

The CH algorithm module 100 is used to use the same CH algorithm to generate the channel sequence of the intersection time slot corresponding to each user in the cognitive wireless network, and independently start the channel channel of the user in different time periods;

The least recent channel access algorithm module 200 is configured to use the least recent channel access algorithm to generate new time slot channel sequences corresponding to the two users when there is a crossover of two user channels, and use the new time slot channel sequence as the intersection time slot channel sequence;

The rendezvous module 300 is configured to use the rendezvous time slot channel sequence corresponding to each user to perform rendezvous.

Optionally, the least recent channel access algorithm module 200 includes:

an information length determining unit, configured to determine a value of an information length;

The least recent channel access algorithm unit is used to generate a new time-slot channel sequence corresponding to an information length for each of the two users by using the least-recent channel access algorithm when there are two user channel intersections, and convert the new time-slot channel sequence as a cross-slot channel sequence.

Optionally, the least recent channel access algorithm unit includes:

The rendezvous time slot subunit is used to compare the rendezvous time slot channel sequences of two users with channel rendezvous, and determine the rendezvous time slot that the two users will rendezvous on the same channel within one message length;

a target user subunit, configured to determine the user with more available channels among the two users as the target user;

The channel changing subunit is configured to count the number of visits of each available and non-overlapping channel of the target user, and select the channel with the least number of visits as the access channel of the rendezvous time slot.

Optionally, the target user subunit is specifically configured to separately count the number of available channels of the two users; select the user with the largest number as the target user; if the number of available channels of the two users is the same, Then randomly select a user as a subunit of the target user.

Optionally, the channel changing subunit is specifically configured to select the channel with the least number of visits as the access channel of the rendezvous time slot; if there are multiple channels with the least number of visits, randomly select the channel from the channels with the least number of visits A channel is selected as the access channel of the rendezvous time slot.

It should be noted that each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. For the same and similar parts in each embodiment, refer to each other, that is, Can. As for the system embodiment, because it is basically similar to the method embodiment, the description is relatively simple, and for the related parts, please refer to the part of the description of the method embodiment.

The channel crossover method and system of the cognitive wireless network provided by the present invention have been introduced in detail above. In this paper, specific examples are used to illustrate the principle and implementation of the present invention, and the descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (8)

1. A channel convergence method for a cognitive wireless network, comprising: Use the same CH algorithm to generate the corresponding intersection time slot channel sequence for each user in the cognitive wireless network, and independently start the user's channel channel in different time periods; Determine the value of a message length; When there are two user channel intersections, use the least recent channel access algorithm to generate a new time slot channel sequence corresponding to an information length of the two users, and use the new time slot channel sequence as the intersection time slot channel sequence; The rendezvous is performed by using the rendezvous time slot channel sequence corresponding to each user. 2. The channel rendezvous method of cognitive wireless network according to claim 1, characterized in that, using the least recent channel access algorithm to generate a new time slot channel sequence corresponding to an information length of two users respectively, comprising: Comparing the crossover time slot channel sequences of two users with channel crossover, determining the crossover time slot that the two users will cross over on the same channel within one message length; Determining the user with more available channels among the two users as the target user; The number of visits of each available and non-overlapping channel of the target user is counted, and the channel with the least number of visits is selected as the access channel of the crossover time slot. 3. The channel rendezvous method of cognitive wireless network according to claim 2, characterized in that determining the user with more available channels among the two users as the target user comprises: respectively counting the number of available channels of the two users; selecting users with a large number of said users as target users; If the numbers of available channels of the two users are the same, one user is randomly selected as the target user. 4. The channel rendezvous method of cognitive wireless network according to claim 2, characterized in that selecting the channel with the least number of visits as the access channel of the rendezvous time slot comprises: Selecting the channel with the least number of visits as the access channel of the rendezvous time slot; If there are a plurality of channels with the least number of visits, a channel is randomly selected from the plurality of channels with the least number of visits as the access channel of the rendezvous time slot. 5. A channel convergence system for a cognitive wireless network, characterized in that it comprises: The CH algorithm module is used to use the same CH algorithm to generate the corresponding intersection time slot channel sequence of each user in the cognitive wireless network, and independently start the user's channel channel in different time periods; The least recent channel access algorithm module is used to generate the new time slot channel sequence corresponding to the two users by using the least recent channel access algorithm when there are two user channel intersections, and use the new time slot channel sequence as the intersection time slot Channel sequence; wherein, the least recent channel access algorithm module includes: an information length determining unit, configured to determine a value of an information length; The least recent channel access algorithm unit is used to generate a new time-slot channel sequence corresponding to an information length for each of the two users by using the least-recent channel access algorithm when there are two user channel intersections, and convert the new time-slot channel sequence as a cross-slot channel sequence; The rendezvous module is configured to use the rendezvous time slot channel sequence corresponding to each user to perform rendezvous. 6. The channel convergence system of cognitive wireless network according to claim 5, wherein the least recent channel access algorithm unit comprises: The rendezvous time slot subunit is used to compare the rendezvous time slot channel sequences of two users with channel rendezvous, and determine the rendezvous time slot that the two users will rendezvous on the same channel within one message length; a target user subunit, configured to determine the user with more available channels among the two users as the target user; The channel changing subunit is configured to count the number of visits of each available and non-overlapping channel of the target user, and select the channel with the least number of visits as the access channel of the rendezvous time slot. 7. The channel crossing system of cognitive wireless network according to claim 6, wherein the target user subunit is specifically used to count the number of available channels of the two users respectively; select the channel with the largest number A user is used as a target user; if the number of available channels of the two users is the same, a user is randomly selected as a subunit of the target user. 8. The channel crossing system of cognitive wireless network according to claim 6, wherein the channel change subunit is specifically configured to select the channel with the least number of visits as the access channel of the crossover time slot; if there are multiple If the channel has the least number of visits, a channel is randomly selected from the channels with the least number of visits as the access channel of the rendezvous time slot.