WO2009057907A2

WO2009057907A2 - Cognitive radio communication device using overlapped signal and method thereof

Info

Publication number: WO2009057907A2
Application number: PCT/KR2008/006210
Authority: WO
Inventors: Dae-Sik Hong; Go-San Noh; Je-Min Lee; Han-Ho Wang; Seung-Jin You
Original assignee: Industry-Academic Cooperation Foundation, Yonsei University
Priority date: 2007-10-31
Filing date: 2008-10-21
Publication date: 2009-05-07
Also published as: JP5002567B2; JP2009112006A; WO2009057907A3; CN101426273A; CN101426273B; KR100934572B1; KR20090044337A

Abstract

Disclosed is a cognitive communication device. A cognitive radio communication device includes a signal receiving unit that receives a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a status information generating unit that uses the sameness between signals included in the overlapped portions to generate status information related to whether the first signal exists; and an operational mode determining unit that determines a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

Description

COGNITIVE RADIO COMMUNICATION DEVICE USING OVERLAPPED SIGNAL AND METHOD THEREOF

Technical Field

[1] The present invention relates to a cognitive radio technology, and more particularly, to a cognitive radio communication device that determines whether a first signal of a primary network exists and a method thereof. Background Art

[2] In recent years, various researches on technologies for efficiently using limited frequency resources have been actively studied. Among them, a cognitive radio (CR) technology has attracted attention.

[3] The cognitive radio technology is a technology that reuses limited frequency resources so as to maximize the use of frequency resources. That is, according to the cognitive radio technology, a communication device that belongs to a secondary network periodically or non-periodically senses frequency resources that are not used in a primary network, so as to recognize available frequency resources, and uses the recognized available frequency resources to transmit/receive data.

[4] However, since the primary network has priority with respect to the available frequency resource, a communication device of the secondary network needs to stop a communication operation or needs to change the frequency resources in a utilization state, when there is the possibility of a signal of the secondary network conflicting with a signal of the primary network.

[5] Accordingly, a communication device that belongs to the secondary network needs to detect whether the signal of the primary network exists or not. At this time, it may be inefficient to set a long sensing period in order that the communication device that belongs to the secondary network detects whether the signal of the primary network exists or not.

[6] For this reason, a technology that removes a sensing period or efficiently determines whether the signal of the primary network exists or not in a short sensing period is required. Disclosure of Invention

Technical Problem

[7] Accordingly, the present invention provides a cognitive radio communication device that uses the sameness between signals included in an overlapped portion where the same signal is repeated in a second signal to determine whether a first signal exists or not, thereby making additional hardware resources and radio resources unnecessary, and a method thereof.

[8] Further, the present invention provides a cognitive radio communication device that uses a difference between signals received during an overlapped time period to determine whether a first signal exists or not, thereby efficiently using a cognitive radio technology, and a method thereof.

[9] Furthermore, the present invention provides a cognitive radio communication device that sets a sensing period to accurately detect whether a first signal exists or not and uses a difference between signals received during an overlapped time period to determine whether the first signal exists or not, thereby maximizing a data transmission rate of a communication system, and a method thereof. Technical Solution

[10] A cognitive radio communication device according to an embodiment of the present invention includes: a signal receiving unit that receives a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a status information generating unit that uses the sameness between signals included in the overlapped portions to generate status information related to whether the first signal exists; and an operational mode determining unit that determines a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

[11] A cognitive radio communication device according to an embodiment of the present invention includes: a signal receiving unit that receives a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a status information generating unit that uses overlapped signals included in the overlapped portions and sensing signals received during a sensing period during which the first signal is sensed and generates status information related to whether the first signal exists; and an operational mode determining unit that determines a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

[12] A cognitive radio communication method according to an embodiment of the present invention includes: a step of receiving a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a step of using the sameness between signals included in the overlapped portions to generate status information related to whether the first signal exists; and a step of determining a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

[13] A cognitive radio communication method according to an embodiment of the present invention includes: a step of receiving a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a step of using a status information generating unit that uses overlapped signals included in the overlapped portions and sensing signals received during a sensing period during which the first signal is sensed, to generate status information related to whether the first signal exists; and a step of determining a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

Advantageous Effects

[14] The present invention can provide a cognitive radio communication device that uses the sameness of signals included in an overlapped portion where the same signal is repeated in a second signal to determine whether a first signal exists or not, thereby making additional hardware resources and radio resources unnecessary, and a method thereof.

[15] Further, the present invention can provide a cognitive radio communication device that uses a difference between signals received during an overlapped time period to determine whether a first signal exists or not, thereby efficiently using a cognitive radio technology, and a method thereof.

[16] Furthermore, the present invention can provide a cognitive radio communication device that sets a sensing period to accurately detect whether a first signal exists or not and uses a difference between signals received during an overlapped time period to determine whether the first signal exists or not, thereby maximizing a data transmission rate of a communication system, and a method thereof. Brief Description of the Drawings

[17] FIG. 1 is a diagram illustrating an example of a primary network and a secondary network according to the present invention.

[18] FIG. 2 is a diagram illustrating a sensing period and a second signal with respect to time in accordance with an embodiment of the present invention.

[19] FIG. 3 is a block diagram illustrating a cognitive radio communication device according to an embodiment of the present invention.

[20] FIG. 4 is a flowchart illustrating the operation of a cognitive radio communication method according to an embodiment of the present invention. Best Mode for Carrying Out the Invention

[21] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. [22] FIG. 1 is a diagram illustrating an example of a primary network and a secondary network according to the present invention.

[23] Referring to FIG. 1, the primary network includes a first base station and a first terminal, and the secondary network includes a second base station and a second terminal. At this time, the second base station and the second terminal can transmit/ receive a signal based on an orthogonal frequency division multiplexing (OFDM) scheme.

[24] At this time, the cognitive radio communication device according to the present invention may be installed in the second terminal or the second base station and operated therein.

[25] At this time, the second terminal or the second base station may recognize a portion or all of the frequency resources allocated to the primary network as available frequency resources using the cognitive radio technology. The second terminal or the second base station may transmit/receive the second signal using the recognized available frequency resources.

[26] That is, the second terminal may use the available frequency resources to transmit the second signal to the second base station at uplink time, and the second base station may use the available frequency resources to transmit the second signal to the second terminal at downlink time. However, the first terminal or the first base station may use previously allocated frequency resources without depending on whether the second terminal or the second base station transmits/receives a signal.

[27] At this time, the second signal transmitted from the second base station or the second terminal may be received by the first terminal or the first base station. Accordingly, interference may occur in the first terminal or the first base station due to the second signal.

[28] However, even when the second terminal or the second base station uses available frequency resources, the first base station or the first terminal may have priority with respect to the available frequency resources. At this time, the second base station or the second terminal needs to change the available frequency resources that are being used or stop a communication operation. Thus, the second terminal or the second base station needs to determine whether the first signal transmitted from the first terminal or the first base station exists or not.

[29] FIG. 2 is a diagram illustrating a sensing period and a second signal with respect to time in accordance with an embodiment of the present invention.

[30] Referring to FIG. 2, the cognitive radio communication device receives the first signal of the primary network during a sensing period N_D. In regards to FIG. 2, it is assumed that the cognitive radio communication device according to the present invention is installed in the second terminal or the second base station. [31] The second terminal or the second base station stops a communication operation for transmitting/receiving data during the sensing period N_D, and receives the first signal. At this time, if the sensing period N_D is lengthened, it is possible to accurately determine whether the first signal exists or not. However, during the sensing period N_D , the second terminal or the second base station stops a communication operation for transmitting/receiving data, and thus a data transmission rate of the entire communication system may be decreased.

[32] Accordingly, the sensing period N_D needs to be appropriately adjusted to accurately determine whether the first signal exists or not, thereby achieving the high data transmission rate of the entire communication system.

[33] Further, the second terminal or the second base station receives the second signal immediately after the sensing period N_D. At this time, although not shown in FIG. 2, if the first signal exists, the second terminal or the second base station can receive the first signal even after the sensing period ends.

[34] The second signal may be a signal that is encoded on the basis of an orthogonal frequency division multiplexing scheme. At this time, the second signal may include a cyclic prefix (CP) and a preamble signal.

[35] The cyclic prefix is generally inserted into a start portion of a data frame of the second signal. At this time, after a signal of a final portion of the data frame of the second signal is copied, the cyclic prefix is inserted into the start portion thereof, and thus the signal of the data start portion of the second signal is the same as the signal of the final portion thereof. That is, when the second signal includes a cyclic prefix, the second signal includes two or more overlapped portions where the same signal is repeated.

[36] Further, the preamble signal may include a symbol that is related to packet synchronization, a symbol that is related to channel estimation, and a symbol for frame synchronization. At this time, similar to the cyclic prefix, the preamble signal may include two or more overlapped portions where the same signal is repeated.

[37] As a result, in FIG. 2, during overlapped time periods N_Gi and N_G2, the same signal repeatedly exists. At this time, the overlapped time periods N_Gi and N_G2 may have the same length.

[38] Accordingly, the second signal includes an overlapped portion where the same signal is repeated, like the portions of the cyclic prefix and the preamble signal. In FIG. 2, only the two overlapped portions are shown, but the present invention is not limited thereto. According to the embodiment of the present invention, two or more overlapped portions may exist.

[39] The second terminal or the second base station receives an effective signal portion during a time period N_E + N_G2. [40] At this time, when the first signal exists, the second terminal or the second base station may receive the first signal as well as the signals included in the overlapped portions of the second signal, during the overlapped time periods N_Gi and N_G2.

[41] For example, when it is assumed that a signal that the second terminal or the second base station receives during the overlapped time period N_Gi is Ri, the signal included in the overlapped portions is X, and the first signal corresponding to the overlapped time period N_Gi is Yi, R₁ can be represented by the following Equation 1.

[42] [Equation 1]

[44] Further, when it is assumed that a signal that the second terminal or the second base station receives during the overlapped time period N_G2 is R₂, the signal included in the overlapped portions is X, and the first signal corresponding to the overlapped time period N_G2 is Y₂, R₂ can be represented by the following Equation 2.

[45] [Equation 2]

[46] R₂=X+Y₂

[47] Referring to Equations 1 and 2, the signal X is commonly included in the signals Ri and R₂. At this time, a difference between Equation 2 and Equation 1 can be represented by the following Equation 3.

[48] [Equation 3]

[50] Referring to Equation 3, a difference between the signal R₂ and the signal Ri does not include a component that is related to the overlapped portion of the second signal, but includes only a component of the first signal. At this time, since the probability of the signals Y₂ and Yi being the same is very low, it is possible to determine whether the first signal exists by using the difference between the signals R₂ and Ri.

[51] That is, it is possible to determine whether the first signal exists or not, on the basis of whether or not the value of a difference between the signal R₂ and the signal Ri is larger than a predetermined threshold value.

[52] FIG. 3 is a block diagram illustrating a cognitive radio communication device according to an embodiment of the present invention.

[53] Referring to FIG. 3, a cognitive radio communication device includes a signal receiving unit 310, a status information generating unit 320, and an operational mode determining unit 330.

[54] The signal receiving unit 310 receives the first signal of the primary network and the second signal of the secondary network. At this time, the second signal includes two or more overlapped portions where the same signal is repeated. In particular, the second signal is a signal based on an orthogonal frequency division multiplexing scheme, and may include a cyclic prefix or a preamble signal. [55] At this time, the status information generating unit 320 uses the sameness between the signals included in the overlapped portions to generate status information, which is related to whether the first signal exists or not. At this time, the status information generating unit 320 may generate status information on the basis of a difference between the signals, which are received during the overlapped time periods corresponding to the overlapped portions.

[56] At this time, the status information generating unit 320 may generate status information in consideration of sensing signals, which are received during a sensing period in which the first signal is sensed.

[57] That is, the cognitive radio communication device according to the embodiment of the present invention can generate status information even if the sensing period is not set. However, if the sensing period is set, the cognitive radio communication device can accurately generate status information.

[58] For example, referring to Equation 3, it is assumed that the sensing signal received during the sensing period is Z, the signal received during the overlapped time period N Gi is Ri, and the signal received during the overlapped time period N_G2 is R2. At this time, since the second signal is not generated during the sensing period, the probability of the sensing signal Z being the portion of the first signal is high. If a difference between the signals R₂ and Ri is added to the sensing signal, the following Equation 4 is obtained.

[59] [Equation 4]

[60] T=Z+R₂- Ri=Z+Y₂- Yi

[61] In Equation 4, in the case of the ideal situation where the first signal and noise do not exist, T may become '0'. However, if the first signal exists, T may be calculated as a value of a specific level or more. Accordingly, when it is assumed that T is status information, it may be possible to determine whether the first signal exists according to whether the value of the status information T is larger than the predetermined threshold value.

[62] The operational mode determining unit 330 determines a communication operational mode of a communication device that belongs to the secondary network, on the basis of the status information. At this time, the operational mode determining unit 330 may compare the status information and the predetermined threshold value and determine a communication operational mode using the compared result.

[63] For example, when a value of the difference between the signals, which are received during the overlapped time periods corresponding to the overlapped portions, is larger than the threshold value, the operational mode determining unit 330 may determine that the first signal exists and determine an operational mode of a communication device that belongs to the secondary network. [64] At this time, the operational mode determining unit 330 may determine a communication operational mode as any one of a first communication operational mode, a second communication operational mode, and a third communication operational mode. In the first communication operational mode, frequency resources that are used by a device belonging to the secondary network are changed. In the second communication operational mode, the communication device stops a communication operation. In the third communication operational mode, a communication operation that is performed by the communication device is continuously performed.

[65] FIG. 4 is a flowchart illustrating the operation of a cognitive radio communication method according to an embodiment of the present invention.

[66] Referring to FIG. 4, a cognitive radio communication method according to the embodiment of the present invention receives the first signal and the second signal (S410).

[67] The cognitive radio communication method according to the embodiment of the present invention detects a sensing signal, which is received using a sensing period during which the first signal is sensed (S420).

[68] The cognitive radio communication method according to the embodiment of the present invention detects the signals, which are received during the overlapped time periods corresponding to the overlapped portions (S430).

[69] The cognitive radio communication method according to the embodiment of the present invention uses the overlapped signals included in the overlapped portions and the sensing signal received during the sensing period to generate status information related to whether the first signal exists (S440).

[70] At this time, Step S440 where the status information is generated may generate status information on the basis of a difference between the signals received during the overlapped time periods and the sensing signal.

[71] The cognitive radio communication method according to the embodiment of the present invention determines whether a value of the generated status information is larger than the predetermined threshold value (S450).

[72] At this time, when the value of the status information is larger than the threshold value, the cognitive radio communication method according to the embodiment of the present invention determines the communication operational mode as the first communication operational mode where frequency resources that are used by a communication device belonging to the secondary network are changed or the second communication operational mode where the communication device stops a communication operation (S460).

[73] In contrast, when the value of the status information is smaller than or equal to the threshold value, the cognitive radio communication method according to the em- bodiment of the present invention determines the communication operational mode as the third communication operational mode where the communication device continuously performs a communication operation, and Step S410 restarts.

[74] The operational principle that is described with reference to FIGS. 1 to 3 may be applied to the cognitive radio communication method according to the present invention, and thus the detailed description thereof will be omitted.

[75] The cognitive radio communication method according to the present invention may be implemented in a form of a program command that can be executed by various computing units and recorded in a computer readable medium. The computer readable recording medium may individually include a program command, a data file, and a data structure or include a combination thereof. The program command that is recorded in the recording medium may be designed and configured to achieve the present invention or easily used by those skilled in the art. Examples of the computer readable recording medium include a magnetic recording medium, such as a hard disk, a floppy disk, and a magnetic tape, an optical recoding medium, such as a CD ROM and a DVD, a magneto-optical media, such as a floptical disk, and a hardware device, such as a ROM, a RAM, and a flash memory, which is configured to store and execute a program command. Examples of the program command include a machine language code that is created by a compiler and a high-level language code that can be executed by a computer using an interpreter. The hardware device may be configured to be operated as one or more software modules in order to perform the operation of the present invention.

[76] Although the present invention has been described in connection with the exemplary embodiments and the accompanying drawings, the present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various modifications and changes may be made thereto without departing from the scope and spirit of the invention.

[77] Therefore, it should be understood that the above embodiments are not limitative, but illustrative in all aspects. The scope of the present invention is defined by the appended claims rather than by the description preceding them, and all changes and modifications that fall within metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the claims.

[78]

Claims

[1] A cognitive radio communication device comprising: a signal receiving unit that receives a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a status information generating unit that uses the sameness between signals included in the overlapped portions to generate status information related to whether the first signal exists; and an operational mode determining unit that determines a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

[2] The cognitive radio communication device of claim 1, wherein the status information generating unit generates the status information on the basis of a difference between signals, which are received during overlapped time periods corresponding to the overlapped portions.

[3] The cognitive radio communication device of claim 1, wherein the operational mode determining unit determines the communication operational mode as any one of a first communication operational mode where frequency resources used by the communication device are changed, a second communication operational mode where the communication device stops a communication operation, and a third communication operational mode where the communication device maintains the communication operation.

[4] The cognitive radio communication device of claim 1, wherein the operational mode determining unit compares the status information and a predetermined threshold value and determines the communication operational mode using the compared result.

[5] The cognitive radio communication device of claim 1, wherein the second signal is generated in the secondary network using an orthogonal frequency division multiplexing (OFDM) scheme.

[6] The cognitive radio communication device of claim 1, wherein the first signal includes a downlink signal or an uplink signal of the primary network and the second signal includes a downlink signal or an uplink signal of the secondary network.

[7] A cognitive radio communication device comprising: a signal receiving unit that receives a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a status information generating unit that uses overlapped signals included in the overlapped portions and sensing signals received during a sensing period during which the first signal is sensed and generates status information related to whether the first signal exists; and an operational mode determining unit that determines a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

[8] The cognitive radio communication device of claim 7, wherein the status information generating unit generates the status information on the basis of a difference between signals, which are received during overlapped time periods corresponding to the overlapped portions, and the sensing signals.

[9] The cognitive radio communication device of claim 7, wherein the operational mode determining unit determines the communication operational mode as any one of a first communication operational mode where frequency resources used by the communication device are changed, a second communication operational mode where the communication device stops a communication operation, and a third communication operational mode where the communication device maintains the communication operation.

[10] The cognitive radio communication device of claim 7, wherein the operational mode determining unit compares the status information and a predetermined threshold value and determines the communication operational mode using the compared result.

[11] A cognitive radio communication method comprising: a step of receiving a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a step of using the sameness between signals included in the overlapped portions to generate status information related to whether the first signal exists; and a step of determining a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

[12] The cognitive radio communication method of claim 11, wherein the step of generating the status information is a step of generating the status information on the basis of a difference between signals, which are received during overlapped time periods corresponding to the overlapped portions.

[13] The cognitive radio communication method of claim 11, wherein the step of determining the communication operational mode is a step of determining the communication operational mode as any one of a first communication operational mode where frequency resources used by the communication device are changed, a second communication operational mode where the communication device stops a communication operation, and a third communication operational mode where the communication device maintains the communication operation.

[14] A cognitive radio communication method comprising: a step of receiving a first signal of a primary network and a second signal of a secondary network, the second signal including two or more overlapped portions where the same signal is repeated; a step of using a status information generating unit that uses overlapped signals included in the overlapped portions and sensing signals received during a sensing period during which the first signal is sensed, to generate status information related to whether the first signal exists; and a step of determining a communication operational mode of a communication device belonging to the secondary network, on the basis of the status information.

[15] The cognitive radio communication method of claim 14, wherein the step of generating the status information is a step of generating the status information on the basis of a difference between signals, which are received during overlapped time periods corresponding to the overlapped portions, and the sensing signals.

[16] The cognitive radio communication method of claim 14, wherein the step of determining the communication operational mode is a step of comparing the status information and a predetermined threshold value and determining the communication operational mode using the compared result.

[17] A computer readable recording medium where a program to execute the method of any one of claims 11 to 16 is recorded.