WO2014193217A1

WO2014193217A1 - A system and method for managing a cognitive radio network

Info

Publication number: WO2014193217A1
Application number: PCT/MY2014/000059
Authority: WO
Inventors: Nuzli MOHAMAD ANAS; Hafizal MOHAMAD @ DIN; Nordin Ramli; Mohammad TAHIR
Original assignee: Mimos Bhd
Current assignee: Mimos Bhd
Priority date: 2013-05-31
Filing date: 2014-04-15
Publication date: 2014-12-04
Anticipated expiration: 2015-11-30

Abstract

The present invention relates to a system and method for managing a cognitive radio network, for eliminating interference to the primary users (20) within the vicinity of the cognitive radio network such that the data transmission service quality of the primary users (20) in a cognitive radio network is ensured while optimal operation of the cognitive radio devices (10) is maintained. The system of the present invention comprises at least one cognitive radio device (10), a fusion center (40) in communication with at least one cognitive radio device (10), and a database (30) for receiving and storing information from the fusion center (40). The present invention further comprises a method for managing a cognitive radio network comprising the step of controlling transmit power of the cognitive radio network in accordance to the presence of primary users (20) as detected by the cognitive radio devices (10).

Description

A system and method for managing a cognitive radio network

Field of the invention The present invention relates to a system and method for managing a wireless radio network, and more specifically the present invention relates to a system and method for controlling transmit power of a cognitive radio network for eliminating interference to the primary users within the vicinity of the cognitive radio network.

Background of the invention

The advent of telecommunication technology nowadays has brought radio communication technology to play a vital role in telecommunication and has become one of the most researched subjects. The radio communication technology has been advancing at a rapid pace and it is evident that our daily lives have been very much dependent and affected by such technological development. As virtually all communication devices necessitate access to the radio frequency wireless spectrum, the radio frequency spectrum is being allocated to the designated licensed users by regulatory bodies. As a radio frequency band can be only assigned to one licensed user on a regional basis, the finite radio frequency resources have thus become increasingly scarce. However, a majority of the frequency being assigned to licensed users is either unused or underutilized. Examples of such frequency bands include amateur radio and paging frequencies.

To solve the problem of frequency shortage, cognitive radio system has emerged as a way for alleviating the problem and maximizing utilization of the radio frequency spectrum. The cognitive radio system is an agile radio system which is able to obtain operational and geographical knowledge of its environment and utilizes available spectrum dynamically and opportunistically by adjusting its operational parameters and protocols according to its obtained knowledge, without causing harmful interference to the licensed primary users. The operational parameters that can be adjusted include operating frequency, power output, antenna orientation, modulation, and transmitter bandwidth. Therefore, the cognitive radio users are able to fill in the spectrum holes in terms of frequency, spatial, and temporal aspect.

Ideally, the cognitive radio users should vacate a spectrum band instantly in the presence of licensed primary users to avoid harmful interference. As such, the cognitive radio system must continuously sense the spectrum being used. One of the most challenging issues faced by the cognitive radio system is that the cognitive radio users must be able to detect the presence of licensed primary user at any instant and specific location. Problems of interference may arise when the cognitive radio users accessing a license spectrum band fail to notice the presence of licensed primary users at a later time when the licensed primary users occupy the spectrum band again. Furthermore, detection of licensed primary users may not be effective due to path loss and shadowing. US Patent Publication No. 2009/0305639 A1 discloses a method of transmitting data which includes sensing whether a frequency band is idle or not during a sensing block. A power level is derived based upon the probability of non- interfering for a plurality of periods in an inter-sensing block. This prior art employs an alternating time period of sensing block and inter-sensing block for performing spectrum sensing and data transmission respectively. This may reduce the efficiency of radio transmission which has an interrupted transmission. Furthermore, in this prior art, the cognitive radio device acts independently and the effectiveness of sensing may not be satisfactory. US Patent Publication No. 2012/0100883 A1 discloses a method for controlling transmit power of a cognitive radio device to minimize interference to licensed primary users. The method includes acquiring cognitive radio environment information regarding a licensed user or an unlicensed user occupying adjacent spectrum band and determining transmit power value of the cognitive radio device. The transmit power control information is generated for the cognitive radio device. This prior art describes the use of a single cognitive radio device for detecting primary users and determine its transmit power value. However, this prior art does not provide a method for managing multiple cognitive radio devices in the network simultaneously.

US Patent No. 8351861 B2 discloses a method for managing wireless communications by a secondary device user in a cognitive radio environment comprising one or more secondary users and one or more primary licensed users. The method requires receiving information indicative of a location and movement of one or more secondary users. Information regarding frequency channel usage pattern and spatial distribution of one or more primary licensed units is also obtained. A guard distance is allocated to one or more primary licensed units, within which the secondary users units will not have spectrum access. This method does not allow the use of adjacent spectrum bands by the secondary users when they are in the guard distance of the primary users. This lack of flexibility has unnecessarily limited the transmission by the secondary users.

Therefore, there is a need to provide a system and method for managing a cognitive radio network which operates in the presence of the primary users, while eliminating interference towards the primary users.

Summary of the invention

It is an object of the present invention to provide a system and method for managing a cognitive radio network, while eliminating interference to the primary users within the vicinity of the cognitive radio network. It is also an object of the present invention to provide a system and method for managing a cognitive radio network which employs cooperative spectrum sensing for increasing the efficiency of spectrum sensing. It is yet another object of the present invention to ensure the data transmission service quality of the primary users in a cognitive radio network while maintaining optimal operation of the cognitive radio devices.

It is a further object of the present invention for providing a system and method for dynamically controlling transmit power of the cognitive radio network in accordance to the presence of primary users as detected by the cognitive radio devices.

It is also an object of the present invention to assign grid contours in a cognitive radio network coverage so that the cognitive radio devices in the grid contours can be classified to perform spectrum sensing and data transmission using transmit power which has been determined to avoid causing interference to the primary users. The present invention relates to a system for managing a cognitive radio network comprising at least a cognitive radio device for obtaining information on spectrum availability by performing spectrum sensing, a fusion center in communication with at least a cognitive radio device for receiving said information from at least one cognitive radio device, a database for receiving and storing information from the fusion center, and updating the information thereof, characterized in that the fusion center performs grid contour classification on at least a cognitive radio device based on the distance between the cognitive radio device and the fusion center, collects information on the presence of primary users in each grid contour and determines transmit power for managing the network. The present invention further relates to a method for managing a cognitive radio network, wherein transmit power of the network is managed by the steps of performing grid contour classification on the cognitive radio devices based on the distance between the cognitive radio devices and the fusion center, acquiring information on the presence of at least one primary user in each grid contour, wherein said information is obtained by spectrum sensing of the cognitive radio devices and feedback to the fusion center, storing and updating information on the presence of primary user in each grid contour to the database, and controlling transmit power of the cognitive radio devices based on the information obtained from the database.

Brief descriptions of drawings

Figure 1 is a diagram showing a system for managing a cognitive radio network according to the present invention.

Figure 2 is a flow chart showing a method for managing a cognitive radio network according to the present invention. Figure 3 is a flow chart showing a method for controlling transmit power of the cognitive radio devices according to the present invention.

Figure 4 is a diagram showing a system for managing a cognitive radio network with a first distribution pattern of the primary users and the cognitive radio devices according to the present invention.

Figure 5 is a diagram showing a system for managing a cognitive radio network with a second distribution pattern of the primary users and the cognitive radio devices according to the present invention. Figure 6 is a diagram showing a system for managing a cognitive radio network with a third distribution pattern of the primary users and the cognitive radio devices according to the present invention. Detailed description of preferred embodiments

The present invention will now be described in more detail with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The present invention relates to a system for managing a cognitive radio network comprising at least a cognitive radio device (10) for obtaining information on spectrum availability by performing spectrum sensing, a fusion center (40) in communication with at least a cognitive radio device (10) for receiving said information from at least a cognitive radio device (10), a database (30) for receiving and storing information from the fusion center (40), and updating the information thereof, characterized in that the fusion center (40) performs grid contour classification on at least a cognitive radio device (10) based on the distance between the cognitive radio device (10) and the fusion center (40), collects information on the presence of primary users (20) in each grid contour and determines transmit power for managing the network.

With reference to Figure 1 , the cognitive radio network system of the present invention comprises multiple cognitive radio devices (10) for performing spectrum sensing to obtain information on the spectrum availability. The cognitive radio devices (10) are devices capable of wireless communication which can adjust its operational parameters to make use of the vacant spectrum band being allocated to the primary users (20). Examples of the cognitive radio devices (10) include cell phones and laptops integrated with software and hardware which confer them the ability to be aware of the environment and change the operational parameters accordingly. The cognitive radio device (10) is essentially an opportunistic communication device adapted to perform transmission with a temporal or spatial spectrum hole. In a preferred embodiment, the cognitive radio device (10) accesses a spectrum band which is available as detected by spectrum sensing without causing interference to the primary user (20) due to the controlled transmit power. The fusion center (40) of the present invention is located at the central point of the cognitive radio network for receiving information on the availability of the spectrum band within the cognitive radio network coverage. The fusion center (40) acts as a central coordinating unit which is in communication with the cognitive radio device (10). The fusion center (40) can be an access point, a base station, or another cognitive radio device. In addition, the fusion center (40) performs grid contour classification on the cognitive radio device (10) based on the distance between the cognitive radio device (10) and the fusion center (40). Having the grid contour classification, the fusion center (40) collects information on the presence of primary users (20) from the cognitive radio devices (10) in each grid contour and controls transmit power of the cognitive radio devices (10) in the grid contours.

Being in connection with the fusion center (40), the database (30) of the present invention primarily stores and updates information on the availability of the spectrum band in the network coverage. In a preferred embodiment, the database (30) further stores information on the location of the primary user (20) and the grid contour to which the cognitive radio devices (10) belong. This is preferably implemented by having separate dedicated databases, for example, geolocation database for storing information on the location of the primary user (20), grid contour database for storing information on the classification of cognitive radio devices (10), and sensing result database for storing information on the spectrum availability in the grid contours. The coverage of the cognitive radio network is divided into multiple concentric grid contours, with the fusion center (40) at the central of the network. Each grid contour has a different radius from the fusion center (40) and the grid contour with the largest radius has the widest coverage and is farthest away from the fusion center (40). Each of the cognitive radio devices (10) is classified based on the grid contour to which each of the cognitive radio devices (10) belongs. In a preferred embodiment, the grid contours coverage may be divided equally or non-equally depending on the factors such as the density and distribution of the cognitive radio devices (10).

Figure 2 is a flow chart illustrating an overview of the method for managing a cognitive radio network by controlling transmit power of the cognitive radio device (10) so that harmful interference to the primary users (20) is avoided. The method is initiated by performing grid contour classification on the cognitive radio device (10) based on the distance between cognitive radio device (10) and the fusion center (40). In a preferred embodiment, the grid contour classification on the cognitive radio device (10) is achieved by first separating the network coverage area into multiple grid contours and then classifying the cognitive radio devices (10) based on the grid contour to which the cognitive radio devices (10) belong.

The method then proceeds to acquire information on the presence of at least a primary user (20) occupying a spectrum band in each grid contour. This information is obtained by the cognitive radio device (10) by way of spectrum sensing. The method of spectrum sensing includes but not limited to matched filtering, energy detection, cyclostationary detection, and wavelet detection. In a preferred embodiment, the cognitive radio devices (10) perform transmission using an available spectrum band as detected from spectrum sensing.

In a preferred embodiment, the cognitive radio devices (10) in each grid contour are randomly selected for providing feedback on the spectrum sensing result to the fusion center (40). In a preferred embodiment, cooperative spectrum sensing is conducted so that the multipath fading and shadowing effect can be alleviated. In cooperative spectrum sensing, the spatially distributed cognitive radio devices (10) share the information obtained and convey to the fusion center (40) so that a decision on the presence of the primary users (20) can be made. To reduce the redundancy of information and to increase the cooperative sensing gain, the number of cognitive radio devices selected for providing feedback of the sensing result is determined based on randomness metric, namely the cooperative sensing index (CSI). The CSI for the number of cognitive radio devices, L, is defined by the equation as below:

H(U) = CSI (L) = - _Pi log_{2 Pi}

where H(U) is the Shannon Entropy for a discrete random variable i that takes on 2^L values each with probability p,

The information obtained by the cognitive radio device (10) is then feedback to the fusion center (40) on instructions from the fusion center (40). The obtained information is stored and updated in the database (30). In a preferred embodiment, the database (30) is updated periodically to keep track of the primary users (10) so as to avoid interference thereto. The fusion center (40) determines transmit power of the cognitive radio devices (10) for each grid contour, with the information on the presence of the primary users (20) occupying a spectrum band in each grid contour. In this way, the cognitive radio devices (10) communication does not cause harmful interference to the primary user (20) occupying another spectrum band in the same grid contour.

Figure 3 is a flow chart illustrating the method for controlling transmit power of the cognitive radio device (10) according to the information on whether a primary user (20) is present in the grid contour. The grid contour classification on the cognitive radio devices (10) is performed by the fusion center (40). In a preferred embodiment, an incremental sensing feedback is performed so that an optimum number of cognitive radio devices (10) is determined for providing feedback of the spectrum sensing result to the fusion center (40). If the CSI value does not meet a threshold value, then the number of cognitive radio devices (10) for providing feedback of the spectrum sensing result will be increased until the threshold value is met. Then, the transmit power scheme of the cognitive radio devices (10) is derived based on the grid contours, wherein a transmit power value is assigned to each grid contour such that the value of the transmit power increases proportionally with the grid contour area coverage. Then, the fusion center (40) determines whether a spectrum band is available for use by the cognitive radio devices (10). The detected available spectrum band will then be updated to the sensing result database (30). Subsequently, the cognitive radio devices (10) perform spectrum sensing to acquire information on the presence of at least a primary user (20) in each grid contour regularly. The fusion center (40) determines the transmit power of the cognitive radio devices (10) in each grid contour, depending on whether at least one primary user (20) is present. If a primary user (20) is present in a particular grid contour, then the transmit power of the radio cognitive devices (10) in that particular grid contour will be decreased to a power level less than the transmit power value assigned to the previous smaller grid contour to reduce interference caused to the primary users. On the other hand, if at least one primary user (20) is not present in the particular grid contour, transmit power of the radio cognitive radio devices (10) in that grid contour will be adjusted to a power level not greater than the transmit power value assigned to that particular grid contour.

Figures 1 , 4, 5, and 6 show different distribution pattern of the cognitive radio devices (10) and the primary users (20), wherein the cognitive radio devices (10) perform transmission with specific transmit power accordingly. In these exemplary embodiments, the radio cognitive network coverage is divided into three grid contours, designated first, second, and third grid contour from the smallest to the largest. Each grid contour is assigned with a transmit power value. The grid contours from the smallest to the largest coverage are assigned transmit power of Pi, P₂, and P₃ respectively, wherein the transmit power value Pi is the smallest and P₃ is the largest.

Figure 1 shows a distribution pattern where a primary user (20) and a cognitive radio device (10) coexist in the second grid contour while only a cognitive radio device (10) is found in the first grid contour. As such, transmit power of the cognitive radio device (10) in the second grid contour will be set at a power level less than P-i. The transmit power of the cognitive radio device (10) in the first grid contour will be set at a power level not greater than PL

In the distribution pattern as shown in Figure 4, a cognitive radio device (10) is found in the smallest grid contour and a primary user (20) is found in the other two grid contours. Transmit power of the cognitive radio device (10) will be adjusted to power level not greater than P^

In another distribution pattern as shown in Figure 5, cognitive radio devices (10) are found in first and second grid contours, and a primary user (20) is found in the third grid contour. As such, the cognitive radio device (10) in the first grid contour will be assigned with transmit power not greater than P^ while the cognitive radio device (10) in the second grid contour will be assigned transmit power not greater than P₂.

Figure 6 shows a distribution pattern where only cognitive radio devices (10) are found in all the grid contours. The transmit power of cognitive radio device (10) in first, second, and third grid contour will be set to a power level not greater than Pi , P₂, and P₃ respectively.

Although the present invention has been described in a specific embodiment as in the above description, it is understood that the above description does not limit the invention to the above given details. It will be apparent to those skilled in the art that various changes and modification may be made therein without departing from the principle of the invention or from the scope of the appended claims.

Claims

1. A system for managing a cognitive radio network comprising:

at least a cognitive radio device (10) for obtaining information on spectrum availability by performing spectrum sensing;

a fusion center (40) in communication with the cognitive radio device (10) for receiving said information from the cognitive radio device

(10);

a database (30) for receiving and storing information from the fusion center (40), and updating the information thereof;

characterized in that the fusion center (40) performs grid contour classification on the cognitive radio device (10) based on the distance between the cognitive radio device (10) and the fusion center (40), collects information on the presence of at least a primary user (20) in each classified grid contour and determines transmit power for managing the network.

2. A system for managing a cognitive radio network according to claim 1 , wherein the classified grid contour of the cognitive radio network is formed by equal or non-equal separation of the cognitive radio network coverage.

3. A system for managing a cognitive radio network according to claim 1 , wherein the database (30) further stores information on the grid contour to which the cognitive radio device (10) belongs.

4. A system for managing a cognitive radio network according to claim 1 , wherein the database (30) further stores information on the location of the primary user (20).

5. A method for managing a cognitive radio network, comprising the steps of: performing grid contour classification on the cognitive radio device (10) based on the distance between the cognitive radio device (10) and the fusion center (40);

performing spectrum sensing by the cognitive radio devices (10) for obtaining spectrum sensing result comprising information on the presence of at least a primary user (20) in each grid contour, and the spectrum sensing result is provided to the fusion center (40);

storing and updating information on the presence of the primary user (20) in each grid contour to the database (30); and

controlling transmit power of the cognitive radio devices (10) based on the information obtained from the database (30).

A method for managing a cognitive radio network according to claim 5, wherein the cognitive radio devices (10) perform transmission using an available spectrum band as detected from spectrum sensing.

A method for managing a cognitive radio network according to claim 5, wherein the cognitive radio devices (10) are randomly selected for providing the spectrum sensing result to the fusion center (40).

A method for managing a cognitive radio network according to claim 5, wherein the spectrum sensing is performed by a number of cognitive radio devices (10), said number is determined based on a cooperative sensing index metric.

A method for managing a cognitive radio network according to claim 5, wherein the database (30) is updated periodically.

10. A method for managing a cognitive radio network according to claim 5, wherein transmit power of the cognitive radio devices (10) is determined by the steps of: determining transmit power scheme based on the grid contour classification, wherein each grid contour, from nearest to the fusion center (40), is assigned a transmit power value;

acquiring information on the presence of at least a primary user (20) in each grid contour from the database (30);

determining transmit power of the cognitive radio device (10) in each grid contour according to the information on the presence of at least a primary user (20);

wherein the transmit power of the cognitive radio device (10) in a grid contour is decreased to a power level less than the transmit power value assigned to the previous grid contour, when at least a primary user (20) exists in the grid contour, to reduce interference caused to the primary user (20);

wherein transmit power of the cognitive radio device (10) is set at a power level not greater than the transmit power value assigned to the current grid contour when no primary user (20) exists in the current grid contour.