KR20090098590A - Method for setting communication parameter on the wireless network of ad-hoc - Google Patents

Abstract

A method for setting a communication parameter on an ad-hoc wireless network is provided to improve the communication efficiency by adaptively a parameter value based on the probability distribution of link distance. Between a transmission node and a reception node that form an ad-hoc wireless network, feedback information is received from the reception node(100). The communication parameter value between the transmission node and the reception node is determined by using the information about the probability distribution between the transmission and reception nodes and the feedback information(102). The feedback information includes at least one of retransmission request signal and an SNR(Signal to Noise Ratio).

Description

Method for setting communication parameter on the wireless network of ad-hoc}

The present invention relates to a method for improving communication performance by optimizing parameter values using a probability distribution of link distances in an adaptive optimization algorithm used for wireless ad hoc communication.

In wireless ad hoc communication, it is required to maximize communication efficiency due to limited communication resources. In the wireless ad hoc communication environment, the error rate of a channel changes very rapidly due to the distance between links and mutual interference between nodes. Therefore, it is necessary to change the parameter value quickly and appropriately according to the channel state using the adaptive algorithm to increase the communication efficiency.

If the receiving node notifies the side that continuously transmits the specific receiving channel information such as its location information or receiving sensitivity, the transmitting node can set the appropriate parameter value according to the channel to improve communication efficiency. There is a number.

However, most wireless communication protocols are designed to feed back only the essential elements such as the successful reception or retransmission of data due to limited radio resources, so that the information on link distance cannot be known. Therefore, in most cases, the transmitting node resets parameters based on feedback such as whether or not such data has been received or retransmission request.

However, most of the wireless communication protocols are designed to feed back only essential elements such as successful reception or retransmission request due to limited radio resources, so that information on link distance cannot be known. Therefore, when there is no information about the link distance, the parameter is determined by estimating the information on the distance based on the feedback information transmitted by the receiving node, but there is a limit in determining the parameter adaptively to the link distance.

The technical problem to be solved by the present invention is to improve communication efficiency by adaptively changing parameter values according to changing channel conditions using probability distribution of link distance, which is not considered in the conventional method, in a wireless ad hoc communication environment requiring high efficiency. The purpose is to increase.

In order to achieve the above object, a communication parameter setting method in an ad hoc wireless network according to the present invention comprises: receiving feedback information from the receiving node between a transmitting node and a receiving node forming an ad hoc wireless network; And determining the communication parameter value between the transmitting node and the receiving node using the feedback information and the information on the link distance probability distribution between the transmitting node and the receiving node.

Here, the feedback information includes any one or more of a retransmission request signal and a signal to noise ratio.

In addition, the information on the link distance probability distribution is characterized by being expressed as a beta probability function.

The communication parameter value may correspond to any one of a transmission packet size according to a bit error rate, a transmission rate value according to a signal-to-noise ratio, and a transmission power value.

The present invention can provide the effect of improving the communication efficiency than the conventional method by adaptively resetting the parameter value from the information fed back by the receiving node by using the probability distribution of the link distance that was not considered in the conventional adaptive method. . The present invention provides a probability distribution of link distances between arbitrary nodes in a wireless ad hoc network. Therefore, the probability distribution of the link distance provided in the present invention provides a useful mathematical background for the wireless ad hoc communication environment. In the mobile wireless communication, since the channel changes in time, the adaptive parameter control method guarantees excellent communication efficiency compared to the fixed parameter use method. In the adaptive parameter control scheme, the present invention guarantees improved communication efficiency with the link distance estimation capability superior to the conventional scheme using the probability fraction of the link distance. It is also applicable to all adaptive systems, regardless of system configuration or type. The probability distribution of the link distance can be expressed as a beta probability function, so that the mean, variance, and characteristic functions can be known immediately.

Hereinafter, a method of setting communication parameters in an ad hoc wireless network according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart of an embodiment for explaining a method for setting communication parameters in an ad hoc wireless network according to the present invention.

Between the transmitting node and the receiving node forming the ad hoc wireless network, the transmitting node receives the feedback information from the receiving node (step 100). Here, the feedback information provided from the receiving node includes at least one of a retransmission request signal and a signal-to-noise ratio (SNR). The receiving node transmits a retransmission request signal of an automatic retransmission request (ARQ) as feedback information on data that has not been successfully received to the transmitting node. The transmitting node counts the number of times of receiving this retransmission request signal. On the other hand, the receiving node transmits information on the signal-to-noise ratio in addition to the retransmission request signal to the transmitting node.

After operation 100, the communication parameter value between the transmission node and the reception node is determined using the information on the link distance probability distribution between the transmission node and the reception node and feedback information (step 102).

2 is a diagram showing a link distance between any two nodes in a circular area. In the ad hoc wireless communication environment, any transmitting node (B) and receiving node (C) that can communicate with the core node (A) communicate with each other, and the arbitrary node communicates only within the circular area around the core node. Done.

Referring to FIG. 2, the process of deriving the probability distribution f _d (d) of the link distance in the circular region may be described as follows.

3 compares the link distance probability distribution and the beta probability function in the circular region. The solid line represents the equation and the dotted line represents the beta function. As you can see, the two graphs are nearly identical. The variable values of the beta function are 2.0392 and 2.4579. The probability distribution of the link distance d between any two nodes in the circular region of radius R is expressed as

The probability distribution of the link distance provides a complete equation for the link distance in the circular area ED hog, so that the link distance can be estimated using the probability distribution of the link distance in the ad hoc network. In addition, it can be applied to any adaptive system regardless of the system configuration or type, and can be expressed as a beta function so that the average, variance, and characteristic function (CF) can be immediately known.

After step 102, it is determined whether data transmission is required (step 104), and if there is data transmission, steps 100 to 102 are repeated. However, if the transfer of data is not required, the above-described process ends.

On the other hand, the communication parameter value includes a transmission packet size according to the bit error rate, a transmission rate value according to the signal-to-noise ratio, a transmission power value, and the like. A detailed determination method for such a communication parameter value will be described through the following embodiments.

4 is a flowchart illustrating an embodiment of the present invention for controlling the adaptive packet size using a retransmission request and link distance probability distribution in the ARQ scheme. The receiving node feeds back a retransmission request using an ARQ (Automated Retransmission Request) method, and the transmitting node adaptively adjusts the packet size to increase communication efficiency. The receiving node makes a request for retransmission of an ARQ (Automatic Retransmission Request) to the transmitting node for the data that has not been successfully received. After transmitting a certain amount of data, the transmitting node calculates the optimal packet size based on the number of retransmission requests and the probability distribution of link distance, which is used for the next transmission.

First, M packets are transmitted from a transmitting node to a receiving node (step 200).

After the step 200, if the receiving node receives the packet and requests the transmitting node an ARQ for the packet that needs to be retransmitted among the received packets, the transmitting node receives the retransmission request signal (step 202).

After step 202, the transmitting node counts the number of requests of the retransmission request signal transmitted from the receiving node, detects the number of retransmission requests, and uses the information on the detected number of retransmission requests and the link distance probability distribution provided in advance, Determine the packet size of (step 204).

If the bit error rate is known in advance, the optimal packet size can be known. However, since the bit error rate is not known in advance, the communication efficiency can be maximized by estimating the bit error rate based on the number of Q retransmission requests among the M packets transmitted to the receiving node and selecting the packet size based on the estimated bit error rate. . The estimated bit error rate based on the number of retransmissions is as follows.

p represents the bit error rate, and P (p) represents the probability of the bit error rate.

However, we need to know the probability distribution of the bit error rate to estimate the bit error rate. In the case of random distribution in the circular region as shown in FIG. 2, the probability distribution of the link distance may be expressed as beta probability, and the probability distribution of the error rate is expressed as beta probability according to Equation 2 above.

From this link distance probability distribution, the bit error rate can be calculated according to the channel type and physical layer type as shown in the following equation.

 p = H (snr) = H (X (d))

Here, snr represents a signal-to-noise ratio, H (snr) represents a function of converting the signal-to-noise ratio into a bit error rate, and X (d) represents a function of converting the link distance into a signal-to-noise ratio.

Since the probability distribution of the link distance is known and the bit error rate can be obtained from the link distance, the probability distribution of the bit error rate can be obtained. Since the probability distribution of the bit error rate is known, optimal communication efficiency can be achieved by estimating the bit error rate that is most likely to occur from the number of retransmissions and applying the optimal packet size.

In actual application, the above-described equation may be pre-calculated and embedded in the memory instead of real-time calculation. In this case, the input variables are variables such as the number of packets for data transmission, the number of transmission requests, and the packet size. The probability distribution of the bit error rate varies depending on the communication environment such as channel environment and physical layer communication method.

After step 204, packetize the data with the determined packet size (step 206). It is determined whether the transmission of the packetized data is required (step 208). If the transmission of the data is required, steps 200 to 206 described above are repeated, otherwise, the above-described process is terminated.

Meanwhile, another embodiment of the present invention describes a method of improving communication performance by adaptively adjusting a data transmission rate according to a channel state in a wireless communication system supporting multiple data rates. In the communication performance optimization algorithm using multiple transmission rates, the transmitting node determines the appropriate transmission rate and applies it to data transmission based on the signal-to-noise ratio (SNR) fed back by the receiving node. The SNR section corresponding to the optimal transmission rate is calculated and set in advance, and transmitted at the corresponding transmission rate according to the feedback value. The section of the link distance is also determined according to the above SNR section, so if there is information on the distance, the optimal transmission rate can be determined immediately without any special calculation.

Actual SNR values are multi-path fading, shadowing, or delay, so the SNR value measured by the receiving node is undulating and very unstable on the time axis. When the speed is determined based on the SNR value that fluctuates over time, the value of the speed changes frequently, which reduces the efficiency of the system. Appropriate interval observation is required to obtain and apply a stable mean value. On the other hand, when the SNR is calculated based on the link distance based on the location and the transmission rate is determined, the average SNR value can be obtained and applied stably. In addition to the SNR sent by the receiving node, if it is used for optimization by using the distance information, the communication efficiency can be improved compared to the method that depends only on the existing SNR value. If there is no link distance information, the link distance is estimated and applied or a fixed value is used. At this time, the communication distance is improved by using an improved distance estimation algorithm by using the probability distribution of the link distance used in the present invention. Can be. In addition, this method may be applied to multi-data rate control using only the link distance estimation method when the receiving node cannot feed back the SNR value as in the above-described embodiment. In addition, the information fed back by the receiving node may be RSSI (Received Signal Strength Indecation) or SQE (Signal Quality Estimate).

Meanwhile, another embodiment of the present invention describes a method of improving communication efficiency of the entire network by adaptively adjusting the transmission power in accordance with a channel state in a wireless communication system supporting multiple transmission powers. In the multi-transmission power optimization method, the transmission node determines the optimal transmission power based on the link distance or the SNR value fed back by the receiving node and applies the data to the data transmission. In particular, in the case of a cellular network using CDMA, it is important to keep the power received from the various nodes the same. When considering only one link, maximizing the transmission power can maximize the communication performance, but in this case, power is wasted and other links are interfered. Do. Since the power available to the transmitting node is limited, the transmitting node controls the transmission power to maximize the communication capacity of the network by using a water-filling method based on the SNR sent by the receiving node. In general, since the location information is not fed back, the link distance information cannot be known in advance, so a predetermined value is applied. Application of adaptive value rather than fixed value for link distance can improve communication efficiency.

Based on the various information fed back, it is possible to improve the communication performance than the existing system using the fixed link distance by estimating the distance by using the probability distribution of the link distance used in the present invention and adaptively controlling the power. . In addition, this method may be applied to transmission power control using only the link distance estimation method when the receiving node cannot feed back the SNR value as in the above-described embodiment. In addition, the information fed back by the receiving node may be RSSI (Received Signal Strength Indecation) or SQE (Signal Quality Estimate).

Meanwhile, the above-described method for setting communication parameters in an ad hoc wireless network of the present invention may be implemented by computer readable codes / instructions / programs. That is, the method for setting communication parameters in an ad hoc wireless network according to the present invention comprises the steps of: receiving feedback information from the receiving node between a transmitting node and a receiving node forming an ad hoc wireless network; And using the information on the link distance probability distribution between the transmitting node and the receiving node and the feedback information, determining a communication parameter value between the transmitting node and the receiving node. Readable recording media may be implemented. For example, it may be implemented in a general-purpose digital computer for operating the code / instructions / program using a computer-readable recording medium. The computer-readable recording medium may be a magnetic storage medium (eg, ROM, floppy disk, hard disk, magnetic tape, etc.), optical reading medium (eg, CD-ROM, DVD, etc.) and carrier wave (eg Storage media, such as through the Internet). In addition, embodiments of the present invention may be implemented as a medium (s) containing computer readable code, such that a plurality of computer systems connected through a network may be distributed and processed. Functional programs, codes and code segments for realizing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

The method of setting communication parameters in the present inventors' ad hoc wireless network has been described with reference to the embodiments shown in the drawings for clarity, but this is merely illustrative, and those skilled in the art can make various modifications therefrom. And other equivalent embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

1 is a flowchart for explaining a method for setting communication parameters in an ad hoc wireless network according to the present invention.

2 is a diagram showing a link distance between any two nodes in a circular area.

3 is a graph comparing a link distance probability distribution and a beta probability function between two nodes in a circular region.

4 is a flowchart illustrating an embodiment of the present invention for controlling the adaptive packet size using a retransmission request and link distance probability distribution in the ARQ scheme.

Claims (3)

Receiving feedback information from the receiving node between a transmitting node and a receiving node forming an ad hoc wireless network; And Determining a communication parameter value between the transmitting node and the receiving node by using the information on the link distance probability distribution between the transmitting node and the receiving node and the feedback information. And said feedback information comprises at least one of a retransmission request signal and a signal-to-noise ratio. The method of claim 1, The information on the link distance probability distribution is represented by a beta probability function. The method of claim 1, And the communication parameter value includes any one or more of a transmission packet size according to a bit error rate, a transmission rate value according to a signal-to-noise ratio, and a transmission power value.

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