KR100887396B1 - Apparatus and method for estimating available bandwidth - Google Patents

Abstract

The present invention relates to an apparatus and method for predicting available bandwidth, the method comprising: checking a preset current channel capacity according to a received RSSI value, and predicting an available bandwidth of a channel by using the number and size of packets per second received from a current application stage. And adjusting the channel capacity according to the available bandwidth to adaptively respond to the transmission bit rate according to the network situation, thereby increasing network efficiency.

RSSI, Packets, Available Bandwidth, WLAN

Description

APAPATUS AND METHOD FOR ESTIMATING AVAILABLE BANDWIDTH}

1 is a diagram showing a relationship between data throughput and currently available data throughput;

2 is a graph showing received signal strength (RSSI) and its derivative result;

3 is a flowchart illustrating a process of predicting available bandwidth.

The present invention relates to a technique for predicting an available bandwidth, and more particularly, to estimate an available bandwidth of a WLAN channel currently available in an application layer of a wireless local area network (WLAN) terminal. An apparatus and method for predicting available bandwidth for transmitting data in accordance with a bandwidth are provided.

Data throughput in the existing WLAN was calculated according to the payload length and the current channel capacity as shown in Equation (1) in IEEE 802.11b UDP [Ramjee Prasas and Luis Munoz “WLANs and WPANs towards 4G wireless ”, equ. 5.2 pp. 148].

--- 식 (1)

--- Equation (1)

Where R _b is the current channel capacity, L is the payload length, and T _putUDP is the amount of data transmission. The data transfer amount obtained in Equation (1) means the theoretical data transfer amount given the payload and the current channel capacity.

However, this value does not take into account the currently used traffic and does not mean available bandwidth. In order to obtain this value, the value of R _b must be known in advance in the application stage.

Accordingly, the present invention has been made to solve the above-mentioned problems in the prior art, and an object of the present invention is to estimate the available bit rate of a server in accordance with time when transmitting content such as video to a WLAN terminal. In order to adaptively adjust to a network, the present invention provides an apparatus and method for predicting available channel capacity by using RSSI information to estimate the current channel capacity and using the number and size of packets per second received from the current application stage. have.

In order to achieve the above object, the available bandwidth prediction apparatus of the present invention checks a preset current channel capacity corresponding to a received signal strength of an application terminal, and checks the number and size of packets per second received from the application terminal. Available bandwidth measuring unit for measuring the available bandwidth by the calculation of traffic and data transmission amount; And an encoding bit rate controller for adjusting a data encoding bit rate in response to the available bandwidth measurement result.

In addition, the available bandwidth prediction apparatus of the present invention, a packet check unit for checking the number and size of packets per second to the packet transmitted from the server; And a feedback unit which feeds back the number and size of packets per second of the checked packets to the server so that the server calculates the amount of data transmission corresponding to the number and size of packets per second and the available bandwidth calculated by the operation of the current traffic. Characterized in that.

On the other hand, the available bandwidth prediction method according to the present invention, the step of checking the received signal strength received from the application, the predetermined current channel capacity (Rb) corresponding to the received signal strength in the server; Estimating available bandwidth of the channel at the server using the number and size of packets per second fed back from the application end; And adjusting channel capacity at a server in response to the available bandwidth.

In addition, checking the number and size of packets per second delivered from the server at the application end; And feeding back the number and size of the checked packets per second to the server so that the server can calculate the amount of data transmission corresponding to the number and size of the packets per second and the available bandwidth calculated by the operation of the current traffic. It is characterized by.

Hereinafter, the available bandwidth prediction apparatus and method of the present invention will be described in detail with reference to the accompanying drawings.

First, a value used as a reference for measuring the strength of a radio wave is a Received Signal Strength Indicate (RSSI) value indicating a received signal strength. This is time-varying as the WLAN terminal moves. The use of RSSI values can be found in handoffs between well-known mobile communication terminals and base stations. That is, when the RSSI value received by the base station is continuously checked, the handoff is determined when it falls below the threshold value, and communication is performed to another newly recognized base station.

On the other hand, through the experiment between the payload (L) and the current channel capacity can be obtained as shown in Table 1 below.

TABLE 1

Table 1 shows the results of the conventional data throughput measurement algorithm according to equation (1).

1 is a diagram illustrating a relationship between data throughput and currently available data throughput. According to FIG. 1, the relationship between the current number of bits per second (bps), that is, the current traffic B _C , the available bandwidth B _A , and the data transmission amount T = T _putUDP may be defined as follows.

--- 식 (2)

--- Equation (2)

TABLE 2

condition Packets Per Second (P) Bits per second (B, bps) Bits per packet (L) Current P _C B _C L _C Available P _A B _A L _A Maximum P _T B _T = T L _T = L

[Table 2] is a table that defines the number of packets per second (P), the number of bits per second (B), the number of bits per packet (L) according to each state of Figure 1, the number of packets per second (P _C ) corresponding to the current traffic , Bits per second (B _C ), bits per packet (L _C ) can be measured by the terminal. Accordingly, L (= L _T ) may be defined as follows according to the length of the payload to be sent from the terminal of the terminal, that is, L _A.

--- 식 (3)

--- Equation (3)

In Equation (3), P _A can be obtained as follows.

--- 식 (4)

--- Equation (4)

Substituting Equation (3) above into the L value of Equation (1), the data transfer amount can be obtained as follows.

--- 식 (5)

--- Equation (5)

In Eq. (5), the data transfer amount is R _b , P _C , B _C , L _A , where P _c , B _C are measurable values in the current application, and L _A is the length of the payload to be sent from the terminal. This value is known from the terminal. Therefore, if we know R _b, we can get the data transfer amount (T = T _putUDP ) from Eq. (5) and get the current available bandwidth according to Eq. (2).

R _b may be predicted through a Received Signal Strength Indication (RSSI) value. According to the vendor of the WLAN terminal, the relationship between the RSSI value and the R _b is provided, and R _b can be predicted based on the relationship.

TABLE 3

3Com 802.11b device Channel capacity RSSI 11 Mbps -88 dBm 5.5 Mbps -91 dBm 2 Mbps -92 dBm 1 Mbps -93 dBm

Table 3 shows an example of the relationship between RSSI and R _b provided by a vendor.

The current throughput can be calculated based on the packet length measured by the RSSI and the application terminal of the WLAN terminal.

)를 두어 감 소시킨다. 반대로 미분값이 양수이면 원래 해당하는 채널 용량을 가중치(

)를 두어 증가시킨다. 도 2에서 R(x)은 측정되는 RSSI 값을 의미하며 R'(x)값은 R(x)값의 1차 미분 값이다. 따라서 WLAN 단말이 이동함에 따라 변하는 RSSI 값을 이용하여 채널 용량(R_b)에 반영한다. The RSSI values may be differentiated over time to predict a change in channel capacity. The measured RSSI values are filtered-lowpass filtering such as median filtering-and then use the first derivative of the filtered value. If the derivative is negative as shown in FIG. The channel capacity (R _b )

) To decrease. Conversely, if the derivative is positive, the original corresponding channel capacity is weighted (

) To increase. In FIG. 2, R (x) means the RSSI value to be measured, and R '(x) is the first derivative of the R (x) value. Therefore, using the RSSI value that changes as the WLAN terminal moves to reflect the channel capacity (R _b ).

Based on the above, as shown in FIG. 3, the data rate may be adaptively selected in the WLAN terminal according to the network condition of the WLAN.

)를 두어 현재 채널 용량을 증가시키고(S3), 그렇지 않을 경우에는 가중치(

)를 두어 현재 채널 용량을 감소시킨다(S4). 이후, 현재 채널 용량이 증가되거나 감소된 결과를 고려하여 망 상황에 적응적으로 가용 대용폭을 결정한다(S5). That is, the parameters of the RSSI value and the L _C value are measured (S1), and RSSI filtering and derivatives are performed (S2). As a result of the derivative of the RSSI value, if the derivative is positive, the weight (

) To increase the current channel capacity (S3), otherwise weight (

) To reduce the current channel capacity (S4). Subsequently, in consideration of the result of the increased or decreased current channel capacity, the available substitute width is determined adaptively to the network situation (S5).

Although the present invention has been described in more detail with reference to some embodiments, the present invention is not necessarily limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

As described above, the apparatus and method for predicting the available bandwidth according to the present invention estimates the available bandwidth by using the RSSI value and the length of the received packet of the application stage at the terminal of the WLAN, so that the server adapts to the network situation. By adjusting the transmission bit rate, the image quality deterioration due to packet loss in the wireless network can be reduced.

Claims (9)

Check the preset current channel capacity corresponding to the received signal strength of the application terminal of the terminal, the number of packets per second and the size received from the application terminal of the terminal to check the current number of bits per second at the application terminal of the terminal, the application of the terminal An available bandwidth measuring unit for measuring an available bandwidth by calculating a difference between a current traffic and a data transmission amount defined as a function of a current number of bits per packet at a stage and a payload length to be transmitted to an application stage of a terminal; And An encoding bit rate controller for adjusting a data encoding bit rate in response to the available bandwidth measurement result Available bandwidth prediction apparatus comprising a. delete Checking a preset current channel capacity R _b corresponding to the received signal strength at a server with respect to the received signal strength received from an application end of the terminal; Using the number and size of packets per second fed back from the terminal of the terminal, the current number of bits per second in the terminal of the terminal, the current number of bits per packet in the terminal of the terminal, the payload length to be transmitted to the terminal of the terminal Estimating, at the server, the available bandwidth determined by the difference operation between the current traffic and the data transmission amount defined as a function of the; And Adjusting channel capacity at a server in response to the available bandwidth Available bandwidth prediction method comprising a. delete delete 4. The method of claim 3, wherein the adjustment of the current channel capacity (R _b ) determines the RSSI value as a derivative. 7. The available bandwidth of claim 6, wherein the current channel capacity is increased when the derivative is positive and the current channel capacity is decreased when the derivative is negative. Forecast method. 8. The method of claim 7, wherein a weight is assigned when the current channel capacity is increased or decreased. delete

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