CN102075297A - Mobility-prediction-based wireless fidelity (WiFi) speed self-adapting selecting method - Google Patents

Abstract

The invention provides a mobility-prediction-based wireless fidelity (WiFi) speed self-adapting selecting method, which belongs to the communication field. Firstly a vehicle WiFi device continuously detects the strength of access point (AP) signals nearby, the strength value of the detected AP signal is converted to a corresponding distance value, and the movement trend of the vehicle WiFi device is predicted according to a plurality of distance values; and a data speed of the WiFi device is selected according to the movement trend of the vehicle WiFi device and a distance-data speed table which is obtained through the experiment. By the method provided by the invention, the shaking of the data speed of the WiFi device during the moving process of a vehicle can be reduced, and the data transmission efficiency can be improved.

Description

A kind of WiFi rate adaptation system of selection based on moving projection

Technical field

The invention belongs to the communications field, is a kind of WiFi device-speed adaptive approach, is specifically related to a kind of WiFi speed self-adaption method based on moving projection.

Background technology

The initial design target of WiFi (Wireless Fidelity) technology is for providing the wireless access service the fixed area user, and exemplary apparatus mainly is a notebook computer.Yet along with constantly popularizing and a large amount of utilizations of WiFi equipment of WiFi technology, the WiFi communication module can be integrated in platforms such as mobile phone, palmtop PC or even wearable computer easily.The miniaturization of portable terminal makes the mobility of WiFi equipment improve greatly, has also brought the variation of using scene immediately, such as, a hand-held cellphone subscriber who possesses the WiFi communication function may be sitting on the traveling automobile and the access point of wishing to visit the roadside.The dynamic scene change of this height can cause the communication efficiency of WiFi equipment to descend.Even the user moves the dynamic change that also can cause communication channel in same access point scope, bring very big influence can for the WiFi system, such as energy consumption, channel speed coupling, network service efficient etc.

Channel speed matching problem when rate adaptation algorithm target is the WiFi devices communicating that improves under the vehicle environment.And the channel speed coupling will directly have influence on the bandwidth and the call duration time of WiFi communication.The selection of channel speed need solve the basic contradiction of speed and distance.Usually, the communication distance of higher transmission rate is lower, and lower transmission rate then has communication distance far away.Obviously higher transmission rate can improve communication bandwidth, reduces the transmission time.Prior art does not have a kind of variation along with WiFi equipment and access point communication distance, and suitable traffic rate of total energy coupling guarantees the highest method of communication bandwidth.

Summary of the invention

The objective of the invention is in order to address the above problem, a kind of WiFi speed self-adaption method based on moving projection has been proposed, the AP signal strength signal intensity that this method receives by monitoring (Received Signal Strength Indicator, abbreviation RSSI) variation tendency is predicted vehicle and AP distance, selects WiFi device data transmission rate according to distance value.

A kind of WiFi rate adaptation system of selection based on moving projection is characterized in that, comprises the steps:

Step 1:WiFi equipment is surveyed the AP signal strength signal intensity of current association;

The AP signal strength signal intensity to current association of the WiFi equipment periodic in the vehicle is surveyed, record is also preserved result of detection, described result of detection be triplet information record (RSSI, MAC address, T), wherein, RSSI is the signal strength signal intensity of AP, and MAC address is a MAC Address, and T is for surveying constantly, described MAC represents medium access control, and full name is Media Access Control;

Step 2: judge whether AP signal strength signal intensity detection times reaches m time;

The user preestablishes threshold value m voluntarily according to actual conditions, and described preset threshold m is a positive integer; Information record strip number to same MAC Address is added up, and the information record strip number of same MAC Address is m, if m greater than preset threshold, then execution in step 3, continue to carry out otherwise change step 1;

Step 3: according to the AP signal strength information that detects AP position is on every side estimated, obtain AP the prediction coordinate (a, b);

The prediction coordinate of described AP (a b) specifically obtains by following process:

1) will have the tlv triple record of identical MAC Address by time T _iSequence arrangement from small to large, and the signal strength signal intensity and the time of getting nearest n time result of detection obtain (R ₁, T ₁) ... (R _i, T _i) ... (R _n, T _n), wherein, T _I+1＞T _i, 1≤i≤n, 3≤n≤5, R _iBe the AP signal strength signal intensity that vehicle WiFi equipment receives, T _iBe the detection moment of record;

2) according to conversion formula signal strength values is converted to distance value, wherein conversion formula is:

$d_i={10}^{\frac{-43.4-R_i}{20}}---\left(1\right)$

3) n result of detection made up in twos, calculates the predicted position of AP:

$a_{\mathrm{ij}}=\frac{d_j^2-d_i^2+{\mathrm{\Δ}}_i^2-{\mathrm{\Δ}}_j^2}{2({\mathrm{\Δ}}_j-{\mathrm{\Δ}}_i)}---\left(2\right)$

Wherein, parameter Δ _i=(T _i-T ₁) * v, Δ _j=(T _j-T ₁) * v,

V represents current vehicle speed, a _IjBe (R _i, T _i) (R _j, T _j) abscissa of the AP predicted position value that obtains of combination, 1≤i≤n, 1≤j≤n, i ≠ j;

4) to all a _IjGet the abscissa a that arithmetic mean obtains AP prediction coordinate, that is:

$a=\frac{1}{C_n^2}\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}\underset{j=i+1}{\overset{n}{\mathrm{\Σ}}}{a}_{\mathrm{ij}}---\left(3\right)$

Wherein $C_n^2=n\×(n-1)/2;$

Calculate the ordinate b of AP prediction coordinate:

$b=\left\{\begin{array}{cc}\sqrt{{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HDA0000045176590000031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2}& ({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HDA0000045176590000031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2\&GreaterEqual;0)\\ 0& ({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HDA0000045176590000031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2<0)\end{array}\right.---\left(4\right)$

Step 4: according to estimated coordinates (a, b) distance of prediction AP and vehicle after 0.2 second;

$L=\sqrt{{(a-{\mathrm{\&Delta;}}_n-0.2\&times;v)}^2+b^2}---\left(5\right)$

Step 5: the data rate of selecting WiFi equipment;

Select the suitable data transmission rate according to Prediction distance;

Step 6:, then finish, otherwise return step 1 if be connected with the AP disconnection.

Advantage of the present invention and good effect are:

(1) in the method for the present invention, adopts Forecasting Methodology to estimate the distance of AP and moving vehicle, change WiFi equipment transmission rate in real time, improve data transfer bandwidth in the vehicle moving process.

Description of drawings

Fig. 1 is a method flow diagram of the present invention;

The schematic diagram that Fig. 2 surveys the signal strength signal intensity of AP for vehicle of the present invention;

Fig. 3 is a vehicle scan A P process schematic diagram of the present invention.

Fig. 4 is the rate adaptation algorithm contrast schematic diagram that the present invention and HTC G1 mobile phone are adopted.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples.

A kind of WiFi rate adaptation system of selection based on moving projection, flow process comprises the steps: as shown in Figure 1

Step 1:WiFi equipment is surveyed the AP signal strength signal intensity of current association.

As shown in Figure 2, the AP signal strength signal intensity to current association of the WiFi equipment periodic in the vehicle is surveyed, record is also preserved result of detection, and described result of detection is triplet information record (RSSI, MAC address, T), wherein, RSSI is the signal strength signal intensity of AP, and MAC address is MAC (Media Access Control, medium access control) address, T is for surveying constantly.

Step 2: judge whether AP signal strength signal intensity detection times reaches m time.

Preestablish threshold value, described preset threshold is a positive integer.Information record strip number to same MAC Address is added up, and the information record strip number of same MAC Address is m, if m greater than preset threshold, then execution in step 3, continue to carry out otherwise change step 1.

Step 3: according to the AP signal strength information that detects AP position is on every side estimated, obtain AP the prediction coordinate (a, b).

The prediction coordinate of described AP (a b) specifically obtains by following process:

1) will have the tlv triple record of identical MAC Address by time T _iSequence arrangement from small to large, and the signal strength signal intensity and the time of getting nearest n time result of detection obtain (R ₁, T ₁) ... (R _i, T _i) ... (R _n, T _n), wherein, T _I+1＞T _i, 1≤i≤n, 3≤n≤5, R _iBe the AP signal strength signal intensity that vehicle WiFi equipment receives, T _iBe the detection moment of record;

2) according to conversion formula signal strength values is converted to distance value, wherein conversion formula is:

$d_i={10}^{\frac{-43.4-R_i}{20}}---\left(1\right)$

3) n result of detection made up in twos, calculates the predicted position of AP:

$a_{\mathrm{ij}}=\frac{d_j^2-d_i^2+{\mathrm{\&Delta;}}_i^2-{\mathrm{\&Delta;}}_j^2}{2({\mathrm{\&Delta;}}_j-{\mathrm{\&Delta;}}_i)}---\left(2\right)$

Wherein, parameter Δ _i=(T _i-T ₁) * v, v represents current vehicle speed, a _IjBe (R _i, T _i) (R _j, T _j) abscissa of the AP predicted position value that obtains of combination, 1≤i≤n, 1≤j≤n, i ≠ j.

4) to all a _IjGet the abscissa a that arithmetic mean obtains AP prediction coordinate, that is:

$a=\frac{1}{C_n^2}\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}\underset{j=i+1}{\overset{n}{\mathrm{\&Sigma;}}}{a}_{\mathrm{ij}}---\left(3\right)$

Wherein $C_n^2=n\&times;(n-1)/2.$

Calculate the ordinate b of AP prediction coordinate:

$b=\left\{\begin{array}{cc}\sqrt{{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HDA0000045176590000031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2}& ({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HDA0000045176590000031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2\&GreaterEqual;0)\\ 0& ({\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HDA0000045176590000031.png"\; state="\{\{state\}\}">d</figure-callout>}}_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2<0)\end{array}\right.---\left(4\right)$

Step 4: according to estimated coordinates (a, b) distance of prediction AP and vehicle after 0.2 second.

$L=\sqrt{{(a-{\mathrm{\&Delta;}}_n-0.2\&times;v)}^2+b^2}---\left(5\right)$

Step 5: the data rate of selecting WiFi equipment.

Select the suitable data transmission rate according to Prediction distance, distance is as shown in table 1 with the corresponding relation of data transmission rate.

Table 1WiFi equipment " distance-data rate " correspondence table

Distance range	Iptimum speed
			0～10 meter	54Mbps?
10～15 meters	48Mbps?
		15～20 meters	36Mbps?

20～30 meters	24Mbps?
		30～45 meters	18Mbps?
45～65 meters	12Mbps?
		65～70 meters	9Mbps?
More than 70 meters	6Mbps?

Step 6:, then finish, otherwise return step 1 if be connected with the AP disconnection.

Embodiment

As Fig. 2, shown in Figure 3, vehicle along the x direction of principal axis with the speed of v=20m/s through roadside AP, vehicle keeps related with AP, and the signal strength signal intensity of AP is surveyed, the vehicle trace interval is 0.2 second, establish vehicle with speed v along x axle forward travel, at t _i(i=1,2...) moment is measured the RSSI value of AP, obtains a series of sample (R _i, t _i), adopt method of the present invention to carry out the WiFi rate adaptation and select, change WiFi equipment transmission rate then in real time, make that the WiFi data rate of setting is more consistent with practical radio communication environment, improve data transfer bandwidth in the vehicle moving process.Fig. 4 has shown the difference of rate adaptation algorithm aspect rate selection that this method and HTC G1 mobile phone are adopted, improve speed among the figure for using result of the present invention, rate curve of the present invention is compared with the rate curve of G1 mobile phone, this method speed jitter phenomenon reduces in a large number, more helps mobile phone with rational rate sending data.

Claims (2)

1. the WiFi rate adaptation system of selection based on moving projection is characterized in that, comprises the steps:

Step 1:WiFi equipment is surveyed the AP signal strength signal intensity of current association;

The AP signal strength signal intensity to current association of the WiFi equipment periodic in the vehicle is surveyed, record is also preserved result of detection, described result of detection be triplet information record (RSSI, MAC address, T), wherein, RSSI is the signal strength signal intensity of AP, and MAC address is a MAC Address, and T is for surveying constantly, described MAC represents medium access control, and full name is Media Access Control;

Step 2: judge whether AP signal strength signal intensity detection times reaches m time;

The user preestablishes threshold value m voluntarily according to actual conditions, and described preset threshold m is a positive integer; Information record strip number to same MAC Address is added up, and the information record strip number of same MAC Address is m, if m greater than preset threshold, then execution in step 3, continue to carry out otherwise change step 1;

Step 3: according to the AP signal strength information that detects AP position is on every side estimated, obtain AP the prediction coordinate (a, b);

The prediction coordinate of described AP (a b) specifically obtains by following process:

1) will have the tlv triple record of identical MAC Address by time T _iSequence arrangement from small to large, and the signal strength signal intensity and the time of getting nearest n time result of detection obtain (R ₁, T ₁) ... (R _i, T _i) ... (R _n, T _n), wherein, T _I+1＞T _i, 1≤i≤n, 3≤n≤5, R _iBe the AP signal strength signal intensity that vehicle WiFi equipment receives, T _iBe the detection moment of record;

2) according to conversion formula signal strength values is converted to distance value, wherein conversion formula is:

$d_i={10}^{\frac{-43.4-R_i}{20}}---\left(1\right)$

3) n result of detection made up in twos, calculates the predicted position of AP:

$a_{\mathrm{ij}}=\frac{d_j^2-d_i^2+{\mathrm{\&Delta;}}_i^2-{\mathrm{\&Delta;}}_j^2}{2({\mathrm{\&Delta;}}_j-{\mathrm{\&Delta;}}_i)}---\left(2\right)$

Wherein, parameter Δ _i=(T _i-T ₁) * v, Δ _j=(T _j-T ₁) * v,

V represents current vehicle speed, a _IjBe (R _i, T _i) (R _j, T _j) abscissa of the AP predicted position value that obtains of combination, 1≤i≤n, 1≤j≤n, i ≠ j;

4) to all a _IjGet the abscissa a that arithmetic mean obtains AP prediction coordinate, that is:

$a=\frac{1}{C_n^2}\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}\underset{j=i+1}{\overset{n}{\mathrm{\&Sigma;}}}{a}_{\mathrm{ij}}---\left(3\right)$

Wherein $C_n^2=n\&times;(n-1)/2;$

Calculate the ordinate b of AP prediction coordinate:

$b=\left\{\begin{array}{cc}\sqrt{d_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2}& (d_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2\&GreaterEqual;0)\\ 0& (d_1^2-{(a-{\mathrm{\&Delta;}}_1)}^2<0)\end{array}\right.---\left(4\right)$

Step 4: according to estimated coordinates (a, b) distance of prediction AP and vehicle after 0.2 second;

$L=\sqrt{{(a-{\mathrm{\&Delta;}}_n-0.2\&times;v)}^2+b^2}---\left(5\right)$

Step 5: the data rate of selecting WiFi equipment;

Select the suitable data transmission rate according to Prediction distance;

Step 6:, then finish, otherwise return step 1 if be connected with the AP disconnection.

2. a kind of WiFi rate adaptation system of selection based on moving projection according to claim 1 is characterized in that in the described step 5, the corresponding relation of Prediction distance and data transmission rate is:

The distance range iptimum speed

0～10 meter 54Mbps

10～15 meters 48Mbps

15～20 meters 36Mbps

20～30 meters 24Mbps

30～45 meters 18Mbps

45～65 meters 12Mbps

65～70 meters 9Mbps

6Mbps more than 70 meters

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