CN1312869C - Method for measuring radio communication system propagation delay - Google Patents

Abstract

The invention discloses a method for measuring the propagation delay of a wireless communication system, which is applied to the communication system. The involved communication system is composed of at least one base station and a terminal. The invention has the following steps: estimating or fitting the wireless propagation delay of the base station Loss model; the base station broadcasts the propagation loss model to the terminals in its coverage area; the terminal obtains the wireless propagation loss model of the base station through demodulation; the terminal measures the received power, and calculates the distance between it and the base station according to the received power and the propagation loss model of the base station Distance and propagation delay of air signals. The method improves the accuracy of calculating the transmission delay time of the terminal, so that the coverage radius of the base station can be increased through the method of transmitting in advance, and the terminal can be positioned accurately.

Description

A Method for Measuring Propagation Delay in Wireless Communication System

technical field

The invention relates to a wireless communication system, especially a method for measuring wireless propagation delay in a mobile communication system.

Background technique

The mobile communication system structure involved in the present invention is as shown in accompanying drawing 1, at least comprises a CN (core network), an RNC (radio access network controller), a Node B (node B), that is generally said A base station, and a UE (terminal).

Between the Node B and the UE, there is a propagation delay, and this propagation delay increases as the distance between the UE and the Node B increases. Due to the propagation delay, when the UE's signal reaches the Node B, a propagation delay of 2 times occurs.

The Chinese Patent Office has published a patent entitled "Equipment and Method for Measuring Propagation Delay in Narrowband Time Division Duplex Code Division Multiple Access Mobile Communication System" with publication number 1404668, which discloses a commonly used method for estimating propagation delay. In this method, the UE estimates the round-trip delay based on the comparison between the transmit power of the Node B and the receive power of the UE. Due to the different wireless environments of different Node Bs, in wireless environments such as cities, suburbs, and villages, the attenuation speed of Node B signals varies with distance. The method of this patent only estimates the delay based on the comparison between the transmit power of the Node B and the receive power of the UE, which is not accurate enough, and the mobile station needs to use different estimation methods according to different wireless environments.

Contents of the invention

The purpose of the present invention is to provide a method for measuring the propagation delay of a wireless communication system, which solves the technical problem that UE estimates the propagation delay in different wireless environments inaccurately, and improves the accuracy of propagation delay estimation.

The communication system involved in the present invention is composed of at least one Node B and one UE, the Node B includes at least one transmitter and a receiver, and the transmission signal includes at least one overhead channel; the overhead channel completes the transmission of public information ; The UE includes at least one transmitter and a receiver, and the UE obtains the state of the communication system through the overhead channel of the demodulation system, such as the propagation characteristics of the wireless environment where the Node B is located, and the UE obtains the status of the communication system through demodulation The overhead channel of the system obtains the current state of the system.

The method for measuring the propagation delay of the wireless system described in the present invention comprises the following steps:

Step 1 estimates or fits to obtain the wireless propagation loss model of the base station;

Step 2: The base station broadcasts the propagation loss model to the terminals in its coverage area;

Step 3: The terminal obtains the wireless propagation loss model of the base station through demodulation;

Step 4 The terminal measures the received power;

Step 5 The terminal calculates its distance from the base station according to the received power and the propagation loss model of the base station;

Step 6: The terminal calculates the propagation delay of the air signal.

In step 1, the existing model can be used directly, or the model can be obtained by the user through retesting and fitting.

In the step 2, the base station broadcasts the propagation loss model to the terminals in the coverage area of the cell through a broadcast synchronization channel or a common control channel.

By adopting the method of the present invention, compared with the prior art, the accuracy of the transmission delay time is improved by considering the differences in the environments of different Node Bs, so that the coverage radius of the Node B can be further increased by launching in advance, or precise positioning UE et al.

Description of drawings

Fig. 1 is a prior art mobile communication system structural diagram involved in the present invention;

Fig. 2 is a flow chart of the method of the present invention;

Fig. 3 is a schematic diagram of the time slot structure of the uplink and downlink of the prior art TD-SCDMA system;

Fig. 4 is a schematic diagram of a propagation delay sequence of a TD-SCDMA system in the prior art.

Detailed ways

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a general mobile communication system diagram of the present invention, the radio network controller RNC works under the control of the core network CN, and the Node B communicates with the UE under the control of the RNC. Since different Node Bs have different wireless environments, their propagation models are also different. That is to say, at the same distance, the signal power of the Node B received by the UE varies depending on the wireless environment in which the Node B is located.

Fig. 2 is a flow chart of the method of the present invention, and concrete steps are as follows:

Step 1 estimates or fits to obtain the wireless propagation loss model of the Node B.

When an operator designs a mobile communication network, it first needs to plan the network and determine the positions of the transmitting antennas of each base station. Once the location of a base station's transmit antenna is determined, the radio propagation model for that base station can be estimated. There are many methods for this estimation, which are already mature technologies. Existing models can be used directly, such as the famous Hata model, which is based on the results measured by Okumura and fitted to obtain the propagation model of 800MHz radio waves in urban, suburban, and rural areas. However, using this Hata model directly is not accurate enough for a specific base station. Therefore, in order to improve the accuracy, users can also test and fit by themselves.

The user self-test method is to use a fixed power transmitter to send a standard test signal, and then use a field strength meter to measure the signal power of each point in the coverage area of the base station, and then use a logarithmic representation of the relationship between power and distance to perform a linear test. Fitting, a propagation model that is unique to the site is obtained. Assuming that the transmitting power of the transmitter is Pt, an omnidirectional antenna is used, and the power received by the field strength meter at a distance r is Pr, then:

$\mathrm{<span\; class="notranslate">\; PR</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; A</span>}\frac{\mathrm{<span\; class="notranslate">\; Pt</span>}}{{\mathrm{<span\; class="notranslate">\; r</span>}}^{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Here A is a constant, and μ is an exponential factor representing the change of path loss with distance,

Express (1) logarithmically, we have:

10logPr＝10logPt+10logA-10μlogr (2)

If the power is expressed logarithmically, then there are:

P _r =P _t +α-10μlogr (3)

Let r=1, use p _r1 to represent the signal power received by the mobile station at 1 km, there are:

P _r1 =p _t +α (4)

Substitute (4) into (3) to get:

P _r =P _r1 -10μlogr(5)

Wherein, μ specifically represents the exponential power of the mobile station received power signal changing with the distance.

It can be seen from formula (5) that the received power of the mobile station is related to p _r1 , μ and the distance r between the mobile station and the base station.

Using measurement, a set of p _r1 and μ values that change with r can be obtained, so that μ and p _r1 can be fitted by the least square principle, and the propagation model of Node B represented by μ and p _r1 is obtained (5 ).

It should be noted that although this paper introduces the most simple propagation loss expression formula (5), other parameters and formulas representing the Node B propagation loss model can also be used.

Step 2 is to send the propagation model (5) of the base station represented by μ and p _r1 to the mobile station. The specific implementation depends on different communication systems, and it is generally sent through the broadcast channel or common control channel of the base station.

Step 3, after demodulation, the mobile station receives μ and p _r1 contained in the common control channel, then step 4, measures its own received power p _r , step 5, uses (5) to obtain r,

$\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

The unit of r in (6) is kilometer. Let the speed of light be c, then

r=cΔt (7)

Step 6, according to (6) and (7), the propagation path delay from the mobile station to the base station is obtained as:

$\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; \&mu;</span>}}}}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Knowing Δt, the mobile station can transmit 2Δt earlier, eliminating the possibility that the mobile station signal may fall outside the search window due to propagation delay.

Embodiment one:

For mobile communication systems that use TDD (Time Division Duplex) as a duplex communication method, such as TD-SCDMA, PHS (Personal Handset System), etc., the downlink and uplink work on the same frequency band, but up and down in a certain way This frequency band is time-shared between rows. Fig. 3 is a TD-SCDMA system time-sharing mode between uplink and downlink in a subframe, where a subframe is the minimum time interval for a burst transmission. Slot 0 is generally a common channel, and the downlink pilot is sent by the Node B to the UE, so that the UE can synchronize with the system according to the received downlink pilot. The guard band GP is a guard period to prevent overlapping of uplink pilots and downlink pilots. Time slot 1--time slot 6 are user time slots for transmitting voice or data services. When the system transmission switches between uplink and downlink, it is called a transition point. There are two transitions between uplink and downlink in one subframe, so there are two transition points.

The system generally sends a broadcast message on a common channel to explain the current configuration of the system. For example, TD-SCDMA sends system configuration information on the basic common control channel P-CCPCH and auxiliary common control channel S-CCPCH of TSO. In the TD-SCDMA system, the mobile station receives the downlink pilot time slot channel, obtains synchronization with the system, and then sends an uplink synchronization signal to Node B in the uplink pilot time slot, trying to access the system. Node B will search the uplink synchronization signal sent by UE in the guard band GP and uplink pilot.

As can be seen from Figure 4, due to the transmission delay between the Node B and the UE, which is marked by Td in the figure, if the UE does not add any processing to compensate for the transmission delay, it will take the time when it receives the Node B signal as its own reference time, and as the reverse The start time of transmitting the signal, then the time for the UE signal to reach the Node B will be delayed by 2Td in total. Node B generally detects the uplink access signal sent by UE within the time interval of "guard band GP + uplink pilot". If 2Td>uplink pilot, then it falls outside the detection window of Node B and cannot be detected by Node B arrive. This also limits the coverage of Node B.

In order to overcome the shortcomings of the existing technology, we hope that the UE can estimate Td, then the UE can transmit 2Td in advance, so that the UE signal just falls on the starting position of the uplink pilot, and makes up for the signal that may not be received due to air delay. Node B detects the condition. The specific implementation steps are as follows:

In the first step, in the network planning of the TD-SCDMA system, use the existing propagation model, or obtain the propagation model of each Node B in the form of formula (5) after measurement. It should be noted that for the accuracy of the measurement, the power of the downlink pilot channel is used here, because the power of the downlink pilot is continuously transmitted and the power is constant, which can facilitate the UE to measure;

In the second step, the obtained propagation model parameters prl and u are sent to each UE in the coverage area of the Node B through the common control channel CCCH broadcast;

In the third step, the UE demodulates the CCCH channel to obtain prl and u, thereby obtaining the wireless propagation loss model of the Node B;

In the fourth step, the UE measures the power of the downlink pilot channel to obtain pr:

In the fifth step, UE calculates the distance r between itself and Node B according to the formula (6);

In the sixth step, UE calculates its propagation delay Td with Node B according to formula (8);

Finally, using the propagation delay Td obtained through the above steps, the UE transmits 2Td ahead of time, and finally eliminates the influence of the propagation delay.

Embodiment two:

In the IS95A system, the access signal of the mobile station is often searched through a fixed window. Sometimes, because the mobile station is too far away from the base station, its access signal falls outside the search window of the base station, so it cannot be found by the base station, resulting in failure to access the system.

By transmitting the propagation model of the pilot channel of the current base station in the synchronous channel of the base station, the mobile station calculates the distance and propagation delay from the base station by measuring the power of the pilot channel, and transmits a certain time in advance, which can Let the long-distance mobile station signal fall within the search window of the base station. The implementation steps are as follows:

The first step is to use the existing propagation model in the network planning of the IS95A system, or obtain the propagation model of each Node B in the form of formula (5) after measurement. It should be noted that, for the accuracy of measurement, the power of the downlink pilot channel is used here, because the power of the downlink pilot channel remains constant and is higher than the general traffic channel, which can facilitate the UE to measure;

In the second step, the obtained propagation model parameters prl and u are sent to each UE in the coverage area of the Node B through a synchronous channel broadcast;

In the third step, the UE demodulates the synchronization channel to obtain prl and u, thereby obtaining the wireless propagation loss model of Node B;

In the fourth step, the UE measures the power of the downlink pilot channel to obtain pr;

In the fifth step, UE calculates the distance r between itself and Node B according to the formula (6);

In the sixth step, UE calculates its propagation delay Td with Node B according to formula (8);

Finally, using the above steps to get the propagation delay Td, the UE transmits 2Td ahead of time, solving the problem that the air propagation delay causes the UE's access signal to fall outside the Node B search window, and eliminating the impact of propagation delay.

Claims (2)

1. A method for measuring propagation delay in a wireless communication system, the communication system involved is at least made up of a base station and a terminal, characterized in that it comprises the following steps: Step 1 estimates or fits to obtain the wireless propagation loss model of the base station; The wireless propagation loss model is: p _r =p _r1 -10μlogr Among them, the power received by the field strength meter at a distance r is Pr, μ is an exponential factor representing the path loss as the distance changes, and p _r1 represents the signal power received by the mobile station at r=1 km; Step 2: The base station broadcasts the propagation loss model to the terminals in its coverage area; Step 3: The terminal obtains the wireless propagation loss model of the base station through demodulation; Step 4 The terminal measures the received power; Step 5 The terminal calculates its distance from the base station according to the received power and the propagation loss model of the base station; Step 6: The terminal calculates the propagation delay of the air signal. 2. The method according to claim 1, wherein in the step 2, the base station broadcasts the propagation loss model to the terminals in the coverage area of the cell through a broadcast synchronization channel or a common control channel.

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