FIELD OF THE DISCLOSURE

Embodiments of the present disclosure generally relate to a method of estimating a transmission direction of a transmitter. Further, embodiments of the present disclosure relate to a system for estimating a transmission direction of a transmitter.

BACKGROUND

In the state of the art, it is known to analyze cellular networks or mobile networks based on a drive test scanner. The respective scanner is moved through an area of interest with the aim to find network cells, namely transmitters, in the wireless spectrum, and to obtain respective measurement values for analysis, for instance a receive power of the respective cells. Typically, three cells or rather transmitters assigned to one frequency band are mounted on a single tower wherein each of these cells is equipped with a directional antenna that covers an angular range of 120°, particularly a 120° azimuth sector. Accordingly, the transmitters together cover 360°.

Currently known solutions estimate the transmission direction of a respective cell based on measurement values of the respective cell to be investigated. For example, the solutions known in the state of the art chose the direction with the maximum receive power from all measurement results obtained for the respective transmitter.

However, the respective measurements can be influenced or rather affected by objects or obstacles in the measurement area that have a shadowing effect on the signals transmitted by the transmitter or rather cell to be investigated. For instance, large buildings may shadow the respective transmitters depending on the measurement direction.

SUMMARY

Accordingly, there is a need for a simple and cost-efficient way to estimate the transmission direction of a transmitter with high accuracy.

The present disclosure provides a method of estimating a transmission direction of a transmitter. In an embodiment, the method comprises the steps of:

performing a first measurement by means of a measurement system, thereby obtaining a first measurement value of a first transmitter;

performing a second measurement by means of the measurement system, thereby obtaining a second measurement value of a second transmitter;

obtaining position information of the first transmitter and the second transmitter;

determining a position of the measurement system; and

taking the first measurement value, the second measurement value, the position information as well as the position of the measurement system into account in order to estimate the transmission direction of the first transmitter.

Further, the present disclosure provides a system for estimation a transmission direction of a transmitter. In an embodiment, the system comprises a measurement circuit or module, a position circuit or module, and an analysis circuit or module. The measurement module is configured to gather measurement values of a first transmitter and a second transmitter, and to forward these measurement values to the analysis module. The position module, for instance a global navigation satellite system circuit or module, is configured to gather a position of the measurement system itself and to forward the position to the analysis module. The analysis module is configured to obtain position information of the first transmitter and the second transmitter and to estimate the transmission direction of the first transmitter based on the first measurement value, the second measurement value, the position information as well as the position of the measurement system.

Accordingly, the present disclosure is based on the finding that the transmission direction of the transmitter of interest is estimated based on the measurement results for this respective transmitter as well as at least one further transmitter that is located in proximity to the transmitter of interest. Thus, measurement values assigned to different transmitters are taken into consideration in order to determine the transmission direction of a single transmitter, namely the first transmitter, more accurately.

Since at least two different measurement values associated with different transmitters are taken into consideration, a possible shadowing of the signals transmitted can be cancelled out effectively. In other words, such shadowing is compensated appropriately as it is assumed that the shadowing effects the signals transmitted by both transmitters in a similar manner.

Generally, this increases the robustness of the method as well as the accuracy of the system.

Besides the measurement values obtained, the position information of the respective transmitters as well as the position of the measurement system itself are also taken into consideration such that the transmission direction can be estimated appropriately.

Accordingly, it is possible to obtain accurate estimates about the respective transmission direction of the transmitter of interest while taking measurement values into account that may be recorded during a drive test. The drive test may be performed by the measurement system, wherein the measurement system is associated to a movable object, for instance a vehicle or an unmanned aerial vehicle (UAV) like a drone that may be remote-controlled.

The first transmitter and the second transmitter may relate to co-located transmitters that are associated with a sector antenna. In some embodiments, a sector antenna is a type of directional antenna with a sector-shaped radiation pattern. Thus, the term sector is used in the geometric sense.

Generally, each of the transmitters may comprise an antenna, for example a segmented antenna, as well as a remote radio head. The remote radio head (RRH), also called remote radio unit (RRU), is a remote radio transceiver used in wireless networks.

An aspect provides that a ratio or a difference is determined that is based on the first measurement value and the second measurement value, wherein the ratio or the difference is used to estimate the transmission direction of the first transmitter. In some embodiments, the measurement values obtained that are associated with the different transmitters may be subtracted from each other in a certain way in order to obtain a difference.

In some embodiments, a difference metric may be provided, wherein the respective transmission direction is obtained by the maximum metric.

In a similar manner, the respective measurement values associated with the different transmitters may be used by dividing the measurement values in a certain way in order to obtain a ratio.

Hence, a ratio metric may be provided, wherein the respective transmission direction is obtained by the maximum metric.

Furthermore, a model may be used, wherein the measurement values obtained are evaluated in order to identify the best fit of the measurement values with regard to the model applied for estimating the transmission direction of the first transmitter, namely the transmitter of interest. In other words, an optimization metric may be provided wherein the transmission direction is selected such that the best fit of the measurement values obtained with regard to the model applied is achieved.

This can be done by a least-squares method or any other optimization process known. The model applied may be based on typical parameters of an antenna, for instance beam width, and typical wireless channel parameters. Thus, the model applied takes the measurement values obtained into account in order to estimate the transmission direction of the first transmitter, namely the transmitter of interest.

Moreover, an artificial intelligence may be used to estimate the transmission direction of the first transmitter, wherein the artificial intelligence was trained by training data comprising measurement values of transmitters with known transmission direction. The artificial intelligence receives the measurement values in order to output the estimated transmission direction of the first transmitter, namely the transmitter of interest. Accordingly, the transmission direction of the first transmitter is estimated based on an artificial intelligence that was trained previously with training data. For instance, the artificial intelligence may relate to a trained machine-learning algorithm.

In general, the respective steps mentioned above for estimating the transmission direction, for example the ratio metric, the difference metric, the optimization metric associated with the model applied, and/or the artificial intelligence may be used solely or in any combination in order to improve the accuracy of the estimation.

According to another aspect, several measurements are performed such that the first measurement value and/or the second measurement value are/is determined several times from different measurement directions. Therefore, the respective metric can be generated in an appropriate manner. Hence, enough measurement data is provided for the artificial intelligence or rather the model used for estimating the transmission direction. For instance, the first measurement value associated with the first transmitter is measured several times from several measurement directions, wherein the same applies for the second transmitter that is also measured several times from different measurement directions (as well as further transmitters). Accordingly, the estimation of the transmission direction is not only based on the maximum receive power measurements of the transmitter of interest.

In some embodiments, a metric is generated based on the results of the several measurements performed from the different measurement directions. As discussed above, the metric may relate to the difference metric, the ratio metric and/or the optimization metric.

For instance, the first measurement value and the second measurement value comprise at least one of the receive power, a signal-to-interference-noise ratio (SINR), a receive-quality indicator, a delay spread or any combination thereof. Thus, the respective measurement value may relate to at least one value directly measured, a value derived from a measurement value or rather a combination thereof.

The SINR is a quantity used to give theoretical upper bounds on channel capacity (or the rate of information transfer) in wireless communication systems such as networks. The receive-quality indicator is an indicator derived from the receive power measured. The delay spread is a measure of the multipath richness of a communications channel.

In addition, the position information may be obtained from a database or from an estimation result provided by a position-estimation circuit or module. The database may be provided by an internal storage medium of the measurement system or an external data store that can be accessed by the measurement system.

Furthermore, the position information of the respective transmitters may be estimated by a position-estimator module that may rely on image analysis or other known techniques.

Another aspect provides that the position information of the first transmitter and the position information of the second transmitter are substantially identical since the first transmitter and the second transmitter are co-located. As mentioned above, the respective transmitters may be co-located transmitters such that the respective antennas relate to sector antennas. For instance, the transmitters are located on a single tower, wherein the respective transmitters cover a certain angular sector, for instance a 120° azimuth sector.

According to another embodiment, the position information and the position of the measurement system each comprise geographic position information. Accordingly, the respective information can be processed appropriately by the measurement system, for example the analysis module.

Another aspect provides that the position of the measurement system is determined by a global navigation satellite system (GNSS) circuit or module. The position module may be established by the global navigation satellite system circuit or module, for instance a global positioning system (GPS) circuit or module. Therefore, the geographic position information of the measurement system itself can be determined easily. The GNSS module may be integrated within the measurement system.

Alternatively, a separate GNSS module may be provided that is connected with the analysis module in order to forward the respective position information to the analysis module for further processing.

Another aspect provides that the transmission direction is estimated with regard to azimuth and/or elevation. Thus, the azimuth transmission direction, the elevation transmission direction or both directions may be estimated. The elevation transmission direction may be estimated by an unmanned aerial vehicle such as a drone easily that can move in the respective direction in order to obtain measurement values that permit to estimate the elevation transmission direction. The transmission direction with regard to azimuth can be estimated by a vehicle like a car investigating the area of interest.

According to another aspect, the measurement values are filtered and interpolated over an angular measurement range. This may be done in a pre-processing step such that the respective measurement values gathered are filtered and interpolated prior to estimating the respective transmission direction. For instance, large angular ranges covered by the respective measurements can be filled with nulls or constant values prior to the interpolation in order to simplify the respective interpolation. In addition, the filtering can cancel artefacts or other false measurement values.

Moreover, a path-loss compensation may be applied on the measurement values. The path-loss compensation may also relate to a pre-processing step that is performed prior to estimating the transmission direction. In some embodiments, the path-loss compensation may be done for each measurement value obtained. The path loss to be compensated may also be estimated based on the respective position information and/or position of the measurement system that can be used to determine the respective distances. In some embodiments, measurements from a far distance can be scaled appropriately such that they appear to be made close to the transmitters. This contributes to a more accurate measurement and, therefore, an improved estimation of the transmission direction.

Another aspect provides that a joint estimation of the respective transmission direction is performed for the first transmitter and the second transmitter. Thus, the transmission directions of two or more transmitters may be estimated simultaneously by the joint estimation. In some embodiments, the joint estimation may be done for all transmitters, for example all co-located transmitters. In the joint estimation, a limited number of possibilities for the transmission direction distances is provided and considered since the respective position information of the transmitters is taken into account (a priori knowledge). Put differently, the transmission direction distance is regarded as an additional optimization parameter.

Moreover, a probability-density function is taken into consideration for the respective estimation. The probability-density function corresponds to a-priori information about the transmission direction(s).

Further, a confidence interval may be calculated for the respective estimation. The confidence interval defines an angular range where the transmission direction shall be assigned to with a specific probability. For instance, bad measurements will have a confidence interval about +/−180° whereas good measurements will have a confidence interval lower than +/−180°, for example lower than +/−120°, for instance about +/−30°.

In general, the measurement system is configured to perform embodiments of the method described above.

Accordingly, the analysis module may be configured to:

determine a ratio or a difference that is based on the first measurement value and the second measurement value;

apply a model that is used to identify a best fit of the measurement values with regard to the model applied; and/or

use an artificial intelligence that was trained by training data comprising measurement values of transmitters with known transmission direction, wherein the artificial intelligence receives the measurement values in order to output the estimated transmission direction of the first transmitter.

