Method for operating a base station in a wireless radio network

Abstract

The present invention relates to a method for operating a base station (11) in a wireless radio network (10). The base station (11) comprises a plurality of antennas (12) for transmitting radio frequency signals between the base station (11) and a user equipment (UE1, UE2, UE3). According to the method, a transmission slot (47) is provided for receiving at each antenna (12) of a subset of the plurality of antennas (12) a training signal sent from the user equipment (UE1, UE2, UE3). For each antenna (12) a corresponding configuration parameter is determined based on the training signal received at the corresponding antenna (12) and payload information blocks (36, 37) to be transmitted between the base station (11) and the user equipment (UE1, UE2, UE3) are transmitted using the determined configuration parameters for the antennas (12). A deterioration parameter indicating a deterioration of a transmission between the base station (11) and the user equipment (UE1, UE2, UE3) due to a change in the transmission requiring adaption of the configuration parameters is determined. Based on the deterioration parameter, a timing parameter is determined for controlling when a further transmission slot (47) is to be provided for receiving at each antenna (12) a next training signal sent form the user equipment (UE1, UE2, UE3).

Description

FIELD OF THE INVENTION[0001]The present invention relates to a method for operating a base station in a wireless radio network. Especially, the present invention relates to a method for operating a base station comprising a plurality of antennas for transmitting radio frequency signals according to a so-called multiple-input and multiple-output (MIMO) technology. The present invention relates furthermore to a base station which implements the method, and a user equipment which is configured to be used in connection with the base station.BACKGROUND OF THE INVENTION[0002]For increasing data transmission performance and reliability, the so-called multiple input and multiple-output technology (MIMO) may be used in wireless radio frequency telecommunications for transmitting information between a base station and a user equipment. The MIMO technology relates to the use of multiple send and receive antennas for a wireless communication at for example a base station or a user equipment. Th...

AI Technical Summary

Benefits of technology

[0009]For example, in a typical massive MIMO system a lot of user equipments may be arranged within a cell served by the base station. However, especially in the scenario of a massive MIMO system in buildings such as offices or shopping malls, a lot of the user equipments may be stationary, for example desktop computers, cash registers, supervision cameras and so on. Such stationary user equipments may have the same or even a higher need for bandwidth as mobile user equipments like mobile phones, especially smart phones, tablet PCs and so on. However, adaption of the configuration parameters for transmitting data between the base station and the stationary user equipments is required less frequently than an update of configuration parameters used for data transmissions between the base station and user equipments which are changing their position with the respect to the base station. Therefore, according to the above-described method, a timing for controlling when a further transmission slot is to be provided for receiving a next training signal from each user equipment is determined individually for each user equipment based on a deterioration parameter indicating a deterioration of a transmission between the base station and the corresponding user equipment. For example, a fast moving user equipment may transmit training signals more frequently than slow moving user equipments or stationary user equipments. A fast moving user equipment may transmit a training signal each frame, while stationary or slow moving user equipments may transmit training signals less often, for example every other frame or every third frame. Further, also user equipments in idle mode having no active payload communication may transmit training signals less often, for example every other frame or even less often, in order to verify that they are still in the coverage of the base station. The determined timing or allocation scheme may need to provide synchronization between the user equipments and the base station. For example, the base station may allocate an appropriate timing for each user equipment taking into account the individual mobility of each of the user equipments. This may enable to set up a system with a smaller header in each frame, or it may allow more user equipments to be connected to the same base station. This implies that the cells payload capacity may be improved compared to a system in which a transmission slot is allocated for each user equipment in each frame independent of the mobility. Furthermore, due to adapting the timing for providing the transmission slots for receiving training signals, the header size of each frame may be allocated dynamically to reflect the collective mobility of the user equipments attached to the base station. This may increase system performance, since the header may dynamically become smaller when the number of stationary user equipments grows. Therefore, the relative size of the header may decrease versus the payload. Vice versa, the header may dynamically become larger when the number of moving user equipments is growing. This information may be communicated and synchronized with neighboring cells.

[0013]According to another embodiment, based on the deterioration parameter, a next point in time, at which the further transmission slot for receiving the next training signal is to be provided, is determined as the timing parameter. For example, based on the deterioration parameter, for a certain user equipment it may be determined that it is sufficient to provide a transmission slot for receiving the next training signal in a few hundred milliseconds, for example in 700 milliseconds. Thus, an appropriate frame may be selected and in this frame a corresponding transmission slot for receiving the next training signal may be provided. Thus, the transmission slots for receiving the training signals may be used very efficiently.

[0014]According to another embodiment, based on the deterioration parameter, a training sequence rate value may be determined which controls a rate at which further transmission slots are to be provided for receiving at each antenna of the subset of the plurality of antennas next training signals from the user equipment. For example, when a very slow relative movement between a user equipment and a base station is determined, the training sequence rate value may be determined such that transmission slots for receiving training signals from this certain user equipment are provided in every other frame or in every fifth frame. However, when a fast relative movement between the user equipment and the base station is determined or the bit error rate of the transmission between the base station and the user equipment is varying significantly, the training sequence rate value may be determined such that a corresponding transmission slot for receiving the training signals from this user equipment is provided in every frame. Therefore, an efficient usage of the transmission slots for the training signals may be ensured and thus the amount of overhead for receiving training signals can be reduced and the payload performance may be increased.

[0016]According to another embodiment, the plurality of antennas of the base station is configured for transmitting radio frequency signals between the base station and a plurality of user equipments. For each user equipment of the plurality of user equipments a corresponding transmission slot is provided for receiving at each antenna of a subset of the plurality of antennas a training signal sent from the corresponding user equipment. The training signals need to be orthogonal in order for the base station to identify the configuration parameters for the plurality of antennas for each of the individual user equipments. Orthogonality may be achieved by using time division multiple access (TDMA), code division multiple access (CDMA) or frequency division multiple access (FDMA) technologies or a combination thereof. For each antenna of the subset a corresponding configuration parameter is determined based on the training signal received at the corresponding antenna. Payload information blocks to be transmitted between the base station and the corresponding user equipment are transmitted using the determined corresponding configuration parameters for the antennas. Furthermore, for each user equipment a corresponding deterioration parameter indicating a deterioration of a transmission between the base station and the corresponding user equipment due to a change in the transmission and requiring adaption of the configuration parameters is determined. Based on the corresponding deterioration parameter, for each user equipment a corresponding timing parameter is determined for controlling when a further transmission slot is to be provided for receiving at each antenna of the subset of the plurality of antennas a next training signal sent from the corresponding user equipment. By adapting the timing for providing the training signal transmission slots for each user equipment individually, the header space in each frame containing the transmission slots for the training signals and the payload information blocks may be used efficiently. Furthermore, the header size may be adapted accordingly and therefore the available bandwidth may be used more efficiently.

[0017]According to another aspect of the present invention, a base station for a wireless radio network is provided which comprises a plurality of antennas for transmitting radio frequency signals between the base station and a user equipment, and a processing device. The processing device is configured to provide a transmission slot for receiving at each antenna of a subset of the plurality of antennas a training signal sent from the user equipment. The training signals need to be orthogonal in order for the base station to identify the configuration parameters for the plurality of antennas for each of the individual user equipments. Orthogonality may be achieved by using time division multiple access (TDMA), code division multiple access (CDMA) or frequency division multiple access (FDMA) technologies or a combination thereof. For each antenna of the subset a corresponding configuration parameter is determined based on the training signal received at the corresponding antenna. Then, payload information blocks to be transmitted between the base station and the user equipment may be transmitted using the determined configuration parameters for the antennas. The configuration parameters for the antennas may be different for receiving payload information blocks and for sending information blocks. However, the configuration parameter for an antenna for sending as well as a configuration parameter for the antenna for receiving may be determined based on the training signal. The processing device is furthermore configured to determine a deterioration parameter indicating a deterioration of a transmission between the base station and the user equipment due to a change in the transmission. Especially, the processing device is configured to determine a deterioration which requires an adaption of the configuration parameters to remedy the deterioration. Based on the deterioration parameter, the processing device determines a timing parameter for controlling when a further transmission slot is to be provided for receiving at each antenna of the subset of the plurality of antennas a next training signal from the user equipment. In other words, the processing device is configured to determine if a more frequent transmission of training signals is needed to maintain the configuration parameters of the antennas in the above-described MIMO system updated, or if a less frequent transmission of training parameters and update of the configuration parameters is sufficient. Therefore, an amount of overhead data to be transmitted may be reduced and thus the provided bandwidth may be used more efficiently for payload information.

Problems solved by technology

However, when there is a fast relative movement determined between the base station and the user equipment, for example when the base station is arranged stationary and the user equipment is moving along in a vehicle, a significant deterioration is expected when the user equipment is moving out of the focus of the antennas of the base station defined by the configuration parameters.

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