Communication terminal and method for selecting a transmission antenna

Abstract

Communication terminal device comprising: a plurality of antennas; a transmitter-receiver configured to receive a message indicating to a first antenna of the plurality of antennas for use as a transmission antenna by the communication terminal device;a control device configured to determine whether a second antenna of the plurality of antennas has a higher power margin than the first antenna according to a previously determined power measurement, wherein the power measurement involves a comparison of the power margin of the first antenna with the power margin of the second antenna over a predetermined time interval, and to control the transmitter-receiver to use the second antenna for transmission if the second antenna has a higher power margin than the first antenna, wherein the control device is configured, when controlling the transmitter-receiver, to use the second antenna for transmission, and to control the transmitter-receiver to use the first antenna for the transmission of a reference signal scheduled for the second antenna.

Description

Technical field The embodiments described herein generally relate to communication terminal equipment and methods for selecting a transmission antenna. Background of the invention Modern communication devices can incorporate a variety of antennas to support advanced communication technologies. For example, data can be received simultaneously via multiple antennas to achieve greater robustness and higher throughput. However, many devices use only a single antenna for transmission (i.e., sending), so one of the antennas must be selected as the transmit antenna. To accomplish this, a network can employ a closed-loop transmit antenna selection (CL-TAS) system to require a communication terminal to use a specific antenna as its transmit antenna.However, depending on the intended use of the CL-TAS system by the network, the communication terminal may be required to use an antenna that is not the one with the best transmission performance from the communication terminal's perspective. Therefore, approaches are desirable that allow a communication terminal to use an optimal antenna as its transmission antenna. US 2014 / 0233665 A1 describes a communications terminal device comprising a plurality of antennas and a selection circuit. The selection circuit is configured to select at least one of the plurality of antennas as the transmitting antenna for transmission to a radio communications network, whereby the selection of the transmitting antenna may be based on a selection criterion. Brief description of the drawings In the drawings, identical reference numerals in the various figures generally refer to the same components. The drawings are not necessarily to scale; rather, they are generally intended to illustrate the principles of the invention. In the following description, various aspects are described with reference to the following drawings; where: Fig. 1 shows a communication system, e.g., an LTE (Long Term Evolution) communication system. Fig. 2 shows an example of a temporal antenna design resulting from a partial CL-TAS implementation under maximum uplink throughput conditions. Fig. 3 shows a flowchart illustrating a metric update and a cancellation decision by the UE upon receiving a DCI0 when CL-TAS is configured. Fig. 4 illustrates the behavior of the communication terminal when the procedure of Fig. 3 is applied.Figure 5 shows the behavior of the communication terminal when the procedure of Figure 3 is applied with an additional exchange of the antenna used for SRS transmission. Figure 6 shows a communication terminal. Figure 7 shows a flowchart illustrating a method for selecting a transmission antenna. Summary An arrangement and a method according to the invention are specified in the independent claims. Additional features for advantageous embodiments are specified in the dependent claims. Description of embodiments The following detailed description refers to the accompanying drawings, which, for illustrative purposes, depict specific details and aspects of the present disclosure in which the invention can be practically implemented. Other aspects may be used, and structural, logical, and electrical modifications may be made without departing from the scope of the invention. The various aspects of the present disclosure are not necessarily mutually exclusive, since some aspects of this disclosure may be combined with one or more other aspects of this disclosure to form new aspects. Fig. 1 shows a communication system 100, e.g. an LTE (Long Term Evolution) communication system. The communication system 100 comprises a radio access network (e.g., an E-UTRAN, Evolved UMTS (Universal Mobile Communications System), terrestrial radio access network according to LTE (Long Term Evolution)) 101 and a core network (e.g., an EPC, Evolved Packet Core according to LTE) 102. The radio access network 101 can include base (transmitter-receiver) stations (e.g., eNodeBs, eNBs, according to LTE) 103. Each base station 103 provides radio coverage for one or more mobile radio cells 104 of the radio access network 101. A mobile terminal (also referred to as UE, User Equipment, or MS, Mobile Station) 105, located in a mobile cell 104, can communicate with the core network 102 and with other mobile terminals 105 via the base station that provides coverage in the mobile cell (in other words, that operates the mobile cell). Control data and user data are transmitted between a base station 103 and a mobile terminal 105, which is located in the mobile radio cell 104, which is operated by the base station 103 via the air interface 106 on the basis of a multiple access procedure. The base stations 103 are interconnected via a first interface 107, e.g., an X2 interface. The base stations 103 are also connected to the core network, e.g., a Mobility Management Entity (MME) 109 and a Serving Gateway (S-GW) 110, via a second interface 108, e.g., an S1 interface. For example, the MME 109 is responsible for controlling the mobility of mobile devices located within the E-UTRAN coverage area, while the S-GW 110 is responsible for handling the transmission of user data between mobile devices 105 and the core network 102. The radio access network 101 and the core network can support communication according to various communication technologies, such as mobile communication standards. For example, each base station 103 can provide a radio communication link over the air interface between the base station itself and the mobile terminal 105 according to the radio access technologies LTE, UMTS, GSM (Global System for Mobile Communications), and EDGE (Enhanced Data Rates for GSM Evolution). Accordingly, the radio access network 102 can operate as an E-UTRAN, UTRAN, or GSM radio access network, or as a GERAN (GSM EDGE Radio Access Network). Similarly, the core network 102 can include the functionality of an EPC, a UMTS core network, or a GSM core network. For radio communication via the air interface 106, the mobile terminal 105 has a radio transmitter-receiver 111 and, in this example, numerous antennas 112. The mobile terminal 105 (e.g., an LTE user equipment, UE) can, for example, use the numerous antennas 112 for downlink reception. However, due to hardware costs and power consumption, the UE 105 may be limited to a single RF transmission (TX) chain (e.g., the transmitter-receiver 111), which is time-division multiplexed on only one of the available transmission antennas (which could be, for example, some or even all of the antennas 112). The network, e.g., the E-UTRAN 101, can configure closed-loop transmission antenna selection (CL-TAS) according to the 3GPP specification to control the UE 105 to use the best available TX antenna among its available TX antennas.Within the TAS in the closed-loop control system (CL), the antenna port (AP) used by the UE 105 for the physical uplink shared channel (PUSCH) can be selected by the network within the scrambling of the DCI0 (downlink control information format 0), whereas the TX AP for sounding reference signals (SRS) changes semi-statically according to a pattern defined by the network. Aside from upstream capacity optimization, the network may implement CL-TAS for other reasons. SRS transmissions on switching UE-TX APs can be used to obtain accurate and up-to-date channel state information (CSI). Assuming channel reciprocity (typically valid in TD (Time Division) LTE systems), the network can utilize the CSI within downstream beamforming to improve downstream capacity. In fact, network vendors and operators may consider this use case the primary reason for implementing CL-TAS. The term "partial implementation" of CL-TAS is used below to refer to a network setup where CL-TAS is used (on the network side) to improve downstream beamforming performance, whereas in such a setup, the TX AP for PUSCH is not time-adaptively scheduled based on channel conditions and TX power limitations. During a voice call, the user can obscure a large portion of the UE with their hand and head. Thus, the performance of individual UE-TX APs can be severely affected due to shadowing effects. Modem vendors generally address this problem with proprietary TX antenna selection systems. With a partial implementation of CL-TAS, the UE may be forced by the network to the worst TX AP due to a lack of network-side adaptation. Fig. 2 shows an example of a temporal antenna design resulting from the partial CL-TAS implementation under maximum uplink throughput conditions. It is assumed that there are two available transmission antennas, a first antenna is referred to as antenna #A and a second antenna is referred to as antenna #B. A first curve 201 shows the power range (increasing from bottom to top in accordance with the vertical axis 203) over time (increasing from left to right in accordance with the horizontal axis 204). In this example, the power of the first antenna begins to decrease at time t1 until it reaches its minimum power at time t3. The first antenna is, for example, shaded by the user. The second antenna has a constant power, as shown by a second curve 202. An allocation diagram 205 shows the assignment of the antennas as transmission antennas, where a block with an ascending diagonal hatching indicates that the first antenna is assigned as the transmission antenna at the respective time, and a block with a descending diagonal hatching indicates that the second antenna is assigned as the transmission antenna at the respective time. Among the wider blocks, which represent the transmission antenna assignment for the transmission of upstream data, e.g.,For PUSCH (Physical Uplink Shared Channel) data transmission and PUCCH (Physical Uplink Control Channel) transmission, the allocation diagram 205 also shows smaller blocks which, by means of similar hatching, indicate which antenna is used for SRS (Sounding Reference Signal) transmission at the respective time. Each wider block in the allocation diagram 205 corresponds, for example, to a transmission time interval (TTI) according to the LTE framework structure, whereby if a PUSCH transmission is scheduled for a TTI without SRS transmission, the PUSCH occupies the entire TTI, whereas with an SRS transmission, the PUSCH transmission is shortened by the duration of the SRS transmission. In the example shown in Fig. 2, the network schedules the TX-AP A (i.e., the first antenna) as the transmit antenna, regardless of the observed degradation. This can have the following consequences for the UE: • The UE must increase its TX power, resulting in higher energy consumption. • If the UE's TX power is already limited, its uplink throughput must be reduced to maintain connectivity. • In the worst case, the UE loses connectivity with the network. In CL-TAS, the network may further adjust the UE-TX-AP according to the received SRS power (rather than the power margin) if the maximum TX power differs among the UE-TX-APs (i.e., among the transmitting antennas). This difference can arise due to AP-specific P-MPR (Power Management Maximum Power Reduction) settings, as well as due to UE-TX-APs that are not 3GPP compliant. According to network configurations obtained from the field, the SRS power is often 9 to 13 dB lower compared to a high-bandwidth push. Thus, the TX power of the SRS transmission might not be limited, whereas that of the subsequent high-bandwidth push will be. It should be noted that in the case of TAS with open loop (OL), the TX-AP selection for SRS is left to the UE implementation when OL-TAS is configured. In general, according to CL-TAS implementation-specific rules, whether and how the network selects the UE-TX-AP for PUSCH is determined by the implementation. The following design choices exist: 1. The network schedules only one fixed TX-AP, similar to the default behavior when 3GPP-TAS is not configured. This is illustrated in the example in Fig. 2. 2. The network schedules the TX-AP based on the received signal power from SRS, as mentioned above. In this case, as mentioned above, variations in the maximum TX power per UE-TX-AP, as well as AP-specific P-MPR, are not properly accounted for according to the network configurations obtained from the field. However, the maximum TX power may be AP-specific due to the front-end design.Furthermore, the P-MPR can be AP-specific due to specific absorption rate (SAR) regulations to reduce radiated power at the antenna closer to the user's head. 3. The network schedules the TX-AP based on power headroom (PH) reports. The following describes an approach where the UE detects whether the network has established a partial implementation of CL-TAS. In this case, the UE can override the CL-TAS network decision based on a long-term best TX-AP estimated on the UE side. According to various examples, the UE estimates the best TX-AP based on the power headroom (PH), which includes path loss and TX power limitations. To decide whether to override the CL-TAS network selection, a metric is introduced, as described in an example below. This metric reflects both the PH variation between TX-APs and the network's scheduling decision. The metric is filtered (i.e., it undergoes time filtering, such as a (possibly weighted) averaging of past values ​​representing antenna power) to reveal long-term behavior. If the metric exceeds a predefined threshold, the UE does not follow the TX-AP signaled in the DCI0 but instead inverts the DCI0 information (e.g., in the case of two antennas, it uses the other one instead of the one signaled by the DCI0 information).In this way, the UE can ensure that it uses the best TX antenna in the long term, regardless of the network implementation of CL-TAS. The following is a more detailed description of an example of the approach where the UE can override the network decision (i.e., the transmission antenna allocation specified by the network), based on a communication system architecture as shown in Fig. 1. It is assumed that the two TX-APs are configured in the UE-HF front end, meaning that two of the antennas 112 can be used as transmit antennas, whereas the UE 105 can only use one of them for transmission at a time. It is further assumed that the UE 105 supports TAS (e.g., according to 3GPP) and that the network (e.g., E-UTRAN 101) has CL-TAS enabled. As described above, without network decisions being overridden by UE 105, behavior as shown in Fig. 2 can occur: The network selects TX-AP #A for all PUSCH transmissions, even though the PH (Power Headroom) at TX-AP #A decreases between t1 and t3 due to an increase in path loss, e.g., the user shading the respective antenna. TX-AP #B is not affected in this example, and the hypothetical PH at AP #B remains constant. From t2 onward, the hypothetical PH at TX-AP #B would be greater than the actual PH at AP #A. Since the network does not control the UE-TX-AP based on the PH, the UE is forced to use the less efficient AP. Without degradation, this can lead to the following: • Increased TX power: Higher battery consumption and therefore shorter device lifespan. • Degradation of upstream throughput: If the TX power of UE 105 is already limited, its upstream throughput must be reduced to maintain connectivity. • Link loss: UE 105 can lose connectivity to network 101 if both the TX power and link adjustment are unable to compensate for the path loss increase at the respective AP. To avoid this, the UE 105, as shown in the example, is configured to detect a partial CL-TAS implementation. It can ensure that, in the long run, the best TX antenna is used, regardless of the network implementation of CL-TAS. According to the 3GPP standard, when CL-TAS is enabled, the UE 105 should use the TX-AP (i.e., the transmit antenna) indicated in the latest DCI0 received by the UE 105. The network provider is free to choose how the UE TX-AP is selected. Depending on the design choices described above, the UE 105 may experience reduced battery life, UL throughput degradation, and link loss. Design choice 1 (fixed TX-AP) described above can lead to these deficiencies; however, design choice 2 (SRS based on TX-AP selection) described above can also be affected for the following reasons: • The second antenna may be incompatible with 3GPP Performance Class 3 in some way (in a scenario like the example in Fig. 2), resulting in a maximum TX power lower than, for example, 23 dBm.This might be the case, for example, for the front end of a Tier 1 UE provider with a high market share. The P-MPR contributions may differ between the two antennas. Due to SAR rules, the antenna closer to the user's head may receive greater power reduction. According to network configurations obtained from the field, SRS power is often 9 to 13 dB lower compared to a high-bandwidth push. Thus, the TX power of the SRS transmission might not be limited, whereas that of the subsequent high-bandwidth push will be. Fig. 3 shows a flowchart illustrating a metric update and cancellation decision by the UE upon receiving a DCI0 when CL-TAS is configured. In 301, the UE 105 receives a DCI0 at time t1 indicating TX-AP x for push transmission. The remaining TX-AP is subsequently referred to as y. In section 302, UE 105 updates the cancellation decision metric m to its value m(t1) at time t1 according to where: • m(t0) is the value of the metric after the latest update at time t0 < t1, • PH(x) - PH(y) is the difference in headroom between the used and unused TX-AP. A positive value indicates that the currently used TX-AP offers more headroom. • The filter function M removes short-term variations. Function M filters both short-term variations in the PH and in the network TX-AP selection. An implementation of M could be an (IIR) filter (e.g., the Layer 3 filter according to 3GPP) with a long filter delay to ensure a response time of several hundred milliseconds. In 303, UE 105 compares the value of the metric m(t1) with a predetermined threshold m_thres (which can be zero without hysteresis or a non-zero value to implement hysteresis). If m(t1) < m_thres, then in 304, UE 105 sets the cancellation reversal bit to "true" (i.e., assuming the initial value is "false," it is negated). Furthermore, UE 105 negates the value of the metric m(t1). The process then terminates in 305. The power margin is measured, for example, in dB relative to the maximum TX power, and a threshold m_thres of -3 dB can be used as a typical "low" threshold (i.e., for an aggressive design). A more conservative value for the threshold m_thres might be, for example, -6 dB or -9 dB. On the other hand, the reverse bit and the metric value remain unchanged, and the process ends in 305. If the cancellation reverse bit is set to incorrect after the process of Fig. 3, the UE 105 uses the transmitting antenna as shown in the DCI0, i.e., follows the DCI0. When the cancellation reversal bit is set to true, the UE uses the other of the transmit antennas for push transmission than the one signaled as turned on by the network in DCI0. Specifically, if the network signals TX-AP #A (i.e., if x corresponds to A), the UE uses #B (corresponding to y in this case), and vice versa. The mobile device 105 can maintain the SRS transmission on the TX-APs configured by the network to prevent fluctuations. The filter delay of the filter function M, as well as the threshold value m_thres, can be selected according to the desired response time and hysteresis. Fig. 4 shows the behavior of the communication terminal when the procedure of Fig. 3 is applied. As in the example of Fig. 2, a first curve 401 shows the power range (increasing from bottom to top in accordance with the vertical axis 403) over time (increasing from left to right in accordance with the horizontal axis 404) and at time t1 the power of the first antenna (antenna connection #A) starts to deteriorate until it reaches its minimum power at time t3 (e.g. by being shaded by the user), whereas the second antenna (antenna connection #B) has a constant power, as shown by a second curve 402. Furthermore, similar to Fig. 2, an allocation diagram 405 shows the assignment of the antennas as transmission antennas, wherein a block with rising diagonal hatching indicates that the first antenna is assigned as the transmission antenna at the respective time, and a block with falling diagonal hatching indicates that the second antenna is assigned as the transmission antenna at the respective time. Among the wider blocks that indicate the transmission antenna assignment, the allocation diagram 405 also includes smaller blocks which, by means of similar hatching, indicate which antenna is used for SRS (Sounding Reference Signal) transmission at the respective time. It is assumed that at time t4 the filtered metric falls below the threshold m_thres. Accordingly, mobile device 105 selects the second antenna (TX-AP #B) at time t4. Fig. 5 shows the behavior of the communication terminal when the procedure of Fig. 3 is applied with an additional swap of the antenna used for transmitting SRS. As in the example of Fig. 4, a first curve 501 shows the power range (increasing from bottom to top in accordance with the vertical axis 503) over time (increasing from left to right in accordance with the horizontal axis 504), and at time t1 the power of the first antenna (antenna connection #A) starts to deteriorate until it reaches its minimum power at time t3, whereas the second antenna (antenna connection #B) has a constant power, as shown by a second curve 502. Starting at time t5, the first antenna improves and reaches maximum performance at time t7. Furthermore, similar to Fig. 2, an allocation diagram 505 shows the assignment of the antennas as transmission antennas, wherein a block with rising diagonal hatching indicates that the first antenna is assigned as the transmission antenna at the respective time, and a block with falling diagonal hatching indicates that the second antenna is assigned as the transmission antenna at the respective time. Among the wider blocks, which specify the transmission antenna assignment (e.g., for PUSCH transmission), the allocation diagram 505 also includes smaller blocks which, by means of similar hatching, indicate which antenna is used for SRS (Sounding Reference Signal) transmission at the respective time. Furthermore, a third curve 508 (in an additional diagram) shows the behavior of the metric according to the performance margins shown in the curves 501, 502 (based on the same time scale, i.e. as specified by the horizontal axis 504). It is assumed that at time t4 the filtered metric falls below the threshold m_thres. Accordingly, mobile device 105 selects the second antenna (TX-AP #B) at time t4. Furthermore, it is assumed that at time t8 the filtered metric falls below the threshold m_thres again, as the performance margin of the first antenna has increased, such that the mobile device 105 reverts to using the first antenna at time t8. Furthermore, in this example, when the antenna used for transmission is changed, the mobile device 105 also changes the antenna used for SRS messaging. Specifically, the mobile device 105 executes SRS message 506 after time t4 using the second antenna (although the first antenna would be next according to the change) and continues alternating until it executes SRS message 507 after time t8 using the first antenna (although the second antenna would be next according to the change). Reasons for switching the antenna for SRS transmission together with the antenna for PUSCH / PUCCH transmission, as in the example of Fig. 5, could be, for example, the following: - The TX-AP relationship between SRS transmission and PUCCH / PUSCH transmission remains: By observing the received quality of SRS, the eNodeB might be able to derive the quality of PUSCH / PUCCH. - This approach can be easily implemented in the UE. Reasons for not changing the antenna for SRS transmission along with the antenna for PUSCH / PUCCH transmission (i.e., keeping the SRS transmission pattern unchanged), as in the example of Fig. 4, could be, for example: - If the eNodeB implementation uses SRS for TX-AP selection, then the UE's decision to reverse the SRS-TX-AP (i.e., to change the antenna used for SRS transmission) will most likely cause the eNodeB to also change the antenna to be used, resulting in fluctuations. - If the eNodeB uses SRS in TD-LTE for DL ​​channel estimation, then there is no discontinuity in the estimation because the UE always uses the SRS-TX-AP. It should be noted that if the network implements the aforementioned design choice 3 (PH based on TX-AP selection), it will regularly request PH reports from the TX-AP indicating that it should not be used (i.e., that it should not signal its use). Using the approach shown in Figure 3, the filtering prevents the network investigations from causing the metric to exceed the threshold. Assuming a reasonably long response time is configured on the UE side, the network will react more quickly to PH changes, thus ensuring coexistence with the approach shown in Figure 3. In this case, both the UE and the network are pursuing the same goal, and the approach shown in Figure 3 can be considered to incur neither benefit nor cost. Furthermore, it is noted that if the network does not favor a particular antenna but instead switches between them on a TTI basis to generate diversity, the metric approaches zero. Since the network does not favor a specific antenna, it can be argued that there is no long-term advantage in selecting the best antenna on the UE side. The approach shown in Fig. 1 can be implemented with low complexity in the LTE baseband of the mobile device's cellular modem. It ensures that, in the long run, the best UE-TX antenna is used, regardless of the CL-TAS network implementation. This enables: - Better allocation of UL resources and thus improved UE and system capacity, - longer UE battery life, and - a reduced risk of service loss. According to another example, the network side can be enabled to avoid a detrimental transmit antenna selection, for example, through explicit network signaling (e.g., Radio Resource Signaling, RRC) to enable or disable the TX-AP selection for PUSCH within the DCI0 when CL-TAS is configured. In this way, the network can request TX-AP switching for SRS to improve DL beamforming performance, whereas the TX-AP decision for PUSCH can be left to the UE implementation, and the mobile device can, for example, follow the procedure shown in Fig. 3. The UE can then autonomously select the TX-AP for PUSCH. Since DCI0 is no longer used to promote the TX-AP, i.e., the antenna selection mask is not applied to the scrambled CRC (Cyclic Redundancy Check), this also reduces the risk of false positive DCIs on the PDCCH. The signaling can be implemented, for example, by extending the 3GPP specification, such as by adding a Boolean field, "antennaSelectionMaskEnabled," to the 3GPP "ue-TransmitAntennaSelection" field. Mobile device 105 only evaluates this field if CL-TAS is signaled. If "antennaSelectionMaskEnabled" is true, mobile device 105 applies normal CL-TAS behavior. Conversely, if "antennaSelectionMaskEnabled" is false, the CL-TAS behavior is modified so that mobile device 105 disregards the UE transmit antenna selection mask during DCI0 detection. Furthermore, the selection of the TX-AP for PUSCH is left to the UE implementation. It should be noted that the approaches described above for an implementation as described by 3GPP OL-TAS, as well as a UE provider ownership extension of TAS, can be used if 3GPP-TAS is not configured. In these cases, for example, the input for the procedure in Fig. 3 is not DCI0, but the latest TX-AP, which is selected by the procedure itself. Furthermore, it should be noted that the approaches described above can be extended for application to cellular modems with which more than two transmission antennas are set up. In summary, according to the various examples, a communication terminal device as shown in Fig. 6 is provided. Fig. 6 shows a communication terminal 600. The communication terminal 600 has a plurality of antennas 601, 602 and a transmitter-receiver 603 (e.g. having a transmitter and a receiver) configured to receive a message which has a first antenna 601 of the plurality of antennas for use as a transmission antenna by the communication terminal. The communication terminal also includes a control unit 604, which is configured to determine whether a second antenna 602 of the plurality of antennas has a higher transmission power than the first antenna 601 according to a previously determined power measurement, and to control the transmitter-receiver 603 to use the second antenna 602 for transmission if the second antenna has a higher transmission power than the first antenna 601. In other words, a communications terminal checks, according to various examples, whether an antenna which the communications terminal is supposed to use for transmission (e.g., indicated by a control message from the network side of a cellular communications network) has a lower power than the other antenna of the communications terminal, and, if this is the case, it overrides the requirement and uses the other antenna instead. The transmission consists, for example, of data transmission, such as user data or payload data (as opposed to a reference signal), which may also include control data. The transmission may, for example, be a push transmission, a push-to-click transmission, or both. The components of the communication terminal (e.g., the transmitter-receiver and the control unit) can be implemented, for example, by one or more circuits. A "circuit" can be understood as any type of logic implementation entity, which may be a specialized circuit arrangement or a processor that executes software stored in memory, firmware, or any combination thereof. Thus, a "circuit" can be a hard-wired logic circuit or a programmable logic circuit, such as a programmable processor, e.g., a microprocessor. A "circuit" can also be a processor that executes software, e.g., any type of computer program. Any other type of implementation of the respective functions, which are described in more detail below, can also be considered a "circuit." The communication terminal 600, for example, performs a procedure as shown in Fig. 7. Fig. 7 shows a flowchart 700, in which a method for selecting a transmission antenna is depicted, which is carried out, for example, by a communication terminal device. In 701, the communications terminal receives a message indicating the first antenna of a multitude of antennas for use as a transmission antenna. In 702, the communication terminal determines whether a second antenna of the plurality of antennas has a higher transmission power than the first antenna according to a previously determined power measurement. In 703, the communication terminal uses the second antenna for transmission if the second antenna has a higher transmission power than the first antenna. The following examples refer to further embodiments. Example 1 shows a communication terminal device as depicted in Fig. 6. In Example 2, the object of Example 1 may optionally include the control device configured to control the transmitter-receiver to use the second antenna for transmission when it has a higher transmission power than the first antenna by a predetermined margin. In Example 3, the object from any of Examples 1 to 2 can optionally include the transmitter-receiver configured to receive the message from a communication device. In Example 4, the object can optionally include, from any of Examples 1 to 3, the communication terminal, which is a subscriber terminal of a cellular mobile communications network, and the sender-receiver configured to receive the message from a network component of the cellular mobile communications network. In Example 5, the object can optionally include, from any of Examples 1 to 4, the communication terminal, which is a subscriber terminal of a cellular mobile communications network, and the sender-receiver configured to receive the message from a base station of the cellular mobile communications network. In Example 6, the object can optionally include from any of Examples 1 to 5 the message which is an antenna signaling message according to a closed-loop transmission antenna selection. In Example 7, the item from any of Examples 1 to 6 can optionally include the message that is a downward-stretch control information message. In Example 8, the object can optionally include, from any of Examples 1 to 7, the control device configured to use the second antenna for transmission when controlling the transmitter-receiver, or to use the second antenna for transmitting a reference signal scheduled for the first antenna. In Example 9, the object can optionally include the control device from any of Examples 1 to 8, which is further configured, when controlling the transmitter-receiver, to use the second antenna for transmission, and to control the transmitter-receiver to use the first antenna for the transmission of a reference signal scheduled for the second antenna. In Example 10, the object can optionally include the control device from any of Examples 1 to 9, which is further configured, when controlling the transmitter-receiver, to use the second antenna for transmission, to control the transmitter-receiver, to keep the first antenna for transmitting a reference signal scheduled for the first antenna, and to keep the second antenna for transmitting a reference signal scheduled for the second antenna. In Example 11, the item can optionally include the reference signal from any of Examples 8 to 10, which is a reference signal for upstream channel quality estimation. In Example 12, the object can optionally include, from any of Examples 1 to 11, the power measurement which compares the transmission power of the first antenna with the transmission power of the second antenna over a predetermined time interval. In Example 13, the object from any of Examples 1 to 12 can optionally have power measurement based on values ​​representing the transmission power of the first antenna and the second antenna, filtered over time. In Example 14, the object can optionally have the transmission power from any of Examples 1 to 13, which consists of the power margin. In Example 15, the item from any of Examples 1 to 14 may optionally include the transmitter-receiver configured to receive a second message indicating that the communication terminal is permitted to use a different antenna for transmission than the first antenna, and the control device configured to control the transmitter-receiver to use the second antenna for transmission based on the reception of the second message. In Example 16, the object of Example 15 may optionally include the control device configured to control the transmitter-receiver to use the second antenna for transmission when the transmitter-receiver receives the second message. Example 17 is a method for selecting a transmission antenna, as shown in Fig. 7. In Example 18, the subject of Example 17 may optionally include the use of the second antenna for transmission if it has a higher transmission power than the first antenna by a predetermined margin. In Example 19, the object can optionally feature the reception of the message from the communication device, as in any of Examples 17 to 18. In Example 20, the subject can optionally feature any of Examples 17 to 21 being carried out by a subscriber terminal of a cellular mobile communications network, and can optionally feature receiving the message from a network component of the cellular mobile communications network. In Example 21, the subject can optionally feature any of the examples in 17, being carried out by a subscriber terminal of a cellular mobile communications network, and can optionally feature receiving the message from a base station of the cellular mobile communications network. In Example 22, the item can optionally feature from any of Examples 17 to 21 that the communication is an antenna signaling communication according to a closed-loop transmission antenna selection. In Example 23, the item from any of Examples 17 to 22 can optionally indicate that the message is a down-track control information message. In Example 24, the object can optionally have from any of Examples 17 to 23, if the second antenna is used for transmission, the second antenna to be used for the transmission of a reference signal scheduled for the first antenna. In Example 25, the object can optionally have from any of Examples 17 to 24, if the second antenna is used for transmission, the first antenna to be used for the transmission of a reference signal scheduled for the second antenna. In Example 26, the object can optionally have from any of Examples 17 to 25, if the second antenna is used for transmission, to retain the first antenna for the transmission of a reference signal scheduled for the first antenna, and to retain the second antenna for the transmission of a reference signal scheduled for the second antenna. In Example 27, the subject of Example 26 may optionally have the reference signal being a reference signal for upstream channel quality estimation. In Example 28, the object of any of Examples 17 to 27 may optionally include the power measurement of a comparison of the transmission power of the first antenna with the transmission power of the second antenna over a predetermined time interval. In Example 29, the object can optionally feature from any of Examples 17 to 28 that the power measurement is based on values ​​representing the transmission power of the first antenna and the second antenna, which are filtered over time. In Example 30, the object can optionally have the transmission power of any of the examples 17 to 29 consisting of the power margin. In Example 31, the object can optionally feature, from any of Examples 17 to 30, the reception of a second message indicating that the communication terminal is enabled to use a different antenna for transmission than the first antenna, and to use the second antenna for transmission based on the reception of the second message. In Example 32, the subject of Example 31 may optionally include the use of the second antenna for transmission if the second message is received. Example 33 is a computer-readable medium containing instructions which, when executed by a processor, cause the processor to perform a procedure for selecting a transmission antenna according to any one of Examples 17 to 32. It should be noted that one or more features from any of the above examples can be combined with any feature from any of the other examples. Although certain aspects have been described, it is readily apparent to a person skilled in the art in this field that various changes in form and detail can be made without departing from the spirit and scope of protection of the aspects of this disclosure defined by the accompanying claims. The scope of protection is thus defined by the accompanying claims, and all modifications falling within the conceptual content and scope of the claims are intended to be included therein.

Claims

Communication terminal device comprising: a plurality of antennas; a transmitter-receiver configured to receive a message indicating to a first antenna of the plurality of antennas for use as a transmission antenna by the communication terminal device;a control device configured to determine whether a second antenna of the plurality of antennas has a higher power margin than the first antenna according to a previously determined power measurement, wherein the power measurement involves a comparison of the power margin of the first antenna with the power margin of the second antenna over a predetermined time interval, and to control the transmitter-receiver to use the second antenna for transmission if the second antenna has a higher power margin than the first antenna, wherein the control device is configured, when controlling the transmitter-receiver, to use the second antenna for transmission, and to control the transmitter-receiver to use the first antenna for the transmission of a reference signal scheduled for the second antenna. Communication terminal device according to claim 1, wherein the control device is configured to control the transmitter-receiver to use the second antenna for transmission when the second antenna has a higher power margin than the first antenna by a predetermined margin. Communication terminal device according to claim 1 or 2, wherein the transmitter-receiver is configured to receive the message from a communication device. Communication terminal device according to any one of claims 1 to 3, wherein the communication terminal device is a subscriber terminal device of a cellular mobile communications network, and wherein the sender-receiver is configured to receive the message from a network component of the cellular mobile communications network. Communication terminal device according to any one of claims 1 to 4, wherein the communication terminal device is a subscriber terminal device of a cellular mobile communications network, and wherein the sender-receiver is configured to receive the message from a base station of the cellular mobile communications network. Communication terminal device according to any one of claims 1 to 5, wherein the message is an antenna signaling message according to the transmission antenna selection in the closed control loop. Communication terminal device according to any one of claims 1 to 6, wherein the message is a downstream control information message. Communication terminal device according to any one of claims 1 to 7, wherein the control device is configured, when controlling the transmitter-receiver, to use the second antenna for transmission, to control the transmitter-receiver, to use the second antenna for the transmission of a reference signal scheduled for the first antenna. Communication terminal device according to any one of claims 1 or 8, wherein the reference signal is a reference signal for upstream channel quality estimation. Communication terminal device according to any of claims 1 to 9, wherein the power measurement is based on values ​​representing the power margin of the first antenna and the second antenna, which are filtered over time. Communication terminal device according to any one of claims 1 to 10, wherein the transmitter-receiver is configured to receive a second message indicating that the communication terminal device is enabled to use a different antenna for transmission than the first antenna, and the control device is configured to control the transmitter-receiver to use the second antenna for transmission based on the reception of the second message. Communication terminal device according to claim 11, wherein the control device is configured to control the transmitter-receiver to use the second antenna for transmission when the transmitter-receiver receives the second message. A method for selecting a transmission antenna, comprising: receiving a message indicating a first antenna of a plurality of antennas for use as the transmission antenna; determining whether a second antenna of the plurality of antennas has a higher power margin than the first antenna according to a previously determined power measurement, wherein the power measurement involves comparing the power margin of the first antenna with the power margin of the second antenna over a predetermined time interval; and using the second antenna for transmission if the second antenna has a higher power margin than the first antenna, wherein, when the second antenna is used for transmission, the first antenna is used for transmitting a reference signal scheduled in time for the second antenna. Computer-readable medium on which instructions are stored which, when executed by a processor, cause the processor to execute a method for selecting a transmission antenna according to claim 13.

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