Abstract:
A method of adapting the output power of a radio transmitting entity within a cage having at least one aperture. The method includes the steps of providing at least one sensor to sense the condition of the at least one aperture and providing a controller to adjust the output power of the radio transmitting entity in accordance with the sensed condition of the at least one aperture.

Description:
TECHNICAL FIELD  
       [0001]    The present invention relates to a method of adapting the output power of a radio transmitting entity within a cage having at least one configurable aperture and to a corresponding device. 
       BACKGROUND 
       [0002]    The mobile broadband business is growing rapidly. Devices become cheaper, data rates higher and new services and applications can be supported. Users want to access a mobile network from home and also while on the move. A particular scenario for mobile access are vehicles, like cars, trucks, but also trains, aircrafts and the like. Because these vehicles move often very fast and have typically metallic surfaces the communication in such environment bears additional challenges. Also the walls of buildings often contain structural steel work. Hence cabins in vehicles and rooms in buildings (both herewith named as cages) often affect as a Faraday cage on radio transmission or signal. If mobile devices like mobile broadband devices are operated in cabins of vehicles or rooms in buildings they often suffer from a poor connection quality to a mobile network. In mobile networks, e.g., according to the 3GPP (3rd Generation Partnership Project), it is known to use relaying for improving capacity and/or coverage of the network. For example, in 3GPP LTE (Long Term Evolution) relaying was introduced in the Release 10 Technical Specifications (TSs). The general idea of relaying is that a relay node (RN) receives a transmission from a sender and forwards this transmission to a receiver. For example, a transmission can be received from a base station, in 3GPP LTE referred to as “evolved Node B” (eNB), and be forwarded to a mobile terminal or other type of user equipment (UE), or vice versa. 
         [0003]    One can distinguish between decode and forward relays as in the case of the LTE Release 10 and an amplify and forward repeater. In the first case, the relay node receives the signal, it tries to reconstruct the data and sends the data in the same or a potentially different format to the ultimate receiver. In the case of LTE Release 10 this also implies that the relay node maintains its own cell with its corresponding reference and control signaling. The end user terminal does not notice that the node it is communicating with is a relay node and not a base station. This implies also that hand over procedures need to be performed when moving between relay nodes or between a relay node and a base station. 
         [0004]    In case of an amplify and forward repeater, the repeater receives the signal and amplifies it without any link layer interactions. Thus in this case no own cell is created, only the original cell is extended by amplifying the signal. The presence of the repeater is transparent for the end user terminal. 
         [0005]    There exist many different definitions for relays and repeater. For example repeaters are sometimes referred to as layer 1 relays or RF relays. Also the terms L2 relay or L3 relay are sometimes mentioned. The differences between them are related to the protocol layer where the transmission on the first link is terminated and the signal or data is transferred to the protocol stack of the second link. 
         [0006]    Both repeaters and relays can be operated in both directions, uplink and downlink, i.e. from a base station via this intermediate node to an end user terminal and vice versa. Also in case of multihop operation, there could be several relay nodes involved in the communication path and in this case even relay nodes would communicate with relay nodes. Another special flavor of a relay node could be also a cooperative relay node. 
         [0007]    To improve the connection quality in a cage it is known to install a repeater or RN inside the cage so that a pick-up antenna is able to feed the received radio signal into the repeater or RN and a second antenna inside the cage is used to convey the radio signal further to the mobile device or UE in the cage. 
         [0008]    If a repeater or RN is operated in a cage it can be dimensioned in a way that these devices have enough output power to serve the limited space within the cage. Typically only a small output power is needed. Due to the metallic surface of the cabins and the structural steel work in walls of buildings, the interference caused to the outside radio signals is also limited and does typically not cause problems. 
         [0009]    However, a lot of cabins in vehicles, like cars and also a lot of rooms have windows and other openings or apertures which can be configured between a closed position into an open-position and vice versa. Today a lot of windows comprise a metallic surface to protect against heat due to sun shine. If a window with a metallic surface opens, the attenuation of the cage will be reduced which can cause significant interference between the repeated radio signal inside the cage and the radio signals outside the cage. 
         [0010]    In LTE a RN creates an own cell. If an LTE relay is operated in a vehicle (e.g. a car or truck) it can provide access to other LTE devices in the vehicle. A car having a LTE RN installed which is driving down a street with an open window could trigger all devices of pedestrians to connect to the installed RN in the car. This would cause a lot of signalling traffic for the mobile network since such a connection would typically hold only for a very short time. As soon as the car has moved a few meters the pedestrian&#39;s devices have to make another hand-over to a base station that typically serves the area. 
         [0011]    In case of a repeater that is operated in a vehicle, a closed window implies an additional attenuation between an out side pick/up antenna and an inside sending antenna. If the window is opened, the additional decoupling between pick up and sending antenna is reduced. This may cause excessive feedback interference from the output to the input, which corrupts the signal quality. 
       SUMMARY  
       [0012]    It is an object of the present invention to improve the relaying or repetition of radio signals of a mobile communication network in a cage. This object is achieved by the independent claims. Advantageous embodiments are described in the dependent claims. 
         [0013]    The invention relates to a method of adapting the output power of a radio transmitting entity within a cage having at least one aperture. The method comprises the step of providing at least one sensor operable to sense the condition of the at least one aperture. Further the method comprises the step of providing a controller operable to adjust the output power of the radio transmitting entity in accordance with the sensed condition of the at least one aperture. The aperture can e.g. be a moveable window, a moveable roof of an open-topped car or a door in a building. The cage can be a cabin of a vehicle or a room in a building. The radio transmitting entity can be a relay node or a repeater. The condition of the at least one aperture can e.g. be the amount or character of attenuation of radio signals or transmission based on different metallic surfaces. It is also possible that the condition of the at least one aperture is an open-position of the at least one aperture. 
         [0014]    In a further embodiment the output power is reduced if the at least one aperture opens and the output power is increased if the at least one aperture closes. This will reduce the possibility that an external mobile terminal will be connected with the radio transmitting entity. 
         [0015]    In another embodiment the controller adjusts the output power of the radio transmitting entity as a linear function or a non-linear function of the condition of the aperture. 
         [0016]    In another embodiment the controller adjust the output power of the radio transmitting entity in accordance with a mapping table which maps conditions of the aperture to a value of the output power. 
         [0017]    The invention relates also to a radio transmitting entity, comprising an antenna, adapted to transmit a radio signal, a data receiving entity, adapted to receive condition information of at least one aperture from at least one sensor and a controller, adapted to adjust the output power for the antenna in accordance with the received condition information. The radio transmitting entity can be adapted to perform all the steps of the before mentioned methods. The controller can be e.g. an amplifier or any other kind of RF entity. 
         [0018]    The invention further relates to a vehicle with at least one aperture, comprising a pick-up antenna for receiving a radio signal, at least one sensor which is adapted to monitor the condition of the at least one aperture, and a radio transmitting entity. The vehicle can be adapted to perform all the steps of the before mentioned methods. 
         [0019]    The present invention also concerns computer programs comprising portions of software codes in order to implement the method as described above when operated by a respective processing unit of a user device and a recipient device. The computer program can be stored on a computer-readable medium. The computer-readable medium can be a permanent or rewritable memory within the user device or the recipient device or located externally. The respective computer program can also be transferred to the user device or recipient device for example via a cable or a wireless link as a sequence of signals. 
         [0020]    In the following, detailed embodiments of the present invention shall be described in order to give the skilled person a full and complete understanding. However, these embodiments are illustrative and not intended to be limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0021]      FIG. 1  shows a schematic diagram of an embodiment of the invention; 
           [0022]      FIG. 2  shows a further schematic diagram of an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIG. 1  shows a schematic diagram of a car  1  comprising a moveable window  7  and a moveable door as apertures according to the invention. The car  1  further comprises a repeater or a transceiver  2  which is adapted to receive a radio signal via a pick-up antenna  3 . The transceiver can e.g. be a LTE relay node which serves its own cell. It is also possible that the transceiver is a wireless LAN repeater or any other kind of radio signal transceiver. The radio signal can be a radio transmission from a base station or an eNodeB of a mobile communication network located outside the car  1  which serves an area or cell in which the car  1  is currently located. The transceiver  2  is further connected to a serving antenna  4  which is adapted to send signals to mobile devices inside the cabin of the car  1 . The cabin mostly comprises a metallic surface so that the cabin is a Faraday cage on radio transmission because the cage of the car  1  causes significant attenuation to the radio transmission of the external base station or eNodeB towards the inner location of the cage. 
         [0024]    The car  1  further comprises sensors  5 ,  6  which are adapted to detect the opening status as a condition of moveable parts of the car  1 . In this embodiment sensor  5  is adapted to detect the opening status of the moveable window  7  wherein the other sensor  6  is able to detect the opening status of a door  8 . It is possible that more sensors are located inside the car to sense the status of further moveable apertures like a moveable roof of an open-topped car. The sensors can also detect the amount of attenuation caused by the moveable window  7  in case that the attenuation characteristics will change. 
         [0025]    The sensors  5 ,  6  are connected to the transceiver  2  to provide status data or information to the transceiver  2 . The connection between the sensors and the transceiver can be performed as a wireless link, a wired link or a mixture of both. If e.g. a moveable window  7  has been opened fully, the sensor  5  sends back the information that the moveable window  7  has been opened or has an open-position of 100%. If the window  7  has been half-opened, as depicted in 
         [0026]      FIG. 1 , the sensor  5  sends information to the transceiver  2  which indicates an open-position of 50%. It is possible that many more open-positions or opening-status of a moveable window  7  can be reported in a more fine grained way by the sensor  5  to the transceiver  2 . It is further possible that each moveable window or any other aperture in a car  1  is monitored by a sensor  5 ,  6 . The same situation can apply for each door  8  of the car  1 . It is also possible that the sensors  5 ,  6  only detects in a binary way whether a moveable window  7  or door  8  is opened or closed. 
         [0027]    In another non depicted embodiment a room in a building comprises a transceiver  2 , a pick-up antenna  3  and at least one serving antenna  4 . Windows, doors or other apertures of the room in the building can be monitored by sensors  5 ,  6  in the same way as it is explained under  FIG. 1 . 
         [0028]      FIG. 2  depicts an embodiment of a transceiver  2 , comprising a controller  21  and a data receiver  22  which is connected to the controller  21 . The data receiver  22  is connected or linked to at least one sensor  5  so that the at least one sensor  5  is able to provide open-position or condition data via the data receiver  22  to the controller  21 . The controller  21  is adapted to adjust the output power of a radio signal over the serving antenna  4  which has been received via a pick-up antenna  3  in accordance with the received sensor data. It is possible that the minimum output power is “0” which means that no transmission will be done via the serving antenna  4  if all apertures in the vehicle or room are completely open or the attenuation to radio transmission is very low. So if there is only low attenuation the user device can typically be connected directly to an external serving base station without using a relay node. The minimum and maximum output power can also be certain output power values which can be defined in accordance with the strength of the outer field or in accordance with the attenuation value of the cage. 
         [0029]    In one embodiment of the invention the relationship between the open-position of an aperture  7 ,  8  and the output power of the transceiver  2  is a linear function. It means that the amount of change of a condition of an aperture  7 ,  8  is directly transferred to the amount of change of output power of the transceiver  2 . If e.g. a window moves from a closed position into a half open position the output power of the transceiver will be reduced by half. In another embodiment of the invention the relation between the open-position of an aperture and the output power is a non-linear function. Further it is possible that for each open-position or attenuation condition of an aperture a value for a specific output power is stored in a mapping table in the controller. If there are several sensor data available like for several windows/doors  7 ,  8  in the car  1 , multiple sensor data can be used by the transceiver  2  to derive a decision for adjusting the output power of the transceiver  2 . 
         [0030]    The description refers to a downlink situation wherein the mobile device inside the car receives information from a mobile communication network. The invention also relates to uplink communication wherein the mobile device inside the car  1  sends data to a mobile communication network. Then the pick-up antenna  3  works as a serving antenna  3  and the serving antenna  4  inside the car  1  works as a pick-up antenna  4 . In uplink situation the controller  21  is adapted to adjust the output power of a radio signal over the antenna  3  which now acts as a serving antenna  3 .