Abstract:
The invention provides a method of operating a first base station ( 100 ) as a reception station for a wireless uplink communication connection with a wireless appliance ( 102 ), wherein the method comprises: controlling the wireless uplink communication with the wireless appliance, receiving a signal ( 127 ) from the wireless appliance, receiving a rest signal ( 126 ) from at least one second base station ( 104 ), and analyzing the rest signal from the at least one second base station for detecting a signal ( 129 ) from the wireless appliance that is above a threshold.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    A base station of a wireless communication network typically receives different kinds of signals. A wireless appliance communicating with a base station sends a signal to that base station that is processed by the base station. Each base station also receives noise and interference signals from other wireless appliances that communicate with other base stations. The interferences and the noise are filtered out by the base station for the wireless communication with the wireless appliance. 
         [0002]    For example, when a wireless appliance is connected to a first base station while the wireless appliance is located in a region where a connection to a second base station would also be possible, the second base station receives a high interference signal from the wireless appliance that is filtered out by the signal processing unit of the second base station. 
       SUMMARY OF THE INVENTION 
       [0003]    Embodiments of the invention provide a method of operating a first base station, a computer program product for operating the first base station, a method of operating a second base station, a computer program product for operating the second base station and a base station apparatus being operable to perform the methods in the independent claims. Embodiments of the invention are described in the dependent claims. 
         [0004]    It is the object of the invention to improve the uplink communication of a wireless appliance in a wireless communication network. For this purpose the wireless uplink communication of the wireless appliance is controlled by a first base station that receives a signal from the wireless appliance. At least one of the other second base stations of the wireless communication network receives an interference signal from the wireless appliance and additionally some noise. The interference signals and the noise are called rest signal. This rest signal is received by the first base station that controls the uplink communication connection with the wireless appliance from the at least one second base station. The first base station analyzes the rest signal from the at least one second base station for detecting the interference signal of the wireless appliance whose connection is controlled by the first base station. The rest signal is used for improving the wireless uplink communication connection with the wireless appliance by filtering out the noise and using the interference as a source of uplink communication data. 
         [0005]    In an embodiment of the invention the first base station that controls the wireless uplink communication connection with the wireless appliance utilizes the rest signal of the at least one second base station for determining the signal power of the wireless appliance in the rest signal and for the wireless uplink communication connection if the rest signal contains a signal from the wireless appliance that is above a threshold A. 
         [0006]    The threshold A can be fixed so that it is used to determine a minimum level of the signal power. Below this minimum level it is not advantageous to take the rest signal into account for the wireless uplink communication connection with the wireless appliance. 
         [0007]    Advantageously, the threshold A has a dynamic character. For example, it can be adjusted to the signal level of the wireless uplink communication connection between the wireless appliance and the first base station. 
         [0008]    Advantageously, the threshold A is defined differentially. A differential measurement of the signal power of the wireless appliance in the rest signal, that is sent from one of the at least one second base station to the first base station, results in a measurement of the change of the signal power of the wireless appliance in the rest signal. When defining a differential threshold A for the differential measurement of the signal power, the decision if the rest signal is used by the first base station for the wireless uplink communication connection is based on the change of the signal power. By using an extrapolation algorithm it is conceivable how the power of the signal of the wireless appliance in the rest signal develops. This means that the rest signal can be utilized for the wireless uplink communication connection when it is conceivable that the signal power rises in a predefined grade and the rest signal can be ignored when it is conceivable that the signal power diminishes in a predefined grade. 
         [0009]    In an embodiment of the invention the rest signal contains a signal that is above a certain threshold A from the wireless appliance whose connection is controlled by the first base station and the first base station decides to transfer the control of the wireless uplink communication connection with the wireless appliance to one of the at least one second base stations. For this purpose the first base station sends a transfer request message to the one of the at least one second base station where the control of the wireless uplink communication connection shall be transferred to. The decision if the control of the wireless uplink communication connection with the wireless appliance shall be transferred to a second base station is based on the rest signal that is received by the first base station from the at least one second base station. The transfer of the control of the wireless uplink communication connection can be done for example by a handover process or fast cell selection. 
         [0010]    In an embodiment of the invention the first base station ignores the rest signal from the at least one second base station for the uplink communication connection with the wireless appliance. This decision can for example be made after the first base station has analyzed the rest signal and has detected that there is no signal that is above a certain threshold A. 
         [0011]    Preferably the invention is used in coordinated multipoint (CoMP) reception schemes that are potential candidates for LTE advanced (Long Term Evolution), see 3GPP (third generation partnership project) specification TR36.814 V0.4.1 (2009-02), and WiMAX, IEEE 802.16e-2005. 
         [0012]    In a coordinated multipoint reception (CoMP) network the first base station decides if one of the at least one second base station is added to the coordinated multipoint wireless uplink communication with the wireless appliance. This decision can also be made from a central network element that controls the wireless uplink communication of the wireless appliance instead of the first base station. The first base station is called CoMP master and the at least one second base station is a CoMP slave. 
         [0013]    A transfer request message can be sent to the one of the at least one second base station after the analysis of the rest signal has shown that the rest signal contains a signal that is above a certain threshold B so that it can be advantageous to transfer the control of the wireless uplink communication with the wireless appliance to one of the at least one second base stations. 
         [0014]    Advantageously, the communication between the first base station and the at least one second base station is done via a logical X2 interface. 
         [0015]    In another aspect, the invention provides a computer program product comprising machine executable instructions for performing any of the above mentioned methods on a base station. The base station comprises a computer system, a microprocessor and/or a microcontroller. This is advantageous, because the machine executable code can be used for automating the above mentioned procedures. 
         [0016]    In another aspect, the invention provides a method of operating a second base station for processing signals from at least one wireless appliance. The wireless uplink communication connection of the wireless appliance is not controlled by the second base station. The second base station does not receive the direct uplink communication signal from the wireless appliance, only a rest signal consisting of noise and an interference signal from the wireless appliance. The second base station can provide the rest signal to a first base station. 
         [0017]    In another embodiment, the rest signal provided from the second base station to the first base station contains a signal that is above a certain threshold A from the wireless appliance that is connected to the first base station via a wireless uplink communication connection controlled by the first base station. 
         [0018]    In another embodiment, the second base station receives a transfer request message from the first base station and the control of the wireless uplink communication connection of the wireless appliance is transferred from the first base station to the second base station which can be done for example by a handover procedure or fast cell selection. The second base station can decline the transfer request message. 
         [0019]    In another embodiment, the rest signal that is provided from the second base station to the first base station does not contain a signal that is above a certain threshold A from a wireless appliance whose wireless uplink communication connection is controlled by the first base station. Even so, the second base station can continue providing the rest signal to the first base station. 
         [0020]    In another embodiment, the first base station is part of a coordinated multipoint wireless uplink communication with the wireless appliance and the second base station can be added to the coordinated multipoint wireless uplink communication with the wireless appliance by the first base station or a central network element. Advantageously, this is done when the second base station provides a rest signal that contains a signal for the wireless uplink communication between the wireless appliance and the first base station that is above a certain threshold A. 
         [0021]    In another embodiment, the second base station receives a transfer request message from the first base station or the central network element and the control of the wireless uplink communication with the wireless appliance is transferred from the first base station or the central network element to the second base station. Advantageously, this is done when the rest signal from the second base station contains a signal for the wireless communication connection that is above a certain threshold B or has other advantages compared to the uplink communication signal from the wireless appliance to the first base station. 
         [0022]    In another aspect the invention provides a computer program product comprising machine executable instructions for performing the methods mentioned above of operating a second base station for processing signals from at least one wireless appliance in order to provide a rest signal to a first base station. 
         [0023]    In another aspect, the invention provides a base station apparatus being operable to perform any of the method steps described above. 
         [0024]    Advantageously, a base station can function as a base station that controls the wireless uplink communication connection of at least one first wireless appliance and at the same time as a second base station for at least one second wireless appliance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    In the following preferred embodiments of the invention will be described, by way of example only, and with reference to the drawings in which: 
           [0026]      FIG. 1  illustrates the situation where a first base station controls the coordinated multipoint reception of the wireless uplink communication connection with a wireless appliance, 
           [0027]      FIG. 2  illustrates the signal processing in the second base station and the subsequent providing of a rest signal to the first base station, 
           [0028]      FIG. 3  illustrates the processing of the rest signal provided by the second base station to the first base station in the first base station, and 
           [0029]      FIG. 4  is a block diagram illustrating a base station apparatus being operable to perform the methods according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Like numbered elements in these figures are either identical elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is identical. 
         [0031]      FIG. 1  illustrates the situation where a first base station  100  controls the wireless uplink communication connection of a wireless appliance  102 . The first base station  100  acts as a master of a coordinated multipoint (CoMP) reception network. This means the first base station has the control of the wireless uplink communication. The two second base stations  104 ,  106  receive an interference signal from the wireless appliance  102 . The two second base stations  104 ,  106  provide their rest signals to the first base station, the CoMP master  100 , for example on request by the CoMP master or periodically. The two second base stations are called CoMP slaves. 
         [0032]    The rest signal consists of noise and interferences from wireless appliances in the transmission area of the two second base stations  104 ,  106 . The rest signal can be received by the first base station  100  for example via a X2 interface  108 . After reception of the rest signals the first base station  100  analyzes the rest signal for detecting an appropriate signal level of the wireless appliance  102  in the rest signal of one of the second base stations  104 ,  106 . Based on this analysis the first base station  100  decides if one of the second base stations  104 ,  106  is added to the CoMP reception network for the wireless appliance  102 . The first base station  100  that functions as a CoMP master can also remove one of the second base stations  104 ,  106  from the CoMP reception network if the signal level has no benefit to the wireless uplink connection of the wireless appliance  102 . The CoMP master functionality can be moved from the first base station  100  to one of the second base stations  104 ,  106  if the signal of the wireless appliance  102  in the rest signal from one of the second base stations  104 ,  106  is above a certain threshold B. 
         [0033]      FIG. 2  shows a more detailed illustration of an embodiment of the invention. The wireless uplink communication connection of the wireless appliance  102  is controlled by the first base station  100  that functions as the CoMP master. The second base stations  104 ,  106  receive signals from the wireless appliances whose connections they control  110 , interferences  112  also from the wireless appliance  102  and noise  114 . The signals  110 , the interferences  112  and the noise  114  are transmitted by the receiver  116  to the signal buffer  117  once per transmit time interval. The receiver  116  performs the channel estimation  118 . The acknowledgement for the signal  110  is done by a CRC check  120 . If the CRC check  120  is successful the uplink data  111  from the signal  110  is processed in the base station  104 . The transmit signal estimator  122  estimates the estimated transmitted radio signal  113  that was transmitted by the wireless appliance. With the help of the channel estimation  118  the received signal estimator  124  generates the estimated received signal  119 . 
         [0034]    Per successfully received uplink data  111  the estimated received signal  119  is subtracted from the signal that is buffered in the signal buffer  117  consisting of the signal  110 , the interferences  112  and the noise  114  such that the rest signal  126  consists of the interferences and the noise. The rest signal  126  is again buffered in the signal buffer  117  and then transmitted to the first base station  100  via an X2 interface  108  for example. 
         [0035]    The same procedure is done in the second base station  106  that also receives signal data  110 , interferences  112  and noise  114 . The data is processed in the same way as in the second base station  104 . The rest signal  126  is transmitted to the first base station  100  via an X2 interface  108  for example. 
         [0036]      FIG. 3  is a flowchart showing the processes in the first base station  100 . The first base station  100  receives signals  127  from the wireless appliances whose connections it controls, interferences  112  and noise  114  in the receiver  116 . The receiver  116  performs the channel estimation  118 . The acknowledgement for the signal is done by a CRC check  120 . If the CRC check is successful the uplink data  131  from the signal  127  is processed in the first base station  100 . The transmit signal estimator  122  estimates the transmitted radio signal  133 . 
         [0037]    The rest signal  126  is buffered in the signal buffer  128 . By knowing the signal  133  of the wireless appliance  102  the signal  129  of the wireless appliance  102  inside the rest signal  126  can be identified. The analysis  130  of the rest signal  126  is done once for every uplink data  131  that is successfully received from the wireless appliance  102  whose connection is controlled by the first base station  100 . If the signal  129  of the wireless appliance  102  inside the rest signal  126  of the second base station  104  is not above a certain threshold A the procedure  132  not to add the second base station  104  to the CoMP network for the wireless appliance  102  is triggered. Then the first base station  100  continues to analyze the signals for the next wireless appliance. 
         [0038]    If the signal  129  of the wireless appliance  102  inside the rest signal  126  is above the threshold A a second analysis  134  is carried out detecting if the signal inside the rest signal  126  is above a certain threshold B. If so, procedure  136  to transfer the control of the wireless uplink communication with the wireless appliance  102  to the second base station  104  is triggered. 
         [0039]    If the second base station declines the transfer of the control of the wireless appliance, the procedure  138  is started to add a second base station  104  to the CoMP network as a slave to provide its rest signal for the first base station  100  regularly. 
         [0040]    If the signal  129  of the wireless appliance  102  inside the rest signal  126  is not above the threshold B, procedure  138  is started to add a second base station  104  to the CoMP network as a slave to provide its rest signal for the first base station  100  regularly. 
         [0041]    The thresholds A and B can be either fixed values, have a dynamical character or have a differential character so that the change of the received signal power is taken as the basis for the decisions. 
         [0042]      FIG. 4  is a block diagram illustrating a base station apparatus  140  being operable to perform the methods according to the invention. For example, this can be in a CoMP network where the base station apparatus can function as a CoMP master for a first plurality of wireless appliances and at the same time as a CoMP slave for a second plurality of wireless appliances. 
         [0043]    The receiver  116  receives the signals of the first plurality of wireless appliances  110 , interferences  112  and noise  114 . The signals of the first plurality of wireless appliances  110 , the interferences  112  and the noise  114  form together the signal  115 . In the interferences  112  there are signals from the second plurality of wireless appliances. 
         [0044]    The signal  115  is transmitted by the receiver  116  to the signal buffer  141  once per transmit time interval. The receiver  116  performs the channel estimation  118 . The acknowledgement for the uplink data is done by a CRC check  120 . If the CRC check  120  is successful the uplink data  111  from the signal  110  is processed by the means for processing uplink data  142 . The transmit signal estimator  122  estimates the transmitted radio signal  113  for this uplink data  111 . From this estimated signal  113  the estimated received signal  119  can be estimated in the received signal estimator  124  with the help of the channel estimation  118  that is done in the receiver  116 . 
         [0045]    Per received signal  110  the signal  110  is subtracted by the substracter  144  from the signal that is buffered in the signal buffer  141  consisting of the signal  110 , the interferences  112  and the noise  114  such that the rest signal  126  consists of the interferences and the noise. The rest signal  126  is again buffered in the signal buffer  141  and then transmitted by means for sending the rest signal  126  to another base station apparatus via an X2 interface  108 . 
         [0046]    The rest signal  148  received from another base station apparatus is buffered in the signal buffer  141 . By knowing the signals  110  of the first plurality of wireless appliances a suitable signal for a wireless appliance of the first plurality of wireless appliances can be identified in the rest signal  148  received from another base station apparatus. Means for analyzing the rest signal with regard to threshold A  150  analyze the rest signal  148  once for every signal that is estimated to be transmitted by the corresponding wireless appliance. If the suitable signal for the wireless appliance of the first plurality of wireless appliances inside the rest signal  148  is not above the threshold A means  152  perform the procedure to not to add the second base station to the CoMP network. Then the base station apparatus  140  continues to analyze the signals for the next wireless appliance. 
         [0047]    If the suitable signal for the wireless appliance of the first plurality of wireless appliances inside the rest signal  148  is above the threshold A means  154  analyze the rest signal  148  with regard to threshold B. If the rest signal  148  is above the threshold B, means  156  for performing the procedure to change the master send a transfer request message  157  to the CoMP slave having sent the rest signal  148  via the X2 interface  108 . 
         [0048]    If the second base station declines the transfer of the control of the wireless appliance, means  158  perform the procedure to add the base station having sent the rest signal  148  to the CoMP network as a CoMP slave. The addition is done by an addition request message  159  via the X2 interface  108 . 
         [0049]    If the suitable signal inside the rest signal  148  is not above the threshold B, means  158  perform the procedure to add the base station having sent the rest signal  148  to the CoMP network as a CoMP slave. The addition is done by an addition request message  159  via the X2 interface  108 . 
         [0050]    The thresholds A and B can be either fixed values, have a dynamical character or have a differential character so that the change of the signal power is taken as the basis for the decisions. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           100  first base station 
           102  wireless appliance 
           104  second base station 
           106  second base station 
           108  X2 interface 
           110  signals of other wireless appliances 
           111  uplink data of the signals of other wireless appliances 
           112  interferences 
           113  estimated transmit signal of the wireless appliance 
           114  noise 
           115  signals of other wireless appliances+interferences+noise 
           116  receiver 
           117  signal buffer of second base station 
           118  channel estimation 
           119  estimated received signal of the wireless appliance 
           120  CRC check 
           122  transmit signal estimator 
           124  received signal estimator 
           126  rest signal 
           127  signal of the wireless appliance 
           128  signal buffer of first base station 
           129  signal of the wireless appliance inside the rest signal 
           130  analysis of the rest signal with regard to threshold A 
           131  uplink data of the signal of the wireless appliance 
           132  procedure to not to add the second base station to the CoMP network 
           133  estimated transmit signal of the wireless appliance 
           134  analysis of the rest signal with regard to threshold B 
           136  procedure to change the master 
           138  procedure to add the second base station to the CoMP network 
           140  base station apparatus 
           141  signal buffer 
           142  means for processing uplink data 
           144  substracter 
           146  means for sending rest signal 
           148  rest signal received from another base station 
           150  means for analyzing the rest signal with regard to threshold A 
           152  means for performing the procedure to not to add the second base station to the CoMP network 
           154  means for analyzing the rest signal with regard to threshold B 
           156  means for performing the procedure to change the master 
           157  transfer request message to change the master 
           158  means for performing the procedure to add the second base station to the CoMP network 
           159  addition request message to add a slave to the CoMP network