Abstract:
A method of measuring sensitivity of the receiving end in a transceiver that includes a transmission path between the transmitting end and the receiving end and a switching mechanism for connecting a signal along the transmission path from the transmitting end of the transceiver to the receiving end. The transceiver also includes an attenuator for changing the level of the signal to be connected from the transmitting end to the receiving end and a mechanism for transmitting a test signal for determining properties of the transmission path, a mixer for transmitting the signal changed by the attenuator to the frequency band of the receiving end, a switching mechanism for connecting the signal transferred by the mixer through the receiving end, and a controller for comparing the signal transmitted from the transmitting end with the signal that has passed through the receiving end to determine sensitivity of the receiving end.

Description:
FIELD OF THE INVENTION 
   This is a Continuation of U.S. patent application Ser. No. 10/116,756, filed Apr. 5, 2002 now U.S. Pat. No. 6,990,325, which is a Continuation of International Application PCT/FI00/00856 filed Oct. 4, 2000, which relies for priority upon Finnish Application No. 19992144, filed Oct. 5, 1999. The contents of all of these applications are incorporated herein in their entireties by reference. 
   The invention relates to a method of measuring sensitivity of the receiving end in a transceiver. 
   BACKGROUND OF THE INVENTION 
   Radio systems employ different transmitters which transmit information signals to the receivers in the systems. In addition to information signals, the receivers receive different interference signals, which may include e.g. noise. The receiver always has a certain sensitivity which describes the receiver&#39;s ability of detecting signals sent by the transmitter from among noise or similar interference. Receiver sensitivity is particularly significant to succeeding of data transmission in the radio system. It is important to measure sensitivity because the sensitivity of a receiver may change due to a change in the temperature, for example. The temperature may have a considerable influence on the receiver sensitivity. The higher the quality of the components in the receiver, the smaller the influence of the temperature. 
   In GSM radio systems, for example, the sensitivity of a receiver, which is part of a base station, is measured by an external measurement device, which feeds a measurement signal to the receiver. From the receiver the measurement signal is connected to the transmitting end of the base station, from which the measurement signal is supplied back to the measurement device, which measures e.g. bit errors from the measurement signal. The measurement device sends measurement signals attenuated with various attenuation values to the receiver, in which case the receiver sensitivity can be determined. 
   The purchase price of the measurement device used in sensitivity measurement is still rather high, for which reason a measurement device is not always bought, and thus the receiver sensitivity is not measured at all. In practice, however, the receiver sensitivity is always measured one way or another because the receiver has to fulfil the sensitivity requirements set for it. In some cases deficiencies may occur in the function of a radio network if it is not checked by means of sensitivity measurement before the radio network is used that the receivers fulfil the sensitivity requirements set for them. In a prior art method sensitivity measurement requires service personnel at the location of the base station, where they measure sensitivity with a separate measurement device. The above-mentioned method is, however, slow and very laborious to implement in practice. 
   BRIEF DESCRIPTION OF THE INVENTION 
   An object of the invention is to provide a method and an apparatus implementing the method to solve the above-mentioned problems. This is achieved with the method described in the introduction, which is characterized by connecting a signal along a transmission path in the transceiver from the transmitting end of the transceiver to the receiving end of said transceiver, changing the signal level of the signal to be transmitted from the transmitting end to the receiving end and taking into account the influence of the transfer on the signal transmitted from the transmitting end to the receiving end, transferring the signal entering the receiving end through the receiving end, comparing the signal transmitted from the transmitting end with the signal that has passed through the receiving end and determining sensitivity of the receiving end on the basis of the comparison. 
   The object is also achieved with a method described in the introduction, which is characterized by connecting a signal along a transmission path in the transceiver from the transmitting end of the transceiver to the receiving end of said transceiver, adding a noise signal to the signal to be transmitted from the transmitting end to the receiving end to form a sum signal and taking into account the influence of the transfer on the signal transmitted from the transmitting end to the receiving end, transferring the sum signal entering the receiving end through the receiving end, comparing the signal transmitted from the transmitting end with the sum signal that has passed through the receiving end and determining sensitivity of the receiving end on the basis of the comparison. 
   The invention also relates to a transceiver which comprises a transmitting end and a receiving end. 
   The transceiver of the invention is characterized in that the transceiver comprises a transmission path between the transmitting end and the receiving end, a switching means for connecting a signal along said transmission path from the transmitting end of the transceiver to the receiving end of the same transceiver, an attenuation means for changing the level of the signal to be connected from the transmitting end to the receiving end, a means for transmitting a test signal for determining properties of said transmission path, a mixing means for transmitting the signal adapted by the attenuation means to the frequency band of the receiving end, a switching means for connecting the signal transferred through the receiving end by the mixing means, a control means for comparing the signal sent from the transmitting end with the signal that has passed through the receiving end to determine sensitivity of the receiving end. 
   The transceiver of the invention is also characterized in that the transceiver comprises a transmission path between the transmitting end and the receiving end, a switching means for connecting the signal along said transmission path from the transmitting end of the transceiver to the receiving end of the same transceiver, a generator for generating noise in said signal, a means for sending a test signal to the transmission path for determining properties of the transmission path, a switching means for connecting a signal to which noise has been added through the receiving end, a control means for comparing the signal connected by the switching means with the signal that has passed through the receiving end to determine sensitivity of the receiving end. 
   The preferred embodiments of the invention are disclosed in the dependent claims. 
   The invention is based on connecting a signal from the transmitting end of a transceiver to the receiving end of this transceiver. The signal to be connected is attenuated or noise is added to it. The amount of attenuation or noise in the signal is changed, which enables determination of receiver sensitivity. The method comprises determining a sensitivity value corresponding to each attenuation coefficient for the receiving end. The amount of noise to be added is changed from time to time, which allows determination of a sensitivity value corresponding to each amount of noise for the receiving end. 
   The method and transceiver according to the invention provide several advantages. Sensitivity measurement is integrated into the transceiver, which is e.g. a base station. Since the components that measure sensitivity of the receiving end of the transceiver are in the transceiver itself, there is no need for an external measurement device. One important advantage is that sensitivity measurement can be performed from the remote end by means of suitable management software. Thus service personnel do not need to go to the location of the base station to perform the measurement. The sensitivity measurement is quick to perform because no separate measurement connections or external measurement devices are needed. In addition, the sensitivity measurement provides a reliable result because measurement wires are unnecessary. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which 
       FIG. 1  illustrates a first preferred embodiment of a transceiver according to the invention, and 
       FIG. 2  illustrates a second preferred embodiment of a transceiver according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates a transceiver of the invention which utilizes e.g. the CDMA method (CDMA=Code Division Multiple Access) or the WDCMA method (WDCMA=Wideband CDMA). The transceiver of the invention, which in practice is e.g. a base station, comprises a means  10 , scaling means  20 , D/A conversion means  30 , modulation means  35 , switching means  40 , transmission antenna  45 , channel generation means  50 , control means  60 , attenuation means  70  and generator  80 . The means  10 ,  20 ,  30 ,  35 ,  40  and  45  are included in the transmitting end of the transceiver, which can also be called the downlink. 
   The transceiver also comprises a receiving means  90 , A/D conversion means  100 , generator  110 , mixing means  120 , adding means  130 , receiver  140 , receiving antenna  155 , means  150  and switching means  160 . The reception means  90  is preferably a RAKE receiver. The means  140 ,  100 ,  90  are included in the receiving end of the transceiver, which can also be called the uplink. The method according to the invention is suitable for measuring sensitivity of the receiving end. 
   Both switching means  40 ,  160  of the transceiver are preferably implemented with separate directional couplers. The generator  80  generates a predetermined signal, which may be e.g. a sine signal. In practice, the signal level of the predetermined signal at a given time is known or can be found out, if necessary. 
   If the transceiver is a GSM-type transceiver, the means  10 ,  20 ,  50  and  90 , which are typically used in the CDMA system, are replaced with means that are suitable for a GSM-type transceiver. The receiver may apply e.g. the TDMA (TDMA=Time Division Multiple Access), the FDMA (FDMA=Frequency Division Multiple Access) or the CDMA multiple access methods. It can be seen in the figure that the transceiver comprises an uplink signal path  141  along which a signal is supplied to the transceiver. In practice, the receiving antenna  155  of the transceiver first receives an input signal arriving at the transceiver along the radio path. The transceiver receives the input signal arriving at its Rx band. The control means  60  in the transceiver generates different control and adjustment signals for controlling and adjusting the function of the transceiver. The control means can be implemented with a microprocessor, for example. 
   The transceiver sends a signal to the radio path along a downlink signal path  41 . The transceiver sends the downlink signal to its Tx band by means of its transmission antenna  45 . The method according to the invention comprises determining sensitivity of the receiving end, in which sensitivity is taken into account from the receiving antenna  155  to output of the receiving means  90 . Sensitivity can be determined up to the output of the receiver because the control means can utilize the output signal of the receiving means  90  in the determination of sensitivity. The transceiver according to the invention includes the components used for measuring sensitivity, and thus no external measurement devices are needed in the sensitivity measurement. 
   In the following, the structure of the transceiver according to the invention will be described more closely. The output of a generation means  50  of the transceiver, which forms at least one physical channel, is connected to the means  10 . The means  10  spreads a signal on the physical channel with a spreading code if the transceiver is of the CDMA type. The output of the means  10  is connected to the means  20 , the output of which is connected to the input of the D/A converter  30 . The output of the D/A converter  30  is connected to the input of the modulation means  35 . 
   The output of the modulation means  35  is connected to the means  40 , which can be implemented with a directional coupler, for example. The modulation means  35  and the switching means  40  are connected to the transmission antenna  45  on the downlink transmission path  41 . The switching means  40  is connected to the attenuation means  70  by means of the transmission path  42 , and the switching means is connected to the mixing means  120  by means of the attenuation means. In principle, the transmission path  42  continues up to the switching means  160 . The output of the generator  80  is connected to the transmission path  42  between the switching means  40  and the mixing means. 
   The mixing means  120  is connected to the adding means  130 , to which the output of the generator  110  is also connected. The output of the adding means  130  is connected both to the switching means  160  and to means  150 . The attenuation means  70 , mixing means  120  and adding means  130  are implemented with analogue parts which cause some noise in the signal that propagates via these means. The switching means  40 , attenuation means  70 , mixing means  120 , adding means  130  and switching means  160  connect the transmitting end of the transceiver to the receiving end of the transceiver. This means that at least the attenuation means  70 , mixing means  120  and adding means  130  are on the transmission path  42 . 
   The receiving antenna  155  of the transceiver is connected to the receiver  140  via the uplink transmission path  141 , and the output of the receiver is connected to the A/D conversion means  100 . The output of the A/D conversion means is connected to the control means  60  via the receiving means  90 , and the control means are connected to the generation means  50 . The control means  60  is also connected to the attenuation means  70  and the generator  110 . Furthermore, the control means is connected to both switching means  40 ,  160 . 
   The method comprises first determining the noise caused by the components need to measure the sensitivity, which allows to take noise into account in the determination of sensitivity. This way the sensitivity value can be determined as accurately as possible. In practice, the method comprises determining the noise caused in the signal by the attenuation means  70 , mixing means  120  and adding means  130  via which the signal is transmitted. A test signal is used for determining the nominal noise of the above-mentioned means. Determination of noise is very important because the signal that is used for determining the actual sensitivity is also transmitted via the above-mentioned means. The noise signal caused in the signal by the above-mentioned means is determined using a test signal generated by the generator  80 , which may be e.g. a sine signal. 
   The method also comprises determining the attenuation caused by the attenuation means  70 , mixing means  120  and adding means  130  in the signal connected by the switching means  40 . Attenuation is measured according to the same principles as the above-mentioned nominal noise. A test signal is used in the measurement of attenuation. Attenuation is measured in the means  150 , which transmits the result of attenuation measurement to the control means  60 . The attenuation caused in the signal by the attenuation means  70 , mixing means  120  and adding means  130  is take into account in the measurement of sensitivity. 
   The transceiver generates a signal which is transmitted to the channel established by the generation means  50 . The signal transmitted to the channel is spreading-coded if the transceiver applies the CDMA or the WCDMA method. In the transceiver according to  FIG. 1  the means  10  performs spreading-coding on the signal on the channel. A spreading-coded signal consisting of bits is supplied to the means  20 , which scales the received signal. 
   According to the uplink channel model, the transceiver shown in  FIG. 1  receives a signal which arrives at the receiving antenna  155  first. The uplink channel model or information on it can be transmitted from the uplink to the downlink. After this, a channel model corresponding to the channel model used at the uplink can be formed at the downlink. In practice, the uplink channel model is formed in the generation means  50 . After this, the signals of the channel model formed by the generation means  50  are scaled in the means  20 . In practice, the generation means  50  forms the channel model on the basis of a control signal which enters the generation means  50  from the control means  60 . 
   Scaling means that the channel model formed by the means  50  is adapted so that it can be received at the uplink of the same transceiver. In scaling the length of a downlink channel is adapted to the length of the uplink channel. After scaling the downlink channel is as long as the uplink channel. The means  20  can change the number of bits on the channel in scaling. In addition to the means  20 , scaling can be performed e.g. in the generation means  50 . 
   A digital signal included in the uplink channel model formed by the generation means  50  is converted into analogue form in a D/A converter  30 . After this, the analogue signal is modulated in the modulation means  35 , and then the modulated signal is sent towards the switching means  40  in the downlink direction. The modulation means  35  modulates the received signal so that the receiver  140  can receive it. If necessary, the modulation means  35  can amplify the signal converted into analogue form. The uplink channel model formed by the generation means  50  is supplied up to the switching means  40  in the downlink direction. In other words, the antenna  45  does not receive any signal from the modulation means  35  in this situation. 
   In the measurement of sensitivity, a channel model differing from the channel model sent in the downlink direction in a normal situation is sent in the downlink direction. In this case the normal situation refers e.g. to a situation in which the transceiver sends a signal according to the downlink channel model to the radio path by means of the antenna  45 . In a normal situation the signal transmitted in the downlink direction is used for establishing a connection to another transceiver. 
   In the solution according to the invention the switching means  40  connects the signal included in the channel model to the attenuation means  70 . When sensitivity is measured, the switching means  40  prevents the signal from accessing the transmission antenna  45 . It can be seen in  FIG. 1  that a test signal generated by the generator  80  is inserted into the signal connected by the switching means  40 . The switching means  40  thus connects the channel model which has propagated via the means at the downlink and corresponds to the uplink channel model to the uplink of the transceiver. The means  40 ,  70 ,  120 ,  130  and  160  in the transceiver constitute a feedback loop to which the signal which has been modulated by the modulation means  35  at the transmission end and corresponds to the uplink channel model is connected. 
   It can be seen in  FIG. 1  that the control means  60  communicates with the attenuation means  70  which form part of the feedback loop. Furthermore, the control means communicates with the feedback loop via the generator  110 . The control means  60  sends an adjustment signal to the attenuation means  70 , which changes its attenuation on the basis of the received signal. Thus the control means adjusts the level of the signal that the signal switching means  40  transmits to the attenuation means  70 . The level of the signal connected to the attenuation means  70  by the switching means  40  and the level of the output signal from the attenuation means  70  to the mixing means  120  are unequal if the attenuation used by the attenuation means  70  is changed. The mixing means  120  places the modulated and received signal, which is on the TX band, on the RX band of the receiver. 
   The influences of the attenuation means  70 , mixing means  120  and adding means  130  on the modulated signal are eliminated from the output signal of the adding means  130 , and the modulated signal is transmitted to the receiving end via the above-mentioned means. These influences are taken into account by reducing the noise of the signal received from the output of the adding means by an amount which was found out using the test signal. 
   During sensitivity measurement the signal arriving at the transceiver from the radio path is prevented from mixing into the signal which is transmitted to the receiver  140  via the adding means  130  and the switching means  160 . The switching means  160  may even totally prevent a signal arriving from the radio path from accessing the receiver  140 . In the last-mentioned situation the switching means  160  switches the transmission path  141  off for the duration of sensitivity measurement. 
   As stated above, the switching means  160  connects the analogue signal from the adding means to the receiver  140 . The receiver  140  can apply automatic gain control (AGC), for example, on the received signal. After this, the signal received from the output of the receiver  140  is converted into digital form in the A/D conversion means  100 . The analogue signal is supplied to the control means via the RAKE receiver  90 . The control means calculates the bit errors that the means  140 ,  100  and  90  at the receiving end have caused in the signal connected by the switching means. More precisely, the control means calculates the bit error ratio using the signal that the switching means  40  connected to the attenuation means  70  and a signal which is received from the output of the RAKE receiver  90 . It is easy to determine the bit error ratio because the bits of the transmitted and the received signal are known, in which case it is easy to compare the bits with one another. 
   The sensitivity value can also be expressed as a signal-to-noise ratio. In that case the control means  60  sends a control signal to the generator  110 , which forms a noise signal including a certain amount of noise on the basis of the control signal, and the noise signal is transmitted to the adding means  130 . In the adding means the noise signal is added to the signal from the means  120 . The sum signal formed by the adding means is supplied to the switching means, which connects the sum signal to the means  140 , from which the sum signal is supplied to the A/D conversion means  100 . The A/D conversion means converts the sum signal into a digital signal, which is supplied to the means  90 . 
   The control means  60  compares the sum signal with a signal to which no noise has been added. After this, the control means determines a sensitivity value corresponding to the added noise signal for the receiving end. This is followed by generating a new noise signal and calculating a sensitivity value of the receiver corresponding to this signal. The control means  60  thus controls the attenuation value of the attenuation means and the magnitude of the noise signal formed by the generator  110 . It is possible to define a condition in advance that the sensitivity measurement and thus controlling of the attenuation and noise is continued e.g. until the bit error ratio obtained as a result of signal comparison decreases due to the controlling. 
     FIG. 2  illustrates a transceiver which comprises, in addition to the means mentioned above, means  11 ,  12 ,  13  and  14 . The transceiver shown in  FIG. 2  also comprises an adding means  15  and generation means  51  and  52 . Each of the generation means  50 ,  51 ,  51  is connected to a separate means  10 ,  11 , 12 . It also appears from  FIG. 2  that the output of the means  10  is connected to the adding means  15 . The output of the means  11  is connected to the adding means  15  via the means  14 . The output of the means  12  is also connected to the summing means  15  via the means  13 . 
   Each of the generation means  50 ,  51 ,  52  forms a separate channel model. As stated above, the generation means  50  transmits the channel model it has formed to the means  10 . Instead, the generation means  51  transmits the channel model it has formed to the means  11 , and the generation means  52  transmits the channel model it has formed to the means  12 . Each of the means  10 ,  11 ,  12  spreads the signal on the channel received by it with a spreading code. Each of the means  50 ,  51 ,  52  places the signal on a channel formed by it. The data transmission speeds of signal placed on different channels may vary. 
   The signal spread by the means  11  is sent to the means  14 , which alters the phase of the spreading-coded signal. The signal spread in the means  12  is sent to the means  13 , which also alters the phase of the received signal. The signals to which phase shift has been applied are supplied to the adding means  15 , which adds these signals to the signal from the means  10 . 
   The sum signal obtained from the output of the adding means  15  is supplied to the scaling means  20 , which scales the sum signal according to the principles explained above. After scaling, the sum signal is converted into analogue form, and then the analogue sum signal is modulated. In modulation several channels are modulated into the same carrier wave. In other words, the output signal of the modulation means  35  comprises several channels. 
   The sub-signals that constitute the sum signal may have different data transmission properties. This means that the number of bits or symbols to be transmitted on the channel formed by each of the means  50 ,  51 ,  51  may vary depending on the channel. The different transmission speeds used on the channels cause interference, which causes bit errors in the signal which are measured as described above. Using the method related to  FIG. 2  it is possible to find out how many bit errors the data transmission speed, transmitting end and receiving end cause in the signal. By means of this method it is also possible to find out how well the receiving end can receive a signal which comprises several signals each of which has a different data transmission speed. Thus the measurement related to  FIG. 2  is particularly suitable for determining the capacity, for example. 
   Even though the invention has been described with reference to an example according to the accompanying drawings, it is clear that the invention is not limited thereto, but may be modified in various ways within the scope of the inventive concept disclosed in the appended claims.