Abstract: The invention pertains in general to the testing of the operation of radio and other data transmission apparatus. In particular the invention pertains to the testing of the operation of a digital radio apparatus on the basis of error statistics. In order to test functions relating to data transmission, a simulation system produces a pseudorandom bit sequence or some other test sequence which is packed into downlink frames and sent to the data transmission apparatus tested. In accordance with the invention, a known number of errors are generated in the test sequence. As the data transmission apparatus tested compares the received test sequence to the sequence it has produced, it detects the errors in the received sequence and compiles various error statistics, e.g., in the form of bit error ratio (BER) or frame erasure ratio (FER).

Abstract: The invention concerns a method and associated hardware units for testing the functioning of downlink data communication in a mobile station (202, 802, 902). The mobile station is equipped for receiving (302, 805) a signal in the downlink direction and for sending (312, 808) a signal in the uplink direction. As a part of the method, a test signal (711, 715, 716, 805) is received in the downlink direction. The received test signal is compared (208, 713, 908) to a known form of the test signal. There is produced and temporarily stored (209, 806, 909) information about errors which were detected in the received test signal during the comparing step. In the uplink direction a signal is sent (714, 717, 808) representing the stored information about errors.

Abstract: To test the functioning of downlink data communication a mobile station comprises means (301, 302, 303, 304, 326) for receiving a signal in the downlink direction and means (331, 310, 311, 312, 313) for sending a signal uplink. It receives a test signal in the downlink direction (301, 302, 602) and compares the received test signal to a known form of the test signal (208, 603). In addition, the mobile station stores information produced by the comparison about errors detected in the received test signal (209) and sends uplink a signal representing the information stored (312, 313, 604).

Abstract: Disclosed is a method and a device for compensating the DC offset (dU) of a D/A converter (2), particularly in the base frequency modulator of a mobile phone. The method and the device use an error correction register (5), whose value is changed on the basis of the DC offset, and which is added to each signal sample to be converted for compensating the DC offset. The value of the error correction register (5) is changed in a testing mode so that a preset control value is fed into the D/A converter (2), corresponding to the zero voltage of the output of an ideal D/A converter; the voltage values of outputs of a differential output pair (2a, 2b) arranged in connection with the D/A converter (2) are compared to verify the polarity of the voltage difference (dU) of the outputs and the polarity, i.e.