Abstract: A frequency tracking loop (100) includes: a mixer (122) for correcting frequency offset of an input radio signal that includes bursts of known data; a frequency offset estimator (134), for providing an estimate of frequency offset; a variable bandwidth filter (142), for providing a filtered signal; an oscillator (146) for supplying a second input of the mixer with a signal whose frequency depends on the filtered signal; the frequency tracking loop (100) is adapted to change the bandwidth of the variable bandwidth filter (142) in dependence on at least one characteristic of the currently received burst of known data.

Abstract: A method of estimating signal quality, the method including a) taking a plurality of complex samples of a decoded signal at its symbol rate for a plurality of slots, for each of the slots b) partitioning the samples into a plurality of partitioned sample sets, for each of the partitioned sample sets c) deriving data symbols from the samples, d) re-encoding the data symbols into a re-encoded symbol set, e) forming a vector of length L that is orthogonal to a set of vectors formed from L consecutive samples of the re-encoded symbol set, where L is an integer less than or equal to the number of samples in the partitioned set, and f) forming an estimate of the signal quality from the plurality of complex samples for the plurality of slots using at least one of the orthogonal vectors.

Abstract: A frame timing lock detector circuits and a methods of frame timing lock detection for a digital communications system. A known data sequence is extracted from a received radio signal and multiplied, in a multiplier, together with a reference signal that includes the symbols of the known data sequence raised to the power of a multiple of three. The phase of the multiplier output is measured and an average of an absolute value of this measured phase is compared with a threshold to detect correct frame timing lock.

Abstract: A method and apparatus for smooth transitions of background noise as a mobile communication unit roams from a first communication system having a first speech encoder (310) to a second communication system having a second speech encoder (330). As the mobile communication unit roams into the second communication system, the first communication system will transfer the communication signal to the second communication system. Background noise from the first communication system is sampled (320), and as the communication signal is transferred, the noise signal sampled in the first communication system is mixed in a mixer of the second communication system with background noise sampled (340) from the second communication system. As the change in noise progresses, the noise from the first communication system will gradually be decreased and faded out while the noise from the second communication system will be gradually increased to a high power level.

Abstract: A method is disclosed for determining current channel state information in a communications system having a first communications unit communicating to a second communications unit, wherein the first communications unit sends a channel sounding packet (32) to the second communications unit. The channel sounding packet (32) is sent a time period, t, prior to the transmission of a signal by the second communications unit to the first communications unit. The second communications unit receives the channel sounding packet (46) and processes the channel sounding packet to determine at least one channel characteristic. In response to receiving the channel sounding packet (46) the second communications unit appends frame code information (48) to the signal to be transmitted from the second communications unit to the first communications unit, to inform the first communications unit of the communications parameters that have been optimized.

Abstract: In a radio communication system (100), enhanced communication capability is provided while maintaining standard channel modulation compatibility. At a transmitter (110, 200, 600), a first information signal is generated from data according to a predefined standard modulation scheme (212, 613). A second information signal is generated from data that provides supplemental information to the standard modulated data (213, 616). For transmission, the first and second information signals are combined into a composite signal (214, 619) that represents the first information signal when interpreted according to the predefined standard modulation scheme.