Showing papers by "Amitava Ghosh published in 1996"

Method and apparatus for location finding in a cdma system

Abstract: A method and apparatus for determining the location of a communication unit in a CDMA system includes in a first embodiment, sending a location request via a spread spectrum signal to the subscriber (140), and receiving in return a subscriber signal including a response message showing a receive time of a particular symbol of the base's spreading sequence and a transmit time of a particular symbol of the subscriber's spreading sequence. The base (130), along with other receiving base(s) (140), also receives a predetermined symbol of the subscriber spreading sequence, and each determines a respective receive time of the predetermined symbol. The received information is then processed, along with known base location and delay information, to determine the subscriber location. If insufficient number of bases are capable of communicating with the subscriber, for example due to high loading/interference, auxiliairy bases (121) are also provided for receiving from or transmitting to the subscriber.

Power control for CDMA communication systems

Abstract: A transmitter transmits the desired signal using a continuous duty cycle at transmission rates of less than full rate (Fig. 6). The energy used in each power control group is related to the transmission rate. By repeating the power control groups, time division diversity (Fig. 6) is provided. In the receiver, the received power control groups are analyzed and compared to several levels of energy thresholds (73, 75, 77, 79). The results of the comparisons are converted into a power control signal (74, 76, 78, 80, 81) and returned to the mobile. The mobiles are capable of selecting the appropriate bit (93) and adjusting their power (94). Alternatively, an indicator of the transmission rate can be forwarded (155) in advance of the frame. The receiver compares a power estimate with the threshold for the transmission rate indicated (166).

Method and apparatus for receiving a signal in a digital radio frequency communication system

Abstract: The apparatus includes a demodulator (70) responsive to a first received symbol (68) associated with a first transmitted symbol (39). The demodulator has a plurality of outputs (72) and produces a first set of outputs (99). The demodulator (70) is also responsive to a second received symbol (68) associated with a second transmitted symbol (39), and produces a second set of outputs (99). A coherent detector (100) receives some outputs from the first set of outputs (99), producing an estimate of the first transmitted symbol. The coherent detector also receives some outputs from the second set of outputs (99), producing an estimate of the second transmitted symbol. A first energy value (135) and an index (101) are associated with the first estimate, while a second energy value (135) is associated with the second estimate. A comparator (130), which determines an average of the first energy value (135) and the second energy value (135) to produce an average energy value (140), is responsive to the coherent detector (100). A first combiner (130) is responsive to the coherent detector (100), combining the index (101) and the first energy value (135) to produce a weighted index (131). A second combiner (133) is responsive to the coherent detector (100) and is also responsive to the first combiner (130), combining the weighted index (131) and the average energy value (135) to produce a channel-coded index (141). A deinterleaver (80) is responsive to the second combiner (133), receiving the channel-coded index (141).