Abstract:
A demodulator such as a Fast Hadamard Transform (FHT) based demodulator is used to demodulate all channels in a code space with code length equal to the data channel code. Since the codes for overhead control channels are usually longer, the control channel data is only partially uncovered. Once the necessary further processing is performed and the information to fully uncover the control channels is available, the control channel data is fully demodulated. By only processing one partially uncovered secondary control channel, the present invention reduces the implementation complexity. A hardware implementation of the above method, requires fewer data processing operations, and reduces data processing delays, resulting in lower power consumption.
Abstract:
A sleep control system and method are provided that permit a reference clock and the direct sequence spread spectrum (DSSS) modem in a mobile station receiver to be turned off and turned back on at arbitrary points in time while still maintaining accurate base station system time. Accurate timing is made possible through a number of techniques including precise initial calibration using a rising edge/falling edge averaging system, determining the sleep clock and reference clock frequencies, and the determination of the frequency drift of the sleep clock that occurred during the previous sleep interval.
Abstract:
A CDMA receiver (500) minimizes the use of hardware by taking advantage of the fact that Walsh sequences of a predetermined length (e.g., 16) are comprised of inverted and non-inverted versions of smaller length (e.g., 4) sequences. The receiver (500) performs the necessary uncovering operations for example of a Walsh sequence of length 16 by performing uncovering operations using smaller length Walsh sequences such as of length 4 and then performing subsequent summing operations with inverted and non-inverted versions of the results of such uncovering operations.
Abstract:
System and method for decoding punctured subframes. A preferred embodiment comprises a first deinterleaver unit (for example, 5-ms deinterleaver 502) and a second deinterleaver unit (for example, 20-ms deinterleaver 504) operating in parallel, deinterleaving one symbol stream using 5- and 20-ms duration frame formats, for example. After the reception of each 5-ms subframe, the subframe is decoded in a decode unit (for example, rate matching, decoding, and CRC checking (RDC) unit 530) to verify that the subframe contains 5 ms duration frame data. If so, the subframe is noted. If all 5-ms subframes in a 20-ms duration frame contain 5-ms duration data, no decoding of results by the second deinterleaver unit is needed. If the entire 20-ms duration frame is not all 5-ms duration data, then the 5-ms duration data subframes are zeroed and the remaining data is decoded as 20-ms duration data.
Abstract:
This disclosure is generally directed to communication systems, devices used in communication systems and associated methods which may implement parallel hypothesis search techniques. The disclosed parallel hypothesis search techniques may permit a hypothesis to be dismissed early (i.e., before hypotheses in other searchers have completed their evaluation). Early hypothesis dismissal permits a new hypothesis to be loaded into the searcher while other searchers advantageously continue to evaluate their hypotheses.
Abstract:
A signal filter employs digital control signals to selectively establish and adjust analog impedance components of the filter. In the case of a first-order R-C filter, adjustable resistance and reactance assemblies are coupled in series. The resistance assembly has multiple parallel signal paths sharing a common input and output. Each signal path includes a prescribed electrical resistance and a digital switch to selectively enable and disable the resistance. Between the common input and output, the signal paths provide a collective resistance which varies depending upon which switches have been activated. The reactance assembly is similar to the resistance assembly, with capacitors or inductors instead of resistors. A digital controller selectively activates the switches to adjust the assemblies' respective resistance and reactance.
Abstract:
A method of generating one or more pseudorandom noise (PN) sequences for use in spread spectrum communications includes the steps of providing data at an input of memory which stores bits associated with a pseudorandom noise (PN) sequence: changing the data; and for each of a plurality of changes of the data, providing a selected PN bit of the PN sequence at an output of the memory based on the data.
Abstract:
A method and system for processing the results of searches for signals in a direct sequence spread spectrum communications system in an intelligent and efficient manner. A preferred embodiment comprises a search engine (for example, search engine 405) and a hardware result processor (for example, result processor 410) with a memory (for example, memory 415) as an interface. The search engine may perform multiple correlations of a pilot channel and then writes the correlation results exceeding a specified threshold to the memory. The result processor reads the correlation results from the memory and performs result filtering and builds a list of maximum value correlation results. The result processor and the search engine functions with independence from one another therefore, there is therefore, little wasted overhead where one has to wait for the other. The result filtering also makes it simpler to combine signal multipaths and simplifies pilot channel strength comparisons.
Abstract:
Methods and apparatus for use in generating data sequences for direct sequence spread spectrum (DSSS) communications are described. One exemplary method includes the steps of serially generating a pseudo random noise (PN) sequence by, for each count value i of a plurality of count values, retrieving from memory a bit of the PN sequence corresponding to the (i)th position in the PN sequence. The exemplary method includes the further steps of serially generating a Gold code sequence by, for each count value i of the plurality of count values, retrieving from memory a bit of the PN sequence corresponding to the (i+n)th position in the PN sequence, retrieving from memory a bit of the PN sequence corresponding to the (q*i)th position in the PN sequence, and adding the bit corresponding to the (i+n)th position with the bit corresponding to the (q*i)th position.
Abstract:
A Direct Sequence Spread Spectrum (DSSS) receiver system (100) combines and orders the soft symbols from associated information channels. The system permits a QPSK channel to be demodulated as a pair of BPSK channels, and the soft symbols of the demodulated BPSK channels to be multiplexed into a single information channel. The receiver system (100) includes a plurality of demodulating fingers (102–106). Each demodulating finger accepts modulation parameters and a sample stream, while supplying soft symbols with indexing information so that information channels can be subsequently multiplexed into a single information channel. A method for ordering the soft symbols of associated information channels in a DSSS system is also provided.