Random access preamble coding for initiation of wireless mobile communications sessions
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Abstract
A wireless communications network, including a base station (10) and wireless units (UE), is disclosed. The wireless units (UE) request a connection with the base station (10) by the transmission of a preamble within time slots designated by the base station (10). The disclosed preambles are Walsh Hadamard code symbols, repeated a number of times so as to have the same length as a cell-specific scrambling code. The wireless unit (UE) requesting a connection pseudo-randomly selects a time slot from those available, and one of the Walsh Hadamard code symbols, replicates the code symbol into a spread interleaved bitstream, scrambles this bitstream and transmits it to the base station (10). Upon receipt, the base station (10) applies the incoming bitstream to a matched filter (98) to descramble the signal, following which the symbol is de-interleaved by way of a sequence of delay lines (100). Despreaders (102) generate each bit of the symbol from corresponding taps of the delay lines (100), and the symbol is applied to a correlator (104, 126, 136) to determine the transmitted preamble.
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Citations
45 Claims
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1-24. -24. (Canceled)
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25. A method of decoding a preamble, comprising the steps of:
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extracting a first number of groups of signals having a second number of signals in each group from a data stream having a predetermined length, wherein each group has a third number of subgroups;
applying one signal from each subgroup to each respective despreader circuit of a third number of despreader circuits, each despreader circuit producing a respective output signal; and
producing a first number of transforms from the output signal from each respective despreader circuit of each subgroup, each transform having the third number of signals. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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37. A method of decoding a data sequence having a group of signals repeated a predetermined number of times, comprising the steps of:
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applying one signal from each group to a respective despreader circuit of a plurality of despreader circuits, each despreader circuit of the plurality of despreader circuits producing a respective output signal; and
producing a first number of transforms from the output signal from each respective despreader circuit, each transform having a second number of signals. - View Dependent Claims (38, 39, 40, 41, 42, 43)
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44. A method of encoding a preamble, comprising the steps of:
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selecting a first code from a plurality of orthogonal codes;
repeating the first code a plurality of times to produce a sequence having a predetermined length; and
combining the sequence with a second code having the predetermined length. - View Dependent Claims (45)
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Specification