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.
48 Citations
67 Claims
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1-45. -45. (canceled)
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46. A communication circuit, comprising:
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a first circuit coupled to receive a first plurality of repetitions of a first code having a length, the first code selected from a plurality of orthogonal codes; and a multiplier circuit coupled to receive the first plurality of repetitions of a first code and a second code having the length, the multiplier circuit producing a product of the first plurality of repetitions of a first code and the second code. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53)
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54. A method of communicating with a remote device, 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 length; combining the sequence with a second code having the length; and transmitting the sequence to the remote device. - View Dependent Claims (55, 56, 57, 58, 59, 60, 61)
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62. A method of operating a wireless communications unit to request a connection with a remote device, comprising the steps of:
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receiving a signal indicating at least one time slot within which a preamble may be transmitted by the wireless communications unit; selecting one of a plurality of orthogonal codes for the preamble; generating a spread code using the selected orthogonal code repeated a selected number of repetitions; multiplying the spread code by a scrambling code associated with the remote device, wherein the spread code has a length equal to a length of the scrambling code; and transmitting, to the remote device, a preamble signal corresponding to the multiplied spread code. - View Dependent Claims (63, 64, 65, 66, 67)
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Specification