Random access in a mobile telecommunications system
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorBranislav M. Popovic
Life of this patent
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Abstract
For one embodiment, a Random Access Channel (RACH) preamble modulation method and apparatus are disclosed in which the real and imaginary components of a complex RACH preamble are filtered in corresponding pulse shaping filters. Consequently, the phase transitions in the resulting signal are limited at all chip positions, and the resulting quadriphase codes produce transmitted signals with lower Peak-to-Average Power Ratios (PAPRs) than those that result using conventional Hybrid Phase-Shift Keying (HPSK) modulation schemes. On the other side, the resulting quadriphase synchronization code retains the same aperiodic autocorrelation magnitude as the original binary code, optimized to produce the minimum probability of incorrect synchronization.
Claims34
A method for modulating at least a portion of a synchronization signal in a mobile communication system, comprising the steps of:
- multiplying said at least a portion of said synchronization signal by a constant complex signal to produce a second complex signal;
- multiplying said second complex signal by a sequence of real and imaginary values to produce a phase rotation of said second complex signal;
- and
- filtering said phase rotation of said second complex signal.
A method for demodulating at least a portion of a synchronization signal in a mobile communication system, comprising the steps of:
- down-converting said at least a portion of said synchronization signal to produce a plurality of real and imaginary components of a complex signal;
- filtering said plurality of real and imaginary components of said complex signal to produce a second plurality of real and imaginary components of said complex signal;
- phase de-rotating said second plurality of real and imaginary components of said complex signal to produce a plurality of phase de-rotated real and imaginary components of said complex signal;
- and
- correlating said plurality of phase de-rotated real and imaginary components of said complex signal with a complex conjugate of a transmitted complex preamble to produce a complex correlated signal.
An apparatus for modulating at least a portion of a synchronization signal in a mobile communication system, comprising:
- a first multiplier stage for multiplying said at least a portion of said synchronization signal by a constant complex signal to produce a second complex signal;
- a second multiplier stage coupled to said first multiplier stage, for multiplying said second complex signal by a sequence of real and imaginary values to produce a phase rotation of said second complex signal;
- and
- a plurality of filters, each filter of said plurality of filters coupled to a respective multiplier component of said second multiplier stage, for filtering said phase rotation of said second complex signal.
An apparatus for demodulating at least a portion of a synchronization signal in a mobile communication system, comprising:
- a down-converter stage for down-converting said at least a portion of said synchronization signal to produce a plurality of real and imaginary components of a complex signal;
- a filter stage coupled to said down-converter stage, for filtering said plurality of real and imaginary components of said complex signal to produce a second plurality of real and imaginary components of said complex signal;
- a phase de-rotation stage coupled to said filter stage, for phase de-rotating said second plurality of real and imaginary components of said complex signal to produce a plurality of phase de-rotated real and imaginary components of said complex signal;
- and
- a correlating stage coupled to said phase de-rotation stage, for correlating said plurality of phase de-rotated real and imaginary components of said complex signal with a complex conjugate of a transmitted complex preamble to produce a complex correlated signal.
In a radio communications system having a modulator unit and a demodulator unit, a method of modulating or demodulating at least a portion of a synchronization signal, the method comprising:
- multiplying said at least a portion of said synchronization signal by a constant complex signal to produce a second complex signal;
- multiplying said second complex signal by a sequence of real and imaginary values to produce a phase rotation of said second complex signal;
- and
- filtering said phase rotation of said second complex signal.
Dependencies are inferred from the claim text.