A realization structure and realization method of prach baseband signal generation

Abstract

The invention discloses an implementation structure and method of PRACH (Physical Random Access Channel) baseband signal generation. The structure is an FPGA structure comprising a DFT (Discrete Fourier Transform) implementation structure and an IDFT (Inverse Discrete Fourier Transform) implementation structure, the DFT implementation structure comprises a read-only memory ROM1, an ROM2, an ROM3,a first phase index number calculation module, a second phase index number calculation module, a first adder, a modulo module and a multiplier, and the inputs of the read only memory ROM1, the ROM2 and the ROM3 are all read addresses; and the IDFT implementation structure comprises an enable module, a secondary read only memory ROM1, a secondary ROM2, a secondary first phase index number calculation module, a secondary second phase index number calculation module, a secondary first multiplier, an IFFT operation module and a secondary second multiplier, the enable module comprises a second counter, a random access memory RAM, and the inputs of the RAM, the secondary ROM1 and the secondary ROM2 are all read addresses. The particularity of a ZC sequence is fully utilized during DFT calculation, and the characteristics that an input signal has a large number of zero values are fully utilized during IDFT calculation, so that the calculation of the DFT and the IDFT in a signal generation process is simplified, thereby simplifying the entire signal generation process.

Description

technical field [0001] The present invention relates to the field of communications, in particular to a realization structure and method for generating a PRACH (Physical Random Access Channel, Physical Random Access Channel) baseband signal. Background technique [0002] In the LTE protocol, the time-continuous random access signal s(t) on the PRACH channel is defined by the following formula: [0003] [0004] Where t represents time, 0≤t<T SEQ +T CP ,T SEQ , T CP The value is related to the preamble format, see Table 1. k 0 Indicates the starting position of the RB occupied by the PRACH, k indicates the RB index within the occupied bandwidth, K indicates the subcarrier spacing difference between the random access preamble and the uplink data, β PRACH Indicates the PRACH signal transmission power coefficient, n indicates the ZC sequence index, T CP Indicates the length of the cyclic prefix, f RA Indicates the random access subcarrier spacing, Indicates the f...

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Problems solved by technology

[0030] DFT / IDFT transformation is a very complicated operation. When the formula is directly used for transformation, the amount of complex multiplication operation is proportional to the square of the number of points. Therefore, the DFT / IDFT transformation of the above-mentioned points, especially the DFT / IDFT transformation of the format 0--3, is not suitable for direct calculation. , using the DFT / IDFT transformation fast algorithm Cooley-Tukey algorithm can greatly reduce the calculation amount of DFT / IDFT transformation, but the Cooley-Tukey algorithm is a fast algorithm for general signal DFT / IDFT transformation , if the algorithm is used directly when generating the baseband signal of the PRACH channel, the particularity of the ZC sequence is not fully utilized; and the DFT operation is a prime point DFT operation (839 points or 139 points), it is not suitable to use Cooley Tukey (cooley- tukey) algorithm to decompose; IDFT is 24576 points in format 0--3, and 4096 points in format 4, especially in format 0--3, it is a large-point IDFT operation, using cooley-tukey (cooley-tukey) The algorithm still has a lot of computation

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