Apparatus for reception and detection of random access channel (RACH) data
An apparatus for reception and detection of RACH data in an LTE input signal includes a hardware accelerator that has a decimator that filters and down-samples the input signal, a first Fourier transform circuit that transforms the decimated signal from the time domain to the frequency domain, and a second transform circuit that multiplies the resulting signal by a complex Z-C sequence and performs an inverse Fourier transform (iFT) operation to transform the multiplied signal from the frequency domain to the time domain. A DSP performs a delay profile analysis operation on the signal resulting from the iFT operation.
1. An apparatus for reception and detection of random access channel (RACH) data in an input signal, comprising:
a random access memory (RAM) that stores the input signal;
a direct memory access (DMA) coupled to the RAM;
a hardware accelerator that receives the stored signal from the DMA, wherein the hardware accelerator has (i) a decimator that filters and down-samples the input signal, (ii) a first transformer that performs a Fourier transform (FT) operation that transforms the decimated signal from the time domain to the frequency domain, (iii) a second transformer that multiplies a resulting frequency domain signal by a complex reference sequence and performs an inverse Fourier transform (iFT) operation that transforms the multiplied signal from the frequency domain to the time domain, and (iv) an interface that buffers the frequency domain decimated signal and provides the buffered frequency domain signal to the second transformer; and
a digital signal processor (DSP) that performs a delay profile analysis operation on a signal resulting from the iFT operation,
wherein the delay profile analysis is used to access a wireless network.
2. The apparatus of claim 1 , wherein the first transformer also removes guard intervals from the frequency domain decimated signal.
3. The apparatus of claim 1 , wherein the second transformer multiplies the frequency domain decimated signal by the complex conjugate of a RACH Zadoff-Chu (Z-C) reference sequence.
4. The apparatus of claim 1 , wherein the second transformer includes:
a multiplier that multiplies the frequency domain decimated signal by the complex reference sequence; and
an iFT module that performs the iFT operation on the multiplied signal.
5. The apparatus of claim 1 , wherein the DSP includes an interface that buffers the time domain signal resulting from the iFT operation, wherein the buffered time domain signal is used by the DSP for the delay profile analysis operation.
6. The apparatus of claim 1 , wherein the hardware accelerator and the DSP are integrated in a common single semiconductor chip.
7. An apparatus for reception and detection of random access channel (RACH) data in an input signal, comprising:
a memory that stores the input signal;
a direct memory access (DMA), coupled to the memory, that accesses the stored signal;
a hardware accelerator coupled to the DMA for receiving the stored input signal, wherein the hardware accelerator includes:
a decimator that performs a finite impulse response (FIR) filter and down-sample operation on the stored input signal,
a first transformer that performs a Fourier transform (FT) operation to transform the decimated signal from the time domain to the frequency domain,
an interface that buffers the frequency domain decimated signal, and
a second transformer that multiplies the buffered decimated frequency domain signal by a complex reference sequence and performs an inverse Fourier transform (iFT) operation to transform the multiplied signal from the frequency domain to the time domain; and
a digital signal processor (DSP) that performs delay profile analysis on the time domain signal resulting from the iFT operation, wherein the delay profile analysis is used to perform at least one of: (i) access a wireless network when the apparatus loses synchronization to the network, (ii) request radio resources, (iii) carry control information and reference signals for time offset and adjusting transmit power, (iv) transmit small amounts of data over the network, and (v) facilitate contention resolution when more than one apparatus attempt to access a same node simultaneously.
8. The apparatus of claim 7 , wherein the first transformer also removes guard intervals from the frequency domain filtered signal.
9. The apparatus of claim 7 , wherein the second transformer multiplies the frequency domain decimated signal by the complex conjugate of a RACH Zadoff-Chu (Z-C) reference sequence.
10. The apparatus of claim 7 , wherein the second transformer includes:
a multiplier that multiplies the frequency domain decimated signal by the complex reference sequence; and
an iFT module that performs the iFT operation on the multiplied signal.
11. The apparatus of claim 7 , wherein the DSP includes an interface that buffers the time domain signal resulting from the iFT operation and provides the buffered time domain signal to the DSP for the delay profile analysis operation.
12. The apparatus of claim 7 , wherein the hardware accelerator and the DSP are integrated in a common single semiconductor chip.
13. The apparatus of claim 7 , wherein:
the input signal has a physical uplink shared channel (PUSCH),
the hardware accelerator performs a fast Fourier transform (FFT) operation on PUSCH data at a common rate for operation of the decimator and the PUSCH FFT, and
the DMA fetches the RACH data from the RACH decimator for the PUSCH data FFT.