Telefonaktiebolaget Lm Ericsson (publ)

Björn Forsberg

Gunnar Peters

Henrik Olson

Georg Mesko

Erik Nordhamn

Henrik Olsson

In a hardware accelerator for preamble detection of a Physical Random Access Channel (PRACH) in a CDMA based communication system, buffering means stores input samples received at an antenna at a first rate, addressing means read a predetermined consecutive number of the input samples in parallel at a second different rate. The hardware accelerator is further partitioned into a reusable unit providing code correlation, and a preamble detection dedicated unit providing signature code despreading. The reusable unit comprises means for correlating at least a subset of the previously read input samples with a predetermined code to provide a correlation output for a number of time lags. The preamble detection dedicated unit comprises means for preamble detection configured for providing Hadamard Transformation of the correlation output to enable preamble detection, and all means are arranged on a single hardware chip to enable high-speed data transmissions between the respective means.

Method and arrangement for preamble detection

A flexible and resource-efficient despreading-on-demand (DoD) technique is described where only channels that actually contain data to be despread are despread, and only a single despreading operation need be performed using the actual spreading factor associated with that data. In one example, the data portion of the received signal is buffered for a frame so that an associated transport format, including the actual spreading factor, can be determined before the data is despread. The data is buffered in a memory at a first rate and then subsequently read out at a second rate that is considerably faster than the first rate. The fast data read-out allows despreading at a high rate so that the despread data symbols from the buffered frame are available for further processing shortly after the last sample belonging to the frame has been received.

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Stockholm, Sweden

Björn Forsberg