A RAKE receiver is a final receiver that separates multipath signals and efficiently combines the energy of multipath signals.
RAKE receiving technology is an important technology in the third generation CDMA mobile communication system. In the CDMA mobile communication system, due to the wide signal bandwidth, there are complex multipath radio signals, and communication is affected by multipath fading. The RAKE receiving technology is actually a multipath diversity receiving technology, which can distinguish fine multipath signals in time, and weight-modulate these resolved multipath signals to form a strengthened signal. Since the transversal filter in the receiver has a saw-like tap like a dice, the receiver is called a RAKE receiver.
In mobile communication systems, the receiver requires an equalizer to eliminate interference between adjacent symbols due to multipath propagation. Since the spread spectrum system adopts a spread spectrum sequence with good autocorrelation characteristics, as long as the correlation delay of the multipath component is larger than the chip interval, the interference caused by the multipath propagation is only multipath interference, and does not affect the demodulation of the signal. Therefore, the spread spectrum communication system does not require an equalizer. At the same time, due to the error judgment of the receiver in each depth fading, the performance of the system is degraded. Therefore, the spread spectrum communication system should adopt the RAKE receiving technology of multipath diversity to improve the performance of the system.
The RAKE receiving technology is actually a multipath diversity receiving technology, which can distinguish fine multipath signals in time, and weight-modulate these resolved multipath signals to form a strengthened signal. With this feature, the RAKE receiver can achieve diversity reception, achieving anti-multipath interference and anti-fading.
Advantages: Rake receiver achieves multipath diversity reception, overcomes multiple path effects, and improves acceptance performance. At the same time, it is very resistant to fast fading. The more the multipath diversity path, the better the effect of resisting fading.
Disadvantages: Rake achieves the control of branching data due to the data of multiple antennas, which increases the complexity of baseband processing. Moreover, the algorithm for multi-user Rake receiver bit error rate is more complicated and needs further improvement.
In view of the advantages and disadvantages of the above Rake receivers, the complexity of the application is still being improved. The research hotspots include : how to reduce the complexity of the RAKE receiver; the optimal algorithm for multi-user detection; the MIMO system and The combination of OFDM and the like.
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