Digital communications: fundamentals and applications
Digital communications: fundamentals and applications
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the main issue of symbol synchronization in Zigbee modem is how to find low cost and low complexity synchronization method for Zigbee application. The traditional method is too complex for low cost Zigbee modem. So this paper introduces extremely low complexity symbol synchronization method named direct sample level compensation (DSLC). DSLC does not use band-pass filter, correlator, VCO as traditional symbol synchronization method. DSLC doesn't perform phase tracking. DSLC just estimates frequency offset during preamble period and compensates frequency offset on incoming signal samples. The frequency estimation performs through differential complex conjugated multiplication between incoming sample and delayed sample. This differential style receiver is common for non-coherent detection of Zigbee signal. Thus frequency-offset estimation doesn't need any additive component except receiver itself. Compensation is performed by one sample adding or discarding. This direct sample level compensation can be realized with 1-2 register for a control of samples and simple look-up table for determine control point. If we accept slight performance degradation compare to perfect symbol synchronization, this method would be best choice for Zigbee modem.