Hybrid Cramer-Rao Bound On Carrier And Sampling Frequency Offset Estimation For OFDM Systems In Rayleigh Fading Channels

For carrier frequency offset (CFO) and sampling (clock) frequency offset (SFO) estimation, the hybrid Cramer-Rao bound (HCRB) is developed when the CFO, SFO, information-bearing symbols are deterministic (non-random) and channel coefficients are random. Both noise and channel coefficients are complex Gaussian. For the HCRB to be applicable, it is necessary for deterministic parameters to be identifiable (uniquely determined). Some necessary identifiability conditions of some deterministic parameters are found and presented. The HCRB is dependent on the initial time instant. The HCRB is compared with some existing methods via simulation. Our results demonstrate that this bound is not tight enough. Further effort is needed to develop a tighter bound.

Analysis of synchronous interpolated signals in Tactical Sensor Network-Visible light communication (TSN-VLC) link

Sampling frequency offset (SFO) is an important issue in the tactical sensor network (TSN) based visible light communication (VLC) systems in Tactical Sensor Network. A digital interpolation can be used to effectively compensate the SFO. In such case, oversampling at the receiver ADC is required to mitigate the aliasing effect due to imperfect DACs and nonlinearity of visible light sources that cause extra frequency components inside/outside the signal spectrum. The oversampling factor is mainly determined by the order of the digital interpolation filter and TSN links. The design of the TSN-VLC receiver incorporating the digital interpolation filter is vital as it affects not only the transmission performance but also the complexity of signal processing. To evaluate the feasibility of the digital interpolation-based SFO compensation schemes for cost-sensitive TSN applications. Based on the real-time VLC tactical sensor network, the comparison in the VLC-TSN transmission performance and DSP complexity between different interpolation-based SFO compensation schemes is analyzed.