Brief Summary

From Figure 4-7 and Table 4-3, by using the proposed methods, FD-IQME, PEAM, the performance can increase to 19.16dB; by using the proposed methods, FD-IQME, PEAM and TD-AVM, the performance can increase to 22.25dB.

Compared with using only FD-IQME, about 10 dB of improvement is obtained. In the future, some digital signal processing (DSP) techniques such as linear regression can be used to reach higher IRR .

Figure 4-7 IRR, comparison of FD-IQME w/o jamming, FD-IQME with jamming, PEAM+ FD-IQME with jamming, and TD-AVM+PEAM+ FD-IQME with jamming.

Table 4-3 IRR, comparison of FD-IQME w/o jamming, FD-IQME with jamming, PEAM+ FD-IQME with jamming, and TD-AVM+PEAM+ FD-IQME with jamming.

Methods FD-IQME PEAM TD-AVM IRR (dB)

w/o CW Jamming

ˇˇˇ

ˇ 35.96

ˇˇˇ

ˇ 11.93

Chapter 5

Conclusions and Future Work

5.1 Conclusions

The currently existing methods which are evaluated seem to provide some resistance to CW jamming. However, a robust method for solving CW jamming is needed. Therefore, time-domain estimator for IQ mismatch with CW jamming is considered to evaluate. As mentioned in the Section 3, while the power of CW jamming is reduced once, the IRR will improve significantly. The proposed methods and the simulation results demonstrate this idea. This concept also can be applied to the time-domain estimator.

The main contribution for this paper is as follows. First, by making use of STF, one shot calculated algorithm is proposed to estimate IQM coefficients without too complicated computations. Second, by defining image-rejection-ratio (IRR), the simulation time can be effectively reduced to obtain estimated IQM coefficients.

5.2 Future Work

In this section, three works are suggested to solve in the future. First, a I/Q mismatch estimation in time domain is proposed to resist CW jamming. Second, a

accurate channel-estimation is needed. Finally, the hardware implementation is continued.

5.2.1 I/Q Mismatch Estimation in Time Domain

From time domain view, the amplitude of CW jamming covers the one of desired signal due to SJR equal to -10 dB. By reducing the power of CW jamming, the performance of estimating IQ mismatch will improve greatly. Some property of STF can be used to reduce the power of CW jamming. For many positions of STF are null subcarriers in the frequency domain. If CW jamming corrupted the signal, the values of these positions will become nonzero. However, these values are forced to set to ZERO and that will not destroy the original signal because the values of these positions do not include the values of the original transmitted signal. And then the results are transformed from frequency domain to time domain by IFFT. After that, the power of CW jamming is reduced mostly and makes little effects on the signal.

But this method needs a time-domain estimator for I/Q mismatch.

5.2.2 Channel Estimation

Although a smooth filter is used to resist CW jamming, the performance of IRR is not good enough. For I/Q estimation in frequency domain, the estimation of channel frequency response (CFR) also affects the estimation of IQM coefficients. If a rough value of estimated CFR cannot be compensated, IRR is always very low.

Therefore, an anti-jamming channel-estimation is needed.

5.2.3 Hardware Implementation

The FD-IQME algorithm of 4X4 MIMO-OFDM system will be performed by verilog and then tap out. Therefore, RTL coed, gate-level verification, and layout need

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