Sungdon Moon

Effects of fast frequency hopping multiple access systems due to the frequency and timing offset under Rayleigh fading

In order to investigate effects of fast frequency hopping multiple access (FHH-MA) systems due to the frequency and timing offset, we evaluate the bit error rate (BER) performance of the FFH-MA system using noncoherent M-ary frequency shift keying (FSK) modulation in the Rayleigh fading channel. While the frequency or timing offset increases at a given SNR, the BER is severely degraded. When the system is affected only by either of two offsets, and normalized offset is less than 0.3, the timing offset has a worse influence upon the FFH-MA system than the frequency offset. For the SNR of more than 20 dB, the threshold level of the receiver suffering from the frequency and timing offsets should be greater than that of the perfectly synchronized receivers.

Performance analysis of OMC-CDMA on two-ray multipath fading channels

Orthogonal multi-carrier-code division multiple access (OMC-CDMA) is a scheme that combines multi-carrier modulation with direct sequence-spread spectrum (DS-SS) and allows the efficient utilization of the bandwidth, the resistance against frequency selective fading in broadband mobile radio channels and the efficient implementation by the FFT algorithm. We analyze the bit error probability (BER) of OMC-CDMA on two-ray Rayleigh multipath fading channels and compare the BER performance of OMC-CDMA according to the number of users and subcarriers, attenuation factor of the delayed path, the delay time. We found that the attenuation factor of the delayed path is more sensitive to the BER of OMC-CDMA than the delay time.

Exact Closed-Form Performance Analysis of MFSK Demodulator Based on FFT

In this paper, we investigate the BER performance of M-ary FSK modulation system using FFT-based demodulator scheme. An explicit BER expression of the FFT demodulator scheme is analytically derived in terms of a closed form and compared with a typical demodulation scheme, the non-coherent detection method. In addition, in order to verify the derived results, the simulation results are together compared. It is noteworthy that the performance of M-ary FSK system with the FFT method is equal to that with non-coherent detection.

Performance comparison between FH-FDMA and FHMA systems under the worst case band multitone jamming

The bit error rate (BER) performance of a fast frequency-hopped (FH) frequency division multiple access (FDMA) system is evaluated under the environment with band multitone jamming (MTJ), with the clipper receiver and the normalized envelope detection (NED) receiver as combining alternatives. As the number of groups increases at the cost of system complexity, eventually becoming a FHMA system, the worst case performance of FH-FDMA with the clipper receiver is gradually improved, while that of the NED receiver is hardly improved when SJR is less than 10 dB. Although the clipper receiver has a practical disadvantage because the clipping level depends on measurements of the signal output energy, the FHMA system with the clipper receiver can be an effective solution among the FH-FDMA systems in the presence of worst case band MTJ if a clipping level can be feasibly set.