Jeungmin Joo

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.

Effects of timing jitter in low-band DS-BPSK UWB system under Nakagami-M fading channels

The effects of timing jitter in direct sequence binary phase shift keying (DS-BPSK) ultra wideband (UWB) systems applying the FCC-constraint pulses are investigated under at Nakagami-m fading channel and additive white Gaussian noise (AWGN). The numerical results show that two FCC-constraint pulses, Low band (LB)-PSP and LB-MMNHP, have almost same sensitivity to the timing jitter even though they have different transceiver complexity. Additionally, the additional power caused by the timing jitter exponentially increases, but the additional power caused by the amplitude fading is not exceeded over 7 dB.

Detection of an Unknown FH Signal Using Scanning Receiver and DF Receiver in Practical Environments

This paper proposed a detection process of effectively detecting an unknown frequency hopping signal in practical environments. For the detection process, the scanning receiver and direction finding receiver are used, and the frequency histogram, azimuth histogram and frequency versus azimuth diagram analyses are performed. The simulation results show that an unknown frequency hopping signal can be successfully extracted by the proposed detection process in practical environments.

Analysis of asynchronous FFH-MA systems with a hard-limited combining in Rayleigh fading

The bit error rate (BER) performance of the asynchronous fast frequency hopping multiple access (AFFH-MA) system with multiple hops per symbol is investigated considering the noncoherent M-ary frequency shift keying (MFSK) modulation and hard-limited linear combiner in Rayleigh fading. We present a method for the accurate evaluation of the BER of the AFFH-MA system, and verify the analytic works by Monte Carlo simulations.

Performance Analysis of Asynchronous FFH-MA Systems with a Linear-Combining Receiver in Rayleigh Fading

The performance of asynchronous fast frequency hopping-multiple access (AFPH-MA) systems with multiple hops per bit is investigated with a linear-combining receiver in Rayleigh fading. We present an accurate approximation method for evaluating the error probability by using the characteristic function, Taylor series, and Gauss-Chebyshev quadrature rule. We will show that the proposed method provides an accurate approximation, compared with a simple Gaussian approximation. The validity of proposed analytic works is verified through Monte Carlo simulations.

Effects of Frequency and Timing Offsets on the FFH-MA System Over a Rician Fading Channel

The bit error rate (BER) degradations of fast frequency hopping multiple access (FFH-MA) systems due to the frequency and timing offsets are investigated over a Rician fading channel. It is shown that as the received average SNR increases, the BER is affected much larger by frequency and timing offsets. When the frequency offset or the timing offset exists alone, the BER of the FFH-MA system is degraded much more due to the timing offset than due to the frequency offset. The BER degradation due to both the frequency offset and the timing offset is larger than the sum of the degradations due to each offset.

Performance analysis of asynchronous FFH-SSMA communication systems with frequency errors in Rayleigh fading channels

We derive expressions for the bit error rate (BER) for an asynchronous FFH-SSMA system using a Markov hopping pattern and consider the occurrence of all possible hits by multiple interfering users for outdoor radio communications. The modulation scheme considered is the noncoherent M-ary frequency shift-keying (MFSK) with a threshold level, which is selected properly depending on channel and system conditions. The outdoor environment is described as the Rayleigh fading channel with an RMS delay spread of 10 to 25 /spl mu/s. The normalized frequency error of 0.4 requires about 6 dB additional SNR compared with the perfect frequency synchronized case at BER=10/sup -3/.