This paper presents a mathematical design of a CEM (Constant Envelope Multiplexing) scheme for three equal power signals to achieve any target CEM power efficiency. The proposed scheme assumes that the chip pulses have one or two sample magnitude values. The design method and the results can be applied to a new satellite navigation system such as KPS (Korea Positioning System.)

This paper proposes noise reduction methods to improve the channel estimation performance in terrestrial-digital multimedia broadcasting (T-DMB) receivers. In the T-DMB, the channel estimation is performed by the pilot signal extraction and the channel coefficient estimation. Since the performance of the channel estimation highly depends on the estimated channel coefficients whose accuracy is associated with the received signal-to-noise ratio (SNR), it is important to reduce noise existing at the estimated channel coefficients. To reduce such noise components, various noise reduction methods of the estimated channel coefficients based on the Ad-point weighted moving average are proposed. Computer simulations show that the proposed methods improve the estimation performance by more than 2 to 3 dB in terms of the symbol error rate after equalization.

A simple algorithm is proposed for carrier frequency synchronization after PN code acquisition using FFT (fast Fourier transform) in a direct-sequence code division multiple access mobile satellite communications system. The proposed algorithm shows almost the same performance as the phase differential algorithm under additive white Gaussian noise channel environments. The proposed algorithm, however, largely reduces hardware complexity when a two-dimensional search algorithm is employed for PN code timing acquisition and coarse Doppler shift compensation since the proposed algorithm shares the FFT operator with the two-dimensional search.

Uncoded antijamming capability of the multicarrier direct-sequence spread-spectrum system proposed by Kondo and Milstein (see ibid. vol.44, p.238-46, 1996 ) is analyzed. Joint pulse/partial-band noise jamming is considered with various subcarrier demodulator output combining schemes. We find that full-band pulse jamming maximizes the error probability for all cases considered. With Rayleigh fading and maximal-ratio combining, the multicarrier system achieves performance very close to that of the single-carrier system without fading even with a very small number of subcarriers.