Gen Marubayashi

Performance evaluation of parallel combinatory SSMA systems in Rayleigh fading channel

The multiple access performance of parallel combinatory spread spectrum (PC/SS) communication systems in Rayleigh fading channel is studied. The PC/SS system has the high-speed data transmission capability by transmitting multiple pseudo-noise sequences out of the pre-assigned sequence set. The performance is evaluated in terms of average bit error rate by numerical computation. Focus is put on the frequency-nonselective, slowly fading channel. It is found that the multiple access performance of the PC/SS system including diversity is superior to that of conventional direct-sequence spread spectrum systems. Applying Reed-Solomon coding to the PC/SS system improves of the multiple access performance.<<ETX>>

Studies on Fundamental Properties of MMFSK Systems

To compare the transmission system suitability for power-line communications the spectral efficiency and the required transmission power are two important fundamental factors. In this paper these two factors are studied for our proposed MMFSK (M-ary multilevel FSK) system. Spectral efficiency eta of MMFSK system is a function of number of frequency levels n, number of time chips L, number of hopping patterns h. An equation connecting eta and n, L, h is derived and quantitative relationships between these parameters are studied. As a comparison spectral efficiency of existing systems such as OFDM, MFSK, multilevel FSK are also shown. Results show that compared to ordinary OFDM systems one tenth of spectral efficiency can be achieved by the proposed system which may not be attained by the other systems. The required transmission power for a fixed error rate directly relates to the radiation power. To obtain the required transmission power, relation between error rates and signal to noise ratio should be clarified. Transmission feature between the output of the transmitter and the input of the receiver for MMFSK is same as that for MFSK and the symbol error probability at the receiver input is same. Difference in bit error rate comes from difference of symbol to bit transformation process. A consideration on the relation between bit error probability and symbol error probability in MMFSK is given and a formula representing worst case probability of bit error is derived. A comparison between the worst case bit error probability and the bit error probability obtained by a simulation is shown. Using these results it is cleared that the radiation power of MMFSK is 20~50 times smaller than that of OFDM.

Extended even-odd discrimination method of hopping pattern synthesis for MMFSK power-line transmission system

Transmission capacity of the MMFSK frequency hopping system (FH/M-ary multilevel FSK system) is largely dependent on the number of frequency hopping patterns available. Increase the number of hopping patterns with small size circuit and less error probability is the most important problem to realize the system. In this paper to solve the problem a novel frequency hopping pattern synthesis modulation system is proposed. Principle of the new system is an extension of the even-odd discrimination method previously proposed to more than three hopping pattern groups. Realizability of the MMFSK system is greatly enhanced by the new modulation system.

Performance of differential multiphase parallel combinatory spread spectrum communication systems

This paper presents the performance of differential multiphase parallel combinatory spread spectrum (DMPC/SS) communication systems. In the PC/SS system, multiple pseudo-noise (PN) sequences are simultaneously transmitted out of a pre-assigned spreading sequence set. In the proposed systems, q-ary DPSK is applied to the states of each simultaneously transmitting PN sequences. The symbol error rate and average bit error rate are calculated to evaluate the performance of the proposed PC/SS systems. It is found that the 4-ary DMPC/SS system gives a superior performance compared with the conventional DPC/SS system if the number of assigned PN sequence and information bit rate are constant.

Error Rate Simulation for a MMFSK System Using Even-Odd Discrimination Method

Error rate simulations under AWGN environment are made for a MMFSK (M-ary multilevel FSK) system, which use a novel hopping pattern synthesis method named even-odd discrimination method. There can be found great many number of systems for a MMFSK system using even-odd discrimination method depending on the system parameters such as number of chips, number of levels, and the selection of basic hopping pattern configurations however in this paper as a typical example 6 chips, 16 levels, and 8 hopping patterns for each group A and B are assumed. Through the course of computer simulations comparisons are made between direct input and soft decision, hard decision methods results show the effectiveness of these decision methods. Results of error rate simulation show the effectiveness of proposed system

Performance of parallel combinatorial CDMA systems with side information

This paper investigates the effects of using error-and-erasure decoding in coded parallel combinatorial spread spectrum (PC/SS) systems over Rayleigh fading channels. The PC/SS system is an advanced multi-code direct sequence spread spectrum system for high-speed data transmission. Our previous works have shown that the Reed-Solomon (RS) coded PC/SS systems provide significant improvement in error rate performance over conventional DS/SS systems. To achieve further performance improvement in the PC/SS systems, error-and-erasure decoding techniques are implemented in the RS coded PC/SS receiver. To obtain the erasure location information, a threshold for the signal-to-noise ratio is set at the correlator output. Numerical results show that the coded PC/SS systems with error-and-erasure decoding provides significant improvement in the bit error rate (BER). With errors-only decoding, the PC/SS systems cannot improve the error rate performance because of large SNR penalty introduced by coding. On the contrary, error-and erasure decoding still improves the performance of PC/SS systems under multiple access environment.

Performance of differential parallel combinatorial CDMA systems in Rayleigh fading channels

This paper investigates the error rate performance of a multi-code DS/CDMA systems using the combination of PN codes and DPSK: differential parallel combinatorial code-division multiple access (DPC/CDMA) systems in Rayleigh fading channels. The bit error rate (BER) are calculated based on the average SNR with the standard Gaussian approximation of the multiple access interference. It is assumed that the explicit and implicit diversity are employed in the receiver. The BER performance of uncoded and coded DPC/CDMA systems are presented, and are compared pared with that of conventional DPSK-DS/CDMA systems.

MMFSK-EOD System Using Binary Hopping Pattern in FH/SS Communications

In this paper a detailed explanation of our newly proposed frequency hopped spread spectrum system named “MMFSK-EOD System Using Binary Hopping Pattern” is presented. First, to make clear the concept of FH/M-ary Multilevel FSK modulation (abb. FH/ MMFSK or MMFSK), the waveform and the spectrum differences between MFSK and FH/MFSK or FH/MMFSK are reviewed. Next, to understand the error propagation phenomena from the first demodulation stage to the second demodulation stage, system principle of FH/MMFSK using EOD is explained of some length. In an EOD system, a hopping pattern is synthesized from a group A hopping pattern and a group B hopping pattern, which are different properties on even and odd levels. Finally, to prevent the error propagation novel binary hopping pattern method is proposed, and its effectiveness on improving error performance is shown by illustrative computer simulations. Some additional improving method in the design of group A hopping pattern are also shown.

MMFSK-EOD system using binary hopping patterns

In power-line communications reduction of the radiation power is becoming one of the most important problems. In our previous paper, advantage of the spread spectrum system over OFDM system in the radiation power was shown. In this paper, to reduce the radiation power further, improving methods of error performances of the MMFSK-EOD system (MMFSK system using even odd discrimination method) have been studied. In our old MMFSK-EOD system we specify even- odd patterns (EO patterns) only for Group A hopping patterns. However, when we use a hopping pattern in which even numbers and odd numbers are chosen freely, errors arisen in the first demodulation stage, which select the transmitted A hopping pattern out of group A hopping patterns , influence the second demodulation stage operation and deteriorate the error probability characteristics of the system considerably. To improve the error performance of the system, in this paper use of a new category hopping patterns named binary hopping patterns is proposed. Binary hopping patterns are defined as a hopping pattern group in which E and O represent one of specified neighboring level values. In the second demodulation stage, majority decision logic is used to determine the transmitted hopping pattern Bj and the level Lh. When binary hopping patterns are used, errors arisen from the first demodulation stage can be removed through the majority decision logic, as a result, the error probability characteristics of the system can be considerably improved. In this paper, principle of the improving effect of the binary hopping pattern system is presented, and, to verify the effectiveness the system a result of computer simulation is shown. Some other additional results of studies to improve the error performance of the MMFSK-EOD systems are shown also.