Tsuyoshi Arai

Performance evaluation of the M-ary/SSMA ALOHA system with CLSP

The M-ary spread spectrum multiple access (M-ary/SSMA) ALOHA system applying channel load sensing protocol (CLSP) as the traffic control is evaluated by a theoretical analysis. In particular, the throughput performance and the delay property of the M-ary/SSMA slotted ALOHA system with CLSP under additive white Gaussian noise are analyzed. Moreover, the M-ary/SSMA slotted ALOHA system with CLSP is compared with the conventional direct sequence spread spectrum multiple access (DS/SSMA) slotted ALOHA system with CLSP. As a result, it is shown that the CLSP improves the performance of the M-ary/SSMA slotted ALOHA system. The M-ary/SSMA slotted ALOHA system with CLSP is superior to the conventional DS/SSMA slotted ALOHA system with CLSP.

A comparison of the M-ary/SSMA ALOHA system and the DS/SSMA ALOHA system

A comparison of the M-ary spread spectrum multiple access (M-ary/SSMA) ALOHA system and the direct sequence spread spectrum multiple access (DS/SSMA) slotted ALOHA system is evaluated when using the channel load sensing protocol (CLSP) as the traffic control. In particular, the throughput performance and the delay property of the both systems under additive white Gaussian noise and Rayleigh fading are derived. As a result, it is shown that the CLSP takes effect to improve the system performance of the M-ary/SSMA slotted ALOHA system and the DS/SSMA slotted ALOHA system under Rayleigh fading channel. The performance improvement of the M-ary/SSMA ALOHA system by using CLSP is larger than that of the DS/SSMA ALOHA system. The M-ary/SSMA slotted ALOHA system with CLSP is superior to the DS/SSMA slotted ALOHA system with CLSP.

Theoretical analysis of M-ary/SSMA systems utilizing multicarrier techniques

In this paper, M-ary spread spectrum multiple access (M-ary/SSMA) communication systems utilizing multicarrier techniques are evaluated by theoretical analysis. The multiple access capability of the multicarrier M-ary/SS system is evaluated by theoretical analysis in the presence of frequency selective fading and partial band interference. Moreover, the multicarrier M-ary/SS system is compared with the multicarrier direct-sequence spread-spectrum (multicarrier DS/SS) system. As a result, the BER of the multicarrier M-ary/SSMA system is better than that of the multicarrier DS/SSMA system when the number of users is small and E/sub b//N/sub 0/ is low. The BER of the multicarrier M-ary/SSMA system can he improved by increasing the number of carriers. Moreover the multicarrier M-ary/SSMA system is superior to the single carrier M-ary/SSMA system using a RAKE receiver in the presence of narrowband interference.

Novel code selecting/spacing ALOHA system

In this paper, a code selecting/spacing ALOHA system is proposed. The proposed system not only use Nm spreading codes but also M time slots. The proposed system varies in packet size from KNm Tc to KMNmTc, where K is the number of symbols per packet and Tc is the chip duration. So, the length of the packet for the proposed system changes according to the source data although the message bits per packet are constant. The number of symbols per packet of the proposed system is smaller than that of the conventional direct sequence spread spectrum multiple access (DS/SSMA) ALOHA system. Therefore, the proposed system is expected for improving the throughput performance of the conventional DS/SSMA ALOHA system. In the result of the throughput performance evaluation on the additive white Gaussian noise (AWGN) channel, it is shown that the throughput performance of the proposed system is about 2 times higher than that of the DS/SSMA ALOHA system

M-ary/SSMA slotted ALOHA with traffic control scheme on erroneous feedback channels

This paper discusses the influence of the erroneous feedback to the M-ary spread spectrum multiple access (Mary/SSMA) ALOHA system with the traffic control. In particular, the throughput performance which takes into account the detection error of the transmission control signal for channel load sensing protocol (CLSP) and the automatic repeat request (ARQ) notifying signal is evaluated by theoretical analysis. As a result, it is shown that the detection error of the traffic control signal and the ARQ notifying signal causes serious performance degradation.

Performance analysis of orthogonal multicarrier M-ary/SSMA systems

The performance of orthogonal multicarrier M-ary spread spectrum multiple access (M-ary/SSMA) systems are analyzed under frequency selective fading and partial-band interference. Orthogonal multicarrier M-ary/SSMA systems are the M-ary spread spectrum (M-ary/SSMA) systems utilizing orthogonal multicarrier transmission scheme. In this paper, the bit error rate (BER) performance, the effect of time diversity techniques and the influence of partial-band interference are investigated. As a result, the BER performance of the orthogonal multicarrier M-ary/SSMA system is superior to the conventional multicarrier M-ary/SSMA system without time diversity scheme. Also, the time diversity scheme improves the BER performance against partial-band interference.