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In this research, we propose an industrial Wireless Local Area Network (iWLAN) system compatible with asynchronous communication for industrial robots (iRBs) control in factory automation (FA) environments. In FA, iRBs are not only controlled by synchronous communication but also by asynchronous communication. As our conventional system is not compatible with asynchronous communication, it causes delay when iRBs are controlled by asynchronous communication. In order to target iRBs using asynchronous communication, we propose the utilization of specific memory writing technique. The register transfer level (RTL) simulation results show that our proposals can communicate with iRBs in faster throughput, better than the conventional system. Furthermore, the field-programmable gate array (FPGA) implementation are carried out to confirm that motors can be controlled by our iWLAN system compatible with asynchronous communication.

A design of wireless communication system, particularly Media Access Control (MAC) and Physical layer system (PHY) for Factory Automation (FA) system based on Wireless Local Area Network (WLAN) communication system, is proposed in this paper. The designed of MAC is synchronous multi-user round-robin transmission protocol. Low overhead Packet Division Multiple Access (PDMA) scheme is utilized for Multi-user Downlink transmission up to 80 MHz, while Frequency Division Multiple Access (FDMA) is employed for the uplink transmission. The designed of PHY system is developed based on a fast and deterministic communication featuring the synchronous multi-user system. For efficient of multi-user transmission in the proposed protocol, the transmission time of the proposed iWLAN with 40 MHz bandwidth can achieve 500% better than PROFINET wireless standard. Furthermore, the implementation results of MAC and PHY layer of the proposed system show that FPGA logic utilization can fit with the target FPGA which is promising for a full implementation and evaluation combining with radio frequency.

Recently, 802.11ax has introduced uplink Orthogonal Frequency Division Multiple Access (UL OFDMA)-based random access transmission to provide uplink multiuser capability to stations (STA) with unknown buffer status. These STAs include those that are waking up from sleep and unassociated STAs trying to establish connection for the first time. Due to the absence of carrier sensing per resource unit, this procedure has a maximum efficiency of only about 37% for high number of STAs. The efficiency will decrease further without properly choosing the random access parameters. In this paper, we first build an analytical model of the performance of UL OFDMA random access transmission and verify it using simulations. In addition, we propose methods to optimize various random access parameters to maintain a system efficiency near the 37% limit. Simulation results show that our optimization methods can increase the throughput of UL OFDMA random access by as much as 39% when compared to randomly chosen parameters.

Random access Orthogonal Frequency Division Multiple Access (OFDMA), a method for uplink multi-user transmission (UL-MU) for STAs with unknown transmit buffer has been adopted in the upcoming IEEE802.11ax next generation wireless LAN standard. In this paper, we propose a performance analysis model which use bidimensional Markov chain model of OFDMA random access. Via computer simulation, we show the usefulness of the proposed method even in the case of dense environment. In addition, we present a method in calculating the optimal number of resource units, which in 802.11ax refer to a subset of subcarriers to assign the user for OFDMA random access from numerical results.

Hybrid aggregation is a frame aggregation scheme in IEEE 802.11 Medium Access Control (MAC) which combines the use of MAC Service Data Unit Aggregation (A-MSDU) and MAC Protocol Data Unit Aggregation (A-MPDU) together. Using hybrid aggregation, we can get higher throughput than using either A-MSDU or A-MPDU only scheme. However, the throughput may decrease in some high Bit Error Rate (BER) conditions depending on the length of each A-MSDU frames in the hybrid aggregated frame. An A-MSDU frame has only one Frame Check Sequence (FCS) because A-MSDU is treated as one MSDU. Therefore, even if only one MSDU in an A-MSDU frame has bit errors, whole frame retransmission is needed. This is the disadvantage of A-MSDU aggregation scheme which affects the throughput of hybrid aggregation. To reduce this A-MSDU influence on hybrid aggregation, in this paper, we propose a novel channel adaptive aggregation scheme. By controlling the number of the MSDUs for A-MSDU aggregation, we can adapt the hybrid aggregation scheme to the channel condition. Using computer simulations, we show that the proposed hybrid aggregation scheme can reduce the frame error probability and improve the throughput more efficiently than conventional one.

In mobile environment, decode quality is largely influenced by multipath fading and Doppler shift. In this paper, we reported improvement of mobile reception for high-definition television (HDTV) of integrated services digital broadcasting — terrestrial (ISDB-T) by using maximum ratio combining (MRC) diversity and using two-dimensional (2D) filter in channel estimation. From computer simulations, we show that the bit error rate (BER) of the proposed method is improved compared to that of conventional systems. Finally, we verify reception quality of a received movie signal using our proposed system via computer simulation.