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In this paper, we propose self-interference (SI) cancellation in cooperative multiple-input multiple-output (Co-MIMO) for full-duplex (FD) wireless communication systems. This proposal solves SI by applying the block diagonalization used in multi-user MIMO. Therefore, there is no need for a radio frequency (RF) canceller, which has a large hardware (HW) size and is difficult to extend to MIMO. Furthermore, we can achieve higher throughput by applying Co-MIMO, in which multiple access points (APs) work together to communicate. The proposed method's implementation uses field-programmable gate array (FPGA) and software-defined radio (SDR). In the experiment, a total of 33 [dB] SI can cancel with two cooperative APs and two antennas per AP in the IEEE 802.11 system.

We demonstrate a self-interference (SI) cancellation in cooperative multiple-input multiple-output (Co-MIMO) for full-duplex (FD) wireless communication systems by applying the block diagonalization used in multi-user MIMO. The proposed method's implementation uses a field-programmable gate array (FPGA) and software-defined radio (SDR). In the experiment, a total of 33 [dB] SI can cancel with two cooperative APs and two antennas per AP in the IEEE 802.11 system.

This paper proposes a full-duplex wireless communication system applying cooperative multiple-input multiple-output (Co-MIMO). This proposal solves self-interference (SI) in full-duplex wireless communication systems by applying the block diagonalization used in multi-user MIMO (MU-MIMO). Therefore, there is no need for a radio frequency (RF) canceller, which has a large hardware size and is difficult to extend to MIMO. Furthermore, higher throughput can be achieved by applying Co-MIMO, in which multiple access points work together to communicate. We also introduce the implementation of the proposed method using a field-programmable gate array (FPGA) and software-defined radio (SDR) in this paper. It shows that SI cancellation can be realized by using them. The proposed method is implemented based on the IEEE 802.11n frame format as an example. In the experiment, a total of 30 [dB] SI cancellation is confirmed with a transmission power of -12 [dBm]. The SI cancellation amount can be further increased by increasing the transmission power.

The Markov chain based model by Bianchi for IEEE802.11 distributed controlled access is a highly accurate analytical tool for estimating the system throughput when a single Basic Service Set (BSS) network operates in isolation. However, with the increase of wireless LAN access points being deployed on the same area, an environment with multiple BSS interfering with each other has become the default network scenario. The purpose of this work is to extend the single BSS Markov chain model into a multi-BSS model by incorporating the influence of STAs’ interference range and carrier sense range to their own transmission and collision probabilities. We verify the proposed multi-BSS analytical model using the latest version of the ns3 simulator which has recently supported accurate PHY abstractions for multi-BSS simulation. We show that the proposed model has a high accuracy (within 1%) independent of the multi-BSS network topology.

Wireless video transmission through multiple-input multiple-output (MIMO) channels has become more and more popular recently. In the superposition MIMO system which non-orthogonally multiplexes several signals in the power domain, the receiver performs non-linear detection to estimate the transmitted signals, which is called postcoding. This paper proposes a multistage postcoder which combines maximum likelihood detection (MLD) with codeword-level interference cancellation (CWIC) to balance the accuracy and complexity. It is shown from simulations that the proposed postcoder outperforms the conventional minimum mean square error-based detection with CWIC, where its improvement in peak signal-to-noise ratio comes up to 11 dB.

The demand for high-resolution wireless video transmission technology is expected to increase greatly as the video resolution increases, and as the Wi-Fi devices spread. Wireless transmission of high-resolution video requires high throughput, therefore it is necessary to use a multiple-input multiple-output (MIMO) system. In this paper, we propose an evaluation platform for video transmission method based on joint source-channel coding (JSCC) that suppresses the degradation of received video by combining source coding and precoding, and efficient hardware software co-design for implementing it on hardware such as field-programmable gate array (FPGA) board. As a result of simulation, beamforming based on eigenbeam-space division multiplexing (E-SDM), one of the precoding method, is performed and the effectiveness of the proposed method has been confirmed.

With the spread of mobile devices, image and video transmission is in great demand. The use of multiuser multiple-input multiple-output (MU-MIMO) systems, where multiple data can be sent to multiple users, is highly expected. This paper proposes a novel power allocation scheme for MU-MIMO systems, which minimizes the variance of channel capacities of each spatial stream of all users to achieve user fairness in terms of video quality. In addition to the user fairness, we make the spatial streams which convey visually more important information be high-quality for achieving high video quality. Simulation results show that the proposed power allocation enables to equalize video quality even if the distances between a transmitter and users are different.

Recently, video distribution over wireless networks has become more common due to the spread of smart devices. This paper proposes an optimal power allocation algorithm for the transmission of layered video streams over point-to-point multiple-input multiple-output (MIMO) systems combined with superposition coding. The proposed power allocation scheme is derived from the maximization of the weighted sum-rate, where two-step optimization leads to a closed-form solution. First, the power distribution between eigen-channels is optimized, and then the optimal power allocation to quality layers is obtained. Results demonstrate that the proposed scheme attains higher peak signalto-noise ratio on average in a wide range of signal-to-noise ratio than conventional fixed power allocation schemes.

In this paper, we propose a design of asynchronous communication for an industrial wireless LAN system. In our design, MAC is synchronous multi-user round-robin transmission protocol. Low overhead Packet Division Multiple Access scheme is utilized for Multi-user Downlink transmission up to 80 MHz, while Frequency Division Multiple Access 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. In this paper, the industrial robots are not only controlled by synchronous communication but also by asynchronous communication via our industrial WLAN (iWLAN) system. This paper presents the hardware and software cooperative design. In the verification, up to 10 motors can be controlled by our iWLAN system by asynchronous communication, and the delay of each robot measured is 188 μs on average. Besides, the time synchronization captured by oscilloscope is from 40 to 100 ns as in our target.

During natural disasters, normal data communication gets affected due to destruction of communication infrastructure and excessive simultaneous access by huge number of people. Satellite links provide promising alternative to terrestrial communication infrastructure in such situations. Despite the disaster tolerance and wide area coverage, satellite links have their characteristic large propagation delay which may often affect the performance of data communication over such links. Hence, with a view to utilizing satellite links or networks during disaster situations, it is important to learn about the performance of desired applications in such environment. One application that is likely to be widely used in disaster situation is Skype video call. However, the performance of Skype video over satellite links have not been studied so far. In this paper, we therefore evaluate the performance of Skype video call over satellite links. Also, we also evaluate how packet loss rate affects the performance of Skype video call. Results from our experiments show that the throughput of the current version (desktop version 8.38.0.138) of Skype video call depends on both Round Trip Time (RTT) and packet loss rates.

In this paper, we propose a system that verifies and corrects the accuracy of symbol timing synchronization processing to determine reception time in Wi-Fi system. Time-of-flight (ToF) based Wi-Fi indoor mobile position estimation uses transmission and reception time stamp of radio waves between the mobile terminal targeted for estimation and fixed Wi-Fi receivers. However, it is known that the accuracy of radio reception time stamp in existing Wi-Fi receivers may be deteriorated due to the influence of multipath environment. Therefore, this paper proposes a system that corrects the accuracy of symbol timing synchronization processing that determines the reception time of radio wave in Wi-Fi system. This will improve the estimation accuracy of Wi-Fi indoor mobile position estimation.

Currently, Global Positioning System (GPS) is widely used as a representative position estimation system. However, GPS suffers from poor position estimation accuracy in an indoor environment. Moreover, time synchronization between devices needs to be performed for position estimation which is a resource intensive process. In previous studies, an asynchronous protocol (i.e., no synchronization requirement) called Grid Search was proposed to handle this problem. However, this method also has high complexity and takes a lot of search time to estimate the position. In this paper, we propose a method to narrow the search range using intersecting chord under the condition that generated circles intersect with each other. The proposed position estimation method has low complexity but can achieve accuracy comparable to Grid Search, i.e., a maximum estimation error less than 2 meters with 80% of the trials are within 1 meter. In addition, the calculation time can be reduced up to 6 times compared to the Grid Search when the search range extends to 5 times.

We demonstrate a precision time protocol (PTP) used to synchronize clocks in industrial wireless local area network (iWLAN) communication systems. The implementation of the system on FPGA boards for accurate verification and to test the feasibility of the system in a real environment. The result has been confirmed that time synchronization is high accuracy from 40 to 100 ns., IEEE International Symposium on Circuits and Systems (ISCAS 2019), May 26-29, 2019, Sapporo Japan

In this paper, we propose an industrial Wireless Local Area Network (iWLAN) system compatible with asynchronous communication for industrial robots (iRBs) control in factory automation (FA) environments. The design of our media access control layer 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 system is developed based on a fast and deterministic communication featuring the synchronous multi-user system. In general, the iRBs are not only controlled by synchronous communication but also by asynchronous communication via this iWLAN system. In this paper, we present the Field-programmable gate array (FPGA) implementation are carried out to confirm that our iWLAN system by asynchronous communication can control up to four motors. Based on the result of FPGA implementation, the time synchronization of the proposed system in high accuracy from 40 to 100 ns is also captured by an oscilloscope.

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.

In recent years, wireless video streaming has become very popular due to the widespread of Wi-Fi terminals supporting multiple-input multiple-output (MIMO) techniques. High-quality video streaming in wireless networks is a challenging topic. This paper proposes a greedy power allocation algorithm (GPA) for video streaming by overloaded MIMO systems. The proposed GPA adaptively controls power distribution based on received signal-to-noise ratio (SNR) so that the required bit error rate can be achieved. Simulation results demonstrate that GPA shows better performance than a conventional equal power allocation (EPA) scheme in terms of peak-signal-to-noise ratio (PSNR). The minimum SNR for achieving 35 dB in PSNR is 6 dB with GPA while EPA requires 10 dB in SNR to achieve 35 dB in PSNR.

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.

Wireless video transmission over multiple-input multiple-output (MIMO) systems is a challenging theme. Eigen beam-space division multiplexing (E-SDM) is an optimal beamforming technique in terms of channel capacity when the transmitter and receiver can share channel state information. E-SDM sorts the channel quality from the highest signal-to-noise ratio (SNR) to the lowest one. This paper presents the video transmission scheme for H.264 scalable video streams over MIMO E-SDM with optimized packetization. The proposed method controls the ratio of a base layer and enhancement layers contained in a packet. The result shows that the optimized ratio is obtained when a packet consists of the lowest base layer ratio. This ratio provides the 39.9 dB of peak-signal-to-noise ratio after decoding while no frame can be decoded with the other ratio at SNR of 10 dB.