Yoshiaki Morino

A Novel Contention Window Control Scheme Based on a Markov Chain Model in Dense WLAN Environment

In IEEE 802.11[1] wireless LANs based onCSMA/CA (Carrier Sense Multiple Access with CollisionAvoidance), parameters such as contention window (CW)significantly affects its throughput performance. In this paper,we propose a novel CW control scheme in order to achievethe high throughput performance in dense user environments.While the standard CSMA/CA mechanism employs an adaptiveCW control according to the number of packet retransmissions,the proposed scheme uses the optimum CW size, which is afunction of the number of terminal stations (STAs). In theproposed scheme, an access points (AP) estimates the numberof STAs from the measured packet collision probability, andderives the optimum CW size based on a theoretical analysisusing a Markov chain model. With simulation experimentsin a dense environment, we evaluate the performance of theproposed scheme and show that it significantly improves thethroughput performance.

Analysis evaluation of collision detection scheme utilizing MIMO transmission

In this paper, we analyze by theoretical calculation of the proposed scheme for collision detection in wireless local area networks (WLANs). The proposed scheme utilizes the medium access control (MAC) procedure of multiple input multiple output (MIMO) transmission technology, which is used to achieve high-speed transmission in WLANs in recent years; however, the transmission efficiency degrades at the MAC layer level, although a high transmission link rate is achieved at the physical (PHY) layer. The proposed scheme were performed high transmission efficiency of approximately 90% by the computer simulation in our previous work. In this paper, the results of our theoretical calculations correspond with the computer simulation results, indicating that the proposed scheme is indeed efficient and reliable.

Proposal of overhead-less access control scheme for multi-beam massive MIMO transmission in WLAN systems

In recent years, advances in wireless local area network (WLAN) systems have led to large increases in the transmission speed. The IEEE 802.11ac standard allows for very high transmissions by using multi-user multiple input multiple output (MU-MIMO) techniques in the physical (PHY) layer. However, the transmission efficiency is decreased by the channel state information (CSI) estimation algorithm in the medium access control (MAC) sub-layer. Massive MIMO transmission has attracted attention as a new technology for wireless communication in 5th-generation mobile communication systems (5G). We propose a novel access control scheme for multi-beam massive MIMO technology called overhead-less access control. The proposed scheme allows random access control without CSI estimation for massive MIMO technology. Thus, it greatly reduces the overhead of the MAC sub-layer and improves the transmission efficiency. The proposed scheme can be used to control new massive MIMO systems. We evaluated our proposed overhead-less access control scheme for multi-beam massive MIMO transmission in WLAN systems.

Analysis evaluation of multiplex transmission using MIMO transmission and A-MPDU for a collision detection scheme in WLAN

In this paper, we evaluate and analyze a proposed scheme for collision detection in wireless local area networks (WLANs) by computer simulations and theoretical calculations. The proposed scheme utilizes the medium access control (MAC) procedure of multiple-input multiple-output (MIMO) transmission technology, which has been used to achieve transmission with a high link rate in WLANs in recent years; however, the transmission efficiency degrades at the MAC data service access point (SAP), although a high transmission link rate is achieved at the physical (PHY) layer. The transmission efficiency achieved by the proposed scheme is confirmed at a high level of approximately 97% when used with an aggregation MAC protocol data unit (A-MPDU) by computer simulations, which is better than that of Ethernet. An A-MPDU has the effect of improving the transmission efficiency because it achieves a burst transmission of data packets. Furthermore, the results of our theoretical calculations correspond with the computer simulation results, indicating that the proposed scheme is indeed efficient and reliable.