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The increase of wireless devices due to the implementation of wireless sensor networks, cyber-physical systems with wireless communication interfaces and mobile monitoring as well as the installation of diagnosis applications into the shop floor improves real-time transparency of machine conditions and production processes. For a minimal invasive integration of such technologies into the brownfield...
Inversely proportional setting (IPS) of the transmission power and carrier sense threshold (CST) to a portion of access points/stations is discussed through numerical evaluation and experiments to examine coexistence with legacy devices. In densely deployed wireless local area networks (WLANs), tuning CST is a promising approach to facilitate spatial channel reuse. Particularly, IPS of the transmission...
This paper aims to improve the QoS of IEEE802.11e standard. It is intelligently performed by adjusting the contention parameters of the MAC layer based on desired priorities of the nodes. We focus on CW and AIFS that are used for calculating the back-off time to have traffic priority in accessing the channel in EDCA part of IEEE802.11e standard. The proposed scheme is called SN-EDCA (Smart Node-EDCA)...
This paper presents our research in developing high performance but low complexity MIMO decoders for the newest WLAN, i.e. 802.11ac. K-best and Trellis methods are proposed to develop the MIMO decoders. Their performances are observed and compared to MIMO decoders which are based on linear and optimal methods, i.e. ZF, MMSE, and ML. Run test of 2×2 MEMO, 64-QAM, Coding rate 3/4, and 40MHz of bandwidth...
IEEE 802.11 Wireless Local Area Network (WLAN) supports multiple transmission rates according to the channel condition. In multi-rate IEEE 802.11 WLAN, the performance of stations with high rates may decline due to the relatively long channel occupation time of the stations with low rates. In order to mitigate this performance anomaly problem, we propose a new Medium Access Control (MAC) protocol...
In case that a selfish terminal generates a large amount of traffic with high priority control of IEEE 802.11e, an access point (AP) and terminals in the AP cannot get transmission opportunities because of the media access control technique. In our previous work, we proposed traffic suppression method for the selfish terminal by cooperative controls between AP and terminals with considering the fairness...
WiFi networks based on the IEEE 802.11 standard are currently penetrating into our daily life in many ways. With increasing demand for higher data rates by mobile applications, better network performance is required. Since link adaptation algorithms can play a key role in improving performance, they have been extensively investigated in the last decade. However, the relative impact of different approaches...
For connected vehicles, vehicle ad-hoc network is capable to support various communication-based applications. Specially, WLAN-based vehicular Internet access can be a complementary and cost-effective solution considering the cost of cellular service. For WLAN-based Internet connected vehicles, we propose an efficient load-aware association mechanism which allocates vehicles to roadside APs properly,...
Presently, wireless local area networks (WLANs) are experiencing a tremendous increase of wireless bandwidth hungry devices and the increasing deployment of cloud-based enterprise networks. Additionally, mobile operators with heavily congested cellular networks are exploring the strategy of offload traffic from their cellular networks to WiFi hotspots. Technologies that were originally proposed for...
Recently, IEEE 802.11ax Task Group has adapted OFDMA as a new technique for enabling multi-user transmission. It has been also decided that the scheduling duration should be same for all the users in a multi-user OFDMA so that the transmission of the users should end at the same time. In order to realize that condition, the users with insufficient data should transmit null data (i.e. padding) to fill...
The IEEE 802.11 DCF (distributed coordination function) employs a random backoff method for collision avoidance. The random backoff approach, however, cannot eliminate collisions completely: i.e., a number of stations may randomly select a same BC(backoff counter) and access the channel simultaneously. In this paper, we propose a collision-free backoff method that enables the stations to reserve their...
In this paper, high reliable broadcasting protocol in WLAN using retransmission is proposed. Broadcast in conventional WLAN has advantage of high efficient use of wireless resource, but has disadvantage of low reliability and data rate. Broadcasting frame includes the sequence indicating which nodes send ACK frame first. If some nodes fail to receive the frame, the node which success to receive the...
An incentive problem of ad hoc networks still remains for relaying frames from other nodes. By utilizing the Social Network System such as Twitter and Facebook, it is possible to estimate the degree of intimacy of friendship links not only to direct friends but also indirect friends such as friends-of-friends. If we provide links of ad-hoc network in relation to direct/indirect friends instead of...
This paper deals with the problem of severe wireless performance degradation when multiple wireless technologies are concurrently utilized in a same user device. This type of usage is already frequent in most smartphones and laptops, such as streaming Bluetooth audio while using a Wi-Fi download, and is more intensifying with IoT device deployment which triggers the coexistence of heterogeneous wireless...
Traffic load balancing and radio resource management is key to harness the dense and increasingly heterogeneous deployment of next generation “5G” wireless infrastructure. Strategies for aggregating user traffic from across multiple radio access technologies (RATs) and/or access points (APs) would be crucial in such heterogeneous networks (HetNets), but are not well investigated. In this paper, we...
With the evolution of smart devices, mobile nodes are commonly equipped with multiple communication interfaces. Users and network operators can benefit from multipath TCP to achieve more reliable and efficient video streaming in heterogeneous networks. We develop a dynamic multipath TCP control mechanism to enable seamless vertical handover during network transition and use a single radio technology...
A heavy deployment of IEEE 802.11 Wireless LANs and limited number of orthogonal channels make lots of Access Points (APs) overlap their interference regions, which greatly increases interferences between APs and stations. In order to cope with the performance degradation caused by the interferences, we propose Co-Fi, a centralized Wi-Fi architecture that effectively coordinates downlink transmissions...
The ubiquity of WLAN networks bears inherently a risk of generating considerable interference level. Measurements have been obtained to demonstrate that densely, though randomly deployed Access Points cannot operate at maximum bit rates due to mutual interference. A simple non-collaborating algorithm has been proposed and verified under carefully controlled measurement conditions providing a proof...
We study the uplink multi-user multiple-input multiple-output (UL MU-MIMO) channel in a wireless local area network (WLAN) with multiple access points (APs) and multiple stations (STAs). APs are allocated with different orthogonal frequency-division multiplexing (OFDM) subcarriers. Each AP has multiple antennas and applies zero-forcing successive interference cancellation (ZF-SIC) as in [1] for spatial...
Wireless Gigabit (WiGig) access points (APs) using 60 GHz unlicensed frequency band are considered as key enablers for future Gbps WLANs. Due to its short range transmission with high susceptibility to path blocking, a multiple number of WiGig APs should be installed to fully cover a typical target environment. However, using autonomously operated WiGig APs with IEEE 802.11ad DCF, the exhaustive search...
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