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This paper addresses the problem of indoor location for devices that are connected to WLAN. Nowdays most of the smart terminals: mobile phones, portable computers and tablets are WLAN enabled. Location of these devices is of interest to network security issues as well as employee and company security and reliability. Most of the algorithms on the market use triangulation as a basic rule for location...
Voice capacity over IEEE 802.11 networks can be increased with time synchronized medium access, but it is restricted to single hop networks only. We propose a collaborative mechanism that enables client nodes to carry out the time synchronization on ad hoc basis, thereby extends the time synchronized access mechanism over multiple hops, and increases voice capacity considerably. To model real scenario...
Cognitive radio technology solves the problem of spectrum underutilization by allowing the unlicensed users to opportunistically access available spectrum without affecting the activity of licensed user. Channel assignment and routing in cognitive radio networks is especially challenging in networks where nodes are equipped with only a single transceiver (as is the case in commodity wireless networks...
Between the wired and the wireless world a synchronization gap in terms of accuracy obviously exists due to the different possibilities of the technologies. This paper investigates means to access WLAN functionality in order to gain system-wide synchronization between access points and clients in order to establish a common notion of time in IEEE 802.11 systems. For this, a novel approach is presented,...
Position messages will be the foundation for many emerging traffic safety applications based on wireless communications. These messages contain information about the vehicle's position, speed, direction, etc. and are broadcasted periodically by each vehicle. The upcoming IEEE 802.11p standard, intended for vehicle ad hoc networks (VANETs) has flaws caused by the unpredictable behavior of its medium...
Time based localisation methods like GPS are widely used for outdoor navigation, whereas indoor navigation is typically performed only on a cell-basis or based on the Received Signal Strength Indicator. Since RSSI is not able to fulfil all current requirements, Time of Arrival and Time Difference of Arrival based approaches have recently gained focus. As time based localisation has high demands on...
In this paper we address the Quality of Service (QoS) issues for applications such as voice and video that generate bursty traffic in mobile ad hoc networks while asynchronous power saving protocols are applied to wireless hosts. To provide QoS, we propose our new quorum-based power saving protocol called "consecutive quorum-based power saving (CQPS)". Within this torus-based protocol each...
This paper presents a hardware-efficient autocorrelation scheme for the synchronization of MIMO-OFDM based wireless local area network (WLAN) systems, such as IEEE 802.11n. Carrier frequency offset (CFO) estimation for the frequency synchronization requires high complexity autocorrelation operations of many training symbols. In order to reduce the hardware complexity of the MIMO-OFDM synchronization,...
Clock synchronization is one of the enabling technologies for real-time networking. This paper is motivated by the need for WLAN support of real-time factory automation networks. These networks need synchronized clocks for the typical time-slotted arbitration schemes. As this type of service is not yet available wireless LANs, this work investigates possibilities for synchronizing clocks, based on...
Communication networks for industrial automation are usually heterogeneous, i.e. a combination of different wired and wireless technologies. A possible setup could be a Real-time Ethernet (RTE) extended by a wireless local area network (WLAN) for all mobile system components. However, the required clock synchronization with IEEE 1588v2 for such a system can only be accomplished for the wired RTE part...
The traditional task of a sensor network is data collection and aggregation for further processing. In the case of mobile networks this is usually done via wireless technologies. However, with the establishment of mobility another problem occurs: The question of the actual location of the measured data. This paper proposes a localisation scheme for Wireless LAN, where an existing WLAN infrastructure...
This paper presents an efficient multipolling scheme that improves the IEEE 802.11 MAC protocol efficiency and does not suffer from the hidden terminal problem or inefficient channel usage problems. To design an efficient polling scheme, the access point (AP) needs to obtain information about the current transmission status and channel state for each station. In this new scheme, we propose the use...
We present in this paper the analytical evaluation of a simple mechanism to reduce the average transmission delay of master stations in a network based on the Distributed Queuing MAC protocol for Ad hoc Networks (DQMAN). When DQMAN is executed, the network is self-organized into dynamic and spontaneous master-slave clusters. Within each cluster, a high performance MAC protocol based on a tree-splitting...
This paper proposes TD-uCSMA a synchronous distributed coordination function which is meant to provide CSMA/CA with a mechanism for QoS provisioning and bandwidth management over WiFi networks. TD-uCSMA relies on synchronization among nodes and the time-driven switching of contention parameters inside nodes. The TD-uCSMA operating principles and preliminary synchronization issues are presented here...
A high-density wireless environment could not avoid cell/BSS (Basic Service Set) overlapping, which may cause Co-channel interference. Such interference makes it difficult to support QoS. It is desirable that BSSs can share a single frequency channel without interference and at the same time, QoS is supported. Additional functionalities particularly in MAC layer are required to achieve interference-free...
With the development of wireless positioning and popularity of OFDM (orthogonal frequency division multiplexing) as a key technology in wireless systems, such as 3GPP LTE, WLAN, and WiMAX, precise OFDM-based ranging has become of particular interest. In this paper, we propose a ranging method measuring the round-trip time-of-flight of an OFDM symbol. Timing measurements are vulnerable to symbol-timing...
This paper presents a many-core heterogeneous computational platform that employs a GALS compatible circuit-switched on-chip network. The platform targets streaming DSP and embedded applications that have a high degree of task-level parallelism among computational kernels. The test chip was fabricated in 65nm CMOS consisting of 164 simple small programmable cores, three dedicated-purpose accelerators...
The Timeslot Boundary Synchronization Problem occurs when timeslot boundaries become aligned leading to an increase in the probability of message collisions. This alignment, which can occur in Vehicular Ad Hoc Networks using the 802.11p protocols, adversely affects the performance of multi-hop message broadcasts. This paper describes the causes of this phenomenon and describes link and network layer...
Based on the technology of Mobile Ad-hoc Network (MANET), we design and implement an Audio Conferencing Testbed (ACT) that is used for a group of people to set up virtual audio conferencing room to complete certain mission in places where network infrastructure is unavailable. ACT is built on popular Windows operating system with off-the-shelf IEEE802.lt (a.k.a. Wi-Fi) adapters as the enabling technology...
In this paper, we propose a new digital duplexing scheme, called synchronous digital duplexing (SDD), which can increase data efficiency and flexibility of resource by transmitting uplink signal and downlink signal simultaneously in wireless communication. In order to transmit uplink and downlink signals simultaneously, the proposed SDD obtains mutual information among subscriber stations (SSs) with...
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