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To deal with problems that queuing information is not included in cognitive information when performing Resource Allocation (RA), a dynamic cross-layer scheme is proposed for the multimedia cognitive radio (CR) system with Orthogonal Frequency Division Multiplexing (OFDM). In this scheme, we consider that several crucial factors influence the RA decision, including channel state information, interference...
With the successful deployment of IEEE 802.11a/b/g wireless local area networks (WLANs) and the pent-up market demand for high speed wireless access, the IEEE 802.11n protocol has emerged as a promising standard with major enhancements. In order to scale to the high physical layer transmission rate of up to 600 Mbps, the current medium access control (MAC) protocol requires significant improvements...
In IMT-Advanced system, carrier aggregation makes use of continuous or non-continuous spectrum which may be scattered in many channels, and then the individual component carrier frame is combined to form a new frame structure named frame aggregation. In this paper, flexible frame aggregation strategies are designed for different carrier aggregation situation in order to reduce the duplex delay existed...
Push-to-Talk over Cellular (PoC) system in mobile communication network, such as TD-SCDMA, is considered to have more wide coverage and more flexibility than traditional trunk communication systems. It is ideal for group communication in many cooperative work environments. But the foremost block for wider application of PoC system is the longer session setup latency comparing to other trunk communication...
In this paper, a channel modeling method based on random-propagation-graph is elaborated, validated, and applied to characterizing time-variant channels observed in typical environments for high-speed railway wireless communications. The advantage of the proposed method is that the frequency-tempo-spatial channel coefficients, as well as the multi-dimensional channel impulse responses in delay, Doppler...
This paper introduces concept and merits and demerits of wireless local area network (WLAN), analyzes the IEEE 802.11 series standards of WLAN. Based on simulation platform OPNET, the network model, node model and process model of distributional WLAN are constructed. The network performances of WLAN under 802.11 series standards are studied. The results indicate that setting different network parameters...
This paper studies feedback based instantly decodable network coding with the aim of minimizing decoding delay per transmission over wireless broadcast erasure channels with memory. We model such channels with a Gilbert-Elliott two-state Markov model with good and bad states. We first present a weighted sum generalized instantly decodable network coding (G-IDNC) scheme, where the aim is to service...
Increasing cellular traffic is the driving force for innovations in wireless communications. While voice traffic is not expected to increase much and does not require 4G systems, traffic for video and data applications is expected to grow with a rate of 100% per year. Smart mobile devices, tablets and laptop dongles will certainly make this a reality. On the other hand the supply side cannot grow...
Several reliable packet routing approaches have been studied to achieve a high reliable VANET by using the Car-to-car communications and Inter-Vehicle Communications. VANET suffers from high mobility, diverse road topologies, and wireless interference, and thus significantly degrades the connectivity of packet transmissions and network performance. The mathematical analysis can help the approach efficiency,...
Measurements of the 60 GHz UWB indoor channel done in a modern office building at the University of L'Aquila, Italy, are presented. The channel sounder is based on a PN-sequence correlation technique with a pulse width of 0.8 ns. Signals are recorded in different locations in line-of-sight and non-line-of-sight scenarios, and for each location the receiver is moved over a grid of 9×9 positions, in...
In this paper we validate and extend through simulations the trends revealed by the analytical results of our prior work concerning the throughput-delay trade-off that can be achieved by forwarding schemes exploiting path diversity and different degrees of redundancy focusing on the case of hop-by-hop retransmissions at the link-layer. The simulation environment is based on 802.11 Physical and Mac...
In this paper we analyze and study the impact of cloudlets in interactive mobile cloud applications. To study the impact we propose the design of cloudlet network and service architectures. Our study focuses on file editing, video streaming and collaborative chatting which are representative enterprise application scenarios. Initial simulation results show the performance gains of using cloudlets...
In this paper we exploit the characteristics of Physical layer Network Coding (PNC) in multicast short range networks. We present a scalable scenario of partially overlapping short range networks, where collisions are resolved through indirect inter-group cooperation based on the features of PNC. Our scenario consists of a central network, which is our network of interest, and several surrounding...
This work deals with M-sequence UWB Radio architectures for high-precision indoor localization and low data rate radio transmission. So far, UWB M-sequence devices were only used in Radar mode which applies wired synchronization between transmitter and receiver. Radio systems have different architecture since receiver and transmitter are spatially separated from each other. This paper focuses on the...
In networked control systems, the network uncertainties can degrade the control performance and even result in instability, especially for the Internet-based control system with wireless communication in which the transmission delay could be many times of the sampling period of control systems. NPC (Networked Predictive Control) is an active method to compensate for the effects of network uncertainty...
Although the Wireless Sensor and Actuator Networks (WSANs) have many advantages than the wired networks, the nature of sharing wireless media and the complicated behavior of Media Access Control (MAC) introduce adverse impacts on the control system. In contrast to most work on networked control systems using simplified models of network induced delays, this paper considers the study the random access...
Wireless Underground Sensor Networks (WUSNs) can be widely adopted to monitor the environment in agricultural, security and ecological applications. In most applications, besides underground sensor motes, aboveground motes are deployed to gather information. However, due to the different communication ranges of the channels, hidden terminal problem occurs when multiple underground motes send data...
ZigBee wireless technology is a global standard of short-range and low-data-rate for wireless sensor networks. To reduce the redundant overhead and to conserve nodes' energy in energy-constrained and multi-PAN ZigBee networks, we propose in this paper a cross-layer energy-balanced inter-PAN routing algorithm (CEIPR). The proposed algorithm has three key functionalities: (1) establishes the multipath...
Network connectivity, as a fundamental issue in a wireless sensor network(WSN), has been receiving considerable attention during the past decade. Most works focused on how to maintain full connectivity while conserving network resources. However, full connectivity is actually a sufficient but not necessary condition for many WSNs to communicate and function successfully. In addition, full connectivity...
This paper presents results of the Seventh Framework Programme (FP7) LOLA (achieving LOw LAtency in wireless communications) project about the design of a cooperative broadcast (CB) technique based on a decode and forward (DF) protocol, in the context of a clusterized wireless mesh network (WMN) based on 3GPP LTE PHY/MAC layers. The CB technique is compared to a baseline broadcast technique, obtained...
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