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In future fourth generation wireless networks OFDM and MIMO techniques will be heavily exploited to provide connectivity to heterogeneous users offering different data traffic types. This paper proposes a low complexity resource allocation strategy for MIMO-OFDMA (Multiple-Input Multiple-Output Orthogonal Frequency Division Multiple Access) broadcast channel to support delay-sensitive traffic with...
Wireless sensor networks (WSNs) should handle multiple sensing tasks for various applications. How to improve the quality of the data acquired in such resource constrained environment is a challenging issue. In this paper, we propose a sensor-channel co-allocation model for scheduling the sensing tasks. The proposed model considers the capability, coupling and load balancing constraints for sensing...
In wireless cooperative networks, the asynchronism between the relays can be a source of diversity which is similar in its essence to the multipath diversity of frequency selective channels. In this context, an asynchronous two-relay cooperative wireless network using the Decode-and-Forward protocol is studied. Two strategies for relay coding are studied: independent coding and repetition coding....
In this work, we propose a new criterion for blind channel shortening based on high order statistical information. This method overcomes the weakness of two existing channel shortening criteria derived from only second order output statistics of the unknown channel. It is applicable to both single-input-single-output and single-input-multiple-output frequency selective channels. The optimization criterion...
We consider a wireless system with a small number of delay constrained users and a larger number of users without delay constraints. We develop a scheduling algorithm that reacts to time varying channels and maximizes throughput (to within a desired proximity), stabilizes all queues, and satisfies the delay constraints. The problem is solved by reducing the constrained optimization to a set of weighted...
In this paper, we propose a predictive resource allocation algorithm for multicast downlink OFDM systems with imperfect channel state information (CSI). We assume that the CSI is fed back to the base station (BS) through a delayed channel. To avoid the system degradation caused by the outdated CSI, we present a channel prediction scheme at the user side, which takes the delay time into account. Then,...
Push-to-Talk or PTT is ideal for group communication in a cooperative work environment, since conversations tend to be terse, and single-point to multipoint communication is the norm. PTT is generally run using simple two-way devices communicating on a common channel. However, field experience has repeatedly exposed the need for better range and higher robustness, particularly since Departments of...
Cognitive radio (CR) is a revolution in radio technology. Cognitive radio networks (CRN) is featured by the dynamic spectrum sharing of the secondary nodes coexisting with the primary nodes. Secondary nodes in cognitive radio networks (CRN) need the ability to work on different frequency bands and intelligently adjust their configuration to changes in the communication environment. It is a complicated...
This paper addresses the real-time transmission optimization of loss tolerant information streams over Vehicular Ad Hoc Networks. The proposed FEC and Interleaving Real Time Optimization (FIRO) technique dynamically adapts the two well-known error resilience techniques to the actual channel conditions, according to the stream constraints in terms of maximum allowed packet loss rate and tolerated delay...
Many efforts have been devoted to maximizing network throughput in a multi-channel multi-radio wireless mesh network. Current solutions are based on either pure static or pure dynamic channel allocation approaches. In this paper, we propose a hybrid multi-channel multi-radio wireless mesh networking architecture, where each mesh node has both static and dynamic interfaces. We first present an Adaptive...
Multipoint-to-multipoint message broadcast is a demanding application scenario in ad-hoc networks. Adaptive management of wireless resources is necessary to support such applications in a safety critical context. In this work we study adaptation of transmission rate and power to varying densities of ad-hoc nodes. Our approach is to construct a cross-layer model building on existing models for physical...
A random periodic spectrum sensing scheme is proposed for cognitive radio networks. The sensing period is extended to a general form as a random variable. A generalized Markov analytical model for sensing period optimization is presented, and the optimal sensing period to maximum rewards generated by the channel is derived. Numerical examples show that sensing period does affect the maximum rewards...
This paper provides a tutorial treatment of recent stochastic network optimization techniques, including Lyapunov network optimization, backpressure, and max-weight decision making. A new technique of place holder bits that improves delay for networking problems with general costs is also presented. An example application is given for the problem of energy-aware scheduling and routing in a wireless...
The IEEE 802.11 e defines the hybrid coordination function (HCF) which specifies the QoS algorithms in the MAC layer of the WLAN. HCF controlled channel access (HCCA) is based on centralized polling mechanism and provides parameterized QoS. This paper proposes an optimized traffic scheduling algorithm for variable bit rate (VBR) over HCCA, which can allocate network resource based on actual flows...
Enhanced Uplink operation of WCDMA-UMTS systems utilizes fast Node B scheduling and a short Transmission Time Interval (TTI) of 2ms. The scheduling decisions are based on scheduling information (SI) sent by each UE to the Node B. The main drawback of the current scheduling procedure is that the SI does not include any information regarding the delay sensitivity of each traffic flow, as well as the...
Ant colony optimization is being used to solve problems in many scientific fields. In this paper we apply an ant routing algorithm to multi-radio and multi-channel wireless mesh networks. The proposed algorithm introduces ants encountering scheme to imitate the natural process of information sharing between the individuals of an intelligent swarm. Simulation of the routing shows that this new routing...
The variable nature of the wireless channel may cause the quality of service to be intolerable for certain applications. To combat channel variability, we consider rate adaptation at the physical layer. We build an adaptive communication system based on uncoded QAM in which the available information on the channel state is obtained using the mere packet-level ACK/NACK sequence. Our system chooses...
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