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In this paper, an adaptive hybrid automatic repeat request (HARQ) scheme is proposed for unicast wireless video communication systems. In the proposed scheme, the receiver controls the HARQ feedback messages based on not only error detection, but also video content and playback deadline. The adaptation algorithm utilizes a delay model to estimate the transmission time of a video frame and its delivery...
In this paper, we consider one of the main disadvantages of Ergodic Interference Alignment, i.e., delay. We propose two methods to solve the open problem of finding the best choice of user sets in order to minimize the delay. With these methods we are able to find the best JAP-B scheme which aims to trade off rate for delay in Ergodic Interference Alignment. First, we provide the solution based on...
Lattice network coding is recently proposed as a practical implementation of Nazer-Gastpar's compute-and-forward relaying strategy. Previous investigation of lattice network coding is mainly over finite fields. In this paper, we extend lattice network coding from finite fields to finite rings. In addition to having its own theoretical interest, this extension provides an alternative viewpoint of Nazer-Gastpar's...
A network consisting of a point-to-point (P2P) link and a multiple access channel (MAC) sharing the same medium is considered. The resulting interference network, with three transmitters and two receivers is studied from degrees of freedom (DoF) perspective, with and without cognition. Several cognition variants are examined. Namely, the setup is studied with (1) no cognitive transmitters, (2) a cognitive...
Home area networks (HANs) promise to enable sophisticated home automation applications such as smart energy usage and assisted living. However, recent empirical study of HAN reliability in real-world residential environments revealed significant challenges to achieving reliable performance in the face of significant and variable interference from a multitude of coexisting wireless devices. We propose...
In this paper we present the implementation of a FPGA based high data rate BPSK receiver specifically designed to withstand the high dynamics of airborne vehicles (i.e. aircraft, sounding rockets, satellites, etc.). The carrier recovery is implemented through a Costas loop, and a Gardner detector is used for the timing recovery. This architecture was chosen because it provides almost independent carrier...
In cognitive radio networks, secondary users conduct local sensing to use underutilized spectrum bands. However, every secondary user's local sensing usually gives rise to much sensing overhead. Moreover, a globally synchronized quiet period cannot be determined in a decentralized network. In this paper, we propose a zone-based distributed sensing scheme, in which multiple secondary users alternate...
Space diversity is a simple and cost-effective technique to combat fading in wireless channels. For small handheld devices with limited space and power for multiple antennas, cooperative diversity is proposed. In cooperative diversity, adjacent users to a certain user, using their own antennas, act as relays to create ”virtual space diversity” for the source user. The success of cooperative diversity...
Point-to-point connectivity through FPGA high-speed serial I/O is an important component for many space-based applications. The susceptibility of high-speed transceivers to soft errors is still under investigation and is a matter of concern in reliable point-to-point communications. This work develops a technique to provide full-bandwidth, lossless data transmission across high-speed transceivers...
Wireless Sensor Networks are event based systems that consists of a collection of autonomous sensor nodes that are spatially distributed and cooperatively monitor physical and environmental conditions. When an event has been detected these sensor nodes become active in transmitting the information and the load becomes heavy, increasing the data traffic and this might lead to congestion that results...
Next generation wireless networks will be heterogeneous, where several primary users (PU e.g. licensed users) and secondary users (SU e.g. unlicensed users) can operate in the same dynamic and reconfigurable networks at a given time. The major challenge in this heterogeneous radio environment is to enable the coexistence between PU and SU which will further improve the efficient use of radio spectrum...
In the current internet, Transmission Control Protocol (TCP) is used as the most popular transport layer protocol. However, the end-to-end throughput of TCP degrades significantly when operates in wireless networks. Frequent retransmission timeout is one of the well-known problems of TCP end-to-end throughput degradation over wireless networks. In wireless networks, a retransmission timeout is inevitable,...
In this paper, the problem of initial link establishment in multi-channel Cognitive Radio Networks (CRN) is investigated. Different from the traditional scenario, in which the transceiver pair can establish an initial link through exchanging the control messages on the Common Control Channel (CCC), a more realistic scenario in the absence of CCC is considered in our work. Without the help of CCC,...
Wake-up radio technology is a means to improve energy efficiency in low-power wireless sensor networks. In such radios, low-power low-complexity designs are considered, often based on narrow-band transmission, simple modulation techniques, noncoherent detection and matched filter receivers. In order to improve the performance of wake-up radios in interference limited scenarios, while keeping the power...
One of the key technologies introduced in LTE-Advanced in order to increase the capacity is carrier aggregation (CA). Based on this scheme, continuous and non-continuous sub-bands are aggregated in order to achieve larger bandwidth. Such a new technique introduces various challenges in both system aspect and the modeling of the wireless channel. In particular, the traditional channel models that was...
This paper considers the problem of uplink scheduling in wireless networks supporting successive interference cancellation (SIC) at the physical layer. By allowing concurrent interfering transmissions, SIC enables multi-packet reception at the receiver resulting in increased network throughput. Specifically, we consider maximum throughput scheduling and proportional fair scheduling problems and study...
The problem of stochastically robust minimum mean square error (MMSE) transceiver design is addressed for multiple-input multiple-output (MIMO) point-to-point channels with different imperfect channel state information (CSI) at the receiver and the transmitter. While the receiver has distribution knowledge of the doubly correlated Gaussian channel that is conditioned on pilot-based training observations...
Transmission power control can significantly improve energy-efficiency of wireless sensor network communications. Power consumption models are typically based on dependence of channel attenuation on distance. However, in practice, information on distance is usually not available and the dependence of channel attenuation on distance is not sufficiently accurate. Therefore, we propose more accurate...
Underwater acoustic channels (UACs) have a large fractional bandwidth and are well modeled by a multiscale-multilag model, which is a generalization of the commonly employed single time-scale model. The path-dependent time scaling introduces significant channel variation, destroying carrier orthogonality and yielding intercarrier interference (ICI) in an orthogonal frequency division multiplexing...
We evaluate the outage probability and the spectral efficiency of cooperative multi-hop networks, where L relay nodes are placed at each hop and an MDS (Maximum Distance Separable) code of coding rate 1/L is employed at the link-layer. A codeword of the MDS code is partitioned into L blocks. When each relay node receives two or more codeword blocks of the MDS code, it aggregates the blocks, corrects...
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