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This work proposes methods for estimating the responses of time-varying underwater acoustic channels using ℓ2 - ℓ1 basis pursuit and quantifying their similarity. This is motivated by problems where environmental information is to be extracted from communications signals through high-frequency ocean acoustic tomographic techniques. We view underwater channels as time-varying linear systems and characterize...
The underwater electric conduction channel characteristics, such as the path loss and time dispersion, are obtained from a channel measurement campaign in open sea waters. A distance-frequency dependent path loss model is developed for frequencies up to 1.2 MHz and distances up to 5 m. The mean and rms excess delay spread, maximum excess delay and coherence bandwidth are obtained for systems that...
Since several years, communications between fixed and mobile units have been studied in areas in underground tunnels. The leaky feeder (LF) is one of the most useful results of these studies. The LF technology in combination with other communication systems allows us to reduce the transmission power of the mobile entities without sacrificing quality of service. Because the leaky feeder cables are...
For the issue of resource allocation in a heterogeneous multi-user downlink OFDMA system with both delay-constrained (DC) and non-delay-constrained (NDC) traffic, this paper proposes suboptimal joint subcarrier and power allocation (JSPA) for channel-aware queue-aware(CAQA) scheduling. The objective is to maximize the sum of all NDC users' logarithmic utility functions (achieving proportional fairness)...
A hierarchical routing concept with key enabling mechanisms: hierarchical neighbor and route discovery, network optimization and service discovery, are provided and evaluated in this paper. The hierarchical routing concept is novel in the sense that both physical neighbors and logical neighbors are discovered to optimize the route and service discovery process as well as enable optimization of the...
Protocol sequences are used for distributed multiple accessing in the collision channel without feedback. In this paper we consider user-detectable sequences with the property that each active user can be detected by looking at the channel activity only, within some bounded delay. It is important in some applications such as ad hoc networks. Some lower and upper bounds of its minimum period are investigated...
In this work, we are interested in designing scheduling algorithms for multihop wireless networks that can achieve good end-to-end delay performance. There has been evidence that some of the well-known queue-length-based throughputoptimal algorithms, such as the back-pressure algorithm, could have poor end-to-end delay performance. In particular, the end-to-end delay of the back-pressure algorithm...
In this paper, the problem of acquiring new composite Global Navigation Satellite System (GNSS) signals of the next generation systems (such as Galileo and GPS modernization) is addressed and analyzed, focusing on the problem of sign reversal transition due to the navigation data message in the data channel and to the secondary code in the pilot channel. Moreover, the sign transition present on the...
Ultrawideband frequency modulated continuous wave (FMCW) signals are using for ionospheric sounding by chirp sounders. We can use two techniques of digitizing. The first one is digitizing at intermediate frequency. The second one is digitizing at double maximum frequency of signal. Both of them use uniform sampling. In this paper we propose technique of non uniform sampling of FMCW signal. We describe...
This paper investigates stability and robustness of a gradient-type power control algorithm for multicell CDMA wireless communication networks in the presence of time-delays and disturbances. The time-delays in individual communication channels between mobiles and base stations are allowed to take place independently. The disturbances represent power noises, unmodeled secondary interference and variation...
In this paper, a quality of service (QoS) based resource allocation for orthogonal frequency division multiplexing (OFDM)-based Cognitive Radio (CR) System with mixed services is proposed. We consider the resource allocation problem for downlink with unoccupied frequency sensed by CR users (CRUs) and total transmission power constraint of the CR base station. In mixed services CR system, the objective...
Delay-constrained video applications have stringent bandwidth, delay and loss requirements, which is a great challenge to support such real-time applications in wireless ad hoc networks. In this paper, to minimize the distortion of video received at the decoder, we propose a cross layer design (CLD) approach which combines the network layer and MAC layer to meet the stringent requirements by dynamically...
In this paper, we study the VoIP capacity in cognitive radio system. As the cognitive user, VoIP packets arrival from a poisson process and use the wireless channels transparently. We formulate the whole dispose procedure as a birth and death processes, and establish preemptive multi-channel model under the consideration of delay and dropping rate constraints to analysis the capacity of VoIP service...
A land-to-ship (L2S) radio channel measurement mission at 2.075 GHz has been established in Trondheim, Norway, being fully described in this paper. The transmitter (TX) was installed onboard the High Speed Craft (HSC) M/S "Trondheimsfjord I" and the receiver (RX) was located at the building in the harbor. A frequency chirp with 20 MHz bandwidth is emitted by the TX on the moving craft within...
The sensitivity of MIMO error performance to imperfect receiver channel state information is examined. Measurements made at three different UHF frequencies are used to show the effect of parameters such as training and frame lengths on error performance. The results show that the amount of training directly influences the supportable symbol rate and that the level of degradation in performance due...
With the increasing convergence and cooperation among wireless networks, network awareness of user equipment (UE) has become very important. A practical solution for network information delivery for UE, Cognitive Pilot Channel (CPC), has recently been proposed. It can provide UE with the necessary network information for network selection by using the public signaling channel. In this paper, a cognitive...
The spacial distribution of nodes in the Opportunistic networks is uneven in the real scenarios. There are some landmarks with high node density distributed in the network area. Based on the uneven distribution character of nodes in the Opportunistic Networks, a landmark aware content searching scheme (LACS) is proposed. The scheme proposed here is composed of two sub-schemes, latent spray scheme...
We address the problem of routing for multi-radio multi-channel wireless mesh networks, and propose a novel routing metric, named DARM. Compared with the prior routing metrics focus on the network throughput, DARM aims to minimize the end-to-end delay, which is a significant requirement for multimedia applications. Our routing metric captures the effects of variation in link loss-ratio, the length...
In ad hoc networks, performance objectives are often in contention with each other. Indeed, due to the transmission errors incurred over wireless channels, it is difficult to achieve a high rate of transmission in conjunction with reliable delivery of data and low latency. In order to obtain favorable throughput and delay performances, the system may choose to compromise on its reliability and have...
In this paper, we present AEROMAN (Architecture to Evaluate Routing Protocols for Multi-hop Ad-hoc Networks) which is designed and implemented for evaluation of routing protocols for multi-hop wireless networks. AEROMAN uses QOMET, a wireless link emulation tool, to compute parameters of wireless links, such as bandwidth, delay, packet loss rate, in contention-free conditions. In order to take into...
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