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In this paper, we derive fundamental performance limits of underwater (UW) networks via an analysis of the average behavior of random deployments. In particular, we consider an UW network that consists of a Poisson point process of transmitters, each with a receiver at a given distance. The link channel model accounts for path-loss, frequency-dependent absorption, and Rayleigh fading. We evaluate...
Relay transmission or cooperative communication is an advanced technique that can improve the performance of data transmission among wireless nodes. However, while the performance (e.g., throughput) of a source node can be improved through cooperation with a number of relays, this improvement comes at the expense of a degraded performance for the relay nodes due to the resources that they dedicate...
In this paper, we propose a new QAPM scheme for improving power efficiency. A proposed QAPM scheme is build on QAM. And BER performance of QAPM is better than existing PSSK because BER performance of QAM is better than PSK. In this paper, we find the BER performance closed form of QAPM modulation. Also, we compare to PSSK and QAPM with regard to BER performance and throughput in AWGN channel.
High throughput and lifetime are both crucial design objectives for a number of multihop wireless network applications. As these two objectives are often in conflict with each other, it naturally becomes important to identify the trade-offs between them. Several works in the literature have focused on improving one or the other, but investigating the trade-off between throughput and lifetime has received...
This paper takes into account the uncertainty of the primary users' locations and transmission power in designing an optimal downlink scheduling scheme for cognitive radio cellular networks (CogCells). Localization technique is exploited to estimate the position and transmission power of the primary user (PU) transmitting on specific channel. The objective of our scheduling scheme is to maximize the...
We analyze the characteristics and performance of a wireless ad hoc network where nodes are connected via random channels and information is transported in the network in a cooperative multihop fashion using amplify and forward relay strategy. We characterize the network by studying important parameters such as: (1) SNR degradation with hop, (2) outage probability, (3) maximum permissible number of...
A wide variety of network applications require the use of reliable multicast protocols to disseminate data from one source to a potentially large number of receivers simultaneously. We focus on multicast in single channel multi-access wireless networks and consider Automatic Repeat reQuest (ARQ) based error control algorithms. We propose a simple NACK based method, called overlapped NACKs, that exploits...
Proportional Fair (PF) algorithm is known to achieve a good trade-off between efficiency and fairness by allocation opportunistically resources to users with good radio conditions, without sacrificing fairness considerations towards the other users of the system. On the other hand, Hierarchical Modulation (HM) is a means to increase the spectral efficiency of a given system by superposing an additional...
Multiple antennas have become a common component of wireless networks, improving range, throughput, and spatial reuse, both at the link and network levels. At the same time, carrier sensing is a widely used method of improving spatial reuse in distributed wireless networks, especially when there is limited coordination among non-communicating nodes. While the combination of carrier sensing and multiple...
This paper proposes two optimal power allocation (OPA) schemes for two-hop wireless relay networks operating in amplify-and-forward (AAF) manner. All the relay nodes in the network participate in relaying information from the source to the destination. We explore the OPA schemes among the cooperative relays to maximize the received SNR at the destination. When the instantaneous channel state information...
Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity to one antenna. Recently, a new class of methods called cooperative communication has been proposed that enables single antenna mobiles in a multiuser environment to share their antennas and generate a virtual multiple-antenna transmitter that allows...
In this paper, we consider a wireless network consisting of a BS (Base Station) and MSs (Mobile Stations) where the BS employs the one-bit feedback quantized proportional fair scheduler for downlink transmission. We then examine the effect of the threshold value in the scheduler on the throughput and that on the information theoretic capacity. Numerical results exhibit that the characteristics of...
This paper addresses a transmission scheduling for wireless multi-hop network employing physical layer wireless network coding (PL-WNC). With PL-WNC, two distant nodes first transmit packets to an intermediate relay simultaneously, which then amplifies and forwards the received signal. The destination nodes decode the desired signals by using the a priori information which are their own packets or...
Wireless networks are characterized by having limited resources accessed by a large number of mobile stations with distinct capabilities. In such challenged environment the dynamic control of resources is of major importance to mitigate the limitations of wireless networks, such as the impact of low data rate stations and wireless channel oscillations. Such augmented usage of wireless resources can...
Relay selection enhances the performance of the cooperative networks by selecting the links with higher capacity. Meanwhile link adaptation improves the spectral efficiency of wireless data-centric networks through adapting the modulation and coding schemes (MCS) to the current link condition. In this paper, relay selection is combined with link adaptation for distributed beamforming in a two-hop...
In this paper, it is shown that the achievable throughput capacity of wireless networks suffers from a fundamental limitation under finite node resource constraints. It is shown that this reduction results from a fundamental lower bound on the error performance of the wireless-channel model. In particular, the problem is addressed for the classic parallel-unicast problem introduced by Gupta-Kumar...
This paper introduces a novel paradigm for designing the physical and medium access control (MAC) layers of mobile ad hoc or peer-to-peer networks formed by half-duplex radios. A node equipped with such a radio cannot simultaneously transmit and receive useful signals at the same frequency. Unlike in conventional designs, where a node's transmission frames are scheduled away from its reception, each...
This paper proposes an adaptive bandwidth control scheme for autonomous distributed networks. Based on the consideration that the carrier sense multiple access with collision avoidance (CSMA/CA) is not efficient in terms of throughput due to its strict collision avoidance process, this paper employs a dynamic spectrum control (DSC) in which a certain number of discrete spectra having the highest signal...
Distributed beamforming has the great potential of performance improvement in wireless networks while the carrier synchronization overhead will reduce its performance gain. In this paper the effects of carrier synchronization on link throughput of distributed beamforming is studied. The expressions of the frequency and initial phase used by each cooperative node are derived for the existing round-trip...
It has long been recognised that a wireless communication system can be more efficient if link-layer parameters such as modulation order are adapted to the channel conditions. The most common optimising criterion is spectral efficiency (bps/Hertz) subject to very low bit-error constraint. But this criterion is not appropriate for practical communication networks fitted with strong data-packet error...
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