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In this paper, we investigate the capacity of wireless hybrid networks, in which a wired network of base stations is used to support long-range communications between wireless nodes. We introduce the multiple access technique by allowing more than one source node to transmit simultaneously and utilizing successive interference cancellation to decode information at the destination node. Our results...
We consider a wireless network in which a source terminal communicates with a destination and a relay terminal is occasionally present in close proximity to the source without source's awareness, suggesting oblivious protocols. We incorporate a two-layer broadcast approach into two cooperative strategies based on the decode-and-forward scheme - Sequential Decoded-and Forward (SDF) and the Block-Markov...
We consider a cognitive radio network, where M distributed secondary users search for spectrum opportunities among N independent channels without information exchange. The occupancy of each channel by the primary network is modeled as a Bernoulli process with unknown mean which represents the unknown traffic load of the primary network. In each slot, a secondary transmitter chooses one channel to...
This paper presents a link adaptation strategy for non-binary LDPC code over a time-variant frequency-selective channel. The algorithm is based first on the adoption of waterfilling technique to wisely adapt the transmitted power. It is shown that as long as best subchannels are identified with the waterfilling algorithm, an equal power distribution can be applied with performance comparable to the...
Spatial processing techniques are considered as means to enhance the performance of WLANs systems. Different multi-antenna methods exploit different properties of the radio channel, so in this paper, we identify, based on the channel state, the physical layer parameters that can be controlled in the attempt to satisfy the user/application requirements, with an efficient use of the available radio...
User scheduling and multiuser multi-antenna (MU-MIMO) transmission are at the core of high-rate data-oriented downlink schemes foreseen in the next-generation cellular systems (e.g., LTE-Advanced). Scheduling exploits the knowledge of the users' instantaneous achievable coding rates. However, when it is applied independently in each cell, the level of inter-cell interference (ICI) experienced by each...
Consider a wireless system where a transmitter may send data to a set of receivers, or on various channels, experiencing random time-varying fading. The transmitter can send data to a single receiver or on a single channel at a time and may adapt its transmission power to the radio conditions of the chosen receiver/channel. Its objective is to implement a strategy defining at each time how to select...
Limited feedback beamforming improves link reliability with a small amount of feedback from the receiver to the transmitter. The performance of such a closed loop MIMO system is unknown in interference limited cellular environments, when the base stations have limited or no coordination. This paper establishes the degradation in throughput due to uncoordinated other cell interference and delay on...
In this paper a communication system operating over a Gilbert-Elliot channel is studied. The goal of the transmitter is to maximize the number of successfully transmitted bits. This is achieved by choosing among three possible actions: (i) betting aggressively by using a weak code that allows the transmission of a high number of bits but provides no protection against a bad channel, (ii) betting conservatively...
We propose a MAC for wireless ad hoc cognitive radio networks where secondary users employ cooperative spectrum sensing to mitigate the degradation of the channel between primary transmitter and secondary users. The sensing reports and fused decisions are transmitted based on random access of CSMA/CA and 802.11e EDCA on the control channel, whose access scheme determines the overall achievable throughput...
In this paper, we consider the use of cooperative transmissions in multi-hop wireless networks to achieve virtual MISO (multiple input single output) links. Specifically, we investigate how the physical layer VMISO benefits translate into network level performance improvements. We show that the improvements are non-trivial (15% to 300% depending on the node density) but rely on two crucial algorithmic...
This paper studies the throughput scaling of wireless networks over channels with random connections, in which the channel connections are independent and identically distributed (i.i.d.) according to a common distribution. The channel distribution is quite general, with the only limitations being that the mean and variance are finite. Previous works have shown that, when channel state information...
A major problem in wireless networks is coping with limited resources, such as bandwidth and energy. These issues become a major algorithmic challenge in view of the dynamic nature of the wireless domain. We consider in this paper the single-transmitter power assignment problem under time-varying channels, with the objective of maximizing the data throughput. It is assumed that the transmitter has...
The recent advance in the intelligent transportation system (ITS) has led the FCC to allocate 7 channels at 5.9 GHz band for wireless access for vehicular environments (WAVE) systems. The key challenge of multi-channel access in vehicular ad-hoc networks (VANET) is to cope with the dynamic channel condition due to highly mobile nodes, while providing fair spectrum share among nodes. In this paper,...
A transmitter with cognitive capability can sense talk between the other transmitter-receiver pairs. When this transmitter knows full or partial message of the others, it can choose an efficient strategy to access the transmission medium. This is referred to as cognitive radio channel. This work aims to investigate multi-tone transmission over two-user cognitive radio channels where cross-talk interference...
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