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Channel allocation schemes

About: Channel allocation schemes is a research topic. Over the lifetime, 10656 publications have been published within this topic receiving 182117 citations.


Papers
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Journal ArticleDOI
TL;DR: This work develops a fast retrial scheme that is based on slotted Aloha and exploits the structure of OFDMA, and finds that full sharing, i.e., a reuse factor of one, performs best for given random access channels.
Abstract: Orthogonal frequency-division multiple access (OFDMA) systems are considered promising candidates for implementing next-generation wireless communication systems. They provide multiple channels that can be accessed via random access schemes. However, traditional random access schemes could result in an excessive amount of access delay. To address this issue, we develop a fast retrial scheme that is based on slotted Aloha and exploits the structure of OFDMA. A salient feature of this scheme is that when collisions occur instead of retrials occuring randomly in time, they occur randomly in frequency, i.e., the scheme randomly selects the subchannels for retrial. To further achieve fast access, retrials are designed to follow the 1-persistent type, i.e., no exponential backoff. To achieve the maximum throughput, we limit the maximum number of allowed retrials according to the load condition. We also consider the issue of designing for an appropriate reuse factor for random access channels in order to overcome the intercell interference problem in OFDMA multicell environments. Our finding is that full sharing, i.e., a reuse factor of one, performs best for given random access channels. Through analysis and simulation, we confirm that our fast retrial algorithm has the advantage of high throughput and low access delay, and the full sharing policy for random access channels shows high throughput as well as low collision.

190 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the downlink communications of intelligent reflecting surface (IRS) assisted non-orthogonal multiple access (NOMA) systems and formulated a joint optimization problem over the channel assignment, decoding order of NOMA users, power allocation, and reflection coefficients.
Abstract: This article investigates the downlink communications of intelligent reflecting surface (IRS) assisted non-orthogonal multiple access (NOMA) systems. To maximize the system throughput, we formulate a joint optimization problem over the channel assignment, decoding order of NOMA users, power allocation, and reflection coefficients. The formulated problem is proved to be NP-hard. To tackle this problem, a three-step novel resource allocation algorithm is proposed. Firstly, the channel assignment problem is solved by a many-to-one matching algorithm. Secondly, by considering the IRS reflection coefficients design, a low-complexity decoding order optimization algorithm is proposed. Thirdly, given a channel assignment and decoding order, a joint optimization algorithm is proposed for solving the joint power allocation and reflection coefficient design problem. Numerical results illustrate that: i) with the aid of IRS, the proposed IRS-NOMA system outperforms the conventional NOMA system without the IRS in terms of system throughput; ii) the proposed IRS-NOMA system achieves higher system throughput than the IRS assisted orthogonal multiple access (IRS-OMA) systems; iii) simulation results show that the performance gains of the IRS-NOMA and the IRS-OMA systems can be enhanced via carefully choosing the location of the IRS.

190 citations

Journal ArticleDOI
01 Sep 1994
TL;DR: In this article, a hierarchical overlaid scheme suitable for high-capacity microcellular communications systems is considered as a strategy to achieve high system performance and broad coverage, where high-teletraffic areas are covered by microcells while overlaying macrocells cover low-TEFL areas and provide overflow groups of channels for clusters of microcells.
Abstract: A hierarchical overlaid scheme suitable for high-capacity microcellular communications systems is considered as a strategy to achieve high system performance and broad coverage. High-teletraffic areas are covered by microcells while overlaying macrocells cover low-teletraffic areas and provide overflow groups of channels for clusters of microcells. New calls and handoff calls enter at both the microcell and macrocell levels. Handoff calls are given priority access to channels at each level. The layout has inherent load-balancing capability, so spatial teletraffic variations are accommodated without the need for elaborate coordination of base stations (wireless gateways). An analytical model for teletraffic performance (including handoff) is developed. Theoretical performance characteristics that show carried traffic as well as blocking, handoff failure, and forced termination probabilities are derived. Effects of nonuniform teletraffic demand and channel allocation strategies on system performance are discussed. >

190 citations

Book
28 Feb 1999
TL;DR: In this article, the authors present a more accurate analysis of radio propagation in cellular networks using the proven techniques described in this book, which shows how to improve the design of microcellular network systems by combining propagation models with topographical/morphological databases and ray-tracing acceleration techniques.
Abstract: From the Publisher: Obtain a more accurate analysis of radio propagation in cellular networks using the proven techniques described in this book. Cell Planning for Wireless Communications surveys the principle tools used in the planning of micro/pico cellular systems for personal communication networks. Engineers, researchers, consultants, and mobile communication graduate students learn how to use specific computer codes to perform a reliable analysis of the major aspects of micro/pico cellular design including propagation, fading estimation, mutual interference, cell geometry, teletraffic, and channel allocation. The book shows you how to improve the design of microcellular network systems by combining propagation models with topographical/morphological databases and ray-tracing acceleration techniques. The authors explain Physical Optic (PO), Geometrical Optic (GO), and the Uniform Theory of Diffraction (UTD) for the analysis of propagation in complex urban or indoor scenarios. The book also surveys select empirical propagation models. With over 100 illustrations, 300 equations, computer models and applications to PCS planning, a tutorial presentation of the application of UTD to wireless problems, and new ray tracing algorithms, you get all the information you need to compute propagation in micro/pico cells in one reference. Furthermore, the approaches presented may also be applied to macrocellular systems.

187 citations

Proceedings ArticleDOI
06 May 2012
TL;DR: Computer simulation results demonstrate that the DAN using proposed DCA achieves higher spectrum efficiency than the conventional CN.
Abstract: In this paper, we propose a dynamic channel assignment (DCA) scheme for distributed antenna networks (DANs). DANs, in which many antennas are distributed in each cell, significantly reduce the transmit power compared to conventional cellular networks (CNs). In DAN, a different group of channels should be assigned for each distributed antenna to avoid the interference. Since DAN can also reduce the interference power due to its low transmit power property, the same channel groups can be reused even within the same cell. Proposed DCA scheme dynamically assigns the channels based on the co-channel interference measurement. Computer simulation results demonstrate that the DAN using proposed DCA achieves higher spectrum efficiency than the conventional CN.

185 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202315
202259
2021181
2020268
2019293
2018292