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About 7,390 papers for “Channel access method”

Bi-code channel access method for ad hoc networks

Jarmo Prokkola, Timo Bräysy · 2005

Ad hoc networks operate conventionally on a contention based common channel where harmful collisions bring problems with increasing traffic load. The use of code division multiple access (CDMA) increases the capacity by allowing multiple successful transmissions simultaneously within the limits of multiple access interference (MAI). However, so far, most of the studies on CDMA ad hoc networking have concentrated on complex schemes like transmitter based orthogonal coding. This paper takes a cross-layered design approach for ad hoc networking, and proposes a CDMA-based bi-code channel access methods. In this method, two channels are tracked at the receiver. One is used as a dedicated receiver based channel for robust data transmission, and the other is used as a common access channel. It is shown that this method outperforms traditional methods and still is easy to implement over different platforms, robust for the design parameters and different conditions while maintaining the original idea of ad hoc networking.

Cited by 9

MACA-a New Channel Access Method for Packet Radio

P. Karn · 1990

n a The existing Carrier Sense Multiple Access (CSMA) method widely used i mateur packet radio on shared simplex packet radio channels frequently suffers from l the well-known hidden terminal problem and the less well known but related prob em of the exposed terminal. This paper proposes a new scheme, Multiple Access c with Collision Avoidance (MACA), that could greatly relieve these problems. MACA an also be easily extended to provide automatic transmitter power control. This could increase the carrying capacity of a channel substantially.

Cited by 1,327

A Novel Hybrid Access Point Channel Access Method for Wireless-Powered IoT Networks

Xiaoyu Song, Kwan‐Wu Chin · IEEE Internet of Things Journal · 2021

This article considers data collection in a wireless-powered Internet-of-Things (IoT) network. Specifically, it addresses the novel problem of determining the mode of each time slot, where a hybrid access point (HAP) needs to decide whether to charge or collect data from devices. Also, in data time slots, HAP has to decide on a device for data transmission. To this end, we outline an integer linear program (ILP) to determine the mode and the transmitting device over a given planning time horizon. We also propose a rolling horizon (RollH) approach that uses a Gaussian mixture model (GMM) to estimate channel gains. Our results indicate that the amount of data collected by HAP is affected by its charging power, distance between HAP and each device, number of devices, and planning horizon length. The RollH approach allows the HAP to collect 740% more data as compared to competing approaches.

Cited by 6

New Channel Assignment Method for Access Points in Wireless LANs

Dr. Mohammed, Fawzi Al-hunaity · 2014

Wireless LANs topology communicates using radio frequencies. The number of these frequencies is limited and not enough to assign a special frequency for each Access Point, this means that the communication topology should use a "re-use " mechanism, which allows the system to assign the same frequency that assigned previously for another access point. In this paper, we suggest a method to assign frequency channels to access points in a Wireless LANs system. The goal of this paper is to reach the assignment that prevents interference between access points especially neighbor ones. We used Genetic Algorithm to work on this issue, it is considered as an Expert System and one of the main multi point search technique used in computing to solve optimization and search problems.

Cited by 0

Analysis of a slotted access channel with average cycle method

Zhao Dong-feng, Li Bihaiy, Zheng Sumin · 2002

Random access techniques in the packet broadcasting environment are a very important research topic. A broadcast channel is a radio packet communication channel, and the relative distances between the users and the receiver can vary greatly. Thus, packets from different transmitters arrive at the receiver with substantially different power levels. These phenomena give rise to a capture effect at the receiver. The packet arriving with the highest power level has a good chance of being detected accurately, even when other packets arrive at the same time. This capture effect improves the system throughput and other performance measures. The mean cycle times of the slotted access channel are analyzed by using the average cycle method. Analytic formulae for mean values of a successful period and a colliding period and an idle period are derived. Also, the upper bounds on the throughput of the system with capture effect are provided.

Cited by 5

Analysis of a new channel access method for home base station

M.I. Silventoinen, Maija Kuusela, P.A. Ranta · Proceedings of ICUPC - 5th International Conference on Universal Personal Communications · 2002

This paper addresses the problem of allocating frequencies in a GSM-based home base station (HBS) system. A novel solution called total frequency hopping (TFH) is presented in order to overcome the frequency allocation and the inter-HBS synchronisation problems. The HBS system will use the same frequency band as the overlaying GSM network and thus creates more interference to it. The simulation results reveal that the negative impact of the underlying HBS system on the GSM network performance is minimal provided that the HBS transmission (TX) power is reasonable low. The TX power cannot be arbitrarily low, however, since the HBS system must be able to function in the presence of the interference from the overlaying high power GSM network. When the power ratio between GSM base station and HBS is around 40 dB, the both networks can co-exist at the same frequency band.

Cited by 10

A Bidirectional Channel Access Method in Millimeter Wave Dense Deployment Scenario

Qi Wang, Yujin Bu, Hao Wu · 2022 IEEE 5th International Conference on Electronics Technology (ICET) · 2022

Due to the high path loss, directional transmission and reception are adopted in millimeter wave band which provides the possibility for spatial multiplexing. Traditional microwave access technologies usually use omnidirectional channel assessment to avoid transmission interference. But this will greatly suppress the spatial multiplexing in beam-based transmission, and the transmitter only needs to perform carrier sensing at the direction of the target receiver. However, directional carrier sensing may lead to potential hidden terminal problems. This paper proposes a bidirectional carrier sensing scheme, which aims to reduce the interference caused by the hidden terminal while ensuring the spatial reuse rate of the directional transmission. The key idea is to perform carrier sensing in the direction of the receiver and the opposite direction at the same time before the transmitter accesses the channel. Numerical results prove that proposed scheme can effectively reduce hidden terminals, avoid interference, and improve system throughput.

Cited by 2

A method to estimate the spatial coherence of photoacoustic channel data without access to channel data

Kelley M. Kempski, Mardava R. Gubbi, Muyinatu A. Lediju Bell · 2021

Channel signal-to-noise ratio (SNR) is a metric to assess photoacoustic image quality based on the raw photoacoustic channel data. Current methods for measuring channel SNR require access to raw data or delay data prior to summation (e.g., prior to DAS beamforming) in addition to knowledge of the noise profile to differentiate signal from noise. However, access to pre-beamformed data is not always feasible with clinical ultrasound scanners, and knowledge of noise profiles are typically not available. This paper introduces a new method for calculating channel SNR based on the probability density functions (PDFs) of beamformed data and shows how this method is related to not only channel SNR, but also other properties of channel data and image data for photoacoustic images.

Cited by 1

Prototyping of a new Multi-channel Multi-hop Access Method without RendezVous

Mahamat Habib Senoussi Hissein, Adrien van den Bossche, Thierry Val · Open Archive Toulouse Archive Ouverte (University of Toulouse) · 2017

One of the most important issues for wireless LANs is the access and the share of wireless radio medium. Several single-channel MAC protocols have been proposed and address this issue with interesting solutions, but some major problems related to channel access (hidden node, synchronization, propagation of RendezVous...) still persist in a multi-hop transmission context and are still the subject of intensive studies by the scientific community, especially when it is related to extended topologies on distributed Wireless Sensors Networks. This article proposes a new multi-channel MAC for all types of multi-hop wireless network topologies, without RendezVous, its prototyping and performance analysis.

Cited by 0Open access

A Three-Tier Deep Learning-Based Channel Access Method for WiFi Networks

Yiwei Huang, Kwan‐Wu Chin · IEEE Transactions on Machine Learning in Communications and Networking · 2023

Future WiFi networks require a channel access method that provides users with high capacity. Such a method must consider (1) channel bonding, which improves the transmission capacity of Access Points (APs), and (2) spatial reuse, where APs tune their Clear Channel Assessment (CCA) threshold and transmit power in order to transmit concurrently with neighboring APs. To date, there are no solutions that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">jointly</i> optimize the channels used by an AP, and the CCA threshold and transmit power of a bonded channel. To this end, we outline a three-tier deep learning approach. Briefly, at Layer-1, it selects a set of transmitting channels. At Layer-2 and Layer-3, it respectively determines the transmit power and CCA threshold for each selected channel. An AP then employs deep reinforcement learning to learn the optimal policy for each layer given its interference intensity and queue length. The simulation results show that when compared to three competing solutions, an AP that uses our approach is able to reduce its queue length by up to 62.52% under realistic traffic load.

Cited by 7Open access

Toward Order Optimal Channel Access in Unknown Environments: An Online Learning Method

S B Ye, Shaowei Wang · IEEE Transactions on Communications · 2024

We investigate the opportunistic channel access problem in a centralized cognitive radio network, where the cognitive base station (CBS) periodically detects spectrum holes in the licensed network and coordinates the unlicensed secondary users to utilize the idle channels. Existing spectrum access mechanisms typically rest on the assumption that the spectrum environment is known in advance, i.e., licensed channel states exhibit either stochastic or adversarial variations across different time instances and locations. These approaches address the spectrum access problem from the perspective of online learning, which relies heavily on the prior knowledge of network parameters such as the time horizon and the user activities to tune hyperparameters. In this paper, we tackle the multiuser channel access task by formulating it as a combinatorial multi-armed bandit problem in an unknown environment, where we propose an online mirror descent-based channel access method for the CBS that does not require any prior knowledge of the environment. Our proposed method adaptively adjusts the probability of secondary users accessing the licensed channels based on the historical transmission feedback, achieving order-optimal performance in both stochastic and adversarial environments. Numerical results validate the theoretical analysis and also demonstrate that the proposed method outperforms others under various network settings.

Cited by 1

Frequency occupancy prediction and its application in a novel channel access method

Keyvan, A. · Publikationsdatenbank der Fraunhofer-Gesellschaft (Fraunhofer-Gesellschaft) · 2011

This thesis was written with the motivation of further maintaining the rapid growth in wireless technologies by reducing the burden from the spectrum specifically in the industrial environments. Wireless sensor networks are used extensively in industrial environments which they commonly transmit packets periodically. Using the cognitive radio paradigm, spectrum can be sensed and later the periodic pattern in a specific channel can be determined. The periodic pattern is used in order to predict the future status of the channel. As part of this task, two frequency occupancy predictors have been implemented and evaluated. Moreover, using the channel occupancy prediction, a novel channel access method has been developed and was named CSMA/PCA. Compared to the conventional CSMA/CA, packet error rate has been found to be significantly lower and throughput has found to be much higher using CSMA/PCA.

Cited by 0