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基于多信道预约可冲突避免的多址接入协议 总被引:3,自引:0,他引:3
本文为多跳分布多无线网络提出了一套灵活而有效的自适应获取冲突避免(AACA)的多址接入协议。在该协议中,各节点竞争公共信道,利用RTS/CTS对话形式来预约各业务信道,成功预约后的分组传输不会受到其他节点的干扰。它使用任意确定数目信道,以异步方式工作,并且使得各节点利用半双工无线电台就可以灵活、简便地实现资源预约。分析和比较结果说明,所提出的多信道预约协议可以有效地解决隐藏终端、暴露终端以及侵入终端的问题。 相似文献
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一种基于服务质量(QoS)的分组预约多址协议 总被引:2,自引:1,他引:1
本文从用户角度和实际通信情况考虑,提出了一种基于服务质量的分组预约多址协议(ET-PRMA)。该方法利用用户信息之间的相关性,适当地调整分组预约多址(PRMA)协议中的话音用户再次竞争信道的概率,提高PRMA系统中话音终端获取信道的速度,从而达到提高话音业务性能,从计算机仿真的结果看,该方法对提高PRMA系统中话音业务的性能确有帮助。 相似文献
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ATMAC: adaptive token‐based medium access control protocol for cognitive radio wireless mesh network
Ramesh Babu Battula Manoj Singh Gaur Dinesh Gopalani 《International Journal of Communication Systems》2016,29(17):2503-2516
In next generation wireless communication, cognitive radio technology facilitates to utilize underutilized licensed frequency bands that help to enhance the spectrum utilization. Cognitive radio wireless mesh network (CRWMN) is a promising and reliable technology to experience high throughput with low cost. Existing IEEE 802.11 based medium access control (MAC) protocols offer high data rates with decreasing efficiency at the MAC layer. Hence, most of the researchers applied aggregation mechanisms to provide the solution to bandwidth craving applications. In CRWMN, MAC design is significant because stability, efficient resource utilization, and scalability are predominating problems; however, the specified MAC issues are not yet resolved. The proposed MAC is novel, which aims to ensure reliability and scalability for CRWMN. The common control channel is used to exchange handshaking frames between the transmitter and receiver. It helps us to schedule the data transmission as well as reserve the channel in a discrete time interval. It introduces a token‐based channel accessing mechanism with resource‐aware channel assignment, which resolves the problems of efficiency and stability. The proposed MAC simulated using the network simulator (ns‐2), and the simulation results demonstrate that the proposed protocol improved the performance compared with the existing protocols. 相似文献
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声通信是水下传感网的主要通信方式之一,但是它具有长延迟和低带宽的特点,这是水下传感网MAC(media access control)协议研究面临的主要挑战。为提高网络吞吐量,提出了一种接收者发起的多会话MAC协议(RIM-MAC)。它利用接收者发起会话,通过一次会话的4次握手完成所有邻居数据分组的传输,有效地减少握手次数。同时利用侦听到的本地信息(邻居延迟图和邻居的传输调度)避免信道冲突并发起多个会话,这解决了长传播延迟带来的信道利用率低的问题。RIM-MAC通过增强节点间并行传输的能力,在接收者和发送者两端提高时空复用率,与经典水下MAC协议比,网络吞吐量提高了至少36%。除此之外,基于自适应数据轮询策略提出了一种网络负载公平算法(FTA),它保证了网络中竞争节点间的信道访问的公平性。仿真实验表明,在长传播延迟的场景下,RIM-MAC取得了比典型的水下传感网MAC协议更好的吞吐量性能。 相似文献
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VanDung Nguyen Tran Trong Khanh Xuan‐Qui Pham Ga‐Won Lee Eui‐Nam Huh 《International Journal of Communication Systems》2020,33(1)
The existing adaptive multichannel medium access control (MAC) protocols in vehicular ad hoc networks can adjust themselves according to different vehicular traffic densities. These protocols can increase throughput and guarantee a bounded transmission delay for real‐time safety applications. However, the optimized control channel interval is computed based on the maximum throughput while ignoring the strict safety packet transmission delay requirements. In this paper, we analyze the effects of the throughput and strict safety packet transmission delay with adaptive multichannel MAC protocols, such as connectivity‐aware MAC (CA MAC), adaptive multi‐priority distributed MAC (APDM), multi‐priority supported p‐persistent MAC (MP MAC), and variable control channel interval MAC (VCI) protocols. The performance and analysis results show that: (a) under a low data rate condition, CA MAC does not guarantee a strict safety packet transmission delay; (b) APDM not only satisfies the safety packet transmission requirement, but also provides the lowest safety packet transmission delay; (c) under a high data rate condition, we suggest APDM for use as an adaptive MAC protocol because it allows for high throughput for nonsafety packets and preserves low safety packet transmission delay; (d) under a low data rate condition with various data packet sizes, we suggest MP MAC for high throughput, which satisfies the safety packet transmission requirement; and (e) under low vehicle density and low data rate conditions, VCI can support high throughput. A balance between transmission delay and throughput must be considered to improve the optimal efficiency, reliability, and adaptability. 相似文献
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In a regular wireless ad hoc network, the Medium Access Control (MAC) protocol coordinates channel access among nodes, and the throughput of the network is limited by the bandwidth of a single channel. The multi-channel MAC protocols can exploit multiple channels to achieve high network throughput by enabling more concurrent transmissions. In this paper, we propose a hybrid and adaptive protocol, called H-MMAC, which utilizes multi-channel resources more efficiently than other multi-channel MAC protocols. The main idea is to adopt the IEEE 802.11 Power Saving Mechanism and to allow nodes to transmit data packets while other nodes try to negotiate the data channel during the Ad hoc Traffic Indication Message window based on the network traffic load. The analytical and simulation results show that the proposed H-MMAC protocol improves the network performance significantly in terms of the aggregate throughput, average delay, fairness and energy efficiency. 相似文献
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Cross-Layer Based Opportunistic MAC Protocols for QoS Provisionings Over Cognitive Radio Wireless Networks 总被引:6,自引:0,他引:6
Hang Su Xi Zhang 《Selected Areas in Communications, IEEE Journal on》2008,26(1):118-129
We propose the cross-layer based opportunistic multi-channel medium access control (MAC) protocols, which integrate the spectrum sensing at physical (PHY) layer with the packet scheduling at MAC layer, for the wireless ad hoc networks. Specifically, the MAC protocols enable the secondary users to identify and utilize the leftover frequency spectrum in a way that constrains the level of interference to the primary users. In our proposed protocols, each secondary user is equipped with two transceivers. One transceiver is tuned to the dedicated control channel, while the other is designed specifically as a cognitive radio that can periodically sense and dynamically use the identified un-used channels. To obtain the channel state accurately, we propose two collaborative channel spectrum-sensing policies, namely, the random sensing policy and the negotiation-based sensing policy, to help the MAC protocols detect the availability of leftover channels. Under the random sensing policy, each secondary user just randomly selects one of the channels for sensing. On the other hand, under the negotiation-based sensing policy, different secondary users attempt to select the distinct channels to sense by overhearing the control packets over the control channel. We develop the Markov chain model and the M/GY/1-based queueing model to characterize the performance of our proposed multi-channel MAC protocols under the two types of channel-sensing policies for the saturation network and the non-saturation network scenarios, respectively. In the non-saturation network case, we quantitatively identify the tradeoff between the aggregate traffic throughput and the packet transmission delay, which can provide the insightful guidelines to improve the delay-QoS provisionings over cognitive radio wireless networks. 相似文献
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Daneshgaran F. Laddomada M. Mesiti F. Mondin M. Zanolo M. 《Communications, IEEE Transactions on》2008,56(7):1178-1188
In this paper, we provide a saturation throughput analysis of the IEEE 802.11 protocol at the data link layer by including the impact of both transmission channel and capture effects in Rayleigh fading environment. Impacts of both non-ideal channel and capture effects, specially in an environment of high interference, become important in terms of the actual observed throughput. As far as the 4-way handshaking mechanism is concerned, we extend the multi-dimensional Markovian state transition model characterizing the behavior at the MAC layer by including transmission states that account for packet transmission failures due to errors caused by propagation through the channel. This way, any channel model characterizing the physical transmission medium can be accommodated, including AWGN and fading channels. We also extend the Markov model in order to consider the behavior of the contention window when employing the basic 2-way handshaking mechanism. Under the usual assumptions regarding the traffic generated per node and independence of packet collisions, we solve for the stationary probabilities of the Markov chain and develop expressions for the saturation throughput as a function of the number of terminals, packet sizes, raw channel error rates, capture probability, and other key system parameters. The theoretical derivations are then compared to simulation results confirming the effectiveness of the proposed models. 相似文献
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Cognitive radio was introduced to fill up the imbalance between spectrum scarcity and spectrum underutilization. So to make such an ideology work, a network which can utilize all the available channel in the best efficient manner, without causing any harmful interface to primary user (PU) and maintaining the Quality of Service (QoS) for cognitive user (CU) is required. In both Mesh as well as ad-hoc networks, effective utilization of the white-spaces by the CUs maintaining the QoS for both primary and CU is a challenging task due to the frequent and instant change in their channel status. In this paper an intelligent-MAC (i-MAC) for cognitive radio (CR) using two transceivers based on hybrid approach of combination of cooperative decision and contention-free approach is proposed. Cooperative decision, to overcome hidden node or the case when there is no common channel between the CU’s and contention-free approach, to solve the issues in contention mechanism, where same channel is selected simultaneously by multiple CU’s. Proposed CR-i-MAC permits an effective dynamic spectrum access to CUs without effecting the QoS for PU’s. The simulative performance analysis of proposed CR-i-MAC is tested in various critical cases like multi-channel single-radio and multi-channel multi-radio over different on demand routing protocols like dynamic source routing, ad-hoc on demand distance vector and weighted cumulative expected transmission time using network simulator (NS-2). The performance of the network is measured on the basis of parameters like throughput, delay and interference. The analysis of the simulation results shows that the proposed CR-i-MAC outperforms various other CR MAC’s in terms of both increased throughput and reduced delays thereby making the system stable and efficient. 相似文献