Binary exponential backoff (beb) algorithm, the de-facto standard contention resolution algorithm providing collision avoidance over ad hoc wireless networks, has several technical limitations. For instance, high coll...
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ISBN:
(纸本)9781424456383
Binary exponential backoff (beb) algorithm, the de-facto standard contention resolution algorithm providing collision avoidance over ad hoc wireless networks, has several technical limitations. For instance, high collision rate problem, unfair channel access, and throughput degradation are several widely known issues. In this paper, a self-adaptive backoff algorithm, namely slow start backoff (SSB) algorithm, is proposed and analyzed for ad hoc networks. Numerical results show that the proposed SSB algorithm outperforms the legacy beb algorithm. In addition to the theoretical analysis, simulations were conducted to verify the analysis, showing that the proposed scheme works very well in ad hoc wireless networks.
In wireless networks, MAC protocols determines the use of wireless channels, which is used to allocate limited communication resources among nodes. In traditional networks, nodes can continuously obtain energy. Someti...
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ISBN:
(纸本)9781538681787
In wireless networks, MAC protocols determines the use of wireless channels, which is used to allocate limited communication resources among nodes. In traditional networks, nodes can continuously obtain energy. Sometimes they can be supplied at any time when they are interrupted, and the topology of the network is relatively stable. Hence the researches on MAC protocols are generally carried out in the ideal state and focus on the performance of data transmission to improve the utilization of bandwidth and increase the real-time performance of the network. However, in some specific networks, the energy of nodes is limited and the network topology is dynamic. It can be seen that the differences of network structure make it necessary to design suitable MAC protocols to control the transmission process of data. This paper mainly introduces the back-off algorithm of the MAC layer protocols in the ideal state, and makes some comparative analyses between the binary exponential back-off algorithm and the related improved mechanisms. Then it introduces the S-MAC protocols for wireless sensor networks and the methods of calculating the throughput, delay and energy loss of the network. Finally the conclusions are drawn from the analyses of the network performance based on the main factors that affect the networks.
Channel efficiency and channel throughput in any network are affected by packet collisions. Reduction of packet collisions plays a greater role in Mobile Ad hoc Networks (MANETs), due to the open medium topology where...
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ISBN:
(纸本)9789532330762
Channel efficiency and channel throughput in any network are affected by packet collisions. Reduction of packet collisions plays a greater role in Mobile Ad hoc Networks (MANETs), due to the open medium topology where carrier sensing is not practical or feasible. Consequently, these collision issues introduce a key problem in MANET networks where researches proposed back-off mechanism to overcome packet collisions. Back-off algorithm is proposed to reduce collisions that happen when more than one node tries sending data on the channel simultaneously. The Binary Exponential Back-off (beb), the first Back-off algorithm that is deployed in Medium Access Control layer, is used by IEEE 802.11 to avoid collision in MANETs. beb algorithm uses a uniform random distribution Back-off values to solve the collision problem. In this paper, we propose Fibonacci Liner Increment Back-Off (FLB) algorithm to achieve an effective value for the Back-off timer of the nodes before accessing the channel to avoid collision. We carried on simulations using ns-2 to compare the performance of the proposed protocol with existing protocols like Fibonacci Increment Back-off (FIB), Binary Exponential Back-off (beb), Pessimistic Linear-Exponential Back-off (PLEB) in terms of packet delivery ratio (PDR), average End-End delay and normalized routing load. Simulation results demonstrated that our FLB algorithm outperforms existing protocols and achieves the best results in routing packets, normalized routing load and End-End delay.
Ad Hoc Network is a decentralized type of network where wireless devices are allowed to discover each other and communicate in peer to peer fashion without involving central access points. In most ad hoc networks, nod...
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ISBN:
(纸本)9781479981267
Ad Hoc Network is a decentralized type of network where wireless devices are allowed to discover each other and communicate in peer to peer fashion without involving central access points. In most ad hoc networks, nodes compete for access to shared wireless medium, often resulting in collision (interference). IEEE 802.11, a well-known standard, uses medium access control (MAC) protocol to support delivery of radio data packets for both ad hoc networks and infrastructure based network. But designing a Medium Access Control(MAC) protocol for ad hoc wireless networks is challenging, particularly when the protocol needs to achieve optimal performance both in terms of throughput and efficiency to deliver a packet. Error-prone channel has a significant impact on unsuccessful transmission probability which is often ignored by previous researches. Standard DCF (Distributed Coordination Function) operation of IEEE 802.11 enacted by binary exponential back-off (beb) algorithm cannot differentiate collision from corruption and therefore sets forth a (time) separation between multiple nodes accessing the channel by (appropriately) adjusting contention window (CW) upon a failure. This leads to increased delay in error-prone network when nodes are not contending at all. Since packet corruption depends on bit error rate (BER) and length of packets, packet size can have significant impact on the throughput in error-prone environment. In this paper, we analyze effect of packet size in determining optimal CW to improve throughput and efficiency for error prone networks. We propose a dynamic learning based scheme to adaptively select CW sub-range instead of whole selection range for different packet distribution. To validate our scheme extensive simulations have been done and simulation results show significant improvement in E2E delay performance.
Most studies on performance of IEEE 802.11 distributed coordination function (DCF) have proved that the binary exponential backoff (beb) algorithm suffers from low throughput, long transmission delays and low transmis...
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ISBN:
(纸本)9781479930838
Most studies on performance of IEEE 802.11 distributed coordination function (DCF) have proved that the binary exponential backoff (beb) algorithm suffers from low throughput, long transmission delays and low transmission reliability, for a high traffic load. In this paper, we propose a two-phase contention window (TPCW) access mechanism that enhances the aggregate throughput and transmission reliability while decreasing the medium access delay. In addition, this scheme aims at being computationally simple. This work characterizes the performance of the TPCW mechanism for different parameterization values. An analytical model is proposed for the TPCW access mechanism, which characterizes the frame transmission reliability, the total transmission delay and the aggregate throughput. The validity of our analytical model is verified through extensive simulations. By comparing the performance results, we conclude that the proposed scheme can significantly enhance IEEE 802.11 in terms of frame transmission reliability, total transmission delay and aggregate throughput.
Since the IEEE 802.11 DCF adopted the Binary Exponential Back-off (beb) algorithm in its contention window adjustment scheme, many alternative back-off algorithms were proposed in order to enhance the performance. Amo...
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ISBN:
(纸本)9781424456383
Since the IEEE 802.11 DCF adopted the Binary Exponential Back-off (beb) algorithm in its contention window adjustment scheme, many alternative back-off algorithms were proposed in order to enhance the performance. Among them is an Exponential Increase Exponential Decrease (EIED) back-off algorithm, whose performance was simulated and analyzed in a special case of doubling or halving the contention window size. This paper provides an analytical analysis for the general EIED algorithm. A closed form saturation throughput and a closed form saturation delay are derived. Our analytical results further establish the performance improvement of the general EIED algorithm over the beb algorithm and the basic EIED algorithm.
As the mainstream standard of WLANs, analyzing the performance of IEEE 802.11 protocol has been a research hotspot in the field of communication. In many research methods, the mathematical model based on Markov chain ...
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ISBN:
(纸本)9781538645093
As the mainstream standard of WLANs, analyzing the performance of IEEE 802.11 protocol has been a research hotspot in the field of communication. In many research methods, the mathematical model based on Markov chain is one of the most popular methods for performance analysis of IEEE 802.11 DCF. This paper classifies Markov chains as one-dimension, two dimension and three-dimension, introduces their application in analyzing the performance of 802.11 DCF respectively and summarizes their characteristic. The results proposed in this paper show that the appropriate dimension of Markov chain needs to be selected according to the complexity of the improved MAC protocol and considered communication scenarios.
A Q-Learning based back-off algorithm was proposed in this paper because the traditional DCF approach used for IEEE 802.11p MAC protocol to access the channel has some problems of the low packet delivery rate, high de...
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ISBN:
(纸本)9781509034383
A Q-Learning based back-off algorithm was proposed in this paper because the traditional DCF approach used for IEEE 802.11p MAC protocol to access the channel has some problems of the low packet delivery rate, high delay and the poor scalability in VANETs. The proposed algorithm which is quite different from the traditional beb algorithm was adopted by the nodes(agents) to interact with surroundings continuously and learn from each other. The vehicle nodes adjust the size of CW(Contention Window) dynamically according to the results learned from the surroundings so that the nodes can access the channel with the optimal CW eventually minimizing the packet collisions and end-to-end delay. The simulation results show that the communication nodes using the proposed algorithm can adapt to the unknown vehicular environment rapidly, and simultaneously the high packet delivery ratio, low end-to-end delay and high fairness can be achieved for vehicular network with various load.
Channel contention significantly contributes to TCP's poor performance in wireless ad hoc networks (WANET), where the IEEE 802.11 medium access control (MAC) protocol is used to access the medium. This article aim...
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Channel contention significantly contributes to TCP's poor performance in wireless ad hoc networks (WANET), where the IEEE 802.11 medium access control (MAC) protocol is used to access the medium. This article aims to boost the functionality of the IEEE 802.11 MAC protocol, which guarantees the effective and fair utilization of shared channel resources. Therefore, a novel method known as the channel usage based backoff (CHUBB) algorithm has been proposed to fine-tune the binary exponential backoff (beb) algorithm of the IEEE 802.11 MAC protocol. Using the CHUBB algorithm, each node's contention window (CW) is computed based on channel usage. Extensive simulation results demonstrate that by employing the suggested CHUBB algorithm, TCP has gained higher throughput and decreased the unfair impact on the network, such as the improvement in throughput ranges from 3.66% to 31.01% in a chain topology, 6.52% to 11.56% in a 7x7 grid topology, and 5.86% to 11.23% in a 9x9 grid topology. Compared to the beb algorithm, the suggested approach makes more efficient use of channel resources, leading to fewer retransmissions. Even when the user datagram protocol (UDP) was utilized, it functioned admirably at the transport layer.
Expansion of using SmartPhones last few years changed all data usage forecasts and it seems that only macro-cellular network layer will not be sufficient in meeting users request. Definition for HeterogeneousNetwork(H...
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ISBN:
(纸本)9789532330731
Expansion of using SmartPhones last few years changed all data usage forecasts and it seems that only macro-cellular network layer will not be sufficient in meeting users request. Definition for HeterogeneousNetwork(HetNet) according to Wikipedia is : 'Mobile Experts defines the Heterogeneous Network as a network with complex interoperation between macrocell, small cell, and in some cases WiFi network elements used together to provide a mosaic of coverage, with handoff capability between network elements.' HetNet is an attractive means of expanding mobile network capacity. A HetNet is typically composed of multiple radio access technologies, architectures, transmission solutions, and radio base stations(RBS) of varying transmission power. The aim of this paper is to explain main aspects of increasing mobile networks capacity using HetNet. It will be explained design aspects of HetNet deployment also expected capacity gains and main concerns and problems which might occure while introducing HetNet in existing mobile networks such as signal imbalance between macrocellular layer and HetNet.
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