Euler spiral based backoff algorithm for MAC protocol in mobile Ad Hoc networks

In IEEE 802.11 standard, distributed coordination function (DCF) uses binary exponential backoff (BEB) algorithm to resolve collisions. However, performance of DCF with BEB decreases as the number of contending stations increases. To solve this problem, enhanced gentle DCF (EGDCF) and binary negative-exponential backoff algorithm (BNEB) have been proposed. In EGDCF algorithm, each station counts the number of consecutive successful transmissions in present backoff stage. If the number of consecutive successful transmissions reaches the predefined maximum value, station decreases its backoff stage. BNEB algorithm maintains a maximum contention window size during collisions and reduces a contention window size into half after complete transmission without retransmission. Since these two algorithms control backoff stage and contention window based on estimation of the number of stations, they improve performance of DCF. However, DCF cannot support differential quality of services (QoS) So IEEE 802.11e has adopted EDCA for contention-based medium access mechanism. In this paper, we adopt EGDCF and BNEB algorithms into EDCA to effectively support differentiated services in wireless LAN. We evaluate performance of conventional EDCA and EDCA with EGDCF and BNEB under saturation environment.

The distributed coordination function (DCF) of IEEE 802.11 standard adopts the binary exponential backoff (BEB) for collision avoidance. In DCF, the contention window is reset to an initial value, i.e., CWmin, after each successful transmission. Much research has shown that this dramatic change of window size may degrade the network performance. Therefore, backoff algorithms, such as gentle DCF (GDCF), multiplicative increase-linear decrease (MILD), exponential increase-exponential decrease (EIED), etc., have been proposed that try to keep the memory of congestion level by not resetting the contention window after each successful transmission. This paper proposes a multichain backoff (MCB) algorithm, which allows stations to adapt to different congestion levels by using more than one backoff chain together with collision events caused by stations themselves as well as other stations as indications for choosing the next backoff chain. The performance of MCB is analyzed and compared with those of 802.11 DCF, GDCF, MILD, and EIED backoff algorithms. Simulation results show that, with multiple backoff chains and collision events as reference for chain transition, MCB can offer a higher throughput while still maintaining fair channel access than the existing backoff algorithms

A new medium access control (MAC) scheme for mobile ad-hoc networks (MANETs) has been proposed with the goal of achieving fairness at the MAC layer. Most of the recently proposed contention-based MAC for MANET still use binary exponential backoff (BEB) algorithm to solve the contention problem, which contributes partially to instability and unfair medium sharing. In this paper, we propose to combine the exponential increase exponential decrease backoff algorithm (EIED) with an existing MANET MAC called fair MAC with cooperation between sender and receiver (FMAC/CSR), aiming to achieve fairer medium sharing between contending connections and more stable behavior. Preliminary simulation results show that our scheme outperforms existing MAC schemes, with respect to stability and fairness

Mobile devices are able to build their own networks, which are referred to as mobile ad hoc networks. These networks do not require any kind of permanent wiring or other infrastructure (MANETs). The success of MANETs and their adaptability to a variety of tasks is, to a considerable extent, based on the routing protocols that they use. Using metrics such as routing overhead, end-to-end delay, and packet delivery ratio, we compare and contrast the various routing protocols that can be employed in MANETs, including proactive, reactive, and hybrid protocols. This comparison and contrast is carried out in this study. In addition to this, we discuss the simulation tools that are utilized to evaluate the efficacy of MANET routing algorithms and define the several performance indicators that may be utilizedin the course of this endeavor. This paper makes a contribution to an ongoing body of research into the analysis of routing protocols in MANETs by offering guidance to network engineers and researchers on how to select the most appropriate routing protocol and simulation tool for a particular MANET scenario. In doing so, the paper maximizes the potential for effective and efficient communication between mobile nodes, which is one of the main goals of the research.

User Datagram Protocol (UDP) is proposed for the efficient servicing of multimedia traffic flows in Internet and it does not make use of any congestion control mechanism. The Internet Engineering Task Force (IETF) is working on development of a protocol standard that is suited to the needs of multimedia applications, known as the Datagram Congestion Control Protocol (DCCP) [6]. DCCP combines the end-to-end transport and congestion control semantics of TCP with the low-delay unreliable service provided by UDP. DCCP performance over the wired network with bursty traffic has been tested and has shown that DCCP holds promise as a wired network transport protocol [4]. However, to the best of our knowledge, the working of DCCP over Mobile Ad hoc Networks has not been evaluated. In this paper, we have evaluated the performance of DCCP over Mobile Ad Hoc Networks [10]. The two congestion control schemes made available under DCCP (TCP-like - CCID2 and TFRC - CCID3) were evaluated in a simulation environment, comparing with TCP considering throughput, end-to-end delay and packet loss as metrics [7,8]. Our results show that DCCP achieves considerably better throughput than TCP.

A mobile ad hoc network (MANET) is a distinctive example of a decentralized, self-organizing, and self-managing wireless ad hoc network. MANET is utilized in several domains such as rescue operations, real-time information dissemination, interpersonal communication, information exchange, and network partitioning. MANET exhibits dynamic alterations in both its structure and nodes to facilitate rapid data transmission. The mobility of nodes presents numerous opportunities for routing design difficulties among them. A list of routing protocols exists, each with unique characteristics, developed for certain locations,, and compared based on various metrics. This study provides a comprehensive overview and comparison of several MANET routing strategies, along with their limitations in ad hoc routing networks.

A mobile ad hoc network (MANET) consists of a set of mobile hosts that can communicate with each other without the assistance of base stations. In MANETs, the high mobility of mobile nodes is a major reason for link failures. In this paper, we propose a stable weight-based on-demand routing protocol (SWORP) for MANETs. The proposed scheme uses the weight-based route strategy to select a stable route in order to enhance system performance. The weight of a route is decided by three factors: the route expiration time, the error count, and the hop count. Route discovery usually find multiple routes from the source node to the destination node. Then we select the path with the largest weight value for routing. Experimental results show that the proposed SWORP outperforms DSR and AODV especially in the high mobility environment.

Mobility management is a key aspect of designing and evaluating protocols for Mobile Ad Hoc Networks (MANETs). The high mobility of nodes in a MANET constantly causes the network topology to change. Mobility patterns of nodes have a direct effect on fundamental network characteristics, such as path length, neighborhood size, and link stability. Consequently, the network performance is strongly affected by the nature of mobility patterns. While evaluating protocols for a specific MANET application, it becomes imperative to use a mobility model that is able to capture the movement of nodes in an accurate manner. The objective of this work is to produce mobility models that are able to describe tactical mobility in military applications of MANETs. We provide models of four tactical scenarios, show that these models are accurate compared to synthetic traces, and that when used to evaluate network protocols, they provide different conclusions than when using generic mobility models.

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.

The control and routing performances of mobile ad hoc networks (MANETs) depend upon the efficiency of the network-wide broadcasting schemes that are in place. Ad hoc networks are often characterized by poor infrastructure quality, limited resources, dynamic variation and a need for mobility; therefore, ease of deployment, adaptability and potential for energy-savings are the primary drivers considered in the design of typical broadcasting schemes. This paper proposes a distributed intelligent broadcasting protocol (DIBP) that is capable of dynamically determining the broadcasting nodes in a MANET, based upon the distribution of network nodes. This eliminates the need for active network monitoring and periodical maintenance is not required. In addition, the distributed intelligent broadcasting protocol employs an adjustable parameter for determining the broadcasting node, broadcasting timing and the number of broadcasting nodes. This parameter can be changed dynamically based on different operational requirements; such as energy savings, hop count, network delay and other similar targets. Simulations of networks employing the protocol yield results showing that the DIBP performs better in terms of delivery delay, number of rebroadcast nodes, and delivery ratio.

Even without possible interference from external radio sources, the problem of guaranteeing quality-of-service (QoS) routing in mobile ad hoc networks (MANETs) is a difficult problem. Difficulties arise because node mobility can cause frequent network topology changes, communication channels can have high error rates, the jitter rate is high and several different applications can be sharing the use of the communication medium. This paper addresses these issues and proposes a new QoS routing protocol for MANETs that combines aspects of a MAC protocol and a path reservation protocol. The proposed QoS routing protocol can be implemented based on any routing method that supports multiple paths (e.g., DSDV, TORA, PDR). The QoS performance of the proposed protocol is verified with simulations conducted using NS-2.KeywordsMobile ad hoc network (MANET)quality-of-service (QoS)routingtime division multiple access (TDMA)

Mobile Adhoc Networks (MANETs) is a wireless infrastructure-less network, where nodes are free to move independently in any direction. The nodes have limited battery power; hence we require energy efficient routing protocols to optimize network performance. This paper aims to develop a new routing algorithm based on the energy status of the node. In this paper, it has been proposed a new Protocol for Mobile Adhoc Networks which is expected to achieve energy efficiency and reliability. The gossiping probability of a node is determined by the throughput. Differently from other proposals no external location service support, e.g., via GPS, is not required. Rather, the throughput is estimated from the “inside” of the network using feedback factor through the node propagation to the destination and the value of gossiping probability is adaptively adjusted. This results in less energy consumption and more reliability in the network.

The IEEE 802.15.4 standard utilizes the Binary Exponential Backoff (BEB) algorithm to control nodes' access to the shared wireless medium. The main drawback of BEB is that it updates the size of the contention window (CW) without taking into consideration the number of competing nodes and the conditions in the communications medium. Therefore, BEB has been shown to be inefficient in terms of channel utilization and fairness among the contending nodes. In this paper, we propose Adaptive Backoff Algorithm (ABA), a new backoff algorithm that adaptively determines the appropriate size of CW based on the collisions experienced by the nodes. That is, while BEB updates CW in a deterministic fashion, we introduce a probabilistic methodology to achieve that update. Our simulations compare the performance of ABA with that of BEB as well as three other algorithms proposed in the literature, namely, NO-BEB, KEB, and IBEB. The performance is studied in terms of power consumption, reliability, and channel utilization. Our results show that ABA outperforms the aforementioned algorithms while granting each node a fair access to the wireless medium.

The development of protocol standards and the low cost of wireless equipment increased the number of wireless network installations in public (airports, universities campuses) and private (enterprises, homes) areas all over the world. This research effort examines the IEEE 802.11 protocol that dominates wireless local area networks (WLANs). Specifically, it investigates the performance of the Distributed Coordination Function (DCF) of ΙEEE 802.11 Medium Access Control (MAC) protocol. The objective of this thesis is to contribute in the research for the development of a simple and effective MAC sub-layer for WLANs that utilize the IEEE 802.11 protocol. Mathematical models are developed to calculate the following metrics in order to examine the performance of DCF that use Binary Exponential Backoff (BEB) algorithm: a) average packet delay per backoff stage and probability per backoff stage b) average packet delay, c) packet jitter, d) packet drop probability, e) average packet drop time, f) packet delay distribution, and g) cumulative packet delay distribution. An admission control algorithm is also presented. The proposed mathematical models are a) simple, as expressed with relatively simple mathematical relations, b) accurate, since they are validated by comparing analytical against simulation results and show that the proposed models are fairly accurate, and c) provide results in short period of time. Different scenarios of WLANs are examined to investigate the effect of DCF parameters in performance and to define the system parameters values that improve the performance of the IEEE 802.11 protocol. The analysis of metrics and the application of their outcomes to WLANs contribute in the design and development of more efficient access methods to wireless medium. The main contribution of this thesis is that packet delay is investigated thoroughly as a measure of WLAN performance.%%%%Η ανάπτυξη προτύπων για τα ασύρματα τοπικά δίκτυα σe συνδυασμό μe το χαμηλό κόστος της ασύρματης τeχνολογίας eπέτρeψe την ραγδαία eξαπλωση των ασυρμάτων δικτύων σe κοινόχρηστους και σe ιδιωτικούς χώρους όπως πανeπιστήμια, πλατeίeς, αeροδρόμια, γραφeία eπιχeιρήσeων, οικίeς, κλπ. Η παρούσα διατριβή μeλeτά το πρωτόκολλο ΙEEE 802.11 το οποίο κυριαρχeί στα ασύρματα τοπικά δίκτυα. Eιδικότeρα eρeυνά την απόδοση της κατανeμημένης διαδικασίας πρόσβασης DCF του υποeπιπέδου MAC του ΙEEE 802.11. Σκοπός της παρούσας eρeυνητικής προσπάθeιας eίναι η συμβολή στην έρeυνα για την ανάπτυξη eνός απλού και αποτeλeσματικού υποeπιπέδου πρόσβασης μέσου MAC στα ασύρματα δίκτυα που βασίζονται στο πρωτόκολλο ΙEEE 802.11. Αναπτύσσονται μαθηματικά μοντέλα για τον υπολογισμό των ακόλουθων μeτρικών για την απόδοση της διαδικασίας DCF που χρησιμοποιeί τον αλγόριθμο eκθeτικής οπισθοχώρησης ΒEΒ: α) την μέση καθυστέρηση των πακέτων ανά βαθμίδα οπισθοχώρησης και την πιθανότητα ανά βαθμίδα οπισθοχώρησης, β) την μέση καθυστέρηση των πακέτων, γ) την κατανομή των καθυστeρήσeων των πακέτων, δ) την αθροιστική κατανομή των καθυστeρήσeων, e) την διακύμανση των καθυστeρήσeων των…

SUMMARYThe medium access control protocol determines system throughput in wireless mobile ad hoc networks following the ieee 802.11 standard. Under this standard, asynchronous data transmissions have a defined distributed coordination function that allows stations to contend for channel usage in a distributed manner via the carrier sensing multiple access with collision avoidance protocol. In distributed coordination function, a slotted binary exponential backoff (BEB) algorithm resolves collisions of packets transmitted simultaneously by different stations. The BEB algorithm prevents packet collisions during simultaneous access by randomizing moments at stations attempting to access the wireless channels. However, this randomization does not eliminate packet collisions entirely, leading to reduced system throughput and increased packet delay and drop. In addition, the BEB algorithm results in unfair channel access among stations. In this paper, we propose an enhanced binary exponential backoff algorithm to improve channel access fairness by adjusting the manner of increasing or decreasing the contention window based on the number of the successfully sent frames. We propose several configurations and use the NS2 simulator to analyze network performance. The enhanced binary exponential backoff algorithm improves channel access fairness, significantly increases network throughput capacity, and reduces packet delay and drop. Copyright © 2013 John Wiley & Sons, Ltd.