IEEE 802.11 MAC Research Papers (original) (raw)

The exponential rise in wireless communication systems and allied applications has revitalized academiaindustries to achieve more efficient data transmission system to meet Quality-of-Service (QoS) demands. Amongst major wireless communication techniques, Mobile Ad-hoc Network (MANET) is found potential to provide decentralized and infrastructure less communication among multiple distributed nodes across network region. However, dynamic network conditions such as changing topology, congestion, packet drop, intrusion possibilities etc often make MANET’s routing a tedious task. On the other hand, mobile network feature broadens the horizon for intruders to penetrate the network and causes performance degradation.
Unlike classical MANET protocols where major efforts have been made on single network parameter based routing decision, this research paper proposes a novel Elitist Genetic Algorithm (EGA) Multi-Objective Optimization assisted Network Condition Aware QoS-Routing Protocol for Mobile Ad-hoc Networks (MNCQM). Our proposed MNCQM protocol exhibits two phase implementation where at first it performs
node-profiling under dynamic network topology for which three factors; irregular MAC information exchange, queuing overflow and topological variations have been considered. Towards this objective node features like Packet Forwarding Probability (PFP) at the MAC layer, Success Probability of Data Transmission (SPDT) of a neighboring node, and Probability of Successful Data Delivery (PSDD) have
been obtained to estimate Node-Trustworthiness Index (NTI), which is further used to eliminate untrustworthy nodes. In the second phase of implementation, a novel Evolutionary Computing assisted nondisjoint best forwarding path selection model is developed that exploits node’s and allied link’s connectivity and availability features to identify the quasi-sub-optimal forwarding paths. EGA algorithm intends to reduce hop-counts, connectivity-loss and node or link unavailability to estimate best forwarding
node. One key feature of the proposed model is dual-supplementary forwarding path selection that enables alternate path formation in case of link outage and thus avoids any iterative network discovery phase.

- by
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- Evolutionary Computation, Computer Networks, Routing, MANET Routing protocols

Many new routing protocols have been proposed for wireless sensor networks to maximize throughput, minimize delay or improve other QoS metrics in order to solve the problems of resource-constrained sensor nodes in large networks. However, many of them are based on flooding or its variants. Many routing messages are propagated unnecessarily and may cause different interference characteristics during route discovery phase and in the actual application data transmission phase. As a result, incorrect routes may be selected. Epidemic algorithms have been used to limit flooding in the field of wireless sensor networks. Directed diffusion has been commonly used in wireless sensor networks because it is designed to improve energy efficiency and scalability. However, the intrinsic flooding scheme for interest subscriptions prevents it from achieving the maximal potential of these two goals. We propose a routing protocol that uses ID-free epidemic flooding to limit interference in conjunction with metrics for increasing throughput and reducing delay. Simulation results in ns2 show that there is an optimal number of neighbors to achieve the best throughput and delay performance. For a fixed topology of a certain size, there exists an optimal percentage of neighbors that forward the flooding message to achieve the best throughput and delay performance.

A critical need in Mobile Wireless Sensor Network (MWSN) is to achieve energy efficiency during routing as the sensor nodes have scarce energy resource. The nodes' mobility in MWSN poses a challenge to design an energy efficient routing protocol. Clustering helps to achieve energy efficiency by reducing the organization complexity overhead of the network which is proportional to the number of nodes in the network. This paper proposes a novel hybrid multipath routing algorithm with an efficient clustering technique. A node is selected as cluster head if it has high surplus energy, better transmission range and least mobility. The Energy Aware (EA) selection mechanism and the Maximal Nodal Surplus Energy estimation technique incorporated in this algorithm improves the energy performance during routing. Simulation results can show that the proposed clustering and routing algorithm can scale well in dynamic and energy deficient mobile sensor network.

Platooning is both a challenging and rewarding application. Challenging since strict timing and reliability requirements are imposed by the distributed control system. Rewarding since considerable fuel reductions are possible. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. IEEE 802.11p has problems with its medium access method causing packet collisions and random delays. Therefore, we suggest a token-passing medium access method, where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in case of extra time in each beacon interval. We show that our token-based method is able to reduce the data age and increase reliability considerably compared to the standard.

Traditional TCP cannot detect link contention losses and route failure losses which occur in MANET and
considers every packet loss as congestion. This results in severe degradation of TCP performance. In this
research work, we modified the operations of TCP to adapt to network states. The cross-layer notifications
are used for adapting the congestion window and achieving better performance. We propose Cross-layer
information based Transmission Control Protocol (CTCP) which consists of four network states.
Decelerate state to recover from contention losses, Cautionary state to deal with route failures, Congested
state to handle network congestion and Normal state to be compatible with traditional TCP. Decelerate
state makes TCP slow down if the packet loss is believed to be due to contention rather than congestion.
Cautionary state suspends the TCP variables and after route reestablishment resumes with conservative
values. Congestion state calls congestion control when network is actually congested and normal state
works as standard TCP. Simulation results show that network state based CTCP is more appropriate for
MANET than packet loss based traditional TCP.

In this research, we study the optimization challenges of MANET and cross-layer technique to improve its performance. We propose an adaptive retransmission limits algorithm for IEEE 802.11 MAC to reduce the false link failures and predict the node mobility. We implemented cross layer interaction between physical and MAC layers. The MAC layer utilizes the physical layer information for differentiating false link failure from true link failure. The MAC layer adaptively selects a retransmission limit (short and long) based on the neighbour signal strength and sender node speed information from the physical layer. The proposed approach tracks the signal strength of each node in network and, while transmitting to a neighbour node, if it's received signal strength is high and is received recently then Adaptive MAC persists in its retransmission attempts. As there is high probability that neighbour node is still in transmission range and may be not responding due to some problems other then mobility. In this paper, we evaluate the performance of MANET and show that how our Adaptive MAC greatly improves it. The simulation is done using Network Simulator NS-2.

This paper presents an implementation of IEEE 802.15.4 MAC Layer of ZigBee protocol in order to monitor and control home appliances. This standard is applied to a communication protocol with small data packets, low transmission rate, and low energy consumption. The paper shows the development of a hardware and software prototype to monitor, control and configure washing machines with a wireless network interface using a PDA (Personal Digital Assistant). The results indicate the feasibility of building a household-electric network reaching the main features described above, by implementing the IEEE 802.15.4 protocol.

In the 802.11 protocol, DCF can be termed as an important mechanism in order to access the medium (Channel). This scheme is a random access based scheme which has its fundamentals based upon the efficient usage of CSMA/CA protocol. The retransmission of various collided packets is effectively managed in accordance with the Binary exponential Back-off rules. The waiting time of the BEB is exponentially increased by 2 after every unsuccessful transmission. Every successful transmission sets the back-off stage to initial stage and the contention window is also subsequently set to minimum regardless of any network conditions like the various n number of competing nodes. As the number of competing
nodes rises, it can cause substantial performance deprivation as a result of the new collisions caused. This paper highlights and investigates the various modifications possible in the basic calculating methodology of the CW size after every successful transmission and collision of the BEB algorithm and it also evaluates the performance through different simulations possible for it. This paper also throws some significant light on the comparative study conducted on the throughput, end to end delay and packet loss ratio of the investigated schemes along with conventional DCF & one –another.

Providing QoS requirements like good throughput and minimum access delay are challenging tasks with regard to 802.11 WLAN protocols and Medium Access Control (MAC) functions. IEEE 802.11 MAC layer supports two main protocols: DCF (Distributed Coordination Function) and EDCF (Enhanced Distributed Coordination Function). During the evaluation of EDCF, the performance of various access categories was the determining factor. Two scenarios, with same Physical and MAC parameters, one implementing the DCF and other EDCF, were created in the network simulation tool (OPNET MODELER [5]) to obtain the results. The results showed that the performance of EDCF was better in providing QoS for real-time interactive services (like video conferencing) as compared to DCF, because of its ability to differentiate and prioritize various services. Whereas the DCF's overall performance was marginally better for all kinds of services taken together.

ABSTRACT This paper presents an implementation of IEEE 802.15.4 MAC Layer of ZigBee protocol in order to monitor and control home appliances. This standard is applied to a communication protocol with small data packets, low transmission rate, and low energy consumption. The paper shows the development of a hardware and software prototype to monitor, control and configure washing machines with a wireless network interface using a PDA (Personal Digital Assistant). The results indicate the feasibility of building a household-electric network reaching the main features described above, by implementing the IEEE 802.15.4 protocol.

IEEE 802.11 networks have a great role to play in supporting and deploying of the Internet of Things (IoT). The realization of IoT depends on the ability of the network to handle a massive number of stations and transmissions and to support Quality of Service (QoS). IEEE 802.11 networks enable the QoS by applying the Enhanced Distributed Channel Access (EDCA) with static parameters regardless of existing network capacity or which Access Category (AC) of QoS is already active. Our objective in this paper is to improve the efficiency of the uplink access in 802.11 networks; therefore we proposed an algorithm called QoS Categories Activeness-Aware Adaptive EDCA Algorithm (QCAAAE) which adapts Contention Window (CW) size, and Arbitration Inter-Frame Space Number (AIFSN) values depending on the number of associated Stations (STAs) and considering the presence of each AC. For different traffic scenarios, the simulation results confirm the outperformance of the proposed algorithm in terms of throughput (increased on average 23%) and retransmission attempts rate (decreased on average 47%) considering acceptable delay for sensitive delay services.

Previous studies have shown that the actual handoff schemes employed in the IEEE 802.11 Wireless LANs (WLANs) do not meet the strict delay constraints placed by many multimedia applications like Voice over IP. Both the active and the passive supported scan modes in the standard handoff procedure have important delay that affects the Quality of Service (QoS) required by the real-time communications over 802.11 networks. In addition, the problem is further compounded by the fact that limited coverage areas of Access Points (APs) occupied in 802.11 infrastructure WLANs create frequent handoffs. We propose a new optimized and fast handoff scheme that decrease both handoff latency and occurrence by performing a seamless prevent scan process and an effective next-AP selection. Through simulations and performance evaluation, we show the effectiveness of the new adaptive handoff that reduces the process latency and adds new context-based parameters. The Results illustrate a QoS delay-respect required by applications and an optimized AP-choice that eliminates handoff events that are not beneficial.

In the design of wireless networks the medium access control (MAC) protocols have a very high impact on the performance of the network. The IEEE 802.11 is widely accepted technology for the Wireless LANs has been used by wireless networks. Delay is one of the important parameter to measure the performance of the wireless networks. We give a delay analysis of the Distributed Coordination Function of IEEE 802.11 under modified Binary Exponential Backoff (BEB) Algorithm using Frequency Hoping Spread Spectrum (FHSS). In the modified BEB, initially the contention window size increases with the factor of √2 for first four collisions and after that for more collisions the size of contention window gets double. The size of contention window varies between CW min and CW max. Markov chain has been used for the analysis of IEEE 802.11 DCF for both modes basic and RTS/CTS. We have considered number of nodes and transmission probability to compute the delay for both the modes. The results show that the performance of RTS/CTS mode is better than the basic access mode. In this paper, we have numerically analyzed the IEEE 802.11 DCF by varying different parameters (i.e. number of nodes, transmission probability etc.).

In this paper, we present a distributed flow-based access scheme for slotted-time protocols, that provides proportional fairness in ad-hoc wireless networks under constraints on the buffer overflow probabilities at each node. The proposed scheme requires local information exchange at the link-layer and end-to-end information exchange at the transport-layer, and is cast as a nonlinear program. A medium access control protocol is said to be proportionally fair with respect to individual end-to-end flows in a network, if the product of the end-to-end flow rates is maximized. A key contribution of this work lies in the construction of a distributed dual approach that comes with low computational overhead. We discuss the convergence properties of the proposed scheme and present simulation results to support our conclusions.

Remote health care monitoring system (RHCMS) has dr
awn considerable attentions for the last decade. As
the aging population are increasing and at the same
time the health care cost is skyrocketing there ha
s
been a need to monitor a patient from a remote loca
tion. Moreover, many people of the World are out o
f
the reach of existing healthcare systems. To solve
these problems many research and commercial version
s
of RHCMS have been proposed and implemented till no
w. In these systems the performance was the main
issue in order to accurately measure, record, and a
nalyze patients’ data. With the ascent of wireless
network RHCMS can be widely deployed to monitor the
health condition of a patient inside and outside o
f
the hospitals. In this work we present a ZigBee bas
ed wireless healthcare monitoring system that can
provide real time online information about the heal
th condition of a patient. The proposed system is a
ble to
send alarming messages to the healthcare profession
al about the patient’s critical condition. In addit
ion
the proposed system can send reports to a patient m
onitoring system, which can be used by the healthca
re
professionals to make necessary medical advices fro
m anywhere of the World at any time.

Mobile Ad-hoc Networks (MANETs) are self configurin
g, decentralized and dynamic nature wireless
networks which have no infrastructure. These offer
a number of advantages, however the demand of high
traffic flows in MANETs increases rapidly. For thes
e demands, limited bandwidth of wireless network is
the
important parameter that restrains the development
of real time multimedia applications. In this work,
we
propose a solution to utilize available bandwidth o
f the channel for on demand multiple disjoint paths
.
The
approximate bandwidth of a node is used to find the
available bandwidth of the path. The source choose
s
the primary route for data forwarding on the basis
of path bandwidth. The simulation results show that
the
proposed solution reduces the frequency of broadcas
t and performs well in improving the end to end
throughput, packet delivery ratio, and the end to e
nd delay.

- by Maria Papadopouli
- •
- IEEE 802.11 MAC