Medium Access Control

The main contribution of this paper is to propose a novel context aware priority-based medium access control (MAC) scheme for multichannel buffer-aided cognitive radio networks. The proposed scheme allows management of the average waiting time of the primary and secondary packets more efficiently based on the context of the packets. In particular, we consider a multichannel cognitive radio network with multiple primary users and multiple secondary users. Unlike [10], each channel in the considered network has its own service time for transmission the primary and secondary packets. Two different context aware prioritization methods are presented. In the first proposed scheme, delay sensitive packets in both the primary and secondary networks are given a higher priority compared to delay tolerant packets. Therefore, urgent primary and secondary packets are transmitted via best channels in terms of service time. In the second proposed scheme, the primary packets and short packets are given higher priority over the secondary packets and long packets, respectively. Thus, in each of the primary and secondary networks, the packets are served in an order which depends on the packet length. Hence, based on slow truck effect, the overall average waiting time of the primary and secondary packets is minimized, and therefore, the average primary and secondary throughput is maximized. By using a preemptive queuing system, we then calculate the average waiting time of the primary and secondary packets and the average throughput of the primary and secondary networks for the first and second proposed schemes, respectively. Simulation results show that the proposed priority based MAC scheme achieves lower average waiting time of packets and higher average primary and secondary throughput compared to the

Abstract-- One of the most active research areas for computer science and telecommunication researcher is the wireless sensor networks. Usually after the deployment of sensor nodes in the hazardous, hostile or remote areas, these nodes work on their own. These sensors nodes will have to perform their function with scare and none replenish able power resources. One of the main design objectives for these networks is Energy efficiency. This paper presented the obstacle and challenges in the design and development of power aware medium access control protocol for wireless sensor networks. In this paper we depict numerous medium access control protocols for the sensor networks, and highlight their potency and limitations wherever possible. In the end some future research directions are describe for the design of medium access control protocol for wireless sensor networks.

To improve the efficiency of node cooperation and multiple access performance in multihop wireless networks, a rapid cooperation-differentiated medium access control (MAC) protocol is proposed. In the protocol, the helper selection process is divided into a priority differentiation phase and contention resolution phase for helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase for the same priority helpers can use any existing collision resolution scheme, such as the k-round elimination contention scheme. Helpers sending a busy tone first can proceed to the next round, while others, sensing the busy tone, subsequently withdraw from contention. Therefore, a unique optimal helper is selected from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted, which allows a high data rate helper with its own data packets, to transmit these to their recipient without reservation. This significantly decreases the reservation overhead and effectively improves cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of the proposed protocol is 39.6% and 9.6% higher than those of the

previous work of Nasipuri [4] and Choudhury et al [5] showed that the link performance of communication systems using carrier sensing multiple access (CSMA) protocols can be improved by the use of directional antennas, due to the possibility of spatial reuse. However, both studies assumed that there was no overlap between the antenna beams in their simulation. Fahmy and Todd [6] have shown some performance improvement in a CSMA protocol with directional antenna using an adaptive antenna array on all sensor nodes. In this paper, we propose a simple medium access control (MAC) protocol method for the hub node based on the ALOHA protocol with multiple antennas. This proposed method has the advantage over CSMA protocols that it does not require the sensor nodes to perform carrier sensing and does not require all nodes to be equipped with directional antennas. Atmaca and Erturk [7] evaluated the link capacity improvements of spatial division multiple access (SDMA) and TDMA protocols by using directional antennas. However in this protocol, it was assumed that the hub knows the location of all the sensor nodes in the network, and all nodes are synchronised so that they know when they can transmit. It was also assumed that all packets with lower signal-to-noise (SNR) compared to the desired packet will be eliminated. They remove all packets with SNR below a certain quality threshold at the antenna without sending it to the MAC layer in order to maintain better link performance. Mudliar and Pillutla evaluated a memory guided MAC protocol based on CSMA protocol in [9], using directional random scanning to locate neighbour nodes in order to estimate their current position and select the directional antenna for communication. This method allows sensor nodes to either scan for neighbour nodes uniformly, sector by sector, or scan by probability using the target node’s previous position. However, this method requires sensor nodes all to have directional antennas for carrier sensing which increases the energy consumption significantly. The random scanning will also increase the delay before transmission. In our proposed protocol method, the MAC layer uses the successfully received packets to determine the optimum antenna on the hub to communicate with a given node.

A medium access control (MAC) protocol for spread-spectrum ad hoc networks with dynamic channel allocation (DCA) is pre- sented. DCA can support large systems with a smaller number of channels by dynamically assigning channels only when a node has a packet to transmit. The protocol extends cross layer, with the scheduling at the MAC, and assignment of channels at the physical layer by means of a query. It is shown that DCA is collision free under ideal conditions. By assigning channels dynami- cally, DCA offers improved throughput normalized by available bandwidth. Analytical results are presented for the performance of the query detection and the throughput for a fully connected network.

Hybrid medium access control (MAC) design in Wireless Sensor Network (WSN) brings a new research challenge nowadays. Hybrid MAC gives significant improvement in network performance especially in terms of energy efficiency and reliability of the network. Some of the data are sensitive to loss in the medium such as video data and data for emergency application. In MAC protocol, a contention access method which is Carrier Sense Multiple Access (CSMA) encounters collision problem when the number of nodes in the network increases. Meanwhile, the issue of slotted access which is Time Division Multiple Access (TDMA) is a strict synchronization problem. To avoid the weakness of both access methods, a hybrid MAC layer is proposed with unsynchronized TDMA, which is a token approach that calls the HMAC-TA. Token approach will be used in this protocol to avoid synchronization problems that can degrade network performance in TDMA protocol. The performance analysis of HMAC-TA shows 48% significant improvement in terms of energy efficiency compared to MAC IEEE 802.15.4 standard. The packet delivery ratio of proposed protocol also shows the good performance.

There is increasing demand for wireless sensor networks (WSN) to be able to carry real-time information. However, current WSN technologies are not yet capable of offering quality-of-service (QoS) guarantees, which are required to support these types of applications. Achieving QoS is especially challenging in WSNs due to their multi-hop nature and their processing-power, memory, and energy constraints. In this article, we propose a cross-layer architecture in which the medium access control (MAC) and routing protocols collaborate to organize nodes into clusters and to achieve a coordinated time-shared access to the transmission medium. The resulting protocol is called QUAlity- of-service-capable clusTer-based Time-shared ROuting (QUATTRO)-assisted MAC protocol. Our performance evaluation results show that the protocol overhead observed in terms of configuration time, transmitted control messages, and consumed energy is very reasonable and that not only QoS is achieved but also great energy savings by eliminating collisions and considerably reducing idle listening.

Before initiating this work, a substantial amount of time is spent on studying algorithms related to improving performance of and MAC protocol [4] in Wireless Sensor Network by selecting a best relay node based on following parameters, Optimal Data Rate, No. of Retry<Threshold, Minimum Contention Window Size, Minimum RTS/Frame, Minimum Node Delay Time, Minimum Node Buffer Size and Maximum PDR. The major objectives of the work are: - To implement an algorithm for increasing the performance of WSN by selecting best of sensor node relays. To simulate a proposed model in NS.2.34 and to validate &analyzes the performance of proposed OrnMAC with the help of a number of parameters like Throughput, PDR, End-to-End delay, Overhead. Comparison of the Performance of Proposed an OrnMAC with respect to normal scenario. 2.1 Ornamental Medium Access Control Protocol (OrnMAC) For WSN OrnMAC-Protocol

Existing medium access control (MAC) schemes for wireless local area networks (WLANs) have been shown to lack scalability in crowded networks and can suffer from widely varying delays rendering them unsuited to delay sensitive applications, such as voice and video communications. These deficiencies are mainly due to the use of random multiple access techniques in the MAC layer. The design of these techniques is highly linked to the choice of the underlying physical (PHY) layer technology. The advent of new PHY schemes that are based on orthogonal frequency division multiple access (OFDMA) provides new opportunities for devising more efficient MAC protocols. We propose a new adaptive MAC design based on OFDMA technology. The design uses OFDMA to reduce collision during transmission request phases and makes channel access more predictable. To improve throughput, we combine the OFDMA access with a carrier sense multiple access (CSMA) scheme. Data transmission opportunities are assigned through an access point that can schedule traffic streams in both time and frequency (subchannels) domains. We demonstrate the effectiveness of the proposed MAC and compare it to existing mechanisms through simulation and by deriving an analytical model for the operation of the MAC in saturation mode.

Wireless sensor networks (WSNs) are composed of hundreds of wireless sensors which collaborate to perform a common task. Because of the small size of wireless sensors, they have some serious limitations including very low computation capability and battery reserve. Such resource limitations require that WSN protocols to be extremely efficient. In this thesis, we focus on the Medium Access Control (MAC) layer in WSNs. We propose a MAC scheme, V-MAC, for WSNs that extends that lifetime of the network. We compare V-MAC with other MAC schemes. V-MAC uses a special mechanism to divide sensors in different groups and then all the members of a group go to sleep at the same time. V-MAC protects WSNs against denial of sleep and broadcast attacks. We present the V-MAC scheme in details and evaluate it with simulations. Our simulations show that V-MAC enjoys significantly higher throughput and network lifetime compared to other schemes.

The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a part of the data link layer specified in the seven-layer of OSI model (layer 2). It provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multipoint network, typically with a local area network (LAN) or metropolitan area network (MAN). A MAC protocol is not required in full-duplex point-to-point communication. In single channel point-to- point communications full-duplex can be emulated. This emulation can be considered a MAC layer. The MAC sub- layer acts as an interface between the Logical Link Control sub layer and the network's physical layer. The MAC layer provides an addressing mechanism called physical address or MAC address. This is a unique serial number assigned to each network adapter, making it possible to deliver data packets to a destination within a sub network, i.e. a physical network without routers, for example an Ethernet network. FPGA area and speed optimization to implement computer network protocol is subject of research mainly due to its importance to network performance. The objective of resource utilization of field programming gate array(FPGA) is to allocate contending to embed maximum intricate functions. This approach makes design cost effective and maximizing IEEE 802.3 MAC performance. Binary exponential back off algorithm. Very high speed integrated circuit hardware description language (VHSIC- HDL) VHDL coding to implemented synchronous counter

Abstract— One approach to maximizing the efficiency of medium access control (MAC) on the uplink in a future wideband code-division multiple-access (WCDMA)-based third-generation radio access network, and hence maximize spectral efficiency, is to employ a low-complexity distributed scheduling control approach. The maximization of spectral efficiency in third-gen- eration radio access networks is complicated by the need to provide bandwidth-on-demand to diverse services characterized by diverse quality of service (QoS) requirements in an interfer- ence limited environment. However, the ability to exploit the full potential of resource allocation algorithms in third-generation radio access networks has been limited by the absence of a metric that captures the two-dimensional radio resource requirement, in terms of power and bandwidth, in the third-generation radio access network environment, where different users may have different signal-to-interference ratio requirements. This paper presents a novel resource metric as a solution to this fundamental problem. Also, a novel deadline-driven backoff procedure has been presented as the backoff scheme of the proposed distributed scheduling MAC protocols to enable the efficient support of services with QoS imposed delay constraints without the need for centralized scheduling. The main conclusion is that low-com- plexity distributed scheduling control strategies using overload avoidance/overload detection can be designed using the proposed resource metric to give near optimal performance and thus main- tain a high spectral efficiency in third-generation radio access networks and that importantly overload detection is superior to overload avoidance.

Health monitoring using biomedical sensors has witnessed significant attention in recent past due to the evolution of a new research area in sensor network known as Wireless Body Area Networks (WBANs). In WBANs, a number of implantable, wearable, and off-body biomedical sensors are utilized to monitor various vital signs of patient’s body for early detection, and medication of grave diseases. In literature, a number of Medium Access Control (MAC) protocols for WBANs have been suggested for address- ing the unique challenges related to reliability, delay, collision and energy in the new research area. The design of MAC protocols is based on multiple access techniques. Understanding the basis of MAC protocol designs for identifying their design objec- tives in broader perspective, is a quite challenging task. In this context, this paper quali- tatively reviews MAC protocols for WBANs. Firstly, 802.15.4 and 802.15.6 based MAC Superframe structures are investigated focusing on design objectives. Secondly, dif- ferent multiple access techniques such as TDMA, CSMA/CA, Slotted Aloha and Hybrid are explored in terms of design goals. Thirdly, a two-layered taxonomy is presented for MAC protocols. First layer classification is based on multiple access techniques, whereas second layer classification is based on design objectives and characteristics of MAC protocols. Critical and qualitative analysis is carried out for each considered MAC proto- col. Comparative study of different MAC protocols is also performed. Finally, some open research challenges in the area are identified with initial research directions.

G UARANTEEING message deadlines is a key issue in distributed real-time applications. The timed token medium access control (MAC) protocol [1], [2] is suitable for real-time applications due to its special timing property of bounded token rotation time. With this protocol [2], messages are distinguished into two types: synchronous and asynchronous. Synchronous messages are periodic with delivery time constraints. Asynchronous messages are nonperiodic with no delivery time constraints. During network initialization time, all nodes negotiate a common value for the Target Token Rotation Time (T T RT) which should be small enough to meet responsiveness requirements of all nodes. Each node i is assigned a fraction of the T T RT, denoted as H i , as its

In Wireless Sensor Networks (WSNs), a robust and energy-efficient Medium Access Control (MAC) protocol is required for high energy efficiency in harsh operating conditions, where node and link failures are common. This paper presents the design of a novel MAC protocol for low-power WSNs. The developed MAC protocol minimizes the energy overhead of idle time and collisions by strict frame synchronization and slot reservation. It combines a dynamic bandwidth adjustment mechanism, multi- cluster-tree network topology, and a network channel allowing rapid and low-energy neighbor discoveries. The protocol achieves high scalability by employing frequency and time division between clusters. Performance analysis shows that the MAC protocol outperforms current state-of-the-art protocols in energy efficiency, and the energy overhead compared to an ideal MAC protocol is only 2.85% to 27.1%. The high energy efficiency is achieved in both leaf and router nodes. The models and the feasibility of the protocol were verified by simulations and with a full-scale prototype implementation.

Mobility in Wireless Sensor Network (WSN) presents distinctive challenges in Medium Access Control (MAC) scheme. Numerous MAC protocols for sensor networks assume that sensor nodes are static and focus primarily on energy efficiency. This work seeks to develop an improved mo- bility conscious medium access control scheme for wireless sensor networks with a view to en- hance energy conservation on mobile sensor nodes. On this note, mobility patterns of different scenarios are modelled using Gauss Markov Mobility Model (GMMM) to determine the position and distance of the sensor nodes and how they are correlated in time.

This paper studies the main performance characteristics of the SCP protocol, a medium access control protocol for sensor networks (WSN). SCP-MAC was designed taking into account the characteristics of energy shortage and processing capacity of the sensor nodes and seeks to reduce the consumption of energy at the expense of other performance parameters such as delay, flow and bandwidth. Our contributions through this work are the following: first, a physical layer model corresponding to the radio transmitter/receiver CC2420 was implemented in Qualnet®, including a model of energy consumption and a model of the SCP protocol based on the specifications of the authors; second, a detailed performance analysis of the protocol was made based on different metrics.

In this paper, a novel Medium Access Control (MAC) protocol for industrial Wireless Local Area Networks (WLANs) is proposed and studied. The main challenge in industry automation systems is the ultra-low network latency with a target upper bound in the order of 1 ms while maintaining high net- work reliability and availability. The novelty of the proposed wireless MAC protocol resides in its similar latency performance as its counterpart in wired industrial LAN. First, the functional design of the MAC protocol is intro- duced. Then its performance results gained from hardware implementation (SystemC and VHDL) on an FPGA platform are presented. Finally, a real-time communication module which achieves the ultra-low latency re- quired in industrial automation is described.

The flexible use of sensors has made them an attractive device to be deployed in almost every field of life such as health, military and home. Recent advancement in electronics and wireless commu- nications has witnessed the development of low cost-sensor devices. While wireless sensor net- works (WSNs) are flexible to use and less costly, they need to be more energy-efficient as they are operated by the battery. Mostly they are deployed in harsh environments where it is very difficult to change the batteries frequently. Several medium access control (MAC) algorithms have been developed for the energy-efficient acquisition of the wireless channel, however, none of them are satisfactory. In this paper, we proposed a medium access control algorithm called MAC-PE. MAC- PE is based on the concept of prioritized frames where prioritized frames are transmitted urgent- ly. In addition, it uses scheduled-based MAC instead of accessing channel randomly. We found MAC-PE (Power-Efficient MAC) was efficient in terms of power consumption without sacrificing on the performance using NS-2.

Opportunistic usage selection of a licensed channel by a secondary user (SU) and its contention for data transmission is a challenging problem in coexisting cognitive radio network (CCRN). This is caused by the presence of many SUs from different CRNs in a shared environment, and the problem is further intensified when the user applications, with heterogeneous quality-of-service (QoS) requirements, require prioritized access to the opportunistic spectrum. The state-of-the-art protocols did not address the problem of efficient coexistence following both the dynamic spectrum availability and prioritized medium access. In this paper, a weighted fair medium access control protocol, namely WF-MAC, has been developed for overlay CR network that gives users proportionate accesses to the opportunistic spectrum following their application QoS requirements. The channel availability prediction using autoregression (AR) model and channel utility perception using exponentially weighted moving average (EWMA) facilitate WF-MAC to achieve more stable and fair access to the opportunistic spectrum. Our simulation experiment results depict the efficiency of the proposed WF-MAC protocol in achieving better spectrum utilization, weighted fairness, throughput, and medium access delay compared to the state-of-the-art protocols.