06-10-2016, 12:38 PM
Improving Energy Efficient Using Novel Sleep Scheduling Approach for Wireless Ad-Hoc Network
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Abstract— Wireless Adhoc Networks are deployed in emergency situations, military kind of applications, surveillance monitoring and in healthcare industry. The Nodes are dynamic and can accommodate by themselves in any existing infrastructures, placed randomly in the network. Each node can communicate with any other node and/or to the Base station directly. Since entire node communicates simultaneously there are chances for collision or jamming can occur in the network. Various approaches are available in the existing literatures which are concentrating only in avoiding collision or jamming. In this paper approach is introduced to save the energy efficiently. NSS follows an ESR-MAC protocol which is derived from TDMA and CSMA based slot allocation. ESR utilizes the slot allocation method from CSMA and utilizes scheduling methodology from TDMA. NSS improves the energy efficiency by changing the states of the node with level by level offset way and collision/Jamming is avoided by scheduling method. The simulation result shows that the performance of NSS is better than the existing approaches in terms of throughput, delay and energy.
INTRODUCTION
In this paper the problem of collision, jamming and congestion due to broadcasting or multicasting, resource allocation in a multi hop WAHN are considered. Since the network protocol structure are layered structures and each layer is independent to other layers collision occurs. Also WAHN supports multiple senders and multiple receivers. The channel I WAHN follows IEEE-802.11 standards. An ordinary tactic to improve the network capability is to use frequency assortment [17, 18].Since multi communication in WAHN, multi radio networks necessitates certain resource allocation problems like channel assignment, scheduling and routing to improve the network efficiency. These problems are controlled by some protocols for channel assignment, scheduling and routing can be obtained via the throughput-optimal algorithms in [19] and [20] which achieve the maximum capacity, reduce the computational complexity and increase the throughput.
Various existing approaches concentrate on improving the energy by reducing the energy wastage. Various MAC protocols are controlling the packet scheduling. MAC is an important technique which provides successful operations on the network. MAC is more important for collision reduction in which no two nodes will transmit at the same time. TDMA, CDMA, CSMA and CSMA-CA are some of the latest techniques which are providing collision free network with more energy saving
Over the past few years several MAC protocols have been developed for WSNs. They can be categorized into centralized and decentralized MAC protocols. Most of the centralized protocols operate as a cluster-based scheme. In a cluster-based scheme the base station or cluster header will allocate time slots to each member for creating a collision free operation within the cluster. Therefore, accurate time synchronization protocol is essential in centralized protocols. The other type of protocol is the decentralized-based MAC protocol. These protocols can be divided into scheduled and random access schemes. In the scheduled schemes, all nodes need to periodically broadcast their wake-up schedule and maintain their neighbours' schedule information. The nodes are then allowed to transmit data during the active periods of the receivers and save energy according to their own schedules
Only rough time synchronization is required in the scheduled schemes, such as S-MAC, T-MAC, P-MAC, and D-MAC.Ease of Use
S-MAC and T-MAC are two well-known MAC protocols in WSNs. In S-MAC [6] the four major sources of energy waste are: collision, overhearing, control packet overhead, and idle listening. Therefore, S-MAC tries to reduce waste by putting sensor nodes into a periodical sleeping mode at a low and fixed duty cycle. T-MAC [7] improves on S-MAC by using an adaptive duty cycle. Sensor nodes go to sleep when there is no activity at time TA = (C + R + T ) × 1.5), where C is the length of the contention interval, R is the length of an RTS packet, and T is a short time between the end of the RTS packet and the beginning of the CTS packet. Figure 1 shows the difference between S-MAC and T-MAC protocols. T-MAC provides a better throughput than S-MAC under variable traffic. When the traffic load is heavy, the throughput of T-MAC performs more efficiently than S-MAC. However, both the throughputs of S-MAC and T-MAC are influenced by packet collisions. Thus, an efficient collision avoidance method is needed to decrease the waste of battery energy of sensor nodes and to improve the overall network performance.
P-MAC [8] is a time-slotted and pattern-based scheduling protocol. Each sensor node determines its sleep/wake-up schedule based on its own traffic and the traffic patterns of its neighbours. D-MAC [9] presents a continuous packet forwarding scheme along the data gathering tree to solve the data forwarding interruption problem. A node skews its wake-up schedule d head of the schedule of the sink (d is the depth of the tree and t is the period of sending or receiving a packet).
In this paper NSS concentrates two major problems. The first problem is the energy efficiency where the energy is saving in each node by make the node to sleep during the free time. The second problem is avoided collision and jamming by applying scheduling. Some of the earlier approaches for collision and energy efficiency is discussed in the literature survey.
B. LITERATURE SURVEY
Several methods and approaches were used in earlier studies which concentrate on various purposes like reducing the delay, increasing the throughput, improving the energy efficiency and so on. MLBS approach was introduced to solve the problem of congestion using unit disk method [2]. A wake-up scheduling schemes was used for improving the energy on sensor nodes [3] in WAHN combined with bi-directional end to-end delay constraints. To improve the QoS using MAC layer configuration is applied for multiple connections in WAHN [4]. One more collision free channel protocol for WAHN is presented in [5]. A fully distributed algorithm was introduced for scheduling and routing problems for WAHN in [6]. A periodic energy update with sleep cycle was introduced to minimize the end-to-end communication delay [7]. Energy consumption was obtained using idle, listening and sleep periods applied for nodes using S-MAC protocol in [8]. Also a DWOP protocol was introduced in [9] which do distributed scheduling joined with MAC algorithm in WAHN. Some of the decentralized protocols [10] were applied to WAHN to improve the energy efficiency in the network. SSCH [11] and CATA [12]are some of the protocols introduced in which do channelization for ad-hoc networks. An optimal approach for cross layer protocol was introduced which controls routing using scheduling for WAHN in [13]. CSMA [14, 15, and 16] was applied for power consumption, synchronization and reduce the delay.
III. A.EXISTING SYSTEM
The existing system studies the problem of congestion controlling with scheduling in WAHN which supports traffic [1]. The packet transmission is optimized in a framework for controlling congestion. The existing system provides for fixed size network and same delay. Elastic and Inelastic traffic model with more number of parameters is configured and concentrated for data transmission. Also the existing system more depends on the link weight and queue length.
In this existing system, a optimization framework for the problem of congestion control and scheduling of elastic and inelastic traffic in adhoc wireless networks . The model was developed for the general interference graph, general arrival of arrival and time varying channel.
Using a default function approach, it is discussed that it presented a decomposition of the problem into an online algorithm that is able to make a optimal decision which keeping the network stable and fulfilling the inelastic flow of quality of service requirement. And the key result is that the use of deficit counters. One can treat the scheduling problem for elastic and inelastic flows in a common framework. Similarly the traffic model for inelastic packet assumes that the packet arrives at the beginning of the frame and all have the same delay.
But in the proposed approach the MAC layer, Phy-Wireless layers are configured with the slot allocation for each node and the slots are restricted according to the number of nodes. Since configuration is a part of the routing protocol the results of the slot allocation is good.
C. PROBLEM STATEMENT
Wireless Ad-Hoc networks need to be improving its QOS in terms of energy, traffic, avoid collision and delay. Various approaches introduced in literature survey are providing solution in various aspects. In this paper the problem to be tackled is to provide a complete solution for collision avoidance with less energy consumption.
PROPOSED APPROACH
In the ESR-MAC slot reservation scheme, if there is no traffic in the network, then nodes must wake up at the contention slot for receiving a data packet and at the control slot for broadcasting the schedule of the reservation slots. Contrary to S-MAC and T-MAC, our protocol is a slotted MAC protocol. Contrary to S-MAC and T-MAC, our protocol is a slotted MAC protocol is termed as AMAC. Nodes can handle their traffic more efficiently based on the slotted architecture. With the time slotted architecture, receiver can reserve slots to the senders and perform a collision free transmission. Therefore, our protocol can improve the network throughput and reduce transmission delays without impacting on the conservation of energy.
But in this paper we proposed NSS approach. This technique dynamically adjust the number of contention slots needed to resolve collisions according to the traffic load, considerably improving overall system performance. In NSS mode, a node can be in two states: Low Contention (LC) and High Contention (HC). A node is in HC state when it receives a notification message from its one hop or two-hop neighbors. Otherwise, the node is running in LC state. In this AMAC - Adaptive MAC, a node can stay in HC state for a predefined duration of THC. If a node does not receive new notification messages during that period, it will go back to LC state automatically.
While in LC state, all nodes are allowed to transmit in any time slot, implying that all nodes run in CSMA mode. Nonetheless and unlike conventional CSMA, each node is assigned a priority and needs to compete for a time slot according to its priority. The owner of the slot possesses the highest priority against other nodes. Specifically the priority of a node is associated with its Contention Window (CW).
Suppose slot n begins at time t0 and the owner of the slot is node A. Then the CW for node A is defined as [t0, t1] while the CW for other competitors is [t1, t2], where t0 < t1 < t2. Fig. 2 shows the mechanism of slot competition by priorities. Such dual-state operation can improve the channel utilization significantly. Given a time slot, if the state of the owner is HC then the owner’s two-hop neighbors are not allowed to transmit in this slot. In other words, only the owner and its one-hop neighbors can compete for the slot access. Thus, the collisions caused by hidden terminal problem can be significantly reduced. Similarly, each node is assigned a priority in HC state and the slot competition follows the same strategy as that of LC state.
Accordingly, it is the sender who controls when to switch its operation mode. If a node is experiencing high collision rate, the packet loss rate tends to increase accordingly. As A-MAC does not use RTS/CTS mechanism to avoid collisions, current contention level is proportional to the collision rate. Therefore, the contention level can be estimated by counting the number of lost ACKs. If a node misses Nth (Mode switch threshold) ACKs consecutively, a notification message is sent to all of its two-hop neighbors informing them not to act as hidden terminals such that the collisions can be avoided. Accordingly, the node switches to the HC state.
CONCLUSION
This paper discussed about the scheduling process to save the energy in each node and improve the network life time. In this paper the slot allocation mechanism and scheduling for each slots is implemented to avoid un-necessary packet transmission and avoid collision, traffic jam etc,. Since each node transmits and receives its data only in their contention slot and not more than one node communicated simultaneously. This approach improves the quality of service of the network in terms of PDR, Throughput and energy comparing with the existing systems. This ESR-MAC slot allocation combines the functionality of MAC- TDMA with CSMA. From the figure-3, Figure-4 and Figure-5 it concludes that the proposed approach is efficient