Cross Layer Design in Wireless Sensor Networks

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Cross Layer Design in Wireless Sensor Networks Neelu Walia, Department of Systems and Computer Engineering Carleton University [email protected]  Abstract— Wireless Sensor Networks are made up of large number of sensing nodes having computing and communication capabilities. A network has various protocols that help in efficiently communicating between these nodes. TCP/IP networks have end to end connections established with the help of five layers which are designed to maintain a limited interface with their neighboring layers. The encapsulation of information among these layers results in side effect on Quality of Service (QoS), latency, extra overload, etc. Here comes the emergence of Cross Layer Design (CLD) in Wireless Sensor Networks. Cross Layer Design helps in sharing information among all the five layers to improve wireless network functionality, mobility. Quality of Service (QoS). It helps in enhancing the performance of already existing architectures by enabling interaction between different non-adjacent nodes also. It helps in increasing the efficiency of the network and network throughput. In this paper, various cross layer design characteristics, classifications are explained. The need for CLD in WSN is also shown. At the end the paper highlights some issues faced in implementing CLD in ESN. Index Terms— Cross Layer Design, Wireless Sensor Networks, TCP/IP networks, QoS.

I. INTRODUCTION

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owadays, Wireless Sensor Networks and Cross Layer Designs, both are emerging trends. A lot research is being presented in various papers regarding WSN showing interaction between various non-adjacent layers of the network stacks by implementing CLD [1], [35]. The black box characteristics of the network results in the extraction of internal details of each layer, which leads to information hiding. The main aim of cross layer design is to improve the performance of the system and get the desired Quality of Service (QoS) required for the various applications. The implementation of CLD can result in increasing the network efficiency and optimizing the throughout. The CLD in WSN is very useful, energy efficient, scalable and secured in comparison to the traditional approaches [32]. Cross layer designs consider the inter relationship and reconfiguration of the network layers to identify and improve the connection failures that might arise in the root. Cross layered approach helps in reducing the overhead by

sharing data between different layers, this is because the protocol stack is treated system instead of independent layers which was in traditional approach. The implementation of cross layered architecture results in increasing network flexibility, interoperability and maintainability. Cross layer design is an approach that helps in breaking the traditional waterfall concept that was considered in traditional network protocols. A lot of research and solutions are achieved to overcome this problem from which cross layer design is most efficient one. Cross layer design does not destroy the layer structure of the network. It provides the inter layer communication between non-adjacent layers also. With the help of cross layer design, the internal status and parameters of each layer can be revealed to the other layers resulting in removal of redundancy. Also, CLD helps in determining the behavior of other layers by retrieving and receiving the data from them [2]. Hence there is a sharing of parameters, status and information among all the layers without any effect on the layer structures of the network. For Example, in Cognitive Radio (CR), in which the key feature is to allow unlicensed (secondary) users to operate in the licensed spectrum band [3]. A device with cognitive capability can sense the radio environment and adjusts its parameters of physical and data link layer. Primary users of the network do not require to change the infrastructure of the shared spectrum. It is the task of secondary users to sense the spectrum individually or cooperatively. In CR, based network, secondary users may have low Quality of Service (QoS). In cognitive radio networks, resource allocation is also one of the great issues among secondary users which is discussed in [4]. In [4], computational complexity is reduced in two steps. First, they have solved the optimal power allocation problem using assumption of known channel allocation. Then, the joint power and channel allocation problem is solved using stochastic optimization method. Security is also one of the main problems in CR networks. False local sensing calls can be send by malicious CR’s. In [5], a scheme has been proposed to differentiate the trustworthiness of spectrum sensing terminals. In this, authentication scheme using ID based cryptography is also presented.

2 II. CHALLENGES

Fig. 1 Cognitive system model [3]

More related work regarding resource allocation and QoS in CR network is discussed in [6]. There are basically three issues being considered in cross layer design: Security, Quality of Service and Mobility. These three issues can also be viewed as the three major goals of cross layer design. To achieve this goal, sharing of data among the layers and exchanging of data among the nodes is required in cross layer design. According to the sharing of data inside one node can be classified into two categories: Managerial method that allows a vertical plane to act as a public library having all the required information that can be shared among the nodes and the other is non-manager method in which one layer directly communicates with the other layer. There is another classification based upon the sharing of information among the nodes in a network. There are two categories under this scheme: First, centralized method, in which a central node is used to control the information sharing in cross layer. Secondly, distributed method, in this, the information is organized and shared without the use of a central node. Therefore, there are two kinds of classification depending upon the sharing of information among the five layers and organization of the network. In this paper, I am going to explain the various concepts of cross layer designs and how it is implemented in wireless sensor networks. The organization of the paper is as following: In section II, a brief overview of the challenges faced while implementing cross layer design has been discussed. Section III describes the goals of cross layer design. In Section IV, I am going to explain the classifications discussed above. In Section V, a brief introduction regarding routing and TCP/IP protocol embedded with cross layer design is highlighted. In Section VI, need for cross layer design in wireless sensor network is explained. Section VII will explain the various cross layer approaches followed in wireless sensor networks. Section VIII will enlist the various cross layer design drawbacks. Finally, IX will conclude this paper.

In cross layer design, there is specific manner for the communication among the layers, that results in two major challenges that the cross-layer design has to deal with: Coexistence and Signaling. Another major concern in cross layer design is the extra overhead that arises due to the exchanging of information among the cross layers. There is no uniform cross layer design that can be used for all the applications, as different applications have different requirements of the design. The role of physical layer in a wired network is to receive and send packets but in wireless networks, physical layer plays a major role. CLS’s relaying on advanced signal processing at physical layer. Also, cross layer design violates the encapsulation policy of the layers resulting in destruction of well-organized layered structure into a flat and disordered architecture. It is very difficult to modify one layer without considering the other layers in cross layer design. So, the fundamental disadvantage of cross layer design is the destruction of cross layered architecture. There are some open challenges that a designer keeps in mind while proposing a cross-layer design [7]: 1) How do different cross-layer design proposals coexist with one another? 2) Will a given cross-layer design idea possibly stifle innovation in the future? 3) What are the cross-layer designs that will have most significant impact on performance of a network and hence should be most closely focused on? 4) Has a given design proposal been made with a thorough knowledge of the effect of the interactions between parameter at different layers on network performance? 5) Under which network and environment condition would a particular cross layer design proposal be invoked? 6) Can the mechanism or interfaces used to share information between the layers be standardized? What should be the role of physical layer in a wireless network? There are certain challenges faces by Wireless Sensor Networks in term of QoS [30]: 1) Limited Resources Wireless sensor nodes have very small memory and battery life. 2) Traffic Asymmetry Traffic near the sink node is high as compare to the remaining network areas. 3) Scalability Sensor network has millions of nodes and nodes can be added or put to sleep mode time to time. 4) Heterogeneous Traffic Sensors nodes collect different types of data from the environment and these data are in different formats. 5) Security III. GOALS OF CROSS LAYER DESIGN The three major goals that needs to be considered while designing a cross layer architecture are QoS, security and

3 mobility. A cross layer design scheme basically aims at fulfilling at least one of these three goals. Fig. 2 illustrates the coordination model having three coordination planes (Security plane, QoS plane and mobility plane), extended over the five TCP/IP protocol layers [8]. A. Security The security coordination plane implements the protocols that are concerned with the security issues among the five layers of TCP/IP protocols. Various encryption methods like Wi-Fi protected access must be deployed to perform secured communication across the cross layered design. [33], [34] discusses the security plane with cross layer design implementation. Various encryption methods might be deployed at application layer like end to end encryption, at network layer and/or data link layer and physical layer to help perform secure communication in cross layer design. B. Quality of Service (QoS) The main aim of QoS coordination plane is to provide high quality of service in the wireless communication across five layers. In the wireless networks to get improved quality, upper layers must be aware of the information and characteristics of the two lower layers (physical layer and data link layer) [39]. This direct sharing of information among the upper three layers and lower two layers is not possible in the traditional waterfall like concept of wireless network model. Hence, the QoS coordination plane helps in achieving the improved QoS communication in cross layer design.

Fig. 2 Goals of Cross Layer Designs: Security, QoS and Mobility [8].

In wireless networks, most of the applications uses TCP protocol at transport layer which is very sensitive to the problems in physical and data link layer. The various issues can be: channel fading resulting route scheduling, transmission delay or high bit error rate that may require

retransmission, to many retransmissions may cause congestions. Hence with the improvement of QoS, by cross layer designs, these problems can be solved easily. C. Mobility This coordination plane helps in guarantying an uninterrupted communication in wireless networks. Nodes in wireless sensor network can be stable or mobile in nature [39]. For the mobile nodes, the events like channel switch or route change must be discovered and solved to get uninterrupted communication throughout the session. There are two categories of hand-over discussed in [8]: horizontal handover and vertical handover. In horizontal handover, the movement of nodes is among different access points of the same wireless access technology. While in vertical handover, the nodes are moving between access points of different wireless technologies. In both these categories, the events like channel switch and route change must be informed to the upper layers, so that the communication remains uninterrupted even if there is a change of events at lower layers. Channel fading, high bit error rate, transmission delay, etc. may also affect the mobility as well as QoS. For example, in centralized networks like cellular networks, there is a limited number of users that are served because of limited number of channels available. Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) are used to solve these problems. But these two techniques result in waste of time slots and bandwidth whenever there is no data transmission between [8]. The base station and the mobile station. So, cross layer design helps to overcome these problems. In [9], the Passenger Information System (PIS) provides the passengers in the metro trains with real-time dynamic multimedia information like live news, live matches, train schedules, forecast etc. In case of any natural disaster and accidents, this system also provides information regarding safety and evacuation. Video communication network is a major sub system in metro PIS. A high-quality video information transmission between high speed train and ground gives the passengers a comfortable journey when they commute. Unfortunately, traditional WLAN’s were not designed for high speed environments resulting in poor QoS. Whenever a train moves away from one access point and enters the coverage of another access point, moving from one station to another, there takes place a handover of communication resulting in interruption and long latency. Because of highly compressed video signals, in wireless metro environments, video communication gets extremely vulnerable. Despite of multiple optimized models being proposed to get better quality video transmissions over lossy channels, most of them focus on improving the transmission performance. In [nF], an integrated design approach to optimize application layer QoS for video transmission in metro PIS is designed. To optimize the video transmission QoS in highly mobile environments, IEEE 802.11p network and fountain codes are used at application layer. Also in [10], a linear quadratic cost for the train controller is

4 used to measure the performance, in the hand of design. Depending upon the channel information of the channel state, handoff decisions are made and physical layer Multiple Input Multiple Output (MIMO) parameters are adapted to optimize the performance of train controls. This problem was modeled as Semi-Markov Decision Process (SMDP). In [11], the paper, they have discussed the vertical handover using SCTP. In UMTS networks, a wide area connectivity with a very low data rate and high mobility is provided while WLAN’s provide with small area coverage, high data rate but low mobility. Nowadays, mobile devices are equipped with multiple network interfaces (UMTS/WLAN) which allows users to get access to the internet with high bandwidth offered by WLAN whenever and wherever possible, and use UMTS services for the remaining time. Many proposals to solve the mobility management problem in heterogeneous wireless networks are discussed. In [11], a vertical handover between UMTS and WLAN is considered as the next evolutionary step from roaming. Stream Control Transmission Protocol (SCTP) method helps in significantly improving the performance of the network communication based on delay and throughput. It helps the sender as well as receiver to adapt to the sudden changes in the characteristics of the link, easily and quickly during and after the vertical handover. In [12], the statistical predicted user mobility based upon the mobility history of the users is used to guarantee the handoff dropping probability. Due to mobile handoffs, a user may experience degradation in the performance, this problem magnifies in micros as well as pico-cellular networks, where the handoff events are at higher rates as compared to macro cellular networks. To address this problem, call admission control and bandwidth reservation are used. IV. CLASSIFICATION OF CROSS LAYER DESIGNS Depending upon the sharing scheme inside one node, we can classify the design into manager method and non-manager method. A. Non-Manager Method In this method, a direct communication between the pair of layers is allowed. There is no change in the structure of the network model layers. The only change that occurs is in the functionality of the protocols in certain layers by allowing the direct communication between two layers. Fig 3. Shows a model of non-manager method. B. Manager Method In this, a vertical plane acts as a manager that is used to share the data with all or some layers of the protocol stack. In this, there is no change in the structure of the model layers but, there is a change in the functionality of the layer protocols that allows them to share the data with the vertical plane. Fig 4 shows the manager method in which, the vertical plane is used to share information with the stack of the layers. Depending upon the sharing scheme among the nodes in a network, we can classify the design into centralized method and distributed method.

Fig. 3 Non-Manager Method [2].

Fig. 4 Manager Method [2]

A. Centralized Method In this method, a central node or a base station is introduced in a hierarchical manner. This central node is used to share and manage information sharing of the layers between two nodes. This method is basically adapted for cellular network. Fig 5. shows the centralized method. B. Distributed Method In this method, the information is shared using the organization of the network. In this method, there is not central node to manage and share information. All the nodes directly share the information with other nodes and mange individually. Fig 6. shows the direct communication having distributed method implemented.

Fig. 5 Centralized Method

5 networks. These protocols can predetermine the performance on the bases of packet loss ratio, end to end delay and network throughput. D. Transport Layer The main function of this layer is to control congestion, do error recovery, flow control, packet sequencing (reordering) and end-to-end connection setup. It also helps the application layer in mapping and allocating the flow to routes which are found at network layer.

Fig. 6 Distributed Method

E. Application Layer This layer acts as an interface between the end user and the TCP/IP model. It considers the requirements of the end users and divides the services into multiple categories like real time services or non-real time services, multimedia services etc.

V. CROSS LAYER IMPLEMENTATION AT TCP/IP WSN has widely been used in military applications, crisis response, medical area etc. Each sensor node plays a vital role of being a terminal and a router under the assumption that they do not communicate directly with each other. Various topologies are existing in WSN [27] Multiple protocols are implemented to get efficient and economical routing path for communication among them. Mostly applications are dependent on TCP for communication. In TCP/IP protocol there are five layer. Each layer cooperates with the layer above it and layer below it. Because of Transmission Control Protocol (TCP) of transport layer and Internet Protocol (IP) of Network layer, TCP/IP model is most desirable for quick and efficient communication. TCP/IP model consists of five layers: application layer, transport layer, NETwork (NET) layer, Data Link (DL) layer and PHYsical (PHY) layer [13]. Fig 7. shows the layer structure of TCP/IP model. The functions of each layer are discussed briefly: A. Physical Layer This layer focus on physical devices and transmission media. It provides multiple antenna gains and improve integrity and throughput of data transmissions. This is the layer responsible for coding and modulation implementations. Also, it adjusts the transmitting power and controls the effects of mobility and propagation effects. B. Data Link Layer It is the media access layer, helps in error recovery, manages retransmissions and queueing of packets. It is further divided into two sublayers: Medium Access Control (MAC) sublayer and Logical Link Control (LLC) sublayer. C. Network Layer The main responsibilities of this layer is to discover the neighbors, routing and allocate resource functions. The main part is routing in which it guides the packet in the network from source to destination [31]. There are multiple routing protocols designed to satisfy the requirements of Wireless

Fig. 7 Layered Stack and main functions of each layer [13]

As cross layer design requires more interaction among the layers as compared to the one shown in fig 7 which has just the interaction among the adjacent layer only. Therefore, it violates the layered architecture of the model. Cross layer design requires information exchange of layer with every other layer as well as adaptability to this information by each layer. This kind of design results in more robust structure. The cross-layer solutions for the problems in the layered architecture are listed below [13]: A. Layer-centric Solution In this a certain layer acts as a central layer that helps to control the cross-layer adaptation by accessing the internal parameters and algorithms of other layers. Despite of significant improvement in the systems performance by this approach, still the layer structure is destroyed because of the need to access the internal parameter of all the other layer. B. Centralized Solution A centralized optimizer is used for estimating both the availability of resources and the environment dynamics, this optimizer can be a middleware or a system level monitor. In

6 this approach, each layer forwards its information, complete protocol parameters, characteristics and algorithms to the central optimizer. Each layer also must obey the instructions requested by the central optimizer. Unfortunately, this approach also violates the layered architecture. VI. NEED FOR CLD IN WIRELESS SENSOR NETWORK The concept of cross layer design was first proposed for the wireless links deployed using TCP/IP networks. The basic concept of cross layer design was exchange of parameter information between two or more layers to get optimized result. There are different kinds of wireless sensor networks each having different set of problems[40]. The major challenge is quality of service at application layer. Congestion is one of the most difficult problems faced in wireless sensor networks which results in wastage of huge amount of energy due to multiple retransmissions that takes place because of packet dropping. There are two kinds of congestion that can occur in sensor networks: Node level congestion and link level congestion. In node level congestion, the packet arrival rate exceeds the packet service rate which results in buffer overflow and packet loss. This also increases the queuing delay. In link level congestion, collision occurs when multiple active sensor nodes try to exceed the channel at same time. Hence it is related to several nodes sharing same wireless channel. There is a need to implement cross layer design in wireless sensor networks. Some of the parameters that can be optimized by cross layer design are discussed below: A. Throughput There are many causes that influence the throughput of wireless sensor networks. The major causes that affect the data throughput are limited connectivity and Medium Access Control (MAC). The main requirements of the MAC protocol are minimum latency and high throughput. Each node, routes their packet towards the sink node. Hence, the nodes that are placed near the sink node will have high volume of load as compared to the remaining nodes in the network. These heavy load nodes will be consuming more energy and high congestion in large networks. The area near the sink node has significant collisions and packet loss. B. Quality of Service (QoS) The major parameters to get desired quality of service are resource constraints like bandwidth, buffer size, energy that helps in determining the quality of performance and manage the resources. Also, time delay, data redundancy, topology of network, heterogeneity of nodes, distributed network affects the Quality of Service. C. Resource constraint There is limited number of resources in wireless sensor network. Various resources like energy, memory, bandwidth, buffer size, etc. are scarce in network. Power constraint is a major issue in wireless senor network. If one or more nodes in Wirelesses sensor networks reaches a low-level energy, the

while network may compromise its performance. One of the approach for efficient energy consumption in WSN is discussed in [26]. In this orthogonal modulation and CAODV routing protocol is used to get better results. D. Scalability There are millions of sensor nodes deployed in wireless sensor network applications. These large amount of sensor nodes have a potential impact on the hardware components and might affect its communication bandwidth and storing capabilities. Each protocol in these kinds of networks must be scalable and simple. The network middleware should also support scalability. E. Security In wireless sensor networks, the node senses the physical environment directly. Hence security is a major challenge to both the nodes and the network. Different attacks are possible at different layers. For example, collision at data link layer, false routing at network layer, jamming at physical layer, etc. Some other parameters that can be optimized by Cross Layer Design approach are: Network Lifetime, Node distortion, Mobility, Heterogeneity, Accuracy, Latency, Functionality etc [28]. VII. CROSS LAYER APPROACHES IN WIRELESS SENSOR NETWORKS Traditional layer design approaches have been used to develop cross layer design techniques. There are basically three approaches for the implementation of cross layer design: Conventional design approach, complex design approach and unified Design approach. Mostly all the proposed cross layer designs fall under one of these categories. A brief explanation for the three approaches is discussed below [1]: A. Conventional Design Approach In this approach, the traditional OSI model structure is maintained between the layers. At runtime, new interfaces are developed between the layers so that they can interact with each other. This interaction can be done from downward to upward or upward to downward. This approach is a kind of feedback mechanism which can be used to stabilize the performance of the system. Urgent messages are described as a prioritized traffic having top down interactions. This approach is more efficient where few information exchange is required. The system throughput reduces significantly with each additional cross layer feedback. If one layer needs to interact with many other layers, it will negatively impact the system throughput. The interface can be maintained by a direct communication [14], by sharing database or by adding a new interface [16]. Various approaches are proposed to overcome the problems faced in this approach like CLASS [14]. Cross Layer Signaling concept and optimization agent [15] for communication among layers.

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Fig. 9 Triangular Cross Layer Architecture for WSN.

Fig. 8 Conventional Approach

B. Complex Design Approach In this approach, the main focus is on integrating the functionality of two or more layers. There is more ease of information flow between the joint layers. In this approach, there is a better performance and a longer time span of the network. But, debugging for the errors and adaptation for different scenarios is a difficult task in theses architectures. In comparison to the conventional approach, complex design approach is more error prone and if there is a bad merging, it might result in negative direction. In [17] a wireless senor network, networking architecture is explained: Triangular Cross Layer Architecture (TCLA). Fig 9. Shows the three modules in triangular cross layer architecture for WSN having two or three layers in each module and a bi-directional communication among each module. In this architecture, adjacent layers are merged into virtual functional modules in which, communication overhead is very high. In TCLA, a new module AppM is formed by merging application layer, presentation layer and session layer. NetM module is made by merging transport layer nad networking layer and linkM module is formed by merging data link layer and physical layer. In this architecture, appM module is responsible for the tasks that are responsible for specific application aspect. The main responsibility of NetM module is to manage the issues like routing, congestion control and resource allocation. Wireless transmissions are handled by LinkM module. Each module is having its own agent which is responsible for distribution of information among different layers. Each functional agent can communicate with another functional module through an interface. This approach requires high energy and a lot of memory. C. Unified Design Approach In this approach, all the traditional layers are replaced and all the functions of the layers (application layer, transport layer, MAC layer, network layer and physical layer) are combined to share the information. A common interface is required to abstract network capabilities to the applications. This approach is more energy efficient.

Each cross-layer design approach focus on improving the quality of service and performance under different conditions of operation. Different types of cross layer designs have their own strong and weak points. In conventional approach, interactions can be performed from both sides that is upward and downward and this approach is best for few information exchanges. This approach is more compatible with wired system as it maintains traditional OSI model. Unfortunately, there are some drawbacks also like the throughput of the layers can be reduced because of each additional block. It is also difficult to ensure the correctness of layers in this approach. This approach is not efficient for synchronous reactions. In complex approach, information flow between joint layers is done easily, with better performance and adaptability. There are more number of benefits as compared to the complexity of the system. In unified approach, resources are efficiently utilized, better abstraction can be provided to the network. But, in this approach, if any modifications done unplanned, there might be a negative impact on the performance of the system. This approach is not efficient on wired systems. VIII. DRAWBACKS OF CROSS LAYER DESIGN Although there are a lot of benefits of implementing cross layer design but, still there are some challenges and drawbacks faced by these systems. Some of them are enlisted below [1], [2], [29]: A. Coexistence of Cross Layer Designs Although there are multiple cross layer designs being proposed but still, a common widely accepted cross layer design do not exist. It is very difficult to integrate two different types of cross layer designs into one uniform design because of different communication standards of each approach. In order to communicate with wireless networks having different technologies, a standardized cross layer design needs to be implemented to provide an interface to a heterogeneous wireless network [8]. The coexistence of different cross layer designs needs to be transparent in nature. There are some solutions to avoid this problem of cross layer design coexistence discussed in [18]. If the following problems can be solved, a coexisting cross layer design can be handled.

8 1) Unintended Cross layer interaction that is caused because of the interaction between layers and might result in unforeseen dependencies. 2) Stability of the network that uses cross layer design. 3) A long-term sustainability. This means the cross-layer design that has considered coexistence in its scheme will be able to coexist with other cross layer designs. B. Cross Layer Signaling Local files are used to store the cross-layer information in each node. Cross layer signaling is considered whenever this information needs to be exchanged between the nodes in a wireless network. The format and exchange of this information is controlled by cross layer signaling in wireless networks. The signaling is one of the most important problems that needs to be solved in cross layer designs. Packet headers are used in cross layer signaling. To avoid designing a new signaling protocol, cross layer signaling is stored in IPv6 packet header as the in-band message carriers. Also in TCP headers, the unused bits can be used for in-band signaling. C. Universal Cross Layer Design Mainly each cross-layer design in application specific like video streaming, secure transmission etc. Hence, cross layer design for one application might not be compatible or suitable for other application. For example, the video streaming requires a low TCP retry value but the text transmission can have a long TCP retry limit in poor network connection resulting for channel interference. Therefore, one of the challenge is the lack of universal cross layer design that can automatically adapt to different applications. As there are multiple applications, therefore, a potential universal cross layer design should be able to consider all the requirements of all these applications. It is still an open research issue to find a universal cross layer design. There are some partial solutions for this challenge. There is no universal cross layer design but still the existing cross layer designs can be categorized based upon their design and purpose. These categorized cross layer designs can fulfil the requirements of a certain number of applications. For example, video streaming cross layer designs are the popular ones because of large amount of network resources and the cost required by the transmission of a video. There are multiple designs proposed for video streaming with cross layer design implementation. Multiple researches have been done like ref [19], [20], [21]. Out of these, a common interest topic can be extracted and used to find a common final design. In [25] detailed solution for video streaming with efficient power consumption and QoS is studied using cross-layer design. Similarly, secured transmission in cross layer design is discussed in ref [22], [23], [24], which can be linked together to get a common cross layer design to perform secure transmissions. D. Destruction of the Layered Architecture Layered cross layer designs might destroy the encapsulation of the layers. A well-organized layered architecture can be

disordered due to direct or indirect communication performed between the layers due to cross layer designing. As seen in TCP/IP model, the functions and protocols can be modified and improved from one layer without disturbing the functionality of other layers. But, the modification in cross layer designs is difficult due to the interactions and existing dynamics between multiple layers. Instead of modifying one layer, all the layers need to be considered even if a small modification is to be done in cross layer design. This is one of the fundamental challenge in cross layer design. E. Hard to Redesign Cross layer designs are more attracted for wireless networks because of uncovering properties, interaction between layers, sharing of information about its dynamic states. Unlike OSI layer which is tightly coupled and more suited for wired networks. But, it is very hard to re-design and review cross layer designs because even a minor change in sub system needs to be considered by whole system. F. Coexistence with other Wireless Protocols Multiple algorithms are implemented in cross layer designing depending upon different network entities. It is very difficult to cover the dynamic nature of environment. CLD’s have difficulties in coexistence among themselves and other wireless network protocols. IX. CONCLUSION In dynamic environment, implementation of a potential cross-layer design can improve the energy efficiency, reliability of packet deliver and stability of multi-hop [29]. There are several factors other than energy efficiency in WSNs that have been discussed in this paper. The paper concludes the general discussion about implementation of cross-layer design in wireless sensor networks. It highlights the various challenges faced in this implementation and the desired solutions for these problems. The paper highlights the major cross-layer design approaches with their advantages and disadvantages. Some of the parameters that shows the need of implementing CLD in WSN has been described. Furthermore, the paper discussed certain drawbacks of cross layer design and mentioned various researches that are providing solution to overcome those. The paper also endeavored some open challenges that can be addressed in future research works. REFERENCES [1]

[2]

[3]

[4]

Ranjan, Rajeev, and Shirshu Varma. "Challenges and Implementation on Cross Layer Design for Wireless Sensor Networks." Wireless Personal Communications86.2 (2015): 1037-060. Web. B. Fu, Y. Xiao, H. J. Deng and H. Zeng, "A Survey of Cross-Layer Designs in Wireless Networks," in IEEE Communications Surveys & Tutorials, vol. 16, no. 1, pp. 110-126, First Quarter 2014. C. Luo, F. R. Yu, H. Ji and V. C. M. Leung, "Cross-Layer Design for TCP Performance Improvement in Cognitive Radio Networks," in IEEE Transactions on Vehicular Technology, vol. 59, no. 5, pp. 2485-2495, Jun 2010. R. Xie, F. R. Yu and H. Ji, "Dynamic Resource Allocation for Heterogeneous Services in Cognitive Radio Networks With Imperfect Channel Sensing," in IEEE Transactions on Vehicular Technology, vol. 61, no. 2, pp. 770-780, Feb. 2012.

9 [5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14] [15]

[16] [17] [18]

[19]

[20]

[21]

[22]

[23]

[24]

[25]

[26]

H. Tang, F. R. Yu, M. Huang and Z. Li, "Distributed consensus-based security mechanisms in cognitive radio mobile ad hoc networks," in IET Communications, vol. 6, no. 8, pp. 974-983, May 22 2012. R. Xie, F. R. Yu, H. Ji and Y. Li, "Energy-Efficient Resource Allocation for Heterogeneous Cognitive Radio Networks with Femtocells," in IEEE Transactions on Wireless Communications, vol. 11, no. 11, pp. 39103920, November 2012. V. Srivastava and M. Motani, "Cross-layer design: a survey and the road ahead," in IEEE Communications Magazine, vol. 43, no. 12, pp. 112119, Dec. 2005. F. Foukalas, V. Gazis and N. Alonistioti, "Cross-layer design proposals for wireless mobile networks: A survey and taxonomy," in IEEE Communications Surveys & Tutorials, vol. 10, no. 1, pp. 70-85, First Quarter 2008. L. Zhu, F. R. Yu, B. Ning and T. Tang, "Cross-Layer Design for Video Transmissions in Metro Passenger Information Systems," in IEEE Transactions on Vehicular Technology, vol. 60, no. 3, pp. 1171-1181, March 2011. L. Zhu, F. R. Yu, B. Ning, T. Tang and H. Wang, "Cross-Layer Handoff Design in Communication-Based Train Control (CBTC) Systems Using WLANs," 2012 IEEE Vehicular Technology Conference (VTC Fall), Quebec City, QC, 2012, pp. 1-5. Li Ma, Fei Yu, V. C. M. Leung and T. Randhawa, "A new method to support UMTS/WLAN vertical handover using SCTP," in IEEE Wireless Communications, vol. 11, no. 4, pp. 44-51, Aug. 2004. Fei Yu and V. C. M. Leung, "Mobility-based predictive call admission control and bandwidth reservation in wireless cellular networks," Proceedings IEEE INFOCOM 2001. Conference on Computer Communications. Twentieth Annual Joint Conference of the IEEE Computer and Communications Society (Cat. No.01CH37213), Anchorage, AK, 2001, pp. 518-526 vol.1. J. Zuo, C. Dong, S. X. Ng, L. L. Yang and L. Hanzo, "Cross-Layer Aided Energy-Efficient Routing Design for Ad Hoc Networks," in IEEE Communications Surveys & Tutorials, vol. 17, no. 3, pp. 1214-1238, thirdquarter 2015. Wang, Q., & Abu-Rgheff, M. A. (2003). In Wireless Communications and Networking (Vol. 2, pp. 1084–1089). IEEE Su, W., & Lim, T. L. (2006). In Seventh ACIS international conference on software engineering, artificial intelligence, networking, and parallel/distributed computing, 2006. SNPD 2006 (pp. 278–284). 
 Merlin, C. J., & Heinzelman, W. B. (2006). In second IEEE workshop on wireless mesh networks, 2006. WiMesh 2006 (pp. 103–105). 
 Lin, D., & Li, S. (2009). In Fourth international conference on Frontier of computer science and 
 technology, 2009. FCST ’09 (pp. 272–278). J. Mehlman, Case for “Cross-Layer Standardization.” Design: A Available: http://www.jeffreymehlman.com/EE359 Research Project Final JAM.pdf A. Goldsmith, and B. Girod, “Cross-Layer Design of Ad- hoc Wireless Networks for Real-Time Media.” Available: 
 http://www.stanford.edu/ zhuxq/adhoc project/ 
 E. Setton, T. Yoo, X. Zhu, A. Goldsmith, and B. Girod, “Cross-Layer 
 Design of Ad Hoc Networks for Real-Time Video Streaming,” IEEE 
 Wireless Communications, August 2005. 
 S. Khan et al., “Application-Driven Cross-Layer Optimization for Video Streaming Over Wireless Networks,” IEEE Communication Mag., Vol. 44, No. 1, pp. 122-130, 2006 I. Chuang, C. Hsieh, and Y. Kuo, “An adaptive cross-layer design approach for network security management,” 13th International Conference on Advanced Communication Technology (ICACT), pp. 1085- 1089, 2011. 
 C. Huang, M. Matthews, M. Ginley, X. Zheng, C. Chen, M. Chang, “Efficient and Secure Multicast in WirelessMAN: A Cross-Layer Design,” Journal of Communications Software and Systems 3(3), pp. 199-206, 2007. 
 S. Khan, K. Loo, Z. Din, “Cross Layer Design for Routing and Security in Multi-hop Wireless Networks,” J. Information Assurance and Security, pp. 170-173, 2009 
 Garcia-Sanchez, Antonio-Javier, Felipe Garcia-Sanchez, Joan GarciaHaro, and Fernando Losilla. "A cross-layer solution for enabling realtime video transmission over IEEE 802.15.4 networks U. Khatri and S. Mahajan, "Cross-layer design for wireless sensor networks: A survey," 2015 2nd International Conference on Computing for Sustainable Global Development (INDIA Com), New Delhi, 2015, pp. 73-77.

[27] Lucas, D., Mendes, P., & Rodrigues, J. (2011). A survey on cross-layer solutions for wireless sensor networks. Journal of Network and Computer Applications, 34(2), 523–534 [28] R.K. Saini, Ritika, S. Vijay, “A Survey on Cross Layer Design implementation in Wireless Sensor Network”, International Journal of Advanced Information Science and Technology (IJAIST), Vol.51, No.51, July 2016 [29] X. Ren and J. Zhang, "Review of the Cross-Layer Design in Wireless Ad Hoc and Sensor Networks," 2010 6th International Conference on Wireless Communications Networking and Mobile Computing (WiCOM), Chengdu, 2010, pp. 1-3. [30] I. Al-Anbagi, M. Erol-Kantarci and H. T. Mouftah, "A Survey on CrossLayer Quality-of-Service Approaches in WSNs for Delay and Reliability-Aware Applications," in IEEE Communications Surveys & Tutorials, vol. 18, no. 1, pp. 525-552, First quarter 2016. [31] J. N. Al-Karaki and A. E. Kamal, "Routing techniques in wireless sensor networks: a survey," in IEEE Wireless Communications, vol. 11, no. 6, pp. 6-28, Dec. 2004. [32] A. Balobaid, "A survey and comparative study on different energy efficient MAC-protocols for Wireless Sensor Networks," 2016 International Conference on Internet of Things and Applications (IOTA), Pune, 2016, pp. 321-326. [33] V. Kawadia, and P. R. Kumar, “A cautionary perspective on cross-layer design,” Wireless Commun., Vol. 12, No. 1, pp. 3-11, 2005. 
 [34] I. Chuang, C. Hsieh, and Y. Kuo, “An adaptive cross-layer design approach for network security management,” 13th International Conference on Advanced Communication Technology (ICACT), pp. 10851089, 2011 [35] Srivastava, V., & Motani, M. (2005). Communications Magazine, IEEE, 43(12), 112. doi:10.1109/ MCOM.2005.1561928.
 [36] H. Wang, Y. Yang, M. Ma, J. He and X. Wang, "Network lifetime maximization with cross-layer design in wireless sensor networks," in IEEE Transactions on Wireless Communications, vol. 7, no. 10, pp. 3759-3768, October 2008. [37] V. Kawadia and P. R. Kumar, “A Cautionary Perspective on Cross Layer Design,” IEEE Wireless Communication, vol. 12, no. 1, Feb. 2005, pp. 3–11. [38] Shah Ghalib A, Liang Weifa and Shen Xiaojun (2010), “Cross-Layer Design for QoS Support in Wireless Multimedia Sensor Networks” Proc.IEEE. 
 [39] Gupta Munish, Singh Paramjeet and Rani Shveta (2012), “Cross-Layer Energy Efficient Protocols for WSN: A Survey”, Apeejay Journal of Computer Science and Application 
 [40] I. Akyildiz et al., “A Survey on Sensor Networks,” IEEE Commun. Mag., vol. 40, no. 8, Aug. 2002, pp. 102–14.