Wireless Sensor Network: At a Glance 319 S.N. Energy Efficient Protocol Major Theoretical Aspects 1. TEEN (Threshold sensitive Energy Efficient sensor Network protocol) (Manjeshwar & Agarwal, 2001) - First protocol for reactive networks with enhanced efficiency. - Time critical data reaches the user almost instantaneously. Eminently well suited for time critical data sensing applications. - Message transmission consumes much more energy than data sensing. So, even though the nodes sense continuously, the energy consumption in this scheme can potentially be much less than in the proactive network, because data transmission is done less frequently. - The soft threshold can be varied, depending on the criticality of the sensed attribute and the target application. - A smaller value of the soft threshold gives a more accurate picture of the network, at the expense of increased energy consumption. Thus, the user can control the trade-off between energy efficiency and accuracy. - At every cluster change time, the attributes are broadcast afresh and so, the user can change them as required. - The main drawback of this scheme is that, if the thresholds are not reached, the nodes will never communicate; the user will not get any data from the network at all and will not come to know even if all the nodes die. Thus, this scheme is not well suited for applications where the user needs to get data on a regular basis. - Another possible problem with this scheme is that a practical implementation would have to ensure that there are no collisions in the cluster. 2. APTEEN (Adaptive Periodic Threshold- sensitive Energy Efficient Sensor Network Protocol) (Manjeshwar & Agarwal, 2002) - A Protocol for Hybrid network (inherit best characteristics of both proactive and reactive network). - To provide periodic data collection as well as near real-time warnings about critical events. - By sending periodic data, it gives the user a complete picture of the network. It also responds immediately to drastic changes, thus making it responsive to time critical situations. Thus, it combines both proactive and reactive policies. - It offers a flexibility of allowing the user to set the time interval (TC) and the threshold values for the attributes. - Energy consumption can be controlled by the count time and the threshold values. - The hybrid network can emulate a proactive network or a reactive network, by suitably setting the count time and the threshold values. - The main drawback of this scheme is the additional complexity required to implement the threshold functions and the count time. However, this is a reasonable trade-off and provides additional flexibility and versatility. 3. HEED (Hybrid Energy-Efficient Distributed clustering) (Younis & Fahmy, 2004) - An energy-efficient clustering protocol, using residual energy as primary parameter and network topology features (e.g. node degree, distances to neighbors) as secondary parameters. - Here all nodes are assumed to be homogenous nodes (with same initial energy). - It extends the basic scheme of LEACH. - The clustering process is divided into a number of iterations, as well as in each iteration nodes which are not covered by any cluster head doubles their probability of becoming a cluster head. - Since it enable every node to independently and probabilistically decide on its role in the clustered network, thus cannot guaranteed optimal elected set of cluster heads. Table 17. Major theoretical aspects of some major energy efficient protocols for WSNs Recent Advances in Wireless Communications and Networks 320 6. PEGASIS (Power-Efficient Gathering in Sensor Information Systems) (Lindsey & Raghavendra, 2002) - A near optimal chain-based protocol and an enhanced descendant of LEACH. - It has two main objectives: increases the lifetime of each node by using collaborative techniques and allow only local coordination between nodes that are close together so that the bandwidth consumed in communication is reduced. - Nodes route data destined ultimately for the base station through intermediate nodes. - In determining the routes only consider the energy of the transmitter and neglect the energy dissipation of the receivers. - It assumes that each sensor node can be able to communicate with the base-station directly and all nodes maintain a complete database about the location of all other nodes in the network. - The method of which the node locations are obtained is not outlined. - It also assumes that all sensor nodes have the same level of energy and they are likely to die at the same time. 7. Hierarchical- PEGASIS (Savvides et al., 2001) - Its objective is to decrease the delay incurred for packets during transmission to the base-station. - In its concept only spatially separated nodes are allowed to transmit at the same time. - This chain-based protocol with CDMA capable nodes, constructs a chain of nodes, that forms a tree like hierarchy, and each selected node in a particular level transmits data to the node in the upper level of the hierarchy, that ensures data transmitting in parallel and reduces the delay significantly. - Results shows that this hierarchical extension of PEGASIS performs better than the regular PEGASIS scheme by a factor of about 60. S.N. Energy Efficient Protocol Major Theoretical Aspects 4. H-HEED (Heterogeneous - HEED) (Kour & Sharma, 2010) - A protocol for heterogeneous WSN. - Cluster head selection is primarily based on the residual energy of each node. Since the energy consumed per bit for sensing, processing, and communication is typically known, and hence residual energy can be estimated. - Intra cluster communication cost is considered as the secondary parameter to break the ties, tie means that a node might fall within the range of more than one cluster head. - Different level of heterogeneity is introduced: 2-level, 3-level and multi-level in terms of the node energy. - In 2-level H-HEED, two types of sensor nodes, i.e., the advanced nodes and normal nodes are used. - In 3-level H-HEED, three types of sensor nodes, i.e. the super nodes, advanced nodes and normal nodes are used. - In this heterogeneous approach all the sensor nodes are having different energy as a result nodes will die randomly. - Multi-level H-HEED prolongs lifetime and shows better performance than other level of H-HEED and HEED protocol. 5. Reactive Energy Decision Routing Protocol (REDRP) (Ying- Hong et al., 2006) - To solve the problem of limited energy, the loading of nodes have to be distributed as possible as it can. - If the energy consumption can be shared averagely by most nodes, then the lifetime of sensor networks will be enlarged. - This protocol will create the routes in reactive routing method to transmit the data node gathered. - It uses the residual energy of nodes as the routing decision for energy-aware. 8. SHPER (Scaling Hierarchical Power Efficient Routing) (Kandris et al., 2009) - Enhanced integration of a hierarchical reactive routing protocol. - It supposes the coexistence of a base station and a set of homogeneous sensor nodes which are randomly distributed within a delimited area of interest. - Consists of two phases: the initialization phase and the steady state phase. - Hard and soft thresholds are utilized in the SHPER protocol as with TEEN. - Best suited in real life applications where imbalance in energy distribution is the common case. - Network scalability is retained because it adopts both multi-hop routing and hierarchical architecture. Table 17. (continues) Major theoretical aspects of some major energy efficient protocols for WSNs Wireless Sensor Network: At a Glance 321 S.N. Energy Efficient Protocol Major Theoretical Aspects 9. TREnD (Timely, Reliable, Energy-efficient and Dynamic) (Marco et al., 2010) - A novel cross-layer WSN protocol for control applications. - The routing algorithm of TREnD is hierarchically subdivided into two parts: a static route at inter clusters level and a dynamical routing algorithm at node level. This is supported at the MAC layer by hybrid TDMA/CSMA solution. - The protocol parameters are adapted by an optimization problem, whose objective function is the network energy consumption, and the constraints are the reliability and latency of the packets. - It uses a simple algorithm that allows the network to meet the reliability and latency while minimizing for energy consumption. - It is best fit for industrial environments. 10. LEACH (Low Energy Adaptive Clustering Hierarchy) (Heinzelman et al., 2000) - A most popular cluster-based protocol, which includes distributed cluster formation. - The idea is to form clusters of the sensor nodes based on the received signal strength and use local cluster heads as routers to the sink. - It randomly selects a few sensor nodes as cluster-heads and rotates this role to evenly distribute the energy load among the sensors in the network. - Its operation is separated into two phases: setup phase where clusters are organized and CHs are selected and steady state phase where the actual data transfer to the base station takes place. - It uses a TDMA/CDMA MAC to reduce inter-cluster and intra-cluster collisions. - Optimal number of cluster heads is estimated to be 5% of the total number of nodes. - This protocol is most appropriate for the applications when there is a need for constant monitoring. 11. SEER (Simple Energy Efficient Routing) (Hancke & Leuschner, 2007) - A protocol that considers energy saving and balancing, with poor idea about energy balancing. - Once the network has been deployed in the area where it is to operate, the sink transmits a broadcast packet. - Each node in the network is assumed to have a unique address within the network. - When a node observes new data, it initiates the process of routing. Two types of data packets can be sent: normal data and critical data. - When nodes receive a data message they update the remaining energy value in the neighbor table for the neighbor that sent the message. Nodes that forward data messages follow the same process, except for minor differences. - If node's remaining energy falls below a certain threshold, it transmits an energy message to all of its neighbors to inform them of its energy level. - The sink node periodically sends a broadcast message through the network so that nodes can add new neighbors that joined the network to neighbor tables and remove neighbors that have failed from the neighbor tables. - Nodes also update remaining energy values stored in the neighbor tables. 12. BEAR (Balanced Energy-Aware Routing) (Ahvar & Fathy, 2010) - An extended version of SEER protocol with some visible difference specially in forwarding data procedure that saves and balance energy consumption in WSNs. - Finds optimal route in energy level and hop count both. - Routing decisions in BEAR are based on the distance to the base-station as well as on remaining battery energy level of nodes on the path towards the base station. - BEAR is better than the SEER protocol in energy managing, due to the fact that BEAR sends data packet along a balanced path. Table 17. (continues) Major theoretical aspects of some major energy efficient protocols for WSNs Recent Advances in Wireless Communications and Networks 322 Fig. 4. Security threats and their usual defenses in Wireless Sensor Networks (Dwivedi et al., 2009b) 19. Reference Dwivedi, A. K. & Vyas, O.P. (2010). 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Secure routing in wireless sensor networks: Attacks and countermeasures. Proceedings of 1st IEEE International Workshop on Sensor Network Protocols and Applications. Dwivedi, A.K. & Vyas, O.P. (2011). An Exploratory Study of Experimental Tools for Wireless Sensor Networks. Wireless Sensor Network,Vol. 3, ISSN 1945-3078 (Print), 1945-3086 (Online). Available from http://www.scirp.org/journal/wsn 0 Software Defined Radio Platform for Cognitive Radio: Design and Hierarchical Management Amor Nafkha, Christophe Moy, Pierre Leray, Renaud Seguier and Jacques Palicot SUPELEC/IETR, Avenue de la Boulaie, Cesson Sévigné Cedex, France 1. Introduction Cognitive Radio (CR) Mitola (2000) is a promising technology to improve spectrum utilization of wireless communication systems. Current investigations in CR have been focused on the physical layer functionality. The cognitive radio, built on a software-defined radio, assumes that there is an underlying system hardware and software infrastructure that is capable of supporting the flexibility needed by the cognitive algorithms. As already foreseen by Mitola Mitola & Maguire (1999), a Cognitive Radio is the final point of Software Defined Radio (SDR) platform evolution: a fully reconfigurable radio that changes its communication functions depending on network and/or user demands. Mitola’s definition on reconfigurability is very broad and we only focus here on the reconfigurability of the hardware platform for Cognitive Radio. SDR basically refers to a set of techniques that permit the reconfiguration of a communication system without the need to change any hardware system element. As explained in the schematic of figure 1, this relies on a cognitive circle. Figure 1 (a) is from Mitola (2000) and figure 1 (b) is a simplified view of the cycle summarized in three main steps: • Observe: gathers all the sensing means of a CR, • Decide: represents all that implies some intelligence including learning, planning decision taking, • Adapt: reconfigures the radio, designed with SDR principles, in order to be as flexible as possible. The figure 2 draw the general approach that can help the radio to better adapt its functionality for a given service in a given environment without restriction on the sensors nature. Sensors are classified in function of the OSI layers they correspond to, with a rough division in three layers. Corresponding to the lower layers of the OSI model, we find specifically all the sensing information related to the physical layer: propagation, power consumption, coding scheme, etc. At the intermediate level are all the information that participate to vertical handover, or can help to make a standard choice, as a standard detection sensor for instance. The network load of the standards supported by the equipment may also be of interest. It also includes the policies concerning the vicinity, the town or the country. The highest layer is related to the applications and all that concerns the human interaction 15 2 Will-be-set-by-IN-TECH Fig. 1. (a) Mitola’s cognitive cycle, (b) simplified version Fig. 2. Simplified OSI model for cognitive radio context with the communicating device. It is related to everything that concerns the user, his habits, preferences, policies, profile. If a user has the habit to connect to a video on demand service every evening while coming back home from office by metro, a CR terminal should be aware of it to plan all the requirements in terms of battery life, sufficient quantity of credit on his contract, vertical handover succession depending on each area during the trip, etc. The equipment can be aware of its environment with the help of sensors like microphone, video-camera, bio-sensors, etc. As we are at the early beginning of such technology, it is difficult to foresee all the possibilities. We can think, for instance, that user’s biometric information and/or facial recognition will ensure equipment security. Video-camera could also be used to indicate if the terminal is outside or inside a building. This may impact propagation features, but also the capability or not to receive GPS signals. Another example could be given in the context of video conferencing, a separation between the face of the speaker and the background could help decreasing the data rate while refreshing slowly the background of the image Nafkha et a l. (2007). Note that this classification is also related to three well-known concepts of the literature: • Context aware for higher layers Chen & Kotz (2000), • Interoperability for intermediate layers Aarts et al. (2001), • Link adaptation for lower layers Qiu & Chuang (1999). All this may be combined to achieve cross-layer optimizations. This is one of the responsibilities of the cognitive engine in our mind. However, due to the high financial pressure on spectrum issues, CR is often restricted in the research community to spectrum management aspects as in Fan et al. (2008); Ghozzi et al. (2006). Opportunistic spectrum 328 Recent Advances in Wireless Communications and Networks [...]... somewhat lacking Therefore, the integration of these tools into a working tool flow to achieve the goal of a partial reconfiguration for example required research from numerous sources and some experimentation with the tools For the partial reconfiguration implementation, we need the following Xilinx tools: 334 8 Recent Advances in Wireless Communications and Networks Will-be-set-by -IN- TECH • Xilinx EDK provides... Modeling Approach in Software Defined Radio System Design", IEEE Workshop on Signal Processing Systems, Athens (Greece), Nov 2005 344 18 Recent Advances in Wireless Communications and Networks Will-be-set-by -IN- TECH B Blodget and S McMillan and P Lysaght, "A lightweight approach for embedded reconfiguration of FPGAs," in Design, Automation and Test in Europe Conference and Exhibition, 2003 T Grandpierre,... (MME) and two user plane nodes, the Serving Gateway and the Packet Data Network Gateway (PDN Gateway or P-GW) These control planes handle the data packet routing within the LTE and towards non-3GPP data networks, respectively 346 Recent Advances in Wireless Communications and Networks Fig 1 LTE Architecture and functional split between E-UTRAN and EPC LTE provides service differentiation by adopting... for innovation in the area of digital radio communications OpenAirInterface implements in software the Physical and Medium-access layers for wireless communications as well as providing a IPv4/IPv6/MPLS network device interface under Linux The initiative targets 4th generation wireless systems (UMTS Longterm-evolution (LTE), 802.16e/j) and rapidly-deployable MESH networks using a similar radio interface... to interconnect the Micro-blaze to the ICAP internal configuration interface In this case, small partial bit-streams can be stored inside the FPGA, and the use of endo-configuration lets free the other HW resources of the platform At a 338 12 Recent Advances in Wireless Communications and Networks Will-be-set-by -IN- TECH larger scale, configuration for the HW accelerator is external This implies to interconnect... type, 348 Recent Advances in Wireless Communications and Networks the modulation and the coding scheme level of the particular user However, the results show that the proposed CAC is beneficial only in terms of packet delay, since the average data rate and the cell utilization are decreased Regarding the bandwidth reservation, a downlink CAC algorithm with look-ahead calls for 3GPP LTE mobile networks. .. Xilinx Virtex2 FPGA and supports gigabit Ethernet and PCI-express connections back to a host computer This allows for all, or almost all processing to be implemented on the platform 330 4 Recent Advances in Wireless Communications and Networks Will-be-set-by -IN- TECH • OpenAirInterface: The mobile communications department at EURECOM proposed an open-source hardware/software development platform and. .. systems The radio interface of LTE is based on Orthogonal Frequency Division Multiplexing (OFDM) and supports Multiple-Input-Multiple-Output (MIMO) technology The standard defines asymmetrical data rates and modulations for uplink and downlink, using different access schemes for each link In particular, Orthogonal Frequency Division Multiple Access (OFDMA) is employed in the downlink, while the technically... other modules In our platform the DSP is used as a control device for the ADC/DAC and memory modules and to set the parameters for the pre-distortion filter running in real-time on the FPGA at the module SMT350 Based on the Xilinx Virtex4 range, the SMT348 features 16MB 332 6 Recent Advances in Wireless Communications and Networks Will-be-set-by -IN- TECH of blistering fast QDRII memory, ensuring ample capacity... link according to the compression of the source in a video-telephony context A person switches-on his terminal in order to perform an audio-video conversation with another person At the beginning of the communication, 340 14 Recent Advances in Wireless Communications and Networks Will-be-set-by -IN- TECH Fig 8 example of the hierarchical configuration management mapping the face of the speaker and the background . Architecture for Integrating Wireless Sensor Networks into the Internet of Things, Proceedings of 3rd Symposium of Ubiquitous Computing and Ambient Intelligence 2008, Springer Berlin/Heidelberg,. Scenario: Prospects and Challenges, Proceedings of National Conference on Wireless Communication and Networking (WINCON), pp. 138- 148. Recent Advances in Wireless Communications and Networks 326. efficient protocols for WSNs Recent Advances in Wireless Communications and Networks 320 6. PEGASIS (Power-Efficient Gathering in Sensor Information Systems) (Lindsey & Raghavendra,