War Literature Essay Example for Free

War Literature Essay Turkey and Armenia have not had the greatest diplomatic relations in recent years. Therefore, it was somewhat surprising that the leaders all of these two nations sat down to watch a football game between the two countries. To say that this is somewhat bizarre would be a dramatic understatement. In 1915, during the First World War, Turkey was responsible for the genocide of scores of Armenians. Needless to say, the relationship between these two group has been tenuous at best over the years. For some, all of this appears to be a form of political theater. However, there is more to the situation than mere grandstanding. Russias recent aggression has sparked fear in Eastern Europe. So, it is not surprising that Turkey and Armenia might forge an alliance out of mutual distrust of Russia. How long such a shaky alliance lasts is anyones guess. Much of this is ironic considering it occurs in light of the legendary football match between the Germans and the British during World War One. Thomas Hardy chronicles this legend in a short article that also points out the strange irony of how mortal enemies can become friendly rivals when they share a common love. In this case, the love is for the game of football. It would seem that to the soldiers, a love for a cultural sport overrides any serious concerns that are at the center of a declaration of war. Or, perhaps, war becomes boring after a while and both sides need a break. Whatever the reason, it is odd to see enemies converge based on a love for a mere past time. It would be absurd to assume that a love for football can eliminate aggression between nations. However, it does show that aggression and competitiveness can be used for more fruitful pursuits other than direct conflict. Then again, football is a form of conflict with enthusiasm replacing aggression most of the time. While sitting in front of the TV watching teams play make the world a better place? Doubtful; but it is at least worth a try. Bibliography Hardy, Thomas. (Date Unknown) â€Å"A Satire of Circumstance† Retrieved October 13, 2008, from http://net. lib. byu. edu/english/wwi/children/captain_nevill. html Palomaa, Erik. (2008) â€Å"Turkey and Armenia Engage in Football Diplomacy. † Retrieved October 13, 2008, from http://www. worldpoliticsreview. com/Article. aspx? id=2694

Superman - All American Essay -- essays research papers

Superman, All-American Hero Gary Engle describes Superman as the ultimate American, â€Å"Superman is the greatest American hero† (Engle, 677). After reading three comic books I notice an occurring theme of wanting to protect what is good, even though the comic books chosen span over eleven years. Several distinct things to Superman’s personality are his cape, the respect he has for others, the respect others have for him, his intelligence, his protection of all life and what is right, his origin, and the sacrifices he makes. Superman is considered to be the greatest American hero of all time. The Superman epic has gone on for years and years; yet the story line has always remained the same: The core of American myth is Superman consists of a few basic facts that remain unchanged throughout the infinitely varied ways in which the myth is told – facts with which everyone is familiar, however marginal their knowledge of the story. Superman is an orphan rocketed to Earth when his native planet Krypton explodes; he lands near Smallville and is adopted by Jonathan and Martha Kent, who inculcate in him their American middle-class ethic; as an adult he migrates to Metropolis there he defends America – no, the world! no, the universe – from all evil and harm while playing a romantic game in which, as Clark Kent, he hopelessly pursues Superman, who remains aloof until such time as Lois proves worthy of him by falling in live with his feigned identity as a weakling. That’s it. (Engle, 678). This is the same in any tale of Superman, the same occurring theme. This adds character to Superman, and explains why he is so all-American. Firstly, Superman is an alien, to the United States and to the world. But is he really that different from you and me? We are all descended from people who were immigrants to America. Engle writes: â€Å"All Americans have immediate sense of their origins elsewhere† (Engle, 678). So doesn’t it make sense that everyone that fights or works for our natural freedoms are aliens, the soldiers, the doctors, the teachers, and Superman himself? â€Å"Like the peoples of the nation whose values he defends, Superman is an alien† (Engle, 678). Like all aliens the reason for coming to this country is to make something better of ones self. Where one may run any kind of business they please and not worry about someone else intervening because they simply can. Superman ... ..., to stand up and fight for what he/she believes in. Superman finally kills the creature but in the process end up dying himself. This is the sacrifice Superman makes for his people: he loses his life and his true love Lois. But it was all worth it in his eyes because he was protector of his nation. Superman had many things going for him, his invincibility against the humans, his strength, and most of all his love for Lois Lane. Superman could have easily fled and would have never been seen or herd from again. But to him America was worth his sacrifice of everything he has, including his life. Any true American is expected to sacrifice his life for his country. Superman is an astonishing being. His self-sacrifice presents an ideal of what any soldier should do for his country. His politeness is an ideal for how every person should behave. His ability not to overreact is an example of what to be like in a dangerous situation. Superman is a glorified all-American and would do anything for the people. He goes beyond the call of duty to make life easier on at least one other person. Without a doubt everyone should know why Superman is considered the greatest American hero of all time.

My Last Duchess and Othello: Striking Comparisons

In the dramatic form, be it monologue, dialogue or full theatrical scene, the author cannot step into the action to comment or interpret for us, as he can in a novel.   We must draw our own conclusions from what we see and hear, and this makes for powerful effects, as a character reveals him- or herself to us by what he or she says or does.   In the monologue My Last Duchess Browning misleads us with great skill before we realize that we are listening to a criminal lunatic.The dramatic force lies in the surprise we feel as the truth finally emerges.   In Act IV, scene iii of Othello there is again an agonizing irony for the viewer, who knows more than Desdemona and is of course impotent to help her.   Shakespeare works like a dentist without an anesthetic, and the pain for the audience derives from the unbearable innocence of the doomed Desdemona, who is surely something like the Duchess in Browning’s poem, helpless and bewildered in the face of a murderous insanity in her husband.Browning’s Duke sounds so sane!   He is wonderfully gracious and articulate – â€Å"Will’t please you sit and look at her?† (5).   As he tells his story he seems to weigh his words with great caution, as if he is quite free of the distorting power of anger or any other passion, and is keen to avoid any unfairness in his judgment: â€Å"She had / A heart – how shall I say? – too soon made glad† (21-2), â€Å"†¦but thanked / Somehow – I know not how – as if she ranked†¦Ã¢â‚¬  (31-2). He never raises his voice, and speaks with a measured confidence that quite takes us in.At first we might be tempted to believe that his attitudes are reasonable: â€Å"Sir, ‘twas not / her husband’s presence only, called that spot / Of joy into the Duchess’ cheek† (13-15).   His manner is restrained even as he hints at her infidelity.   The painter flattered her about her appearance, as of course he would, being a Renaissance artist totally dependent on patronage, but she was charmed by it – foolishly, the Duke suggests.   â€Å"She liked whate’er / She looked on† (23-24).   She was delighted by the beauty of the sunset, and the little tribute from the man who gave her the cherries, just as much as â€Å"My favor at her breast† (25).What he seems to be objecting to is her failure to be properly selective and aristocratic in her tastes.   This is a rather extreme sort of snobbery, but perhaps not unprecedented; we may not find it attractive, but we may accept it as a feature of a proud man. In Browning’s My Last Duchess, the murder is implied. It is not described in explicit terms as in Othello. In the lines, â€Å"Paint/Must never hope to reproduce the faint /Half-flush that dies along her throat† ,the speaker adores the ‘faint half-flush’ on his wife’s face that no paint could re-add and at th e same time leaves a slight hint that she had been throttled to death[dies along her throat].The intelligent monologue is enough to make the point overt and covert at the same time.All the time, Browning is luring us up the garden path.   We begin to detect the problem.   The Duke is immensely proud, a man of great heritage, while she is free of snobbery, charmed by the delights of the world and human kindness, and genuinely innocent. (Infidelity does not now seem to be the Duke’s concern.)   Then we begin to see how his pride is really pathological arrogance.   â€Å"Even had you skill / In speech – (which I have not)† (35-36), (he lies, of course) to explain your objection to her behavior – which is clearly quite â€Å"normal† – it would involve â€Å"stooping, and I choose / Never to stoop† (42-3).So, rather than speak to her about his dissatisfaction, which would involve impossible condescension by him, he chose to solve t he problem rather more radically: â€Å"This grew; I gave commands; / Then all smiles stopped altogether† (45-6).   It takes a moment for us to register what he did, so unbelievable is it and so evasively phrased.â€Å" †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦..She thanked men,—good; but thanked /Somehow†¦.I know not how †¦.as if she ranked /My gift of a nine-hundred-years-old name /With anybody’s gift,†-   the last part of the speech clearly brings forth the envy rankling in the speaker’s heart!The unbending pride of the Duke comes out through the turns of phrases of this part of this long monologue, â€Å"†¦.and if she let/Herself be lessoned so, nor plainly set/Her wits to yours ,forsooth and made excuse,/-E’en then would be some stooping and I choose/Never to stoop.†The Duke can hardly ‘chose to stoop’to give in to the childish demeanors of his beautiful wife.Again, jealousy seems to be prevalent in the tone of these words: â€Å"†¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦..Oh ,Sir, she smiled no doubt,/Whene’er I passed her; but who passed without /Much the same smile?†Then having confessed to murder, or, rather, boasted of it, he continues his negotiations for his next Duchess, celebrating, incidentally, one of his favorite art works, â€Å"Neptune†¦ Taming a sea-horse† (54-5), the very image of the brutal control that he has himself exerted over his innocent last Duchess.The willow scene from Othello works differently, of course, because it is a dialogue, though it is the inner workings of Desdemona’s mind that the dramatic form reveals here, just as much as is the case in Browning’s poem There is an almost intolerable pathos about this scene because Desdemona is so helpless.   She has a good idea of what is going to happen – â€Å"If I do die before thee, prithee shroud me /   In one of those same sheets† (24-5) and is impotent in the face of her fa te.There seems to be no defence against the ruthless execution of Othello’s enraged will. She is in a sort of trance, a hypnosis of shock.   All she can do is wait for the end, and the pathetic simplicity of her reflections here is the sign of a wounded spirit in retreat from reality.   The tragic atmosphere is given additional poignancy by the occasional interruption of the everyday details of â€Å"undressing for bed†, the habitual continuing because there is nothing else to do in the face of the worst – â€Å"Prithee unpin me† (21).She continues at moments to pretend that this is just an ordinary night: â€Å"This Lodovico is a proper man† (35), not a comparison of Othello with her country forms, but a pathetic attempt at gossip. But her real thoughts emerge in the obsession with the willow song, which she cannot resist. It is the perfect mirror of her own fortune: â€Å"And she died singing it; that song tonight / Will not go from my mindà ¢â‚¬  (30-1). Like a detail from a psychoanalyst’s casebook comes the unprompted line in the song that gives away the deepest thoughts of the willing victim.–Let nobody blame him, his scorn I approve, —Nay, that’s not next.   Hark!   Who’s that knocks?–It is the wind.† (51-3)She corrects herself, but the absolute terror of realisation goes through her.   Compared with Desdemona’s helplessness in the face of the corruption of Othello, Emilia’s jokes have an immensely remedial health.   It is not a criticism of Desdemona, but it is a firm placing of trust in the human by Shakespeare.In Shakespeare’s Othello,the Moor can hardly be blamed for his rash decision of murdering Desdemona, who had been black-painted   by his ‘honest Iago’ and it was Iago again who had sown the seeds of jealousy in his mind. Desdemona pleaded her innocence at last and asked to call for Cassius but Othello ran berserk m addened by sexual jealousy.Othello could hardly be blamed for the attitude, as he was a Moor and unfamiliar with the ways and manners of the Venetian Republic. Naturally, he fell victim to Iago’s insinuations and committed the murder of hi beautiful wife, Desdemona, who was actually, innocence incarnate.In Act IV, sc ii, Othello in reply to Desdemona’s pleading innocence disgustingly cried out, â€Å"O Desdemona, away! away! away!†Desdemona , being totally unaware of the handkerchief she lost tried to reason with her husband, â€Å"Am I the motive of these tears my Lord?†It might have been possible that Othello could have turned deaf ears to Iago’s   vitriolic comments or aspersions cast on Desdemona, but as he was new to their society and culture, it became easy for Iago to prison him against his wife, a paragon of beauty.By way of rejoinder , when Othello speaks out, â€Å"Had it pleased Heaven/To try me with affliction ;had they rained/All ki nds of sores and shame on my bare head/Steeped me in poverty to the very lips/Given to captivity me and my utmost hopes/I should have found in some place of my soul/A drop of patience†¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦.†and at last turns to the question of â€Å"complexion† , â€Å"Turn thy complexion thee..  Ã‚   †¦Ay there look as grim as hell!†, we find Othello a dejected, frustrated ,lost soul feeling small for being a Black Moor who was lien to the Venetian culture! Question of Culture and Identity assails him, no doubt!  Othello decided to put an end to the life of his unfaithful wife at last and as he uttered the words in Act V, Sc ii, â€Å"Yet, I’ll not shed her blood;/Nor scar that whiter skin of hers than snow/And smooth as monumental alabaster/Yet she must die,else she’ll betray more men†,Did he not sound the same as the Duke of My Last Duchess who had been driven mad by sexual jealousy? The murder could not be justified, but , Othello was quite a lover and a compassionate person than the Duke. He needed evidence to prove Desdemona’s betrayal, he had to fight immensely with his own conscience to come to the decision of murder.As a person, Duke was cold-blooded, but Othello was emotional and irrational at he same time. If this had not been so,   â€Å"†¦I will kill thee,/ And love thee after.One more and this the last./So sweet was ne’er so fatal. I must weep/ But they are cruel tears ;this sorrow’s heavenly ;/IT STRIKES WHERE IT DOTH LOVE,†could he utter such words? The Duke of My Last Duchess was never so overpowered with emotions to give vent to his pent-up goodness. Did he have any goodness, if at all?In Act V, sc i, Othello is making his mind up to vent his rage upon Desdemona. Here he again finds enough reason to slaughter Desdemona. On hearing the footsteps of Cassius, he blurt forth, â€Å"’Tis he;-O brave Iago, honest and just†¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢ € ¦minion your dear lies dead/and your unblest fate hies, strumpet I come†Till Lines 31 of Act V   Sc ii, we find Othello raves and rails on the murder of Desdemona. Othello seemed to give a chance to Desdemona to prove her innocence by saying, â€Å"If you bethink yourself of any crime/Unreconciled as yet heaven and grace /Solicit for it straight.†But he meant the murder and perpetrated it! In Act III ,Sc iii, when Othello grows blind in rage provoked by â€Å"honest Iago’s† words, he finds every reason to kill Unfaithful Desdemona and utters, â€Å"Monstrous , monstrous!!†On hearing Cassio’s dream-mutterings on his secret affair with Desdemona, Othello got green with anger and envy and saw betrayal from the cruelest possible angle.He found terrible monstrosity in it, profound mendacity in the whole episode, running on the sly.When Emilia came after the murder talking of Desdemona’s profound love for her husband ,Othello could not keep his cool, he blurted, â€Å"O cursed slave!/Whip me ye devils/From the possession of this heavenly sight/Blow me about in the winds, roast me in sulphur/Wash me in steep-down gulfs of liquid fire†¦O Desdemona, Desdemona, DEAD!!†[Act V, Scii] Could we ever expect the Duke speaking in such touchy, sentimental terms after committing the murder?No, never!!!Works Cited1.Shakespeare, William:Othello, Arden, London, 1974.2.Young, W.T.:Browning’s poems,Macmillan, London, 1975.

Wireless sensor network - Free Essay Example

Sample details Pages: 22 Words: 6677 Downloads: 1 Date added: 2017/06/26 Category Statistics Essay Did you like this example? 1 Wireless Sensor Network In this chapter, wireless sensor network (WSN) principles are being shortly introduced and discussed. In order to increase the level of understanding for analyzing Wireless Sensor Network (WSN) systems it is useful to study the technology behind them the technologies which are presented in this section. Wireless Sensor Networks (WSNs) are distributed and independent sensors that are connected and worked together to measure quantities such as temperature, humidity, pressure, noise levels or vibrations [5]. WSNs can measure vehicular movement (velocity, location, etc.) and monitor conditions such as lightning condition, soil makeup and motion [5]. Nowadays, WSNs are utilized in many common applications such as vehicle applications. Some of vehicle applications are: vehicle tracking and detection, tire pressure monitoring, vehicle speed detection, vehicle direction indicator, traffic control, reversing aid sensors etc. Such applications can be divided in major categories such as safety, security, environment and logistics. Don’t waste time! Our writers will create an original "Wireless sensor network" essay for you Create order To implement WSN in an application and have an efficient system, first we need to consider about WSN technology, components and communication topology and protocols. Therefore, first, in this chapter, basic information about WSN components, the communication devices and process unit of WSN will be described. Then, the chapter will be followed by a description of the WSN topologies and protocols emphasizing on mesh WSN technology with ZigBee Protocol. 1.1 Wireless Sensor Network component To provide comprehensive view of WSN hardware, understanding of WSN components structure is required. Wireless sensors are small microcontrollers equipped with wireless communication device and an energy supplier. The architecture of WSNs is illustrated in Figure 31 . As Figure 31 shows the components of WSNs are sensing unit, processing unit, power supplier and communication device. The sensing unit consists of sensors and Analog to Digital Converters (ADCs). ADCs are responsible for gathering the signals and converting them into digital signals data and transfer them through each other using network topology to the processor unit. In the sensing unit, each sensor is called an end node and varies in size and cost. The mission of these multifunction sensor nodes are to sense, process data and collaborate with other nodes [8]. Wireless sensor network can be positioned in two ways, either using a complex technique with the large sensors far from the object or using several sensors with an engineered design on position and topology [5]. In addition, each node provided with a wireless communication transceiver as a communication component. In the process unit, the controller and small memory storage are responsible for managing the collaboration within the sensors to achieve the assigning task. In addition, the communication device with a transceiver makes the network connection. Above all, the essential component of WSN is the power unit, which supports the power for all units [5]. One of the unique characteristics of sensor networks is that they are equipped with an on-board processor. This feature enables them to locally process some simple computations and broadcast only necessary processed data [5]. Network communication is really complicated and needs years of study [8], but to be able to implement WSN, we need to know some basic primary concepts of communication technology such as; network topologies, network protocol and their standards and specifications. 1.2 Communication technology To cover technical aspects of WSN, network topology and network protocol studying is needed. This study will help to provide information about reliability, robustness, security and stability and of WSNs software aspect to answer the research questions RQ. 1 ,RQ. 2 and RQ. 3 . 1.2.1 Topologies in WSN Communication In network communication, the big issue is how data transfers through nodes and nodes interconnect with each other. Several basic network topologies may be used for transmitting to and receiving from a node. The Alliance for Telecommunications Industry Solutions (ATIS) the standards organization of telecommunication industry explained the network topology as The physical, real, logical or virtual arrangement of the nods/elements of a network [9]. The topology shows the diameter and the number of nodes between any two nodes. Moreover how a data process and the data routing complexities are relied on the chosen topology. Consequently, some characteristics of a sensor networks such as latency, robustness and capacity are changed by their topology [10]. Figure 32 is a graphic mapping of networks topology which shows the links of one or more nodes and explains the physical topology of the network. Despite having the same topology, two networks can differ in transmission rates because of their physical interaction, signal types and distance between nodes [9]. Table 31 describes the different types of network topology. Name Types Description Basic topology types Point-to-point Permanent A permanent connection between two endpoints and nodes Switched A dynamic point-to-point circuit that can be dropped if needed. Bus topology Linear topology All nodes are linked to a common transmission medium (bus) which has exactly two endpoints and all data is able to transfer through all nodes. Distributed bus All nodes of the network are linked like a branch to a main bus which causes more than two endpoints. Data goes in all directions to all nodes connected on the bus cable until it finds unique addresse.g. the MAC address or IP address on the network and transmit the data. Ring topology Each node is linked in a ring or loop to the closest node. The data travels in the ring only in one direction and each node can transmit only one piece of data at a time. Ring topology used control access in the network and if one node fails entire network will fail. Star topology Each node has exactly two branches linked to it. External nodes are connected to a central node. The external nodes are only permitted to communicate with the center node and a failure of an external node will cause it to be isolated from the others. Tree topology Each node is linked in different tree paths. In each branch, each node transfers the data to upper node. So, a node failure causes the whole connected branch to fail. Mesh topology Partially connected At least two nodes linked with two or more node in a network. Fully connected Direct link between any two nodes. There will be n(n-1)/2 links Mix topology types Hybrid topology An arrangement of any two or more different basic network topologies. Table 31 Topology TYPES [9]. Since Mesh topology is a main topic in the thesis, it is studied more in-depth in this section 1.2.1.1 Mesh Wireless Network Wireless mesh network is a term used when all wireless nodes are connected to each other within an ad-hoc multi-hob and mesh topology. In this network, any pair of nodes is able to communicate between each other within more than one path. In this network each node is used as a router to forward packets to the neighbor nodes which they have linked to. That means all nodes communicate directly or through other midway nodes without any manual configuration. Therefore, this network also called a self-configuration and self-organized network [11; 12]. As described in Table 31, there are two types of mesh topology Partially connected and Fully connected (See Figure 33). In a fully connected topology each node has the ability to communicate with all other nodes in the network and creates an interconnection links. By increasing the number of nodes in a mesh network, the number of links increases as well. On the other hand, in a partially connected topology, instead of direct interconnection between nodes, each node has two or more links to others to provide alternate routing and traffic balancing. Due to more links and indirect connections between nodes, traffic can flow through one or more router nodes to the destination [7] and create more reliable interconnections between nodes. Moreover, in partial network, the nodes are connected to either the node with higher rate of data transaction or the nearest neighbor node while in fully connected network all nodes have a direct links with each other. This multiple link path conducts a reliable communication. Therefore, whenever a connection fails or a node breaks down, the packages can automatically change their path by jumping from a disconnected node. This is often called the self-healing of the network. This means that the networks connection stability and reliability are not essentially affected by node failures [11]. Due to the characteristics of wireless sensor network mesh, this network is self-configuring and self-organizing network in which each end-node is also used as a router (dual role- data originator /data router) to forward the signal packages all the way back of the main gateway. Therefore, due to the characteristics of mesh networks, this network is becoming one of the most implemented networks which able to have the flexible architecture for the network, easy self-configuration and robust fault tolerance connectivity [11; 12]. Additionally, the self-configuring characteristic of mesh WSN, bring the ability for the network to connect or disconnect nodes from the network. This brings the ability to grow/decrease the network by adding/removing nodes of a system. Mesh WSN has reliable self-healing and robust fault tolerance. This means if a node fails or breaks down the signal packages jump from the disconnected node and automatically conducts a new path through the nearest node. However, the new path imposes re-routing and re-organizing to the network [5], which consumes too much power from the system. Therefore, having a power-aware protocol and algorithm is necessary for mesh network. ZigBee protocol is one of the protocols which provides this ability for WSN. 1.2.2 Protocols in WSN Communication WSN systems include variety of protocols for communication. Protocols need to program in different architectural layers. One of these architectural standard is OSI (Open System Interconnection) framework. In this session a brief introduction of each protocol and OSI are delineated. Figure 34 shows the graphic overview of all wireless network technologies. This figure illustrated IEEE PAN/LAN/MAN technologies and clearly shows how these standards and protocols can be used in different conditions. For instance, 3G protocol is used to cover a long range of audio information in a wide area network (WAN) while for the same information in a short range and personal area network (PAN), Bluetooth is better. The standard conceptual rules set for data representation, data communication and error detection across two ends in telecommunication, are called communication protocols. These abstract rules represent in different layers of communication. There are different protocol stacks introducing different architectures for these layers such as AppleTalk, Distributed Systems Architecture (DSA), Internet protocol suite (TCP/IP) and Open Systems Interconnect (ISO/OSI). Figure 35 (a) illustrates the different layers of an OSI Model and their functionalities. The OSI model has seven layers and each layer provides services for the upper layer and requests services from the lower layer. Figure 35 (b) shows the typical communication protocols layers. Each of these layers has to deal with different issues regarding the communication procedure. As the typical protocol stack model shows in Figure 35 the communication protocols should implement all layers from bottom to top. In addition, a management protocol needs to be applied in each layer to manage power efficiency, robust connectivity and connection reliability (see: Figure 35 b). Below, rules and functionality for each layer are described: * Physical layer: is responsible for signal processing and physical interface connectivity between a device and physical medium and used bit stream in its data unit. It acted as communication channel for sensing and actuation in cost-efficient and reliable manner. Some examples of this layer are: IEEE 802.11b/g Wi-Fi, IEEE 802.15.1 Bluetooth, IEEE 802.15.4 ZigBee, etc. [7] * Data link layer: provides functionality toward channel sharing, Medium Access Control (MAC-Layer), timing (e.g. data time arrival), local link and capacity. It is responsible for detecting and correcting the data errors in physical layer and control the locality data comparison. It follows the protocols such as point-to-point protocol (PPP) and IEEE 802 Local Link Control (LLC). [7] * Network layer: is responsible for network routing functionality, network security, energy and power efficiency and reliability of the communication. It includes the network topology management and manages the information and detects errors in data transfer from router to router. A number of protocols is address in this layer such as: Internet protocol (IP), Threshold Sensitive Energy Efficient Sensor Network Protocol and etc. [7]. * Transport layer: provides end-to-end transportation (distributing and gathering) of data between end users. It includes storage and responds for caching and controlling the data to recover them back to the initial message that has been sent. Best-known protocols for this layer are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) [7]. * Upper layers: The Upper Layers are responsible for application processing, external query processing and etc. Upper layers include presentation layer session layer and application layer [7]. The summary of these standards and protocols are shown in Figure 36 Among all the standard and protocols, IEEE PAN/LAN/MAN technologies are the ones applied in the majority of commercialWSNs to support physical layer and link-data layer signal transmission. As SOHRABY and ZNATI (2007) mentioned, the most common best-known protocols are: (1) the IEEE 802.15.1 (also known as Bluetooth); (2) the IEEE 802.11a/b/g/n series of wireless LANs; (3) the IEEE 802.15.4 (ZigBee); (4) the MAN-scope IEEE 802.16 (also known as WiMax); and (5) radio-frequency identification (RFID) tagging [7]. Each of these protocols has their own benefits and constraints. The comparisons between IEEE technologies are mentioned in Table 32. As Table 32 shows the IEEE 802.15.4 standard provides data rate of 20 to 250 kbps and operates in the 2.4-GHz ISM band. This standard covers signals in range of 10 m and requires the lowest power among other IEEE class. While IEEE 802.11a/b/g/n transmits the data in the rate of 54 Mbps ideal for wireless internet connections and operates in the 2. 4-GHz ISM (Industrial, Scientific and Medical) radio band as well as the 5-GHz ISM / 5-GHz U-NII (Unlicensed National Information Infrastructure) radio band. However, it requires much higher power consumption than IEEE 802.15 [7]. Recently, researchers put much effort to develop a cost-effective standards-based wireless networking solution that supports low-to medium data rates, has low power consumption, and guarantees security and reliability [7]. ZigBee Alliance is an association of companies which aims to provide such a standard for WSN consumers. Their mission is to have a simple, reliable, low-cost, low-power and standards-based wireless platform 1.2.2.1 ZigBee standard The ZigBee standard builds on IEEE 802.15.4 and is suitable for remote monitoring and controlling applications. Although it has lower-data-rates than the other standards, its reliability, security, long life battery with less complexity mechanism make it ideal for building automation in industrial network applications. The architecture of the ZigBee stack is established on the Open System Interconnection (OSI) model. The IEEE 802.15.4 defines the physical layer (PHY) and medium access control (MAC) sub-layer and In addition, ZigBee Alliance defines other functionalities for upper layers [7]. Figure 37 is a graphic overview of ZigBee protocol stack and shows the responsibility areas of IEEE 802.15.4, ZigBee Alliance platform and users applications [7]. This picture also shows the basic functionality of each layer. The data transmission service is provided by PHY layer and the protocol in this layer enables the connection between data units and the physical radio channel. ZigBee provides three different frequency band options for PHY layer. First, the transmission data-rate of 250kbps in 16 channels at 2.45GHz (Global) frequency. Second, with 40Kbps in 10 channels at 915MHz (Americas). And the last one, with 20kbps in 1 channel at 868MHz (Europe). The higher data-rate causes a higher order in modulation design and the lower frequency cause a larger cover area and better sensitivity. Depending on the power output, the transmission distance rate can change from 1 to 100 meters. (For more detail information see: Table 71 in Appendix A) ZigBee WSN has the ability to have static or dynamic network/component with either star or mesh topology and it has three types of nodes: a ZigBee Coordinator (ZC), ZigBee Routers (ZR), and ZigBee End-Devices (ZED). In order to have a communication protocol and physical connection both PHY layer and MAC sub-layers of the architecture should be defined upon agreement between server and clients. These layers require manual administrative procedures setting for server/client gateway. The next three levels namely: the network layer, security protocol and transport layer are defined by ZigBee alliance platform automatically. The last layer, application layer, has to interact with the user-interface and other applications; it ought to be programmed with high-level language so that integration with any existing devices applications becomes more conveniently practical. The ZigBee stack in gateway is responsible for all the network functionality such as network process management, authentication of the joined nodes, binding nodes and routing the messages throughout the network. ZigBee stack as a standard protocol, has clusters and libraries for improving the implementation process, therefore, using ZigBee compare to other protocols makes the system (including both hardware and software) development process much faster and easier. On the other hand, such standardisation provides easiness of adopt with third party sensors regardless of manufacturer, which might be attached to the network later. 2 Software Aspects To address the research question regarding the reliability, robustness, and security of any WSN application, it is essential to investigate the software architecture of that network. For convenience in description of the architecture of a WSN application, it is divided into three segments: Physical devices (such as lamps, sensors, nodes), Communication Protocol (terminals and servers, bridge, switch, network topology and standard) and Carried Information (application, functions, etc.). Any attempts to retain a precise design on software architecture for each part will cause an effective data transmission, which ensures reliability and security of the system [7]. Hence achieving any desired data transmission precision level in a WSN, network management (NM) techniques are applicable. Such techniques assist in network status monitoring, reliability and security amendment, and cooperation supervision between components [7]. NM techniques could also detect and resolve network faults in addition to restoring the system respectively [7]. In practice, designing WSN application necessitates tailoring NM techniques for each architectural segment. Various NM techniques regarding each segment are summarized as follows [7; 12; 5]: a) Physical architecture: Sensing and processing management, operation and administration, fault tolerance, maintenance, energy efficiency management, configuration management, performance management, security management, network element management. b) Communication architecture: Network management, networking protocols, network topology, function management, monitoring functions, fault management, performance management, security management, service management and communication, maintenance management, network configuration and organization, network behavior, data delivery model, sensor mobility, naming and localization, sensing coverage area, communication coverage area energy efficiency management c) Information architecture: Real-time information management, mapping management, service management, analyze information, control application, business application management report management, sending and receiving commands or response, naming, localization, maintenance, fault tolerance Aforementioned NM techniques enhance quality of the system. According to ISO 9126-1 software quality model Table 41 [13; 14; 15], the quality characteristics of a system could be divided into six fundamental properties: functionality, reliability, usability, efficiency, maintainability, and portability. According to the same documentation, these characteristics are broken to sub-characteristics such as suitability, security, maturity, fault tolerance, adaptability, analyzability, stability, testability and so on [13]. However, focusing on all subcategories collectively exceeds the time horizon of this research, from this stance three dimensions namely reliability, robustness and security are brought into attention. This section will be divided to two subsections describing the architecture issues and NM techniques for (1) Reliability and Robustness, (2) Security, of WSN and other characteristics is relegated to future studies. 2.1 Reliability and Robustness In WSNs context, the probability that a network functions properly and aggregates trustworthy data without any interruption continuously, is usually referred to as reliability characteristic of the network [23; 20]. According to ISO 9126-1 software quality documentation, reliability characteristic shows the capability of a network to maintain or re-built (re-start) the service in certain period of time [13]. So, it is important that during long sensing, the network has to service up continuously. Reliable service of a network includes precise and proper sensing, delivering and sending acceptable data to the base station. In other words as Taherkordi et al. (2006) put: The less loss of interested data, leads us to higher reliability of a system. Systematic approach perceives reliability as probability of data delivery to the base station rather than point-to-point reliability [16]. Robustness defined by Sohraby et al. (2007) as: a combination of reliability, availability, and dependability requirements, reflects the degree of the protocol insensitivity to errors and misinformation. Achieving system robustness in WSN, necessitates system capability to detect, tolerate and confine errors as well as reconfigure and restart the network respectively [7]. According to the given definition by Sohraby et al. (2007), it is apprehensible that reliability and robustness share commonalities with each other; this is the main rational behind discussing these two attributes together in this section [7]. Considering the nature of communication in WSN, a network is unpredictable and prone to fail caused by any physical damages in hardware devices, energy depletion, communication link error, information collapses in packages and etc. [17; 16]. Therefore, one of the critical issues in design phase of WSN is applying fault tolerance techniques to optimize the network so that reliability and robustness attained [17]. These techniques enable the network to withstand and recover any upcoming failure and restart operation [13]. Liu et al. (2009) categorized fault tolerance techniques into: node placement, topology control, target and event detection, data gathering and aggregation, and sensor surveillance. Reminding from the beginning of this chapter architecture design divided into three segments. Table 42 depicted a summary of the plausible related faults and their solutions in each segment. In the following, each aforementioned fault tolerance techniques are being discussed in each design segment. a) Reliability and Robustness in Physical Architecture Fault: any interruption in sensor surveillance, sensors failure Solution: Node placement management, signal-effect management, hardware replacement b) Reliability and Robustness in Communication Architecture Fault: communication link errors, energy depletion Solution: topology control and event detection , replicated services in communication model, Power consumption management c) Reliability and Robustness in Information Architecture Fault: Losing the data package Solution: data gathering and aggregation management Table 42 The most probable fault and their fault tolerance solutions in WSN [17; 7; 18] 2.1.1 Reliability and Robustness of Physical Architecture: a) Reliability and Robustness in Physical Architecture Fault: any interruption in sensor surveillance Solution: Node placement management, signal-effect management Fault sensors failure Solution: hardware replacement Fault: any physical interruption in sensor surveillance Solution: Node placement management and signal-effect management First item that should be considered in designing physical components architecture for reliability and Robustness is: physical placement and signal-effect management. As it is mentioned in section 3, although the mesh network communication is self-organize topology and does not need any manual configuration to bind the network for mobile sensors, the physical architecture and the location schema of the hardware components, sensors and gateways need to be designed carefully [7]. As a characteristic of mesh WSN, the sensors in network are free of any installation restrictions, even though, the placement should be far from any physical destruction or hostile locations. Inappropriate physical placement of sensor transmitters and gateway antenna can cause noise or significant lost in signals [7]. In addition, the signal coverage is decayed by surrounding objects and materials such as metal wall and the like. (E.g. exterior wooden, concrete, brick or gypsum frame, block or wall). Especially in the case of vehicles, the main body can impose such problem and henceforth installation of the sensors in this manner would be delicate. Moreover, the signal waves might be faded and affected during the transmission, due to various physical phenomena such as reflection, diffraction or scattering [7]. These effects would cause significant interruption in sensor surveillance. Therefore, it is important to manage these signal-effects in early stage of WSN physical architecture design. Reflection occurs when electromagnetic wave of signals is duplicated due to impinge of the wave on large object or surface such as walls, buildings and the Earth [7]. Therefore, all the reflection of the walls and also the Earth should be acknowledged in physical architecture design. Diffraction refers to any defection and obstruction in waves caused by irregular sharp edges during the data transmission between the transmitter and receiver [7]. In this case, designers have to be prudent in sensors placements in the proximity of sharp edges and corner angels. Scattering refers to any deviation from straight line. Environmental obstacles in the propagation path affect passing waves from their original structure. Even small irregular object such as street signs, and lampposts might encounter and scatter the wave. Hence WSN should be design to face with any irregular scattering during the wave transmission. Above all, the mobility of sensors and surrounding objects might fade the signals and add noises that should be considered in architecture design [7]. These issues are the basic physical factors, which cause major fault in data aggregation of WSN and cut down reliability and robustness. These destructive signals need to be subtracted from the received signal paths [7] before sending the data to gateway. Therefore, reflection, diffraction and scattering should be considered not only by designers in the physical components placements, but also by programmers in network development. Fault: Sensors failure Solution: Hardware replacement The next issue that needs to be considered in designing the physical architecture of a WSN is hardware failure. Sensors energy suppliers or any damages to the sensors and/or their transmitters are the sources of hardware failure. Regardless of source of failure, the WSN must be capable of functioning as well as replacing and switching sensors when necessary. Additionally, any changes in the physical components, on one hand, needs an explicit and well-defied consideration on security issue to prevent any potential threats, and on the other hand, needs an adaptable and configurable communication connection network [18]. 2.1.2 Reliability and Robustness of Communication Architecture b) Reliability and Robustness in Communication Architecture Fault: communication link errors Solution: topology control and event detection , replicated services in communication model, Fault: energy depletion Solution: Power consumption management Fault: communication link errors Solution:Topology control and event detection , Replicated services in communication model, Communication link error is an important concern in dealing with reliability and robustness of a network in communication architecture. The sensors in WSN are prone to fail and make link errors in point-to-point reliability of communication protocol. Therefore, it is the network topology responsibility to detect the errors and guarantee the overall reliability of the system. As it is explained in section 3.2.2.1, applying mesh topology fosters the network to conduct an acceptable performance and flexible network architecture. This topology allows the sensors to organize in an easy deployment and easy configuration network [19; 12]. The mesh topology brings reliable self-healing and robust fault tolerance characteristics for the network. This means that, without any manual configuration, all sensors communicate with each other directly or through other midway sensors and generate a self-configuration and self-organized network [19; 12]. Therefore, any pair of sensors will be able to communicate between each other within more than one path. The multiple paths link between sensors would conduct a reliable communication for WSN. In this way, if a sensor fails or breaks down during the operation, the system detects the sensor failure and disconnects it from the network in response. Then, the signal packages jump from the disconnected sensor and automatically conduct a new path through the nearest sensor. Although the fault does not essentially affect the whole system functionality and the network reliability via few sensors failures, the system should be programmed in a manner that detect, locate and report the emerging failure to the base station [19]. This fault tolerance topology and re-configuration of new path imposes re-routing of the packages and re-organizing of the network [5], which consumes too much power from the system. Therefore, having a power-aware protocol and algorithm such as ZigBee is necessary for the network for energy efficient function. Fault: Energy depletion Solution:Power consumption management Energy depletion is another fault in communication. High power consumption of a sensor or power supply failure is usually the main sources of depletion. For instance, dealing with reflection, diffraction, and scattering of signals, consumes lots of power; this implies a definite need to manage the power consumption in programming WSN communication. To solve the issue regarding power consumption, three solutions are suggested: 1. Utilization of the resource-efficient algorithm for the network: The algorithm should be energy efficient, provide the most efficient power solution for the network, and enable WSN to operate in a low power level [7]. ZigBee standard protocol perceives to be a suitable solution for network communication between the sensors. As stated in previous chapter, ZigBee stack provides lightweight protocol for network, which can be used as a communication interface between bounded sensors and gateway. One of the characteristic of ZigBee is: low-data-rate transmission, which makes ZigBee as a power-efficient protocol. ZigBee standard also provides reliable binding and data transfer within WSN components. Basic ZigBee devices operate at 1mW radio frequency (RF) power and can switch to sleep mode when it is not involved in data transmission. Since wireless communication wide bandwidth demands high energy, using as narrow bandwidth as possible will assist in retaining efficient power consumption. For this purpose, the network can use channel 2.4 MHz transmission rates. Also ZigBee protocol in a network provides the ability to use 2.4 GHz Global standard, 868-868.8 MHz European standard or 902-938 MHz American s tandard as the transmission rate for different situation and manage the energy. 2. The other approach to manage the power could be programming the sensor to switch between active and sleep mode sequentially. Keeping the sensor sleep, consumes no energy. This would help the system to be more energy efficient and reduce failures regarding the energy of the system [20]. 3. Kumar Kishore (2009) suggested the third solution as applying aggregation point to reduce total of number of transmitted messages during communication network segment programming. Aggregation point is a regular sensor with the processing capability to filter out any unwanted information from the main data package before transmitting it across the network. This technique reduces both the number of the transmission messages and energy consumption and increases system power-efficiency [20]. 2.1.3 Reliability and Robustness of Information Architecture: c) Reliability and Robustness in Information Architecture Fault: Losing the data package Solution: data gathering and aggregation management Fault: Losing the data package Solution:Data collection and aggregation management As it is mentioned before, the communication links in WSNs are prone to fail and these failures always affect the transmission of the information. Also it is possible to lose the data package along the data transmission path because of either hardware or network connection failure. Obtaining reliable data transmission requires both managing the data aggregation and programming a reliable protocol for the system from the early stage of software development. In mesh WSN, every sensor is responsible to dispatch data package to the gateway. Each package of data has a selected cluster head for sending through MAC-layer. As it is mentioned in 3.2.2.1, for the communication protocol, ZigBee provides predefined data transmission clusters and libraries for MAC and PHY layers that make transfer possible. Cluster heads sequences data package dispatches during information transfer. Each node (or sensor) in the path gets the data package and checks the cluster head to make sure of the accuracy of the receiving data. To be sure that the messages have reached the destination the receiver node sends an acknowledgement to the sender node about delivering the messages. If the sender does not get the acknowledgement within its time interval, the node finds an alternative path to send the package. The message is retransmitted in certain time intervals until it is received correctly. These techniques help the real-time network to provide reliable informational communication [21; 22]. According to what is discussed, programmers have to prudently develop the cluster heads, acknowledgment message and response interval messages to increase reliability of information transmission. 2.2 Security According to ISO 9126-1 software quality documentation Table 41, Security is sub-characteristic of functionality of a system and is related to unauthorized access to system functions [23]. In WSNs, security of the network is one of the great challenges [24]. Like reliability, the security of WSN should be considered from the first stage of designing. For instance, table below shows different issues and their solution that should be monitored during each of physical architecture, communication architecture and information architecture design [25; 7; 26]. a) Security in Physical architecture Issues: Attack and damage a light or sensor, Adding an extra light or sensor, Solution: Secure protocol ,Shared Keys, naming , Localization, Secure Groups, authorization monitoring , Encryption, b) Security in Communication architecture Issues: Attack and hack the protocol, sending fake data package to the network Solution: Secure protocol, Encryption, naming , Localization, authorization monitoring c) Security in Information architecture Issues: pick off the data stream, Solution: Secure protocol, Encryption , authorization monitoring , Table 43 The Probable Issues or Threat in WSN and Their Security Solutions [25; 7; 26] As Table 43 shows, the solutions to security architecture for WSN are: Naming, Localization, Secure protocol, Secure Groups, Authorization Monitoring, Shared Keys and Encryption [25]. For more convenience all solutions are divided into two sub-categories: (a) Secure Protocol mechanism, and the (b) Naming and Localization mechanism each of which are described in the following: 2.2.1 Secure protocol WSN, by using ZigBee protocol, provides different effective security techniques to solve any security flaws [26]. Some of these techniques are: Cryptographic, Key-Transport, Frame Protection, Security Key, Access Control List, and Authorization Monitoring. To coordinate the security services on WSN, ZigBee assigns a trusted sensor as the Trust Center on the network. The responsibility of this dedicated sensor would be first to authenticate other sensors requesting to be connected into the network and second to distribute security keys to other sensors and finally enable end-to-end security between sensors and gateway [26]. Trusted Center enlists all trusted sensors. The content of the list includes the MAC addresses of sensors that are authorized to communicate. ZigBee has access control to the list and detects any unauthorized devices from the legitimate ones. In order to accept or reject the joining request, ZigBee sends authenticity message to the higher layer application where a message is observable by the end user whether in base-station or other clients. So the trust center rejects the message sent from unauthorized devices and isolates them from the network [7]. ZigBee applies security services, identified in 802.15.4 for low-level PHY and MAC layer. Additionally, ZigBee has standard security architecture for higher-level Network (NWK) and Application (APS) Layers as a comprehensive security system suit for inter-network communications [26]. In MAC layer, ZigBee secures confidentiality, integrity, and authenticity by two mechanisms with respect to hop transmission. In a single-hop transmission, it secures MAC command messages by using cryptographic algorithm, Advanced Encryption Standard (AES). In multi-hop messaging, ZigBee cannot secure the network without interaction with upper layers like the NWK layer [27]. In MAC security command for single-hop, an increased count tag is added in every message frame sent inside the network. The receiver node keeps the tags. If the node detects an old or wrong count tag, it is recognized as a security error [27]. This mechanism makes generating invalid messages difficult and reduces the threat of attacks from spamming. However The MAC layer cannot secure the process by itself, therefore security relies on the upper layers to control this process by setting up the keys and the applicable security level [27]. ZigBee uses Security Key plus Advanced Encryption Standard (AES) in upper layers for the multi-hop messaging and controlling secure processing [27].The NWK and APS are in charge of secure frames transport and APS also establishes a secure relationship between different devices in the network [26]. The detail of the Mac and upper layer security process are described in [27]. A very high-security, key-basedcryptographyalgorithm applied in upper layer by ZigBee standard is based on 128-bit keys and the AES encryption standard [7]. These keys can be categorized in three groups, described as follows: Network security Key: A shared Common key for all sensors in the network. This key is given to each sensor during the first installation or via key-transport. The network can be secured by the use of this key by all components of WSN system and prevent any illegitimate joining request [26; 7] (physically or spamming). Link security Key: A secret session key, unique between any two devices which communicate with each other. The link key is a representative of the relative Master keys [26; 7]. This key prevents any illegitimate messaging in communication and messaging level. Master security Key: Each light (senor) or component in WSN uses this key to create the link keys [26; 7]. It is noteworthy to mention that as security is not enabled in ZigBee stack by default, programmers must deploy the application at the desired security level in the planning and designing of a ZigBee network. More information regarding how to organize security and manage encryption keys are described in Section G: Security Best Practice Recommendation in the article [7]. Beside all these advantages of using ZigBee security services, ZigBee also has its own disadvantages. One of the disadvantages of ZigBee is related to the run-time for traffic based devices where they cannot be locally separated. The reason could be due to the limited power supplies and small memory size of the lights and sensors in WSN. Therefore some applications might use the same keys as cryptography key. In current ZigBee standard, the application is running on the same node at a time, referred to as an open trust model. This is especially becomes a drawback in scalability of ITS where the intention is growing the network among different vehicles. 2.2.2 Naming and Localization: Naming is used for identifying the sensor nodes. Several security applications can be built based on naming sensors. The naming can be done in two ways: low-level naming depends on location and sensor topology and high-level naming embeds on application layer. The latter is independent of location and sensor topology [7]. Both naming approaches can be used in a system simultaneously. While the high-level naming is useful for communication between different applications (like domain name in the Internet), the low-level naming is utilized for package forwarding in physical layer applications (Like IP address in the Internet) [7]. Localization schemes allocate a position to each sensor for many applications such as monitoring and tracking interrupted object, enhancement in security application and many more. The naming and localization approaches introduce the following advantages for WSN programming: In physical layer, whenever a light or sensor is enhanced to the network, the security name of the light or sensor should be authenticated by base-station or vehicle to increase the security. This minimizes the threats of adding any unauthorized extra light or sensor to the network. Also the localization helps the system to determine the exact physical location of any unauthorized movement around the vehicle. By a robust fault tolerance topology and protocol, it is possible to recognize exact broken sensor. Neighboring sensors are responsible to send a message containing location and type of the broken sensor to the base-station. A proper naming proposes lower computation and data transmission traffic on protocol, which leads into less energy consumption and efficient communication. They are additional by-products to sensor naming and localization such as vehicle defect diagnostics, and accident prevention alerting sensor. 2.3 Software Quality Framework As promised earlier in the research questions, in this section, the main quality framework is generated through merging all presented faults and NM techniques associated to reliability, robustness and security. To keep cohesiveness and coherence with the previous sections of this chapter, the framework is presented into three network architecture segments. The complete table quality software framework can be found in AppendixB. Table 44, Table 45 and Table 46 exhibit the framework for physical, communication and information architecture. Each table consists of discussed NM techniques and each of which exercising implications both in mesh network and ZigBee protocol. Also the tables indicate whether the practicality of the techniques is tested in real world or it is merely lab-proved for ZigBee protocol. Because ZigBee protocol is quiet fledgling network system compare to Bluetooth, Internet protocols and WiMAX, many of the NM techniques have been tested and provided with practical implications in real world for older existing network systems, while they have not been applied in ZigBee applications yet. For instance, techniques such as Communication Availability, Signal Effect Management and Encryption have been fully exercised in other WSNs and their associated real world practical faults and errors have been resolved. Additionally, for some NM techniques such as Energy Supply and Node Placement Management, no promising concrete practical solution have not been presented in ZigBee yet.