SAP ERP systems Essay Example | Topics and Well Written Essays - 1000 words

SAP ERP systems - Essay Example SAP product design and development deals with business expansion and advancements. The system reduces marketing time while increasing productivity from the developed products. As the product design cycles are reduced, collaboration also improves under the integrated SAP software dealing with product development. It connects development and design, manufacturing, procurement and services seamlessly via flexible collaborations’ environment. Its other tasks are to raise the innovation speed, lower marketing duration through aligning products developments and designs with manufacturing and procurement. It allows for flawless environments collaboration to avoid time wastage and minimizes the cost of the designed products through streamlining design and optimizing components. The system ensures regulatory compliance under transparency during the phases in product definition. Decision-making becomes speedy to maximize quality in 3D visualization embedding. Production and inventory co ntrol offers a suite full of features essential for the success of supply chain management and inventory controls. The objective is to a kitty, track objects, industry specified customization to ultimately assist in boosting the bottom line. It has several benefits in that it increases revenue, accelerates decision making and identifies non-moving and discounted products in real-time. The I.T infrastructure is simplified whilst optimizing inventory levels by ensuring production of the right products at the right time.

Analysis of Terracotta Army Research Paper Example | Topics and Well Written Essays - 2000 words

Analysis of Terracotta Army - Research Paper Example   The artifacts are contained in three pits and so far, documented evidence indicates that up to 7000 warriors and weapons have been excavated by the archeologists. The artifacts contain foot soldiers and war chariots that are made from wood. Foot soldiers are basically lifelike figures that resemble human soldiers. In his study, Dillon indicates that the size of each warrior is approximately 1.8 meters (Dillon 43). Further, they are characterized by broad foreheads and thick-lipped mouths. A significant percentage of these have ornate hairstyles. Nonetheless, they generally show a distinct dedication and determination in their duties. This is because their eyes are directly focused ahead into some distance. The soldiers are also presented to be in a fighting position. Their positions are realistic and their eyes very bright. They have wide nostrils and muscular yet very strong legs. These attributes imply that the horses were well maintained and relatively serviceable. It cannot b e disputed that this particular population invested a significant percentage of resources in war. This also implies that the communities surrounding the region were hostile and equally invested in different wars in social security. The position of their hips and legs imply that they are ready to gallop. Notably, the artifacts show that there were two different types of soldiers; the artillery and infantry. The artillery soldiers are presented dressed in knee-length tunics and short trousers. In addition, they carry crossbows with them, ready to engage in a fight at any time. Seemingly, their uniforms were made from light materials, enabling them to move around with ease. Under battle conditions, these soldiers would probably be dispatched to engage in fighting at any time. The infantry faction, on the other hand, was heavily armored. In particular, they were presented while carrying swords. With respect to the mode of dress, Dillon cites that they wore shin guards and caps in additi on to their normal uniform (Dillon 77). Comparatively, they were also taller than their counterparts.  Ã‚  

Henry Ford Essay Example for Free

Henry Ford Essay Henry Ford was the creator of one of the largest automobile manufacturing companies, influencing society in a number of ways and forever changing the face of the auto industry. One of the reasons for his success was the high priority he placed on his employees’ satisfaction. While Ford had much strength he also had weaknesses that held the company back and threatened to destroy it at times. Ford was a notable member of society and a great peace promoter. Ford’s business style and leadership skills throttled him to success. Background Henry Ford was born in 1863 to farmers in Dearborn, Michigan. Ford grew up living on the farm and attending school, neither of which he was satisfied with (â€Å"Henry Ford: The Innovator†). At the age of 16 his dissatisfaction led him to leave home and travel to Detroit to find work (â€Å"Henry Ford: The Innovator†). He found work at Edison Illuminating Company under Thomas Edison who constantly encouraged him to toy with engines and be creative (â€Å"Henry Ford: The Innovator†). Ford’s tinkering led to the Quadricycle and eventually his first motor company, Detroit Automobile Co. in 1899 (â€Å"Henry Ford: The Innovator†). The Detroit Automobile Co. ailed shortly after it began and he created a new company, Henry Ford, Co. , which lasted about one year (â€Å"Henry Ford: The Innovator†). Ford turned to racing and managed to attract investors with $28,000 to begin his new company, Ford Motor in 1903 (â€Å"Henry Ford: The Innovator†). The auto industry was young and robust at the time (â€Å"Henry Ford: The Innovator†). Most companies were just starting with more and more entering the industry every week (â€Å"The Great Leaders Series†). Competition was fierce and the threat of new entrants was very high (â€Å"Henry Ford: The Innovator†). Ford ran the company until 1919 when he retired, letting his son Edsel take control (â€Å"Henry Ford: The Innovator†). Edsel died in 1943 and Henry came out of retirement until 1947 when he retired for the final time (â€Å"Henry Ford: The Innovator†). Treatment of Employees Henry Ford created a healthy, efficient, and attractive workplace so that he could retain his employees and attract the best. When Ford learned that his turnover rate was becoming a problem, he increased the pay rate to $5 and decreased the shift length to eight hours (â€Å"The Great Leaders Series†). This was unheard of in society at the time (â€Å"The Great Leaders Series†). Many people criticized Ford for this change but Ford knew that by decreasing the shift length, he could create three shifts (â€Å"The Great Leaders Series†). Creating three shifts would allow the factories to work around the clock without tiring the employees extensively (â€Å"The Great Leaders Series†). By making the process more efficient, Ford decreased his costs and was able to make up for the increased employee wages and even was able to lower the cost of the car for consumers (â€Å"The Great Leaders Series†). Henry Ford believed in some form of the Helzberg model. He understood the importance of work and how without work, man cannot reach fulfillment (Wood). Ford believed we were created for work and constantly challenged his employees to work harder and achieve more (Wood). Ford was concerned for the welfare of his workers and created a department of welfare sociology in his company (â€Å"Innovator, Industrialist, Outdoorsman†). Part of this department ensured that the higher wages he paid his employees were not being used to buy alcohol or cigarettes (â€Å"Innovator, Industrialist, Outdoorsman†). This policy kept his workers healthy and thus more efficient. Henry Ford valued his employees and showed that by paying extremely high wages compared to the industry average. He created a healthy work environment and was able to retain his current employees while attracting the best engineers and mechanics from all over the region to his workforce. Henry Ford proved that as a leader if you show that you value each of your workers you will create a loyal workforce. Employees care about more than just high salary, they want to be a part of an organization that places value on their skills and allows them to be part of a team. By following this strategy you will be able to attract a more numerous and higher quality workforce. Strengths Henry Ford believed that self-belief was essential (Wood) . He preached about self-belief to his employees and made an effort to hire those that knew no limitations and did not have the word impossible in their vocabulary (Wood). Henry Ford daily challenged his employees to be creative and think outside the box (Wood). The assembly line, Ford’s legacy and greatest innovation, greatly improved and forever changed the auto industry (â€Å"The Great Leaders Series†). The moveable conveyor belt cut manufacturing time from half a day to 93 minutes (â€Å"The Great Leaders Series†). Henry Ford also changed the way cars were sold by introducing a network of roughly 7,000 dealerships across the country (â€Å"The Great Leaders Series†). Ford was known for his strict, dictatorial style of management, he made most decisions for the company and even was known to monitor employees’ life outside of work (â€Å"The Great Leaders Series†). Even when the public and investors criticized his work and tried to influence him to go a certain way he held fast and proved them wrong (â€Å"The Great Leaders Series†). Weaknesses Ford’s single-handed, dictatorship was also one of his greatest weaknesses (â€Å"The Great Leaders Series†). His stubbornness and dictatorial style almost brought the company to ruin when he refused to allow innovation on his prized model T (â€Å"The Great Leaders Series†). His cars were being surpassed by the competition but Ford refused to update his model (â€Å"The Great Leaders Series†). Another weakness was his anti-Semitic beliefs (â€Å"Anti-Semitism†). Ford was a great admirer of Adolf Hitler’s dictatorial style and thus modeled his leadership style after his role model (â€Å"Anti-Semitism†). This mentality caused Ford to lose a large market of Semitic and pro-Semitic consumers. His competitors gained an advantage not because their product was superior, but because of conflicting values. A leader should avoid letting personal beliefs and values conflict with business. International Strategy After World War II ended, Ford Motor Co. was among the first companies to begin producing again (Wood). Ford’s innovation and vision for the future led him to be able to move into 33 global markets overseas before its competitors even began thinking about international markets (Wood). Henry Ford was a promoter of peace (Wood) . Although this may seem to conflict with his anti-Semitic views, Ford was adamant that international peace was necessary (Wood). He believed that through cooperation and international trade we could achieve this long sought after goal (Wood). Henry Ford was pressured by the president to run for senator but he preferred to be a peace senator (Wood). Working under Henry Ford According to some subordinates of Henry Ford, working in the factories was â€Å"living hell† (â€Å"Henry Ford: Witness Biographies†). The auto-manufacturer was very anti-union and the working conditions difficult (â€Å"Henry Ford: Witness Biographies†). The employees were always pushed to go faster but to produce perfect products (â€Å"Henry Ford: Witness Biographies†). The dictatorial style of Ford was very strict and difficult to manage, but despite the physical and mental toll the employees bared, they wore their Ford badges with pride and honor (â€Å"Henry Ford: Witness Biographies†). Working at Ford demanded respect and they would often wear their badges to church and formal events (â€Å"Henry Ford: Witness Biographies†). Many employees describe the working conditions as hot, dusty, and noisy with vibrations that made you consider finding another job (â€Å"Henry Ford: Witness Biographies†). Some employees mentioned that after an eight hour shift workers would get on the streetcar to go home and fall asleep immediately because they were so physically exhausted (â€Å"Henry Ford: Witness Biographies†) . However others described the factories as kept so white and clean that if an employee was chewing tobacco and spit on the ground it was noticeable immediately and the employee would be reprimanded (â€Å"Henry Ford: Witness Biographies†) . The witness accounts on this subject vary greatly (â€Å"Henry Ford: Witness Biographies†). Although the work was hard and some believed the conditions to be less than desirable, the employees respected Ford’s strict policies and were loyal to the company no matter what. They were proud to work for one of the most innovative leaders in the world. Leadership Implications Henry Ford had a dictatorial leadership style. In terms of Goleman’s situational leadership styles Henry Ford used a combination of Coercive and Affiliative. Ford can be described as coercive because he demanded immediate compliance. He did not stand for imperfect work or lazy employees. His factories were described as stressful and strictly structured. The workforce was mechanistically organized and everyone had a specific place. This style of leadership conflicts with America’s low power-distance status but at that time Ford seemed to be able to make it successful. However, Ford was able to retain his employees with an Affiliative style. He valued his workers and therefore paid them well and created shorter work days. This developed employee loyalty and satisfaction. While researching Henry Ford, it can be learned that his strict, dictatorship and innovative vision was the reason for his success, but it was also his greatest weakness. His stubbornness and self-pride prohibited him from taking advice from others and realizing that his products needed improvement. His leadership style did not allow him to gather opinions and advice on decisions from employees who were also his greatest and most loyal consumers. Conclusion Henry Ford is one of the greatest leaders in American history. He was an industrialist, innovator, peace promoter, and a man with great dedication. He was very successful and changed the auto industry and American society in numerous ways. Although his personal values and personality challenged the success of his company at times, he managed to keep the Ford Motor Co. in a good position and left it in the hands of his son Edsel when he retired. As a leader Ford had both strengths and weaknesses but his strengths overshadow the weak points. Henry Ford is a great American leader that can be looked upon for inspiration.

Rowhammer and Microarchitectural Attacks

Rowhammer and Microarchitectural Attacks Problem 1: Hardware Oriented Security and Trust Problem 2: Wireless Networking Problem 1 Introduction The analyzed paper deals with Side-Channel attacks on mobile devices, providing a thorough categorization based on several factors. Side-channel attacks aims to extract sensitive information taking advantage of apparently harmless information leakage of computing devices, both from the SW and HW point of view. Side-channel attacks are initially categorized as active or passive, depending on the level of influence and involvement the attack has on the system. The concept of Software and Hardware attacks are identified to separate attacks that exploit, respectively, logical and physical properties of a device. Also the distance of an attacker is a relevant element in the analysis of Side-channel attacks. The authors distinguish among Local, Vicinity and Remote Side Channel Attacks, depending on how close is the attacker to the attacked device. A comprehensive list of examples for every type of attacks is given, along with a constructive discussion on possible countermeasures. In this report, we will focus on the Rowhammer and Microarchitectural attacks that will be discussed in the following paragraphs. a) Rowhammer Attack As miniaturization of hardware architectures is pushed more and more, the density of memory cells of the DRAM drives the size of these cells to a dramatic reduction in dimensions. For the intrinsic properties of DRAMs, this leads to a decreases in the charge of single cells and could cause electromagnetic coupling effects between cells. Rowhammer attack takes advantage of this Hardware vulnerability. a.i) Principle The Rowhammer glitch takes place in a densely-populated cell hardware environment allowing an attacker to modify memory cells without directly accessing it. The aforementioned vulnerability in DRAM cells can be exploited by repeatedly accessing a certain physical memory location until a bit flips in an adjacent cell. A well-orchestrated Rowhammer attack could have devastating power, even getting to have root privileges. Rowhammer base its strength on a principle called Flip Feng Shui [2] where the attacker abuses the physical memory allocator to strike precise hardware locations and cause bits to flip in attacker-chosen sensitive data. Rowhammer can be either probabilistic [3] or deterministic [4]. The latter shows a greater impact as the lack of control of the first one could corrupt unintended data. The most effective Rowhammer attack is the double-sided Rowhammer [5], capable of having more flips in less time than other approaches. a.ii) Architecture The objective of Rowhammer attack is the DRAM. DRAM usually stores electric charges in an array of cells, typically implemented through a capacitor and an access transistor. Cells are then organized in rows. Thus memory cells inherently have a limited retention time and they have to be refreshed regularly in order to keep their data. From an OS point of view, a page frame is the smallest fixed-length adjacent block of physical memory that maps an OS memory page. From a DRAM point of view, a page frame is just a contiguous collection of memory cells with a fixed page size (usually 4KB). With this in mind, triggering bit flips through Rowhammer is basically a race against the DRAM internal memory refresh scheme to have enough memory accesses and cause sufficient disturbance to adjacent rows. a.iii) Instruction Set Architecture The Instruction Set Architecture (ISA) is a functional specification of a processor programming interface. It is used to abstract over microarchitecture implementation details (e.g. pipelines, issue slots and caches) that are functionally irrelevant to a programmer. Even though it is practically transparent, the microarchitecture incorporates a hidden state, which can be observed in several ways. To test whether Rowhammer can be exploited, a precise knowledge of memory cells dimension is crucial. In mobile devices, ARM processor represents the most widespread and used microprocessor. In [4] the authors determine the minimum memory access time that still results in bit flips by hammering 5MB of physical memory while increasing the time between two read operations by means of inserting NOP instructions. The rows are all initialized to a certain value, therefore all the changes are due to Rowhammer. Results show that up to 150 bit flips happen per minutes with around 150 ns read time. a.iv) Procedure The Rowhammer attack procedure is a combination of three main system primitives: P1. Fast Uncached Memory Access: Enable attackers to activate alternating rows in each bank fast enough to trigger the Rowhammer bug; P2. Physical Memory Massaging: The attacker tricks the victim component into storing security-sensitive data (e.g., a page table) in an attacker-chosen, vulnerable physical memory page. P3. Physical Memory Addressing: To perform double-sided Rowhammer, an attacker needs to repeatedly access specific physical memory pages. Mobile devices have Direct Memory Access (DMA) mechanisms that facilitates the implementation of P1 and P3. In particular, Android devices run ION, a DMA that allows user unprivileged apps to access uncached physically contiguous memory. To enforce P2 the attacker tricks the physical memory allocator built in Linux (buddy allocator) so as to partition the memory in a predictable way. Accurately selecting the dimensions of memory chunks to allocate, memory cells can be exhausted through Phys Feng Shui. Once the position of Page Table Pages (PTPs) and Page Table Entries (PTEs) is indirectly known, double-sided Rowhammer is performed. Once the desired flip triggered, write access is gained to the page table by mapping into the attacker address space. Modifying one of the attacker PTPs, any page in physical memory can be accessed, including kernel memory. b) Microarchitectural attack  ­The evolution of hardware architecture lead to a wide use of cache memories. Having several levels of cache between a CPU and the main memory, helps optimizing the memory access time with respect to the clock frequency. Microarchitectural attacks take advantage of the timing behavior of caches (e.g. execution times, memory accesses) to read into sensitive information. In [6] a comprehensive survey that presents microarchitectural attacks is given. b.i) Principle Microarchitectural attacks are based on different cache exploitations. Among them, three main methods are identified: Prime + Probe: The attacker fills one or more sets of the cache with its own lines. Once the victim has executed, the attacker accesses its previously-loaded lines, to probe if any were evicted showing the victim have modified an address mapping the same set. Flush + Reload: Its the inverse of Prime+Probe where the attacker first flushes a shared line of interest. Once the victim has executed, the attacker then reloads the evicted line by touching it, measuring the time taken. A fast reload indicates that the victim touched this line (reloading it), while a slow reload indicates that it didnt. Evict + Time: The attacker first tricks the victim to run, through the preload of its working set, and establish a baseline execution time. In a second step the attacker then eliminates a line and runs the victim again. The difference in execution time indicates that the analyzed line was accessed. All microarchitectural attacks are a combination of those previously explained principles. Another noteworthy approach is causing Denial of Service (DoS) saturating the lower-level cache bus [7]. .b.ii) Architecture As mentioned before, microarchitectural attacks objective is the cache. Caches are organized into lines. A cache line holds a block of adjacent bytes that are taken from memory. Cache are further organized in levels. Each level has a different size and is carefully selected to balance service time to the next highest (smaller in dimension therefore faster) level. Caches can enforce either Virtual or Physical addressing. In Virtual addressing, L1 cache level stores the index of virtual-to-physical addresses. .b.iii) Instruction Set Architecture The inference process of the internal state of the cache is a key parameter to perform devastating microarchitectural attacks. Analyzing the ISA of a cache can provide an attacker with useful information about the hardware structure. Several different states can be exploited and are briefly summarized here: Thread-shared State: cache stores information that are shared between threads. Accessing them could lead to performance degradation of the involved threads. Core-shared state: Analyzing L1 and L2 cache contention usage between competing threads, it is possible to infer the encryption keys for algorithm used in internal communication (e.g. RSA, AES). Package-shared State: Running a program concurrently in different cores residing in the same package, could lead to the saturation of that packages last-level cache (LLC). The saturation affects all the lower levels, exposing sensitive data. Numa-shared State: Memory controllers memory in multi-core systems are exploited to enforce DoS attacks. .b.iv) Procedure A plethora of attacks are presented in [6], therefore the procedure of the Flush + Reload for Android systems using ARM processors [8] is discussed. The most powerful methods to perform Flush + Reload is to use the Linux System Call clflush. However it is provided by the OS on x86 systems, on mobile devices using ARM this function is not available. A less powerful version of it is clearcache and is used in [8]. When the attack starts, the service component inside the attacker app creates a new thread, which calls into its native component to conduct Flush-Reload operations in the background: Flush: The attacker invokes clearcache to flush a function in the code section of this shared line. Flush-Reload interval: The attacker waits for a fixed time for the victim to execute the function. Reload: The attacker executes the function and measures the time of execution. With a small execution time, the function has been executed (from L2 cache) by some other apps (possibly the victims). In [8] the authors show that this method is capable of detecting hardware events (touchscreen interrupts, credit card scanning) and also tracing software executions paths. c) Rowhammer vs Microarchitectural attack Following the categorization used in [1], both Rowhammer and Microarchitectural attacks are active software attacks that exploits physical properties of the victim device. In particular Rowhammer uses the coupling effect of DRAM cells while Microarchitectural attacks gather sensitive information through the analysis of cache timing. The two attacks act at two different levels: while Rowhammer needs to work fast on an uncached DRAM, Microarchitectural attack objective are cache memories that are usually SRAM. Both of them can be applied to desktop and to mobile OS [4][8], as well as cloud environments. c) Mobile vs Desktop attacks Mobile devices are inherently more vulnerable than Desktop computers. Their portability and close integration with everyday life make them more available to attackers. Moreover, apps are way more easy to install on mobile devices and general carelessness helps hackers in installing malicious software. Also, with respect to desktop computers, mobile phones have several sensors that can be exploited to gather information about users behavior. But from a OS point of view, mobile OS are way more limited than Desktop OS. Specifically, Rowhammer suffers from the limited subset of features available in desktop environments (e.g. no support for huge pages, memory deduplication, MMU paravirtualization). Same limitations happens in Microarchitectural attacks for ARM , where clflush function to perform Flush + Reload is not supported. 2) NAND Mirroring NAND mirroring is categorized in [1] as an active local Side Channel attack that exploits physical properties out of a device chip. In particular, in [13] a NAND mirroring attack is performed on an iPhone 5c. The security of Apple iPhone 5c became an objective of study after FBI recovered such mobile device from a terrorist suspect in December 2015. As FBI was unable to retrieve data, NAND mirroring was suggested by Apple technology specialists as an optimal way to gain unlimited passcode attempts so as to bruteforce it. As the encryption key is not accessible from runtime code and its hardcoded in the CPU, it is impossible to brute-force the Passcode key without the getting at the hardware level. In iPhones such memory is a NAND flash memory. In NAND memories the cells are connected in series which reduces the cell size, but increases the number of faulty cells. For this reason, external error correction strategies are required. To help with that, NAND memory allocates additional sp ace for error correction data. In [13] the authors desoldered the NAND memory and mirrored it on a backup file. Although this method seems promising, several challenges were encountered by the authors, who had to balance some electrical anomalies with additional circuitry and also mechanically plug in a PCB at every attempt of bruteforcing the iPhone code. Such method could be applied to Desktop Computers, but the complexity of NAND memories would be way higher and it may unfeasible, in terms of time and complexity, to perform such attack. Countermeasures Side-channel attacks are discovered and presented to the scientific world on a daily basis and suitable defense mechanisms are often not yet implemented or cannot be simply deployed. Even though countermeasures are being studied, it looks like a race between attackers and system engineers trying to make systems more secure and reliable. 3.a) Rowhammer Attack Countermeasures against Rowhammer have already been thoroughly explored, but not many are actually applicable in the mobile context. Powerful functions as CLFLUSH [9] and pagemap [10] have been disabled for users apps, but Rowhammer can still be performed through JavaScript. Furthermore, analyzing the cache hits and miss could raise a flag of alarm, but methods such as [4] dont cause any miss. Error correcting codes arent even that efficient in correcting bit flips. Most hardware vendors doubled the DRAM refresh rate, but results in [11] show that refresh rate would need to be improved by 8 times. Moreover, the power consumption would increase, making this solution not suitable for mobile devices. In Android devices Rowhammer attacks, the biggest threat is still user apps being able to access ION. Google is developing mechanisms so as to avoid it to happen in a malicious way. One solution could be to isolate ION regions controlled by user apps from kernel memory, in order to avoid ad jacent regions. But even in the absence of ION an attacker could force the buddy allocator to reserve memory in kernel memory zones by occupying all the memory available for users apps. Prevention of memory exhaustion need to be considered to avoid Rowhammer countermeasures workarounds. 3.b) Microarchitectural Attack As the final goal of microarchitectural attack is deciphering cryptographic codes (e.g. AES), a straightforward approach to protect them would be to avoid having tight data-dependencies (e.g sequence of cache line accesses or branches must not depend on data). If they depend on private data, the sequence, the program is destined to leak information through the cache. The constant-time implementation of modular exponentiation approach [12] represents a good way to fight data dependency. These are more general rules to follow, whether to combat specific attacks such as Flush + Reload in mobile devices with ARM [8]. Disabling the system interfaces to flush the instruction caches, the Flush-Reload side channels can be removed entirely from ARM- based devices, but feasibility and security of this method havent been studied yet. Also, by removing system calls to have accurate time from Android could mitigate all timing side channels. Another way to fight Flush + Reload would be by preventing physical memory sharing between apps, but that would cause the memory footprint to expand and therefore exposing the system to other Sidechannel attacks. Problem 2 Protocol Design The proposed solution for Problem 1 is represented in Figure 1. To solve this problem, four moments in which the Path-centric channel assignment algorithm from [14] are identified: : B receives a packet on its Channel 1 and, as an interferer is acting on Channel 1 on node A, B cant transmit. B1 is the active subnode, B2 and B3 are inactive subnodes. : B switches from Channel 1 to Channel 2 (total cost: 3), and forward the packet to A through Channel 2 (total cost: 3+6=9). B2 is the active subnode, B1 and B3 are inactive subnodes. A2 is the active subnode, A1 and A3 are inactive subnodes. : A can either transmit on Channel 2 and Channel 3, but transmitting on Channel 2 is more expensive, so it switches to Channel 3 (total cost: 9+3=12). A3 is the active subnode, A1 and A2 are inactive subnodes; : A send the packet at C through Channel 3 (total cost: 12+2=14). Network Applications In our K-out-of-N system we are interested in understanding how much is a probability of getting errors in sensing from N sensor, where K represent a threshold for accepting a reliable measurement. This reasoning follows the binomial distribution: In our case at each node, errors can be induced by a false measurement (with probability ) or by channel flipping a bit during the over-the-air time (with probability ). Therefore for our N-out-of-K nodes system we have: Assuming that and are independent, the final probability of having an erroneous detection is a linear combination of the two: For completion, the probability of a successful measurement and transmission is . Network Standards Spectrum scarcity is a widely known problem in the world of wireless communications. The explosive wireless traffic growth pushes academia and industry to research novel solutions to this problem. Deploying LTE in unlicensed spectrum brings up the conflict problem of LTE-WiFi coexistence. This conflict can be analyzed with a close look at 802.11 MAC level. In Figure 2, a comparison between WLAN MAC layer and what is casually called MAC in LTE is depicted [19]. WiFi 802.11 uses CSMA/CA to regulate accesses in MAC layer. In CSMA, a node senses the traffic before transmitting over the channel. If a carrier signal is sensed in the channel, the node waits until its free. In particular, in CSMA/CA the backoff time of a node is exponential. In LTE, multiple access is handled through TDMA (Time Division Multiple Access) meaning that all accesses to the channel are scheduled. Historically LTE has been developed for environments with little interference, while WiFi combats interference in ISM with CSMA. Using them in the same spectrum would see LTE dominating over WiFi, causing sever performance degradation in both the cases. Several solutions has been proposed and implemented in the past years. Qualcomm [15] and Huawei [16] proposed a separation in time and frequency domain. In [17] a Technology Independent Multiple-Output antenna approach is presented so as to clean interfered 802.11 signals. This method was made more robust in [18] but still they relied on the fact that at least one signal from the two technologies had a clear reference. Traffic demands analysis could help mitigate the performance drop due to interference, but even with an accurate demand estimation, only one can be active at a certain time and frequency, limiting the overall throughput. When interference is high, packet transmission is corrupted and error correction strategies are needed. In WiFi, standard Forward Error Correction (FEC) is used. In FEC, a redundancy is added to the transmitted packet, so as a receiver can detect and eventually correct the wrong received bits. On the other hand, LTE uses HARQ (Hybrid-Automated Repeat reQuest) which is a combination of FEC and ARQ. In the standard implementation of ARQ, redundancy bits are embedded in the packets for error detection. When a corrupted packet is received, the receiver request a new packet to the transmitter. In HARQ, FEC codes are encoded in the packet, so as the receiver can directly correct wrong bits, when a known subset of errors is detected. If an uncorrectable error happens, the ARQ method is used to request a new packet. Hybrid ARQ performs better than ARQ in low signal conditions, but leads to an unfavorable throughput when the signal is good. To better see this interference behavior, a small simulation has been performed using ns3, in particular the LAA-WiFi-coexistence library [20]. The scenario was built using two cells whose radio coverage overlaps. The technologies used are LTE Licensed Assisted Access (LAA) operating on EARFCN 255444 (5.180 GHz), and Wi-Fi 802.11n operating on channel 36 (5.180 GHz). Two base station positioned at 20 mt distance from another, and they both have one user connected to them at a distance of 10 mt. Both BS are connected to a backhaul client node that originates UDP in the downlink direction from client to UE(s). In Figure 3(a) and Figure 3(b), we see how the throughput and the number of packets received by the WiFi BS varies when the two BSs coverage area overlaps and when they are isolated (e.g. their distance is 10 Km). Other scenarios were tested: Figure 4 (a) represent the scenario of two WiFi BSs and Figure 4(b) two LTE BSs. It is possible to see the behavior of the two technologies . Table 1 Throughput A Throughput B Packet loss A Packet loss B Distant BSs Figure 3(a) 73.78 Mbps 77.55 Mbps 4.6% 0% Interfering BSs Figure 3(b) 73.62 Mbps 4.95 Mbps 4.8% 93% Two WiFi BSsFigure 4(a) 53.45 Mbps 54.41 Mbps 27% 25% Two LTE BSsFigure 4 (b) 30.88 Mbps 30.4 Mbps 60% 61% In Figure 4(a) we can see how the channel is split between the two BSs and the Carrier Sensing Multiple Access keeps a high throughput and a low packet loss. In Figure 4(b) we can see how the interference between the two LTE cells affects the throughput and gives a high packetloss. In Table 1 results from simulations are summarized. References [1] R. Spreitzer, V. Moonsamy, T. Korak, S. Mangard. Systematic Classification of Side-Channel Attacks on Mobile Devices ArXiv2016 [2] K. Razavi, B. Gras, E. Bosman, B. Preneel, C. Giurida, and H. Bos. Flip Feng Shui: Hammering a Needle in the Software Stack. In Proceedings of the 25th USENIX Security Symposium, 2016. [3] D. Gruss, C. Maurice, and S. Mangard. Rowhammer.js: A Remote Software-Induced Fault Attack in JavaScript. In Proceedings of the 13th Conference on Detection of Intrusions and Malware Vulnerability Assessment (DIMVA), 2016. [4] V. van der Veen, Y. Fratantonio, M. Lindorfer, D. Gruss, C. Maurice, G. Vigna, H. Bos, K. Razavi, and C. Giuffrida, Drammer: Deterministic Rowhammer Attacks on Mobile Platforms, in Conference on Computer and Communications Security CCS 2016. ACM, 2016, pp. 1675-1689. [5] Z. B. Aweke, S. F. Yitbarek, R. Qiao, R. Das, M. Hicks, Y. Oren, and T. Austin. ANVIL: Software-Based Protection Against Next-Generation Rowhammer Attacks. In Proceedings of the 21st ACM International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS), 2016. [6] Ge, Q., Yarom, Y., Cock, D., Heiser, G. (2016).A survey of microarchitectural timing attacks and countermeasures on contemporary hardware. Journal of Cryptographic Engineering [7] Dong HyukWoo and Hsien-Hsin S. Lee. Analyzing performance vulnerability due to resource denial of service attack on chip multiprocessors. In Workshop on Chip Multiprocessor Memory Systems and Interconnects, Phoenix, AZ, US, 2007. [8] X. Zhang, Y. Xiao, and Y. Zhang, Return-Oriented Flush-Reload Side Channels on ARM and Their Implications for Android Devices in Conference on Computer and Communications Security CCS 2016. ACM, 2016, pp. 858-870. [9] M. Seaborn and T. Dullien. Exploiting the DRAM Rowhammer Bug to Gain Kernel Privileges. In Black Hat USA (BH-US), 2015. [10] M. Salyzyn. AOSP Commit 0549ddb9: UPSTREAM: pagemap: do not leak physical addresses to non-privileged userspace. http://goo.gl/Qye2MN,November 2015. [11] Y. Kim, R. Daly, J. Kim, C. Fallin, J. H. Lee, D. Lee, C. Wilkerson, K. Lai, and O. Mutlu. Flipping Bits in Memory Without Accessing Them: An Experimental Study of DRAM Disturbance Errors. In Proceedings of the 41st International Symposium on Computer Architecture (ISCA), 2014. [12] Ernie Brickell. Technologies to improve platform security. Workshop on Cryptographic Hardware and Embedded Systems11 Invited Talk, September 2011. [13] S. Skorobogatov, The Bumpy Road Towards iPhone 5c NAND Mirroring, arXiv ePrint Archive, Report 1609.04327, 2016. [14] Xin, Chunsheng, Liangping Ma, and Chien-Chung Shen. A path-centric channel assignment framework for cognitive radio wireless networks Mobile Networks and Applications 13.5 (2008): 463-476. [15] Qualcomm wants LTE deployed in unlicensed spectrum. http://www.fiercewireless.com/story/qualcomm-wants-lte-deployed-unlicen% sed-spectrum/2013-11-21 [16] Huawei U-LTE solution creates new market opportunities for mobile operators. http://www.huawei.com/ilink/en/about-huawei/newsroom/ press-release/HW 3%27768. [17] S. Gollakota, F. Adib, D. Katabi, and S. Seshan. Clearing the RF smog: making 802.11 robust to cross-technology interference. In Proc. of ACM SIGCOMM, 2011. [18] Y. Yubo, Y. Panlong, L. Xiangyang, T. Yue, Z. Lan, and Y. Lizhao. ZIMO: building cross-technology MIMO to harmonize Zigbee smog with WiFi flash without intervention. In Proc. of MobiCom, 2013. [19] Long-Term Evolution Protocol: How the Standard Impacts Media Access Control Tim Godfrey WMSG Advanced Technology, http://www.nxp.com/files-static/training_presentation/TP_LTE_PHY_MAC.pdf [20] https://www.nsnam.org/wiki/LAA-WiFi-Coexistence

Theres One In Every Group :: essays research papers

There's one in every Group As time passes many of us will experience an array of trials and tribulations. As we go on our many journeys though out life you’ll find that you have to be strong to make it though hard times. During Elaine’s adolescence’s she is abused physically and mentally by her peers, but later gains self-confidence. Many people may find the novel Cat’s Eye by Margaret Atwood to be very disturbing at certain times in the book. When we are first introduced to Elaine, we learn that she is a shy, young girl that doesn't have friends, all she had was her brother Stephen and her Parents. The war has just ended, and Elaine and her family have finally got a house to call there own. The only thing that Elaine is unhappy about is that she has no friends. But that would soon change. Elaine meets 3 girls from he neighborhood Grace, Cordelia, and Carol, and these are the three girls that would change Elaine's life forever. As the friendship between the 4 girls gets older, we begin to see a change. Cordelia slowly begins to take charge of the group, becoming the ringleader. " Don't do it like that or Cordelia will punish you" is the attitude that you begin to get. As time carries on in the book we see that Elaine is the one that is always getting singled out, the one that is always being picked on. The 4 girls decided to put on a play, Elaine plays the headless Mary Queen of Scots, Cordelia has been digging the hole for a while, and has collected boards to cover the hole with. "They pick me up by my the underarms and the feet and lower me in into the hole. They arrange the boards over the top. The daylight air disappears, and there's the sound of dirt hitting the boards†¦ Up above outside I can here their voices, and then I can't here them. I lie there wondering when it will be time to come out. Nothing happens. When I was put into the hole I new it was a game; now I know it is not one." Here were we see the Physical abuse, just one of the many harsh incidents that takes place in Elaine's Childhood. As time carries on in the book we notice that the relationship between the girls has changed a great deal.

Iago’s Manipulation of Othello in Shakespeare’s Othello Essay -- Othel

Iago’s Manipulation of Othello in Shakespeare’s Othello Once a seed of suspicion or doubt is planted in a person’s mind, the noxious effect of jealousy is soon to ensue. Jealousy and suspicion are Othello’s flaws hubris throughout the play and foreshadow to the audience his imminent downfall. He believes what Iago tells him so strongly that he compromises his close relationship with his best friend and his love for his wife. Iago manipulates Othello through the use of extortion, literary techniques, and his keen judge of character. His syntax and diction are so simple yet so powerful because he uses the correct rhetorical questions and addresses Othello with respectful terms such as â€Å"my lord.† He allows Othello do most of the talking and the thinking; then begins to twist his mind usi...

Love Is Not All, or Is It? Essay

Edna St. Vincent Millay, â€Å"Love is Not All† Love is not all: it is not meat nor drink Nor slumber nor a roof against the rain; Nor yet a floating spar to men that sink And rise and sink and rise and sink again; 5Love can not fill thickened lung with breath, Nor clean the blood, nor set the fractured bone; Yet many a man is making friends with death Even as I speak, for lack of love alone It well may be that in a difficult hour, 10 Pinned down by pain and moaning for release, Or nagged by want past resolution’s power, I might be driven to sell your love for peace, Or trade the memory of this night for food It well may be I do not think I would. Part I: Paraphrase the Poem. Love isn’t everything, it’s not food, beverages, sleep and it sure won’t act as a roof against the rain. Love cannot offer a sinking man in peril a life-saving â€Å"floating spar†. As he rises, he sinks, only to rise and sink again. Love cannot give the air we need to fill our â€Å"thickened lung†, it can not clean blood or heal broken bones. Yet for all the things love can’t do, a man without love is a man â€Å"making friends with death†. The lack of love alone in a difficult hour will pin you down by pain, whine for release or harass you by the power of past resolution’s. One might be driven to sell love for peace, trade their memories for a meal, but never give up love even if it was to release horrible pains or to get food to live. Part II: Scan the Poem. / = stressed syllable ^ = unstressed syllable = half-stressed syllable || = significant pause ^ / | ^ / | ^ / | ^ / | ^ / | 1Love is not all: it is not meat nor drinkA ^ / | ^ / | ^ / | ^ / | ^ / | 2Nor slumber nor a roof against the rain;B ^ / | ^ / | ^ / | ^ / | ^ / | 3Nor yet a floating spar to men that sinkA ^ / | ^ / | ^ / | ^ / | ^ / | 4And rise and sink and rise and sink again;B ^ / | ^ /| ^ /| ^ / | ^ / | 5Love can not fill thickened lung with breath,C ^ / | ^ / | ^ / | ^ / | ^ / | 6Nor clean the blood, nor set the fractured bone;D ^ / | ^ / | ^ / | ^ / | ^ ^ / | 7Yet many a man is making friends with deathC ^ / | ^ / | / ^ | / ^ | ^ ^ / | 8Even as I speak, for lack of love aloneD ^ / | ^ / | ^ / | ^ / |^ / | || 9It well may be that in a difficult hour,E ^ / | ^ / | ^ / | ^ / | ^ / | 10Pinned down by pain and moaning for release,F ^ / | ^ / | ^ /| ^ / | ^ /| || 11Or nagged by want past resolution’s power,E ^ / | ^ / | ^ ^ / | ^ / | ^ / | 12I might be driven to sell your love for peace,F ^ / | ^ / | ^ / | ^ / | ^ ^ / | 13Or trade the memory of this night for foodG ^ / | ^ / | ^ / | ^ / | ^ / | 14It well may be I do not think I would. G * Line 1-6 are composed with Iambic pentameters, which are ten syllables for each line in five Iambic pairs. * Line 7 is mostly Iambic with the last feet being Anapest. * Line 8 is the most complexe, the foot division are: Iamb, Iamb, Trochee, Trochee, Anapest. * Line 9-11 are composed with Iambic pentameters as well, line 9 and 11 both have a significant pause at the end. * Line 12 has 4 feet of Iamb and one feet of Anapest directly in the middle. * Line 13 has 4 feet of Iamb ended with a feet of Anapest. * Line 14 is a Iambic pentamerter. The Rhyme scheme is ABAB, CDCD, EFEF, GG. Part III: Write a Short Essay. Love is Not All, Or is It ? In Edna St. Vincent Millay’s sonnet â€Å"Love is Not All’, the speaker depicts that love isn’t the most important thing in life, but you would do anything for it. In the first half, Millay declares that love is useless and unsubstantial to life’s requirement. The second half of the sonnet successfully outshines the previous half because although she has shown that love isn’t needed to live, Millay makes it clear that life isn’t worth living without it. Furthermore, love is not something that will help you physically; however, it always goes back to the fact that it’s the most influential and overpowering thing over you. Millay elaborates on the aspect of love, love can’t do everything, love can’t save a life, nor be a shelter or a doctor. Each section of the sonnet reflects a human need: food, shelter, health and emotion. Love cannot fill our stomach with â€Å"meat† (1) nor can it hydrate us, as illustrated by â€Å"drink† (1). Also, love will not regenerate a worn out man from â€Å"slumber† (2) and sure won’t offer shelter or a â€Å"roof against the rain†(2). Millay effectively shows that love is worthless on a physical level: as love can’t offer a man in peril a life saving â€Å"floating spar† (3), offer the precious air our lungs need to breathe, heal our body from illness nor â€Å"clean the blood† (6) or fix the broken bones. Millay writes: â€Å"I might be driven to sell your love for peace / Or trade the memory of this night for food† (12-13), to produce a scenario in which she is forced to choose between love and life. The imagery you imagine reading this sonnet is very concrete, even spine-tingling at times; therefore, far from the sweet sentimental ones normally associated with love sonnets. Love, as described by Millay, seems almost as if it’s worth nothing. For all the things that love cannot do, the author insists that we still need love to live. Millay makes it evident when she writes: â€Å"Yet many a man is making friends with death / Even as I speak, for lack of love alone† (7-8), trying to give her readers the point of view that men can die without love. A lovelorn man is closer to death. Line eight really changes the direction of this sonnet because at first, Millay’s definition of love was worthless and now the reader notices that she starts restoring the significant importance of love. The next lines begin with â€Å"It well may be† (9), which introduces the reader to a hypothetical situation being â€Å"Pinned down by pain and moaning for release / Or nagged by want past resolution’s power† (10-11). These two lines influence how the reader portrays love because nothing is more important, then filling that hole in our heart when love is missing. At the end of the sonnet, Millay offers a plausible solution to fill her human needs as she â€Å"might be driven to sell your love for peace† (12) for it would release her from the horrible pains. She might â€Å"trade the memory of this night for food† (13) to feed her starving stomach. For all that love is, Millay reveals everything when she writes: â€Å"It well may be I do not think I would† (14) meaning that love is not all, but she would rather be dead than not have it. What exactly is love? It is the hardest emotion to control, one does not simply choose whom to love, it just happens. Love’s not something you can see or touch, but you are well aware when love touches you. Love is not all, it doesn’t answer to life’s requirements; however, love is indispensable to meet those requirements and live peacefully. While reading Edna St. Vincent Millay’s sonnet â€Å"Love is Not All† the reader realizes that love is so powerful and rewarding. In an attempt to bring agreement between love and life, Millay chooses love because life is nothing without love. Work Cited Edna St. Vincent Millay, â€Å"Love is Not All† (456)