Low-Power Folded Tree Architecture for DSP Applications

Low-Power Folded Tree Architecture for DSP Applications Low-Power Folded Tree Architecture for DSP applications Abstract— Wireless communication exhibits the highest energy consumption in wireless sensor network (WSN) nodes. Due to their limited energy supply from batteries, the low power design have become inevitable part of today’s wireless devices. Power has become a burning issue in VLSI design. In modern integrated circuits, the power consumed by clocking gradually takes a dominant part. Reducing the power consumption not only enhance battery life but also avoid overheating problem. By employing a more appropriate Processing Element (PE), the power consumption is significantly reduced. In this paper the novel method for low power design is achieved by using Folded Tree Architecture (FTA) and high speed adder design for on-the-node data processing in wireless sensor networks using Parallel Prefix Operations (PPO) and data locality in hardware. Besides power reduction the objective of minimizing area and delay is also considered. Index Terms— Folded Tree Architecture (FTA), Parallel Prefix Operation (PPO), Processing Element (PE), Wireless Sensor Network (WSN). INTRODUCTION Power optimization is always one of the most important design objectives in modern nanometer integrated circuit design. Especially for wireless sensor networks (WSNs), power optimization have become inevitable part in today VLSI design. Power optimization not only can enhance battery life but also reduce the overheating problem. Self-configuring wireless sensor networks can be invaluable in many civil and military applications for collecting, processing, and disseminating wide ranges of complex environmental data. Because of this, they have attracted considerable research attention in last years. Sensor nodes are battery driven and hence operate on an extremely frugal energy budget. Further, they must have a lifetime on the order of months to years. Since battery replacement is not an option for networks with thousands of physically embedded nodes. In some cases, these networks may be required to operate solely on energy scavenged from the environment through seismic, photovoltaic or thermal conversion. This transforms energy consumption into the most important factor that determines sensor node lifetime. The another important application in wireless sensor networks is event tracking, which has widespread use in applications such as security surveillance and wildlife habitat monitoring. Tracking involves a significant amount of collaboration between individual sensors to perform complex signal processing algorithms such as kalman filtering, Bayesian data fusion and coherent beamforming. This applications will require more energy for their processing. In general Wireless Sensor Networks (WSNs) can operate in four distinct mode of operation: Transmit, Receive, Idle and Sleep. An important observation in the case of most radios is that operating in Idle mode results in significantly high power consumption, almost equal to the power consumed in the Receive mode. The data-driven nature of WSN applications requires a specific low power data processing approach. By employing more appropriate Processing Element (PE), the power consumption in all the four mode of operation will be reduced significantly. In present VLSI technology, reducing power consumption is an important issue. Especially for WSN, due to their limited battery lifetime the low power VLSI design is become inevitable for wireless commmunication. The goal of this paper is to design an low-energy Folded Tree and Multi-Bit Flip-Flop Merging technique for WSN nodes. II. RELATED WORKS In paper [2], the author proposed low-energy data processing architecture for WSN nodes using folded tree method. This paper identifies that many WSN applications employ algorithms which can be solved by using parallel prefix-sums. Therefore, an alternative architecture is proposed to calculated them energy-efficiently. It consists of several parallel Processing Elements (PEs) structured as a folded tree. The folded tree method with parallel prefix operations reduces the number of processing element and memory bottleneck. Due to clock distribution for more flip-flops, it consumes more clock power and also parallel prefix operations has high delay. In paper [3], a novel method is proposed for low clock power consumption in WSN nodes. A previously derived clock energy model is briefly reviewed while a comprehensive framework for the estimation of system wide (chip level) and clock sub-system power as function of technology scaling is presented. This framework is used to study and quantify the impact that various intensifying concerns associated with scaling will have on clock energy and their relative impact on the overall system energy. This technology scaling method reduces power clock power consumption (both static and dynamic), but due to large number of processing element- area, inverter chain, Power-Delay Product is increased. III. PROPOSED SCHEME Folded Tree Architecture with Parallel Prefix Operation is used to reduce the total number of Processing Elements (PEs) in the VLSI design. By reducing the number of processing elements, the total area is reduced. Area is proportional to power, so power consumption is also reduced. During processing and transmission of signals, the WSN nodes will consume more power. Especially for clock distribution nearly 70% power will be consumed. In order to optimize the power during clock distribution, multi-bit flip-flop merging technique is used. A. Folded Tree Architecture A straightforward binary tree implementation of Blelloch’s approach costs a significant amount of area as n inputs require p = n − 1 PEs. To reduce area and power, pipelining can be traded for throughput. With a classic binary tree, as soon as a layer of PEs finishes processing, the results are passed on and new calculations can already recommence independently [8]. Fig 1. Binary tree equivalent to folded tree The idea presented here is to fold the tree back onto itself to maximally reuse the PEs. In doing so, p becomes proportional to n/2 and the area is cut in half. Area is proportional to power, so power is also cut in half. Note that also the interconnect is reduced. This folded tree topology is depicted in Fig. 1, which is functionally equivalent to the binary tree on the left. By using the Folded Tree architecture power consumption, area and wirelength is reduced considerably. Folded Tree Architecture (FTA) for on-the-node data processing in wireless sensor networks, using parallel preà ¯Ã‚ ¬Ã‚ x operations and data locality in hardware reduces both area and power consumption. TABLE I LEAKAGE POWER AND DYNAMIC ENERGY FOR ONE PE UNDER NORMAL CONDITIONS FTA is designed to reuse the PE nodes to reduces half of the total area. It limiting the data set by preprocessing with parallel preà ¯Ã‚ ¬Ã‚ x operations. The combination of data à ¯Ã‚ ¬Ã¢â‚¬Å¡ow and control à ¯Ã‚ ¬Ã¢â‚¬Å¡ow elements to introduce a local distributed memory, which removes the memory bottleneck while retaining sufà ¯Ã‚ ¬Ã‚ cient à ¯Ã‚ ¬Ã¢â‚¬Å¡exibility. Several processing element consumes more power, so by using FTA the PE can be reused and power is reduced. Fig 2. Folding Architecture In folding architecture, we can reuse the PEs with the help of counter and FSM. Iteration count in the counter contains the total number of times the specified PE going to be reused. The FSM enables and reset the iteration count based on the instructions. B. Parallel prefix adder. Adders are also very important component in digital systems because of their extensive use in other basic digital operations such as subtraction, multiplication and division. Hence, improving performance of the digital adder would greatly advance the execution of binary operations inside a circuit compromised of such blocks. The performance of a digital circuit block is gauged by analyzing its power dissipation, layout area and its operating speed. The main idea behind parallel prefix addition is an attempt to generate all incoming carries in parallel and avoid waiting until the correct carry propagates from the stage of the adder where it has been generated.Parallel prefix adders are constructed out of fundamental carry operators denoted by  ¢ as follows (G, P)  ¢ (G, P) = (G+G ·P, P ·P) where P and P indicate the propagations, G and G indicate the generations. The fundamental carry operator is represented as Figure Fig 3. Carry operator   Ã‚   A parallel prefix adder can be represented as a parallel prefix graph consisting of carry operator nodes. The parallel prefix Ladner Fischer adder structure has minimum logic depth, but has large fan-out requirement up to n/2. Ladner Fischer adder has less number of delay compared to other parallel prefix adders. Power Delay Product should be less inorder to achieve high throughput and speed. Fig 4. Ladner Fischer Parallel Prefix Adder The Ladner Fischer adder construct a circuit that computes the prefix sums in the circuit, each node performs an addition of two numbers. With their construction, one can choose a tradeoff between the circuit depth and the number of nodes. V CONCLUSION This paper presented the Folded Tree Architecture and Multi-Bit Flip-Flop Merging technique for WSN applications. The design describes many data processing algorithms for WSN applications along with parallel prefix operations and clock distribution networks. Power is saved using flip flop merging technique by providing single clock signal to mergeable flip flops with the help of combinational lookup table. Thus this technique can be effectively used for clock distribution in integrated circuits requiring low power consumption in clock distribution network and low skew clocks. Area is reduced using folded tree architecture by reusing processing element. Ladner Fischer parallel prefix adder reduces the delay constraints and achieve high throughput. The proposed architecture significantly reduces both power and area in WSN nodes, can save up to half of the power in total sensor node. REFERENCES V. Raghunathan, C. Schurgers, S. Park, and M. B. Srivastava, â€Å"Energy-aware wireless microsensor networks,† IEEE Signal Process.Mag., vol. 19, no. 2, pp. 40–50, Mar. 2002. C. Walravens and W. Dehaene, â€Å"Design of a low-energy data processing architecture for wsn nodes,† in Proc. Design, Automat. Test Eur. Conf. Exhibit., Mar. 2012, pp. 570–573. D. Duarte, V. Narayanan, and M. J. Irwin, â€Å"Impact of technology scaling in the clock power,† in Proc. IEEE VLSI Comput. Soc. Annu. Symp.,Pittsburgh, PA, Apr. 2002, pp. 52–57. H. Kawagachi and T. Sakurai, â€Å"A reduced clock-swing flip-flop (RCSFF)for 63% clock power reduction,† in VLSI Circuits Dig. Tech. Papers Symp., Jun. 1997, pp. 97–98. Y. Cheon, P.-H. Ho, A. B. Kahng, S. Reda, and Q. Wang, â€Å"Power- aware placement,† in Proc. Design Autom. Conf., Jun. 2005, pp. 795–800. Y.-T. Chang, C.-C. Hsu, P.-H. Lin, Y.-W. Tsai, and S.-F. Chen, â€Å"Post-placement power optimization with multi-bit flip-flops,† in Proc.IEEE/ACM Comput.-Aided Design Int. Conf., San Jose, CA, Nov. 2010,pp. 218–223. P. Sanders and J. Traff, â€Å"Parallel prefix (scan) algorithms for MPI,† in proc, Recent ADV. Parallel Virtual Mach Message Pass, Interf., 2006, pp.49-57. G. Blelloch, â€Å"Scans as primitive parallel operations,† IEEE Trans. Comput.,Vol.38, no 11, pp. 1526-1538, Nov. 1989. D. B. Hoang, N. Kamyabpour â€Å"An Energy Driven Architecture for Wireless Sensor Networks† International Conference on parallel and Distributed computing Applications and technologies., Dec 2012. Nazhandali, M. Minuth, and T. Austin, â€Å"SensBench:Toward an accurate evaluation of sensor network processors,†in Proc. IEEE Workload Characterizat. Symp., Oct. 2005. M. Hempstead, D. Brooks, and G. Wei,† An accelerator-based wireless sensor network processor in 130 nm cmos,† J, Emerg. Select. Topics Circuits Syst., vol. 1, no. 2, pp. 193-202, 2011. B. A. Warneke and K. S. J. Pister, â€Å"An ultra-low energy micro- controller for smart dust wireless sensor networks,† in Proc. IEEE Int.Solid-state circuits conf. Dig. Tech. Papers. Feb. 2004, pp. 316-317. M. Hempstead, M. Welsh, and D.Brooks,†Tinybench: The case for a standardized benchmark suite for TinyOS based wireless sensor network devices,† in Proc. IEEE 29th Local comout. Netw, conf., Nov.2004, pp. 585-586. O. Girard. (2010). â€Å"OpenMSP430 processor core, available at opencores.org,† [online]. Available: http://opencores.org/project, openmsp430. H. Stone, â€Å"Parallel processing with the perfect shuffle,† IEEE Trans. Comput., vol. 100, no.2, pp. 153-161, Feb. 1971. M. Hempstead, J. M. Lyons, D. Brooks, and G-Y. Wei,† Survey of hardware systems for wireless sensor networks,† J. Low Power Electron., vol.4, no. 1, pp. 11-29, 2008. C.C. Yu. Design of low-power double edge-triggered flip-flop circuit. In IEEE Conference on Industrial Electronics and Applications, pp. 2054-2057, 2007. M. Donno, A. Ivaldi, L. Benini, and E. Macii. Clock tree power optimization based on RTL clock-gating. In Design Automation Conference, pp. 622-627, 2003.

Bill of Rights Assignment

I started my assignment by really reading over the Bill of Rights and thinking really hard. It occurred to me that this was going to be a very tough assignment. Though I don’t think that a lot of the Amendments are upheld much anymore, such as freedom of speech, I could not think of any that needed to be removed or changed. So I started thinking about things that I thought should be added. It came to my attention that I shouldn’t try of think of things that should be added because of personal reasoning, but instead, things that seem to be aggravating a lot of people nowadays. I came up with three. The first thing I thought really needed to be added to the Bill of Rights was the right to marry any person of your choosing. Now I know that gay marriage is a really touchy subject for a lot of people but I feel like if you love someone it shouldn’t matter what gender they are. It seems to me that the only problem that there is with gay marriage being passed everywhere is that the churches do not allow it. Thomas Jefferson once sent a letter to the Danbury Baptist in 1802 stating â€Å"†¦ I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should ‘make no law respecting an establishment of religion, or prohibiting the free exercise thereof,' thus building a wall of separation between Church & State†. I do not believe that the states should not grant people the right to marry whom they please simply because it is considered an abomination in the church. This is the 21st century and there are so many religions, people following so many different ones and then there are also people, like myself, that do not believe in a â€Å"God† or â€Å"Creator† or whatever you want to call it. Gay marriage is a choice just as big as a man and woman marrying and if two people make that decision they should be allowed to make it official. The second thing I came up with for the Bill of Rights is the right to not have to pay for illegal immigrant’s welfare or jailing via state or federal taxes. Are country is in a $14,136,022,715,367 deficit, approximately as of 2/2/11. It does not seem far that some of our money is going into paying for illegal aliens to be jumping the border and living off welfare or being imprisoned and we end up having to pay for them to stay in our prisons and keeping them alive and such. I feel that if a person does not have a green card or was not born into this country by someone who is a legal citizen, they should not be here, making money off us when our country is having a bad enough problem dealing with our own money issues. I’m no expert on finances or on morality but it just seems like it should be every person’s right to not have to pay for people who are in our country illegally. There is an astonishing amount of aliens in our country that live here and manage to con our government out of thousands if not millions of our hard earned money. And lastly, the third thing I could think of that should be in the Bill of Rights is our right to medical care. There are so many people in our country dying every day because they could not receive medical care because of lack of funds. I was recently almost added to the number of people without medical care. I have two kids, live in Connecticut, and my kids are currently temporarily living with their grandparents. Was forced into homelessness due to the economy’s lack of job availability in my area and had to make the decision to either bring myself and my children to a homeless shelter or let them go live with family while I went to a homeless shelter or a friend’s. When staying at a friend’s house didn’t work, I moved back in with my father and the state of Connecticut threatened to shut off my welfare. They shut off my food stamps because I’m living with my father and are under 22 and almost shut off my health insurance due to the same reasoning. Now, unlike a lot of people out there, I’m lucky in the fact that I don’t have a life threatening disease. But I still require doctor attention unless I want to end up either in a wheelchair, which without money; I wouldn’t be able to afford one and would have to second hand which is never a guaranteed thing. But the fact that our country can afford to be helping people in Africa, Haiti, everywhere around the world with disease but cannot afford to make it a constitutional right for its own citizens to receive medical care is just unacceptable. It seems to me that our country is more worried about everyone else’s health but its own. I think it’s time that they look at ours and make it a constitutional right. In conclusion, I have personal found that there is three things that our country absolutely needs in its Bill of Rights. As I’ve said, I’m no expert in any way possible, but I feel that if these three things were added, we could be even just a little more well off: The right to medical care; the right to not have to pay money via taxes for aliens; and the right to marry whom we please, regardless of gender. I know that there are many people out there that would not agree with me on these, but as the assignment was to write what I thought should be added, edited, or removed, these are my ideas. Hope you enjoyed reading.Reference http://www.loc.gov/loc/lcib/9806/danpre.html

Want to Know More About Short Expository Essay Samples?

Want to Know More About Short Expository Essay Samples? The Secret to Short Expository Essay Samples Every term paper is centered on developing particular skills letting college students obtain necessary expertise in writing several types of essays. If you still find it difficult to work on your expository essay, get in touch with our on-line writing team made from professional writers with 10 or more decades of experience to receive your own personal academic lifebuoy! Some college students could be requested to compose an expository essay for a number of classes like history, literature, or social sciences, and it may also turn into a task on an exam. Therefore, many students and employees decide to get inexpensive essay rather than writing it themselves. Now you are prepared to get started drafting. Keep in mind, though you might not be crafting the upcoming great novel, you are trying to leave an enduring impression on the folks evaluating your essay. Your writing has to be brief and concise. More than every other sort of writing, expository writing is a daily requirement of the majority of careers. New Ideas Into Short Expository Essay Samples Never Before Revealed Choose the one which you liek to compose an ideal expository essay! Locate the trustworthy information for the essay topic you are likely to work on. There are lots of expository essay topics to pick from. Obviously, the subject of an essay is distinguished based on the students' age. The overall definition of the expression expository is something meant to explain or describe. Before anything else, it's required to think over a winning and intriguing topic. It's much better to pick out a topic from daily life to make it even more relatable. When you get a we ll-formulated topic, it's a half success of your final writing. The goal of the expository essay is to expand the info on this issue in a logical method. Students often lose an excessive amount of time trying to find the ideal option and wind up having no time left for writing. Expository essay is a significant means to educate your readers on any topic by only providing useful information without attempting to convince a reader to modify their beliefs. The majority of the moment, expository essays are presented by offering a range of topics and methods to bring up the idea. An expository essay is composed of facts. It is a piece of academic writing aimed to provide explanations of various things. While it should be clear and concise, it can also be lively and engaging. Writing a great expository essay isn't difficult whatsoever. As you're most likely already aware, it's very rare to get a wholly open-ended expository essay assignment. An expository essay's objective is to define and explain a subject chosen by means of an author. A good thesis statement contributes to a good essay. A thesis can help to bring the remainder of your essay together. What You Should Do About Short Expository Essay Samples Starting in the Next Nine Minutes When you compose a brief essay, you have to keep in mind that there are not any elements to be sacrificed. While writing an expository essay, specificity regarding the topic is vital. Now as you understand what an expository writing is, I want to suggest you several topics that could inspire composing a wonderful expository essay. An expository essay, thus, is a part of prose that is well organized to provide an explanation on ideas and assorted topics to a particular kind of audiences. The thesis of the expository essay needs to be based on factual information which will be displayed in the body of the essay. Composition of the essay is very important to compose an effective essay. It is most expedient to get started writing essays once you have read a sample of the very same sort of essay. As stated by the context, the period of your essay might vary. Also, consider In actuality, there are lots more issues to compose a great expository essay about. Do not think it will be that easy to write because you will need to do a lot of research and analyzes. What Does Short Expository Essay Samples Mean? As an example, finding essays from a difficult copy of a textbook is difficult as you may have to peruse through several pages. Without an essay outline, it would be tough to recall the necessary sections, arguments, logical stream of essay, and general structure. An expository essay outline presupposes a crystal clear structure, which isn't really hard to embody. A thesis isn't a mere fact or statement.

Profile of Child Killer Susan Smith

Susan Vaughan Smith of Union, S.C. was convicted on July 22, 1995, and sentenced to life in prison for murdering her two sons, Michael Daniel Smith, 3, and 14-month-old Alexander Tyler Smith. Susan Smith - Her Childhood Years Susan Smith was born on September 26, 1971, in Union, South Carolina, to parents Linda and Harry Vaughan. She was the youngest of three children and the couples only daughter. Her parents divorced when Susan was seven and five weeks later Harry, age 37, committed suicide. Her parents tumultuous marriage and the death of her father left Susan a sad, empty and oddly distant child. Within weeks of the Vaughans divorce, Linda married Beverly (Bev) Russell, a successful local businessman. Linda and the children moved from their small modest home into Bevs house located in an exclusive subdivision of Union. Friendliest Female As a teen, Susan was a good student, well-liked and outgoing. In her junior year, she was voted president of the Junior Civitan Club, a club which focused on volunteering in the community. In her final year of high school, she received the Friendliest Female award and was known for her cheerful and fun disposition. Family Secrets Exposed But during those years of enjoying her popularity and positions of leadership, Susan was harboring a family secret. At the age of 16. her stepfather turned from caretaker to molester. Susan reported the inappropriate behavior to her mother and to the Department of Social Services and Bev moved out from the home temporarily. Nothing of any consequence resulted from Susans report and after a few family counseling sessions, Bev returned home. Susan was chastised by her family for making the sexual abuse a public affair and Linda appeared more concerned that the family would be subjected to public embarrassment than protecting her daughter. Unfortunately for Susan, with Bev back in the house, the sexual molestation continued. In her senior year of high school, Susan turned to a school counselor for help. The Department of Social Service was contacted again, but Susan refused to press charges and the matter was swiftly swept under the proverbial carpet of lawyers agreements and sealed records which protected Bev and the family from the feared public humiliation. Rejection and an Attempted Suicide During the summer of 1988, Susan got a job at the local Winn-Dixie grocery store and moved quickly up the ranks from cashier to bookkeeper. In her senior year at high school, she was sexually active with three men - a married older man who worked at the store, a younger co-worker and with Bev. Susan became pregnant and had an abortion. The married man ended their relationship and her reaction to the breakup was to attempt suicide by taking aspirin and Tylenol. While being treated in the hospital she admitted to having tried a similar suicide attempt when she was 13-years-old. David Smith At work, another relationship was beginning to form with the co-worker and high school friend David Smith. David ended his engagement with another woman and started dating Susan. The two decided to marry when Susan discovered she was pregnant. Susan and David Smith married on March 15, 1991, and moved into Davids great-grandmothers house. Davids parents were suffering the recent loss of another son who died from Crohns disease just 11 days before Susan and David married. By May 1991, the strain of the loss of a son proved to be too much for Davids parents. His father attempted suicide and his mother left and moved to another city. This kind of family drama fit right into what Susan was used to and the young couple, both very needy, spent the early months of their marriage comforting one another. Michael Daniel Smith On October 10, 1991, the Smiths first son, Michael, was born. David and Susan showered the child with love and attention. But having a child could not help the differences in the newlyweds backgrounds which began to put a strain on their relationship. Susan was more materialistic than David and often turned to her mother for financial help. David found Linda to be intrusive and controlling and resented Susan always doing what Linda wanted her to do, especially when it came to raising Michael. First Separation By March 1992, the Smiths were separated and over the next seven months, they tried on and off to mend the marriage. During the breakups, Susan dated a former boyfriend from work which did not help matters. In November 1992, Susan announced she was pregnant again which seemed to bring David and her into clearer focus and the two reunited. The couple borrowed money from Susans mother for a down payment on a house, believing having their own home would fix their troubles. But over the next nine months, Susan became more distant and complained continuously about being pregnant. In June 1993, David felt lonely and isolated in his marriage and began a relationship with a co-worker. After the birth of their second child, Alexander Tyler, on August 5, 1993, David and Susan reunited, but within three weeks David had once again moved out and the two decided the relationship was over. Regardless of their broken marriage, both David and Susan were good, attentive and caring parents who seemed to enjoy the children. Tom Findlay Susan, not wanting to work in the same place as David, took a job as a bookkeeper at the largest employer in the area, Conso Products. She was eventually promoted to the executive secretary position for the president and CEO of Conso, J. Carey Findlay. For Union, S.C. this was a prestigious position which exposed Susan to wealthy people with extravagant lifestyles. It also gave her the opportunity to get closer to one of Unions most eligible bachelors, the son of her boss, Tom Findlay. In January 1994 Susan and Tom Findlay began casually dating, but by spring she and David were back together. The reconciliation only lasted a few months and Susan told David she wanted a divorce. In September she was dating Tom Findlay again and planning their future together in her mind. Tom, in the meantime, was trying to figure out how to end it with Susan. Nice Girls Dont Sleep With Married Men On October 17, 1994, just days before David and Susans divorce papers were filed, Tom Findlay sent a Dear John letter to Susan. His reasons for wanting to end their relationship included the differences in their backgrounds. He was also emphatic about not wanting children or wanting to raise her children. He encouraged Susan to act with more  self-respect and referred to an episode when Susan and a friends husband were kissing each other in a hot tub during a party at Toms fathers estate. Findlay wrote, If you want to catch a nice guy like me one day, you have to act like a nice girl. And you know, nice girls dont sleep with married men. Narcissistic Delusions Susan was devastated when she read the letter, but she was also living out delusional dreams which in reality were a combination of grotesque lies, deceit,  lust, and narcissism. On one  hand, she was deeply depressed that Tom ended their  relationship but unknown to him, she was still sexually involved with David and her stepfather, Bev Russell, and had allegedly had a sexual affair with her boss who was Toms father. In an attempt to get Toms sympathy and attention, Susan confessed to him about her ongoing sexual relationship with Bev. When that didnt work, she told him of her alleged affair with his father and warned him that the details of the relationship might come out during her divorce with David. Toms reaction was one of shock and he reiterated that the two of them would never again have a sexual relationship. Any hopes to maneuver her way back into Toms life had now been permanently severed. Obsessions On October 25, 1994, Susan Smith spent the day  obsessing  over the breakup with Tom Findlay. As the day progressed she became increasingly upset and asked to leave work early. After picking up her children from daycare, she stopped to talk to a friend in a parking lot and expressed her fears over Toms reaction to her sleeping with his father. In a last-ditch effort to sway Toms feelings, she asked her friend to watch the children while she went to Toms office to tell him the story was a lie. According to her friend, Tom did not appear happy to see Susan and quickly got her out of his office. Later that evening she phoned her friend who she knew was having dinner with Tom and friends. Susan wanted to know if Tom had said anything about her, but he had not. The Murder of Michael and Alex Smith At around 8 p.m. Susan put her barefooted sons in the car, strapped them in their car seats and began driving around. In her  confession, she stated that she wanted to die and was headed to her mothers house, but decided against it.  Instead, she drove to John D. Long Lake and drove onto a ramp, got out of the car, put the car in drive, released the brake and watched as her car, with her children sleeping in the back seat, plunged into the lake. The car drifted out  then slowly sank. Nine Days of Deceit Susan Smith ran to a nearby home and hysterically knocked on the door. She told the homeowners, Shirley and Rick McCloud, that a black man had taken her car and her two boys. She described how she had stopped at a red light at Monarch  Mills when a man with a gun jumped into her car and told her to drive. She drove around some, and then he told her to stop and get out of the car. At that point, he told her he wouldnt hurt the kids and then drove off with the boys who she could hear were crying out for her. For nine days Susan Smith stuck the story of  being abducted. Friends and family surrounded her in support and David had returned to his wifes side as the search for their children intensified. The national media showed up in Union as the tragic story of the boys abduction circulated. Susan, with her  face, spotted with tears, and David looking distraught and desperate, made a public plea for the safe return of their sons. In the meantime, Susans story was beginning to unravel. Unraveling the Truth Sheriff Howard Wells, the lead investigator on the case, had David and Susan polygraphed. David passed, but Susans results were inconclusive. Throughout the nine days of the  investigation, Susan was given numerous  polygraphs  and questioned about the inconsistencies in her carjacking story. One of the biggest clues that led the authorities to believe Susan was lying was her story about stopping at a red light on Monarch Mills Road. She stated that she saw no other cars on the road, yet the light turned red. The light on Monarch Mills was always green and only turned red if it was triggered by a car on the cross street. Since she said that there were no other cars on the road, there was no reason for her to come up to a red light. Leaks to the press about discrepancies in Susans story resulted in accusatory questions by reporters. Also, people around her noticed her displaying questionable behavior for a mother whose children were missing. She seemed overly concerned with how she looked in front of the television cameras and at times asked about the whereabouts of Tom Findlay. She also had dramatic moments of deep  sobbing but would be dried eyed and  tearless. Susan Smith Confesses On November 3, 1994, David and Susan appeared on CBS This Morning and David voiced his full support of Susan and her story about the abduction. After the interview, Susan met with Sheriff Wells for another  interrogation. This time, however, Wells was direct and told her that he did not believe her story about the carjacking. He explained to her about the light on Monarch Mills staying green and discrepancies in other adaptations she had made to her story during the past nine days. Exhausted and emotionally badgered, Susan asked Wells to pray with her then  afterward  she began crying and telling how ashamed she felt for what she had done. Her confession to pushing the car into the lake began to spill out. She said she had wanted to kill herself and her children, but in the end, she got out of the car and sent her boys to their deaths. A Small Hand Against the Window Before breaking the news of Susans confession, Wells wanted to locate the bodies of the boys. A previous search of the lake had failed to turn up Susans car, but after her confession, she gave police the exact distance the car had floated out before it sank. Divers found the car turned upside down, with the children dangling from their car seats. One diver described that he saw the small hand of one of the children pressed against a window. Also found in the car was the Dear John letter Ton Findlay had written. An autopsy of the children proved that both  boys were still alive  when their tiny heads were submerged under water. Who is Susan Smith Really? Incredibly, Susan reached out to David in a letter filled with, Im sorry, then complained that her feelings were being overshadowed by everyones grief. Stunned, David questioned who Susan really was and felt a brief moment of sympathy for her confused and demented state of mind. But it did not take long for the sympathy to turn to horror as more  facts about the murders  of his sons surfaced. He had assumed Susan had shown mercy by killing the boys prior to pushing the car into the lake, but after finding out the truth he was haunted by images of his sons last moments, in the dark, scared, alone and drowning to death. When he discovered Susan had supplied the police with the exact location of the car and that the car lights had been on when she lifted the break, he knew she had stayed and watched the car sinking, motivated by her desires to rebuild her relationship with the wealthy Tom Findlay. The Trial During the trial, Susans defense lawyers relied heavily on Susans littered childhood of tragedy and sexual abuse which manifested itself into a lifetime of untreated depression and suicidal thoughts. They explained that her abnormal need to depend on others for happiness led to the multiple sexual relationships she was involved in during her life. The bottom line was that Susan, as outwardly normal as she might have appeared, was in truth hiding a deep-seated mental illness. The prosecution showed the jury a more devious and manipulative side of Susan Smith whose only concern was her own desires. Her children had become a major handicap in Susans ability to get what she wanted. By killing them she would not only get the sympathy of her former lover Tom Findlay but with the children gone, it was one less reason for him to end their relationship. Susan Smith was unresponsive  during her trial  except when her sons were mentioned which sometimes led to her sobbing and shaking her head as if in disbelief that the boys were dead. The Verdict and Sentence It took the jury two-and-a-half hours to return a verdict of guilty of two counts of murder.  Despite Davids protests, Susan Smith was spared the death sentence and  received a sentence  of 30 years to life in prison. She will be eligible for parole in 2025 when she is 53 years old. David has sworn to attend every parole hearing to try to keep Susan Smith in jail for life. Aftermath Since her incarceration at South Carolinas Leath Correctional Institution, two guards have been punished for having sex with Smith. Her sexual activity in prison was discovered after she developed a sexually transmitted disease. Michael and Alex Smith Michael and Alex Smith were buried together in the same casket in the Bogansville United Methodist Church cemetery on November 6, 1994, next to the grave of Davids brother and the childrens uncle, Danny Smith. The Dear John Letter This is the Dear John letter that John Findlay gave to Susan  October. 17, 1994. Many believe it is what motivated Susan Smith to kill her children. (Note: This is how the original letter was written. Corrections have not been made.) Dear Susan, I hope you dont mind, but I think clearer when I am typing, so this letter is being written on my computer. This is a difficult letter for me to write because I know how much you think of me. And I want you to know that I am flattered that you have such a high opinion of me.  Susan, I value our friendship very much. You are one of the few people on this earth that I feel I can tell anything. You are intelligent, beautiful, sensitive, understanding, and possess many other wonderful qualities that I and many other men appreciate. You will, without a doubt, make some lucky man a great wife. But unfortunately, it wont be me. Even though you think we have much in common, we are vastly different. We have been raised in two totally different environments, and therefore, think totally different. Thats not to say that I was raised better than you or vice versa, it just means that we come from two different backgrounds. When I started dating Laura, I knew our backgrounds were going to be a problem. Right before I graduated from Auburn University in 1990, I broke up with a girl (Alison) that I had been dating for over two years. I loved Alison very much and we were very compatible. Unfortunately, we wanted different things out of life. She wanted to get married and have children before the age of 28, and I did not. This conflict spurred our breakup, but we have remained friends through the years. After Alison, I was very hurt. I decided not to fall for anyone again until I was ready to make a long commitment. For my first two years in Union, I dated very little. In fact, I can count the number of dates I had on one hand. But then Laura came along. We met at Conso, and I fell for her like a ton of bricks. Things were great at first and remained good for along  [sic] time, but I knew deep in my heart that she was not the one for me. People tell me that when you find the person that you will want to spend the rest of your life with ... you will know it. Well, even though I fell  enlove  Ã‚  [sic]  with Laura, I had my doubts about a long and lasting commitment, but I never said anything, and I eventually hurt her very, very deeply. I wont do that again. Susan, I could really fall for you. You have so many endearing qualities about you, and I think that you are a terrific person. But like I have told you before, there are some things about you that arent suited for me, and yes, I am speaking about your children. Im sure that your kids are good kids, but it really wouldnt matter how good they may be ... the fact is, I just dont want children. These feelings may change one day, but I doubt it. With all of the crazy, mixed-up things that take place in this world today, I just dont have the desire to bring another life into it. And I dont want to be responsible for anyone  elses  [sic] children, either. But I am very thankful that there are people like you who are not so selfish as I am, and dont mind bearing the responsibility of children. If everyone thought the way that I do, our species would eventually become extinct. But our differences go far beyond the children issue. We are just two totally different people, and eventually, those differences would cause us to break-up. Because I know myself so well, I am sure of this. But dont be discouraged. There is someone out there for you. In fact, its probably someone that you may not know at this time or that you may know, but would never expect. Either way, before you settle down with anyone again, there is something you need to do. Susan, because you got pregnant and married at such an early age, you missed out on much of your youth. I mean, one minute you were a kid, and the next minute  you were having kids. Because I come from a place where everyone had the desire and the money to go to college, having the responsibility of children at such a young age is beyond my comprehension. Anyhow, my advice to you is to wait and be very choosy about your next relationship. I can see this may be a bit difficult for you because you are a bit boy crazy, but as the proverb states good things come to those who wait. I am not saying you shouldnt go out and have a good time. In fact, I think you should do just that ... have a good time and capture some of that youth that you missed out on. But just dont get seriously involved with anyone until you have done the things in life that you want to do, first. Then the rest will fall in place. Susan, I am not mad at you about what happened this weekend. Actually, I am very thankful. As I told you, I was starting to let my heart warm up to the idea of us going out as more than just friends. But seeing you kiss another man put things back into perspective. I remembered how I hurt Laura, and I wont let that happen again; and therefore, I cant let myself get close to you. We will always be friends, but our relationship will never go beyond that of friendship. And as for your relationship with B. Brown, of course you have to make your own decisions in life, but remember ... you have to live with the consequences also. Everyone is held accountable for their actions, and I would hate for people to perceive you as an unreputable person. If you want to catch a nice guy like me one day, you have to act like a nice girl. And you know, nice girls dont sleep with married men. Besides, I want you to feel good about yourself, and I am afraid that if you sleep with B. Brown or any other m arried man for that matter, you will lose your self-respect. I know I did when we were messing around earlier this year. So please, think about your actions before you do anything you will regret. I care for you, but also care for Susan Brown and I would hate to see anyone get hurt. Susan may say that she wouldnt care (copy unintelligible) husband had an affair, but you and I know, that is not true. Anyhow, as I have already told you, you are a very special person. And dont let anyone tell you or make you feel any different. I see so much potential in you, but only you can make it happen. Dont settle for mediocre in life, go for it all and only settle for the best ... I do. I havent told you this, but I am extremely proud of you for going to school. I am a firm believer in higher education, and once you obtain a degree from college, there is not stopping you. And dont let these idiot boys from Union make you feel like you are not capable or slow you down. After you graduate, you will be able to go anywhere you want in this world. And if you ever wanted to get a good job in Charlotte, my father is the right person to know. He and Koni know everyone who is anyone in the business world in Charlotte. And if I can ever help you with anything, dont hesitate to ask. Well, this letter must come to an end. It is 11:50 p.m. and I am getting very sleepy. But I wanted to write you this letter because you are the one who is always making the effort for me, and I wanted to return the friendship. Ive appreciated it when you have dropped me nice little notes, or cards, or the present at Christmas, and it is about time that I start putting a little effort into our friendship. Which reminds me, I thought long and hard about getting you something for your birthday, but I decided not to because I wasnt sure what you might think. Now I am sorry I didnt get you anything, so you can expect something from me at Christmas. But do not buy me anything for Christmas. All I want from you is a nice, sweet card ... Ill cherish that more than any store (copy illegible) present. Again, you will always have my friendship. And your friendship is one that I will always look upon with sincere affection. Tom p.s. Its late, so please dont count off for spelling or grammar. Source: Court Document