Multiplexing and Data Rate Essays

Multiplexing and Data Rate Essays Multiplexing and Data Rate Essay Multiplexing and Data Rate Essay Multiplexing CHAPTER 4 Outline * Frequency Division Multiplexing(FDM) * Synchronous Time Division Multiplexing * Statistical Time Division Multiplexing * Asymmetric Digital Subscriber Line(ADSL) Multiplexing * Set of techniques that allows the simultaneous transmission of multiple signals across a single link * allows several transmission sources to share a larger transmission capacity Link = physical path Channel = portion of a link that carries a transmission between a given pairs of lines 2 CATEGORY OF MULTIPLEXING WDM FDM TDM ADSL Frequency Division Multiplexing * FDM – numerous signals are combined for ransmission on a single communications line or channel. Each signal is assigned a different frequency (subchannel) within the main channel. * Useful bandwidth of medium exceeds required bandwidth of channel * e. g. broadcast radio and cable television * Channel allocated even if no data Frequency Division Multiplexing Diagram * Each signal is modulat ed to a different carrier frequency * Carrier frequencies separated by guard bands (unused bandwidth) – to prevent interference so signals do not overlap. 3 FDM System FDM is an analog multiplexing technique that combines signals. FDM process FDM Demultiplexing Example 1 Assume that a voice channel occupies a bandwidth of 4 KHz. We need to combine three voice channels into a link with a bandwidth of 12 KHz, from 20 to 32 KHz. Show the configuration using the frequency domain without the use of guard bands. Solution Shift (modulate) each of the three voice channels to a different bandwidth, as shown in next figure Example 2 Five channels, each with a 100-KHz bandwidth, are to be multiplexed together. What is the minimum bandwidth of the link if there is a need for a guard band of 10 KHz between the channels to prevent interference? Solution For five channels, we need at least four guard bands. This means that the required bandwidth is at least 5 x 100 + 4 x 10 = 540 KHz, as shown in next Figure. Example 3 Four data channels (digital), each transmitting at 1 Mbps, use a satellite channel of 1 MHz. Design an appropriate configuration using FDM Solution The satellite channel is analog. We divide it into four channels, each channel having a 250-KHz bandwidth. Each digital channel of 1 Mbps is modulated such that each 4 bits are modulated to 1 Hz. One solution is 16- QAM modulation. Figure 6. 8 shows one possible configuration. Analog Carrier Systems ATT (USA) * Hierarchy of FDM schemes * Group 1. 12 voice channels (4kHz each) = 48kHz 2. Range 60kHz to 108kHz * Supergroup 1. 60 channel 2. FDM of 5 group signals on carriers between 420kHz and 612 kHz * Mastergroup 1. 10 supergroups Analog Hierarchy To maximize the efficiency infrastructure, multiplexed signals from lower bandwidth lines onto higher-bandwidth signals FDM of Th ree Voiceband Signals FDM Applications 1. Common used radio broadcasting AM and FM * AM (530 – 1700KHz) – shared with all radio stations * FM uses a wider band (88 – 108MHz) – each station needs more bandwidth, 200KHz 2. Television Broadcasting * Each TV channel has own bandwidth of 6 Mhz 3. 1st Generation of Cellular telephones * Voice signal 3KHz (300 – 3300Hz) channels * Bt = 10 x Bm , therefore each channel has 30KHz channels * each user has been allocated two 30KHz channel, therefore 60KHz. Example 4 The Advanced Mobile Phone System (AMPS) uses two bands. The first band, 824 to 849 MHz, is used for sending; and 869 to 894 MHz is used for receiving. Each user has a bandwidth of 30 KHz in each direction. The 3 5 Four 1-Kbps connections are multiplexed together. A unit is 1 bit. Find : (1) the duration of 1 bit before multiplexing, (2) the transmission rate of the link, (3) the duration of a time slot, and (4) the duration of a frame? Solution We can answer the questions as follows: 1. The duration of 1 bit is 1/1 Kbps, or 0. 001 s (1 ms). 2. The rate of the link is 4 Kbps. 3. The duration of each time slot 1/4 ms or 250 ms. 4. The duration of a frame 1 ms. Interleaving switches are synchronized and rotate at the same speed but opposite direction process of sending a unit data onto the path when the connection on the multiplexing and de 6 Four channels are multiplexed using TDM. If each channel sends 100 bytes/s and we multiplex 1 byte per channel, show the frame traveling on the link, the size of the frame, the duration of a frame, the frame rate, and the bit rate for the link. Solution The multiplexer is shown in Figure 6 Example 7 A multiplexer combines four 100 8 We have four sources, each creating 250 characters per second. If the interleaved unit is a character and 1 synchronizing bit is added to each frame, find (1) the data rate of each source, (2) the duration of each character in each source, (3) the frame rate, (4) the duration of each frame, (5) the number of bits in each frame, and (6) the data rate of the link. Solution Answer as follows: 1. The data rate of each source is 250 x 8 = 2000 bps = 2 Kbps. 2. The duration of a character is 1/250 s = 4 ms. 3. The link needs to send 250 frames per second. 4. The duration of each frame is 1/250 = 4 ms. 5. Each frame is 4 x 8 + 1 = 33 bits. 6. The data rate of the link is 250 x 33 = 8250 bps. Example 9 Two channels, one with a bit rate of 100 Kbps and another with a bit rate of 200 Kbps, are to be multiplexed. How this can be achieved? What is the frame rate? What is the frame duration? What is the bit rate of the link? Solution We can allocate one slot to the first channel and two slots to the second channel. Each frame carries 3 bits. The frame rate is 100,000 frames per second because it carries 1 bit from the first channel. The frame duration is 1/100,000 = 10 ms. The bit rate is 100,000 frames/s x 3 bits/frame = 300 Kbps. Pulse Stuffing * Problem Synchronizing various data sources * Each source has separate clock, variation among clock cause loss synchronization * Data rates from different sources not related by simple rational number * Solution Pulse Stuffing as effective remedy * Outgoing data rate (excluding framing bits) higher than sum of incoming rates * Stuff extra dummy bits or pulses into each ncoming signal until it matches local clock * Stuffed pulses inserted at fixed locations in frame and removed at demultiplexer TDM of Analog and Digital Sources Digital Carrier Systems * Long distance carrier system * Designed to transmit voice signal over high capacity transmission lonks usuch as optical fiber, coax and microwave * ATT developed hierarchy of TDM structures of various capacities * USA/Canada/Japan use one system * ITU-T use a similar (but different) system * US system based on DS-1 format which Multiplexes 24 channels * Each frame has 8 bits per channel plus one raming bit, 24 x 8 +1 =193 bits per frame Digital Carrier Systems (2) * For voice each channel contains one word of digitized data (using PCM at 8000 samples per sec) * Data rate 8000193 = 1. 544Mbps * Five out of six frames have 8 bit PCM samples * Sixth frame is 7 bit PCM word plus signaling bit * Signaling bits form stream for each channel containing control and routing info * Same format for digital data * 23 channels of data * 7 bits per frame plus indicator bit for data or systems control * 24th channel is sync DS Hierarchy TDM Carrier Standard North American and International TDM Carrier Standards Statistical TDM * In Synchronous TDM many slots are wasted * Statistical TDM allocates time slots dynamically based on demand * Multiplexer scans input lines and collects data until frame full * Data rate on line lower than aggregate rates of input lines * Improve efficiency is to allow multiple data resources to be packed in one single frame Statistical TDM Frame Formats Performance * Output data rate less than aggregate input data rates cause by average amount of input capacity of multiplexed line * Difficulty: May cause problems during peak periods when the input exceed capacity * Solution Buffer inputs to hold temporary excess input * Keep buffer size to minimum to reduce delay Cable Modem Outline * To support data transfer to and from a cable modem, two channels from cable TV provider dedicated to data transfer * One in each direction * Each channel shared by number of subscribers * Scheme needed to allocate capacity * Statistical TDM Cable Modem Operation Downstream * Cable sc heduler delivers data in small packets * If more than one subscriber active, each gets fraction of downstream capacity May get 500kbps to 1. 5Mbps * Also used to allocate upstream time slots to subscribers Upstream * User requests timeslots on shared upstream channel Dedicated slots for this * Headend scheduler sends back assignment of future time slots to subscriber Cable Modem Scheme Asymmetrical Digital Subscriber Line ADSL Link between subscriber and network * Local loop Uses currently installed twisted pair cable * Can carry broader spectrum * 1 MHz or more ADSL Design Asymmetric -Greater capacity downstream than upstream -Expected for video on demand and related services – high speed access -Users require higher capacity for downstream than upstream Frequency division multiplexing (FDM) element of ADSL strategy Reserve lowest 25kHz for voice – Plain old telephone service (POTS) – Voice carried only 0 – 4KHz band – Additional bandwidth for prevent crosstalk between voice and data channel Use echo cancellation or FDM to give two bands – smaller upstream band and larger downstream band Use FDM within upstream and downstream bands  œ Single bit stream multiple parallel bit streams – each portion carried separate frequency band Range up to 5. 5km -Depending of diameter cables and quality ADSL Channel Configuration Discrete Multitone * DMT * Use multiple carrier signals at different requencies * Sending some bits on each channel * Available transmission band =4kHz subchannels * Send test signal and use subchannels with better signal to noise ratio * ASL/DMT design employ 256 downstream subchannels at 4kHz (60kbps) * Possible to transmit at rate15. 36MHz * Impairments bring this down to 1. 5Mbps to 9Mbps DTM Bits Per Channel Allocation Each channel can carry data rate from 0-60 Kbps Shows increasing attenuation and decreasing signalto- noise ratio at higher frequencies DMT Transmitter xDSL * High data rate DSL * Single line DSL * Very high data rate DSL

Minmi - Facts and Figures

Minmi - Facts and Figures Name: Minmi (after Minmi Crossing in Australia); pronounced MIN-mee Habitat: Woodlands of Australia Historical Period: Middle Cretaceous (100 million years ago) Size and Weight: About 10 feet long and 500-1,000 pounds Diet: Plants Distinguishing Characteristics: Unusually small brain; primitive armor on back and belly About Minmi Minmi was an unusually small, and unusually primitive, ankylosaur (armored dinosaur) from middle Cretaceous Australia. This plant-eaters armor was rudimentary compared to that of later, more famous genera like Ankylosaurus and Euoplocephalus, consisting of horizontal bony plates running along the sides of its backbone, a noticeable thickening on its belly, and spiky protrusions at the end of its long tail. Minmi also had an unusually small, narrow head, which has led some paleontologists to speculate that its encephalization quotient (the comparative size of its brain to the rest of its body) was lower than that of other dinosaurs of its timeand considering how stupid the average ankylosaur was, thats not much of a compliment. (Needless to say, the dinosaur Minmi shouldnt be confused with the Japanese-born, Caribbean-style singer Minmi, or even Mini-Me from the Austin Powers movies, who are both presumably much more intelligent!) Until recently, Minmi was the only known ankylosaur from Australia. That all changed at the end of 2015, when a team from the University of Queensland re-examined a supposed second Minmi fossil specimen (discovered in 1989) and determined that it actually belonged to an entirely new ankylosaur genus, which they dubbed Kunbarrasaurus, Aboriginal and Greek for shield lizard. Kunbarrasaurus appears to be one of the earliest known ankylosaurs, dating to the same middle Cretaceous time frame as Minmi, and given its relatively light coating of armor, it seems to have only recently evolved from the last common ancestor of both stegosaurs and ankylosaurs. Its closest relative was the western European Scelidosaurus, a clue to the different arrangement of the earths continents during the early Mesozoic Era.

Human Sexuality Personal Statement Example | Topics and Well Written Essays - 250 words

Human Sexuality - Personal Statement Example An in-depth understanding of these aspects of human sexuality drew me to become a part of this class so that I can gain better knowledge with regard to this subject and pass it on to others. On a scale of 1 (very comfortable) to 10 (a significant amount of reservation or nervousness), where would you rank your level of current comfort or discomfort regarding what to expect while studying human sexuality? Why did you select the rating that you did? With regard to my expectations of studying human sexuality, my level of comfort on this scale is 4. Despite of the fact that I am interested in studying about human sexuality, I have been discouraged by a few members of my family as well as my peers. They provided me with reasons that this class is not very fruitful and it does not provide good learning. These account for a few reasons why I am nervous regarding my expectations of the human sexuality class. It is owing to my own interest and research with regard to this subject that I am still more than willing to become a part of this class. I believe that studying this subject will provide me with good knowledge regarding all the aspects of human sexuality and it is for this reason that I am joining this

Imac Assignment Example | Topics and Well Written Essays - 500 words

Imac - Assignment Example The system was also not able to fully take the modules of programming that had used other similar Microsoft software packages. The failure of the highly expensive and hard to replace iMac to run Ronny’s software unfortunately effected his confidence level. Ronny’s computer skills were well known because he had created a very interesting geography puzzle for his classmates. He had also been working on the creation of a new video game in secret, which would be designed to increase the mental skills of younger people. He needed to run the program on the latest version of the computer so he could test his many creative ideas using multimedia and fix the mistakes if he found any. The failure of the iMac very much saddened and worried him. The many trips to repair shop also made him lose important time as he wanted to send his video game to the online contest set up by IBM. The creation of video games involves very advanced computers that can run hard computer programs using multimedia. The testing of software is an important part of software creation and a lucky run of each module lifts the confidence of the creator. The failure of iMac to fully accept the program modules that needed other similar Microsoft software turned out to be the biggest problem to Ronny’s wish to join the contest. iMac is supposed to be the most advanced computer that is able to perform huge numbers of tasks at high speeds. The weaknesses in the machine to run the important parts of Ronny’s programs majorly shook his confidence in Apple’s products. Ronny’s father was also not able to buy another computer for him because of the huge amount of money already spent on the first iMac. While iMacs are known for their power and skills, they are also known for their high prices. The father was very proud of his son and knew that an advanced computer like the iMac would make it easier for

Ice Cream Making Essay Example for Free

Ice Cream Making Essay Some may call it a comfort food, others a family tradition, but we all know sweet potatoes pie is delicious. This pie is common around the colder holidays such as Thanksgiving and Christmas. Sweet potatoes pie common ingredients are of course sweet potatoes, butter, eggs, sugar, milk, vanilla extract, nutmeg, cinnamon, and pie crust. The pie color can vary from light orange to dark orange. The flavor of pie is sweet with a combination of different spices. The texture of the pie is usually smooth, but it is not uncommon to have small pieces of sweet potatoes in it; also some sweet potatoes pies have nuts has toppings which makes it not smooth. The smell of sweet potatoes pie is one that brings up memories to people, the smell of sweet potatoes with various species has a sweet smell. The ice cream mix is liquid, it is thick and creamy; it is tasteless similar to milk and is white in color. After the sweet potatoes mix, which consist of, cinnamon, butter, sugar, nutmeg, pecans, and sweet potatoes was added to the ice cream mix. The mix turned a light orange color. The color adds to the appeal of the product because it is orange just like sweet potatoes. The texture of the ice cream is not smooth because of small pieces of sweet potatoes chucks and walnuts in it. However, we didn’t want it to be too smooth because sweet potatoes pies aren’t smooth and the nuts add texture to it. The different spices are also seen and tasted in the ice cream. The pecans were coated with cinnamon, sugar and nutmeg. This added a sweeter flavor to the ice cream as well as additional spices. The group did a very good job of maintaining the sweet potatoes flavor with ice cream. It has the spices and taste similar to regular sweet potatoes pie. The smell is similar to the smell of sweet potatoes pie; it smells sweet and has a smell of spices like cinnamon and nutmeg. We first made an unhealthy recipe, added 60.2g of butter to sweet potatoes to make it creamy which also made it easy for it to be smashed. After the sweet potatoes were smashed until the texture we desired, we added 2g of cinnamon, 12g of sugar, 1g of nutmeg, to the 308 g of sweet potatoes mixed. After the ingredients were mixed the 25g of pecans were added to the mix. Then the sweet potatoes mix was added to 900mL of the Mayfield ice cream mix gradually. It was then churned for 20 minutes. Then the ice cream was taken out a placed in a blast freezer for storage. Then we made a healthy version of the ice cream, the recipe for the healthy version is 308g of sweet potatoes, 1g of nutmeg, 2g of cinnamon, 30.1g of margarine salted and 5g of Splenda.

Free Argumentative Essays: We Need Trauma Centers :: Argumentative Persuasive Essays

We Need Trauma Centers Due to the advanced state of industry a number of devices and machines have come into common use which, often through intentional misuse, result in very serious injuries. Two examples are the automobile and the gun. When a serious injury results from something such as an automobile accident the victim usually has a very short period in which to obtain emergency medical intervention before the shock resulting from his or her injuries is irreversible. Usually this period of time is not longer than one hour, and is often less. If measures to treat shock and the cause of the shock, massive internal bleeding for instance, are not instituted within this first hour after the injury the mortality rate increases exponentially every fifteen to twenty minutes. The state of emergency medical care currently practiced in this community involves an excellent pre-hospital phase under the jurisdiction of Los Angeles City paramedics. The paramedics have jurisdiction of about thirty-five emergency rooms to which their patients can be transferred after beginning medical treatment at the scene of the accident. This is where the problem occurs. To provide the best possible emergency care at the hospital, two factors play an important part. First, the staff must work on at least two to three severely injured patients daily to maintain their technical skill at top level. Second, surgeons and operating rooms must be available within 15 minutes notice, twenty-four hours a day, 365 days a year. In the San Fernando Valley, this level of care is not met anywhere. In greater Los Angeles, this level of care is met at less than six hospitals. The problem involves too many emergency rooms for the population. The cost of maintaining an operating room on fifteen minute standby day and night would put hospitals out of business, since even the busiest hospitals only receive three to four severely injured patients each week. The patient load would not support the very high cost of this service. The best remedy to this situation would be to designate "Trauma Centers". Instead of having thirty five emergency rooms taking care of the critically injured patients three or four selected emergency rooms would be geographically designated to receive all of the critical patients.

The first Olympic Games

The year is 776BC, and in Athens the first Olympic Games are about to start, the festivities have begun with a feast and sacrifices for the gods. The Olympic Spirit was a key part of their society. It was the one-time cultures from all of Greece could come together and celebrate, compete and enjoy. In the past few weeks we have been discussing the pros and cons of different issues and today it's the tur of Olympics. Approximately 2000 years later, what has changed, not much? But this Olympic spirit is ingrained within the Games, the international community spirit along with the best athletes coming together and competing in one of the most prestigious sporting competition in the world. I'd like to give you three reasons to explain why and Why the games will benefit Britain Firstly because of urban regeneration; this has been put at the heart of the London bid, and is a massive benefit to hosting the Olympic Games; there is the opportunity to redevelop areas that are dilapidated and have physical disorders. Although many locations in and around London will be used for Olympic Games the core location for most of the events will be the 500-acre Olympic Park in the Lower Lea Valley in East London, Which stretches over 5 boroughs: namely Tower Hamlets, Hackney, Camden, Greenwich and Stratford. 3 years ago Lower Lea Valley, was literally a dump site, with muggings at an all time high, knife crimes were going up and up. And you know why? Because no one cared about the place, it was considered to be a dirty, dangerous and dilapidated. And know gentlemen, due to the Olympic Committee's regeneration programme, the streets are clean, the alleys are well light The most important venue of the 2012 has been described as an architect's dream. Planned and already in building the 500 acre park promises an excellent site for sporting activities, with over 9 competition events, and is claimed to be the biggest sports site in Europe for nearly 150 years. Outside of the new Olympic Park, which will principally host indoor sports and track and athletic events, all of England will join in as hosts. However it is not just London that is going to benefit. Throughout the countries there will be facilities available. Already the Olympic Committee, has set up brilliant badminton centers in Birmingham, superb swimming pools in Swansea and even mountain biking in Manchester! However to gain the most from the Olympics we need to maximize the legacy effect. Currently the plan is to sell the Olympic stadium to West Ham Football Club, so that they can keep the sporting spirit alive. The legacy effect is in essence the only thing that will keep allow us to maintain the investment of hosting the Olympic Games. Britain, has the highest number of sports fans in the world, we have a pride in our sport, when we hear our national anthem at any event our hearts swell with pride. Recently in the last Commonwealth Games over a thousand British supporters flew out to India to support Team GB. We are proud to be British, Londoner, but the 2012 Olympics is not just about London. It's about team GB, it's about national pride, it's about an amazing, historical event taking place on our doorstep, it's about getting excited and involved, and it's about making sure that we maximise the legacy and the investment. As Lord Coe said â€Å"The Games will inspire the nation and give us the ability to showcase all that is great about Britain.†