Bluetooth Connection GFSK

Bluetooth Connection GFSK BACKGROUND OF BLUETOOTH TECHNOLOGY: Bluetooth was originally formed by the following five entities: IBM INTEL ERICSSON NOKIA TOSHIBA The initial five have grown to well over a thousand companies at this point and the number is increasing. Though Bluetooth is not quite as popular as 802.11, there are number of applications for a wide array of divergent wireless devices. For interesting background where exactly Bluetooth get its name? Contrary to what your dentist might think it is not from eating blueberries. The actual origin of this term is formed from a tenth century Scandinavian king whose name was HARALD BLUETOOTH. The connection is that in his real life he managed to unite several disparate kingdoms under one area. The idea was to make Bluetooth encompass a kingdom of different devices and to create a convergence of many different devices under the umbrella of one global specification. 1.2 WHAT IS BLUETOOTH WIRELESS TECHNOLOGY? Bluetooth wireless is an open specification for a low-cast , low power, short-range radio technology for ad hoc wireless communication of voice and data any where in the world. Lets examine each of these attributes An open specification means that the specification is publicly available and royalty free Short range radio technology means device can communicate over the air using radio waves at a distance of 10 meters. With higher transmission power the range increases to approximately 100 meters. Because communication is with in a short range, the radios are low power and are suited for portable, battery-operated devices. Bluetooth wireless technology supports both voice and data, allowing devices to communicate either type of content 2. BLUETOOTH MODULATION 2.1 Modulation Introduction Bluetooth uses Gaussian frequency shift keying (GFSK). More explicitly, Bluetooth 0.5 BT Gaussian filtered frequency shift keying (2FSK) also referred to as binary frequency shift keying (BFSK) at one M symbols/s with a channel spacing of 1MHz. Since only two frequencies are used one bit is one symbol (i.e. one indicates a positive frequency deviation (normally 157.5 KHz) from the carrier, and a zero indicates a negative frequency deviation (normally 157.5 KHz) from the carrier). The figure shows that amplitude versus time as well as constellation diagram plot of 2FSK modulation that is used for Bluetooth. The frequency deviation range is between 140 175 KHz. 2.2 Summary of Bluetooth modulation requirements To receive Bluetooth qualification, a radio must have the following modulation characteristics: GFSK with BT at 0.5 Symbol rate of 1 mega symbols per second (Ms/s), corresponding to a data rate of 1 Mb/s modulation index beta between 0.28 0.35 Binary 1 with a positive fd and 0 with a negative fd Symbol timing better than +20, -20 parts per million (PPM) Zero crossing error not greater than 1/8 of a symbol period The fd corresponding to a 1010 sequence to be at least 80 % of fd corresponding to a 00001111 sequence Minimum fd equal to 115 KHz Most of the previous modulation characteristics are self explanatory except perhaps the last two. If the modulation index is between 0.28 0.35, then equation 3.18 tell us that the corresponding fd must be between 140 175 KHz. This can be considered a â€Å"steady state† fd for a long sequence of binary ones or zeroes. Due to the ISI inherent in GFSK its possible that fd may not reach its maximum value for a binary sequence that alternates between 1 0. The specification requires that fd under these conditions reach at least 115 KHz, which is about 80 % of the minimum steady state fd of 140 KHz. 2.3 Bluetooth Data Rates and Data Packets The theoretical maximum data rate is 1 Mbps, but due to overhead, the maximum realizable asymmetric data rate is reduced to 723.2 Kbps. This is also a bit misleading because the reverse link has a much lower data rate. The table shows is a summary of the possible data rates for the various packet sizes. The information is transmitted in a packet in a time slot. Each time slot corresponds to an RF hop frequency. A packet of information can be transmitted in one time slot, three time slots, or five time slots. Naturally, a five slot packet carries more information than a three slot packet, which carries more than a one slot packet. Data high rate (DH) achieves higher data rates by using less error correction in the packets. Data medium (DM) rate achieves a lower bit error rate probability by using more error correction in the packets. A Bluetooth packet is shown in the figure. 2.4 Bluetooth Modulated Signal A modulated signal can be denoted as: Where fc is the carrier frequency, T is the bit period, h is the modulation index and x(t) is the input of the modulator. The above equation can be viewed as the output of a voltage controlled oscillator with an input of x(t). In FSK modulation, x(t) is a binary signal whereas in GFSK modulation, the binary signal is first passed through a low pass Gaussian filter to produce x(t). This is shown in below figure. GFSK modulation is determined by two parameters: the modulation index (h) and the bandwidth of the Gaussian filter. The Gaussian filter is usually characterized by the bandwidth-time product (BT), which is equal to the 3-db bandwidth of the Gaussian filter (B) times the bit period (T). In Bluetooth the bit rate is 1Mb/s, BT is 0.5 in the modulation index varies from 0.28 to 0.35, the figure above shows the simulated spectrum of a Bluetooth signal. Note that the well known Gaussian minimum shift keying (GMSK) is a special case of GFSK in the modulation index 0.5. 2.5 Frequency Hopping The physical connection of Bluetooth uses frequency hopping at 1 MHz hops at the actual carrier is spread spectrum modulated. This is known as frequency hop spectrum and is used to improve immunity from interference mainly from IEEE 802; WiFi WLAN shares the same spectrum as other users of the ISM band for example transitorily operated microwave ovens. There is a fundamentally sound reason for this approach. WLANs occupy significantly more bandwidth than 1 MHz and employ SS techniques, in which a pseudo-random code is used to modulate the information transmitted. At the receiver the same pseudo-random code has to be available to de-modulate it successfully called co-relation. As a result, many WLANs using different pseudo codes can transmit simultaneously without mutual interference. The Bluetooth frequency-hop system appears as an un-correlated noise like signal to a WLAN receiver and what is more its signal energy is spread over the entire band of the WLAN by the de-correlated demodulation process. SO in practice mutual interference amounts only to a raised noise floor for both systems. A raise noise floor simply reduces the available carrier to noise and hence reduces the range possible. This is the main effect of mutual interference. An exception can occur when signals are so strong because of the close proximity of the antenna s, that they overwhelm a receiver. Bluetooth frequency rate is chosen to be 1600 hops per second with a 625 us dwell time per hop. The minimum dual time of 625 us corresponds to a single time slot. Part of this hop timing is taken up by the guard time 220 us allowing the hardware based frequency synthesizer time to settle. The transmission channel is derived from the time slots, spread over 79 or 23 frequencies. The frequency hoping scheme uses time division multiplexing (TDMA), as illustrated in the figure, where the frequency step n=1MHz. 2.6 Piconets A piconet is formed by two or more devices discover each other and begin to communicate. A piconet can have up to eight devices, with one device acting as a master and the rest acting as slsaves. The first device initiates transmission becomes the master, although the specification provides for a master and slave unit to exchange roles. A specific frequency-hopping sequence is used by all devices within each piconet. The figure shows the simplest example of a piconet. In the figure, a cell phone is downloading the address book and telephone number information to the users laptop. In this example the laptop acts as the master. The application software running on the laptop contacts the cell phone when it is within range, and requests that it synchronize its database with the one stored on the laptop. As stated earlier a single piconet can have up to eight devices. The reason for this limit is simple: The address is only three bit long. This means that in binary only the value of 0 7 can be stored in the address field. The master has no address but zero is reserved for broadcast messages; so the only addresses remaining for use by slaves are 1 7. However, a device can participate in two different piconets called a scatternet. The figure shows an example of a larger piconet, in which one master controls multiple slaves in a piconet. You can see that its possible to link various devices in a piconet. You can download digital images from your digital camera to the laptop, use more than one Bluetooth-enabled cell phone to place voice calls and even contact a personal digital assistant PDA to the laptop to exchange information. Another interesting thing to note in this figure is that you can also use a single connection to the internet without having to have a direct cable connection to the modem or broadband connection. 2.7 Scatternets A device can be master of only one piconet. The device can, at the same time, also be a slave in another piconet that is within range. A slave can also participate in two different piconets that are within its range. However, because the master device determines the hoping pattern used for a piconet, a device cannot be a master of more than one piconet. An example of a simple scatternet is shown in figure. In this figure, a laptop computer communicates with devices in both piconets. Note that the laptop is a slave in both piconets. It is possible, however, for the laptop to be a master in one piconet and a slave in another (as shown in the figure). When a device is member of two piconets it keeps track of both frequency-hoping patterns and occasionally listens in on the correct frequency on each of the two piconerts so that it can stay in touch with both piconets. A master device transmits a packet to its slaves occasionally to maintain the link, base band on negotiations between the master and its slave devices. Thus, a device that is a member of two piconets must listen for these transmissions (or make them if its the master in one piconet) within the time frame negotiated for each of the piconets of which it is member. The above explanation can be understand better with the below figure. Bluetooth transmitter consists of CODE MAPING PFD BALUN AMPLIFIERS AMPLIFIER DETECTOR CHARGE PUMP T/R SWITCH PFD/CP CAP ARRAY 3. Advantages and Disadvantages of Bluetooth The main advantage of Bluetooth is its compact form and portability. This technology can be manufactured cheap and can be integrated to micro-levels easily. Bluetooth signals are very resistant to weather conditions and can often operate where other technologies may fail. Despite its short range the technology can be very effective and cheap where long distance coverage is not required. In modern hardware Bluetooth is being used widely. Almost all platforms are benefiting from its cheap production such as cell phones, gaming consoles, computer peripheral devices etc. Even computers can achieve LAN connectivity using Bluetooth. Another great feature of this technology is its less power consumption. The only disadvantage of this technology is perhaps its short range and limited connections i.e. only up to eight devices can connect be connected simultaneously. 4. Conclusion The main aims of Bluetooth are to provide universal radio interference for ad hoc wireless connectivity at low cost, delivering modest speed (1-3Mbps) short range (1-100M) and low power consumption. Bluetooth is a very powerful tool. This technology has proven to be very cost effective and powerful. Over the years we have seen rapid enhancements in this technology. This technology has replaced the previously famous infrared technology which was dependent on line of sight connections. Through Bluetooth one can achieve an effective data transfer rate and easier connectivity regardless the weather conditions. References 1. Kumar Bala C, Klien Paul, Thomson Tin, Thomson J. Timothy; Bluetooth application programming with Java applications 2. Iniewski Krzysztof; Wireless Technologies: Circuit, Systems, Devices 3. Miller Stewart S.; WiFi Security 4. Patrick David, Morrow Robert; Wireless network Co-Existence 5. Ganguly Madushree; Getting Started With Bluetooth 6. Kelly Jod, Schaub Keith B.; Production Testing of RF and System-on-Chip Devices for Wireless 7. Nicholas Randall K., Lekkas Panos C.; Wireless Security: Models, Threats and Solution 8. Golrnie Nada; Coexistance in Wireless Networks: Challenges and System Solutions 9. Prabhu C. S. R., Reddi Prathap A.; Bluetooth Technology and its Applications with Java and J2ME 10. Zolfaghari Ali Raza; Low-Power CMOS Design for Wireless Transceivers 11. Morrow Robert, Laroka James; Demystified: Operation and Use 12. Muller Scott; Upgrading and Repairing Networks 13. Hill Goff; The Cable and Telecommunication Professional References PSTN, IP

Going for the Look but Risking Discrimination Essay

In the society we all live in today, where outside beauty is emphasized more than inner beauty, businesses have realized how to utilize that view to their own benefit They have looked at trends and realized that it is profitable to hire those with outer beauty. However, since certain businesses are only hiring certain ethnicities in order to project that image, it has been questioned whether these businesses are discriminating. In the article, Going for the Look, but Risking Discrimination, it says that † hiring attractive people is not necessarily illegal, but discriminating on the basis of age, sex, and ethnicity is. The companies cannot help it that only certain types of people fit their marketing image and their hiring strategies are not exactly discrimination because they have nothing else against other people except that they aren’t selling material. Although it might be seen as discrimination in only hiring certain types of peoples, I agree with Cohen that it is a smart move to hire based on image because if is an effective marketing strategy. Image plays an important role in determining how much certain products can be sold. The differences in the prices of the clothes sold in for example, Walmart, and those of Nordstrom or Neiman Marcus is due to image. When you walk into places that look cheap and wear the clothes there, you do not feel all that glamorous. However, in designer stores, where all the models are what we call chic and all the products are in a fancy arrangement, everyone feels compelled to buy the product so that they can look like a million bucks. Also, chic models are featured in designer magazines such as Bazaar that give the impression to readers that if they have these certain items they can also be beautiful Because of this, Gucci,Louis Vuitton, and other brand items that are considered designer items can be sold at the price of thousands of dollars. This is beneficial for businesses because they can make a lot of money from items that do not take much to produce and also come from cheap labor probably. No one buys those bags because they are of particular good quality but just because the brand name tells others that you are â€Å"in† and that you are possibly rich. Looks are attractive to the eyes; that is human nature since it is the strongest sense and will not likely be subject to change. The first impression that someone always gets from another person is fbased on the way they look. Everyone basically has the same view on what is pretty and what is not and that view influences their decisions on what to buy. In a society where most people care about what they look like, it is essential for companies to portray an image that is attractive and makes the person want to look that certain way. Abercrombie and Fitch is an example of a store that excels at doing this. They hire buff guys and attractive white girls to portray a preppy, American style to be models and sellers. They also attract customers by appealing to another important human sense, smell; they spray the store with an intriguing perfume. When girls see good looking guys, they would want to walk into the store to check them out and the same for guys toward girls. This gives them an opportunity to also look at the clothes at the same time. This leads to increases in sales that generate profit and future profit. For the future profit, I mean that if many people go to a certain store, it would soon turn into a trend. Those that shop at the store would influence their friends to do so too. In some cases, businesses have to hire for image. If they do not do so, things become awkward and may not reflect a business’s culture. Since the United States is a diverse country with many ethnicities, this situation applies directly to this nation. Throuhout ths country, there are many restaurants that are designated to sell certain types of food such as Japanese, Chinese, Mexican, and many others. There are also areas that are designated to certain cultures such as Chinatown and Japantown. When customers walk in to those restaurants or areas, they immediately think that they should see people of a certain ethnicity working there. Also, the setup of the table and other decorations also seeks to portray a cultural image that influenced people’s views. Ths might seem stereotypical, but it has its practcalities. This cultural image gives the consumer an impression that the food made or the products sold are authentic, which is the whole reason that they visit those cultural places in the first place, which is to get a taste of other cultures. Cohen is correct in that hiring for image is essential for good business. It must be effective since all businesses pursue to do so. Hiring for image leads to the increased prices of product, increased sales of products, and can give the impression of authenticity which eventually leads to what businesses want, profit. It also is an important aspect in attracting the teenager group which is a large portion of consumers; Teens are well known for wanting to have a good image due to peer pressure and to be popular at school. The claim that businesses are discriminating are unreasonable; they may only be hiring certain types of people , but that is uncontrollable in pursuing to satisfy their customers’ wants and needs. They are only trying to do what they think will generate the most profit. If most people ask themselves, they would rather choose a place with good looking people than without. However, although it is beneficial for companies, the question of whether is it moral is another question. Is it right to not give others a chance just because they are not attractive even if they have more experience? That’s a very deep question that I think is very debatable.

If winter comes can spring be far away Essay

The quotation referred to is the last line of shelley’s famous poem, â€Å"Ode to the West Wind†. In the poem, the poet identifies himself with West Wind, which, to him, is both the destroyer and the preserver. The poet has dead thoughts which he would like to be scattered by the West Wind like dead leaves. In place of these dead thoughts, he wants new and fresh thoughts to be born in him. As from an extinguished hearth, ashes and sparks are spread by the wind so the poet wants his message of hope to be delivered to the frustrated mankind. As winter is sure to be followed by spring, in the same way, dark and unhappy days of life are bound to be followed by a period of happiness and joy. Winter is the symbol of desolation and barrenness whereas spring stands for joyousness and fruitfulness. The quotation assumes significant application to the present state of affairs. The man today is passing through a period of miserable existence. The days of darkness and frustration constitute the life of man. The world today is collapsing into a helpless state of boredom. The weariness, fret and fever of life have made man to deduce, â€Å"where but to think is to be full of sorrow†. We are crumbling under the mounting pressure of defeatism and self-frustration. Today various factors of life have made man morbidly tired of himself. In the midst of intellectual, moral and spiritual bankruptcy, the forces of optimism though bleak, appear to be the only sustaining force. We in our frustration are made to think that life is not entirely devoid of joy and happiness. It is wrong on our part to lose faith in the ultimate goodness of things. We must realize that in the course of life good and evil days follow in succession. Each follows the other as night follows the day. Indeed, it is human nature to welcome joys and condemn sorrows. But we must bear sufferings with patience and fortitude in the hope that as spring follows winter, joy will follow sorrow. To be able to be the streak of silver lining that edges the threatening clouds of despair is the prerogative of only a few. Most of us only concern ourselves with the present and blink at future. Our vision is circumscribed by the difficulties and problems which confront us. The limits of the immediate cripple us. We wish but dare not hope. We work but dare not expect. We are apologists in anticipation and defeatist in our performance. The buoyant spirit of hope and happiness is lacking in us. It is essential that we cultivate the spirit of hopefulness. Optimism is the attitude of life which must be formed. An optimistic attitude is the healthy sign of life and struggle. It makes us self- reliant and grant fixity of purpose. It infuses a new spirit in our timid hearts and injects a vitalizing energy in our veins. Instead of being mere puppets in the hands of chance, faded notions and sordid illusions, it makes us persons of indomitable will and, lofty aspirations. It takes away passivity and grants pertinacity of efforts. It teaches fortitude, patience and perservance. It is rightly said, â€Å"Practice begets facility† therefore, it is better to wear out than to rust out in inactivity. Victor Hugo rightly said, â€Å"People do not lack strength, they lack will†.

A Rogerian Analysis of the Debate over Arizonas...

A Rogerian Analysis of the Debate over Arizonas Immigration Law 1. An introduction to the problem and a demonstration that the opponents position is understood. Americas illegal immigration problem is one of the most remarkable failures of the U.S. federal government. Undocumented illegal immigrants, many in our very own neighborhoods, are able evade the reach of our nations laws and regulations with remarkable ease. This is a huge source of anxiety for many tax-paying Americans, who perceive illegal immigrants as a strain on our public goods More pragmatically, illegal immigration causes economic uncertainty for Americans. Employers do not know what their payroll is going to look like and how the hiring of undocumented immigrants will affect their business. Moreover, the current illegal immigration problem promotes the exploitation of illegal immigrants for labor. Illegal immigrants, because of their precarious legal position, are often employed at sub-standard wages, without the employee benefits or job security enjoyed by U.S. residents. Arizonas new immigration law seeks to correct this problem by bringing illegal immigration out into the light. The law would require all immigrants to carry immigration papers on them at all times. (Archibold, 2010). In addition, it gives the police the authority to arrest and detain anyone that they suspect of being an illegal immigrant. Those people found to be in the country illegally will be sent back to their home