Saturday, September 21, 2019

Moduation Techniques | An Overview

Moduation Techniques | An Overview The evolution of wireless cellular technology from 1G to 4G has a similar aim that is capable to deliver high data rate signal so that it can transmit high bit rate multimedia content in cellular mobile communication. Thus, it has driven many researches into the application of higher order modulations. One of the focuses of this project is to study and compare the different types of Digital Modulation technique that widely being used in the LTE systems. Hence, before being able to design and evaluate this in computer simulation. A study is carried out on digital modulation and drilled down further on QPSK modulation schemes, and followed by the QAM modulation schemes. What is modulation? There are several definitions on modulation taken from several references as follows: Modulation is defined as the process by which a carrier wave is able to carry the message or digital signal (series of ones and zeroes). Modulation is the process of facilitating the transfer of information over a medium. Voice cannot be sent very far by screaming. To extend the range of sound, we need to transmit it through a medium other than air, such as a phone line or radio. The process of converting information (voice in this case) so that it can be successfully sent through a medium (wire or radio waves) is called modulation. Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information. One of the three key characteristics of a signal is usually modulated: its phase, frequency or amplitude. There are 2 types of modulations: Analog modulation and digital modulation. In analog modulation, an information-bearing analog waveform is impressed on the carrier signal for transmission whereas in digital modulation, an information-bearing discrete-time symbol sequence (digital signal) is converted or impressed onto a continuous-time carrier waveform for transmission. 2G wireless systems are realized using digital modulation schemes. Why Digital Modulation? The move to digital modulation provides more information capacity, compatibility with digital data services, higher data security, better quality communications, and quicker system availability. Developers of communications systems face these constraints: available bandwidth permissible power inherent noise level of the system The RF spectrum must be shared, yet every day there are more users for that spectrum as demand for communications services increases. Digital modulation schemes have greater capacity to convey large amounts of information than analog modulation schemes. Different types of Digital Modulation As mentioned in the previous chapter, there are three major classes of digital modulation techniques used for transmission of digitally represented data: Amplitude Shift Keying (ASK) Frequency Shift Keying (FSK) Phase Shift Keying (PSK) All convey data by changing some aspect of a base signal, the carrier wave (usually a sinusoid) in response to a data signal. For ASK, FSK, and PSK the amplitude, frequency and phase are changed respectively. Bit rate and symbol rate To understand and compare different PSK and QAM modulation format efficiencies, it is important to first understand the difference between bit rate and symbol rate. The signal bandwidth for the communications channel needed depends on the symbol rate, not on the bit rate. Bit rate is the frequency of a system bit stream. Take, for example, a radio with an 8 bit sampler, sampling at 10 kHz for voice. The bit rate, the basic bit stream rate in the radio, would be eight bits multiplied by 10K samples per second or 80 Kbits per second. (For the moment we will ignore the extra bits required for synchronization, error correction, etc.). A Quadrature Phase Shift Keying (QPSK) signal. The states can be mapped to zeros and ones. This is a common mapping, but it is not the only one. Any mapping can be used. The symbol rate is the bit rate divided by the number of bits that can be transmitted with each symbol. If one bit is transmitted per symbol, as with BPSK, then the symbol rate would be the same as the bit rate of 80 Kbits per second. If two bits are transmitted per symbol, as in QPSK, then the symbol rate would be half of the bit rate or 40 Kbits per second. Symbol rate is sometimes called baud rate. Note that baud rate is not the same as bit rate. These terms are often confused. If more bits can be sent with each symbol, then the same amount of data can be sent in a narrower spectrum. This is why modulation formats that are more complex and use a higher number of states can send the same information over a narrower piece of the RF spectrum. Phase Shift Keying (PSK) PSK is a modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (i.e. the phase of the carrier wave is changed to represent the data signal). A finite number of phases are used to represent digital data. Each of these phases is assigned a unique pattern of binary bits; usually each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. There are two fundamental ways of utilizing the phase of a signal in this way: By viewing the phase itself as conveying the information, in which case the demodulator must have a reference signal to compare the received signals phase against; (PSK) or By viewing the change in the phase as conveying information differential schemes, some of which do not need a reference carrier (to a certain extent) (DPSK). A convenient way to represent PSK schemes is on a constellation diagram. This shows the points in the Argand plane where, in this context, the real and imaginary axes are termed the in-phase and quadrature axes respectively due to their 90 ° separation. Such a representation on perpendicular axes lends itself to straightforward implementation. The amplitude of each point along the in-phase axis is used to modulate a cosine (or sine) wave and the amplitude along the quadrature axis to modulate a sine (or cosine) wave. In PSK, the constellation points chosen are usually positioned with uniform angular spacing around a circle. This gives maximum phase-separation between adjacent points and thus the best immunity to corruption. They are positioned on a circle so that they can all be transmitted with the same energy. In this way, the moduli of the complex numbers they represent will be the same and thus so will the amplitudes needed for the cosine and sine waves. Two common examples are binary phase-shift keying (BPSK) which uses two phases, and quadrature phase-shift keying (QPSK) which uses four phases, although any number of phases may be used. Since the data to be conveyed are usually binary, the PSK scheme is usually designed with the number of constellation points being a power of 2. Applications of PSK and QAM Owing to PSKs simplicity, particularly when compared with its competitor quadrature amplitude modulation (QAM), it is widely used in existing technologies. The most popular wireless LAN standard, IEEE 802.11b, uses a variety of different PSKs depending on the data-rate required. At the basic-rate of 1 Mbit/s, it uses DBPSK. To provide the extended-rate of 2 Mbit/s, DQPSK is used. In reaching 5.5 Mbit/s and the full-rate of 11 Mbit/s, QPSK is employed, but has to be coupled with complementary code keying. The higher-speed wireless LAN standard, IEEE 802.11g has eight data rates: 6, 9, 12, 18, 24, 36, 48 and 54 Mbit/s. The 6 and 9 Mbit/s modes use BPSK. The 12 and 18 Mbit/s modes use QPSK. The fastest four modes use forms of quadrature amplitude modulation. The recently-standardised Bluetooth will use p / 4-DQPSK at its lower rate (2 Mbit/s) and 8-DPSK at its higher rate (3 Mbit/s) when the link between the two devices is sufficiently robust. Bluetooth 1 modulates with Gaussian minimum shift keying, a binary scheme, so either modulation choice in version 2 will yield a higher data-rate. A similar technology, ZigBee (also known as IEEE 802.15.4) also relies on PSK. ZigBee operates in two frequency bands: 868-915MHz where it employs BPSK and at 2.4GHz where it uses OQPSK. Notably absent from these various schemes is 8-PSK. This is because its error-rate performance is close to that of 16-QAM it is only about 0.5dB better but its data rate is only three-quarters that of 16-QAM. Thus 8-PSK is often omitted from standards and, as seen above, schemes tend to jump from QPSK to 16-QAM (8-QAM is possible but difficult to implement). QPSK QPSK is a multilevel modulation techniques, it uses 2 bits per symbol to represent each phase. Compared to BPSK, it is more spectrally efficient but requires more complex receiver. Constellation Diagram for QPSK The constellation diagram for QPSK with Gray coding. Each adjacent symbol only differs by one bit. Sometimes known as quaternary or quadriphase PSK or 4-PSK, QPSK uses four points on the constellation diagram, equispaced around a circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with Gray coding to minimize the BER twice the rate of BPSK. Figure 2.5 depicts the 4 symbols used to represent the four phases in QPSK. Analysis shows that this may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the data-rate of BPSK but halve the bandwidth needed. Four symbols that represents the four phases in QPSK Although QPSK can be viewed as a quaternary modulation, it is easier to see it as two independently modulated quadrature carriers. With this interpretation, the even (or odd) bits are used to modulate the in-phase component of the carrier, while the odd (or even) bits are used to modulate the quadrature-phase component of the carrier. BPSK is used on both carriers and they can be independently demodulated. As a result, the probability of bit-error for QPSK is the same as for BPSK: However, with two bits per symbol, the symbol error rate is increased: If the signal-to-noise ratio is high (as is necessary for practical QPSK systems) the probability of symbol error may be approximated: As with BPSK, there are phase ambiguity problems at the receiver and differentially encoded QPSK is more normally used in practice. As written above, QPSK, are often used in preference to BPSK when improved spectral efficiency is required. QPSK utilizes four constellation points, each representing two bits of data. Again as with BPSK the use of trajectory shaping (raised cosine, root raised cosine etc) will yield an improved spectral efficiency, although one of the principle disadvantages of QPSK, as with BPSK, is the potential to cross the origin, that will generate 100% AM. QPSK is also known as a method for transmitting digital information across an analog channel. Data bits are grouped into pairs, and each pair is represented by a particular waveform, called a symbol, to be sent across the channel after modulating the carrier. QPSK is also the most commonly used modulation scheme for wireless and cellular systems. Its because it does not suffer from BER degradation while the bandwidth efficiency is increased. The QPSK signals are mathematically defined as: Implementation of QPSK QPSK signal can be implemented by using the equation stated below. The symbols in the constellation diagram in terms of the sine and cosine waves used to transmit them is being written below: This yields the four phases p/4, 3p/4, 5p/4 and 7p/4 as needed. As a result, a two-dimensional signal space with unit basis functions The first basis function is used as the in-phase component of the signal and the second as the quadrature component of the signal. Therefore, the signal constellation consists of the signal-space 4 points The factors of 1/2 show that the total power is divide evenly among the two carriers. QPSK systems can be implemented in a few ways. First, the dual data stream is divided into the in-phase and quadrature-phase components. These are then independently modulated onto two orthogonal basis functions. In this implementation, two sinusoids are used. Next, the two signals are superimposed, and the resulting signal is the QPSK signal. Polar non-return-to-zero encoding is also being used. These encoders can be located before for binary data source, but have been located after to illustrate the theoretical dissimilarity between digital and analog signals concerned with digital modulation. The matched filters can be substituted with correlators. Each detection device uses a reference threshold value to conclude whether a 1 or 0 is detected. Quadrature Amplitude Modulation (QAM) Quadrature amplitude modulation (QAM) is both an analog and a digital modulation scheme. It is a modulation scheme in which two sinusoidal carriers, one exactly 90degrees out of phase with respect to the other, which are used to transmit data over a given physical channel. Because the orthogonal carriers occupy the same frequency band and differ by a 90degree phase shift, each can be modulated independently, transmitted over the same frequency band, and separated by demodulation at the receiver. For a given available bandwidth, QAM enables data transmission at twice the rate of standard pulse amplitude modulation (PAM) without any degradation in the bit error rate (BER). QAM and its derivatives are used in both mobile radio and satellite communication systems. The modulated waves are summed, and the resulting waveform is a combination of both phase-shift keying (PSK) and amplitude-shift keying, or in the analog case of phase modulation (PM) and amplitude modulation. In the digital QAM case, a finite number of at least two phases and at least two amplitudes are used. PSK modulators are often designed using the QAM principle, but are not considered as QAM since the amplitude of the modulated carrier signal is constant. In 16 QAM 4 different phases and 4 different amplitudes are used for a total of 16 different symbols. This means such a coding is able to transmit 4bit per second. 64-QAM yields 64 possible signal combinations, with each symbol representing six bits (2^6 = 64). The yield of this complex modulation scheme is that the transmission rate is six times the signaling rate. This modulation format produces a more spectrally efficient transmission. It is more efficient than BPSK, QPSK or 8PSK while QPSK is the same as 4QAM. Another variation is 32QAM. In this case there are six I values and six Q values resulting in a total of 36 possible states (66=36). This is too many states for a power of two (the closest power of two is 32). So the four corner symbol states, which take the most power to transmit, are omitted. This reduces the amount of peak power the transmitter has to generate. Since 25 = 32, there are five bits per symbol and the symbol rate is one fifth of the bit rate. The current practical limits are approximately 256QAM, though work is underway to extend the limits to 512 or 1024 QAM. A 256QAM system uses 16 I-values and 16 Q-values giving 256 possible states. Since 2^8 = 256, each symbol can represent eight bits. A 256QAM signal that can send eight bits per symbol is very spectrally efficient. However, there is some drawbacks, the symbols are very close together and are thus more subject to errors due to noise and distortion. Such a signal may have to be transmitted with extra power (to effectively spread the symbols out more) and this reduces power efficiency as compared to simpler schemes. BPSK uses 80 K symbols-per-second sending 1 bit per symbol. A system using 256QAM sends eight bits per symbol so the symbol rate would be 10 K symbols per second. A 256QAM system enables the same amount of information to be sent as BPSK using only one eighth of the bandwidth. It is eight times more bandwidth efficient. However, there is a drawback too. The radio becomes more complex and is more susceptible to errors caused by noise and distortion. Error rates of higher-order QAM systems such as this degrade more rapidly than QPSK as noise or interference is introduced. A measure of this degradation would be a higher Bit Error Rate (BER). In any digital modulation system, if the input signal is distorted or severely attenuated the receiver will eventually lose symbol clock completely. If the receiver can no longer recover the symbol clock, it cannot demodulate the signal or recover any information. With less degradation, the symbol clock can be recovered, but it is noisy, and the symbol locations themselves are noisy. In some cases, a symbol will fall far enough away from its intended position that it will cross over to an adjacent position. The I and Q level detectors used in the demodulator would misinterpret such a symbol as being in the wrong location, causing bit errors. In the case of QPSK, it is not as efficient, but the states are much farther apart and the system can tolerate a lot more noise before suffering symbol errors. QPSK has no intermediate states between the four corner-symbol locations so there is less opportunity for the demodulator to misinterpret symbols. As a result, QPSK requires less transmitt er power than QAM to achieve the same bit error rate. Implementation of QAM First, the incoming bits are encoded into complex valued symbols. Then, the sequence of symbols is mapped into a complex baseband waveform. For implementation purposes, each complex multiplication above corresponds to 4 real multiplications. Besides, and will be the real and imaginary parts of = + iand assume that the symbols are generated as real and imaginary parts (as opposed to magnitude and phase, for example). After being derived, we will get and. From (1), x (t) becomes. This can be understand as two parallel PAM systems, followed by double-sideband modulation by quadrature carriers and. This realization of QAM is called double-sideband quadrature-carrier (DSB-QC) modulation. A QAM receiver must first demodulate the received waveform y(t). Assuming the scaling and receiver time reference discussed before, this received waveform is assumed to be simply y(t) = x(t) + n(t). Here, it is being understood that there is no noise, so that y(t) is simply the transmitted waveform x(t). The first task of the receiver is to demodulate x(t) back to baseband. This is done by multiplying the received waveform by both and. The two resulting waveforms are each filtered by a filter with impulse response q(t) and then sampled at T spaced intervals. The multiplication by at the receiver moves the positive frequency part of x(t) both up and down in frequency by, and does the same with the negative frequency part. It is assumed throughout that both the transmit pulse p(t) and the receive pulse q(t) are in fact baseband waveforms relative to the carrier frequency (specifically, that and for). Thus the result of multiplying the modulated waveform x(t) by yields a response at baseband and also yields responses around and. The receive filter q(t) then eliminates the double frequency terms. The effect of the multiplication can be seen by both at transmitter and receiver from the following trigonometric identity: Thus the receive filter q(t) in the upper (cosine) part of the demodulator filters the real part of the original baseband waveform, resulting in the output Assuming that the cascade g(t) of the filters p(t) and q(t) is ideal Nyquist, the sampled output retrieves the real part of the original symbols without intersymbol interference. The filter q(t) also rejects the double frequency terms. The multiplication by similarly moves the received waveform to a baseband component plus double carrier frequency terms. The effect of multiplying by at both transmitter and receiver is given by Again, (assuming that p(t) * q(t) is ideal Nyquist) the filter q(t) in the lower (sine) part of the receiver retrieves the imaginary components of the original symbols without intersymbol interference. Finally, from the identity, there is no crosstalk at baseband between the real and imaginary parts of the original symbols. It is important to go through the above argument to realize that the earlier approach of multiplying u(t) by for modulation and then by for demodulation is just a notationally more convenient way of doing the same thing. Working with sines and cosines is much more concrete, but is messier and makes it harder to see the whole picture. Modulation and transmission of QAM In general, the modulated signal can be represented by Where the carrier cos(wct) is said to be amplitude modulated if its amplitude is adjusted in accordance with the modulating signal, and is said to be phase modulated if (t) is varied in accordance with the modulating signal. In QAM the amplitude of the baseband modulating signal is determined by a(t) and the phase by (t). The in phase component I is then given by This signal is then corrupted by the channel. In this case is the AWGN channel. The received signal is then given by Where n(t) represents the AWGN, which has both the in phase and the quadrature component. It is this received signal which will be attempted to demodulate. Reference Fundamentals of Communication SystemsDescription:, by John G. Proakis, Masoud Salehi Description: Cross-layer resource allocation in wireless communications: techniques and Models from PHY and MAC Layer Interactionby Ana I. Pà ©rez-Niera, Marc Realp Campalans Digital Communication: Third Edition, by John R. Barry, Edward A. Lee, David G. Messerschmit OFDM for wireless multimedia communications by Richard Van Nee, Ramjee Prasad Modern Quadrature Amplitude Modulation by W.T Webb and L.Hanzo Digital Signal Processing in Communication Systems by Marvin E.Frerking COPD: a Clinical Case Study COPD: a Clinical Case Study Jerry Corners Introduction Chronic Obstructive Pulmonary Disease (COPD) is the fifth leading cause of morbidity and mortality in the UK and fourth in the world (Hurd 2000; Soriano 2000). Though other causes exist, like genetics and environmental pollution, tobacco smoke is by far the leading etiology of this disease (Pride 2002). It may seem axiomatic that if cigarette smoking is the cause of COPD, cessation (or avoidance) of smoking is the prevention. However, despite extensive public education, smoking is still common among men and women in the UK and even when people do quit, relapse within the first year is common (Lancaster et al. 2006). Therefore our attention as caregivers needs to be focused upon methods of cessation that produce lasting results. To illustrate the diagnosis, management, both short- and long-term, and what Mike can expect from treatment as reflected in the medical literature, we present the following case. Pathophysiology of COPD COPD is a chronic disease in which decreased airflow is related to airway smooth muscle hypereactivity due to an abnormal inflammatory reaction. Inhalation of tobacco products causes airway remodeling, resulting ultimately in emphysema and chronic bronchitis (Srivastava, Dastidar, Ray 2007). COPD is a complex inflammatory disease that affects both lung airways and lung parenchyma. The modern focus of the pathophysiology of COPD is centered around this inflammation and it is now recognized that systemic inflammation is responsible for many of the extrapulmonary effects of cigarette smoke inhalation (Heaney, Lindsay, McGarvey 2007). The Clinical Case Study Diagnosis Mike is a 54 year old, self-employed grandfather who smokes 40 cigarettes daily. He was recently diagnosed with COPD based on an FEV1 of 66% of predicted (Halpin 2004). According to Halpin (2004), â€Å"There are still no validated severity assessment tools that encompass the multidimensional nature of the disease, and we therefore continue to recommend using FEV1 as a percentage of the predicted as a marker of the severity of airflow obstruction, but acknowledge that this may not reflect the impact of the disease in that individual. We have changed the FEV1 cut off points and these now match those in the updated GOLD and new ATS/ERS guidelines, although the terminology is slightly different: an FEV1 of 50–80% predicted constitutes mild airflow obstruction, 30–49% moderate airflow obstruction, and According to these criteria, Mike has mild airflow obstruction and will be treated accordingly. But no matter what stage he is at or what pharmacologic interventions are prescribed, we are nevertheless obliged to offer this patient access to an effective nicotine cessation program while in hospital. Treatment Acutely, the mainstays of treatment for Mike’s level of disease are inhalation and possibly oral therapy along with pulmonary rehabilitation (Cote Celli 2005;Paz-Diaz et al. 2007). Of course underlying bronchpulmonary infection is treated with appropriate anitmicrobial therapy. Inhalation and Oral Therapy Bronchodilators Of the three classes of bronchodilator therapy, ÃŽ ²-agonists, anticholinergic drugs and methylxanthines, all appear to work by relaxation of the airway smooth muscles, which allows emptying of the lung and increased tidal volume, with an increase in FEV1 with increase in the total lung volume and dyspnea, subjective air-hunger, significantly improved, especially during exercise (Celli Macnee 2004c). Combining short- and long-acting bronchodilators appears to improve lung function better than either alone, and so Mike will be treated with a combination of salbutamol and (albuterol)/ipratropium. There are many other agents that could be used that have shown to be effective in mild disease, such as Mike’s (Celli Macnee 2004b). Corticosteroids Inflammation is often part of the acute phase of COPD exacerbations and therefore part of Mike’s therapy will be inhaled corticosteroids. Many studies have shown that inhaled corticosteroids produce at least some improvement in FEV1 and ventilatory capacity. It is often necessary for a trial of medication to confirm that a given patient will respond to inhaled corticosteroid treatment (Celli Macnee 2004a). Ries ( 2007) claims that inhaled corticosteroids have become the standard of care for patients with COPD, in all phases of severity (Salman et al. 2003). Mike will be offered inhaled corticosteroids. Pulmonary Rehabilitation According to a statement of the American Thoracic Society, â€Å"[Pulmonary rehabilitation is] a multidisciplinary programme of care for patients with chronic respiratory impairment that is individually tailored and designed to optimise physical and social performance and autonomy†. The Pulmonary Rehabilitation Program Exercise Garrod ( 2007) has shown convincing evidence that exercise significantly modifies systemic inflammation, as measured by CRP and IL-6 levels, that plays such an important role in the pathogenesis of COPD. But rather than target just the pulmonary musculature, Sin et al. ( 2007) have suggested that the skeletal muscle dysfunction and reduced exercise tolerance, which are important extrapulmonary manifestations of COPD, could in fact be due to the systemic inflammation that is important in COPD. Therefore, Mike will be placed on a regimen of weight training designed to improve his over all muscle strength. In addition he will be offered aerobic exercise treadmill sessions to improve his exercise tolerance, similar to cardiac rehabilitation (Leon et al. 2005). Nutritional Support General nutritional status is related to COPD severity (Budweiser et al. 2007;Ischaki et al. 2007) and mortality (Felbinger Suchner 2003). The cachexia of COPD is a common sign of end-stage pulmonary disease. Mike has mild disease and would not be expected to be suffering from malnutrition. However, an evaluation by a nutritionist and possible early correction of any deficits are part of his pulmonary rehabilitation. Psychological Support Depression, anxiety, and somatic symptoms are valid indicators of psychological distress in COPD (Hynninen et al. 2005) and quality of life (Arnold et al. 2006), two very important nursing issues. Much of the psychological distress is related to a sense of personal control because the illness, especially in its late stages, is so often accompanied by a feeling of loss of control in one’s life. Mike is still self-employed and with his mild impairment, he is not likely to be feeling these issues, yet. However caregivers need to be acutely aware that his quality of life may depend upon recognition and early intervention in the future (Gudmundsson et al. 2006;Oga et al. 2007). To that end he will have a psychological evaluation while in hospital to screen for depression or anxiety symptoms. Educational Support There are many areas that are very important to Mike as he goes through his pulmonary rehabilitation. In an initial interview, he needs to know what he can and cannot expect from treatment. He needs a person to explain that the damage done so far is not reversible but that there are many treatments available that will allow him to live a good life, if he stops further cigarette use. Issues of promoting a healthy lifestyle, muscle wasting and psychological adjustment are all treatable with information, when it is presented in a sympathetic, firm, supportive atmosphere. Mike needs to know what to expect in the future, if he is able to quit smoking, and if he does not quit smoking. He may not like to hear the truth, but his quality of life will benefit in the years to come from a clear, honest educational program. In addition Mike needs to understand that he may have exacerbations from time to time and that early intervention by his generalist or pulmonologist are mandatory to avoid more serious consequences. Education that stresses the value of a healthy lifestyle, including regular exercise according to the regimen established in hospital, is very important. Also, education can help considerably in preventing the wasting that, though probably not present now, may become important in the future. Smoking Cessation No subject in the COPD literature is more clear than the need for immediate cessation of exposure to all cigarette smoke; and, no subject is more frustrating to caregiver and patient alike, at least in those instances where there is poor compliance with the cigarette smoke proscription. We will explore with Mike some of the recommended strategies to accomplish this sometimes elusive, if vitally necessary goal. Nicotine Replacement Therapy (NRT) A recent article by West, et al. ( 2007) reported a prospective study of NRT that was large (2009 smokers), multicultural, involving smokers from the US, UK, Canada, France, and Spain, and of sufficient duration to render generalizable (â€Å"real world†) results. They concluded that NRT helps smokers’ cessation attempts and long-term abstinence rates. However, the 6% improvement rate was not large and this form of cessation therapy should be reserved for those who have tried and failed other methods or programmes. There are many forms of NRT, including nasal and oral nicotine sprays, gum, and patches of varying dosages, currently on the market, but whether they have significant one-year success rates over counselling is an arguable point in the literature. Since Mike now smokes 40 cigarettes daily, he will be offered the 15mg nicotine patch to help for the initial 20 weeks of cessation. Bupropion Therapy Buproprion is a dopamine agonist that has antidepressant effects but is also marketed as a smoking cessation agent. In a study comparing the nicotine patch with buproprion and controls (counselling only) by Uyar, et al. (Uyar et al. 2007), reported success of 26 % for the nicotine patch, 26% for buproprion, and 16% for counselling-only at the end of 24 weeks. As an interesting aside, they reported that those who had a Beck depression inventory above 13, i.e. were depressed at the onset of the study, were unsuccessful regardless of treatment or control group. However, because of the small numbers of smokers involved, there was no statistically significant difference between these groups. The authors conclude that counselling is as effective for cessation attempts as these pharmacologic treatments, and there are no known side effects of being in a control group. However, other studies (Tonnesen et al. 2003) have shown a significant effect of bupropion over placebo. Internet-Based Assistance Various groups have tried using an interactive website to help smokers stop smoking. Unfortunately they have yet to show significant positive findings. All that can be said about them is that the more often the smoker logs on to the site, the better his chances are that he will be successful (Japuntich et al. 2006;Mermelstein Turner 2006;Pike et al. 2007). Nurse-Conducted Behavioral Intervention In the UK Tonnesen et al. (Tonnesen, Mikkelsen, Bremann 2006) found that a combination of nurse-based counselling in conjunction with NRT in patients with COPD was more effective than placebo at 6 and 12 months. As one can readily imagine, there are a plethora of cessation strategies available to assist people in smoking cessation. However, there is no â€Å"silver bullet†, i.e. one method that fits everybody. It comes down to proper motivation, which we believe is related to education and perhaps other factors. All we can really be sure of is of that those who try, many will be successful, and try, try, again seems to be the best advice we can offer. But the most important lesson we can learn is to prevent use of this harmful and addictive substance in the first place. Teenage smoking prevalence is around 15% in developing countries and around 26% in the UK and US. Studies have shown that those who make it past 20 years of age are much less likely to succumb to this addiction (Grimshaw Stanton 2006). Conclusion Assuming Mike ceases to smoke cigarettes, and given a regimen of exercise appropriate to his physical functioning, and with a detailed and robust COPD rehabilitation programme, his prognosis is excellent. By far the most challenging days are yet to come as Mike begins to feel better and the educational materiel fades from his mind. Many smokers return to their fatal habit within a year. Many, though perhaps not all, could benefit from periodic follow-up sessions with a motivational nurse-counselor. 1902 words not counting references References Arnold, R., Ranchor, A. V., Koeter, G. H., de Jongste, M. J., Wempe, J. 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Medication versus motivation, Saudi.Med.J., vol. 28, no. 6, pp. 922-926. West, R. Zhou, X. 2007, Is nicotine replacement therapy for smoking cessation effective in the real world? Findings from a prospective multinational cohort study, Thorax. Page 1 of 11 Is Power the Same as Violence? Is Power the Same as Violence? Huang Li Introduction For a long time in history, the coercive side that power involves and the destructive results that power rivalry brings have all along depicted power as horrible and deterrent. It has been viewed as closely related to force and violence, or to a large extent very similar. It is only until the time of modern democratic societies that the meaning of power is gradually enriched with the increasing role of rational recognition in power relations. This essay intends to show that power is not the same as violence; it is more than that because of the most fundamental difference: rational recognition. Power is not only composed of coercive force that resembles violence, more importantly it involves the force of social recognition which violence is short of. Power is a mutually regulated communicative process rather than simply exercised by the powerful over the powerless. After identifying some basic differences between power and violence, this essay will focus on the discussion of power and power relations, to explore the major difference between power and violence rational recognition and why it is so. On one hand, it will show that power can create violence and it consists of coercive elements by demonstrating why power is not a one-way event; on the other hand, this essay will proof why power is more of mutual constraint that rational recognition and willingness of acceptance from others can identify power from violence. Scholars like Weber views power as means than ends, backed by violence, threat or inducement; Mann illustrates power as resources that can be occupied; Parsons and Foucault both intend to reconstruct power but still proceed in the realm of violence theory. This essay mostly follows the ideas of Honneth, Arendt, and Habermas, but attempts to avoid another extreme of equalizing power to purely power of rationality or power of consensus through communicative process. It sees power as a combination shaped by both coercive and rational forces, avoiding placing power in the opposite of violence since in history power has been devastating too and violence could be â€Å"an attempt to achieve justice† (Gilligan, 2000, 11). Basic Differences: Power Dependent on Numbers and Violence on Implements Arendt defines power in the context of groups of individuals, as â€Å"the human ability not just to act but to act in concert† (1972, 143). One individual alone does not generate power; power is the aggregate strength of all the individuals in a group. So the exercise of power is preconditioned with numbers. Unlike power, violence does not require numbers or groups in order to be violence. Rather, it depends on implements to â€Å"multiply strength, to a point at which they can replace it† (Arendt, 1972, 145), instead of becoming power. Violence is designed and applied for expanding one’s physical strength that it is totally instrumental and always a means for certain purpose; but power in itself can serve as an end. There is categorical distinction in this sense. Is Power a One-way Event? If violence is not the end, it is a â€Å"blinding rage that speaks through the body† (Gilligan, 2000, 55) and the hope of those who do not possess power. So violence could start from the powerless against the powerful, such as slaves against slave owners, or the ruled against the ruling. Such power relations see those in power as subjects and those under the power objects, to be controlled and manipulated. Power in such a one-way model is pillared by certain condition which is understood as its source. Mann identifies four sources of power: ideology, economy, military and politics (1970, 35) that people who occupy these resources will own power. A society is thus divided into two kinds of people in a one-way power structure. If the will of those in power is not executed, the ruled will be punished, possibly by violence, and they stand up to resist, with violence, for power. It is not difficult to reach the conclusion that in a binary opposition, power and violence can be cause and effect of each other and they are actually two sides of one coin. Derived from the Hobbesian proposition, it should be admitted that power do contain certain aspects of violence, historically or theoretically, when it is understood as something can be possessed like resources. However, what can be relied upon by the ruled class for their struggle if they don’t have any resources at all? In the case of ideology, any interpretation by the powerless will be meaningless and invalid, why would those in power necessitate oppressing and controlling them? Will there be any struggle inside the powerful and the powerless? Power is Mutually Agreed: Rational Recognition of Imbalance Clearly such violence-illustrated power is not the whole picture. Power is more than something can be owned and preserved; it only exists when is â€Å"exercised by some on others† (Foucault, 2003, 126) and will be â€Å"dispersed once the group ceases to exist† (Arendt, 1972, 143). Power is the â€Å"structural feature of human relations† (Elias, 1998, 188). Slaves have power over the slave owner too as long as they are valuable to him; their power depends on the degree to which their owner relies on them; so is the case between parents and children, and teachers and students. In reality, if an individual or group acquires the power to implement self will, such power is not fully discovered if the ruled do not acknowledge it; they do not just accept power, they make certain responses to it based on their own will. So power is not necessarily a unilateral process where one is dominated and controlled by the other; it exists in interdependence and mutual constraint among people with differentiated level of resources; it is both â€Å"pervasive and negotiated† (Gosling, 2007, 3). Not only will power be regulated and negotiated between the ruling and the ruled, but also within themselves. The former power relations are coercive because the power is legitimized by laws, regimes or organizations. The latter may be absent from these elements but power relations and interactions still takes place because some individuals will still tend to persuade and influence others in exchange for recognition of authoritative positions, through knowledge, money and pers onal network, in order to implement one’s own will and better response to such power relations at the â€Å" most micro levels† ( In fact, power relations at the micro level are where those power relations between hierarchies originate. At the very micro level, it is to a larger extent the power of rational recognition rather than the power of force that leads to certain power relations. Since interdependence always exists among people regardless of their power positions, power relation is a dynamicequilibrium and mutual power regulation is always there, even in the extreme case of slaves and slave owner. However if the power relations regulated by rational recognition are neglected, those based on them at the macro levels will be shaken. Although power relations are mutually regulated and communicative rational, the degrees of interdependence are different, which lead to unbalanced relationships among the players. In fact, power to some extend is just demonstrated by such imbalance; violence too is demonstrated in kind of imbalance; but power goes further if it is identified different as it means others’ recognition of such imbalance. When the imbalance is maintained in the form of pure coercive force, it is violence; when rational force is included, it starts to turn into power. Under any circumstance, power is the combination of both. Bifacial Nature of Power When examined under Habermas’s context, in the terms of â€Å"facts and norms†, power includes two dimensions as well, described as â€Å"facticity and validity†. The facticity dimension reveals the coercive nature of power that power, in any kind of form, potentially contains coercive forces in realizing goals and excluding all impediments. Such aspect of power is underpinned by violence or the threat of violence which exist as real and concrete facts. The other dimension is validity that refers to power’s tendency of gaining rational recognition from the others. Though the two dimensions coexist in power and so does the tensions between them, they are not always equally demonstrated. In a tyrannic society, power shows more coercive side of its nature whereas the power of rational recognition is more compelling in a democratic society. Violence Does Not Create Power but Destroys It As discussed so far, power involves elements of coercion and it can generate violence. But is it the case the other way around that violence can also produce power? In many scholars’ understanding, violence is viewed as a resource that â€Å"can be mobilized to enforce the compliance of others† (Ray, 2011, 13). Usually exercised by those in power, it creates the ability of an individual or group to achieve their own goals or aims even if others are trying to prevent them from realizing them. Thus violence is naturally seen as a source of power. However, is what one has gained by using violence, or what violence has created, truly power? When a government turns into violence against its own people or a foreign country, or an individual uses violence to acquire what is wanted, it is generally because power in their hand is running out and violence is the last resort. While such a government or individual does not lack means of violence, they are in fact in short of power; to be more accurate, they are lack of recognition of their wills by others. When violence as a resource is utilized against another, it not only consumes the resource itself but also diminishes what little power is left over. Violence is always the choice of the impotent, not the powerful. Viewed in this sense, violence only equals to coercive means regardless of other’s recognitions. It emerges when â€Å"social ensembles are incoherent, fragmented and decadent† (Wieviorka, 2009, 165). Therefore, as violence â€Å"inevitably destroys power, it can never generate power† (Arendt 1972, 152). There is no â€Å"continuity between obedience to command (the enactment of power) and obedience to law (as legitimate authority)† (Ray, 2011, 13). A government that solely relies on violence has no power and â€Å"tyranny is both the least powerful and the most violent form of government† (Arendt, 1972, 140). Reproduction of Power and Violence In the past, power is largely associated with gains of interests, or occupation of social resources like those identified by Michael Mann. In Honneth’s Struggle for Recognition, he reveals the â€Å"force of recognition† behind power. Once this point is taken into consideration, the reproduction of power will no longer be just about violent competition, or rivalry for social resources, rather, the willingness of others to acknowledge and accept. Arendt insists that violence does not give rise to power because she believes that social recognition is missed in violence. When power is taken as a combination of coercive and rational forces, it may be understood as a relationship of mutual recognition among a group of people backed by the potential threats each have for others. Therefore, the reproduction of power naturally includes attempts of occupying as much resources as possible for greater coercive capability; it is indispensible and more important to gain recognition from others. If authoritative coercion is a source of power, it is not the only source. Rational recognition also generates power. So political power is not the potential capability to implement one’s own goals or realize one’s own interests, it relies on those over whom the power is exercised to define what power truly is. The power of a government is conferred through people’s recognition, or in another word, the coercive force of the government is agreed by the people. When applied at the micro level, it can also be stated that the power between individuals does not only arise in the lure of interests or in the constraint of violence, it rests in the one’s recognition of others’ will and authority over oneself. Only when such recognition exists, the will can be implemented without enforcement and power becomes power rather than violence. Right to the contrary, what violence concerned is how one’s own goals are reached through forceful means. Violence is always destructive but never constructive. Terrorist attacks do not increase the power of the terrorists, it grows intimidation and controls; meanwhile it gives the government power to do what it cannot do in the past and to expand its sphere of influence. Violence reinforces state power and makes more violence necessary in order to maintain and reproduce violence. Conclusion When power is perceived under violence theory, man is to be controlled and manipulated, instrumentalized in a subject-object relationship which is all about one trying to dominate the other in struggles for power resources, in order to preserve power and oppress others from grabbing it. Power in that sense equals to violence, which is observed throughout history. While power will fail should it be not supported by forceful and compulsory means, it is not sufficient to have these only. What cannot be overlooked is an â€Å"infinitely complex network of ‘micropowers’, of power relations that permeate every aspect of social life† (Sheridan 1980: 139). Where rational recognition also creates power, power can be compellent but not violent simultaneously. Thus, viewed in a rational context, man becomes a dialogue partner with the coexistence of competition, compromise and cooperation. Mutual regulation and interdependence is the one of the features of such power relationship and mutual understanding and respect is part of the foundation of power reproduction. Recognition of imbalance between people, particularly from those over whom power is exercised, legitimizes power and differentiates it from violence. Power and violence are not the same; the former is more than the latter. Power â€Å"cannot be overthrown and acquired once and for all by the destruction of institutions and the seizure of state apparatuses† (Sheridan 1980: 139). Unlike violence, power is not unitary and its exercise binary; it is interactive; a very important part of power struggle is the rivalry for recognition. In modern democratic societies, the violence aspect of power is decreasing and increasingly giving way to the role of rational recognition in shaping power. The major resources of power is no longer just about military or economy of one’s own capability, it is more about how convincing it is for others to accept, and in the end, how well one’s power is recognized and received by others. Bibliography: Arendt, Hannah, (1972), â€Å"On Violence† inCrises of the Republic, New York: Harcourt Brace Company, pp. 103-184. Elias, Norbert, (1998), â€Å"On Civilization, Power, and Knowledge†, Chicago: University of Chicago Press, chapter 7. Foucault, Michel, (2003), â€Å"The Subject and Power† inThe Essential Foucault, P. Rabinow, ed., New York: The New Press, pp. 126-144. Gilligan, James, (2000), â€Å"Violence: Reflection on Our Deadliest Epidemic†, London: Jessica Kingsley, pp. 1-60. Gosling, David, (2007), â€Å"Micro-Power Relations Between Teachers and Students Using Five Perspectives on Teaching in Higher Education†, available at: power relations isl 2007.pdf, last accessed on 7 Dec. 2014. Habermas, J., (1996), â€Å"Between Facts and Norms†, Massachusetts: the MIT Press. Honneth, Axel, (1996), â€Å"The Struggle for Recognition: The Moral Grammar of Social Conflicts†, Massachusetts: the MIT Press. Mann, Michael, (1970), â€Å"The Source of Social Power†, Cambridge University Press, chapter 2, pp. 34-72., (2007), Key concepts, available at:, last accessed on 6 Dec. 2014. Ray, Larry, (2011), â€Å"Violence and Society†, London: Sage, pp. 6-23. Shabani, A. Payrow, (2004), â€Å"Habermas’Between Facts and Norms: Legitimizing Power?† available at:, last accessed on 6 Dec. 2014. Wieviorka, Michel, (2009), â€Å"Violence: A New Approach†, London: Sage, pp. 165.

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