Modulation Techniques in Wireless Communication - Term Paper Example

MODULATION TECHNIQUES IN WIRELESS COMMUNICATION Student‘s Name: Course Title: Date: Abstract 2 1.0 Introduction 3 2.0 Usability of Modulation Technique 4 3.0 Technologies involved in wireless communication modulation technique 5 3.1 Image based modulation techniques 5 3.1.0 M-Ary Quadrature amplitude modulation 5 3.1.1 Hierarchical quadrature amplitude modulation (HQAM) 5 3.2 Digital based techniques of modulation 6 3.2.0 On-off keying (OOK) 6 3.2.1. 6 3.2.2 D 7 3.2.3. Diffe 7 3.3.4. 8 3.3.5.) 9 5.0 Conclusion 10 Abstract Modulation techniques is an important aspect that should be consider in the design of all communication system so as to ensure accurate and effective communication takes place. This paper analyses modulation techniques in wireless communication system in depth. The first section contains introduction part that gives background information of wireless communication modulation techniques as well as the aim of this paper. The second section discusses usability of modulation techniques in image transmission and infrared transmission. The third section discusses various modulation techniques uses in wireless communication. In the section the following techniques intensively discusses; M-ary Quadrature Amplitude Modulation, Hierarchical Quadrature Amplitude Modulation, on-off key, , Modulation Data Header and Digital Pulse Interval. In addition, the paper states limitation found in a few techniques as well as the advantages enjoyed for employing modulation in a system. Finally, the paper gives a brief summary of the discussion. 1.0 Introduction With modern technique of communication fast development, there is a significant increase in the demand for quality and reliability in transmission of data, an aspect that stimulate huge interest in techniques of modulation. Diversity in techniques of modulation permits transmission of varied bits per symbol and therefore attaining different efficiencies or throughputs (Kader et al. 2007). Infrared transmission being one of the modern techniques has gained popularity as an attractive high-speed indoor technology of wireless communication. Infrared transmission has got advantages: huge amount of available unregulated bandwidth; operation frequencies reuse in adjacent cells; has no electromagnetic interference over radio medium of transmission, that promote its use even where infrared communication is not desirable (Grubor et al. 2006). Selecting a technique of modulation is the one of the chief technical decision of all communication system design. Additionally, a modulation technique must be assessed against vital metrics which include Bandwidth efficiency, power efficiency and implementation simplicity (Ghassemlooy et al. 2007). This paper focuses on in depth analysis of wireless modulation techniques in free-space and optic fiber communication links. In this analysis different modulation techniques will be evaluated based on the vital metrics of modulation. 2.0 Usability of Modulation Technique Modulation techniques are used differently depending on the particular purpose to be accomplished. Different techniques are suitable for a certain form of transmission or can work best in a certain transmission condition than the other. For wireless image transmission HAQM is the best technique that can be applied because of its simplicity and efficiency in constellation of non-uniform signal that is applied to produce different protection degrees. The greatest strength for this modulation method is that different protection degrees are attained without bandwidth increase (Kader et al., 2007). According to Grubor et al. (2006) infra-red transmission has extensively different techniques of modulation technique and consequently it has gained popularity in wireless transmission technology. In order to attain the best signal output in infra-red systems, one has to deal with multipath dimension and channel dynamics simultaneously. To achieve this, one must consider modulation-adaptive schemes based on transmission of multiple-sub-carrier (Memon et al., 2009). As acknowledged from radio transmission multicarrier techniques of modulation, modulation deals intrinsically with multipath distortion and also permits for equalization of frequency-domain at the receiver. The systems of this kind adjusts the rate of transmission to the state of channel by assigning suitable formats of modulation to individual sub-carriers, giving assurance of exploiting the channel capacity effectively, while applying relatively simple electronic and optics signal processing. (Grubor et al., 2006). 3.0 Technologies involved in wireless communication modulation technique 3.1 Image based modulation techniques 3.1.0 M-Ary Quadrature amplitude modulation In M-ary signaling system, at least two bits are combined to create symbols as well as units of M attainable signals are transmitted in every period of a symbol. Generally, the probable signals’ number is M=2n , whereby n represents an integer. Based on frequency difference in repsect to amplitude or phase, this technique is termed as M-ary ASK, M-ary FSK or M-ary PSK. The modulation that changes both phase and amplitude is known as M-ary QAM (Kader et al. 2007). 3.1.1 Hierarchical quadrature amplitude modulation (HQAM) HQAM is a more efficient spectral, DC-free modulation system. Hierarchical system of transmission is comprised of hierarchical source coder as well as the matching channel coder, which divides information into a number of layers depending on layers significance, and communicates each layer according to the layers reliability. HQAP is a different way of offering an unequal error protection (UEP) to the transmitted bits of data, in which image data bits of high priority are positioned to most significant bit (MSB) in constellation points of modulation while the image data bits of low priority are positioned at least significant bits constellation points of modulation(Ibid, 2011). 3.2 Digital based techniques of modulation 3.2.0 On-off keying (OOK) OOK is the most image and diagrams reported technique of modulation in optical communication. It is a simple technique in which an optical pulse represents a bit one that occupies part of or entire bit duration while an optical pulse absence represent a bit zero. of communication –OOK signaling optimum receiver is the a threshold detector, match filter place that falls between 1-bit and 0-bit energies. In this kind of a channel, on-off keying with return-to-zero signaling need optical power of around 5logϒ (dB) above that would be needed by OOK containing data format of non-return-to-zero to attain similar bit error performance level, in presence of ϒ duty cycle. Without dispersion, the bit error probability Pbe for NRZ-OOK is calculated as Where R is photodiode responsively, P-1 is the mean transmission power, Rb represents bit rate of data and η represents spectral density of power of the double-sided noise (Ghassemlooy et al. 2007; Sui et al., 2009). 3.2.1. is a well-researched is a technique of orthogonal baseband used mainly in because of in contrast base-band renders PPM to be more suitable for hand-held devices where the main concern is reduced power consumption. PPP is commercially applied in such as palmtop, IrDA and laptop among others. contains one slot (whereby M represents an f a value greater than 0), probable time slots with empty residual slots. Pulse position corresponds to M-bit data input decimal value. In order to attain similar throughput, pulse duration of PPM is shorter than that of OKK by L/M factor. Certainly, its power efficiency superiority is attained at bandwidth requirement increase cost. With receiver threshold level set at the central point of high and low levels, the PPM error rate slot Pse is given as (Ghassemlooy et al. 2007). 3.2.2 D DPPM is an advanced PPM version where efficiency of power and bandwidth throughput or efficiency is improved by eliminating every empty slot, which goes after a pulse in symbol of a PPM. Therefore, length timeslot The average no. of DPPM slots in every symbol is given by which is approximately half of PPM. This gives likelihood for bandwidth efficiency or data throughput improvement. With each and every symbol of DPPM terminating with a pulse, there is capacity for an innate symbol harmonization to occur (Ibid, 2007). 3.2.3. Diffe D is the most recently proposed digital modulation technique. It is the most advantageous of all other schemes of modulation including DPPM, PPM, as well as Header Pulse Position Modulation (HPPM) with regard to capacity, bandwidth requirement, and power ratio of peak-to-average. DAPPM is comprised of Pulse Amplitude Modulation (PAM) and DPPM. The length of the 3…………L} whereas pulse amplitude is chosen A,}, in which case L and A represents The bits’ given by M = log2 (A x L). The empty slots’ average number prior the pulse may be reduced by aggregating the amplitude number within level A thus raising the attainable output in the practice. A DAPPM that is well designed will demand least bandwidth as compared to other similar techniques of modulation. Considering identical and independent distributed symbols, a DAPPM error rate slot can be given by: Where Po is the chance of getting empty slot, θi are levels of optimum threshold, chance of getting whereas Pc is maximum transmit power (Ibid, 2007). 3.3.4. data bits block is positioned to a unit symbols, which differs in length. All symbols starts with a pulse, followed by empty slots series, whose numerical value is dependent on data bits bloc decimal value being encoded. Actually, symbols of DPIM are the DPPM symbols reflection; thus they need the same average power and bandwidth. Additionally, the DPPM slot spectral properties and error rate are as well valid for DPIM. To minimize the inter-symbol interference induced by the channel, the utilization of one or more protector slot/band immediately after introduction of the pulse should be done. But to attain a suitable error performance for a channel that is highly dispersed, equalizer will still be required at the receiver (Ghassemlooy et al., 2007). 3.3.5.) a symbol may contain any of the two pre-defined title based on information of the input. The DH-PIM nth symbol Sn (hn, dn) sequence is comprised that information slots dn and symbol. code word input of the most significant bit, two varying headers Hi and Ho are considered to correspond to most significant bits (MSB) = 1 and 0, respectively. Hi and Ho contains equal time period of Th = ( +1) Ts, where Ts is the duration of the slot,  > 0 is an integer and are comprised of a guard and pulse band. For Hi and Ho the duration of the pulse is  Ts and  Ts/2 correspondingly. A is employed to accommodate symbols in lieu of zero. This information is comprised of dn empty slots. the data word input in case the symbol begins with Hi. 4.0 Limitation of modulation in wireless communication Modulation experiences limitation depending on the modulation technique applied. The QAM is more vulnerable to noise since are closer to each other thus a reduced noise level is required to take the signal to another decision point. Receivers for frequency or phase modulation are forced to employ limiting amplifiers, which are capable of removing any amplitude noise so as to improve reliance of noise. Additionally, when amplitude component of QAM is used, signal linearity has to be maintained. Regrettably, linear amplifiers consume extra power and they are low efficiency an aspect that makes them unattractive for mobile applications. Another technique with a limitation is DAPPM. DAPPM suffers from exaggerated DC component as well as high standard power therefore restricting its application to systems where power quality is not much considered. 5.0 Conclusion Wireless communication modulation is a technology applied to enhance efficient and reliable communication. Modulation is commonly applied in the communication system to reduce noise. the techniques used in Image transmission modulation includes M-ary QAM and HQAM and digital communication modulation contains techniques that are used in infrared transmission as well as wireless optical communication. The techniques used in the two forms of modulation though different they all tend to better the quality of the output. In digital transmission, communication is in form of pulse and thus the modulation techniques applied are meant to ensure no distortion takes place in the transmitted bits. The M-ary QAM, which a technique used in image transmission, is the only technique that has a lot of limitation which include vulnerability to noise a problem that is quite a challenge to many communication systems. References Read More

According to Grubor et al. (2006) infra-red transmission has extensively different techniques of modulation technique and consequently it has gained popularity in wireless transmission technology. In order to attain the best signal output in infra-red systems, one has to deal with multipath dimension and channel dynamics simultaneously. To achieve this, one must consider modulation-adaptive schemes based on transmission of multiple-sub-carrier (Memon et al., 2009). As acknowledged from radio transmission multicarrier techniques of modulation, modulation deals intrinsically with multipath distortion and also permits for equalization of frequency-domain at the receiver.

The systems of this kind adjusts the rate of transmission to the state of channel by assigning suitable formats of modulation to individual sub-carriers, giving assurance of exploiting the channel capacity effectively, while applying relatively simple electronic and optics signal processing. (Grubor et al., 2006). 3.0 Technologies involved in wireless communication modulation technique 3.1 Image based modulation techniques 3.1.0 M-Ary Quadrature amplitude modulation In M-ary signaling system, at least two bits are combined to create symbols as well as units of M attainable signals are transmitted in every period of a symbol.

Generally, the probable signals’ number is M=2n , whereby n represents an integer. Based on frequency difference in repsect to amplitude or phase, this technique is termed as M-ary ASK, M-ary FSK or M-ary PSK. The modulation that changes both phase and amplitude is known as M-ary QAM (Kader et al. 2007). 3.1.1 Hierarchical quadrature amplitude modulation (HQAM) HQAM is a more efficient spectral, DC-free modulation system. Hierarchical system of transmission is comprised of hierarchical source coder as well as the matching channel coder, which divides information into a number of layers depending on layers significance, and communicates each layer according to the layers reliability.

HQAP is a different way of offering an unequal error protection (UEP) to the transmitted bits of data, in which image data bits of high priority are positioned to most significant bit (MSB) in constellation points of modulation while the image data bits of low priority are positioned at least significant bits constellation points of modulation(Ibid, 2011). 3.2 Digital based techniques of modulation 3.2.0 On-off keying (OOK) OOK is the most image and diagrams reported technique of modulation in optical communication.

It is a simple technique in which an optical pulse represents a bit one that occupies part of or entire bit duration while an optical pulse absence represent a bit zero. of communication –OOK signaling optimum receiver is the a threshold detector, match filter place that falls between 1-bit and 0-bit energies. In this kind of a channel, on-off keying with return-to-zero signaling need optical power of around 5logϒ (dB) above that would be needed by OOK containing data format of non-return-to-zero to attain similar bit error performance level, in presence of ϒ duty cycle.

Without dispersion, the bit error probability Pbe for NRZ-OOK is calculated as Where R is photodiode responsively, P-1 is the mean transmission power, Rb represents bit rate of data and η represents spectral density of power of the double-sided noise (Ghassemlooy et al. 2007; Sui et al., 2009). 3.2.1. is a well-researched is a technique of orthogonal baseband used mainly in because of in contrast base-band renders PPM to be more suitable for hand-held devices where the main concern is reduced power consumption.

PPP is commercially applied in such as palmtop, IrDA and laptop among others. contains one slot (whereby M represents an f a value greater than 0), probable time slots with empty residual slots. Pulse position corresponds to M-bit data input decimal value. In order to attain similar throughput, pulse duration of PPM is shorter than that of OKK by L/M factor.

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