I j e e e c international journal of electrical, electronics issn no. Compared to the qpsk modulation now we have doubled the transfer rate when using the same symbol clock. We demonstrate fiber nonlinearity mitigation by using multiple optical phase conjugations opcs in the wdm transmission systems of both 8 x 32gbaud pdm qpsk channels and. Modulation is necessary in all of the above scenarios. So finally it can be concluded that qpsk has better ber performance than that of 16 qam but at the expense of spectral width. The following safety and common symbols may be used in this manual and on. As a result of their 90 phase difference they are in quadrature and this gives rise to the name. Nr supports quadrature phase shift keying qpsk, 16 quadrature amplitude modulation qam, 64 qam and 256 qam modulation formats for both uplink and downlink, as in lte. Often one signal is called the inphase or i signal, and the other is the quadrature or. You can select c as a number slightly less than 1, i.
If 8 different phases and 2 different amplitudes are used in a 16qam modulation system, sketch a constellation diagram that could be associated with the system you do not need to label the bits for each symbol, just show the symbols. The iq modulator is the same as the one we saw for the qpsk modulation. I am trying to do modulation and demodulation for 16qam and then trying to compare theoretical and simulated ber. Many data transmission systems migrate between the different orders of qam, 16qam, 32qam, etc. Modulation and data throughput are programmable from qpsk to 256 qam or up to 380 mbps, channel scheme programmable programmable. Any rectangular qam constellation is equivalent to superimposing two ask signals on quadrature carriers i and q components. With three bits per baud, the modulation becomes 8psk for eight different phase shifts representing three bits. In qpsk, modulation is symbol based,where one symbol contains 2 bits. The modulationdemodulation techniques were also checked in a real time. That is, the same constellation can be referred to by different names. Qam uses a mix of different amplitude levels and phase shifts to create. All about modulation part i basic concepts, signal space, constellations and phase shift keying modulations psk, qpsk, oqpsk, mpsk.
Pdf we propose a spatially superposed 16quadrature amplitude modulation qam system composed of two offsetquadrature phaseshift keying oqpsk. Publishers pdf, also known as version of record includes final page, issue. Ber over awgn channel for bpsk, qpsk, 8psk and 16qam the following matlab program illustrates the ber calculations for bpsk over an awgn channel. Quadrature phase shift keying 4 transitions, 2bitssymbol 8psk. Application note adaptive modulation qpsk, qam figure 4. This disadvantage can be overcome by using quadrature amplitude modulation qam. In qam two dsb signals are transmitted using the carrier of the same frequency but in phase quadrature. In this video, i will explain what is qam modulation and what is 16qam. Quadrature phase shift keying is more complex but doubles the data rate or achieves the same data rate with half the bandwidth. It is widely used for wireless lans, rfid and bluetooth communication any digital modulation scheme. And with 16psk, 16 phase shifts represent the four bits per symbol.
Here are three examples of commonly used modulation techniques, showing modulated signals in the time. But the bitssymbols mapping functions are different. A first quadrature phase shift keying qpsk modulator receives the first and second bits of received data and generates a first qpsk signal. Mary quadrature amplitude modulation qam 4 ee4900ee6720 digital communications suketu naik quadratureamplitude modulation qam applications qam rhymes with guam and vietnam is commonly used in communications example1. The i and q parts of the modulation symbol are given by the real and imaginary parts of the symbol mapping in the complex space. Docsis cable modems use 64qam, 256qam for downstream channel to home and qpsk, 16qam for the upstream channel. If 8 different phases and 2 different amplitudes are used in a 16 qam modulation system, sketch a constellation diagram that could be associated with the system you do not need to label the bits for each symbol, just show the symbols. Pdf spatially superposed 16qam system with two offsetqpsk.
Pratima sharma received 05 march, 2014 accepted 12 june, 2014. The implementation of digital modulator psk phase shift keying modulation and qam quadrature amplitude modulation on fpga is designed. Note that occasionally the phase shift is 180 degrees. Quadrature phase shift keying qpsk the generation and demodulation. A block diagram of such a system is shown in figure 2 below.
Then, the second stage will be the implementation of 16 qam using usrp hardware. The advantage of ofdm is its ability to cope with severe channel conditions compared to a single carrier modulation scheme but still maintaining the data rates. Hardware implementation of qpsk modulator for satellite communications 1. Digital communication relies on numerous different, albeit related, forms of digital modulation such as phase shift keying psk, biphase shift keying bpsk, quadrature phase shift keying qpsk or 4psk, and quadrature amplitude modulation qam. The qam modulation is more useful and efficient than the others and is almost applicable for all the progressive modems. Qpsk, 16 qam, 32 qam, 64 qam, 128 qam, 256 qam with true, low power lp. The epmp series can transport data over the wireless link using a number of different modulation modes ranging from 64qam to qpsk.
We can choose the signal constellation such that the amplitude is the same for all signal alternatives, by placing the signal vectors on a circle in the signal space. Performance of pm qpsk and pm 16qam coherent optical. Jan 24, 2014 the motivation for using qam in wireless communication comes from the fact that double side band am occupy twice the bandwidth requirement for base band signals. Dec 07, 2018 for the love of physics walter lewin may 16, 2011 duration. Digital to analog encoding modulation techniques ask. Quadrature phase shift keying an overview sciencedirect. Quadrature amplitude modulation, qam is a signal in which two carriers shifted in phase by 90 degrees i. The motivation for using qam in wireless communication comes from the fact that double side band am occupy twice the bandwidth requirement for base band signals. Determine if a qam signal is present at the receiver this power estimate can be easily formed by averaging the squared adc output samples rn. For 4 qam modulation, each symbol is of size k log2m log24 2 bits. Apr 25, 20 in this video, i will explain what is qam modulation and what is 16qam. When the power estimate pn exceeds a predetermined threshold for a period of time, a received qam signal is declared to be present.
Using different vector signal analyzers, the evm values for 16 quadraticamplitude modulation qam and 64 qam digitally modulated signals with certain distortions are measured. As mentioned above in the table, bpsk represents binary input 1 and 0 w. From basics to adaptive trelliscoded, turboequalised and spacetime coded ofdm, cdma and mccdma systems by l. We will now have a look at qam modulations, quadrature amplitude modulation.
The modulation scheme in an ofdm system can be selected based on the requirements of power or spectrum efficiency. Qam is better than qpsk in terms of data carrying capacity. Phaseshift keying psk is a digital modulation process which conveys data by changing modulating the phase of a constant frequency reference signal the carrier wave. Likewise, for 16psk modulation, the, ilar example can be supplied for 16psk modulation. Pdf design and realization of bpsk, qpsk and 16qam digital.
In this lab, you will observe the 16 qam modulation and demodulation building simulink simulation. In one embodiment, the 16quadrature amplitude modulation qam modulator includes a logic operation device performing a logic operation on firstfourth bits of received data to generate first and second logic outputs. Binary phase shift keying 2 transitions, 1 bitsymbol qpsk. Quadrature amplitude modulation 16qam adaptive modulation different order modulations allow you to send more bits per symbol and thus achieve higher throughputs or better spectral efficiencies. Quadrature means that two carrier waves are being used, one sine wave and. For 4qam modulation, each symbol is of size k log2m log24 2 bits. Qpsk is a special case of mary psk, where the phase of the carrier takes on one of m possible values real imaginary. Analysis of qpsk and 16qam modulator and demodulator is done on matlab. Quadrature amplitude modulation 16 qam in figure 4 showing 16 qam, each symbol can now represent four bits instead of just the two bits per symbol with qpsk. The two common forms of analog modulation are amplitude modulation. For a given channel bandwidth and tdd frame structure, each modulation mode transports data at a fixed rate. Qam, quadrature amplitude modulation provides some significant benefits for data transmission. Quadrature amplitude modulation qam pam signals occupy.
Analysis of ber for transmission of image using qpsk and 16 qam. If the bit rate associated with either of these 16 qam systems was 1. Amplitude and phase of the baseband signal changes bpsk. Comparison of traffic performance of qpsk and 16qam modulation. Analysis of ber for transmission of image using qpsk and 16qam. Quadrature means that two carrier waves are being used, one sine wave and one cosine wave. Differential quadrature phase shiftkeying dqpsk format provides a promising alternative as it, like qpsk, transmits 2 bits per symbol and hence the symbol. The performance of polarization multiplexed, quadrature phase shift keying pm qpsk and polarization multiplexed 16ary quadrature amplitude modulation pm 16qam is considered with an emphasis on the signal processing algorithms that compensate transmission impairments and implement key receiver functions. Figure 4 shows all 16 qam modulation symbols superposed on the same axes. This set of data communication and networking multiple choice questions and answers mcqs focuses on digital to analog to encoding modulation techniques amplitudeshift keying ask frequencyshift keying fsk phaseshift keying psk quadrature amplitude modulationqam.
This modulation technique is a combination of both amplitude and phase modulation techniques. As we expected, the results for bpqk and qpsk are the same. Quadrature amplitude modulation 16qam in figure 4 showing 16qam, each symbol can now represent four bits instead of just the two bits per symbol with qpsk. The modulation is accomplished by varying the sine and cosine inputs at a precise time. But compared to the qpsk, points are closer to each other and so the allowed noise. But here, we are only talking about qam as a digital modulation. Also, the receiver requires a given signal to noise ratio in order to successfully demodulate a given. Using different vector signal analyzers, the evm values for 16quadraticamplitude modulation qam and 64qam digitally modulated signals with certain distortions are measured. Mar 19, 2009 16qam vs qpsk now with the 16 possible points in the constellation diagram we have 16 possible symbols. Understanding mcs values cambium networks community. If the bit rate associated with either of these 16qam systems was 1.
However, it must also be noted that when using a modulation technique such as 64qam, better. The following equation outlines qpsk modulation technique. For 16 qam modulation, the symbol size is k log2 16 4 bits. Bpsk vs qpsk difference between bpsk and qpsk modulation. Qam is both an analog and a digital modulation method. Hardware implementation of qpsk modulator for satellite communication presented by. Apr 24, 20 qam is both an analog and a digital modulation method. Docsis cable modems use 64 qam, 256 qam for downstream channel to home and qpsk, 16 qam for the upstream channel from. Eight phase shift keying 8 transitions, 3bitssymbol 16qam 16 transitions, 4bitssymbol. If each symbol carries 4 bits k 4 or it is a m 16ary alphabet and the bit rate is 4 mbps.
Quadrature amplitude modulation an overview sciencedirect. The type of modulation used in this work is 16qam since it allows higher spectral efficiency than bpsk or qpsk. Hardware implementation of qpsk modulator for satellite. The first spectrum lobe occupies the spectral band from dc to 2fsym. One unique form of multilevel modulation is quadrature amplitude modulation qam. While qpsk represents two bits using complex carrier symbol each having 90 degree shift with one another. After understandig the modulation types individually, now let us examine the difference between bpsk and qpsk.
Singlecycle subcarrier modulation is a specific case of the quadrature amplitude modulation qam where the carrier is equal to the symbol rate. We demonstrate fiber nonlinearity mitigation by using multiple optical phase conjugations opcs in the wdm transmission systems of both 8 x 32gbaud pdm qpsk channels and 8 x 32gbaud pdm 16 qam. The qam modulator is so named because, in analog applications, the messages do in fact vary the amplitude of each of the dsbsc signals. The spectral width of 16 qam is more than that of qpsk. The full form of qam is quadrature amplitude modulation technique. Quadrature amplitude modulation qam conveys two bit streams by changing the amplitude of two carrier waves that have the same frequency and a 90 shift. The drawbacks are the increased snr required and the increase in the complexity of the system. In case of 16 qam modulation, a group pf 4 bits s3,s2,s1,s0 are mapped into the signal constellation as given below. The two bit streams would typically be band limited andor pulse shaped before reaching the modulator. Constructing a rectangular constellation for 16qam. For 16qam modulation, the symbol size is k log216 4 bits. As 16qam transitions to 64qam, 64qam to 256 qam and so forth, higher data rates can be achieved, but at the cost of the noise margin.
Qpsk 8psk 16 qam 32 qam 64 qam 128 qam 256 qam 6 78 11 , 23 20 22 19 standard power sp. Quadrature amplitude modulation qam pam signals occupy twice the bandwidth required for the baseband transmit two pam signals using carriers of the. Differential quadrature phaseshift keying dqpsk format provides a promising alternative as it, like qpsk, transmits 2 bits per symbol and hence the symbol. Pdf analysis of ber for transmission of image using qpsk. Linear modulation techniques are bandwidth more efficient but power less efficient. Fiber nonlinearity mitigation of wdmpdm qpsk16qam signals. Each point indicates a unique amplitude and phase of the wave for example, point 1, 1 indicates 90 degrees and amplitude of 1. In quadrature phase shift keying qpsk two sinusoids sin and cos are taken as basis functions for modulation. Qpsk in the case of qpsk, the i and q inputs are momentary dc values. In analog modulation we were interested in the snr, but recall from chapter 10. Qpsk, 16qam, 32 qam, 64 qam, 128 qam, 256 qam with true, low power lp. Pdf ber estimation from evm for qpsk and 16qam coherent. The type of modulation used in this work is 16 qam since it allows higher spectral efficiency than bpsk or qpsk.