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What is spectral efficiency in GSM?
Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system.
What is the spectral efficiency of the GMSK modulation scheme used in GSM?
Spectral Efficiency ASK/OOK and FSK have efficiencies of <1. Special forms of FSK, such as GMSK used with older GSM cell phones, are a bit better. BPSK has a spectral efficiency of 1.
How does GMSK achieve better spectral efficiency than MSK?
GMSK is preferred over MSK because there is an efficient reduction in side lobes [1]. MSK is being derived from the Offset. Quadrature Phase Shift Keying. The difference is sinusoid’s are used as quadrature and In-phase components instead of Square signals.
What is spectral efficiency for digital modulation?
The spectral efficiency is 2 bits/Hz, meaning twice the data rate can be achieved in the same bandwidth as BPSK. 3. Modulation can be represented without time domain waveforms.
How is spectral efficiency measured?
For example, a system uses channel bandwidth as 2 MHz and it can support a raw data rate of say 15 Mbps, assuming 2 Mbps as overhead then net date rate will be as 13 Mpbs, then its spectrum efficient can be calculated as follows: Spectral efficiency= 13 x 10^6 / 2 x 10^6 = 6.5 bits/second/Hz.
Why is spectral efficiency important?
Link spectral efficiency usually determines the efficiency of the digital modulation approach or lines of code. Wireless networks with spread spectrum, frequency reuse and FEC reduce spectral efficiency. However, they also reduce the necessary signal-to-noise ratio in comparison to non-spread spectrum techniques.
What is GMSK modulation in GSM?
The Gaussian Minimum Shift Keying (GMSK) modulation is a modified version of the Minimum Shift Keying (MSK) modulation where the phase is further filtered through a Gaussian filter to smooth the transitions from one point to the next in the constellation.
How does GMSK work in GSM?
GSM uses a digital modulation format called 0.3GMSK (Gaussian minimum shift keying). The 0.3 describes the bandwidth of the Gaussian filter with relation to the bit rate. GMSK is a special type of digital FM modulation. 1’s and 0’s are represented by shifting the RF carrier by plus or minus 67.708KHz.
What is the difference between MSK and GMSK?
GMSK is the derivative of MSK modulation scheme and MSK is derived from Offset QPSK modulation. In MSK modulation scheme instead of rectangular pulse wave; half cycle sine wave is used. Frequency of logical zero and logical one differs by half of data rate. Modulation index is 0.5 here.
Which modulation is spectrally more efficient?
Explanation: MSK is spectrally more efficient than the other modulation schemes.
What is meant by GMSK?
Gaussian minimum shift keying (GMSK) is a form of frequency shift keying (FSK) used in GSM systems. The tone frequencies are separated by exactly half the bit rate. It has high spectral efficiency.