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IMPLEMENTATION OF 4G
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IMPLEMENTATION OF 4G
• OFDM• UWB• Millimeter wave technology• Scheduling • Long term prediction• Smart antennas• Adaptive modulation
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OFDM
• Multi carrier modulation• Closely spaced orthogonal sub-carriers• Slow & low bandwidth modulator
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OFDM
• Sinc shaped pulse
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OFDM
Non-overlapping sub-carriers:• Allowed channel bandwidth=2/Rs• BW α 1/Rs
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OFDM
• Overlapping sub-carriers:• Allowed channel bandwidth=1/Rs
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ADVANTAGES OF OFDM
• High spectral efficiency • Can easily adapt to severe channel conditions without complex
time-domain equalization• Robust against narrow-band co-channel interference• Efficient implementation using Fast Fourier Transform(FFT)• Tuned sub-channel receiver filters are not required• Facilitates single frequency networks(SFNs)• SNR improves
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DISADVANTAGES OF OFDM
• Sensitive to Doppler shift• Sensitive to frequency synchronization problems• High peak-to-average power ratio (PAPR)
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APPLICATIONS OF OFDM
• Digital TV• Audio broadcasting• Wireless networks• Wimax technologies
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UWB
• FCC defines UWB as a radio transmission with a spectrum that occupies more than 20% of the centre frequency or a minimum of 500MHz while adhering certain output power limits
• Base band modulation• Large bandwidth, typically 3.1 to10.6GHz• Shorter range of about 10 meters• It offers flexibility, robustness, good ranging capabilities• Operates below noise level
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PRINCIPLES OF UWB
Time domain:
• Extremely short pulses• Very low duty cycles
Frequency domain:• Ultra wide spectrum• Low spectral power density
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UWB
Two classes:• Multiband UWB• Impulse radio
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ADVANTAGES OF UWB
• Spectrum reuse• Large channel capacity• Ability to work with low signal-to-noise ratio• Hartley-Shannon’s capacity equation:
C=B*log(1+S/N)
Where C is channel capacity
B is signal bandwidth
S is signal power
N is noise power
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ADVANTAGES OF UWB
• High data rate in short distance—500Mbps at 10 meters• Low power consumption• Low cost• SNR improves
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APPLICATIONS OF UWB
• Radar sensing• Military communications• target sensors data collection• Precision locating & tracking applications• ITS(Intelligent Transport Systems)
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MILLIMETER WAVE TECHNOLOGY• Need• High standard• Applications like campus & facility enterprise network,
connection redundancy and failure recovery
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SCHEDULING
• Among sectors• Among users
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LONG TERM PREDICTION
• Distribution
• Channel properties
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SMART ANTENNAS
• Smart antennas are antenna arrays with smart signal processing algorithms
• High Efficiency • Frequency range from
450MHz to 6GHz• Wide bandwidth• Very Low Cost• One antenna replaces all others• Can reduce costs by 100x• Flexible implementation in foil
or copper
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• The antenna arrays have input or output as RF signals in the analog domain
• The baseband signals received from each antenna is then combined using the smart algorithms in a digital processing section
• One smart‐antenna variation in particular, MIMO, shows promise in 4G systems
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MIMO• Multiple Input Multiple
Output (MIMO) requires array processing at the transmitter and receiver
• There are two different types of MIMO schemes:
• Spatial Multiplexing • Space Division Multiplexing• Multiple antennas at both the
transmitter and the receiver• It provides essentially
multiple parallel channels that operate simultaneously
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ADAPTIVE MODULATION• Adaptive Modulation is not Fixed Modulation• Idea of Adaptive Modulation• Types of Adaptive Modulation• AMQAM-Non blocking• AMQAM-Blocking• AMPSK-Non blocking• AMPSK-Blocking
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THANK YOU
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