34 Data and Pilot Carriers Used as reference for phase and amplitude to

34 data and pilot carriers used as reference for

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34 Data and Pilot Carriers Used as reference for phase and amplitude to demodulate the data in the other sub-carriers. Carriers -1 to -n Carriers 1 to n Sub-carrier -1 Pilot Carriers Sub-carrier 1 Frequency
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 35 Example: WLAN (802.11a/g) Modulation Technique OFDM Bandwidth 16.25MHz Number of sub-carriers 52 Sub-carrier numbering -26 to + 26 Sub-carrier spacing 312.5kHz Maximum sub-carrier symbol rate 250 kHz (64QAM) Pilot sub-carriers -21, -7, +7 and +21 (BPSK) Packet Structure – Preamble – Header – Data Block SUB Carrier Modulation Types - BPSK, QPSK, 16-QAM or 64-QAM
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 36 WLAN Summary WLAN implies Wireless LAN compatible with one the IEEE 802.11 sub standards. It is what you have in your laptop. WiFi is an industry consortium that defines a required subset of 802.11 to ensure better operation between different vendor’s equipment. EWC is an industry consortium that took the unfinished N standard, agreed upon a version, and is attempting to field solutions prior to 802.11n ratification. • Not a finished standard yet. • Like g, but up to 600Mbps • OFDM • MIMO • 20 & 40 MHz channels n Japanese version of g that uses half the sample rate. j What you can easily buy now – same as a , but at 2.4 GHz g 11 Mbps CCK, 2.4 GHz (Legacy, not OFDM) b 54 Mbps OFDM, 5.9 GHz Band, 20 MHz channels a Means 802.11
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 37 demo WLAN OFDM - Test Equipment Requirements Frequency Coverage up to 5.8GHz Modulation Bandwidth up to 16.25MHz 802.11a/g Signal Creation and Analysis Capability Keithley instruments 2820 and 2920 VSA and VSG have a frequency range of 6 GHz and 40 MHz bandwidth as standard.
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 38 OFDM to OFDMA OFDM as a modulation technique is not multi user* – all sub-carriers in a channel are used to facilitate a single link. OFDMA assigning different number of sub-carriers to different users in a similar fashion as in CDMA. * 802.11 WLAN supports multiple users with FDMA (frequency-division multiple access)
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 39 WiMAX 802.16d/e OFDMA W orldwide I nteroperability for M icrowave Access Fixed – 802.16d, point-to-point backhaul applications Mobile – 801.16e, enhanced data services mobile applications. WiMAX enhanced Mobile Devices BTS Mobile Fixed
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc. 40 RF Characteristics 802.16e Mobile WiMAX IFFT size determines carriers Carriers Guard Band Guard Band Pilot Carriers Data Carriers Subcarrier Spacing: 10.94 kHz 20 MHz 2048 10 MHz 1024 5 MHz 512 1.25 MHz 128 Channel Bandwidth FFT Size Frequency
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A G R E A T E R M E A S U R E O F C O N F I D E N C E © Copyright 2007-2008 Keithley Instruments, Inc.
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  • Spring '16
  • WiMAX, Keithley Instruments

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