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Modified over 4 years ago
Anatomy of Radio LAN Onno W. Purbo Onno@indo.net.id
Reference http://www.hpl.hp.com/personal/Jean_ Tourrilhes/Linux/Linux.Wireless.wlan.ht ml
Spread Spectrum Techniques Direct Sequence Frequency Hopping
Comparisons DS modem more complicated, MAC in DS much simpler. FH appears to be cheaper. BW sharing, DS tends to have lower overhead on the air. DS vs. FH = religion war …
Diversity Redudancy in the system to overcome noise and to increase the reliability of the system. Antenna Diversity
Antenna Directional Antenna Sectoral Antenna Beam forming Antenna
Range Issues Propagation Attenuation Reflection Fading
Transmitter Power Higher power: Drain battery quickly Frequency reuse drawback
Sensitivity Defined as Point at 3% packet loss (400 byte packet in Gaussian channel). 7 dB worse if we use Raleigh channel + antenna diversity. Normally –80 dBm, better –90 dBm.
Attenuation: Propagation & Range
SNR Signal-to-Noise Ratio Difference of power in the receiver between a valid signal and noise.
Multi-rate system Better throughput more bandwidth. The higher the signalling rate, the shorter the distance.
2FSK B = base frequency d = deviation symbol 0 B + d 1 B – d
Frequency Modulation 2FSK
4FSK B = base frequency d = deviation Symbol 00 B+ 1/2d 01 B – 1/2d 10 B + 3/2d 11 B – 3/2d
IEEE 802.11 (11Mbps) CCK – Complementary Code Keying 11 Mbps 5.5Mbps
IEEE 802.11a (OFDM) Orthogonal Frequency Division Multiplex (OFDM). Using equalization in post processing, overcome delay spread. OFDM is pre-processing technique. Use in 5Ghz UNII Band.
Interference & Noise
Fading Variation in time. Microwave oven & other interferer. Forward Error Correction (FEC) Not effective, better retransmit the packet. Delay Spread
Multipath & Delay Spread
UAbove Law fahrul hakim2003 Wireless LAN implications Project managers and design engineer should be aware, the following potential problems from the implementation.
OFDM Transmission Technique Orthogonal Frequency Division Multiplexer
Quiz Sketch the time domain waveform and spectrum, labeling all important features, of a rectangular pulse of 2.4 Ghz having 1 uS duration.
WLAN System Capacity Zahid Iqbal. WLAN Technologiess IEEE802.11a IEEE802.11b IEEE802.11g.
Design MAN WLAN Onno W. Purbo Understanding.. WLAN Bandwidth Channels Propagation Designing the MAN Inserting Point to Point (P2P) Links.
Direct Sequence Spread Spectrum. Spread Spectrum Spread power of signal over larger than necessary bandwidth in order to: 1. Reduce interference by signal.
The Reliability of Wireless Mesh Networks in Industrial Environments Brian Cunningham.
© 2007 Cisco Systems, Inc. All rights reserved.ICND1 v1.0—3-1 Wireless LANs Exploring Wireless Networking.
Wireless Networks and Spread Spectrum Technologies.
FHSS vs. DSSS Presented by Ali Alhajhouj. Presentation Outline Introduce the issues involved in the system behaviors for FHSS and DSSS systems used in.
Wireless Networks. Anatomy of a radio LAN The radio modem –Analog transmitter The MAC controller –Interface to transmitter –At least partly in hardware.
CWNA Guide to Wireless LANs, Second Edition
© 2003, Cisco Systems, Inc. All rights reserved. FWL 1.0— © 2003, Cisco Systems, Inc. All rights reserved.
Advanced Topics in Next- Generation Wireless Networks Qian Zhang Department of Computer Science HKUST Wireless Radio.
Presented By: Nishant Divecha
IS250 Spring 2010 Physical Layer IS250 Spring 2010
#7 1 Victor S. Frost Dan F. Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr. Lawrence,
802.11g Update Byron Early & Chad Burnham University Technology Services Westnet Meetings: July 8-10, 2003.
© 2003, Cisco Systems, Inc. All rights reserved. FWL 1.0—3-1 Wireless Radio Technology Olga Torstensson Halmstad University.
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