L3_physical - EEC173B/ECS152C Spring 2010 Characteristics...

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Page 1 EEC173B/ECS152C, Spring 2010 Fundamentals of Wireless Communications #1: Frequencies #2: Radio Propagation Model #3: Modulation 2 Characteristics of Wireless Medium Comparison to wired media Unguided link Unreliable Low bandwidth Untethered: supports mobility Broadcast nature Shared medium Capacity limitation Frequency of operation and legality of access differentiates a variety of alternatives for wireless networking 3 Frequencies for Communication VLF = Very Low Frequency UHF = Ultra High Frequency LF = Low Frequency SHF = Super High Frequency MF = Medium Frequency EHF = Extra High Frequency HF = High Frequency UV = Ultraviolet Light VHF = Very High Frequency Frequency and wave length: = c/f - Wave length , speed of light c 3x10 8 m/s, frequency f 1 Mm 300 Hz 10 km 30 kHz 100 m 3 MHz 1 m 300 MHz 10 mm 30 GHz 100 m 3 THz 1 m 300 THz visible light VLF LF MF HF VHF UHF SHF EHF infrared UV optical transmission coax cable twisted pair 4 Frequencies for Mobile Communication VHF /UHF ranges for mobile radio Simple, small antenna for cars Deterministic propagation characteristics, reliable connections SHF and higher for directed radio links, satellite communication Small antenna, focusing Large bandwidth available Wireless LANs use frequencies in UHF to SHF spectrum Some systems planned up to EHF Limitations due to absorption by water and oxygen molecules (resonance frequencies) • Weather dependent fading, signal loss caused by heavy rainfall etc. 5 Operational Ranges 1 GHz (cellular) 2 GHz (PCS and WLAN) 5 GHz (WLANs) 28 60 GHz (local multipoint distribution services (LMDS) and point to point base station connections) IR frequencies for optical communications 6 Licensed and Unlicensed Bands Licensed: Cellular/PCS Expensive (PCS bands in US were sold for around $20B) Time consuming to deploy new applications rapidly at low costs Unlicensed: Industrial, Medical, and Scientific (ISM) Bands Free, component costs are also low New applications such as WLAN, Bluetooth are easily developed With the increase in frequency and data rate, the hardware cost increases, and the ability to penetrate walls also decreases
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Page 2 7 Frequencies and regulations ITU R holds auctions for new frequencies, manages frequency bands worldwide (WRC, World Radio Conferences) Europe USA Japan Phones 486/460-467,489- 496, 890-915/935- 960, 1710-1785/1805- 1880 UMTS (FDD) 1920- 1980, 2110-2190 (TDD) 1900- 1920, 2020-2025 824-849, 869-894 TDMA , CDMA , GSM 1850-1910, 1930-1990 810-826, 940-956, 1429-1465, 1477-1513 Cordless CT1+ 885-887, 930- 932 CT2 864-868 DECT 1880-1900 PACS 1850-1910, 1930- 1990 PACS-UB 1910-1930 PHS 1895-1918 JCT 254-380 Wireless LANs IEEE 802.11 2400-2483 HIPERLAN 2 5150-5350, 5470- 5725 902-928 5150-5350, 5725-5825 IEEE 802.11 2471-2497 5150-5250 Others RF-Control 27, 128, 418, 433, 868 315, 915 RF-Control 426, 868 8 Radio Propagation Three most important radio propagation characteristics used in the design, analysis, and installation of wireless networks are: Achievable signal coverage Maximum data rate that can be supported by the channel Rate of fluctuations in the channel 9 Signals 1
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This note was uploaded on 04/29/2010 for the course ECS 152 taught by Professor Mr. during the Spring '10 term at University of Great Falls.

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L3_physical - EEC173B/ECS152C Spring 2010 Characteristics...

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