W I F I.

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Presentation transcript:

W I F I

Frekvencie 802.11 2.4 GHz 13 kanálov - Európa; (11 kanálov – USA)

Modulácia FHSS - Frequency Hopping Spread Spectrum 802.11 (1997 - BreezNet, max. 2 mbps) EEE 802.15.1 - Technologie Bluetooth DSSS - Direct Sequence Spread Spectrum 802.11 (1997 - 2 mbps, 1999 - HR/DSSS, 11 mbps) IR - Infra Red OFDM - Orthogonal Frequency Division Multiplexing 802.11a (1999) a 802.11g (2003) PBCC - Packet Binary Convolution Coding 802.11b+ (2002)

topológie: IBSS; BSS; ESS Ad-hoc (resp. IBSS „Independent Service Basic Set“)

Infrastructure hoc (resp. BSS „Basic Service Set“)

ESS „Extended Service Set“

Rozdelenie a administrácia staníc

Max. 100 [mW]

Zisk (Útlm) [dB] [dBm] [W] 0,001 2 0,002 5 0,003 8 0,006 11 0,013 14 0,001 2 0,002 5 0,003 8 0,006 11 0,013 14 0,025 17 0,05 20 0,1 23 0,2 26 0,4 29 0,8 32 1,6 35 3,2 38 6,3 41 12,6 44 25,1

Koaxiálne káble OEM RLA-10 0,22 dB/m Belden H1000 Cavel RG-213 Times LMR-195 Andrew CNT-195 OEM LX-195 0,65 dB/m OEM RG-58 0,99 dB/m

Prostredie (vzduch) 50 m : - 74 dB 100 m : - 80 dB 200 m : - 86 dB

Všesmerové antény Vyžarovací diagram z boku Vyžarovací diagram zhora

Sektorové antény Vyžarovací diagram z boku Vyžarovací diagram zhora

Smerové antény Vyžarovací diagram z boku Vyžarovací diagram zhora

Polarizácia horizontálna Lineárna vertikálna kruhová pravotočivá

Konektory

dvojcestné útlumové členy

Bleskoistky

2 x DWL-900AP+ v režime bridge; 1,5 km + 17 dBm výstupný výkon - 2 dB pigtail - 2 dB bleskoistka - 2 dB konektory - 1 dB 5 m kábla H1000 + 7 dB všesmerová anténa mezivýsledok +17 dBm, ( < 20 dB ) - 103 dB trasa 1500 m vzduchom + 15 dB anténa smerová YAGI anténa - 2 dB 4 m kábla LX-195 výsledok -82 dBm Typické údaje o citlivosti DWL-900AP+ -85 dBm (11 Mbit/s) -88 dBm (5,5 Mbit/s) -89 dBm (2 Mbit/s) -92 dBm (1 Mbit/s)

Koordinácia prístupu k médiu Použité správy protokolu CSMA/CA: (Carrier Sense Multiple Access /with Collision Avoidance) RTS – Request to Send CTS – Clear to Send ACK – Acknowledge [ NAV (Network Allocation Vector) ]

Bezpečnosť MAC filtrácia WEP (64; 128) (Wired Equivalent Privacy) rotácia kľúčov WPA (WiFi Protected Access)

Šifrovací algoritmus RC4 (prúdová symetrická šifra) KSA – Key Scheduling Algorithm PRGA – Pseudo Rangom Generator Algorithm XOR – eXclusive OR

WEP proces