CWNA Study Guide

Chris:/*

After studying for the CWNA exam these past 12 days i have compiled a number of notes that I found were not presented anywhere concisely. I am sharing these in hopes they help other people attempting to earn the certification. Please let me know if I missed something or you notice something is wrong.



Clause 15 802.11 DSSS & FHSS 2.4 GHZ
- 11 MHz Center Channel or 22 MHz wide (DSSS)
- Non-Overlapping is 30 MHz of spacing between CF
- 2.402 to 2.48 (FHSS)
- Data Rates 1 or 2 Mbps
Clause 16 infrared - 800 nm to 950 nm
Clause 17 802.11 a OFDM 5 GHz
- Must have 20 MHz of spacing between center frequencies
- Data Rates 6, 9, 12, 18, 24, 36, 48 and 54 Mbps
Clause 18 802.11 b HR/DSSS 2.4 GHz
- 11 MHz from Center Channel or 22 MHz wide
- Must have 25 MHz of spacing between center frequencies
- Data Rates 1, 2, 5.5 and 11 Mbps
Clause 19 802.11 g ERP 2.4 GHz
- 11 MHz Center Channel or 22 MHz wide
- Must have 25 MHz of spacing between center frequencies
- Data Rates 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48, 54
Clause 20 802.11 n HT 2.4 & 5 GHz
- 2o MHz & 40 MHz Channels (HT only)
- 1 to 600 Mbps
Isotropic Radiator = dBi, used mostly by vendors because of the bigger number
Half Wave Dipole Radiator = dBd
dBd to dBi
- dBd + 2.14 = dBi
dBi to dbd
- dBi - 2.14 = dBd
1:1 Rule:
- For every 3 dB of antenna gain you must reduce the IR output power by 3 dB.
3:1 Rule:
- For every 3 dBi of antenna gain above the initial 6 dBi requires a reduction of 1 dB of IR output power.
6 Decibel Rule:
- For each doubling of the distance decrease the power by 6 Db
- For each halving of the distance increase the power by 6 Db
Rule of 10’s and 3’s:
- For every 3 Db gained double the power
- For every 3 Db lost half the power
- For every 10 Db gained multiply the power by 10
- For every 10 Db lost divide the power by 10

PtMP = Point to Multi-Point
- Omni-directional Antennas
PtP = Point to Point
- Directional or Semi-Directional Antennas

Guard Interval (GI)
- GI .8 microseconds (default)
- Short GI .4 microseconds (Introduced in HT)
- Double GI 1.6 microseconds (Not mentioned in Official CWNP Books)
DSSS, HR/DSSS & ERP-OFDM Channels:
- 1 through 14
- Channel 1 Center Frequency 2.412 GHz
- Add 5 MHz to 2.412 GHz for each Channel to get the Center Frequency
- Math to get the Channel’s Center Frequencies
o (Channel #-1)*.005 GHz + 2.412 GHz = Channel’s Center Frequency
- Exception Channel 14 = 2.484 (Not used except in Japan)

UNII Channels:
- Edge Channels Need 30 MHz of Separation in UNII-1, UNII-2 and UNII-2E
- Edge Channels Need 20 MHz of Separation in UNII-3
- Each Channel has 52 Subcarriers: 48 Data, 4 Error Checking
- Each Subcarrier is 300 kHz
- UNII-1 Lower 100 MHz 5.15 - 5.25 GHz 4 Channels
o Channels 36 – 48
o Channel Numbers Increment by 4
o Center Frequencies increment by 20 MHz
o Channel 36 Center Frequency is 5.180 GHz
- UNII-2 Middle 100 MHz 5.25 - 5.35 GHz 4 Channels
o Channels 52 – 64
o Channel Numbers Increment by 4
o Center Frequencies Increment by 20 MHz
o Channel 52 Center Frequency is 5.260 GHz
- UNII-2E Extended 255 MHz 5.47 - 5.725 GHz 11 Channels
o 11 OFDM Channels which are not assigned by IEEE
o Made available because of DFS and TPC in 802.11h
- UNII-3 Upper 100 MHz 5.725 - 5.825 GHz 4 Channels
o Channels 149 – 161
o Channel Numbers Increment by 4
o Center Frequencies Increment by 20 MHz
o Channel 149 Center Frequency is 5.745 GHz
- ISM Channel
o Channel 165 is the ISM Channel 5.825 GHz
PoE
- PoE Class Determination
o PSE power supplied nominally is 48 Volts or (44 to 57 volts)
o When a PD connects to a PSE it presents itself at 25K ohms
o PSE applies a 10.1 V charge to identify the detection signature
o The PSE will then up the voltage to 20.5 V and measure the current
o The results will determine the Class of the PoE Device
o If none of the currents match the PSE will default to Class 0
- PoE Mode A = Wires 1, 2, 3, 6 Used by Endpoint Devices only
- PoE Mode B = Wires 4, 5, 7, 8 Used by Midspan Devices only cannot support Gigabit Ethernet devices because it blocks data traffic on spare pairs instead using them for power only.
- 802.3af
o Now part of 802.3-2005 under Clause 33
- 802.3at
o Doubles power of 802.3-2005 clause 33 to 30 W

Access Point Modes
- Root Mode
o Wireless Clients can have the Same IPs as Wired Clients
o Communications are bridged to the clients on the same subnet
- Bridge Mode
o Multiple AP can communicate to each other using Bridging
o Connects wired networks using wireless AP
- Repeater Mode
o Reduces Throughput
o Connects a Wireless AP to a another AP that is in root mode
- Workgroup Bridge
o Provides wireless connectivity for devices that do not have a radio card
- Scanner Mode
o The access point is converted into a sensor for a WIDS/WIPS system

FCC Power Regulations (Not tested in the CWNA per the Official Study Guide):
- 2.4 GHz Power Limit PtMP = 1W from the IR, and 4 Watts from the EIRP
- 1:1 Rule
- 2.4 GHz Power Limit PtP = 1W from the IR, and 158 Watts from the EIRP
- 3:1 Rule
- UNII-1 Power Limit PtMP = IR 40 mW, with 6 dBi antenna = EIRP 160 mW
- 1:1 Rule
- UNII-2 Power Limit PtMP = IR 200 mW, with 6 dBi antenna = EIRP 800 mW
- 1:1 Rule
- UNII-2E Power Limit PtMP = IR 200 mW, with 6 dBi antenna = EIRP 800 mW
- 1:1 Rule
- UNII-3 Power Limit PtMP = IR 800 mW, with 6 dBi antenna = EIRP 3200 mW
- 1:1 Rule
- UNII-1 Power Limit PtP = Same as PtMP
- UNII-2 Power Limit PtP = Same as PtMP
- UNII-2E Power Limit PtP = Same as PtMP
- UNII-3 Power Limit PtP = Can have a 23 dBi antenna, use 1:1 Rule after that



Additional CWNA Study Resources:
CWNA: Official Study Guide PW0-104
All-In-One CWNA/CWSP Exam Guide
GT Hill's Study Guide
OnlineExpert.com's video training

Bokeh

Thanks for the notes. Hope youre enjoying Misawa, was my favorite assignment while in.

Unforg1ven

Some good notes m8. All of mine for this exam are on a giant notepad w/ good ol'e chicken scratch.

One extra note for all test takers :

-After the 802.11-2007 standard wrapped up all the previous amendments, the IEEE references by clause only. The exam references clause and technology ie: OFDM, not 802.11a.

*Clause 14 = FHSS
*Clause 15= DSSS
...
...
...

-Don't assume because a technology is legacy, it will not be covered. For example : FHSS devices can pose multiple issues and threats(interference, hidden nodes etc.)

As Chris points out you will not be testing on a specific country's power output levels. Please understand that every country has a regulatory authority for regulating such as well as the specific channels allowed in the ISM band.

Chris:/*

Glad I could help.

veritas_libertas

Nice list!

JDMurray

Yes, thanks for the study notes!

Amco

Good looking out, taking the exam in a few weeks