Netgear CG814M ユーザーズマニュアル
Reference Manual for the Model CG814M Wireless Cable Modem Gateway
B-14
Networks, Routing, and Firewall Basics
The 128-bit WEP data encryption method consists of 104 user-configurable bits. Similar to the
forty-bit WEP data encryption method, the remaining 24 bits are factory set and not user
configurable. Some vendors allow passphrases to be entered instead of the cryptic hexadecimal
characters to ease encryption key entry.
forty-bit WEP data encryption method, the remaining 24 bits are factory set and not user
configurable. Some vendors allow passphrases to be entered instead of the cryptic hexadecimal
characters to ease encryption key entry.
Wireless Channel Selection
IEEE 802.11b wireless nodes communicate with each other using radio frequency signals in the
ISM (Industrial, Scientific, and Medical) band between 2.4Ghz and 2.5Ghz. Neighboring channels
are 5Mhz apart. However, due to spread spectrum effect of the signals, a node sending signals
using a particular channel will utilize frequency spectrum 12.5Mhz above and below the center
channel frequency. As a result, two separate wireless networks using neighboring channels (for
example, channel 1 and channel 2) in the same general vicinity will interfere with each other.
Applying two channels that allow the maximum channel separation will decrease the amount of
channel cross-talk, and provide a noticeable performance increase over networks with minimal
channel separation.
ISM (Industrial, Scientific, and Medical) band between 2.4Ghz and 2.5Ghz. Neighboring channels
are 5Mhz apart. However, due to spread spectrum effect of the signals, a node sending signals
using a particular channel will utilize frequency spectrum 12.5Mhz above and below the center
channel frequency. As a result, two separate wireless networks using neighboring channels (for
example, channel 1 and channel 2) in the same general vicinity will interfere with each other.
Applying two channels that allow the maximum channel separation will decrease the amount of
channel cross-talk, and provide a noticeable performance increase over networks with minimal
channel separation.
The radio frequency channels used are listed in
:
Table B-1.
802.11b Radio Frequency Channels
Channel
Center Frequency
Frequency Spread
1
2412Mhz
2399.5Mhz - 2424.5Mhz
2
2417Mhz
2404.5Mhz - 2429.5Mhz
3
2422Mhz
2409.5Mhz - 2434.5Mhz
4
2427Mhz
2414.5Mhz - 2439.5Mhz
5
2432Mhz
2419.5Mhz - 2444.5Mhz
6
2437Mhz
2424.5Mhz - 2449.5Mhz
7
2442Mhz
2429.5Mhz - 2454.5Mhz
8
2447Mhz
2434.5Mhz - 2459.5Mhz
9
2452Mhz
2439.5Mhz - 2464.5Mhz
10
2457Mhz
2444.5Mhz - 2469.5Mhz
11
2462Mhz
2449.5Mhz - 2474.5Mhz
12
2467Mhz
2454.5Mhz - 2479.5Mhz
13
2472Mhz
2459.5Mhz - 2484.5Mhz