User's Manual

Troubleshooting Procedures
203
SMCD3GNV Wireless Cable Modem Gateway User Manual
If you use or are considering using 802.11n in your wireless network, observe the following
guidelines:
 If your maximum data rate is 54 Mbps or lower, confirm your NIC is an 802.11n
adapter and not an older 802.11g adapter. Although 802.11g NICs can connect to the
newer 802.11n devices, high speeds and performance are possible only on connections
between a wireless N device (such as the Gateway) or access point (AP) and a wireless
N adapter. Therefore, you may need to upgrade your older wireless equipment to
achieve faster speed and performance.
 While devices certified by the Wi-Fi Alliance are designed to work together regardless
of manufacturer, some proprietary features require compatible equipment to work.
Additionally, there may be interoperability issues with wireless 802.11n devices because
the official standard is not complete. Therefore, manufacturers are releasing
products. To prevent potential problems, use devices from the same manufacturer for
your wireless network.
 Because the wireless 802.11n standard does not support WEP encryption, 802.11n
connections using WEP are limited to maximum wireless 802.11g speeds of 54 Mbps,
even on mixed 802.11/GN networks. Moreover, the first WPA version does not provide
maximum wireless performance on 802.11n networks. For these reasons, either:
– Upgrade your 802.11g equipment for 802.11n devices, or
– Configure the devices on your wireless network to use WPA2 (on the Gateway, this
setting is configured in the Encryption Method field in step 2 of the Home Network
Wizard – see page 63). For old 802.11g devices that support WEP encryption only,
check the vendor's Web site for updated drivers.
 Wireless 802.11 N is backward compatible with older 802.11g wireless devices and
even older 802.11b devices. However, traffic on a wireless network is managed
differently when older devices connect to an 802.11n network that can adversely affect
speed and performance. Therefore, if you are not realizing optimum data and throughput
rates, you may want to configure the Gateway so it only offers connections to wireless
802.11n clients. To limit the types of clients allowed to connect, configure the Operation
Mode setting in the Wireless menu to allow only wireless 802.11n connections (see
page 50).
 To exceed 130 Mbps on wireless 802.11n connections, the channel width must
double from 20 to 40 MHz. By default, the Gateway is configured for 20/40 MHz
operation. However, if this default setting has a negative impact on clients with low
signals, you might want to select 20 MHz operation in the Gateway’s Channel
Bandwidth setting in the Wireless menu (see page 51) to limit connections to 20 MHz
only.