Campbell Scientific NL240 Wireless Network Link Interface - Manual (Page 21)

NL240 Wireless Network Link Interface
easiest wireless network to connect the NL240 to. (See Section 8.1, Wi-Fi
Connection, for details.) The network password/key (if required) and SSID
can be obtained from your network administrator.
FIGURE 6-1. Infrastructure network
Unlike infrastructure networks, ad hoc or peer-to-peer networks do not have a
single device (like a WAP) that controls access to the wireless network (see
FIGURE 6-2, Ad hoc network). Instead, network management and access is
decentralized. Ad hoc networks are created on the fly and all network devices
communicate directly with each other. Usually the first device on the network
(a NL240, PC, or iOS smart phone) establishes the security type, the SSID, and
the channel (frequency) that the wireless network will operate on. IP addresses
can be set statically or via AutoIP. It can take up to two minutes to find a
usable IP address using AutoIP.
FIGURE 6-2. Ad hoc network
Once the network is established by the first wireless device, subsequent
wireless devices can connect to the ad hoc network if the correct SSID and
password (if needed) are specified in the configuration settings. Ad hoc
networks are usually small with up to five wireless devices connecting to the
wireless network. Also, ad hoc networks can only use WEP security or no
security (open). WPA security is not available in ad hoc networks.
6.3 RSSI
RSSI is Received Signal Strength Indication. It is a generic radio receiver
technology metric used to determine the strength of the link between a receiver
and a transmitter. In the NL240’s case, RSSI is the measurement between the
NL240 and a wireless access point, a computer in ad hoc or another NL240 in
ad hoc. The strength of this link is recorded in dBm (power ratio in decibels)
and can be found under the Wi-Fi tab under the Settings Editor in DevConfig.
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