X-Micro Tech. XWL-11GRTX Manual Do Utilizador

¾ Electrical devices: microwaves, monitors and electrical motors.

Solutions to overcome the interferences:

9  Minimizing the number of walls and ceilings.
9  Position the WLAN antenna for best reception.
9  Keep WLAN devices away from other electrical devices, eg: microwaves,

monitors, electric motors, … etc.

9 Add additional WLAN Access Points if necessary.

4.8 What are the Open System and Shared Key authentications?

IEEE 802.11 supports two subtypes of network authentication services: open

system and shared key. Under open system authentication, any wireless station

can request authentication. The station that needs to authenticate with another

wireless station sends an authentication management frame that contains the

identity of the sending station. The receiving station then returns a frame that

indicates whether it recognizes the sending station. Under shared key

authentication, each wireless station is assumed to have received a secret

shared key over a secure channel that is independent from the 802.11 wireless

network communications channel.

4.9 What is WEP?

An optional IEEE 802.11 function that offers frame transmission privacy similar to

a wired network. The Wired Equivalent Privacy generates secret shared

encryption keys that both source and destination stations can use to alert frame

bits to avoid disclosure to eavesdroppers.

WEP relies on a secret key that is shared between a mobile station (e.g. a laptop

with a wireless Ethernet card) and an access point (i.e. a base station). The

secret key is used to encrypt packets before they are transmitted, and an

integrity check is used to ensure that packets are not modified in transit.

4.10 What is Fragment Threshold?

The proposed protocol uses the frame fragmentation mechanism defined in

IEEE 802.11 to achieve parallel transmissions. A large data frame is fragmented

into several fragments each of size equal to fragment threshold. By tuning the

fragment threshold value, we can get varying fragment sizes. The determination

of an efficient fragment threshold is an important issue in this scheme. If the

fragment threshold is small, the overlap part of the master and parallel

transmissions is large. This means the spatial reuse ratio of parallel

transmissions is high. In contrast, with a large fragment threshold, the overlap is

small and the spatial reuse ratio is low. However high fragment threshold leads