PLANET WNAP-7205 - Manual (Page 85)

User’s Manual of WNAP-7205
Solutions to overcome the interferences:
 Minimizing the number of walls and ceilings.
 Position the WLAN antenna for best reception.
 Keep WLAN devices away from other electrical devices, eg: microwaves, monitors, electric
motors…etc.
 Add additional WLAN Access Points if necessary.
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.
9. What is WEP?
An option of IEEE 802.11 function is 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.
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 to low
fragment overhead. Hence there is a trade-off between spatial re-use and fragment overhead.
Fragment threshold is the maximum packet size used for fragmentation. Packets larger than the size
programmed in this field will be fragmented.
If you find that your corrupted packets or asymmetric packet reception (all send packets, for example).
You may want to try lowering your fragmentation threshold. This will cause packets to be broken into
smaller fragments. These small fragments, if corrupted, can be resent faster than a larger fragment.
Fragmentation increases overhead, so you'll want to keep this value as close to the maximum value as
possible.
- 85 -