[Olsr-dev] Strategy for ETT metric

[sebastian sauer]

Hi Henning,

Sat 05 Apr 2008 19:55, Henning Rogge wrote:
> Another thing I just heared from a coworker is that bandwith is nearly
> always correlated with the received signal strength ?
.. in the literature there are quite diverse opinions about it. and even
the quite new informational rfc 4907 reflects that.

http://www3.tools.ietf.org/html/rfc4907#section-2.7.3

|  Within the link layer, metrics such as signal strength and frame loss
|  may be used to determine the transmission rate, as well as to
|  determine when to select an alternative point of attachment.  In
|  order to enable stations to roam prior to encountering packet loss,
|  studies such as "An experimental study of IEEE 802.11b handover
|  performance and its effect on voice traffic" [Vatn] have suggested
|  using signal strength as a mechanism to more rapidly detect loss of
|  connectivity, rather than frame loss, as suggested in "Techniques to
|  Reduce IEEE 802.11b MAC Layer Handover Time" [Velayos].
|
|  [Aguayo] notes that signal strength and distance are not good
|  predictors of frame loss or throughput, due to the potential effects
|  of multi-path interference.  As a result, a link brought up due to
|  good signal strength may subsequently exhibit significant frame loss
|  and a low throughput.  Similarly, an Access Point (AP) demonstrating
|  low utilization may not necessarily be the best choice, since
|  utilization may be low due to hardware or software problems.  "OSPF
|  Optimized Multipath (OSPF-OMP)" [Villamizar] notes that link-
|  utilization-based routing metrics have a history of instability.

s.