Cisco Cisco Aironet 1522 Lightweight Outdoor Mesh Access Point 디자인 가이드

Because there could be many nodes attempting to join or re-join the network after an expected or 
unexpected event, a hold-off time of 16 minutes is implemented. This means that no nodes are 
exclusion-listed during this period of time after system initialization.

This exponential backoff and advance algorithm is unique and has the following useful properties:

It allows a node to correctly identify the parent nodes whether it is a true honeypot or is just 
experiencing temporary outage conditions.

It credits the good parent nodes according to the time it has enabled a node to stay connected with 
the network and the crediting requires lesser and lesser time over period in order to bring the 
exclusion-list conviction period to be very low for real transient conditions and not so low for 
transient to moderate outages.

It has built-in hysteresis for encountering the initial condition issue where many nodes try to 
discover each other only to find that those are not really meant to be in the same network.

It has built-in memory for nodes that can appear as neighbors sporadically so they are not 
accidentally considered as parents if they were, or are supposed to be, on the exclusion-list database.

The node exclusion-listing algorithm is constructed to guard the mesh network against serious stranding, 
which was observed in customers’ networks. It integrates into AWPP in such a way that a node can 
quickly (re-)converge and find the correct network under many kinds of adversities.

Throughput depends on packet error rate and hop count.

Throughput is calculated as:

Throughput = BR * 0.5 * 1/n * PSR

BR = Raw backhaul rate, i.e. 18, 24 Mb/s

n = Backhaul hop count

PSR = Packet success rate = (1.0-PER) = (0.0 .. 1.0)

Two assumptions apply to this calculation:

There is no other traffic on the mesh

1/n factor is based on all hops hearing each other.

Generally, the throughput numbers per hop are as shown in 

Capacity and throughput are orthogonal concepts. Throughput is one user's experience at node N and 
total area capacity is calculated over the entire sector of N-nodes and is based on the number of ingress 
and egress RAPs, assuming separate non-interfering channels. 

For example, 4 RAPs at 10 Mb/s each deliver 40 Mb/s total capacity. So, one user at 2 hops out, logically 
under each RAP, could get 5Mb/s each of TPUT, but consume 40 Mb/s of backhaul capacity.

One

Approximately 14 Mb/s

Two

Approximately 8 Mb/s

Three

Approximately 3 Mb/s

Four

Approximately up to 1 Mb/s