B. Quorum-Based Protocols
For the same purpose, to reduce the number of nodes involved in forming a
read quorum and write quorum as in the hashing-based method, the quorumbased
method also never needs all nodes to collaborate in each data accessing.
The number involved in each quorum is significantly reduced to O(???n), where
n is the total number of nodes residing in the network. Moreover, there is no
preliminary information about the hash function in each node. Authors in [21]
have discussed several methods for generating quorum systems.
In [22], the author applied a similar idea, as in [3] with some modification,
to form a simple and e?±cient quorum system to wireless networks. Recall
that in [3], n servers in the system are evenly partitioned into ???n rows and ???n columns, so that intersections occur between rows and columns. However,
there are no strict rows or columns inside real networks. Nevertheless, with
some modification, the protocol works well as follows: nodes exchange location
information with immediate neighbors whenever a link associated with
the nodes is broken or created. After the number of such link changes reaches
a certain threshold value, the node broadcasts a location update packet to
its neighbors. Then the packet is retransmitted along the north-south direction
of this node (forming a column) by the northernmost and southernmost
neighbor of each iteration until it reaches the end of this ???column??™.
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