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MANET Working Group                                         Sanghyun Ahn
Internet Draft                                       University of Seoul
Expires: November 4, 2013                                     Hyogon Kim
                                                        Korea University
                                                            May 13, 2013


                   Architecture for MANET Clustering
            draft-ahn-manet-clustering-architecture-01.txt

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Abstract

   This document describes the architecture for clustering in the MANET
   which can be an efficient communication structure for the case
   when MANET nodes have the tendency of forming groups. In this type of
   MANET, each group of nodes forms a cluster which is represented by a
   cluster head. In this draft, we define the terminology for the MANET
   clustering and the related communication procedure.


Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Cluster Formation Procedure  . . . . . . . . . . . . . . . . .  4
   5.  Data Exchange Procedure  . . . . . . . . . . . . . . . . . . .  5
   6.  Cluster Reformation Procedure  . . . . . . . . . . . . . . . .  5
   7.  Other Considerations . . . . . . . . . . . . . . . . . . . . .  6
   References . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  6






























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1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


2.  Introduction

   A MANET is a wireless multihop network with a number of mobile nodes.
   Especially in a military or office MANET, nodes tend to form groups.
   In this type of MANETs, the traditional flat communication structure
   does not perform efficiently. Instead, the clustering architecture is
   a better communication structure since it fits well to the physical
   network topology of this type of MANETs [1]. We call the MANET
   employing the clustering architecture the MANET clustering.

   In a MANET with clustering, there can be a number of MANET clusters
   and a node called a cluster head (CH) represents each MANET cluster.
   A MANET cluster consists of a CH and a number of cluster members
   which are within the range of the cluster size of the CH.
   All CHs have the same fixed cluster size (in the number of hops).
   A node can be a member of only one cluster. That is, if a node is
   within the range of the cluster size of more than one CHs, it has
   to choose only one CH as its cluster head.

   In this draft, we define the terminology and the communication
   architecture for the MANET clustering.


3.  Terminology

   Cluster Head         The representative node of a cluster; the
                        cluster head receives data from its cluster
                        members and forwards the data to the cluster
                        head of the cluster to which the destination
                        belongs, and vice versa.

   Cluster Member       The node belonging to a cluster

   Cluster Size         The maximum number of hops from a cluster head
                        to any one of its cluster members; in this
                        draft, we assume that the cluster size is fixed
                        to k

   Cluster Formation Procedure
                        The procedure that cluster heads and cluster
                        members are determined; composed of the cluster
                        announcement phase and the cluster join phase


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   Cluster Announcement Phase
                        The cluster head sends the Cluster Announcement
                        message to its k-hop neighbors to indicate its
                        willingness of forwarding data from its cluster
                        members

   Cluster Join Phase   The node wishing to act as a cluster member
                        sends out a Cluster Join message to the cluster
                        head upon receiving a Cluster Announcement
                        message from the cluster head

   Data Exchange Procedure
                        The procedure that a node sends data to another
                        node via their cluster heads; data exchange
                        between two nodes in different clusters must
                        be forwarded by their cluster heads

   Cluster Reformation Procedure
                        The procedure that a cluster head gives up its
                        role and its members change clusters to belong


4.  Cluster Formation Procedure

   For the MANET clustering to work, MANET nodes have to form clusters
   by following the cluster formation procedure which is composed of the
   cluster announcement phase and the cluster join phase. The cluster
   formation procedure is carried out either periodically or when a
   prespecified event occurs (e.g., when a CH gives up its role).
   After the cluster formation procedure, two nodes in different
   clusters can communicate via their CHs.

   The algorithm for a node to determine itself to be a CH is out of the
   scope of this draft. Once a node decides to beomce a CH, it sends out
   a Cluster Announcement message to its k-hop neighbors, where k is the
   cluster size. We call this phase the cluster announcement phase.

   Once a node receives a Cluster Announcement message, it replies back
   to the corresponding CH (i.e., the originator of the Cluster
   Announcement message) with a Cluster Join message, if it wishes to
   join the cluster announced by the Cluster Announcement message.
   If a node receives more than one Cluster Announcement messages, it
   has to reply back to only one CH by sending a Cluster Join message
   only to the chosen CH. We call this phase the cluster join phase.

   Steps (1) and (2) of figure 1 shows the message exchange scenario of
   the cluster formation procedure initiated by cluster heads n2 and n4
   In this scenario, node n3 receives Cluster Announcement messages from
   both n2 and n4, and replies back only to n4.


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                        n1         n2(CH)        n3         n4(CH)

   (1) Cluster
       Announcement      <-----------+-----------><-----------+
       Phase

   (2) Cluster
       Join              +----------->            +----------->
       Phase

   (3) Data              +===========>
       From n1
       To n3                         +========================>

                                                  <===========+

   Figure 1. A message exchange scenario of MANET cluster formation


5.  Data Exchange Procedure

   Once cluster formation procedure is completed, the data sent from
   nodes in different clusters must be forwarded by their cluster heads.
   Step (3) of Figure 1 shows the message exchange scenario for data
   delivery from n1 to n3 via cluster heads n2 and n4. First, n1 sends
   a data packet to its CH n2 and n2 forwards it to the destination
   CH n4 and, finally, n4 forwards it to the destination node n3.
   In order for this data delivery to work, a source CH is required to
   know the destination CH. How to determine the destination CH will be
   defined later.

   If source and destination nodes are in the same cluster and reachable
   via 1-hop, then those nodes can directly communicate without the help
   of the cluster head. However, if they are more than 1-hop away, they
   must communicate via their cluster head even though they are in the
   same cluster.


6.  Cluster Reformation Procedure

   The cluster reformation procedure can be initiated by either (i) a
   periodic CLAN message or (ii) a Cluster Giveup (CLGU) message.
   The cluster reformation procedure of the case (i) is the same as
   the cluster formation procedure in section 4. The cluster reformation
   procedure of the case (ii) is started when a CH broadcasts a CLGU
   message to its members. A CLGU message is generated by a CH when it
   faces some circumstances that it can not continue its role as a CH
   such as the energy depletion or some other events prespecified by
   a cluster management mechanism.


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   When a member receives a CLGU message from its CH, it decides whether
   it will become a CH or send a CLJN message to another CH. If it
   decides to become a CH, it has to go through the cluster formation
   procedure described in section 4. Otherwise, it sends a CLJN message
   to one of the CHs from which it has received CLAN messages recently.


7.  Other Considerations

   TBD.


References

   [1] I. G. Shayeb and et. al., "A Survey of Clustering Schemes for
       Mobile Ad-Hoc Network (MANET)," Americal Journal of Scientific
       Research, pp. 135-151, 2011.


Authors' Addresses

   Sanghyun Ahn
   University of Seoul
   90, Cheonnong-dong, Tongdaemun-gu
   Seoul 130-743
   Korea
   Email: ahn@uos.ac.kr

   Hyogon Kim
   Korea University
   145, Anam-ro, Seongbuk-gu
   Seoul 136-701
   Korea
   Email: hyogon@gmail.com

















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