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Concurrent Programming with Java
Lab Manual, Version 1.0, F. Astha Ekadiyanto, 2002.

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Lab 1: Introduction to Lab. Environment and Object Orientation

Object First
- Cell Class
- RBS Class (Radio Base Station)
- MSC Class (Mobile Switching Center)

Rbs Class

The Rbs Class is an individual Class (only extends Object Class) to represent the Radio Base Station entity in the Mobile Network. An RBS is a gateway for Mobile Stations (or Mobile Users) to connect to the Mobile Network. An RBS should only serve one cell (thus RBS should have a Cell object). In order to use an RBS, one should register them in their MSC. This means that RBS should serve all the inquiries demanded by MSC.

To help defining RBS classification, a simple demonstration of properties and behaviour is performed here.

What an RBS should have?

A Cell being served
RBS ID
Records of Neighbor RBSs (stored in an array or Rbs).

What an RBS should behave?

Provide information about the Cell being served
This behaviour is simply returns the reference to the serviced Cell so that any objects can directly communicate to the Cell, but not changes the Cell's reference stored in the Rbs object (Think as if it is a read only behaviour)
Register neighboring RBSs
This will enables other objects to communicate with the Rbs to ask it to register its neighboring Rbs. This behaviour is necessary by the Msc to be able to setup a Mobile Network topology.
Enable other objects to query all the registered neighboring RBSs
In some cases, an Msc needs to query all the registered neighbors of an Rbs to find better service quality for a Mobile Station. Java API suggests an interface called Enumeration to classify enumerated behaviour of an object. Thus, any classes that implements Enumeration should implement the two methods so called hasMoreElements() and nextElement().

These definitions can be implemented in Java Language as follows :

File name: Rbs.java

Class Fields :

MAXNEIGHBOR : A constant represents the maximum number of neighbors that an Rbs can register.
numOfNeighbor : A field that indicates the number of neighbor currently registered
cellAssigned: A field to refer to the cell assigned to be served
id: A String field that represents the Rbs Identification String
neighborRbs: An array of Rbs that stores all the references of registered neighboring Rbs.
current: This field is a pointer used for enumeration when other objects queries the registered Rbs.

Class Constructors:

Rbs() : Initializes all Class Fields without arguments
Rbs(String id) : Initializes all Class Fields and set Rbs Identification String.
Rbs(String id, Cell) : Initializes all Class Fields and set Rbs ID and registers serviced cell.

Class Methods:

setID(String) : set the Rbs ID.
setCell(Cell) : set the reference of Cell serviced by the Rbs.
getID() : get the Rbs ID.
getCell() : get the reference to the Cell serviced by the Rbs.
toString() : returns the String representation of this Rbs (used in direct String operation).
addNeighbor(Rbs) : registers the Rbs argument as one of the Rbs neighbors.
isNeighbor(Rbs) : check whether the Rbs argument is registered as neighbor.
resetElements() : reset the current pointer for Enumeration of the neighboring Rbs.
hasMoreElements() : implements the Enumeration method to check is there are more elements.
nextElement() : implements the Enumeration method to return the next element.

import java.util.*;
/**
 * Radio Base Station
 * 
 * @author CPwJ
 * @version 1.0 (2002)
 */
public class Rbs implements Enumeration //Enumeration is an interface defined in Java API
{
    // instance variables 
    private static final int MAXNEIGHBOR=6; //Maximum number of neighbors
    private int numOfNeighbor=0; //Number of neighbor currently registered
    private Cell cellAssigned; //The cell assigned to be served
    private String id; //The RBS identification String
    private Rbs[] neighborRbs=new Rbs[MAXNEIGHBOR]; //The array of neighbors
    private int current = 0; //The pointer to neighbor index (Enumeration interface)

 	/**
    * Rbs Constructor 
    */
    public Rbs()
    { 
         setID("Unidentified");
         setCell(null);
    }
    public Rbs(String id)
    {
         setID(id);
         setCell(null);
    }
    public Rbs(String id, Cell servicecell)
    {
         setID(id);
         setCell(servicecell);
    }
   /**
    * Change the Rbs Identification string
    * @param ID Identification String
    */
    public void setID(String id)
    {
         this.id = id;
    }
   /**
    * Change the Rbs Cell assignment
    * @param servicecell The Cell assigned to the Rbs
    */
    public void setCell(Cell servicecell)
    {
         cellAssigned = servicecell;
    }
   /**
    * Read the Rbs Identification String
    * @return String ID, Rbs Identification 
    */
    public String getID() 
    { 
         return id; 
    }
   /**
    * Get the Cell assigned to this Rbs
    * @return The Cell served by this Rbs
    */
    public Cell getCell() 
    { 
         return cellAssigned; 
    }
   /**
    * Regiters all neighboring Rbs
    * @param Rbs The neighboring RBS
    */
    public void addNeighbor(Rbs neighbor) 
    {
         if ((neighbor!=this) && (numOfNeighbor<MAXNEIGHBOR) 
                        && !(isNeighbor(neighbor)) ) 
         { 
               neighborRbs[numOfNeighbor++] = neighbor; 
         }
    }
    private boolean isNeighbor(Rbs neighbor) 
    { 
         for (int x=0; x<numOfNeighbor; x++) 
         {
               if ( neighborRbs[x]==neighbor ) return true;
         }
         return false;
    }
   /**
    * Represent the Rbs content information
    * @return String RBS Information
    */
    public String toString()
    {
         return "RBS ID:"+ getID() + ", " + getCell();
    } 
   /**
    * Reset the pointer of neighbor Rbs element enumeration
    */
    public void resetElements() 
    {
         current=0;
    }
   /**
    * Check if there are more neighbor Rbs element in the enumerated list
    * @return True if the RBS has been registered as neighbor
    * @return False if the RBS has been registered as neighbor
    */
    public boolean hasMoreElements() 
    {
         if (current < numOfNeighbor)
              return true;
         else 
              return false;
    }
   /**
    * Get the next neighbor Rbs element in the enumerated list
    * @return Rbs reference of the next registered neighbor
    */
    public Object nextElement()
    {
         if (hasMoreElements())
              return neighborRbs[current++];
         return null;
    }
}

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