Method and apparatus for preferred roaming list compression

A processor implemented apparatus of accessing a compressed preferred roaming list (PRL) resulting from generating a subnet address by performing a bitwise AND operation on a network identification (ID) and a subnet mask, the subnet address consisting of a plurality of most significant bits and a plurality of least significant bits, the most significant bits of the subnet address representing a common part of a subnet to be factored out, storing the most significant bits of the subnet address in a subnet table, storing the least significant bits of the subnet address in a system table, factoring out at least one set of data common to two or more subnets, storing said at least one set of data common to said two or more subnets in the subnet table, generating an indicator for accessing said at least one set of data, and storing the indicator in the system table:

• means for retrieving from the system table remaining data not common to said two or more subnets;
• means for retrieving from the system table the indicator for accessing said at least one set of data common to said two or more subnets;
• means for retrieving from the subnet table said at least one set of data common to said two or more subnets corresponding to the indicator;
• and
• means for concatenating said at least one set of data common to said two or more subnets with said remaining data to form a complete subnet record.

A processor implemented apparatus of accessing a compressed preferred roaming list (PRL) resulting from generating a subnet address by performing a bitwise AND operation on a network identification (ID) and a subnet mask, the subnet address consisting of a plurality of most significant bits and a plurality of least significant bits, the most significant bits of the subnet address representing a common part of a subnet to be factored out, storing the most significant bits of the subnet address in a subnet table, storing the least significant bits of the subnet address in a system table, factoring out at least one set of data common to two or more subnets, storing said at least one set of data common to said two or more subnets in the subnet table, generating a subnet tag for indicating whether there are any sets of data common to said two or more subnets and for accessing said at least one set of data, and storing the subnet tag in the system table:

• means for retrieving the subnet tag from the system table;
• means for determining whether the subnet tag is 0;
• if the subnet tag is 0:
• means for retrieving from the system table data not common to said two or more subnets;
• and
• means for forming a complete subnet record by filling in the subnet record with data not common to said two or more subnets;
• if the subnet tag is not 0:
• means for retrieving from the subnet table said at least one set of data common to said two or more subnets corresponding to the subnet tag;
• means for retrieving from the system table remaining data not common to said two or more subnets;
• and
• means for concatenating said at least one set of data common to said two or more subnets with said remaining data to form a complete subnet record.

A processor implemented apparatus of accessing a compressed preferred roaming list (PRL) resulting from generating a subnet address by performing a bitwise AND operation on a network identification (ID) and a subnet mask, the subnet address consisting of a plurality of most significant bits and a plurality of least significant bits, the most significant bits of the subnet address representing a common part of a subnet to be factored out, storing the most significant bits of the subnet address in a subnet table, storing the least significant bits of the subnet address in a system table, factoring out at least one set of data common to two or more subnets, storing said at least one set of data common to said two or more subnets in the subnet table, generating a subnet common offset index for accessing said at least one set of data, and storing the subnet common offset index in the system table:

• means for retrieving from the system table a system record comprising a subnet least significant bit length indicator, a subnet least significant bit field, and the subnet common offset index;
• means for retrieving from the subnet table a subnet record comprising a subnet common length indicator and a subnet common field corresponding to the subnet common offset index;
• and
• means for concatenating the subnet common field with the subnet least significant bit field to form a complete subnet field.