Thanks PMM ! but is studying outside Canada is considered as an exceptional circumstance ?
and thanks Leon , I just recieved a mail from Canadian embassy . It says -
" You may proceed to Canada with your valid Indian passport and Permanent Resident Card. However, be advised that when you arrive at the Canadian Port of Entry, you will have to undergo a residency determination.
Upon arrival in Canada, an officer will determine if you meet the residency obligation required to maintain your status as a permanent resident. If you meet the residency obligation, you will be allowed to enter Canada. If, however, the officer determines that you have lost your permanent resident status, the officer may issue a report and refer it to the Minister's delegate for review. If the Minister’s delegate finds the report to be well-founded and insufficient humanitarian grounds exist, the Minister’s delegate shall issue a removal order against you. You would have the right to appeal a negative residency determination made at the port of entry to the Immigration Appeal Division (IAD). As such, you would be allowed to enter Canada only in order to lodge an appeal.
Since you are outside Canada and wish to return to Canada, but are not certain you have met the residency obligation, you may choose to apply for a Travel Document (Permanent Resident Abroad) before attempting to enter Canada. A permanent resident determination will be completed as part of the process. In this way you will know in advance whether you met the residency obligation, and thereby avoid having a removal order issued against you if the determination is negative."
"Upon receipt of an application for a Travel Document, a visa officer will determine if you meet the Canadian residency obligations required to maintain your status as a permanent resident. If you meet the obligations, you will be issued a Travel Document that will allow you to re-enter Canada from abroad.
Note that if a determination is made that you have lost your permanent resident status, you must submit a new immigration application if you wish to resume permanent residence in Canada at some time in the future. Your new application will be evaluated in accordance with the legislation in force at the time of submission. "