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ABSTRACT: Radio Frequency Identification (RFID) systems have emerged as an affordable solution for object identification. They are a cheap and error proof alternative to traditional object identification techniques such as bar codes and visual recognition. The problem is to identify objects attached with passive tags. If there are multiple objects within the range of the tag reader, then all objects send their identification to the tag reader at the same time in response to the tag reader's query. This causes collisions at the tag reader and no tag is identified, leading to retransmission of tag IDs which results in wastage of bandwidth and an increase in the total delay in identifying all the objects. Hence protocols need to be devised between the tags and the tag reader to avoid or minimize collisions. Typical collision resolution protocols for a generic multi-access communication system cannot be directly applied to our problem due to constraints on the design of the tag such as lack of battery, low memory, minimum computation power, etc. The main focus of this paper is to discuss collision resolution protocols between the tag and the tag reader. We have surveyed four protocols for the above problem and discussed their merits and demerits. We also explain the applicability of each of the protocols to a scenario where objects need to be identified and updated in an inventory management system.