A client with weak transmission power when connected to an ap with a strong transmission power can cause assumption of packet losses by the ap. This could occur due to the fact that the acks sent by the client never make it to the access point. Since the ap does not receive the acks it assumes there is packet loss, this could lead to performance degradation(slowing down rate) and wastage of bandwidth(retransmissions).

Listed below are some relevant references.

• John Bicket's thesis - http://dspace.mit.edu/bitstream/handle/1721.1/34116/67618196.pdf?sequence=1
• Diagnosing wireless packet losses - http://www.citeulike.org/group/10643/article/5205992