use of bandwidth is determined by time used for valid data transfer with respect to time thus as seen in fig4 a which is an example of a frame size which is too large i e one exhibiting inefficient latency the total response frame size 24 is made up of a time sequential array of individual time slots 26 a non collided valid data packet transfer is a tag response 28 indicated by a blacked out slot 26 from a corresponding rfid tag 12 where no other tag responded simultaneously to the polling interrogator issuing interrogation command 32 the presence of the successful tag response 28 i e successful bandwidth use is indicated by a corresponding elevation in signal strength illustrated as square waveform 30 in fig4 b fortunately as illustrated in fig5 a and 5 b elevated signal strength also indicates unsuccessful tag responses 34 shown x 39 d in time slots 26 resulting from collisions where a plurality of rfid tags 12 respond to the same interrogation command 32 so as to produce overlapping or simultaneous responses thus the number of successful tag responses 28 can be compared with the total bandwidth use to estimate the number of response collisions 34 this enables the estimation of the collision.