Wednesday, December 19, 2007
Max Throughput = 1 / e = 36.79%
Simulator generates the result around 34% (above 1000 tags)
Now the concentrates are on:
Reduce Q parameter update frequency: as far as we know, Q parameter decreases as the detection process going. Fluctuating Q causes redundant data in transmission.
Find an out of box method to break the slot Aloha throughput limit.
Friday, December 14, 2007
Thursday, December 13, 2007
I use Java to implement this algorithm. This can simulate the communication between tags and reader, and statistics can be collected in each cycle or slot.
It is still unclear about when to update tag's Q parameter. This algorithm assumes it updating each collision or some empty cycles.
The performance is mentioned in previous blog entry. Basically, three cycles for identifying one tag.
Wednesday, December 12, 2007
How frequent to update Q parameter using that official algorithm?
Every queryRep queryAdjust or follow other rule
The rule, or the way to adjust the gap (the C parameter) in each update of Q parameter.
Brief Performance Summary:
Tags Number * 3 = Query Number (20 - 5000 tags)
Three query messages needed to identify one tag
Wednesday, December 05, 2007
5.2. Reader-Tag Half-Duplex Communication
As specified in Section 6, the Reader-to-Tag and Tag-to-Reader communication occurs in a half-duplex manner. The Reader initiates communication by modulating a complete command. The Reader then transmits an unmodulated continuous wave (CW) signal. The Tag modulates its reflection of the CW signal (backscatter communication).
5.3. Reader-to-Tag Communication Signals
A Reader may emit no signals at any frequency, may emit a CW signal at a single frequency, or may emit a modulated signal at a single frequency.
5.3.1. Reader-to-Tag Signal Modulation Depth
The Reader communicates with tags using Amplitude Shift Keying (ASK) with a minimum modulation depth of 30% and a maximum modulation depth of 100%. Modulation shape, depth and rate of modulation are variable within the limits described below. Compliant Tags will adjust their timing over a range of modulation rates to lock to reader transmissions automatically during the [CLKSYNC] period of a Reader command.
Have read Class 1 Gen2 specification, draft the pesudo-code framework using Java. Thinking about a whether a discrete simulation is necessary, and the means of performance measurement.
In implement simulation of Gen2, a simplification is made in message transmission, like ACK and Session selection etc., which have no influence in the anti-collision measurement so far.
Session selection deals with Reader-to-Reader collision.
ACK is reliable transmission and for further processing in tag.