MPSK Orthogonal Coset Identification for Massive RFID Network

Efficient tag identification is critically important for the application of radio frequency identification (RFID). The recently proposed orthogonal coset identification (OCSID) achieves orthogonal tag ID scanning without spectrum spreading so that the tag IDs can be recovered from collision. In the OCSID, the IDs are generated from binary vector set
$\{-1, +1\}^{B}$
, which is only available for binary modulation. In this letter, we show that
$B$
dimensional
$M$
order vector set
$\left\{{1, e^{\mathrm {i}\frac {2\pi }{M}}, {\dots }, e^{\mathrm {i}\frac {2\pi (M-1)}{M}}}\right\}^{B}$
can be decomposed to
$\frac {M^{B}}{B}$
disjoint orthogonal subsets, where
$M$
is the modulation order,
$B$
is a positive integer power of 2. Based on this, we generalize the OCSID from binary to arbitrary order and propose
$M$
-ary phase shift keying (MPSK) OCSID. We show a possible way to adopt the MPSK OCSID into EPC global C1 Gen2 standard, and with the consideration of the synchronization error, we also present a hybrid of the MPSK OCSID and the Aloha. Numerical results show that the MPSK OCSID based protocol can considerably improve the efficiency, even for the non-perfect synchronization cases.