  Consider a time slotted communication channel shared by $K$ active users and
a single receiver. It is assumed that the receiver has the ability of the
multiple-packet reception (MPR) to correctly receive at most $\gamma$ ($1 \leq
\gamma < K$) simultaneously transmitted packets. Each user accesses the channel
following a specific periodical binary sequence, called the protocol sequence,
and transmits a packet within a channel slot if and only if the sequence value
is equal to one. The fluctuation in throughput is incurred by inevitable random
relative shifts among the users due to the lack of feedback. A set of protocol
sequences is said to be throughput-invariant (TI) if it can be employed to
produce invariant throughput for any relative shifts, i.e., maximize the
worst-case throughput. It was shown in the literature that the TI property
without considering MPR (i.e., $\gamma=1$) can be achieved by using
shift-invariant (SI) sequences, whose generalized Hamming cross-correlation is
independent of relative shifts. This paper investigates TI sequences for MPR;
results obtained include achievable throughput value, a lower bound on the
sequence period, an optimal construction of TI sequences that achieves the
lower bound on the sequence period, and intrinsic structure of TI sequences. In
addition, we present a practical packet decoding mechanism for TI sequences
that incorporates packet header, forward error-correcting code, and advanced
physical layer blind signal separation techniques.
