In this paper multiple-access interference is characterized for cellular mobile networks, in which users are assumed to be Poisson-distributed on the plane and to employ direct-sequence or hybrid (frequency-hopped/direct-sequence) spread-spectrum signaling with a transmitter-oriented assignment of signature sequences and/or frequencyhopping patterns. Approximations for the bit- and packet-error probabilities are derived for data modulation schemes like binary phase-shift-keying (BPSK) with noncoherent demodulation and forward-error-control codes (like Reed-Solomon codes). In all cases, the effect of varying interference power of the desired signal and the other interfering signals and of Rayleigh nonselective channel fading is taken into account accurately. The throughput in the mobile- to-base transmission mode is then evaluated for the aforementioned data modulation, demodulation, and forward-error- control coding schemes. Furthermore, a comparison of the performance of frequence-hopped, direct-sequence, and hybrid spread-spectrum signaling schemes with the same bandwidth is carried out, to show that, under the varying interference power model, the frequence-hopped system performs best among them.