Resource Allocation for OTFS with High Mobility

Orthogonal Time Frequency Space (OTFS) modulation has emerged as a promising waveform for next-generation wireless communications. OTFS demonstrates robust non-fading properties even under doubly-dispersive conditions, making it a preferred modulation scheme in complex scenarios involving high mobility. Despite its advantages, developing a low-complexity multiaccess OTFS protocol for environments with a large number of user terminals (UTs) and high mobility remains challenging due to severe multiuser interference (MUI) and rapidly changing channel states. In this paper, we propose a low-complexity algorithm to find a suboptimal solution for the joint resource block and power allocation problem in multiple access OTFS systems. Specifically, we decompose the resource block allocation and power allocation into two sub-problems. First, we perform the resource block allocation algorithm by considering the channel conditions. Then, we employ a two-stage water-filling algorithm to achieve a suboptimal power allocation. Numerical results indicate that our proposed resource allocation scheme achieves higher sum-rate than existing schemes in both 8-user and 16-user systems while reducing the complexity from exponential to linear in terms of the number of users. This makes our approach practical even in high mobility and larger user scenarios.