Joint user grouping and frequency allocation for multiuser SC-FDMA transmission

This paper proposes strategies for user pairing and frequency allocation for a virtual multiple-input multiple-output (V-MIMO) single-carrier frequency-division multiple access (SC-FDMA) transmission over intersymbol interference (ISI) channels. Nu users, equipped with a single antenna each, compose one pair/group and transmit their data in the same frequency band to the base station (BS), equipped with multiple antennas. Multiuser equalization is applied at the BS. The pairs (Nu=2) are either transmitting in subsequent time slots in a time division multiple access (TDMA) scheme using all available bandwidth or in different frequency chunks in a frequency division multiple access (FDMA) scheme. A generalization for Nu>2 users, called user grouping, is given for the FDMA scheme. For the optimization of joint frequency allocation and pairing/grouping, a low complexity solution is proposed and evaluated by simulations for the uplink of Long Term Evolution (LTE). As optimization criteria, the capacity of the resulting V-MIMO channel and the bit error rate (BER) after equalization are evaluated, respectively. The simulation results show that the proposed algorithms yield significant gains compared to random user pairing and frequency allocation and that using BER as an optimization criterion yields a significantly better performance.