Abstract
Despite its efficiency in conventional multiple-input multiple-output (MIMO) wireless systems, quadrature spatial modulation (QSM) becomes less efficient in massive MIMO systems since it does not adapt to the number of antennas but always uses one or two out of them. To adopt QSM in massive MIMO systems, a parallel quadrature spatial modulation (PQSM) scheme is proposed in this paper. In PQSM, the transmit (Tx) antennas are divided equally into P > 1 groups, and the bit sequence to be transmitted during a time slot is divided into P+1 parts. Then, the first part is applied to map an M-QAM complex constellation symbol while the remaining P parts of the bitstream are used to perform P QSMs in parallel. By allowing a tradeoff between the spatial modulation order and signal constellation order, PQSM enables lower bit error rate (BER) with no loss of spectral efficiency compared with QSM. For a fixed signal constellation, PQSM yields higher spectral efficiency than QSM since more selected antenna indices can carry more data bits. The algorithm pertaining to the proposed scheme is designed, and an upper bound on the average bit error rate (ABER) is derived. Moreover, to minimize the ABER, an algorithm is developed to optimize the number of Tx antenna groups and the signal constellation order. Monte-Carlo simulation results demonstrate the superiority of PQSM over generalized SM and QSM, as well as the effectiveness of the developed performance analysis.
Highlights
Since massive multiple-input multiple-out (MIMO) technology can greatly improve system capacity and spectral efficiency, it is widely recognized as a key technology in 5G and beyond wireless communication systems [1]
Compared with generalized spatial modulation (GSM) and quadrature spatial modulation (QSM), the proposed parallel quadrature spatial modulation (PQSM) presents attractive features including, i) PQSM can achieve the best tradeoff between the order of signal constellation and the order of spatial modulation, reducing the average bit error rate (ABER); ii) PQSM can obtain higher spectral efficiency than conventional QSM by activating an optimal number of Tx antennas groups instead of one or at most two antennas; and iii) By transmitting the same data symbol in parallel, PQSM retains the key advantage of SM, namely, the complete avoidance of ISI and inter-channel interference (ICI)
SIMULATION RESULTS AND DISCUSSIONS Monte-Carlo simulation results pertaining to the proposed PQSM scheme with different Tx antenna groups and signal constellation orders are presented and compared with the conventional QSM [7] and GSM [5] schemes
Summary
Since massive multiple-input multiple-out (MIMO) technology can greatly improve system capacity and spectral efficiency, it is widely recognized as a key technology in 5G and beyond wireless communication systems [1]. G. Huang et al.: PQSM for Massive MIMO Systems With ICI Avoidance interference (ISI), its spectral efficiency can only increase logarithmically rather than linearly with the number of Tx antennas. To adapt QSM for massive MIMO systems, a parallel quadrature spatial modulation (PQSM) scheme is proposed in this paper. Compared with GSM and QSM, the proposed PQSM presents attractive features including, i) PQSM can achieve the best tradeoff between the order of signal constellation and the order of spatial modulation, reducing the average bit error rate (ABER); ii) PQSM can obtain higher spectral efficiency than conventional QSM by activating an optimal number of Tx antennas groups (denoted Popt) instead of one or at most two antennas; and iii) By transmitting the same data symbol in parallel, PQSM retains the key advantage of SM, namely, the complete avoidance of ISI and ICI.
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