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Space‐time block code (STBC)–based multiple‐input–multiple‐output techniques have been considered recently to enhance the performance of mobile satellite communication systems in terms of link reliability. Uncoded space‐time labelling diversity (USTLD) is a diversity technique that is a direct extension of the STBC system and further improves its performance. A USTLD system is proposed in this paper that is designed specifically for satellite to mobile station links. The circular M‐ary Amplitude Phase‐Shift Keying (MAPSK) constellation, which is adopted by the most recent satellite broadcasting standard Digital Video Broadcasting standard for nonlinear satellite links (DVB‐S2X), is applied to the USTLD system. The most critical aspect of developing a USTLD system is the design of the secondary mapper to achieve labelling diversity. Existing square M‐ary Quadrature Amplitude Modulation (MQAM) approaches to USTLD mapper design are adapted for appropriate 16APSK and 64APSK constellations from the DVB‐S2X standard. Various metrics are derived to quantitatively compare mapper designs for a Nakagami‐q fading channel. Theoretical results, verified by Monte Carlo simulations, show that the best of the MAPSK USTLD mappers considered achieve a gain of approximately 4 dB for 16APSK and 5 dB for 64APSK when compared to the Alamouti STBC system. Furthermore, a study is conducted to analytically compare USTLD mappers using the derived metrics for both MQAM and MAPSK. It is concluded that a two‐stage approach is the most accurate methodology for comparing USTLD mapper designs.

Summary Greater spectral efficiency has recently been achieved for Uncoded Space Time Labelling Diversity (USTLD) systems by increasing the number of antennas in the transmit antenna array. However, due to constrained physical space in hardware, the use of more antennas can lead to degradation in error performance due to correlation. Thus, this paper studies the effects of spatial correlation on the error performance of USTLD systems. The union bound approach, along with the Kronecker correlation model, is used to derive an analytical expression for the average bit error probability (ABEP) in the presence of Nakagami‐q fading. This expression is validated by the results of Monte Carlo simulations, which shows a tight fit in the high signal‐to‐noise ratio (SNR) region. The degradation in error performance due to transmit and receive antenna correlation is investigated independently. Results indicate that transmit antenna correlation in the USTLD systems investigated (3 × 3 8PSK, 2 × 4 16PSK, 2 × 4 16QAM, and 2 × 4 64QAM) causes a greater degradation in error performance than receive antenna correlation. It is also shown that 2 × 4 USTLD systems are more susceptible to correlation than comparable space‐time block coded systems for 8PSK, 16PSK, 16QAM, and 64QAM.