Space Shift Keying (SSK) Robustness to Imperfect Channel State (CSI) Information

Di Renzo, M.; De Leonardis, D.; Graziosi, F.; and Haas, H., "On the Performance of Space Shift Keying (SSK) Modulation with Imperfect Channel Knowledge", in Proc. of the Global Communications Conference (Globecom 11), IEEE, (Huston, Texas, USA), 5-9 December 2011, 5 pages (to appear)

In this paper, we study the sensitivity and robustness of SSK modulation to imperfect channel knowledge at the receiver. Unlike the common widespread belief, we show that SSK modulation is more robust to imperfect channel knowledge than other state-of-the-art transmission technologies, and only few training pilots are needed to get reliable enough channel estimates for data detection. More precisely, we focus our attention on the so-called Time-Orthogonal-Signal-Design (TOSD) SSK modulation scheme, which is an improved version of SSK modulation offering transmit-diversity gains, and provide the following contributions:

  • i) we develop a closed-form analytical framework to compute the Average Bit Error Probability (ABEP) of a mismatched detector for TOSD-SSK modulation, which can be used for arbitrary transmit-antenna, receive-antenna, channel fading, and training pilots;
  • ii) we perform a comparative study of the performance of TOSD-SSK modulation and the Alamouti code under the same imperfect channel knowledge, and show that TOSD-SSK modulation is more robust to channel estimation errors;
  • iii) we point out that only few pilot pulses are required to get performance very close to the perfect channel knowledge lower-bound;
  • iv) we verify that transmit-and-receive-diversity gains of TOSD-SSK modulation are preserved even for a mismatched receiver.

SSK requires about 10 dB less SNR to achieve the same BER than Alamouti for high spectrum efficiency (4 bit/s/Hz) and imperfect channel estimation. We assume that channel estimation is performed by using a Maximum-Likelihood (ML) detector and by observing Np pilot pulses that are transmitted before the modulated data. During the transmission of one block of pilot-plus-data symbols, the wireless channel is assumed to be constant, i.e. a block-fading channel is considered.

Table Comparison SSK with Alamouti