The Spatial Modulation Saga: Single- vs. Multiple-rf Chains and All That..

The classic Shannon-Hartley law suggests that the achievable channel capacity increases logarithmically with the transmit power, which is not a ’good deal’! More beneficially, the MIMO capacity increases linearly with the number of transmit antennas, provided that the number of receive antennas is equal to the number of transmit antennas. With the further proviso that the total transmit power is increased proportionately to the number of transmit antennas, a linear capacity increase is achieved upon increasing the transmit power, which justifies the spectacular success of MIMOs... However, there are huge challenges, which have to be tackled, before these ’massive MIMOs’ might become an off-the-shelf reality. For example, estimating all the (N x M) MIMO channels imposes a potentially excessive complexity, hence perhaps somewhat surprisingly owing to its potential performance erosion non-coherent detection might become an attractive low-complexity solution, as demonstrated in this lecture. Another challenge is the provision of numerous Radio-Frequency (RF) chains, which is THEmost costly part of a transceiver. This problem might be circumvented wiht the aid of Spatial Modulation (SM), where only a single one or a limited fraction of the transmit antennas is activated during any symbol interval. This ’win-win saga’ continues, since apart from the potential benefit of requiring only a single RF chain, SM also has the potential of implicitly conveying extra bits by inferring say log2(M) bits from the specific index of the activated transmit antenna, as discussed in this light-hearted overview... Lajos Hanzo FREng, FIEEE, FIET, RS Wolfson Fellow, received his 5-year Master degree in electronics from the Technical University of Budapest in 1976, his doctorate in 1983 and his Doctor of Sciences (DSc) degree in 2004. During his career in telecommunications he has held various research and academic posts in Hungary, Germany and the UK. Since 1986 he has been with the School of ECS, University of Southampton, UK, where holds the Chair in Telecommunications. His current research interests are featured at (http://www-mobile.ecs.soton.ac.uk)