  Space Time Block Codes (STBCs) from orthogonal designs have attracted
significant interest in recent years. However, with the growing demand for
higher capacity schemes, the multiantenna transmission techniques must support
and achieve higher symbol transmission rates. In this article, we focus on
three and four transmit antenna schemes. For over two decades, STBC schemes for
three and four transmit antennas that achieve a very high symbol transmission
rate while being orthogonal, fully diverse, delay-efficient, and with very low
decoding complexity have not been achieved. The schemes proposed so far trades
off orthogonality, delay, diversity, or decoding complexity while achieving
rate or vice-versa. This work is first of its kind to solve this problem while
fulfilling all the desired properties.
  In this work, we carefully study the various aspects that must be considered
in designing higher symbol transmission rate STBCs. The proposed designs,
hereby referred to as, Jagannath schemes - for 4 x 3 and 4 x 4 configurations
are orthogonal, achieve full diversity, and support a symbol transmission rate
of 2 symbols/s/Hz. The design methodology follows a coding gain maximization
approach. The low decoding complexity procedure to decode the proposed
transmission schemes are proposed as well as extensively evaluated in
simulations under diverse settings. The performance of proposed schemes are
empirically compared to two state-of-the-art schemes; ACIOD and Jafarkhani.
Jagannath 4 x 3 was shown to outperform ACIOD by ~12 dB while Jagannath 4 x 4
exhibited a ~7 dB superior performance in contrast to Jafarkhani at 4 bpcu.
This motivates the adoption of Jagannath schemes in tactical and commercial
communication systems to effectively double the throughput or to extend the
