# Averting BER Floor with Iterative Source and Channel Decoding for Layered Steered Space-Time Codes
## 1 Introduction
### Related Work  
Owing to the potential increase in wireless devices, the burden on available bandwidth is inevitable and therefore the compression of data is required to transmit and store expansive data. In the transmission of data, reliability at the destination is an utmost desire for suitable processing. Source codes are particularly employed for the compression of data, whereas channel codes primarily resolve emerging errors or at least assist in detectingerrors for ensuring reliability [4]. According to [PERSON], source and channel coding designs can be designed independently from each other under ideal but valid conditions. The chief pitfall associated with independent designs is the poor performance due to the finite length and complexity of source and channel codes deployed, deriving low target error rates [4]. The technique of joint source-channel decoding (JSCD) was formulated [5] for improvements in performance by utilizing the residual redundancy in source coded stream [6; 7]. Until now, turbo codes result in the highest performance and are deemed as the best codes with little required encoding and decoding complexity [8]. The principle of JSCD was adopted in turbo coding by iteratively exchanging information between the constituent decoders and referred to as iterative source-channel decoding (ISCD) [7]. Systems with ISCD exhibited lower bit-error rate (BER) and better performance gain than the systems with non-iterative schemes [9; 10; 11]. Typically, the number of iterations is restricted to two or three iterations as source coding renders the data to have limited residual redundancy [12; 13]. Authors in [12] demonstrated the effects of incorporating redundancy in the source coded stream and declared that the ISCD performance improves with artificial redundancy. Contemporary cellular communication relies heavily on the multiple-input multiple-output (MIMO) technique for an enhanced performance by offering diversity and multiplexing gain improvements. Modern telecommunication is entirely based upon the mechanism of antennas to perform high speed and distant communication. One simple example of an antenna is a piece metal attached to a radio. With the aim of improving BER performance and attaining power reductions, the concept of MIMO can be viewed as an extension to smart antennas [14]. The reason for the enhanced performance of MIMO systems lies in the fact that they exploit the multipath environment of wireless channel. Coherent MIMO systems are complex in terms of channel estimation and impose throughput loss [15]. Therefore, the differential space-time spreading (DSTS) technique was designed to overcome the issue of complexity while providing diversity gain [16], however no improvement in throughput was recorded. The DSTS is an attractive alternative design despite a 3 dB performance loss in comparison to the coherent systems [14]. The DSTS symbols work differentially between successive symbols during its encoding and decoding. Orthogonal spreading codes are used to spread the differentially encoded symbols as discussed in [14]. For throughput improvements, a spatial multiplexing technique based on multi-layer design, known as Vertical-Bell Labs Layered Space-Time (V-BLAST) [17], was developed as a simpler alternative to the Diagonal-Bell Labs Layered Space-Time (D-BLAST) scheme. The D-BLAST scheme is proficient enough to approach the MIMO capacity, but it is way complicated than V-BLAST. More explicitly, the V-BLAST scheme exploits the capacity potential due to multiple transmitters by performing layer by layer detection and decoding for high-speed transmission without any additional power or bandwidth. The drawback associated with BLAST signal is that it is unable to exploit transmit diversity [15]. However, luckily, transmit diversity gain can be relished with the multiplexing techniques of space-time block codes (STBCs). Therefore, an enhanced transmit diversity gain was recorded in [18] due to the linkage of V-BLAST and STBC.