Analog joint source-channel coding in several communication scenarios

Resumen

The complexity and delay introduced by efficient digital coding strategies may be a barrier in some real-time communications where the delay is critical and a low complexity coding techniques are necessary. In this regard, these last years, joint source-channel coding schemes have gained prominence precisely for their simplicity and their implicit low delay. Inside joint schemes, those using analog mappings are especially suitable for their minimum delay and ease of implementation. The basic idea of analog mappings for joint source-channel coding consists of mapping the source symbols directly into the channel symbols by using parametric curves or surfaces as ``continuous codebooks''. For example, the most widely used analog mapping is the ``Arquimedes Spirals'' or ``Shannon-Kotelnikov'' mapping. These analog mappings have been used in point-to-point communications with a satisfactory performance. However, most of the previous works in the literature have focused on this particular scenario and there is a lack of joint coding approaches for other communications problems. In this sense, the main purpose of this thesis is to design joint source-channel coding schemes based on analog mappings suitable for more general communications scenarios and to pave the way for a wider embrace of such approaches. Particularly, it proposes single and multiple description joint source-channel coding schemes for scenarios with and without a side information available at the receiver. In addition, this thesis also investigates the design of digital coding schemes for multihop transmission. In particular, it proposes also proposes a decode-combine-forward scheme for the multihop transmission in ad-hoc wireless networks, where the information generated by a source has to be sent to a destination based on multiple-relay cooperation. To this end, the proposed scheme blends together convolutional channel coding with linear combination of blocks of data over a finite field. This scheme outperforms clearly similar schemes found in the literature and using short-length codewords. This fact makes the proposed scheme particularly attractive for low latency applications. Furthermore, this good performance is corroborated through an EXIT chart analysis of the proposed network code. Finally, we provide some insight on a communications system simulation tool that has helped this and other thesis through their research lines.