Deep indoor scenarios are one of the most challenging areas of application for Global Navigation Satellite Systems (GNSS) in personal navigation devices. Especially severe signal attenuation, as well as heavy multipath constrain the use of GNSS in this environment. The project DINGPOS is focusing on the development of a platform for pedestrian users which can acquire and track GNSS signals also under most adverse indoor signal conditions. The main idea of the concept is the extension of the coherent signal integration time of the GNSS receiver to the length of several seconds, which increases the correlation gain significantly. To facilitate this goal, a very long and very precise signal replica is needed. Therefore the system must reproduce the user motion, the navigation message data bits and the satellite constellation precisely. Hence, the system uses a sensor suite of several state of the art indoor positioning sensors and innovative fusion algorithms. The integrating element of the system is a software receiver using Ultra-Tightly Coupling (UTC) implemented by vector tracking. The presented work was performed under the ESA funded contract DINGPOS, ESTEC Ctr. No. 20834.

We present a bandwidth-efficient channel coding scheme that has an overall structure similar to binary turbo codes, but employs trellis-coded modulation (TCM) codes (including multidimensional codes) as component codes. The combination of turbo codes with powerful bandwidth-efficient component codes leads to a straightforward encoder structure, and allows iterative decoding in analogy to the binary turbo decoder. However, certain special conditions may need to be met at the encoder, and the iterative decoder needs to be adapted to the decoding of the component TCM codes. The scheme has been investigated for 8-PSK, 16-QAM, and 64-QAM modulation schemes with varying overall bandwidth efficiencies. A simple code choice based on the minimal distance of the punctured component code has also been performed. The interset distances of the partitioning tree can be used to fix the number of coded and uncoded bits. We derive the symbol-by-symbol MAP component decoder operating in the log domain, and apply methods of reducing decoder complexity. Simulation results are presented and compare the scheme with traditional TCM as well as turbo codes with Gray mapping. The results show that the novel scheme is very powerful, yet of modest complexity since simple component codes are used.

We extend turbo trellis coded modulation (TTCM) with punctured component codes to allow higher bandwidth efficiency. Two techniques, that can also be combined, were investigated that achieve this: the inclusion of uncoded bits in TTCM in conjunction with high order modulation (e.g. 64-QAM), and the replacement of two dimensional component codes (e.g. Ungerboeck codes) with multi-dimensional codes. In the first approach, the inter-set distance of the partitioning tree can be used to fix the number of coded and uncoded bits, which will strongly determine the complexity of the decoder. Simulation results are presented for 8-PSK with 2.5 bits per symbol and 64-QAM with 5 bits per symbol; they indicate that the scheme can achieve good bit error rates close to Shannon's limit.