2 research outputs found
Coding with side information
No full textSource coding and channel coding are two important problems in communications. Although side information exists in everyday scenario, the effect of side information is not taken into account in the conventional setups. In this thesis, we focus on the practical designs of two interesting coding problems with side information: Wyner-Ziv coding (source coding with side information at the decoder) and Gel??fand-Pinsker coding (channel coding with side information at the encoder).
For WZC, we split the design problem into the two cases when the distortion of the reconstructed source is zero and when it is not. We review that the first case, which is commonly called Slepian-Wolf coding (SWC), can be implemented using conventional channel coding. Then, we detail the SWC design using the low-density parity-check (LDPC) code. To facilitate SWC design, we justify a necessary requirement that the SWC performance should be independent of the input source. We show that a sufficient condition of this requirement is that the hypothetical channel between the source and the side information satisfies a symmetry condition dubbed dual symmetry. Furthermore, under that dual symmetry condition, SWC design problem can be simply treated as LDPC coding design over the hypothetical channel.
When the distortion of the reconstructed source is non-zero, we propose a practical WZC paradigm called Slepian-Wolf coded quantization (SWCQ) by combining SWC and nested lattice quantization. We point out an interesting analogy between SWCQ and entropy coded quantization in classic source coding. Furthermore, a practical scheme of SWCQ using 1-D nested lattice quantization and LDPC is implemented.
For GPC, since the actual design procedure relies on the more precise setting of the problem, we choose to investigate the design of GPC as the form of a digital watermarking problem as digital watermarking is the precise dual of WZC. We then introduce an enhanced version of the well-known spread spectrum watermarking technique. Two applications related to digital watermarking are presented
ON ANALYTICAL MODELING OF MOBILITY SIGNALLING IN ULTRA DENSE HETNETS
No full textMulti-band and multi-tier network densification is being considered as the most promising solution to overcome the capacity crunch problem in emerging cellular networks. To this end, small cells (SCs) are being deployed within macro cells
(MC) to off-load some of the users associated with the MCs. This deployment scenario gives birth to several new problems. Amongst others, handovers (HOs), signalling overhead and mobility management are becoming increasingly critical
challenges. Frequent HOs in ultra-dense SC deployments can lead to a degraded mobility performance and increase signalling overhead significantly. Recently, a new cellular architecture with control/data plane separation has been proposed to
overcome these challenges. However, the state of the art analysis of the feasibility of the CDSA remains mostly qualitative. There is dire need for mathematical models to analyze the performance of various aspects of CDSA and quantify its gains, if
any, compared to conventional architecture. In this dissertation, we derive several analytical models to compare HO performance in the control/data separation architecture (CDSA) and conventionally deployed networks under various scenarios
and configurations. Our developed mathematical framework advances the state of the art by considering HO success, HO failure and no HO scenarios. The proposed models can be used to quantify HO signalling as a function of key cellular system
design parameter such as cell density, session duration, velocity, HO duration(s) and intercell overlap coverage factor. Using the developed analytical models, we perform a comparative analysis of HO signalling generated during various HO scenarios in
CDSA and conventionally deployed networks. Building on the insights drawn from this analysis, we introduce new parameters for improving the HO execution process in emerging cellular networks viz-a-viz 5G and beyond. These new parameters,
when tuned optimally, can significantly reduce the HO signalling load. Closed form expressions are also derived for continuous and continual (intermittent) mobility scenarios, while considering both HO success and HO failure likelihoods. In addition,
we propose an analytical model which enables more radio resource efficient network planning by quantifying HO signalling and success probabilities as function of intercell overlap coverage factor. Analysis indicates that cell density, actual HO
time duration and average velocity can be used as the key metrics to optimally plan intercell overlap coverage factor in order to minimize mobility signalling load. Numerical results and analysis based on the developed overall analytical framework
indicate that, compared to conventional networks, CDSA offers promising gains in terms HO performance and reduced HO signaling overhead
