| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 103 === Direct short range device-to-device (D2D) communications offer many potential advantages against conventional base station based cellular technology, e.g., high transmission rates, lower latency, reduced transmit power and interference level. It also offloads traffics from existing macro-cellular networks (MCNs) and support emergency communications (public safety) when the core network breaks down.
To achieve the above-mentioned advantages in a D2D network, a device or user equipment (UE) must be able to discover other devices or UEs in its vicinity and establish the corresponding links. The purpose of this thesis is to present feasible and efficient distributed solution to these two critical issues for a D2D communication system underlaying an MCN.
In our scheme, device ID is based on the spectrum sensed by each D2D device. We presume that devices in close proximity would observe similar spectra thus are more likely to have same ID. These devices with the same ID are to be assigned to the same cluster. Since Reed-Solomon (RS) codes are non-binary maximum distance separable (MDS) codes, they are perfect candidate codes to model the sensed quantized spectra and generate frequency-hopped (FH) probing waveforms that have near-optimal dissimilarity.
To detect multiple probing signals, we develop an efficient scheme which takes advantage of the RS code's errors-and-erasure decoding capability. We are able to detect spectra not only those which are similar to that sensed by the detector but also those which are dissimilar. An enhanced probing signal design is proposed to enable a receiving device to find the most appropriate device among multiple probing devices which bear the same ID.
To estimate the discovery and link setup probabilities, we adopt an analytic simulation
scheme. This scheme is very efficient in that it combines the analysis on the effects of both small and large scale fading and the simulated averaging on the geometry of devices and neighboring base stations.
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