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Abstract-For Rayleigh fading channels, Ricean fading channels with a small parameter and shadowed Rician channels with the code design criteria are to maximize the effective length as well as the minimum product distance of the code. In this paper, we use two different asymmetric 8-PSK signal sets in 4-state and 8-state rate 2/3 trellis-coded modulation (TCM) schemes and show performance gain over TCM schemes with symmetric 8-PSK constellations. The performance gain is due to an increase in the minimum product distance compared to that of the best known TCM schemes of comparable states using symmetric 8-PSK signal sets while the effective length remains same. Simulation is performed over the Rayleigh, Ricean, and shadowed Rician fading channels to demonstrate the performance gain of the asymmetric 8-PSK TCM schemes over the symmetric 8-PSK TCM.

Call centers handle customer queries from various domains such as computer sales and support, mobile phones, car rental, etc. Each such domain generally has a domain model which is essential to handle customer complaints. These models contain common problem categories, typical customer issues and their solutions, greeting styles. Currently these models are manually created over time. Towards this, we propose an unsupervised technique to generate domain models automatically from call transcriptions. We use a state of the art Automatic Speech Recognition system to transcribe the calls between agents and customers, which still results in high word error rates (40%) and show that even from these noisy transcriptions of calls we can automatically build a domain model. The domain model is comprised of primarily a topic taxonomy where every node is characterized by topic(s), typical Questions-Answers (Q&As), typical actions and call statistics. We show how such a domain model can be used for topic identification of unseen calls. We also propose applications for aiding agents while handling calls and for agent monitoring based on the domain model.