Optimized Live 4K Video Multicast

4K videos are becoming increasingly popular. However, despite advances in wireless technology, streaming 4K videos over mmWave to multiple users is facing significant challenges arising from directional communication, unpredictable channel fluctuation and high bandwidth requirements. This paper develops a novel 4K layered video multicast system. We (i) develop a video quality model for layered video coding, (ii) optimize resource allocation, scheduling, and beamforming based on the channel conditions of different users, and (iii) put forward a streaming strategy that uses fountain code to avoid redundancy across multicast groups and a Leaky-Bucket-based congestion control. We realize an end-to-end system on commodity-off-the-shelf (COTS) WiGig devices. We demonstrate the effectiveness of our system with extensive testbed experiments and emulation

Resource management for cellular networks in shared spectrum

We are witnessing tremendous growth in mobile data traffic. Ericsson predicts [34] that the total mobile traffic is expected to increase by a factor of 5 over the next 6 years, reaching 136 EB/month by the end of 2024. Given this high capacity requirement and constraints on spectrum access because of traditional regulatory approaches, cellular network providers have started to feel the spectrum crunch. In order to address the scarcity of spectrum, we explore the use of cellular radio technology in the shared spectrum. There are several challenges to realize this. First of all, cellular technology, such as LTE, has been designed for planned operator deployments. They dont support unplanned interference management, interoperability with spectrum databases, etc. Secondly, assigning optimal channel resources to interfering nodes requires precise channel estimation and prediction which is very challenging in current LTE systems especially when clients are highly mobile. In this dissertation we design techniques to support unplanned interference management and robust channel estimation and prediction scheme for LTE. First, we study an LTE based network architecture for unlicensed cellular networking in shared spectrum. We design an LTE-compatible interference management component for distributed coordination among users operating in the same frequency channel. Our proposed interference management requires no explicit communication between base stations, and is more efficient than CSMA for long links. Second, we develop a decentralized spectrum management system for unlicensed LTE users in a shared band. We design a channel allocation scheme to efficiently utilize spectrum and incentivise collaboration. This also includes a simple, non-disruptive channel change scheme to frequently and efficiently change channels to accommodate dynamic traffic and environments. Third, we develop a novel channel estimation and prediction algorithm for next generation cellular networks. Instead of directly predicting the channel in the widely used frequency time domain, we predict the channel in the delay-Doppler domain. Our intuition is that mobility is easier to predict than the channel since mobility has inertial correlation, whereas wireless channel is the outcome of complicated interaction between mobility, multipath, and noise. Reliably estimating and predicting the wireless channel is necessary for optimal resource allocation among highly mobile nodes operating in shared spectrumComputer Science

Making Foreign Aid Work: Issues of Cost Effectiveness of Educational Aid in Pakistan

The quality of inclusive and accountable institutions in a donor-recipient country determines the effectiveness of foreign aid. This study examined whether the role of donor agency or the implementing agency was more helpful in the successes of two foreign-funded educational interventions in Northern Pakistan. The two interventions, each focusing on teachers’ development program and the capacity development of principals, were funded by two different international donors. The study also provided a comparison of the two international donors working styles and their strategies applied for the execution of their respective projects. The findings of the study, which were generated through qualitative methods, noted wide variations not only in the working strategies of the two donors, but also the role of the executing agency. It was noted that multiple factors determined the productivity of the two projects; one of the elements that contributed the success or failure of the two project was their design or road map. Based on the findings of this study, it was maintained that a proactive role of both the entities is crucial for the success of such interventions. &nbsp

Towards unlicensed cellular networks in TV white spaces

In this paper we study network architecture for unlicensed cellular networking for outdoor coverage in TV white spaces. The main technology proposed for TV white spaces is 802.11af, a Wi-Fi variant adapted for TV frequencies. However, 802.11af is originally designed for improved indoor propagation. We show that long links, typical for outdoor use, exacerbate known Wi-Fi issues, such as hidden and exposed terminal, and significantly reduce its efficiency. Instead, we propose CellFi, an alternative architecture based on LTE. LTE is designed for long-range coverage and throughput efficiency, but it is also designed to operate in tightly controlled and centrally managed networks. CellFi overcomes these problems by designing an LTE-compatible spectrum database component, mandatory for TV white space networking, and introducing an interference management component for distributed coordination. CellFi interference management is compatible with existing LTE mechanisms, requires no explicit communication between base stations, and is more efficient than CSMA for long links. We evaluate our design through extensive real world evaluation on of-the-shelf LTE equipment and simulations. We show that, compared to 802.11af, it increases coverage by 40% and reduces median flow completion times by 2.3x