Michael L. Needham

Predictive Caching for Video on Demand CDNs

Video on Demand (VoD) services provide a wide range of content options and enable subscribers to select, retrieve and locally consume desired content. In this work we propose caching solutions to improve the scalability of the content distribution networks (CDNs) of existing VoD architectures. We first investigate metrics relevant to this caching framework and subsequently define goals that should be satisfied by an efficient solution. We propose novel techniques for predicting future values of metrics of interest. We use our prediction mechanisms to define the cost imposed on the system (network and caches) by items that are not cached. We use this cost to develop novel caching and static placement strategies. We validate our solutions using log data collected from Motorola equipment from several Comcast VoD deployments.

Utility-function-based optimal resource allocation with a mixture of reallocation-tolerant and reallocation-intolerant users

In this work, we consider the problem of utility function-based resource allocation when a mixture of reallocation-tolerant and reallocation-intolerant users are present. Unlike reallocation-intolerant users, reallocation-tolerant users can be reallocated a different amount of resource during the course of their call. We develop a resource allocation mechanism that maximizes the average aggregate utility per unit time. By formulating the resource allocation problem as a Markov decision process (MDP), we determine the optimal quantity of resource to be allocated to newly arriving and the optimal reallocation of resources to reallocation-tolerant calls whenever there is a change in the state of the system. We present numerical results that show that our resource allocation scheme performs better than the greedy resource allocation scheme. To reduce the computational complexity involved in determining the optimal policy, we identify problem-specific model reduction techniques that do not compromise the optimality of the solution.

A framework for network aware caching for video on demand systems

Video on Demand (VoD) services allow users to select and locally consume remotely stored content. We investigate the use of caching to solve the scalability issues of several existing VoD providers. We propose metrics and goals that define the requirements of a caching framework for CDNs of VoD systems. Using data logs collected from Motorola equipment from Comcast VoD deployments we show that several classic caching solutions do not satisfy the proposed goals. We address this issue by developing novel techniques for predicting future values of several metrics of interest. We rely on computed predictions to define the penalty imposed on the system, both network and caching sites, when not storing individual items. We use item penalties to devise novel caching and static content placement strategies. We use the previously mentioned data logs to validate our solutions and show that they satisfy all the defined goals.

A wireless packet data link protocol with performance enhancements

A packet data protocol is described which provides connectionless packet data services for wireless and mobile radio data systems. Features of the protocol such as selective automatic repeat-request (S-ARQ) and multi-packet streaming allow efficient operation with error-prone channels and radio units limited to half-duplex operation. A detailed analytical model of the protocol is described, and protocol performance results are obtained.

Open base situation transport (OBAST)architecture

This paper outlines the requirements for a set of open IP based protocols enabling seamless mobility across diverse radio access networks. We begin by stating some architectural tenets upon which the requirements for the OBAST protocol set are based. Furthermore, what the authors currently believe to be the eventual desirable wireless Internet architecture is described. This architecture is shown to enable a common protocol set that we refer to as the open base station transport (OBAST) protocol set.