BACKGROUND

1. Field of the Invention

The present invention relates generally to content delivery networks (CDNs), and more particularly, to media distribution in wireless communication networks.

2. Introduction

Limited storage of mobile devices is driving cloud services in which data and software are stored on the network. However, in wireless networks, limited wireless bandwidth, variable reliability of the communication channels, and mobility of the client devices discourages off-site data storage and produces significant challenges to media distribution.

The trend in 4G cellular is to make wireless client devices part of the network infrastructure by enabling them to communicate with each other and cooperate. For example, Cooperative MIMO, cooperative diversity, and ad-hoc peer-to-peer networking are being incorporated into the 4G wireless standards. These technologies expand coverage, extend range, and greatly increase bandwidth with minimal cost to wireless service providers. These technologies also provide a significant change to the network topology, as the conventional server-client topology is overlaid with some clients functioning as gateways and routers for other clients. As a result, the nature of media distribution needs to adapt to these new network topologies, especially when client devices generate content or relay content to other client devices.

For conventional media distribution over the Internet, providers of web content and applications typically deliver content from multiple servers at diverse locations in order to sustain a good end-user experience under high traffic loads. In a wireless network, mobile client devices may function as part of the CDN infrastructure. In some cases, mobile devices may be configured to function as “surrogate” origin servers (e.g., Edge Servers). In some cases, mobile client devices may generate content for localized data and software services, such as maps, weather, and traffic.

The extension of a CDN to a wireless ad-hoc network introduces challenges, including, among others, how to guarantee fault-tolerance as the location, availability, and link quality of each mobile terminal may be continuously changing; how to control how requests from end-users are distributed to each Edge Server; and how to guarantee high performance for end-users as network conditions change.

Accordingly, content delivery mechanisms need to adapt to highly variable network topologies and operating conditions in order to provide reliable media and data services. These and other needs in the field may be addressed by aspects of the present invention.

SUMMARY

In accordance with an aspect of the present invention, methods, systems, and software are provided for routing media in a CDN. In wireless wide area networks (WWANs), aspects of the invention employ network layer protocols that exploit special properties of the wireless physical layer. In peer-to-peer networks, WWAN nodes may be configured to perform edge server functionality, such as to reduce WWAN congestion.

A method of selecting an edge-server set from a plurality of nodes comprises determining the network topology state in a CDN. The network topology state may comprise bit-rate estimates for communication links based on network congestion and channel quality. A plurality of candidate edge-server sets is selected, and a performance metric for each set is calculated. At least one of the candidate edge server sets is selected based on the performance metric.

In one aspect of the invention, an iterative method is employed for selecting the candidate edge-server sets. In each iteration, a new candidate set is generated by appending, deleting, or changing at least one node in a previous set. The network topology state may be updated for the new set. A performance metric is calculated for the new set, comprising a benefit minus a cost associated with implementing the new set. At the completion of the iterations, a best set is determined.

In accordance with one aspect of the invention, the performance metric is calculated from a backpressure routing algorithm.

In accordance with another aspect of the invention, the iterative process of selecting and evaluating candidate edge server sets employs a trellis exploration algorithm. A trellis may be constructed using a number of candidate edge servers. A fitness function is derived from a mathematical relationship quantifying costs and network performance improvements corresponding to each edge server. The best edge server sets correspond to paths having optimal path metrics (i.e., branch metrics) derived from the fitness function. Multiple iterations through the trellis may be performed to refine the selection of edge servers.

In another aspect of the invention, a method for processing a request by a client for an object comprises determining if the requesting client is a wireless device in a wireless network; determining if another client on the wireless network has the requested object; determining if the requesting client can communicatively couple to the other client; and directing the request to the other client. The method may be performed by an edge server, a parent server, an origin server, or another network device configured to intercept requests. In some aspects, the method may be performed by requesting client.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth herein.

