Optimal allocation of electronic content

The delivery of large files to single users, such as application programs for some versions of the envisioned network computer, or movies, is expected by many to be one of the main requirements of communication networks. This requires expensive high bandwidth capacity as well as fast and high storage servers. This motivates multimedia providers to optimize the delivery distances, as well as the electronic content allocation. A hierarchical architecture for providing the multimedia content was introduced by Nussbaumer, Patel, Schaffa, and Sternbenz (1994). They also introduced the trade-off between bandwidth and storage requirements for the placement of the content servers on the hierarchy tree. They found the best level of the hierarchy for the server location to minimize the total of the costs of communication and storage. Their algorithm is centralized. We solve the more general ease where servers can be located at different levels of the hierarchy. Our algorithm is distributed, and each node requires a limited memory capacity and computational power. Results for related approaches to caching design are of higher complexity. Results for related classic operations research problems are for centralized algorithms, mostly linear programming, that are not easy to convert into distributed algorithms. Instead, we observe that the use of dynamic programming is more natural for distributed implementations. For the specific problem at hand, we also managed to find a natural function (a generalization of the problem) that simplifies the combination operation used in dynamic programming. We also show how to map such contemporary problems to the area of classical plant location problems in operations research.

http://iew3.technion.ac.il/~kutten/dblp_65.pdf

Network architectures and data communication protocols for supporting both downstream and upstream transport of digital data between a headend facility and multiple downstream network terminals over a shared communication medium include downstream framing protocols compatible with DVB modem transmission framing synchronization and FEC standards at the physical layer, which support a full range of 16 to 256 QAM transmission rates in both 6 MHz and 8 MHz channels. The downstream data frames are formed by one or more repeating pairs of DVB compatible frame slots, wherein each downstream frame is transmitted over the same interval, e.g., 250 usec in preferred formats, regardless of the number of DVB slot pairs it contains. All downstream frame rates are supported by a single upstream data rate. Upstream bandwidth is allocated based on a selected set of operating criteria and service type priorities, based on both a polling basis and a contention basis, on one or more in-band RF subcarrier channels.

Protocol for broadband data communication over a shared medium

Bidirectional cable TV networks using hybrid fiber coaxial (HFC) systems are good examples of broadcast environments where a contention resolution algorithm is needed in order to allocate the multiaccess medium (in this case the upstream link) among the various nodes. Recent activities of the IEEE 802.14 working group aimed at defining the physical and medium access control (MAC) layer protocols for HFC cable networks have focused on the study and evaluation of several contention resolution solutions for inclusion in the MAC protocol specifications. In this article several contention resolution algorithms considered by the IEEE 802.14 group are reviewed. Different implementations for several well known contention resolution algorithms such as tree-based and p-persistence are presented. Their performance is evaluated in the HFC context with respect to upstream channel allocation, roundtrip delay, various traffic types, and number of stations in the network. Simulation results for configurations and scenarios of interest are also presented.

A review of contention resolution algorithms for IEEE 802.14 networks

Network architectures and data communication protocols for supporting both downstream and upstream transport of digital data between a headend facility and multiple downstream network terminals over a shared communication medium include downstream framing protocols compatible with DAVIC/DVB modem transmission framing synchronization and FEC standards at the physical layer. The downstream data frames are formed by two or more repeating pairs of DVB compatible frame slots, wherein each downstream frame is transmitted over the same interval, e.g., 250 usec in preferred formats, regardless of the number of DVB slot pairs it contains. All downstream frame rates are supported by a single upstream data rate. Upstream bandwidth is allocated based on a selected set of operating criteria and service type priorities, based on both a polling basis and a contention basis, on one or more in-band RF carrier channels. Low delay services such as synchronous telephony are provided with requisite delivery and priority.

Network architecture for broadband data communication over a shared medium

Interactive residential broadband/multimedia services are expected to be the next main event in the cyberspace experience. The large excess bandwidth (well over 300 MHz) available in today's cable TV (CATV) hybrid fiber/coaxial (HFC) plants is an ideal candidate to provide the underlying communications infrastructure for interactive digital services to the home; cable operators that have not yet upgraded their all-coaxial plants to HFC are quickly moving in this direction. MLAP is a flexible ATM-friendly MAC protocol that is capable of supporting various types of traffic with diverse quality-of-service requirements. We introduce a very versatile MAC protocol for the HFC 802.14 network. MLAP can provide integrated broadband services to the home, internetwork easily with ATM wide area networks, support QoS constraints for various types of traffic, and operate over a variety of physical layer protocols. Our presentation is only an extended summary of our medium-sharing protocol proposal to the IEEE 802.14 WG. We consider only error-free system operation. MLAP provides for the use of timers for the recovery of error situations in the network. MLAP is also supported by a management suite of protocols for management of the overall system.

B. McNeil

Papers

MLAP: a MAC level access protocol for the HFC 802.14 network