THE COMPLETE TECHNICAL PAPER PROCEEDINGS FROM: ADVANCED MONITORING OF SWITCHED BROADCAST SYSTEMS Ludovic Milin and Ran Oz BigBand Networks Abstract such as an unanticipated growth, that may lead to insufficient bandwidth being available Switched broadcast has become a viable to support all channel requests. Early technology for reclaiming bandwidth and identification of such trends can allow pro- optimizing spectrum, allowing richer program active remedies, minimizing negative lineups and increasing personalization of subscriber impact. content. By leveraging switched broadcast The authors also highlight the imperative cable operators are able to offer subscribers of protecting consumers’ privacy and hundreds of high definition programs and describe how the techniques used to collect long tail content, such as coverage of local viewership data can be made to comply with sporting events, without requiring plant the 1984 US Cable Privacy Act. upgrades to expand capacity. This paper presents data gathered from INTRODUCTION multiple switched broadcast deployments to illustrate the imperative of monitoring system Switched broadcast came of age recently performance and the resulting benefits to as two major North American cable operators operators. deployed the technology in several markets. The authors assert that performance Switched broadcast currently supports over monitoring should be applied at three key six million homes passed and switches one stages of deployment of a switched broadcast million set-top boxes. With other cable system: operators evaluating the technology and undertaking field trials, the footprint of 1) Prior to Deployment – during this stage deployed switched broadcast systems is set to an operator must assess which programs in its grow rapidly. broadcast lineup are viable candidates for putting on a switched tier. A non-intrusive By reclaiming the bandwidth that would analytical tool is, arguably, the best way to otherwise be consumed by delivering collect viewership statistics for all available unwatched content, switched broadcast programming, allowing identification of provides cable companies the opportunity to “long tail” content. expand the amount of programming they offer subscribers. However, the oppprtunity to 2) During Deployment – while a switched provide thousands, even tens of thousands, of broadcast system is being implemented an programs requires operators to evolve the operator will benefit from leveraging the methodologies used to track viewership of same monitoring platform used in the prior that content. The ability to collect statistics, in characterization effort, potentially still real-time, about which programs subcribers gathering viewership data on broadcast are watching is necessary for successful programming. capacity planning and deployment of switched 3) After Deployment – once the installation broadcast systems. The insights gained from has been completed the monitoring focus can collection of this data facilitates rapid and be broadened to allow identification of trends, smoother deployment of switched systems. Valuable statistics include the viewership • Diagnostics; of linear and switched broadcast programs, • Content personalization; the number of active STBs (set-top boxes) per service group, and the bandwidth utilization • Addressable advertising; within service groups. • Market research. Additionally, the ongoing collection of This paper discusses each of these information enables round-the-clock applications in depth and cites the specific performance monitoring, leading to benefits of a statistics monitoring platform in opportunites for pro-active network each instance. It begins, however, with a maintenance. Data about blocking events, description of how the platform functions. failures for STBs to tune to the requested channel and network response times can all be ARCHITECTING NETWORKS FOR analyzed, leading to enhanced performance STATISTICS RETRIEVAL and, ultimately, increased subscriber satisfaction. The statistics monitoring / diagnostics In addition to the operations benefits platform proposed by the authors consists of obtained from deploying a statistics the following components: monitoring tool, the ability to build accurate • Collection Engine – gathers STB activity and complete records of viewership behavior logs from the servers, known as SBSSs introduces new revenue possibilities. (switched broadcast session servers), Personalized news is one example of ways used to manage a switched broadcast that precise viewership records collected by a network; statistics monitoring tool could be leveraged for new revenue generation. Another is • Analytical Engine – processes the STB addressable advertising, which matches ads activity logs gathered from the network; more closely to subscribers’ interests, by • Data Warehouse – stores the data and leveraging insights into which content metadata obtained from the both the viewers are habitually tuning to. network and analytical components, and Finally, while the use of third-party market supports long-term storage for trending research firms has generally been sufficient to analysis; obtain insights into subscriber viewing habits, the plethora of new programs that will be • Webserver – provides a user-friendly available to subscribers in switched interface to customize and view reports. environments makes this task more daunting. Figure 1 shows how these elements are The value of this information is high because combined in a generic switched network. it provides insights into the viewing patterns of all subscribers on the switched tier, not just the subset of viewers that have been enlisted and whose viewing habits may not necessarily represent those of the majority. This paper describes a method for collecting statistics that supports the applications described above, namely: • Capacity planning; Figure 1: Components of a statistics management platform Rather than the traditional store and The real-time metrics derived from the forward approach in which each STB protocol messages can be grouped into dedicates a portion of its mem ory footprint to general audience metrics and specific recording activity and, on a regular basis, switched broadcast performance metrics. sends large UDP (user datagram protocol) packets over the OOB (out-of-band) upstream General audience metrics (for both path to some collection server, the authors switched and linear programming) include: recommend an approach that has no impact on • Number of viewed channels per the STB memory footprint or the OOB service group; network. This feature stems from each message requiring only about 64 bytes. This • Overall bandwidth utilization per approach, which leverages standard switched service group; broadcast protocols, is not sensitive to packet • Number of active STBs per channel loss between an STB and the data collection and per service group; engine. It is not tied to a specific switched broadcast client or headend environment – • Number of tune-ins and tune-outs per any LOB (load on boot) or native switched channel and per service group. broadcast client can be utilized to send STB Switched broadcast performance metrics activity messages to the SBSS. include: An example of these STB messages is • Switched broadcast QAMs occupation presented in Figure 2. ratio per service group; The same protocols can also be leveraged • Number of tune-ins to previously to monitor linear broadcast channel activity unmapped channels per service group; via simple reconfiguration of the switched broadcast client on an STB. This enables • Time to map previously unwatched activity messages for all channels to be sent channels per service group; upstream instead of only those on the • Upstream bit rate per servce group; switched tier. • Number of blocking events (bandwidth not available) per channel and per service group; • Number of other errors per service group (unresponsive STBs, tuning errors, and so on). SBSS STB Init Request Init Init Response Program Select Channel Change Program Response Query Request STB <-> SBSS Session Maint. Query Response Event Indication Force Barker / Record Indication Event Response Force Channel Program Indication Prog. Ind. Response User Activity User Activity Report Tracking Figure 2: Example of protocol messages communicated between the STB and the SBSS The following assumptions were made and enables the analysis it performs to be during development of the statistics collection more effective / broadly applicable. and analysis tool described in this paper: The figures presented throughout this • A service group is a group of nodes; paper are screen captures from the web-based user interface of the diagnostics tool. The • Each node serves multiple households reports can also be configured to output pdf • A hub serves multiple service groups; files for easy sharing amongst a working group, and CSV (comma–separated values) • An SBSS supports multiple service files so the raw data in the reports can be groups; analyzed further. The data was gathered from • All nodes in a service grup are served deployed switched broadcast systems in by common switched RF spectrum; multiple cable networks. • The SBSS shares the RF spectrum; APPLYING PERFORMANCE • The SBSS logs all STB activity in MONITORING: THREE SCENARIOS real-time (channel changes, keep alives, last user activity, and so on.) There are at least three scenarios where the A common set of assumptions simplified ability to collect viewership statistics and and accelerated creation