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Scheduler

A Scheduler for a Television Transmission System


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Prepared by

Elena Volynskaya (Icon Solutions)


Overview

Facilities

Scheduler Application

Use Cases

Glossary


Overview

The television broadcasting companies or "networks" own and lease equipment for composing, transmitting and receiving shows and non-show material. Such equipment includes studios and tape devices for composing shows and playing them back; transmitters, antennae and transponders for distributing the programs; receivers for receiving at the affiliate stations and monitoring the transmissions at the Master Earth stations where the programs are composed and where they are distributed from. Sometimes, because of the weather conditions the programs cannot be distributed over the satellites and then the network leases or uses its own phone or fiber lines that can be used to transmit the signal terrestrially.

The network has to use this equipment efficiently, as well as make sure that there are no conflicts between different programs in using it and therefore there are no outages on the air, which is not only embarrassing, but may also cost a lot of money. Therefore, there is a need to schedule and manage the use of various network and non-network composition and distribution facilities as well as affiliate station facilities, required to play back and distribute program feeds to the destination affiliate stations.

Fundamentally, scheduling refers to the decision making process of assigning resources to activities over time. In this design we will be concerned with resource allocation, i.e. identifying and allocating the resource(s) required to handle an activity and manage the on-going availability of the resource(s) over time.

We would like you to design an object-oriented scheduling module that provides a basic scheduling algorithm that can be extended to support the specific resource allocation requirements outlined in this document. These requirements are simplified for the purposes of this design problem.

Facilities

There are two major groups of facilities in a network inventory: the ones needed for the composition of shows and the ones needed for show distribution.

Ordering Facilities

In order to create a transmission that will be executed in production, a facility order has to be composed which will provide information on how and in what combination those facilities will be used, at what time, etc. However, to design a facility order module would constitute its own problem, so for our purposes you can consider a facility order to be a separate module that will have an interface to the Scheduler application.

The important types of facility orders you will need to know about are (1) reservation orders and (2) air date orders. Reservation orders are created to tentatively schedule a group of transmissions to happen at a certain time on certain days of the week for a range of dates, for example, schedule a transmission to happen from April 1 to June 15 from 9am till 9:30am on Mondays. Air date orders are either created from reservation orders or independently for a certain date.

Scheduling Facilities

A scheduled usage of a facility is also called a "booking".

Constraints

Constraints can be existing scheduled activities, or they can denote general unavailability of a facility such as when a facility is scheduled for maintenance or a particular user group has no rights to use it. However, the right to use a facility can be granted to the group of users for a period of time. Recurring constraint means that a facility will be unavailable for the specified period of time on the specified days of the week for a range of dates.

Bookings

A recurring booking means that a facility has been reserved to be used in a transmission for the specified period of time, although it does not mean that it will actually be used in production. These bookings are requested by reservation orders and are converted into production bookings at the time an air date order is created.

OTO booking means that a facility is going to be used in production for the specified time period. It can also be referred to as a "production booking".

Conflicts

A conflict will occur if a booking or a constraint for a facility is requested that overlaps in time with an existing booking or constraint. A conflict also occurs if two bookings are scheduled so that no ample time is available for the guardband adjustments.

However, if a booking for an air date order is requested that overlaps with a recurring booking created for the corresponding reservation order, this situation is not considered a conflict and has to be resolved by translating existing reservation into a production booking.

Scheduler Application

The Scheduler application should implement resource allocation for the transmission scheduling. It should have an interface to the Facilities Inventory and the Facility Order modules. The major requirements to the application are:

Use Cases

Case 1: Constraint request for aFacility

Take aFacility down for maintenance from May 1, 1998 8:30pm till May 1, 1998 11:30pm. There are no existing bookings for the specified period of time.

Booking is accepted.

Case 2: Constraint request for aFacility

Take aFacility down for maintenance from May 1, 1998 8:30pm till May 1, 1998 11:30pm. There is an existing booking for May 1, 1998 from 7:30pm till 9:00pm.

Booking is rejected.

Case 3: Reservation booking request for aFacility

Reserve aFacility from October 1, 1998 till May 1, 1999 from 8:30pm to 9:00pm on Mondays. There are no existing bookings for the specified period of time.

Booking is accepted.

Case 4: Reservation booking request for aFacility

Reserve aFacility from October 1, 1998 till May 1, 1999 from 8:30pm to 9:00pm on Mondays. There is an existing booking for October 19, 1998 (Monday) from 8:00pm till 9:00pm.

Booking is rejected.

Case 5: Production booking request for aTransmitter

Reserve aTransmitter for May 1, 1998 from 8:30pm to 9:00pm on a transmission path with aTransponder2. There is an existing booking for aTransmitter for May 1, 1998 from 8:00pm to 8:30pm on a transmission path with aTransponder1.

Booking is rejected.

Case 6: Production booking request for aFacility from an air date aOrder created from a booked reservation order rOrder

Book aFacility for October 19, 1998 from 8:30pm to 9:00pm. There is a booking for the specified period of time created for rOrder.

Booking is accepted.

Case 7: Production booking request for aTransmission

Book all facilities forming aTransmission, aFac1, aFac2, aFac3 for May 1, 1998 from 8:30pm to 9:00pm. There are no existing bookings for any of the facilities for the specified period of time.

Bookings are created for all the facilities.

Case 8: Production booking request for aTransmission

Book all facilities forming aTransmission, aFac1, aFac2, aFac3 for May 1, 1998 from 8:30pm to 9:00pm. There are no existing bookings for facilities aFac1 and aFac2 for the specified period of time. There is an existing booking for aFac3 for May 1, 1998 from 8:30pm till 8:45pm.

Bookings are created for facilities aFac1 and aFac2, booking is rejected for aFac3.

Case 9: Production booking request for a composition facility of class Studio aCmpFac

Book aCmpFac for May 1, 1998 from 8:30pm till 9:00pm for aShow1; aShow1 can share composition facilities of class Studio with aShow2. There is an existing booking for aCmpFac for May 1, 1998 from 8:30pm till 9:00pm for aShow2.

Booking is accepted.

Case 10: Production booking request for a composition facility of class Studio aCmpFac

Book aCmpFac for May 1, 1998 from 8:30pm till 9:00pm for aShow1; aShow1 can share composition facilities of class Studio with aShow2. There is an existing booking for aCmpFac for May 1, 1998 from 8:45pm till 9:45pm for aShow3.

Booking is rejected.

Case 11: Production booking request for aFacility by a user from aUserGroup1

Book aFacility for October 19, 1998 from 8:30pm to 9:00pm; aUserGroup1 does not have rights to book aFacility.

Booking is rejected.

Case 12: Production booking request for aFacility by a user from aUserGroup1

Book aFacility for October 19, 1998 from 8:30pm to 9:00pm; aUserGroup1 does not have rights to book aFacility; however, there is an existing constraint transferring rights to aUserGroup1 for October 19, 1998 from 9:00am till 9:00pm.

Booking as accepted.

Glossary

Transmission a process of carrying electromagnetic waves (e.g. a video signal) through space from one point to another
Facility a resource used to generate or carry a video transmission
Studio a facility where a TV program is filmed
Channel a facility that is a video cable connecting two points
Transmitter a facility that is capable of beaming a video signal into space
Transponder a facility that resides on a satellite and is able to receive video signal from the transmitter on Earth convert it to another signal and retransmit it back to Earth
Receiver a facility that is capable of receiving a video signal from space
Antenna a facility that serves as an aiming device in transmission of the video signal from the transmitter to the satellite

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