The highest level is the subscriber management system and computer control. This is where the subscriber information is stored and controlled. The data generated by -SMS is then passed to a Conditional Access Module (CA). The CA, which is second level of hierarchy, takes data and assigns it in a conditional manner. The access and security are then applied before encrypted data is passed on. The third level of hierarchy is the encoding unit, where depending on exact set up, upto 128 channels are scrambled. 128 channels are necessary to allow for future developments involving wide bandwidth cable. After the signal encoding, the signals are modulated, combined and distributed in a normal way. It is to be further noted that addressable systems do have an upper user limit, but for most systems, this figure is one million and thus unlikely to be a serious drawback. The number shown on the diagram i.e.16 million implies allowing upto 16 million users, is provided by some professional addressable system manufacturers.
Addressable System • Breakdown
In a hierarchical structure the following sections make up the system:
(a) The Subscriber Management System (SMS)/Computer Control
(b) Conditional Access (CA)
(c) The Encoder
(d) The Signal Distribution/ Decoder
The Management System
The computer management of a modern cable TV network is known as a ‘Subscriber Management System’ (SMS). This is the most important component of cable TV package for system operator. To run a seamless and smooth system the SMS must be both user friendly and complete with control function to make operation easy. The management system is where the subscriber information is stored and controlled. The operator has a whole range of options to manipulate addressability through management system: management of the system can be almost fully automated or manually controlled, users can be assigned levels of authorization, be grouped together or be individually addressed. A few addressable system manufacturers provide their own purpose-designed software, which offers smooth operation.
Features of SMS packages
(i) Inventory Management
(ii) Subscriber Maintenance
(iv) Work Orders
(v) Pay-per-view modules
(vi) Hardware set of’
(vii) Programme Category/Scheduling enquiries
(viii) Full feature help
(ix) Message control
Software management is the key to operator control of the whole addressable network. It controls the management in a way that smoothly and securely runs the system, allowing the cable TV bosses to worry about other things.
Conditional Access (CA)
Conditional Access, deals with conditionally allowing access to broadcast channels and their associated services. It performs the access control by processing a series of decisions for each SMS information exchange.
When the system control parameters are identified in SMS and processed with CA, the information is transferred to processing computers. Physically, these may be separate units operationally transparent to the user. The processing computers handle the timing of the control signal and convert control information (for SMS/ CA) into control data. This conversion is necessary so that data becomes suitable for embedding into the vertical blanking interval (VBI) of a TV channel video signal.
Actual embedding of data is performed in an encoding unit called the Encoder. The Encoder has two primary functions:
1. To add (embed) the controlling data into unseen region of the video (VBI)
2. To collect all incoming video and audio signals and scramble them as directed.
When the encoder completes these two tasks, the signals can be sent as output and modulated, ready for transmission.
Signal Distribution and Decoders
After the data is embedded by the encoder and the video and audio signal scrambled (if necessary), the signal can be treated like any normal channel for modulating and combining at the head-end before system transmission. The completion of the distribution stage is the tapping of signal to subscriber home and then on to the decoder. The decoder is the final stage of a standard addressable system where all signals are decoded and authorization is verified. The unscrambled signal now reaches the subscriber’s TV set.
Advantages of Addressable System Flexibility
Addressable systems cater to the varying needs of TV broadcasters and subscribers by incorporating flexibility in every aspect of design, from the management software, right through to the range of decoder models. Users, for example, can be provided with an extensive range of programme control; Class status, Pay-per-view authorisation, Time control and Master On/ Off control, to cater to their individual viewing needs. For the operator, the Management Information System (MIS) provides a ‘tailor made’, user friendly, GUI-based interface for easy operation.
Piracy is the problem for subscription broadcasting and is universally documented; inadequate precautions can cripple any operator. The system deters it by raising the economic resources and technical sophistication demanded of potential pirates. Many coding techniques, including, for example, control data encryption, control data encoding, video scrambling and audio scrambling are combined to create a highly secure system.
Increased subscriber control
The level of control is maintained by the management software, assigning almost limitless control levels in a simple remote click away.
Again, within the management system, many options provide smooth operation whilst maintaining user-friendliness.
Addressable systems have been operating worldwide for more than 10 years. The technology is established and reliable.
Long Term Costs Lower
Although the initial cost of an addressable system is high, when considered over time, its main advantage is that you can maximise the revenue from customers who might otherwise not subscribe.
Future Enhancement Capability
Any good addressable system vendor will incorporate enhancement potential to ensure the system will always keep up with the upcoming technologies.
Disadvantage of Addressable Cable TV System
Immediate outlay costs are very high.
Change-over period troubles
The first few months of operation sometimes highlight teething’ troubles.
Studio operators, software operators and field technicians must all be familiar with the new set-up.
Future service requirements
In the event of post-implementation problems or future expansion, initial vendor contacts must be maintained (most addressable systems are incompatible).