Data Dissemination Broadcast-disk Models

Data Dissemination Broadcast-disk Models:

·         Presumed that all the n records to be broadcast are stored on a circular disk from 0° to 360°

·         A hypothetical disk revolves and the angle changes from 0°to 360°

·         The entire N bits in n records get pushed through a hypothetical reading-head over the disk.

·         The head continuously reads each bit of a record just beneath it and broadcasts it instantaneously on the wireless network

·         During next revolution each bit in the records positioned from 0° to 360° broadcast once again in the same sequence as in earlier revolution

Number of adaptations and algorithms for broadcast:

1. Circular Multi-disk Model

2. Flat Disk Model

3. Multi-disk Model with repetition rate proportional to priority

4. Skewed disk model

Circular multi-disk model

• Each block of records pushed with a repetition rate proportional to its hierarchical level

Each rotating disk cycle:

• Record blocks R0, R1, R2, R3, R0, R1, R2, R3, transmitted in a single broadcast cycle

• All record blocks have an equal priority level

• Using the flat-disk model, the server broadcasts the data as per cyclic requests (subscriptions)

Multi-disk model:

• Entails multiple levels of records on the broadcast disk

Flat Disk model:

·         The server broadcasts the data as per cyclic requests (subscriptions) without taking into account the number of devices that subscribe to a particular record

·         Multi-disk Model with repetition rate proportional to priority

Skewed-disk model:

·         The block of records repeated as per their priorities for pushing or as per number of subscribers of a given record

·         However, unlike the multi-disk model, the skewed-disk model entails consecutive repeated transmissions of a record block, followed by consecutive repeated transmissions of another record block, and so on

·         High priority record blocks pushed more often than the low priority ones because these are repeated one after one more often

Real-time environment:

·         The records to be pushed in real time

·         The instants at which a record pushed also matters

·         Each data record (or each set of data records) represents an independent disk rotating at a speed inversely proportional to the time constraint associated with the record

·         Independent disk rotating at different speed

·         Facilitates the delivery of data records within a deadline in a real-time environment