timetoinformation

Time to information (TTI) is a metric used in information theory and communication engineering to describe how long a system must operate to deliver a specified amount of information to a receiver, or for the receiver to obtain sufficient information to make a decision with a given reliability.

In its simplest form, if a channel transmits information at a fixed rate R (bits per second), the time to transfer I bits is I divided by R. In practice, rates vary due to fading, scheduling, and coding, so TTI is often defined as the expected time to accumulate a target information amount, or the time until a decision threshold based on information density is reached.

The information density i(X;Y) represents the amount of information gained per observation. The time to information can be framed as the time until the cumulative information density reaches a prescribed level I*, linking to sequential analysis and thresholds for log-likelihood ratio decisions. TTI depends on channel conditions, bandwidth, coding, modulation, and reliability requirements.

TTI complements latency and throughput and emphasizes the time dimension of information acquisition. It is related to but distinct from channel capacity and instantaneous information rate; it focuses on how long it takes to obtain a given amount of information.

Applications include wireless system design, streaming, sensor networks, and real-time control where timely decisions depend on information accumulation. Estimating TTI requires models for channel variation, traffic, and decoding strategies; uncertainties can complicate measurements.

See also: information theory, channel capacity, information rate, latency, throughput, sequential hypothesis testing.