bitperiod

Bit period, denoted Tb, is the time duration of a single bit in a digital communication system. It is the reciprocal of the bit rate Rb, measured in bits per second: Tb = 1 / Rb seconds. Thus, increasing the bit rate shortens the bit period. The bit period establishes the fundamental timing for sampling the received signal and for shaping transmitted pulses. In systems where each symbol carries exactly one bit, the bit period equals the symbol period and the baud rate equals the bit rate.

If symbols encode more than one bit, the relationship changes. Let k be the number of bits per symbol. Then the symbol period Ts = Tb / k, and the symbol rate Bs = Rb / k. Equivalently Tb = k / Rb. For example, with Rb = 10 Mbps and k = 2, the symbol period is Ts = 0.2 microseconds and the symbol rate is 5 Msymbols per second. In asynchronous serial communication, the bit period determines the spacing of bits in framing, so a baud rate of 9600 implies Tb ≈ 104.17 microseconds per bit. In synchronous systems, a clock with period close to Tb is used to sample at bit centers; jitter, clock drift, and timing recovery affect bit timing.

See also: bit rate, baud rate, symbol rate, Nyquist, modulation.