Megabaud

Megabaud, abbreviated MBd, is a unit of symbol rate equal to one million symbols transmitted per second. The term baud, named after Émile Baudot, denotes the rate at which signaling events or symbols occur in a communication channel. Megabaud measures how many symbols are sent each second, not how many data bits are carried.

The data rate that results from a given megabaud value depends on how many bits each symbol conveys. If each symbol encodes k bits, the information rate is MBd × k. For M-ary signaling, k = log2(M). For example, 1 MBd with binary signaling (M = 2) yields 1 Mbps; 1 MBd with 16-QAM (M = 16) yields 4 Mbps; 1 MBd with 8-PSK (M = 8) yields 3 Mbps. In practice, error correction, protocol overhead, and noise reduce the usable data rate below this theoretical maximum.

Megabaud is commonly encountered in older or specialized telecommunications equipment and serial links. Many modern high-speed systems report symbol rates in baud or in larger units such as Gbaud, while data rates are stated in bits per second. Because baud measures symbol rate and not bits per second, MBd can be misleading if one assumes a fixed relationship to Mbps without specifying the modulation scheme.

In summary, megabaud is a symbol-rate unit equal to one million symbols per second, with the actual data throughput determined by the modulation method and system efficiency.