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A diversity combining technique is applied on the receiver side. Polarization diversity : Multiple versions of a signal are transmitted and received via antennas with different polarization.A special case is phased antenna arrays, which also can be used for beamforming, MIMO channels and Space–time coding (STC). If the antennas are at a distance in the order of one wavelength, this is called microdiversity. If the antennas are far apart, for example at different cellular base station sites or WLAN access points, this is called macrodiversity or site diversity.

In the latter case, a diversity combining technique is applied before further signal processing takes place. In the case of wireless transmission, it can be achieved by antenna diversity using multiple transmitter antennas ( transmit diversity ) and/or multiple receiving antennas ( reception diversity ). In the case of wired transmission, this can be achieved by transmitting via multiple wires.

Space diversity : The signal is transmitted over several different propagation paths.

Spread spectrum, for example frequency hopping or DS-CDMA.

OFDM modulation in combination with subcarrier interleaving and forward error correction.

Middle-late 20th century microwave radio relay lines often used several regular wideband radio channels, and one protection channel for automatic use by any faded channel.

Frequency diversity : The signal is transmitted using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading.

Thus, error bursts are avoided, which simplifies the error correction. Alternatively, a redundant forward error correction code is added and the message is spread in time by means of bit-interleaving before it is transmitted.

Time diversity : Multiple versions of the same signal are transmitted at different time instants.

The following classes of diversity schemes can be identified: Other microcontrollers may serve performance-critical roles, where they may need to act more like a digital signal processor (DSP), with higher clock speeds and power consumption. They will generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt power consumption while sleeping (CPU clock and most peripherals off) may be just nanowatts, making many of them well suited for long lasting battery applications.

Some microcontrollers may use four-bit words and operate at clock rate frequencies as low as 4 kHz, for low power consumption (milliwatts or microwatts). Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes.

Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, and toys. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. A microcontroller (sometimes abbreviated ♜, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals.