What is 1024-QAM?

What is 1024-QAM or QAM1024 modulation? What technologies use this type of modulation? What data rate does it support?

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- everything RF

Jul 21, 2022

1024-QAM is a type of higher-order Quadrature Amplitude Modulation (QAM) technique in which a carrier waveform of fixed frequency can exist in one of 1024 possible discrete and measurable states in the constellation plot. The constellation diagram contains two component axes namely the in-phase (X-axis) and the quadrature (Y-axis). The two axes are orthogonal to each other or 90˚ out of phase.

Each symbol in 1024-QAM is a constellation state that consists of ten bits and each symbol is one possible combination out of 1024 different states that range from 00000 00000 to 11111 11111. Since, this modulation scheme uses binary data, the total number of possible combinations is 210 i.e. 1024. Conversely, the number of bits can be computed in terms of its logarithmic value as (1/10 of bit rate).

The maximum data rate that can be achieved using 1024-QAM scheme is up to 472 Mbps (for a channel size of 56 MHz). When using 1024-QAM, a capacity increase of 11.98% is achievable compared to 512-QAM, 25% from 256-QAM, and up to 66.66% from 64-QAM schemes. As with other QAM schemes, QAM-1024 varies both the amplitude and phase of the high frequency carrier waves and can transmit a relatively larger number of bits, thereby having an improved spectral efficiency. This helps in serving a relatively larger number of users and users compared to lower order QAMs schemes such as 256-QAM, 64-QAM, and 16-QAM, QPSK, and BPSK.

Many technologies like Wi-Fi 6 (802.11 ax) use 1024QAM. These technologies use multiple channels, MIMO, beamforming and other algorithms to further enhance the data rate that they can support. 

However, as the data rate is increased from 256-QAM to 1024-QAM, the parameter, Error Vector Magnitude (EVM) on the RF front-end becomes more important. With 1024 subcarrier signals allocated in Wi-Fi 6 (802.11ax), the constellation plot becomes very dense. Therefore, it takes a relatively more sophisticated receiver to accurately distinguish one constellation point from the other and requires these receivers to offer better EVM characteristics.

Applications of 1024-QAM

This 1024-QAM scheme is utilized by mmWave front-haul and back-haul systems, 802.11 b/g/n/ac/ax WLAN front-end modules, Wi-Fi 6 (802.11ax), Homeplug AV2 500 Mbps powerline Ethernet devices, and to achieve ultra-high capacity in point-to-point microwave outdoor backhaul links in the E-band.