802.11ad Tutorial : WiGig technology basics

IEEE 802.11ad, also known as WiGig, is a wireless communication standard that operates in the 60 GHz frequency band. It is designed to deliver multi-gigabit data rates, with theoretical speeds up to 7 Gbps over short distances. The high frequency enables ultra-fast data transmission, making it ideal for applications like wireless docking stations, HD video streaming, and VR/AR experiences. However, due to its limited range and poor obstacle penetration, 802.11ad is primarily suited for indoor environments and point-to-point communication. This tutorial on 802.11ad (60 GHz) technology covers WiGig basics, channels, frame types, modulation-code rate, spectrum mask, 11ad physical layer and conformance testing.

802.11ad channels

Following table-1 mentions country wide frequency allocations of 802.11ad.

Table-1: WLAN-11ad Country wide Frequency allocations:

Following are the 11ad channel-1, channel-2, channel-3 and channel-4 used in WLAN 802.11ad. The table-2 mentions frequency range as well as RF center frequency used for these channels. The bandwidth for all the channels is about 2.16GHz wide.

Table-2: WLAN-11ad Channels:

WLAN 802.11ad frame types

The figure-1 depicts different physical layer frame formats. As shown in the figure, there are four different PHY modes. They are control, single carrier, low power single carrier and OFDM.

802.11ad frame consists of three parts preamble, header and payload. The preamble is known data pattern which helps in front end synchronization at the receiver. The front end synchronization covers time, frequency and channel correction modules.
The header contains information useful to decode the rest of the packet i.e. payload. Modulation and coding scheme of the payload is carried by the header. Following are the supported 802.11ad modulation code rates.
Control packet header = {1 bit(diff.detector initialization, 4 bits(scrambler init., 10 bits(length), 1 bit(packet type), 5 bits(training length), 1 bit (turnaround), 2 bits(reserved), 16 bits(HCS) }
Single carrier header = {7 bits(scrambler init.), 5 bits(MCS), 18 bits(Length), 1 bit(add.PPDU), 1 bit(packet type), 5 bits(training length), 1 bit(aggregation), 1 bit(beam tracking request), 4 bits(last RSSI), 1 bit(turnaround), 4 bits(reserved), 16 bits(HCS) }
OFDM header = {7 bits(scrambler init), 5 bits(MCS), 18 bits(length), 1 bit(add. PPDU), 1 bit(packet type), 5 bits(training length, 1 bit(aggregation), 1 bit(bram tracking request), 1 bit(tone pairing type), 1 bit (DTP indicator), 4 bits( Last RSSI), 1 bit(turn around), 2 bits(reserved), 16 bis( HCS) }

STF stands for Short Training Field and CEF stands for Channel Estimation Field.

802.11ad modulation-code rate

Following tables 3 to 5 mentions modulation code rate information for these different physical layer modes. This information is mapped to MCS index which is carried in the header part of the 802.11ad packet. This MCS index indicates the modulation/code rate of the data payload/control information.

Table-3:Modulation code rate for control PHY

Table-4:Modulation code rate for Single Carrier PHY

Table-5:Modulation code rate for OFDM PHY

Table-6:Modulation code rate for Low Power Single carrier(SC) PHY

WLAN 802.11ad Spectrum Mask

Figure-2 depicts 802.11ad spectrum mask. The X-axis is frequency and Y-axis is decibels relative to teh signal level at band center(dBr). This spectrum mask is approved by the ITU-WPA5. This 802.11ad spectrum mask is different compare to lower frequency masks provided in other wireless standards. The breakpoins in the mask are at -17 dBr level. This is for single carrier as well as OFDM modulation types. Out of band rejections are kept higher to make it easy for RF circuit designs for these WiGig 60 GHz transmitters. Usually 10dBm is used as maximum allowed transmit power. It varies slightly country by country. The transmit spectrum mask will be measured on the data packets greater than 10 µs without the training fields.

This 11d spectrum mask measurements have been carried with RBW of 1MHz. The nominal bandwidth used is 1830.47 MHz for OFDM PHY and 1760 MHz for single carrier PHY.

Conclusion

802.11ad (60 GHz) technology significantly enhances wireless performance by offering extremely high data rates over short distances, providing a key solution for bandwidth-intensive applications. While its limited range and sensitivity to obstacles restrict its use to specific environments, the technology’s potential for high-speed wireless connectivity makes it ideal for applications in home networks, entertainment systems, and enterprise environments where high throughput and low latency are essential. As wireless demand grows, 802.11ad complements other WiFi technologies to offer versatile connectivity options for different use cases. This 802.11ad tutorial is very useful for beginners who would like to start learning WiGig basics.

WLAN 802.11ad physical layer

The 802.11ad Physical layer helps encode the MAC layer data packet suitable to be transmitted over 802.11ad air interface. There four different physical layer used in the transmitter. Hence physical layer modules are different in each of them. In general physical layer composed of scrambler, LDPC encoder or RS encoder used as FEC techniques, modulation, interleaver, guard insertion, spectrum shaping and RF up conversion. IFFT is included in the OFDM Phy version. Refer WLAN 802.11ad physical layer for detailed description of each of these physical layer transmitters and their functional modules.

11ad device conformance testing

Refer 11ad conformance testing page which covers RF and PHY layer testing as per 11ad standard. This conformance tests are useful for 11ad device testing.

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