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M9077A WLAN 802.11a/b/g/n/ac

Technical Overviews

WLAN 802.11a/b/g/n/ac X-Series Measurement Application for Modular Instruments

Expand the capabilities of your M9391A and M9393A PXIe vector signal analyzers (PXI VSAs) with the Keysight Technologies, Inc. library of measurement applications – the same applications used to increase the capability and functionality of its X-Series signal analyzers. Eleven of the most popular applications are now available for use with Keysight's new M9393A PXI performance VSA and the M9391A PXI VSA. When you combine the raw hardware speeds of the PXI VSAs and the X-Series measure­ment applications for modular instruments, you can test more products in less time while ensuring measurement continuity from design to manufacturing.

The M9077A WLAN X-Series measurement application for modular instruments transforms the M9391A PXI VSA into IEEE 802.11 standards-based WLAN transmitter testers by adding fast RF conformance measurements that will help you speed up manufacturing of your WLAN transmitters. The software’s capabilities are closely aligned with the IEEE standards—including a/b/g/n/ac as well as j/p/a-turbo—allowing you to stay on the leading edge of design and manufacturing challenges.

The WLAN measurement application is one in a common library of measurement applications in the Keysight X-Series, an evolutionary approach to signal analysis that spans instru­mentation, measurements and software. Proven algorithms and a common user interface across the X-Series analyzers and modular PXI VSAs create a consistent measurement framework for signal analysis that ensures repeatable results and measurement integrity so you can leverage your test system software through all phases of product development. You can further extend your test assets by utilizing up to four PXI VSAs with one software license.

Keysight’s X-Series applications for modular instruments also include a unique “Resource Manager” that provides direct access to PXI VSA hardware drivers for the fastest power and spectrum-based measurements, while simultaneously using the X-Series applications for fast modulation quality measure­ments and 89600 VSA for fast spectrum measurements.

WLAN Technology Overview

IEEE 802.11 standards were introduced in 1997 and are now more commonly referred to as Wi-Fi. The first published WLAN standard was 802.11-1997. The original standard received very little recognition due to its relatively low bit rate of 1 or 2 Mbps and high cost. It wasn’t until the 802.11 standard was updated in 1999 with the “a” and “b” designations that the WLAN technology gained widespread acceptance.

Table 1 compares the elements of the standard at the various introduction dates.

802.11b inherited direct sequence spread spectrum (DSSS) from the original 802.11-1997 standard, along with an operating fre­quency of 2.4 GHz. This frequency is unregulated and therefore cheaper for manufacturers to implement. The major change in 802.11b was that the maximum data rate reached 11 Mbps, which was comparable to the traditional ethernet speeds widely available in 1999 and 2000.

802.11a was an improvement over 802.11-1997 because of its increased throughput. 802.11a could transmit data at 54 Mbps. This increase in the data transfer rate was due mostly to the use of the 5 GHz frequency band. Apart from the increase in speed, another advantage of using the 5 GHz frequency band was that not very many devices were using that frequency so there was less interference. However, since the 5 GHz frequency band uses shorter wavelengths, the technology had a shorter range and the signals could not easily pass through walls. Another major contribution of 11a was a new modulation technique called orthogonal frequency division multiplexing (OFDM), which allows higher data transmission rates in the smaller bandwidth. The 5 GHz U-NII bandwidth is not continu­ous—the sections are separated by 802.11a into 12 overlapping carriers spaced at 20 MHz intervals.

In 2003, IEEE ratified the 802.11g standard as Ethernet speeds increased. 802.11g operates at the 2.4 GHz frequency, like 802.11b, but it uses OFDM, as does 802.11a. As with 802.11a, OFDM allowed 802.11g to operate at 54 Mbps, a significant increase over 802.11b’s 11 Mbps. Like 802.11b, 802.11g gained widespread adoption amongst consumers and businesses alike. The optional PBCC modulation type also supports data rates of 22 and 33 Mbps.

The 802.11n standard, ratified in 2009, includes multiple-input multiple-output (MIMO), 40 MHz channels in the PHY layer, and frame aggregation in the MAC layer. High-throughput (Greenfield) mode, non-HT (legacy) mode, and HT mixed mode are the three operating modes of 802.11n. 802.11n delivers higher speed, up to 600 Mbps, which is more than 10 times the throughput of 802.11a/g.

The latest WLAN technology, 802.11ac, as an extension of 802.11n, will provide a very high throughput (VHT) of 1 Gigbit/sec and only run on 5 GHz bands, as there is not enough spectrum available at 2.4 GHz for this level of performance. Like previous standards, 802.11ac builds on similar strategies of wider RF bandwidth (up to 160 MHz), higher order modulation types (up to 256 QAM), and more MIMO spatial streams (up to 8) to increase data rates over existing 802.11n products. The 11ac standard finalization is anticipated in late 2013, with final 802.11 working group approval in early 2014.

There are two other amendments to IEEE 802.11 which are not listed in Table 1—802.11j for Japan and 802.11p for vehicular applications, both use the half-clock rate as defined in the standard and are supported by M9077A with manual setup for modulation analysis..

Some new standards that are currently under development, but will not be covered in this technical overview, are 802.11ad for “very high throughput” in the 60 GHz band and 802.11af, which allows WLAN operation in the TV white space frequencies that are available with the transition from analog to digital TV. For more information on these standards, please refer to the appli­cation note, Testing New-Generation Wireless LAN, literature number 5990-8856EN.

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