WLAN / Wi-Fi

Technology Overview

WLAN is a wireless local area network technology that uses OFDM as the multiple access scheme (except 11b). The maximum communications distance is 100 meters. WLAN communicates in the ISM bands (2.4 GHz and 5.8 GHz), which are available all over the world. WLAN is highly optimized for IP and Ethernet. Therefore, it is ideally suited for wireless Internet access.

The standards association approved the IEEE 802.11n amendment to the IEEE 802.11-2007 standard in September 2009. The high throughput (HT) enhancement IEEE 802.11n includes MIMO technologies with up to four antennas and a higher bandwidth of 40 MHz. In addition to higher throughput, handover capabilities are being developed to improve the quality of service (QoS). This includes media-independent handover (MIH), specified in IEEE 802.21, and unlicensed mobile access (UMA), which increases usability by providing roaming between a 3GPP cellular standard and IEEE 802.11.

Amendment IEEE 802.11j and proposal 802.11p use the half clock rate as defined in the IEEE 802.11 standard. This increases robustness to achieve higher mobility, and reduces the required spectrum bandwidth to 10 MHz.

Applications

WLAN is widely deployed for computer networking in businesses and private homes. Wireless Internet access in the form of hotspots is commonly available in hotels, coffee shops, at airports and numerous other locations. An increasing number of mobile devices already provide both cellular radio access and WLAN technology. The complementary functionality to cellular systems ensures extensive penetration in the wireless market.

IEEE 802.11p is specifically defined for car-to-car (C2C), vehicle-to-vehicle (V2V) and vehicle-to-infrastructure communications.

Rohde & Schwarz Test Solutions

Rohde & Schwarz offers a broad range of test and measurement equipment for WLAN. This includes unique test instruments such as the R&S®SMU200A vector signal generator, which features a two-path concept to generate the precoded signals for two MIMO transmit antennas in one box. This compact solution can easily be extended up to a 4x2 and 2x4 test setup by using two synchronized R&S®SMU200A generators. Optimized for speed and high data throughput, the R&S®FSV signal and spectrum analyzer offers a 40 MHz signal analysis bandwidth, which is ideal for the IEEE 802.11n wideband technology. The R&S®CMW500 Wideband Radio Communication Tester and R&S®CMW270 Wireless Connectivity Tester are based on multistandard platforms offering fast and accurate WLAN RF testing for R&D and production.

Key Parameters

Standardization

The physical layers (PHY) of WLAN are defined in the released IEEE 802.11-2007 standard, commonly known as IEEE 802.11 a, b, g, j. The high throughput (HT) PHY of the IEEE 802.11n amendment is commonly referred to as 11n and was released in September 2009. Standardization for the C2C WLAN, IEEE 802.11p is in progress.

The next steps in WLAN PHY standardization are the 802.11ac and 802.11ad amendments, which focus on higher data rates. While 802.11ad targets the 60 GHz frequency bands, 802.11ac targets the frequency bands below 6 GHz like today’s IEEE 802.11-2007 standard. To achieve higher data rates, bandwidths of 80 MHz and even above are in discussion.

Interoperability tests and marketing are defined by the Wi-Fi Alliance.