The IEEE 802.11ah Task Group (TG) is under way to standardize wireless local area networks (WLANs) that will use carrier frequencies in the 900 MHz industry, scientifi, and medical (ISM) bands.
These so-called sub-1 GHz (S1G) WLANs, operating in the ultra high frequency (UHF) band, will offer unique features, such as longer outdoor coverage range and energy consumption reduction to enable so-called Wi-Fi sensor networks.
Additionally, IEEE 802.11ah WLAN will be an alternative to IEEE 802.15 short-range sensor systems and will enable cost-efficient machine-to-machine (M2M) and Internet of Things (IoT) wireless access networks.
Compared to the upcoming IEEE 802.11af standard, both WLAN protocols aim to exploit the increased penetration of wireless signals at lower frequencies. However, IEEE 802.11af requires a set of additional architectural elements, including spectrum a data base and a location server to enable TV white space (TVWS) access.
Hence, the IEEE 802.11ah WLAN is a cost-efficient and practical solution for long-range shortburst data traffic in the S1G ISM band. A challenge withthe IEEE 802.11ah WLAN is the limited channel bandwidthof 1 MHz (Japanese region). The use of an IEEE 802.11ahWLAN prototype would be beneficial to evaluate the bandwidth constraints.
To meet this demand the creation of a software-based WLAN is an alternative to chip-based WLANs in which new physical layer (PHY) functions and media accesscontrol (MAC) schemes can be implemented and evaluated.
We propose a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) WLAN that uses software defined radio (SDR) in combination with open-software GNU Radio. We will use it to demonstrate an IEEE 802.11ah wireless local area network (WLAN) prototype that is configuredas a self-contained machine-to-machine (M2M) wireless sensor system.
Because the IEEE 802.11ah protocol standardization isunder way, no commercial off-the-shelf (COTS) IEEE 802.11ahWi-Fi product is available yet. However, the proposed prototypehas the potential to solve this issue and allows an over-the-air protocol performance assessment. The SDR platform iconsists of universal software radiop eripheral (USRP) devices combined with radio frequency (RF)daughter-boards operating at the 900 MHz ISM-band.
Additionally, the 2×2 multiple-input multiple-output (MIMO) orthogonalfrequency division multiplexing (OFDM) operation is realized,which requires modifications on the PHY implementation. This demo provides a practical and cost-efficient research platform forthe upcoming IEEE 802.11ah WLAN and its use in M2M and Internet of Things (IoT) wireless long-range access networks.
In this paperwe argue that the proposed system has many advantages. Firstly, it is simple and cost-efficient, because the required S1G radio frequency RF front-end is realized using universal software radio peripheral (USRP). Secondly, it is modular, because RF components can be changed to different frequencies and the required software can be extended.
These advantages come with a cost in performance limitations, because almost all system calculationsare executed in software on a host (a personal computer) andtherefore cannot be as fast as customized field programmablegate array (FPGA) boards or chip-based WLANs.
To read this external content in full, download the complete paper from the author archives at the IEEE Local Computer Networks website.