  A great number of Internet of Things (IoT) and machine-to-machine (M2M) based
applications require energy efficient, long range and low data rate wireless
communication links. In order to offer a competitive solution in these areas,
IEEE 802.11 standardization group has defined the "ah" amendment, the first
sub-1GHz WLAN standard, with flexible channel bandwidths, starting from 1MHz,
up to 16MHz, and many other physical and link layer improvements, enabling
long-range and energy efficient communications. However, for some regions, like
Europe, the maximum transmitted power in dedicated frequency band is limited to
only 10mW, thus disabling the achievement of ranges which would be close to
targeted of up to 1km. In this paper we examine possibilities for range
extension through implementation of half-duplex decode-and forward (DF) relay
station (RS) in communication between an access point (AP) and an end-station
(ST). Assuming a Rician fading channel between AP and RS, and a Rayleigh fading
channel on the RS-ST link, we analytically derive results on achievable ranges
for the most robust modulation and coding schemes (MCSs). Analyses are
performed for two different standard adopted deployment scenarios on the RS-ST
link. Moreover, we have analyzed whether the considered most robust MCSs, known
for supporting the longest range, but the lowest data rates, can meet the
defined requirement of at least 100kb/s for the greatest attainable AP-RS-ST
distances. We examine data rate enhancements, brought by coding and using of
short packets, for both downlink (DL) and uplink (UL). Finally, we present bit
error rate (BER) results, obtained through simulations of a dual-hop DF IEEE
802.11ah relay system for the considered MCs. All presented results confirm
that IEEE 802.11ah systems, through deployment of relay stations, become an
interesting solution for M2M and IoT based applications.
