In 2004 the aim of the 802.16 protocol was changed to
support residential access and non line of sight (NLOS). The
second version is called the IEEE 802.16-2004 standard [2]
and it supports two operating modes of the MAC layer: 1)
point to multipoint (PMP), where traffic occurs only
between the Base Station (BS) and Subscriber Stations (SS),
and 2) Mesh topology, where traffic can be routed through
other SSs and can occur directly between SSs. In addition,
IEEE 802.16-2004 also includes OFDM modulation and
supports 256 carries, which reduces considerably multipath
fading effects.