  Bandwidth request-grant mechanisms are used in 802.16 networks to manage the
uplink bandwidth needs of subscriber stations (SSs). Requests may be sent by
SSs to the base station (BS) by means of several mechanisms defined in the
standard. Based on the incoming requests, the BS (which handles most of the
bandwidth scheduling in the system) schedules the transmission of uplink
traffic, by assigning transmission opportunities to the SSs in an
implementation-dependent manner. In this paper we present a study of some
bandwidth allocation issues, arising from the management of the perception of
subscriber stations' bandwidth needs at the base station. We illustrate how the
bandwidth perception varies depending on the policy used to handle requests and
grants. By means of ns-2 simulations, we evaluate the potential impact of such
policies on the system's aggregate throughput when the traffic is composed of
Best-Effort TCP flows.
