On the Uplink Capacity of an 802.16j System

A multihop relay extension for IEEE 802.16e systems is the subject of ongoing standardization activities within the IEEE 802.16j Task Group. The emerging IEEE 802.16J standard enhances the 802.16e PHY and MAC to enable support of multihop routes between a mobile station and a base station through intermediate relay stations. Since it is believed that the capacity of a single-hop 802.16e system is uplink-limited, this paper evaluates potential capacity gains attained with the relay enhancement of the 802.16e uplink. The capacity here denotes either cumulative throughput for data traffic or total number of users for voice traffic supported, under certain system-specific constrains detailed below. We first develop a simplified one-dimensional model of a relay-enhanced 802.16e system and estimate the capacity gains via analysis and numerical optimization. Motivated by the capacity gains predicted by this first-order analysis, simulation results obtained from a full two-dimensional simulator modeling a realistic deployment of a relay-enhanced system are then presented. Based on the simulation results, a parametric analysis of relay deployment cost vs. the capacity gain is also presented.