IEEE 802.16J MULTIHOP RELAYS FOR AEROMACS NETWORKS AND THE CONCEPT OF MULTIHOP GAIN

The potential benefits and challenges of applications of IEEE 802.16j-based relays in AeroMACS networks are discussed at the outset. Perhaps the most important advantage of application of multihop relays in AeroMACS networks is the flexible and cost effective radio range extension that it may allow for airport areas shadowed by large constructions and natural obstacles with virtually no increase in the required network power levels. With respect to PHY layer RSs may be classified as Transparent Relays (TRS) and Non-Transparent Relays (NTRS). While a TRS essentially functions as a repeater and bears no logical connection to the subscriber station (SS), a NTRS operates as a "mini base station (BS)" and is physically and logically connected to the SSs that it serves. Regarding MAC sublayer functionalities, RSs may operate in centralized or distributed modes. Distributed mode means that the RS is capable of scheduling network resources in coordination with multihop relay base station (MR-BS); otherwise the RS is in centralized mode. The RS can be in distributed or centralized mode with respect to security arrangements as well. The NTRS relays may further be divided into two categories; time-division transmit and receive relays (TTR) and simultaneous transmit and receive (STR) relays; both of which are supported by IEEE 802.16j standard. The TTR relay communicates with its subordinate and superordinate nodes using the same radio channel. The employment of relays in an AeroMACS network requires no alteration in the subscriber system. The key concept of "multihop gain", which explains how the application of multihop relay enables performance enhancement in AeroMACS networks, is introduced. Under a reasonable set of assumptions and using a simple analysis, multihop gain is quantified in the form of an equation that provides a raw measure of this gain in Decibel.