s to allow them to discover minimal delay routes. heuristic heuristic An exploratory method of problem solving in which solutions are discovered through an interactive, self-learning method. hexadecimal A system of numbers in base 16. Hexadecimal digits range from 0 through 9 and A (10) through F (15). Each hexadecimal digit is represented by 4 binary bits. HFC (hybrid fiber coax) A networking arrangement that supports a wide range of services, including traditional telephony, broadcast video, and interactive broadband services. It involves the use of fiber in the backbone and in the access network. The fiber terminates at a neighbor- hood node, and from that neighborhood node, coax (normally 750MHz or 1,000MHz) is run to the home, in a two-way subsplit system. hierarchical routing Routing that is based on a hierarchical addressing scheme. Most TCP/ IP routing is based on a two-level hierarchy in which an IP address is divided into a network por- tion and a host portion. Routers use only the network portion until the datagram reaches a router that can deliver it directly. Subnetting introduces additional levels of hierarchical routing. high frequency The portion of electromagnetic spectrum that is typically used in shortwave radio applications. High frequencies are approximately in the 3MHz to 30MHz range. HiperAccess (High-Performance Radio Access) A fixed wireless broadband access work standard that gives broadband access to both the home and small-and medium-sized enter- prises, as well as providing backhaul for mobile systems. HiperAccess was developed to provide a truly broadband system, with bit rates of up to approximately 100Mbps, although 25Mbps is expected to be the most widely deployed rate. HiperAccess is targeted at high frequency bands, especially the 40.5GHz to 43.5GHz band. HiperLAN (High-Performance Radio LAN) A mobile broadband short-range access net- work standard. This WLAN standard is defined by the BRAN project of ETSI and is a European alternative for the IEEE 802.11 standards. The first ve