er Internet access to mobile clients via handheld devices. The standard uses 100 MHz of licensed RF spectrum, from 2.30 to 2.40 GHz, allocated by the South Korean Ministry of Information Wireless MAN Standards Table 12-10: WiBro Key PHY Layer Parameters Parameter WiBro standard RF band 2.300-2.400 GHz Network topology Cellular structure, ca. 1 km range Maximum data rate; User Downlink; 6 Mbps, uplink; 1 Mbps Maximum data rate; Cell Downlink; 18.4 Mbps, uplink; 6.1 Mbps Multiple access OFDMA Modulation QPSK, 16-QAM, 64-QAM Channelisation 9 MHz channel widths Duplex method and Communication for mobile wireless Internet usage, and adjacent to the international unlicensed 2.4 GHz ISM band. The IEEE 802.16-2004 and Draft 3 of the 802. 16e standard were the basis for the development of WiBro, and the key PHY layer parameters, shown in Table 12-10, are compatible between the two standards. The WiBro MAC supports three service levels including guaranteed QoS for delay sensitive applications, based on real time polling of station requirements, and an intermediate QoS level for delay tolerant application that require a minimum guaranteed data rate. Phase 2 of the standard is planned to focus on network capacity enhancement technology, including MIMO radio, adaptive antenna systems and space time coding, as well as further standardisation with 802.16e-WiMAX Metropolitan Area Mesh Networks The wireless MAN standards described above, enable point-to-point or point-to-multipoint solutions for metropolitan area networking, with dedicated base stations providing centralised control. Although no metropolitan area mesh networking standard is currently under development, the work of 802.11 Task Group TGs described in the Section "Mesh networking (802.11s), p. 167" will blur the boundary between Chapter Twelve LAN and MAN scales, allowing 802.11 based mesh networks to operate effectively over metropolitan areas. A mesh based approach will have a number of advantages over the traditional MAN topologies, including making optimum use o