Kaohsiung County Unified Broadband Mobile Network

2. Mobile Wimax Wireless Network

In 2006, the National Communications Commission (NCC) of Taiwan allocated the frequency band of 2.5 GHz to 2.69 GHz for mobile WiMAX transmission. In 2007, NCC granted three 30- MHz channels from 2.5 GHz to 2.59 GHz in an open-bid procedure to six licensees, three in northern Taiwan and three in southern Taiwan. For reducing co-channel interferences, each licensee further divided its 30 MHz channel into three equal segments, 10 MHz each. The antenna of a base station has three sectors; each sector operates in one of the frequency segments. The frequency reuse plan is shown in Figure 1.

Figure 1.

M-Taiwan mobile WiMAX frequency reuse plan

The physical layer of mobile WiMAX follows the OFDMA (Orthogonal Frequency Multiple Access) specification defined in the IEEE 802.16e-2005 standard (IEEE 802.16-2004, 2004; IEEE 802.16e-2005, 2005). It operates in a TDD (Time Division Duplex) mode; that is, the time domain of the 10MHz channel is divided into fixed-size time frame intervals in which the base station (BS) and the mobile stations (MS) transmit alternatively in time. The key time frame parameters and both the maximum downlink (from BS to MS) and the maximum uplink (from MS to BS) transmission bit rates with different levels of modulation and coding are shown in Table 1.