Wimax standards and Security The Wimax

Simulation Handover Model and Results

We use the QualNet 3.9.5 developer command-line simulator and design new embedded handover module of PHS, L₀, and L₂ to simulate average service DT and handover, dropping probabilities during handover process. In our simulation model, there are seven BSs each of them dominating a hexagon cell and six hexagons are around one hexagon. The diameter of each hexagon is 1000 m long. The range of operating spectrum is from

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2.40 to 2.46 GHz and is divided by a fixed bandwidth (BW) 10 MHz into several independent channels. The simulation model is operating in TDD mode. The fast fourier transform (FFT) (N_FFT) size is 1024. The sampling frequency (F_s) can be calculated by F_s (n BW 8000)/8000 as 11.42 MHz. The subcarrier spacing (∆f ) can be calculated by ∆f F_s/N_FFT as 11.16 kHz. T_u, the useful symbol time can be calculated by T_u 1/∆f as 89.64 µs. Guard time T_g T_u/8 as 11.2 µs. Each orthogonal frequency-discussion mul- tiple access (OFDMA) symbol time (T_s) is evaluated by T_s T_u T_g as
100.84 µs. The downlink and uplink (DL/UL) ratio is 3:2. The number of subchannels is 30.
The OFDMA frame length is 5 ms and is also the minimum one-time trans- mission unit. Therefore, any message transfer must follow frame by frame and the time of one-way transmission cannot be less than 5 ms. The initial BS’s transmission power of the BS is 300 mW. The simulation model-specific parameters of the IEEE 802.16e MAC protocol we used are shown in Table 7.2.