| | S/N. | Channel models | Brief description |
| | 1 | Stanford University Interim channel models | Towards the development of the SUI model by researchers at Stanford University, IEEE 802.16 provided specifics for fixed wireless access (FWA) systems [200]. The group worked on frequency bands below 11 GHz after establishing guidelines for frequency bands above 11 GHz. The SUI models are classified into terrain types A, B, and C. In particular, terrain type A deals with huge path loss, and it is most suited for hilly terrain with densities of moderate to heavy foliage. Type C is closely related to minimal path loss, and it is specific to flat terrain with densities of light trees. Specifically, type B can be suitably applied to hilly terrains with light tree densities or mostly flat terrains with moderate to heavy tree densities. The path loss equation and the correction factors relevant to the SUI model are given in [200]. Six SUI tap-delay lines are presented in the SUI channel models, with three taps valid for a distance of 7 km between the transmitter and the receiver. For channels 1 to 4 of the SUI model, Ricean is distributed as the first tap, and Rayleigh fading characterizes the others. Another prominent feature of the SUI models is that a rounded shape centered very close to zero is given to each tap’s Doppler spectrum, and this has limited information in the Jakes spectrum [126]. | | 2 | IEEE 802.11n channel models | The IEEE 802.11n is a simplified form of the extended SV model. This set of models is carefully built with bandwidths up to 100 MHz [201], and the model finds useful applications in indoor MIMO LAN networks at 2 GHz and 5 GHz. Here, six canonical channels are modeled systematically to cover flat fading situations, residential, traditional workplace, large office, small office, and large open spaces. MATLAB implementation of the model is given in [202]. | | 3 | IEEE 802.16a channel models | Following the modification to the popular SUI channel models, which find useful applications in directional and omnidirectional antennas, the IEEE 802.16 models were derived. The IEEE 802.16 models use directional antennas to increase the Ricean taps’ K-factor and decrease the spread of global delay. One key advantage of the IEEE 802.16a model is that it does not alter the user terminal’s correlations when reducing the antenna beamwidth. This is contrary to the assumption that as the beamwidth decreases, the correlation coefficients will increase. Further to this, the IEEE 802.16a includes a path loss model, an appropriate model depicting the Ricean K-factor narrowband, and an antenna gain reduction factor model. Here, three terrain categories are included in the path loss model. These are hilly terrain with moderate-to-heavy tree densities as category A, category B as terrain with intermediate path loss state, and category C is mostly flat terrain with light tree densities. Category A would find useful applications in models 5 and 6 of the SUI, category B for models 3 and 4 of the SUI, and category C for models 1 and 2 of the SUI [28]. A typical example of a spatial channel model is derived based on this standard [99]. | | 4 | IEEE 802.16d/e channel models | The IEEE 802.16d/e models are an updated version of the interim SUI channel model intended for fixed macrocellular connectivity. The model is true for the directional and omnidirectional antennas, which contribute to an increase in the global K-factor, while the distribution of delays tends to decrease. The log-normal model of shadowing path loss forms the basis of the IEEE 802.16d. Three types of model categorizations (type A, type B, and type C) are derived. These depend on the density (e.g., tree densities) of the obstacle separating the transmitter from the receiver, considering a microsuburban environment. The MIMO channel models in the IEEE 802.16e standard have been established in the WiMAX Forum, following several reports [203–206]. |
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