These protocols can be classified according to different criteria, such as spectrum sharing modes, spectrum allocation behaviors, spectrum access modes, the usage of common, number of radios, spectrum usage strategies, spectrum sensing techniques, etc. Figure 1 presents such classifications based on the above criteria.
Next, we present the novel strategy of spectrum arrangement, hybrid spectrum arrangement, as a natural consequence of above proposed criterion and the enabled selection capability of femtocells.
Although such a scheme is effective in protecting the rights of the incumbent license holders, a completely new strategy of spectrum allocation is needed in order to accommodate the increasing need for efficiently utilizing the wireless spectrum.
This is why we call the proposed strategy hybrid spectrum arrangement.
To tackle the drawbacks of two traditional strategies of spectrum arrangement, we propose a novel strategy of spectrum arrangement, called hybrid spectrum arrangement, to take advantage of their merits.
Comparing two traditional strategies of spectrum arrangement, there are pros and cons of them from the perspective of achievable network capacity.
When deploying two-tier LTE cellular networks with coexistence of macrocells and underlaid femtocells, the strategies of spectrum arrangement need to be investigated to efficiently utilize the scarce spectrum resource.
The main purpose of studying the strategies of spectrum arrangement for two-tier LTE cellular network is to increase the overall spectrum utilization, which can be measured by area spectral efficiency (ASE).
Due to the static licensing and allocation strategies, current spectrum regulation has resulted in extreme scarcity of available spectrum, while plenty of radio frequencies are actually unused temporally/geographically [1].
