Chapter 3Cognitive Radio Sensors1
Throughout this book, we define sensors broadly as tools for transmitting useful information for the cognitive cycle. The information is used to optimize the radio link to enhance the quality of service (QoS) provided. The sensing tools range from classic sensors, such as microphones, to cognitive sensors that provide information acquired through advanced processing techniques, for example, the impulse response of the channel. Sensors are chosen according to the environment considered, as illustrated in Table 3.1. The classification of sensors presented in Table 3.2 is explained in the rest of the chapter. This is consistent with the model proposed in Figure 1.11. It introduces a non-exhaustive list of sensing tools divided according to the layer served (lower, intermediate, or higher).
3.1. Lower layer sensors
The lower layer sensors contain, amongst others, the physical layer sensors (see Table 3.2). In this section, we focus on the physical layer sensors.
3.1.1. Hole detection sensor
This sensor is extensively studied in the literature under the name sensing. The cognitive radio (CR) is often limited to this sensor for detecting holes (or white spaces) in the spectrum, as already discussed in Chapter 1. CRs require that the secondary network users are able to detect free spaces in the spectrum and use them in such a way that they do not interfere with the transmissions of the primary network. The QoS required by the primary network will ...