# Challenges in Wireless System Integration as Enablers for Indoor Context Aware Environments
## 3 Wireless Sensor Network Radioelectric Analysis
#### Total Surface of Test Scenario: 216 \(m^{2}\)  
-Uniform Distribution:  
- 7 antennas (1 transceiver/room): 1, 42, 74, 86, 90, 92, 107. - 27 antennas (1 transceiver/8 m\({}^{2}\)): 1, 5, 9, 13,..., 105. (numbering scheme \(n+4\))  
- 54 antennas (1 transceiver/4 m\({}^{2}\)): All odd-numbered nodes. - 108 antennas (1 transceiver/2 m\({}^{2}\)): All nodes except wearables  
Figure 2: Transceiver Location within the scenario as a function of transceiver node density (**a**) 108 transceivers, (**b**) 54 transceivers, (**c**) 27 transceivers, (**d**) 7 transceivers. The results for the different node densities are depicted in Figure 3 for the case of seven nodes/scenario and 27 nodes/scenario and in Figure 4 for 54 nodes/scenario and 108 nodes/scenario, in both cases for bi-dimensional received power planes at 0.5 m and 2 m height, respectively. Results highlight that node distribution significantly modifies received power levels, as a function of node density (with values ranging from approximately \(-\)50 dBm in the case of seven nodes/scenario to \(-\)30 dBm in the case of 108 nodes/scenario) and node location (node height provides additional power variation in the order of 5-10 dB). It is worth noting that individual transceivers lead to localized regions with higher power levels, i.e., hot-spots, within the scenario, which convey into power clusters as the number of nodes increases. This results is relevant in terms of interference analysis, as well as on the operation of mitigation schemes, such as power handling or distributed routing algorithms/aggregation schemes. Node density variation also impacts on deviation of received power levels, with values in order of 20 dB for the low density case to lower than 10 dB in the high density case (excluding the vicinity of hot-spots). Moreover, different zones can be identified within the simulation scenario, in which power distributions differ, such as upper region and lower region. These zones are delimited by the boundaries of the scenario, given in this case by the separation walls between office zones (upper part of the scenario), hallway (middle part) and lab zone (lower part). The existence of such boundaries, inherent in indoor scenarios, gives rise to different effects in terms of wireless channel behavior, such as highlighting the presence of hot-spots (clearly visible at cut-planes which are closer to the transmitter sources, for all of the proposed node densities) and increasing path loss values, given the increase in losses mainly due to absorption and scattering. Figure 3: Estimation of received power levels, for an operating frequency of 2.4 GHz, for a scenario with 7 nodes and 27 nodes, at bi-dimensional planes at a height of 0.5 m and 2 m, respectively. It is also worth noting that power level distributions tend to be more uniform as the number of transceivers increases, which is a direct consequence of the fact that as node density increases, propagation mechanisms will be mainly driven by Line of Sight operation. In this way, transceiver nodes will tend to have similar behavior, with higher average received power levels in the potential communication links that can be established. This is however strongly influenced by the communication scheme employed, since received power level distribution profiles also hold for the potential interference also sources (which also potentially increase, especially in the case of intra-system and inter-system interference), which will increase as node density increases. In terms node density variation, when transceiver locations are uniformly spaced, power level distributions tend to be more uniform, given that potential receivers can be equidistant to embedded transceivers within the scenario and hence, link balances tend to be similar for all of those potential receivers. As node density increases, path loss tends to decrease, which (if no interference is considered) provides higher values of received power.