# An Architecture for Reliable Transportation of Delicate Goods
## 4 The Main Scenario
### The Monitoring Device  
The monitoring of the transport conditions is ensured by a small and lightweight IoT device, designated as Tag, allowing its use in a large number of situations, and achieve a low production and operational cost. The device also comprises a Real Time Clock (RTC), initiated at the beginning of the contract, to control time and validate data. Most probably, this device is potentially more useful to companies with hundreds or thousands of goods to control. Moreover, since the device follows the goods until they are delivered, the device can only be reused after being returned to a shipping point. It is also expected that the device is subjected to rough conditions and treatments which will contribute to reducing its useful life. Moreover, many will certainly get lost. In other words, it is paramount to keep the production costs of the device as low as possible. To guarantee a small size and weight, that does not compromise the portability, a non-rechargeable battery powers the device (less components implying lower cost and smaller size). The goal is to reduce the power consumption to the minimal, allowing the device to work for years using a small size battery, like CR2032. To achieve that goal, our specification recommends the use of ultra-low power chips and to maximize the time that they are on sleep mode or equivalent mode (when consumption is so low that it remains in order of few uA or even nA). To maintain the chip as much as possible on the sleep mode state, all efforts must be done to avoid waking it up with non-useful activities. Instead of periodic and continuous sampling of the transport conditions, our specification recommends only to track the non-compliances. The continuous sampling is an ineffective approach because it requires waking up the chip periodically, most of the times only to confirm what is supposed to be the regular scenario (transport conditions under the agreed values). Instead, in the proposed specification, it is recommended the use of digital sensors to continuously perform the monitoring without the chip involvement, and with the possibility of defining reference limits which, when exceeded, trigger a physical interruption to wake-up the microcontroller. Thus, only in situations of non-compliance of transport conditions, the microcontroller is activated to temporarily contextualize and register the non-compliance. Even considering that the sensor is continuously monitoring the environment, this solution  
Figure 2: High-level architectural view. is much more efficient because sensors, especially digital ones, require much less energy than the chip. In addition, it is also fundamental to minimize the communication periods, in which power consumption, even with low-power technologies, is considerable. The problem is that in order to be able to have connectivity to a BLE device, it must be in advertise mode, which means that there is transmission of an RF signal and, as such, high energy consumption. There are basically two options: keep the device continuously advertising, allowing the establishment of connectivity at any time but reducing drastically battery life; or provide a way to activate the advertise mode with a push button or through RFID. The former requires that the device is physically reachable, and the latter requires bringing the reading device close to the RFID tag. It is also important to consider that RFID technology is not so common in mobiles. In both options, one way to minimize the consumption is to reduce the range of the transmission signal, since the energy consumed is proportional to the radio signal range. Device Types and Topologies  
The architecture proposed by the authors considers the following types of Tag devices, covering all the options above discussed for BLE advertising:  
* Type A--devices are continuously advertising or advertising periodically, with it being possible to define the power of the transmission signal.