## 3 Design of Isl Network for IoT
### Design Process  
The network design process is driven by a set of design parameters derived from various M2M application scenarios. Some selected high-level design parameters which affect the OSI layer specification are:  
* Communication latency: Extending the network to space increases latency, not only due to increased distance but mainly due to link availability. Thus, latency affects orbit design, revisit time, and constellation coverage. \begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline  & **NB-IoT** & **LTE-CATM1** & **EC-GSM-IoT** & **Sigfox** & **LoRa** & **RPMA** & **MIOTY** \\ \hline \multirow{4}{*}{Modulation} & OFDMA & OFDMA & TDMA, FDMA, GMSK, 8 PSK & (EU) & \multirow{4}{*}{CSS} & DSSS, & TDD \\  & Half duplex & Full duplex & M1 dPuplex & & Pseudo-random & modulation & \multirow{2}{*}{TS-UNB} \\  & & & & & frea-hopping & & & structure \\ \hline \multirow{4}{*}{Frequency} & typ. 800 MHz & typ. & \multirow{4}{*}{900 MHz} & \multirow{4}{*}{typ. 900 MHz} & \multirow{4}{*}{868 MHz (EU)} & \multirow{4}{*}{\
\begin{tabular}{} \end{tabular} } & \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } \\  & BW & 1900 MHz & & & & & \\  & 180–200 kHz & BW 1.4 MHz & & & & & \\ \hline \multirow{4}{*}{Data Rate} & \(>\) 250 kbps & \(>\) 1 Mbps & 70 & kbps & \multirow{4}{*}{100 bps} & \multirow{4}{*}{typ. 10 kbps} & \multirow{4}{*}{typ. 10 kbps} & \multirow{4}{*}{typ. 407 bps} \\  & typ. 100 kbps & typ. & & & & & \\  & 384 kbps & & (8 PSK) & & & & \\ \hline \multirow{4}{*}{Distance} & LTE/GSM & LTE/GSM & GSM & carrier range, & \(<\)3–10 km city & \(<\)15 km city & 25 km city & 5 km city \\  & carrier range, & carrier range, & & range & \(<\)30-50 km rural & \(<\)50 km rural & 80 km rural & 15 km rural \\  & 20 km & 25 km & & & & & 30 km free space \\ \hline Topology & star & star & star & star & star & star & star \\ \hline \multirow{2}{*}{\#nodes} & \multirow{2}{*}{\(>\) 200 k} & \multirow{2}{*}{\(>\) 1 M} & \multirow{2}{*}{\(>\) 190 k} & \multirow{2}{*}{\(>\) 25 k} & \multirow{2}{*}{\(>\) 40 k} & \multirow{2}{*}{\(>\) 500 k} & 1.5 mio mssg/day or 500 k nodes (3 mssg/day) \\ \cline{1-1} \cline{5-5}  & & & & & & & 14 dBm (EU), \\ \cline{1-1} \cline{5-5}  & & & & & & 16 dBm (US) \\ \hline Link budget & \multirow{2}{*}{164 dB} & \multirow{2}{*}{155.7 dB} & \multirow{2}{*}{160 dB} & \multirow{2}{*}{149 dB} & \multirow{2}{*}{157 dB} & \multirow{2}{*}{177 dB} & \multirow{2}{*}{\(\frac{154}{\text{dB}}\) (\(-\)140 dBm} \\ \cline{1-1} \cline{5-5}  & & & & & & & \\ \hline \multirow{2}{*}{Latency} & \multirow{2}{*}{1.5–10 s} & \multirow{2}{*}{10–15 ms} & \multirow{2}{*}{0.7–2 s} & \multirow{2}{*}{2 s} & \multirow{2}{*}{2 s} & \multirow{2}{*}{2.3 s} & \multirow{2}{*}{\(\frac{3.6-30}{\text{s}}\) (10–245 byte} \\ \cline{1-1} \cline{5-5}  & & & & & & & msgs) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Current terrestrial IoT protocols. * Power of ground terminal: The M2M ground terminal is constrainted in size, volume, and power (i.e., battery life and solar cell availability). This affects the transmission power, duty cycle, frequency, protocol, and link budget. * Required bandwidth for Earth-to-Space: The data types that need to be exchanged define the access rates and transmission speed. This affects the selection of frequency, protocol, coding, and modulation. * Onboard processing power: More processing power is required for centralized topologies and to process a high number of simultaneous IoT links (e.g., \(\mathsf{CDMA}\))
* Network topology: Arrangement of satellite nodes. Variable topology allows for flexible orbits and distances among satellites. * Link connectivity: A continuous link is required for voice communication or safety-related (and, thus, mission-critical) applications. * Inter-satellite link: ISL can drastically reduce the data forwarding latency, especially for small constellations. * Reconfigurability/Scalability: The layers should be designed to handle node failures or newly deployed nodes.