Link Budget, Joules Budget and User Capacity III: Trade-Offs & Limits of IoT Link Budget and Battery Life
Less than two years ago, I had a client who challenged me to improve the downlink sensitivity of a LTE receiver by 10 dB while maintaining its small form factor and battery life. At the beginning, I was so puzzled by her intention and tried hard to convince her that the mobile network in whole may not benefit much from such a single improvement. There are many other factors, e.g., battery life, downlink-uplink coupling, device cost, inter-cell interference and user capacity, to consider. One year later, I was again amazed by the rapid rise of so many internet of things (IoT) systems each pretty much claiming a ~170 dB link budget and a ~10 years battery life , in addition to its ultra-low device cost, enormous user capacity supporting tens-thousand devices per base station per channel user, and, did I mention this, in a very noisy unlicensed ISM band. goo.gl/pJb0KF . Think about this,...