Do Multiple Bits per Symbol Increase the Throughput of Ambient Backscatter Communications?

Backscatter wireless communications have exceptionally stringent power constraints. This is particularly true for ambient backscatter systems, where energy and wireless carrier are both extracted from weak existing radio signals. The tight power constraints make it difficult to implement advanced coding techniques like spread spectrum, even though such techniques are effective in increasing the communication range and robustness in this type of systems. We draw inspiration from μcode, a previous backscatter coding approach, where data bits are encoded in single-data-bit chip sequences of considerable length to gain robustness. We introduce a new coding technique that encodes several bits in a single symbol in order to increase the data rate of ambient backscatter, while maintaining an acceptable compromise with robustness. We study the proposed technique by means of simulations and characterize the bit error rate and data rate dependencies. A comparison with μcode is drawn and the benefits of each approach are analyzed in search for the best strategy for increasing data rate while maintaining robustness to noise.