Influence of Manchester encoding over spreading codes used in multiple access techniques for IoT purposes

This paper presents a new approach for the use of spreading codes in multiple access systems. Such systems have a number of drawbacks, the most important one being that, with the increasing of used code length, the overall system rate increases, so, consequently, the Bit Error Rate (BER) performances at the receiver end might decrease. In order to partially circumvent those disadvantages, we combine the spreading codes with Manchester encoding, avoiding thus the apparition of long sequences of '0' or '1'. Extensive simulations have been performed in Matlab in order to evaluate the BER performances versus Signal to Noise Ratio (SNR) for different types of spreading codes used (PN, Gold, Walsh Hadamard), and different modulation techniques (BPSK, QPSK, 16-QAM). The results are compared with the standard techniques, without Manchester encoding, and a number of interesting results will be highlighted.