Path-Permutation Codes for End-to-End Transmission in Ad Hoc Cognitive Radio Networks
Abstract—Cognitive radios < Final Year Projects 2016 > CRs improve the spectrum efﬁciency in wireless communications. Nonetheless, owing to the intrinsic randomness of ad hoc cognitive radio networks (CRNs), e.g., the opportunistic links, the traditional realization of ad hoc networking that demands the end-to-end control information, is un scalable and impractical. A virtual multiple-input multiple output (MIMO) framework has been recently developed for the realization of error-resilient end-to-end transmission without the necessity of feedback information. In this paper, we propose an end-to-end path-permutation coded (PPC) transmission in which one relay path is accessed at a time and the transmission is hopped among multiple relay paths. The hopping order is speciﬁed by a permutation array that encodes the data, meaning that the data is conveyed by the order of indices of the accessed paths. With the PPC scheme, the control overhead and data processing complexity of the end-to-end transmission become relatively low. The PPC technique can also be utilized as a multiuser technique. At the destination node, a joint sphere decoder efﬁciently implements the maximum a posteriori (MAP) probability decoding that simultaneously identiﬁes the order of accessed paths and erasures. Comprehensive theoretical analyses and simulations are conducted to demonstrate the superior performance of the PPC technique in ad hoc CRNs. Instead of simultaneously transmitting multiple packets through multiple relay paths, end-to-end multipath PPC trans-mission only accesses one relay path at a time. This accessed path is selected based on the data sequence in the packet. Specifically, PPC encodes the data packet in two ways, i.e., by using the transmitted symbols with quadrature amplitude modulation (QAM) and by using a permutation array (PA) consisting of a set of path indices. The term permutation code comes from the fact that the PPC code word comprises these PAs. Consider a toy example of PPC using two relay paths and two time instants.
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