An underlay communication channel for 5G cognitive mesh networks: Packet design, implementation, analysis, and experimental results

Abstract

This paper proposes and presents the design and implementation of an underlay communication channel (UCC) for 5G cognitive mesh networks. The UCC builds its waveform based on filter bank multicarrier spread spectrum (FB-MC-SS) signaling. The use of this novel spread spectrum signaling allows the device-to-device (D2D) user equipments (UEs) to communicate at a level well below noise temperature and hence, minimize taxation on macro-cell/small-cell base stations and their UEs in 5G wireless systems. Moreover, the use of filter banks allows us to avoid those portions of the spectrum that are in use by macro-cell and small-cell users. Hence, both D2D-to-cellular and cellular-to-D2D interference will be very close to none. We propose a specific packet for UCC and develop algorithms for packet detection, timing acquisition and tracking, as well as channel estimation and equalization. We also present the detail of an implementation of the proposed transceiver on a software radio platform and compare our experimental results with those from a theoretical analysis of our packet detection algorithm.

Spread Spectrum Symbol Detection With Blind Interference Suppression in FBMC-SS

“…Before we dive into the details of our proposed receiver, we recall that in packetized data transmission, each packet starts with a preamble that consists of a sequence of pilot symbols which are known to the receiver. In some of the earlier implementations of FBMC-SS, e.g., [7], the first segment of preamble consists of a sequence of alternating BPSK symbols. Once passed through the matched filter, a periodic series of peaks with alternating phase will appear at the output.…”

“…5 presents a block diagram of the receiver that was outlined above. The portion appearing to the left of the NMF block has been addressed in some previous works, e.g., [7], hence, is not discussed here. The rest of the receiver blocks, after the NMF, extensively make use of the properties of the ZC sequence to design an effective channel estimator as well as a method of obtaining any residual CFO that may have remained after the coarse CFO correction which occurs before the NMF.…”

“…For this purpose, we consider the case where K = 64, L = 128, and Z = 16. The channel covariance matrix used in these simulations matches the TDL-A model recommended by [39] with an RMS delay spread of 30 ns, and the symbol rate is 1/T s = 250 kHz following the FBMC-SS implementation of [7]. We also choose the diagonal elements of the power normalization matrix Q f as a set of random numbers uniformly distributed in the range of 0 to 1.…”

“…The preamble symbols are also added. Following the implementations of [7], the symbol rate is set to 1/T s = 250 kHz, and the prototype filter h(t) is a squareroot raised-cosine pulse-shape with roll-off factor α = 1, truncated to a period of N = 6 symbols. The generated transmit signal is then passed through a multipath channel c(t) following ( 14), and AWGN with the two-sided noise power spectral density N o /2 is added to this signal.…”

“…In this implementation, each data packet comes with a known preamble which is used to extract the relevant channel state information (CSI), including the interference level at different subcarrier bands. The CSI is then used to set up the receiver for optimum detection of the data portion of the packet through an analysis filter bank (AFB), [7]. Among the many challenges that were faced in this development, successful detection of the preamble of each packet, by far, seemed to be the most challenging problem.…”