Preamble Design for Non-Contiguous Spectrum Usage in Cognitive Radio Networks

Abstract

Abstract-Cognitive radios can significantly improve spectrum efficiency by using locally available spectrum. The efficiency, however, depends heavily on their transceiver design. In particular, being able to use non-contiguously aligned spectrum bands simultaneously is a critical requirement. Prior work in this area requires a control channel so that transmitter/receiver pairs can synchronize on their spectrum usage patterns. However, this approach can suffer from high cost and control congestion. In this paper, we propose an in-band solution for informing receivers the spectrum usage patterns. By judiciously designing packet preambles, we embed the spectrum usage patterns in each data packet. Using the legacy 802.11 preamble structure, we focus on choosing the appropriate preamble sequences to maintain reliable packet detection in the presence of noise and interference. We verify our design using simulation and show that it can lead to reliable packet transmissions comparable to those of contiguous spectrum usage. We also identify the impact of interference on our design and propose refinements to choose the preamble sequence using information on the interference.

An architecture for software defined cognitive radio

“…A close look at the current wireless protocols re veals that we can define a more fundamental set of operations or primitives, beyond just the the parameters or functional operation of a particular transceiver subsystem: e.g., instead of having cor relators with fixed coefficients, we should have a method to feed the coefficients required for a particular packet encoded using a particular protocol. This is typically required in a cognitive radio environment where the available spectrum varies over time and so does the number of available OFDM subcarriers which changes the time domain correlation coefficients [17,33].…”

“…• SDCR should be able to transmit and receive in any set of subcarriers [24,35,17]. Essentially it should support non contiguous OFDM transmission and reception.…”

Design and implementation of an underlay control channel for NC-OFDM-based networks

“…Under such circumstances, traditional techniques for OFDM timing recovery that rely on some form of symmetry in the time domain waveform [19]- [22] are no longer reliable. Although techniques involving custom preamble design for NC-OFDM are available [23], they are not well suited to be applied in dynamic environments. This paper aims to solve this problem by designing a UCC to specifically aid timing and frequency offset recovery in addition to providing a lowrate communication link to share the control data.…”

TDCS-Based Cognitive Radio Networks with Multiuser Interference Avoidance

“…Under such CR constraints, those existing spreading schemes, e.g., MC-CDMA, are with randomspreading. Importantly, the (quasi-)orthogonality of spreading codes, e.g., Walsh-Hadamard [13], DRAFT October 18,2018 and Zadoff-Chu [14] [15], is destroyed [16]. In contrast, when the entire spectrum band is available, multiple users in those schemes are assigned unique and orthogonal spreading codes.…”