Abstract
This paper experimentally validates the basic feasibility of our proposed blind adaptive array (BAA) with subcarrier transmission power assignment (STPA) scheme using a prototype. The proposed STPA-BAA enables spectrum superposing without any channel state information between two different wireless communication systems: employing STPA-BAA to the secondary system, inter-system interference from/to the primary system can be suppressed. Exploiting the characteristics of constant modulus algorithm (CMA) and power inversion (PI), the secondary transmitter provides two levels of power density for each subcarrier: high and low levels. It enables the secondary receiver to suppress interference with almost the same level of the desired signal. It is also effective in reducing interference to the primary receiver that has no interference suppression function. This paper conducts laboratory experiments of spectrum superposition in two multicarrier systems by wired setup. Though the practical performance of STPA-BAA is limited due to the quantization level or dynamic range of the transceiver, effectiveness of the proposed scheme is confirmed.
Highlights
Since many kinds of wireless communication systems such as wireless fidelity (Wi-Fi), worldwide interoperability for microwave access (WiMAX) or long-term evolution (LTE) (-Advanced) have emerged, frequency resources are becoming exhausted, especially in the microwave band
Once the desired signal is captured by power inversion (PI), residual interference signal can be further suppressed in the iteration process of constant modulus algorithm (CMA) [19]
This paper experimentally verified the fundamental feasibility of our spectrum superposing scheme enabled by the proposed subcarrier transmission power assignment (STPA)-blind adaptive array (BAA)
Summary
Since many kinds of wireless communication systems such as wireless fidelity (Wi-Fi), worldwide interoperability for microwave access (WiMAX) or long-term evolution (LTE) (-Advanced) have emerged, frequency resources are becoming exhausted, especially in the microwave band. The basic principle is opportunistic spectrum access (OSA) or dynamic spectrum access (DSA) [4,5]: the secondary system detects which time/frequency resources are active or which are idle, and instantly accesses vacant channels so as not to interfere with the primary systems. The null-steering approach [12,13] disclosed the spectral efficiency improvement by suppressing inter-system interference in the superposed spectrum. Constant modulus algorithm (CMA) [14,15] and power inversion (PI) [16,17] are well known BAA algorithms that do not require any a priori information such as a reference signal or direction of arrival These algorithms are limited to some operational signal-to-interference power ratio (SIR) range at the input of receiver antenna elements.
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