SATCOM link adaptive configuration design in radio frequency interference environment

Abstract

Radio frequency interference (RFI) is ubiquitous in wireless communications which could greatly degrade communication system performances in an open environment. For satellite communications (SATCOM), the system performances degradation could be even worse considering the large round trip time (RTT) delay. To mitigate RFI effects, cognitive radio with adaptive waveform configurations could be effective. To quantify the cognitive radio system performance, spectral efficiency and energy efficiency are two metrics. Spectral efficiency (SE), defined as the average data rate per unit bandwidth, quantifies how efficiently the available spectrum is utilized. Energy efficiency (EE), defined as the successful transmitted information bits per unit energy from transmitter to receiver, quantifies how efficiently the energy is utilized. However, the two metrics construct a fundamental trade-off in communication system design. Basically, with higher average energy per bit to noise power spectral density ratio at the receiver, the packet can be more successfully detected, thus utilizing the spectrum more efficiently, giving higher SE; which however requires more energy, lowering EE, and vice versa. In this paper, we design adaptive configuration of SATCOM link operating in the RFI environment, and study the system trade-off between SE and EE, by greatly exploiting cognitive radio configurability for SATCOM interference mitigation capability. A general metric SEE (Spectral/Energy Efficiency), which quantifies the preference of SE or EE, has been formulated with practical system parameters, including information bit length, overhead bits, modulation and channel coding schemes, frequency hopping, wireless channel conditions, frame retransmissions, etc, to facilitate the system analysis. A closed-form solution for information bits rate control is obtained in various RFI environments. An iteration algorithm is presented for cognitive radio joint transmission power control, information bits rate control, and modulation and channel coding adaptation, to optimize the system performances in the RFI environment.