Abstract
This paper presents a cognitive satellite communication based wireless sensor network, which combines the wireless sensor network and the cognitive satellite terrestrial network. To address the conflict between the continuously increasing demand and the spectrum scarcity in the space network, the cognitive satellite terrestrial network becomes a promising candidate for future hybrid wireless networks. With the higher transmit capacity demand in satellite networks, explicit concerns on efficient resource allocation in the cognitive network have gained more attention. In this background, we propose a sensing-based dynamic spectrum sharing scheme for the cognitive satellite user, which is able to maximize the ergodic capacity of the satellite user with the interference of the primary terrestrial user below an acceptable average level. Firstly, the cognitive satellite user monitors the channel allocated to the terrestrial user through the wireless sensor network; then, it adjusts the transmit power based on the sensing results. If a terrestrial user is busy, the satellite user can access the channel with constrained power to avoid deteriorating the communication quality of the terrestrial user. Otherwise, if the terrestrial user is idle, the satellite user allocates the transmit power based on its benefit to enhance the capacity. Since the sensing-based dynamic spectrum sharing optimization problem can be modified into a nonlinear fraction programming problem in perfect/imperfect sensing conditions, respectively, we solve them by the Lagrange duality method. Computer simulations have shown that, compared with the opportunistic spectrum access, the proposed method can increase the channel capacity more than for in a perfect sensing scenario. In an imperfect sensing scenario, dB and dB, the optimal sensing time achieving the highest ergodic capacity is about 2.34 ms when the frame duration is 10 ms.
Highlights
Wireless sensor networks (WSNs) have been widely used in many fields, such as agriculture, monitoring, and geographical routing [1,2,3,4]
We present an integrated wireless sensor and sensing-based cognitive satellite terrestrial network, where the satellite user acts as the sink node in the wireless sensor network for gathering and transmitting sensing data by the satellite network
Where i = 1, 2, · · ·, N, N is the sample number of one frame and follows N ≥ τ f s, f s is sample frequency, y(i ) is the signal received by the satellite user that acts as the sensor sink, x (i ) denotes the signal sent by the terrestrial user, c represents the channel gain of sensor network which is changed in different frame but fixed in one frame, and n(i ) is AWGN with zero mean and variance σn2
Summary
Wireless sensor networks (WSNs) have been widely used in many fields, such as agriculture, monitoring, and geographical routing [1,2,3,4]. The underlay paradigm is widely employed in spectrum sharing, and the precondition is that the SUs control the transmit power to avoid deterioration of the communication quality of PUs. many authors focus on the efficient power allocation approaches for the satellite users in the uplink. In [23], the novel power and rate allocation approach for multi-users is proposed for the cognitive satellite uplink, where satellite users reuse the channels of fixed-service terrestrial microwave systems. The aim of the above-mentioned research is to share the channels by taking a strictly power control approach and does not consider the higher capacity performance and wide coverage of satellite networks, which are the main characteristics of satellite communication systems.
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