On the other hand, there are only a few researches on NC-based cognitive primary-secondary cooperation.
The presented network-coded primary-secondary cooperation is a promising paradigm to improve the spectrum efficiency for the future 5G systems.
Comparatively speaking, there are a few researches on network-coded cognitive cooperation which mainly focus on non-primary-secondary cooperation [22,23].
Different from the conventional one-to-one/one-to-more primary-secondary cooperation, the paper concentrates on two-to-one primary-secondary cooperation, in which one secondary user (SU) cooperates with two primary users (PUs) to gain more spectrum access opportunities.
The simulation shows that the proposed cooperation scheme guarantees not only the minimum transmission rate requirements of PUs but also provides much higher transmission rate for SUs than that provided by traditional non-NC primary-secondary cooperation schemes.
Although cognitive beamforming has been well developed for several years, existing researches mainly focus on beamformer design at cognitive base stations, either for secondary users' data transmission with restricted transmit power [9,10] or for primary-secondary cooperation with careful designed cooperation protocols [11,12].
This paper investigates resource allocation for network-coded primary-secondary cooperation in orthogonal frequency division multiplexing (OFDM -based cOFDM -basedlticognitiveorks, in which cognitive radio (CR), network coding (NC), multicast, anetworksare effectinely combined towhichthe specognitiveicient fifth generadion (5G) wireless CRmmunetworkn systems.
Subject to per-primary-user minimum rate requirement and the total power budget at the secondary transmitter, the investigated primary-secondary cooperation strategy is formulated as a mixed integer optimization problem with the aim of maximizing the average multicast transmission rate.
For the primary-secondary cooperation in cognitive multicast networks (CMNs), the secondary source (SS) with limited transmit power needs to broadcast message to multiple secondary destinations (SDs), and hence, the transmission data rate is confined to the worst channel condition among all SDs.
The transmit power on the SC l at the PT i is (P^{l}_{text {PT}i}, lin Omega _{i}), and the minimum transmission rate requirement at the PR i is r i. Assume that SC set 1 and SC set 2 have different elements, i.e., Ω 1∩Ω 2=∅. Figure 1 System model for network-coded primary-secondary cooperation in OFDM-based CMNs.
We call the above tradeoff case as utility issue of secondary user cooperation.
