The recent increasing interest in cognitive radio networks has motivated the study and development of new approaches capable of coping with the intrinsic challenges of this kind of network,such as dynamic spectrum availability,distributed and heterogeneous network architectures,and soaring complexity.The bio-inspired approaches,with appealing characteristics such as autonomy,adaptation and collective intelligence of collaborative individuals,have been extensively studied.This paper presents a comprehensive survey of bio-inspired approaches for cognitive radio networks,emphasizing their domains of application.Specifically,ant colony optimization and particle warm optimization are further investigated with examples and numerical simulation.
HE ZhiQiangNIU KaiQIU TaoSONG TaoXU WenJunGUO LiLIN JiaRu
In this paper, we investigate the polarization effect of the amplitude phase shift keying(APSK) constellations. We find that the polarization effect of the APSK constellations is affected by the bit mapping and the bit loading. Traditionally, the Gray mapping is usually adopted in APSK constellations. Based on the given Gray mapping, we firstly propose the bit interleaved coded modulation polar-APSK(BICM-PA) scheme, which neglects the correlations between the bit levels by using the bit interleaver. In the BICM-PA scheme, a new metric called cumulative Bhattacharyya parameter is introduced to optimize the bit loading of the APSK constellations under the Gray mapping. Second, the multilevel coded modulation polar-APSK(MLCM-PA) is proposed to further improve the performance. A twostage optimization approach is adopted to select the bit mapping and the bit loading in the MLCM-PA scheme. The semi-set partitioning mapping is introduced to achieve a better system performance in the MLCM-PA scheme. Simulation results verify the effectiveness of all the proposed metrics. In addition to this, BICM-PA and MLCM-PA both outperform the coded modulation Turbo-APSK scheme up to 1 dB.
This paper proposes a joint nonlinear transceiver design scheme based on minimum mean square error （MMSE） criterion for non-regenerative multiple input multiple output （MIMO） relay system. The proposed scheme decomposes the error covariance matrix, reformulates the original joint design problem as two separate optimization problems, and then provides a closed-form solution with only local channel state information （CSI） available at the source and destination. Performance evaluation shows that the proposed scheme significantly outperforms linear schemes, and has a competitive performance compared with existing global CSI based nonlinear schemes, both iterative and non-iterative.
Soft decode-and-forward(DF) can combine the advantages of both amplify-and-forward and hard DF in relay channels. In this paper, we propose a low-complexity soft DF scheme based on polar codes, which features two key techniques: a low-complexity cyclic redundancy check(CRC) aided list successive cancellation(CALSC) decoder and a soft information calculation method. At the relay node, a low-complexity CALSC decoder is designed to reduce the computational complexity by adjusting the list size according to the reliabilities of decoded bits. Based on the path probability metric of the CALSC decoder, we propose a method to compute the soft information of the decoded bits in CALSC. Simulation results show that our proposed scheme outperforms the soft DF based on low-density parity-check codes and the soft DF with belief propagation or soft cancellation decoder, especially in the case when the source-relay channel is at the high signal-to-ratio region.
A novel scheme to joint phase noise （PHN） correcting and channel noise variance estimating for orthogonal frequency division multiplexing （OFDM） signal was proposed, The new scheme was based on the variational Bayes （VB） method and discrete cosine transform （DCT） approximation. Compared with the least squares （LS） based scheme, the proposed scheme could overcome the over-fitting phenomenon and thus lead to an improved performance. Computer simulations showed that the proposed VB based scheme outperforms the existing LS based scheme
In this paper, the general efficiency, which is the average of the global efficiency and the local efficiency, is defined to measure the communication efficiency of a network. The increasing ratio of the general efficiency of a small-world network relative to that of the corresponding regular network is used to measure the small-world effect quantitatively. The more considerable the small-world effect, the higher the general efficiency of a network with a certain cost is. It is shown that the small-world effect increases monotonically with the increase of the vertex number. The optimal rewiring probability to induce the best small-world effect is approximately 0.02 and the optimal average connection probability decreases monotonically with the increase of the vertex number. Therefore, the optimal network structure to induce the maximal small-world effect is the structure with the large vertex number （〉 500）, the small rewiring probability （≈0.02） and the small average connection probability （〈 0.1）. Many previous research results support our results.
Multi-cell processing （MCP） is capable of providing significant performance gain, but this improvement is accompanied by dramatic signaling overhead between cooperative base stations. Therefore, balancing the performance gain and overhead growth is crucial for a practical multi-base cooperation scheme. In this paper, we propose a decentralized algorithm to jointly optimize the power allocation and beamforming vector with the goal of maximizing the system performance under the constraint of limited overhead signal and backhaul link capacity. In particular, combined with calculating the transmission beamforming vector according to the local channel state information, an adaptive power allocation is presented based on the result of sum capacity estimation. Furthermore, by utilizing the concept of cell clustering, the proposed framework can be implemented in a practical cellular system without major modification of network architecture. Simulation results demonstrate that the proposed scheme improves the system performance in terms of the sum capacity and cell-edge capacity.
