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TV White Spaces (TVWS) refer to segments of the TV spectrum not used by licensed users in a given location. In recent years, regulation agencies throughout the world consider the possibility to open TVWS to unlicensed use, which is followed by standardization activities to realize it. One of the important aspects of unlicensed operation in TVWS is coexistence between heterogenous networks. This paper...
This paper introduces NICT's two current on-going projects regarding heterogeneous type and spectrum sharing type cognitive wireless network: Project CWC (Cognitive Wireless Cloud) and Project ASTRA (Advanced Spectrum-Management Technology for Radio Access innovation). For both projects, this paper summarizes the scope, usage model, system requirement, system architecture, prototyping, and standard...
In cognitive radio networks, secondary users need to conduct spectrum sensing to properly detect the presence of primary signals that may have much lower power than noise plus interference power. In such a case, time-varying noise plus interference, which is briefly called noise uncertainty in this paper, can substantially degrade the sensing reliability of hard information combining (HIC) and soft...
Fixed multiplexed access radio networks can realize collision-free transmission while suffering low flexibility, especially in ad hoc communication. This paper demonstrates that a dynamic spectrum access based cooperative relay technology, defined as cognitive relay, contributes toward improving the flexibility of fixed radio networks to bursty heavy traffic, unbalanced traffic loads and terminal...
Owing to retransmission of lost packets and bursty nature of source data, even an ad hoc network with low average traffic may suffer heavy traffic in some certain periods, which in further may degrade system performance, particularly in multi-hop wireless communication. Aiming to provide a solution to above problem, in this paper, we construct a hybrid system based on plural ad hoc networks, which...
In cognitive radio (CR), primary users have exclusive privilege to access their licensed channels. Therefore, a transmission failure occurs when one or more primary users access the licensed channel during a transmission by users in secondary radio network (SRN). We define such channel access by primary users as return of primary users. Transmission failure caused by return of primary users may not...
M-ary Elliptical Phase Shift Keying (M-EPSK) have been proposed and evaluated through simulations in our previous works. According to the simulation results, M-EPSK (M=4,8) can achieve better noise performance than MPSK; in particular, M-EPSK can adaptively realize trade-offs between bandwidth efficiency and power efficiency by varying the eccentricity. Eccentricity is the main modulation variable...
In this paper, Iterative Unequal Length Search (ULS) Syndrome Decoding for Product Codes is proposed by introducing an idea of unequal length search space. The principle and realization of the algorithm is presented. Moreover, a mathematical performance and decoding complexity analysis is illustrated. Compared to the conventional Equal Length Search (ELS) Syndrome algorithm, experimental results indicate...
M-ary elliptical phase shift keying (M-EPSK, M=2,4,8) have been proposed in our previous works. Evaluation results show that M-EPSK can achieve advantage over MPSK on noise performance. In particular, M-EPSK can adoptively make trade-offs between bandwidth efficiency and power efficiency by varying eccentricities. However, the analysis in previous works also shows that the achieved performance of...
In this paper, 8-ary Elliptical Phase Shift Keying (8EPSK) Trellis-Coded Modulation and set partitioning based on the sum of soft metric distance are proposed and developed. The criterion to design and search for good TCM codes is also presented. The performance of 8EPSK-TCM has been evaluated through Matlab simulation in terms of BER. The results show that the performance of 8EPSK-TCM outperforms...
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