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Wireless network capacity has been studied extensively in the literature. Due to its dependence on traffic profile there are many variations in how the capacity of a wireless network is defined. The traffic profile is heavily influenced by the MAC layer, and in a CSMA implementation, RTS and CTS messaging rules dictate which nodes are able to transmit to others and when. In this manner the RTS/CTS...
This paper proposes a new TDMA-based cooperative MAC scheme for a two-hop relay network in which there are several helpers besides a default relay node. Here, a helper has lower obligation than the default relay to help packet forwarding. The proposed method is developed from the existing CR-TDMA scheme, and named as opportunistic CR-TDMA or OCR-TDMA. We derive the throughput performance of CR-TDMA...
This paper presents the results for a combined Coordinated MultiPoint (CoMP) and Dynamic Sectorization (DS) approach for energy saving at the Base Station (BS) in LTE-A cellular networks. The DS scheme is based on ecological self-organization where BSs are dynamically reconfigured based on their tempo-spatial traffic diversity. The compatibility of CoMP and DS is explored and improved upon independent...
Distributed compressed sensing (DCS), exploiting the correlation among multiple signals, enjoys the advantage of reduced number of measurements. This paper considers a type of joint sparsity model in DCS, where each signal contains a common component and an innovation component. In order to reduce the transmission cost, the measurements are derived as the sign information of the compressed samples...
Orthogonal Frequency Division Multiple Access (OFDMA) is considered as one of promising wireless access techniques which can accommodate multiple users flexibly and efficiently. In the uplink OFDMA system, it is required to estimate all users' channel frequency responses (CFRs) simultaneously which are used in the equalization for the data information at the base station (BS). To realize this requirement,...
Reconstruction algorithm is a significant research field of compressed sensing (CS). Among existing algorithms, regularized orthogonal matching pursuit (ROMP) enjoys the merit of implementing fast recovery procedures. Recent studies have recognized that sparse signals have special sparse structure, which is useful for reconstruction as prior information. In this paper, by utilizing the sparse tree...
With the widespread popularity of mobile terminals, mobile video has become an indispensable part of daily life. The conventional wireless video transmission scheme which consists of separate digital source coding and digital channel coding is now unable to meet the broadcast and mobile scenarios owing to the dramatic changes in its channel condition. However, an uncoded transmission scheme called...
The cyclic-SLM which implements delayed correlation with a matched filter (DC-MF) is proposed in this paper. The cyclic-SLM reduces a peak-to-average power ratio (PAPR) on an orthogonal frequency divison multiplexing (OFDM) signal. This scheme combines the original OFDM signal and its cyclic shifted ones. However, it needs side information (SI) of the cyclic shifts to recover the original signal that...
Cognitive Radio is utilized to exploit the existing wireless spectrum opportunistically, in which way to alleviate the spectrum shortage problem. It is of fundamental importance in cognitive radio adhoc networks for users to meet on a common channel via rendezvous and thereby establish communication links. In this paper, we investigate the probability analytic model to discuss the problem of rendezvous...
When a cognitive radio network shares the spectrum with a primary network, the harmful interference to the primary users is one of the most important concerns. In this paper, we propose a new cognitive scheme which has two cognitive sub-networks sharing the same relay station, considering the interference to the primary user. We study the Weighted Rate Balance problem with the constraint of the transmit...
In [1], a new frame structure is introduced to improve throughput and spectrum sensing capabilities compared to conventional cognitive radio (CR) systems that use the frame structure with a periodic sensing. However, even though employing two levels of power only for primary users (PUs) can be considered for CR systems, it may not be practical as the PUs often transmit with multiple levels of power...
In this paper, a novel opportunistic protocol is proposed for the two-way relaying systems with direct link. Unlike the existing protocols, the proposed protocol opportunistically exploits analog network coding and the direct link. The proposed protocol switches its strategies to support two traffic flows simultaneously or support only one traffic flow based on instantaneous channel conditions. An...
In cognitive radio (CR) systems, we often use jamming schemes to improve the physical-layer security in the presence of passive eavesdroppers. However, it also needs additional signal sources to transmit artificial noise. In this paper, we investigate the multiple-input single-output (MISO) cognitive radio system where two secondary links secure each other's communication. Each secondary transmitter...
In this paper, lattice network coding (LNC) is studied in the multiple-antenna (MA) two-way relay channel (TWRC), where each user has a single antenna and the relay has multiple antennas. We propose two relay computation schemes for the MA TWRC with nested lattice codes, namely the receive antenna selection (RAS) scheme and the receive antenna combining (RAC) scheme. In the RAS scheme, the relay calculates...
The secrecy transmission performance of cognitive radio ad hoc networks is investigated in this paper. The existing work on secrecy capacity of cognitive radio networks focus on order sense results like scaling laws, however, these results only give asymptotic predictions without an exact expression. In order to overcome this limitation, we propose a new method to derive the closed-form expression...
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