A novel slotted dual channel medium access control (SDC-MAC) protocol is proposed for multihop wireless networks to maximize concurrent packet transmissions. By leveraging a slot-optimized scheme, the channel reservation and data packet transmissions can be simultaneously carried out on the control channel (CCH) and data channel (DCH) reducing packet collisions. Multichannel hidden and exposed terminal problems are also alleviated to greatly improve the channel access efficiency. Numerical results show that compared to the IEEE 802.11 DCF protocol, the SDC-MAC protocol has obvious performance improvement under the same total bandwidth.

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With shortest path bridging MAC (SPBM) in an access network, the paths of high rate flows can overlap on specific links and this results in congestion. It is important to avoid congestion by selecting the optimal path for each flow. This paper proposes a path selection algorithm for access networks with SPBM. The proposed algorithm avoids selecting a congested path. When a new flow arrives at an edge SW, the SW selects the path with the highest average input rate of assigned flows. We confirmed with computer simulations that the proposed algorithm could efficiently utilize links and improve throughput fairness.

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This paper outlines an experimental investigation of an over-gigabit indoor visible light transmission system employing a quasi-phase-matching (QPM) device. To evaluate the effect of collecting lenses with different diameters, we measured the relationship between received optical power and bit error rate by using collecting lenses with diameters of 5, 8, 10, and 15mm. The experimental results confirmed that the relationship between the received optical power and the receiving area of the collecting lens was consistent with the analytical solution. We confirmed that a larger collecting lens is effective against the degradation caused by increased transmission distance, even if the optical output power of the wavelength converter is constant.

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From the secrecy perspective, conventional cooperation communication is not always positive since it improves the link qualities of both the legitimate receiver and the eavesdropper node. To overcome this drawback, we propose an adaptive cooperation scheme, which activates the relay only when it has better secrecy capability than the source. This adaptive scheme is combined with secure user scheduling strategy to harvest the multiuser diversity (MUD) gain in the relay networks serving multiple sources. The results show that our scheme achieves a much higher secrecy capacity than alternatives. Meanwhile, the relay becomes less beneficial for a large number of sources.

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While using applications on mobile terminals, user quality of experience (QoE) often degrades. There are two methods for QoE improvement, carrier actions and user actions. We focus on the latter, which requires less time and money for improving QoE than the former. Efficient actions for improving QoE differ by user because each user may be in a different environment. We propose a methodology for specifying QoE degradation factors in order to suggest appropriate user actions. With our methodology, we collect the logs of many users and specify QoE degradation factors by referring to high QoE users.

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In this letter, we analyze the impacts of outdated channel state information (CSI) on the secrecy performance for multiple-input single-output multiple-eavesdropper (MISOME) systems using transmit antenna selection (TAS) scheme and derive the exact closed-form expressions for the secrecy outage probability and the probability of non-zero secrecy capacity. Then, we present the asymptotic secrecy outage probability which reveals the secrecy diversity order and the secrecy array gain. The analysis and simulation results show that the security performance of TAS scheme is quite sensitive to outdated CSI and the achievable secrecy diversity order is only one under the effect of outdated CSI.

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We propose a novel time-division multiplexing method with a dedicated frame structure for transmitting digital broadcasts to homes over FTTH. By using experimental equipment, it was revealed that the proposed method can be expected to serve more subscribers than does the conventional frequency-division multiplexing method, and it achieves a low transmission latency and short period of program selection time. In this paper, we introduce and investigate the advantages and challenges for the future of the proposed method from the aspect of the requirements for broadcasting.

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This paper introduces a technique to suppress FWM-induced crosstalk and demonstrates its performance as applied to phase locked 10Gbit/s OOK-signal 6-carrier transmission. The initial carrier phases are set to cancel out 56% of the generated crosstalk. Successful transmission over DSF is achieved with a power penalty of 1dB even though the crosstalk level was -15dB.

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This paper proposes a coding scheme to securely store a secret file in a distributed storage system that uses an arbitrary regenerating code. Our scheme encodes the secret file to the input of a certain regenerating code by using the coset coding scheme with a maximum rank distance (MRD) code. We show that our scheme can protect the secret file from being leaked to an eavesdropper in the distributed storage system. Existing security schemes for distributed storage systems are based on specific regenerating codes, and they cannot be used with other regenerating codes. In contrast, our scheme can guarantee the security against the eavesdropper independently of the construction of the underlying regenerating code.

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This paper proposes a low complexity MIMO detection using ordering SIC (OSIC) with conditional list generation. Combined with lattice-reduction (LR) technique, OSIC further gains the BER performance compared to SIC, since the more reliable signal is prior to being detected. However OSIC based on LR (LR-OSIC) has inferior performance to the maximum likelihood (ML) detection in large size MIMO systems. In this paper, we investigate the mean square error in LR domain to evaluate the condition of the channel. The proposed detection applies the conditional list detection to update the estimate of the LR-OSIC. The simulation results exhibited that the proposed detection achieved near-ML performance in the 8×8 MIMO and required almost same complexity of the LR-OSIC in the high E_b/N₀ region.

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This paper proposes a new forwarding algorithm over lossy wireless link that increases network performance in terms of received traffic at the sink (R₀ packets/s) and network lifetime in wireless sensor networks (WSNs). Due to lossy wireless links, each sensor node forms around itself three different communication regions, each characterized by different packet reception rates (PRRs). The results of simulations indicate that, the proposed FOLLA (Data forwarding with lossy link awareness) algorithm outperforms the conventional algorithms with respect to R₀ and network lifetime.

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This letter proposed a user selection with swap (USS) algorithm based on zero-forcing beamforming (ZFBF). USS starts with an initial user group with the largest channel 2-norms, iteratively swap the “worst” user (has the minimal achieved rate) among the scheduled users with the “best” user (has the maximum channel 2-norm) among the remaining users. Based on the simulation results, we can confirm that the proposed USS algorithm can provide a comparable performance with previous algorithms with greatly reduced complexity of O(KN²).

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To develop the effective feeding structure for the leaky wave antenna using the composite right/left-handed transmission line with monopolar radiation, a broadband center-feed structure composed of a triangular element is proposed in this paper. The dispersion characteristics and flat Bloch impedance are obtained by complex S-parameters of 2 ports on the structure. The CRLH leaky wave antenna is fabricated, and bandwidth of 60% is achieved while its radiation characteristics are similar to monopolar radiation.

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