Applied Mechanics and Materials Vols. 548-549

Abstract: Heterogeneous networks have attracted a lot of attention for supporting high data rate and high mobility wireless communications. Since the base station density in heterogeneous networks is much larger than that in homogeneous networks, and the deployment of low power base stations in heterogeneous networks may be unplanned, a mobile user may see a large number of base stations simultaneously. Thus handover management in heterogeneous networks is much more challenging than that in homogeneous networks. In this paper, we address these challenges and propose a heuristic handover algorithm for use in heterogeneous networks. The proposed algorithm uses estimates of user velocity (speed and direction) and the transmission environment to improve the handover performance, i.e., the handover rate and the handover failure rate. Simulation results show that the proposed algorithm performs better than the conventional scheme in typical scenarios of heterogeneous networks.

Abstract: This paper proposes a joint linear precoding and power allocation design scheme for multiuser multiple-input multiple-out (MU-MIMO) cognitive radio (CR) systems, where secondary users share the same spectrum with one primary user. The interference power constraint required by the primary user and the multiuser interference generated by secondary users impose negative influence on each secondary user. As a result, it is difficult for secondary users to achieve the ideal information rate. In order to solve the above problem, we respectively adopt Channel Inversion (CI) and Block Diagonalization (BD) for precoding matrices which are set at the transmitter of each secondary user, and then make the system reach a steady state by power allocation. In fact, perfect CSI cannot exist in wireless systems. Therefore, it’s necessary to consider imperfect CSI. Simulation results show BD gains a higher rate for secondary users, but imperfect CSI causes less loss to CI.

Abstract: Partial interference alignment (PIA) strategies for the K-user interference channel are considered. Two schemes are proposed to align the partial interference for the downlink interference channel in the case of K>3. In the first scheme, strong interferences are limited as much as possible by aligning the two strongest interferers into a same subspace at the receiver. While the second scheme is to design its precoding matrix (or vector) by selecting the precoder pair which maximizes the chordal distance between designed signal subspace and interference signal subspace in the set of pecoding matrices (or vectors) at each transmitter. Simulation results show that compared with the existing schemes which don’t optimize the precoder, such as Fixed-PIA, the proposed schemes can improve the sum rates significantly by selecting IA forms in multi-input multi-output (MIMO) systems.

Abstract: As the third Generation mobile communication technology develops quickly, all sorts of smartphone development platform are constantly launched, including Google's Android mobile phone, and the promising future of Android cannot be ignored. Allow for the situation, the design and implementation of the Video on Demand System based on Android has realistic significance. Our article mainly states the development of Android Video on Demand application, JAVA service application and network communication. Summarize the principle of VOD system and draw flow-process diagram of it. We develop VOD application using JAVA language on Android which is based on the flow-process diagram successfully. Finally, debugging the programming on a Google's Android mobile phone, finding the bugs existing in the program and modify the mistakes to improve the software. My paper concluded the framework of VOD system on Android and verified it’s availability by realizing it on a Android cellphone to provide a model for future VOD system.

Abstract: The curtain array was usually composed of folded dipoles as elements for their high input impedance, but its bandwidth had a limitation for its antenna mode. This paper proposed a method for broadband folded dipoles using branch arms for current redistribution, which increased the bandwidth of input impedance and VSWR effectively by choosing the proper positions of the branch wires. The current distribution on branch model showed an unbalanced condition as the branch wires moved. As verification, a practical model with cage antenna had been analyzed by the present method and FEKO. The results illustrated that when factor k was between 0.4 and 0.5, the bandwidth would be maximum.

Abstract: A 5.8 GHz band smart antenna system of 4-elements microstrip linear array antenna with Butler matrix beamforming network is designed. The Butler matrix smart antenna is designed for WLAN applications using microstrip technology. System’s design and optimization was based on computer simulations using ADS momentum. The Butler matrix components like the hybrids couplers, the cross-couplers, and the phase shifters are designed and optimized one by one to get the best performances. The prototype is simulated on Rogers RT /duroid 5880 substrate with a relative permittivity of 2.2 and height of 0.787mm. Finally, the isolations of the Butler ports, the power distributions at the outputs, the return loss and the radiation pattern are presented in detail, in order to prove the system’s performance.

Abstract: Based on the EECP off-duty eligibility rule which is improvement of the popular CCP, this paper proposes a new off-duty rule. The new rule with much lower time complexity can overcome the misjudgment issue of ECCP, and be suitable for large high densely-deployed WSNs.

Abstract: In our Study, we Find that Location-Assisted on-Demand Routing (LAOR) Algorithm has Redundancy Control Overhead. Furthermore, LAOR does Not make Full Use of the Effective Information of New Path to Complete the Follow-up Path. to Address these Issues, an Improved Effective on-Demand Routing, Effective Improved on-Demand Routing (EIOR) Algorithm, is Proposed in this Paper. EIOR Makes Full Use of the Information of Control Packet to Update more Routing Paths, Reduces the Control Overhead for Finding Path and Increases the Real Time of Routing Updates. Moreover, EIOR Increases the Probability of Intermediate Satellite Replies Request Instead of the Destination Satellite, which Shortens the Setup Time of Path and Reduces the End-to-End Delay. it also Designs the RREP Immune Mechanism to Reduce the Control Overhead of the Network. Theoretical Analysis and Simulation Results Show that EIOR Outperforms LAOR. the EIOR can Reduce at Least 7% of the Normalized Control Overhead and 4% of the Average End-to-End Delay.

Abstract: The coexistence of various network protocol standards at present creates a huge barrier against network interconnection and interoperability. This paper proposes an IOT gateway system to implement various heterogeneous networks interconnection and interworking. The multi-protocol conversion gateway system is developed on top of the WMMP framework to integrate heterogeneous networks and incorporates a semantic model of an IOT software system. And then the protocol conversion method is designed on the basis of the protocol driver template, which is configurable for different communication protocols. The gateway communication process is implemented to report and transmit data and forward command to the bottom layer devices. As a result, the analysis test results show that dynamic protocol conversion mechanism of the gateway provides a good operating environment for different service functions for stable, scalable and real-time remote control system.

Abstract: For disadvantages of the present mine voice communication systems, a kind of wireless voice communication system based on Zig Bee is put forward. The paper provides detailed informations about hardware and software of the wireless voice communication device. In the system, adopt CC2530 as RF sending-receiving unit of voice communication node, convert speech signals to digital or analog signals by CSP1027, encode or decode quantized voice data by AMBE voice codec technology and realize voice message two-way wireless communication over the Zig Bee wireless communication protocol IEEE 802.15.4 between voice communication devices. Experiments have shown that voice communication device can get a clear voice and have a high reliability in the effective distance of communication, meet the requirements of voice communication.