In order to reduce the power consumption of the sensor nodes in WSN,when data is being transmitted or received,the wireless communication module of the nodes are supposed to start operation to send the data or listen to the channel,otherwise it enters a sleep mode. However,the biggest problem is that the sensor nodes are unable to receive data when being in the sleep mode. Without a better protocol designed,data will be failed to be received since the nodes are in sleep mode,and thus the entire network performance is re-duced. For this problem,a new traffic-aware adaptive MAC protocols with ultra-low power for WSN is proposed. In the designed MAC protocol,the sleeping time and wake-up time in real time of the nodes are scheduled based on the network traffic. If network traffic is low,it enters the phase of non-scheduling or else the phase of scheduling. In addition to the advantages of synchronous network and asyn-chronous network,the algorithm is further improved in this designed MAC protocol. Compared with the existing traditional MAC proto-cols,the power consumption and the delay of the sensor network is reduced greatly with the designed MAC protocol.

The design of the Android shopping system based on the geographic location information is employed to solve the problem of stores shopping around.On the basis of the study of agglomerative algorithm,smart filtering algorithm,IR2 Tree,the method of the Android shopping system based on the geographic location information has been proposed.It is divided into the following process with three steps:the function of the localization,search,navigation is achieved with the help of LBS services space operations;the interaction of the LBS cloud services platform is completed with the client,and the client's user interface and business logic are built through the network requests made by the client;the access to the server-side data structure is completed by the client through the HTTP protocols.By using this application customers can search the favorite shop in his local area up to 3/4 km when all the shops related to that particular area have been displayed with the help of GPS system.The nearest store have be found with the map provided by the APP and the goods can be purchased online.The shopping system commissioning results show that the consumer can quickly search to their surrounding the nearest shops and purchase the required goods,and save a lot of time.Thus the strong practicability and convenience of the system have been verified.

With the evolution of the development of wireless sensor networks,its applications are increasingly widespread. For example, existing public utilities meter reading system,the construction of real-time monitoring systems and environmental future 4. 0 intelligent industrial plant monitoring system will use a lot of wireless sensor for monitoring and data collection. These data acquisition systems often require monitoring to support remote data collection and mobile data collection. By using different characteristics of these two modes, which are waking the different needs of delays and supporting different data transfer rates,the hybrid method of listening period is pro-posed. This approach can support real-time data monitoring collection,and significantly reduce power consumption compared with a sin-gle listening period and extend the operating time of sensor nodes,in full compliance with the real-time requirements of data collection in close distance for the mobile terminal.

An improved minimum mean square error (MMSE) channel method with low complexity is proposed for the massive multiple input multiple output (MIMO) system. In the method, the covariance matrix in the MMSE method is firstly approximately estimated by the received signal, where the optimal approximated weight is given, and then the Sherman-Morrison theorem is employed to transform the matrix inversion into the product of the matrix and vector. The simulation results show that the proposed method can greatly reduce the computational complexity of the MMSE method and only has a little performance loss. Moreover, compared with the available methods, the proposed method has a better performance and lower complexity.

We investigate device-to-device (D2D) communication underlaying cellular networks with M-antenna base stations. We consider both beamforming (BF) and interference cancellation (IC) strategies under quantized channel state information (CSI), as well as, perfect CSI. We derive tight closed-form approximations of the ergodic achievable rate which hold for arbitrary transmit power, location of users and number of antennas. Based on these approximations, we derive insightful asymptotic expressions for three special cases namely high signal-to-noise (SNR), weak interference, and large M. In particular, we show that in the high SNR regime a ceiling effect exists which depends on the received signal-to-interference ratio and the number of antennas. Moreover, the achievable rate scales logarithmically with M. The ergodic achievable rate is shown to scale logarithmically with SNR and the antenna number in the weak interference case. When the BS is equipped with large number of antennas, we find that the ergodic achievable rate under quantized CSI reaches a saturated value, whilst it scales as log2M under perfect CSI.

In this paper, we consider the device-to-device (D2D) communications with multiple antennas underlaying single-cell cellular networks, in which D2D transmission links reuse the cellular downlink (DL) resource. We propose an iterative distributed interference alignment (IA) algorithm to reduce the cellular interference towards D2D UEs, which utilizes the reciprocity of wireless networks with local channel knowledge at each node. The iteration algorithm continues until it converges, judged by the weighted leakage interference (WLI). Simulation results demonstrate that using the distributed interference alignment algorithm can effectively improve the system capacity and energy efficiency.

描述了基于放大转发中继underlay模式下的D2D传输模型,研究了用户最大发射功率受限前提下利用单向放大转发中继的D2D通信系统功率分配方法.首先从D2D系统端到端信干噪比表达出发,推导出D2D链路和蜂窝上下行链路的可达和速率,据此建立了可达和速率的联合功率优化模型,根据功率约束条件将双目标优化模型转化为单目标优化模型;然后采用Pareto优化方法最大化可达和速率,并提出相应的低复杂度实现算法.仿真结果表明:在中低信噪比区域,基于放大转发中继辅助的D2D通信性能显著优于传统D2D通信模式,采用Pareto功率优化方法可进一步提升D2D通信以及蜂窝上下行链路的系统可达和速率.

In cellular networks, Device-to-Device (D2D) communications can improve spectral efficiency and increase overall throughput. However, D2D users may cause interference to the cellular users (CU) due to sharing resource with CUs. In this paper, we proposed a resource allocation scheme to maximize the system throughput while guaranteeing the quality-of-service (QoS) requirements of all communication links. The proposed scheme allows as many D2D pairs as possible to reuse resource and includes three steps. Firstly, an exhaustive search method is used to search out all the reuse combinations, in which all users share the same resource. Secondly, transmit power for each reuse combination is allocated. Lastly, a suboptimal but simple algorithm is proposed to select suitable reuse combinations in order to maximize the overall throughput. Simulation results show that the proposed scheme can significantly increase system throughput and D2D access rate.

Considering the case in which Cellular User Equipment(CUE)and multi-pair Device-to-Device(D2D)link exploit the same resources in the uplink period, the performance of cellular networks is studied in this paper. Under the multi-pair D2D link aggregate interference constraint, the outage probability of the cellular system is deduced and simulated. Simulation results show that the interference received by BS increases with the increase of D2D link. The results also indi-cate that the overall system capacity can be improved with the increase of D2D link when the distance constraint between D2D link and the BS is met.

Device-to-Device (D2D) communication is proposed as a transmission approach to improve resource efficiency and lighten the load of base station (BS) in heterogeneous networks. In this paper, two scenarios that the heterogeneous system contains relay node or not are considered, and the research focuses on the relative distance from D2D receiver to cellular user. The simulation results demonstrate that the probability of choosing underlay mode is inversely proportional to the system threshold value of Signal to Interference plus Noise Ratio (SINR), which is determined by system parameters. Moreover, the introduction of relay node can increase the probability of selecting underlay mode, as well as increase the spectrum efficiency.

在蜂窝网络中引入终端直通(D2D)技术,能有效提升系统频谱效率。文中在研究了物理层自适应调制编码(AMC)策略与数据链路层自动请求重传(ARQ)技术相结合的跨层设计理论基础上,提出了D2D中继通信场景下AMC与HARQ相结合的跨层设计方案。仿真结果表明,采用AMC与HARQ相结合的跨层设计策略能显著提升D2D通信的频谱效率,增加D2D中继通信的吞吐量。

Device-to-Device (D2D) communication assisted with relay transmission could efficiently optimize the system performance when D2D users are too far away from each other. In this paper, considering the individual QoS requirements, we propose a cross-layer relay selection algorithm which combines channel state information (CSI) at physical layer with queue state information (QSI) of buffer for each relay node at data link layer. Then we deduce the relay selection rule based on the CSI and QSI. Our method could make up for the problem that traditional relay selection schemes fail to consider the limited buffer capacity of relays. Simulation results illustrate that the cross-layer relay selection strategy can obtain a substantial system throughput gain. Meanwhile the algorithm leads to a decrease in average transmission time delay and packet error probability compared with the traditional ones.

In cellular networks, the introduction of device-to-device (D2D) technology could promote cell coverage and improve user experience. In this paper, we consider the scenario of relay assisted D2D communications, and propose a relay selection and resource allocation joint algorithm. The algorithm takes relay selection and resource allocation into consideration simultaneously. And we determine the optimal relay node based on maximum capacity of D2D relay link while guaranteeing the QoS requirement of cellular user (CU) who shares spectrum resources with D2D user. Simulation results show that the proposed algorithm could absolutely fulfill the QoS requirement of the partner CU, and significantly promote the capacity of D2D relay link and spectral efficiency.

文中对异构网络下用户接入选择和网络资源分配的联合优化问题进行研究,在传统资源分配方法的基础上,加上用户对网络的主动选择,侧重考虑用户满意度,建立接入选择和资源分配的联合优化模型。在资源分配之前,让用户根据接入每种网络的概率优先选择接入概率最大的网络,在此基础上网络再调整价格来获得最佳的网络效益。仿真结果表明,文中所提出的联合优化方法在保证了网络效益的同时,又兼顾了用户的满意度。

文中在研究移动用户中继的基础上,对AF协同接收型中继模式链路容量的公式进行了推导,并根据空闲用户的分布,提出一种中继选择和资源分配的联合算法。仿真结果显示,该算法不仅能够提高系统的容量,还可以大大改善小区边缘用户的链路吞吐量。

Recently, FCF (Fountain-Coding-and-Forward) relay has been proposed as an effective method to improve the performance of the wireless system. In addition, device-to-device(D2D) communication can effectively improve the system's resource usage efficiency and reduce the user's energy consumption. In this paper, we study the performance of a hybrid cellular network with the FCF relay strategy considering D2D communication. In our proposed approach, the resource user transmits its data to the relay user in D2D communication mode and then the relay user transmits data to the base station directly. In this paper, we investigate the resource usage efficiency and the power efficiency. Numerical results show that the proposed FCF relay with D2D communication can have a better resource usage efficiency and power efficiency performance than the traditional direct cellular communication.

The introduction of Device-to-Device (D2D)technology into the LTE systems in a non-orthogonal way of reusing re-sources may bring about interferences,i.e.mutual interferences between the cellular users and the D2D users.In the D2D sys-tems,cross-layer resource optimization can cope with instantaneous channel worsening arising from the interferences for the cellular users,thus improving their average spectral efficiency and increasing the system capacity.This thesis studies a link-a-daptive cross-layer optimization scheme for the D2D system,which combines the adaptive modulation and coding technology in the physical layer with the auto repeat request technology in the data link layer,aiming at lowering the interferences arising from the introduction of the D2D technology.Simulation results indicate that in a single cell scenario with 4 cellular users and 4 pair of D2D users,the total capacity of the D2D communication system is increased by about 5% when the link-adaptive cross-layer optimization scheme is adopted.

Due to the severe interference from the cellular users who share the same spectrum resources in cellular networks, the reliability of D2D communication has been a great concern. Relay has always been considered a importantl tool in improving the quality of wireless system. This paper combines D2D communication system with relay to make D2D communication more reliable. We can conclude from the simulation results that relay does help efficiently to reduce the outage probability of D2D communication by making the D2D received signal-to-interference-and-noise-ratio (SINR) more stable, under the condition that the target SINR of D2D communication is in low regime.

Introducing relaying nodes to D2D (Device to Device) communication system can effectively improve the system performance. However, the quality of direct D2D communication cannot be guaranteed when the users are far from each other, the effect of relaying node becomes particularly important in this case. In this paper, we studied different relaying selection strategies of D2D communication in cellular network, in which we take the mutual interference between the D2D pairs and cellular users into consideration. The selection strategies we proposed can adaptively determine the number of relaying nodes according to specific context. Finally we compare the proposed relaying selection strategy with simulation results and analyze their performances.