混合多址接入的无线传感器网络设计及实现

针对实际应用中无线传感器网络多区域分布、任务多元化的特点,为解决簇间通信的相互干扰,提出一种改进的FD-MA/TDMA混合机制的无线传感器网络.簇间采用FDMA避免干扰,簇内节点采用TDMA实现睡眠调度.此外,在TDMA机制中分配监测时隙,如有突发情况,簇内节点可通过CSMA竞争与簇头节点实现通信,以此增加上报的公平性.对系统进行了工程实现验证,测试证明达到预期效果.     

分簇无线传感器网络动态时隙分配MAC协议

为降低大规模无线传感器网络的平均能耗,提出了一种基于动态分配的调度型无线传感器网络MAC协议（SDC-MAC）。该协议簇间使用FDMA方式分配无线信道,簇内通过TDMA方式给各个节点分配可变长的时隙。随着簇结构的变化,簇头通过时隙分配通知,对簇内节点的时隙分配进行动态调整,簇成员节点则根据控制信息进行休眠和唤醒。仿真结果显示,该算法有效地降低了网络的平均能耗,当网络流量高时还可降低平均数据包时延。     

DEAMC：一种分布的，节能的，自适应的动态的分簇无线传感器网络协议

分簇结构的无线传感器网络可以更容易的进行数据融合,可以减少网络能量消耗,增加网络的健壮性,因此分簇算法被广泛的用在无线传感器网络中。但现存的算法不能满足网络拓扑变化较大、较频繁的网络。针对移动性较大的无线传感器网络,提出了DEAMC,一种分布的、节能的、自适应的、动态的分簇协议。根据DEAMC,剩余能量越多,成为簇头的可能性越大,且簇头均匀分布。DEAMC用是一种TDMA协议,利用TDMA可以减少能量消耗,延长网络的寿命。DEAMC是一种FDMA协议,利用FDMA可以避免信号碰撞。     

DEAMC:一种分布的,节能的,自适应的动态的分簇无线传感器网络协议

分簇结构的无线传感器网络可以更容易的进行数据融合,可以减少网络能量消耗,增加网络的健壮性,因此分簇算法被广泛的用在无线传感器网络中.但现存的算法不能满足网络拓扑变化较大、较频繁的网络.针对移动性较大的无线传感器网络,提出了DEAMC,一种分布的、节能的、自适应的、动态的分簇协议.根据DEAMC,剩余能量越多,成为簇头的可能性越大,且簇头均匀分布.DEAMC用是一种TDMA协议,利用TDMA可以减少能量消耗,延长网络的寿命.DEAMC是一种FDMA协议,利用FDMA可以避免信号碰撞.     

一种基于分簇的无线传感器网络MAC协议

本文提出了一种基于分簇结构的无线传感器网络MAC协议.在基于层次式路由协议的分簇网络结构中,通过综合基于竞争和基于时分复用协议的优缺点,将时间划分为交替的随机访问和调度访问两个阶段,在随机访问阶段簇内节点采用CSMA/CA实现无线信道共享.在调度访问阶段,节点根据簇首分配的时隙实现数据无冲突通信.在簇与簇之间采用FDMA避免信道干扰实现网络的扩展.分析和仿真结果表明本协议在能量效率、时间同步和网络扩展上都有所改进.     

无线传感器网络能量高效混合MAC算法

针对无线传感器网络MAC协议中存在的能耗问题,提出了能量高效的无线传感器网络混合MAC(EEH-MAC)算法,采用基于TDMA机制的时槽系数动态调整簇内节点的时槽大小来降低数据的传输时延;同时,对部分不需要数据传输的节点不分配时槽来减少能耗;按簇内节点剩余能量系数形成时槽分配顺序来减少状态转换的能耗;在簇头之间采用CSMA/CA机制的随机分配策略进行通信.仿真结果表明,EEH-MAC协议能有效减少能耗并延长网络生命周期.     

无线传感器网络环境下基于事件 驱动应用的节能TDMA协议

媒质接入控制是无线传感器网络设计的关键问题之一.由于媒质接入控制协议直接控制着节点无线通信模块的活动,而无线通信模块是传感器节点能量消耗的主要来源,因此MAC协议节能效率的好坏将严重影响网络的性能.基于TDMA的MAC协议具有固有的节能特性,即通过合理的TDMA调度避免传输碰撞以及减少节点空闲监听的时间.本文提出了ED-TDMA协议,一种面向事件驱动的传感器网络应用的TDMA协议.该协议根据当前源节点的数目动态地改变TDMA帧的长度,提高了信道利用率;同时采用位图方式的TDMA调度,极大地减少了TDMA调度的开销,节约了能量.此外,通过引入簇内覆盖的思想,使得簇内的活动节点数目为一常数,同时减少了工作节点的数目,从而延长网络的生命周期,并在一定程度上提高了系统的可伸缩性.实验结果显示,ED-TDMA协议更适用于网络负载较低、节点密度高的无线传感器网络.     

基于分簇的MACA协议改进算法

针对大规模水声传感器网络,本文提出一种新的MACA协议改进算法,将TDMA协议与MACA协议进行融合,对整个大规模传感器网络的节点进行分簇,簇内通信和簇首通信采用不同的协议:一种更加适合簇内小规模网络的TDMA协议;一种更加适合长距离多数据的MACA协议.改进MACA协议预约方式和数据传输方式,使其更加适应复杂的信道.同时使它们工作在不同的频段上,防止干扰以及不需要对整个网络节点进行时间同步.     

无线传感器网络中一种动态节能的MAC协议

媒体访问控制(MAC)协议是无线传感器网络的关键协议之一,它对无线传感网络的运行和性能具有重要的影响.针对基于簇的TDMA机制存在问题,文中提出了一个动态节能的DE-MAC协议,该协议能够根据簇成员节点数目和通信负载动态地分配成员节点的时隙,减少节点的空闲侦听时间.仿真结果表明,DE-MAC协议能够有效地提高信道的利用率和网络能量有效性.     

基于能量均衡的无线传感器网络路由算法

为了提高无线传感器网络的生存时间,针对当前LEACH算法存在的能量不均衡难题,提出一种能量均衡的无线传感器网络节点路由算法。首先将监测区域看成以基站为中心的扇形区域,并将扇形区域分割成不同大小的弧形方块,每个弧形方块中的节点组成一个簇,根据节点剩余能量产生簇头,然后采用单跳和多跳相结合的簇间通信机制,最后采用仿真实验测试算法的性能。结果表明,本文算法有效提高了网络的能量利用率,能够实现节点之间的能耗均衡,使无线传感器的网络生存时间得到延长,适用于对网络生命周期要求较高的应用。     

Minimizing inter-cluster interference by self-reorganizing MAC allocation in sensor networks

This paper presents a Self-Reorganizing Slot Allocation (SRSA) mechanism for TDMA based Medium Access Control (MAC) protocols in wireless sensor networks. With TDMA, a node can achieve significant energy savings by remaining active only during allocated slots for transmissions and receptions. In multi-cluster networks, it is often necessary for nodes to use either CDMA or FDMA for preventing interference across neighbor clusters. The goal of this paper is to provide an alternative design that can reduce inter-cluster TDMA interference without having to use spectrum expensive CDMA or FDMA. The primary contribution of this paper is to demonstrate that with adaptive slot allocation, it is possible to reduce such interference under low loading conditions, which is often the case for sensor networks with monitoring applications. The second contribution is to design a feedback based adaptive allocation protocol that can significantly reduce those interferences without relying on any global synchronization mechanisms. We present the design of SRSA and provide a simulation based characterization of the protocol in comparison with TDMA-over-CDMA, TDMA with random slot allocation and CSMA MAC protocols. The results indicate that with moderate cluster overlapping and low traffic loading, SRSA can significantly reduce inter-cluster TDMA interference while delivering TDMA-over-CDMA like energy efficiency, at the cost of higher delivery latency. Assuming its low complexity and narrow-band operation, SRSA can be an ideal sensor MAC protocol for applications that can tolerate relatively larger delivery latency but not frequent packet drops. This work was partially supported by a grant from National Science Foundation (SCI-0438271) Tao Wu received B.E. degree in automatic control and M.S. degree in pattern recognition from University of Electronic Science and Technology of China, Chengdu, China in 2001 and 2004 respectively. He is currently a Ph.D. student in electrical and computer engineering at Michigan State University. His research interests include wireless sensor networks and distributed computing. Subir Biswas is an Associate Professor and the director of Networked Embedded and Wireless Systems laboratory at the Electrical and Computer Engineering Department of Michigan State University. Subir received his Ph.D. from University of Cambridge and he held various research positions in NEC Research Institute, Princeton, AT&T Laboratories, Cambridge, and Tellium Optical Systems, NJ. He has published over 50 peer-reviewed articles in the area of wireless network protocols, and a co-inventor of 4 U.S. patents. Subir’s current research interests include the broad area of wireless data networking, low-power network protocols, application-specific sensor networks and wireless network security. He is a senior member of IEEE and a fellow of Cambridge Philosophical Society.     

Channel Borrowing Without Locking for Asynchronous Hybrid FDMA/TDMA Cellular Communications

The use of real time channel borrowing in digital cellular asynchronous hybrid FDMA/TDMA systems is considered. These systems, which are exemplified by North American digital cellular (IS-54), are asynchronous in the sense that time slots in different cells are not aligned. CBWL (channel borrowing without locking) techniques can be applied but (without cell-to-cell synchronization) borrowing individual time slots from adjacent cells would violate co-channel interference constraints. Instead, frequency carriers can be borrowed. In IS-54, a carrier supports three TDMA slots. So if only one TDMA slot is needed in the borrowing cell, two TDMA slots are unnecessarily transferred. We devised an appropriate carrier borrowing scheme and an analytical model to determine the traffic performance of TDMA/CBWL. Fast carrier returning is used to increase channel utilization by returning borrowed carriers as soon as possible. An efficient computational method that uses macro-states, decomposition, combinatorial analysis and the convolution algorithm is devised to find blocking probabilities. The results show that in comparison with FCA, the new CBWL scheme can significantly improve system performance of asynchronous TDMA cellular systems that use FDMA/TDMA multiplexing.     

移动Adhoc网络的动态网络管理研究

介绍了一种移动Adhoc网络的网络管理系统,研究并实现了基于定向天线的动态网络管理方案。将分支限界算法引入时隙分配中,采用了空分技术,增加了信道利用率。实验表明其具有较好的公平性和较低的数据碰撞率,有效的增加了网络容量。     

CATV return path characterization for reliable communications

The authors have examined the basic characteristics of hybrid-fiber coax (HFC) return systems to evaluate their ability to support bidirectional communications. The ability to support bidirectional communications on cable plants will allow deployment of two-way video applications as well as telecommunications services over the HFC plant. The results of the studies indicate that ingress in the cable return path is primarily due to broadcast signals which accumulate due to the noise-funneling effect of the cable return. Although this ingress can manifest itself in strong narrowband interferers which will prevent the use of large bandwidth channels, a reduction of node size to nodes on the order of 500 homes or lower will reduce the amount of interference. Filtering, in which a portion of the spectrum is blocked from the subscriber residence may also result in a significant reduction of ingress. Other phenomena on the return path can be dealt with by means of sound communication system design, including forward error correction to deal with impulse noise, and adaptive equalizers to deal with reflections in high data rate designs. TDMA, FDMA, and CDMA can all be utilized on the cable return path, but the capacities which result when less than perfectly synchronized CDMA is utilized are substantially lower than for TDMA and FDMA. A single carrier TDMA approach will be highly susceptible to narrowband interferers, and is unlikely to be successful. For these reasons a TDMA/FDMA or pure FDMA approach with narrow channels is likely to be the most robust multiple access technique for the cable return path     

Reduced‐frame TDMA protocols for wireless sensor networks

Time‐division multiple‐access (TDMA) is a common medium access control paradigm in wireless sensor networks. However, in its traditional form, the TDMA‐based protocols suffer from low channel utilization and high message delay because of a long frame length needed to provide collision‐free transmissions, which is particularly damaging in dense wireless sensor networks. In this paper, we investigate the performance and the energy efficiency of a class of TDMA‐based protocols, called reduced‐frame TDMA, where every TDMA slot is augmented with a short time period dedicated for carrier sense multiple access‐based contention resolution mechanism. Because of their ability to dynamically resolve collisions caused by conflicting slot assignments, the reduced‐frame TDMA protocols can be configured with any frame length, independently of node density. In addition, we present a distributed heuristic slot assignment algorithm that minimizes interslot interference in the presence of limited number of slots per frame. The simulation results indicate that the reduced‐frame TDMA protocols significantly reduce the message delay and increase the maximum throughput without incurring significant penalty in energy efficiency compared with the traditional TDMA scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

Spread SCPC/FDMA,spread TDMA/FDMA and SSMA/FDMA transmission through A non-linear satellite channel with an earth-station off-axis emission constraint

This paper analyses and compares possible access schemes to be used in satellite networks with a large number of small earth-stations. Basically, frequency division (FDMA), time division (TDMA), and spread spectrum multiple access (SSMA) are considered. For TDMA, one single carrier originated in one particular earth-station is transmitted in each sub-band and therefore a single-channel-per-carrier system results (SCPC/FDMA). For TDMA and SSMA, it is assumed that groups of earth-stations using either of these access schemes share the full available band in FDMA. The corresponding systems are thus TDMA/FDMA and SSMA/FDMA. Moreover, for SCPC/FDMA and TDMA/FDMA individual carriers may be spread to the extent that the available bandwidth is always fully occupied. Spectral efficiencies for these three access modes (Spread SCPC/FDMA, Spread TDMA/FDMA and SSMA/FDMA) are computed and compared for transmission through a non-linear satellite channel and optimum operating points for the non-linear amplifier are also determined. Comparisons are also performed for the situation in which transmitting earth-stations are bounded to obey an off-axis emission constraint.     

多跳无线网中基于空分TDMA的时隙分配策略

空分TDMA（STDMA）是基于TDMA的信道接入协议,该技术被应用于实时性要求较高的多跳（multi-hop）无线网络中,并可使多个在地理位置相互独立的移动终端使用相同的时隙来增加网络容量,不同移动终端之间的数据传输通过对终端调度安排来实现。调度算法一般分为基于节点或基于链路的分配方式。对这两种方式对比发现,在一定条件下两者都有不理想的特性。因此,结合两种方式优点提出了一种新颖的分配策略。仿真结果表明：该分配策略在高业务负载情况下能满足链路分配的高吞吐量,也能达到低业务负载下节点分配的低延迟。     

一种高效可靠的无人机自组网多跳TDMA协议

设计无人机自组网媒体接入控制(Medium Access Control,MAC)协议时,需要考虑其控制开销和数据传输的可靠性。鉴于此,结合现有无线自组网多跳时分多址接入(Time Division Multiple Access,TDMA)协议和无人机自组网特点,提出了一种高效可靠的无人机自组网多跳TDMA协议。首先采用高效负载均衡的时隙请求信息上传机制,选择一个负载较小的节点转发节点时隙请求信息;然后根据相互通信的父节点删除重复节点的时隙请求信息,减少相同节点的时隙请求信息转发次数;最后通过实时更新节点时隙请求信息机制,提高节点时隙请求信息传输的可靠性。仿真结果表明,该协议在数据传输成功率、平均时延、控制开销方面优于现有协议,可较好地应用在无人机自组网中。     

分布式TDMA网络的时隙设计技术

时隙分配是分布式TDMA组网的一个基础性工作,直接影响到Adhoc网络的性能。为支持低延迟数据业务,通常选择TDMA组网技术,但常规的固定时隙TDMA网络对时隙的利用率较低。提出了一种基于跳频的固定时隙分配和动态时隙分配相结合的TDMA时隙资源管理技术,有效地解决了TDMA网络的不同类型用户信息传输时隙分配问题。     

TDMA+TDD系统中高速无线数据传输的实现

针对浮空平台搭载的载荷重量、体积、功耗受限的问题,提出了一种时分多址结合时分双工的通信模式。使用该通信模式,网内所有节点均工作于一个频率之上,只需配备一套收发通道,解决了浮空平台载荷受限的问题。在此基础上,通过软硬件设计,实现了该通信系统的信号收发流程、帧协议和参数设置,并构造出一套完整的通信系统。仿真实验和实测结果表明,利用该方案构造出的通信系统较传统的频分多址通信方式在体积、重量、成本等方面均有优势,更适用于浮空平台的远距离、高码率传输。