基于UWB通信系统的MAC协议研究

目前,超宽带(UWB)技术由于其特有的优点受到越来越多的关注,其中,针对于UWB系统的MAC协议的设计逐渐成为热点。与现有无线通信系统相比,UWB系统占有更宽的频带,具有更高的传输速率,发射功率谱密度非常低,因此,需要设计符合该系统特点,满足该系统节能、高吞吐量以及低时延等要求的MAC协议。文章通过对现有用于UWB通信系统的MAC协议的综合分析和比较,提出对UWB-MAC协议设计的要求。     

基于光纤光栅的超宽带信号产生与传输

针对现有方法功率利用率低与调制实现困难的问题,采用基于光纤光栅（FBG）的超宽带（UWB）调制信号产生方法,建立了UWB信号产生系统。不仅可以实现UWB信号的调制,而且提高了产生信号的信噪比。实现了二进制相位调制（BPM）、脉冲幅度调制（PAM）和脉冲位置调制（PPM）等UWB信号产生。分析了光纤传输对产生信号的影响,...     

Medium access control in ultra-wideband wireless networks

Ultra-wideband (UWB) transmission is an emerging wireless communication technology with unique potential merits such as high-rate, low-transmission power, immunity to multipath propagation, and capability in precise positioning. It has received significant interests for future wireless communications from both academia and industry. In UWB wireless networks, medium access control (MAC) is essential to coordinate the channel access among competing devices. The unique UWB characteristics not only pose significant challenges but also offer great opportunities in efficient UWB MAC design. This paper presents a comprehensive overview of UWB MAC development on four important aspects: multiple access, overhead reduction, resource allocation, and quality of service (QoS) provisioning, and identifies some future research issues.     

Energy consumption of the IEEE Std 802.15.3 MAC protocol in communication link set-up over UWB radio technology

This paper examines the overhead associated with the IEEE Std 802.15.3 medium access control (MAC) protocol when used in conjunction with Ultra Wide-Band (UWB) radio technology. Particular features of the protocol examined include establishing, modifying and terminating data streams. The main focus of the paper is to investigate the overhead introduced in terms of energy consumption to manage the communication links. One of the main UWB technology candidates, Impulse-Radio (IR-UWB), utilizes very short time domain pulses which are low power and difficult to detect. This raises the question of how to design an efficient MAC protocol to harness the potential of the physical layer (PHY). For high data rate WPAN applications, the IEEE Std 802.15.3 protocol has been proposed as a suitable MAC. In the simulations the data source rate and the number of devices in the network are varied and the considerable overhead produced by command frames is observed.     

Scheduling and power control for MAC layer design in multihop IR‐UWB networks

Recently, a number of researchers have proposed media access control (MAC) designs for ultra‐wideband (UWB) networks. Among them, designs based on scheduling and power control seem to be of great promise, particularly for quality‐of‐service (QoS) traffic. We investigate the efficiencies of many different choices for scheduling and power allocation for QoS traffic in a multihop impulse radio (IR)‐UWB network, with the objective of achieving both high spectral efficiency and low transmission power. Specifically, we compare different scheduling schemes employing a protocol interference‐based contention graph as well as a physical interference‐based contention graph. We propose a relative distance to determine adjacency in the protocol interference‐based contention graph. Using our improved protocol interference model with graph‐based scheduling, we obtained better performance than the physical interference‐based approach employing link‐by‐link scheduling. Copyright © 2009 John Wiley & Sons, Ltd.     

Improved Delay‐Locked Loop in a UWB Impulse Radio Time‐Hopping Spread‐Spectrum System

As ultra‐wideband impulse radio (UWB‐IR) uses short‐duration impulse signals of nanoseconds, even a small number of timing errors can cause a detrimental effect on system performance. A delay‐locked loop (DLL) is proposed to synchronize and reduce timing errors. The design of the DLL is vital for UWB systems. In this paper, an improved DLL is introduced to a UWB‐IR time‐hopping spread‐spectrum system. Instead of using only two central correlator branches as in a conventional DLL, the proposed system uses two additional correlator branches with different delay parameters and different weight parameters. The performance of the proposed schemes with the optimal parameters is compared with that of traditional schemes through simulation: the proposed four‐branch DLLs achieves less tracking jitter or a longer mean time to lose lock (MTLL) than the conventional two‐branch DLLs if proper parameters are chosen.     

Energy efficient TDMA-based MAC protocol associated with GAF for wireless sensor networks

The design of media access control (MAC) protocol for wireless sensor networks (WSNs) with the idea of cross layer attracts more and more attention. People can improve the MAC protocol by obtaining certain information regarding the network layer and physical layer. This article synthesizes and optimizes certain cross-layer protocols which have existed. On the basis of the routing, topology information in the network layer, and transmission power information in the physical layer, the time slot assignment algorithm has been improved in the MAC layer. By using geographical adaptive fidelity algorithm (GAF) to divide the grids, controlling of transmission power and scheduling the work/sleep duty cycle for sensor nodes, a new MAC protocol has been proposed to decrease energy consumption and enlarge the lifetime of WSNs. Simulation results show that the MAC protocol functions well.     

Power controlled channel allocation for multiuser multiband UWB systems

Emerging ultra-wideband (UWB) technology offers a great potential for the design of high-speed short-range communications. However, in order for a UWB device to coexist with other devices, the transmitted power level of UWB is strictly limited by the FCC spectral mask. Such limitation poses a significant design challenge to any UWB system. An efficient management of the limited power is thus a key feature to fully exploit the advantages of UWB. In this paper, a cross layer multiuser multiband UWB scheme is proposed to obtain the optimal subband and power allocation strategy. Optimization criteria involve minimization of power consumption under the constraints on the packet error rate, the data rate, and the FCC limit. To ensure the system feasibility in variable channel conditions, an algorithm to jointly manage the rate assignment of UWB devices, subband allocation, and power control is proposed. A computationally inexpensive suboptimal approach is also developed to reduce the complexity of the problem, which is found to be NP hard. Simulation results under UWB channel model specified in the IEEE 802.15.3a standard show that the proposed algorithm achieves comparable performances to those of the complex optimal full search approach, and it can save up to 61% of transmit power compared to the current multiband scheme in the standard proposal. Moreover, the proposed algorithm can obtain the feasible solutions adaptively when the initial system is not feasible for the rate requirements of the users     

Radio resource sharing for ad hoc networking with UWB

Ultra-wideband (UWB) radio is becoming a promising field for new generation's digital communication systems. This technique, based mainly on the impulse radio paradigm, offers great flexibility and shows enormous potential in view of a future broadband wireless access. We present the main principles to design a multiaccess scheme based on UWB. The potential of UWB is exploited within a distributed ad hoc wireless system, where we describe the principles for the definition of a medium-access control (MAC) for mobile computing applications and we analyze the main performance results derived from simulations. A general framework for radio resource sharing is outlined for classes of traffic requiring both elastic-dynamic and guaranteed-reserved bandwidth. Then, we discuss the issue of supporting the proposed radio resource sharing scheme by means of a distributed MAC protocol.     

An investigation of Bluetooth mergence with Ultra Wideband

This article investigates the viability of a merger between Bluetooth and Ultra Wideband by developing and implementing a Bluetooth over Ultra Wideband data channeling system with an emphasis on the design of an economically feasible system and the viability of the proposed merger points. The designed system is then applied to transfer Bluetooth data over a compliant UWB Medium Access Control (MAC) and Physical (PHY) layer radio channel to prove its functioning and unveil the advantages UWB may provide to Bluetooth with regards to speed and distance.     

小型平面超宽带天线的研究进展

对小型平面超宽带(UWB)天线的研究现状进行了分析总结.首先介绍超宽带无线通信的技术背景,描述了超宽带天线的几种常见定义.然后分别对小型超宽带印刷单极子天线的设计、小型超宽带缝隙天线的设计、具有陷波功能的小型超宽带天线的设计进行了详细的评论,并讨论了超宽带天线的性能评价方法.最后展望了小型平面超宽带天线的未来研究方向.     

Parallel relay‐assisted three‐phase MIMO space division multiple access transmission for multi‐hop throughput improvement

Multi‐hop communications equipped with parallel relay nodes is an emerging network scenario visible in environments with high node density. Conventional interference‐free medium access control (MAC) has little capability in utilizing such parallel relays because it essentially prohibits the existence of co‐channel interference and limits the feasibility of concurrent communications. This paper aims at presenting a cooperative multi‐input multi‐output (MIMO) space division multiple access (SDMA) design that uses each hop's parallel relay nodes to improve multi‐hop throughput performance. Specifically, we use MIMO and SDMA to enable concurrent transmissions (from multiple Tx nodes to single/multiple Rx nodes) and suppress simultaneous links' co‐channel interference. As a joint physical layer (MAC/PHY) solution, our design has multiple MAC modules including load balancing that uniformly splits traffic packets at parallel relay nodes and multi‐hop scheduling taking co‐channel interference into consideration. Meanwhile, our PHY layer modules include distributive channel sounding that exchanges channel information in a decentralized manner and link adaptation module estimating instantaneous link rate per time frame. Simulation results validate that compared with interference‐free MAC or existing Mitigating Interference using Multiple Antennas (MIMA‐MAC), our proposed design can improve end‐to‐end throughput by around 30% to 50%. In addition, we further discuss its application on extended multi‐hop topology. Copyright © 2012 John Wiley & Sons, Ltd.     

Location‐aided medium access control for low data rate UWB wireless sensor networks

This paper presents a distributed medium access control (MAC) protocol for low data rate ultra‐wideband (UWB) wireless sensor networks (WSNs), named LA‐MAC. Current MAC proposal is closely coupled to the IEEE 802.15.4a physical layer and it is based on its Impulse‐Radio (IR) paradigm. LA‐MAC protocol amplifies its admission control mechanism with location‐awareness, by exploiting the ranging capability of the UWB signals. The above property leads to accurate interference predictions and blocking assessments that each node in the network can perform locally, limiting at the same time the actions needed to be performed towards the admission phase. LA‐MAC is evaluated through extensive simulations, showing a significant improvement in many critical parameters, such as throughput, admission ratio, energy consumption, and delay, under different traffic load conditions. Copyright © 2010 John Wiley & Sons, Ltd.     

无线传感器网络中数据链路层和网络层设计

作为无线通信网络的一个新的研究热点,无线传感器网络正以其独有的特点和全新的应用而得到人们的广泛关注.本文简要介绍无线传感器网络的体系结构、节点构成和协议层次.分类阐述了几种典型的数据链路层和网络层的设计方案和设计思想.数据链路层中MAC协议可分为两大类:基于竞争的MAC协议和基于预约的MAC协议;网络层的路由算法也分为两大类:平面路由协议和分级路由协议.最后提出一些研究构想.     

陷波特性平面超宽带天线的研究进展

对陷波特性超宽带(UWB)天线的研究现状进行了分析总结.介绍了陷波特性超宽带天线的技术背景,分别对近年来陷波功能超宽带天线的设计进行了详细的评论,最后展望了陷波特性超宽带天线的未来发展方向.     

Performance Analysis for a New Medium Access Control Protocol in Wireless LANs

One fundamental issue in high-speed wireless local area networks (LANs) is to develop efficient medium access control (MAC) protocols. In this paper, we focus on the performance improvement in both MAC layer and transport layer by using a novel medium access control protocol for high-speed wireless LANs deploying carrier sense multiple access/collision avoidance (CSMA/CA). We first present a recently proposed distributed contention-based MAC protocol utilizing a Fast Collision Resolution (FCR) algorithm and show that the proposed FCR algorithm provides high throughput and low latency while improving the fairness performance. The performance of the FCR algorithm is compared with that of the IEEE 802.11 MAC algorithm via extensive simulation studies on both MAC layer and transport layer. The results show that the FCR algorithm achieves a significantly higher efficiency than the IEEE 802.11 MAC and can significantly improve transport layer performance.     

Medium access control protocols for wireless mobile ad hoc networks: issues and approaches

In this article, a comprehensive survey of the medium access control (MAC) approaches for wireless mobile ad hoc networks is presented. The complexity in MAC design for wireless ad hoc networks arises due to node mobility, radio link vulnerability and the lack of central coordination. A series of studies on MAC design has been conducted in the literature to improve medium access performance in different aspects as identified by the different performance metrics. Tradeoffs among the different performance metrics (such as between throughput and fairness) dictate the design of a suitable MAC protocol. We compare the different proposed MAC approaches, identify their problems and discuss the possible remedies. The interactions among the MAC and the higher layer protocols such as routing and transport layer protocols are discussed and some interesting research issues are also identified. Copyright © 2003 John Wiley & Sons, Ltd.     

短距离低功率无线通信接入系统

短距离低功率无线通信接入技术主要集中在物理层和媒体访问控制（MAC）层,包括蓝牙、超宽带（UWB）和Wi-Fi等。蓝牙是链接近距离设备的电缆数据传送的辅助技术;UWB作为窄脉冲无线电技术链接众多电子设备,提供宽带无线接入的灵活性和移动性;Wi-Fi给快速接入设备和WLAN内移动设备提供无线链接,用于较长距离链接,支持一定功率的移动终端接入。短距离低功率无线通信接入系统的标准化进程非常快,辅助标准多,但目前仍以蓝牙和Wi-Fi为主。     

IEEE 802.11 medium access control enhancements based on simultaneous multiple‐input multiple‐output bandwidth sharing

The demand for higher data rate has spurred the adoption of multiple‐input multiple‐output (MIMO) transmission techniques in IEEE 802.11 products. MIMO techniques provide an additional spatial dimension that can significantly increase the channel capacity. A number of multiuser MIMO system have been proposed, where the multiple antenna at the physical layer are employed for multiuser access, allowing multiple users to share the same bandwidth. As these MIMO physical layer technologies further evolve, the usable bandwidth per application increases; hence, the average service time per application decreases. However, in the IEEE 802.11 distributed coordination function‐based systems, a considerable amount of bandwidth is wasted during the medium access and coordination process. Therefore, as the usable bandwidth is enhanced using MIMO technology, the bandwidth wastage of medium access and coordination becomes a significant performance bottleneck. Hence, there is a fundamental need for bandwidth sharing schemes at the medium access control (MAC) layer where multiple connections can concurrently use the increased bandwidth provided by the physical layer MIMO technologies. In this paper, we propose the MIMO‐aware rate splitting (MRS) MAC protocol and examine its behavior under different scenarios. MRS is a distributed MAC protocol where nodes locally cooperate with one another to share bandwidth via splitting the spatial channels of MIMO systems. Simulation results of MRS protocol are obtained and compared with those of IEEE 802.11n protocol. We show that our proposed MRS scheme can significantly outperform the IEEE 802.11n in medium access delay and throughput. Copyright © 2012 John Wiley & Sons, Ltd.     

基于粒子群算法的超宽带脉冲波形设计

首先分析了在超宽带系统中高斯脉冲成形因子和微分阶数对其能量谱密度的影响,并在此基础上,为了提高高斯脉冲波形的频谱利用率,采用高斯导函数线性组合来产生脉冲波形,提出并分析了一种基于粒子群（PSO）优化算法的超宽带无线脉冲波形优化设计方法,仿真表明该方法产生的高斯导函数线性组合脉冲能够很好地满足FCC的频谱掩模限制。