Interference Evaluation of Bluetooth and IEEE 802.11b Systems

The emergence of several radio technologies, such as Bluetooth and IEEE 802.11, operating in the 2.4 GHz unlicensed ISM frequency band, may lead to signal interference and result in significant performance degradation when devices are colocated in the same environment. The main goal of this paper is to evaluate the effect of mutual interference on the performance of Bluetooth and IEEE 802.11b systems. We develop a simulation framework for modeling interference based on detailed MAC and PHY models. First, we use a simple simulation scenario to highlight the effects of parameters, such as transmission power, offered load, and traffic type. We then turn to more complex scenarios involving multiple Bluetooth piconets and WLAN devices.     

干扰环境中提高蓝牙系统性能的技术

主要针对蓝牙设备在IEEE802.11无线局域网环境下所受干扰的问题,提出了两种提高蓝牙系统性能的方案。     

Interference Mitigation in Asynchronous Slow Frequency Hopping Bluetooth Networks

In asynchronous slow frequency hopping Bluetooth networks, packet collisions diminish the total link throughput. However, interference mitigation capability can reduce packet losses due to collisions. In this paper, an interference cancelling dual decision feedback (IC-DDF) Bluetooth receiver is proposed and its performance is evaluated for slow fading indoor channels. In addition to the bit error rate (BER) performance, the system level performance is evaluated by using the packet error rate (PER). To integrate the BER performance into the PER performance, a new geometric interpretation of packet error rate is introduced that uses an ensemble average of the received carrier to interference ratio (CIR). Also, a generalized packet collision probability is derived to analyze total link throughput.     

A Fair and Traffic Dependent Scheduling Algorithm for Bluetooth Scatternets

The Bluetooth specification defines the notion of interconnected piconets, called scatternets, but does not define the actual mechanisms and algorithms necessary to set up and maintain them. The operation of a scatternet requires some Bluetooth units to be inter-piconet units (gateways), which need to time-division multiplex their presence among their piconets. This requires a scatternet-scheduling algorithm that can schedule the presence of these units in an efficient manner. In this paper, we propose a distributed scatternet-scheduling scheme that is implemented using the HOLD mode of Bluetooth and adapts to non-uniform and changing traffic. Another attribute of the scheme is that it results in fair allocation of bandwidth to each Bluetooth unit. This scheme provides an integrated solution for both intra- and inter-piconet scheduling, i.e., for polling of slaves and scheduling of gateways.     

LTE小区间干扰抑制技术分析

LTE系统采用更灵活的频率复用策略,任何一个小区都有可能使用所有的频谱资源,因此小区间的干扰不可避免。本文从干扰协调和干扰消除两方面介绍了LTE小区间干扰抑制的最新研究成果,对学术界及3GPP标准提案中的主流算法进行了综合评述。最后,结合LTE标准的演进,分析了LTE系统小区间干扰抑制技术的发展趋势。     

无线局域网系统对蓝牙piconet干扰的理论分析

从理论的角度阐明了无线局域网系统(802.11b)对蓝牙piconet产生干扰的原因及后果。     

基于信道转换的蓝牙微微网之间同频干扰抑制方法

多个蓝牙微微网之间的同频干扰十分严重,该文针对此问题提出一种基于信道转换的同频干扰抑制方法。该方法在蓝牙微微网重传时进行信道转换,以同频不一定会产生干扰为前提,综合考虑了返回分组、跳频保护间隔、3种时隙分组共存等多种情况,使分析更加接近真实情况。对网络性能指标进行大量仿真,由仿真分析可见,该方法有效地降低了蓝牙微微网的分组错误率,提高了微微网的吞吐量,尤其当网络数量在14~57范围内时,微微网吞吐量最大可增加260 kbps。     

Polling Best Effort Traffic in Bluetooth

Bluetooth [1] is a wireless access technology where polling is used to sharebandwidth among the nodes. We have introduced a new poller named PredictiveFair Poller (PFP) in [2, 3]. In this paper we explain the operation of thePredictive Fair Poller and compare it with the conventional Round Robin pollerand the Fair Exhaustive Poller (FEP) [4] for two Best Effort trafficscenarios. We show through simulations that the Predictive Fair Poller is ableto divide bandwidth in a fair and efficient manner.     

Energy-Efficient Operation through Interference Avoidance for Interconnected Bluetooth WPANs

A Wireless Personal Area Network (WPAN) provides wireless networking among proximate devices, usually carried by an individual. Bluetooth is a first instance of the WPAN technology. The basic networking entity in Bluetooth is a piconet. Several piconets (WPANs) can be interconnected into a scatternet, which can be considered as an extendable multi-hop ad hoc networking structure. Since Bluetooth operates in the unlicensed ISM band, each piconet uses pseudorandom frequency hopping. If collocated piconets use the same channel simultaneously, the piconets interfere with each other and the transmitted packets are lost in collisions. This interference is termed self-interference. The piconets that are networked into scatternet exhibit spatial overlapping and naturally produce multi-piconet self-interference. The collisions cause retransmissions and increase the energy spent per data portion, which results in energy-inefficient operation. To tackle this problem, in our previous work we have proposed a self-interference avoidance (SIA) mechanism. However, this basic SIA mechanism is oblivious with respect to the physical topology and does not account for the mitigation of self-interference due to the propagation effects. Furthermore, the basic SIA mechanism relies on the assumption that all piconets are using packets of identical and fixed length. In this paper we will generalize the SIA mechanism to overcome the stated restrictions. We propose the adaptive SIA (A-SIA) algorithm, which adapts the SIA algorithm to the actual interference. The simulation results show that A-SIA largely retains the energy gain offered by the SIA algorithm, while significantly improving the goodput. We also design an instance of the SIA mechanism that operates with variable-length packets, referred as generalized SIA (G-SIA) algorithm. Our simulation results show that the G-SIA algorithm offers good performance in terms of goodput and energy efficiency, but the goodput is degraded if inappropriate segmentation/reassembly policy is used. Petar Popovski received the Dipl.-Ing. in electrical engineering and M.Sc. in communication engineering from the Faculty of Electrical Engineering, Sts. Cyril and Methodius University, Skopje, Macedonia, in 1997 and 2000, respectively and a Ph.D. degree from Aalborg University, Denmark, in 2004. He is currently Assistant Research Professor at the Department of Communication Technology at the Aalborg University. His research interests are focused on wireless ad hoc networks, wireless sensor networks, and high-speed wireless multi-carrier communications. Hiroyuki Yomo received B.S. degree in communication engineering from Department of Communication Engineering, Osaka University, Osaka, Japan, in 1997, and M.S. and Ph.D. degrees in communication engineering from Department of Electronic, Information, and Energy Engineering, Graduate School of Engineering, Osaka University, Osaka Japan, in 1999 and 2002, respectively. From April 2002 to March 2004, he was a Post-doctoral Fellow in Department of Communication Technology, Aalborg University, Denmark. From April 2004 to September 2004, he was working at NEC Corporation, Japan. Since October 2004, he has been an Assistant Research Professor in Center for TeleInfrastructure (CTIF), Aalborg University, Denmark. His research interests include medium access protocols, link-layer techniques, routing protocols, and their interactions in wireless networks. Liljana Gavrilovska received her B.Sc., M.Sc. and Ph.D. from University of Skopje (76), University of Belgrade (85) and University of Skopje (95) respectively. She joined the Faculty of Electrical Engineering, University of Skopje, Republic of Macedonia, where she currently holds positions of Professor at the Institute for Telecommunications, chief of Telecommunications Laboratory and head of CWMC (Center for Wireless and Mobile Communications), working in the area of networking and mobile communications. During 2001–2002 she joined the Centre for PersonKommunikation, Aalborg University, Denmark, where she was holding a position as Associate Research Professor and was involved in several EU (ASAP, PACWOMAN, MAGNET) and national/international projects. She is still working part-time for CTiF, Aalborg University, Denmark. Her major research is concentrated on ad hoc networking, wireless and personal area networks, cross layer optimizations, future mobile systems, traffic analysis and admission techniques. She is a senior member of IEEE and serves as a Chair of the Macedonian Communications Chapter. Ramjee Prasad is a distinguished educator and researcher in the field of wireless information and multimedia communications. During February 1988–May 1999 he has been with the Telecommunications and Traffic-Control Systems Group of Delft University of Technology (DUT), The Netherlands, where he was actively involved in the area of wireless personal and multimedia communications (WPMC). He was head of the Transmission Research Section of International research Centre for Telecommunications Transmission and Radar (IRCTR) and also Founding Program Director of the Centre for Wireless Personal Communications (CWPC). As from June 1999 Ramjee Prasad joined as the Wireless Information Multimedia Communications chair and co-director of Centre for PersonKommunikation at Aalborg University, Denmark. From January 2004 he is Founding Director of the “Centre for Teleinfrastruktur (CTIF)”. He has published over 500 technical papers, and authored and co-edited 15 books about Wireless Multimedia Communications (Artech House). His research interest lies in wireless networks, packet communications, multiple access protocols, adaptive equalisers, spread-spectrum CDMA systems and multimedia communications. Prof. Prasad is the founding chairperson of the European centre of Excellence in Telecommunications known as HERMES Partnership. He is the General Chairman of International Wireless Summit (IWS 2005) to be held in Aalborg, Denmark in September 17–22, 2005. He is a fellow of the IEE, a fellow of IETE, a senior member of IEEE, a member of NERG, and a member of the Danish Engineering Society (IDA). He is advisor to several multinational companies.     

Efficient Scheduling Algorithms for Bluetooth Scatternets

When more than seven devices are connected in a Bluetooth scatternet, bridge devices are used to connect two piconets to the scatternet. To deal with possible data transmissions between different piconets, the bridge device must frequently switch to different masters. Suppose, however, that a bridge is serving a piconet and the master in another piconet is calling it at the same time, the calling master has to wait until the bridge completes the previous service. Such transmission delay may accumulate over a long period and the performance of the whole Bluetooth network will degrade significantly. In this work, two new scheduling protocols, namely the static schedule and the hybrid schedule were implemented in an effort to smooth this kind of transmission delay in Bluetooth networks. In this static schedule the rendezvous points between piconets are coordinated by distributing them by using a graph edge coloring technique. In case of a heavy traffic load, the static schedule is expected to perform well. On the other hand, in case of a light traffic load, the static schedule may cause long and unavoidable routing delays even when there is no transmission between piconets; in this case a naive random round-robin (RR) schedule in each piconet is more appropriate. Thus, in the hybrid schedule, each master initially runs a RR scheme in its piconet. When the traffic load is heavier than a predefined threshold value, it runs the static schedule. Finally, simulations were conducted by using an ns-2 simulator and Bluehoc to demonstrate the efficiency and effectiveness of the proposed scheduling protocols.

Performance of Bluetooth Bridges in Scatternets with Limited Service Scheduling

The performance of two Bluetooth piconets linked through a bridge device is analyzed using the tools of queueing theory. We analyze both possible cases, i.e., when the bridge device is the master in one of the piconets and a slave in the other (MS bridge), as well as when the bridge device is the slave in both of the piconets (SS bridge). Analytical results are derived for the probability distribution of access delay (i.e., the time that a packet has to wait before being serviced) and end-to-end delay, for both intra- and inter-piconet bursty traffic. The scatternet with an SS bridge was found to provide lower end-to-end delay for local traffic as well as lower access delay, while the scatternet with an MS bridge offers lower end-to-end delay for non-local traffic. The scatternet with an SS bridge was also found to be less sensitive to increased probability of non-local traffic and low values of time interval between bridge exchanges, than its counterpart with an MS bridge. All analytical results have been confirmed through simulations.     

家用电器微波炉对WLAN、蓝牙的干扰测试分析

无线通信已经融入到家庭里的每一个角落,成为生活中的一部分.家庭无线Wi-Fi设备、蓝牙设备、无绳电话等,在带给我们生活便捷的同时,也给家庭电磁环境带来了考验.由于ISM频段的开放性,在当今的家庭电磁环境中,越来越多的无线设备工作在该频段,同时还存在其他可能会在ISM频段产生辐射干扰的电子设备,例如：计算机和微波炉.这使得家庭电磁环境变得越来越恶劣,于是不得不对各种电子设备在此恶劣工作环境下的电磁兼容性进行研究和分析.     

多个蓝牙皮克网共存的系统建模与性能仿真

本文根据应用目的和地理分布特征，将配备多个蓝牙皮克网（piconet)的场所分为两类，不仅阐述了已有模型对第一类场所的适用性，而且讨论了第二类场所的特点，提出了新的系统模型。考虑设备间的同频道干扰和邻频道干扰，对两类系统的性能进行了理论分析和数值仿真。讨论了干扰、同步/异步、皮克网间距离、Rayleigh衰落等因素对蓝牙系统性能的影响，总结了两类场所配备多个蓝牙设计时的设计要点。     

无线局域网在蓝牙干扰下的性能分析

IEEE802.11b是目前最主要的无线局域网组网方式,与蓝牙技术分享同一频段。通过建立两者的数据帧相互干扰的概率模型,从物理层与网络层两方面定量地分析了蓝牙设备对无线局域网整体性能的影响,为实际中无线局域网的建立提供了参考。     

Talk and let talk: performance of Bluetooth piconets with synchronous traffic

This paper investigates the possibility of replacing the Bluetooth SCO connection with a QoS-constrained asynchronous link that uses multi-slot ACL packets. We have analyzed the performance of this scheme, dubbed pseudo-SCO, under three different scheduling policies: limited service, exhaustive service, and E-limited service, using the theory of M^[x]/G/1 queues with vacations. It was found that the pseudo-SCO scheme allows asynchronous traffic to experience much lower access and end-to-end delays than with the regular SCO connection, while supporting the bandwidth requirements of SCO traffic. The E-limited service scheduling policy was found to provide better performance than the other two policies, and its performance may be tuned to minimize the end-to-end packet delays under known traffic burstiness; moreover, it is able to guarantee minimum bandwidth for asynchronous traffic. Analytical results were confirmed through simulations.     

蓝牙认证解读

只有经过蓝牙认证测试的产品才是真正的蓝牙产品。通过介绍蓝牙认证相关的蓝牙技术知识,蓝牙认证涉及的测试内容、认证流程以及蓝牙认证费用等内容。希望对蓝牙产品开发和认证测试的人员、以及需要做蓝牙认证的公司有所帮助。     

Scheduling Constraints and Interference Graph Properties for Graph-based Interference Coordination in Cellular OFDMA Networks

The currently emerging 802.16e (WiMAX) and 3GPP Long Term Evolution (LTE) cellular systems are based on Orthogonal Frequency Division Multiple Access (OFDMA). OFDMA suffers from heavy inter-cell interference if neighboring base stations use the same frequency range. One approach to solve this issue is the application of beamforming antennas in combination with interference coordination (IFCO) mechanisms between base stations. In this paper, we trace the problem of IFCO back to the graph coloring problem and investigate the achievable resource utilization of the interference coordinated system. We develop a heuristic that allows the combination of arbitrary scheduling algorithms with the IFCO mechanism. This allows an efficient utilization of the radio system’s frequency resources while still obeying scheduling constraints, such as Quality of Service requirements. Finally, we study the tradeoff between fairness and the total system throughput.

蓝牙技术数据传输综述

比较了蓝牙协议各个版本对其数据传输性能的影响,分类讨论了分组选择算法、重传机制、数据传输的干扰及安全等.针对目前存在的问题,提出了引入扩展戈莱编码和最小频移键控(MSK)调制的数据分组改进方案,提高了系统的抗干扰性和吞吐量,并提出了基于信道转换与MSK调制的同频干扰抑制方法,使皮可网的载干比和吞吐量有明显改善,最后总结并对未来工作提出设想和展望     

Packet Error Rate Distribution Between Random Bluetooth Piconet Pairs

The packet error rate between two piconets depends on the temporal alignment of their packets and the spectral alignment of the intervals from which the frequencies in their hop sequence are chosen. The relationship between two randomly paired piconets is one of over 828 billion possible relationships. We define these relationships and derive an expression for determining the packet error rate for a specific pair of piconets using single-slot packets. We derive the probability mass function for the packet error rate and extend it to provide the possible packet error rates for an arbitrary number of neighboring piconets. We also derive a probability mass function for the goodput of a piconet with a neighboring piconet. The probability mass functions for the packet error rate is bimodal, meaning the expected value of the goodput or packet error rate is not a good choice for piconet performance analysis. Brian S. Peterson is Chief of the Advanced MASINT Research and Requirements Branch at the National Air and Space Intelligence Center, Wright-Patterson AFB, Ohio. He received the B.S.E.E degree in 1991 from the United States Air Force Academy, an M.S. degree in Systems Engineering in 1995 from, and an M.S.E.E. degree from Florida State University in 1998. He received his Ph.D. degree in Electrical Engineering in 2005 from the Air Force Institute of Technology. Dr. Peterson's research interests include computer communication protocols and wireless networking. Dr. Peterson is a member of the IEEE. Rusty O. Baldwin is an Associate Professor of Computer Engineering in the Department of Electrical and Computer Engineering at the Air Force Institute of Technology, Wright-Patterson AFB, Ohio. He received the B.S.E.E degree (with honors) in 1987 from the New Mexico State University and the M.S. degree in Computer Engineering in 1992 from AFIT. He received his Ph.D. degree in Electrical Engineering in 1999 from Virginia Polytechnic Institute and State University. Dr. Baldwin's research interests include computer communication protocols, information warfare, and wireless networking. Dr. Baldwin is a Senior member of the IEEE. Richard A. Raines is an Associate Professor of Electrical Engineering in the Department of Electrical and Computer Engineering at the Air Force Institute of Technology (AFIT), Wright-Patterson AFB, Ohio. He received the B.S.E.E degree (with honors) in 1985 from the Florida State University and the M.S. degree in Computer Engineering in 1987 from AFIT. He received his Ph.D. degree in Electrical Engineering in 1994 from Virginia Polytechnic Institute and State University. Dr. Raines' research interests include computer communication protocols, information security, and wireless networking. Dr. Raines is a Senior member of the IEEE.