灯光照明系统对扩声系统的干扰

分析了可控硅调光器对电网和扩声系统的严重干扰,从理论上指出了市售低质的荧光灯镇流器同样会对扩声系统产生不可忽视的干扰;并提出了控制干扰的一系列有效措施,同时介绍了新一代几乎无干扰的IGBT正弦波调光技术。     

Capacity of Interference Channels With Partial Transmitter Cooperation

Capacity regions are established for several two-sender, two-receiver channels with partial transmitter cooperation. First, the capacity regions are determined for compound multiple-access channels (MACs) with common information and compound MACs with conferencing. Next, two interference channel models are considered: an interference channel with common information (ICCI) and an interference channel with unidirectional cooperation (ICUC) in which the message sent by one of the encoders is known to the other encoder. The capacity regions of both of these channels are determined when there is strong interference, i.e., the interference is such that both receivers can decode all messages with no rate penalty. The resulting capacity regions coincide with the capacity region of the compound MAC with common information.     

Competition Versus Cooperation on the MISO Interference Channel

We consider the problem of coordinating two competing multiple-antenna wireless systems (operators) that operate in the same spectral band. We formulate a rate region which is achievable by scalar coding followed by power allocation and beamforming. We show that all interesting points on the Pareto boundary correspond to transmit strategies where both systems use the maximum available power. We then argue that there is a fundamental need for base station cooperation when performing spectrum sharing with multiple transmit antennas. More precisely, we show that if the systems do not cooperate, there is a unique Nash equilibrium which is inefficient in the sense that the achievable rate is bounded by a constant, regardless of the available transmit power. An extension of this result to the case where the receivers use successive interference cancellation (SIC) is also provided. Next we model the problem of agreeing on beamforming vectors as a non-transferable utility (NTU) cooperative gametheoretic problem, with the two operators as players. Specifically we compute numerically the Nash bargaining solution, which is a likely resolution of the resource conflict assuming that the players are rational. Numerical experiments indicate that selfish but cooperating operators may achieve a performance which is close to the maximum-sum-rate bound.     

Interference Mitigation and Joint Decoding for Uplink LDPC-Coded Relay Cooperation

This paper proposes an efficient inter- ference mitigation and joint decoding scheme for uplink LDPC-coded relay cooperation over a Rayleigh fading channel, where a concatenation of Minimum-mean-squared error linear detectors （MMSE） and BP-based joint itera- tire decoding based on the introduced treble-layer Tanner graph are effectively designed to filter and decode the cor- rupted received sequence at a base station. It is demon- strated by theoretical analysis and numerical simulations that the proposed design can well combine the gains from coding and diversity, which consequently leads to a sig- nificant performance improvement over the conventional cooperation system under the same conditions.     

HRPD系统中基站协作式迭代并行小区间干扰消除技术

高速分组数据(HRPD)技术能够很好地支持移动通信网络中各种类型数据分组应用,采用干扰消除技术能够有效提高系统的容量和对各用户信号正确接收.基于基站协调器的协作式迭代并行小区间干扰消除算法利用基站协调器监视相邻小区的强干扰用户,并且通过信令传递强干扰用户的特征信息,利用基站协调器的协作采实现迭代式的并行小区间干扰消除.仿真结果表明,该算法可以有效的消除邻近小区对本小区的干扰,与不使用小区间千扰消除技术相比较,其性能有所提高.     

大尺度信干比共享下的基站协作干扰协调

在基于正交频分多址接入(OFDMA)技术的蜂窝移动小区中,小区间的干扰是影响系统性能的主要因素。多点协调(CoMP)技术被视为能够协调小区间干扰的主要手段。在下行多点协作传输系统中,小区基站采用三向天线来对小区划分扇区,从而消除了相邻小区边缘处的干扰。各扇区分别计算扇区内用户的大尺度信干比(SIR),小区之间通过共享大尺度信干比信息,对各自服务的用户按照一定的规则进行匹配,对小区中心用户的SIR和边缘用户的SIR进行了折中,从而有效解决小区边缘用户由于小区间干扰带来的低信干噪比(SINR)问题。仿真结果表明,本文提出的用户匹配算法以较小的反馈开销,较大的提高了小区边缘用户的信干噪比和系统吞吐量。      

A Non-Orthogonal Selection Cooperation Protocol with Interference in Multi-Source Cooperative Networks

This work proposes a non-orthogonal selection cooperation scheme with interference for multi-source and single destination cooperative networks. In our model, the source nodes can cooperate for one another, i.e., each source node plays the dual role of a source and a relay, thus there is no need for relays. In addition, the source nodes can be continuously transmitted and without dedicated timeslots for cooperative transmissions, which can save system resources and improve spectral efficiency. However, by this way, it will introduce interference with the non-orthogonal transmission mechanism. To overcome this problem, we use general reception scheme in source nodes and successive interference cancellation technology in the destination node, which can reduce the effect of interference effectively. For interference-limited networks, we also derive the theoretical upper bound and lower bound of outage probability of our method. Through the outage probability analysis and comparison, the results show that the spectral efficiency is improved while the system still keeps acceptable transmission reliability.

     

Interference from mobile satellite systems through terrain scattering

The emerging generation of personal communications satellites, built to communicate with handheld telephone units, will generate power flux on earth that is orders of magnitude higher than that of the present satellite service, and its potential interference with terrestrial-based systems is of concern. It is proposed here that the flux scattered from the ground surface into the antenna main beam and near sidelobes may cause higher interference than direct coupling into the antenna. This mechanism, previously observed in terrestrial systems, may not be mitigated by adaptive nulling techniques, and is less angle-dependent. A simple model is developed, to be used as a computational tool for assessing the interference and its functional dependence on governing parameters. In the absence of proper terrain scattering models, examples are evaluated by borrowing results from interference observed in terrestrial microwave links, which indicate the possible severity of the effect.     

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.     

Interference Suppression and Receiving Performance Improvement for Local Cooperation with Channel Estimation Error

In the next-generation wireless communication systems, the local cooperation between different units may be deployed to satisfy communication requirements. In this case, the interference suppression between different units and the receiving performance improvement for each single unit should be considered. Multiple schemes have been utilized to solve these problems. However, these schemes ordinarily require sufficiently accurate information of channel, if this accuracy can not be maintained (e.g., channel estimation error can not be ignored), these schemes may not obtain the satisfactory performances. To overcome this disadvantage, in this paper, a novel scheme is proposed. The proposed scheme has several characteristics: (i) a low-complexity extra estimation is implemented to acquire more information of channel estimation error; (ii) with the help of channel estimation error information, each unit can separately execute a two-step process for interference suppression and receiving performance improvement; (iii) no exorbitant information interaction and high-overhead algorithm are needed between multiple units. Through characteristic analysis and numerical results, it is found the proposed scheme can achieve the satisfactory effect in the locally cooperative network.

     

厂校结合 促进研发

中国的电子电路迈向世界强国之列还有很长很长的路……其中拥有自主知识产权的研发就是一项重要内容。我们中国的电子电路企业,尤其是国有、民营和股份制企业,目前还是处于发展阶段,从规模、效益、资金运作上与国际上的先进企业相比还有不少差距,企业自己开展技术、研发条件大多还不够成熟。另一方面,中国的大专院校有很多的专家、学者还有许多的“海归派”,他们有知识、有抱负,他们希望为我们祖国的科技做出更多的、更大的贡献,但他们缺少行业的信息。我们中国的电子电路行业需要许多具有自主知识产权的科技项目,怎么实现?从国外的经验告诉…     

Interference cancellation enhancement through generalized widely linear equalization in QAM systems

In this paper, we introduce a generalized widely linear (WL) equalizer for quadrature amplitude modulation (QAM) systems with single/multiple antennas. In our proposed implementation, the WL receiver first separates the in-phase (I) and quadrature (Q) parts of the complex-valued baseband received signal and jointly filters the two branches for signal detection. Infinite length WL minimum mean-square error (WL-MMSE) linear, and WL decision-feedback-equalizer (WL-DFE) settings are derived and performance is analyzed in co-channel interference limited channels. It is shown that, in frequency selective Rayleigh fading channels, the interference cancellation (IC) gain depends mainly on the rank (r) of the interference correlation matrix (ICM) which is defined as the covariance of the vector-valued signal which consists of the real and imaginary parts of the noise-plus-interference signal collected at multiple antenna branches. Assuming that the DFE feedback path is error free, we show that a WL QAM receiver with N antennas exhibits full IC capability (that is complete interference removal) when the ICM is rank deficient i.e., when: r ≪ 2N. This condition implies that a WL-DFE receiver can reject any combination of M1 pulse-amplitude-modulation (PAM) and M2 QAM interferers satisfying the constraint: M1 + 2M2 ≪ 2N. Simulation results show that, in the presence of PAM-type interference, the gain of WL-DFE is reduced by decision feedback errors while the IC benefit of WL-MMSE is limited by the noise enhancement problem. Nevertheless, the proposed receivers are shown to be useful in cellular systems that employ a combination of PAM and QAM schemes.     

Managing Femto to Macro Interference without X2 Interface Support through POMDP

We present a self-organized downlink power control for interference management when Home eNodeBs (HeNBs) work in co-channel operation with the macrocell system. The main novelty with regards to previous works is that we provide a completely autonomous framework, considering 3GPP release?11 hypothesis of non availability of X2 interface between evolved NodeBs (eNBs) and HeNBs. In this situation, the HeNB has to make autonomous decisions without receiving any feedback from the macro network. We model the HeNBs as a multiagent system where each node is an independent agent able to learn through Reinforcement Learning (RL) techniques a downlink power allocation policy for different interference situations. To deal with the lack of information in the scenario, we rely on the theory of Partially Observable Markov Decision Process (POMDP). POMDP works on the basis of a set of beliefs that the HeNB builds considering the impact it causes to the macrocell system. To gather this system performance information, we propose that HeNBs use spatial interpolation techniques, such as ordinary Kriging. Results show that the proposed approach allows HeNBs to autonomously learn a power allocation policy to coexist with the macro network, in a 3GPP compliant fashion, and without introducing overhead signaling in the system.     

Interference mitigation in wireless mesh networks through radio co-location aware conflict graphs

Wireless Networks - Wireless Mesh Networks (WMNs) have evolved into a wireless communication technology of immense interest. But technological advancements in WMNs have inadvertently spawned a...     

Capacity Enhancement of Uni-directional In-band Full-Duplex Cellular Networks through Co-channel Interference Cancellation

As implementation of the in-band full duplex (IFD) transceiver becomes feasible, research interest is growing with respect to using IFD communication with cellular networks. However, the cellular network in which the IFD communication is applied inevitably suffers from an increase of the co-channel interference (CCI) due to IFD simultaneous transmission and reception. In this paper, we analyze the performance of a cellular network based on uni-directional IFD (UD-IFD) communication, wherein an IFD base station simultaneously supports downlink and uplink transmissions of half-duplex (HD) users. In addition, a multi-pair CCI cancellation (MP-CCIC) method combining CCIC and user pairing is proposed to improve the performance of the UD-IFD network. Simulation results showed that, compared to a conventional HD cellular network without using CCIC, capacity gain was not obtained in the UD-IFD cellular network. On the other hand, when applying the proposed MP-CCIC, the capacity of the UD-IFD cellular network greatly improved compared to that of an HD cellular network.     

State Amplification

We consider the problem of transmitting data at rate over a state-dependent channel with state information available at the sender and at the same time conveying the information about the channel state itself to the receiver. The amount of state information that can be learned at the receiver is captured by the mutual information between the state sequence and the channel output . The optimal tradeoff is characterized between the information transmission rate and the state uncertainty reduction rate , when the state information is either causally or noncausally available at the sender. In particular, when state transmission is the only goal, the maximum uncertainty reduction rate is given by . This result is closely related and in a sense dual to a recent study by Merhav and Shamai, which solves the problem of masking the state information from the receiver rather than conveying it.     

Amplification effects of the send rate of TCP connection through an optical burst switching network

This paper investigates support for TCP RENO flows in an Optical Burst Switching (OBS) network. In particular we evaluate the TCP send-rate, i.e., the amount of data sent per time unit taking into account the burst assembly mechanism at the edge nodes of the OBS network and burst loss events inside the network. The analysis demonstrates an interesting phenomenon, that we call correlation benefit. This phenomenon is introduced by the aggregation mechanism and can give rise, in some conditions, to a significant increase in the TCP send-rate. These results are obtained by means of an analytical model, based on a Markovian approach, and have been validated via an intensive simulation campaign.     

从与互联网音乐的合作,谈运营商与OTT企业的鱼水关系

移动互联网时代的竞争是生态环境的竞争,运营商需要开放并积极引入互补者。文章以中国联通与音乐类互联网公司的合作模式为例,提出要积极跟外部合作共赢,谋求共同做大市场蛋糕。同时,体现出联通3G网络领先、业务领先、服务领先的的差异化竞争优势,助力增强企业的市场竞争力。     

Interference Avoidance through Pilot‐Based Spectrum Sensing Algorithm in Overlaid Femtocell Networks

Co‐channel interference between macro–femtocell networks is an unresolved problem, due to the frequency reuse phenomenon. To mitigate such interference, a secondary femtocell must acquire channel‐state knowledge about a co‐channel macrocell user and accordingly condition the maximum transmit power of femtocell user. This paper proposes a pilot‐based spectrum sensing (PSS) algorithm for overlaid femtocell networks to sense the presence of a macrocell user over a channel of interest. The PSS algorithm senses the pilot tones in the received signal through the power level and the correlation metric comparisons between the received signal and the local reference pilots. On ensuring the existence of a co‐channel macrocell user, the maximum transmit power of the corresponding femtocell user is optimized so as to avoid interference. Time and frequency offsets are carefully handled in our proposal. Simulation results show that the PSS algorithm outperforms existing sensing techniques, even at poor received signal quality. It requires less sensing time and provides better detection probability over existing techniques.