Distributed traffic adaptive channel allocation

Dynamic channel allocation (DCA) schemes adapt to the time variant demand for channels in cellular mobile telephony systems. In this paper we propose a DCA scheme that smoothly changes the channel allocation by solving the following problem. Given a cell structure, a collection of channels, the frequency reuse distance, an allocation of channels to cells, and the number of active connections per cell, accommodate a new call or a new handover by minimally reconfiguring the established allocation of channels to cells. First, this problem is formulated as 0–1 quadratic programming problem. Next, we present a distributed, heuristic solution to the problem, which is based on the observed behaviour of the optimal algorithm. Finally, we present some simulation results on the performance and the feasibility of the distributed algorithm. © 1997 John Wiley & Sons, Ltd.     

Adaptive channel allocation for wireless PCN

In cellular networks, forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. In order to maintain an acceptable call dropping probability rate, we propose, in this paper, two new guard channel schemes: an adaptive one – New Adaptive Channel Reservation (NACR) – and a dynamic one – Predictive Reservation Policy (PRP). In NACR, for a given period of time, a given number of channels is guarded in each cell for handoff traffic. In PRP, the number of reserved channels depends on the actual number of calls in progress in the neighboring cells. An approximate analytical model of NACR is presented. A Tabu search method has been implemented in order to optimize the Grade of Service. Discrete event simulations of PRP and NACR were run. The effectiveness of the proposed methods is emphasized on a complex configuration.     

Distributed dynamic channel allocation algorithms in microcells under light traffic loading

We consider distributed dynamic channel allocation (DCA) algorithms for wireless cellular networks. Two algorithm extremes are the baseline of our investigation: Theaggressive type algorithms, where channel assignments of ongoing calls may be reconfigured to make room for a new access request; and thetimid one, where reconfigurations are not permitted. While, generally, analyses of DCA algorithms appear very difficult, we show here that a light traffic analysis can be tractable. For that realm, we derive performance expressions showing significant reductions in access blocking probability when an aggressive, rather than the timid, access algorithms is used. The relative efficacy of various algorithms that we present can be analytically probed in this range. Certain aggressive algorithms are observed to attain the best performance possible therein. The advantage over timid is particularly substantial for planar cellular arrays. These results hint that there may be significant channel savings, associated with the type of aggressive algorithms described here, in the important, yet much more difficult to analyze, operating realm where the blocking, but not necessarily the loading, is low; and lead us to devise a family of hybrid DCA algorithms that are both stable and low blocking.     

Distributed fault-tolerant channel allocation for cellular networks

A channel allocation algorithm includes channel acquisition and channel selection algorithms. Most of the previous work concentrates on the channel selection algorithm since early channel acquisition algorithms are centralized and rely on a mobile switching center (MSC) to accomplish channel acquisition. Distributed channel acquisition algorithms have received considerable attention due to their high reliability and scalability. However, in these algorithms, a borrower needs to consult with its interference neighbors in order to borrow a channel. Thus, the borrower fails to borrow channels when it cannot communicate with any interference neighbor. In real-life networks, under heavy traffic load, a cell has a large probability to experience an intermittent network congestion or even a communication link failure. In existing distributed algorithms, since a cell has to consult with a large number of interference neighbors to borrow a channel, the failure rate will be much higher under heavy traffic load. Therefore, previous distributed channel allocation algorithms are not suitable for real-life networks. We first propose a fault-tolerant channel acquisition algorithm which tolerates communication link failures and node (MH or MSS) failures. Then, we present a channel selection algorithm and integrate it into the distributed acquisition algorithm. Detailed simulation experiments are carried out in order to evaluate our proposed methodology. Simulation results show that our algorithm significantly reduces the failure rate under network congestion, communication link failures, and node failures compared to nonfault-tolerant channel allocation algorithms. Moreover, our algorithm has low message overhead compared to known distributed channel allocation algorithms, and outperforms them in terms of failure rate under uniform as well as nonuniform traffic distribution     

Distributed dynamic fault-tolerant channel allocation for cellularnetworks

Efficient allocation of communication channels is critical for the performance of cellular systems. The centralized channel allocation algorithms proposed in literature are neither robust nor scalable. Several of these algorithms are unable to dynamically adjust to spatial and temporal fluctuations in channel demand (load). We present a distributed dynamic channel allocation (DCA) algorithm in which heavily loaded regions acquire a large number of communication channels, while their lightly loaded neighbors get assigned fewer channels. As the spatial distribution of channel demand changes with time, the spatial distribution of allocated channels adjusts accordingly. The algorithm described in this paper requires minimal involvement of the mobile nodes, thus conserving their limited energy supply. The algorithm is proved to be deadlock free, starvation free, and fair. It prevents cochannel interference and can tolerate the failure of mobile as well as static nodes without any significant degradation in service. Simulation experiments demonstrate that the performance of the proposed distributed dynamic algorithm is comparable to, and for some metrics, better than that of efficient centralized dynamic algorithms where the central switch has complete and latest information about channel availability. The major advantages of the proposed algorithm over its dynamic centralized counterparts are its scalability, flexibility, and low computation and communication overheads     

Bandwidth allocation strategies for transporting variable bit ratevideo traffic

Large-scale deployment and successful commercialization of digital video services over computer networks strongly depend on the cost effectiveness of these services. Network bandwidth is one of the major factors that impact the cost of a video service. We survey various approaches to reducing the bandwidth requirement for transporting compressed video traffic over high-speed networks     

A rate‐based overload control method for the radio channel in PCN

Third‐generation wireless digital communication systems, currently being developed, are intended to integrate all the existing wireless systems and cover a wide range of services, including voice, video and multimedia. A difficult problem towards this direction is the efficient use of the limited available bandwidth. Although considerable improvements have been made recently in transmitter and receiver technology, the capacity of the air interface is still considerably smaller compared to other media such as fiber optics. Accordingly, traffic congestion is an important problem, especially for bandwidth demanding applications (e.g., video), leading to poor quality‐of‐service (QoS). This paper presents an overload control method, for TDMA systems, to temporarily reduce the source rate requirements to a sustainable level, in order to avoid a sudden degradation in QoS. The control is activated when the aggregate rate crosses a predefined threshold that identifies congestion. To ensure fairness, the selection of the sources whose rate will be reduced is performed in co‐operation with a priority‐based scheduling technique. The performance of the system under the proposed method is analyzed and system parameter values are optimized. It is shown that the method attains considerable improvement in the loss probability performance. This revised version was published online in June 2006 with corrections to the Cover Date.     

蜂窝通信网络中的分布式无线信道分配方法

文中提出了一种适用于蜂窝通信网的分布式无线信道分配方法。当网络部署环境中出现干扰后,终端用户通过控制信道,发送反馈信息至基站;基站接收到反馈信息后,对可用信道进行扫频,利用广播帧通知受干扰的终端用户可用信道信息;然后终端用户收到基站发送的广播帧后,根据优先级机制,选择新的信道重新建立与基站的通信,当蜂窝通信网中终端用户受外部干扰而信道中断后,该方法可减少终端用户和基站之间信令的开销。     

MPEG-4 video object-based rate allocation with variable temporalrates

In object-based coding, bit allocation is performed at the object level and temporal rates of different objects may vary. The proposed algorithm deals with these two issues when coding multiple video objects (MVOs). The proposed algorithm is able to successfully achieve the target bit rate, effectively code arbitrarily shaped MVOs with different temporal rates, and maintain a stable buffer level     

Distributed power allocation and scheduling for parallel channel wireless networks

In this paper we develop distributed approaches for power allocation and scheduling in wireless access networks. We consider a model where users communicate over a set of parallel multi-access fading channels, as in an orthogonal frequency division multiple access (OFDMA) system. At each time, each user must decide which channels to transmit on and how to allocate its power over these channels. We give distributed power allocation and scheduling policies, where each user’s actions depend only on knowledge of their own channel gains. Assuming a collision model for each channel, we characterize an optimal policy which maximizes the system throughput and also give a simpler sub-optimal policy. Both policies are shown to have the optimal scaling behavior in several asymptotic regimes. Xiangping Qin received the B.S. and M.S. degrees in Electrical Engineering from Tsinghua University,China in 1998 and 2000 respectively, and the Ph.D. degree in Electrical Engineering from Northwestern University in 2005. She is currently a senior engineer at Samsung Information Systems America. In 2005/2006, She was a postdoctoral associate in the Department of Electrical and Computer Engineering at Boston University. In 2004, she was an intern on the technical staff of Intel Cooperate Technology Laboratory, Oregon. Her primary research interests include wireless communication and data networks. She is the recipient of aWalter P. Murphy Fellowship for the 2000/2001 academic year from the ECE Department at Northwestern University. Randall A. Berry received the B.S. degree in Electrical Engineering from the University of Missouri-Rolla in 1993 and the M.S. and Ph.D. degrees in Electrical Engineering and Computer Science from the Massachusetts Institute of Technology in 1996 and 2000, respectively. In September 2000, he joined the faculty of Northwestern University, where he is currently an Associate Professor in the Department of Electrical Engineering and Computer Science. In 1998 he was on the technical staff at MIT Lincoln Laboratory in the Advanced Networks Group, where he worked on optical network protocols. His current research interests include wireless communication, data networks and information theory. Dr. Berry is the recipient of a 2003 NSF CAREER award and the 2001-02 best teacher award from the ECE Department at Northwestern. He is currently serving on the editorial board of IEEE Transactions on Wireless Communications and is a guest editor of an upcoming special issue of IEEE Transactions on Information Theory on “Relaying and Cooperation in Networks.”     

Optimised power allocation for mixed rate traffic in DS-CDMAcellular system

An approach for determining the optimum power allocation for different types of traffic in a CDMA cellular system is presented. The system capacity can be improved significantly by simply employing suitable transmission power for different types of traffic     

Efficient rate allocation,routing and channel assignment in wireless mesh networks supporting dynamic traffic flows

In this paper we address the issue of joint routing, channel re-assignment and rate allocation in multi-radio multi-channel Wireless Mesh Networks (WMNs) with the goal of optimizing the performance of the current set of flows in the WMN. The objective is to balance the instantaneous traffic in the network at the flow level, optimize link-channel assignment and allocate flow rates to achieve proportional fairness given the current traffic and network constraints, including the topology, interference characteristics, number of available channels and radios. Unlike prior work, we do not assume a priori knowledge of traffic, and instead take into account the instantaneous traffic conditions to optimize performance at the flow level, taking both throughput and fairness into account. In this work we analyze the problem and, due to its hardness, propose a fast heuristic algorithm (JRCAR) to solve it. We evaluate this algorithm through numerical experiments, including comparisons against optimal solutions. In addition, we show that JRCAR can be used in a highly responsive system in practical scenarios with time-varying traffic conditions. We implement such a system under the ns-3 simulator, where the simulation results obtained corroborate the behavior observed in the numerical experiments and show that JRCAR is effective in dynamic and practical conditions.     

Optimal channel allocation policies for access control ofcircuit-switched traffic in ISDN environments

The problem of adaptively managing the transmission bandwidth of an integrated network by implemented optimal partitioning policies for the access control of circuit-switched traffic is studied. Precise formulations within an optimization framework of access control problems, both at an isolated multiplexer level and at the overall network level, are developed. For the simple case of a single multiplexer supporting traffic with identical bandwidth requirements, an iterative scheme with guaranteed fast convergence is presented for the determination of optimal channel allocations. For the more general scenario of a multiplexer supporting traffic with nonidentical bandwidth requirements, a methodology is developed to handle the access control problem by a mixed-integer programming formulation. This methodology is further extended to the network-wide access control scenario, and some implementational issues are discussed. A detailed quantitative evaluation of the proposed algorithm is conducted under different loading conditions, and the corresponding performance and efficiency are compared with those of other known procedures     

Source and channel rate allocation for channel codes satisfying theGilbert-Varshamov or Tsfasman-Vladut-Zink bounds

We derive bounds for optimal rate allocation between source and channel coding for linear channel codes that meet the Gilbert-Varshamov or Tsfasman-Vladut-Zink (1984) bounds. Formulas giving the high resolution vector quantizer distortion of these systems are also derived. In addition, we give bounds on how far below the channel capacity the transmission rate should be for a given delay constraint. The bounds obtained depend on the relationship between channel code rate and relative minimum distance guaranteed by the Gilbert-Varshamov bound, and do not require sophisticated decoding beyond the error correction limit. We demonstrate that the end-to-end mean-squared error decays exponentially fast as a function of the overall transmission rate, which need not be the case for certain well-known structured codes such as Hamming codes     

Real time variable bit rate video traffic prediction

Real time variable bit rate (VBR) video traffic prediction plays an important role in dynamic bandwidth allocation schemes by providing an accurate estimation of the instantaneous bandwidth requirement of VBR video traffic and it has been widely used in dynamic bandwidth allocation. A number of prediction algorithms were proposed in the literature and they can be broadly classified into two categories: time domain approaches and wavelet domain approaches. In this paper, we first present a survey of the existing algorithms in the literature. On the basis of the survey, new algorithms are proposed in the time domain and in the wavelet domain, respectively. Simulations using real VBR video traces are conducted which show that the proposed algorithms achieve better performance than those in the literature. Copyright © 2006 John Wiley & Sons, Ltd.     

基于比例速率保证的信道误差OFDMA中继系统资源分配

针对存在有信道估计误差的正交频分多址( OFDMA)中继系统,在考虑用户传输中断概率的同时,提出了满足不同用户最小服务质量( QoS)需求和比例公平性约束条件下的中继选择、子载波分配和功率分配的联合优化问题,建立了以最大化系统总容量为目标的优化模型。在此基础上以速率最大化为目标进行最佳中继选择,并通过动态子载波分配来满足用户的最小QoS需求和比例公平性,最后采用拉格朗日乘子法来得到最优功率分配方案。仿真结果表明,此算法在降低用户中断概率的同时,提高了系统吞吐量并保证了用户速率的比例公平性。     

Online traffic smoothing for delivery of variable bit rate media streams

Traffic smoothing for delivery of online variable bit rate (VBR) media streams is one of the most important problems in designingmultimedia systems. Given an available client buffer, a window size, and a window-sliding size, previous window-based online smoothing methods have tried to reduce the peak bandwidth allocated in each window. However, as bandwidths allocated in different windows are minimized independently, these methods require a large peak bandwidth for transmitting an entire stream. In this paper, a new window-based method is proposed. It introduces two new ideas, the dynamic windowsliding size and the aggressive workahead, for delivery of online VBR media streams. Our aggressive and dynamic window sliding (ADWS) method can automatically decide on the suitable window-sliding sizes for different windows. Thus, the allocated peak bandwidth can be further reduced. By examining various media streams, ADWS is shown to be effective and efficient. Considering the online transmission of the movieStar Wars with a 90-kB client buffer, ADWS yields 13% less in peak bandwidth, compared with the bestknown window-based online smoothing algorthm SLWIN(1). Its computation cost (the window-sliding number) is 75% of that required by SLWIN(1).This work was partially supported by NSC, Taiwan, under grants. NSC88-2213-E-001-011, NSC88-2213-E-001-012, and NSC88-2213-E-001-025. A primitive version of this work appeared in IEEE INFOCOM'99 [7].     

Dynamic channel allocation in interference-limited cellular systemswith uneven traffic distribution

Most recently proposed wireless dynamic channel allocation methods have used carrier-to-interference (C/I) information to increase the system performance. Power control is viewed as essential for interference-limited systems. However, the performance of such systems under an imbalance of load among cells, as may occur often in microcells, is largely unknown. Here, we study a typical interference-limited dynamic channel allocation policy. Calls are accepted if a channel can be assigned that will provide a minimum C/I, and power control and intracell handoffs are used to maintain this level. We focus on the relationship between system performance and the amount of imbalance in load among neighboring cells. Previous studies for systems that do not use C/I information have found that dynamic channel allocation (DCA) outperforms fixed channel allocation (FCA) in all but heavily loaded systems with little load imbalance. We present two principal new results. First, we find that with use of C/I information, the difference in performance between FCA and DCA (in terms of throughput or blocking probability) is increasing with load imbalance. DCA was found to be more effective in congestion control at the cost of a slightly lower call quality. Second, we find that use of power control to maintain a minimum C/I results in two equilibrium average power levels for both DCA and FCA, with DCA using a higher average power than FCA, and that while DCA's power is increasing with load imbalance, FCA's average power is decreasing with load imbalance     

Dynamic bandwidth allocation for multimedia traffic with rate guarantee and fair access in WCDMA systems

Packet scheduling in a WCDMA system poses a new challenge due to its nature of variable bit rates and location-dependent, time-varying channel conditions. In this work, three new downlink scheduling algorithms for a WCDMA base station are proposed to support multimedia transmissions. Using a credit management and a compensation mechanism, our algorithms provide rate guarantee and fair access to mobile terminals. In particular, we propose to allow a user to simultaneously use multiple OVSF codes in a time-sharing manner, which we call a multicode, shared model. Using multiple codes allows us to compensate those users suffering from bad communication quality or even errors. The proposed schemes can tolerate a multistate link condition (compared to the typically assumed two-state, or good-or-bad, link condition) by adjusting the number of OVSF codes and the spreading factor of each code. Simulation results show that the proposed schemes do achieve higher bandwidth utilization while keeping transmission delay low.