Integrated predictive power control and dynamic channel assignment in mobile radio systems

It is known that dynamic allocation of channels and power in a frequency/time-division multiple access system can improve performance and achieve higher capacity. Various algorithms have been separately proposed for dynamic channel assignment (DCA) and power control. Moreover, integrated dynamic channel and power allocation (DCPA) algorithms have already been proposed based on simple power control algorithms. In this paper, we propose a DCPA scheme based on a novel predictive power control algorithm. The minimum interference DCA algorithm is employed, while simple Kalman filters are designed to provide the predicted measurements of both the channel gains and the interference levels, which are then used to update the power levels. Local and global stability of the network are analyzed and extensive computer simulations are carried out to show the improvement in performance, under the dynamics of user arrivals and departures and user mobility. It is shown that call droppings and call blockings are decreased while, on average, fewer channel reassignments per call are required.     

A compact dynamic channel assignment scheme based on Hopfield networks for cellular radio systems

In this paper, a new channel assignment strategy named compact dynamic channel assignment (CDCA) is proposed. The CDCA differs from other strategies by consistently keeping the system in the utmost optimal state, and thus the scheme allows to determine a call succeeding or failing by local information instead of that of the whole network. It employs Hopfield neural networks for optimization which avoids the complicated assessment of channel compactness and guarantees optimum solutions for every assignment. A scheme based on Hopfield neural network is considered before; however, unlike others, in this algorithm an energy function is derived in such a way that for a neuron, the more a channel is currently being allocated in other cells, the more excitation the neuron will acquire, so as to guarantee each cluster using channels as few as possible. Performance measures in terms of the blocking probability, convergence rate and convergence time are obtained to assess the viability of the proposed scheme. Results presented show that the approach significantly reduces stringent requirements of searching space and convergence time. The algorithm is simple and straightforward, hence the efficient algorithm makes the real‐time implementation of channel assignment based on neural network feasibility. Copyright © 2008 John Wiley & Sons, Ltd.     

Neural network-based dynamic channel assignment for cellular mobilecommunication systems

Conventional dynamic channel assignment schemes are both time-consuming and algorithmically complex. An alternative approach, based on cascaded multilayered feedforward neural networks, is proposed and examined on two cellular systems with different configurations. Simulation results showed that the blocking performance of our multistage neural network approach can match that of an example conventional scheme with less complexity and higher computational efficiency. The example scheme considered here is the ordered channel search, which can achieve a reasonably high spectral efficiency as compared to that of an ideal dynamic channel allocation algorithm. We conclude that our neural network approach is well-suited to the dynamic channel allocation problem of future cellular or microcellular systems with decentralized control     

Capacity allocation and channel assignment in cellular radio systems using reuse partitioning

Reuse partitioning is a technique for providing more efficient spectrum reuse in cellular radio systems. A cell in such a system is divided into concentric zones, each associated with an overlaid cell plan. For these schemes an optimum channel assignment strategy is proposed. Numeric examples show capacity improvements of about 50% compared to conventional systems.<>     

Prioritized channel assignment in a cellular radio network

Dimensioning procedures for prioritized channel assignment in a cellular radio network are considered. Under the cutoff priority discipline, the prioritized channel assignment procedures for a single cell and multicell system are formulated as nonlinear discrete capacity allocation problems. Exact incremental algorithms which efficiently solve the proposed problems are devised. They are based on the properties of the blocking probabilities of new calls and handoff calls. Given the number of available frequency channels together with the arrival rates and the grade of service (GOS) for both types of calls in each cell, algorithm SP1 generates an optimal channel assignment which ensures priority for handoff calls. Given the arrival rates and distinct GOSs for new and handoff calls, algorithm SP2 finds the minimum number of channels required in each cell. Algorithm MP extends algorithm SP1 to a multicell system and provides the prioritized channel assignment for all calls in the system. The algorithms are very fast and are appropriate for the fair allocation of frequency channels among cells     

蜂窝移动通信中一种分级紧致的动态信道分配方案

本文提出一种分级紧致的动态信道分配（CCDCA）方案。文中首先根据信道使用情况与业务量的关系，将小区分成“冷态”和“热态”，并给出了相应的阈值，然后在对“热态”的处理过程中利用“冷态”的先验信息，对不同状态的小区给出了不同的紧致措施。该方案还能保证小区间有较小的服务偏差，提高了整个系统的服务质量。文中还根据冷、热态的特点构造了一个二维马尔科夫链模型，计算出了模型的主要参数；其思想可用于分析多种信道分配问题。仿真结果证明CCDCA方案有较小的呼阻率和较高的频谱利用率。     

Multibeam cellular communication systems with dynamic channel assignment across multiple sectors

In cellular communication systems, directional multibeam antennas at cell sites can be used to reduce cochannel interference, increase frequency reuse and improve system capacity. When combined with dynamic channel assignment (DCA), additional improvement is possible. We propose a multibeam scheme using dynamic channel assignment across multiple sectors. A cell is divided into several sectors, each of which is covered by several directional beams. Specific channels are allocated to each sector as in fixed channel assignment (FCA). A channel of a sector is dynamically assigned to a wireless user who communicates through one of the several beams of the sector. The assignment is made so that constraints on the allowable cochannel interference are satisfied. Limitations due to cochannel interference are analyzed. A tractable analytical model for the proposed scheme is developed using multidimensional birth–death processes. Theoretical traffic performance characteristics such as call blocking probability, forced termination probability, handoff activity, carried traffic and channel rearrangement rate are determined. With the proposed scheme, call blocking probability can be reduced significantly for a fixed offered traffic. Alternatively, system capacity can be increased while blocking probability is maintained below the required level. Smaller forced termination probability is obtainable in comparison with corresponding FCA schemes.     

Comparison of two novel heuristic dynamic channel allocation techniques in cellular systems

Dynamic channel assignment (DCA) has been discussed in the literature as a way to achieve improved resource management in cellular networks. In the simplest dynamic allocation scheme, all channels are kept in a central pool and are used on a call-by-call basis. DCA is therefore a complex real time operation and various heuristic methods have been devised as mechanisms to give a fast and reliable solution to this problem. This paper examines the implementation of a DCA model using two approaches from the field of evolutionary computation. The first is the so called genetic algorithm (GA) and the second is the combinatorial evolution strategy (CES). Computer simulations evaluate and compare these proposed heuristic DCA schemes concerning their application to a cellular model for both uniform and non-uniform traffic load conditions. © 1998 John Wiley & Sons, Ltd.     

Uplink PID power control technique for TDMA‐based cellular radio systems

The efficient management of wireless resource is essential to the success of wireless systems. While power control is traditionally considered to be a means to counteract the detrimental effects of channel fading, it is also a flexible mechanism that achieves high link quality, high bandwidth utilization, and low power consumption, which are mainly driven in cellular radio systems. Once the power control algorithm provides a lower outage probability, the SUs experienced adequate link quality need not to competitively increase their transmission power. Spontaneously, the systems with lower power consumption and better bandwidth efficiency are achieved. In this paper, a novel power control based on the proportional‐integration‐derivative (PID) controller is proposed, and its performance with an autonomous closed‐loop uplink power control model under the time division multiple access (TDMA) systems is presented. Computer simulation is used to illustrate the performance of the proposed power control algorithm in a cellular radio system with Rayleigh fading channels. The results show that our proposed power control algorithm is remarkably superior to several previous power control methods, especially in a short power control period. Copyright © 2006 John Wiley & Sons, Ltd.     

Channel assignment for cellular radio using extended dynamic programming

The channel assignment is an important aspect of cellular radio networks. Because of the limitations on the frequency spectrum, the optimal or near-optimal channel assignment has become an essential part of the network operations of wireless personal communication systems. We formulate a new strategy for the channel assignment problem in agreement with the electromagnetic compatibility constraints. We introduce and formulate the extended dynamic programming (EDP), as an extension of dynamic programming for solving the channel assignment problem in a cellular system. Using EDP an algorithm is developed for fixed channel assignment problem and it is tested and compared with other existing methods by solving different problems. In agreement with electromagnetic compatibility constraints, solution strategy based on EDP algorithm finds many valid solutions with minimum possible bandwidth.     

Performance bounds for power control supported DCA-algorithms inhighway micro cellular radio systems

To achieve a high spectrum efficiency in cellular radio systems, the radio resource allocation algorithms have to be adaptive to the actual traffic and interference situation. The focus of the paper is on performance bounds of a cellular radio system using dynamic channel assignment (DCA) combined with power control (PC). A trivial upper bound on the performance is identified. The bound is given by the performance of a hypothetical system which is able to use all channels simultaneously in all cells. A lower bound on the performance is derived from a theoretical PC supported DCA-algorithm. For a highway micro cellular system and a deterministic propagation model, numerical results show that the lower and upper bounds are tight. That is, the results indicate that it is possible to use all channels in all cells simultaneously and still provide an acceptable signal-to interference ratio in all assigned communication links     

Integrated dynamic channel assignment and power control in TDMAmobile wireless communication systems

With the evolution of analog mobile wireless communications systems into digital second- and third-generation systems, there is growing interest in finding more efficient ways of managing the available resources, in particular radio spectrum and power. In the context of time division multiple access (TDMA) systems, this interest has led to the development of a variety of dynamic channel assignment (DCA) and power control (PC) algorithms. Despite the intense activity in both the DCA and the PC arenas and some proposals for combined DCA with PC, not enough work has been devoted to effectively integrating them. In this paper, the integration of DCA and PC is investigated and a family of integrated algorithms is presented. These algorithms, fully distributed and cost adaptive, achieve capacity levels significantly higher than those of a system with only DCA or PC. With respect to a system without any DCA or PC, several-fold capacity increases are obtained. Furthermore, these capacity levels are attained with user mobility included in the analysis     

Fixed channel assignment in cellular radio networks using amodified genetic algorithm

With the limited frequency spectrum and an increasing demand for cellular communication services, the problem of channel assignment becomes increasingly important. However, finding a conflict-free channel assignment with the minimum channel span is NP hard. Therefore, we formulate the problem by assuming a given channel span. Our objective is to obtain a conflict-free channel assignment among the cells, which satisfies both the electromagnetic compatibility (EMC) constraints and traffic demand requirements. We propose an approach based on a modified genetic algorithm (GA). The approach consists of a genetic-fix algorithm that generates and manipulates individuals with fixed size (i.e., in binary representation, the number of ones is fixed) and a minimum-separation encoding scheme that eliminates redundant zeros in the solution representation. Using these two strategies, the search space can be reduced substantially. Simulations on the first four benchmark problems showed that this algorithm could achieve at least 80%, if not 100%, convergence to solutions within reasonable time. In the fifth benchmark problem, our algorithm found better solutions with shorter channel span than any existing algorithms. Such significant results indicate that our approach is indeed a good method for solving the channel-assignment problem     

Power control and channel allocation for real‐time applications in cellular networks

The next‐generation packet‐based wireless cellular network will provide real‐time services for delay‐sensitive applications. To make the next‐generation cellular network successful, it is critical that the network utilizes the resource efficiently while satisfying quality of service (QoS) requirements of real‐time users. In this paper, we consider the problem of power control and dynamic channel allocation for the downlink of a multi‐channel, multi‐user wireless cellular network. We assume that the transmitter (the base‐station) has the perfect knowledge of the channel gain. At each transmission slot, a scheduler allots the transmission power and channel access for all the users based on the instantaneous channel gains and QoS requirements of users. We propose three schemes for power control and dynamic channel allocation, which utilize multi‐user diversity and frequency diversity. Our results show that compared to the benchmark scheme, which does not utilize multi‐user diversity and power control, our proposed schemes substantially reduce the resource usage while explicitly guaranteeing the users' QoS requirements. Copyright © 2007 John Wiley & Sons, Ltd.     

多业务无线网络中基于最佳等信干比的功率控制

功率控制技术是无线网络的关键技术之一。为改进多业务无线网络中基于非合作博弈的功率控制算法中纳什均衡的帕累托有效性,引入数据终端的最佳等信干比概念,使得系统中所有数据终端都工作在最佳的等信干比下,语音终端工作在语音通信服务质量门限的目标信干比门限之下。推导出一个新的分布式基于最佳等信干比的功率控制算法。仿真表明,该算法明显提高了系统的服务质量,系统中终端均具有相对较高的效用和较低的发射功率,还使得无线网络资源的使用更加合理和公平。     

Centralized power control in cellular radio systems

This paper describes a centralized power control scheme for cellular mobile radio systems. The power for the mobiles in the proposed scheme is computed based on signal strength measurements. All the mobiles using the same channel in this scheme will attain a common carrier-to-interference ratio. The proposed scheme is analyzed and shown to have an optimal solution     

Optimal channel reuse in cellular land mobile radio systems

Origination probability for cochannel interference is introduced to the study of the influence of all cochannel interferers surrounding the base station of interest. In addition, the probability of cochannel interference, which is of importance in determining system parameters in a cellular communication scheme, is evaluated for the mobile radio environment as expressed by Rayleigh fading and shadowing. As a consequence, the optimal number of radio channels to allocate to each cell is derived through the use of a simple mathematical model. The theoretical results obtained are useful not only as a step in the maturation of the cellular land mobile radio system, but also for the development of the portable radio telephone system.     

Distributed dynamic channel assignment in TDMA mobile communication systems

Dynamic channel assignment (DCA) has been a topic of intense research for many years, and a variety of DCA algorithms have been proposed. Nonetheless, some important issues have been neglected because of the complexity involved in their study. In particular, the impact of user motion on the performance of DCA systems has not received enough attention. In this paper, we quantify the impact of motion on the capacity and cost-in terms of average number of reassignments per call-of a variety of representative distributed fixed-power DCA algorithms. A novel adaptive algorithm especially suited for mobility environments is proposed, which achieves high capacity while controlling the reassignment rate. We also prove that most of this capacity can be effectively realized with a reduced number of radio transceivers per base station. Finally, we evaluate the degradation associated with the use of estimates of local-mean signal and interference levels-obtained by averaging instantaneous measurements-instead of the actual local-mean values.     

一种改进的分散功率控制算法

在现有的分散定步长功率控制算法基础上,通过引入多个功率控制步长,得到一种改进的分散功率控制算法。通过分析可知,新算法具有更好的收敛精度,仿真结果表明与原有算法相比,本算法收敛速度获得了提高。     

Performance analysis of dynamic channel assignment algorithms in cellular mobile systems with hand‐off

In this paper, the traffic performance of dynamic channel assignment (DCA) in cellular mobile system with hand‐off is investigated. A traffic model for cellular system incorporating hand‐off is established first. Under the framework of the model, a hand‐off priority scheme is developed to reduce the forced termination of calls in progress. This paper analyses and derives the traffic performance bound for DCA strategies with hand‐off by extending the maximum packing (MP) scheme to include the hand‐off procedure. For practical implementation, a distributed DCA algorithm (DDCA) is also proposed. A non‐priority scheme and the proposed priority scheme can be combined with either MP or DDCA. It is shown that the simulation results of DDCA scheme are comparable with the analytical bounds given by MP for both the non‐prioritized case and prioritized case. A reasonable trade‐off between the new call blocking probability and forced termination probability can be achieved by using the proposed prioritized scheme in DCA. Copyright © 2002 John Wiley & Sons, Ltd.