Resource allocation for cellular radio systems

High terminal traffic densities are expected in urban multiuser radio systems. An efficient allocation of resources is the key to high system capacity. In this paper, a distributed dynamic resource allocation (DDRA) scheme based on local signal and interference measurements is proposed for multiuser radio networks. It offers “soft capacity” for time division multiple access (TDMA) and frequency division multiple access (FDMA) systems, bounded above by N per base station, where N is the total number of channels in the system. The decisions are made local to a terminal and its base and are essentially independent of the rest of the system. A distributed dynamic channel assignment scheme is used to assign channels to new calls. This scheme assigns a channel that offers the maximum carrier to interference ratio (CIR) to a new call. A distributed constrained power control (DCPC) scheme based on CIR measurements is used for power control. The channel assignment scheme and the power control scheme are coupled to obtain an interactive resource allocation scheme. We compare the capacity of a system which uses the distributed dynamic resource allocation scheme described above with the capacity of a system which uses the channel assignment scheme alone. The system capacity is measured by simulation as the number of terminals that can be served by the system with a CIR above an acceptable minimum. In a 1D cellular system, coupling the channel assignment scheme with power control is discussed. Simulations were also used to show the effect of varying the maximum transmitter power on system capacity     

Network-assisted resource management for wireless data networks

We propose a framework for network-assisted radio resource management in wireless data networks. This type of radio resource management techniques offer implementation and capacity benefits compared to conventional, interference-measurement based, dynamic channel assignment (DCA) algorithms. The basic idea is to use interbase signaling to shift most of the burden of the resource allocation from the air interface to the backbone infrastructure. By exchanging channel assignment as well as other relevant information in real time through the backbone network, each base can calculate the impact of a resource assignment on the system. As a result, rapid interference measurements, which are typically needed to implement DCA schemes, are replaced by a limited amount of path loss measurements and the computation of interference conditions by the base stations. This significantly reduces the measurement and over-the-air signaling requirements, and can also provide an opportunity for a better optimization of the system performance. We focus on two specific algorithms: network-assisted least-interference-based dynamic packet assignment (NA-LI-DPA) and network-assisted dynamic packet assignment with throughput optimization (NA-DPA). NA-LI-DPA closely resembles a least-interference-based dynamic channel assignment algorithm, and NA-DPA attempts to further improve the overall system throughput. The algorithms, as defined, are appropriate for a best-effort data service, where the primary goal is to provide a higher throughput. However, it will be clear from the discussion that it is also feasible to alter the algorithms to optimize performance metrics other than throughput, e.g., to ensure a certain quality of service. We show through simulation that, for a system like enhanced general packet radio service (EGPRS) system, NA-DPA can provide a throughput that is 50% higher than random packet assignment, and 25% higher than that obtained by conventional DCA algorithms     

Pseudo-handover based subchannel and power adaptation scheme for interference mitigation in OFDMA two-tier femtocell networks

In the two-tier femtocell network,a central macrocell is underlaid with a large number of shorter range femtocell hotspots,which is preferably in the universal frequency reuse mode.This kind of new network architecture brings about urgent challenges to the schemes of interference management and the radio resource allocation.Motivated by these challenges,three contributions are made in this paper:1) A novel joint subchannel and power allocation problem for orthogonal frequency division multiple access (OFDMA) downlink based femtocells is formulated on the premise ofminimizing radiated interference of every Femto base station.2) The pseudo-handover based scheduling information exchange method is proposed to exchange the co-tier and cross-tier information,and thus avoid the collision interference.3) An iterative scheme of power control and subchannel is proposed to solve the formulated problem in contribution 1),which is an NP-complete problem.Through simulations and comparisons with four other schemes,better performance in reducing interference and improving the spectrum efficiency is achieved by the proposed scheme.     

Optimized BS assignment and resource allocation in cooperative OFDM networks

Cooperative transmission (CT) and orthogonal frequency division multiple (OFDM) are promising technologies for extending coverage and increasing throughput in broadband wireless access (BWA) networks. Therefore, we propose a novel BWA network architecture, that can set up inter-cell collaboration using physical layer cooperative transmissions among distributed wired access networks with a powerful coordination capability at the central office. However, conventional base station (BS) assignment and resource allocation schemes cannot be used directly because a user can be serviced by more than one BS with cooperative transmission technology. This study proposes a novel framework of BS assignment and resource allocation in a cooperative OFDM network. We provide three approaches of resource allocation for minimizing bandwidth usage, minimizing transmission power consumption, and balancing resource costs respectively. An optimized resource allocation scheme can be implemented by flexibly choosing one of these approaches based on network load. The simulation results show the efficiency of the proposed mathematical formulations and linearization approach of our scheme. The performance benefit of CT technology on the bandwidth saving is demonstrated by comparing the new BS assignment and resource allocation scheme with conventional non-cooperative transmission.     

Impact of radio resource allocation policies on the TD-CDMA systemperformance: evaluation of major critical parameters

This paper investigates the impact of major critical parameters and the effect of some radio resource allocation policies on the TD-CDMA system performance. Critical parameters are related either to the user behavior (e.g., user mobility, activity factors) or to processing techniques and algorithms implemented to control network performance and individual radio link quality (e.g., joint detection imperfection, handover margin, timeout for maintaining alive bad radio links). Network topology (e.g., distance between neighboring base stations) also undoubtedly influences capacity results. Analysis is carried out through accurate modeling of user behavior, interference scenarios, and power budget limitations at both terminals and infrastructure, allowing for proper implementation of radio resource allocation algorithms. Among these algorithms, power management (both at the initial channel assignment and during communication), dynamic channel allocation (DCA), and ongoing calls management are explored. An event-driven simulation approach was considered to model realistic system behavior and address system stability under various events generating traffic/interference fluctuations (e.g., call arrivals and departures, handovers, steps of power control loops). Such an approach is expected to offer a good estimate of the real conditions provided the propagation models are close to real life. As a consequence, measures to be taken to avoid/control overloading in a TD-CDMA (CDMA in general) environment can be naturally derived and tested with this methodology     

Fusion of artificial intelligence and game theory for resource allocation in non-orthogonal multiple access-assisted device-to-device cooperative communication

Device-to-device (D2D) communication offers a low-cost paradigm where two devices in close proximity can communicate without needing a base station (BS). It significantly improves radio resource allocation, channel gain, communication latency, and energy efficiency and offers cooperative communication to enhance the weak user's network coverage. The cellular mobile users (CMUs) share the spectral resources (e.g., power, channel, and spectrum) with D2D mobile users (DMUs), improving spectral efficiency. However, the reuse of radio resources causes various interferences, such as intercell and intracell interference, that degrade the performance of overall D2D communication. To overcome the aforementioned issues, this paper presents a fusion of AI and coalition game for secure resource allocation in non-orthogonal multiple access (NOMA)-based cooperative D2D communication. Here, NOMA uses the successive interference cancellation (SIC) technique to reduce the severe impact of interference from the D2D systems. Further, we utilized a coalition game theoretic model that efficiently and securely allocates the resources between CMUs and DMUs. However, in the coalition game, all DMUs participate in obtaining resources from CMUs, which increases the computational overhead of the overall system. For that, we employ artificial intelligence (AI) classifiers that bifurcate the DMUs based on their channel quality parameters, such as reference signal received power (RSRP), received signal strength indicator (RSSI), signal-to-noise ratio (SNR), and channel quality indicator (CQI). It only forwards the DMUs that have better channel quality parameters into the coalition game, thus reducing the computational overhead of the overall D2D communication. The performance of the proposed scheme is evaluated using various statistical metrics, for example, precision score, accuracy, recall, F1 score, overall sum rate, and secrecy capacity, where an accuracy of 99.38% is achieved while selecting DMUs for D2D communication.     

A Framework for Cognitive WiMAX With Frequency Agility

Cognitive radios have the ability to sense the radio spectrum environment and to switch dynamically to available frequency ranges. Mobile WiMax is an emerging wireless networking standard that could potentially benefit from cognitive radio technology. We develop a framework for applying cognitive radio technology to mobile WiMax networks to increase capacity and simplify network operations. In the proposed cognitive WiMax architecture, base stations are equipped with sensitive detectors and assign channels to subscriber stations dynamically based on spectrum availability. Power control is employed to increase frequency reuse in conjunction with spectrum sensing. Using computer simulation, we evaluate the performance of ldquocognitive channel assignmentrdquo relative to conventional dynamic channel assignment. Our numerical results show that cognitive radios can substantially increase the capacity of emerging WiMax networks by exploiting inherent spectrum hole opportunities. The key performance parameters determining the achievable capacity of cognitive WiMax networks are the detection and interference range, which depend in turn on characteristics of the radio propagation environment.     

5G室内密集立体覆盖的计算通信:架构、方法与增益

提出了一种新型的室内密集立体覆盖的计算通信一体化架构,通过挖掘信道计算、容量计算以及网络资源优化计算之间的内在联系,并利用基于云计算和雾计算的密集分布式接入网络的优势,该架构完成了计算电磁学、计算信息论与大规模优化理论到计算通信理论的深度融合.介绍了该架构的实现方法,即以密集异构分布式无线接入网络作为通信接入网络基础架构,利用分布式的计算资源结合计算电磁学理论实现并行化的信道计算,据此进一步依据计算信息论实现容量计算,并基于大规模优化理论完成多用户的网络资源优化计算,最终实现由传播环境到信道容量与资源分配的计算通信.     

Performance Analysis of an OFDMA Transmission System in a Multicell Environment

The paper deals with design and performance analysis of orthogonal frequency-division multiple-access (OFDMA)-based downlink cellular wireless communications. Due to a high degree of user mobility, the base station is assumed to have only a statistical knowledge of the users' channels. Relying on the ergodic capacities connected to the user rates, a subcarrier and power allocation that minimizes the total transmitted power is proposed. The allocation strategy requires only the knowledge of the channel statistics and the rate requirements for all users. An extension and a performance analysis of this allocation algorithm in a multicell environment working with a frequency reuse factor equal to one is also conducted. A condition for the multicell network to be able to satisfy all rate requirements is derived     

Dynamic Resource Allocation in Non-orthogonal Multiple Access Using Weighted Maximin Fairness Strategy for a UAV Network

Non-orthogonal multiple access (NOMA) with power domain multiplexing and successive interference cancellation (SIC) is one of the promising technologies for future wireless communication. The performance of NOMA is highly dependent on resource allocation such as power allocation and channel assignment. In this paper, we investigate the power allocation (PA) scheme, to optimize the weighted maximin fairness (MMF) for 2-user and 3-user clusters. We utilize the particle swarm optimization (PSO) based algorithm for power allocation due to its promising behavior. Application area of NOMA is becoming broader, then, we considered a cellular network, assisted by an unmanned aerial vehicle (UAV) as the base station (BS) which is integrated with the NOMA system. The PA for weighted MMF problem in NOMA is non-convex, it is difficult to find out the optimal solution directly. Simulation results show the performance of PSO-based algorithm in different adaptive weights and its convergence characteristics. We have also shown that the rate and fairness tradeoff using weighted maximin fairness. Numerical results compare the performance of NOMA and orthogonal multiple access (OMA) and prove the significance of the proposed algorithm.

     

多射频无线Mesh网中的接口分域信道分配

在多射频多信道无线Mesh网中,是无线宽带接入的重要候选技术之一.为了满足无线宽带接入的容量要求,Mesh路由器节点常需要配置多个无线接口并使用多个正交信道.已有的信道分配方法虽能减少干扰和碰撞,但不能完全避免.本文提出一种域内中心式调度的接口分域信道分配(ICCA)方案,旨在完全避免干扰与碰撞以提高网络吞吐量,尤其能...     

OFDM中继系统中能效优化的资源联合分配算法

在协作正交频分复用系统中,合理的资源分配对于提高系统性能具有重要的意义。针对中继、子载波和功率的联合分配,对最大化系统能效为目标的分配算法进行研究,提出了一个最低容量限制下的最大能效次优化资源联合分配算法(JRAA,joint resource allocation algorithm)。该算法使用冲突图表示系统资源冲突关系,根据冲突图的最大独立集结果进行资源分配。经过仿真验证,该资源分配算法实现了中继一子载波和功率的联合分配,在能效性能方面优于现有的算法。     

Tradeoff Analysis of Fixed Cell Assignment in Wideband TDMA Networks

This paper analyzes tradeoffs within a dynamic allocation method, called the fixed cell assignment, which employs wideband time division multiple access transmission for the forward link in broadband (10 Mbit/s) wireless networks. This high data rate at the operating frequency 2 GHz is considered. The system is configured with directional base station antennas and omnidirectional mobile antennas, with each cell divided into six sectors, and sectors numbered in the same order for every cell. Access is controlled based on availability and sector number, and half the sectors in each cell reuse the same spectrum. The frequency reuse factor of two and power control technology mitigate the effects of co-channel interference. Differential phase shift keying modulation is employed. Computer simulations are performed showing maximum capacity tradeoffs.     

A matching game framework for users clustering and resource allocation with wireless power transfer in a CR-NOMA network

This paper investigates the resource allocation in a massively deployed user cognitive radio enabled non-orthogonal multiple access (CR-NOMA) network considering the downlink scenario. The system performance deteriorates with the number of users who are experiencing similar channel characteristics from the base station (BS) in NOMA. To address this challenge, we propose a framework for maximizing the system throughput that is based on one-to-one matching game theory integrated with the machine learning technique. The proposed approach is decomposed to solve users clustering and power allocation subproblems. The selection of optimal cluster heads (CHs) and their associated cluster members is based on Gale-Shapley matching game theoretical model with the application of Hungarian method. The CHs can harvest energy from the BS and transfer their surplus power to the primary user (PU) through wireless power transfer. In return, they are allowed to access the licensed band for secondary transmission. The power allocation to the users intended for power conservation at CHs is formulated as a probabilistic constraint, which is then solved by employing the support vector machine (SVM) algorithm. The simulation results demonstrate the efficacy of our proposed schemes that enable the CHs to transfer the residual power while ensuring maximum system throughput. The effects of different parameters on the performance are also studied.     

A new adaptive MAC layer protocol for broadband packet wirelessnetworks in harsh fading and interference environments

A new medium-access protocol is proposed for sharing a high-speed radio channel among a number of small wireless packet-access units, some of which may be stationary and some of which may be within moving vehicles. Such a system could provide fixed-point pedestrian and remote users with wireless access to CPU and database resources of an underlying asynchronous transfer mode (ATM) wireline network, essentially extending the ATM bandwidth-upon-demand interface directly to the wireless units and enabling delivery of multimedia services (albeit at the lower peak rate afforded by the radio channel). A primary goal of the proposed medium-access protocol is the pre-delivery of a signal from each packet-access unit as needed to rapidly compute the weights needed by a base station's adaptive array processor or a space-time processor, thereby protecting the packet flow in each direction from the effects of both multipath propagation and adjacent channel interference arising in neighboring radio cells. An impairment-robust direct sequence spread-spectrum-based polling signal is invoked to stimulate a pilot tone from a given remote immediately prior to packet transfer in either direction, thereby permitting the base station to determine a good set of antenna element combining or power splitting weights to be used for that packet. Reasonable approximations are invoked to study the performance of the proposed protocol and the link utilization efficiency and average message delay are found. By proper choice of protocol parameters, a radio resource utilization efficiency of about 95% is readily achieved. The accuracy of the approximations is confirmed by extensive computer simulations     

Joint backhaul bandwidth and power allocation in heterogeneous cellular networks: A two‐level approach

We investigate the problem of joint downlink wireless backhaul bandwidth (WBB) and power allocation in heterogeneous cellular networks (HCNs). A WBB partitioning scheme is considered, which allocates the whole bandwidth between the macrocell and small cells for data transmission and backhauling. We formulate an optimization problem to maximize the weighted sum logarithmic utility function by jointly optimizing WBB portion and fronthaul power allocation of each base station with consideration of the backhaul capacity limitation on each small cell. In order to solve this joint optimization problem, we propose a hierarchical two‐level approach and decompose the original problem into two independent subproblems: the WBB allocation at the macrocell base station (MBS) and the power allocation at both the MBS and small cell base stations (SBSs). Accordingly, the optimal WBB portion and power allocation solutions are obtained, respectively. Furthermore, we develop a distributed algorithm to implement the joint WBB and power allocation. Numerical results verify the effectiveness of the proposed approach and analyze the impact of the weighted coefficient and backhaul capacity limitation on the network performance. In addition, significant performance gains can be achieved by the proposed approach over the benchmark.     

Radio resource management in wireless LANs

Some chief information officers and information technology managers are reluctant to deploy wireless LANs. Among their concerns are reliability, availability, performance, and deployment. Each of these concerns can be directly addressed through the radio resource management techniques used in a new generation of wireless LAN equipment. The new capabilities include dynamic channel assignment, dynamic power control, and load sharing. Changing from the relatively static radio resource management techniques generally in use today to dynamic methods like those highlighted in this article helps to increase the capacity and improve the performance of large-scale wireless LANs.     

Performance Analysis of Cognitive Radio Multiple-Access Channels Over Dynamic Fading Environments

In dynamically changing environments, the spectrum-sharing method is a promising method to address the spectrum underutilization problem for cognitive radio (CR) systems. This paper investigates the capacity of cognitive radio multiple-access channel (CR-MAC) over a dynamic fading environment. Multiple secondary users (SUs) transmit to the secondary base station under the transmit power (TP) and interference temperature (IT) at the primary base station constraints. In order to perform a general analysis, a theoretical dynamic fading model termed hyper-fading model, which is suitable to the dynamic nature of cognitive radio channel, is considered. The optimal power allocation method is employed to maximize the capacity of CR-MAC for hyper-fading channel with TP and IT constraints and full channel side information. Through the numerical simulations, the capacity of the hyper-fading channels are compared with that of other channel fading models such as Rayleigh, Nakagami-2, and with an additive white Gaussian noise channel. Additionally, the impacts of the number of SUs on capacity is investigated.     

Effects of some nonuniform spatial demand profiles on mobile radio system performance

The design of future mobile radio systems will be based upon an estimated user demand. Systems probably will be engineered to serve the "average business day" spatial distribution of call attempts, which for the purpose of this study was assumed to be uniform. There will be day-to-day fluctuations about this long-term average, the magnitudes of which are only to be conjectured at this time. This paper compares the performance of computer simulated mobile radio systems operating with several demand profiles. The profiles were selected to give an indication of the effects on system performance of either uncompensated changes in average traffic or normal fluctuations which occur in the randomly offered traffic even when the long-term average value does not change. The dynamic channel assignment systems increased the traffic capacity at low blocking levels even over a perfectly designed fixed channel assignment system. In addition, it was found that the dynamic channel assignment systems were relatively insensitive to the periodic spatial demand distributions studied by this computer simulation. Even though new call attempts were made to fluctuate markedly between adjacent base stations within a reuse interval, the blocking rate of each base station remained constant. It appears that the blocking rate within a reuse interval depends (in the dynamic channel assignment systems) mainly on the average demand within that interval and not very strongly upon the distribution of that demand. In the fixed channel assignment system, uncompensated fluctuations in the spatial demand distribution away from the design value always degrade system performance.     

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.