Efficient Use Of Radio Resources Research Articles

Performance Comparison of Massive MIMO System with Orthogonal and Nonorthogonal Multiple Access for Uplink in 5G Systems

In the attempt to respond to market demands, new techniques for wireless communication systems have been proposed to ensure, to all active users that are sharing the same network cell, an increased quality of service, regardless of any environmental factors, such as their position within the cell, time, space, climate, and noise. One example is the nonorthogonal multiple access (NOMA) technique, proposed within the 5G standard, known for supporting a massive connectivity and a more efficient use of radio resources. This paper presents two new sets of complex codes— multiple-user shared-access (MUSA) and extended MUSA (EMUSA), and an algorithm of allocation such that the intercorrelation should be as reduced as possible that can be used in MUSA for 5G NOMA-based technique scheme. Also, it analyzes the possibility of creating complex codes starting from PN (cPN), which is a novel idea proposed in this paper, whose results are promising with respect to the overall system performances. First, a description of the basic principles of MUSA are presented; next, the description of the proposed system will be provided, whose performance will be tested using Monte Carlo MATLAB simulations based on bit error rate (BER) versus signal-to-noise ratio (SNR). The system performances are evaluated in different scenarios and compared with classical code division multiple access (CDMA) having the following system parameters in sight: the number of antennas at the receiver side and the number of active users.

Analysis of Control Overhead Reduction by Semi-Persistent Scheduling

For the efficient use of radio resource, semi-persistent scheduling (SPS) has been adopted to reduce control overhead required for resource allocation. In this letter, for voice over Internet protocol traffic, a lower bound on blocking probability and a closed-form maximum achievable control overhead reduction ratio are derived through a novel Markov chain model. Also, the performance evaluation of SPS under various resource assignment algorithms is provided on the blocking probability and overhead reduction ratio. Analytical expressions are validated through simulations.

Reconfigurable optical‐radio wireless networks: Meeting the most stringent requirements of future communication systems

AbstractIn this paper, we propose a reconfigurable optical‐radio wireless network characterized by high flexibility and performance. The hybrid network can be dynamically configured, adapting itself to the changing requirements of users or operating environments, dynamics of the transmission medium, and availability of resources. First, the basic concept, system architecture, and key operating modes are introduced. Possible operating scenarios and their relationship to the operating modes are discussed. Then, a practical implementation of the hybrid network is introduced, describing the network components, architecture, modulation scheme, and implementation technologies. Implementation was carried out using mostly off‐the‐shelf components and universal software radio peripheral blocks. Particular attention has been put in implementing a fast handover mechanism between modes, an essential requirement for seamless network reconfiguration. Network performance is evaluated and different switching approaches are compared. The paper demonstrates practically the proposed concept based on dynamic system reconfiguration. For the implementation, a mode switching algorithm was developed making decisions based on the quality of the wireless channels. The system was tested with live video packets transmitted through the network. System performance was assessed through data throughput and packet loss measured for different modulation parameters. The proposed concept, essentially a software‐defined hybrid network, is flexible and makes efficient use of radio resources. Moreover, the network has the potential to achieve high performance. All these characteristics make reconfigurable optical‐radio networks an attractive candidate for fifth generation and beyond.

An Efficient Small Data Transmission Scheme in the 3GPP NB-IoT System

This letter proposes an efficient small data transmission scheme in the narrow band (NB)-Internet of Things (IoT) system. For the efficient use of radio resources, the proposed scheme enables devices in an idle state to transmit a small data packet without the radio resource control connection setup process. This can improve the maximum number of supportable devices in the NB-IoT system which has insufficient radio resources. Numerical results have shown that the proposed scheme can increase the maximum number of supportable devices by about 60% compared with the conventional scheme.

Energy Efficient IoT Data Collection in Smart Cities Exploiting D2D Communications.

Fifth Generation (5G) wireless systems are expected to connect an avalanche of “smart” objects disseminated from the largest “Smart City” to the smallest “Smart Home”. In this vision, Long Term Evolution-Advanced (LTE-A) is deemed to play a fundamental role in the Internet of Things (IoT) arena providing a large coherent infrastructure and a wide wireless connectivity to the devices. However, since LTE-A was originally designed to support high data rates and large data size, novel solutions are required to enable an efficient use of radio resources to convey small data packets typically exchanged by IoT applications in “smart” environments. On the other hand, the typically high energy consumption required by cellular communications is a serious obstacle to large scale IoT deployments under cellular connectivity as in the case of Smart City scenarios. Network-assisted Device-to-Device (D2D) communications are considered as a viable solution to reduce the energy consumption for the devices. The particular approach presented in this paper consists in appointing one of the IoT smart devices as a collector of all data from a cluster of objects using D2D links, thus acting as an aggregator toward the eNodeB. By smartly adapting the Modulation and Coding Scheme (MCS) on the communication links, we will show it is possible to maximize the radio resource utilization as a function of the total amount of data to be sent. A further benefit that we will highlight is the possibility to reduce the transmission power when a more robust MCS is adopted. A comprehensive performance evaluation in a wide set of scenarios will testify the achievable gains in terms of energy efficiency and resource utilization in the envisaged D2D-based IoT data collection.

Uplink Blocking Probabilities in Priority-Based Cellular CDMA Networks with Finite Source Population

Fast proliferation of mobile Internet and high-demand mobile applications necessitates the introduction of different priority classes in next-generation cellular networks. This is especially crucial for efficient use of radio resources in the heterogeneous and virtualized network environments. Despite the fact that many analytical tools have been proposed for capacity and radio resource modelling in cellular networks, only a few of them explicitly incorporate priorities among services. We propose a novel analytical model to analyse the performance of a priority-based cellular CDMA system with finite source population. When the cell load is above a certain level, low-priority calls may be blocked to preserve the quality of service of high-priority calls. The proposed model leads to an efficient closed-form solution that enables fast and very accurate calculation of resource occupancy of the CDMA system and call blocking probabilities, for different services and many priority classes. To achieve them, the system is modelled as a continuous-time Markov chain. We evaluate the accuracy of the proposed analytical model by means of computer simulations and find that the introduced approximation errors are negligible.

On prioritised opportunistic spectrum access in cognitive radio cellular networks

AbstractCognitive radio (CR) networks allow secondary users (SUs) to opportunistically access licensed spectrum, thus providing efficient use of radio resources. Different studies carried out on CR networks have focused on the procedure of spectrum handoff of SUs such as the data transmission in a communication that can be carried out in different channels. In this paper, we consider cellular networks enhanced with facilities for CR communication where a user with a call in progress moves across neighbouring cells, that is, the so‐called inter‐cell handoff. Our model assumes that the cell gives priority to inter‐cell handoff calls over the calls originating within it. A finite queue is used in every cell for SUs, and a fixed number of buffer slots are reserved for the inter‐handoff SU calls. With these considerations, we study the transmission performance of SUs by using Markov chains‐based modelling approach. The numerical analysis is validated by simulation experiments. We also suggest a fuzzy logic‐based hybrid decision‐making algorithm to select the best solution for inter‐handoff prioritisation. The goal is to optimise the transmission performance of SUs by leveraging their requirements on service completion throughput and waiting time in each cell. Copyright © 2014 John Wiley & Sons, Ltd.

Optimal deactivated sub‐carriers guard bands for spectrum pooling systems based on wavelet‐based orthogonal frequency division multiplexing

Cognitive radio (CR) is an advanced technology for efficient use of radio resources. In the CR system, the spectrum pooling technique is used to enhance spectrum utilisation, which enables public access to the spectral ranges of the licenced frequency bands which are seldom used by overlaying an unlicenced user (unLU) on an existing licenced user (LU). The spectrum pooling system constructed by implementing wavelet-based orthogonal frequency division multiplexing (WOFDM) owns better flexibility and bandwidth efficiency. However, the interference between the LU and the unLU is severe in the multipath wireless channel. In the study, the intercarrier interference (ICI) interference energy of the spectrum pooling-based WOFDM is analysed and an optimal deactivated subcarriers algorithm for the guard bands is proposed to mitigate the ICI between the unLU and the LU by intelligently deactivating one or more of the optimal deactivated subchannels which generates the maximum ICI interference in the LU. The numerical and the simulation results show that the data transmission rate of the unLU is ensured, the ICI of the LU is reduced and the bit error rate performance of the LU is, respectively, improved by implementing the algorithm.

A User Selection Algorithm Using Angle between Subspaces for Downlink MU-MIMO Systems

One of major issues in the efficient use of radio resource for multiuser multiple-input/multiple-output (MU-MIMO) systems is the selection of users to achieve the maximum system throughput. The optimal user selection algorithm, which requires exhaustive search, is prohibitive due to its high computational complexity where Block diagonalization (BD) method is applied and known as a suboptimal precoding technique for downlink MU-MIMO systems, which intents to perfectly eliminate inter-user interference. In this paper, we propose efficient, iterative user selection algorithms with low complexity, where the product of eigenvalues of effective channels is utilized as a selection metric by applying the concept of principal angles between subspaces. And, we further examined the applicability of the proposed algorithms to limited feedback systems and proportional fair (PF) scheduling. Through computational complexity analysis, we show that the proposed algorithm has low complexity with a little loss in throughput. Simulation results validate that the proposed algorithm achieves almost the same system throughput by a capacity-based algorithm under high SNR regime with considerable reduction in complexity.

Resource Optimization in Wireless Networks

#(WSNs) are under rapid deployment. Planning and optimization techniques play a vital role in the deployment and operation of almost types of networks. Specifically, the adoption of optimization and planning procedures are still in progress during the lifetime of a broadband radio access network. The proper adoption of planning and optimization procedures enables the successfully deployment and expansion of the BRANs. In the initial phase, planning deals with issues of network dimensioning and configuration, including the number and locations of base stations (BSs) and their configuration parameters. (Re-) optimization tasks take place during network operation; frequently, a network is subject to reoptimization in order to adapt to changing demands and additional service requirements. It is worth noting the direct application of the optimization and/or planning solutions obtained in the context of broadband cellular system-based networks is not optimal for the adhoc networks. Resource optimization (RO) techniques, primarily power/energy consumption minimization, are becoming increasingly important in wireless systems and networks design, since battery technology evolution has not followed the explosive demand of mobile devices. Specifically, typical optimization problem in WSNs consists in efficiently reduce the required energy consumption while maximizing the lifetime of the network sensors. For that, source and path redundancy techniques is commonly used. As a result, the number of active sensor nodes can be optimized in order to sense and communicate with base station (BS), while a time slots duration strategy to each sensor nodes is assumed. Due to the large amount of investments spent on radio access, appropriate planning and optimization procedures are crucial to any business model. As a benefit, a well-planned network, especially BRAN, requires less infrastructure, mainly fewer BS sites, which has been proven to be a severe constraint in provisioning 3G/4G networks. Besides, well-planned BRAN makes more efficient use of radio resource, offering extra capacities under the same infrastructure.

Resource Sharing and Bandwidth Allocation for WiMAX Mesh Networks Using Centralized Scheduling

IEEE 802.16, also known as WiMAX, is considered to be an important technology for next-generation wireless metropolitan area network (WMAN) and has received great attention for its potential applications. WiMAX supports two types of modes: point-to-multipoint mode and mesh mode. While the point-to-multipoint mode is well developed, the mesh mode still has many design issues to be addressed, such as routing and packet scheduling algorithms. This paper investigates the routing and packet scheduling algorithms of WiMAX mesh networks. Three sets of routing and packet scheduling algorithms are proposed: (1) interference-based optimal routing and parallel-relay-based packet scheduling, (2) link-prioritization-based routing and link-group-based packet scheduling, and (3) minimal-conflict-cost routing and deficiency-fair priority-based packet scheduling. The simulation results show that the proposed algorithms can make efficient use of radio resource.

A Cross-Layer Design of User Cooperation for Rate Adaptive Wireless Local Area Networks

In this paper, we propose a cross-layer design of packet level cooperation for wireless LANs that support rate adaptation. While keeping compatibility with legacy wireless LANs, distributed control of multi-hop packet transmission is enabled without pre-negotiation of routing or pairing. These features are provided by prioritization scheme based on IEEE 802.11e EDCF in which we set the parameters according to the measured link condition at each terminal. Relaying packets with high transmission rate makes much efficient use of radio resource, and it leads not only to improve performance of the total system, but also to overcome the fairness issue known in rate adaptation, where the terminals with good link conditions cannot gain enough resource because of the time consumed by low data rate transmission. These advantages are confirmed through computer simulations considering packet error rate at each transmission which is assumed by receiving power calculated from the distance between source, relay, and destination terminals. Furthermore, we also discuss about the fairness between cooperation-enabled and legacy terminals when they coexist in the same system, in order to make gradual deployment feasible.

Access point selection strategy in IEEE802.11E WLAN networks toward load balancing

AbstractIEEE802.11 WLAN (Wireless LAN) has been widely used in enterprises and public spaces such as airports. In these large WLAN networks, RRM (Radio Resource Management) is necessary for efficient use of radio resources, and also load balancing among APs (Access Point) has to be taken into account. Since, in IEEE802.11, STA (Station) has the right to select an AP with which it will associate, the AP selection mechanism implemented in STA is important for load balancing. This paper proposes an association mechanism called HRFA (High‐Rate First Association) in order to achieve load balancing and efficient use of radio resources. Furthermore, IEEE802.11e was developed by Task Group E of the IEEE802.11 working group and specified a MAC protocol to provide QoS in the MAC layer and to support real‐time traffic over WLAN. In order for WLAN to be more widely used, the functionalities of IEEE802.11e must be provided in WLAN devices. Our proposed HRFA can be applied to WLANs compliant with IEEE802.11e. Since the HRFA can be implemented without any modifications in the IEEE802.11 and IEEE802.11e standards, it is useful from the implementation‐cost and compatibility point of views. Simulation results show that HRFA can efficiently utilize radio resources and can also achieve load balancing in IEEE802.11e WLAN networks. © 2006 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(4): 35–45, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20347

An efficient demand-assign medium access control protocol for high-speed wireless networks

With the convergence of mobile and fixed communication networks, mobile users are increasingly demanding applications offering the same quality of service (QoS) as provided by wired access. High-speed time division duplex access mode is typical of high-speed mobile communication systems in order to simultaneously handle real-time, interactive, and best effort traffic classes. This paper proposes a medium access control (MAC) protocol that makes efficient use of radio resources for access. The proposed protocol, named dynamic-time division duplexing (D-TDD), is based on a multiple-access TDD air interface capable of supporting uplink and downlink traffic asymmetries. Validation of the D-TDD good performance was achieved by comparison with an ideal scheme and a different MAC protocol recently proposed in the literature on this subject.

Traffic control schemes and performance analysis of multimedia service in cellular systems

This paper presents several traffic control schemes for improving the quality of service (QoS) in cellular systems. Traffic control schemes are devised for the efficient use of the limited radio resources with the increasing number of users and multimedia traffic. Both numerical analysis and computer simu- lations are carried out for the performance evaluation in terms of performance measures. Important performance measures of the suggested traffic control schemes such as the blocking probability of new traffic, the forced termination probability of handoff traffic, and the noncompletion probability for four input multimedia streams are investigated. It reveals that a finite queueing scheme for real-time handoff traffic guarantees QoS metrics, such as the blocking probability of new traffic and forced termination probability of handoff traffic, as well as efficient use of radio resources. In this paper, the priority with reserved channel and queue scheme turns out to provide significant performance improvement.

Efficient power control via pricing in wireless data networks

A major challenge in the operation of wireless communications systems is the efficient use of radio resources. One important component of radio resource management is power control, which has been studied extensively in the context of voice communications. With the increasing demand for wireless data services, it is necessary to establish power control algorithms for information sources other than voice. We present a power control solution for wireless data in the analytical setting of a game theoretic framework. In this context, the quality of service (QoS) a wireless terminal receives is referred to as the utility and distributed power control is a noncooperative power control game where users maximize their utility. The outcome of the game results in a Nash (1951) equilibrium that is inefficient. We introduce pricing of transmit powers in order to obtain Pareto improvement of the noncooperative power control game, i.e., to obtain improvements in user utilities relative to the case with no pricing. Specifically, we consider a pricing function that is a linear function of the transmit power. The simplicity of the pricing function allows a distributed implementation where the price can be broadcast by the base station to all the terminals. We see that pricing is especially helpful in a heavily loaded system.

Cdma2000 physical layer: An overview

cdma2000 offers several enhancements as compared to TIA/EIA-95, although it remains fully compatible with TIA/EIA-95 systems and allows for a smooth migration from one to the other. Major new capability include: 1) connectivity to GSM-MAP in addition to IP and IS-41 networks; 2) new layering with new LAC and MAC architectures for improved service multiplexing and QoS management and efficient use of radio resource; 3) new bands and bandwidths of operation in support of various operator needs and constraints, as well as desire for a smooth and progressive migration to cdma2000; and 4) flexible channel structure in support of multiple services with various QoS and variable transmission rates at up to 1 Mbps per channel and 2 Mbps per user. Given the phenomenal success of wireless services and desire for higher rate wireless services, improved spectrum efficiency was a major design goal in the elaboration of cdma2000. Major capacity enhancing features include: 1) turbo coding for data transmission; 2) fast forward link power control; 3) forward link transmit diversity; 4) support of directive antenna transmission techniques; 5) coherent reverse link structure; and 6) enhanced access channel operation. As users increasingly rely on their cell phone at work and at home for voice and data exchange, the stand-by time and operation-time are essential parameters that can influence customer's satisfaction and service utilization. Another major goal of cdma2000 was therefore to enable manufacturers to further optimize power utilization in the terminal. Major battery life enhancing features include: 1) improved reverse link performance (i.e., reduced transmit power per information bit); 2) new common channel structure and operation; 3) quick paging channel operation; 4) reverse link gated transmission; and 5) new MAC states for efficient and ubiquitous idle time operation. This article provides additional details on those enhancements. The intent is not to duplicate the detailed cdma2000 radio access network specification, but rather to provide some background on the new features of cdma2000 and on the qualitative improvements as compared to the TIA/EIA-95 based systems. The article is focused on the physical layer structure and associated procedures. It therefore does not cover the MAC, LAC, radio resource management [1], or any other signaling protocols in any detail. We assume some familiarity with the basic CDMA concepts used in TIA/EIA-95.