Showing papers by "Barry G. Evans published in 2013"

A Survey of Self Organisation in Future Cellular Networks

Abstract: This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks.

Cognitive radio scenarios for satellite communications: The CoRaSat approach

Abstract: This paper presents initial results of the recently kicked-off FP7 ICT STREP project “CoRaSat” (Cognitive Radio for Satellite Communications) [1]. Focus is put on the preliminary identification of the scenarios which are suitable for the applicability of Cognitive Radio technology over Satellite Communications (SatCom). The considered frequency bands include Ka-band, Ku-band, C-band and S-band, where regulatory and coordination constraints exist. An initial mapping of broadband and narrowband SatCom use cases on each identified scenario is also provided. Moreover, several challenges associated to the applicability of Cognitive Radio over SatCom in the identified scenarios are presented, which form the basis of the market/business, regulatory, standardization and technological framework of CoRaSat. Furthermore, ongoing and future work of the CoRaSat project is outlined.

Comparison of reliability, delay and complexity for standalone cognitive radio spectrum sensing schemes

Abstract: The ability to reliably and autonomously identify unused frequency bands plays an extremely important role in cognitive radio networks. Relying on the spectrum sensing, ongoing licensed operation must not be compromised and the secondary spectrum usage efficiency should be maintained. Thus, it is critical to ensure that the confidence level of the estimated signal status satisfies the primary user's requirement, while keeping the delay and computational complexity to a minimum. This study provides a comprehensive comparison in terms of performance, reliability and complexity of standalone sensing schemes for various cognitive radio application areas. The authors first give some new results on reliability performance, and then evaluate the sensing time required to achieve the target performance. Finally, the authors compare the computational complexity of various sensing approaches by calculating the number of arithmetic operations required by each approach.

Irregular beam sizes and non-uniform bandwidth allocation in HTS multibeam satellite systems

Abstract: Current HTS multibeam satellite systems assume a uniform offered traffic per beam, but it is foreseen that future traffic demands will be highly uneven over the coverage area. Then imbalances result in some user beams being overprovisioned whilst others are under provisioned resulting in lower satisfaction for user traffic demands. One of the major challenges in designing a future broadband satellite system is how to increase the operators revenue and cope with the uneven traffic demands simultaneously. In the literature, it has been proposed to overcome these imbalances either by applying non-uniform bandwidth distribution (in the frequency domain or beam hopping in the time domain) or by engineering the beam sizes such as to balance the traffic demands over the beams. In this paper, we propose a joint optimisation of non-uniform bandwidth allocation and non-uniform beam sizes to better match the traffic demands, increase the total useful capacity and utilise the limited space resources more efficiently. The proposed method is applied for a hypothetical traffic scenario over Europe, where a maximum number of 200 user beams is assumed. Only the forward direction is studied herein. The DVB-S2 air interface is considered. A transparent payload is considered, where the user links operate in Ka-band. The results of the forward link are presented and compared with a uniform design and a case with only non-uniform bandwidth allocation. The improvements due the joint optimisation are presented, and the implications to the system design are discussed.

Gateway Diversity via Flexible Resource Allocation in a Multibeam SS-TDMA System

Abstract: This letter addresses the problem of gateway diversity for a future broadband multibeam satellite system. A system architecture which employs a Satellite Switched TDMA payload is considered in an effort to introduce more flexibility and reduce the total number of gateways in the system while minimising the capacity losses and ensuring the necessary feeder link availability. Herein, an architecture and a framework based on assignment of a number of time slots that each gateway uplink is connected to a user beam is proposed allowing a match to the user demands with the offered capacity of the gateways. Three resource allocation schemes are proposed, which take into account the uplink propagation conditions and the users demands. One of the proposed schemes attempts to maximise the throughput and the others attempt to balance the traffic amongst beams, are tested under a scenario where four feeder uplinks are used to serve four user beams. Rain models are applied to generate precipitation fades, and the schemes performance is examined in terms of loss of capacity.

Irregular beam sizes and non-uniform bandwidth allocation in HTS

Abstract: Current HTS multibeam satellite systems assume a uniform offered traffic per beam, but it is foreseen that future traffic demands will be highly uneven over the coverage area. Then imbalances result in some user beams being overprovisioned whilst others are under provisioned resulting in lower satisfaction for user traffic demands. One of the major challenges in designing a future broadband satellite system is how to increase the operators revenue and cope with the uneven traffic demands simultaneously. In the literature, it has been proposed to overcome these imbalances either by applying non-uniform bandwidth distribution (in the frequency domain or beam hopping in the time domain) or by engineering the beam sizes such as to balance the traffic demands over the beams. In this paper, we propose a joint optimisation of non-uniform bandwidth allocation and non-uniform beam sizes to better match the traffic demands, increase the total useful capacity and utilise the limited space resources more efficiently. The proposed method is applied for a hypothetical traffic scenario over Europe, where a maximum number of 200 user beams is assumed. Only the forward direction is studied herein. The DVB-S2 air interface is considered. A transparent payload is considered, where the user links operate in Ka-band. The results of the forward link are presented and compared with a uniform design and a case with only non-uniform bandwidth allocation. The improvements due the joint optimisation are presented, and the implications to the system design are discussed.

Optimal power allocation for MIMO-OFDM based Cognitive Radio systems with arbitrary input distributions

Abstract: In Cognitive Radio (CR) systems, the data rate of the Secondary User (SU) can be maximized by optimizing the transmit power, given a threshold for the interference caused to the Primary User (PU). In conventional power optimization algorithms, the Gaussian input distribution is assumed, which is unrealistic, whereas the Finite Symbol Alphabet (FSA) input distribution, (i.e., M-QAM) is more applicable to practical systems. In this paper, we consider the power optimization problem in multiple input multiple output orthogonal frequency division multiplexing based CR systems given FSA inputs, and derive an optimal power allocation scheme by capitalizing on the relationship between mutual information and minimum mean square error. The proposed scheme is shown to save transmit power compared to its conventional counterpart. Furthermore, our proposed scheme achieves higher data rate compared to the Gaussian optimized power due to fewer number of subcarriers being nulled. The proposed optimal power algorithm is evaluated and compared with the conventional power allocation algorithms using Monte Carlo simulations. Numerical results reveal that, for distances between the SU transmitter and the PU receiver ranging between 50m to 85m, the transmit power saving with the proposed algorithm is in the range 13-90%, whereas the rate gain is in the range 5-31% depending on the modulation scheme (i.e., BPSK, QPSK and 16-QAM) used.

Optimum Power Allocation for OFDM Based Cognitive Radio Systems with Arbitrary Input Distributions

Abstract: In the literature, optimal power allocation assuming Gaussian input has been evaluated in OFDM based Cognitive Radio (CR) systems to maximize the capacity of the secondary user while keeping the interference introduced to the primary user band within tolerable range. However, the Gaussian input assumption is not practical and Finite Symbol Alphabet (FSA) input distributions, i.e., M-QAM are used in practical systems. In this paper, we consider the power optimization problem under the condition of FSA inputs as used in practical systems, and derive an optimal power allocation strategy by capitalizing on the relationship between mutual information and minimum mean square error. The proposed scheme is shown to save transmit power in a CR system compared to its conventional counterpart, that assumes Gaussian input. In addition to extra allocated power, i.e., power wastage, the conventional power allocation scheme also causes nulling of more subcarriers, leading to reduced transmission rate, compared to the proposed scheme. The proposed optimal power algorithm is evaluated and compared with the conventional algorithm assuming Gaussian input through simulations. Numerical results reveal that for interference threshold values ranging between 1mW to 3mW, the transmit power saving with the proposed algorithm is in the range between 55-75%, 42-62% and 12-28%, whereas the rate gain is in the range between 16.8-12.4%, 13-11.8% and 3-5.8% for BPSK, QPSK and 16-QAM inputs, respectively.

A Cellular Automata Approach towards Self Organisation in Wireless Cellular Networks

Abstract: This paper gives an introduction to a key tool that can help provide various self organised solutions in wireless cellular networks. We begin by describing the need for self organised networks and the challenges associated with it. An introduction to cellular automata theory is then given with an easy to follow example. We provide an analysis of such solutions and discuss its stability and convergence criterion. Finally, we formulate a specific problem for Inter-Cell Interference Coordination (ICIC), describing how the cellular automata approach can be applied to achieve ICIC. In addition, we discuss the prospective use case of applying cellular automata in achieving energy efficiency in heterogeneous networks. This paper will serve as a guide for anyone willing to develop self organising solutions in wireless cellular networks. © VDE VERLAG GMBH.

Designing a QoE aware intelligent home gateway for future smart homes

Abstract: The future smart homes will be equipped with a variety of devices that are connected to the internet to provide a multitude of services to consumers. An adequate and reliable broadband connection is a must to support smart home services such as E-Health, home automation, smart energy management and seamless usage of multimedia. To realize such advanced networked applications, especially for households in geographical areas that are unserved or underserved with broadband connectivity, the European Union's 7th Framework Programme funded the BATS integrated project (Broadband Access via integrated Terrestrial and Satellite systems). The main objective of the BATS project is to integrate satellite and terrestrial networks to provide broadband connectivity to households through a home gateway. The envisaged home gateway is intelligent such that it is able to determine in real time the QoS requirements of applications and accordingly make routing decisions to optimize Quality of Experience (QoE) of the end user. In this paper we introduce future smart home applications and devices that would benefit from the BATS concept and discuss the different aspects of designing an intelligent home gateway that is both QoE aware and standard compliant.

Results of simultaneous low elevation Ku-band propagation effects at two sites in southern England

Abstract: This paper reports on satellite beacon measurements at 12.7 GHz from late October 2010 until the end of June 2012 at two geographically separated Arqiva Teleport sites in Southern England in order to obtain propagation data to be used in operational decision making and improvement of the scientific understanding of such effects. These sites operate at very low elevation angles 4.1 and 5.3 degrees and therefore experience significant propagation effects. Measurements are on-going to achieve meaningful long term statistics, however there is value in comparing the results obtained at both sites over the common period of measurement data to date approximately 20 months. The measurements are performed at 1/2 second intervals and statistical analysis applied. A primary objective of this work is to assess the influence of tropospheric scintillation and consequently the paper will focus on this with the addition of some lesser material on rain fade effects. The measurements and analysis have been performed as a collaborative effort between Arqiva and staff who work at the University of Surrey. It is emphasised that the primary objective of this work is to assess the influence of tropospheric scintillation and rain attenuation from an operational perspective and to a lesser extent from an academic viewpoint.

Frequency sharing between satellite and terrestrial in the 2GHZ MSS band

Abstract: Simultaneous frequency sharing in integrated satellite and terrestrial networks can help to achieve increased network capacity based on an efficient reuse of frequency resources in a way that minimizes interference. In this paper, we investigate the use of the 2GHz MSS frequency allocation for satellite and terrestrial mobile services based on LTE. Results show that uplink frequency sharing is not feasible due to the predominant terrestrial interference into the satellite service. On the other hand, downlink frequency sharing is feasible for pedestrian microcells and vehicular macrocells but not for the wider rural cells. In this regard, a satellite multimedia broadcast service can be deployed simultaneously with twoway terrestrial mobile service in urban and suburban areas. Furthermore, dynamic radio resource allocation combined with interference coordination can be used to optimize performance throughout the integrated network.

Energy-effcient dynamic deployment architecture for future cellular systems

Abstract: There is a need to develop energy-efficient adaptive systems for future telecommunication networks. While traffic varies at different times, the power consumption of the radio access network does not scale with it effectively. To make significant energy savings, a dynamic deployment approach is required to allow the system to operate in an energy-efficient mode with respect to traffic load. By deploying small base stations within the area of a conventional macro station, we are able to reduce energy consumption while maintaining QoS. This paper proposes an energy-efficient dynamic deployment architecture based on fuzzy-logic. The algorithm aids in the decision of the architecture layout deployment. Moreover, by implementing the proposed adaptive energy-efficient algorithm, the network gains flexibility that can increase coverage or throughput throughout the same network by adapting its operation to source its requirements better and change them when new requirements arise.

Collaborative radio resource allocation for the downlink of multi-cell multi-carrier systems

Abstract: This study investigates collaboration among neighbouring base stations for the downlink of multi-carrier cellular networks, in the absence of a centralised control unit, which is a defining characteristic of future wireless networks. The authors propose a novel scheme for collaboration in resource allocation among a cluster of three neighbouring base stations. In this scheme, the results of an initial calculation are shared among neighbouring cells, then the scheduling decision is made locally and independently by each cell. This scheme does not require complex and iterative calculation. The information is exchanged only once during each scheduling epoch, which results in reduced overhead on the backhaul links. The scheme is implemented in a distributed manner. Simulation-based performance analysis demonstrates effectiveness of the proposed collaborative resource allocation scheme among the neighbouring base stations for multi-carrier systems, particularly for the users located near the cell edges.

Dynamic resource allocation for a future satellite system employing an time switched payload

Abstract: The continuous increase of traffic demands for satellite networks has resulted in the consideration and use of higher bands such as Ka (20/30 GHz) and Q/V (40/50 GHz) bands. Additionally, it is foreseen that the traffic demands will be unevenly distributed. Recent studies 1 argue that more than 200 user beams at Ka band and more than 25 active gateways at Q/V bands are required in order to satisfy demands by 2020. The non-uniform traffic demand distribution can be accommodated with flexible bandwidth allocation (Beam Hopping). But considering that the feeder links operate at Q/V bands, they are subject to severe precipitation fades. As each gateway will carry very high capacity, it is essential to ensure very high availabilities for the feeder links. In an effort to reduce the total number of gateways in the system, the concept of Smart gateways has emerged which dictates that a user beam is served by a pool of gateways instead of just one. In this paper, we consider that each user beam is served by a number of gateways via time multiplexing. This architecture is consistent with beam hopping (on the user side) and the payload architecture resembles the already implemented Satellite Switched TDMA (SS-TDMA). The rationale for this system is to introduce more flexibility not only to the user side but also in the feeder links, and reduce the total number of gateways in the system while minimising the capacity losses and ensuring the necessary feeder link availability. A framework which takes into account the atmospheric conditions of each gateway and the traffic demands of the beams, decides the number of time slots that each gateway uplink is connected to a user beam is proposed allowing a match to the instantaneous user demands with the offered capacity of the gateways. The scheduling of the switching matrix is discussed, as now it depends also on the predefined beam hopping sequence. The results are presented for a hypothetical scenario, and the improvements provided by this architecture are presented along with the impact on the system design.

Cognitive Radio Systems: Multicarrier Modulation and Power Allocation

Abstract: The rapid development of modern communication services results in high data rate requirements from the end user. It is challenging to meet high data rate requirements because of prevailing issues such as spectrum scarcity and spectrum underutilization due to fixed spectrum assignment policy. Cognitive Radio (CR), being the enabler of dynamic spectrum management techniques, has the capability to tackle these issues by proficiently implementing spectrum sharing schemes using Multicarrier Modulation (MCM) techniques. In CR system, where the Primary User (PU) and the Secondary User (SU) co-exist in the same frequency band, mutual interference (i.e., from SU to PU and vice versa) is a limiting factor on the achievable capacity of both the PU and the SU. Power allocation in MCM based CR systems aims to dynamically control the transmit power on each subcarrier of the SU in order to reduce the mutual interference. Furthermore, combining multiple antennas with MCM is regarded as a very attractive solution for the CR communications to effectively enhance data rate without demanding additional bandwidth and transmit power.

Dynamic resource allocation for a future satellite system employing an SS-TDMA payload

Abstract: The continuous increase of traffic demands for satellite networks has resulted in the consideration and use of higher bands such as Ka (20/30 GHz) and Q/V (40/50 GHz) bands. Additionally, it is foreseen that the traffic demands will be unevenly distributed. Recent studies 1 argue that more than 200 user beams at Ka band and more than 25 active gateways at Q/V bands are required in order to satisfy demands by 2020. The non-uniform traffic demand distribution can be accommodated with flexible bandwidth allocation (Beam Hopping). But considering that the feeder links operate at Q/V bands, they are subject to severe precipitation fades. As each gateway will carry very high capacity, it is essential to ensure very high availabilities for the feeder links. In an effort to reduce the total number of gateways in the system, the concept of Smart gateways has emerged which dictates that a user beam is served by a pool of gateways instead of just one. In this paper, we consider that each user beam is served by a number of gateways via time multiplexing. This architecture is consistent with beam hopping (on the user side) and the payload architecture resembles the already implemented Satellite Switched TDMA (SS-TDMA). The rationale for this system is to introduce more flexibility not only to the user side but also in the feeder links, and reduce the total number of gateways in the system while minimising the capacity losses and ensuring the necessary feeder link availability. A framework which takes into account the atmospheric conditions of each gateway and the traffic demands of the beams, decides the number of time slots that each gateway uplink is connected to a user beam is proposed allowing a match to the instantaneous user demands with the offered capacity of the gateways. The scheduling of the switching matrix is discussed, as now it depends also on the predefined beam hopping sequence. The results are presented for a hypothetical scenario, and the improvements provided by this architecture are presented along with the impact on the system design.