At 5G and beyond networks, accurate localization services and nanosecond time synchronization are crucial to enabling mission-critical wireless communications technologies and techniques such as autonomous vehicles and distributed multiple-input and multiple-output (MIMO) antenna systems. This paper investigates how to improve wireless time synchronization by studying time correction based on the Real-Time Kinematics (RTK) positioning algorithm. Using the multiple Global Navigation Satellite System (GNSS) receiver references and the proposed binary GNSS satellite formation to reduce the effect of the ionosphere and troposphere delays and recede the measurement phase-range and pseudorange errors. As a result, it improves user equipment’s (UE) localization and measures the time difference between the Base Station (BS) and the UE local clocks. The results show that the positioning accuracy has been increased, and a millimetre accuracy has been achieved while attaining the sub-nanosecond time error (TE) between the UE’s and BS local clocks.

The term Tactile Internet broadly refers to a communication network that is capable of delivering control, touch, and sensing/actuation information in real-time. The Tactile Internet is currently a topic of interest for various standardization bodies. The emerging IEEE P1918.1 standards working group is focusing on defining a framework for the Tactile Internet. The main objective of this work is to present the IEEE P1918.1 reference architecture framework for the Tactile Internet. The paper provides an indepth survey of various architectural aspects including the key entities, the interfaces, the functional capabilities, and the protocol stack. A case study has been presented as a manifestation of the architecture. Performance evaluation demonstrates the impact of functional capabilities and the underlying enablers on user-level utility pertaining to a generic Tactile Internet application.

The IEEE “Tactile Internet” (TI) Standards working group (WG), designated the numbering IEEE 1918.1, undertakes pioneering work on the development of standards for the TI. This paper describes the WG, its intentions, and its developing baseline standard and the associated reasoning behind that and touches on a further standard already initiated under its scope: IEEE 1918.1.1 on “Haptic Codecs for the TI.” IEEE 1918.1 and its baseline standard aim to set the framework and act as the foundations for the TI, thereby also serving as a basis for further standards developed on TI within the WG. This paper discusses the aspects of the framework such as its created TI architecture, including the elements, functions, interfaces, and other considerations therein, as well as the novel aspects and differentiating factors compared with, e.g., 5G Ultra-Reliable Low-Latency Communication, where it is noted that the TI will likely operate as an overlay on other networks or combinations of networks. Key foundations of the WG and its baseline standard are also highlighted, including the intended use cases and associated requirements that the standard must serve, and the TI's fundamental definition and assumptions as understood by the WG, among other aspects.

The Tactile Internet will enable users to physically explore remote environments and to make their skills available across distances. An important technological aspect in this context is the acquisition, compression, transmission, and display of haptic information. In this paper, we present the fundamentals and state of the art in haptic codec design for the Tactile Internet. The discussion covers both kinesthetic data reduction and tactile signal compression approaches. We put a special focus on how limitations of the human haptic perception system can be exploited for efficient perceptual coding of kinesthetic and tactile information. Further aspects addressed in this paper are the multiplexing of audio and video with haptic information and the quality evaluation of haptic communication solutions. Finally, we describe the current status of the ongoing IEEE standardization activity P1918.1.1 which has the ambition to standardize the first set of codecs for kinesthetic and tactile information exchange across communication networks.

TV White Spaces (TVWS) has taken a major step forward with the UK regulator Ofcom initiating a pilot of the technology and associated procedures in the UK, and TVWS rules being harmonized at the European level. This paper considers some aspects of our trial within the Ofcom TV White Spaces Pilot, namely, investigation of aggregation in TVWS and the deployment and testing of IEEE 802.11 white space devices that are capable of aggregating up to 4 TV channels, contiguously or non-contiguously. Our trial is the only deployment of these devices, developed at InterDigital in the USA, within the Ofcom TV White Spaces Pilot. This paper discusses the specifics of the InterDigital devices, including their design and capabilities. Further, results are presented highlighting what is possible in TVWS through contiguous aggregation. These results are achieved through per-channel allowed EIRP and capacity analyses based on feedback from a TVWS database within the Ofcom Pilot, using TVWS functionality developed at King's College London. Additional results outline the added benefit of optimal non-contiguous aggregation. Finally, this paper performs a like-for-like comparison of the performance of the InterDigital devices against what is theoretically possible in TVWS through capacity analyses using feedback from the TVWS database.

A few steps from Shakespeare's spiritual home The Globe Theatre in London, the UK regulator Ofcom is formulating its own well-crafted play based on TV White Spaces (TVWS). We have been leading a major trial under the Ofcom TVWS Pilot in the UK, where it is noted that the same approach to TVWS is employed across Europe through the ETSI EN 301 598 Harmonized European Standard. Our trial has led to numerous observations on white space availability, use cases, and achievable performance in TVWS particularly under aggregation scenarios, among other aspects. This paper expands on some of our prior publications highlighting such outcomes and observations, particularly based on real testing within our trial. It draws fundamental conclusions around scenarios in which TVWS could and should be used. For example, it is observed that TVWS is often most appropriate for below-rooftop receiver or indoor scenarios, and for lower-power (e.g., 20 dBm) deployment scenarios which achieve excellent, and far more consistent, usable channel availability than higher-power alternatives. Further, aggregation in TVWS is heavily covered, attempting to match to various example deployment cases mirroring current and future communication systems. Observations are made on radio design under aggregation, particularly for the European TVWS case.

TV White Spaces (TVWS) and associated spectrum sharing mechanisms represent key means of realizing necessary prime-frequency spectrum for future wireless communication systems. We have been leading a major trial of TVWS technology within the Ofcom TV White Spaces Pilot. As one aspect of the work of our trial, we have investigated solutions for aggregation in TVWS and as part of that the performance of InterDigital White Space Devices (WSDs), capable of aggregating a IEEE 802.11 enabled technology for operation in up to 4 TVWS channels, non-contiguously as well as contiguously. This paper reports on some of our assessment of aggregation in TVWS, as well as our assessment of the InterDigital WSDs. It reports on the white space channel availabilities that can be achieved through aggregation, based on a real implementation of a WSD exhaustively testing a large area of England with a high resolution. The considerable benefit that is achieved through allowing non-contiguous aggregation as compared with contiguous-only aggregation is shown. Further, this paper assesses the TCP and UDP throughput performances of the InterDigital WSDs against the number of channels aggregated and received signal powers, in highly controlled scenarios. Statistics on performance of the WSDs for the studied large area of England are derived based on this. These results are compared with theoretical similar WSDs with one major difference that they can only achieve contiguous channel aggregation. Results show almost a doubling of capacity through non-contiguous aggregation with the InterDigital WSDs; this performance benefit would be increased significantly if more than 4 channels were supported for aggregation.

Operating at ultra-high frequency (UHF), TV white space (TVWS) can achieve long-distance communication and good in-building penetration, and has attracted increasing attention of regulators, researchers and stakeholders. This paper explores the potential of TVWS for network provisioning within a cluster of buildings, through a succession of tests. Different transmission distances, from 10m to over 120m, and through multiple layers of walls as well as complex transmission environment imposed by other factors like office and construction facilities, are considered. Further, a compact ultra-wide band (UWB) printed monopole antenna is designed for the client white space terminal, and compared with a commercial directional UHF antenna on the same client. Measurement results show that the in-house compact antenna achieves fast network speed and a high signal-to-interference-plus-noise ratio (SINR), and it is orientation independent.

To underpin the predicted growth of the Internet of Things (IoT), a highly scalable, reliable and available connectivity technology will be required. Whilst numerous technologies are available today, the industry trend suggests that cellular systems will play a central role in ensuring IoT connectivity globally. With spectrum generally a bottleneck for 3GPP technologies, TV white space (TVWS) approaches are a very promising means to handle the billions of connected devices in a highly flexible, reliable and scalable way. To this end, we propose a cognitive radio enabled TD-LET test-bed to realize the dynamic spectrum management over TVWS. In order to reduce the data acquisition and improve the detection performance, we propose a hybrid framework for the dynamic spectrum management of machine-to-machine networks. In the proposed framework, compressed sensing is implemented with the aim to reduce the sampling rates for wideband spectrum sensing. A noniterative reweighed compressive spectrum sensing algorithm is proposed with the weights being constructed by data from geolocation databases. Finally, the proposed hybrid framework is tested by means of simulated as well as real-world data.

TV White Spaces (TVWS) technology allows wireless devices to opportunistically use locally-available TV channels enabled by a geolocation database. The UK regulator Ofcom has initiated a pilot of TVWS technology in the UK. This paper concerns a large- scale series of trials under that pilot. The purposes are to test aspects of white space technology, including the white space device and geolocation database interactions, the validity of the channel availability/powers calculations by the database and associated interference effects on primary services, and the performances of the white space devices, among others. An additional key purpose is to perform research investigations such as on aggregation of TVWS resources with conventional resources and also aggregation solely within TVWS, secondary coexistence issues and means to mitigate such issues, and primary coexistence issues under challenging deployment geometries, among others. This paper provides an update on the trials, giving an overview of their objectives and characteristics, some aspects that have been covered, and some early results and observations.

Cooperative routing and spectrum aggregation are two promising techniques for Cognitive Radio Ad-Hoc Networks (CRAHNs). In this paper, we propose a spectrum aggregation-based cooperative routing protocol, termed as SACRP, for CRAHNs. To the best of our knowledge, this is the first contribution on spectrum aggregation-based cooperative routing for CRAHNs. The primary objective of SACRP is to provide higher energy efficiency, improve throughput, and reduce network delay for CRAHNs. In this regard, we design the MAC and Physical (PHY) layer, and proposed different spectrum aggregation algorithms for cognitive radio (CR) users. We propose two different classes of routing protocols;Class Afor achieving higher energy efficiency and throughput, andClass Bfor reducing end-to-end latency. Based on stochastic geometry approach, we build a comprehensive analytical model for the proposed protocol. Besides, the proposed protocol is compared with the state of the art cooperative and non-cooperative routing algorithms with spectrum aggregation. Performance evaluation demonstrates the effectiveness of SACRP in terms of energy efficiency, throughput, and end-to-end delay.

This paper investigates energy and interference aware Cooperative Routing algorithms in Cognitive Radio Ad-Hoc Networks. Two routing algorithms have been proposed. In Algorithm I, we propose to minimize transmission power based on the rate required, and investigate the total transmission power consumption of the shortest path from source to destination whereby each link on the path is given the option of selecting a relay to further reduce transmission power. In Algorithm II, we consider Primary User (PU) receiver protection by reducing the fractional overlap area of each secondary node with the primary coverage area, and use the average interference probability to optimize route choice again allowing a cooperative relay to be chosen for each link on each possible path. Simulation results show that the proposed Algorithm I can achieve a transmission power saving of up to 30%, while Algorithm II can reduce interference probability for PU receivers by up to 6%.

This paper introduces a transmit beamforming strategy taking into account the positions of primary, secondary victim and intended secondary receivers, to achieve underlay secondary access in multihop cognitive radio networking. The transmit beamforming strategy defines a novel path optimization scheme that deviates from a preselected path given by the routing module, based on local information and according to a relay selection metric. This metric is designed to improve both coexistence with primary/secondary victim receivers and performance of the secondary cognitive network. Simulations compare the proposed strategy with a baseline solution that does not adopt beamforming, and with a strategy that applies beamforming on each hop without modifying the original path. Results show that the proposed strategy is capable of improving coexistence with primary/secondary victims, and highlight that a trade-off exists between the meeting of coexistence constraints and maximisation of secondary network performance.

In spectrum bands where spectrum sharing is allowed by national regulators, radio access technology recognition is an important technique for reducing interference and facilitating cooperation among cognitive radios. Unlicensed users (secondaries) need to be able to differentiate between transmissions of licensed users (primaries) and other unlicensed users. Furthermore, secondaries should only free a band when the licensed primary user starts to transmit. In this regard, secondary users' transmission technology classification will have a vital role for coexistence/cooperation purposes in such shared spectrum bands. For the purpose of this work, a practical testbed made up of software defined radio transceivers and a set of computing units was put together. A classification neural network was trained in a supervised learning method. Testbed results demonstrate the efficiency of the classification in differentiating among different radio access transmissions.

We present results from an 8-day spectrum measurement campaign in the centre of the London metropolis. We analyze results from one of the densest central areas in our campaign from the perspective of spectrum measurements at a very exposed location at the roof of a high building. We present the main results of this measurement campaign in terms of spectrum utilization, powers received, and evolution of the activity among different days. The results presented in this paper here are very close to an upper bound of what one might expect to find in any given radio environment in terms of utilization and received power measurements. In addition to producing valuable measurement data on its own, special attention was given on acquiring comparable datasets with previous measurements campaigns we have conducted to allow direct comparisons with other European cities we have studied. In particular, we show a detailed comparison between the downtown London results against measurements carried out in other cities, quantifying the significantly higher levels of spectrum occupancy in London compared to other locations.

This paper investigates the green or energy efficient operation of cellular access networks through dynamic spectrum and traffic load management techniques. Different energy saving techniques are discussed along with applications in realistic multi-cellular scenarios. The use of base station cooperation is discussed. The outage probability analysis is also discussed for different energy saving techniques in order to satisfy a particular Quality-of-Service (QoS) threshold for different services. The analysis is supported by different base station power consumption models, traffic models, and realistic statistics of different base stations in London, UK. Results show a considerable power saving potential of up to 65% or more in base station power.

This paper investigates the energy savings a cellular operator can achieve in the access network by dynamically offloading users or traffic loads to Wi-Fi networks. The method used to analyze energy savings is presented, followed by detailed simulations using different traffic types. Results show that significant savings of up to 65-70% can be achieved by opportunistically powering down cellular radio network equipment as facilitated by the offloading of users to Wi-Fi.

Dynamic load and spectrum usage management techniques can significantly improve the energy efficiency of mobile communications systems. This paper considers: (i) the opportunistic reallocation of traffic loads between bands to allow radio network equipment in the bands that the traffic is originated from to be powered down, and (ii) the opportunistic selection of more appropriate spectrum based on propagation characteristics to minimize necessary transmission power through improving propagation and/or reducing power leaking into co-channel cells in frequency reuse cases. This paper addresses the simulation of video, FTP and HTTP (web browsing) traffic sources for configurations representing LTE and HSDPA telecommunications networks, and shows that the opportunistic reallocation of users between bands to power down radio equipment achieves a significant saving of 50% or more in from-the-socket power. Furthermore, it shows that the opportunistic reallocation of users/links to minimize transmission power through using more appropriate propagation spectrum leads to a further modest reduction in from-the-socket power consumption.

Various facets of cognitive radio technology have been studied in recent years. However, one possibility that is only thus-far marginally investigated is the ability to perform secondary access at the same time, band and location as ongoing primary transmissions through beamforming to secondary users. Clearly one reason why this has not been at the forefront of research is that it could imply a significant interference to primary users. This paper, however, demonstrates that such an approach is not only feasible, but derives an optimisation problem to constrain interference to primary users while keeping the received signal-to- interference-plus-noise ratio at the secondary users to above a threshold to maintain an acceptable level of quality of service, even taking into account positioning errors. It analyses the described concept and shows good performance against effective beam width increases in secondary transmissions, enacted to improve coverage to account for angular positioning error.

Abstract-In this paper, we propose a dynamic OFDMA based subcarrier/power allocation scheme, which aims to balance the aggregate rate and the achieved TCP throughput of competing TCP flows. The proposed allocation utilizes the theoretical TCP throughput which can be accomplished in the end-to-end path. In doing so, the TCP aware scheme attempts to minimize the gap between the allocated rate and the theoretical upper bound under the system constraints. Such a technique can be of significant importance since due to its popularity, TCP is commonly used for streaming video or other ultimedia applications. Numerical investigations reveal that the proposed approach, provides more balance towards the TCP throughput, and under some considerations significantly increase the fairness among competing TCP flows over end-to-end paths of different characteristics. In addition to that, it also manages to avoid starvation of TCP flows with poor channel conditions.

A plethora of modifications to transmission control protocol (TCP) have recently been proposed, a major aim being to improve its performance over wireless links. Two schools of thought have emerged: the first investigates changes to the transport-layer protocol, whereas the second explores the potential to enhance the characteristics of lower layers to improve the end-to-end performance of TCP. This study focuses on the latter, and, in contrast to most research in this area, which thus-far has concentrated on a single TCP flavour, examines the case where different TCP flavours are competing over a wireless link. To this end, the authors present and assess a cross-layer solution to adapt the coding rate at the link-layer based on the detected TCP flavour, to maximise fairness among TCP flows. Through both analysis and simulation, the authors show that the proposed scheme considerably improves the fairness among different TCP flavours that compete over a wireless link. Furthermore, the proposed approach has minimal detrimental effect on the aggregate throughput of TCP flows.

In fixed worldwide interoperability for microwave access (WiMAX), radio and network planning can be optimised by tuning a cost/revenue function which incorporates the cost of building and maintaining the infrastructure and the effect of the available resources on revenues. Supported throughput typically decreases with larger cells because of the implied greater average distance of users from the base station, although the use of sub-channelisation can keep throughput steady up to a larger radius. Sectorisation can improve the throughput of the cell by facilitating the use of higher order modulation and coding schemes; besides, sectorisation equipment is more expensive, and there is the need for three times more spectrum bandwidth, increasing costs while increasing system capacity by a factor of 3. On a multi-cell level, system capacity is determined by the chosen frequency reuse pattern, K. In this study, under the assumption of a revenue per Mbyte of information transfer somewhere between 0.0025 euro and 0.010 euro, the choice of K=3 or 4 with sectorial cells is preferable to the use of omnidirectional cells with K=7. This study also concludes that a cell radius in the range 1000–1500 m is preferable, corresponding to profit in percentage terms of near the achievable maximum, while keeping costs acceptable.

Cognitive radio is presently being researched as a means to greatly improve spectrum usage efficiency, connectivity and QoS among wireless devices and systems. In parallel, efficient and fair resource allocation strategies are being studied in order to address the requirements of future wireless technologies. In this paper, we assess a novel resource allocation scheme for OFDM systems which aims to maximize performance while limiting received interference at each user to below a defined threshold. We show that our scheme is relevant to cognitive radio, and demonstrate that through our approach, significant power savings can be achieved in wireless systems.

A significant body of recent research has analyzed the problematic behavior of TCP over wireless links, and a plethora of modifications to TCP have been proposed in order to increase its performance in such contexts. Two schools of thought have emerged: the first proposes changes to the end-to- end protocol, while the second explores the potential to enhance lower layers as a means to improve the end-to-end performance of TCP. This paper focuses on the latter, and in contrast to most research in this area, which thus-far has concentrated on a single TCP flavor, examines the case where different TCP flavors are competing over a wireless link. To this end, we present and assess a cross-layer solution that involves the adaptation of lower layer characteristics (i.e., the coding rate) based on the detected TCP flavor, in order to maximize the fairness among TCP flows. Through extensive numerical investigations, we show that the proposed scheme considerably improves the fairness over wireless links among different TCP flavors. Our approach also has a minimal effect on the aggregate throughput of the TCP flows, and in cases where the packet error rate is very low, has a small positive effect on throughput.

A range of flavors of TCP are already in existence, and further flavors are being introduced in order to, for example, cope with the packet loss characteristics of wireless links. Moreover, the proliferation new wireless standards and the relative performance differences among them have been mushrooming in recent years. Given the increasingly heterogeneous nature of the Internet, mechanisms do not usually exist for a server to specifically select an appropriate TCP flavor for each individual download. In this paper, we therefore present and assess a cross-layer solution for a node (e.g. a base-station) to quickly adapt lower-layer characteristics (the coding rate and local ARQ retransmissions threshold) based on the detected TCP flavor, in order to optimize the end-to-end performance of the download for that utilized flavor. We demonstrate that the proposed scheme has considerable potential to improve the overall download throughput, while placing no burden on the server and requiring no changes to existing TCP implementations.

Cognitive wireless system encompass the notion of intelligent network elements and terminals working together to utilize resources in a far more efficient way. The focus of this paper is on the introduction of cognitive functionalities to mobile terminals to enhance their resilience and to assist the optimized selection and auto-configuration of protocols. To fulfill these objectives, we introduce a framework that will facilitate reconfiguration decisions while supporting dynamic and optimal selection, download and replacement of necessary protocol functionalities. Specifically, this paper proposes the interoperation of the Software Download Management module and the Cognitive Self-Healing and -Configuration module, thereby leveraging the outcomes of our previous work. The component-based approach is argued in this paper to facilitate the optimum configuration of the protocol stack to a given environment, based on cognitive orientation schemes. Moreover, we demonstrate that the delay in realizing dynamic replacement of targeted functional components introduces minimum performance overhead to the system.

Spectrum sharing methods, such as secondary spectrum access, are powerful candidates to improve spectrum utilization and efficiency. In this paper, we develop a novel resource allocation scheme for WiMAX networks, which is designed to maximize performance while limiting the received interference at each user. By defining different interference tolerances for different sets of users, the proposed allocation scheme can be exploited in a secondary spectrum access scenario where two WiMAX operators, one as the primary operator and the other one as the secondary operator, are using a shared band. The primary system benefits either by charging the secondary system for the use of its resources, or by some form of reciprocal arrangement allowing it to use the secondary system's licensed bands when needed. Numerical results show our resource allocation approach to achieve an excellent fairness, while incurring only a slight reduction in system throughput compared with the theoretical upper limit of opportunistic scheduling.

Efficient and fair resource allocation strategies are being extensively studied in current research in order to address the requirements of future wireless applications. A novel resource allocation scheme is developed for orthogonal frequency-division multiplexing (OFDM) networks designed to maximise performance while limiting the received interference at each user. This received interference is in essence used as a fairness metric; moreover, by defining different interference tolerances for different sets of users, the proposed allocation scheme can be exploited in various cognitive radio scenarios. As applied to the scheme, the authors investigate a scenario where two cellular OFDM-based networks operate as primary and secondary systems in the same band, and the secondary system benefits by accessing the unused resources of the primary system if additional capacity is required. The primary system benefits either by charging the secondary system for the use of its resources or by some form of reciprocal arrangement allowing it to use the secondary system's licenced bands in a similar manner, when needed. Numerical results show our interference-limited scheduling approach to achieve excellent levels of efficiency and fairness by allocating resources more intelligently than proportional fair scheduling. A further important contribution is the application of sequential quadratic programming to solve the non-convex optimisation problems which arise in such scenarios.

In this paper, we discuss the development of a Software Download Management (SDM) module, envisioned to handle the implications and associated operations of downloads for mobile terminal reconfiguration. We highlight the SDM operations in the pre-, during-, and post-download phases, and some emphasis is also placed on the transport-layer decision making capabilities of the SDM. An important emerging capability is mass-reconfiguration, involving the alteration of common functionalities in many terminals concurrently. Relevant scenarios here might include the adaptation of a protocol or codec, an upgrade of an operating system capability, or indeed a change in network configuration which requires a large number of terminals to be adapted accordingly. A particular emphasis is also therefore on one-to-many download functionalities.

Transmission control protocol (TCP), the almost universally used reliable transport protocol in the Internet, has been engineered to perform well in wired networks where packet loss is mainly due to congestion. TCP throughput, however, degrades over wireless links, which are characterized by a high and greatly varying bit error rate and by intermittent connectivity. Over such wireless links, the performance achieved by TCP can be improved through the use of cross-layer algorithms at the link-level, which interact with the TCP state machine. In this paper, a TCP-aware dynamic ARQ algorithm is therefore proposed, which utilizes TCP timing information to prioritize ARQ packet retransmissions. Numerical investigation of the proposed algorithm demonstrates the performance improvements that can be attained through this approach, in comparison with TCP-agnostic link-layer approaches.

Cognitive radio is certain to transform our traditional radio resource allocation regimes. Through cognitive radio, better spectrum efficiency can be leveraged by radios intelligently altering their radio resource usages dependent on locally available information about radio conditions. A significant challenge for cognitive radio, however, is awareness of these local radio conditions. One crude solution is for the radio to periodically scan the complete spectrum band over which cognition in radio resource usages can apply. Such an operation would be time-consuming and wasteful of power, and ultimately would be entirely impractical. In this paper, we therefore propose the concept of a resource awareness channel (RAC)-a single universally available channel on a fixed frequency, on which information about resource usage is conveyed by all radios using the cognitive radio spectrum band. This allows cognitive radios that want to alter their transmission resources to make an informed decision about the practicality or these prospective changes in terms or interference for the system as a whole, simply by listening to the RAC. We analyse the performance or this proposed RAC concept, and show it to be practical even in areas that are highly populated by radios

To facilitate upgrades to software, firmware, or FPGA functionality in terminals, over-the-air downloads can provide in-the-field solutions. For mobile terminals, over-the-air downloads provide a security-conscious option due to the ubiquitous availability of the radio interface as they guarantee that the upgrade will be performed if the terminal is to be allowed to use the operator's network. Ensuring system stability through urgent upgrades, this provides a degree of certainty which has hitherto not been present in other forms of downloads. In this paper, we concentrate on mass-upgrades, as might apply to an OS, codec, or urgent security upgrade in a number of terminals concurrently. We investigate relative performances of a range of one-to-many reliable data transfer techniques. Based on these performances, we introduce a unified protocol, able to dynamically switch between the one-to-many download methods many-unicast, multicast, and broadcast during a file download, thereby achieving enhanced performance of the mass-upgrade download from both user and system perspectives, as well as from the perspectives of other users in the network which have to share the same resources as the one-to-many download.

A number of methods have been suggested for reducing the risk of feedback implosion in reliable multicast. In tandem with the use of negative acknowledgements (NAKs), one of the most effective of these is the router-assist function of feedback aggregation. Feedback aggregation has hitherto only applied to conventional per-packet NAKs; however, it would be far more efficient if used in conjunction with bitmapped feedback. Hence in this paper, we describe a scheme for aggregation of bitmapped NAK feedback packets, and we show its simplicity, practicality and interoperability with basic router functions. We present some useful analysis of the scheme, which might also apply to NAK aggregation in general under certain circumstances. Finally, we perform simulations showing the benefits of the scheme to uplink traffic load.

The Universal Mobile Telecommunications System (UMTS) is already realizing its ability to provide a rich tapestry of media to mobile users, including audio, video, data, and a combination of these termed `multimedia'. The high speed downlink packet access (HSDPA) solution within UMTS can greatly enhance bit rates on the downlink; however, given HSDPA using a shared channel, carefully considered scheduling of packet transmissions at HSDPA-enabled base stations is important. Hence in this paper, we present an effective inter-user and inter-class multimedia packet scheduling algorithm for HSDPA. We optimize the traffic class weightings that are central to the packet prioritization approach of the scheduling algorithm. Finally, we show our optimized algorithm to perform well through simulations of complex multimedia sessions being concurrently transmitted to users over the HSDPA link in a single cell

Mobile ad-hoc networks (MANETs) potentially satisfy a long-standing dream of mobile users: networking without limitations. A significant challenge in MANETs is radio resource allocation, where it is assumed that the available unregulated bandwidth over which such systems can operate is limited, hence resource allocation should be efficient and dynamically reactive to resource clashes due to node mobility. Subject to this consideration, we propose a novel hierarchical radio resource allocation scheme to operate in MANETs, able to distribute resources between nodes using a number of radio access technologies acting in parallel. The use of a hierarchy is shown to assist in the allocation of radio access functions in constituent parts (e.g. FDMA, TDMA, CDMA etc), and to help provide efficient operation of resource allocation schemes by aiding functions such as frequency reuse.