This paper presents a joint resource allocation and network slicing framework for hybrid radio frequency (RF) and visible light communication (VLC) systems based on a proportional-fairness (PF) objective. The proposed approach formulates a convex optimization problem that jointly allocates bandwidth resources across multiple slices and access technologies to balance aggregate throughput and user fairness. A relaxed PF solution is first derived via projected gradient optimization, followed by two practical rounding strategies, a simple threshold-based method and a greedy assignment heuristic that produce integer allocations with low complexity. Simulation results for a 20 MHz hybrid RF/VLC system (10 MHz per band) demonstrate that the proposed PF-based allocation achieves aggregate sum-rates of approximately 450–500 Mbps with Jain’s fairness indices greater than 0.9, thus outperforming static and rounding baselines by 10–15% in throughput while maintaining high fairness. The analysis is further extended to asymmetric RF/VLC bandwidth conditions, demonstrating that the proposed PF-based slicing maintains high fairness while scaling throughput effectively. These results confirm that the PF formulation effectively captures the throughput fairness trade-off and provides near-optimal slicing performance under realistic indoor bandwidth and power constraints.

To meet the needs of connected vehicles, the wireless devices deployed in vehicles and on roadside infrastructure may need access to more spectrum than is allocated today. This paper proposes a new approach that would allow connected vehicle devices using C-V2X technology (and successors such as NR-V2X) to share spectrum with Wi-Fi and other kinds of unlicensed devices, thereby gaining access to additional spectrum. The proposed approach requires no change in Wi-Fi technology, and only modest changes in C-V2X. Simulation results show that it is possible to protect the quality of service of both C-V2X and Wi-Fi communications, while employing sharing that greatly improves spectrum efficiency. This paper describes steps that spectrum regulators such as the Federal Communications Commission and standards bodies such as IEEE 802.11 and 3GPP could take to advance this spectrum-sharing approach. One place this approach could be used is adjacent to the Intelligent Transportation System (ITS) band, where it could help meet the spectrum needs of both connected vehicles and Wi-Fi 6.

This work aims at evaluating the impact of considering Ultra High Frequency (UHF), Super High Frequency (SHF) and millimetre wavebands (mmWaves), in the optimization of economic trade-off of small cell networks, by considering different path loss models. The two slope urban micro Line-of-Sight (UMiLoS) model for UHF/SHF bands (from the ITU-R 2135 Report) is compared with the modified Friis propagation model for frequencies above 24 GHz. The variation of the carrier-to-noise-plus-interference ratio with the coverage distance is assessed, and its influence in the radio and network optimization process is explored by means of the study of the variation of the equivalent supported throughput at the 2.6, 3.5, 28, 38, 60 and 73 GHz frequency bands. The observed higher supported throughput for the longest cell lengths at the UHF/SHF bands (compared to the millimetre wavebands), is mostly due to the reduction caused by the behaviour of their two-slope propagation model. By assuming null fixed costs (license) for the millimetre wavebands and equal values of the fixed cost at 2.6 and 3.5 GHz, we have analysed the economic trade-off of these pico-cellular networks in regular cellular topologies. We have learned that, on the one hand, at 60 GHz, owing to the oxygen absorption excess, there is an optimum of the revenue in percentage terms for values of the cell length, R, equal to 35 m and a decreasing behaviour after this optimum value, while for the 28, 38 and 73 GHz bands the profit starts to decrease after R ≈ 15 m. On the other hand, in the UHF/SHF bands, the profit is very low for the shortest Rs, and starts to increase at a distance equal to the ratio between the break-point distance and the co-channel reuse factor and achieves maxima for values of R equal to circa 200 and 240 m, at 2.6 and 3.5 GHz, respectively.

Traditionally, a cell phone remains on a single primary mobile network operator (MNO) as long as it is available, and uses another MNO only when the primary is unavailable and a roaming agreement exists. Multi-network access (MNA), where a cell phone can use any one of multiple MNOs at any point in space and time, can greatly increase cellular network capacity. This paper investigates how much MNA can improve cellular network capacity in the context of a multi-operator mobile virtual network operator (MO-MVNO), such as Google's Project Fi, and explores how the capacity gain varies with the MNOs' resource allocation scheme, and the MO-MVNO's market share and MNO selection algorithm. Simulations show that MNA can expand cellular network capacity by as much as 80% without additional spectrum or infrastructure. Resource allocation schemes affect both total capacity gain and how the gain is shared among operators. We also show that an MNO selection algorithm that is rational for an individual MO- MVNO subscriber can hurt the overall performance of both the MO-MVNO and MNOs.

Vehicular networks have the potential to improve road safety using dedicated short-range communications (DSRC) technology, but substantial investment in roadside units (RSUs) is required. DSRC can be simultaneously used for safety and non-safety applications. If local governments share RSUs deployed for safety or smart streetlights with other kinds of service providers, then the respective costs can also be shared, thereby reducing costs for the government. We estimate that government could save about one-fifth of the nationwide cost of safety RSUs in the U.S. if they are shared with Internet service providers. We also estimate an increase in social welfare from sharing safety RSUs. In the case of sharing smart streetlights, we find that nationwide benefits could be up to one-third higher than with sharing of safety RSUs. The prices that maximize government savings and social welfare may differ. However, we find that maximizing government savings results in near-optimal social welfare. The benefits of sharing would increase significantly if the Internet traffic or DSRC penetration grow over time, as expected.

Mobility and multihoming have become the norm in Internet access, e.g. smartphones with Wi-Fi and LTE, and connected vehicles with LTE and DSRC links that change rapidly. Mobility creates challenges for active session continuity when provider-aggregatable locators are used, while multihoming brings opportunities for improving resiliency and allocative efficiency. This paper proposes a novel migration protocol, in the context of the eXpressive Internet Architecture (XIA), the XIA Migration Protocol. We compare it with Mobile IPv6, with respect to handoff latency and overhead, flow migration support, and defense against spoofing and replay of protocol messages. Handoff latencies of the XIA Migration Protocol and Mobile IPv6 Enhanced Route Optimization are comparable and neither protocol opens up avenues for spoofing or replay attacks. However, XIA requires no mobility anchor point to support client mobility while Mobile IPv6 always depends on a home agent. We show that XIA has significant advantage over IPv6 for multihomed hosts and networks in terms of resiliency, scalability, load balancing and allocative efficiency. IPv6 multihoming solutions either forgo scalability (BGP-based) or sacrifice resiliency (NAT-based), while XIA's fallback-based multihoming provides fault tolerance without a heavy-weight protocol. XIA also allows fine-grained incoming load-balancing and QoS-matching by supporting flow migration. Flow migration is not possible using Mobile IPv6 when a single IPv6 address is associated with multiple flows. From a protocol design and architectural perspective, the key enablers of these benefits are flow-level migration, XIA's DAG-based locators and self-certifying identifiers.

Vehicular networks have the potential to improve road safety using Dedicated Short Range Communications (DSRC) technology, but substantial investment in roadside units (RSUs) is required. DSRC can be simultaneously used for safety and non-safety applications. If local governments share RSUs deployed for safety or smart streetlights with other kinds of service providers, then the respective costs can also be shared, thereby reducing costs for the government. We estimate that government could save about one fifth the nationwide cost of safety RSUs in the U.S. if they are shared with Internet service providers. We also estimate an increase in social welfare from sharing. The prices that maximize government savings and social welfare may differ. However, we find that maximizing government savings results in near-optimal social welfare.

Vehicular mesh networks can be used to carry Internet data traffic for mobile users. We use data from a real vehicular network that is operating in Portugal to estimate the relationship between network throughput and offered load of Internet traffic, quantity of vehicles, quantity of infrastructure and the use of Request-to-Send/Clear-to- Send (RTS/CTS) handshaking. We show that achievable throughput remains close to its maximum even for high levels of offered load per vehicle or high density of vehicles, so congestion control mechanisms in mesh networks can effectively prevent throughput from collapsing as these factors increase over time. This achievable throughput can be increased with the deployment of additional roadside infrastructure that serves as a gateway to the Internet, although the throughput gain per gateway decreases as more are added. Deploying these gateways is cost-effective, i.e. economic benefits of the resulting throughput exceed costs of infrastructure, when vehicle density is sufficiently high. We also find that use of RTS/CTS decreases achievable throughput in this scenario.

This paper considers gray-space spectrum sharing when rotating radars are primary spectrum users, and multiple cells from one or more cellular networks are secondary users. A cellular network may share spectrum to supplement its dedicated spectrum, or provide a broadband hotspot service. A secondary device is allowed to transmit as long as cumulative interference is not harmful to nearby radars, probably because no radar is pointing its directional antenna at the device at this moment. This paper presents mechanisms that would support such sharing, and quantifies performance when spectrum is considered 100% utilized under traditional spectrum management. It is shown that the sharing allows cells to sustain significant mean data rates. For example, if 5% of a cellular network's cells need more capacity than dedicated spectrum can provide, a cell can get almost 1.2 bps/Hz on average from shared spectrum. By evaluating quality of service, it is found that shared spectrum could be used efficiently for applications such as non-interactive video streaming, peer-to-peer file sharing, large file transfers, and web browsing, but not for applications such as real-time transfers of small files, and VoIP.

This paper considers opportunistic gray-space primary-secondary spectrum sharing when the primary is a rotating radar. We assume that a secondary device is allowed to transmit when its interference does not exceed the radar's tolerable level, probably because the radar's directional antenna is pointing elsewhere, in contrast to current approaches that prohibit secondary transmissions if radar signals are detected at any time. The secondary system is a cellular system using the shared spectrum in some but not all of its cells; this may occur when the cellular system needs the shared spectrum to supplement its dedicated spectrum, or for a broadband hotspot service. It is shown that, even fairly close to the radar, extensive secondary transmissions are possible, although subject to interruptions as the radar rotates. For example, with 20% of the cells transmitting in the shared spectrum, on average the cellular system can achieve a data rate close to the one obtained in dedicated spectrum, even at less than 9% of the distance that secondary transmissions will not cause harmful interference in the radar's main beam. By evaluating quality of service, it is shown that spectrum shared with radar is attractive for applications that generate much of the traffic on the Internet, including video streaming, peer-to-peer file sharing, downloads of large files, and web browsing, but not for an application sensitive to interruptions, like VoIP.

This paper considers opportunistic primary-secondary spectrum sharing when the primary is a rotating radar. A secondary device is allowed to transmit when its resulting interference will not exceed the radar's tolerable level, in contrast to current approaches that prohibit secondary transmissions if radar signals are detected at any time. We consider the case where an OFDMA based secondary system operates in non-contiguous cells, as might occur with a broadband hotspot service, or a cellular system that uses spectrum shared with radar to supplement its dedicated spectrum. It is shown that even fairly close to a radar, extensive secondary transmissions are possible, although with some interruptions and fluctuations as the radar rotates. For example, at 27% of the distance at which secondary transmissions will not affect the radar, on average, the achievable secondary data rates in down- and upstreams are around 100% and 63% of the one that will be achieved in dedicated spectrum, respectively. Moreover, extensive secondary transmissions are still possible even at different values of key system parameters, including cell radius, transmit power, tolerable interference level, and radar rotating period. By evaluating quality of service, it is found that spectrum shared with radar could be used efficiently for applications such as non-interactive video on demand, peer-to-peer file sharing, file transfers, automatic meter reading, and web browsing, but not for applications such as real-time transfers of small files and VoIP.

Traditionally, interference protection is guaranteed through a policy of spectrum licensing, whereby wireless systems get exclusive access to spectrum. This is an effective way to prevent interference, but it leads to highly inefficient use of spectrum. Cognitive radio along with software radio, spectrum sensors, mesh networks, and other emerging technologies can facilitate new forms of spectrum sharing that greatly improve spectral efficiency and alleviate scarcity, if policies are in place that support these forms of sharing. On the other hand, new technology that is inconsistent with spectrum policy will have little impact. This paper discusses policies that can enable or facilitate use of many spectrum-sharing arrangements, where the arrangements are categorized as being based oncoexistenceorcooperationand assharingamongequalsorprimary-secondarysharing. A shared spectrum band may be managed directly by the regulator, or this responsibility may be delegated in large part to a license-holder. The type of sharing arrangement and the entity that manages it have a great impact on which technical approaches are viable and effective. The most efficient and cost-effective form of spectrum sharing will depend on the type of systems involved, where systems under current consideration are as diverse as television broadcasters, cellular carriers, public safety systems, point-to-point links, and personal and local-area networks. In addition, while cognitive radio offers policy-makers the opportunity to improve spectral efficiency, cognitive radio also provides new challenges for policy enforcement. A responsible regulator will not allow a device into the marketplace that might harm other systems. Thus, designers must seek innovative ways to assure regulators that new devices will comply with policy requirements and will not cause harmful interference.

This study investigates mobility patterns in microcellular wireless networks, based on measurements from the 802.11 based system that blankets the Carnegie Mellon University campus. We characterize the distribution of dwell time, which is the length of time that a mobile device remains in a cell until the next handoff, and sign-on interarrival time, which is the length of time between successive sign-ons from the same mobile device. Many researchers have assumed that these distributions are exponential, but our results based on empirical analysis show that dwell time and sign-on interarrival time can be accurately described using heavy-tailed arithmetic distributions that have infinite mean and variance. We also show that the number of handoffs per sign-on can be modeled accurately with a heavy-tailed distribution.

This paper describes PayCash, an Internet payment system that was designed to offer strong security and privacy protection. This system is based on the concept of electronic cash, extended to support a flexible anonymity policy so as to accommodate privacy and security laws that differ from nation to nation. PayCash includes novel techniques to generate trustworthy records of all transactions, making it possible to detect many forms of fraud. This system also allows users to send a variable number of "electronic coins" in a single message, so both large and small amounts of money can be transferred efficiently.

It is now well known that Internet traffic exhibits self-similarity, which cannot be described by traditional Markovian models such as the Poisson process. In this work, we simulate a simple network with a full implementation of TCP-Reno. We also assume Poisson arrivals at the application layer specifically to determine whether TCP can cause self-similarity even when input traffic does not exhibit long-range dependence. Our study shows that, at some loads TCP can induce the appearance of self-similarity. In particular, when load is low and loss is rare, traffic looks Poisson. When load is high and the network is overloaded, TCP congestion control can smooth out the burstiness of the aggregate stream so that traffic at the bottleneck tends to Poisson. However, when load is intermediate and the network is prone to occasional bouts of congestion, as is typical of many networks, traffic can become self-similar. Moreover, factors such as round trip time and number of streams passing through the bottleneck can cause the network to become congested at different loads, and consequently affect the range of load over which self-similarity can be observed. The impact of one self-similar TCP stream has also been observed. In particular, our study show that if one or more streams passing through the bottleneck is self-similar and the aggregate flow does not exceed the capacity, traffic observed at the bottleneck will also be self-similar.

This study investigates mobility patterns in microcellular wireless networks, based on measurements from the 802.11-based system that blankets the Carnegie Mellon University campus. We characterize the distribution of dwell time, which is the length of time that a mobile device remains in a cell until the next handoff, and sign-on interarrival time, which is the length of time between successive sign-ons from the same mobile device. Many researchers have assumed that these distributions are exponential, but our results based on empirical analysis show that dwell time and sign-on interarrival time can be accurately described using heavy-tailed arithmetic distributions that have infinite mean and variance. We also show that the number of handoffs per sign-on can be modeled accurately with a heavy-tailed distribution.

In the unlicensed spectrum, any device is free to transmit without a license. Such a spectrum has significant benefits, but serious challenges must first be overcome. Foremost is the risk of drastic performance degradation due to a lack of incentive to conserve shared resources. Previous work has identified this problem for devices that transmit for longer duration than necessary. This paper demonstrates this problem for devices that always transmit at maximum power to maximize throughput. For devices that can vary transmission power, the problem is solved if devices reduce transmission power when received interference exceeds defined thresholds. We propose a co-existence algorithm to optimize system throughput when each of two such devices can transmit up to the maximum power allowed on a given channel. We show the device performance with current unlicensed band regulations is rarely optimal, and that the proposed algorithm is better.

Due to the explosive growth of the Internet and increasing demand for multimedia information on the Web, streaming video over the Internet has received tremendous attention from academia and industry. Transmission of real-time video typically has bandwidth, delay, and loss requirements. However, the current best-effort Internet does not offer any quality of service (QoS) guarantees to streaming video. Furthermore, for video multicast, it is difficult to achieve both efficiency and flexibility. Thus, Internet streaming video poses many challenges. In this article we cover six key areas of streaming video. Specifically, we cover video compression, application-layer QoS control, continuous media distribution services, streaming servers, media synchronization mechanisms, and protocols for streaming media. For each area, we address the particular issues and review major approaches and mechanisms. We also discuss the tradeoffs of the approaches and point out future research directions.

In the unlicensed spectrum, any device can transmit without a license. Such spectrum has major benefits, but serious challenges must first be overcome. Foremost is the risk of drastic performance degradation due to a lack of incentive to conserve shared resources. Previous work has shown this problem for devices that transmit for longer duration than necessary. This paper demonstrates this problem for devices always transmitting at maximum power to improve the throughput. For devices with fixed transmit powers, the problem is solved if devices defer transmission when the received interference exceeds defined thresholds. We propose a co-existence algorithm designed to optimize system throughput when each of two devices can transmit at the maximum power allowed. We show device performance with current unlicensed band regulations is rarely optimal, and that the proposed algorithm is better.

This paper takes a known approach for scheduling and admission control in integrated services networks, the priority token bank (PTB), whose mechanism and performance have been studied in a single queue, and extends the algorithm to address the challenges of implementing it in a network of queues. An integrated services network must handle traffic streams with disparate arrival processes and performance objectives, and efficiently supporting these streams becomes more difficult when performance guarantees must be met across a number of switches and when a stream's burstiness can dramatically increase from source to destination. Three variations on the basic mechanism are proposed to address this problem: PTB-separate classes, PTB-minimum interdeparture time, and PTB-weighted fair queuing. It is shown that the PTB scales well to a network of queues, and that, under the constraint that performance requirements for guaranteed traffic such as packet voice, HDTV, and packet video must be met, the mean delay experienced by other traffic is much better with the priority token bank mechanisms than with other proposed algorithms.

Applications with diverse performance objectives must be supported on a single packet-switched network. The efficiency of such networks can be greatly improved through the use of sophisticated scheduling and dropping algorithms within the queues that form at the network access points and in switches throughout the network. In the present approach, arbitrary performance objectives are expressed in the form of cost functions, which map the queueing delay experienced by each packet to a cost incurred. The heuristic algorithms, cost-based scheduling (CBS) and cost-based dropping (CBD), then attempt to optimize network performance as perceived by the applications by minimizing the total cost incurred by all packets. Appropriate cost functions are presented for common applications. Scheduling and dropping algorithms are defined from these cost functions. It is demonstrated that network performance is better when these algorithms are used as opposed to the common alternatives. Also, contrary to conventional wisdom, some evidence is presented indicating that sophisticated scheduling may be preferable to sophisticated dropping as a means of adjusting loss rates.

The paper analyzes the fault tolerance of a class of double-loop networks referred to as forward-loop backward-hop (FLBH), in which each node is connected via unidirectional links to the node one hop in front of it and to the node S hops in back of it for some S. A new measure of fault tolerance is described, along with techniques based on Markov chains to calculate upper and lower bounds on the fault tolerance of this network topology quickly and efficiently. The results of these calculations provide a more precise description of network fault tolerance than has been achieved with previously published techniques.>

H. Masuyama and T. Ichimori (see IEEE Trans. Comput., vol.38, no.5, p.738-41, 1989) quantitatively evaluated the ability of a class of double-loop networks called forward-loop-backward-hop (FLBH) networks to tolerate node failures. Their approach was based on the enumeration of all possible sets of failures. The authors prove that their results are incorrect and demonstrate that it is difficult to solve this problem using an approach based on the enumeration of failure sets, suggesting that other approaches may be preferable.>

Heuristic scheduling and dropping algorithms are presented for improving the efficiency of single packet-switched networks with diverse traffic. In the authors approach, arbitrary performance objectives are defined in the form of cost functions, which map the queueing delay experienced by each packet to a cost incurred. The algorithms, cost-based scheduling (CBS) and cost-based dropping (CBD), then attempt to optimize network performance as perceived by the applications by minimizing the total cost incurred by all packets. Cost functions are presented that are appropriate for the most common applications. Scheduling and dropping algorithms are defined based on these cost functions. It is demonstrated that network performance is better when these heuristic algorithms are used as opposed to the common alternatives. The relative importance of scheduling and dropping is also considered.>

An analysis is made of the fault tolerance of a class of double-loop networks referred to as forward-loop backward-hop (FLBH) networks, in which each node is connected by unidirectional links to the node one hop in front of it and to the node S hops in back of it for some S. A measure of fault tolerance is described along with techniques based on Markov chains to calculate quickly and efficiently the upper and lower bounds on the fault tolerance of this network topology. The results of the calculations provide a more precise description of network fault tolerance than has been achieved with previously published techniques. >

The author describes an algorithm for interconnecting stations on multichannel networks. The algorithm is completely distributed and requires no global information. An immediate application is in a two-channel network, a dual ring with single-media-access-control stations. There are also important applications in networks consisting of two or more local area networks, such as those with hot backups. Two variations of the algorithm are presented: the general algorithm and a simplified version optimized for two-channel networks. It is concluded that the proposed approach will facilitate configuration by reducing restrictions and the need for correct global data. It will also reduce the chances of miswiring a network, which improves the network's availability.>