Search

Cache memory is controlled by hardware, resulting in significant hardware overhead and power consumption. This situation necessitated the use of scratchpad memory as an alternative. Specifically, for utilizing scratchpad memory in multi-core systems, a Local Memory Storage (LMStr) structure has been proposed. However, the LMStr structure must address fragmentation issues caused by the use of variable-sized data blocks. In this paper, we propose a new structure called 'Paging LMStr' that applies paging to solve this problem. We implement a system capable of simulating it in gem5 and evaluate its performance through a comprehensive testbench. The results demonstrate that the proposed structure improves the hit rate by 3.6% and reduces system ticks by approximately 10.68%, leading to a significant overall performance improvement compared to the existing structure. This indicates that Paging LMStr can effectively enhance memory management efficiency in multi-core systems, providing a viable solution to the challenges posed by traditional cache memory systems. [ABSTRACT FROM AUTHOR]

In order to connect an incoming call to the user equipment (UE) in a mobile communication network, the location information of the UE must be always kept in the network database. Therefore, the efficiency of the location registration method of reporting new location information to a mobile communication network whenever the location information of the UE changes directly affects the performance of the radio channel, which is a limited resource in a mobile communication network. This study deals with distance-based registration (DBR). DBR does not cause the ping-pong phenomenon known to be a main problem in zone-based registration. It shows good performance when assuming a random walk mobility model. To improve the performance of the original DBR with one location area (1D), a DBR with two location areas (2D) was proposed. It is known that 2D is better than 1D in most cases. However, unlike 1D, an accurate mathematical model for 2D has not been presented in previous studies, raising questions about whether an accurate performance comparison has been performed. In this study, we present an accurate mathematical model based on the semi-Markov process for performance analysis of 2D. We compared performances of 1D and 2D using the proposed mathematical model. Various numerical results showed that 2D with two-step paging was superior to 1D in most cases. However, when simultaneous paging was applied to 2D, 1D was better than 2D in most cases. In real situations, optimal performance can be achieved by reflecting the network situation in real time and dynamically changing the operating method using a better-performing model among these two methods. [ABSTRACT FROM AUTHOR]

Numerous studies have been conducted on wireless communication networks to reduce the costs associated with location registration and paging traffic caused by the movement of user equipment (UE). Among them, a zone-based registration scheme is commonly used due to its convenience of implementation. In a zone-based scheme, a set of non-overlapping cells are managed as a single zone called a registration area (RA). The UE requests registration each time it enters a new RA. The most significant drawback of the 1Z system (an RA consisting of one zone) is the degradation in the service quality due to the registration traffic that frequently occurs at the RA boundaries. To overcome this drawback, a 2Z system that can manage two zones with one RA has been proposed. However, in the 2Z system, the paging costs for the UE that has returned to the previous zone increase, which can significantly degrade the performance compared to the 1Z system if the call-to-mobility ratio (CMR) is large or if the probability of returning to the previous zone is small. In this study, a new 2Z_Timer scheme is proposed to enhance the performance of the 2Z system. This method involves initiating a Timer for the previously visited zone when the UE enters a new zone, making it possible to retain the information of the previous zone for a specified threshold period. Simulations were conducted using flowchart-based RAPTOR software to compare its performance to those of the 1Z and 2Z systems. The results showed that the 2Z_Timer system effectively reduced the paging costs, even when the CMR was high or the probability of returning to the previous zone was low. Numerical results for various Timer thresholds showed that the 2Z_Timer system could lead to cost reductions of 10.6% and 28.6% compared to the 1Z and 2Z systems, respectively. [ABSTRACT FROM AUTHOR]

Given the complexities of communication within health systems, we investigated how the implementation of secure messaging in addition to traditional paging would impact hospital communication. This study was implemented at Grady Health System (GHS), a large safety net academic hospital system in metro Atlanta that includes inpatient and ambulatory settings. GHS uses Epic Electronic Health Record (EHR), and secure messaging was performed using Epic Haiku Platform. To assess states of communication, we implemented pre- and post-surveys. The secure messaging data tracked from 2018 to 2022 demonstrated a rise in usage from 9,378 chats per month when it went live in August 2018 to greater than 200,000 monthly messages during the pandemic when social distancing measures were enacted. Monthly usage peaked in March 2022 with 378,932 messages. Pre-and-post survey questions using a Likert scale (1–4) showed increased agreement in the ability to reach all team members through secure chat amongst healthcare workers. Within our unit staff, communication improved by being more rapid and reliable, as the Likert scale means increased from 2.18 pre-survey to 2.63 post survey. Pre-and-post survey analysis indicates improved satisfaction across GHS stakeholders with the implementation of secure chat in addition to the existing direct-paging system. Next steps could include exchanging digital media through secure messaging to facilitate faster diagnosis and treatment of certain medical conditions. Secure messaging integrated within the EHR (including mobile devices) enhances communication between healthcare team members in a HIPAA-compliant way reducing the number of pages and phone calls. [ABSTRACT FROM AUTHOR]

Traditional online algorithms encapsulate decision making under uncertainty, and give ways to hedge against all possible future events, while guaranteeing a nearly optimal solution, as compared to an offline optimum. On the other hand, machine learning algorithms are in the business of extrapolating patterns found in the data to predict the future, and usually come with strong guarantees on the expected generalization error. In this work, we develop a framework for augmenting online algorithms with a machine learned predictor to achieve competitive ratios that provably improve upon unconditional worst-case lower bounds when the predictor has low error. Our approach treats the predictor as a complete black box and is not dependent on its inner workings or the exact distribution of its errors. We apply this framework to the traditional caching problem--creating an eviction strategy for a cache of size k. We demonstrate that naively following the oracle's recommendations may lead to very poor performance, even when the average error is quite low. Instead, we show how to modify the Marker algorithm to take into account the predictions and prove that this combined approach achieves a competitive ratio that both (i) decreases as the predictor's error decreases and (ii) is always capped by O(log k), which can be achieved without any assistance from the predictor. We complement our results with an empirical evaluation of our algorithm on real-world datasets and show that it performs well empirically even when using simple off-the-shelf predictions. [ABSTRACT FROM AUTHOR]

For wireless communication networks, researchers have proposed many schemes to reduce the cost of location registration and paging signals caused by the mobility of user equipment (UE). Among them, a zone-based method that designates one zone (1Z, group of cells) as a registration area (RA) and then performs registration whenever the UE leaves the RA is commonly adopted due to its convenient implementation. However, the performance of 1Z is known to be very poor when the UE frequently crosses the RA's boundary requesting location updates. Two or three zone-based schemes (2Z or 3Z) have since been recommended to overcome these limitations. In our previous work, we analyzed the performances of 1Z, 2Z, and 3Z systems while assuming a square-shaped zone. However, there is no reason why the shape of the zone is limited to a square. This paper analyzes the performance of 3Z while assuming a hexagonal-shaped rather than a square-shaped zone. Using a semi-Markov process theory, registration and paging costs are evaluated after defining states in 3Z operations and calculating the transition probability between states. Based on various realistic parameters, the numerical results showed that the 3Z outperformed 1Z and 2Z for most call-to-mobility ratio (CMR) values. The performance of 3Z was improved more when the registration cost decreased if the probability of returning to the previously registered zone increased or the time staying in the zone decreased. The 3Z system is easy to implement with simple software modifications. It can be dynamically applied as an efficient mobility management method in the future for various devices that will emerge in the 5G/6G environment. [ABSTRACT FROM AUTHOR]

Supplemental Digital Content is Available in the Text. Paging and text messaging to request new orders remain common means of communication between clinicians and nurses in the hospital setting. However, sending and triaging multiple pages can lead to interruptions in other clinical duties. A medication order delegation protocol allowing for nurse-driven ordering of low-risk medications was developed with an objective of decreasing potentially avoidable pages. The aim of this study was to evaluate the impact of implementing this protocol on nurse and clinician perceptions of clerical burden and satisfaction. A survey assessing satisfaction with the process of obtaining medications in this protocol and the perception of clerical burden associated with ordering them before and after delegation protocol implementation was completed by over 160 clinicians and nurses. Survey respondents reported increased satisfaction and decreased clerical burden associated with the implementation of the delegation protocol. These results suggest the potential for delegation protocols to limit clerical burden associated with paging. [ABSTRACT FROM AUTHOR]

The signaling resources expended and the power consumed by User Equipments (UEs) in the Location Management (LM) procedures are expected to be higher in Fifth Generation (5G) than in legacy wireless communications networks. To mitigate this challenge, this work proposes a hybrid scheme that mitigates the signaling resources expended in paging and RAN-based Notification Area Update (RNAU) procedures in 5G. The approach utilizes a hybrid scheme that embeds a UE Identifier (UEID) partitioning scheme that directional pages UEs into a gNB-based UE Mobility Tracking (UEMT) scheme. The approach configures a gNB in an RRC_Inactive state to beam sweep a UEs last registered cell area before directionally paging the UE. The approach proposed in this work is implemented on a modified network architecture to reduce the signaling resources expended on both paging and RNAU of UEs at higher frequencies which is an enabling factor for mmWave systems. Simulation results of the total accumulated cost of paging showed a 65.13 % and 8.69 % reduction in signaling resources expended against the conventional approach and the existing gNB-based UEMT approach, respectively. Additionally, the total accumulated resources expended in both procedures over 24 hours showed that the modified gNB-based UEMT scheme outperformed the conventional scheme and the gNB-based UEMT scheme by 90.96 % and 38.36 %, respectively. [ABSTRACT FROM AUTHOR]

For wireless communication networks, researchers have proposed many schemes to reduce the cost of location registration and paging signals caused by the mobility of user equipment (UE). Among them, a zone-based method that designates one zone (1Z, group of cells) as a registration area (RA) and then performs registration whenever the UE leaves the RA is commonly adopted due to its convenient implementation. However, the performance of 1Z is known to be very poor when the UE frequently crosses the RA’s boundary requesting location updates. Two or three zone-based schemes (2Z or 3Z) have since been recommended to overcome these limitations. In our previous work, we analyzed the performances of 1Z, 2Z, and 3Z systems while assuming a square-shaped zone. However, there is no reason why the shape of the zone is limited to a square. This paper analyzes the performance of 3Z while assuming a hexagonal-shaped rather than a square-shaped zone. Using a semi-Markov process theory, registration and paging costs are evaluated after defining states in 3Z operations and calculating the transition probability between states. Based on various realistic parameters, the numerical results showed that the 3Z outperformed 1Z and 2Z for most call-to-mobility ratio (CMR) values. The performance of 3Z was improved more when the registration cost decreased if the probability of returning to the previously registered zone increased or the time staying in the zone decreased. The 3Z system is easy to implement with simple software modifications. It can be dynamically applied as an efficient mobility management method in the future for various devices that will emerge in the 5G/6G environment.

The signaling resources expended and the power consumed by User Equipments (UEs) in the Location Management (LM) procedures are expected to be higher in Fifth Generation (5G) than in legacy wireless communications networks. To mitigate this challenge, this work proposes a hybrid scheme that mitigates the signaling resources expended in paging and RAN-based Notification Area Update (RNAU) procedures in 5G. The approach utilizes a hybrid scheme that embeds a UE Identifier (UEID) partitioning scheme that directional pages UEs into a gNB-based UE Mobility Tracking (UEMT) scheme. The approach configures a gNB in an RRC_Inactive state to beam sweep a UEs last registered cell area before directionally paging the UE. The approach proposed in this work is implemented on a modified network architecture to reduce the signaling resources expended on both paging and RNAU of UEs at higher frequencies which is an enabling factor for mmWave systems. Simulation results of the total accumulated cost of paging showed a 65.13 % and 8.69 % reduction in signaling resources expended against the conventional approach and the existing gNB-based UEMT approach, respectively. Additionally, the total accumulated resources expended in both procedures over 24 hours showed that the modified gNB-based UEMT scheme outperformed the conventional scheme and the gNB-based UEMT scheme by 90.96 % and 38.36 %, respectively.

Among the characteristics in fifth generation (5G) networks, a massive number of devices and a network densification stand out. Hence, efficient location management is a key factor in enabling the network to track each user under the coverage area. In order to fulfill the requirements of 5G, a novel location management strategy was introduced by the 3rd Generation Partnership Project (3GPP) based on a new Radio Resource Control (RRC) state. This article presents a new methodology to find out an optimum network configuration that minimizes the signaling costs associated with the location management scheme for 5G networks. In addition to procedures triggered by the core network, the signaling costs are calculated taking into account the paging and update procedures performed in the Radio Access Network (RAN). A genetic algorithm is applied to optimize the network by reducing signaling costs caused by location management procedures, obtained from a 5G network system-level simulator focusing on mobility events. The proposed approach is compared to the schemes used in previous mobile networks. The results indicate that the new scheme decreases the signaling cost and reduces latency in various network sizes and user profile.

User experience, characterized by not only data rate and latency but also power consumption, is one of the major drivers for the success of 5G and Beyond-5G (B5G) networks. User Equipment (UE) power saving enhancements are at the forefront of ongoing discussions in 3GPP for next generation radio standards. Idle mode Discontinuous Reception (IDRX) is an important mechanism for UE’s power saving. However, IDRX in 5G/B5G networks is more challenging than in legacy networks. UE is required to measure Synchronization Signal Block(s) (SSBs) for Physical Downlink Shared Channel (PDSCH) and Physical Downlink Common Control Channel (PDCCH) reception in every paging occasion (PO) of IDRX cycle in 5G/B5G networks. Furthermore, PDSCH decoding is very sensitive to the time-frequency synchronization error and requires multiple SSB measurements before every PO. In this paper we present an Enhanced Paging Monitoring (EPM) for reducing the impediments on IDRX in 5G/B5G due to SSB measurements and related overheads. We also extend our EPM proposal by incorporating paging early indication. The proposed EPM can manifest up to 37% more power saving compared to existing system while considering multiple SSB measurements that are essential to 5G/B5G networks.

Recently, technologies such as big data, artificial intelligence, and machine learning have been applied to intelligently and effectively operate fourth-generation (4G) and fifth-generation (5G) network systems. In particular, we are interested in using them in 4G mobility management entities and 5G access and mobility management functions (AMFs), where functional enhancement or performance improvement is required. This paper presents an enhanced paging approach based on supervised machine learning and a Markov process for the performance improvement of paging in 5G AMFs. User equipment (UE) profile information in 5G AMFs classifies subscribers into two types using a UE classifier model with k-nearest neighbors (KNN)-supervised learning. In this paper, UE movement data between next-generation NodeBs (gNodeBs) are analyzed, and the Markov process is applied to construct a transition probabilistic model. When a UE moves to an adjacent gNodeB in the 5G connection management-idle state, a method for predicting the gNodeB movement is required to perform paging effectively on the predicted gNodeBs. In the proposed paging method, the AMF applies the UE profile information to the KNN-supervised learning model and classifies the subscriber UE type. In addition, on the UE movement between gNodeBs statistics, it generates state-transition probabilities and then performs paging on the gNodeB list. Experimentally, the paging responses and signals of the proposed method are compared with the existing paging methods and presented with the result that the UE location is identified using the recently visited gNodeB list in the tracking area of the AMF. [ABSTRACT FROM AUTHOR]

In this study, we have considered zone-based registration (ZBR), which is the most widely adopted type in mobile communication networks. Based on a performance comparison between one-zone-based registration (1ZR) and two-zone-based registration (2ZR), 2ZR is known to be superior to 1ZR in most cases. However, the existing studies on the comparison of 1ZR and 2ZR have a critical problem: The basic assumption in 1ZR is that the entire zone is paged simultaneously when a call arrives, whereas, in 2ZR, the zone is paged by two steps. With these different paging schemes, a proper comparison cannot be made. Therefore, in this study, we analyzed the performance of 1ZR by adopting 2-step paging (2SP) such as 2ZR for a proper performance comparison under equivalent conditions. This study also presents an analytical model of assigning paging areas under 2SP in 1ZR when the zone consists of multiple cells. Considering the mobility characteristics assumed in the previous studies on 2ZR, we have presented the mobility model for movement among cells in a zone, obtained the steady-state probability of each cell by using the Markov chain model to calculate the paging cost under 2SP, and ultimately calculated the total signaling cost. Through various numerical results, it was observed that, when 1ZR also adopts 2SP such as 2ZR, 1ZR can be superior to 2ZR in many cases. In conclusion, by adopting 2SP in both 1ZR and 2ZR, it would be possible to reduce the total signaling cost by selecting the better 1ZR and 2ZR while considering traffic changes. [ABSTRACT FROM AUTHOR]

IEEE 802.11 Wireless Local Area Network (WLAN) is becoming the prevailing technology for the broad band wireless Internet access. However, IEEE 802.11 WLAN has been discovered to be naturally weak in supporting the mobility of mobile host (MH) when there is no traffic to be served for the MHs. Quite a number of commendable works have been done to introduce paging in WLAN and, thereby properly manage scarce network resources such as bandwidth and power. In this work, the authors consider it pertinent to go a step further and design a paging algorithm for campus WLAN, which will take advantage of the unique campus setting and activities. We, therefore, propose a User-Activity Dependent Paging Scheme (UADPS) in a Multi-Cell Campus WLAN Environment; a paging algorithm that considers mobile devices in a multi cell WLAN. This is because we believe that such algorithm will not only be simple to implement, but will make a great positive impact on resource savings for on-campus WLAN users. Results obtained shows that the UADPS utilizes less network resources in searching for an MH when compared to the IEEE 802.11 power save mode algorithm.

Many registration schemes have been proposed to reduce the signaling cost required for user's mobility management in wireless communication networks. Various results on mobility management schemes to minimize the total signaling cost have been reported. The objective of this study was to analyze a registration scheme that could deal with mobility prediction and corresponding flexible tracking area list (TAL) forming. In this scheme, based on mobility prediction and corresponding TAL forms, a new TAL was constructed such that the registration cost could be minimized. In addition, a semi-Markov process model was newly presented for the registration scheme considering mobility prediction and corresponding flexible TAL forming for two different environments: urban and rural. Simulation studies were also performed to validate the accuracy of the semi-Markov process model. Numerical results showed that analytical and simulation results were very close (average relative error of 1.4%). The registration cost decreased as the moving probability (q) to the predicted direction increased. The performance of the proposed scheme was superior to distance-based registration (DBR) or TAL-based scheme especially when q was high. When call-to-mobility ratio was less than or equal to 1 corresponding to current small cell configurations, the proposed scheme outperformed the DBR or TAL-based scheme. [ABSTRACT FROM AUTHOR]

Objective: A pediatric surgery fellow is often regarded as a cornerstone of an academic children's hospital due to the need for their clinical services with overnight coverage being an important aspect of the care provided. There is little known about the objective sleep patterns and work-related communications of a pediatric surgery fellow during overnight home call. The aim of this study is to better understand the sleep patterns and interruptions of an on-call pediatric surgery fellow., Design: A prospective observational study of 60 call nights and 60 non-call nights of a pediatric surgery senior fellow was performed from September 2022 to February 2023., Setting: An academic Children's Hospital., Participant: An ACGME-accredited clinical pediatric surgery fellow., Results: On average, the pediatric surgery fellow spent 6.9 and 5.8 total hours in bed and asleep each night, respectively. The total sleep time was less for call nights compared to non-call nights (5.4 versus 6.3 h, p  < 0.0001). The mean number of work-related communications per 12-hour night shift was four. The majority of communications were regarding new consults (63.8 %). The pediatric surgery fellow spent an average of 5.9 min per communication and approximately 23.8 min total during each 12-hour night shift. Approximately half of these communications occurred during sleep hours., Conclusions: This study reveals overall sleep duration was below recommended levels. There were significant alterations in sleep patterns during call nights. Work-related communications further compounded sleep disturbances. Further research and interventions in this area are warranted., Competing Interests: The authors have indicated they have no potential conflicts of interest to disclose., (© 2024 The Authors.)

In this study, we have considered zone-based registration (ZBR), which is the most widely adopted type in mobile communication networks. Based on a performance comparison between one-zone-based registration (1ZR) and two-zone-based registration (2ZR), 2ZR is known to be superior to 1ZR in most cases. However, the existing studies on the comparison of 1ZR and 2ZR have a critical problem: The basic assumption in 1ZR is that the entire zone is paged simultaneously when a call arrives, whereas, in 2ZR, the zone is paged by two steps. With these different paging schemes, a proper comparison cannot be made. Therefore, in this study, we analyzed the performance of 1ZR by adopting 2-step paging (2SP) such as 2ZR for a proper performance comparison under equivalent conditions. This study also presents an analytical model of assigning paging areas under 2SP in 1ZR when the zone consists of multiple cells. Considering the mobility characteristics assumed in the previous studies on 2ZR, we have presented the mobility model for movement among cells in a zone, obtained the steady-state probability of each cell by using the Markov chain model to calculate the paging cost under 2SP, and ultimately calculated the total signaling cost. Through various numerical results, it was observed that, when 1ZR also adopts 2SP such as 2ZR, 1ZR can be superior to 2ZR in many cases. In conclusion, by adopting 2SP in both 1ZR and 2ZR, it would be possible to reduce the total signaling cost by selecting the better 1ZR and 2ZR while considering traffic changes.

Recently, technologies such as big data, artificial intelligence, and machine learning have been applied to intelligently and effectively operate fourth-generation (4G) and fifth-generation (5G) network systems. In particular, we are interested in using them in 4G mobility management entities and 5G access and mobility management functions (AMFs), where functional enhancement or performance improvement is required. This paper presents an enhanced paging approach based on supervised machine learning and a Markov process for the performance improvement of paging in 5G AMFs. User equipment (UE) profile information in 5G AMFs classifies subscribers into two types using a UE classifier model with k-nearest neighbors (KNN)-supervised learning. In this paper, UE movement data between next-generation NodeBs (gNodeBs) are analyzed, and the Markov process is applied to construct a transition probabilistic model. When a UE moves to an adjacent gNodeB in the 5G connection management-idle state, a method for predicting the gNodeB movement is required to perform paging effectively on the predicted gNodeBs. In the proposed paging method, the AMF applies the UE profile information to the KNN-supervised learning model and classifies the subscriber UE type. In addition, on the UE movement between gNodeBs statistics, it generates state-transition probabilities and then performs paging on the gNodeB list. Experimentally, the paging responses and signals of the proposed method are compared with the existing paging methods and presented with the result that the UE location is identified using the recently visited gNodeB list in the tracking area of the AMF.

In this article, we introduce the online service with delay problem. In this problem, there are n points in a metric space that issue service requests over time, and there is a server that serves these requests. The goal is to minimize the sum of distance traveled by the server and the total delay (or a penalty function thereof) in serving the requests. This problem models the fundamental tradeoff between batching requests to improve locality and reducing delay to improve response time, which has many applications in operations management, operating systems, logistics, supply chain management, and scheduling. Our main result is to show a poly-logarithmic competitive ratio for the online service with delay problem. This result is obtained by an algorithm that we call the preemptive service algorithm. The salient feature of this algorithm is a process called preemptive service, which uses a novel combination of (recursive) time forwarding and spatial exploration on a metric space. We also generalize our results to k > 1 servers and obtain stronger results for special metrics such as uniform and star metrics that correspond to (weighted) paging problems. [ABSTRACT FROM AUTHOR]

The limited memory capacity of mobile devices leads to the popular use of compressed swap schemes, which reduce the I/O operations involving the swapping in and out of infrequently accessed pages. However, most of the current compressed swap schemes indiscriminately compress and store all swap-out pages. Considering that both energy and computing power are scarce resources in mobile devices, and modern applications frequently deal with already-compressed multimedia data, this blind approach may cause adverse impacts. In addition, they focus only on anonymous pages and not on file-mapped pages, because the latter are backed by on-disk files. However, our observations revealed that, in mobile devices, file-mapped pages consume significantly more memory than anonymous pages. Last but not least, most of the current compressed swap schemes blindly follow the least-recently-used (LRU) discipline when choosing the victim pages for replacement, not considering the compression ratio or data density of the cached pages. To overcome the aforementioned problems and maximize the memory efficiency, we propose a compressed swap scheme, called enhanced zswap (ezswap), for mobile devices. ezswap accommodates not only anonymous pages, but also clean file-mapped pages. It estimates the compression ratio of incoming pages with their information entropy, and selectively compresses and caches the pages only with beneficial compression ratios. In addition, its admission control and cache replacement algorithms are based on a cost-benefit model that considers not only the access recency of cached pages but also their information density and expected eviction cost. The proposed scheme was implemented in the Linux kernel for Android. Our evaluation with a series of commercial applications demonstrated that it reduced the amount of flash memory read by up to 55%, thereby improving the application launch time by up to 22% in comparison to the original zswap.

This study considers zone‐based registration (ZBR), which is adopted by most mobile cellular networks. In ZBR, a user equipment (UE) registers its location area (or zone) in a network database (DB) whenever it enters a new zone. Even though ZBR is implemented in most networks for a UE to keep only one zone (1ZR), it is also possible for a UE to keep multiple zones. Therefore, a ZBR with two zones (2ZR) is investigated, and some mathematical models for 2ZR are presented. With respect to ZBR with three zones (3ZR), several studies have been reported, but these employed computer simulations owing to the complexity of the cases, and there have been no reports on a mathematical 3ZR model to analyze its performance. In this study, we propose a new mathematical model for 3ZR for the first time, and analyze the performance of 3ZR using this model. The numerical results for various scenarios show that, as the UE frequently enters zones, the proposed 3ZR model outperforms 1ZR and 2ZR. Our results help determine the optimal number of zones that a UE keeps, and minimize the signaling cost for radio channels in mobile cellular networks.

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper describes a simple greedy δ-approximation algorithm for any covering problem whose objective function is submodular and non-decreasing, and whose feasible region can be expressed as the intersection of arbitrary (closed upwards) covering constraints, each of which constrains at most δ variables of the problem. (A simple example is Vertex Cover, with δ=2.) The algorithm generalizes previous approximation algorithms for fundamental covering problems and online paging and caching problems. © 2012 Springer Science+Business Media, LLC.

Many registration schemes have been proposed to reduce the signaling cost required for user’s mobility management in wireless communication networks. Various results on mobility management schemes to minimize the total signaling cost have been reported. The objective of this study was to analyze a registration scheme that could deal with mobility prediction and corresponding flexible tracking area list (TAL) forming. In this scheme, based on mobility prediction and corresponding TAL forms, a new TAL was constructed such that the registration cost could be minimized. In addition, a semi-Markov process model was newly presented for the registration scheme considering mobility prediction and corresponding flexible TAL forming for two different environments: urban and rural. Simulation studies were also performed to validate the accuracy of the semi-Markov process model. Numerical results showed that analytical and simulation results were very close (average relative error of 1.4%). The registration cost decreased as the moving probability (q) to the predicted direction increased. The performance of the proposed scheme was superior to distance-based registration (DBR) or TAL-based scheme especially when q was high. When call-to-mobility ratio was less than or equal to 1 corresponding to current small cell configurations, the proposed scheme outperformed the DBR or TAL-based scheme.

It has long been known that for the paging problem in its standard form, competitive analysis cannot adequately distinguish algorithms based on their performance: there exists a vast class of algorithms that achieve the same competitive ratio, ranging from extremely naive and inefficient strategies (such as Flush- When-Full), to strategies of excellent performance in practice (such as Least-Recently-Used and some of its variants). A similar situation arises in the list update problem: in particular, under the cost formulation studied by Martínez and Roura [2000] and Munro [2000] every list update algorithm has, asymptotically, the same competitive ratio. Several refinements of competitive analysis, as well as alternative performance measures have been introduced in the literature,with varying degrees of success in narrowing this disconnect between theoretical analysis and empirical evaluation. In this article, we study these two fundamental online problems under the framework of bijective analysis [Angelopoulos et al. 2007, 2008]. This is an intuitive technique that is based on pairwise comparison of the costs incurred by two algorithms on sets of request sequences of the same size. Coupled with a well- established model of locality of reference due to Albers et al. [2005], we show that Least-Recently-Used and Move-to-Front are the unique optimal algorithms for paging and list update, respectively. Prior to this work, only measures based on average-cost analysis have separated LRU and MTF from all other algorithms. Given that bijective analysis is a fairly stringent measure (and also subsumes average-cost analysis), we prove that in a strong sense LRU and MTF stand out as the best (deterministic) algorithms. [ABSTRACT FROM AUTHOR]

In long-term evolution (LTE) network, service area is composed of tracking areas (TAs) lists (TALs) and a TAL includes a few neighbor TAs. In this paper, we consider paging schemes for TAL-based mobility management in LTE network. In TAL-based mobility management, whenever a user equipment (UE) enters a new TAL, it updates its location so that the current TA becomes the center TA of new TAL. We develop a mathematical model to analyze signaling cost of previous paging schemes for TAL-based mobility management. We then suggest new paging schemes to reduce paging cost. First, in order to mathematically analyze the performance of previous paging schemes, we use a Markov chain model based on 2-D random walk model. In our 2-D random walk model, unlike prior studies, the UE can move to one of four neighbor cells with equal probability to be more realistic. We also suggest new paging schemes to reduce the paging cost of previous paging schemes. With our analytical models, our paging schemes are found to be better than previous paging schemes in most cases. Various numerical results show that the proposed schemes are much more effective than previous paging schemes. These results suggest that the proposed schemes can be used effectively in the design and evaluation of mobility management in LTE network. [ABSTRACT FROM AUTHOR]

Over the last years, considerable attention has been given to the privacy of individuals in wireless environments. Although significantly improved over the previous generations of mobile networks, LTE still exposes vulnerabilities that attackers can exploit. This might be the case of paging messages, wake-up notifications that target specific subscribers, and that are broadcasted in clear over the radio interface. If they are not properly implemented, paging messages can expose the identity of subscribers and furthermore provide information about their location. It is therefore important that mobile network operators comply with the recommendations and implement the appropriate mechanisms to mitigate attacks. In this paper, we verify by experiment that paging messages can be captured and decoded by using minimal technical skills and publicly available tools. Moreover, we present a general experimental method to test privacy exposure by LTE paging messages, and we conduct a case study on three different LTE mobile operators. [ABSTRACT FROM AUTHOR]

Consider the following file caching problem: in response to a sequence of requests for files, where each file has a specified size and retrieval cost, maintain a cache of files of total size at most some specified k so as to minimize the total retrieval cost. Specifically, when a requested file is not in the cache, bring it into the cache and pay the retrieval cost, and remove other files from the cache so that the total size of files remaining in the cache is at most k. This problem generalizes previous paging and caching problems by allowing objects of arbitrary size and cost, both important attributes when caching files for world-wide-web browsers, servers, and proxies. We give a simple deterministic on-line algorithm that generalizes many well-known paging and weighted-caching strategies, including least-recently-used, first-in-first-out, flush-when-full, and the balance algorithm. On any request sequence, the total cost incurred by the algorithm is at most k/(k - h + 1) times the minimum possible using a cache of size h ≤ k. For any algorithm satisfying the latter bound, we show it is also the case that for most choices of k, the retrieval cost is either insignificant or at most a constant (independent of k) times the optimum. This helps explain why competitive ratios of many on-line paging algorithms have been typically observed to be constant in practice.