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Satellite based Internet access system. Links are bidirectional unless otherwise indicated. Dashed lines indicate elements not exploited in existing systems.
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Satellite operators have recently begun offering Internet access over their networks. Typically, users connect to the network using a modem for uplink, and a satellite dish for downlink. We investigate how the performance of these networks might be improved by two simple techniques: caching and use of the return path on the modem link. We examine t...
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... recent development in Internet access technologies is satellite based Internet service. In systems such as DirecPC [1] and Starband [2], users connect to the network via a satellite dish and a modem. Fig. 1 depicts a typical system. When a user visits a web page, his modem transmits the request over the telephone network to the satellite service's Network Operations Center (NOC). The NOC retrieves the web page from its cache or from the origin server over the Internet, and sends the data to a satellite. The satellite echoes the data, ...
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... of the broadcast link, we require storage at the client nodes so that they can later benefit from cache hits. We note that satellite network operators already offer receivers, such as DirecTV Receiver with TiVo [4], with large storage capacity. Given the low and decreasing cost of disks, it is inexpensive to use some storage to cache web objects. Fig. 1 depicts our model. The figure shows a system with a single user node; the generalization to multiple users is straightforward. In our model, each user is connected to the network via a modem, which may be used for bidirectional communication, and a satellite dish, which is capable of reception only 2 . In addition, the user node has a ...
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... file sizes according to the hybrid Lognormal-Pareto models reported in [15]. Fig. 8 shows the load attributable to large objects in the resulting workloads. The models, based on traces of web users at the Boston University Computer Science Department, clearly show heavier tails than PolyMix-4. Fig. 9 and Table 9 give results for BU 95 while Fig. 10 and Table 10 give results for BU98. For both BU 95 and BU 98, we find that setting s large < 500KB achieves little improvement. For BU 95, s large = 500KB improves large object response time by a factor of 2.8, with a 20% slowdown on overall mean response time. GPopLarge performs better on BU98, where it achieves a factor 8 speedup for ...
Citations
... However, in this paper, we only focus on the scheduling minimizing the total service latency to clarify the characteristic of hop-by-hop file delivery system. [13] and [14] investigate scheduling on the link between the satellite and satellite dish. [13] focuses on utilization of satellite broadcast links and modem unicast links by considering the benefits of caches and the popularity of each file. ...
... [13] and [14] investigate scheduling on the link between the satellite and satellite dish. [13] focuses on utilization of satellite broadcast links and modem unicast links by considering the benefits of caches and the popularity of each file. In online scheduling to utilize broadcast links and to improve service latency, they determine the order of transmitted files. ...
Many content distribution systems such as CDN and P2P file sharing have been developed. In these systems, file-type contents require downloads to be completed before they can be played and they have no value before the download finishes. Therefore, a user's satisfaction depends on the length of the service latency. That is, the length of time from when the user issued a request until the user received an entire file. Reducing the sum of that time is necessary for the whole delivery system to satisfy users and maintain dependability on system performance. We discuss a hop-by-hop file delivery system suitable for delivering file contents whereby the sum of service latency is reduced by using the request conditions. Moreover, we propose a file delivery scheduling algorithm for a one-link model given that the content request frequency is unknown. The algorithm is based on a local optimal strategy. We performed a characteristic analysis by computer simulation. The results showed that our algorithm performs at nearly the theoretical efficiency limit of the hop-by-hop system when the request frequency distribution of each content has a deviation.
... Multicast push and multicast pull have been previously combined in a hybrid scheme using static selection of hot documents [2]. Hybrid models with multicast pull and unicast have also been analyzed, and the delivery method for a document is determined by the integrated schedule for both channels [4]. Other work examines hybrid schemes using multicast push and unicast [7,11,23,28]. ...
Web server scalability can be greatly enhanced via hybrid data dissemination methods that use both unicast and multicast. Hybrid data dissemination is particularly promising due to the development of effective end-to-end multicast methods and tools. Hybrid data dissemination critically relies on document selection which determines the data transfer method that is most appropriate for each data item. In this paper, we study document selection with a special focus on actual end-point implementations and Internet network conditions. We individuate special challenges such as scalable and robust popularity estimation, appropriate classification of hot and cold documents, and unpopular large documents. We propose solutions to these problems, integrate them in MBDD (middleware support multicast-based data dissemination) and evaluate them on PlanetLab with collected traces. Results show that the multicast server can effectively adapt to dynamic environments and is substantially more scalable than traditional Web servers. Our work is a significant contribution to building practical hybrid data dissemination services.
... Owing to the constraints resulting from power-limited mobile devices and low-bandwidth wireless networks , designing a power conserving mobile information system with high scalability and high bandwidth utilization becomes an important research issue, and hence attracts a significant amount of research attention . In recent years, data broadcasting is proposed to address such challenge and has been recognized as a promising data dissemination technique in mobile computing environments [1][4][5][10][11]. Most research works on data broadcasting focus on generating a proper broadcast program or designing scheduling algorithms to minimize the average access time, which is defined as the average time elapsed from the moment a client issues a query to the point the desired data item is read. ...
Since only a modest improvement in battery lifetime is expected in the next few years, energy conservation is raised as a key factor in the design of mobile devices. In view of this, we propose in this paper an energy-conserving on-demand data broadcasting system that employs the data indexing technique. Different from prior work, the power consumption of turning on and turning off the wireless network interfaces is considered. In addition, we also employ a server cache to reduce the effect of the time to retrieve data items from the corresponding data servers. Specifically, we first analyze the access and tuning times of data requests, and propose an adaptive index and data organizing algorithm (AIDOA) to adjust the degree of buckets according to the system workload. Several experiments are then conducted to evaluate the performance of algorithm AIDOA. The experimental results show that algorithm AIDOA is able to greatly reduce the power consumption at the cost of a slight increase in the average access time and dynamically adjust the index and data organization to adapt to the change of system workload.
... In recent years, data broadcast [2][3] [29] has been employed as an important technique to design a scalable and power conserving mobile information system. However, most research works in transcoding proxies in mobile computing environments are on the basis of the traditional client-server architecture and do not employ the data broadcast technique. ...
... of a[1], a[2], · · · , a[k] and reset them to zero in each iteration of scheme ODB-QoS-Index. In the time interval between the m-th and (m + 1)-th executions, for each data arrival q, the interarrival time of this arrival is counted. ...
... If the interarrival time of q lies in interval I i , the value of a[i] is increased by one. Otherwise, we take the interarrival time of q as an outlier and do not change the values of a[1], a[2], · · · , a[k]. Let t p = 1 ...
Most research works in transcoding proxies in mobile computing environments are on the basis of the traditional client-server architecture and do not employ the data broadcast technique. In addition, the issues of QoS provision and energy conservation are also not addressed in the prior studies. In view of this, we design in this paper a QoS-aware and energy-conserving transcoding proxy by utilizing the on-demand broadcasting technique. We first propose a QoS-aware and energy-conserving transcoding proxy architecture, abbreviated as QETP, and model it as a queuing network consisting of three queues. By analyzing the queuing network, three lemmas are derived to estimate the load of these queues. We then propose a version decision policy and a service admission control scheme to provide QoS in QETP. The derived lemmas are used to guide the execution of the proposed version decision policy and service admission control scheme to achieve the given QoS requirement. In addition, we also propose a data indexing method to reduce the power consumption of clients. To measure the performance of the proposed architecture, three experiments are conducted. Experimental results show that the average access time reduction of the proposed scheme over the traditional client-server architecture ranges from 45 percent to 75 percent. Experimental results also show that the proposed scheme is more scalable than the traditional client-server architecture and is able to effectively control the system load to attain the given QoS requirements. In addition, the proposed scheme is able to greatly reduce the average tuning time of clients at the cost of a slight increase (around 5 percent in our experiments) in average access time.
... In order to provide power conserving and high scalable services in a mobile environment , a data delivery architecture in which a server continuously and repeatedly broadcasts data to a client community through a single broadcast channel was proposed in [3, 4] . Related research issues about broadcast-based information systems have attracted a considerable amount of studies, including broadcast program generation [3, 5], on-demand broadcast678, data indexing [9, 10], location-dependent data broadcasting [11, 12], dynamic data and channel allocation [13, 14], and dependent data broadcasting15161718. Unfortunately, most of the prior studies in data broadcast only deal with data indexing , broadcast program generation or other issues in a single-system wireless network (i.e., in one network with one or multiple broadcast channel(s)). ...
A multi-system heterogeneous overlayed wireless network with multiple wireless access technologies is deemed a key part of 4G networks. In addition, data broadcast is a promising technique to improve the bandwidth utilization and to conserve the power consumption in a mobile computing environment. However, most of the prior studies in data broadcast only deal with issues in a single-system wireless network (i.e., in a network with one or multiple broadcast channel(s)), and therefore, these prior approaches cannot be directly used in a multi-system heterogeneous overlayed wireless network. In view of this, we propose in this paper a two-phase algorithm, named algorithm Layered-Cutting, to address the problem of broadcast program generation in a multi-system heterogeneous overlayed wireless network. Specifically, in inter-network data allocation phase, algorithm Layered-Cutting allocates a set of data items to each subnetwork. Then, in intra-network data allocation phase, algorithm Layered-Cutting generates one broadcast program for each subnetwork according to the number of channels in the subnetwork and the properties (including data access probabilities and object sizes) of the data items allocated to the subnetwork. To evaluate the performance of algorithm Layered-Cutting, several experiments are conducted. The experimental results show that algorithm Layered-Cutting is able to efficiently generate broadcast programs of high quality for a multi-system heterogeneous overlayed wireless network.
... One objective of designing proper data allocation in the broadcast disks is to reduce the average access time of data items. The research issues have attracted a considerable amount of attention, including on-demand broadcast [3], [4], [5], [6], data indexing [9], [14], [15], [17], [30], [33], and client cache management [4], [27], [31]. In addition, a significant amount of research effort has been elaborated on developing the index mechanisms [16], [20], [25] and data allocation algorithms [22], [23], [28], [34], [35] in multiple broadcast channels. ...
... One objective of designing proper data allocation in the broadcast disks is to reduce the average access time of data items. The research issues have attracted a considerable amount of attention, including on-demand broadcast [3], [4], [5], [6], data indexing [9], [14], [15], [17], [30], [33], and client cache management [4], [27], [31]. In addition, a significant amount of research effort has been elaborated on developing the index mechanisms [16], [20], [25] and data allocation algorithms [22], [23], [28], [34], [35] in multiple broadcast channels. ...
In a mobile computing environment, the combined use of broadcast and on-demand channels can utilize the bandwidth effectively for data dissemination. We explore in this paper the problem of dynamic data and channel allocation with the number of communication channels and the number of data items given. We first derive the analytical models of the average access time when the data items are requested through the broadcast and on-demand channels. Then, we transform this problem into a guided search problem. In light of the theoretical properties derived, we devise algorithm SOM to obtain the optimal allocation of data and channels. Algorithm SOM is a composite algorithm which will cooperate with 1) a search strategy and 2) a broadcast program generation algorithm. According to the analytical mode, we devise scheme BIS-incremental on the basis of algorithm SOM, which is able to obtain solutions of high quality efficiently by employing binary interpolation search. In essence, scheme BIS-incremental is guided to explore the search space with higher likelihood to be the optimal first, thereby leading to an efficient and effective search. It is shown by our simulation results that the solution obtained by scheme BIS-incremental is of very high quality and is in fact very close to the optimal one. A sensitivity study on several parameters, including the number of data items and the number of communication channels, is conducted. The experimental results show that scheme BIS-incremental is of very good scalability, which is particularly important for its practical use in a mobile computing environment.
... To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. a data item, is introduced in [3]. Since employing data indexing will unavoidably introduce some overhead in access time 1 , the data indexing algorithms should reduce tuning time as much as possible at the cost of producing an acceptable increment in access time. Fortunately, since the size of an index item is usually much smaller than that of a data item, such increment is usually small. ...
We propose in this paper an energy-conserved on-demand data broadcasting system by employing the data indexing technique. We also propose algorithm AIDOA to adjust the degree of buckets according to system workload. Experimental results show that algorithm AIDOA is able to greatly reduce power consumption at the cost of slight increment in average access time and adjust the index and data organization dynamically to adapt to change of system workload.
... Since proxybased approaches are transparent to the content providers and users, this kind of approaches is able to simplify the design of servers and clients, and as a result, attracts much research attention, including cache replacement schemes [7][8], system architectures [10][15] and proxy collaboration [7]. In recent years, data broadcast [2][3] has been employed as an important technique to design a power conservation, high scalability and high bandwidth utilization mobile information system. However, most research works in transcoding proxies in mobile computing environments are under the traditional client-server architecture and do not employ the data broadcast technique. ...
The high diversity in the capabilities of various mobile devices such as display capabilities and computation power makes the design of mobile information systems more challenging. A transcoding proxy is placed between a client and an information server to coordinate the mismatch between what the server provides and what the client prefers. However, most research works in transcoding proxies in mobile computing environments are under the traditional client-server architecture and do not employ the data broadcast technique which is has been deemed a promising technique to design a power conservation, high scalable and high band-width utilization. In addition, the issue of QoS provision is also not addressed. In view of this, we design in this paper a QoS-aware transcoding proxy by utilizing the on-demand broadcasting technique. We first propose a QoS-aware transcoding proxy architecture, abbreviated as QTP, and model it as a queueing network. By analyzing the queueing network, several theoretical results are derived. We then propose a version decision policy and a service admission control scheme to provide QoS in QTP. The derived results are used to guide the execution of the proposed version decision policy and service admission control scheme to achieve the given QoS requirement. To measure the performance of QTP, several experiments are conducted. Experimental results show that the proposed scheme is more scalable than traditional client-server systems. In addition, the proposed scheme is able to effectively control the system load to attain the desired QoS
... With this expression for the client-delay upper bound, we now determine how the number of clients affects the use of this bound. 1 Extreme Value Distribution, MathWorld; derivation in Feller, 2/e ...
... There is a large body of research into multicast protocols and systems, including data dissemination systems such as ours [21] and broadcast disks [2,34], as a component of Web caching and service [32,3,12,5], as part of a satellite-based Internet service [1], and as a component of publish/subscribe systems [31] such as Gryphon [28]. ...
... As a result, hybrid data delivery would ideally achieve scalable utilization of server and network resources while avoiding the reception of unneeded contents. Hybrid data delivery receives significant attention in wireless networks [32,43] and satellite broadcast [10], where multicast is an inherent data transmission method. Hybrid data delivery is also studied for disseminating data in the Internet environment [13,19,53]. ...
... Scheduling on multicast pull can also use various approaches [9,10]. The middleware has provided two algorithms so far: FIFO (first-in-first-out) and LTSF (longest total stretch first) [9]. ...
... Compared with previous work, one big difference is that their system models only utilize two of the three channels: multicast push and multicast pull [8], multicast pull and unicast [10], or multicast push and unicast [13,19,43,53]. We will discuss the difference further in Section 3.8. ...
