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ABSTRACT—Non-geostationary (NGEO) satellite communication systems offer an array of advantages over their terrestrial and geostationary counterparts. They are seen as an integral part of nextgeneration ubiquitous communication systems. Given the non-uniform distribution of users in satellite footprints, due to several geographical and/or climatic constraints, some Inter-Satellite Links (ISLs) are expected to be heavily loaded with data packets while others remain underutilized. Such scenario obviously leads to congestion of the heavily loaded links. It ultimately results in buffer overflows, higher queuing delays, and significant packet drops. To guarantee a better distribution of traffic among satellites, this paper proposes an explicit exchange of information on congestion status among neighboring satellites. Indeed, a satellite notifies its congestion status to its neighboring satellites. When it is about to get congested, it requests its neighboring satellites to decrease their data forwarding rates by sending them a self status notification signaling message. In response, the neighboring satellites search for less congested paths that do not include the satellite in question and communicate a portion of data, primarily destined to the satellite, via the retrieved paths. This operation avoids both congestion and packet drops at the satellite. It also ensures a better distribution of traffic over the entire satellite constellation. The proposed scheme is dubbed “Explicit Load Balancing” (ELB) scheme. While the multi-path routing concept of ELB has many advantages, it may lead to persistent packet reordering. In case of connection- oriented protocols, this phenomenon results in unnecessary shrinkage of the data transmission rate. A solution to this issue is also incorporated in the design of ELB. The interactions of ELB with mechanisms that provide different QoS by differentiating traffic (e.g., Differentiated Services) are also discussed. The good performance of ELB, in terms of better traffic distribution, higher throughput, and lower packet drops, is verified via a set of simulations using the Network Simulator (NS).
INTRODUCTION
DESPITE the recent advances in terrestrial communication technologies, the ever-growing community of Internet users poses serious challenges to current terrestrial networks. Terrestrial networks are expected to provide a plethora ofbandwidth-intensive services, with different Quality of Service (QoS), to a potential number of users, dispersed over extensively wide areas and requiring different degrees of mobility. To cope with this issue, network technicians and telecommunication operators have envisaged optical-fiber networks and have considered temporary solutions such as Asynchronous Digital Subscriber Line (ADSL) and High-rate DSL (HDSL) technologies. However, as the demand for advanced multimedia services is growing in terms of both the number of users and the services to be supported, applying such solutions to bridge the last mile between local service providers and end-terminals will require an immense investment in terms of time, infrastructure, and human resources. Building a cost-efficient global ubiquitous infrastructure is one of the major challenges before telecommunication industries in the current century. In this regard, and considering the fact that more than half of the world lacks a wired network infrastructure, satellite communication systems are seen as an attractive solution. The efficiency of satellite-based broadband services is strongly remarkable in remote zones and low-density population areas. The key technologies required to support broadband communications over satellite systems have been already developed [1], [2]. Indeed, with the recent advancements in satellite return channels and on-board processing technologies, satellites are now able to provide full two-way services to and from earth terminals [3]. Additionally, several techniques for on-demand onboard switching have been proposed to make efficient use of satellites capacity [4]. Unlimited connectivity can be accordingly guaranteed. The advent of ka-band guarantees more availability of spectrum to support broadband multimedia communication [5], [6]. This has spurred further on the expansion of multimedia satellite networks. To encourage the deployment of cost-effective terminals with small antennas (e.g., Very Small Aperture Terminals (VSATs) and Ultra Small Aperture Terminals (USATs)), satellite channels with higher frequencies, such as V-band (36–51.4 GHz) and millimeter wave (71–76 GHz), have also been developed. These high frequencies will enable scalable mobility and ubiquitous connectivity across the world. Various mechanisms have also been proposed to cope with the well-known problems associated with rain and atmospheric attenuation at these frequencies. Given these advancements and on-going enhancements in satellite communications, it is now possible to design and implement satellite based communication systems for high bit rate services.
Explicit Load Balancing Technique for
NGEO Satellite IP Networks With On-Board
Processing Capabilities
NGEO Satellite IP Networks With On-Board
Processing Capabilities
ABSTRACT—Non-geostationary (NGEO) satellite communication systems offer an array of advantages over their terrestrial and geostationary counterparts. They are seen as an integral part of nextgeneration ubiquitous communication systems. Given the non-uniform distribution of users in satellite footprints, due to several geographical and/or climatic constraints, some Inter-Satellite Links (ISLs) are expected to be heavily loaded with data packets while others remain underutilized. Such scenario obviously leads to congestion of the heavily loaded links. It ultimately results in buffer overflows, higher queuing delays, and significant packet drops. To guarantee a better distribution of traffic among satellites, this paper proposes an explicit exchange of information on congestion status among neighboring satellites. Indeed, a satellite notifies its congestion status to its neighboring satellites. When it is about to get congested, it requests its neighboring satellites to decrease their data forwarding rates by sending them a self status notification signaling message. In response, the neighboring satellites search for less congested paths that do not include the satellite in question and communicate a portion of data, primarily destined to the satellite, via the retrieved paths. This operation avoids both congestion and packet drops at the satellite. It also ensures a better distribution of traffic over the entire satellite constellation. The proposed scheme is dubbed “Explicit Load Balancing” (ELB) scheme. While the multi-path routing concept of ELB has many advantages, it may lead to persistent packet reordering. In case of connection- oriented protocols, this phenomenon results in unnecessary shrinkage of the data transmission rate. A solution to this issue is also incorporated in the design of ELB. The interactions of ELB with mechanisms that provide different QoS by differentiating traffic (e.g., Differentiated Services) are also discussed. The good performance of ELB, in terms of better traffic distribution, higher throughput, and lower packet drops, is verified via a set of simulations using the Network Simulator (NS).
INTRODUCTION
DESPITE the recent advances in terrestrial communication technologies, the ever-growing community of Internet users poses serious challenges to current terrestrial networks. Terrestrial networks are expected to provide a plethora ofbandwidth-intensive services, with different Quality of Service (QoS), to a potential number of users, dispersed over extensively wide areas and requiring different degrees of mobility. To cope with this issue, network technicians and telecommunication operators have envisaged optical-fiber networks and have considered temporary solutions such as Asynchronous Digital Subscriber Line (ADSL) and High-rate DSL (HDSL) technologies. However, as the demand for advanced multimedia services is growing in terms of both the number of users and the services to be supported, applying such solutions to bridge the last mile between local service providers and end-terminals will require an immense investment in terms of time, infrastructure, and human resources. Building a cost-efficient global ubiquitous infrastructure is one of the major challenges before telecommunication industries in the current century. In this regard, and considering the fact that more than half of the world lacks a wired network infrastructure, satellite communication systems are seen as an attractive solution. The efficiency of satellite-based broadband services is strongly remarkable in remote zones and low-density population areas. The key technologies required to support broadband communications over satellite systems have been already developed [1], [2]. Indeed, with the recent advancements in satellite return channels and on-board processing technologies, satellites are now able to provide full two-way services to and from earth terminals [3]. Additionally, several techniques for on-demand onboard switching have been proposed to make efficient use of satellites capacity [4]. Unlimited connectivity can be accordingly guaranteed. The advent of ka-band guarantees more availability of spectrum to support broadband multimedia communication [5], [6]. This has spurred further on the expansion of multimedia satellite networks. To encourage the deployment of cost-effective terminals with small antennas (e.g., Very Small Aperture Terminals (VSATs) and Ultra Small Aperture Terminals (USATs)), satellite channels with higher frequencies, such as V-band (36–51.4 GHz) and millimeter wave (71–76 GHz), have also been developed. These high frequencies will enable scalable mobility and ubiquitous connectivity across the world. Various mechanisms have also been proposed to cope with the well-known problems associated with rain and atmospheric attenuation at these frequencies. Given these advancements and on-going enhancements in satellite communications, it is now possible to design and implement satellite based communication systems for high bit rate services.
