Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-04-21
2002-09-03
Olms, Douglas (Department: 3632)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S232000
Reexamination Certificate
active
06445707
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and scheme for congestion management in two-way data satellite communications with residential and business terminals—hereinafter referred to as Broadcast Rate Control Allocation (BRCA). More particularly, the invention is directed to a method for supporting efficient transport for Available Bit Rate (ABR) services over a satellite, wherein the satellite switch provides feedback (which is broadcast to all terminals), in order to control the rate at which terminals can send their data to satellite.
While the particular embodiment in this invention is directed to Geostationary Earth Orbit (GEO) satellites supporting Asynchronous Transport Mode (ATM) services, it should be appreciated that the invention is applicable to the transport of data in other (than ATM) packet formats over satellites in other (than GEO) orbits, provided that a grade of service for data is specified, similar to that specified for ABR services.
BACKGROUND OF THE INVENTION
Broadband satellite networks are becoming an important segment of the global communication infrastructure. They are required to provide seamless integration of applications and services that have traditionally been available via terrestrial networks. In order to ensure inter-operability between terrestrial and satellite networks, efforts have been made to expand/adapt the existing protocols for terrestrial networks to satellite environment. These efforts have not always led to full utilization of satellite resources, as these protocols have been optimized for terrestrial applications. New protocols, specifically tailored to satellite environment are therefore required.
In a typical satellite network the satellite bandwidth, buffer and computational resources are shared by a relatively large population of terminals, connected to end-users and sending traffic corresponding to various applications (voice, video, data). The traffic associated with data applications exhibits high variability and unpredictability. Each connection requires certain satellite bandwidth, in order to guarantee the Quality of Service (QoS) expected by the end user. Given the diversity of traffic characteristics and of bandwidth and QoS requirements associated with different applications, future satellite networks will use on- board fast packet switching, in order to ensure efficient use of satellite resources while guaranteeing QoS for all connections. ATM establishes itself as the preferred transport mode in today's Broadband Integrated Services Digital Networks (B-ISDN), including the satellite networks. It is therefore considered in this invention that the traffic will be transported over the satellite in ATM-like packets, i.e. packets which preserve the structure of standard ATM cells, while adding a satellite-specific header to support satellite-specific functions, such as uplink scheduling and on-board routing. A standard ATM cell is fifty three-byte long, consisting of a five-byte header and a forty eight-byte information field, also referred to as payload. Depending on the particular implementation, the On-Bard Processor (OBP) may use some information from the ATM header, in addition to the information contained in the satellite-specific header. After being processed, the ATM packets are stripped of the satellite- specific header before being sent to their downlink destinations. The information in the ATM header may be preserved in order to allow for easy integration of the satellite into a broader ATM network.
The use of on-board switching (of ATM-like packets) allows for statisical multiplexing of the traffic corresponding to various connections, thus improving satellite resources utilization. The most valuable resource is the bandwidth (capacity) of the air interface between terminals and satellite, on both uplink (UL) and downlink (DL). In contrast to the wired networks, in a satellite network the physical medium (link) is shared by all active terminals logged onto the system. Advanced multiple access or Medium Access Control (MAC) protocols are therefore required to provide efficient, dynamic and fair sharing of satellite bandwidth among these terminals, while supporting various levels of QoS guarantees (depending on application), given to sources as part of the traffic contract. A system for efficient transport of multimedia traffic over a satellite network is described in U.S. patent application Ser. No. 08/669,609, submitted by EMS Aerospace Limited (C. Black et al.) on Jun. 24 1998 and entitled “Data Communication Satellite System and Method of Carrying Multi-Media Traffic”. In this system a key element in achieving efficient resource utilization is a novel Dynamic Uplink Access Protocol (DUAP).
The DUAP proposed by EMS is from the Combined Free and Demand Assignment Multiple Access (CFDAMA) family of protocols, which are based on Multiple Frequency-Time Division Multiple Access (MF-TDMA) transmission frame, capable of providing efficient and flexible bandwidth utilization. Protocols from this family distribute transmission bandwidth (capacity) based mainly on demands (or requests) from terminals, following a fairness algorithm. The bandwidth left after all requests have been satisfied is distributed a freely across terminal population.
EMS's implementation of CF-DAMA protocol is based on four capacity request/assignment mechanisms (or strategies), each receiving a different priority from the UL scheduler, an entity responsible for capacity allocation to terminals which can be located on board the satellite or on ground. The request strategies lead to four types of capacity (or channels), tailored to match the needs and priorities of various ATM service classes: Reserved Capacity (RC), Rate-Based Dynamic Capacity (RBDC), Volume-Based Dynamic Capacity (VBDC) and Free Capacity (FC). The capacity types are essential for the invention described in the application, therefore they are briefly reviewed in the following paragraphs.
In the RC assignment strategy a terminal states its need for UL and DL capacity at connection set-up time, in terms of a fixed number of payload slots per frame. If the connection is admitted by the network controller, the terminal will have the requested number of time slots assigned to it every frame (reserved) for the duration of the connection, so that the traffic is not subjected to any delay except for the propagation delay (no scheduling and queuing involved). The network controller must ensure (at connection set-up time) that the total RC for all connections does not exceed the total system capacity. This strategy is aimed toward real-time (RT) connections, such as Constant Bit Rate (CBR) and real time-Variable Bit Rate (rt-VBR), which cannot tolerate or have strict constraints on delay and delay variation (e.g. voice connections), and is especially suitable for applications with smooth traffic characteristics.
In the RBDC assignment strategy, a terminal explicitly requests a number of UL payload slots in each frame. A request remains effective for a number of frames (until it is updated by the terminal or as long as it has not timed out), so that the request is also implicit. In one implementation option of the RBDC strategy, the UL capacity is guaranteed by the scheduler up to the maxRBDC value negotiated at connection set-up time. In contrast to the RC strategy, the RBDC strategy allows for statistical multiplexing among terminals, thus resulting in a more efficient use of satellite bandwidth. Nevertheless, the network controller must also ensure that total RC and maxRBDC of all terminals do not exceed the total available UL and DL capacity. The RBDC strategy can be used for non-real-time connections, such as non real time Variable Bit Rate (nrt-VBR) connections, if scheduling delay is tolerated, and ABR connections.
In the VBDC assignment strategy, a terminal signals its request in terms of total number of UL payload slots required to empty its queue. The network, however, does not provide any guarantee on capacity availability. The UL scheduler will d
Di Girolamo Rocco
Iuoras Augustin
Takats Peter
Wibowo Eko A.
EMS Technologies Canada, Limited
Olms Douglas
Vanderpuye Ken
LandOfFree
Broadcast rate control allocation (BRCA) for congestion... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Broadcast rate control allocation (BRCA) for congestion..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Broadcast rate control allocation (BRCA) for congestion... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2902340