Apparatus and method for efficient TDMA bandwidth allocation for TCP/IP satellite-based networks

Abstract

A communication system balances message traffic between return channel groups and within the groups, so that the user does not control the specific transmission frequency used. Uplink frequencies and bandwidths for the return channels are set by the system in a return channel control message in the broadcast signal so as to account for system and return channel group loading, and to account for user message backlogs. An initial transmission from a remote user may be made using an ALOHA-type burst signal that provides a message backlog to the control station, and is made on a frequency determined from a randomly weighted, load-based frequency selection process. The system, and not the individual users determine the frequency and channel allocations. For large backlogs or priority users, periodic bandwidth is provided. A method for balancing loads among and between groups of return channels in the communication system includes requesting return channel bandwidth in an uplink message from a remote user to a control station. The uplink message may include a both a backlog indicator and a bandwidth allocation request provided to a Network Operations Center (NOC) which can be used to set the return channel bandwidth and frequency for the remote uplink. A user message is transmitted on the designated return channel frequency using bandwidth allocated in accordance with the backlog indicator and a bandwidth allocation request so that traffic loads are maintained in balance between established return channel frequency groups, and within each return channel frequency group.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application of Kelly et al. entitled “Efficient TDMA Bandwidth Allocation for TCP / IP Satellite-Based Networks”, Ser. No. 60 / 188,375, filed on Mar. 10, 2000, and of U.S. Provisional Application of Kelly et al. entitled “Two-way Communications System and Method”, Ser. No. 60 / 197,246, filed on Apr. 14, 2000, the entire contents of each being incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates generally to a bandwidth allocation scheme for Time Division Multiple Access (TDMA) systems, and specifically to efficient bandwidth allocation for Transmission Control Protocol / Internet Protocol (TCP / IP) systems over a TDMA-based satellite network. [0004] 2. Description of the Related Art [0005] Using satellites for Internet and Intranet traffic, in particular multicasting of digital video through us...

AI Technical Summary

Benefits of technology

[0028] The present invention in all its embodiments, collectively and individually, has a number of features that distinguish it over conventional bandwidth allocation schemes. For instance, the present invention dynamically assigns bandwidth based on how much the users actually need, and directs uplink frequency changes to balance traffic load. The approach of the apparatus, system and method of the present invention not only balances the load between return channel groups, but within each return channel group as well, ensuring an optimized bandwidth allocation scheme. The system is set up to automatically load balance every time a remote user starts a new uplink session, and accomplishes the goal of having roughly the same number of uplink users sharing each inroute channel, even with a large and increasing number of system users. This approach is particularly well-suited and optimized for TCP / IP satellite traffic, and is a highly desirable component to operating an efficient TCP / IP system over a TDMA-based satellite system, including multiple satellites networked with the required supporting ground infrastructure.

[0029] Finally, the method and system of the present invention allow expansion to an essentially unlimited number of users on the same return channels without extensive hardware and software modifications, and allows these users to all have approximately equal access to the return channel capacity, or bandwidth. This capability is brought about, at least in part, by sharing system frame timing among all return channel groups, regardless of the broadcast source of the return channel control information sent from the control station, possibly including multi-satellite links. The system preferably shares a common non-real time reference provided to all remote users, regardless of the particular broadcast being received, or its source.

Problems solved by technology

Unfortunately, as these systems are mass-marketed to consumers and the number of users increases, the generally limited number of inbound channels can experience congestion and reduced user throughput as a result of an increasing number of users competing for a finite number of inbound satellite channels.

The potential benefits that VSAT technology bring to consumers in the area of broadband delivery are necessarily diminished by the limited bandwidth, available on the inbound channels.

However, even if the user has nothing to transmit, the time slot is still reserved, resulting in inefficient utilization of the available bandwidth.

In addition, providing each remote user access to needed uplink bandwidth (essentially equivalent to slot access) becomes more difficult when sharing a larger number of different inroute or uplink channels among a large number of users.

Establishing an equitable allocation of uplink bandwidth for each of the uplink or inroute users is difficult due to uneven (i.e. fluctuating heavy or light) loading within a group of uplink channels, and due to relatively uneven loading between groups of uplink channels.

As the market expands, the number of possible uplink users further increases, and the previous approaches to allocation of return channel bandwidth to users in fixed, predetermined uplink channel groups necessarily requires additional hardware and system complexity in order to accommodate the increased uplink demand.

If return channel groups base their frame timing on a particular satellite broadcast which is not common to all remote users across return channel groups, then users are necessarily limited to their pre-assigned return channel group, thus limiting flexibility.

Further, this approach becomes increasingly inefficient both in terms of hardware allocation, cost, and uplink channel bandwidth utilization, since many of the available groups of uplink channels may be either heavily or lightly loaded or subject to load imbalance relative to other inroute groups.

This could be the result of each user being hard-configured for access to a specific inroute channel, or to only a limited number of channels, whether due to hardware or software limitations, or the frame timing considerations discussed above.

This problem is exacerbated by the bursty and somewhat unpredictable nature of such transmissions, which also may result in inefficient use of the available bandwidth.

If another system transmits at the same time, a collision occurs, and the frames that were transmitted are lost.

Further, the delays to users actually having traffic to transmit may not be acceptable in time-sensitive applications, particularly because the ALOHA technique “wastes” bandwidth, and hence time slots, on users having no or low traffic load to transmit.

Also, data may be lost if users contend for the same slot, but not as much data as would be lost in pure ALOHA.

A drawback to this method is that more time is required for channel setup, adding further delay, and there may be too few or too many packets assigned for message transmission for each user, leading to at least some inefficiency in bandwidth utilization.

Further, dynamic reallocation of bandwidth is not efficiently accomplished using this approach.

Even if an ALOHA-type of channel access scheme is successfully used to gain access to bandwidth for uplink, there is still the problem of either over or under-loading the return channels, and also of having an imbalance between groups of return channels.

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