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To efficiently utilize limited RF resources, future packetswitched satellite networks are being designed to dynamically allocate resources on the uplink and downlink. These dynamic resource allocation algorithms may result in uplinks and downlinks with time varying data rates. Providing QoS over these time varying channels is a difficult task. Several issues are examined including the required interaction between the network layer and link layer, the impact of links with time varying data rates on QoS schedulers, and downlink queuing strategies for achieving downlink QoS.

SUMMARYFuture packet switched military satellite communication networks are being designed with dynamic resource allocation on the up-and down-links in order to efficiently utilize the limited Radio Frequency (RF) resources. The resource allocation algorithms must be designed to achieve good system efficiency and user performance in addition to optimizing link-layer efficiency. An OPNET simulation environment is used to model and evaluate system performance for a satellite network with dynamically provisioned upand down-links under dynamic traffic and channel variations. Link-layer resource allocation algorithms are developed and performance is evaluated in terms of application layer throughput, loss, delay, and jitter as well as system resource utilization.

To maximize link layer efficiency, future protected military satellite communication networks will be provisioned dynamically as traffic demands and channel conditions vary. As a significant number of terminals supported by the system will be Comm-on-the-Move terminals, which suffer from channel blockage in addition to weather events, dynamic resource allocation requires careful coordination between terminals and the payload. Via an OPNET simulation, protocols that are robust to control message losses yet allow the system to be dynamic and responsive to changes are studied. A transmit-until-acknowledged approach is usedfor less frequent messages while a periodictransmit approach is used for more frequent messages. The performance of both constant-rate and TCP-based application traffic in blockage environments over this dynamically allocated network is also evaluated.I. INTRODUCTION To increase network capacity, future protected military satellite communication systems will carry packetswitched traffic and dynamically allocate resources to users when they need it rather than provisioning a fixed circuit for each user. This allows the limited RF bandwidth to be shared efficiently among thousands of users and allows the system to achieve significantly higher data rates. There are two main components to dynamic resource allocation (DRA). One is Dynamic Coding and Modulation (DCM), which adjusts the terminal communication modes dynamically to meet time-varying channel conditions induced by weather, mobility, jamming, antenna beam patterns, etc. Compared to always keeping terminals in robust but low-rate modes, DCM allows much higher data rates to be achieved and less resources to be consumed when the channel is good. The other component of DRA is dynamic allocation of bandwidth and time resources to meet dynamic traffic patterns. It is well-known that packetswitched traffic may be highly bursty. By giving a terminal just enough resources when needed and freeing up unused resources, the overall resources can be shared more efficiently and more users can be accommodated. Both components of DRA require careful coordination between the terminals and the payload using control messages. In previous work, link-layer DRA algorithms that optimized link layer efficiency and throughput while achieving network layer performance objectives, including Quality of Service (QoS), were designed [1]. This work extends the study in [1] and incorporates the effects of channel blockages experienced by Comm-OnThe-Move (COTM) terminals. For future satellite networks, a significant number of terminals supported by the satellite will be COTM terminals. The channel blockage experienced by COTM terminals may result in not only loss of data packets but also loss of control messages, which are vital for DRA operation. Inability to handle loss of control messages may further aggravate the effect of blockage on data traffic. In addition to being robust to control message losses, the protocols should also allow the system to be dynamic and responsive...

SUMMARYTo efficiently utilize limited RF resources, future military packet-switched satellite networks will dynamically allocate resources on the uplink and downlink. Designing the resource allocation algorithms to maximize link layer efficiency is insufficient. The resource allocation algorithms must work cooperatively with the network layer and transport layer to optimize network layer performance and provide quality of service (QoS) to applications and users. Several mechanisms for facilitating this required cooperation between the layers are presented. The individual roles and actions of the layers as well as their interaction are defined. QoS schedulers that continue to provide service differentiation in the presence of link variations are illustrated. Downlink scheduling architectures that provide terminal QoS guarantees are demonstrated. Finally, the interaction between TCP and the dynamic resource allocation algorithms is investigated, leading to suggested modifications of either the resource allocation algorithms, the TCP protocol, or both.