| To increase network capacity, future protected military satellite communication systems will carry packet-switched traffic enabling users to access bandwidth on demand. The terminals have various transmission and power capabilities and must operate under time-varying channel conditions induced by weather, mobility, and antenna beam patterns. By dynamically allocating resources to users, the limited RF bandwidth is shared efficiently among tens of thousands users providing significantly higher data rates than can be afforded in a fixed rate system.
In previous work, we designed link-layer dynamic resource allocation algorithms that optimized link layer efficiency and throughput while achieving network layer performance objectives. Here we investigate the impact of dynamic resource allocation for terminals facing the most difficult channel conditions, the Comm-On-The-Move (COTM) terminals. Many terminals supported by the future satellite network will be COTM terminals. The channel blockage endured by COTM terminals not only results in loss of data rate, but also implies a loss of control messages. The control messages request resources and inform the terminal of its access slots and operational mode. Loss of these messages can result in the loss of data access for durations much longer than the blockage and even cause terminals to become disconnected. The goal of this study is to design and evaluate messaging protocols that are robust to channel blockages typically endured by a COTM terminal.
An OPNET simulation for the satellite network is developed. Multiple terminals with varying power and transmission capabilities are connected under a single uplink and downlink satellite beam. Each terminal carries traffic from several types of applications that are serviced using multiple Quality of Service (QoS) queues. Channel degradations due to rain, edge-of-beam effects, minor fading fluctuations, COTM blockage, as well as channel correlations between terminals are modeled. The loss of data packets and control messages due to queue overflow and channel degradation are modeled.
Payload dynamic resource allocation algorithms are developed that incorporate the uplink and downlink messaging protocols designed for both COTM and non-COTM terminals. These uplink and downlink protocol designs trade resource allocation algorithm efficiency for robustness to loss of control messages. The QoS performance for both COTM and non-COTM terminals is evaluated. |