In this paper we focus on demand-assigned multipleaccess (DAMA) MAC protocols utilizing time division multiple access (TDMA). In TDMA, the channel is broken down into time slots of equal duration, and nodes are allocated slots in which to transmit their data. Slots can be preassigned prior to a mission or can be allocated dynamically as the need arises. Herein, we develop and simulate two dynamic allocation algorithms: the first provides fair scheduling of data, while the second provides strict priority scheduling of data. These protocols are simulated in a Tactical Targeting Network Technologies (TTNT) single-strike scenario which is a 78-node scenario with a varied traffic profile.We compare the performance of the fair scheduling and strict priority scheduling algorithms against a preassigned TDMA protocol. In addition to the scheduling algorithms two classification methods are used in these experiments, the first based on packet size and the second based on both message type and packet size. We find that adding dynamic allocation improves overall bandwidth utilization over the preassigned TDMA protocol for either type of classification. However classification based on packet size alone is not effective in providing service differentiation. Classification based on message type and packet size used with the strict priority scheduling offers the best priority treatment for this traffic profile.
I INTRODUCTIONIn this paper we develop a time-division multiple access (TDMA) method, which provides both bandwidthon-demand and QoS for the airborne networking environment. We use a Tactical Targeting and Network Technology (TTNT) single-strike scenario [1], [2] as a model for future airborne networking. Our results show that the QoS capability combined with a bandwidth-ondemand approach enhances the network performance as compared to a bandwidth-on-demand system without QoS.In the current tactical environment, most users are preallocated a fixed amount of bandwidth. As a result, if individual users are not currently using their bandwidth allocations, then this bandwidth is essentially wasted.Other users could be accessing this unused bandwidth to send their information at higher rates.Over the last few years two categories of Layer 3 QoS approaches have been developed: integrated services (intserv) [8]-[13] and differentiated services (diffserv) [14]-[18]. These Layer 3 mechanisms can be effective, especially in a fixed wired infrastructure where links are generally point-to-point.The future airborne network, as part of the planned Global Information Grid (GIG) will be an IP-based network [24], [25]. Also, one possibility for this future IPbased airborne network is that its corresponding Layer-2 access method will be contention-based to provide a bandwidth-on-demand capability. References [26] and [27] provide a general discussion of link-layer waveforms for the Airborne Network and the GIG. Given that in the commercial environment the extension of QoS to Layer-2 has been addressed in Ethernet 802.1p (part of 802.1D; see...
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