Abstract
We focus on the optimization of real-time multimedia transmission over 802.11-based ad hoc networks. In particular, we propose a simple and efficient cross-layer mechanism that considers both the channel conditions and characteristics of the media for dynamically selecting the transmission mode. This mechanism called media-oriented rate selection algorithm (MORSA) targets loss-tolerant applications such as VoD that do not require full reliable transmission. We provide an evaluation of this mechanism for MANETs using simulations with NS and analyze the video quality obtained with a fine-grain scalable video encoder based on a motion-compensated spatiotemporal wavelet transform. Our results show that MORSA achieves up to 4 Mbps increase in throughput and that the routing overhead decreases significantly. Transmission of a sample video flow over an 802.11a wireless channel has been evaluated with MORSA. Important improvement is observed in throughput, latency, and jitter while keeping a good level of video quality.
Highlights
With recent performance advancements in computer and wireless communications technologies, mobile ad hoc networks (MANETs) are becoming an integral part of communication networks
Power control done at the physical (PHY) layer can affect all other nodes in MANETs, by changing the levels of interference experienced by these nodes and the connectivity of the network, which impacts routing
We focus on the optimization of realtime multimedia transmission over 802.11-based MANETs
Summary
With recent performance advancements in computer and wireless communications technologies, mobile ad hoc networks (MANETs) are becoming an integral part of communication networks. We propose a simple and efficient cross-layer protocol which dynamically adjusts the transmission mode, that is, the physical modulation, rate, and possibly the forward error correction (FEC) This protocol called MORSA (media-oriented rate selection algorithm) is convenient for loss-tolerant (LT) applications such as video or audio codecs that do not require 100% transmission reliability (i.e., a certain level of packet error rate (PER) or bit error rate (BER) can be concealed at the receiver). Our results show that MORSA can reach a comparable video quality than the one obtained with the standard mechanism while using only a very low (5%) FEC overhead at the application level instead of the physical layer FEC (50% or 25%) This significantly decreases transmission delay of the application.
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