Once the available network
infrastructure to the video streaming session has been established, we assume that an
overlay network topology can convey (in frequent intervals) information about the
expected bit error rate (BER), the queuing delay for each link, as well as the guaranteed
1 Existing IEEE standards [12] already support such QoS mechanisms, which, barring interference and
environment noise, provide guaranteed transmission time for each admitted application (video flow).
2 HCCA: HCF Controlled Channel Access, where HCF stands for Hybrid Coordinator Function [12].
Cross-layer Optimized Video Streaming over Wireless Multi-hop Mesh Networks
107
bandwidth under the dynamically-changing modulation at the PHY. Several examples of
such application-layer overlay networks have been proposed in the literature [19] [20].
Under the above assumptions, we make the following contributions. For video
packets of each hop in the mesh network, we propose an optimization framework that
jointly determines per packet: (a) the optimal modulation at the PHY, (b) the optimal retry
limit at the MAC, (c) the optimal path (route) to the receiver in the remaining part of the
mesh network and (d) the application-layer optimized packet scheduling, given a
predetermined topology and time reservation per link using the concepts of IEEE 802.
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