## 6 Conclusions and Discussion of Future Work  
Because of the way research is commissioned, it is sometimes not apparent that wireless links suffer not just from an increased level of errors but that the problems of congestion at the input to the wireless channel does not go away either. The errors tend not to be isolated but are correlated as bursts. This paper proposes a scheme that is both error resilient and congestion resilient. The error resilience scheme is multi-faceted as it includes adaptive rateless coding, ARQ error control, and source-coded data partitioning.  
The proposed sized-based scheduling solution, specialized to data-partitioned video streams, will certainly benefit the types of content favored by mobile viewers according to quality-of-experience studies, which are studio scenes with limited motion activity. Active sports clips, especially those with small balls, are less attractive but may become more so as the move to higher resolutions on mobile  
Figure 23: Objective video quality for _Stefan_ when using both scheduling approaches, by “size” and the equi-spaced “norm”.  
Figure 22: Objective video quality for _Paris_ when using both scheduling approaches, by “size” and the equispaced “norm”.  
devices continues (e.g., full Video Graphics Array (VGA) format (640 \(\times\)480 pixels/frame at 30 Hz) for streaming in Apple's FaceTime). However, in that case the problem of packet scheduling regimes may become more acute. Future work will require a robust investigation of appropriate packet scheduling for congested broadband links for a range of content genres.  
High Performance Video Coding (HEVC) [62] emerged as a successor to H.264/AVC during the period of this research. Broadly, HEVC refines and extends the structure of H.264/AVC rather than radically departing from it. However, very few error-resilience tools were included in HEVC, in part because some of these, such as Flexible Macroblock Ordering, were reportedly [63] rarely used in commercial applications. However, this situation provides an opportunity for researchers themselves to add data partitioning to the HEVC source code. Another likely reason why few error resilience tools were built into HEVC is that a full implementation is likely to be computationally demanding, including data partitioning coming at a cost of some other feature of the code. In contrast, direct and efficient implementation of Raptor code has become easier to accomplish with the development of RaptorQ [64], a systematic version of Raptor code software. However, inclusion of such code in a commercial product is subject to a patent in many jurisdictions even if it may be available for educational and research purposes. Such issues do not fall within the scope of this article, though in terms of future research, increased opportunities of confirming the error-correcting performance of Raptor codes now exist. The inner LT code of Raptor is a late decoding type of coding scheme, as sufficient symbols need to be collected before decoding can commence. If network coding is permitted, Switched Code [65] is then a low-latency form of rateless code that is worthy of investigation by us for multimedia applications, as it permits early decoding of packets. Another area for future work is in error resilience. For example, intra-refresh provision in [66] is varied according to an estimate of the rate-distortion trade-off that takes into account expected errors over a wireless channel.