The huge amount of data embodied in a video signal is by far the biggest burden on existing wireless communication systems. Adopting an efficient video transmission strategy is thus crucial in order to deliver video data at the lowest bit rate and the highest quality possible. Unequal error protection (UEP) is a powerful tool in this regard, whose ultimate goal is to wisely provide a stronger protection for the more important data, and a weaker protection for the less important data carried by a video signal. The use of efficient video delivery techniques becomes more important when 3D video content is transmitted over a wireless channel, since it contains twice as much data as 2D video. In this dissertation, we consider the UEP problem for transmission of 3D video over wireless channels. The proposed UEP techniques entail relatively high computational complexity which lend themselves to be more suitable for video-on-demand delivery, where the time-consuming computations are done offline at the transmitter/encoder side.

To adopt UEP for 3D video, we consider a general problem of joint source-channel coding (JSCC). Solving the JSCC problem yields the optimum amount of 3D video compression as well as the optimum FEC (forward error correction) code rates exploited for UEP. We first need to estimate the perceived quality of the reconstructed video at the receiver. The lack of a good objective metric for 3D video makes adopting UEP a more challenging and problematic task compared to 2D video. Fortunately, for 3D video, some quality thresholds are derived in the literature based on the PSNR (peak-signal-to-noise-ratio) metric through experimental tests. These thresholds allow us to formulate the JSCC optimization problem using the PSNR in a straightforward but different way from the typical counterpart optimization problems in the literature. More precisely, we put the constraints of the optimization problem on the quality of the reconstructed 3D video and set our goal to minimize the total bit rate. We adopt the multiview coding (MVC) extension of the H.264/AVC. We also propose a scalable variant of MVC and formulate and solve the JSCC optimization problem for it. We show that significant gains are obtained if the proposed UEP scheme is combined with asymmetric coding.

We also tackle the UEP problem for the video plus depth (V+D) format. We employ the SSIM (Structural SIMilarity) metric for designing UEP for V+D, since it has been shown that PSNR does not properly characterize the perceived quality of a 3D video represented in V+D format. Moreover, the synthesized right view always shows a huge PSNR loss (even in the absence of compression), which does not even allow us to use the asymmetric coding PSNR thresholds. This motivated us to adopt the classical JSCC problem formulation, where our goal is to maximize the quality of the reconstructed left and right views, given that there is a constraint on the sum of the number of source bits and the number of FEC bits. We show that UEP provides significant gains compared to equal error protection. We also derive several interesting results; some of them are in accordance with what have already been published in the literature and some of them are not. We show that the reason for this inconsistency is that we are solving the UEP problem in a more general situation, which yields novel solutions.

Lastly, we focus on UEP for video broadcasting over wireless channels. Our goal here is to design a UEP-based video broadcasting system that well serves all the users within the service area of a base station. In a service area, there exist heterogeneous users with different display resolutions operating at different bit rates. Spatially scalable video is an excellent video compression format for this scenario, since it allows a user to decode that portion of the scalable bit stream that fits its operating bit rate as well as its display resolution. We tackle this problem for a MIMO (multi-input-multi-output) channel which enables us to exploit either spatial diversity or spatial multiplexing in a multipath fading channel to increase channel reliability or throughput, respectively. We employ spatial diversity techniques, in particular the Alamouti code, to encode the base layer. We also adopt spatial multiplexing techniques, in particular the V-BLAST, to encode the enhancement layer. By controlling the power allocation between the base layer and the enhancement layer, we can control the level of protection we provide to each of them. We also show that the adoption of scalable video in our system yields much higher gains compared to non-scalable video.

The perceptual quality of videos has attracted much attention, because it is hard to estimate by objective metrics, and because it is affected by many conditions. Compression, transmission and viewing conditions all impact the perceptual quality. In this dissertation, we aim to preserve and enhance the perceptual quality in different cases.

The impact of ambient illumination on the perceptual quality of traditional 8-bit 2D video is first studied. Some details, especially those in dark areas of videos, are invisible in bright ambient light, because of the reflection of ambient light and the reduction of the sensitivity of human eyes. We analyze the display characteristics and human visual sensitivity, and propose methods to enhance the contrast and details without increasing the peak brightness of the display.

Another viewing condition, viewing distance, is also investigated in this dissertation. A display device held farther away may have fewer details visible compared to a device held closer. The unnoticeable details can be filtered before compression, which can reduce the bit-rate of the video. A subjective test was conducted to demonstrate the bit-rate saving without degrading the perceptual quality.

Besides the traditional 8-bit videos, a new form of video, high dynamic range (HDR) videos, is studied in Chapter 4 of this dissertation. There can be banding artifacts in the inverse tone mapped HDR videos which degrade the perceptual quality, though the impact on the objective quality is subtle. An enhancement filter is proposed to remove the banding artifacts and reduce compression artifacts, and at the same time, preserve true edges and details. The parameters of the filter are determined by minimizing the proposed perceptual distortion metric.

The perceptual quality of 3D video is explored in Chapter 5. In particular, the stereoscopic 3D video of the 2D+depth format is studied. Transmission of such videos through networks can be affected by packet losses. The importance of packets is investigated by a human observer experiment. A prediction model of the importance is developed using features such as the video type, frame type, and spatial location of the packets.

Device-to-device (D2D) communication allows direct transmission between multiple transmitter-receiver pairs in cellular systems by reusing the spectrum, and offloads local traffic from the base station.

In resource allocation for a D2D video transmission system in a block fading environment, the performance improvement by applying the exact symbol error rate (SER) is compared with the conventional signal-to-interference-plus-noise-ratio (SINR) based SER evaluation method that uses a Gaussian approximation (GA) for the aggregated interference. An analytical SER expression for a D2D system using multicarrier bandlimited QAM is derived and then used in the resource allocation algorithm. Centralized resource allocation for the D2D system is considered, given knowledge of the channel state information and the rate distortion information of the video streams, and an iterative algorithm for subcarrier assignment and power allocation is proposed. Bit-level simulations for different numbers of D2D pairs demonstrate a considerable improvement on user capacity and video peak signal-to-noise ratio by incorporating the proposed SER expression compared to the GA. By invoking the conditions under which the central limit theorem holds, and comparing these conditions with the number of interferers and the power ratio of the dominant interferer in the simulated D2D system, the reason why the GA for the interference results in a pessimistic performance is also studied.

Resource allocation algorithms for D2D video transmission with a filter bank multicarrier waveform in a Rayleigh fading environment are investigated. The co-channel interference between D2D pairs is analyzed, and a cross-layer algorithm with a subcarrier assignment outer loop and a power control inner loop, which aims to optimize the overall video quality, is proposed. Unlike the non-convexity in physical layer power control for maximizing the total throughput, the cross-layer power control problem is convex under certain conditions, so a high quality solution for power control can be efficiently found. Simulation results demonstrate a higher overall video quality by the proposed cross-layer algorithm compared to baseline algorithms.