Large Doppler shifts are a challenge in underwater wireless acoustic communication compared to terrestrial wireless radio communication. Resampling and Doppler shift compensation are used at the receiver to counteract the effect of the Doppler shift introduced during transmission. Imperfect resampling can degrade system performance. While the conventional choice of Doppler compensation factor minimizes the intercarrier interference (ICI) around the central subcarrier, we show that using a Doppler compensation factor that treats lower subcarriers preferentially in terms of ICI can significantly improve the system performance in the case of imperfect resampling. Two ad-hoc schemes are proposed in the paper to find suitable Doppler compensation factors for a given Doppler factor and percentage of error in the resampling factor. The knowledge of these parameters facilitates the performance analysis of the schemes, rather than focusing on design aspects. The proposed schemes are tested for various relative vehicular speeds. In addition, different Doppler factors for the paths are considered. In all cases, our proposed schemes achieve higher video peak-signal-to-noise ratio compared to conventional schemes.

Current VR headsets are tethered to computers which limits mobility and poses a tripping hazard. Delivering VR content over a wireless link is challenging due to the high data rates and stringent time delivery requirements. Millimeter wave communication at 60 GHz (WiGig) can meet these requirements, but, it is unreliable due to blockages and beam misalignments. In this poster, we present an idea of using both WiFi and WiGig interfaces to transmit the VR content. We divide a video frame into tiles and prioritize the tiles in the user's field of view. Based on the wireless link conditions, the tiles are encoded with varying qualities and transmitted over either WiFi or WiGig interface. We formulate an optimization framework to deliver the VR video with high reliability and low latency.

Disposable wireless video sensors have many potential applications but are subject to stringent energy constraints. We studied the minimization of end-to-end distortion under an total energy constraint, by means of optimizing FEC code rate, number of source bits, and energy allocation between video encoding and wireless transmission. A two-step approach is employed. First, the FEC rate is optimized by exhaustive search. Then a binary-search-based algorithm is proposed to optimize the energy allocation and number of source bits. Experiments show that the algorithm achieves a PSNR gain up to 1dB over some reasonable baselines. A simpler suboptimal algorithm is also tested and exhibits similar performance.

Cognitive radio is the solution to the scarcity of the licensed spectrum. The achievability of the sum-capacity of the cognitive radio under different channel conditions and message structures were studied in literature, specifically for the linear deterministic approximation (LDA) interference channel with cumulative message sharing (IFC-CMS). It was postulated that the achievability of the sum- capacity of the 2-user LDA interference channel with cognitive relay (IFC#x002B;CR) is sufficient to achieve the sum-capacity of the 3-user IFC-CMS under certain channel gain conditions for symmetric channels. In this paper, we will prove that this is only true under more strict conditions. Consequently, more than one user needs to be non-causally cognizant of the messages of the other users, thus increases the constraints on the cognitive system. Finally, the sum-capacity for the K-user LDA IFC-CMS is computed using the same achievable schemes of the 3-user LDA IFC-CMS.

In Long Term Evolution networks, the handover used is a hard handover. Therefore, choosing the handover parameters is critical for the users' satisfaction. Otherwise they will suffer from a high rate of radio link failures. Usually, there are two contradictory handover problems: radio link failures and unnecessary handovers (ping-pongs). Increasing some handover parameters (e.g. handover margin) leads to less ping-pongs, but higher radio link failure. This is not good for the network operators, as a high ping-pongs rate causes a large unnecessary overhead to the network. However, having a high radio link failure decreases the customers' satisfaction, especially the customers using real time data. For the customers using non-real time data (e.g. web browsing and FTP download), the radio link failure problem will not severely affect their satisfaction. In this paper, a new algorithm is introduced to choose the most suitable values of the handover parameters, based on the user's behavior. This is done by categorizing the users in the network into four categories. The categorization is done according to the users' speeds and the data traffic used (real time traffic versus non-real time traffic). The handover parameters in each category are optimized independent from the other categories. The proposed algorithm shows a better performance for each category of users in terms of the most preferred metric for this category compared to dealing with all users as a single category.