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As the conventional QAM has a square constellation, PAPR is high due to the corner signal points. To overcome this, the (3 × 2m)-ary QAM with even m was proposed recently. For odd m, the rectangular constellation has high PAPR and perfect Gray code, while the diamond constellation has low PAPR and imperfect Gray code. In this paper, we propose a scheme assigning quasi-Gray code to the diamond constellation...
In a massive machine type communication (massive MTC) network, wireless connections between machine type devices (MTDs) and eNodeBs are unreliable due to the interference caused by uncoordinated access of other MTDs. Furthermore, it is with a high probability that the retransmission from the outage source MTD will fail again due to the spatiotemporally correlated interference. In this paper, we design...
The number of signal points of a QAM constellation in LTE is an even power of 2, with the sizes of adjacent constellations differing by a factor of 4, resulting in very coarse granularity in constellation size selection. This paper presents real-number M-ary QAM constellations over multiple dimensions that fill the gap in the existing constellation sizes and result in lower PAPR. In addition, we propose...
For DFT-spread-OFDM or OFDM, if the delay spread varies in a wide range and the symbol duration is relatively short, adapting the cyclic prefix (CP) duration rather than using a fixed one may significantly improve the spectral efficiency while preventing inter-symbol interference (ISI). In practice, it may be beneficial to have a constant overall DFT-spread-OFDM/OFDM symbol time, which is the sum...
The human visual system (HVS) cannot perceive spatial frequency components in an image that are above a certain limit, the value of which is affected by factors such as the viewing distance. This has been exploited to improve the video coding efficiency by first filtering out redundant frequency components and then doing conventional video encoding. To facilitate the deployment of this scheme, we...
Recently HTTP based adaptive video streaming has gained significant attention. A video client predicts the future available bandwidth and then selects the appropriate bit rate for the video content in order to maximize the video quality while avoiding rebuffering. The often severe fluctuation in the available bandwidth in mobile wireless networks poses a challenge to the bit rate selection algorithm...
This paper presents an Active Queue Management (AQM) algorithm for improving the Quality of Experience (QoE) of video telephony over packet switched networks. The algorithm exploits the characteristics of the video coding structure, and builds on the Controlled Delay (Codel) active queue management algorithm recently proposed by Nichols and Jacobson to address the prevalent ‘bufferbloat’ problem in...
It has been shown that various statistics of the peak signal-to-noise ratio (PSNR) time series of a video sequence can be used to construct fairly accurate Quality of Experience (QoE) models. To predict QoE, it is sufficient to predict the PSNR time series. The possibility of predicting QoE further enables QoE-based network resource allocation. We propose two approaches to packet-based prediction...
Dynamic Adaptive Streaming over HTTP (DASH) is being adopted as a cost effective means for multimedia delivery. User Adaptive Video (UAV) is a new technique that exploits the perceptual limits of the human visual system to modulate a video stream's bit rate based on the viewing conditions, such as viewing distance and ambient illuminance, resulting in significant bandwidth reduction without perceived...
This paper presents an end-to-end algorithm for detecting a shared congested router in the internet when communication is established using multiple paths between wireless devices endowed with multiple interfaces (e.g., LTE, and WiFi). The proposed technique is based on one way end-to- end delay observation of packets received through multiple paths at the end hosts to infer whether or not the flows...
We consider improving the performance of WebRTC-based mobile video telephony over a Wi-Fi link, which is susceptible to channel-caused or congestion-caused packet losses. Existing reactive packet loss mitigation mechanisms rely on end-to-end feedback, which takes about one round-trip time (RTT), causing excessive artifacts or video freeze in the received video in typical network scenarios. To address...
In the underlay cognitive radio approach, secondary users (SUs) are allowed to transmit their messages as long as the negative impact on the performance of the primary user (PU) is below a certain threshold. We consider a MIMO underlay cognitive radio network with a single PU and multiple SUs. We propose a practical interference alignment and cancellation scheme that not only avoids interference at...
This paper proposes a cross-layer approach to the delivery of real-time video streams over LTE cellular systems. The objective is to maximally improve video quality by adapting the wireless system (specifically, HARQ retransmission and scheduling rules) to video packet importance. Complying with the LTE framework, video packets are given priorities and assigned to different radio bearers or logical...
The ultimate goal of network resource allocation for video teleconferencing is to optimize the Quality of Experience (QoE) of the video. We consider the IPPP video coding structure with macroblock intra refresh, which is widely used for video teleconferencing. Generally, the loss of a current frame causes error propagation to subsequent frames due to the video coding structure. Therefore, to optimize...
Energy detection is widely used by cognitive radios for spectrum sensing. During a silent period, secondary users (SUs) are kept silent so that the energy detector does not confuse SU signals for primary user (PU) signals. Due to imperfect coordination, an SU may transmit during a silent period and cause possible false alarms. We propose to leverage matched filters that already exist in many SUs to...
The overlay approach to dynamic spectrum access recently proposed in information theory allows both primary users (PUs) and secondary users (SUs) to simultaneously access the same spectrum with comparable power levels while ensuring no degradation to the performance of PUs. However, this approach is based on a number of idealized assumptions that are difficult to satisfy in practice, and existing...
The overlay approach to dynamic spectrum access recently proposed in information theory allows both primary users (PUs) and secondary users (SUs) to simultaneously access the same spectrum with comparable power levels. However, the information theory approach is based on idealized assumptions that are difficult to be satisfied in practice. We propose a practical scheme with the overlay flavor for...
In this paper, we present a rendezvous scheme for dynamic spectrum access (DSA) networks that can achieve approximately optimal throughput while not relying on a common control channel. Compared with existing rendezvous schemes for DSA networks that use a common control channel, the proposed scheme avoids congestion and jamming of the control channel, and also reduces control complexity and overhead...
The dynamic spectrum access (DSA) capability of cognitive radio networks (CRN) promises to resolve both the spectrum scarcity and the low spectrum utilization problems caused by today's static spectrum access (SSA) policy. With DSA, CRN nodes search the dynamically accessible spectrum bands for communication. In this paper, we study a random DSA scheme, where each node randomly selects its operating...
Dynamic spectrum access (DSA) promises to resolve spectrum scarcity and low spectrum utilization caused by today's static spectrum access (SSA) policy. In DSA, secondary users dynamically search and access spectrum bands that are temporarily unused by primary users. In this paper, we propose a control-free DSA algorithm for cognitive radio networks (CRN). Our algorithm enables each CRN node to select...
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