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This paper proposes a novel uncoded digital modulation scheme with high spectral and power efficiency, denominated 32P-3D. This scheme has a symbol constellation that consists of 32 points symmetrically distributed in a threedimensional space. The theoretical analysis and the simulations show a considerably high performance against the noise in comparison to 16-ary Quadrature Amplitude Modulation...
Data centers are considered as the indispensable infrastructure for cloud services nowadays. However, large-scale data centers use the traditional TCP protocol may experience performance issues, such as TCP incast. TCP incast is caused by the deficiency of TCP works for many-to-one traffic patterns on high-bandwidth, low-latency networks. In this paper, we propose a new TCP variant named Threshold...
Due to the rapid growth of Software-Defined Networks, we can manage network traffic easier than before. One of the major issues on SDN is the multipath routing protocols due to its complexity of optimum path selection among the multiple routes. In this paper, we focus on Multipath TCP (MPTCP). MPTCP is an extension of TCP that increases the throughput of TCP communication significantly by utilizing...
An analog adaptive notch filter implementation at 54.1 MHz is presented in this paper. The analog circuit is implemented using discrete components. Implementation issues such as components phase shift and DC offset are discussed and solution for them are proposed. In addition, effect of frequency offset between reference and input signal is discussed. The implemented circuit has −3 dB bandwidth of...
In order to solve the rbuf blocking in concurrent multipath transfer, firstly, this paper analyzes the reason for receiving buffer blocking and the disadvantages of traditional retransmission policies. And then, it proposes an improved retransmission policy — RTX-CR (retransmission-congestion window and RTT), which can reduce rbuf blocking. The simulation indicates that the retransmission policy can...
Non-Coherent Autocorrelation (AR) UWB receivers are preferred over coherent UWB receivers because it requires no channel state information (CSI) and hence is less complex in nature. The paper investigates the performance of Transmitted Reference (TR) and Differential Transmitted Reference (DTR) scheme using AR UWB receivers. Theoretical analysis of BER performance of non-coherent IR-UWB receivers...
Localization of Wireless Capsule Endoscope (WCE) inside the small intestine is a very challenging problem, which is very important for the diagnosis of certain diseases. Previous studies have shown that Time-of-Arrival (TOA) localization can be more effective than Received Signal Strength (RSS) based localization. Performance evaluation of TOA-based localization techniques for WCE requires understanding...
In this paper, we investigated the influence of asymmetric on TCP over HFC-based networks and related methods to improve the TCP performance. Then, a scheme called Modified Adaptive SACK Filtering is proposed to improve the TCP performance by adjusting the size of the block information in SACK option according to the real-time characteristics of network. Furthermore, based on the fact that the forward...
Up to now, the most concurrent multi-path transport (CMT) schemes mainly aim at the issues caused by forward transmission like data reordering at receiver side and neglect the studies on impact of reverse paths' transmission delays. This paper proposes a SACK scheduling mechanism for the CMT schemes to accelerate data transmission in multi-homing environment, in this scheme, the most SACK chunks will...
In this paper, we present an adaptive method for maximizing network bandwidth utilization for the real-time applications. RTP protocol is chosen as the transport protocol and the network utilization is provided by increasing and decreasing the transmission rate of the RTP traffic. Our method employs a PID controller that keeps the RTP packet loss fraction at a predefined reference point. Packet loss...
This paper firstly elaborates the video transmission quality evaluation methods, and gives an overall scheme of video transmission simulation and quality evaluation system, then based on the open-source network simulation software NS-2, realizing the the entire system, finally, simulation experiments are provided to demonstrate the feasibility of the system, the result shows that the video transmission...
In recent years, it has become imperative to teach digital communications to Electronics and Communications engineering majors. In this paper, we present a four-month undergraduate course on digital communications in which students design and implement a complete, real-time interactive communications system that transmits data in digital form between two computers. The only prerequisite is a course...
We evaluate the scalability of a multiple view distributed approach to recording presentations that utilizes camera equipped mobile devices. We show this approach is scalable in terms of video resolution, bandwidth and power. This scalability enables users with a broader range of mobile devices to effectively participate in presentations. We show our approach is less expensive, more scalable, flexible...
Cooperative spectrum sensing is investigated for the purpose of detecting the primary user accurately in cognitive radio systems. As the report channel between cognitive users and fusion center experiences fading or shadowing, a cluster based cooperative sensing method is proposed to improve the sensing performance. However, when the number of the cognitive users in each cluster increases, the bandwidth...
The design of efficient communication mechanisms for small satellite networks is a challenging task, requiring the definition and implementations of specific protocols and architectures appropriate to space's critical conditions. In this paper, we have selected XSTP (eXtended Satellite Transport Protocol) as candidate protocol for nanosatellite networks. Foremost, we implement XSTP in NS-2 simulator...
We propose multicast extensions to the flow oriented routing protocol (M-FORP) and node velocity based stable path (M-NVSP) routing protocol for mobile ad hoc networks. M-FORP predicts the link expiration time and connects the source to each of the multicast receivers through paths with the largest predicted expiration time. M-NVSP connects the source to each of the multicast receivers through paths...
Spectrum sensing is a critical phase in building a cognitive radio network. However, when the number of cognitive user is very large, the bandwidth for reporting cognitive users' sensing results will be insufficient. In this paper, we propose a new cooperative spectrum sensing algorithm to alleviate the bandwidth problem of reporting channel. Compared with conventional method, only the cognitive users...
Quality of service (QoS) support in ad hoc networks relies on admission control to prevent the network from congestion. The collision rate that is experienced by each node on a link plays an important role on the decision made by admission control due to its impact on the available bandwidth estimation. However, most of the existing QoS support schemes in ad hoc networks neglected the fact that the...
This paper presents the performance evaluation of a multi-rate multicast protocol named adaptive smooth simulcast protocol (ASSP) for simulcast video transmission. ASSP implements a single rate TCP-friendly protocol as the underlying congestion control mechanism for each simulcast stream. ASSP is built on top of the RTP/RTCP protocol and exploits the RTCP sender and receiver reports for the dissemination...
It is well known that packet loss is an indication of network congestion. Thus, numerous applications including adaptive control in VoIP detects packet loss and responds to reduce the congestion. However, detecting packet loss provides very limited information about the state of the network. In this paper, we attempt to use observations of the delay and loss correlation to characterize congestive...
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