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In cognitive multimedia mesh networks (CMMNs), unlicensed users (secondary users, SUs) can share the spectrum with licensed users (primary users, PUs) on a non-interfering basis. The main challenge in CMMN is how to implement an efficient optimal control policy that can allocate spectrum and transmission powers for the SUs efficiently and how to adapt these resources to the changing network conditions...
The creation of Ultra-Wideband (UWB) radio platform has allowed the development of high bit-rate Wireless-USB offering High Definition video streaming. Quadrature Phase Shift Keying (QPSK) and Dual Carrier Modulation (DCM) are the current modulation schemes used for Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) in the ECMA-368 defined UWB radio platform. ECMA-368 offers up to 480...
In underwater acoustic sensor networks, the solution to augment sensor nodes' life time is crucial due to the difficulties in retrieving discharged sensor nodes. Thus, many energy efficient MAC protocols have employed mainly logical ways, such as sleep mode, hand-shaking signaling between nodes, and scheduling of transmission time, rarely using the physical characteristics of underwater acoustic channels...
Interference alignment is a new technique recently proposed in physical layer wireless communications research, which purposely align the interference among multiple users thus increase the efficiency of channel use. This paper proposes a new method to enhance throughput of multi-hop wireless networks by utilizing interference alignment at physical layer. At first, it takes a simple network with only...
We present a prediction-based resource allocation algorithm (RA) for OFDMA downlink over mobile wireless channels, where prediction errors are incorporated in the problem formulation. A solution based on the empirical characterization of the prediction error is proposed. We test the proposed scheme on a realistic scenario using a practical low complexity channel predictor, suitable for implementation...
In multi-interface multi-channel (MIMC) based tactical ad hoc networks, QoS support is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop...
Most of the link rate adaptation algorithms reduce transmission rate on a failed transmission assuming the cause of the loss to be due to radio channel impairment. However, if this failure is due to collision, then lowering the transmission rate in response is unnecessary. This paper proposes a solution to address this problem by augmenting the rate adaptation algorithm with a loss classification...
In the current internet, Transmission Control Protocol (TCP) is used as the most popular transport layer protocol. However, the end-to-end throughput of TCP degrades significantly when operates in wireless networks. Frequent retransmission timeout is one of the well-known problems of TCP end-to-end throughput degradation over wireless networks. In wireless networks, a retransmission timeout is inevitable,...
Offering throughput guarantees for cellular wireless networks, carrying real-time traffic, is of interest to both the network operators and the customers. Furthermore, to be able to quantify the soft throughput guarantees for a certain scheduling algorithm without conducting experimental investigations, is valuable for network providers. In this paper, we develop an expression for the approximate...
Heterogeneous cellular networks (HetNets) - conventional macro base stations overlaid with low-power nodes-are being deployed for reasons of improved spectral efficiency, economy, and scalable network expansion. To optimally realize the benefits of HetNets, it is crucial to factor deployment aspects such as cell association, transmission power, spectrum allocation, and deployment density. This paper...
Channel reciprocity is regarded as one of the most important advantages of TDD systems. However, the RF front-ends contribute to the channel experienced, and their TX/RX mismatches might cause reciprocity error, and thus degrade system throughput. Therefore, channel reciprocity calibration is a crucial issue. Among the existing calibration methods, Over-the-air (OTA) calibration is a promising approach...
In this paper we consider a single cognitive radio seeking a transmission opportunity by sequentially sensing a number of statistically independent primary channels. We study the joint optimization of the time spent to sense a channel, the decision threshold to determine whether the channel is free or busy, together with the order with which the channels are sensed. The sensing time and decision threshold...
This paper considers the problem of uplink scheduling in wireless networks supporting successive interference cancellation (SIC) at the physical layer. By allowing concurrent interfering transmissions, SIC enables multi-packet reception at the receiver resulting in increased network throughput. Specifically, we consider maximum throughput scheduling and proportional fair scheduling problems and study...
1TCP is a popular transport layer protocol. The performance of TCP is known to be unsatisfactory in wireless network, due to high bit error rates or drop outs. Employing error correction at the transport layer can alleviate the problem to some extent. We make three contributions in this paper. First, we optimize the efficiency of repetitive codes. In particular, we propose a good estimate on throughput...
One of the traditional MAC protocols used in wireless ad hoc networks is Distributed Coordination Function IEEE 802.11 (DCF). In such protocols, nodes are allowed to access the channel without any base station and omni-directional antennas are used for packet transmission. The main problem in IEEE 802.11 DCF is the existence of silent area which leads to channel spatial reuse reduction and using directional...
A multichannel scheduling based on an extension of modified largest weighted delay first (M-LWDF) scheduling is proposed for heterogeneous traffic. We consider the downlink of an orthogonal frequency division multiplexing (OFDM) system where the wireless channel and queue state information are taken into account to schedule delay-sensitive and ratesensitive traffic. We propose a logarithmic notion...
In this paper, inspired by network coding theory we propose an efficient hybrid encryption-coding algorithm that requires using traditional encryption only for the first small amount of data. This amount of data, which we refer to as the first block, is determined by the traditional encryption algorithm to be applied on this first block. In our proposed algorithm, all the rest of the information will...
In this paper, an adaptive tone reservation technique with optimal subcarrier allocation awareness for multi-user OFDMA systems is investigated. In general, a variety of approaches have been proposed to cope with the PAPR problem in OFDM systems. A tone reservation (TR) is an effective technique for reducing PAPR, in which it does not need to transmit any side information and there is no distortion...
In this paper, we propose a wireless transmission of JPEG 2000 compressed video. The proposed system employs the next generation wireless LAN system based on IEEE802.11ac specification. It reaches more than 33 meter propagation distance by using 80MHz of bandwidth on the 5GHz band. In this system, video data is compressed by JPEG 2000 with error resilience tools. These tools improve error performance...
This paper discusses the possibilities of using the reverberation chamber as a multipath emulator for testing of wireless terminals, especially those with multi-antenna solutions implemented. The tests are consisting of measurements of data bit throughput, in order to relate the performance of the terminal to an end-user experience. The experimental part includes HSDPA measurements with focus on overall...
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