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A joint channel impulse response (CIR) and noise-variance estimation scheme is proposed for multi-user Multiple-Input-Multiple-Output (MIMO) Orthogonal Frequency-Division Multiplexing/Space Division Multiple Access (OFDM/SDMA) systems, which is based on the Expectation Maximization (EM) algorithm. Multiple users communicating over time-invariant and/or time-variant channels are considered in this...
In this paper we consider SC-FDE schemes (Single-Carrier with Frequency-Domain Equalization) employing multi-resolution hierarchical constellations and we consider the design of turbo receivers, implemented in the frequency-domain, for systems where we have different error protections. We present a versatile method to design the receiver that is suitable to any constellation.
When passed through a high power amplifier (HPA), downlink direct sequence-code division multiple access (DS- CDMA) signals result in additional out-of-band emissions, or spectral regrowth, which could affect adjacent channels. In this paper, we explore which characteristics of the input CDMA signal, in relation to the amplifier characteristics, contribute to spectral regrowth. These characteristics...
This paper examines radio wave propagation in underground and subway environments from the perspective of providing digital radio with multimedia and video enhanced services (DAB/DMB) as a continuity of the same services offered above ground. To this end, a preliminary simulation framework of a DAB/DMB transmission system inside a rectangular subway tunnel is proposed. First, the received power and...
In this paper, we consider the co-channel interference mitigation capability of fixed relay aided wireless systems, where the relays are linked to the base station using realistic imperfect optical fibre. Three interference mitigation techniques are investigated, namely an appealing reduced-power transmission technique, the classic eigen-beamforming arrangement and their hybrid. The cellular model...
In this paper we propose a novel connection admission control scheme named Rate Transition Area assisted Guaranteed Handover Scheme (GHS-RTA), which utilizes the geographical information, rate transition areas and overlap areas to intelligently decide when to block a new call. This scheme helps avoid possible inter-cell and intra-cell handover failures for HAP communications systems with adaptive...
This paper focuses on coordinated scheduling to combat uplink inter-cell interference for LTE/LTE-Advanced. In OFDM system, inter-cell interference is the dominant interference which limits system capacity, especially the performance of cell edge users. Meanwhile inter-cell interference in OFDM system has an inherent characteristic of interference fluctuation, which reduces the efficiency of channel...
Multiuser diversity is achieved by maximum C/I scheduler in both fast and slow fading scenarios. However, fairness among multiple users is not guaranteed in slow fading channel because time and frequency resource are always occupied by the user with largest signal to interference and noise ratio(SINR). Opportunistic beamforming using dumb antennas is a multiple antennas transmit technique to increase...
Cooperative communication has been recently proposed as a way to improve the performance of wireless communication. However, due to the half duplex constraint, most of the relay networks face a fundamental challenge in terms of multiplexing loss. In this paper, we present an adaptive cooperation via relay selection (ACRS) protocol that improves spectral efficiency. This protocol lets the source transmit...
As an advanced train control system, communication-based train control (CBTC) system can improve the utilization of railway network infrastructure and enhance the level of safety and service offered to customers. In this paper, we propose a seamless handoff scheme for CBTC systems based on Stream Control Transmission Protocol (SCTP) and IEEE 802.11p. The focus of our work is in the handoff decision...
In this paper, the variational expectation-maximization (VEM) algorithm is used to provide channel estimates in a space-time decoder. The proposed estimator works for many types of space-time codes (STC), including full-rate full-diversity (FRFD) codes, Bell Laboratories layered space-time architecture (BLAST) and orthogonal STC's. The principle idea is to treat the channel coefficients as the unknown...
The error performance, in terms of Bit Error Rate (BER), of multi-stage (multi-hop) Wireless Relay Networks (WRNs) with distributed STBC at the relay stages is presented. One relay stage is defined by a set of relays located at the same distance from the source node where the distance is measured by the number of hops. We develop the multi-stage WRN model for Amplify-and-Forward (AF) and Decode-and-Forward...
The objective of this paper is to combine the antenna downtilt selection with the cell size selection in order to reduce the overall radio frequency (RF) transmission power in the homogeneous High-Speed Packet Downlink (HSDPA) cellular radio access network (RAN). The analysis is based on the concept of small cells deployment. The energy consumption ratio (ECR) and the energy reduction gain (ERG) of...
In this paper, a privacy-preserving chatting scheme is proposed to secure vehicular communication and achieve user privacy preservation in vehicular peer- to-peer networks. In specific, we first introduce identity-based-encryption technique which can protect the confidentiality of chatting content. Furthermore, to preserve user privacy, our scheme employs ring signature technique, which not only provides...
Almost all modern cars can be controlled remotely using a personal communicator (keyfob). However, the degree of interaction between currently available personal communicators and cars is very limited. The communication link is unidirectional and the communication range is limited to a few dozen meters. However, there are many interesting applications that could be supported if a keyfob would be able...
Today, 77GHz FMCW (Frequency Modulation Continuous Wave) radar sensors are used for automotive applications. In typical automotive radar, the target of interest is a moving target. Thus, to improve the detection probability and reduce the false alarm rate, an MTD(Moving Target Detection) algorithm should be required. This paper describes the proposed two-step MTD algorithm. The 1st MTD processing...
Traffic congestion is a serious problem in urban areas of many countries due to the increasing amount of vehicles on surface streets and accompanies fuel-wasting and air-pollution. This problem can be alleviated by adopting a ride-sharing service. The main idea of ride-sharing service is to collect travelers whose travel destinations are nearby into one vehicle. In doing so, we can reduce the amount...
Because of shortage of raw materials, the energy-saving issues become popular in Vehicular Ad-hoc Networks (VANETs). A VANET is formed by traveling vehicles with communicating capability and thus it brings various applications. Navigation system is one of important applications in VANETs. The traditional navigation system usually plans a shortest path for users according to geographic maps but the...
Updating software in vehicle Electronic Control Units (ECUs) will become a mandatory requirement for a variety of reasons, for examples, to update functionality of an existing system, add new functionality, remove software bugs and to cope up with ITS infrastructure. Since multicasting is the most efficient method of group communication, updating software in an ECU of a large number of vehicles could...
Vehicular ad hoc networks (VANETs) provide the means to add convenience, services, and safety to the road. This paper introduces a means to adapt the concepts of Public Key Infrastructure for a VANET environment under the worst case scenario of a pseudonym shift every second. Regions are used to scale down the size of certificate revocation lists (CRLs), administrative overhead, and the search space...
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