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In this paper, we investigate the coexistence problem between Wi-Fi and a pre-standard form of LTE over unlicensed bands, namely, LTE-Unlicensed (LTE-U). We address two coexistence problems. First, the different access mechanisms for Wi-Fi and LTE-U can lead to an increase in the collision rate and higher latency for both systems. We propose a modified Wi-Fi operation mode, whereby Wi-Fi stations...
In this paper, we present a method for time and frequency synchronization in relay based cooperative communication system. The system consists of Source, Destination and two Relay nodes. A generic frame structure is devised to meet the space-time relaying mechanism when a particular node receives plurality of signals from multiple transmitters via different wireless links. We proposed timing synchronization...
The evolving 5G standards promise green communications with enhanced data services and significant link reliability. Massive multi input multi output (MIMO) techniques are the driving force behind green communications, since they provide better energy efficiency with reduced transmit power. The massive data generated from such mobile communication systems, is a rich data source of great value. Procuring...
In signal detection for cognitive radio, it is desirable to calculate a threshold within a short observation period since noise power changes in accordance with the amplification factor and the temperature of a low noise amplifier in a receiver. This paper proposes a threshold calculation scheme with a filter bank. The proposed scheme uses a more number of noise samples output from the filter bank...
In this work we design the precoders/combiners for a multiuser mmWave system considering a frequency selective channel model. We assume that the available channel information is imperfect, and only the estimates of the autocorrelation of the received signal, and the cross-correlation with the transmitted signal are available. Using this knowledge, the precoder and combiners are designed via an iterative...
Consider a two-user MIMO Gaussian Broadcast Channel with two antennas at the transmitter and two single-antenna receivers. While Dirty Paper Coding (DPC) achieves capacity, its practical adoption needs a precise comparison with the popular method of Zero Forcing Beam Forming (ZFBF). In this work, we obtain a simplified expression for the exact difference in sum rate between DPC and ZFBF at all SNRs...
This paper deals with carrier frequency offset (CFO) estimation for interleaved orthogonal frequency division multiple access (OFDMA) uplink systems. Firstly, gravitational search algorithm (GSA) with center-symmetric trimmed correlation matrix and multiple signal classification criterion is presented for the purpose of efficient estimation. It has been shown that the estimate accuracy of the searching-based...
Inspired by the success of multi-carrier waveforms such as Orthogonal Frequency Division Multiplexing (OFDM) in radio communication, multi-carrier based radar waveform designs have gained strong interest recently. Reasons for this include their resistance to multipath fading, ability to overcome the limitations of a congested frequency spectrum, ability to exploit frequency diversity gains, and potential...
This paper examines the low-probability-of-exploitation (LPE) characteristics of a noncontiguous orthogonal frequency division multiplexing (NC-OFDM) system. NC-OFDM transmission is similar to OFDM transmission but only uses a subset of the frequencies either to avoid incumbent transmissions or due to tactical considerations. This paper considers an NC-OFDM transmission with a given set of active...
In this paper, we present the simulation results of FFO(fractional frequency offset) influences on PLC preamble correlation based PLC synchronization in DOCSIS 3.1 Downstream. FFO makes inter-carrier interferences and breaks orthogonality in OFDM based transmission system. It degrades the performance of OFDM by reducing SNR(signal to noise ratio). The performance of PLC synchronization is influenced...
In cognitive radio technology, the overall capacity of communications systems can be improved without allocating additional bands by allowing secondary system to utilize the licensed band when a primary system who has right to use the band does not use it. In this paper, we consider how to set up a common channel for data communication in an ad-hoc networks consisting of a cluster head and member...
The paper introduces a novel method for distance estimation based on an OFDM signal combined with the Zadoff-Chu sequences. By exploiting the properties of these sequences, it is possible to evaluate the distance between two active nodes with a very good precision and accuracy. The technique effectiveness is demonstrated by measuring the distance between a single transmitter and a synchronized receiver...
In this paper, we propose an integer frequency offset estimation and compensation method based on PLC preamble correlation in DOCSIS 3.1 Downstream system. The proposed method finds out the PLC preamble subcarrier location recovered from PLC data and the one obtained from PLC preamble correlation. We showed the performance of PLC preamble detection in the received signal through the maximum value...
A novel family of quadrature amplitude modulation (QAM) Golay complementary sequences (GCSs), in this paper, is presented. The resultant QAM GCSs employ binary signals rather than quaternary signals as their inputs. New sequences are fit for being applied to such QAM systems whose inputs merely are binary signals. In addition, the proposed sequences have the larger family size than the previously-known...
Based on the description Q-type-2 of quadrature amplitude modulation (QAM) constellation and standard Golay-Davis-Jedwab (GDJ) quaternary complementary sequences (CSs), this paper presents a new family of QAM Golay complementary sequences (GCSs), and determines their family size. The proposed QAM GCSs includes the known QAM GCSs from Cases I–III constructions as a special case. It is worthy of mentioning...
Channel estimation is an important issue in orthogonal frequency division multiplexing (OFDM) systems to improve the performance of system. For OFDM based IEEE 802.11ad wireless local area network (WLAN), two types of symbols, training symbols and pilot symbols, can be used for channel estimation in the OFDM receiver. We analyze the algorithms of channel estimation methods based on symbol types, training...
Due to the scarcity of spectrum resources, spectrum sensing techniques are vital for future wireless communication systems. Compared with energy detection methods (ED), feature detection (FD) methods exploit statistical periodicity of transmission signals and have better performance under low signal-to-noise ratio (SNR) conditions. However, for fast time-varying fading channels, the detection accuracy...
The Data Over Cable Service Interface Specification (DOCSIS) provides internet access via cable TV networks. The latest version 3.1 replaces the Physical Layer of previous DOCSIS versions. With DOCSIS 3.1, broadband cable network operators want to accelerate their networks to gigabit-per-second speeds. Enhancements include an increased bandwidth per downstream channel of up to 192MHz, Orthogonal Frequency-Division...
The 3rd Generation Partnership Project (3GPP) has started to investigate feasibility of machine type communication terminal class in Long Term Evolution (LTE) networks in the Release 12 to address the requirements of the Internet of Tings (IoT) targeting low-end device market with improved coverage. Along with that, the 3GPP has defined reference signals to support device discovery, communication...
BS (Base Station) cooperation schemes allow for an improved overall system's capacity and spectral efficiency. This is due to the possibility of MTs (Mobile Terminals) in adjacent cells sharing the same physical channel. The BSs send a quantized version of the received signals to a central unit that performs the separation of the signals associated to different MTs. In this paper we consider the uplink...
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