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This paper investigates a scheme for deriving feedback information for the interference rejection combining (IRC) receiver, which can suppress inter- cell interference, in order to perform adaptive modulation and coding (AMC), user scheduling, and transmission precoding at the serving eNodeB appropriately in the LTE/LTE-Advanced downlink. In this paper, we evaluate the negative impact of inappropriate...
Time varying channel breaks the orthogonality between the subcarriers of Orthogonal Frequency Domain Multiplexing (OFDM). This introduces Intercarrier Interference (ICI). One of the ways to mitigate ICI is to first estimate the channel and then equalize it. In this paper we propose to estimate the channel using Discrete Proplate Spheroidal Sequences (DPS) using pilot carriers interleaved with data...
Wideband code division multiple access (W-CDMA) is a third generation (3G) mobile wireless technology that promises much higher data speeds for mobile and portable wireless devices than those which are commonly offered in today's market. In W-CDMA systems, while transmitting information over multipath channels, both intersymbol interference (ISI) as a result of interchip interference (ICI) and multiple...
Cognitive radio (CR) networks require reliable spectrum sensing techniques in order to avoid interference to the primary users of the spectrum. Most existing spectrum sensing techniques are based on simple energy detection. However, in practice, the signals transmitted by primary users usually also contain known symbol such as pilots and preambles for synchronization and channel estimation purposes...
Full-duplex relays can provide cost-effective cover-age extension and throughput enhancement. However, the main limiting factor is the resulting self-interference signal which deteriorates the relay performance. In this paper, we propose a novel technique for self-interference suppression in full-duplex Multiple-Input Multiple-Output (MIMO) relays. The relay employs transmit and receive weight filters...
This paper presents a novel adaptive multiuser detection scheme for MIMO OFDM, which we refer to as AMUD MIMO OFDM. It combines the adaptive minimum mean square error multiuser detection scheme with prior information of the channel and interference cancelation in the spatial domain. Simulation results show that joint channel parameters estimation has good performance compared to individual parameter...
In the frame of block pilot channel estimation, an ameliorated version of the Least Squares (LS) algorithm is here proposed for OFDM systems. Former studies use the fact that the cyclic prefix (CP) duration upper bounds the length of the channel impulse response (CIR) to cancel the estimation noise lying outside the CIR first taps, equal in number to the CP samples. However, if the channel is sparse,...
In recently years, lattice-reduction (LR) has been proposed to improve the performance of linear and successive interference cancellation (SIC) detectors in MIMO systems. It is proved that LR-aided linear detectors collect the same diversity order as that exploited by the ML detector but with much lower complexity when perfect channel state information (CSI) is available at receiver side. However,...
New channel estimation technique is proposed for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) systems. Several steps have been carried out to achieve this purpose. In first step, refined least square (LS) channel estimation is found out by using subspace-based narrowband interference (NBI) estimation method with prilimonary LS channel. In second step, low rank...
We discuss a novel pilot design for multi-user channel estimation in the OFDM uplink with localized block-type pilot placement. Due to this placement, multiple users' channels interfere with each other. By analyzing the properties of this multi-user interference, a criterium of choosing an appropriate DFT phase shift in frequency domain is derived. With this optimized shift, the multi-user interference...
We propose a first arriving path (FAP) detection algorithm using multipath interference cancellation techniques for indoor positioning systems. In indoor environments, the FAP is very often less significant in magnitude as compared with later arriving paths (LAPs) and therefore the received signal component of FAP is severely interfered by those of LAPs. As a result, it is difficult to identify the...
A new blind adaptive multi-user detection scheme based on the RLS filter and subspace estimation is proposed. It is shown that the detector can be expressed as an anchored signal in the signal subspace and the coefficients can be estimated by the RLS filter just by using the signature waveform and the timing of the desired user. The subspace- based algorithm brings the benefit from the lower computational...
Coordinated multi-point transmission/reception (CoMP), in which base stations (BSs) cooperate during the downlink, has been identified as a tool for improving user rates and mitigating interference. The cost for existing coordination schemes with joint processing is the heavy exchange of channel state information and signal information over backhaul links. In this paper, we propose a decentralized...
This paper proposes a novel channel estimation technique for Single Carrier Frequency Division Multiple Access (SC-FDMA) communications operating on the Long Term Evolution (LTE) uplink over time-varying multipath channels. The proposed method keeping the block-type pilot arrangement (BTPA) can improve the performance of the conventional channel estimation (CE) technique with no assistance from apriori...
In this paper, we propose a simple but effective way to improve the performance of channel estimation and catch the noise variance for pilot cyclic prefixed single carrier (PCP-SC) system. The proposed method utilizes the property that the shift of PCP pilot signal can also be utilized to catch the channel information as a new pilot. Regardless of signal-to-noise ratio (SNR) and pilot type, the proposed...
We introduce a technique to achieve dirty paper coding (DPC) capacity asymptotically with minimum feedback required reported to date in literature. Our approach called opportunistic interference management, is based on a new multiuser diversity scheme designed for wireless cellular networks. When there are K antennas at the base station with M mobile users in the cell, the proposed technique only...
Recently, lattice-reduction (LR) has been proposed to improve the performance of linear and successive interference cancellation (SIC) detectors and precoders in MIMO systems. It is proved that LR-aided linear detectors collect the same diversity order as that exploited by the ML detector but with much lower complexity when perfect channel state information (CSI) is assumed to be available. However,...
The problem of joint blind multiuser detection and equalization in direct-sequence code division multiple access (DS-CDMA) systems is investigated. Based on the minimum output energy (MOE) criterion, the resultant receiver can suppress two kinds of interferences: multiple access interference (MAI) form other users and intersymbol interference (ISI). We develop a low computational complexity algorithm...
Cognitive radio design aims to increase spectrum utilization by allowing the secondary users (SUs) to coexist with the primary users (PUs) as long as the interference caused by the SUs to each PU is properly regulated. At the SU, channel state information (CSI) between its transmitter and the PU receiver is used to calculate the maximum allowable SU transmit power to limit the interference. We assume...
In a system comprising of a multiple antenna enabled base station (BS) and multiple single antenna users, very high data rates can be obtained if BS transmits to multiple users simultaneously. This simultaneous transmission to multiple users over the same bandwidth is realizable only if BS knows the forward channels linking its transmit antennas to these users. We study a time-division duplexed (TDD)...
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