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This paper considers the use of predefined frequency-domain power profiles in downlink LTE-A aiming at making interference predictable across the Physical Resource Blocks, to be combined with fair resource allocation. In particular, the power profile structure is defined depending on the position of the users and fairness-oriented scheduling strategies are considered. Evaluations of the throughput...
IEEE 802.11 Wireless Local Area Network (WLAN) Physical Layer (PHY) offers multiple data rates. In multi-rate WLANs, 802.11 Medium Access Control (MAC) protocol, Distributed Coordination Function (DCF), essentially provides equal transmission opportunities to each sender host, causing the degradation of system throughput due to some hosts using low rates. In this paper we propose a cross-layer link...
The Physical Downlink Control Channel (PDCCH) is used to signal dynamic resource assignment information in the Long Term Evolution (LTE) system. In the presence of numerous active users, the system performance is likely to be hindered by shortage of control channel resource. In this paper, several simple algorithms are brought forward for making efficient PDCCH resource allocation. We first propose...
Block diagonalization is a linear precoding technique which eliminates the multi-user interference at the transmitter side by creating parallel orthogonal single user links. In this technique, the transmit diversity order is fixed for each user and only power can be controlled to satisfy SINR requirements. This restricts the degrees of freedom available for resource allocation and limits the energy...
Spectrum sensing is one of key enabling techniques to advanced radio technologies such as cognitive radios and ALOHA. This paper presents a novel non-cooperative spectrum sensing approach that can achieve a good trade-off between latency, reliability and computational complexity. Our major idea is to exploit the first-order cyclostationarity of the primary user's signal to reduce the noise-uncertainty...
A two-stage coding scheme incorporated with a square M-quadrature amplitude modulation (QAM) scheme is proposed to realize multiple non-discrete data rates while reducing the packet error rate (PER) at small packet sizes. Subject to the intended code rate, Turbo-coded parity packets are generated through bit-wise XOR combinations of the source packets to provide additional soft information which can...
Low Density Parity Check (LDPC) codes have been adopted in a number of wired and wireless communication standards due to their improved error correcting ability and relatively simple decoder structure. However, for very high throughput systems operating in the multi-Gb/s range conventional decoding methods based on message passing are limited, due largely to the sheer volume of messages being exchanged...
Performance of next generation OFDM/OFDMA based Distributed Cellular Network (ODCN) where no cooperation based interference management schemes are used, is dependent on four major factors: 1) spectrum reuse factor, 2) number of sectors per site, 3) number of relay station per site and 4) modulation and coding efficiency achievable through link adaptation. The combined effect of these factors on the...
This paper addresses mobile terminal (MT) relaying in order to improve the performance of mobile satellite broadcasting. It considers selective decode-and-forward (SDF) relaying with BICM-OFDM air interface. The BER upper bound was derived for the threshold-based SDF relaying in Rician fading channels. The suboptimal SNR threshold was then obtained by minimising this analytical upper bound. This scheme...
We propose a data precoded relay-assisted scheme, for a system cooperating with L relays, each one equipped with a single antenna. The use of relays is of significant interest to allow radio access in situations where either the direct path is not available or has poor quality. However because of the half duplex constraint at the relays, transmission of a data rate that would be possible using a modulation...
Air bandwidth is a precious resource for wireless communication. Multiple-antenna (MIMO) systems enable an increase in channel capacity without increasing the air bandwidth. An iterative demapping and decoding at the receiver improves the communications performance remarkably. However, MIMO demapping and channel decoding have a high computational complexity. Energy consumption, latency and throughput...
This paper offers the statistical analysis of relay assignment in cooperative Decode-and-Forward (DF) networks based on order statistics. By assuming a set of N independent Rayleigh fading channels, first the channel with r-th biggest SNR is analyzed. The diversity order and average error probability for this channel are calculated. Then it is assumed that there are two clusters of terminals and the...
This paper focuses on the performance evaluation of LTE uplink in presence of bursty data traffic. First, the performance of different power control (PC) strategies in different load conditions is evaluated. It is shown that the optimal PV policy depends on the load in the network and/or in the own cell. Simulation results demonstrate that in low load conditions applying no PC (or alternatively using...
Careful management of inter-cell interference is important in OFDMA based systems such as LTE. In this paper, we study an uplink ICIC (Inter-cell Interference Coordination) mechanism, which fully utilizes the flexibility of frequency selective scheduling and rate adaptation, while dynamically limiting the interference experienced by the neighboring cells. This technique can be seen as an extension...
The exact expressions for symbol error probability and outage probability of randomized distributed space-time codes (RDSTC) under Rayleigh fading are derived. The diversity gain derived in the literature uses the Chernoff bound which may not be achievable in general. Utilizing the exact expression, the achievable diversity gain of RDSTCs is validated. The analytical expressions are verified by Monte-Carlo...
A cognitive network consists of primary nodes, which have priority access to the spectrum, and cognitive (also referred to as secondary) nodes, which access the spectrum provided that the interference they generate in the primary system remains limited. In practice, it means that the cognitive terminals must remain outside of a region surrounding the primary receiver: the primary exclusive region...
Reduced-complexity receive antenna selection methods are proposed for interference rejection combining receiver of femtocell base stations. The methods are designed for cases with exact channel information and with channel covariance matrix of interference plus noise at the receiver. Simulation results show that the presented methods can almost achieve the same performance obtained by an exhaustive...
In this paper, we review the literature on physical layer energy-efficient communications. The most relevant and recent works are mainly centered around two frameworks: the pragmatic and the information theoretical approaches. Both of them aim at finding the best transmit and/or receive policies which maximize the number of bits that can be reliably conveyed over the channel per unit of energy consumed...
The mobile WiMAX standard (802.16e) uses multiple-input multiple-output (MIMO) limited feedback linear precoding to exploit the channel state information at the transmitter. Although the performance of limited feedback linear precoding in relation to traditional open-loop MIMO-OFDM has been extensively studied in the literature, these studies commonly assume perfect channel estimation at the receiver...
Due to the license-exempt nature of the cognitive radio (CR), multiple CR networks may operate (coexist) on the same channel. In this paper, we first discuss some techniques for self-coexistence of CR local and personal area networks, where the self-coexistence means the coexistence of homogeneous CR networks using the same PHY/MAC protocol. Then, we propose a self-coexistence etiquette for the ECMA...
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