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This paper presents two new techniques employing bandwidth-efficient modulation to enable two partners to cooperatively convey their data to a common destination. Both approaches integrate relaying and channel coding, exploiting the fact that each partner knows the data relayed by the other partner to enhance the partner-to-partner link. The first approach is based on bit-interleaved coded modulation...
In conventional multi-user MIMO systems, Shannon capacity has been used mostly as the performance measure for user selection. In this paper, we propose two new MIMO scheduling techniques based on BER instead of capacity as the performance measure for rate maximization with target BER. One of the key contributions of this paper is to use BER instead of capacity as the user selection metric, and another...
This paper presents indoor experimental results on an implemented real-time downlink multiuser multiple-input multiple-output (DL-MU-MIMO) transceiver for next generation wireless LAN systems. In the transceiver, channel state information (CSI) is estimated at each station (STA) and fed back to an access point (AP) on a real-time basis. At the AP, transmit beamforming weight for DL-MU-MIMO transmission...
In this paper we analyze the performance of several bit-interleaving strategies applied to Non-Binary Low-Density Parity-Check (LDPC) codes over the Rayleigh fading channel. The technique of bit-interleaving used over fading channel introduces diversity which could provide important gains in terms of frame error probability and detection. This paper demonstrates the importance of the way of implementing...
Wireless communication is prone to errors due to always changing channel conditions. Multiple transmissions over independent channels can be leveraged by combining erroneous packets. To be able to combine, reliability information for bits, so-called soft-bits, of the previous messages has to be saved. Especially for systems with limited storage capacity, such as sensor nodes, this poses the question...
3GPP long term evolution (LTE) Turbo coded modulation is well-known for its excellent error-control capability. However, its decoding threshold is still a few decibels away from the constellation-constrained capacity. In this paper, an irregular mapping scheme involving labeling search is proposed to improve the performance of the LTE system. The scheme first predetermines one labeling, and then searches...
In this paper, single amplify and forward (AF) relay is placed between the source and the destination in space shift keying (SSK) multiple-input single output (MISO) system. In SSK, transmit-antenna indices form a spatial constellation diagram where each group of base two logarithm of the input data bits are mapped to one spatial constellation point. Hence, at each time instant, only single transmit...
This paper presents a machine learning approach for link adaptation in orthogonal frequency-division multiplexing systems through adaptive modulation and coding. Although machine learning techniques have attracted attention for link adaptation, most of the the schemes proposed so far are based on off-line training algorithms, which make them not well suited for real time operation. The proposed solution,...
Most of the recent wireless communication systems are interference limited rather than noise limited. In the case of a very strong interferer the conventional assumption of the interference as Gaussian is extremely suboptimal. However optimal (capacity achieving) receivers utilize some prior knowledge about the interference to reach optimality. The link abstraction for such receiver structures is...
This paper presents a new iterative multiuser (MU) detection algorithm for asynchronous spectrally-efficient continuous-phase modulation in additive white Gaussian noise. The proposed detector is derived from the sum-product (SP) algorithm and the factor graph (FG) framework, and performs approximate maximum a posteriori bit detection. A convenient FG of the actual MU detection problem is considered,...
A cognitive radio should be able to detect unused spectrum band and to change its transmission parameters in order to transmit within these free bands. To achieve this, reliable detection of incumbent signals as well as of other opportunistic signals that are using the said spectrum, is necessary. Generalized Frequency Division Multiplexing (GFDM) is a recent multicarrier modulation technique with...
We study the conventional three node cooperative relaying problem. A discrete-estimate-and-forward (DEF) strategy is presented, where a discrete alphabet is utilized for the relay's signal forwarding. Two alternative alphabet designs are provided. The first one is called as minimum distortion alphabet (MDA) and the second one equal space alphabet (ESA). Simulation results show that both designs give...
Spatial Modulation (SM) is a combined multiple-input-multiple-output (MIMO) and digital modulation technique which besides common signal modulation conveys additional information bits in the spatial domain. To this end, only one transmitter is active at any time instance. The actual index of each emitter represents a unique spatial constellation point and thus conveys additional information. As a...
In this paper, we propose a new definition of energy efficiency with respect to a given target packet error rate (PER). It is shown that some previous reported definitions are actually special cases of our definition. Consequently we use the definition to analyze the energy efficiency of Multilevel quadrature amplitude modulation (MQAM) and find that for a specific transmission there exists an energy...
We investigate the performance of a multiuser downlink access scheme based on a post-selection switch and examine algorithm. The studied scheme sequentially switches over the users that experience independent and non-identically distributed fading conditions, and selects a single user with an acceptable channel quality as compared to a pre-selected signal-to-noise ratio (SNR) threshold. If no one...
A low-complexity user pairing algorithm for the broadcast phase of the XOR-based network coding is presented. The proposed scheme achieves the same spectral efficiency as an exhaustive search approach based on maximizing the sum-rate when network coding is utilized for all transmissions. The proposed scheme is further complemented with an adaptive switch, per user pair, between network coding and...
An adaptive Turbo Trellis Coded Modulation (ATTCM) aided Cognitive Radio (CR) scheme is proposed for cooperative communication among Primary Users (PUs) and Cognitive Users (CUs). The new cooperative protocol allows a CU to serve as a Relay Node (RN) for relaying the signal of the first PU, which is a Source Node (SN) to the second PU, which is a Destination Node (DN). More specifically, an active...
Recently developed adaptive modulation schemes for opportunistic decode-and-forward (DF) relaying require knowledge of instantaneous channel-state-information (CSI) of all links. This paper aims at reducing signalling overhead of modulation-adaptive opportunistic DF relaying through exploitation of mixed channel knowledge. A novel semi-deterministic approach is proposed for performing joint rate-adaptation...
With the great expansion of wireless communications, jamming becomes a real threat. We propose a new model to evaluate the robustness of a communication system to jamming. The model results in more scenarios to be considered ranging from the favorable case to the worst case. The model is applied to a TH-UWB radio. The performance of such a radio in presence of the different jamming scenarios is analyzed...
In this paper, we investigate the performance of adaptive modulation in spectrum sharing cognitive relay networks, where the secondary user (SU) transmits the message by one best relay with amplify and forward (AF) relaying scheme. Moreover, to guarantee the primary user (PU)'s transmission quality, the interferences caused by the SU transmitter and the selected relay are less than a predetermined...
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