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4G Long Term Evolution (LTE) mobile system adopts Adaptive Modulation and Coding (AMC) as a link adaption mechanism that is based on the User Equipment (UE) periodically reporting channel condition summarised through Channel Quality Indicator (CQI) which, in turn, is based on Signal-to-Interference-plus-Noise Ratio (SINR) and Reference Signal Received Power (RSRP). Although CQI has a predominant role...
Increasing data demand started to become a common challenge in mobile cellular networks. Various techniques, intelligent approaches and network architectures are being developed to tackle this difficulty, in order to provide high quality of service and to allocate mobile resources effectively. Adaptive modulation and coding is one of those techniques, that provides high quality of service while adapting...
Due to its advantageous properties in multipath propagation scenarios, the Orthogonal Frequency Division Multiple Access (OFDMA) radio transmission scheme is widely spread in current broadband wireless networks. Exemplary emerging systems based on this technology are the UMTS Long Term Evolution (LTE), Mobile WiMAX and some popular WiFi variants (e.g. IEEE 802.11n). Although analytical and simulative...
This paper considers applying hybrid automatic repeat request (HARQ) to the predetermined-rate multicast data channel. The major differences in the HARQ design between multicast data and normal unicast data come from the fact that the multicast data assumes a predetermined data-rate using a given transmission frequency bandwidth and power, and multiple independent acknowledgement (ACK) and negative-acknowledgement...
In this paper, we investigate the system performance on decode and forward based bi-directional relaying based on symbol-wise XOR operation. This technique gives more freedom of selecting modulation and coding scheme at relay station, and significantly relaxes its transmission bottom neck. However, the performance degradation occurs when the modulation orders of both links differ from each other....
This paper deals with the design of a multicarrier multiple-input multiple-output system which performs nonlinear Tomlinson-Harashima precoding at the transmitter and linear equalization at the receiver. The goal is the joint optimization of the processing matrices at both ends of the wireless link, assuming a constraint on the overall transmit power. We consider different design criteria which require...
Orthogonal frequency division multiplexing (OFDM) is the modulation scheme of choice for digital video broadcasting-handheld (DVB-H), which is required to operate under high mobility conditions resulting in significant Inter-carrier Interference (ICI). To mitigate ICI, several cancellation schemes have been proposed but they require reliable channel information at the receiver which is quite challenging...
Three applications in wireless networks where model-free stochastic learning is applicable, are discussed. The learning based optimization problems are formulated and simulation results are presented. Some open issues are also discussed.
In this paper, we propose a cross-layer optimization approach that exploits retransmission diversity in wireless CDMA communications. Conventionally, data packets that are not correctly detected are usually dropped. These dropped packets can be used to help data packet detection. By exploiting all the retransmitted packets, data packets can be correctly detected with higher probability. The proposed...
This paper explores the attributes, layering models and objective functions in cross layer designs for mobile ad hoc wireless networks by taking all the statistical characteristics and constraints from the physical (PHY) layer, media access control (MAC) layer and network (NET) layer into consideration. This paper reviews the entire network optimization across all the PHY/MAC/NET layers. At the PHY...
Correlative minimum shift keying (MSK), a second order polynomial modulation scheme known as tamed frequency modulation (TFM), is a constant envelope type of modulation with a perfect peak to average power ratio (PAPR), besides the property of low out of band power. We apply the linearized TFM to the single carrier transmission with frequency domain equalization (SC/FDE) concept. We then obtain a...
This paper studies efficient complex valued matrix manipulations for multi-user STBC-MIMO decoding. A novel method called Alamouti blockwise analytical matrix inversion (ABAMI) is proposed for the inversion of large complex matrices that are based on Alamouti sub-blocks. Another method using a variant of Givens rotation is proposed for fast QR decomposition of this kind of matrices. Our solutions...
While two-dimensional (2-D) orthogonal variable spreading factor (OVSF) codes were proposed for multicarrier direct-sequence code-division multiple-access (MC/DS-CDMA) systems in order to eliminate multiple-access interference, the number of orthogonal sequences (or code cardinality) was restricted by the number of carrier frequencies. Non-orthogonal 2-D frequency-time-spreading (FTS) codes were then...
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