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We address the problem of multiuser power and bandwidth allocation for a general class of OFDMA-based wireless networks that employ a Type-II Hybrid Automatic Repeat reQuest (HARQ) transmission scheme. We assume that the resource manager has only statistical knowledge of the Channel State Information (CSI) of the Rayleigh-distributed fast-fading links forming the network. We then propose the optimal...
LTE is well on its way to becoming the primary cellular standard, due to its performance and low cost. Over the next decade we will become dependent on LTE, which is why we must ensure it is secure and available when we need it. Unfortunately, like any wireless technology, disruption through radio jamming is possible. This paper investigates the extent to which LTE is vulnerable to intentional jamming,...
The main disadvantage of the orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR). To reduce the PAPR of the OFDM signals, this paper introduced and compared the three multiple signal representation methods, selected mapping (SLM), partial transmit sequences (PTS) and interleaving and presented their simulation results. Then combined interleaving with SLM...
This paper proposes a downlink mapping algorithm for two-level requests in Orthogonal Frequency Division Multiple Access based IEEE 802.16e systems under the Adaptive Modulation and Coding (AMC) mode by which the modulation and coding scheme (MCS) of a user may be different for available subchannels. Given a set of requests each with two priorities, the proposed algorithm efficiently allocates a two-dimensional...
In this paper, a new and efficient approach for Orthogonal Frequency-Division Multiplexing (OFDM) timing offset error estimation has been presented without using pilot signal. The effect of timing offset on bit error rate (BER) has been analyzed using BPSK, QPSK, 8-PSK modulation scheme and an analytical expression has been derived using probabilistic equation to estimate timing offset. This will...
This paper investigates space-frequency (SF) coding for non-coherent (NC) Multiple Input Multiple Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM) fading links, where neither the transmitter nor the receiver knows the channel. Our strategy consists in distributing the convolutional encoded and interleaved bits over the different transmit antennas, OFDM tones and OFDM symbols. The combination...
The power distribution networks are primary employed, in Power line communication (PLC) system, for transferring data during communication process. For achieving even higher data rate in multiple user environments, researchers have proposed various multiple access schemes for power line communication systems including CDMA and OFDM mechanisms. This paper includes the performance analysis of power...
Non-orthogonal access improves the spectral efficiency through sharing the same frequency resource with multiple wireless terminals. In the previous researches, it has been shown that a log likelihood ratio (LLR) calculated from a signal on the sharing spectrum should be masked to zero if a power of an interference signal is stronger than that of a desired signal. This implies that the spectrum is...
Multiple antennas are used in wireless systems to achieve good quality of service and high data rate communication. Multiple-input multiple-output (MIMO) communication systems have a great potential to play an important role in the design of the 4G broadband wireless communication systems. In this paper, performance analysis of combined beamforming with space-time-frequency (STF) coded MIMO-OFDM systems...
This report lays out the idea of introducing LPDC codes along with the spreading sequence to improve noise immunity of the signals traversing in wireless environment. With the need to make communication techniques efficient and reliable, spread spectrum has gained importance for its various added advantages. LDPC (Low Density Parity Check) have been gaining limelight in the past few years. Comprising...
In this paper, we propose an Alamouti coded orthogonal frequency-division multiplexing (OFDM) scheme for amplify-and-forward (AF) relay networks that contain multiple distributed relay nodes. The frequency asynchronous nature of the distributed system is considered in our design. By implementing simple operations, e.g., time reversal, conjugation and amplification, the proposed scheme eliminates the...
Index coding is a new variant of source coding scheme that attempts to exploit the side information at different receivers to minimize the number transmissions to be broadcasted by the source, so that each receiver can derive its intended data with its local side information. However, existing relevant research are focused on the capacity analysis and algorithm design of index coding, while the transmission...
OFDM based wireless communication systems split the available frequency band into so-called sub-carriers, and data is transmitted on each of these sub-carriers in parallel. With frequency selective fading, sub-carriers may experience different channel qualities. Thus, choosing a different modulation and coding scheme (MCS) per sub-carrier improves performance. However, this comes at an increase in...
In this paper, novel modulation classification algorithms for wireless orthogonal frequency division multiplexing (OFDM) systems with adaptive modulation and coding in time division duplex (TDD) mode are introduced. The proposed maximum-a-posteriori (MAP)-based classifiers exploit specific signalling bits which are transmitted along with the information data and can therefore be regarded as a combination...
The IEEE 802.11ah task group has been formed to develop the specification for sub-1GHz WLAN. Due to the low operating frequency, it is expected that the 802.11ah can support coverage up to 1km. Such large coverage is well-suited for machine-to-machine (M2M) or machine-type communication (MTC) applications like smart grid and sensor networks. These applications are characterized by large number of...
IEEE 802.11ad is the new Wi-Fi standard operating at 60 GHz. This paper investigate the performance of specified modulation and coding schemes in additive white Gaussian noise channel and realistic 60 GHz band multipath fading channel. Three 802.11 ad physical layers, namely orthogonal frequency division multiplex physical layer, Single Carrier and Low Power Single carrier physical layer, are designed...
When multiple users in an OFDM system can be synchronized, a novel efficient multiuser precoding approach for reducing out-of-band emission (OOBE) is developed. The main idea is to view all users as a virtual single user and design a common virtual precoder for all users. The precoder of a particular user is then constructed using the corresponding columns of the virtual precoder according to the...
Previous works on space-time-frequency (STF) codes have focused on frequency-selective but independent fading channels for MIMO-OFDM systems. However, insufficient antenna space, mobile scenarios, and multipath in practice cause correlation in the spatial, temporal, and frequency domains. This paper studies the effect of STF coding on the performance of MIMO-OFDM systems with general spatial, temporal,...
This paper presents a robust concatenated coding scheme for OFDM with 64 QAM over AWGN channel. At the forward error correction unit, our proposed concatenated coding scheme employs standard form of BCH code as outer code and LDPC code as inner code. Varying from the code rates of BCH codes, we can find the minimum requirement of signal to noise ratio in the proposed concatenated coding scheme. In...
The conventional resource allocation method is so-called two-step method in OFDM system. The two-step method can reduce the computational complexity. However, it's solution accuracy is not very good. This paper proposes an improved two-step method. This method combines evolutionary algorithm with simulated annealing thought, and can take into account the sub-carrier distribution and power distribution...
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