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In this paper, we propose a decomposition method called Generalized Multi-Unitary Decomposition (GMUD) which is useful in multi-user MIMO precoding. This decomposition transforms a complex matrix H isin Cmtimesn into H = PiRQiH, where R is a special matrix whose first row contains only a non-zero user defined value at the left-most position, Pi and Qi are a pair of unitary matrices. The major attraction...
In a three-node wireless relay network, two nodes, BS1 and BS2, exchange information through a relay node, RL. Suppose time division duplex is used, physical network coding (PNC) uses two time slots for the information exchange instead of four time slots needed by the conventional method. In the first time slot, both BS1 and BS2 transmit simultaneously to RL. The relay node, RL does a PNC mapping...
The XOR network code is widely used in the conventional network coding. However, when the channel is noisy, the XOR code is suboptimal in terms of minimizing distortion in the source signal. We propose to use a new network code for the two-way relay channel, designed to minimize signal distortion due to the channel noise. We assume the source signal X is encoded by a source encoder and the sequence...
We study the secrecy capacity of the frequency-selective wiretap channel. Assuming that a guard interval of L symbols is inserted to avoid the inter-block interference and these symbols are discarded at the receiver, the single-carrier frequency-selective channel is modeled as a multiple-input multiple-output Toeplitz matrix. For this special case of the MIMO wiretap channel and under the assumption...
A continuously increasing demand for higher spectral efficiencies in mobile communications will require next generation cellular systems to employ a very dense reuse of spectrum in combination with smart interference mitigation or cancellation schemes. Recent publications have revealed a large potential in terms of spectral efficiency and system fairness of multi-cell cooperative schemes, where e...
In this paper, we present a rate-distortion analysis for a distributed video coding system, which allows for the selection of a suitable quantization parameter for the H.264 coded key frames, under rate constraints. On the other hand, an adaptive rate allocation and quantization algorithm with a frame dropping strategy is used for the transmission of Wyner-Ziv frames in a multi-user scenario, without...
This paper investigates the problem of ensuring secure communication through error-correcting coding methods. A practical structured secure coding design is considered for a general wiretap channel, in which the main channel and the eavesdropper channel are binary-input symmetric-output memoryless (BISOM) channels. The proposed secure error-correcting code has a nested code structure. The nesting...
In this paper, we consider multiuser space-time block codes (STBCs) for 2times2 multiple-input multiple-output (MIMO) uplink transmissions. Using a truncated union-bound (UB) approximation, we propose design criteria of multiuser STBCs for quasi-static fading MIMO multiple access channels (MACs). Next, we demonstrate how, by combining the structure of algebraic perfect STBCs in [10], a family of multiuser...
In this paper, we present a real-time joint bit-rate and error protection allocation scheme for multiple scalable video streams sharing a single downlink channel. High speed downlink packet access (HSDPA) systems allow for multiple live video streams to share a common downlink channel among multiple mobile users. However, the unreliable nature of the wireless link results in packet losses and fluctuations...
This paper investigates the performance of orthogonal frequency and code division multiplexing (OFCDM) systems with multiple input multiple output (MIMO) multiplexing (MIMO-OFCDM), where multi-code transmission is employed to increase the data rate. An analytical approach is presented to evaluate the performance of the system using joint space-frequency detection with zero-forcing successive interference...
An approximation for the average error probability (AEP) of the pulse amplitude modulation (PAM) impulse radio ultra wide band (IR-UWB) systems in the presence of multi-user interference (MUI) is derived assuming that the spreading codes are fixed in time. The comparison of the proposed theoretical expression and the empirical result shows the accuracy of our approximation for both direct-sequence...
Selected mapping (SLM) is a technique used to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. SLM requires the transmission of several side information bits for each data block, which results in some data rate loss. These bits must be channel-encoded because they are particularly critical to the error performance of the system. This increases...
This paper defines a retransmission scheme for transmitting video data which allows the use of robust decoding (such as joint source and channel decoding) jointly with acknowledgement procedures. Conventional video communications use CRC-based retransmissions to obtain a nominal quality of the video (defined by the source coder). A lot of work has also been done on robust video transmission, which...
This paper introduces a block-based form of rateless channel coding that minimizes energy consumption by reducing the overhead and latency from channel coding. Consequently, results from a Bluetooth (IEEE 802.15.1) wearable wireless network for augmented reality (AR) show a consistent reduction in energy consumption compared to Bluetooth FEC schemes. AR relies on video transmission across a wearable...
In order to increase the performance of joint channel estimation and decoding through belief propagation on factor graphs, we approximate the distribution of channel estimate in the factor graph as a mixture of Gaussian distributions. The result is a continuous downward and upward message propagation in the factor graph instead of discrete probability distributions. Using continuous downward messages,...
This paper concentrates on the dynamic tuning of radio resource management parameters in the context of HSDPA systems coexisting with UMTS Relpsila99. In particular, an automatic tuning system is proposed taking into account the close interdependence between the cell throughput and the users channel quality indicators. From these, appropriate performance indicators are derived and a mid-term allocation...
Cooperative Multi-In Multi-Out (MIMO) schemes can reduce both transmission energy and latency in distributed wireless sensor networks (WSNs). When circuit energy is considered in such networks, the total energy consumed as the number of cooperating nodes increases becomes of particular interest. In addition, most of the previous works focused only on space-time-block-code (STBC) schemes and ignore...
We describe and analyze minimum path difference (MPD), a metric to improve threshold-based selection decode-and-forward (SDF) protocols in cooperative wireless networks with channel coding. By observing the decoding process, MPD provides a more frequent channel quality estimation than CRC or SNR and, thus, allows SDF to forward only the parts of a message that are likely to be correct. In this paper,...
In this paper, we investigate the advantages of applying random network coding in sensor networks for security purpose. In particular, the problem of constructing a secure multi-path in wireless sensor networks is considered. However, unlike previous wiretapping scenarios, where the threat is posed by external wiretappers, we approach the security from an internal angle: all nodes comply with the...
Codebook based multiple-input multiple-output (MIMO) precoding can significantly improve the system spectral efficiency with limited feedback and has been accepted as one of the most promising techniques for the evolved UTRA (E-UTRA). Compared with single-user (SU) MIMO, multi-user (MU) MIMO can further improve the system spectral efficiency due to increased degree of freedom in transmission. In order...
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