Energy consumption is of utmost importance in wireless mesh networks where nodes are battery operated and have limited power resources. In this paper, we develop an analytical model to estimate the throughput-capacity...
详细信息
Energy consumption is of utmost importance in wireless mesh networks where nodes are battery operated and have limited power resources. In this paper, we develop an analytical model to estimate the throughput-capacity of a wireless mesh network and use this model to study the network's bit-per-joule performance. We assume that each node uses an IEEE 802.11 based software controlled radio whose modulation/coding scheme and rate can be dynamically selected. A topology synthesis algorithm is used to elect nodes to act as access points as well as backbone nodes (BNs). The latter form a mesh backbone network infrastructure. We present an algorithm that is used to analytically calculate an approximation of the throughput capacity performance of the network. We use this algorithm to examine the performance efficiency of the network, expressed in terms of the throughput rate per unit energy consumed under the joint setting of nodal transmit power and data rate levels. Our results show that when traffic is uniformly distributed across the area of operations, increasing the nodal transmit power levels, as well as the data rates, tend often to enhance the bit-per-joule performance of the system. We also examine the impact of the selection of the transmit data rate and power levels used in conducting the topology synthesis of the backbone network.
In this paper, we analyze audio watermarking methods based on quantization index modulation and low-density parity-check (LDPC) codes. We found that dither modulation (DM) can achieve better performance using half-rat...
详细信息
In this paper, we analyze audio watermarking methods based on quantization index modulation and low-density parity-check (LDPC) codes. We found that dither modulation (DM) can achieve better performance using half-rate Margulis LDPC code even better than some low-rate codes. Then, we propose a scheme based on LDPC codes and DM with distortion-compensation (DC) property which has a robustness benefit of 6 dB versus uncoded case, 2 dB versus algebraic codes, 1 dB versus DM with LDPC code. In DM with DC property, we show that it is possible to achieve. 5 dB better robustness using a scale parameter alpha lower than the theoretically optimal and LDPC codes. Finally our proposal was evaluated against more practical attacks. These results show that our scheme could be a good option for robust watermarks.
In a multiple-input multiple-output (MIMO) multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system, coherent detection where the channel state information (CSI) is assumed to be exac...
详细信息
In a multiple-input multiple-output (MIMO) multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system, coherent detection where the channel state information (CSI) is assumed to be exactly known at the receiver requires the transmission of a large number of symbols for channel estimation, thus reducing the bandwidth efficiency. This paper examines the use of unitary differential space-time frequency codes (DSTFCs) in MB-OFDM UWB, which increases the system bandwidth efficiency due to the fact that no CSI is required for differential detection. The proposed DSTFC MB-OFDM system would be useful when the transmission of multiple channel estimation symbols is impractical or uneconomical. Simulation results show that the application of DSTFCs associated with dual carrier modulation (DCM) can significantly improve the bit error performance of conventional differential MB-OFDM system (without MIMO), and even provide better bit error performance than the DSTFC MB-OFDM system associated with constant envelope modulation schemes.
Wireless Sensor Networks pose numerous design challenges. They require long term, robust sensing for many applications. One important challenge is to design sensor networks that have long system lifetimes. Since the r...
详细信息
Wireless Sensor Networks pose numerous design challenges. They require long term, robust sensing for many applications. One important challenge is to design sensor networks that have long system lifetimes. Since the radio has the greatest impact on the energy consumption of the WSNs node, we present a physical layer adaptive channel coding and modulation scheme to lower the number of retransmission of package, then decrease the number of retransmission data because of error. So the energy consumption of the WSNs node can be saved and lifetime of the network is been extended. Experiment results show that the total amount of bits that are sent can be reduced by employing this scheme.
In IEEE 802.16e OFDMA system, the system capacity for accommodating VoIP traffic with small-sized PDUs is severely reduced due to a large amount of signalling overhead. In order to mitigate this problem, the IEEE 802....
详细信息
In IEEE 802.16e OFDMA system, the system capacity for accommodating VoIP traffic with small-sized PDUs is severely reduced due to a large amount of signalling overhead. In order to mitigate this problem, the IEEE 802.16 maintenance group has recently proposed a persistent allocation scheme to increase the voice over IP (VoIP) system capacity. However, it is difficult to use the conventional modulation and coding scheme (MCS) selection algorithms, which are based on instantaneous SINR, for the persistent allocation scheme. In this paper, we propose MCS selection algorithms which are effective for using radio resources considering a hybrid ARQ retransmission mechanisms while satisfying given QoS requirements for the persistent allocation scheme. Numerical results show that the proposed algorithms are effective for utilizing radio resources efficiently while satisfying given QoS requirements.
Analyzing the capacity of relay networks is often based on the max-flow min-cut theorem providing an upper bound on the true capacity which is generally still unknown. This paper analyzes the achievable rates of a sim...
详细信息
Analyzing the capacity of relay networks is often based on the max-flow min-cut theorem providing an upper bound on the true capacity which is generally still unknown. This paper analyzes the achievable rates of a simple relay network by a semi-analytical approach considering ideal capacity achieving codes of appropriate rates and optimum symbol-by-symbol soft-output decoding at the relay. Applying the information combining technique, regions are illustrated where the upper bound provided by the max-flow min-cut theorem can be reached. Moreover, the results show that the lower bound obtained by the constraint of error-free decoding at the relay can be exceeded in many scenarios. Simulations with a nearly capacity achieving half-rate repeat accumulate code confirm the semi-analytic results.
Heterogeneous error protection (HEP) of H.264/AVC coded video is investigated using hierarchical quadrature amplitude modulation (HQAM), which takes into consideration the non- uniformly distributed importance of intr...
详细信息
ISBN:
(纸本)9781424440009
Heterogeneous error protection (HEP) of H.264/AVC coded video is investigated using hierarchical quadrature amplitude modulation (HQAM), which takes into consideration the non- uniformly distributed importance of intracoded frame (I-frame) and predictive coded frame (P-frame) as well as the sensitivity of the coded bitsream against transmission errors. The HQAM constellation are used to give different degrees of error protection of the most important information of the video content. The performance of the transmission system is evaluated under additive Gaussion Noise (AWGN). The simulation results indicate that the strategy produces a high quality of the reconstructed video data compared with uniform protection.
In this paper, the waiting time analysis for an OFDMA wireless cellular system with finite buffering and Adaptive modulation and coding (AMC) is addressed. When AMC is considered, several concentric regions within cel...
详细信息
In this paper, the waiting time analysis for an OFDMA wireless cellular system with finite buffering and Adaptive modulation and coding (AMC) is addressed. When AMC is considered, several concentric regions within cells serving users with different data rates are differentiated. Phase type (PHT) distribution functions are used to model the conditional cumulative distribution function of the waiting time for users in the different coverage regions. The representation of the conditional waiting time distribution through PHT distributions allows expressing cumulative distribution function (CDF) as a linear combination of negative exponential distributions. The analytical method proposed here captures the exact behavior of the waiting time and the obtained solution is based on matrix analytic derivation, which allows evaluating system performance for any size of buffer and any number of coverage regions.
The continuing evolution of wireless communication standards and the associated increases in functionality for mobile wireless voice and data devices are driving the growing demand for transmitters that offer enhanced...
详细信息
The continuing evolution of wireless communication standards and the associated increases in functionality for mobile wireless voice and data devices are driving the growing demand for transmitters that offer enhanced performance and greater flexibility while simultaneously consuming less power. Transmitter solutions are typically spawned by separate analysis and design of the RF power amplifier and the modulator functions. One trend in the industry has been to combine these functions while enhancing efficiency and maintaining waveform quality. However, the treatment of architectural synthesis has not been unified. The ideas presented in this paper unify the analysis and synthesis philosophy under the theoretical umbrella of thermodynamics and Shannon's theorem.
We consider a bound for the minimal Euclidean distance of any PSK block code with eight symbols. The main result was established in [6] - here we prove that the bound is in fact stronger than was proven there. The bou...
详细信息
We consider a bound for the minimal Euclidean distance of any PSK block code with eight symbols. The main result was established in [6] - here we prove that the bound is in fact stronger than was proven there. The bound is deduced by generalizing Elias' method of a critical sphere. It is not asympthotic, as previous Elias' sphere bounds, but valid for any specific word length and code size. Many known codes fulfil the bound with equality, proving the sharpness of the bound for these parameter values as well as the optimality of these codes.
暂无评论