Tallal Elshabrawy

Report Success Probability/Battery Liftime Analysis of Dense IEEE 802.15.4-Based Metering Networks With Hidden Nodes

IEEE 802.15.4 and its amendments are among the leading candidates as enabling wireless technologies for metering networks. In a typical IEEE 802.15.4-based metering network, thousands of meter transceivers utilize CSMA/CA to send their metered data to a base station collector. With such enormous scale of devices competing for medium access, it becomes inevitable that meters might occasionally fail in reporting their data successfully. This could be attributed to consistent failure to grab access to the highly loaded shared medium or due to packet collision at the base station collector. Collisions occur due to synchronized channel access from meters within the same collision domain or due to hidden nodes across different collision domains. In this paper, a simple analytical model to evaluate the report success probability as well as meters’ battery lifetime within IEEE 802.15.4-based metering networks is introduced. The model quantifies the hidden node problem in terms of the average percentage of hidden transceivers with respect to each meter device within the network. Comparison with an OMNET++ simulation model shows that the presented analysis behaves as an upper bound on the report success probability. The model is then utilized for proper configuration of the IEEE 802.15.4 network given a target report success probability performance. It is shown that the expected battery lifetime of meters could be optimized by controlling the percentage of hidden nodes combined with proper setting of the maximum number of allowable backoff attempts by each meter.

Adaptive Power Saving Receiver for DVB-H Exploiting Adaptive Modulation and Coding

Broadcasting live digital TV to a small battery-powered handheld device is very challenging. One of the most promising technologies to provide such services is DVB-H (Digital Video Broadcasting over Handheld). Power consumption has always been one of the most crucial challenges for handheld devices. In this paper, a novel Adaptive Modulation and Coding (AMC) framework is proposed for DVB-H systems to address the challenging problem of power consumption. The proposed power saving AMC framework operates by rearranging the transmitted frames in a pre-defined pattern. The adaptive receiver selects the appropriate modulation technique and/or code rate, one that achieves a target Bit Error Rate (BER), and then could be switched off and/or powered down resulting in significant potential for saving of reception and processing powers. Simulation of the DVB-H system under the proposed framework proved that the proposed power saving AMC framework is capable of achieving power saving up to 71.875% in COST207 Typical Urban 6-paths (TU6) channel. Furthermore, numerical analysis for the power saving potential and BER performance of the proposed framework is performed for both flat Rayleigh channel and multipath TU6 channel.

Low energy high speed reed-solomon decoder using two parallel modified evaluator Inversionless Berlekamp-Massey

This paper proposes a low power high throughput Reed Solomon decoder designed optimally for handheld devices under the DVB-H standard. This architecture based on Decomposed Inversionless Berlekamp-Massey Algorithm (DiBM), where the error locator and evaluator polynomial can be computed serially. In the proposed architecture, a new scheduling of 6 Finite Field Multipliers (FFMs) is used to calculate the error locator polynomial in a two parallel way and these multipliers are reused to calculate the error evaluator polynomial in a novel architecture called two parallel modified evaluator decomposed inversionless Berlekamp-Massey (MEDiBM) to achieve low energy. This architecture is tested in a pipelined two parallel decoder. This decoder has been implemented by 0:13μm CMOS IBM standard cells for RS(204; 188) and gave gate count of 33K and area of 1:06mm2. Simulation results show this approach can work successfully at the data rate 100Mbps with power dissipation of 0:266mW.

Computationally efficient implementation for incremental redundancy within wireless networks

Hybrid ARQ (HARQ) is widely used nowadays for error control within diverse wireless networks. HARQ deploys error detection mechanisms to corrected code sequences and enforces successive retransmissions and decoding until the corrected code sequence is presumed to be decoded correctly or a maximum number of retransmissions are reached. Incremental redundancy is a HARQ technique where additional transmissions associated with error correction failures are comprised only of incremental coding bits that increase the robustness of the channel coding. Nevertheless, the throughput and BER advantages of incremental redundancy should not be treated in isolation from the computational cost associated with repetitive decoding of the same information data. In this paper, simple and computationally efficient approaches are proposed for the implementation of incremental redundancy based on rate compatible punctured convolutional codes under hard-decision decoding. The proposed approaches identify code sequences over which the cost-metric remains constant. These sequences are assumed reliable and their associated computations are eliminated whenever decoding should be repeated at lower rates. The proposed approaches are evaluated from the perspective of computations, memory requirements. The corresponding effects on bit error rate and throughput performance are reported. The computational gains (up to 21%) of the proposed approaches would be particularly beneficial in systems where energy resources are scarce such as wireless sensor networks.

An energy-efficient framework for data aggregation in wireless sensor networks based on distributed source coding

This paper presents a data aggregation and forwarding framework in wireless sensor networks (WSNs) that will help in reducing energy consumption and hence prolong network lifetime. This approach is based on the fact that WSNs usually contain a large number of sensor nodes typically with highly correlated data readings. The proposal is to deploy distributed source coding (DSC) in compressing data messages to reduce transmission energy requirements along with avoiding data redundancy. Specifically, a DSC construction is proposed to determine the number of bits needed to encode a data message by a sensor node relative to its correlated neighbors without exchanging excessive communication messages among them.

A low energy high speed Reed-Solomon decoder using Decomposed Inversionless Berlekamp-Massey Algorithm

This paper proposes an area efficient, low energy, high speed pipelined architecture for a Reed-Solomon decoder based on Decomposed Inversionless Berlekamp-Massey Algorithm, where the error locator and evaluator polynomial can be computed serially. In the proposed architecture, a new scheduling of t Finite Field Multipliers (FFMs) is used to calculate the error locator and evaluator polynomials to achieve a good balance between area, latency, and throughput. This architecture is tested in two different decoders. The first one is a pipelined two parallel decoder, as two parallel syndrome and two parallel Chien search are used. The second one is a conventional pipelined decoder, as conventional syndrome and Chien search are used. Both decoders have been implemented by 0.13µm CMOS IBM standard cells. The two parallel RS(255, 239) decoder has gate count of 37.6K and area of 1.18mm2, simulation results show this approach can work successfully at the data rate 7.4Gbps and the power dissipation is 50mW. The conventional RS(255, 239) decoder has gate count of 30.7K and area of 0.99mm2. Simulation results show this approach can work successfully at the data rate 4.85Gbps and the power dissipation is 29.28mW.

An enhanced preprocessing dependent image theory algorithm for indoor coverage solutions

Hot spot coverage requirements of indoor environments necessitate adequate network platforms and optimal network planning. Optimal network planning imposes successive iterative computations and evaluations of network coverage until the best antenna layout is attained. Accordingly, accurate and scalable indoor propagation models become of the ultimate essence. In this paper, an efficient methodology for feasible reflection region assessment is developed to enhance a recently proposed preprocessing dependent image theory based ray tracing algorithm. The feasible reflection region depicts reception point grids of the indoor layout under study that fall within the foot print of a given transmitter image. The methodology proposed in this paper utilizes the intersection points between the stored preprocessing bounds of the feasible reflection region with lines that are drawn parallel to the walls of the indoor layout to achieve significant computational enhancements in the feasible reflection region assessment phase of the indoor coverage computations. The proposed enhanced ray tracing algorithm is tested in different indoor configurations. Simulation results confirm the major computational gain attained through the proposed enhancements while maintaining computational accuracy.

Throughput analysis of IEEE 802.15.4 enabled wireless sensor networks under WLAN interference

In this paper, theoretical analysis of network throughput of IEEE 802.15.4 enabled wireless sensor networks under WLAN interference shall be introduced. Analysis of achievable network throughputs is presented under multiple network configurations and WLAN interference scenarios.

An Adaptive MIMO System Using Incremental Diversity

In the recent years, Multiple Input Multiple Output (MIMO) systems have emerged as a promising technology that offers reliability and spectral efficiency. Since then a great concern was devoted to enhance the performance of MIMO systems through efficient encoding and decoding techniques. Two famous MIMO approaches have emerged; Spatial Multiplexing (SM), and Space Time Block Coding (STBC). On one hand, SM offers high data rates. On the other hand, STBC presents transmission fidelity. This actually imposed a fundamental tradeoff between capacity and reliability. For a more efficient utilization of the MIMO resources, a combination between SM and STBC grasps both spectral efficiency and reliability. Hybrid SM/STBC was introduced as a MIMO system technology that offers the advantages of the two systems simultaneously. In this paper, an adaptive MIMO system that incrementally switches from multiplexing towards diversity or hybrid diversity/multiplexing is proposed. The system is initialized with a pure multiplexing mode. An error detection check is performed at the receiver side and successful detection is fed back to the transmitter via an acknowledgement. A negative acknowledgement due to false detection triggers the transmitter to incrementally switch towards the diversity mode where it sends a part of the redundancy symbols constituting an STBC or a hybrid SM/STBC - diversity mode. The incremental diversity symbols are transmitted until a positive acknowledgment is received or the transmitter exhausts its full diversity capabilities. Results indicate that, the proposed scheme combines the transmission reliability offered by MIMO diversity, while maintaining a gradual increase in the spectral efficiency in correspondence to the increase in the SNR.

Four-level UEP of H.264 Scalable Video Coding using Discrete Wavelet Transform

In this paper, Unequal Error Protection (UEP) is applied to a proposed Scalable Video Coding (SVC) amendment to the H.264/AVC standard. The proposed SVC framework uses Discrete Wavelet Transform (DWT) as a hierarchically signal decomposition for multi-resolution analysis and H.264/AVC as a source coding and compression technique. The output streams are divided into four streams with different priorities. UEP is applied in two different dimensions, the first dimension is defined under the video scalability and the second dimension gives higher priority to I-frames over P-frames. UEP is realized using a combination of Hierarchical Quadrature Amplitude Modulation (H-QAM) and Forward Error Correction (FEC) based on Rate Compatible Punctured Convolutional Codes (RCPC). A method to find the optimal selection of parameters for the H-QAM and the rate used by the RCPC is proposed putting into consideration the gain required in SNR compared to the loss in bitrate. Simulation results show that the proposed UEP scheme outperforms the Equal Error Protection (EEP) for low SNR values while minimizing as much as possible the loss for higher SNR users.