In this section, we show that the proposed modulation and coding scheme is viable even if the real-world con- ditions induce some deviations from the system model assumed in this paper. From a practical point of view, we would be interested mainly in the situation, where a direct channel between a source and its desired destination is present (see Fig. 16). Even though this “direct” channel can be relatively weak, it inevitably affects the destina- tions’ HSI observations. In addition to this, we analyze the system where source phase pre-rotation is switched off (or ineffective due to rapid channel dynamics), and thus the relay faces a multiple-access channel with a vary- ing source channel phase offset. This assumption is valid for a practical system where the applicability of source phase pre-rotation is limited due to the unavailable ideal feedback channel or because of the undesirable delay
In [26,29], the authors exploit the decode and forward mechanism for cooperation, which can be a concern for real-time applications. Importantly, decoding of every single packet at relay nodes is vulnerable to security and privacy attacks [30,31]. Use of clustering may not be possible in all applications of WBSNs, hence the hierarchical clustering-based NC works [24,27]. Due to the complexity of ARQ , NC-integrated ARQ schemes [23,42] are not suitable for WBSNs. The NC-based MAC proposed in  may not be suitable for WBSNs, as it is designed for wireless sensor networks. Moreover, some of the NC-based works  in BANs or WBSNs are not adaptive to the network channel conditions or environments of WBSNs. Most existing NC-based works in WBSNs exploit either linear combinations [24,27] or the XoR [13,26] operation for coding. Security-wise XoR-based coding is better than linear combinations. In a recent work , the authors proposed a cloud-assisted RLNC-based (random linear networkcoding) MAC protocol (CLNC-MAC). It supports guaranteed packet delivery and collision-free relaying, but suffers due to complexity and delay. In summary, most existing NC-based error recovery or performance improvement mechanisms are not QoS-aware of healthcare applications. Existing works which are QoS-aware do not support QoS in both perspectives, and they could be complex (e.g., ). In healthcare applications, inclusion of QoS awareness within these mechanisms is highly necessary.
In this article, we investigate a multi-user video streaming system applying unequal errorprotection (UEP) networkcoding (NC) for simultaneous real-time exchange of scalable video streams among multiple users. We focus on a simple wireless scenario where users exchange encoded data packets over a common central networknode (e.g., a base station or an access point) that aims to capture the fundamental system behaviour. Our goal is to present analytical tools that provide both the decoding probability analysis and the expected delay guarantees for diﬀerent importance layers of scalable video streams. Using the proposed tools, we oﬀer a simple framework for design and analysis of UEP NC based multi-user video streaming systems and provide examples of system design for video conferencing scenario in broadband wireless cellular networks.
MIMO is the current technology that is supported internationally by the Wireless Systems. LTE – Advanced support more sophisticated MIMO techniques, which enable several antennas to send and receive data. One use of MIMO, called multiplexing separates transmissions into many parallel streams, increasing data rates in proportion to the no. of antennas used.
Opportunistic orientation has emerged on the basis of smart codingnetwork to improve the ability of wireless multi-hop network loss by reducing the amount of messages required reactions. Most business coding in network-based opportunistic routing in the literature assumes that independent links. This hypothesis has been invalidated by recent empirical studies have shown that the relationship between the links may be arbitrary. In this paper, we show that opportunistic routing performance based on the coding of the network and greatly affected the relationship between the links. We formulate the problem of productivity maximization while achieving justice under arbitrary channel conditions, and determine the structure of the optimal solution. As is the case in the literature, and the optimal solution requires a lot of instant information messages, which is unrealistic. We propose the idea of network message coding performance reactions, which shows that if the intermediate node waits to receive only one message the votes of each next hip node, we can calculate the optimum level of network redundancy coding form Distributed. Encrypted messages require reaction to a small amount of overhead as it can be integrated with packets. Our approach is also oblivious to losses and mutual relationships between links, but also improves performance without a clear knowledge of these two factors
Lack of efficient ECC in sensor networks contributes their weak bit error rate performance in wireless environments where high levels of noise and interference are unavoidable. For recovering the erroneous packets, three fundamental schemes are Forward Error Correction (FEC), Automatic Repeat Request (ARQ) and Hybrid ARQ (HARQ). ARQ is very simple but it involves additional retransmission energy cost and area overhead. HARQ combines ARQ and FEC. It consumes a lot of energy and is restricted to some specific applications. The main advantage with FEC is that there are no delays in message flows. Energy constrained transmission issue of WSN makes FEC a popular technique to be used in such networks rather than ARQ and HARQ. Reed Solomon codes are long time industry standard codes for WSN.
A wireless sensor network consists of spatially distributed sensor nodes which sense physical and environmental condition like sound, pressure, temperature etc and pass the data to the main location through the network. The recent advances and improvement of micro electro-mechanical systems technology, integrated circuit technologies, microprocessor hardware, wireless communications, Ad-hoc networking routing protocols and embedded systems have made the concept of Wireless Sensor Networks. In WSN network life time and node energy efficiency are two most important terms .The aim of this study is to making an energy- efficient routing protocol which has a significant improvement on the overall lifetime of the sensor network and energy efficiency of nodes. LEACH is energy-efficient hierarchical based protocol that balances the energy efficiency, saves the node energy and hence the lifetime of the network. But Because of certain limitations of routing protocol LEACH, some schemes are proposed using protocols TEEN and APTEEN to overcome the drawback of LEACH. But TEEN and APTEEN has also some drawback and that drawback is removed by an advance scheme that is ADAPTIVE THRESHOLD. It gives better energy efficiency and improved network life time compared to LEACH, TEEN and APTEEN.
This algorithm quantifies wormholes devastating harmful impact on networkcoding system performance through experiments. DAWN explore the change of the flow directions of the innovative packets caused by wormholes. Rigorously prove that DAWN guarantees a good lower bound of successful detection rate and the perform analysis shows on the resistance of DAWN against collision attacks . It is to be found that the robustness depends on the node density in the network and prove a necessary condition to achieve collision- resistance. DAWN does not depend on any location information, global synchronization assumption or particular hardware/middleware. Extensive experimental results have verified the effectiveness and the efficiency of DAWN.
Wireless communications design is diverging from the OSI model, but there is still no standard framework for CLD. The lack of a standard framework can lead to many problems. This leads to reduced overall network performance. There are also fundamental, unanswered questions for CLD. Generally speaking, it is not clear when, where, and how different CLD proposals should be implemented. This paper is organized as follows. Section II describes the introduction of wireless sensor networks & wireless sensor nodes. Section III describes the OSI model. It identifies shortcomings of the OSI model for wireless communication systems, defines the need cross-layer design, and provides an example of how cross-layer design can improve wireless system performance and energy consumption. Section IV describes the network services. Section V shows the simulation result. In section VI, comparison is given. And in section VII, conclusion and future work is given.
Gao Weimin and Zhu et al.  proposed the techniques of distributed data storage in wireless senor networks. Firstly, the challenge and the need for such techniques were summarized; Secondly, some representative distributed data storage and retrieval schemes were introduced in detail; finally, the future research directions and open issues were pointed out..
constellations settings. We first investigate the impact of discrete constellations with respect to Gaussian sig- naling, and Fig. 8 shows the average maximum outage secrecy rate obtained when using infinite-length coding with both the aforementioned signalling schemes. We observe that the use of 16-QAM does not yield any signif- icant performance loss with respect to Gaussian signaling, since the maximum rate of 16 channels with 16-QAM is 256 b/s/Hz, which is well above the average secrecy rate of 25 b/s/Hz achievable in the considered setting with ideal Gaussian signaling. Therefore, constellations with small alphabet already provide close-to-optimal per- formance. Moreover, by increasing the number of relays, the average maximum outage secrecy rate increases, as a diversity gain is available on the links among legitimate nodes. Figure 9 shows results for finite-length coding and both Gaussian signaling and discrete constellations. As regards the Gaussian signaling, comparing Figs. 8 and 9, we note a negligible performance degradation for a code- word length m = 4096 with respect to infinite-length coding, since Q −1 (κ) = 3.1, and from (23), the loss is of the order of K · 10 −3 ≈ 10 −2 . About Fig. 9, we observe that finite-length coding further increases the gap with respect to Gaussian signaling: this is due to the fact that proper matching in the two phases of relaying must be found to achieve an end-to-end secrecy rate and adding constraints further limits this performance, in a non-linear fashion. Lastly, as d E → ∞ , we note that the rate curves flatten
appropriately determined set of rates, which uses successive interference cancelation to resolve packet collision due to wireless broadcast. When the number of transmission rates at each node is equal to the number of users, the achievable total throughput was shown to be at least a constant fraction of the centralized multiple access channel sum rate in slotted Aloha type networks. To facilitate practical protocol design, we also studied the case when only a limited number of transmission rates is available at each node. A game-theoretic framework was proposed to achieve the desired throughput optimal equilibrium in the absence of centralized knowledge of the total number of users. We studied the design of random access games, characterized their equilibria, studied their dynamics, and proposed distributed algorithms to achieve the equilibria. Lastly, we considered secure communications in networks with erasure and unequal link capacities in the presence of a wiretapper. For the case when the location of the wiretapped links is known, we have derived the secrecy capacity region. For the case when the location of the wiretapped links is unknown, we proposed several achievable strategies. We showed that unlike the case of equal link capacities, the secrecy capacity when the location of wiretapped links is known and unknown are generally unequal. We also showed that computing the secrecy capacity for both cases are NP-complete.
Albeit the well-known Orthogonal Variable Spreading Factor (OVSF) direct-sequence spreading codes [49, 87] have originally not been proposed for BbB-based reconfiguration, they can be po- tentially adapted on a near-instantaneous basis in an effort to coun- teract the near-instantaneous channel quality fluctuations of the wireless channel. Controlling the OVSF codes can also be po- tentially combined with near-instantaneous modulation mode con- trol. The advantage of counteracting the near-instantaneous chan- nel quality fluctuations in this way instead of the extensive em- ployment of agile power control is that power control may inflict excessive co-channel interference in an effort to maintain the chan- nel quality of specific users. By contrast, BbB-adaptive transmis- sion constitutes a ’non-intrusive’ way of mitigating the effects of transmission bursts, since only the user of interest adjusts its trans- mission mode appropriately.
Networkcoding (NC) is gaining popularity as a new trans- mission method that can improve network performance in terms of increasing throughput at the coding level. NC was first proposed by Ahlswede et al.  in 2000, and is basically classified into two types. One is called intra-flow networkcoding (IANC) which encodes mul- tiple packets belonging to the same flow. The other is called inter-flow networkcoding (IRNC) which encodes multiple packets from different flows. IANC is a kind of reliable transmission method. For n native packets sent from one flow, the sources and intermediate nodes are allowed to encode these packets together before send- ing them to the destinations. The generated encoded packets are redundant against lossy links until the destina- tion receives and decodes n independent encoded packets for recovering all native packets. By doing this, packet losses are masked and data transmissions are robust .
In this paper, we conducted a comparative analysis be- tween packet forwarding and networkcoding approaches for broadcasting in multihop wirelessnetworks. In our study, for fixed size and fixed density network, a lower bound derived via an unconstrained MCDS was always lower than the lower bound derived by the constrained version. This difference was statistically not significant for larger network sizes, but it does matter for smaller networks. This shows the importance of accurately mod- eling the lower bound, as a fair comparison with any network protocol can only be made using the lower bound derived by the constrained version. In real net- works, when selecting a source, we cannot assume/enforce that the node will naturally be part of the MCDS. In the case of packet forwarding techniques, the lower bound derived via the MCDS heuristic is statistically significant lower than the performance of both PDP and SMF, spe- cifically when there are more than 20 to 30 nodes in the network. This is also true for networkcoding techniques where the number of re-broadcasting nodes in PDP/XOR and SMF/XOR is much higher than the networkcoding lower bound.
We propose a new cut-set upper bound for the error-correction capacity for general acyclic networks. The standard cut-set bounding approach effectively treats all nodes on the same side of a given cut as a single super node. We therefore develop our cut- set bound by first studying the two-nodenetwork shown in Fig. 1.3. In this network, the source node can transmit packets to the sink node along the forward links and the sink node can send information back to the source node along the feedback links. We begin by characterizing the capacity of this network. However, this cut-set abstraction is insufficient to fully capture the effect of network topology relative to the cut since it assumes that all feedback is available to the source node and all information crossing the cut in the forward direction is available to the sink. We therefore introduce the four-node acyclic network shown in Fig. 1.4 as a step towards generalizing the cut-set bound. In this acyclic network, source node S and its neighbor node B lie on one side of a cut that separates them from sink node U and its neighbor A. As in the cut-set model, we allow unbounded reliable communication from source S to its neighbor B on one side of the cut and from node A to sink U on the other side of the cut; this differs from the original cut-set assumption only in that the communication is undirectional. We derive the capacity of this four-nodenetwork and use our result to generalize the cut-set bound. Since the resulting bound, like its predecessor, fails to capture the general network cut capacity, we introduce the zig-zag network model shown in Fig. 1.5 to generalize our four-node acyclic network model. Nodes A i and B i
M ANY physical structures can conveniently be mod- elled by networks. Examples include a communi- cation network with nodes and links modelling cities and communication channels, respectively, or a railroad network with nodes and links representing railroad stations and railways between two stations, respectively. Many problems on networkdesign and optimization, e.g., the file transfer problems on computer networks, building blocks, codingdesign, scheduling problems and so on, are related to the factors, factorizations and orthogonal factorizations in graphs . The file transfer problem can be modeled as (0, f )- factorizations (or f -colorings) in graphs . The designs of Room squares and Latin squares are related to orthogonal factorizations in graphs. It is well known that a network can be represented by a graph. Vertices and edges of the graph correspond to nodes and links between the nodes, respectively. Henceforth we use the term graph instead of network.
posed by terminating it at the last error-free received piece (thanks to the CRC codeword). In this way, any image reconstruction artifact due to wrong/erased codestream bytes has been eliminated, and the reconstructed image MSE is that used by the UEP allocation strategy. The JPEG 2000 header (about 300 bytes) has been considered as transmitted on a reliable channel, since it represents the most critical section of the codestream. At the receiv- ing side, the JPEG 2000 header has been pre-pended to the JPEG 2000 bitstream bytes, and only the portion of the header carrying information on the bitstream size (Psot field of the SOT marker) has been changed accord- ingly. Performance has been evaluated as objective visual quality, and Y-PSNR has been used as objective quality indicator. In addition, we used MSSIM to faithfully repre- sent the subjective evaluation by a human observer. The overall performance has been calculated by averaging the PSNR and MSSIM values calculated at each frame of the video sequence. The performance of the UEP method has been directly compared with that of an EEP method.
Two types of information-theoretic multicast networkerror correction problem are com- monly considered. In the coherent case, there is a centralized knowledge of the network topology and the network code. Networkerror and erasure correction for this case has been addressed in  by generalizing classical coding theory to the network setting. In the non-coherent case, the network topology and/or network code are not known a priori. In this setting,  provided networkerror-correcting codes with a design and implementation complexity that is only polynomial in the size of network parameters. An elegant approach was introduced in , where information transmission occurs via the space spanned by the received packets/vectors, hence any generating set for the same space is equivalent to the sink . Error correction techniques for the noncoherent case were also proposed in  in the form of rank metric codes, where the codewords are defined as subspaces of some ambient space. These code constructions primarily focus on the single-source multicast case and yield practical codes that have low computational complexity and are distributed and asymptotically rate-optimal.