Identity-based attacks (IBAs) are one of the most serious threats to wireless networks. Recently, there is an increasing interest in using the received signal strength (RSS) to detect IBAs in wireless networks. However, current schemes tend to generate excessive false alarms in the mobile scenario. In this paper, we propose a stronger Reciprocal Channel Variation-based Identification and classification (RCVIC) scheme for the mobile wireless networks, which exploits the reciprocity of the wireless fading channel and RSS variations naturally incurred by mobility to improve the detection performance. Different from current schemes only detect IBAs, RCVIC scheme conducts a multi-stage detection processes. If the IBAs are detected, RCVIC scheme partitions the received frames into two classes. The frames in the same class should be sent from the same senders, which could benefit the further analysis, such as network forensics, attacker localizing and trajectory analysis, etc. The feasibility of RCVIC are numerically evaluated through theoretical analysis and simulations. It is further validated through experiments using off-the-shelf 802.11 devices under different attacking patterns in real indoor and outdoor mobile scenarios.

Applications (Apps) in Smart devices make our life connected to Internet all the time. Many of the Apps like Google Apps, Facebook, and Twitter generate periodic background traffic. Due to this background traffic, battery continuously drains in Smart Phones. In this paper, we identify root causes for the background traffic and evaluate Apps' behavior with respect to impacts of TCP connection flow on Smart phone battery. We have conducted extensive experiments and collected data from various operator networks in different countries. We observe that TCP delayed closures not only extend radio wake up time but also lead to prolonged retransmissions. These prolonged retransmissions lead to severe battery drain problem. We propose a solution for such TCP closures at the client side with the objective of controlling unwanted TCP retransmissions. Our proposed solution is energy efficient, light weight, application agnostic, and a client only solution which makes deployment easier. Our solution has been evaluated for Android devices such as Samsung Galaxy S6, S7 variants, J7, and the Tizen device such as Samsung Z3. We have found that our solution consistently achieves 10 to 20 percent of power usage reduction irrespective of varying network and traffic conditions. We provide detailed experimental results considering various corner cases and also present the implementation architecture of our proposed solution.

Applications (Apps) in Smart devices make our life connected to Internet all the time. But, the battery capacity is a major setback for Internet connected Smart phones. We know that TCP is the backbone protocol for these Internet data transmissions. In this paper, we studied the impacts of TCP connection flow on Smart phone battery. We have conducted extensive experiments and collected data from various operator networks in different countries. We observe that TCP delayed closures at the client and prolonged TCP zero Window probes (ZWP) from the server lead to increased signaling overhead and radio ON time. These phenomenon cause unwanted battery drain at the smart phones. To address these problems, we propose a solution that prevents unnecessary packet communication due to TCP delayed closures and ZWPs. Our solution has been evaluated for Android devices such as Samsung Galaxy S7 and S8 variants and Tizen device such as Samsung Z3. We have found that, our solution consistently achieves 10 to 20% of power usage reduction irrespective of varying network and traffic conditions.

Multimedia contents of the popular applications are downloaded generally from the mirror servers. The contents are stored in mirror servers for load balancing. The method of selecting a particular mirror server over other affects the throughput and user experience. The present domain name server (DNS) look up based mirror server selection generally picks up the server from the top of the look up list which is not optimal in most cases. In this paper we propose an alternative mirror server selection policy by constraining the Round Trip Time (RTT), TCP connect time, average throughput and number of retransmissions. The server with the satisfiable values for all the metrics will be chosen as optimal server. The metrics are applied as per preference. If more than one server satisfies all the criteria then a best server is identified from the group which has minimal RTT and connection establishment time. If no server satisfies all the criteria, then the servers which satisfy sub set of criteria will be selected and from that one sub optimal server will be chosen which has minimal RTT and connection establishment time. Our proposed solution is simple, implementable and tested for Android based devices. From the test measurements, we observe that, our proposed policy could achieve better performance in terms of reduced RTT, number of retransmissions, average throughput and energy consumptions.

Smart phones have made our life easier by providing 24×7 connectivity to Internet. But, the battery capacity is a major setback for Internet connected Smart phones. We know that TCP is the backbone protocol for these Internet data transmissions. In this paper, we studied the impacts of TCP flow control mechanism on battery life. Generally, TCP flow control mechanism is used to avoid buffer overflow at the receiver and is achieved by advertising the receive buffer size as TCP window to the sender. When sender receives zero TCP window, it stops sending data and starts sending probes to receiver till space opens up in the input window. During our study, we observed some abnormal behavior, whenever video streaming or downloads were interrupted. We found that there were prolonged TCP Zero Window Probes(ZWPs) from the sender which lead to increased signalling overhead and radio ON time at receiver. This phenomenon causes unwanted battery drain. To address this particular problem, we propose a solution that prevents unnecessary packet communication due to ZWPs. We have implemented our solution for Android devices and analyzed the performance extensively based on real time measurements. In our experiments, we could achieve 10-15% of power gain consistently in smart phones.

Present day users tend to use Smartphone for heavy load multimedia file sharing, and require a lot of upload bandwidth. However, the bandwidth is an expensive affair and upload could take a lot of time in a limited bandwidth scenario. In this work, we aim to develop a solution to estimate time to share or upload multimedia content from a Smartphone to social networks or cloud servers. We propose machine learning approach for the estimation and use support vector regression (SVR) method. Our feature space for SVR includes network parameters such as available bandwidth and round trip time (RTT), received signal strength index (RSSI) as channel parameter, CPU load, Available Battery and file size as system parameters. Based on these features we estimate the time needed to upload the multimedia content. We evaluate our solution for accuracy using cross validation and our findings reveal, 84% of estimates are in 80% confidence interval for LTE and 80% in case of 3G. This estimate can help the user#x002F;system to make decision to schedule delay tolerant uploads in more favorable environment to maximize the Quality of Experience (QoE). We also show by simple experiment power savings of up to 40% when upload in bad signal is rescheduled to good signal conditions. We provide architecture of our solution in Android and implement it on Samsung J7 device.

The volume of best effort traffic is exploded by rapid adoption of peer-to-peer and content applications. Smart phone consumers are spending more times on applications which include video and music streaming, playing games, video chatting, social media like uploading photos to Facebook, Twitter etc. Many such applications are always running in background and sometimes come in foreground based on user preferences. In this work we propose an approach to improve the user experience by giving more bandwidth to preferred applications. We describe a preliminary model explaining our technique in detail. Further, we validate our proposal using real time test setup with Wireshark traffic analyzer, and results are detailed with respect to (1) Percentage of network share (2) Jitter experience and (3) Time taken for the algorithm to adapt. Proposed algorithm has been tested in two different platforms such as Android and Tizen. Our preliminary observations show that our proposed algorithm allocates more bandwidth to high priority applications while maintaining the low priority APPs are intact with above minimum bandwidth. Our approach gives users better jitter free experience for video streaming (high priority) applications in both Android (KitKat) and Tizen (Z1) platforms.

MQTT-SN offers energy efficient data transportation under unreliable wireless environment with limited energy/ bandwidth. However, MQTT-SN faces a new set of challenges for service guarantees when operated for a reliable or time-critical applications. The impact of various network parameters on the MQTT-SN service assurance requires an end-to-end system study, which are unexplored yet. In this paper we analyze in detail about the end-to-end service assurance parameters such as content delivery delay and probability of content delivery for a MQTT-SN to be used in health care Internet of Things (IoT). To model the end-to-end delay, various entities of the MQTT-SN including handshake messages in MQTT-SN Pub/sub architecture over TCP, over UDP and then the queuing delay involved in server have been considered. We model the MQTT content and request server as a round-robin queue scheduler and also model a TOPIC ID based matching station that delivers the content on requested TOPIC ID. With this model we derive the end-to-end content delivery probability and content delivery delay estimate as functions of MQTT-SN system parameters such as content arrival rate, request arrival rate, possession time of content in server, possession time of request in server, number of content arrivals and number of requests arrivals. Both these service assurance parameters will give more insight into the number of content/request arrivals that can be supported for a given service assurance requirement. In addition these service assurance parameters will be of help to design the system more effectively. We carry out a detailed ns2 based simulation to show impacts of various system parameters on the network performances for various QoS services designed for MQTT-SN system.

Non-beacon mode operation is included in IEEE 802.1.5.4 due to low overhead, energy efficient transmission and no tight synchronization requirement as compared to the beacon-mode transmissions. We model non beacon mode operation of an 802.15.4 unslotted CSMA/CA using Markov chain analysis for low data rate unsaturated traffic. Our modeling is reasonably detailed to capture an exact 802.15.4 system. The modeling captures various network features in detail, such as channel access probability, packet collision, acknowledged transmissions, exponential backoff with retry limits. The packet generation process at the sensor nodes is considered as periodic. We thoroughly derive the packet delay distribution and study the system throughput and energy efficiency trade off which is often crucial for the low rate networks. Our exact Markov chain based analysis reveals that the service process of the protocol is close to an exponential distribution. Therefore, we approximate it by a single server queue with an exponential service time. We then analyze a D/M/1 queue with an unsaturated periodic traffic and show that it can be a good fit for the 802.15.4 system. Using D/M/1 queue model, we derive an end-to-end delay and analyze the delay performance. We also study a system with non-exponential backoff and compare the optimal network performance with the legacy exponential backoff system. Our simulation results corroborate with the theoretical analysis. Our analysis can be used as a system design tool where various network system parameters can be configured to meet a desired end-to-end delay, energy efficiency and throughput.

LTE-Advanced (LTE-A) systems support wider transmission bandwidths and hence, higher data rates for bulk traffic, as a result of Carrier Aggregation (CA). However, existing literature lacks efforts on channel-aware CA, especially in the uplink. The cell-edge users particularly suffer from exhaustion of resources, higher fading losses, lower SINR values (hence, requiring a higher power consumption) due to lossy channels that their traffic requirements are least-satisfied by channel-blind CA. This paper addresses the above concern by proposing an edge-prioritized channel- and traffic-aware uplink CA comprising Component Carrier (CC) assignment and resource scheduling. The LTE-A UEs are spatially-grouped and the under-represented edge UE groups, having the least assignable resources (good CCs), are prioritized for CA. This results in assigning the best channels to the edge groups. The frequency resources are scheduled to the groups based on inter-group and intra-group Proportional Fair Packet Scheduling (PFPS) in the time and frequency domains respectively, to resolve resource contention. The proposed approach outperforms the existing channel-blind Round-Robin and channel-aware Opportunistic CA, in terms of overall uplink throughput, by 33% in CC assignment and 21% in PFPS, in addition to significant throughput improvements for the edge UEs.

Trust plays an important role in protecting the security of mobile ad hoc networks. The node mobility brings challenge to trust propagation, where traditional graph-based propagation methods are difficult to apply. In this paper, we propose a trust establishment and propagation scheme by exploiting natural mobility of mobile ad hoc network nodes. We estimate the moving state of neighboring nodes, and select the group of nodes with higher movement diversity as the next hop. In this way, we expedite trust propagation with the help of mobility instead of treating it as a hurdle. Two classes of mobility models are considered: random direction model and cluster-based model. Extensive experiments are conducted on trust propagation performance using our scheme. Results show that the detection rate of highly untrustworthy node is improved by about 400% in random direction mobility model and about 300% in cluster-based mobility model compared to static case. Further, we observe that trust convergence time and communication overhead varies dramatically in different mobility models. Based on these observations, we discuss the usage of different mobility models and metrics in different trust applications in mobile ad hoc networks.

Identity-based attacks (IBAs) are one of the most serious threats to wireless networks. Recently, received signal strength (RSS) based detection mechanisms were proposed to detect IBAs in static networks. Although mobility is an inherent property of wireless networks, limited work has addressed IBA detection in mobile scenarios. In this paper, we propose a novel RSS based technique, Reciprocal Channel Variation-based Identification (RCVI), to detect IBAs in mobile wireless networks. RCVI takes advantage of the location decorrelation, randomness, and reciprocity of the wireless fading channel to decide if all packets come from a single sender or more. If the packets are only coming from the genuine sender, the RSS variations reported by the sender should be correlated with the receiver's observations. Otherwise, the correlation should be degraded, then an attack can be flagged. We evaluate RCVI through theoretical analysis, and validate it through experiments using off-the-shelf 802.11 devices under different attacking patterns in real indoor and outdoor mobile scenarios. We show that RCVI can detect IBAs with a high probability even when the attacker is half a meter away from the genuine user.

The quality of information is crucial for decision making in many dynamic information sharing environments such as sensor and tactical networks. Information trustworthiness is an essential parameter in assessing the information quality. In this paper, we present a trust model to evaluate the trustworthiness of information as well as information publishing entities based on information provenance. In our trust model, decision makers can give an evaluation on the information they receive and further adjust the evaluation result to a more accurate value by considering two factors: information similarity and path difference. We introduce Collusion Attacks that may bias the computation and present a mechanism to detect and reduce the effect of Collusion Attacks. Based on the final adjusted information trust, feedback is given to the information publishing nodes to adaptively update their trust scores. Therefore, our collusion-resistant scheme can dynamically assess the trustworthiness of information as well as participating entities in a network and thus effectively enhance the network security. Detailed analysis of the proposed approach is presented along with simulation results.

Probability density of the received power is well analyzed for wireless networks with static nodes. However, most of the present days networks are mobile and not much exploration has been done on statistical analysis of the received power for mobile networks in particular, for the network with random moving patterns. In this paper, we derive probability density of the received power for mobile networks with random mobility models. We consider the power received at an access point from a particular mobile node. Two mobility models are considered: Random Direction (RD) model and Random way-point (RWP) model. Wireless channel is assumed to have a small scale fading of Rayleigh distribution and path loss exponent of 4. 3D, 2D and 1D deployment of nodes are considered. Our findings show that the probability density of the received power for RD mobility models for all the three deployment topologies are weighted confluent hypergeometric functions. In case of RWP mobility models, the received power probability density for all the three deployment topologies are linear combinations of confluent hypergeometric functions. The analytical results are validated through NS2 simulations and a reasonably good match is found between analytical and simulation results.

In this paper, we present a trust model to evaluate the trustworthiness of information as well as the information publishing nodes based on the information provenance. We consider two factors in evaluating the provenance-based information trust: Path Similarity and Information Similarity. In multihop networks, information can flow through multiple hops from multiple paths. We model the similarity between different paths which deliver information about the same event and the similarity between two information items about the same event which are delivered through different paths. Both path and information similarity factors are considered in determining the trust of the information. This information trust is indeed used as a feedback factor to adaptively adjust trust of the nodes in the network. Detailed analysis of the proposed approach is presented along with simulation results for validation.

Finding an optimal routing path in adverse underwater environment in an Underwater Sensor Network (UWSN) has always been a challenging task. Maintaining the network life for a longer duration by utilizing nodes' energy is also critical. By taking these issues into consideration we propose an Energy optimized Path Unaware Layered Routing Protocol (E-PULRP) for dense underwater 3D sensor networks. An up-link transmission is considered, where a set of underwater sensor nodes report events to the stationary sink node. E-PURLP consists of two phases. In the first phase (layering phase), a layering structure is presented which is a set of concentric spheres, around a sink node. The radii of the concentric spheres as well as the transmission energy of the nodes in each layer are chosen considering probability of successful packet transmissions and minimum overall energy expenditure. In the second phase (communication phase), we propose a method to choose intermediate relay nodes andontheflyrouting algorithm for packet delivery from source node to sink node across the identified relay nodes. The energy analysis of the E-PULRP has been carried out and shown that it is energy efficient. The performance in terms of throughput and delay is also analyzed.

In this paper analytical relationship between transmission range and the network connectivity is obtained as a function of number of nodes for CDMA based multihop cellular network (MCN). We show that for a network of n uniformly distributed nodes in a single cell of unit radius, the transmission range r should be sufficiently larger than radic(2 ln n/n-1) to achieve asymptotic full connectivity. The distribution of the nodes may not be uniform in case of mobility. In such case a mobility model dependent lower bound on transmission range is obtained. We show that for RWP model the lower bound for the nodes which lie completely inside the cell is same as the corresponding uniform node distribution case. However, for nodes on boundary the transmission range lower bound is3radic(ln/n) which is larger than the corresponding uniform node distribution case. Our findings show that more transmission range is required at the boundary to establish better connectivity and hence a variable transmission range control mechanism is necessary. In addition to lower bound, we also propose a method to choose the optimal value of transmission range using a scheduling mechanism and ensure that the optimal value is always greater than the lower bound. Thus obtained transmission range could be used to select the transmission power of the nodes in a meaningful way and hence the nodes' isolation could be avoided and the spectral efficiency can be increased. We demonstrate empirically, that the proposed transmission range control mechanism increases the network connectivity as well as spatial reuse of the resources.

We propose a path unaware layered routing protocol (PULRP) for dense underwater 3D sensor networks. An uplink transmission is considered, where a set of underwater sensor nodes report events to the sink node. PURLP algorithm consists of two phases. In the first phase (layering phase), a layering structure is presented which is a set of concentric spheres, around a sink node. The radius of the concentric spheres is chosen based on probability of successful packet forwarding as well as packet delivery latency. In the second phase (communication phase), we propose a method to choose the intermediate relay nodes and an on the fly routing algorithm for packet delivery from source node to sink node across the chosen relay nodes. The proposed algorithm, PULRP finds the routing path on the fly and hence it does not require any fixed routing table, localization or time synchronization processes. Our findings show that the proposed algorithm has a considerably better successful packet delivery rate compared to the under water diffusion (UWD) algorithm proposed in the paper by Lee et al. (2007) and Dijkstra's shortest path algorithm. In addition the delay involved in PULRP is comparable with that of UWD.

Abstract We propose path unaware layered routing protocol (PULRP) for 2D underwater sensor networks (UWSNs) with mobile nodes. The steady‐state distribution of mobile nodes in UWSNs is nonuniform in general. Hence, we use a mobility model‐dependent node distribution. The proposed PULRP algorithm consists of two phases. In the first phase (layering phase), a layering structure is presented which is a set of concentric circles, around a sink node. The radii of the concentric circles are chosen based on equal distribution of nodes in every layer. A distributed power control mechanism is also introduced. The power level of nodes in a particular layer is chosen such that communication occurs only with nodes in the next layer. In PULRP, we consider multihop communication from source to sink. Therefore, in the second phase (communication phase), we propose a method to choose the intermediate relay nodes and an on the fly routing algorithm for packet delivery from source node to sink node across the chosen relay nodes. The proposed algorithm, PULRP finds the routing path on the fly and hence, it does not require any fixed routing table, localization, or time synchronization processes. We demonstrate the performance of PULRP using random waypoint (RWP) mobility model in a simulated underwater environment. Our findings show that the proposed algorithm has considerably better throughput (successful packet delivery rate) compared to the underwater diffusion (UWD) algorithm for various node densities as well as node velocities. In addition, the delay performance of PULRP is also better than that of UWD. Copyright © 2008 John Wiley & Sons, Ltd.

In order to reduce the complexity of the mobile receiver, we develop a linear preceding filter based only on the statistical knowledge of the channel. Moreover, the proposed prefilter (precoder) is based on minimizing the probability of error in downlink multiuser transmission. We investigate two approaches for the proposed algorithm. In the first approach we consider a common FIR preceding filter for all users, and jointly minimize the probability of error of all users. In the second approach, we assume separate precoders for each user which are obtained by minimizing the probability of error for the respective user. In order to fully utilize the knowledge available at the transmitter, in both the approaches, the filter weights are computed conditioned on the transmitted bit vector sequence. This also makes the computation of the optimal prefilter coefficients linear in the number of users. We compare the results of the proposed approach, with results based on assuming complete knowledge of the channel. Simulation results clearly show that precoders based only on the statistical knowledge of channel, do provide acceptable BERs. Moreover, individual precoders provide better BER as compared to joint precoders.

We propose a CDMA-OFDM access mechanism for Multihop Cellular Networks (MCN). We construct groups within the MCN, where each group comprises of a source node, a destination node, their intermediate relay nodes and assign a correlated PN sequence to each such group. Within a particular group, a single carrier is assigned to each intermediate hop. The sub carriers assigned to the intermediate hops in a given group are mutually orthogonal. Hence the proposed OFDM is FDMA in nature. The sub carriers and transmit power levels to the relay nodes are assigned in such a way as to maximize the end-to-end throughput. The end-to-end throughput is formulated by assuming a Rayleigh flat fading channel between nodes. We present a method to reuse the PN codes assigned to the groups in a particular cell. We also introduce a novel architecture for MCN. Simulation results show that the proposed access mechanism achieves better end-to-end throughput and bit error rate (BER) performance as compared to standard access mechanisms like CDMA and OFDM-FDMA. Furthermore the proposed access mechanism has considerably higher BER performance in the presence of multiple transmit sources.