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Mobile ad hoc networks (MANETs) contain individual nodes exchanging data in a distributed manner. Although each node is capable of determining its own transmission power level, rate adaptation method and routing strategy, few existing routing protocols fully explore the potential performance improvement by the joint optimization of power, rate and routing. This paper proposes and evaluates a cross-layer routing protocol considering power control and rate adaptation by using a delay-based non-selfish cost function with a multi-agent Q-learning coordination mechanism. A simulation-based evaluation, considering node density, node mobility, traffic load and flow number, shows that our algorithm improves the average end-to-end latency and throughput with acceptable power consumption level.

Inter-user interference deteriorates reliable communication in body sensor networks (BSNs) when multiple BSNs are transmitting simultaneously in close proximity to each other. This paper presents a lightweight and distributed inter-user interference mitigation (IIM) scheme, that can be easily integrated with the IEEE 802.15.4 protocol stack. The proposed scheme takes into consideration the generic property of low channel utilization in BSNs and enables affected BSNs to adaptively reschedule their transmission time or switch channels. Based on the detected information from neighboring BSNs, BSNs reschedule their transmissions in a distributed and coordinated manner, so that wireless channels can be effectively utilized by multiple BSNs. Moreover, the IIM scheme is performed only when the performance of the BSN is degraded to an unacceptable level due to severe interference to reduce the rescheduling cost. Simulation results show that the proposed scheme improves the network throughput by 18% and reduces the energy consumption by 22% as compared with the existing beacon schedule scheme.

Using the MUSIC (MUltiple SIgnal Classification) algorithm to estimate the angle-of-arrival (AoA), we derive a new asymptotic error variance bound when the transmitted signal can be pre-processed. We next propose a precoder design to achieve this bound. However, such an optimal precoder requires channel state information at the transmitter (CSIT) exclusive of the receiver array which cannot be separately estimated practically. A more feasible precoder design, which leverages on the feedback CSIT estimated at the receiver, is next proposed. Using the performance of the optimal precoder which achieves the bound asymptotically as a benchmark, the practical precoder design performs close to the optimal precoder even in the high-resolution scenario. Both precoder schemes exhibit performance improvement compared with the case when no precoder is used.

Advances in Ambient Intelligence (AmI) technologies, when combined with user-centric computing, present major opportunities for building new communication pathways between end-users and traditional computer networks. We propose to explicitly take the end-user into account by defining a new functional module called the User Module across the layers of the Internet protocol stack. This new User Module empowers end-users to improve network performance and enhance the end-user Quality of Experience (QoE) based on their interaction activities. To successfully capture the significant interaction information of end-users, we leverage on the well-established Human Information Processing approach to build the end-user model. Subsequently, we present two exemplary User Module applications addressing the Hypertext Transfer Protocol (HTTP) and the Transmission Control Protocol (TCP), respectively. Both applications illustrate how the User Module operates to effectively improve the underlying network performance and eventually enhance the end-user QoE.

Advances in ubiquitous sensing and computing technologies, combined with the well developed theories in cognitive science, present major opportunities for the future Internet. We argue that the future Internet should be a usercentric and context-aware communication network, which goes far beyond today's host-centric and store-forward Internet. In this article we propose to explicitly introduce the end-user's context information into the future Internet framework. We, therefore, define a new functional module called the User-Context Module, and describe its architecture and key design principles. We also present two User-Context Module applications to aid gaining an understanding of its operation and impacts.

When a Body Sensor Network (BSN) that is linked to the backbone via a wireless network interface roams from one coverage zone to another, a handover is required to maintain network connectivity. This paper proposes an optimized BSN handover strategy which utilizes the movement trend of the BSN wearer and makes handover decisions based on the estimated future position of the user. Simulation results indicate that outage probability can be reduced by the proposed approach while unnecessary handover rate remains similar compared to that of the conventional methods. In addition, no extra equipment is needed for the proposed method.

Energy is often identified as the single most important resource in wireless battery-powered sensor networks. While current wakeup schemes in the literature promise to conserve energy in such networks, they apply several assumptions that may not be always true. First, all applications are assumed to require sensing coverage and network connectivity continuously; Second, a random dense deployment of sensors is always assumed possible; And third, the sensing ranges can be easily modeled by some sensing circles. In this paper, we show that these assumptions are not always valid, and propose sensor node wakeup schemes based on combinatorics block design to address energy-related issues when common assumptions fail. Another distinguishing feature of our work is also the proposal of a dual wakeup design for sensing and communications as these are two very different tasks. Finally, we verified our proposed schemes with simulations and experiments.

Our analysis and simulations show that in a practical ATM network environment consisting of a mix of low cost ABR binary switches and higher cost ABR ERICA (explicit rate) switches, partially compliant ABR sources can illegally grab more bandwidth from the network without being detected. Consequently, fully compliant ABR sources lose their available fair share. At the same time, congestion conditions are experienced at the binary switches. Three schemes are contributed, namely SDP (partial-behaving user detection and punishment), DFC (Direct Fairness Control) and IFC (Instantaneous Fairness Control), all of which can be implemented in any ERICA switches with negligible increase in complexity, to overcome ABR source misbehaviour. Of the three, the IFC scheme is the most promising in terms of restoring fair share and reducing congestion in the binary switches.

This paper describes the hardware implementation of Segnet, a bus network based on the CSMA/CD medium access control technique having dynamic segmentation capability. A six-station PC-based network was set up and its performance evaluated. The experimental results obtained are compared with the simulation results; excellent agreement is achieved. It is also found that Segnet performs better under clustered traffic environments and as the number of clusters increases. The performance of individual source-destination pairs is also investigated and the effect of varying packet length examined.

The performance of a dynamically segmentable ring network (R-Segnet) based on the CSMA/CD local area network protocol is studied in this paper. Two routing algorithms for the bidirectional rign are considered. The first transmits a packet in either direction with equal probability while the secons always sends a packet via the shortest path to its destination. Throughput and delay performance comparisons are made against CSMA/CD and against a linear version of this segmentable network (Segnet). These comparisons are conducted for both clustered and nonclustered traffic patterns within the network. The results show that in all cases R-Segnet performs significantly better than conventional CSMA/CD. In the random-destination random-routing case, the performance of R-Segnet is almost similar to that of linear Segnet. When shortest-path routing is used, R-Segnet is shown to be clearly superior. The performance gains are also shown to be shared equitably by all stations in R-Segnet.