Comprehensive study of wireless communication for ingestible electronics is a very challenging task. To initiate the study on wireless capsule endoscopy, an innovative immersive platform containing an enhanced 3D human body model has been developed. This platform allows for flexible placement of a capsule inside the gastrointestinal (GI) tract and multiple receivers around the abdomen area. It is shown that any directionality (or equivalently null) in the antenna radiation pattern can be exploited to sense changes in the orientation of the capsule through observation of the S21vector at a set of on-body receivers. Two methodologies i.e. complex cross-correlation and Minkowski distance were used to assess capsule orientation estimation with respect to a reference position. The study was performed within the Ultra-Wide Band frequency range as this technology is considered to be an attractive candidate for the next generation of wireless capsule endoscopy.

A Body Area Network (BAN) is a wireless protocol for connectivity of wearable and implantable sensors located inside, on the surface or near the human body. Medical applications requirements impose stringent constraints on the reliability, and quality of service (QoS) performance in these networks. Interference from other co-located BANs or nearby devices that share the same spectrum could greatly impact the communication link reliability in these networks. Link adaptation (LA) schemes can be an efficient alternative to preserve link quality in high interference environments. This paper proposes a low complexity link adaptation strategy to mitigate cross-interference in scenarios where multiple BANs are operating adjacent to each other. Each BAN is assumed to be using the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol as outlined by the IEEE 802.15.6 Standard, where different modulation schemes are available at the physical layer. Each node selects the appropriate modulation scheme based on the experienced channel quality indicated by the received Signal-to-Interference and Noise Ratio (SINR). System performance is evaluated in terms of Packet Delivery Ratio (PDR) per link. Simulation results demonstrate significant improvement in the performance and highlight potential benefits of using link adaptation schemes for BAN applications.

IEEE802.15.6 is a radio interface standard for wireless connectivity of wearable and implantable sensors and actuators located inside or in close proximity to the human body i.e., Body Area Network (BAN). Medical applications impose stringent requirements on BAN Quality of Service (QoS), including reliability and on-time availability of data. However, interference from other co-located BANs or other nearby devices sharing the same spectrum, e.g., due to BAN mobility, may cause unacceptable QoS degradation. This paper suggests that the impact of such QoS degradations can be minimized with a queue-size and channel quality based adaptation of the Energy Detection Threshold (EDT) at the transmitting nodes. Guided by known results for Q-CSMA/CA, we propose an adaptive EDT algorithm for use in the IEEE 802.15.6 BAN standard. Our preliminary simulation results demonstrate the performance gain of our algorithm compared to using a fixed EDT, and thus warrant future efforts in the adaptive EDT optimization as a mechanism to maintain QoS in various interference scenarios.

IEEE 802.15.6 is a radio interface standard for a wireless connectivity of wearable and implantable sensors and actuators located inside or in close proximity to the human body i.e. Body Area Network (BAN). Medical applications requirements impose stringent constraints on the reliability, and quality of service performance in these networks. Assuming CSMA/CA MAC protocol as outlined in the IEEE 802.15.6 standard Intra-BAN interference as well as interference from other co-located BANs or nearby devices sharing the same spectrum could greatly impact the data link reliability in these networks. Specifically, inter-BAN interference caused by hidden and exposed nodes could lead to higher packet delays or lower successful packet reception. In this paper, we study the use of a RTS/CTS handshake mechanism to improve the performance of IEEE 802.15.6-based CSMA/CA when multiple co-located BANs are present. Simulation results demonstrate that the introduction of RTS/CTS mechanism is able to significantly reduce packet collisions, resulting in a tangible improvement in system performance.

A Body Area Network (BAN) is a radio standard for wireless connectivity of wearable and implantable sensor nodes that are located inside or in proximity to the human body. Many applications of BANs (e.g. physiological monitoring) require reliable communication of information between the sensor nodes and their controller. As there are currently no coordinating mechanisms among multiple co-located BANs, interference caused by co-channel transmission in adjacent BANs could impact the reliability and in general quality of the service experienced by a receiver node within an individual BAN. Here, we present a simulation platform that allows for statistical evaluation of interference in multi-BAN scenarios and performance of possible mitigation algorithms. Currently, there are no mechanisms for interfering BANs to explicitly coordinate their transmissions. As our analysis show, this may result in unacceptably high interference; and therefore, high link outage probability by the intended receiver. We propose uncoordinated approaches that could help to ease cross-interference among multiple adjacent BANs. Simulation results in our preliminary studies support the effectiveness of our approach.

A wireless Body Area Network (BAN) consists of multiple radio-enabled wearable and implantable sensor nodes for use inside or in proximity to the human body. BANs are expected to balance requirement for reliable communication of their nodes with a need for battery energy conservation to ensure their longevity. The main challenge in managing this tradeoff is the inability of interfering BANs to explicitly coordinate their transmissions. This may result in unacceptably high battery energy draining rates to overcome cross-interference by other BANs in the vicinity. Here, we propose a utility-based, link-layer adaptation framework for balancing these tradeoffs for each BAN as well as across different BANs. The framework accounts for the utility of the BANs data rates and penalties associated with high transmission powers. Our analysis indicates that link-layer adaptation is beneficial for mitigating the interference from multiple adjacent BANs. Simulation results support our mathematical framework, indicating a much better spectral efficiency obtainable by using link layer adaptation techniques.

In this paper, the problem of resource allocation in IS-856 uplink in the presence of time-delay is studied. A set of nonlinear adaptive controllers are designed to stabilize the wireless network and use the system resources efficiently. The controllers obtained are then modified properly to retain network stability and performance in the presence of time-delay. Simulation results are presented to show the effectiveness of the proposed approach.

In this paper, data-rate assignment in IS-856 uplink (reverse link) is studied. The problem is first formulated in an interference model framework, and then a dynamic control strategy is developed for efficient rate assignment. In the first step, the controller is designed for the special case when the number of users in the network is fixed. Then, the minimum time required for a dynamic network (where the number of users is subject to change) to achieve a desired performance is obtained. The simulation results are presented to elucidate the effectiveness of the proposed approach.

Power control is a key air-interface management mechanism for any multiple-access CDMA-based wireless air-interface. Typically it has been used to ensure a target packet-error-rate (PER) for any user connection. In the presence of hybrid-ARQ (HARQ) on the reverse link (as in 3GPP2's EVDO-Rev A), there is additional flexibility that a power control implementation can utilize to ensure quality-of-service (QoS) for any connection. This paper discusses a general framework in which this can be done. It further provides an easily implement able algorithm within this framework, and substantiates its efficacy with simulations.

In this paper, we investigate scheduling in multiuser OFDMA systems. The objective is to maximize the resource utilization in a network, while a required quality of service (QoS) per user is satisfied. A notion of revenue maximization is used to determine the optimal OFDMA subcarrier allocation to different users based on their required QoS. The optimal solution for the problem is presented and its performance and complexity are studied. An iterative low complexity algorithm is also proposed to achieve near optimal performance.

We consider downlink transmission in a multi-user environment, where each base station transmits multiple data streams to its corresponding mobiles using multiple input multiple output (MIMO) OFDM. Using distributed schemes, we find the optimal transmit and receive weight vectors to maximize the total data rate for each user. We consider two scenarios, where in one the total power per user and in the other total power per subcarrier is fixed. In each case, we propose iterative algorithms to maximize the allocated rate per user. We discuss the convergence of our schemes and compare their performances with those of previous work.

The objective of scheduling algorithms in wireless networks is to provide quality of service (QoS) for mobile users in a shared environment and at the same time utilize the system resources efficiently. We have introduced a notion of income maximization to increase throughput for multimedia wireless systems and to maintain the QoS for each user above an agreed level. We have proposed greedy and dynamic programming approaches to solve the optimization problem. The simulation results reveal that our scheduling algorithms provide high network throughput, support QoS even under heavy network loads, and generate high income for service provider.

Suppose that the description of a stochastic process needs to be sent to a destination through a communication network. Also assume there is a risk that the description may be lost. A technique to reduce the risk of losing such descriptions is by sending two (or more) descriptions and hoping that in this way at least one of the descriptions will get through. This problem is referred to as multiple description coding (MDC) and was first introduced by Gersho, Witsenhausen, Wolf, Wyner, Ziv and Ozarow (1979). So far, the main focus of research on this subject has been on the achievable rate-distortion functions and the related structural design issues for such encoders and decoders. Little effort has focused on the performance of such coding schemes in simple communication networks and relation of the overall distortion with respect to some network parameter such as congestion. In this paper, a double description coding (DDC) system in a simple network represented by a set of parallel queues is studied. Comparison is made with a single description coding system and it is shown that DDC significantly improves the overall average end-to-end distortion at high network loading.

A diffusion approximation is proposed for the data section of the source encoding assisted multiple access (SEAMA) protocol, a voice and data communication wireless network. In SEAMA, a reservation mechanism handles the slot assignment for the voice traffic which operates as an M/M/N/sub max//N/sub max/ loss system. The data traffic is a Markovian queueing system with a random number of channels assigned. It is shown that for high loads of voice traffic and high loads of data traffic, the data queueing system is similar to a dam with an input which can be decomposed into three independent components: a Markov AR process, a non-zero mean white Gaussian noise process and a zero mean Gaussian random variable. The data process is shown to be approximated by a Wiener process with a reflecting barrier at the origin. Using this approximation, the system behavior is described and the desired parameters for the data traffic, i.e. average data packet delay and average data queue length are obtained.

This paper presents SEAMA, a source encoding assisted multiple access (MAC) protocol, to integrate voice and data traffic in a wireless network. SEAMA exploits the time variations of the speech coding rate, through statistical multiplexing, to efficiently use the available bandwidth and to increase the link utilization. In each frame, SEAMA allocates bandwidth among calls as needed. Ongoing calls are always assigned some minimum bandwidth to allow for coding of the background noise during silence periods. An embedded voice encoding scheme is employed to allow the network to control the rate of the calls during congestion by selectively dropping some of the less significant packets, thus causing a graceful degradation of quality. It is shown that by employing an appropriate voice coding scheme and exploiting the characteristics of the source encoder in the MAC protocol, SEAMA almost doubles the capacity of the voice section compared to a circuit-switched network, while practically maintaining the quality of voice traffic.

We propose an admission control policy subject to a quality of service constraint for real-time traffic in a packet-switched network. Taking advantage of the statistical multiplexing of voice packets, the calls employ a multi-state source encoder whose state is determined by the level of source activity. Further, in each state, the source encoder outputs an embedded bit stream in the sense that any truncated version of the bit stream is meaningful. This makes it possible to drop some of the less significant packets and suffer some amount of quality degradation in order to handle the congestion problem. An optimal rate assignment among calls is performed which minimizes the average end-to-end distortion. Therefore, the network can admit more calls so long as the average end-to-end distortion is acceptable; consequently, the call blocking probability is decreased.