Vehicular Ad-hoc Networks (VANET) architecture is under research and development over the last two decades. The major challenge in developing a VANET architecture is how to satisfy the diverse safety application requirements in terms of latency, scalability, and dynamic network topology. Different VANET clustering schemes have been proposed to meet various road safety applications that operate in different road traffic scenarios. However, these solutions often fail to cope with the dynamic VANET topology, where communication networks need to adapt with topology variations. The key challenge is how to form a stable cluster for different road types such as highway with many entries and exit points, city roads with roundabouts, variable speed zones, shared roads, etc. In this paper, we focus on developing a 5G-based low delay communication network to enhance road safety applications. To deal with different road structures, we propose to further enhance our previously published multihop communication protocol, also known as the Clustered Multi-hop Multicast Protocol (CMMP) and developed a new Prediction-Based Update, Monitoring and Joining (PUMJ) algorithm referred to as the PB-CMMP protocol to improve the reliability of the DENM transmissions. We also develop an OMNET++/Simu5GNeins/SUMO-based simulation model to analyze the performance of the proposed algorithms and compare the obtained results with existing algorithms. Simulation results show that the proposed PUMJ technique, combined with the CMMP protocol, significantly enhances the VANET's performance compared to existing solutions.

IEEE802.11 standard is continuously evolving to satisfy the increasing throughput and QoS (Quality of Service) requirements of diverse user applications. One of the advanced key features of the IEEE802.11 standard is the introduction of the DL-MU-MIMO (Downlink Multi-user Multiple Input and Multiple Output) techniques which enables a multi-antenna access point to serve multiple download users concurrently. The MAC layer of the 802.11ac protocol utilises the TXOP sharing technique to support the DL-MU-MIMO operating mode. In this paper, we propose a new TXOP sharing algorithm for the 802.11ac MAC protocol to offer high throughput and QoS for multimedia traffic. The proposed algorithm is referred to as FRA-TXOPE (Flow Rate Adaptive Transmission Opportunity Extension), enhancing our previously published FRA-TXOP algorithm. The FRA-TXOP E algorithm adaptively shares the TXOP resources with primary and secondary traffic sources by continuously monitoring different traffic source flow rates and QoS requirements. Simulation results show that the proposed algorithms significantly enhance the QoS performance of all traffic sources by improving the network throughput and channel utilisation in IEEE802.11ac WLANs.

The prevalence of video traffic services over IEEE 802.11 networks increased the incentive for service providers to improve the video quality of experience (QoE). Delivering high quality video on a random access network is a challenging task due to the use of non-deterministic resource allocation techniques. High definition (HD) video services require enhanced viewing quality with similar QoE for all video users in a network. In this paper, we propose two video packet scheduling algorithms for the 802.11 MAC protocol which can offer high QoS for all video streams as well as maintaining fairness among these video streams. We propose two algorithms to achieve above objectives. The first algorithm named FRA-TXOP allocates appropriate network resources to video terminals by identifying congested terminals. The second algorithm is the EAS that works in combination with the FRA-TXOP to offer inter-user fairness in a networks. A NS-3 simulation model was developed to evaluate the performance of proposed algorithms, and compare proposed algorithms performance with the Bi-level algorithm and the standard IEEE 802.11ac MAC protocol. Simulation results demonstrate that the proposed algorithms can improve the perceived video quality and inter-user fairness for all video users in a network.

Cognitive radio (CR) technology allows efficient management of the limited usable radio spectrum for communications. Traditionally, channel sensing has been used by the CR devices to acquire information about the primary users (PU) and to borrow channels for secondary users (SU). However, inherent limitations could make channel sensing often unreliable and energy inefficient when deployed in large numbers. Geolocation database (GDB) has been proposed as an alternative to the channel sensing technique for cognitive radio networks (CRN). A GDB can act as a repository of channel information in a CRN. Such an approach could improve the utilization of primary and secondary channels, and QoS of the networks. This paper compares the performance of channel sensing-based and GDB-based secondary channel allocation techniques in a CRN. This work has developed mathematical models for the GDB-based CRN to estimate SU and PU throughputs, and energy efficiency, which are used as the performance metrices. Numerical calculations show that the GDB-based resource allocation technique can deliver higher SU and PU throughput levels while offering improved energy efficiency compared to channel sensing-based techniques in a CRN.

Vehicular communication networks need to support the exchange of different types of messages using Vehicleto-Anything (V2X) communication modes. Current generation vehicular network is mostly developed using the DSRC and IEEE802.11p standards. For the next generation vehicular networks, the 3GPP based LTE standard is considered as one of the key wireless networking technologies for the V2X communication systems. In this paper, two LTE-based vehicular networking algorithms are presented to support safety message transmissions. An advanced LTE Device-to-Device (D2D) cluster communication technique referred as LTE-DICV2V and a multicast power transmission control technique referred as CMTPC are proposed. Cooperative Awareness Message (CAM) packets which demand higher reliability such as low delay and high packet delivery ratio. These proposed algorithms can offer such a desired high reliability in an LTE vehicular network. An OMNET++/SimuLTE/Veins/SUMO based simulation model is developed to analyze the performance of the proposed algorithms. Simulation results show that the LTE-DICV2V algorithms offer low intra- and inter-cluster CAM message transmission delays compared to a conventional cellular network-based cluster communication algorithm. The CMTPC algorithm offers a high packet delivery ratio that meets the requirements of CAM message transmissions.

With the increasing demand of video services in different application domains including the smart city; it is necessary to offer appropriate QoS support for HD (High Definition) video services on WLAN networks. The IEEE802.11ac is one of the recent WLAN standards which was developed to support high data rate services. The MAC layer of the 802.11ac standard support several advanced features including the TXOP (Transmission Opportunity) to minimise collision levels to improve the QoS of high priority services. In this paper we propose a new adaptive TXOP packet transmission technique which adapts the TXOP period based on the flow rate and congestion levels experienced by video terminals. The proposed flow rate adaptive TXOP algorithm referred as the FRA-TXOP that allocates network transmission resources to each video terminal to improve its QoS and to reduce the overall network congestion level. The FRA-TXOP algorithm also reduces the contention level thus improving the spectrum utilisation of the IEEE 802.11ac WLAN. Simulation results show that the proposed FRA-TXOP algorithm significantly improve the QoS of video traffic as well as increasing the network throughput compared to the fixed TXOP packet transmission technique supported by the IEEE802.11ac MAC protocol.

We investigate a real time (RT) communication and control technique for a user centric stand-alone distributed photovoltaic (PV) system. The current user centric RT techniques for grid-connected systems may not be directly employed in stand- alone systems due to contradiction in their objectives. In this paper, we propose a user centric RT control algorithm for stand-alone PV systems and investigate its communication requirements. Our aim is to minimize an average aggregate system cost considering a joint optimization problem of load scheduling, energy procurement from a peak generator (PG) and battery energy storage (BES) management. By subsequent relaxation and reformulation of the problem, we employ the Lyapunov optimization technique (LOT). Simulation results show the effectiveness of the proposed RT solution in terms of the selected performance metrics.

Radio resource allocation techniques play a key role in enhancing the quality-of-service (QoS) performance of cognitive radio networks (CRN). An important figure-of-merit for system performance, statistical delay-QoS can be expressed in terms of the effective capacity (EC). This paper investigates the problem of optimal power allocation to maximize the EC of a CRN consisting of multiple secondary user (SU)'s transmitters. It is subjected to the maximum transmit power constraints and the primary user (PU)'s protection policies. Current work on optimal power allocation for EC maximization in a CRN is limited to the case of a pair of SU's transmitter and receiver coexisting with a pair of PU's transmitter and receiver. The resulting problem is typically of a simple structure, for which traditional convex optimization techniques can be straightforwardly applied. In contrast, by having multiple SU transmitters, this paper deals with a much more difficult nonconvex problem structure. Two successive convex approximation-based algorithms are proposed to solve the formulated nonconvex problem in an iterative manner, where each iteration corresponds to solving a simple convex problem only. Simulation results show that both proposed techniques quickly converge to the same locally optimal value. Numerical examples are also used to discuss the effects of key network parameters on the EC of the considered CRN.

This paper addresses two of the most critical challenges in today's wireless sensor network (WSN)-based Internet of Things (IoT) applications: the self-sustainable operability and the matching between harvested energy and data transmission demands from sensor nodes. To this end, we propose a self-sustainable radio frequency (RF) energy harvesting algorithm that optimizes the energy harvesting period in order for the sensor nodes to harvest energy from the downlink physical channels of the LTE eNodeB (i.e., PBCH and PDCCH). The proposed algorithm adapts the energy harvesting period in accordance to the stochastic characteristics of the traffic load from the IoT applications and the incoming RF energy at sensor nodes. Simulation results confirm that the developed algorithm allows the sensor node to harvest sufficient energy to operate in a self-sustainable manner. It is also shown that the proposal significantly improves the energy-efficiency while satisfying the quality-of-service requirements of the WSN-based IoT applications.

Energy harvesting (EH) is considered to be the key enabling technology for the mass deployment of wireless sensor networks (WSNs) for Internet of Things (IoT) applications. Efficient EH techniques could remove the needs of frequent energy source replacement, thus offering a near perpetual network operating environment. Advances in EH techniques have shifted the design of routing protocols for EH-WSN from `energy-aware' to `energy-harvesting-aware'. This paper aims to design energy-harvesting-aware routing protocols for heterogeneous WSN-based IoT applications in the presence of ambient energy sources. We propose a new routing algorithm EHARA, which is further enhanced by integrating a new parameter called `extra backoff'. The proposed algorithm improves the lifetime of sensor nodes as well as the quality-of-service (QoS) under variable traffic load and energy availability conditions. Simulation results show that our algorithm outperforms the existing Randomized Minimum Path Recovery Time (R-MPRT) algorithm in terms of network lifetime by about 50%. It also extends the network lifetime by 40% compared to that offered by the existing Energy Harvesting Aware Ad-hoc On-Demand Distance Vector Routing Protocol (AODV-EHA) algorithm.

With the increasing demand of IoT (Internet of Things) applications, the demand for energy efficiency (EE) and quality-of-service (QoS) in IoT networks is on the rise. In IoT networks, the EE and QoS requirements are contradictory where maintaining higher EE is difficult when high QoS requirements are required. This paper aims to propose an adaptive MAC protocol which maintains EE and QoS for an IEEE 802.15.4 standard-based IoT network. To this end, we introduce a new algorithm, referred to as RF-AASP, that dynamically adjust the sleeping period in order for sensor nodes to harvest RF energy from a surrounding LTE eNodeB. The proposed algorithm adapts the active sleeping period in response to varying IoT traffic load conditions, residual energy of sensor nodes and available RF energy from the LTE eNodeB. The RF-ASSP algorithm minimizes the network contention level and maximizes the harvested energy which in turn improves the EE as well as the network throughput. Simulation results confirm that the proposed algorithm offers higher EE and QoS support in an IEEE 802.15.4 IoT network for variable traffic load conditions.

Cognitive networks (CN) introduce an adaptable architecture that enables efficient sharing of transmission resources among heterogeneous networks. While quality-of-service (QoS) provisioning is always an important issue, the channel switching frequency at the secondary networks has a clear impact on the QoS performance of a CN. A secondary network returns a borrowed channel when demanded by the primary network. In this paper, we propose i) a novel secondary channel allocation algorithm and ii) a flexible CN architecture for IEEE802.11 based WLANs. The proposed CN architecture utilizes a Geo-location Database (GDB) as the repository of shared channel information that can be used by secondary networks. The proposed channel allocation algorithm allocates shared spectrum to secondary networks by matching the available channel characteristics with the secondary network's requests to maximize the QoS of traffic in secondary networks. An OMNET++ based simulation model is used to analyse the performance of the proposed network. Simulation results show that the proposed channel allocation algorithm offers significant QoS advantages and stability of secondary networks compared to conventional channel sensing and GDB based secondary channel allocation approaches.

A variety of scheduling strategies can be employed in wireless systems to satisfy different system objectives and to cater for different traffic types. Static persistent resource allocations can be employed to transfer small M2M data packets efficiently compared to dynamic packet-by-packet scheduling, even when the M2M traffic model is non-deterministic. Recently, adaptive persistent allocations have been proposed in which the volume of allocated resources can change in sympathy with the instantaneous queue size at the M2M device and without expensive signaling on control channels. This increases the efficiency of resource usage at the expense of a (typically small) increased packet delay. In this paper, we derive a statistical model for the device queue size and packet delay in static and adaptive persistent allocations which can be used for any arrival process (i.e., Poisson or otherwise). The primary motivation is to assist with dimensioning of persistent allocations given a set of QoS requirements (such as a prescribed delay budget). We validate the statistical model via comparison with queue size and delay statistics obtained from a discrete event simulation of a persistent allocation system. The validation is performed for both exponential and gamma distributed packet inter-arrivals to demonstrate the model generality.

One of the major limitations of the LTE system in context of Machine-to-Machine (M2M) communications is the excessive control signalling required for dynamic scheduling of radio resources. Although the queue awareness and link adaptation features of the dynamic scheduler can be very beneficial for M2M traffic as well, these two properties come at a cost of significant control overhead. In this paper, we propose an adaptive semi-persistent LTE uplink scheduler which reduces the control overhead by a significant level and utilizes the uplink capacity efficiently to satisfy the Quality of Service (QoS) requirements of M2M traffic. The concept of Semi-Persistent Scheduling (SPS) has already been implemented for Voice over IP (VoIP) service in the LTE standard. However, we have further developed this into an adaptive SPS scheme which can adapt to the sudden bursts of stochastic M2M traffic flow by utilizing the device buffer information as well as respond to the channel fluctuations caused by fading while satisfying the M2M packet delay constraints. The performance of the proposed adaptive SPS scheme has been compared to an LTE dynamic scheduler using the OPNET simulation software for fading channels. The simulation results demonstrate the adaptive SPS scheme to outperform the dynamic scheduler in terms of both control channel utilization and satisfying QoS requirements of M2M traffic.

This paper develops power allocation schemes to manage the signal interference in a multiuser multicell network, where full-duplex transceivers are implemented at all base stations (BSs) and user equipment units (UEs). Beside the acute intracell and intercell interferences, the significant residual self-interference at the full-duplex receivers is the limiting factor for any network performance enhancement. To help control such severe interferences, we propose to associate each bidirectional full-duplex link with a net utility function, which consists of a utility and a flexible price. While the utility corresponds to the link throughput, the proposed logarithmic cost function allows for a moderate penalty. Our aim is to maximize the sum network utility subject to the power constraints at the BSs and UEs. To solve the highly nonconvex problem formulation, we propose two successive convex approximation (SCA) algorithms based on the difference-of-convex-functions programming and the geometric programming. In each algorithm, we specifically tailor the generic SCA framework and transform our formulated nonconvex problem into a sequence of convex power allocation programs. We prove that the developed iterative algorithms converge to locally optimal solutions that satisfy the Karush-Kuhn-Tucker conditions of the original problem. Numerical results confirm that our utility-based solutions markedly improve the network throughput by effectively managing the interferences.

With the increasing deployment of wireless sensor networks (WSNs), the demand for energy efficiency (EE) and Quality of Service (QoS) guarantee for such networks is on the rise. In a distributed WSN, the EE could be directly related to the operational expenditure (OPEX) due to the frequent replacement of batteries. An increasing EE helps prolong the network lifetime. Energy efficiency in a WSN can be improved by optimising PHY and MAC layer algorithms. In this paper, we introduce an adaptive energy efficiency algorithm, known as ABSD that changes the MAC parameters of the IEEE 802.15.4 sensor nodes in response to the queue occupancy level of sensor nodes and the offered traffic load conditions. By adapting the transmission parameters, the ABSD algorithm minimises the network contention which could in turn improve the energy efficiency as well as the throughput. The paper also presents a mathematical model to characterise the energy consumption processes controlled by the IEEE 802.15.4 MAC layer. Our ABSD algorithm is simulated by using an OPNET-based discrete event simulation model. Simulation results show that the proposed algorithm offers high EE and maintains high QoS for different offered load conditions.

Some M2M applications such as event monitoring involve a group of devices in a vicinity that act in a co-ordinated manner. An LTE network can exploit the correlated traffic characteristics of such devices by proactively assigning resources to devices based upon the activity of neighboring devices in the same group. This can reduce latency compared to waiting for each device in the group to request resources reactively per the standard LTE protocol. In this paper, we specify a new low complexity predictive resource allocation algorithm, known as the one way algorithm, for use with delay sensitive event based M2M applications in the LTE uplink. This algorithm requires minimal incremental processing power and memory resources at the eNodeB, yet can reduce the mean uplink latency below the minimum possible value for a non-predictive resource allocation algorithm. We develop mathematical models for the probability of a prediction, the probability of a successful prediction, the probability of an unsuccessful prediction, resource usage/ wastage probabilities, and mean uplink latency. The validity of these models is demonstrated by comparison with the results from a simulation. The models can be used offline by network operators or online in real time by the eNodeB scheduler to optimize performance.

We propose a predictive resource allocation scheme for the LTE uplink based upon Maximum Likelihood Estimation of event propagation characteristics for M2M/Smart Grid applications. The LTE eNodeB estimates the inter-sensor propagation time of a disturbance using the pattern and timing of received Scheduling Requests (SRs) from sensors and then proceeds to predict the time at which the disturbance will reach downstream sensors, facilitating predictive uplink grants for these sensors in order to reduce the mean latency of their uplink data packets by up to 50% (according to a performance analysis) compared to the existing standard reactive LTE uplink resource allocation scheme. A further benefit is that when a predictive resource allocation is successful, the sensor does not need to send an SR, thereby freeing up uplink resources which can be critical with M2M communications. We consider various transition strategies from the estimation to prediction phases which reflect the compromise between estimation speed and accuracy, and also examine the concept of early and late prediction.

We explore the problem of resource allocation in a Third Generation Partnership Project (3GPP) long-term evolution (LTE) based cognitive radio network (CRN). The network model consists of a number of service providers (SPs) with fixed licensed spectrum bands. The network offers the wireless services to two types of users: primary and secondary. The primary users (PUs) get prioritized access to the licensed spectrum bands. The secondary users (SUs) are served on the best-effort (non-prioritized) basis. In this paper we consider the specific design features of LTE radio interface associated with the uplink spectrum access, scheduling process, and limited control channel capacity of the LTE system. We establish the relation between the number of users in the system, and the scheduling delay (which is the largest contributor to the packet end-to-end delay in LTE network). Using these results, we propose a simple algorithm to assign the spectrum for the SUs without violating the quality of service (QoS) requirements of the PU, and implement it in an LTE-based CRN. Consistent performance of the algorithm is verified using OPNET-based simulations.

Emergency warning applications in a vehicular ad hoc network (VANET) requires successful dissemination of warning notification within a geographical area spanning multiple hops. Multimedia transmission provides an accurate overview of the emergency event in the form of an image, an audio or a video. However, the reliable transmission of emergency multimedia messages using multi-hop broadcast techniques suffer from broadcast storm and severe interference from the existing periodic single-hop safety messages. In this paper, we propose an efficient time-slotted multi-hop broadcast protocol for emergency multimedia transmission. To avoid interference with the safety messages already in place, we propose to allocate separate multi-hop time slots for the multimedia messages, and devise a signaling mechanism that ensures a reliable delivery of these multimedia messages. The proposed mechanism can also handle the scenario of lost acknowledgment (ACK) and thus effectively reduce the unnecessary retransmissions of the multimedia messages. Simulation results confirm that the developed protocol substantially outperforms existing schemes in terms of both the number of required multi-hop transmissions and the dissemination delay, while maintaining a high reception rate and a low end-to-end delay for the single-hop safety messages.

To notify all vehicles within a geographical area of an urgent situation, multi-hop communication is employed in a vehicular ad hoc network (VANET) to propagate the emergency warning messages. While being interfered by the existing periodic single-hop safety messages, the transmission of warning messages can also be strongly affected by the broadcast storm problem and the collisions due to hidden nodes. This paper develops an efficient tone-based time-slotted multi-hop protocol that significantly improves the performance of the emergency warning message transmissions. Specifically, we assign the responsibility of message forwarding to only a subset of vehicles on the road, known as ``segment leader," as part of our broadcast storm suppression strategy. To avoid the potential interference caused by the safety messages, we employ separate multi-hop time slots for the warning messages, which are reserved by a newly-proposed out-of-band long range CLEAR tone. Such a tone-based reservation mechanism allows the continuous transmission of the safety messages in the absence of a CLEAR tone, giving rise to a much higher network utilization. Our extensive simulation results confirm the timely and reliable delivery of the emergency warning messages while the required number of multi-hop transmissions is significantly reduced. At the same time, a high packet reception rate and a low end-to-end delay are maintained for the existing single-hop safety messages.

In a vehicular ad hoc network (VANET), basic safety messages (BSM) are exchanged among vehicles to provide cooperative awareness and support safety applications. While the periodic generation and transmission of such messages already place a heavy burden on the network load, the hidden nodes further complicate the network situation with packet collisions being undetectable. In this paper, we propose a space-division multiple access (SDMA) technique combined with an adaptive rate control mechanism to improve the efficiency of BSM transmissions. With SDMA to reduce the interference among the vehicles and address the hidden-node problem, only vehicles located sufficiently far apart are allowed to reuse the same time slot to send their BSMs. The developed SDMA approach permits multiple transmissions per road segment and uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) in each segment, giving rise to a much better use of both space and bandwidth. To guarantee that the actual number of BSM transmissions does not exceed the maximum allowable, we devise an adaptive scheme that optimally adjusts the individual packet generation rates in accordance to the vehicle density. Toward this end, we find an optimal bandwidth utilization that maximizes the newly-defined metric, termed as “safety throughput” per vehicle. Such an optimal utilization allows a large number of BSM packets to be generated while maintaining a high reception probability. Our comprehensive simulation results confirm the clear advantages of our proposal over the existing techniques, in terms of safety range, BSM packet inter-arrival time, and safety throughput.

The basic requirement of wireless healthcare monitoring systems is to send physiological signals acquired from implantable or on-body sensor nodes to a remote location. Low-power consumption is required for wireless healthcare monitoring systems since most medical sensor nodes are battery powered. The emergence of new technologies in measuring physiological signals has increased the demand for high data rate transmission systems. Ultra-wide band (UWB) is a suitable wireless technology to achieve high data rates while keeping power consumption and form factors small. Although UWB transmitters are designed based on simple techniques, UWB receivers require complex hardware and consume comparatively higher power. In order to achieve reliable low power two-way communication, a sensor node can be constructed using a UWB transmitter and a narrow band receiver. This paper proposes a new medium access control (MAC) protocol based on a dual-band physical layer technology. Co-simulation models based on MATLAB and OPNET have been developed to analyze the performance of the proposed MAC protocol. We analyzed the performance of the MAC protocol for a realistic scenario where both implantable and wearable sensor nodes are involved in the data transmission. Priority-based packet transmission techniques have been used in the MAC protocol to serve different sensors according to their QoS requirements. Analysis is done with regard to important network parameters, such as packet loss ratio, packet delay, percentage throughput, and power consumption.

Wireless Body Area Network (WBAN) is well known for accessing data from in body and on body devices. Extensive research has been done on Medium Access Control (MAC) protocol for WBAN for different unlicensed ISM bands, such as 868MHz, 915MHz, 2.4MHz and 433 MHz. However, due to vast use of those frequencies for other applications, there is an unavoidable risk for healthcare application. Inductive link method is another conventional way to communicate with an implanted device. But some limitations are also there, such as low data rate and communication range is very low (few centimeters). To emphasize a patient's health safety and to evade the limitation of inductive link method, a new and different frequency band, Medical Implant Communication System (MICS) band (402–405 MHz), has been accepted worldwide for a small range (3 meters) communication between an external device and implanted devices only. But, different international communication authorities have put some rules and restrictions to use the MICS band. Therefore, it is necessary to design a MAC protocol that will comply with the rules and suitable for the traffics of implanted devices communication network. In this paper, we propose a MAC protocol for MICS band considering the proposed rules and probable traffics in the network. A categorization of all the possible traffics is done. The MAC protocol is verified based on our proposed traffic categorization and it is observed that eight patients, each having eight implants, can be monitored simultaneously.

Wireless Network Control Systems (WNCSs) have been developed and deployed in many applications because of the flexibility afforded by the wireless communications medium in accommodating the control loop. In this paper, we examine a wide area WNCS using LTE as the wireless fabric. We introduce a novel concept known as “reflection” which is a subscription model that allows an LTE eNodeB to inform certain nodes in a group about low level radio signalling from certain other nodes in the group before any application data has been sent. The mean Round Trip Time (RTT) for control in an LTE based wide area WNCS which is enhanced for reflection is reduced by at least 6ms compared to a standard LTE based wide area WNCS. This is demonstrated using an OPNET simulation model that compares a reflection based architecture with a reference architecture. The technique has applications in Smart Grid control applications (such as Fault Detection and Isolation) and in other vertical industries in which WNCSs may be relevant.

Safety applications in VANETs relies on various type of information exchanges among vehicles of which Cooperative Awareness Message (CAM) has the largest share in the network load due to their periodic broadcast nature. As the vehicle density grows, the load generated by the CAMs could increase beyond the transmission capacity of a VANET resulting in the loss of neighborhood information and a higher utilization of the control channel. In this paper, we present the concept of a safety zone to adaptively control the transmit power of CAMs to restrict the network load without compromising the safety features of VANET applications. Moreover, we also introduce a new cooperative information sharing technique to increase the vehicle's awareness beyond the transmission range. The simulation results show that the proposed technique could significantly reduce the packet losses and channel utilization for a range of vehicle densities.

Recently, the IEEE 1900.4 standard specified a policy-based radio resource management (RRM) framework in which the decision making process is distributed between network-terminal entities. The standard facilitates the optimization of radio resource usage to improve the overall composite capacity and quality of service (QoS) of heterogeneous wireless access networks within a composite wireless network (CWN). Hence, the study of different RRM techniques to maintain either a load- or QoS-balanced system through dynamic load distribution across a CWN is pivotal. In this paper, we present and evaluate three primary RRM techniques from different aspects, spanning across predictive versus reactive to model-based versus measurement-based approaches. The first technique is a measurement-based predictive approach, known as predictive load balancing (PLB), commonly employed in the network-distributed RRM framework. The second technique is a model-based predictive approach, known as predictive QoS balancing (PQB), typically implemented in the network-centralized RRM framework. The third technique is a measurement-based reactive approach, known as reactive QoS balancing (RQB), anchored in the IEEE 1900.4 network-terminal distributed RRM framework. Comprehensive performance analysis between these three techniques shows that the IEEE 1900.4-based RQB algorithm yields the best improvement in QoS fairness and aggregate end-user throughput while preserving an attractive baseline QoS property.

Next generation wireless networks are expected to integrate harmoniously in an IP-based core network. Such paradigm shift will amalgamate several distinct radio access technologies into a unifying composite network. However, this creates a fundamental problem for handsets which manifests in high power consumption due to network discovery that is typically carried out by performing scanning operations. Since handsets are naturally constrained by its battery lifetime, this paper analyzes the impact of network discovery on the handsets' power consumption from the network architecture perspective. Particular, we focus on network discovery through the scanning (information pulling) and broadcasting (information pushing) approaches. In this context, we extend a unified analytical model to evaluate the performance comparison of energy efficiency between the legacy and terminal oriented network-assisted (TONA) architectures. Comprehensive numerical and simulation results show that the TONA handover architecture provides an energy saving of 8 35% to promote green handsets under various network load and scanning intervals.

Priority based packet transmission techniques are commonly used in communication networks to support multimedia services. In wireless networks mainly type of service or queue measurement based packet transmission priority techniques are used. This paper introduces a novel two stage traffic prediction and type of service based priority technique for an infrastructure based Wireless Local Area Network. The developed algorithm alters the priority of transmission queues and services in a radio access network based on the predicted traffic volume and the conventional type of service priority technique for multimedia packet transmissions. Simulation results show that our proposed algorithm improves the QoS of multimedia traffic significantly. An OPNET based simulation model has been developed to obtain the performance results for a multiple access points based wireless infrastructure network.

Future wireless networks will enjoy ubiquitous connectivity by taking advantage of the IP core convergence which is seen as the lingua franca of heterogeneous access networks ecosystem. It is expected that the prevalence of WLAN and the advent of IEEE 802.11n standard will continue to offer compelling opportunities and therefore be considered as one of the de-facto wireless access network. However, it is known that wireless network conditions in general are diverse owing to both traffic and wireless channel variations. This raises the importance of exploiting diversity across a multiple access points (multi-AP) WLAN, which requires an advanced network control mechanism to effectuate uniform load distribution, so that QoS of users and composite capacity can be improved. Although various load distribution algorithms for WLAN have been investigated in literature, there is a lack of performance comparison between different algorithms. In this paper, we present a comparison of three dynamic load distribution algorithms, viz. predictive load balancing (PLB), predictive QoS balancing (PQB) and reactive QoS balancing (RQB) for infrastructure-based WLAN with DCF access mechanism based on OPNET simulations.

The ubiquitous IEEE 802.11 standard exhibits a significant amount of MAC protocol overhead inherent to contention-based random access protocols. To alleviate this overhead and improve protocol performance, a dynamic protocol timing adaptation scheme is proposed whereby the fundamental 802.11 slot time and inter-frame spacing are reduced based on techniques that exploit the actual maximum propagation distance within a wireless LAN, in addition to advances in PHY layer technologies that facilitate faster MAC processing and carrier sensing. We show through numerical analysis that the proposed scheme has the theoretical potential to increase system throughput and improve the performance of both current and emerging high-throughput 802.11 wireless LAN standards.

This paper examines the effect of cell loadings on the performance of a group based multicast algorithm implemented on the HSDPA air interface. The group based multicast scheme could offer higher QoS and capacity in a HSDPA network. However, the performance of the multicast algorithm could be affected by neighboring cell loadings. In order to compensate the variable SINR conditions caused by the variation in neighboring cell loading it is necessary to optimize the group switching algorithm to maintain high QoS in a cell and to minimize the uplink feedback traffic. The paper presents simulation results showing the effects of cell loading on the performance of the group based multicasting scheme. An OPNET based multi-cell simulation model has been used to obtain the results.

The extensive deployment of 802.11 WLAN has positioned itself as the de-facto wireless access network for the 'last mile' connections. The potential for WLAN to deliver multimedia contents such as VoIP, video conferencing, streaming and data services will become a reality with the advent of 802.11n standard, promising data rate of up to 600 Mbps. Although these QoS demanding multimedia applications can be supported by the 802.11e standard, it offers limited QoS guarantee. Further, its possible adoption by the industry remains unclear due to high cost of hardware replacements. In this paper, we give a solution to provision QoS support for multimedia traffic in commercially deployed 802.11 a/b/g WLAN operating with fundamental distributed coordination function (DCF) access mechanism in a unifying QoS-inspired load optimization framework. We further postulate the notion of QoS balance as load criterion in heterogeneous WLANs where data rates and channel conditions are radically different. In practice, link adaptation employed to combat diverse channel conditions could lead to multirate operation and consequently the long-term throughput of stations are penalized by the lowest data rate peer. We argue that such rate anomaly can be mitigated by maintaining a QoS-balanced system. Simulations show that our solution provides service QoS guarantee for both real-time and non real-time traffic as well as achieves both throughput and QoS fairness under dynamic network conditions in a self-adjusting manner.

Multimedia broadcast and multicast service (MBMS) specification was introduced in the release 6 of the 3GPP standard to deliver multimedia content to a large group of users in the UMTS network. With the MBMS system generally the same content is transmitted to multiple users in a unidirectional fashion, typically by multiple base stations to improve the coverage over a large geographical area. From the radio network point of view the standard supports the point-to-point (p-t-p) and the point-to-multipoint (p-t-m) transmission modes. In this paper we propose a group based p-t-m MBMS algorithm utilising the scalable video coding techniques to improve overall QoS of multimedia services. The group based MBMS algorithm has been proposed to support moderate to high date rate multicasting services over the HSDPA link. The proposed algorithm has been simulated using an OPNET simulation model. Initial results show that the proposed algorithm could offer higher data and improved QoS for MBMS users.

Always best connected (ABC) services allows multi- mode mobile terminals to stay connected to the best available networks, at anytime according to user preferences. One of the key aspects in realizing such ABC service is mainly attributed to an effective and dynamic access network selection process. However, most of the previous works consider the access network selection process as a static optimization problem which fails to address the dynamic QoS conditions intrinsic in wireless networks. One of the main challenges remains as no efficient way in obtaining dynamic QoS parameters such as packet delay, packet loss and jitter. In this paper, we proposed a novel dynamic access network selection algorithm capable of adapting to prevailing network conditions. Our algorithm is a dual stage estimation process where network selection performed using sequential Bayesian estimation relies on dynamic QoS parameters estimated through bootstrap approximation. Simulations demonstrate the effectiveness of our proposed algorithm which outperforms static optimization approach in a highly efficient manner.

This paper analyzes the interdependence between the Iublink characteristics and the HSDPA air interface performance using analytical and simulation techniques. The impact of the Node-B scheduling mechanisms are also investigated in this paper. A Markov chain based analytical model and a simulation model is used to obtain HSDPA air interface performance results.

This paper presents an adaptive bandwidth management technique to improve the transmission efficiency of a high speed downlink packet access (HSDPA) network by adaptively allocating radio access network resources. The radio access network resources are allocated based on the air interface demand. The proposed bandwidth management technique is evaluated by an analytical and a simulation model. Both analytical and simulation results show that the proposed algorithm improves the Iublink utilization, and keep high the HSDPA air interface resource utilization by jointly optimizing the resource allocation processes.

This paper analyzes the impact of the Iublink characteristics on the HSDPA air interface performance. In this work three different transport protocols are used to examine the effect of the Iublink on the HSDPA air interface. The paper uses both analytical and simulation techniques to analyze the relationship between the HSDPA air interface performance and the Iublink characteristics. The paper uses a Markov chain based analytical model and an OPNET based simulation model to obtain HSDPA air interface performance results.

The imminent IEEE 802.11n standard is poised to provide unprecedented throughput experienced at the MAC layer, whilst providing QoS support for the escalating demand in multimedia services and applications. Along with the 802.1 le QoS amendment, 802.11n defines advanced ARQ policies designed to increase the channel utilization efficiency by reducing MAC protocol overhead. Although these techniques provide vast improvements over the legacy 802.11 protocol, opportunities exist within this framework to optimize performance based on the type of traffic being serviced. In this paper we investigate the performance optimization of the 802.11 Block Ack ARQ policy, and propose an adaptive block size algorithm for throughput improvement. Using a comprehensive OPNET simulation model we show that the proposed adaptive algorithm achieves higher link layer throughput and improved QoS.

This paper presents a MICS (medical implant communication service) based body sensor network design and implementation for patient physiological data collection for health monitoring purposes. The MICS band offers the advantage of miniaturized electronic devices that can either be used as an implanted node or as an external node. In this work, a prototype sensor network is implemented by incorporating temperature and pulse rate sensors on nodes. Each developed sensor node has the capability of physiological data acquisition and local processing. The sensor node can also transmit data over the air to a remote central control unit (CCU) for further processing and storage. The developed system offers medical staff to obtain patient's physiological data on demand basis via the Internet. Moreover, the system has been optimized for power consumption by using a polling architecture. Some preliminary performance data is presented in the paper.

The IEEE 802.11 suite of WLAN standards are evolving to support an increase in emerging broadband multimedia applications, with their popularity attributed to simple, scalable and cost effective wireless broadband communication infrastructure. However, the most widely deployed generation of 802.11x based MAC protocols provide limited support for multimedia traffic, as no guarantee is provided on the quality of service (QoS) that a particular type of traffic will receive. Furthermore, the legacy 802.11 MAC exhibits high protocol overhead due to control frames, channel access, and the probability of contention. This article presents an overview of MAC layer enhancements designed to provide QoS support and higher throughputs in next generation WLANs, including IEEE 802.11e and 802.11n standards. Comprehensive simulation results are provided using an OPNET simulation model

This paper presents a scheduling scheme for a FLO based advanced TDMA system to enable service multiplexing from user terminals. The FLO specifications allows different traffic types to use appropriate transport formats to meet QoS requirements of each class of traffic. Service multiplexing can be achieved by selecting appropriate transport formats for each traffic class and then combining them in a single packet and transmitting over a single slot of a TDMA air interface. The paper introduces a scheduling scheme known as LQP which can offer higher throughput for using a FLO based air interface. The paper presents some initial simulation results obtained from an OPNET based simulation model

As the demand for broadband multimedia wireless services increases, the need to provide QoS and higher data rate enhancements to the widely deployed IEEE 802.11 wireless LAN standard has become apparent. We propose a class-based adaptive ARQ scheme with QoS support for multimedia traffic, to facilitate higher throughputs through the reduction of MAC overhead. This scheme operates on top of the EDCA (enhanced distributed channel access) mechanism proposed in the IEEE 802.11e draft standard, which provides QoS support in the MAC layer through the use of service differentiation and traffic class prioritization. An OPNET simulation model is used to show that the proposed ARQ enhancement increases system performance.

This paper presents novel traffic class dependent resource management techniques for packet switched data over the WCDMA uplink in UMTS. A distributed rate scheduling process is integrated with a centralised admission controller to share the radio resource in a single carrier WCDMA system. This combined resource manager prioritises allocations based on traffic classes and transmission delay deadlines. The use of bitrate variability profiles for limited throughput variability is introduced for traffic conditioning. A distributed power control algorithm is also presented. The performance of these processes has been simulated.

Wireless LAN standards have enormous potential to be developed as broadband access networks for future Internet applications supporting multimedia traffic. However, currently deployed IEEE 802.11 standards have little or no QoS support functions built into the MAC layer. The IEEE 802.11e EDCA mechanism is currently being developed to provide QoS functions in the MAC layer based on service differentiation and traffic class prioritization. In this paper, we propose an enhanced ARQ scheme for multimedia traffic, which operates on top of the EDCA mechanism proposed in the IEEE 802.11e draft standard. The performance of the enhanced ARQ algorithm is analyzed using an OPNET simulation model.

As all-IP based mobile communications networks become a reality, it is important to understand how characteristics of these networks such as delay jitter can affect the overall performance of the system. We find that backbone network delay jitter can significantly influence the multiple access performance of an all-IP mobile communications system. To compensate for this, we introduce an adaptive jitter compensation technique that is linked to the system slot allocation and multiple access mechanisms. By linking these mechanisms, we are able to compensate for delay jitter, whilst also introducing novel resource allocation techniques for use with multimedia traffic. We detail the various techniques introduced, and show the performance enhancements possible when using such a scheme.

Not only is the amount of packet traffic carried on mobile communications networks growing, it is also anticipated that such communication networks will eventually use packet-based backbone and core networks. Considering this, characteristics of packet (IP) traffic such as delay jitter will be of growing significance to the performance of these mobile communications systems. Not only will such characteristics affect the quality of service these systems can provide, they will also affect the performance of the multiple access aspect of the mobile network, influencing system capacity, utilization, and delay profiles. We highlight why delay jitter is important to a mobile communications system operating with a packet based backbone and core network, and present a jitter compensation technique that is designed to improve system performance in response to delay jitter, whilst respecting the quality of service requirements of the traffic to be carried. We review the prior work in jitter compensation for fixed networks, and investigate which techniques are appropriate for compensating delay jitter at the multiple access component of a mobile network. We present one such jitter compensation technique, and detail a simulation model and associated results used to study the performance of this technique.

This paper proposes a RLC/MAC (radio link control/multiple access control) protocol architecture suitable for a wireless IP network. The RLC and MAC protocols have been designed to support packet transmission on an air interface. The MAC protocol uses a reservation technique to increase the multiplexing efficiency by minimising collisions. The RLC protocol is based on selective repeat technique; optimises its efficiency by using the efficient architecture of the MAC protocol. Simulation results are presented to evaluate the performance of the combined protocol.

The paper presents strategies for transmitting MPEG-4 video by using rate matching techniques over the WCDMA air interface. We use an OPNET simulation model to analyze the channel utilization and transmission delay performance when transmitting MPEG-4 traffic over dedicated channels in the WCDMA uplink.

This paper presents TDD/TDMA packet transmission strategies developed for use on a cellular packet communications network. We use unique resource allocation strategies between uplink and downlink, paying particular attention to the downlink, which has received little research attention thus far. On the uplink fixed reservation techniques are used for both voice and data traffic, whilst on the downlink an "ad-hoc" reservation technique is used for data traffic. An OPNET based simulation model is used to analyse the performance of the proposed packet transmission strategies.

This paper proposes a combined MAC and ARQ protocol for a packet switched wireless network. A block reservation MAC protocol known as BRTDMA has been developed based on the advanced TDMA architecture which offers reservation to both voice and data traffic. To reliably transmit voice and data packets using the BRTDMA MAC protocol an ARQ technique is proposed for data packet transmission. The ARQ algorithm presented in this paper has been specifically developed for the block reservation protocol. The proposed retransmission protocol minimizes signalling overhead and increases the channel throughput in a co-channel interference limited environment. Simulation results are presented to show the performance of the protocols.

This paper proposes a combination of a block reservation and a multipriority resource allocation technique for a packet switched wireless multiple access protocol. A block reservation protocol has been developed based on ATDMA slot and frame structure. The developed protocol is called BRTDMA which use different slot reservation strategies for multiservice traffic. Capacity and fairness of the protocol are further enhanced by using a multipriority traffic slot allocation technique. The slot allocation technique is used at the base station for traffic slot allocations. Simulation results are presented to show the effectiveness of the block reservation and the multipriority slot allocation techniques.