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This paper studies the secure transmission in a multiuser broadcast channel where only the statistical channel state information of the eavesdropper is available. We propose to apply secret dirty-paper coding (S-DPC) in this scenario to support the secure transmission of one user and the normal (unclassified) transmission of the other users. By adopting the S-DPC and encoding the secret message in the first place, all the information-bearing signals of the normal transmission are treated as noise by potential eavesdroppers and thus provide secrecy for the secure transmission. In this way, the proposed approach exploits the intrinsic secrecy of multiuser broadcasting and can serve as an energy-efficient alternative to the traditional artificial noise (AN) scheme. To evaluate the secrecy performance of this approach and compare it with the AN scheme, we propose two S-DPC-based secure transmission schemes for maximizing the secrecy rate under constraints on the secrecy outage probability (SOP) and the normal transmission rates. The first scheme directly optimizes the covariance matrices of the transmit signals, and a novel approximation of the intractable SOP constraint is derived to facilitate the optimization. The second scheme combines zero-forcing dirty-paper coding and AN, and the optimization involves only power allocation. We establish efficient numerical algorithms to solve the optimization problems for both schemes. Theoretical and simulation results confirm that, in addition to supporting the normal transmission, the achievable secrecy rates of the proposed schemes can be close to that of the traditional AN scheme, which supports only the secure transmission of one user.

Many applications of Wireless Mobile Communication are used in military, defense etc .however this type of network have many constraints mainly including power constrains, less range of communication & insecure transmission channel which makes it more vulnerable to attacks .such as sinkhole and black hole attack which hampers the communication by attacking on data traffic and communication links on which packets are routed. The attack which operates by falsely claiming a fresh route to destination is a kind of denial of service is known as Sink hole attack. On the other hand black hole attack, intentionally dropped the incoming packets through malicious node in between the intermediately nodes. In this research paper we can examine and investigate the impact of sink hole and black hole attack on the performance of MANET network using DSR protocol in terms of throughput ,packet delivery ratio over the network.

In this paper, we extend the interference channel with degraded message sets model by introducing multiple secondaries. The new model allows for multiple concurrent transmissions in a wireless network by employing dirty paper and superposition coding. We apply the proposed scheme to the communication between nodes in a wireless mesh network (WMN). The cases of different WMN topologies are analyzed, and numerical results show that considerable capacity gains are achieved when using the proposed model with multiple secondaries.

User interfaces to control networked household appliances are often inadequate. Either they are too simplistic or they are too complex and complicated relying on a PC-based interface. Therefore, a user interface that supports complex functionalities and is easy to use is required. In this article digital pen and paper are presented as a suitable interface. Digital pens are only marginally larger than their traditional counterparts, and digital paper is ordinary paper with an almost invisible unique pattern printed on it. Pen and paper are well known to users and thus an important barrier to the acceptance of networked appliances is removed. The approach is integrated with an open services gateway initiative (OSGi) gateway, thus allowing for flexibility with respect to the protocol used to communicate with the appliance. It is also shown how the approach can be applied to other appliances in and beyond the home

Wireless Sensor Network(WSN) is an accumulation of sensors with constrained resources that work together to accomplish a common objective. WSNs are often installed in harsh environments where because of the unattended nature and lack of tamper proof hardware, an attacker can compromise nodes from the network, and can replicate these captured nodes to many clones using original node’s parameters like unique ID and hence, easily gaining control over the whole sensor network. The proposed clone detection protocol is an efficient approach which easily detects clones in static Wireless Sensor Networks. It is a witness-based approach where some nodes from the network are randomly selected to increase randomness of the network resulting in increased detection probability of the clones. The proposed approach successfully detects the clones which have forged both unique ID as well as location overcoming the shortcomings of existing approach.

An alternative computing paradigm is explored in this letter with application to wirelessly powered Internet of Things (IoT) devices. Contrary to existing methods that rely on DC computing, the wirelessly harvested AC power is directly used for computation by leveraging charge-recycling theory. The proposed approach has the potential to significantly reduce the energy cost, one of the primary barriers that slows down the global scalability of IoT devices. This opportunity and related challenges are investigated in this letter to provide guidelines for future research in the field.

Cloud computing is an information technology paradigm model which offers clients access to shared pool of resources. Replication and division of data takes into consideration the performance and security issues. A given file is divided into fragments and then replicated. They are placed over the nodes (servers) and every node stores a single fragment of data in order to improve security. The nodes that store the replicas and fragments are not adjacent to each other by applying T-coloring method hence preventing the attacker from gaining access to useful information. The user can download the file from anywhere but has to specify the exact location as well as the time and date in order to get maximum security as compared to other systems. The likelihood of finding andcompromising the nodes that store the fragments of a file is very low.

Small area femtocell increases the energy efficiency of the cellular network as the distance between base station and user is very less. Mobile femtocell causes the spectrum reuse to be used at very large extent making spectral efficiency suffer. This paper discusses recently researched techniques that have been used to increase the spectral efficiency in mobile femtocell network. But these techniques also come with their own limitations. Considering this, data aggregation and compression technique can be consider as one of the best contender to increase the spectral efficiency in cellular network which is also been explained in this paper.

Communication networks are constructed as a multilevel stack of infrastructure, protocols, and mechanisms: links and nodes, topology, routing paths, interconnected realms (ASs), end-to-end transport, and application interaction. The resilience of each one of these levels provides a foundation for the next level to achieve an overall goal of a resilient, survivable, disruption-tolerant, and dependable Future Internet. This paper concentrates on three critical resilience disciplines and the corresponding mechanisms to achieve multilevel resilience: redundancy for fault tolerance, diversity for survivability, and connectivity for disruption tolerance. Cross-layering and the mechanisms at each level are described, including richly connected topologies, multipath diverse routing, and disruption-tolerant end-to-end transport.

Software defined network (SDN) made with basic concepts that are different from traditional networks in controlling the network, the separation between the control layer and forwarding layer on different devices allows the administrator to adjust the control plan for all devices centralized in one action, while in traditional network, the control and forwarding layers are located in the infrastructure making network administrator must manage devices one by one. Research using single board computers on network technology provides an opportunity to implement SDN architecture. Raspberry Pi has sufficient ability. QoS results meet the ITU-T G.1010 reference which indicates that Raspberry Pi can be used on designed networks.

Ever increasing user demands and development of modern communication technologies have led to the evolution of communication networks from 1st Generation (1G) network to 4G heterogeneous networks. Further, 4G with heterogeneous network environment will provide features such as, “Always Best Connected”, “Anytime Anywhere” and seamless communication. Due to diverse characteristics of heterogeneous networks such as bandwidth, latency, cost, coverage and Quality of Service (QoS) etc., there are several open and unsolved issues namely mobility management, network administration, security etc. Hence, Designing proficient mobility management to seamlessly integrate heterogeneous wireless networks with all-IP is the most challenging issue in 4G networks. Mobile IPv6 (MIPv6) developed by Internet Engineering Task Force (IETF) has mobility management for the packet-switched devices of homogeneous wireless networks. Further, mobility management of homogeneous networks depends on network related parameter i.e., Received Signal Strength (RSS). However the mobility management of heterogeneous networks, not only depends on network related parameters, but also on terminal-velocity, battery power, location information, user-user profile & preferences and service-service capabilities & QoS etc. Designing mobility management with all-IP, while, considering issues such as context of networks, terminal, user and services is the main concern of industry and researchers in the current era.

Introduction Hospital patients require physiological monitoring throughout their stay. Monitoring requirements depend on the hospital unit (e.g. Admission, OR, ICU, ward). Currently, monitoring devices are stationary and are connected by wires to sensors and patient. This is cumbersome for both patient and health care providers, and sensors must be disconnected when the patient is prepared for transfer between units. Further, sensors located in one unit are often incompatible with those in another.We propose a novel concept that simplifies patient monitoring throughout the hospital. Method Approach:We propose a two level wireless network (Fig. 1). A personal area network (PAN) is private to the patient and is responsible for the control of data communication. The PAN host device connects to all required sensors using a wide range of supported protocols (e.g. serial, USB,WiFi and Bluetooth), and is attached to the patient during the entire hospital stay. The PAN host then wirelessly transmits the standardized data to a local area network (LAN) that records patient health information in a database. This information can be retrieved in real time by either stationary monitoring devices or mobile devices of health care providers throughout the hospital network. Prototype: The prototype consists of two pulse oximeters (Nonin, USA) connected via Bluetooth and wired connection, respectively, to a computer with a Linux operating system that acts as the host for the PAN. The LAN consists of a server running a web-based sensor actuator network portal called Sense Tecnic [1]. AWiFi enabled mobile device is used as the monitoring display. Results \& Discussion Blood oxygen saturation and heart rate trend signals are recorded and displayed in real time at a 1 Hz update rate. The web-based data portal allows platform independent, real-time monitoring. The PAN allows for easy connection of sensors to the patient and facilitates monitoring during patient movement and transportation. This approach will facilitate the use of elementary sensors without interruption throughout the hospital. Unit specific sensors can be added to the PAN when required. Future work will include geolocation by indoor triangulation using theWiFi network, and size reduction of the PAN host.

Recently, broadband optical access networks were being deployed worldwide to deliver large bandwidth to end users. Currently, the operators have been mainly deploying time-division multiplexing (TDM) passive optical networks (PON) in their networks. As bandwidth demand continues to increase, the industry further selected several next generation optical access (NGA) options to upgrade from current TDM-PON architectures. Besides increasing bandwidth requirement, current TDM-PONs suffers from limited reach and split-ratio. To further reduce the capital and operational expenditure requirements of current TDM-PON, NGA architectures must consolidate the number of central office sites. Long-reach optical access (LROA) architectures are promising solutions that employ optical amplifiers to increase optical budget to support longer reach and higher split-ratio in the distribution network. As more end users are supported over shared physical medium in LROA, access network security is of greater importance. The first part of this article reviews important LROA architectures and their enabling technologies. Moreover, few works in current literature address security weaknesses in LROA. The second part of this article reviews these security weaknesses as well as monitoring and control techniques employed in current TDM-PONs. In addition, a novel class of quasi-passive and reconfigurable devices is presented that addresses aforementioned security weaknesses and is suitable for LROA.

Device placement is a fundamental factor in determining the coverage, connectivity, cost and lifetime of a wireless sensor network (WSN). In this paper, we explore the problem of relay node placement in heterogeneous WSN. We formulate a generalized node placement optimization problem aimed at minimizing the network cost with constraints on lifetime and connectivity. Depending on the constraints, two representative scenarios of this problem are described. We characterize the first problem, where relay nodes are not energy constrained, as a minimum set covering problem. We further consider a more challenging scenario, where all nodes are energy limited. As an optimal solution to this problem is difficult to obtain, a two-phase approach is proposed, in which locally optimal design decisions are taken. The placement of the first phase relay nodes (FPRN), which are directly connected to sensor nodes (SN), is modeled as a minimum set covering problem. To ensure the relaying of the traffic from the FPRN to the base station, three heuristic schemes are proposed to place the second phase relay nodes (SPRN). Furthermore, a lower bound on the minimum number of SPRN required for connectivity is provided. The efficiency of our proposals is investigated by numerical examples.

Wireless Sensor Networks (WSNs) have emerged as perhaps the most important networking paradigm of recent times, both in terms of their commercial potential and also from a scientific point of view. WSNs are important commercially because of their many applications, spanning from civil to military applications such as structural monitoring of bridges, monitoring of wildlife, tracking of contaminants in the soil and atmosphere. Some of these applications have already proved to be commercially viable and indeed financially very attractive. WSNs are also very important from a scientific point of view, because of their unique features with respect to other types of wireless networks: nodes are typically immobile, and are required to carry a specific type of traffic (which is advantageous), have extreme restrictions on the energy they consume, the processing power they have, and the antennas they can use (which is disadvantageous); in addition, the data created at different sensors may be strongly correlated, which can be beneficial but requires only good algorithms that take advantage of it. Therefore, in the last few years we have experienced an important shift in research activities, moving from general purpose wireless networks to more focused topics specifically on WSNs, taking into account their specific advantages and peculiarities. An important recurring theme in research in this field is the need for energy efficiency, which is the thread of this special issue. The papers which appear in this issue have been carefully selected from the best IEEE PIMRC 2008 conference papers addressing the issue of energy efficiency in WSNs. The respective authors have been asked to provide a significantly extended version of the conference paper, which has subsequently undergone a rigorous review process according to the IJWIN publication standards prior to acceptance. The final set of papers addresses issues at physical, medium access control and networking layers, and to some extent at the application layer. All of these papers take into account the unique peculiarities, advantages, and shortcomings of wireless sensor networks, and propose algorithms and analyses that significantly advance research in the field. We sincerely hope you will enjoy reading them as much as we did. The author of the first paper ‘‘Power Management and Data Rate Maximization in Wireless Energy Harvesting Sensors’’ by Chandra R. Murthy, deals with the problem of power management and throughput maximization for energy neutral operation when using increasingly important but so far rarely analyzed Energy Harvesting Sensors (EHS) to send data over wireless links. The EHS is assumed to be able to harvest energy at a constant rate, and use a fixed part of the energy harvested in a slot for measuring the channel state. The rest of the harvested energy is available for transmission, but it can also be stored in an Wireless Sensor Networks (WSNs) have emerged as perhaps the most important networking paradigm of recent times, both in terms of their commercial potential and also from a scientific point of view. The papers that appear in this issue have been carefully selected from the best IEEE PIMRC 2008 conference papers which addressed the issue of energy efficiency in WSNs. The final set of papers addresses issues at physical, medium access control, networking and to some extend application layers. All of these papers take into account the unique peculiarities, advantages, and shortcomings of wireless sensor networks, and propose algorithms and analyses that significantly advance research in the field. Note that this activity has been partly supported by the NoE-216715 NEWCOM++.

1. Interworking Architectures for IP Multimedia Subsystems Arslan Munir and Vincent W.S. Wong 2. Optimal Admission Control Policies for Heterogeneous Wireless Networks Amin Farbod and Ben Liang 3. Comparison of Multimedia Delivery Scenarios Using Parallel Wireless Links and Path Diversity Ki-Dong Lee, Byung K. Yi, and Victor C.M. Leung 4. Towards an FBM Model Based Network Calculus Framework with Service Differentiation Yu Cheng, Weihua Zhuang and Xinhua Ling. This paper was selected for QShine’2007 Best Paper Award. 5. On Throughput Efficiency of Geographic Opportunistic Routing in Wireless Ad Hoc Networks Kai Zeng, Wenjing Lou, Jie Yang, and Donald R. Brown III. This paper was selected for QShine’2007 Best Paper Award Runner-Up.

In this paper, we give a list of ATM related papers. This is not a complete list. Rather, it represents the bulk of the references in this ever-growing area. For easier use of this reference list, we have classified the papers into the following six categories: general, source characterization, switching, congestion control, routing, and transport.

EACH year, the International Conference on Mobile Systems, Applications, and Services, or MobiSys as it is more commonly known, publishes a selection of cuttingedge research papers in mobile computing. MobiSys takes a broad systems perspective of mobile computing. The papers presented at the 2011 conference in June near Washington, DC ranged from smartphones to energy-efficiency, aspects of security, sensor networks and wireless protocols, and mobile applications and services. This special section brings to you revised versions of highly-ranked papers from MobiSys 2011. The conference was very competitive, with 25 papers being selected from 141 submissions in 2011. From the accepted papers, the PC chairs further selected three of the top papers as judged by the PC reviews and invited the authors of these papers to submit a revised paper to the IEEE Transactions on Mobile Computing. The three papers are a diverse set, and they offer you a glimpse into what is exciting in mobile computing today, as well as the different kinds of research that are presented at MobiSys. The first paper in the set is “Leveraging Smartphone Cameras for Collaborative Road Advisories,” by Emmanouil Koukoumidis, Margaret Martonosi, and LiShiuan Peh. In this paper, we learn about a mobile computing application that will advise the driver of a car to slow down or speed up in order to smoothly sail through green traffic lights, rather than wait at red traffic lights. What is new here? The work leverages the rich sensing capabilities of smartphones that make them such a compelling platform. It is not simply a GPS system that receives signal timing information from traffic signal controllers. Rather, placing the mobile on the windshield allows its camera to capture images that are analyzed in real-time to detect the phase of upcoming traffic lights. Information from all sources, including measurements of other nearby participants, is used to estimate traffic signal timings and make recommendations to the driver. As is typical for MobiSys, the system has been prototyped, and the paper reports on how well it works in small scale tests. In “Chameleon: A Color-Adaptive Web Browser for Mobile OLED Displays,” by Mian Dong and Lin Zhong, we shift focus from new mobile applications to the energy consumption of mobile displays. It is well known that the display is a substantial consumer of energy in mobile devices. In this work, Dong and Zhong explore the energy tradeoffs of OLED (Organic Light Emitting Diode) displays, which require no backlight but may be expensive in terms of energy to display bright images. Their answer is a system that targets web browsing to transform the colors of images in real time, shifting them from pixel values that are energyexpensive to alternative choices that are legible yet less expensive in terms of energy. An evaluation with a prototype and field trials shows both the potential to significantly extend battery life and a system that is valued by users. For the last paper of the set, we return to classic problems of mobile communications. In “Avoiding the Rush Hours: WiFi Energy Management via Traffic Isolation,” Justin Manweiler and Romit Roy Choudhury explore the latest in a series of designs to lower the amount of energy that mobile devices need to spend to communicate via 802.11. Standard techniques for power saving (such as 802.11 Power Save Mode) are assumed as a baseline. The problem is that the ever higher density of 802.11 APs (access points) tends to increase power consumption even with traditional power-saving designs. This is because clients will have to share the channel with a larger number of other clients and APs, and hence remain in an active state for longer periods of time to receive a burst of power save mode packets. Manweiler and Choudhury tackle this problem by decorrelating the cycles of overlapping APs, thus allowing the clients of one AP to sleep while the clients of another AP are awake. When prototyped and tested on real mobile applications, this design can greatly reduce the energy needed to power the network interface. We trust you will enjoy these papers. IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 11, NO. 5, MAY 2012 705

The fast growth of Internet applications brings with it new challenges for researchers to provide new solutions that guarantee better Internet access for mobile hosts and networks. The globally reachable, Home-Agent based, infrastructure Network Mobility (NEMO) and the local, multi-hop, and infrastructure-less Mobile Ad hoc Network (MANET) developed by Internet Engineering Task Force (IETF) support different topologies of the mobile networks. A new architecture was proposed by combining both topologies to obtain Mobile Ad Hoc NEMO (MANEMO). However, the integration of NEMO and MANET introduces many challenges such as network loops, sub-optimal route, redundant tunnel problem, absence of communication without Home Agent reachability, and exit router selection when multiple Exit Routers to the Internet exist. This paper aims to review the different proposed models that could be used to implement the gateway selection mechanism and it highlights the strengths as well as the limitations of these approaches.

Femtocells are the feasible solutions to extend the network coverage of indoor users and to enhance the network capacity in long-term evolution advanced (LTE-A)-based 5G networks. However, the femtocell base station shares the same frequency spectrum of microcell base station in unplanned manner. Hence, interference mitigation is a crucial problem in densely deployed femtocell environment and it is more severe with the deployment of femtocells in LTE-A network. In this paper, a modified dirty paper coding is proposed for interference mitigation along with the optimization of feedback bits using natural inspired meta-heuristic firefly algorithm. The proposed meta-heuristic algorithm reduces the interference by periodically unicasting the channel state information. Since the bandwidth of feedback system is limited, it is optimized in such a way that it does not affect the performance of the system. As compared to the conventional zero-forcing pre-coding, the proposed modified dirty paper coding along with firefly algorithm scheme offers improved sum rate of 70% and 64% with increase in the number of feedback bits and number of users, respectively.

A simple diamond half-duplex relay network composed of a source, two decode-and-forward half-duplex relays, and a destination is considered, where a direct link between the source and the destination does not exist. For this network, we study the case of buffer-aided relays, where the relays are equipped with buffers. Each relay can receive data from the source, store it in the buffer, and forward it to the destination, when the channel conditions are advantageous. Thereby, buffering enables adaptive scheduling of the transmissions and receptions over time, which allows the network to exploit the diversity offered by the fading channels. For the considered half-duplex network, four transmission modes are defined based on whether the relay nodes receive or transmit. In this paper, we derive the locally optimal scheduling of the transmission modes over time and investigate the achievable average rate, when the relays are affected by inter-relay interference. Since the proposed buffer-aided transmission policies introduce unbounded delay, we provide a sub-optimal buffer-aided transmission policy with limited delay. Moreover, for inter-relay interference cancellation, we consider two coding schemes with different complexities. In the first scheme, we employ dirty paper coding, which entails a high complexity, whereas in the second scheme, we adopt a low-complexity technique based on successive interference cancellation at the receiving relay nodes and optimal power allocation at the transmitting nodes. Our numerical results show that the proposed protocols, with and without delay constraints, outperform existing protocols for the considered network from the literature.

The existing LTE mobile system uses the vertical model to handle the session-based security management. However, the goal of this paper is to propose a packet key-based security management scheme on the blockchain control plane to enhance the existing session key-based security scheme and overcome the limitation that the existing vertical model, as well as the Software-Defined Networking (SDN) based horizontal model, confronts within solving end-to-end security management. The proposed blockchain-based security management (BSM) scheme enables each peer to easily obtain the necessary parameters required to manage the packet key-based security system. The important features of the BSM scheme include the renewal process, which enables the different packet data streams to use completely different security parameters for the security management. In addition, because even blind values cannot be exposed to the possible attackers, our BSM scheme guarantees very secure end-to-end data transfer against active attacks such as falsification of data and transactions. Finally, this paper compares the BSM scheme with the existing vertical model to prove the advantageous effects on latency.

In this paper, an efficient beamforming technique at the aggregator node in the patient wireless body area network (WBAN) is proposed to improve the communication performance with the gateway node using C-shaped switched-beam antenna arrays. This proposed technique provides high gain beams towards the gateway node which may be located indoor or outdoor based on the medical quarantine or isolation topology and help medical staff monitor patients with less contact and infection probability. Also, a semi-blind switched-beam algorithm is developed to both reduce the processing time required for beam selection and reduce the power loss due to the off-mainlobe orientation of the selected beam with the signal direction. The proposed technique is analyzed at different wearing scenarios and simulation results show that the received power levels are improved with as less as 0.3 dBm standard deviation which helps in extending the communication range between the WBAN aggregator and gateway nodes in the health monitoring system and also extend the battery lifetime at the patient WBAN.

In this paper, we consider a scenario where a source node wishes to broadcast two confidential messages for two respective receivers via a Gaussian multiple-input multiple-output (MIMO) broadcast channel. An eavesdropper also receives the transmitted signal via another MIMO channel. We first consider the discrete memoryless channel and obtain the capacity region of the degraded channel. The secret dirty paper coding (SDPC) region as an achievable rate region for the general discrete channel is introduced. Relying on the results for the discrete channel, we fully characterize the secrecy capacity region of MIMO broadcast channel. It is shown that the SDPC scheme is optimal. The converse part of the proof relies on the generalized Costa's entropy power inequality and a new channel enhancement strategy in which we only need to enhance the channels of the legitimate receivers, and the channel of the eavesdropper remains unchanged.

In this paper, we investigate joint level 2 and 3 dynamic spectrum management (joint DSM 2/3) for downstream (DS) DSL. We consider a DS scenario in which users are divided into a few separate groups, where vector encoding based signal coordination can be applied in each group and spectrum coordination is possible for all users. This can be seen as a mixed interference/broadcast channel (IF/BC) scenario. In order to obtain the optimal transmitter structure, we develop a generalized duality between the vector broadcast and multiple-access channel (MAC) for scenarios in which partial signal coordination is available among users. This theory together with optimal spectrum balancing (OSB) is exploited to calculate the jointly optimal filters and transmit powers for non-linear vector dirty paper coding structures (in the form of Tomlinson-Harashima precoder (THP)) in the groups. The proposed scheme is compared to several other joint DSM 2/3 algorithms for DS DSL. Simulation results show that the proposed scheme (referred to as the IF/BC-OSB algorithm) achieves considerably higher bit rates than the other schemes. IF/BC-OSB encompasses the earlier developed BC-OSB algorithm as a special case. A simplified version of IF/BC-OSB avoiding exhaustive search with near-optimal performance is also proposed. © 2012 IEEE. ispartof: IEEE Transactions on Communications vol:60 issue:10 pages:3111-3122 status: published

This paper considers the problem of interference channel (IFC) with overlay cognitive radio setting. Both achievable rate and outer bounds for an overlay cognitive radio channel are developed, where the cognitive transmitter has partial knowledge of the legitimate transmitter's message. Specifically, an IFC setting is considered where one transmitter (the “cognitive” one) knows the message of the other (“legitimate” transmitter) partially. An outer bound on the capacity region of this channel is found for the “weak” interference case (where the “interference” caused by the cognitive transmitter to the legitimate receiver is weaker than the “signal” from the cognitive transmitter to the cognitive receiver). This outer bound is developed for the discrete-memoryless case and evaluated for a Gaussian channel setting. An achievable region is subsequently determined for a partially cognitive radio channel, and the outer bound on the capacity region is compared with the achievable rate in a Gaussian channel. Subsequently, an achievable region that incorporates elements of the Han-Kobayashi coding strategy with dirty paper coding is developed for this channel.

The objective of this paper is to study the impact of advanced physical layer techniques on the maximum achievable throughput of wireless multihop mesh networks. We formulate a cross-layer optimization framework for the routing and scheduling problem jointly with the following physical layer techniques: successive interference cancellation, superposition coding, dirty-paper coding and their combinations. In the case when each node is enabled with superposition coding, we need to formulate a power allocation subproblem for the optimal power partition of the superimposed signals. We solve these joint problems exactly to compute the maximum achievable throughput in realistic size networks. This allows us to quantify the performance gains obtained by using these techniques (and their combinations). Specifically, we find that the use of dirty-paper coding (only at the gateway) is not justified in networks with mixed uplink and downlink flows. On the other hand, the combination of superposition coding with successive interference outperforms significantly other techniques across all transmission power range for both uplink and downlink flows. We also provide a number of interesting practical insights on throughput improvement by comparing different combinations of these techniques.

In this study, the authors develop a transmission protocol for cognitive radio networks, whereby fountain codes are exploited in the broadcast channels and secondary users help with the broadcast from the base station (BS) to primary users (PUs). With fountain codes, the BS broadcasts to the secondary transmitter (ST) as well as PUs simultaneously, and stops broadcasting once the ST has received sufficient codeword to decode the original information reliably. Then, the ST will resume the broadcasting to PUs until all of them can decode the original information successfully. While broadcasting, the ST transmits information over its own link, that is, to the secondary receiver, based on dirty paper coding technique. As such, the energy expenditure at the BS is reduced and, moreover, secondary links have more opportunities to access the licensed spectrum band. To evaluate the performance of the developed scheme, they analyse its energy expenditure, broadcast time as well as the throughput over secondary links, and achieve the corresponding closed-form expressions. Compared with the traditional broadcast protocol without the secondary's help, illustrative numerical results substantiate the validity of the author's derivations, which also demonstrate the efficiency of the developed scheme both on the energy savings and on the spectrum utilisation.

In this letter, we consider a hybrid broadcast and unicast cellular network ( hybrid cellular for short) with heterogeneous quality of service (QoS) constraints in the low-power regime. In particular, we consider the unicast user with delay constraint and the broadcast user with outage constraint. The transmission energy efficiency of the dirty paper coding (DPC) and time division multiple access (TDMA) schemes are analyzed and compared from information theoretic point of view. Specifically, the minimum energy per bit and the wideband slope region are derived in closed forms. While both DPC and TDMA schemes require the same minimum energy per bit, DPC outperforms TDMA with regard to the wideband slope region. We also obtain the critical points for both schemes beyond which the wideband slope decreases for both unicast and broadcast users. Finally, we show how the heterogeneous QoS constraints affect the energy efficiency in hybrid cellular.

This paper deals with protocol design for cognitive cooperative systems with many secondary users. In contrast with previous cognitive configurations, the channel model considered assumes a cluster of secondary users which perform both a sensing process for transmitting opportunities and can relay data for the primary user. Appropriate relaying improves the throughput of the primary users and can increase the transmission opportunities for the cognitive users. Based on different multi-access protocols, the schemes investigated enable relaying either between the primary user and a selected secondary user or between two selected secondary users. This collaboration can be a simple distributed multiple-input single-output transmission of the primary data or a simultaneous transmission of primary and secondary data using dirty-paper coding (DPC). The parametrization of DPC as well as its combination with opportunistic relay selection yields an interesting trade-off between the primary and the secondary performance which is investigated by theoretical and simulation results under the perspective of a desired primary throughput. The proposed protocols are studied from a networking point of view and the stable throughput for primary and secondary users is derived based on the principles of queueing theory.

We consider the problem of differentiated rate scheduling for the downlink (i.e., multi-antenna broadcast channel), in the sense that the rates required by different users must satisfy certain constraints on their ratios. When full channel state information (CSI) is available at the transmitter and receivers, the problem can be readily solved using dirty paper coding (DPC) and the application of convex optimization techniques on the dual problem which is the multiple access channel (MAC). Since in many practical application full CSI may not be feasible and computational complexity prohibitive when the number of users is large, we focus on other simple schemes that require very little CSI: time-division opportunistic (TO) beamforming where in different time slots (of different lengths) the transmitter performs opportunistic beamforming to the users requiring the same rate, and weighted opportunistic (WO) beamforming where the random beams are assigned to those users having the largest weighted SINR. For single antenna systems we also look at the capacity-achieving superposition coding (SC) scheme. In all cases, we determine explicit schedules to guarantee the rate constraints and show that, in the limit of large number of users, the throughput loss compared to the unconstrained throughput (sum-rate capacity) tends to zero. We further provide bounds on the rate of convergence of the sum-rates of these schemes to the sum-rate capacity. Finally, we provide simulation results of the performance of different scheduling schemes considered in the paper.

The sum capacity of a Gaussian broadcast MIMO channel can be achieved with dirty paper coding (DPC). However, algorithms that approach the DPC sum capacity do not appear viable in the forseeable future, which motivates lower complexity interference suppression techniques. Block diagonalization (BD) is a linear preceding technique for downlink multiuser MIMO systems. With perfect channel knowledge at the transmitter, BD can eliminate other users' interference at each receiver. In this paper, we study the sum capacity of BD with and without receive antenna selection. We analytically compare BD without receive antenna selection to DPC for a set of given channels. It is shown that (1) if the user channels are orthogonal to each other, then BD achieves the same sum capacity as DPC; (2) if the user channels lie in the same subspace, then the gain of DPC over BD can be upper bounded by the minimum of the number of transmit and receive antennas. These observations also hold for BD with receive antenna selection. Further, we study the ergodic sum capacity of BD with and without receive antenna selection in a Rayleigh fading channel. Simulations show that BD can achieve a significant part of the total throughput of DPC. An upper bound on the ergodic sum capacity gain of DPC over BD is proposed for easy estimation of the gap between the sum capacity of DPC and BD without receive antenna selection.

Random beamforming (RBF) has received much attention recently in downlink beamforming because of its simple structure, low-feedback load and same throughput scaling as that obtained using dirty paper coding at the transmitter. In this study, the authors analyse the performance of RBF for cognitive downlink multi-antenna system in terms of the throughput of the secondary network. The authors consider a secondary broadcast station with multiple antennas utilising the licensed spectrum of each primary receiver to broadcast information to multiple secondary users (SUs) simultaneously, as long as the interference power inflicted at each primary receiver is less than a predefined threshold. Firstly, they derived the secondary network closed-form throughput approximation of a single-beam RBF by exploiting extreme value order statistics. Then, closed-form approximation for secondary network throughput on multiple-beam RBF is presented. Simulation results verify the validity of the authors approximation results analysis even with fewer SUs.

We consider the downlink of a wireless cellular network where the base stations are equipped with multiple antennas and operate in the same frequency band. Since scheduling changes the spatial transmit signal processing with each time slot, information from neighboring base stations is required for data encoding. This can, in theory, be accomplished by a high-capacity backhaul network through which the base stations exchange channel state information (CSI) and other control signals. In reality, however, the temporal granularity of the scheduler does not allow for timely distribution of CSI among base stations. We propose a two-phase scheduler which optimizes the precoding in the first phase and allows the users to feed back their instantaneous interference power in the second phase. For the single-user case, we present a practical scheme that combines two-phase scheduling with precoders that maximize the signal-to-leakage-plus-noise ratio. If the users feed back the interference power together with a supported rate, communication between base stations can be limited to integers. By comparing the performance to multi-user two-phase scheduling with dirty paper coding and to algorithms that share CSI among base stations we show that two-phase scheduling is a technically and practically feasible solution to deal with non-stationary intercell interference.

We consider a multiuser multiple-input multiple- output (MIMO) Gaussian broadcast channel (BC), where the transmitter and receivers have multiple antennas. Since the MIMO BC is in general a nondegraded BC, its capacity region remains an unsolved problem. We establish a duality between what is termed the "dirty paper" achievable region (the Caire-Shamai (see Proc. IEEE Int. Symp. Information Theory, Washington, DC, June 2001, p.322) achievable region) for the MIMO BC and the capacity region of the MIMO multiple-access channel (MAC), which is easy to compute. Using this duality, we greatly reduce the computational complexity required for obtaining the dirty paper achievable region for the MIMO BC. We also show that the dirty paper achievable region achieves the sum-rate capacity of the MIMO BC by establishing that the maximum sum rate of this region equals an upper bound on the sum rate of the MIMO BC.

A novel user relaying scheme based on bit concatenation is proposed for multiple-input multiple-output (MIMO) broadcast channels. In a broadcasting phase, a part of information for a destination user is concatenated to data for a relaying user and transmitted to the relaying user. The destination user receives the part of information via the relaying user in a relaying phase in addition to the data in the broadcasting phase. An achievable rate region for the proposed scheme is derived and an algorithm to characterize the boundary of the rate region is proposed. Our analysis shows that the proposed user relaying in a MIMO BC expands the achievable rate region for the zero-forcing dirty paper coding (ZF-DPC) in the MIMO BC without relaying. It is also shown that the proposed user relaying scheme always outperforms a superposition coding (SC) based user relaying scheme. Optimal and suboptimal user pair scheduling algorithms are investigated for a two-user MIMO BC and the proposed suboptimal user pair scheduling scheme is shown to approach the optimal scheduling when the relaying channel gain is large.

In this paper, we propose a simple linear multiuser precoding scheme for downlink cellular systems with a decode- and forward (DF) based relay, where the available information at a base station (BS) and a relay station (RS) is asymmetric. The proposed scheme not only eliminates the interference from a RS for the mobile station (MS) served by a BS but also provides the MS supported by a RS with a macro diversity gain without any information exchange between a BS and a RS. Consequently, the proposed scheme outperforms a conventional scheme and approaches an ideal scheme using dirty paper coding (DPC) in the information asymmetric configuration.

The concept of cognitive radio is to exploit efficiently the spectrum resources by allowing the coexistence of the primary and secondary users in the same bandwidth without interfering the performance of primary users. Three coexisting models (overlay, underlay and interleave) were presented in recent literature. In this study, the authors propose a hybrid cognitive network model with overlay and underlay models, whereby a primary link leases its fractions of transmission time to the secondary users for their cooperation (i.e. these nodes form as a virtual multiple input multiple output (VMIMO) group) under the outage constraints of the primary and secondary systems. A new cooperative protocol between primary and secondary users is presented. The authors attempt to achieve the maximum transmission capacity of the secondary users under the primary and secondary outage constraints, which depend on the secondary density in the cognitive network. This study gives the upper bound density of the secondary transmitters that are modelled as a homogeneous marked Poisson point process. The maximum density is achieved by computing an optimal set of system parameters such as power control factor of the secondary user and the dirty paper coding (DPC) parameter. Simulation results illustrate that the maximum secondary density obtained using VMIMO is superior to that obtained by direct primary transmission.

We investigate the problem of downlink user scheduling in multiple-input multiple-output (MIMO) systems with M transmit antennas and K homogeneous multiantenna receiving users. We develop a simple algorithm to schedule a subset of M active users for data transmission. We first identify a set of L candidate users that should provide channel information feedback. We then select M active users among the L candidates based on joint consideration of their effective channel gains and directions. We derive an asymptotic upper bound for the sum rate gap between the maximum sum rate of the M selected active users, achieved by dirty paper coding, and the full sum capacity of the original MIMO broadcast channel. Utilizing the upper bound, we show that the sum rate gap can be reduced to meet user requirement by suitably choosing a large but still finite L. Furthermore, we also investigate the performance of the low complexity zero-forcing beamforming (ZFBF) for the M active users.

Capacity improvement from transmitter and receiver cooperation is investigated in a two-transmitter, two-receiver network with phase fading and full channel state information available at all terminals. The transmitters cooperate by first exchanging messages over an orthogonal transmitter cooperation channel, then encoding jointly with dirty paper coding. The receivers cooperate by using Wyner-Ziv compress-and-forward over an analogous orthogonal receiver cooperation channel. To account for the cost of cooperation, the allocation of network power and bandwidth among the data and cooperation channels is studied. It is shown that transmitter cooperation outperforms receiver cooperation and improves capacity over non-cooperative transmission under most operating conditions when the cooperation channel is strong. However, a weak cooperation channel limits the transmitter cooperation rate; in this case receiver cooperation is more advantageous. Transmitter-and-receiver cooperation offers sizable additional capacity gain over transmitter-only cooperation at low SNR, whereas at high SNR transmitter cooperation alone captures most of the cooperative capacity improvement., Comment: Accepted for publication in IEEE Transactions on Information Theory

In the paper a discussion on how to optimize LonWorks/EIA-709 sensor networking technology for wireless applications, in presented. Main solutions offered by Local Operating Networks (LON, LonWorks) platform attractive for wireless communication, that is, the send-on-delta concept and the sleep mode, are displayed. The predictive p-persistent CSMA MAC protocol constituting the heart of the communication capability of LON networks is analysed in detail. Next, the message services are described, and the analytical evaluation of delivery reliability is derived. Performance evaluation based on simulation results for unicast traffic is presented first. In order to highlight the robustness of the predictive CSMA to overload situations, the saturation performance for a general case load scenario including multicast transactions is reported. The methods of effective management of energy consumption in LonWorks networks are discussed. Finally, the LON design tradeoffs are summarized.

In multiple-antenna broadcast channels, unlike point-to-point multiple-antenna channels, the multiuser capacity depends heavily on whether the transmitter knows the channel coefficients to each user. For instance, in a Gaussian broadcast channel with M transmit antennas and n single-antenna users, the sum rate capacity scales like Mloglogn for large n if perfect channel state information (CSI) is available at the transmitter, yet only logarithmically with M if it is not. In systems with large n, obtaining full CSI from all users may not be feasible. Since lack of CSI does not lead to multiuser gains, it is therefore of interest to investigate transmission schemes that employ only partial CSI. We propose a scheme that constructs M random beams and that transmits information to the users with the highest signal-to-noise-plus-interference ratios (SINRs), which can be made available to the transmitter with very little feedback. For fixed M and n increasing, the throughput of our scheme scales as MloglognN, where N is the number of receive antennas of each user. This is precisely the same scaling obtained with perfect CSI using dirty paper coding. We furthermore show that a linear increase in throughput with M can be obtained provided that M does not not grow faster than logn. We also study the fairness of our scheduling in a heterogeneous network and show that, when M is large enough, the system becomes interference dominated and the probability of transmitting to any user converges to 1/n, irrespective of its path loss. In fact, using M=/spl alpha/logn transmit antennas emerges as a desirable operating point, both in terms of providing linear scaling of the throughput with M as well as in guaranteeing fairness.

The current challenge for telecommunication networks is to offer new types of services. To achieve this, somehow traffic has to be conditioned. A spacer is a token bucket traffic conditioner that reshapes flows according to a periodic profile. Packets are delayed until they can be inserted according to this profile. This short paper concentrates on packet discard by overflow in the spacer. An upper bound for the overflow probability is given, valid even when it is fully loaded. It shows the ratio of discarded packets is of the same order than the ratio of out-of-profile packets.

Recently, the capacity region of a multiple-input multiple-output (MIMO) Gaussian broadcast channel, with Gaussian codebooks and known-interference cancellation through dirty paper coding, was shown to equal the union of the capacity regions of a collection of MIMO multiple-access channels. We use this duality result to evaluate the system capacity achievable in a cellular wireless network with multiple antennas at the base station and multiple antennas at each terminal. Some fundamental properties of the rate region are exhibited and algorithms for determining the optimal weighted rate sum and the optimal covariance matrices for achieving a given rate vector on the boundary of the rate region are presented. These algorithms are then used in a simulation study to determine potential capacity enhancements to a cellular system through known-interference cancellation. We study both the circuit data scenario in which each user requires a constant data rate in every frame and the packet data scenario in which users can be assigned a variable rate in each frame so as to maximize the long-term average throughput. In the case of circuit data, the outage probability as a function of the number of active users served at a given rate is determined through simulations. For the packet data case, long-term average throughputs that can be achieved using the proportionally fair scheduling algorithm are determined. We generalize the zero-forcing beamforming technique to the multiple receive antennas case and use this as the baseline for the packet data throughput evaluation.

We introduce a new communication model consisting of two interfering broadcast channels with one cognitive transmitter, who knows the message transmitted by the other non-cognitive transmitter, in a non-causal manner. An achievable rate region is derived for this model. The region is computed based on the Marton region for the general broadcast channel and its extension by Steinberg to the broadcast channel with the states known at the transmitter. By using the region evaluated, an achievable rate for the Gaussian broadcast channel is derived.

We characterize the sum capacity of the vector Gaussian broadcast channel by showing that the existing inner bound of Marton and the existing upper bound of Sato are tight for this channel. We exploit an intimate four-way connection between the vector broadcast channel, the corresponding point-to-point channel (where the receivers can cooperate), the multiple-access channel (MAC) (where the role of transmitters and receivers are reversed), and the corresponding point-to-point channel (where the transmitters can cooperate).