During last several years, mobile communications using mmWave spectrum have been intensively researched for 5G wireless networks. Now the mmWave wireless technologies are evolved into direct device‐to‐device communications for a single or multihop communication via Giga‐bit links. Vehicular ad hoc networks (VANETs) are one of the most attractive areas to apply the direct mmWave communications. In this paper, we propose a Giga‐V2V (GiV2V) network, in which vehicles query and deliver high quality video and sensor data of smart and self‐driving cars using mmWave communications instead of current dedicated short‐range communications (DSRC). In the GiV2V networks, vehicles probably form a grid topology along lanes of a road, which leads to align mmWave beams of the vehicles and cause mutual interference among them. As channel diversity can resolve effectively the interference between mmWave beams, we propose several heuristic algorithms for channel assignment of each beam in the GiV2V networks. We investigate the proposed algorithms using simulation and compare performance with well‐known metaheuristic algorithms for this NP‐Hard problem.

A dense deployment of small cells is one of the key characteristics envisioned for future 5G mobile networks in order to provide the required capacity increase. To cut cabling costs, small cells are foreseen to form multihop topologies using high capacity backhaul wireless links in the mmWave bands. Such small cells are deployed within the coverage area of a macro cell (eNB) to provide localized capacity where needed according to the well known Heterogeneous Network concept (HetNet). However, green networking will be very important because powering on unnecessarily a massive amount of small cells may lead to increased OPEX and CO2 emission. In this paper, we propose an optimization model that minimizes the total power consumption of 5G HetNets deployments while providing the required capacity and coverage. Our model jointly optimizes the user association, routing in the multihop backhaul and decides to power on or off the small cells to serve the user demands. Our numerical evaluation show significant power savings over a large range of traffic demand distributions while keeping the blocking probability low.

The data explosion and resource scarcity of mobile cellular networks require new paradigms to effectively integrate heterogeneous radio resources. Of many candidate approaches, smart aggregation of LTE and Wi-Fi radios is a promising solution that bonds heterogeneous links to meet a mobile terminal's bandwidth need. Motivated by the existence of a significant number of carrier operated Wi-Fi APs, we propose an easily deployable mechanism, called LTE-W, which efficiently utilizes LTE and Wi-Fi links only with the minimum change of eNodeBs, LTE backhaul networks, and mobile terminals. LTE-W, which is a link-level aggregation mechanism, has the following two key components: 1) mode selection and 2) bearer-split scheduling. First, in the mode selection, LTE-W internally decides who should be served by either LTE-only or LTE-Wi-Fi aggregation considering intra-cell fairness rather than just following users' intention of aggregation. For the users' preference to be offered the aggregation service, we choose a bearer (roughly defined in LTE as a set of flows with a similar QoS) as a basic unit of aggregation and propose a smart intra-bearer scheduling algorithm that splits a bearer's traffic into LTE and Wi-Fi links, considering the performance of TCP flows that take two heterogeneous wireless links. We evaluate our mechanism using the NS-3 with LENA, under various configurations, including nodes with mobility and HTTP traffic, and compare it with a transport-level aggregation mechanism, multipath TCP (MPTCP), demonstrating that LTE-W significantly improves MPTCP, e.g., up to 75% in terms of Jain's fairness index.

People are seeking solutions in diverse directions to cope with mobile data explosion and resource scarcity in mobile cellular networks. Of many candidate approaches, smart aggregation of LTE and Wi-Fi radios is a promising solution that bonds heterogeneous links to meet a mobile terminal's available bandwidth need. Motivated by the existence of a significant number of carrier-operated Wi-Fi APs, we propose a mechanism, called LTE-W, of efficiently utilizing LTE and Wi-Fi links only with the minimum changes of eNodeBs, LTE backhaul networks, and mobile terminals. Our mechanism has the following two key components: (i) mode selection and (ii) bearer-split scheduling. In the mode selection, LTE-W internally decides who should be served by either of LTE or LTE-Wi-Fi aggregation considering intra-cell fairness rather than just following users' intention of aggregation. For the users decided to be offered the aggregation service, we choose a bearer (roughly defined a set of flows with a similar QoS in LTE) as a basic unit of aggregation and propose a smart intra-bearer scheduling algorithm that splits a bearer's traffic into LTE and Wi-Fi links, considering the tuning of TCP flows that take two heterogeneous wireless links. We evaluate our mechanism using the NS-3 with LENA, and compare it to a transport-level aggregation mechanism, MPTCP, demonstrating that LTE-W significantly improves MPTCP, e.g., up to 75% in terms of Jain's fairness index.

In vehicular safety systems, two types of safety messages are required: Emergency Safety Message (ESM) and Periodic Beacon Message (PBM). The ESM has to be disseminated within a specified area with stringent delay and delivery ratio requirements, while the PBM does not need to meet these requirements. For exchanging the safety messages in Vehicular Ad-hoc NETwork (VANET), Inter-Vehicle Communication (IVC) is necessary whose de facto standard is Dedicated Short-Range Communications (DSRC). However, the effective transmission range in the DSRC-based IVC is short since a signal can be attenuated due to blocking by obstacles. In order to cover a large dissemination area in the DSRC-based IVC, multi-hop dissemination is required, which however causes channel collision and network congestion. Moreover, the coexistence with PBMs aggravates the collision and the congestion, which make it hard to satisfy the requirements of the ESM dissemination. To overcome the limitation of the DSRC, we utilize an extra TV White Space (TVWS) band that has a large communication range for ESM disseminations, and exploit a DSRC band for 1) the exchange of control data and 2) the compensation of ESM reception errors. In this paper, we propose and analyze a distributed channel usage framework that exploits advantages of DSRC and TVWS bands for ESM dissemination under the existence of PBMs. Our scheme employs TVWS Channel Rendezvous Algorithm (TCRA), ensuring that vehicles within a dissemination area select the same channel with the ESM sender. To compensate ESM reception failures in a TVWS band, our scheme adopts Two-Way Recovery Algorithm (TWRA) that uses DSRC and TVWS bands for ESM retransmission. Further, we establish an analytical delivery ratio model that considers a delay bound of an ESM for optimal parameter selections. To the best of our knowledge, this is the first attempt to propose a distributed channel usage scheme that leverages the strengths of TVWS and DSRC bands for safety message dissemination. Through an in-depth simulation study, we show that the proposed scheme satisfies ESM requirements for latency and packet delivery ratio, and outperforms previous approaches in various vehicular scenarios.

ABSTRACT A wireless mesh network has been popularly researched as a wireless backbone for Internet access. However, the deployment of wireless mesh networks in unlicensed bands of urban areas is challenging because of interference from external users such as residential access points. We have proposedUrban‐X, which is a first attempt towards multi‐radio cognitive mesh networks in industrial, scientific, and medical bands.Urban‐Xfirst controls network topology with a distributed channel assignment to avoid interference in large timescale. In such a topology, we develop a new link‐layer transmission‐scheduling algorithm together with source rate control as a small‐timescale approach, which exploits receiver diversity when receivers of multi‐flows can have different channel conditions because of varying interference. For this purpose, mesh nodes probe the channel condition of received mesh nodes using group Request to Send and group Clear to Send. In this study, we establish a mathematicalUrban‐Xmodel in a cross‐layer architecture, adopting a well‐known network utility maximization framework. We demonstrate the feasibility of our idea using a simulation on the model. Simulation results show improved network throughput from exploiting receiver diversity and distributed channel assignment under varying external user interference. Copyright © 2012 John Wiley & Sons, Ltd.

Vehicular communications promise to bring us safer driving and better traffic control. Dedicated Short Range Communications (DSRC) and IEEE 802.11p are now well established standards for the inter-vehicle and vehicle-to-road side unit (RSU) communication. These channels, however, are of limited capacity and are not sufficient to support the broad range of services envisioned in VANETs. Thus, vehicles will utilize WiFi (802.11 a/b/g) and unlicensed ISM band to acquire more capacity. Unfortunately, the WiFi channels in urban area are already heavily subscribed by residential customers. In this paper, we propose CoVanet, a cognitive vehicular ad hoc network architecture that allows vehicles opportunistic access to WiFi channels. CoVanet is the first approach to use cognitive radios in a VANET. It differs from conventional cognitive radio strategies in that it uses unlicensed band and operates in an ad hoc, multihop mode. In CoVanet, network topology and channel environment change frequently due to high node mobility. The main contribution of this work is a Cognitive Ad hoc Vehicular Routing Protocol (CoRoute) that utilizes geographical location and sensed channel information. Simulation results demonstrate CoRoute efficiency and robustness to mobility and external interference.

Cognitive radio network research has mostly focused on licensed spectrum sensing and empty spectrum use while protecting licensed band primary users. However, the wide deployment of WiFi access points in unlicensed bands in urban areas brings difficult challenges regarding co-existence of ad hoc mobile users with residential access points. In this paper, we propose a new mobile user protocol for dynamic channel selection via channel workload estimation. The mobile node senses channel usage in unlicensed ISM band and selects the maximum residual capacity channel for own packet transmission. The new protocol is implemented on Microsoft's SORA software defined radio system that enables fast prototyping. We have evaluated the performance using a Campus deployed SORA testbed. Experimental results show the efficiency of our approach in avoiding external interference.

Urban-X is a new architecture for Multi-Radio Cognitive Mesh Networks based on principles from Dynamic Spectrum Access Networks. In the Urban-X, spectrum sensing and mobility are challenging a transport control protocol (TCP) whose performance is sensitive to varying delay and available bandwidth. Also high packet loss due to primary users lets standard TCP to operate inefficiently. In this study, we propose a new transport protocol TP-UrbanX for the Urban-X which exploits reinforcement based learning techniques to learn an optimal sending rate and adapt this rate given the dynamics of the environment such as spectrum sensing and channel mobility.

ABSTRACT Vehicular communications promise to bring us safer driving and better traffic control. Dedicated short range communications and IEEE 802.11p are now well established standards for vehicular communications. Channels for those systems, however, are of limited capacity and are dedicated to safety applications. Thus, they are not sufficient to support the broad range of services envisioned in VANETs. It is anticipated that vehicles will utilize Wi‐Fi (802.11 a/b/g) to acquire more capacity. Unfortunately, the Wi‐Fi channels in urban areas are already quite heavily subscribed by residential customers. To evade the residential load, in this paper, we propose CoVanet, a cognitive vehicular ad hoc network architecture that allows vehicle radios to access the Wi‐Fi channels ‘opportunistically’, finding least loaded channels. In CoVanet, network topology and channel environment change frequently because of high node mobility. The main contribution of this work is a cognitive ad hoc vehicular routing protocol (CoRoute). CoRoute is a hybrid that utilizes both geographical location and sensed channel information to establish stable, minimum delay routes to the destination. Simulation results show that CoRoute is robust to mobility and to external interference and improves packet delivery ratio on average by 70% with respect to routing without cognitive radios. Copyright © 2011 John Wiley & Sons, Ltd.

A wireless mesh network (WMN) has been popularly researched as a wireless backbone for Internet access with off-the-shelf and inexpensive equipments. Nowadays, several applications like contents sharing, multicast video streaming, vehicular networks encourage to build mesh networks in urban areas. However, the deployment of WMNs in unlicensed bands of dense urban areas imposes many challenges. While previous research has mostly focused on optimal channel allocation under inter or intra-flow interferences within mesh nodes, the practical deployment of WMNs also requires to consider the interference caused by external entities such as residential access points that do not belong to the WMN. To address this issue, we propose Urban-X which is a first attempt towards a new architecture for Multi-Radio Cognitive Mesh Networks. Based on a cross-layer scheme, we develop novel routing and forwarding schemes reflecting the residential traffic state of external users. Through an extensive simulation analysis using the ns-2 simulator, we demonstrate the feasibility of our routing scheme and we show its robustness to the variations of channel environment and external traffics.

Non-optimal path and IP-in-IP encapsulation in Mobile IP cause that normal RSVP does not work well with Mobile IP. Application mobility using SIP can be a counterproposal to Mobile IP in terms of above discordance with RSVP. However, its address allocation delay causes a considerable handoff latency compared to Mobile IP. PAR-SIP application mobility is useful to reduce the handoff latency by reserving a prospective address. Also PAR-SIP proactive handoff allows RSVP modules to reserve resources in advance. This paper presents a resource reservation scheme with PAR-SIP soft handoff to achieve Quality of Service (QoS) of real-time multimedia communications.