Kishor Chandra

Adaptive beamwidth selection for contention based access periods in millimeter wave WLANs

60 GHz wireless local area networks (WLANs) standards (e.g., IEEE 802.11ad and IEEE 802.15.3c) employ hybrid MAC protocols consisting of contention based access using CSMA/CA as well as dedicated service periods using time division multiple access (TDMA). To provide the channel access in the contention part of the protocol, quasi omni (QO) antenna patterns are defined which span over the particular spatial directions and cover a limited area around access points. In this paper, we propose an algorithm to determine the beamwidth of each QO level. The proposed algorithm takes into account the spatial distribution of nodes to allocate the beamwidth of each QO level in an adaptive fashion in order to maximizes the channel utilization and satisfy the required link budget criterion. Since the proposed algorithm minimizes the collisions, it also minimizes the average time required to transmit total packets in a QO level. Proposed algorithm improves the average channel utilization up to 20-30% and reduces the time required to transmit total packets up to 40-50% for the given network parameters.

CogCell: cognitive interplay between 60 GHz picocells and 2.4/5 GHz hotspots in the 5G era

The rapid proliferation of wireless communication devices and the emergence of a variety of new applications have triggered investigations into next-generation mobile broadband systems, i.e. 5G. Legacy 2G-4G systems covering large areas were envisioned to serve both indoor and outdoor environments. However, in the 5G era, 80 percent of all traffic is expected to be generated indoors. Hence, the current approach of macrocell mobile networks, where there is no differentiation between indoors and outdoors, needs to be reconsidered. We envision 60 GHz mmWave picocell architecture to support highspeed indoor and hotspot communications. We envisage the 5G indoor network as a combination of, and interplay between, 2.4/5 GHz having robust coverage and 60 GHz links offering a high data rate. This requires intelligent coordination and cooperation. We propose a 60 GHz picocellular network architecture, called CogCell, leveraging ubiquitous WiFi. We propose to use 60 GHz for the data plane and 2.4/5GHz for the control plane. The hybrid network architecture considers an opportunistic fall-back to 2.4/5 GHz in case of poor connectivity in the 60 GHz domain. Further, to avoid the frequent re-beamforming in 60 GHz directional links due to mobility, we propose a cognitive module, a sensor- assisted intelligent beam switching procedure, that reduces communication overhead. We believe that the CogCell concept will help future indoor communications and possibly outdoor hotspots, where mobile stations and access points collaborate with each other to improve the user experience.

Sensor assisted movement identification and prediction for beamformed 60 GHz links

The 60 GHz frequency band promises very high data rates - in the order of Gb/s - due to the availability of high bandwidth. However, high free-space path loss makes it necessary to employ beamforming capable directional antennas. When beamforming is used, the links are sensitive to misalignment in antenna directionality because of movement of devices. To identify and circumvent the misalignments, we propose to use the motion sensors (i.e., accelerometer and gyroscope) which are already present in most of the modern mobile devices. By finding the extent of misaligned beams, corrective actions are carried out to reconfigure the antennas. Motion sensors on mobile devices provide means to estimate the extent of misalignments. We collected real data from motion sensors and steer the beams appropriately. The results from our study show that the sensors are capable of detecting the cause of errors as translational or rotational movements. Furthermore it is also shown that the sensor data can be used to predict the next location of the user. This can be used to reconfigure the directional antenna to switch the antenna beam directions and hence avoid frequent link disruptions. This decreases the number of beam searches thus lowering the MAC overhead.

Long Reach Hybrid Fiber-Wireless System With Remote Up-Conversion and Local Exchange

A long reach fiber wireless network is proposed for 60-GHz wireless application and all-optical routing/multicasting with simplified structure. This scheme is based on remote upconversion and can provide flexible reach (>100 km) together with a reconfigurable platform for dynamic bandwidth allocation at the physical layer. The experimental results show that 60-GHz wireless signal with 5-Gbps OOK is successfully delivered over 102-km single mode fiber. Moreover, functionalities, such as alloptical routing and optical multicasting are also demonstrated.

An architectural framework for 5G indoor communications

In this paper, we emphasize on indoor networks in 5G era. We explore the possible technologies and architectural solutions for 5G indoor communications. Owing to the fact that requirements for indoor and outdoor communications will be quite different in the next generation networks, we try to define an architectural framework for 5G indoor communications. Our proposed architecture focuses on three aspects of indoor network architecture, namely; air interface, backhaul connectivity and indoor signal distribution.

60 GHz MAC standardization: Progress and way forward

Communication at mmWave frequencies has been the focus in the recent years. In this paper, we discuss standardization efforts in 60 GHz short range communication and the progress therein. We compare the available standards in terms of network architecture, medium access control mechanisms, physical layer techniques and several other features. Comparative analysis indicates that IEEE 802.11ad is likely to lead the short-range indoor communication at 60 GHz. We bring to the fore resolved and unresolved issues pertaining to robust WLAN connectivity at 60 GHz. Further, we discuss the role of mmWave bands in 5G communication scenarios and highlight the further efforts required in terms of research and standardization.

Analysing IEEE 802.15.3c protocol in Fi-Wi hybrid networks

Even though 60 GHz frequency band has limited coverage, due to the availability of higher bandwidth worldwide (unlicensed, approximately 5 GHz between 57-62 GHz), it is one of the promising candidates for future broadband employing both Fiber and Wireless (Fi-Wi) technology. In this article we briefly explain an in-home radio over fiber (RoF) architecture employing 60 GHz spectrum band. The main challenge for designers of such networks is the additional delay introduced by the optical distribution network. Later in the light of this increased delay, we provide an investigation on the feasibility of applying the IEEE 802.15.3c MAC protocol in such a RoF system at 60 GHz. Mainly, we analyse various ACK mechanisms in the IEEE 802.15.3c when it is used in conjunction with RoF network. The analytical results show that the fiber optic network causes a slight drop in the throughput but it could still be easily used in home networks. This gives us an opportunity to sustain high bandwidth at low cost for home networking, also supporting mobility. Modelling of a RoF system with IEEE 802.15.3c and numerical results thereof are the contributions of this article.

Performance Analysis of IEEE 802.11ad MAC Protocol

IEEE 802.11ad specifies a hybrid medium access control (MAC) protocol consisting of contention as well as non-contention-based channel access mechanisms. It also employs directional antennas to compensate for the high free-space path loss observed in 60 GHz frequency band. Therefore, it significantly differs from other IEEE 802.11(b/g/n/ac) MAC protocols and thus requires new methods to analyze its performance. We propose a new analytical model for performance analysis of IEEE 802.11ad employing a 3-D Markov chain considering all the features of IEEE 802.11ad medium access mechanisms including the presence of non-contention access and the different number of sectors due to the use of directional antennas. We show that the number of sectors has a high impact on the network throughput. We show that the MAC packet delay is significantly affected by the duration of the contention period. Our results indicate that a suitable choice of the number of sectors and contention period can improve the channel utilization and MAC delay performance.

Resource management in indoor hybrid Fi-Wi network

In-home networking is becoming a reality. New multimedia applications envisaged for indoor networks require data rate of up to several gigabits per second. In order to meet such a demand for high data rate unlicensed spectrum of 5GHz around 60GHz band is being considered for a potential choice. This pico cellular infrastructure also helps in reducing the interference; at the same time, it is a cause for high deployment cost. Radio-over-fiber infrastructure is an obvious choice to feed this last mile high data rate links. The combination of radio-over-fiber and 60GHz wireless links, which is known as hybrid Fi-Wi, is a promising solution to offer high data rate indoor networking. Because of smaller cell size, handoffs between these small cells occur frequently in such a hybrid network. Because of smaller overlapping area between neighbouring cells, guaranteeing quality of service in this network is highly difficult compared with the traditional wireless cellular networks. Thus, resource management in such network is a challenging task. In indoor environments, techniques such as hidden Markov models can be employed to predict movements with high degree of accuracy. In this article, we propose a handoff scheme that utilises movement prediction to reserve bandwidth in only potential target cells before each handoff is initiated. The simulation results show that the proposed scheme performs better than the two other schemes from the literature in terms of the call dropping probability and the call blocking probability. Copyright

mCRAN: A radio access network architecture for 5G indoor communications

Millimeter wave (mmWave) communication is being seen as a disruptive technology for 5G era. In particular, 60GHz frequency band has emerged as a promising candidate for multi-Gbps connectivity in indoor and hotspot areas. In terms of network architecture, cloud radio access network (CRAN) has emerged as the most promising architectural alternative to enable efficient baseband processing and dynamic resource allocation in 5G communications. In this article, we propose micro-CRAN (mCRAN) -a multi-gigabit indoor network architecture which leverages availability of high bandwidth in 60GHz frequency band. We have discussed in detail about the requirements and research challenges for various system modules for mCRAN based network architecture. We have also investigated the feasibility of IEEE 802.11ad MAC protocol for the proposed mCRAN architecture. We discuss the challenges related to 60GHz beamforming, medium access mechanisms and network architecture, and propose solutions to address them.