Millimeter Waves

The millimeter wave (mmWave) frequency band is seen as a key enabler of multi-gigabit wireless access in future cellular networks. In order to overcome the propagation challenges, mmWave systems use a large number of antenna elements both at the base station and at the user equipment, which lead to high directivity gains, fully-directional communications, and possible noise-limited operations. The fundamental differences between mmWave networks and traditional ones challenge the classical design constraints, objectives, and available degrees of freedom. This paper addresses the implications that highly directional communication has on the design of an efficient medium access control (MAC) layer. The paper discusses key MAC layer issues, such as synchronization, random access, handover, channelization, interference management, scheduling, and association. The paper provides an integrated view on MAC layer issues for cellular networks, identifies new challenges and tradeoffs, and provides novel insights and solution approaches.

Increased density of wireless devices, ever growing demands for extremely high data rate, and spectrum scarcity at microwave bands make the millimeter wave (mmWave) frequencies an important player in future wireless networks. However, mmWave communication systems exhibit severe attenuation, blockage, deafness, and may need microwave networks for coordination and fall-back support. To compensate for high attenuation, mmWave systems exploit highly directional operation, which in turn substantially reduces the interference footprint. The significant differences between mmWave networks and legacy communication technologies challenge the classical design approaches, especially at the medium access control (MAC) layer, which has received comparatively less attention than PHY and propagation issues in the literature so far. In this paper, the MAC layer design aspects of short range mmWave networks are discussed. In particular, we explain why current mmWave standards fail to fully exploit the potential advantages of short range mmWave technology, and argue for the necessity of new collision-aware hybrid resource allocation frameworks with on-demand control messages, the advantages
of a collision notification message, and the potential of multihop communication to provide reliable mmWave connections.

In this work, we present a framework analysis of millimeter waves (mmWaves) vehicular communications systems. Communications between vehicles take place through a cooperative relay which acts as an intermediary base station (BS). The relay is equipped with multiple transmit and receive antennas and it employs decode-and-forward (DF) to process the signal. Also, the relay applies maximal ratio combining (MRC), and maximal ratio transmission (MRT), respectively, to receive and forward the signal. As the vehicles' speeds are relatively high, the channel experiences a fast fading and this time variation is modeled following the Jakes' autocorrelation model. We also assume narrowband fading channel. Closed-form expressions of the reliability metrics such as the outage probability, the probability of error and the channel capacity are derived. Capitalizing on these performances, we derive the low and high power regimes for the capacity, and the high signal-to-interference-plus-noise-ratio (SINR) asymptotes for the outage and error probability to get full insights into the system gains such as the diversity and coding gains.

The IEEE 802.11ad amendment to the 802.11 standard for multi-gigabit communication at 60 GHz was published several years ago, but to date, no precise simulation model for networking in this band is available. In this paper, we present a model for IEEE 802.11ad implemented in the network simulator ns-3. We model new techniques that are essential for IEEE 802.11ad operation such as beamform-ing training and steering, relay support, and fast session transfer. We then evaluate by simulation the performance of IEEE 802.11ad as well as the gains obtained through the aforementioned techniques. The code for our simulation model is publicly available.

This paper present the design and simulation of a single band microstrip patch antenna for 5G wireless application operating at 60GHz. The design is carried on Roger RT5880 with 2.2 dielectric, 0.0009 loss tangent and 0.003 mm thickness using inset feeding. The overall dimension of the patch antenna is 2.9 × 3.5 mm 2 , two rectangular U-slot in conjunction with H-slot were loaded into the radiator to enhance the antenna bandwidth. The antenna is design and simulated and the analysis were carried out on CST studio. The antenna achieve a maximum reflection coefficient of about-41.648731 dB at 60 GHz with a very wide bandwidth of about 30 GHz and 8.82 dB realized gain.

This paper reviews the design and deployment of the EE 5G network. EE owned by BT, launched the UKs first 5G network on the 30th May 2019, initially focused on enhanced mobile broadband use cases. This paper provides an overview of the radio access network and backhaul connectivity that has been deployed along with exploring the initial performance of 5G in EN-DC mode of operation. Particular focus is given to the optical and wireless backhaul solutions which connect the 5G RAN to the mobile core network. The paper goes on to consider what's next as 5G evolves to support massive machine type connectivity and ultra reliable and low latency networks.

Yeryüzünde huzur ve barışın yerleşmesi yerine; katliamların,
zulüm ve ahlaksızlıkların ve çifte standartların arttığını
gördüğümüzde, bunun asıl ve gizli sebepleri olarak şunu kabul
etmek mecburiyetindeyiz. O da; yeryüzünde yaşayan 7
milyar insanın huzur ve barışının, asla Batının ve Siyonist
odakların eline bırakılamayacağı gerçeğidir. Bugün yeni bir
dönüşüme ve yeni bir fethe acilen ihtiyaç duyulduğu kesindir.
İnsanlığın hasretle beklediği bu “Yeni Dünya”ya, inşallah yine
bu Aziz Millet öncülük edecektir.
Müslümanlık dini “Savunma ve zalimlerin himayesine sığınma”
dini değildir; bütün insanlığın saadet ve selameti için,
cesaret ve metanetle yürümek, cihadı sürdürmek ve zulme
karşı “Hücum etmek” dinidir. “Ben daha ne yapabilirim, kimseye
bir kötülüğüm yok” diyenler, bütün insanlığın saadeti için
çalışmadıklarından dolayı, Allah katında suçlu ve sorumlu vaziyettedir.
Bizim davamız İslam'dır. Gayemiz Allah'ın rızasını kazanmaktır.
Hedefimiz Hak nizamı hâkim kılmaktır. Arzumuz tüm
insanlığa saadet ulaştırmaktır. Yolumuz cihattır; Yöntemimiz
ikna metodudur. İnsanlığın kurtuluşu ancak İslam ile mümkün
olacaktır. Çünkü İslam Allah yapısıdır. Dolayısıyla mükemmel
ve tastamamdır, eksiklik ve fazlalık bulunmamaktadır. Bu dava
için çalışmak herkese nasip olmaz. İster gecenizi gündüzünüze
katıp bu hak dava için çalışın, ister yan gelip yatın; bu
hak davanın başarısını ne bir gün öne almak, ne de bir gün geciktirip aksatmak imkânsızdır. Bütün mesele bu şerefli davada nasıl bir imtihan vereceğimizdir ve kazanacağımız puandır.
Dolayısıyla Allah bir kulunu severse onu davasına hizmet
ettirip hayırla meşgul kılacaktır. Allah rızasını esas alan işler
yapınca Allah'ın yardımı ulaşacaktır. Allah'ın yardımı geldi mi
o zaman kimse size galip gelemez, siz galip gelirsiniz. Dünyanın
düzelmesi Millî Görüşçülerin çalışmalarına bağlıdır. Birlik
ve beraberliğinizi bozmayın.
Ey Millî Görüşçüler!
Şu söyleyeceklerime dikkat buyurun; tarih içerisinde, yaşadığımız şu kısa anların kıymeti belki hemen anlaşılmayacaktır. Ama gün gelecek ne kadar mühim bir vazife ifa ettiğinizi, gelecek nesiller sizi hayır ve hayranlıkla anarak ortaya koyacaktır. Bütün bu çalışmalar esnasında her zaman şu duayı yapmalıyız: "Ya Rabbi! Sen bize her zaman Hakk'ı Hak olarak göster; bâtılı bâtıl olarak göster. Hakkı tutmayı nasip et. Bâtıldan muhafaza buyur."
Sizlerin bu çalışmaları ve dünyanın bugünkü gidişatı karşısında
hiç kimse İslam Birliği'nin kurulmasına mani olamayacaktır.
Bu, kaçınılmaz bir zarurettir, takdir olunan bir hakikattir.
İslam Birliği, mutlaka ama mutlaka kurulacaktır. İster
Batı ister Doğu, hangi sistem olursa olsun ahir ömrünü yaşamaktadır. Ne yaparlarsa yapsınlar, hangi oyunları oynarlarsa oynasınlar, hepsi yok olup gidecektir ve zulüm saltanatıları yıkılacaktır.
Herkes bilsin ki Allah nurunu tamamlayacaktır.
Bütün bu önemli konuları tarih karşısında ve milletimizin
yüksek huzurlarında böylece ifade ettikten sonra size şunları
söylemek istiyorum:
Ben bu mücadeleyi; asla ikbal, makam, şöhret veya seçimlerde
bana oy versinler diye başlatmadım. Her ne yaptıysam
Allah rızası için yaptım. En büyük emelim “malıyla ve
canıyla cihat eden bir mü’min” olarak anılmaktır!*
Prof. Dr. Necmettin ERBAKAN

5G is the next generation cellular networks which is expected to quench the ever-ending
thirst of data rates and interconnect billions of smart devices to support not only human
centric traffic, but also machine centric traffic. Recent research and standardization work
have been addressing requirements and challenges from radio perspective (e.g., new spectrum
allocation, network densification, massive multiple-input-multiple-output antenna,
carrier aggregation, inter-cell interference mitigation techniques, and coordinated multipoint
processing). In addition, a new network bottleneck has emerged: the backhaul network
which will allow to interconnect and support billions of devices from the core network.
Up to 4G cellular networks, the major challenges to meet the backhaul requirements
were capacity, availability, deployment cost, and long-distance reach. However, as 5G network
capabilities and services added to 4G cellular networks, the backhaul network would
face two additional challenges that include ultralow latency (i.e., 1 ms) requirements and
ultradense nature of the network. Due to the dense small cell deployment and heavy traffic
cells in 5G, 5G backhaul network will need to support hundreds of gigabits of traffic from
the core network and today’s cellular backhaul networks are infeasible to meet these
requirements in terms of capacity, availability, latency, energy, and cost efficiency. This book
chapter first introduce the mobile backhaul network perspective for 2G, 3G, and 4G networks.
Then, outlines the backhaul requirements of 5G networks, and describes the impact
on current mobile backhaul networks.

Millimeter-wave and mMIMO communications are the most essential success systems for next-generation wireless sensor networks to have enormous amounts of accessible throughput and spectrum. Through installing huge antenna arrays at the base station and performing coherent transceiver processing, mMIMO is a potential technology for enhancing the bandwidth efficiency of wireless sensor networks. The use of mmWave frequencies for mMIMO systems solves the problem of high path-loss through offering greater antenna gains. In this work, we provide a design with a random spatial sample structure that incorporates a totally random step before the analogue is received. It contains a totally random step before the analogue received signals are sent into the digital component of the HBF receiver. Adaptive random spatial based channel estimation (ARSCE) is proposed for channel session measurement collection, and an analogue combiner with valves has been used to estimate the signals at each receiving antenna. The proposed optimization problem formulation attempts to discover the orientations and gains of wideband channel routes. In addition, our proposed model has compared to various state-of-art techniques while considering error minimization.

Data centers (DCs) is becoming increasingly an integral part of the computing infrastructures of most enterprises. Therefore, the concept of DC networks (DCNs) is receiving an increased attention in the network research community. Most DCNs deployed today can be classified as wired DCNs as copper and optical fiber cables are used for intra- and inter-rack connections in the network. Despite recent advances, wired DCNs face two inevitable problems; cabling complexity and hotspots. To address these problems, recent research works suggest the incorporation of wireless communication technology into DCNs. Wireless links can be used to either augment conventional wired DCNs, or to realize a pure wireless DCN. As the design spectrum of DCs broadens, so does the need for a clear classification to differentiate various design options. In this paper, we analyze the free space optical (FSO) communication and the 60 GHz radio frequency (RF), the two key candidate technologies for implementing wireless links in DCNs. We present a generic classification scheme that can be used to classify current and future DCNs based on the communication technology used in the network. The proposed classification is then used to review and summarize major research in this area. We also discuss open questions and future research directions in the area of wireless DCs.

The International Journal of Computer Networks & Communications (IJCNC) is a bi monthly open access peer-reviewed journal that publishes articles which contribute new results in all areas of Computer Networks & Communications.The journal focuses on all technical and practical aspects of Computer Networks & data Communications. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on advanced networking concepts and establishing new collaborations in these areas.

Millimeter-wave radars offer a practical solution to distinguish objects made of different materials, shapes, and compositions. In this work, radar classification of various materials is demonstrated using a broadband millimeter-wave CMOS integrated receiver. The receiver is used to record the transmitted power through multiple solid materials at various distances from the receiver in the W-band (75-110 GHz). Three supervised machine learning tools are trained by the recorded data to classify these materials into different categories. The trained classifiers were used to predict material and thickness of objects with varying distances from the receiver with accuracy levels of higher than 96% in material classification and 88% in thickness classification.

— In microwave remote sensing radiometers, calibration switches are needed in the application of the most internal calibration references. Very low insertion loss is beneficial in view of low receiver noise and good radiometric resolution (NEDT). Very low insertion loss can be achieved with ferrite junction switches. In developing millimeter wave ferrite junction switches, however, the small dimensions of the ferrite becomes a challenge. Targeting towards W band (89 GHz), two frequency-scaled switches at Ka band (36.5 GHz) have been developed in the current work. One of the switches applies higher order mode operation, resulting in larger ferrite dimensions. A reference switch to apply dominant mode operation has been developed as well. In this study, the feasibility of both dominant mode and higher order mode operation switches has been confirmed and good compliance between simulations and measurements observed. The switches have average insertion losses of 0.85 dB and 0.3 dB over 1.0 GHz and 4.5 GHz, respectively.

State of the art communication system pave way for microstrip patch antennas to experience rapid development. Nowadays, patch antennas are becoming increasingly popular due to their light weight and low profile making them easy to fabricate and integrate into the feeding network. This paper presented a single feed dualband band antenna for 5G application operating in the 28 and 38 GHz millimeter wave band with an improved efficiency. The antenna is designed and simulated on Computer Simulation Technology (CST) platform using FR-4 substrate with 0. 8 mm height, 4.67 dielectric constant and 0.002 loss tangent. The total size of the antenna is 8 × 8 mm 2 , the rectangular radiator of the antenna is 3.4 × 3.4 mm 2 in size, where an inverted-L is introduced into the radiator to achieve dual-band capability, The antenna is fed through 50 Ω feed line probe of about 2.3 × 0.4 mm 2 in dimension. The results of the simulation shows that the antenna achieved wide bandwidth in the upper band (38 GHz) of about 3.54 GHz (35.56 GHz-39.12 GHz) with over 6 dB gain and the lower band (28 GHz) produce a bandwidth of about 1430 MHz (27.27 GHz-28.70 GHz) with 2.7 dB gain suitable for 5G applications.

One of the crucial advancements in next-generation 5G
wireless networks is the use of high-frequency signals specifically
those are in the millimeter wave (mm-wave) bands. Using mmwave frequency will allow more bandwidth resulting higher user
data rates in comparison to the currently available network.
However, several challenges are emerging (such as fading,
scattering, propagation loss etc.), whenever we utilize mm-wave
frequency wave bands for signal propagation. Optimizing
propagation parameters of the mm-wave channels system are
much essential for implementing in the real-world scenario. To
keep this in mind, this paper presents the potential abilities of high
frequencies signals by characterizing the indoor small cell
propagation channel for 28, 38, 60 and 73 GHz frequency band,
which is considered as the ultimate frequency choice for many of
the researchers. The most potential Close-In (CI) propagation
model for mm-wave frequencies is used as a Large-scale path loss
model. Results and outcomes directly affecting the user experience
based on fairness index, average cell throughput, spectral
efficiency, cell-edge user’s throughput and average user
throughput. The statistical results proved that these mm-wave
spectrum gives a sufficiently greater overall performance and are
available for use in the next generation 5G mobile communication
network.

Mobile backhaul connectivity is an essential enabler of a mobile network. As networks evolve from 4G LTE to 5G it is vital that the access network connectivity undergoes a transport network transformation to meet new requirements on throughput, PELR, latency, PDV and synchronisation. This talk from the IET 5G Unleashed event, explains the requirements of 5G backhaul and presents a use case from BT UK on the architecture and design of their EE 5G mobile network.

Local multipoint distribution system (LMDS) that operated in millimeter waves can be used to fulfill
the need of bit rate higher than 40 Mbps. However it has problem when applied in tropic country such as
Indonesia because of the high rainfall. Therefore LMDS system was developed by cross-layer mechanism. 
In this research we used joint subcarrier and power allocation (JSPA) technique in multi-user cross-layer
OFDM. This technique is proposed to increase the performance of telecommunication system even there
were disturbance of rain attenuation. The research is discussing the performance of transmission capacity,
data rate, utility and fairness of JSPA algorithm that applied in rain attenuation measurement in Surabaya.
The result shows the increment of performance system using JSPA technique. For 40 dB rain attenuation,
JSPA can achieves respectively average capacity of transmission up to 173,3%, 189,9 % for data rate and
9,6% for fairness system. The application of JSPA technique improve  the performance of utility 13,61-
15,48 bps/Hz

A millimeter-wave antipodal Fermi tapered slot antenna configured with a new corrugation is presented. The corrugation has a sine wave profile for improved design flexibility and radiation performance. The effect of the sine-corrugation parameters is presented in detail, and the optimized design is compared with the measured prototype. The antenna is fabricated using a low-cost printed circuit board process. The measured bandwidth of the antenna covers a wide band (55–65 GHz) with a measured gain of 18.75 dB at 60 GHz. With these features, the antenna is suitable for short-range wireless communications and imaging applications.

Silicate ceramics are of considerable promise as high frequency dielectrics in emerging millimetre wave applications including high bandwidth wireless communication and sensing. In this review, we show how high quality factors and low, thermally stable permittivities arise in ordered silicate structures. On the basis of a large number of existing studies, the dielectric performance of silicate ceramics is comprehensively summarized and presented, showing how microstructure and SiO 4 tetrahedral connectivity affect polarizability and dielectric losses. We critically examine the appropriateness of silicate materials in future applications as effective millimetre wave dielectrics with low losses and tuneable permittivities. The development of new soft chemistry based processing routes for silicate dielectric ceramics is identified as being instrumental towards the reduction of processing temperatures, thus enabling silicate ceramics to be co-fired in the production of components functioning in the mm wave regime.

Article history: This paper presents an enhanced Quadri-band microstrip patch antenna, using defective slots in the ground plane, designed to operate in the millimeter wave band, formulated using cavity model and simulated by an EM-simulator, based on finite element method: HFSSv15 (High Frequency Structure Simulator). The proposed antenna incorporates two symmetric patterns of "U" shaped slots with an "I" shaped slot engraved in the middle of the ground plane. The resulting antenna has four frequency bands; the first resonant frequency is located in the Ka band, at about 27Ghz, the second at nearly 35Ghz, the third at 41Ghz and the last one at 51GHz. Those resonant frequencies could be shifted by tuning the slots dimensions introduced if the ground plane of the proposed antenna Keyword: Circular patch antenna DGS structure Millimeter wave Multiband antenna Wideband antenna

Millimeter-wave technology is one of the main pillars of the future wireless networks. The main reason lies in the quantum leap of capacity it provides with respect to wireless networks operating in the sub 6-GHz band. Nevertheless, efficient and reliable communication in this band demands novel techniques to tackle all the associated barriers related to wireless propagation in those bands. In this paper, we present the extension of our ns-3 IEEE 802.11ad model and provide design and implementation details of the new techniques, including dynamic and static channel access schemes, decentralized clustering, beamformed link maintenance, spatial sharing, and half-duplex relay operation as defined in the IEEE 802.11ad amendment. We show how these techniques can boost and enhance wireless networking operation in the 60~GHz band. Our work is the first to implement these techniques in a networking simulator and make the implementation publicly available.

Broadband sensing and spectroscopy in millimeter-wave and subterahertz frequencies can be facilitated with CMOS coherent detectors as a low-power, low-cost solution. This paper presents a fully integrated coherent detector with a broadband frequency comb as an on-chip reference signal. The receiver incorporates a frequency comb generator, which provides a broadband comb as a reference for heterodyne detection, and an NMOS field-effect transistor as the heterodyne detector. It also includes an on-chip elliptical antenna with a periodic structure which enhances its directivity up to +10 dBi without using a lens. The receiver detects any arbitrary spectrum from 50 GHz to 280 GHz with resolution of 2 Hz by tuning the comb spacing of the reference signal from 100 MHz to 5 GHz. The chip is implemented in a standard 65-nm CMOS process and it consumes 34 mW dc power.

Wireless backhaul communication has been recently realized with large antennas operating in the millimeter wave (mmWave) frequency band and implementing highly directional beamforming. In this paper, we focus on the alignment problem of narrow beams between fixed position network nodes in mmWave backhaul systems that are subject to small displacements due to wind flow or ground vibration. We consider nodes equipped with antenna arrays that are capable of performing only analog processing and communicate through wireless channels including a line-of-sight component. Aiming at minimizing the time needed to achieve beam alignment, we present an efficient method that capitalizes on the exchange of position information between the nodes to design their beamforming and combining vectors. Some numerical results on the outage probability with the proposed beam alignment method offer useful preliminary insights on the impact of some system and operation parameters.

In this work, we provide a framework analysis of dual-hop hybrid Millimeter Wave Radio Frequency (RF)/Free Space Optical (FSO) MIMO relaying system. The source is equipped with multiple antennas and employs conjugate beamforming while the destination consists of multiple apertures with selection combining. The system also consists of a relay operating at amplify-and-forward mode. The RF channels are subject to Nakagami-m fading while the optical links experience the Málaga distribution. In addition, we introduce the impairments to the relay and receiver. In fact, the relay is impaired by the High Power Amplifier (HPA) nonlinearities while the receiver suffers from the In phase and Quadrature Imbalance. Moreover, we assume two types of HPA nonlinearities impairments called Soft Envelope Limiter (SEL) and Traveling Wave Tube Amplifier (TWTA). Closed-forms of the outage probability, the bit error probability, and the ergodic capacity are derived. Capitalizing on these performances, we derive the high SNR asymptotes to unpack insightful metrics such as the diversity gain. We also address the impacts of some key factors on the system performance such as the impairments, the interferers, the number of antennas and apertures and the pointing errors, etc. Finally, the analytical expressions are confirmed by Monte Carlo simulation.

Nowadays, many emerging technologies, such as Augmented and Virtual reality, require extremely high-rate data transmissions. This imposes an increasing demand on the network throughput, which currently surpasses the capabilities of commercially available wireless communication systems. To address this constraint, some companies are considering the implementation of high-throughput wired technologies, such as optical fibers, as part of their products. This approach is effective in terms of communication link capacity, but on the other hand may bring disadvantages and constraints in terms of user mobility (i.e., the limited length of cables). Therefore, we are currently
witnessing much faster development of novel high-rate wireless
technologies, which are considered to be enablers for future 5G
applications. This paper offers an evaluation of the emerging
IEEE 802.11ad (WiGig) wireless technology capable of delivering
multi-gigabit data transfer rates. This hands-on assessment aims
at real-world experimentation as well as simulation-based study
of selected scenarios to assess the usability of the millimeter-wave
technology in prospective 5G applications. All of our practical measurements were conducted on the commercially available WiGig-ready Dell D5000 hardware platforms. The obtained data was comprehensively compared with the corresponding simulation scenario in Network Simulator 3.

As the scarcity of the radio spectrum implies difficulties in the earth-space communication link (ESCL) especially in satellite communication, it is necessary to estimate the amount of attenuation to ensure efficient utilization of the spectrum. By the scarcity in the frequency spectrum, the coming era will demand more data to be transferred at certainly more speed. And, this will demand for the higher frequencies. Keeping in mind the end goal to exploit present day space communications innovation, acknowledgment of a household correspondence satellite systems with impressive communication link at Ku-band is attainable. Climate is exceptionally unverifiable and labile hydrometeor activities make issue in a satellite communication. The real issue connected with the communication links at these high frequency radio waves is the rain attenuation estimation. In this thesis, a productive approach to gauge rain and cloud attenuation is discussed especially to give better execution at 12--40 GHz band. A comparative analysis of rain attenuation estimation models at 12--40 GHz band over ESCL have been carried out at real urban communities of India by considering information of NSS-6 satellite. The conclusion is made at last considering different rain and cloud attenuation models, and the most reliable model has been considered for the satellite link budget computation.

Massive MIMO systems are now well known for their energy efficiency. The ability to focus the energy to a targeted user not only increases the gain of useful signal but also reduces inter-user interference to the point where Spatial Division Multiple Access becomes possible.
Using such systems at high frequencies, thus greatly reducing the array form factor, seems a smart mix and we give an insight into how well an angle based precoder fares compared to well known massive MIMO linear precoders in a highly Line-of-Sight (LOS) environment.

In this paper we prove the optimality of this angle based precoder, called Digital Beamsteering (DBS), in an ideal pure LOS configuration and then we show how it performs in a more realistic environment. Furthermore, its robustness against angle estimation error is illustrated for a specific scenario and serves to back up the importance such a solution represents for future dense 5G networks, angular information being easier to get and especially to keep track of.

—The paper presents the analysis and design of Bessel beam launchers using a finite inward cylindrical traveling wave aperture field distribution. The launcher radiates an electric field whose normal or longitudinal component takes the form of a zeroth-order Bessel function. The nondiffractive behavior of the structure in a well-defined area close to the radiating aperture is analyzed by decomposing the radiated field in its geometrical optics (GO) and diffractive (D) contributions. A closed-form expression is provided for the GO contribution whereas an asymp-totic approximation is provided for the diffractive part. Such theoretical analysis allows a precise definition of the nondiffrac-tive region for the generated Bessel beam. At the same time, it also highlights and predicts the oscillating behavior of the longitudinal component of the electric field along the z-axis due to the diffraction from the edges of the aperture. The proposed analysis is validated by a prototype at 30 GHz made by a radial waveguide loaded with metallic gratings and centrally fed by a coaxial probe. Measurement results for the longitudinal component of the electric field are in excellent agreement with full-wave results. In addition , the nondiffractive behavior for the radiated beam is reported over a bandwidth larger than 6.5% around 30 GHz. This behavior is peculiar of the nonresonant first kind Hankel aperture field distribution used for the generation of the Bessel beam.

Millimeter wave (mmWave) communication systems use large number of antenna elements that can potentially overcome severe channel attenuation by narrow beamforming. Narrow-beam operations in mmWave networks also reduce multiuser interference, introducing the concept of noise-limited wireless networks as opposed to interference-limited ones. The noise-limited or interference-limited regime heavily reflects on the medium access control (MAC) layer throughput and on proper resource allocation and interference management strategies. Yet, these regimes are ignored in current approaches to mmWave MAC layer design, with the potential disastrous consequences on the communication performance. In this paper, these regimes are investigated in terms of collision probability and throughput. Tractable closed-form expressions for collision probability and MAC layer throughput of mmWave ad hoc networks, operating under slotted ALOHA, are derived. The new analysis reveals that mmWave networks may exhibit a non-negligible transitional behavior from a noise-limited regime to an interference-limited one, depending on the density of the transmitters, density and size of obstacles, transmission probability, operating beamwidth, and transmission power. Such transitional behavior necessitates a new framework of adaptive hybrid resource allocation procedure, containing both contention-based and contention-free phases with on-demand realization of the contention-free phase. Moreover, the conventional collision avoidance procedure in the contention-based phase should be revisited, due to the transitional behavior of interference, to maximize throughput/delay performance of mmWave networks. It is concluded that, unless proper hybrid schemes are investigated, the severity of the transitional behavior may significantly reduce throughput/delay performance of mmWave networks.