Towards Massive Connectivity Support for Scalable mMTC Communications in 5G Networks

“This observation was the motivation for the use of Bloom filters – a data structure based on the OR operation for testing set membership [25] – for the construction of the access signatures.”

“…MAC and PHY numerical simulation was conducted over 10 4 trails including the full physical layer processing (encoding, modulation, channel estimation, multi-user detection, demodulation, decoding) with BPSK, a [5 ; 7] 8 convolutional code, least squares multi-user equalization and BCJR decoding.”

“This property led to the so-called compute-and-forward [39], [40], which proved achievable gains, from an information-theory point of view.”

“We follow the common simulation assumptions described in Table I. Note that the pilot-to-data ratio is only 13% so the overhead compared to LTE-4G has significantly reduced (reported to be up to 2000% in [48]).”

“Thus, enhancement of the access reservation procedure for mMTC traffic has been in the focus of both the research community [3] and standardization [4].”

“Focusing on a one-stage protocol early works on sporadic access in combination with Code Division Multiple Access (CDMA) already noted that intermittent user activity leads to a multi-user detection (MUD) problem with sparsity that required novel algorithmic solutions [31].”

“The presented Slotted Compute-and-Forward (SCF) approach is a random access extension of the Compute-and-Forward (CF) relaying scheme introduced in [49].”

“tage protocols by allowing more than one packet transmission per radio resource block and resolving collisions through advanced receivers. The solution falls under the category of coded random access [36], where features of channel coding are exploited both at the slot and frame level. In particular, the scheme partia…”

“The main focus of the NB-IoT is on providing extreme coverage, with supported number of users similar to LTE-M [18].”

“In the emerging paradigm of increasing human and machine inter-connectivity, a significant proliferation in the number of network nodes and data traffic is expected [3], [4].”

“However, reliable massive access for massive connectivity is not supported by the current wireless networks [3].”

“5G mMTC [72] NR-MTC NOMA Coexisting with 4G and Wi-Fi Massive machine-type communications for smart cities and agriculture”

“Within 5G, the massive machine type communications (mMTC) usage scenario is specifically designed for IoVT type of applications in which a massive number of access attempts are common within 5G mMTC [6], [12].”

“However, the reliable support of low-latency massive access for mMTC is still challenging in current wireless networks [3].”

“3) mMTC: In [31], authors focus on the massive mMTC service within a multi-service air interface.”

“Motivation Recently, massive machine-type communication (mMTC) has received much attention due to its wide variety of Internetof-Things (IoT) applications such as smart metering, factory automation, autonomous driving, surveillance, and health monitoring, to name just a few [2].”

“This allows the network to schedule wireless resources to the eMBB enabled devices such that no two eMBB devices compete or access the same resource simultaneously [3].”

“System scalability with massive connectivity [13] is thus a big issue—not only is the latency compromised by a large number of terminals sharing the medium, but the signaling overhead necessary for scheduling decisions also constitutes a major concern considering short packets.”

“2083 [221] distinguishes three main usage scenarios for this technology: enhanced Mobile Broadband (eMBB) [222], massive Machine-Type Communications (mMTC) [223] and Ultra-reliable and Low Latency Communications (uRLLC) [224]; each of them with different requirements ranging from high data rates (+50Mbps) and extensiv…”

“Various applications of the IoT, such as smart cities, connected vehicles, smart agriculture, public safety, and asset tracking, require different levels of coverage area, battery life, and connection capability [102].”

“This section reports the whole landscape of existing IoT standards, in terms of data rate and coverage, and characterizes their key performance indicators, as illustrated in Fig.”

“In this context, authors in [30] have discussed several medium access protocols for massive access attempts in the mMTC scenario.”

“, mMTC and URLLC, which provide connections for the long-range IoT coverage and mission-critical applications, respectively [19], [40], [77].”

“Since botnet is a major threat for IoT verticals [96], 5G roll-out design should be able to dynamically detect botnet traffic pattern and mitigate the attack in 5G network environment by leveraging the combination of SDN and NFV techniques to adapt botnet detection and reaction functions in 5G networks.”

“This service class is meant to support the connection of a large number of low-rate and low-power devices, referred to as machine-type devices (MTDs), within 5G cellu-273 lar networks [2], [3], [26].”

“A traffic arrival rate of 30 arrivals per TTI can be considered high [86].”

“THE fifth generation (5G) of wireless cellular networks has identified the massive machine-type communications (mMTC) as one of its core services [2], [3].”

“As a consequence, several surveys covering various aspects of PHY and MAC layers can be found in literature including [12], [19], [34]–[40].”

“energy-sAvIng-orIented scenArIos Massive machine type communications (mMTC) is widely regarded as one of the three core scenarios in the 5G ecosystem [8], which is also a typical representative of energy-saving-oriented scenarios for spectrum sensing.”

“…including Narrowband Internet of Things (NB-IoT) [6] and LTE-M protocols, although they still yet lacks of some capabilities supported by other cheaper non-cellular LP-WAN (Low-Power WAN Area Networks) networks, such as efficient treatment of sporadic patterns, and short packet transmissions [7].”

“…of fifth-generation (5G) mobile broad-band cellular networks is expected to leverage the delivery of advanced services to end users, such as enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC) as well as massive machine type communications (mMTC) [1], [2], [3].”

“Sporadic access will be expected by a large quantity of devices to transmit small data payloads, which results in an unknown, random subset of active devices at a given transmission instance [2].”

“• 3-GPP standards (protocol stacks): Cat-M1, NB-IoT, ECGSM-IoT [24], [32], [61].”

“, smart factory, smart cities, and intelligent transportation) [4] [5].”

“Furthermore, combining the PHY multi-packet reception capability with the MAC protocol design [11], a drastic performance augment can always be produced.”

“On the other hand, when the direct link (MTD-BS) is under unfavorable propagation conditions, the MTD transmits its data for a long period if it uses the repetition technique [37], increasing the energy consumption, the delay, and the number of radio resources.”

“Note that grant-free random access is also called two-step random access or one-shot approaches [13]–[15].”

“However, in many applications in the mMTC use scenarios, several heterogeneous types of users coexist [4], [28], [29].”

“Currently, two major technology groups providing functionalities to solve defined 5G mMTC requirements are discussed [2].”

“…and efficiency of regular and alarm messages with the goal of finding efficient ways of coordinating massive connectivity—the so-called massive machine-type communications (mMTC) [9], while allowing for reliable alarm messages for protection and security proposes in industrial environments.”

“How to deal with the massive access of hundreds of billion devices with small-sized transmission pay-loads and sporadic features is one of the main challenges of this kind of network [4], [69].”

“MTC networks are engineered to accommodate a vast array of devices concurrently, offering scalability that extends to millions of devices within a square kilometer [44], thereby enabling expansive machine-to-machine (M2M) connectivity.”

“dom access approaches are extensively studied [12], which are also often called compressive random access or one-shot [13]–[16] or grant-free approaches [17]–[20].”

“As the number of Internet of Things (IoT) devices grows, millions of devices with characteristics different from human-type communication will require connectivity [2], [3].”

“Among the various techniques proposed for the enhancement of the RACH procedure, grant-free access schemes, where uplink transmissions can take place without a prior request-grant phase, are considered as a promising and low-overhead mechanism for smart grid operations involving mMTC [1].”

“This way, MTC plays a pivotal role on the concretization of the Internet of Things (IoT) and Internet of Everything (IoE) [2], [3].”

“AnothermajorapplicationisthesupportofmMTCsporadic traffic[19]–[21]whereamassivenumberofdevicesaccessin anuncoordinatedmannerthesamecommunicationresource.”

“Beyond improved speed, or latency, 5G is expected to unleash a massive IoT (Internet of Things) ecosystem [2] in which networks can meet the communication needs of billions of connected devices with the right capabilities [3].”

“…or asynchronous transmission is promising for mMTC since it has advantages such as reduced transmission latency, smaller signalling overhead due to the simplification of the scheduling procedure and improved energy efficiency (battery life) of MTCDs with the reduction in signalling [3], [4].”

“Examples of mMTC systems include smart metering, smart homes, smart agriculture, fleet management, health monitoring, etc [2], [3].”

“While these solutions many C-V2X applications to function properly, ; Luis M. Contreras is with Telefónica I+D/Global CTIO Unit; Verikoukis are with CTTC/CERCA. they struggle to guarantee the ultra-low latency requirements (i.e., equal or less than 10 ms) in volumes for some crucial services [5].”

“11 13 – 15 In MTC, the traffic load is very small, and it is unpredictable in nature leading to signaling overhead making route selection very challenging.”

“ultrareliable and low-latency communications (URLLC) and enhanced mobile broadband (eMBB) [4], [5].”

“This line of work is currently of particular interest in the context of massive Machine-Type Communications (mMTC) for 5G systems [22].”

“The authors in [12] have employed compressive sensing MUD in slotted ALOHA.”

“Because only a small number of machine-type devices are active at a time, the activity indicator vector can be well modeled as a sparse vector [4].”

“The Poisson distribution, i.e., exponentially distributed times between packet arrivals for one device, is appropriate for modeling the traffic in mMTC [1], [25].”

“For more details on synchronization, please refer to [49].”

“is supposed to be sporadic [15], the actual users would be a subset of all users in the network, and the number of active users should be less than the number of all users.”

“For instance, on a Massive Machine-Type Communications (mMTC) 5G network, the numbers can often reach 1 million connections per square meter [11], [12], while with standard ZigBee, as many as 65,536 devices are feasible [13].”

“Several papers have studied the mMTC (massive Machine Type Communications) application for the smart city and smart manufacturing which relied on sensing and monitoring with applying the IoT [22–27].”

“INTRODUCTION The provisioning of massive connectivity has been deemed as one of the key application scenarios in the fifth generation (5G) wireless communication systems [1], [2].”

“One of the hallmarks of the fifth generation (5G) wireless systems and beyond is massive Internet of Things (IoT) connectivity [1].”

“5G is a perfect enabler for V2X applications [12].”

“From the physical and medium access layer perspective, designing the efficient access protocols in 5G networks, such as 5G multiservice air interface, facilitates the improvement of the ability of network to access massive devices [9].”

“, WSN for monitoring high frequency events in [10]), which may be crucial in MTC when there are a large number of sensors [11].”

“The revolutionary solutions aim at a fundamental revision of the access procedure in order to provide low energy consumption [11], [12], with a potential to lower access delay.”

“However, the multiple access scheme of 5G is required to support a wide range of use cases, including a massive number of low-power Internet of Things (IoT) devices, device-todevice (D2D) communications, device-to-everything (D2E), the Internet of Vehicles (IoV), as well as seamless machine-to-machine (M2M) communicat…”

“Hence, open-loop power control is more suitable for GF-NOMA scenarios and thus adopted in this article (consistent with the power control mechanism used in [9], [12], and [34]).”

“Its solution is relevant across a wide range of network design and optimization tasks [4], [5], [6], [8], [9], [10], especially beyond current wireless network protocols based on individual objectives such as the optimized link state routing protocol [36] which only considers hop count and is,…”

“Currently, the procedure for reserving access is limited to a low number of devices and each device requires high data rates [3].”

“…foresee that recent advances in the Internet of Things [44], 5G technologies for vertical applications [45] and machine-type wireless communications [46,47] will also provide the level of reliability and availability required by the proposed energy management system, allowing it to scale up [37].”

“This has led to a surge on research in the area of massive random access [6], [7].”

“The received signal at R, UE1 and UE2 can be given, respectively, as: yR = h1 (√ a1Px1 + √ a2Px2 ) + nR (2)”

“In this way, the transmission rate is not one of the most important figures of merit, but throughput, which evaluates the number of successful transmissions in a given time interval, and the probability of collision, which is the number of collisions that occurs at a certain time interval [2], [3].”

“M ASSIVE machine-type communications (mMTC) play an essential role in the next generation of cellular networks [1].”

“such as different types of sensors [7, 8].”

“As a result, it cannot ensure dedicated pilot allocation to every concurrently activated IoT device [3].”

“In the case of IoT (Internet of Things) using a large number of censors, intermittently communications occur from about tens of thousands of censor devices [7].”

“Random access for mMTC has been studied in many works recently [2], [3] and especially a large focus has been on grant-free random access since the communication overhead will be smaller when there is no contention resolution [4], [5].”

“Most of the devices in IoT applications are low-rate sensors with sporadic characteristics [36]–[39].”

“Thus, standardization agencies, such as 3GPP (3rd Generation Partnership Project), IEEE (Institute of Electrical and Electronics Engineers), ETSI (European Telecommunications Standards Institute), and 5GPPP (5G Public Private Partnership), among others, are devoted to the requirement specifications of M2M communicatio…”