Which Media Access Control Service Provides The Ability To Deliver To A Single Interface In A Set?

Sensor information accumulation methodologies

Amartya Mukherjee , ... Nilanjan Dey , in A Beginner'southward Guide to Information Agglomeration and Intelligent Sensing, 2020

five.5 Selection of MAC layer

The MAC layer is one of the two sublayers that make upwards the data link layer. The main job of the MAC layer is to motion the data from the network interface card of a network to a shared aqueduct. The MAC layer along with data link control is responsible for the complete physical addressing of the data link layer. The advice in WSN occurs from various information sources for the aggregation data, which is relayed toward a single sink node. With the advent in technology, MAC protocols have come a long manner, long before we used the additive links on-line hawaii area (ALOHA) protocols then slotted ALOHA and then on. Then carrier sense multiple access protocols came to light. As the battery in the wireless sensor cannot be replaced, efficient power saving communication is very important.

As information is relayed from multiple sensors, in that location is a gamble that collision might occur. As traffic is event triggered, the traffic of two nodes closing together will be dependent in nature, and every bit traffic is many to one, there is high probability of collision. Fig. 5.5 shows how collision might occur during data aggregation.

In Fig. v.6, we can see that outcome 1 and event two are sensed by all the underlying leaf sensor nodes. The aforementioned information against consequence 1 is relayed to the sensors above it. Information technology might be the case that both try to ship the information in the very same time frame, due to which collision occurs. Collision avoidance is 1 of the basic tasks in any MAC protocols. MAC protocol developed in a way then that they adopt a contention-based scheme. Redundant data transmission makes contention-based protocols less efficient in energy than TDMA protocols. So it has to be avoided.

Collision leads to:

•: Data parcel loss.
•: Decreases reliability and increase the retransmission.
•: Energy consumption increases and latency also increases.

MAC protocol such as contention-free or contention-based MAC protocols can be used to avoid a collision. In contention-based MAC protocols, the acquired channel mostly uses control packets. More often than not used for manual in the independent traffic pattern. Contention-complimentary MAC is used for the dependent network. It can be used if the network traffic is static or changes rarely. Some of the popular MAC protocols are every bit follows:

i.: MACA, MACAW—contention based
2.: TDMA, lawmaking partition multiple access mechanism, frequency-division multiple access (FDMA)—contention free

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128203415000059

Bandwidth part

Jia Shen , Nande Zhao , in 5G NR and Enhancements, 2022

iv.3.two Introduction of bandwidth part activation method based on DCI

There are ii candidate schemes to dynamically actuate a BWP—MAC CE activation and DCI activation [18].

MAC CE is used to activate SCell in the LTE CA. The advantage of using MAC CE is the college reliability (considering Hybrid Automatic Repeat-asking (HARQ) feedback can be used for MAC CE, simply non for DCI) and the abstention of DCI signaling overhead (MAC CE, every bit a high-layer signaling, can bear a larger overhead than DCI). The disadvantage of MAC CE is that it takes a menstruation of time (due east.grand., several slots) to accept effect, which impacts the real-time operation. In dissimilarity, as a physical layer signaling, DCI can take issue in several symbol durations [38], which is more than conducive to fast BWP switching. Although information technology is not necessary or even not preferable quondam to switch BWP too frequently, fast BWP switching can still exist used for many purposes in the NR system. Therefore compared with SCell, BWP needs a faster activation mechanism.

The disadvantage of DCI is the existence of miss detection and false alarm. Especially if the UE missed the DCI indicating downlink BWP switching, the UE still monitors PDCCH on the original DL BWP when gNB already starts to utilize the new DL BWP for DCI transmission for the UE. Then the UE can never receive DCI nether normal circumstances (e.k., the CORESET and search space of two BWPs do not overlap). In order to solve the problem that gNB and UE accept unlike understandings of downlink active BWP caused by DCI miss detection, the timer-based BWP switching is also adopted in NR specification. The timer-based BWP switching enables the UE to autumn back to the default DL BWP in example of DCI miss detection (come across Section iv.three.iii for details), and to some extent makes up for the reliability disadvantage of DCI compared to MAC CE. Finally, NR volition anyway support the reliable BWP activation based on RRC signaling. The combination of RRC signaling and DCI tin can balance the tradeoff between reliability and low latency. Therefore NR finally decided to prefer the dynamic BWP activation method based on DCI [39], instead of MAC CE.

As mentioned in Section 4.2.9, DL BWP and UL BWP are switched independently in the FDD arrangement (i.e., UL BWP can remain unchanged while DL BWP is switched, and vice versa). Nonetheless, in the TDD system, DL BWP and UL BWP must be switched in pair. DL BWP and UL BWP with the same BWPI are always agile simultaneously [33]. The BWP indication design in DCI is shown in Section 4.3.5.

In the technical discussion of NR CA, it was too proposed to raise the CC activation mechanism and support CC activation/deactivation based on PHY signaling (i.e., DCI), but it was non accepted in R15 NR specification. Therefore DCI activation has get an obvious advantage of the BWP mechanism over CA in R15, which makes BWP activation/deactivation faster and more efficient than CC activation/deactivation. This is also 1 of the reasons why BWP has become an obviously new system tool that is unlike from CA.

Finally, for the design of DCI activation of BWP, it is also articulate that merely the BWP "activation" needs to be defined. There is no need to define BWP "deactivation." The key to this question is: is there ever a BWP existence active? If the answer is yes, activating a new BWP naturally deactivates the previous BWP, without a need for a specific BWP "deactivation" mechanism. Even so, if "the system activates a BWP for a UE only when the organization resource is in use by the UE, and the UE can have no active BWP at all when information technology does not utilise whatever system resource," both BWP activation mechanism and BWP deactivation mechanism are needed. Along with report on BWP, the utilise cases of BWP concept were gradually extended, not but for data scheduling, but as well for the transmission/reception of the control channels and RS. Obviously, BWP has become a universal concept and "necessary at whatsoever fourth dimension." And then it is necessary for a UE to e'er have an active BWP. Thus it is non necessary to design a BWP "deactivation" machinery for either dynamic BWP switching or semistatic BWP switching.

Read full affiliate

URL:

https://world wide web.sciencedirect.com/science/article/pii/B9780323910606000040

Emerging wireless advice technologies for smart grid applications

Ersan Kabalci , Yasin Kabalci , in From Smart Grid to Cyberspace of Energy, 2019

5.3.1.two MAC layer of IEEE 802.15.4 standard

The MAC layer comprises two services called MAC data service and MAC direction service. The old service empowers MAC protocol data units (MPDUs) for receiving and/or transmitting data across the PHY data service. The major features of the MAC layer can be listed every bit guaranteed time slot (GTS) management, beacon direction, frame validation, acknowledged frame commitment, channel access, association, and disassociation. In addition, the layer presents several chances to deport out appropriate security schemes for dissimilar type applications. There are two channel access methods in the IEEE 802.xv.4 standard, which are named as buoy-enabled method and non-beacon method. If unslotted carrier sense multiple admission with collision abstention (CSMA/CA) is employed, the standard requires the use of non-buoy mode. In the result of the slotted CSMA/CA is employed, the standard requires the apply of buoy-enabled manner where PAN coordinator periodically conveys buoy frames to whole end-devices existing in the network. The beacons are responsible for three significant purposes that tin be sorted as ensuring synchronization among devices, identifying PAN infrastructure and defining structure of superframes. A superframe is employed in beacon-enabled mode to manage communication in the wireless aqueduct. The duration betwixt two beacons is divers as a beacon interval (BI) that is equanimous of an active menstruum and an optional inactive menstruum. The nodes can preserve their power sources by activating sleeping fashion (depression-ability mode) during the inactive menses. The active menses of the superframes is called every bit superframe elapsing (SD). Every SD is composed of xvi fourth dimension periods with equal lengths. Furthermore, Contention Access Period (CAP) and Contention Gratuitous Period (CFP) sections are likewise defined in the agile periods. The CFP that is managed by a PAN coordinator is generally exploited in low-latency applications, and contains up to seven GTSs. The nodes can contact with each other by employing a slotted CSMA/CA or ALOHA in the CAP. The operational modes of IEEE 802.fifteen.4 MAC layer are illustrated in Fig. 5.5.

A PAN coordinator describes the superframe scheme which is defined on the ground of macBeaconOrder (BO) and macSuperframeOrder (And then) values. The BO defines the time menstruum whereas the And so identifies the active period and beacon frame. A general superframe scheme is illustrated in Fig. five.6 where the beacon-enabled style is taken into account. The relationship betwixt BI and BO can be given equally follows.

(5.one) $BI = aBaseSuperframeDuration \times {two}^{BO} symbols, for 0 \leq BO \leq 14$

In the outcome of the value of BO is fifteen, the value of And then is ignored and buoy frames are not sent unless a special request is available. Furthermore, the relationship between And then and SD tin be given as follows.

(5.ii) $SD = aBaseSuperframeDuration \times {two}^{And then} symbols, for 0 \leq So \leq BO \leq fourteen$

In the event of the value of SO is xv, the superframe will not carry on the active manner after the beacon. When the value of the BO is 15, the value of So volition be ignored.

The MAC layer responsibilities can be given equally follows.

•: Forming of Beacons for Coordinator: A coordinator tin select its operating way as beacon-enabled mode or non-beacon fashion. The coordinator runs by using superframe structure in the beacon-enabled mode where the number of superframes is constrained by network beacons. Every active part of a superframe contains 16 equally spaced slots (aNumSuperframeSlots). Furthermore, coordinators periodically ship network beacons in society to synchronize devices connected to the network.
•: Supplying Synchronization amidst PAN Coordinator and Stop-Device: The synchronization is a critical procedure to determine condition of devices in the network and free energy saving transactions. Therefore, an stop-device operating in beacon-enabled mode should follow beacons for presenting synchronization to the PAN coordinator.
•: Association and Disassociation: In star and mesh network types, automatic setup and cocky-configuration features are enabled through clan and disassociation information provided by the MAC layer.
•: Channel Admission Procedure via CSMA/CA Technique: Channel access process in the IEEE 802.15.4 standard is achieved by employing CSMA/CA method similar to other popular protocols adult for wireless networks. Withal, asking-to-ship (RTS) and clear-to-send (CTS) mechanisms are not utilized in this standard.
•: GTS Organization: While the buoy-enabled mode is active, coordinator can commit some parts of the efficient superframe into a device. These parts of the superframe are chosen GTSs and they as well include CFP of the superframe.
•: Providing Safe Connections betwixt MAC Entities: The MAC layer utilizes various transactions such as CSMA/CA, re-manual, frame acknowledgement and CRC data verification in social club to advance connection reliability between MAC entities.

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128197103000053

Device Drivers

Tammy Noergaard , in Embedded Systems Compages (2nd Edition), 2013

CDMA/CD (MAC Sublayer) Reception Mode

When the MAC sublayer receives the stream of bits from the physical layer, to be afterward transmitted to a MAC client, the MAC sublayer RMAM component receives these bits from the physical layer equally a "frame." Note that, as the bits are being received past the RMAM component, the first two fields (preamble and commencement frame delimiter) are overlooked. When the physical layer ceases transmission, the frame is so passed to the RDD component for processing. It is this component that compares the MAC Destination Address field in this frame to the MAC Address of the device. The RDD component too checks to ensure the fields of the frame are properly aligned, and executes the CRC Error Checking to ensure the frame wasn't damaged en route to the device (the Error Checking field is stripped from the frame). If everything checks out, the RDD component so transmits the remainder of the frame, with an boosted status field appended, to the MAC Client.

Figure 8-38 shows a high-level menstruum chart of the MAC layer processing incoming bits from the physical layer:

It is not uncommon to find that half-duplex capable devices are as well total-duplex capable. This is because but a subset of the MAC sublayer protocols implemented in half-duplex are needed for full-duplex operation. Basically, a full-duplex capable device can receive and transmit signals over the aforementioned communication media line at the aforementioned fourth dimension. Thus, the throughput in a total-duplex LAN is double that of a one-half-duplex arrangement.

The manual medium in a full-duplex system must besides exist capable of supporting simultaneous reception and transmission without interference. For example, 10Base-v, 10Base-2, 10Base-FX, etc., are cables that do not support full-duplex, while 10/100/1000Base-T, 100Base-FX, etc., meet full-duplex media specification requirements.

Total-duplex operation in a LAN is restricted to connecting just two devices, and both devices must be capable and configured for full duplex operation. While it is restricting to only allow bespeak to betoken links, the efficiency of the link in a full-duplex system is actually improved. Having simply two devices eliminates the potential for collisions, and eliminates any need for the CDMA/CD algorithms implemented in a one-half-duplex capable device. Thus, while the reception algorithm is the aforementioned for both full and half duplex, Figure 8-39 flowcharts the high-level functions of full-duplex in transmission fashion.

Now that you take a definition of all components (hardware and software) that make up an Ethernet system, let'south take a await at how architecture-specific Ethernet components are implemented via software on various reference platforms.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978012382196600008X

WBAN: Driving e-healthcare Beyond Telemedicine to Remote Health Monitoring

Pijush Kanti Dutta Pramanik , ... Gaurav Pareek , in Telemedicine Technologies, 2019

6.six.1 PSMA-based MAC

The PSMA-based MAC protocol is based on Preamble Sense Multiple Access (PSMA) [86] medium admission mechanism where a preamble sequence is appended at the starting of a information parcel sent by a sensor node to indicate a busy channel status [57]. For WBAN with a large number of sensors, as the written report [87] suggests, PSMA-based MAC protocol has an edge in terms of throughput and energy efficiency in comparison to slotted ALOHA based IEEE 802.15.4a standard. But the PSMA-based protocols face a problem with the possibility of collision when multiple sensor nodes perform preamble sense simultaneously [57].

Read full affiliate

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128169483000076

Data Communication and Networking

M.L.S. Sharma , in Overview of Industrial Procedure Automation (2nd Edition), 2017

16.v.three.2.1 Media Access Control

This sublayer, which depends on a physical layer, is a procedure controlled by the sender, in which several devices (on multidrop or passenger vehicle networks) compete to gain admission to the medium for data transfer. This sublayer decides, among competing devices, on who should gain the admission to the media and ship information. All devices on the charabanc proceeds admission to the medium in some specified club. The MAC procedure can be deterministic, in which all devices gain admission to the medium without neglect, or nondeterministic, in which there is a possibility that the device(south) will non be able to gain access to the medium within a reasonable time. The receiver has no function in this sublayer irrespective of the network topology.

Fig. 16.12 illustrates some commonly used MAC procedures.

Popular MAC procedures are:

•: Master–slave: Here, the main controls the bus and polls each slave sequentially to receive information or ship data. The polling is cyclic, meaning the master starts polling slave 1 and continues until all slaves are polled, ensuring all slaves get the chance to gain access to the medium for information transfer before returning to slave i. This is a deterministic process because all slaves are served by the master. Slave-to-slave communication is via the primary simply. Slaves tin can exist polled based on their physical or logical address. This procedure is as well chosen polling.
•: Carrier sense, multiple access/collision detection: Here, all devices accept equal right to gain access to the medium whenever they want. The competing device, before attempting data transfer, checks whether the bus is complimentary. If the omnibus is gratuitous, the device takes control of the double-decker and proceeds with data transfer to other device(s). If the bus is not costless, the device drops out and tries after some random time. If more than one device simultaneously competes for the jitney, a standoff takes place. Sensing the collision, competing devices drop out and each will try independently later on some random interval. This process goes on until one of the competing devices gains access to the double-decker. This is a nondeterministic procedure because there is the probability that a device may not proceeds access to the media at all within a reasonable time. The fewer devices there are on the autobus, the better the success rate will be.
•: Token passing: Here, a device on the network property the token becomes the bus master, transfers the data, and passes the token on to the next device in sequence, later on completing the data transfer. This sequence goes on until all of the devices are served and the cycle repeats. This is a deterministic procedure because all of the devices have the take a chance to become the jitney master one time during each cycle. The sequence tin can exist either physical (token ring) or logical (token bus). This procedure is also known as a round robin.
•: Fourth dimension segmentation multiple admission: Hither, each device becomes the bus primary for a fixed time to conduct data transfer and the command goes to the next device in sequence after a stock-still duration whether or not data transfer is completed. This sequence goes on until all devices are serviced and the wheel repeats. This is also a deterministic process because all devices are served fifty-fifty though the devices may complete data transfer in more than i wheel.

There are many derivatives and variations to these methods to suit different applications.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128053546000165

Radio channel access challenges in LoRa low-ability broad-expanse networks

Congduc Pham , ... Muhammad Ehsan , in LPWAN Technologies for IoT and M2M Applications, 2020

4.5.ii LoRa PHY/media control access integration in CupCarbon

Information from the MAC layer to the PHY layer are provided by the user from SenScript program. Then, a radio technology can be assigned: IEEE 802.xi or IEEE 802.fifteen.4 or LoRa. Fig. 4–31 shows the block diagram of the whole procedure. With LoRa, the user must also assign the spreading cistron SF between vii and 12. The receiver technique should also be mentioned. By default, the receiver technique is none and the receiver volition work unremarkably without because CE or successive interference cancellation. Default LoRa setting also uses the bones ALOHA approach and a node transmits a packet equally soon as it has data to send. Equally described previously, ALOHA limits the arrangement performance as information technology can only requite 18.39% of maximum efficiency. Nevertheless, CE and SIC can exist used to enhance the organisation performance. More elaborated aqueduct access methods such as the CSMA variants described in Section iv can also exist selected.

Fig. 4–32 shows the CupCarbon environment for the assignment of the parameters in case of selecting LoRa advice protocol. Information technology shows interconnected sensor nodes placed arbitrarily. All the nodes are assigned the LoRa protocol. Nodes should exist in the radio range of each other to communicate. The LoRa gateway can be defined as one of the nodes.

For the transmission, outset the transmitter generates an upchirp signal using the input SF. By default the $C R$ , SF, and $B Westward$ values are considered to be 0, 8, and 125 kHz, respectively. And then, there are interleaving and modulation operations. Afterward applying the transmission functions, the system calculates the parameters of the selected interference model, the Gaussian model, or the $α$ -stable model, and applies the interference model to the transmitted signal. The receiver generates a downchirp signal using the appropriate SF and performs the demodulation.

Read total affiliate

URL:

https://world wide web.sciencedirect.com/science/article/pii/B9780128188804000041

Networking Sensors

Feng Zhao , Leonidas J. Guibas , in Wireless Sensor Networks, 2004

3.2.2 IEEE 802.15.4 Standard and ZigBee

The IEEE 802.15.4 standard defines both the physical and MAC-layer protocols for most remote monitoring and control, also as sensor network applications. ZigBee is an industry consortium with the goal of promoting the IEEE 802.15.4 standard. ZigBee ensures interoperability past defining higher network layers and application interfaces. The low-cost, depression-power features of 802.15.4 are intended to enable the broad-based deployment of wireless networks able to run for years on standard batteries, for a typical monitoring application. It is optimized for low information throughput (up to 115.2 Kb/s), with simple or no QoS support. Both star or peer-to-peer network topologies are supported. Unlike S-MAC, 802.15.4 achieves its power efficiency from both the physical and MAC layers. The duty bike of communications in an 802.15.iv network is expected to be only around 1 percent, resulting in very depression boilerplate ability consumption. Even so, it is besides up to the higher protocol layers to observe the low duty bicycle requirement.

Figure 3.one shows the landscape of different wireless technologies.

Read full affiliate

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9781558609143500031

QoS in Wireless Networks

XiPeng Xiao , in Technical, Commercial and Regulatory Challenges of QoS, 2008

QoS capabilities enabled past 802.11e

The IEEE 802.11e standard is an enhancement to the MAC sublayer to add QoS functionality to Wi-Fi networks. It does so by adding support for:

•: Prioritizing data packets based on their type.
•: Assuasive user/finish stations to communicate their QoS requirements to the access indicate.
•: Supporting access control.

These basically address the QoS limitations of the 802.11a/b/thou.

In IEEE 802.11e, a new MAC layer access technique chosen the Hybrid Coordination Function (HCF) is introduced. It replaces the DCF access technique of 802.11a/b/1000 technologies. The HCF has ii access methods:

•: Enhanced Distributed Channel Access (EDCA), a contention-based mechanism useful for giving QoS to data traffic.
•: HCF Controlled Channel Access (HCCA), a polling-based mechanism useful for giving QoS to vox and video traffic.

A central feature of the HCF is the notion of a Transmission Opportunity (TXOP), which represents the time duration during which a station is allowed to transmit a burst of information frames.

Read total chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9780123736932000136

Ethernet

William Buchanan BSc (Hons), CEng, PhD , in Computer Busses, 2000

26.5.1 Media access control (MAC)

The CSMA/CD part is implemented in the MAC layer. The functions of the MAC layers are:

•: When sending frames – receive frames from LLC; control whether the information fills the LLC information field, if not add redundant $.25; make the number of bytes an integer, and calculate the FCS; add the preamble, SFD and address fields to the frame; send the frame to the PLS in a serial bit stream.
•: When receiving frames – receive one frame at a time from the PLS in a series scrap stream; bank check whether the destination accost is the same as the local node; ensure the frame contains an integer number of bytes and the FCS is correct; remove the preamble, SFD, accost fields, FCS and remove redundant $.25 from the LLC data field; send the data to the LLC.
•: Avert collisions when transmitting frames and keep the right altitude betwixt frames by not sending when another node is sending; when the medium is free, expect a specified flow before starting to transmit.
•: Handle any standoff that appears by sending a jam signal; generate a random number and back off from sending during that random time.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780340740767500262