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You're paying a premium for the super-slimline design, but this latest version of the MacBook Air provides much improved performance and battery life that will ensure that it earns its keep when you're travelling. Its sleek, metallic design leaves most of its rivals in the ultra-portable laptop category looking like misshapen lumps of plastic. The previous MacBook Air was most comfortable browsing and playing video, but Apple is positioning the model as more of an all-round machine.

We ran Geekbench on our test unit, an entry-level As such, no need for the usual MacBook Pro, right? The obvious device of choice to take on the road is the iPad. Leave it to Apple to make you feel fat. The Downsized from the The MacBook Air is a gold-standard laptop for demanding users seeking a powerful travel companion or others who want the media punch of iLife. MacBooks are subject to a lot of debate.

There are those who think they're amazing with pricing in line with a finish of real quality. The MacBook Air It also gives higher battery life. Of the two Macbook Airs out in , we see this The first MacBook Air will go down in history as one of the most divisive pieces of tech ever created. Either a triumph of design and simplicity or an overpriced, feature-bereft lump depending on your point of view, it split the tech world straight down the middle.

The inch Apple MacBook Air is expensive and in many ways restrictive, but a stunning design, great battery life and brilliant ease of use mean this laptop is more than style over substance. While the inch model will be most attractive if you're looking for the smallest and lightest Mac laptop, those who want to upgrade its drive, processor, and RAM will want to consider its small size versus the slightly larger inch model, which comes equipped with a better set of specs. This light laptop is so slender, in fact, that you may feel like you're carrying a folder rather than a notebook. And even though the MacBook Air may be sliver-thin, it isn't flimsy or underpowered.

The inch MacBook Air's powerful performance, sleek beauty, and decent screen size make it a powerful travel companion for on-the-go users. Processeur bas voltage de la gamme Penryn 3M avec toutes les fonctions Penryn comme Virtualization et Trusted Execution. Benq A82 sur Ciao. Today's thinnest notebook is small enough to fit into an envelope and pleases by its decent design and the high-quality materials used. This review describes, whether this bundle is able to convince despite its minimum interface equipment. Dernier point et non des moindres, son look reste toujours aussi attirant.

Apple still only supplies a single USB port and a non-swappable battery. And of course the optical drive is external and must be purchased separately. The net result is still a system that you will either love a lot or find lacking. That's hardly surprising; I'm entirely sure Apple knew full well it was over-priced, under-featured and would nonetheless sell simply on the basis of it's being, first, a new Apple product and, second, an awesome thing to behold.

Nobody in their right mind would buy one as their sole mode of transport. But you just know that if you could afford one you couldn't help but be very tempted, no matter how ludicrous a purchase it is. It comes with Mac OS X already installed, offering a virus-free and reliable platform for business or home.

The MacBook Air is by no means perfect. Its performance and connectivity options are both more limited than those of conventional but heavier laptops. However, it does perform well when compared to other ultra-portable PCs in the same price bracket. Ultimately, the real clincher for us is the weight, or lack thereof. Instead of leaving it in the office — as we tend to do with our older, heavier White MacBook — undoubtedly, we'd be carrying the MacBook Air around with us and using it, pretty much all of the time.

Although Wi-Fi is still its main means of connecting to networks or the internet, you now get a USB Ethernet adaptor in the box, should you need a wired connection. Trading power for portability and connectivity for convenience means the MacBook Air will never be a machine for everyone, but improved specs at a lower price can only be welcomed.

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It's hobbled by having only a single USB port. There's no FireWire, no optical drive and the only way to connect to an ethernet network is via an included USB adapter. But if the specs that matter most to you are light weight and small size, the MacBook Air is ideal.

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These new models aren't much faster than their predecessors - the high-end system is actually slower than the previous model - but they're cheaper. These new models aren't much faster than their predecessors according to Macworld's findings --in fact, the high-end system is slower than the previous model--but they're cheaper. Unfortunately, we can't give a final score just yet--we're still waiting on PC WorldBench 6 test results--but if the MacBook Air always appealed to you, except for the price tag, it's time to reconsider the Air.

At that point, no one knew what features it had, what parts it ran, or even its price—just that, suddenly, the Air was a must-have. Yet the limitations that came to light after the Air's announcement tarnished its luster. After all, it was the only laptop in its class with a single USB port and a non-removable battery, and many features found in other laptops were absent.

One only assumed that better things were yet to come. The improved graphics performance does make it feel a lot smoother and more responsive than before. Yet, for all its limitations, the sheer quality of the design shines through. Being able to balance the laptop lightly in the palm of one hand, or to simply snap the lid shut and pick it up the way you would with an ordinary A4 notepad really does make it enormously convenient and comfortable to use - and we did not, as one of our esteemed colleagues suggests, feel like a tit while doing so. Aesthetically, the two generations are virtually the same; technologically, the new one offers a speed boost and better storage options at a better price than when the Air debuted.

Having said that, if you don't think you need the ultimate in thinness and style - and to my eye, this really is the ultimate in the looks department - do yourself a favour and check out the new MacBook while you're comparison-shopping. Sure, it's chunkier - compared with the Air, just about everything is - and heavier at 4.

But it's faster, offers more storage and is more expandable. Oh, and it's cheaper. If you are in the market for an all-round light-weight notebook then the Macbook Air is one of the most portable and visually appealing notebooks on the market. Otherwise you may want to consider the MacBook, which is significantly cheaper and provides high performance computing, better connectivity and ample storage. The Air is the best looking MacBook ever, and as far as I'm concerned, one of the best looking notebooks in general. Apple designed it with fashion-minded people in mind and it did a marvelous job.

The good looks come at a price, but many people will be more than happy to sacrifice USBs, Ethernet and an optical drive to enjoy Apple's latest toy. So, what are the drawbacks? Lack of ports springs to mind first. No Ethernet? Some people won't really mind, but others will. Across the internet we've seen similar reactions, with some users embracing the product despite its compromises, and others attacking it as a product with no purpose other than to part fools from their money.

Not wishing to sound like a broken record, but how you see the Air has a lot to do with your priorities. For some, the Air's lack of a swappable battery and its underpowered processor make it a terrible value proposition — like paying for black on a MacBook. We take the point, but have to disagree. For us, the value of dropping down a kilo in weight will make all the difference when on the move.

This may work for an MP3 player, which isn't critical to your work, however, for a machine to be used for business, can you really afford to send it back to Apple when it needs updating? In field tests, where we actually took the MacBook Air out and used it until the battery died, we found it lasted for minutes, which is fine for the morning commute, but isn't going to see you through a day's work. When connected to a wireless network, this dropped to minutes to reflect the chipsets further power drain.

The Apple MacBook Air is a fantastic looking laptop and a joy to use, but there are simply too many sacrifices. Of course it's not going to be the laptop to suit everyone - you can buy cheaper or more capable Macs and PCs - so it's not a must have for the price-conscious buyer or the power-hungry. It's pricey, but with the exception of the tiny, basic Eee, the Air's no more expensive than other slim'n'light laptops. If form-factor is your prime concern, then the Air provides a good computing experience, and if our time with it is anything to go by, its port and optical disc limitations proved no handicap at all.

Again, if you think they're going to be, there are plenty of other laptops out there that'll meet your needs instead. Of course, if you want to run Mac OS X on a thin'n'light machine, this is really your only option. But the exclusion of an optical disc drive, limitations of Remote Disc, and lack of a user-replaceable battery, are shortcomings that will be difficult to ignore for most notebook users.

We also find the Air more suited as a secondary device to a desktop machine because it depends so much on having another computer through which to install new applications. Despite that, we feel it represents a step in the right direction towards making notebooks more portable. It has decent performance for an ultraportable, but few standout features to speak of beyond the superficial. And yet, I still can't help wanting to stop and touch it. It has undeniable appeal, and even us lifelong PC users were not only impressed with its performance and usability but felt drawn to it like we are to our iPhone.

Its a bit lacking in features and performance and for version 2 of Air does that sound weird? A faster hard drive would be nice too but I'm sure that SSDs will decease in price. Also, CPU speeds keep going up so that wont be an issue. Yes, I might be asking too much but I am a demanding user. And from that prespective, the Air is not for everyone- especially as their primary computer.

I feel that its a steup-up from MacBook so if thats what you're eyeing at or want to upgrade from a PowerPC based notebook, then you'll be more than happy with Air. However, if you're a Mac Pro or MacBook Pro type of person, you'll still fall in love at first sight but probably get over the honeymoon within two weeks time and start craving for more. Either you will love it or you will hate it. Design wise it is a beatuiful system that is extremely small and light. The problem is that it lacks a number of standard laptop features that it is very hard to really recommend it to anyone as their sole system.

It is really best used as a business travel system in conjunction with another primary PC. You have to admire Apple's enthusiasm and the MacBook Air is a great design statement but as a practical machine it simply doesn't match anything released by Sony. If you like style over content then you'll be happy, but we feel there are simply too many sacrifices in the MacBook Air to make it a compelling purchase.

Sony does win on weight as its Vaio TZ weighs just 1. However, the Macbook Air has a bigger screen — The ultra-portable design is impressive, but comes at a cost in terms of limited performance and connectivity. On one hand they offer a super thin, lightweight design, but on the other they take away ports and give you a permanent battery. This notebook also suffers from some early release driver quirks, but those should hopefully be resolved in the near future.

Overall I think this is a promising notebook that should force some other manufacturers to wake up and design some lighter and slimmer full-size notebooks. Road warriors who demand long battery life or a better selection of ports should pass, but this work of art is worth considering for corridor warriors who attend lots of meetings, as well as for commuters who do a fair amount of work while traveling to and from the office.

You get an easy-to-use, secure, and fun operating system wrapped in the sexiest, thinnest package money can buy. The answer seems to be no. I experienced only moderate gains in battery life and not very noticeable speed differences. The one major benefit of the SSD model is that it doesn't cause the same types of slowdowns as the HDD model during times of high disk activity, and that's certainly a huge plus.

Speedy read times are great, too, but they are balanced out by pokey write times. Still, even if it's more usable, it's hard to justify the huge price difference for the SSD model. For anyone else looking to buy an Air, the HDD model appears to provide the most bang for the buck. Judged merely on the cold technological specifications, the MacBook Air can't measure up to Apple's other laptops.

For those to whom the tech specs matter above all else, the MacBook Air can't be seen as much more than an overpriced, underpowered toy. But there will be those who, small drive and slow processor be damned, will adopt the MacBook Air as their primary laptop - simply because they want that laptop to be as small as possible. For those who factor size, weight, and — yes, we'll admit it — style into the equation, the MacBook Air begins to make more sense.

While the Apple MacBook Air is an impressive design with some innovative features, the number of sacrifices that had to be made in order to create this ultra-thin notebook severely limits this laptop. The lack of ports, low-capacity slow hard drive, and slow overall performance make the MacBook Air the weakest performing MacBook we've seen in the last few years. Sure, you can fit the MacBook Air in a manila envelope Stay tuned for our full review of the MacBook Air in a few days.

Mimicking the inch silhouette of the current MacBook line, it's only 0.


The design is revolutionary, but Apple's MacBook Air will appeal to a smaller, more specialized audience than the standard MacBook, thanks to a stripped-down set of connections and features. After getting some hands-on time with the MacBook Air at Macworld Expo, we've got some first impressions. At the risk of sounding obvious, the MacBook Air is incredibly light and tiny. Initial impressions of the MacBook Air are almost overwhelmingly positive.

It's incredibly light and tiny, and has all the features we've come to expect from the MacBook line. But there's no optical drive and the hard drive isn't the biggest. For those who pre-ordered already and were sold as soon as Jobs whipped out the manila folder, the MacBook Air is hands down the thinnest and prettiest laptop in the market. The MacBook Air is officially the thinnest laptop, and the lightest of those with a inch screen. But there were compromises that had to be made.

Up close and personal it's very impressive and makes our 6-month old MacBook Pro look like someone from Fat Camp. So why aren't we getting all excited about it as much as we should? Well for us it comes down to that non-replaceable battery. What's the point of having a portable device if you have to be within 5 hours of a power supply. Granted 5 hours is a long time and Apple suggest that if you opt for the SSD option you'll get even longer, but the inability to be able to replace the battery on the fly is a deal breaker for us.

It might be fine when you first get it out of the box, but what happens in 2 years time when you've got to take it back to Apple because the battery is giving you below par performance? Ist weniger mehr? All you need is the Air? Le Oui et non. At least, that's what Apple seems to think, judging by the new MacBook Air. It's so thin you could use it to shave.


In fact, the inch version is the most portable laptop we've ever encountered, even taking netbooks into account. The inch Apple MacBook Air is remarkably thin and really enjoyable to use. It is, in a word, spectacular. The laptop is thinner and lighter than any netbook on the market but provides superior performance. Compared to other ultraportables, it does sacrifice performance, storage and running time to provide its ultrathin profile. While we wouldn't recommend the Air to enthusiasts, it can do a perfectly good job with home movies.

It is gorgeous to look at, has an excellent build quality and is extremely portable, along with being extremely snappy. Had the keyboard featured a backlight, I would have ordered it on the day it was launched but even without that, I am still very tempted to get it as my primary machine. A perfect carry-anywhere notebook? Elsewhere, we have to give due credit. If you need more power than the MacBook Air in an All that competition though and the MacBook Air still reigns as the most drool worthy and well constructed of all these in the inch laptop category.

The aluminum unicast body is extremely solid feeling and the feather light weight just amazing. The screen on the MacBook Air 11 also stands out against any of the competition. In conclusion, I do recommend the MacBook Air Apple claims that the MacBook Air's battery life is five hours; it lasted 4 hours and 27 minutes in our battery rundown test, where we looped an XviD file in full screen mode. Macbook Air Especially when you consider you can get a MacBook with a hour battery, more storage and a 2. The Macbook Air Its brushed aluminium shell is not subject to scratches.

Note however that if size is not a decisive factor in your choice, the MacBook Pro offers better battery life and much better performance. This is not a netbook. MacBook Air As a lover of small, slim, lightweight computers, I sure am. The problem is that, since performance is inevitably limited by form-factor in this and all similar sized machines, it's not going to be radically better than my year-old Acer Aspire Timeline TZ, which, incidentally, can deliver 50 per cent more battery life than the Air and has Gigabit Ethernet, a third USB port and a SD card slot. But it's also heavier and considerably thicker.

And it runs Windows 7. I could hackintosh it, but those who have report that not all the parts work under Mac OS X, in particular the Wi-Fi and sleep mode, two features I rely on. And as anyone who, like me, has dropped an Air before, that aluminium casing can't half take some punishment. The inch MacBook Air is a powerful ultraportable that makes other systems in its class look positively bloated.

More important, this machine never keeps you waiting, thanks to the way it uses flash memory. We just wish the hinge for the display were a bit tighter to prevent unwanted movement. But if you want the thinnest, lightest Mac experience ever, this Air will leave you elated. MacBook Air Source: enet. La nouvelle version du MacBook Air 13 pouces est sortie, mais encore avec son vieux processeur Core 2 Duo. The system is still extremely portable but doesn't sacrifice as much performance, battery life or storage space. It still has its downsides such as not being upgradeable after purchase but it is so hard to really fault Apple on these when there is no other ultrathin laptop to compare with it.

The screen is bright enough that even with sun shining through the window it was viewable despite being a glossy screen. The keyboard is comfortable enough to type even in a bumpy car. The size is perfect for pulling the computer out of the bag even in cramped spaces.

The weight and thickness make carrying the MacBook Air in a bag, with every possible accessory I could possibly need, lighter than my previous monster of a laptop. It has enough power to charge an iPad and other accessories over USB overnight. Sure, but if you need even more power there's always the 13" MacBook Pro.

If you're okay with the simple elegance that the new Macbook Air 13 is designed to deliver, with perhaps a few of the inherent limitations that come within its sleek packaging, you'll have a tough time finding a nicer inch thin and light notebook. The MacBook does deliver, but the accent on thinness does mean sacrifices, like the so-so keyboard, and lack of wired LAN adaptor. Read our review to find out. If you need something that offers a bit more power and a smidge better resolution, go for the inch form factor. This makes it a sizeable investment, but one you're unlikely to regret — the build quality is phenomenal and the components top-notch.

The new Core i5 processor and 4GB of memory are a marked improvement in performance over the past model. Add to this the inclusion of the backlit keyboard and Thunderbolt port and it has become even more functional. Over the previous generations it offers a better processor, a backlit keyboard and a Thunderbolt connector, while leaving everything that made its predecessors so attractive intact. It's still not cheap, but it has gained that vital bit of credibility as a worthwhile premium laptop solution, and is now worth its asking price.

For many, PCs costing half the price offer a better, more sensible solution, but the MacBook Air remains king of the ultraportable brigade. It is thanks to Apple, who persevered in the direction in which they think they should, that we are able to get the MacBook Air today. At the time, we were impressed by the performance of the Air, considering its absurdly thin size.

Now the qualifier to that statement can be removed. The second-gen Intel Core i5 in the new model provides performance that is almost indistinguishable from a larger laptop. Note however that a richer connectivity wouldn't go amiss as there still aren't very many thunderbolt compatible peripherals out there.

Apple claims that the MacBook Air's battery life is "up to seven" hours; it lasted almost six hours in our battery rundown test, where we looped an XviD file in full screen mode. Now that we've posted performance reports for the standard-configuration MacBook Airs, it was time to turn our attention to testing the optional, build-to-order BTO configurations of Apple's latest line of ultra-portable computers.

Its combination of lightning speed, slim profile and the gesture-tastic Mac OS X Lion mean it melds the benefits of tablets portability, usability with the power of traditional laptops. And, to top it all, it's an incredibly lovely thing. We recommend adopting one as soon as financially possible. But with more than enough processing grunt for both work and leisure, decent battery life, and exemplary ergonomics and design out of the box, the MacBook Air 13in is - by the silver skin on its tiny behind - the most desirable executive laptop on the market, bar none.

There's still no dethroning the MacBook Pro although the inch model clearly needs a higher resolution display option , but for the rest of the world there are now some excellent ultra portable options that don't force you to really compromise on performance. If you don't need that extra oomph, a MacBook Air is one of the very finest laptops on the market.

A real statement and pretty handy at every common task. But you're digging pretty deep for the pleasure of owning one. But enough about us, is the new MacBook Air still the best ultraportable laptop you can buy? Alan Lu takes a closer look in our review. Battery life is excellent, instant-resume from standby is a joy and the SSD drive means no moving parts and better speed, and it comes with the impressive new Mac OS X Lion.

It's still light on ports, the missing SD slot on the inch model is a drag, and no, it isn't cheap, but this machine is fast, efficient, and not to be underestimated. It's a supermodel with a law degree from Columbia, a hunky motorcycle racer who looks good in leathers yet is also a concert pianist -- whatever your passion it won't disappoint, all while making a lot more room in your bag.

We for one will be going out to buy one once our review model goes back, and you can't get better praise than that. The latest version of the inch MacBook Air vastly outperforms its predecessor, and can finally be called suitable for mainstream use, instead of relegated as a niche product. Some were charmed by the machine's razor-thin design and light weight.

Apple's new inch MacBook Air offers the same super-slim and sturdy design as its predecessor, but packs in a more powerful processor. It's a fantastic choice for the super-wealthy traveller. In Altogether, the MacBook Air remains our ultraportable of choice. Putting in the Core i5 processor, upping the standard memory configuration to 4GB, and having a new graphics subsystem translate into a significant performance improvement over the previous Air inch.

That and adding a Thunderbolt port, bringing back the backlit keyboard, and the timely release of Mac OS X Lion will surely make it a formidable player in the ultraportable space. When you combine a sleek ultraportable design with a great display and touchpad then nearly double the performance--without sacrificing battery life--you're left with a winner.

Add it all up and you have a machine that not only earns our Editors' Choice award but also a very rare five-star rating. On the outside, it looks almost entirely identical to the late MacBook Air iteration, which was released in October Intel's next-gen processors put the latest Air on performance overdrive. It's one of the most powerful—and beautiful—ultraportables available. But what it lacks in these respects it makes up for in build quality — especially when it comes to the screen — and for giving you the option to have a machine running both Windows 7 and Mac OS X.

It was too slow and an example of form over function. With the refresh, Apple has managed to keep the remarkable form, but also add some internals that make this more than just a rich person's plaything. Now, the Air is an excellent day-to-day laptop, and one that we think most people will find more than adequate for their needs. Unless those needs are crunching the data that comes out of the CERN supercollider. If nothing else, Intel's Ultrabook specification proves that Apple had the right idea when it first launched the Air.

There is demand for these small laptops, and it's possible to build them and make them objects of desire while remaining useful. Add to that the fact that Air's performance statistics trounce those of even some mainstream laptops, makes the option of buying this Mac unit all the more attractive. While the update has brought some marked improvement in performance, it doesn't address enough of the other issues to make it a great replacement for the MacBook Pro. It certainly is extremely small and light but this is not a great primary computer due to the memory and storage concerns.

The laptop is definitely the better option for productivity on the move, and can be used in an office because it has excellent specifications. Those who just want to browse the internet on the move would be better suited to the iPad 2. We recommend buying a Wi-Fi-only iPad 2 and using the extra money to invest in a mobile phone contract with a generous data allowance. The tablet can be tethered to the smartphone when Wi-Fi is not available, and this will save on having to pay two separate contracts.

Given the choice, V3 definitely opts for the laptop over the tablet, as it is so much more useful and is definitely worth the extra investment. The inclusion of the latest version of the operating system, OS X Lion, is the most important change, and it worked well on the Macbook Air. This is an excellent but expensive laptop, but it is a pleasure to use and looks great. If you want your Air as a convenient portable Mac to supplement to your main machine, you might be better off with an entry-level model. This ultraportable laptop continues to get more powerful but Apple hasn't redesigned the cooling system to cope with this.

Plus, the connectivity is still just as lite. Alan Lu finds out in our review. Nonetheless, it is far from a frivolous purchase. The model performance is found analytically extending previous work on this matter. The results show that a better organization of resources is achieved through this scheme. Full Text Available Low power MAC protocols have received a lot of consideration in the last few years because of their influence on the lifetime of wireless sensor networks.

Since, sensors typically operate on batteries, replacement of which is often difficult. A lot of work has been done to minimize the energy expenditure and prolong the sensor lifetime through energy efficient designs, across layers. Meanwhile, the sensor network should be able to maintain a certain throughput in order to fulfill the QoS requirements of the end user, and to ensure the constancy of the network. A new protocol is suggested to improve the energy efficiency, latency and throughput of existing MAC protocol for WSNs.

A modification of the protocol is then proposed to eliminate the need for some nodes to stay awake longer than the other nodes which improves the energy efficiency, latency and throughput and hence increases the life span of a wireless sensor network. Mac protocols for cyber-physical systems. This book provides a literature review of various wireless MAC protocols and techniques for achieving real-time and reliable communications in the context of cyber-physical systems CPS.

The evaluation analysis of IEEE This book wil. Mac protocols for wireless sensor network wsn : a comparative study. Data communication between nodes is carried out under Medium Access Control MAC protocol which is defined at data link layer. The design of a MAC protocol should also address the issues of energy efficiency and transmission efficiency. These nine protocols are classified in contention based and hybrid combination of contention and schedule based MAC protocols. The goal of this comparative study is to provide a basis for MAC protocols and to highlight different mechanisms used with respect to parameters for the evaluation of energy and transmission efficiency in WSN.

This study also aims to give reader a better understanding of the concepts, processes and flow of information used in these MAC protocols for WSN. A comparison with respect to energy reservation scheme, idle listening avoidance, latency, fairness, data synchronization, and throughput maximization has been presented. From the analysis of contention based MAC protocols in term of energy consumption, it was being observed that protocols based on preamble sampling consume lesser energy than protocols based on static or dynamic sleep schedule.

In this paper, we propose the efficient reliable multicast MAC protocol by which the AP Access Point can transmit reliably its multicast data frames to the recipients in the AP's one-hop or two-hop transmission range. The AP uses the STAs Stations that are directly associated with itself as the relays for the data delivery to the remote recipients that cannot be reached directly from itself. Based on the connectivity information among the recipients, the reliable multicast MAC protocol optimizes the number of the RAK Request for ACK frame transmissions in a reasonable computational time.

The IEEE In this research work, some restrictions of this standard are explained and an improvement of traffic efficiency by optimizing MAC layer is proposed. Implementation details for several blocks of communication system are carefully modeled. The protocol implementation is done using VHDL language. The analysis gives a full understanding of the behavior of the MAC protocol with regard to backoff delay, data loss probability, congestion probability, slot effectiveness, and traffic distribution for terminals.

Primarily, we dynamically adjust the backoff exponent BE according to queue level of each node. Secondly, we vary the number of consecutive clear channel assessment CCA for packet transmission. We demonstrate also that slot compensation provided by the enhanced MAC protocol can greatly avoid unused slots. The results show the significant improvements expected by our approach among the IEEE Synthesis results show also hardware performances of our proposed architecture.

Full Text Available We propose the efficient reliable multicast MAC protocol based on the connectivity information among the recipients. Nevertheless, they do not support a differentiated quality of service QoS for the various forms of traffic coexisting in a WBAN. Further, multiple channels are effectively utilized to reduce access delays in a WBAN, in the presence of coexisting systems. WBANs applications consist of heterogeneous and dynamic traffic loads. First, we have categorized them based on their goals, methods, and metrics of evaluation.

Furthermore, a comparative analysis of the protocols is made and their performances are analyzed in terms of delay, packet delivery ratio PDR, and energy consumption. This review work, therefore, could add enhancement to traffic adaptive MAC protocols and will stimulate a better way of solving the traffic adaptivity problem.

A closed formulation of the distributed cooperative ARQ average packet transmission delay in a saturated network is derived in the paper. The analytical equations are then used to evaluate the performance of the protocol under different network configurations. Both the accuracy of the analysis and the performance evaluation of the protocol are supported and validated through computer simulations. The key benefits of directional antennas over omni-directional antennas are longer communication range, less multipath interference, more spatial reuse, more secure communications, higher throughput and reduced latency.

These classes of directional MAC protocols presented in this survey paper include single-channel, multi-channel, cooperative and cognitive directional MACs. A network architecture for precision formation flying using the IEEE Precision Formation Flying missions involve the tracking and maintenance of spacecraft in a desired geometric formation. The strong coupling of spacecraft in formation flying control requires inter-spacecraft communication to exchange information.

In this paper, we present a network architecture that supports PFF control, from the initial random deployment phase to the final formation. IEEE We show that DCF is suitable for the initial deployment phase while switching to PCF when the spacecraft are in formation improves jitter and throughput. We also consider the effect of routing on protocol performance and suggest when it is profitable to turn off route discovery to achieve better network performance.

It also realizes station-based dynamic resource selection Design of an autonomous decentralized MAC protocol for wireless sensor networks. In this document the design of a MAC protocol for wireless sensor networks is discussed. The MAC protocol is an ongoing research. Earlier sensor network MAC protocols focus on energy conservation in low-duty cycle applications, while some recent applications involve real-time high-data-rate signals.

This motivates us to design an innovative localized TDMA MAC protocol to achieve high throughput and low congestion in data collection sensor networks, besides energy conservation. Tree MAC divides a time cycle into frames and frame into slots. Parent determines children's frame assigmnent based on their relative bandwidth demand, and each node calculates its own slot assignment based on its hop-count to the sink.

This innovative 2-dimensional frame-slot assignment algorithm has the following nice theory properties. Firstly, given any node, at any time slot, there is at most one active sender in its neighborhood includ ing itself. Secondly, the packet scheduling with Treel MAC is bufferless, which therefore minimizes the probability of network congestion. The protocol has priority to access high-quality channels for reducing energy consumption of each transmission. It can also balance the energy consumption among cooperative nodes by using high residual energy nodes instead of excessively consuming some node's energy.

Full Text Available Battery energy limitation has become a performance bottleneck for mobile ad hoc networks. However, it was developed without considering energy efficiency. To solve this problem, many modifications on IEEE However, these schemes may degrade network throughput and reduce the overall energy efficiency of the network.

In this paper, the performance of APCMP protocol is evaluated by simulation and is compared with that of other protocols. In order to support applications requiring dedicated bandwidth or bounded delay, it provides a reservation-based scheme named Guaranteed Time Slot GTS.

However, the GTS scheme presents some drawbacks, such as inefficient bandwidth utilization and support to a maximum of only seven devices. This MAC protocol builds on top of LPRT Low Power Real Time and includes various mechanisms designed to increase data transmission reliability against channel errors, improve bandwidth utilization and increase the number of supported devices. A motion capture system based on inertial and magnetic sensors has been used to validate the protocol.

The effectiveness of the performance enhancements introduced by each of the new features is demonstrated through the provision of both simulation and experimental results. Wireless Mesh Networks WMNs have emerged to meet a need for a self-organized and self-configured multi-hop wireless network infrastructure. Low cost infrastructure and ease of deployment have made WMNs an attractive technology for last mile access.

However, With backlogged TCP traffic, nodes which are two or more hops away from the gateway are subject to starvation, while the one-hop away node saturates the channel with its own local traffic. We propose a Markov chain to capture the behavior of TCP sessions, particularly the impact on network throughput performance due to the effect of queue utilization and packet relaying. A closed form solution is derived to numerically derive the throughput. Based on the developed model, we propose a distributed MAC protocol called Timestamp-ordered MAC TMAC , aiming to alleviate the unfairness problem in WMNs via a manipulative per-node scheduling mechanism which takes advantage of the age of each packet as a priority metric.

Simulation is conducted to validate our model and to illustrate the fairness characteristics of TMAC. Our theoretical and empirical findings can be used in future research to develop more fairness-aware protocols for WMNs. Full Text Available Cooperative communication techniques have recently enabled wireless technologies to overcome their challenges. The main objective of these techniques is to improve resource allocation. This technique improves network resource allocation by exploiting the potential capacity of all relay candidates.

Simulation results demonstrate that the FC- MAC protocol presents better performance in terms of throughput, fairness, and network lifetime. The problem of obtaining the transmission rate in an ad hoc network consists in adjusting the power of each node to ensure the signal to interference ratio SIR and the energy required to transmit from one node to another is obtained at the same time.

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Therefore, an optimal transmission rate for each node in a medium access control MAC protocol based on CSMA-CDMA carrier sense multiple access-code division multiple access for ad hoc networks can be obtained using evolutionary optimization. Furthermore, this paper proposes a genetic algorithm that solves the problem of power combining, interference, data rate, and energy ensuring the signal to interference ratio in an ad hoc network.

Therefore, we show by simulation the effectiveness of the proposed protocol in terms of the throughput. Full Text Available The problem of obtaining the transmission rate in an ad hoc network consists in adjusting the power of each node to ensure the signal to interference ratio SIR and the energy required to transmit from one node to another is obtained at the same time.

This issue is termed the reader collision problem and cannot always be solved by assigning them to different frequency channels due to technical and regulatory limitations. The typical solution is to separate the operation of such readers across time. This sequential operation, however, results in a long delay to identify all tags.

The BLSync protocol solves the reader collision problem by allowing all readers to transmit the same query at the same time. The benefits of BLSync, first demonstrated through analysis, are then validated and quantified through simulations on realistic reader-tag layouts. Energy-efficiency is an important requirement in the design of communication protocols for wireless sensor networks WSN.

Energy and bandwidth are the scarce resources in ad hoc networks because most of the mobile nodes are battery-supplied and share the exclusive wireless medium. Integrating the power control into MAC protocol is a promising technique to fully exploit these precious resources of ad hoc wireless networks. Through the elaborate design of the distributed transmit-receive strategy of mobile nodes, i MAC greatly outperforms the prevailing IEEE To the best of our knowledge, i MAC is the first protocol that considers the performance deterioration of power-controlled MAC protocols in mobile scenes and then proposes a solution.

Simulation results indicate that DNP is important and necessary for power-controlled MAC protocols in mobile ad hoc networks. Therefore, a novel wide-band IDMA MAC protocol based on channel quality is proposed in this paper, consisting of a dynamic power allocation algorithm, a rate adaptation algorithm, and a call admission control CAC scheme. Firstly, the power allocation algorithm combining the technique of IDMA SINR-evolution and channel quality prediction is developed to guarantee high power efficiency even in terrible channel conditions. Secondly, the effective rate adaptation algorithm, based on accurate channel information per timeslot and by the means of rate degradation, can be realized.

What is more, based on channel quality prediction, the CAC scheme, combining the new power allocation algorithm, rate scheduling, and buffering strategies together, is proposed for the emerging IDMA systems, which can support a variety of traffic types, and offering quality of service QoS requirements corresponding to different priority levels.

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Simulation results show that the new wide-band IDMA MAC protocol can make accurate estimation of available resource considering the effect of multiuser detection MUD and QoS requirements of multimedia traffic, leading to low outage probability as well as high overall system throughput. Full Text Available The human body communication HBC is a technology that enables short range data communication using the human body as a medium, like an electrical wire.

Thus it removes the need for a traditional antenna. HBC may be used as a type of data communication in body area network BAN, while the devices are being in contact with body. One of important issues in BAN is an emergency alarm because it may be closely related to human life. For emergency data communication, the most critical factor is the time constraint.

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Existing emergency handling methods in BAN are based on the carrier sensing capability on radio frequencies to detect the status of channels. So the previous methods are not well suitable for HBC directly. Additionally, in the environment that the emergency rate is very low, the allocation of dedicated slot s for emergency in each superframe is very wasteful. In this work, we proposed specific emergency handling operation for human body communication's medium access control HBC- MAC protocol to meet the emergency requirements for BAN.

We also showed the optimal number of emergency slots for the various combinations of beacon intervals and emergency rates. Energy-constrained behavior of sensor nodes is one of the most important criteria for successful deployment of wireless sensor net- works. The medium access control MAC protocol determines the time a sensor node transceiver spends listening or transmitting, and hence the energy consumption of the.

The Cognitive Radio Sensor Network CRSN is considered as a viable solution to enhance various aspects of the electric power grid and to realize a smart grid. However, several challenges for CRSNs are generated due to the harsh wireless environment in a smart grid. As a result, throughput and reliability become critical issues.

On the other hand, the spectrum aggregation technique is expected to play an important role in CRSNs in a smart grid. These simulations necessarily abstract away from reality in many ways. However, the impact of these abstractions on the results of the simulations has received only limited attention. Moreover, many studies on the accuracy of simulation have studied either the physical layer and per link effects or routing protocol effects.

To the best of our knowledge, no other work has focused on the study of the simulation abstractions with respect to MAC protocol performance. In this paper, we present the results of an experimental study of two often used abstractions in the simulation of WSN MAC protocols. We show that a simple SNR-based reception model can provide quite accurate results for metrics commonly used to evaluate MAC protocols. Furthermore, we provide an analysis of what the main sources of deviation are and thereby how the simulations can be improved to provide even better results.

Adaptive MAC -layer protocol for multiservice digital access via tree and branch communication networks. The protocol adapts to changing demands for a mix of circuit and cell mode applications, and efficiently allocates upstream and downstream bandwidth to a variety of bursty and isochronous traffic sources. In the case of a hybrid fiber-coaxial HFC network the protocol resides in customer premises equipment and a common head-end controller.

A medium-access control MAC processor provides for dividing the time domain for a given digital bitstream into successive frames, each with multiple STM and ATM time slots. Within the STM region of a frame, variable length time slots are allocated to calls e. A contention access signaling channel is also provided in this region for call control and set-up requests.

These ATM time slots may be reserved for a user for the duration of a call or burst of successive ATM cells, or shared via a contention process. At least one contention time slot is available for signaling messages related to ATM call control and set-up requests. Further, the fixed-length ATM time slots may be reserved by a user for the duration of a call, or shared through a contention process. This paper describes the MAC -layer protocol , its relation to circuit- and ATM- amenable applications, and its performance with respect to signaling throughput and latency, and bandwidth efficiency for several service scenarios.

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  4. Evaluation of video transmission of MAC protocols in wireless sensor network. Wireless Sensor Network WSN is a wireless network which consists of sensor nodes scattered in a particular area which are used to monitor physical or environment condition. Each node in WSN is also scattered in sensor field, so an appropriate scheme of MAC protocol should have to develop communication link for data transferring. Video transmission is one of the important applications for the future that can be transmitted with low aspect in side of cost and also power consumption.

    Obtained results indicate that IEEE We provide the corrected formulae and numerical results. Full Text Available In high diversity node situation, multichannel MAC protocol can improve the frequency efficiency, owing to fewer collisions compared with single-channel MAC protocol. Based on cyclic quorum system and channel slot allocation, it can avoid the bottleneck that others suffered from and can be easily realized with only one transceiver.

    The results of numerical analysis show that the optimal performance of CQM protocol can be obtained in saturation bound situation. And then we obtain the saturation bound of CQM system by bird swarm algorithm. And the simulation results show that the analytic and simulation results match very well; the DCQM performs better in unsaturation situation. The emergence of heterogeneous applications with diverse requirements for resource-constrained Wireless Body Area Networks WBANs poses significant challenges for provisioning Quality of Service QoS with multi-constraints delay and reliability while preserving energy efficiency.

    Full Text Available Although several Directional Medium Access Control DMAC protocols have been designed for use with homogeneous networks, it can take a substantial amount of time to change sensor nodes that are equipped with an omnidirectional antenna for sensor nodes with a directional antenna.

    Thus, we require a novel MAC protocol for use with an intermediate wireless network that consists of heterogeneous sensor nodes equipped with either an omnidirectional antenna or a directional antenna. The MAC protocols that have been designed for use in homogeneous networks are not suitable for use in a hybrid network due to deaf, hidden, and exposed nodes. Therefore, we propose a MAC protocol that exploits the characteristics of a directional antenna and can also work efficiently with omnidirectional nodes in a hybrid network.

    The performance of the proposed MAC protocol is evaluated through a numerical analysis using a Markov model. The code channel is divided into common channel, broadcast channel and several data channels. And dynamic power control mechanism is implemented to reduce near-far interference. Compared with IEEE In wireless sensor networks, in order to satisfy the requirement of long working time of energy-limited nodes, we need to design an energy-efficient and lifetime-extended medium access control MAC protocol.

    In this paper, a node cooperation mechanism that one or multiple nodes with higher channel gain and sufficient residual energy help a sender relay its data packets to its recipient is employed to achieve this objective. We first propose a transmission power optimization algorithm to prolong network lifetime by optimizing the transmission powers of the sender and its cooperative nodes to maximize their minimum residual energy after their data packet transmissions. Based on it, we propose a corresponding power-optimized cooperative MAC protocol.

    A cooperative node contention mechanism is designed to ensure that the sender can effectively select a group of cooperative nodes with the lowest energy consumption and the best channel quality for cooperative transmissions, thus further improving the energy efficiency. Simulation results show that compared to typical MAC protocol with direct transmissions and energy-efficient cooperative MAC protocol , the proposed cooperative MAC protocol can efficiently improve the energy efficiency and extend the network lifetime.

    The investigation of infrastructureless safety applications in dierent transportation systems is a hot research topic. The nodes in thevnetwork are designed to advertise to the rest of the nodes informationabout the current traffic situation by means of short beacon messages containing speed, direction, positions and other relevant safety information. The scheduling should be organized by the MAC layer so that the transmitted messages arrive successfully as soon as possible at the recei We use a Markov chain to capture the behavior of TCP sessions, particularly the impact on network throughput performance due to the effect of queue utilization and packet relaying.

    A closed form solution is derived to numerically determine the throughput. Our protocol uses the age of packet as a priority metric for packet scheduling. Simulation is conducted to validate our model and to illustrate the fairness characteristics of our proposed MAC protocol. We conclude that we can achieve fairness with only little impact on network capacity. Full Text Available A wireless network is made of spatially distributed autonomous devices.

    These devices are called sensors. The sensor is used for monitoring physical or environmental conditions. The potential application of wireless sensor network is environmental monitoring, healthcare applications and tactical systems. Wireless sensor network is deployed for wide range to send and receive data with the help of medium. Here literature survey of MAC protocol based on the synchronized and asynchronized approach is described which is used to meet different objective like access a medium, statistical channel allocation, spectrum utilization.

    Hopping control channel MAC protocol for opportunistic spectrum access networks. In our proposed protocol ,all nodes in the network follow a common channel-hopping sequence; every frequency channel can be used as control channel and data channel. Then,a discrete Markov chain analytical model is applied to describe the channel states and deduce the system throughput. Through simulation,we present numerical results to demonstrate the throughput performance of our protocol and thus validate our work.

    The advancement in electronics, wireless communications and integrated circuits has enabled the development of small low-power sensors and actuators that can be placed on, in or around the human body. A wireless body area network WBAN can be effectively used to deliver the sensory data to a central server, where it can be monitored, stored and analyzed.

    For more than a decade, cognitive radio CR technology has been widely adopted in wireless networks, as it utilizes the available spectra of licensed, as well as unlicensed bands. Unlike other wireless networks, CRBANs have specific requirements, such as being able to automatically sense their environments and to utilize unused, licensed spectra without interfering with licensed users, but existing protocols cannot fulfill them.

    In particular, the medium access control MAC layer plays a key role in cognitive radio functions, such as channel sensing, resource allocation, spectrum mobility and spectrum sharing. We then compare the different MAC protocols with one another and discuss challenging open issues in the relevant research. These simulations necessarily abstract away from reality inmany ways. Applications of implantable sensor networks in the health-care industry have increased tremendously over the last decade. There are different types of medium access control MAC protocols that are designed for implantable body sensor networks, using different physical layer technologies such as.

    In receiver-initiated MAC protocols for Wireless Sensor Networks WSNs , communication is initiated by the receiver of the data through beacons containing the receiver's identity. In this paper, we consider the case of a network intruder that captures and replays such beacons towards legitimate An energy-efficient MAC protocol using dynamic queue management for delay-tolerant mobile sensor networks. Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment.

    Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints and memory limitations of nodes. Via data transfers initiated by the target sink and the use of a dynamic queue management strategy based on priority, EQ- MAC effectively avoids untargeted transfers, increases the chance of successful data transmission, and makes useful data reach the target terminal in a timely manner. Due to the characteristics of underwater acoustic channel, media access control MAC protocols designed for underwater acoustic sensor networks UWASNs are quite different from those for terrestrial wireless sensor networks.

    Moreover, in a sink-oriented network with event information generation in a sensor field and message forwarding to the sink hop-by-hop, the sensors near the sink have to transmit more packets than those far from the sink, and then a funneling effect occurs, which leads to packet congestion, collisions and losses, especially in UWASNs with long propagation delays. In the proposed MAC protocol , both the round-robin method and CDMA technology are adopted to make the sink receive packets from multiple paths simultaneously. Full Text Available Due to the characteristics of underwater acoustic channel, media access control MAC protocols designed for underwater acoustic sensor networks UWASNs are quite different from those for terrestrial wireless sensor networks.

    Device as well as network lifetime are among the most important factors in a WBAN. Prolonging the lifetime of the WBAN strongly depends on controlling the energy consumption of sensor nodes. To achieve energy efficiency, low duty cycle MAC protocols are used, but for medical applications, especially in the case of pacemakers where data have time-limited relevance, these protocols increase latency which is highly undesirable and leads to system instability. In this paper, we propose a low power MAC protocol VLPM based on existing wakeup radio approaches which reduce energy consumption as well as improving the response time of a node.

    We categorize the traffic into uplink and downlink traffic. The nodes are equipped with both a low power wake-up transmitter and receiver. The low power wake-up receiver monitors the activity on channel all the time with a very low power and keeps the MCU Micro Controller Unit along with main radio in sleep mode. When a node [BN or BNC BAN Coordinator] wants to communicate with another node, it uses the low-power radio to send a wakeup packet, which will prompt the receiver to power up its primary radio to listen for the message that follows shortly.

    The VLPM protocol is proposed for applications having low traffic conditions. For high traffic rates, optimization is needed. Moreover, reliability is crucial to the performance of error intolerant applications like file transfer, distributed computing, chat and whiteboard sharing. Our results show that our protocol can deliver high reliability and throughput performance. Full Text Available We introduce a novel medium access control MAC protocol for radio frequency identification RFID systems which exploits the statistical information collected at the reader.

    In order to accomplish this task, ASAP estimates the dynamic tag population and adapts the frame size in the subsequent round via a simple policy that maximizes an appropriately defined efficiency function. We next extend the design to accomplish reliable performance of ASAP in realistic scenarios such as the existence of constraints on frame size, and mobile RFID systems where tags move at constant velocity in the reader's field.

    We also consider the case where tags may fail to respond because of a physical breakdown or a temporary malfunction, and show the robustness in those scenarios as well. In the proposed protocol , nodes selectively awake depending on node density and traffic load conditions and on the state of the buffers of the receiving nodes. In order to characterize the performance of the proposed protocol , we present a Discrete-Time Markov Chain-based analysis that is validated through extensive discrete-event simulations.

    Our results show that SA- MAC significantly outperforms previous proposals in terms of energy consumption, throughput, and packet loss probability. This is particularly true under high node density and high traffic load conditions, which are expected to be common scenarios in the context of IoT applications. We also present an analysis by grade i. Such results can be used as a design guideline for future LSN implementations. The performance of the DCF degrades exponentially as the number of nodes participating in the DCF transmission procedure increases.

    To deal with this problem, we propose a simple, however efficient modification of the DCF by which the performance of the DCF is greatly enhanced.

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    5. Once a station seizes the channel, it becomes the temporary clusterhead of a spontaneous cluster and it coordinates the peer-to-peer communications between the clustermembers. Within each cluster, a near-optimum distributed queuing MAC protocol is executed. The theoretical performance analysis of DQMAN in single-hop networks under non-saturation conditions is presented in this paper.

      The approach integrates the analysis of the clustering mechanism into the MAC layer model. Up to the knowledge of the authors, this approach is novel in the literature. Future wireless communication systems aim at very high data rates. As the medium access control MAC protocol plays the central role in determining the overall performance of the wireless system, designing a suitable MAC protocol is critical to fully exploit the benefit of high speed transmission that the physical layer PHY offers.

      In the latest The procedure of setting the backoff value is the heart of the However, collision avoidance is a problem that can not be solved by a single station. In this paper, we introduce a new MAC protocol called Intelligent Local Avoided Collision iLAC that redefines individual rationality in choosing the backoff counter value to avoid a colliding transmission. The distinguishing feature of iLAC is that it fundamentally changes this decision making process from collision avoidance to collaborative collision prevention.

      As a result, stations can avoid colliding transmissions with much greater precision. Analytical solution confirms the validity of this proposal and simulation results show that the proposed algorithm outperforms the conventional algorithms by a large margin. In particular, two very promising protocols for Boolean circuits have been proposed by Nielsen et al. This gives an asymptotic improvement of the original protocol as well as an 8-fold speed-up of our implementation.

      We compare the resulting protocol to TinyOT for the case of secure computation in parallel Full Text Available Multihop mobile wireless networks have drawn a lot of attention in recent years thanks to their wide applicability in civil and military environments. Since the existing IEEE The protocol first concentrates on the flexible adjustment of the upper and lower bounds of the contention window CW to lower the number of collisions.

      In addition, it uses a power control scheme, triggered by the medium access control MAC layer, to limit the waste of energy and also to decrease the number of collisions. Mc MAC classifies traffic based on their multi-constrained QoS demands and introduces a novel superframe structure based on the "transmit-whenever-appropriate"principle, which allows diverse periods for diverse traffic classes according to their respective QoS requirements.

      Furthermore, a novel emergency packet handling mechanism is proposedto ensure packet delivery with the least possible delay and the highest reliability. Mc MAC is also modeled analytically, and extensive simulations were performed to evaluate its performance. The results reveal that Mc MAC achieves the desired delay and reliability guarantee according to the requirements of a particular traffic class while achieving energy efficiency. It is known from [2,3] that with the A feedback-retransmission based asynchronous frequency hopping MAC protocol for military aeronautical ad hoc networks.

      Full Text Available Attacking time-sensitive targets has rigid demands for the timeliness and reliability of information transmission, while typical Media Access Control MAC designed for this application works well only in very light-load scenarios; as a consequence, the performances of system throughput and channel utilization are degraded. With the mechanism of asynchronous FH, immediate packet transmission and multi-packet reception can be realized, and thus the timeliness is improved. Furthermore, reliability can be achieved via channel coding and feedback retransmission.

      With theories of queuing theory, Markov model, packets collision model, and discrete Laplace transformation, the formulas of packet success probability, system throughput, average packet end-to-end delay, and delay distribution are obtained. The approximation accuracy of theoretical derivation is verified by experimental results. The Media Access Control MAC frame format is variable according to the traffic of uplink and downlink and the traffic of control and data. Uplink control message slots are designed for the GB users to reduce contention.

      The simulation results show that the proposed MAC protocol has better performance in terms of delay, probability of successful access request. Full Text Available Wireless body area networks WBANs are severely energy constrained, and how to improve the energy efficiency so as to prolong the network lifetime as long as possible is one of the most important goals of WBAN research. Low data-rate WBANs are promising to cut down the energy consumption and extend the network lifetime. Longer superframes are exploited to cut down the energy consumed on the transmissions and receptions of redundant beacon frames.

      Insertion time slots are embedded into the inactive part of a superframe to deliver the frames and satisfy the quality of service QoS requirements. The number of the data subsections in an insertion time slot can be adaptively adjusted so as to accommodate low data-rate WBANs with different traffic. Simulation results show that the proposed MAC protocol performs well under the condition of low data-rate monitoring traffic.

      Namely, if the number of network stations is small, MAP-WDMA provides better channel utilization for uniform, quasi-uniform-type, and disconnected-type data traffics at all data traffic loads, as well as for mesh and ring-type data traffics at low data traffic loads.

      Full Text Available Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Full Text Available The emergence of heterogeneous applications with diverse requirements forresource-constrained Wireless Body Area Networks WBANs poses significant challengesfor provisioning Quality of Service QoS with multi-constraints delay and reliability whilepreserving energy efficiency. Mc MAC classifies traffic based on their multi-constrained QoS demands andintroduces a novel superframe structure based on the "transmit-whenever-appropriate"principle, which allows diverse periods for diverse traffic classes according to their respectiveQoS requirements.

      McMACis also modeled analytically, and extensive simulations were performed to evaluate itsperformance. The results reveal that Mc MAC achieves the desired delay and reliabilityguarantee according to the requirements of a particular traffic class while achieving energyefficiency. In this kind of network, sensor nodes are required to sense data from the monitoring environment periodically and then send the data to a sink. The sink determines whether the environment is safe or not by analyzing the acquired data. Sometimes, a command or control message is sent from the sink to a particular node or a group of nodes to execute the services or request further interested data.

      The proposed MAC protocol enables bidirectional communication, controls active and sleep modes of a sensor node to conserve energy, and addresses the problem of load unbalancing between the nodes near a sink and the other nodes. It can improve reliability of communication significantly while extending network lifetime. These claims are supported by the experimental results. Full Text Available With the advent of nano-technology, medical sensors and devices are becoming highly miniaturized. Consequently, the number of sensors and medical devices being implanted to accurately monitor and diagnose a disease is increasing.

      By measuring the symptoms and controlling a medical device as close as possible to the source, these implantable devices are able to save lives. A wireless link between medical sensors and implantable medical devices is essential in the case of closed-loop medical devices, in which symptoms of the diseases are monitored by sensors that are not placed in close proximity of the therapeutic device. Medium Access Control MAC is crucial to make it possible for several medical devices to communicate using a shared wireless medium in such a way that minimum delay, maximum throughput, and increased network life-time are guaranteed.

      To guarantee this Quality of Service QoS, the MAC protocols control the main sources of limited resource wastage, namely the idle-listening, packet collisions, over-hearing, and packet loss. MAC protocols designed for implantable devices are still in their infancy and one of their most challenging objectives is to be ultra-low-power. One of the technological solutions to achieve this objective so is to integrate the concept of Wake-up radio WuR into the MAC design. In this survey, we present a taxonomy of MAC protocols based on their use of Wu.

      This paper proposes a low latency MAC protocol that can be used in sensor networks. However, due to these synchronized sensor nodes, packets in the intermediate nodes must wait until the next node wakes up before it can forward a packet. This induces a large delay in sensor nodes. To solve this latency problem, a clustered sensor network which uses two types of sensor nodes and layered architecture is considered.

      Clustered heads in each cluster are synchronized with different timing offsets to reduce the sleep delay. Using this concept, the latency problem can be solved and more efficient power usage can be obtained. To the best of our knowledge it is the fastest of its kind to date. We start from an efficient actively secure evaluation of general binary circuits that was implemented by the authors of [DLT They presented an optimized implementation of the so-called Mini Mac protocol [DZ13] that runs in the pre-processing model, and applied this to a binary AES circuit.

      In this paper we de- scribe how to dedicate the pre-processing to the structure of AES, which improves significantly the throughput and latency We get a latency of about 6 ms and amortised time about 0. In receiver-initiated medium access control MAC protocols for wireless sensor networks, communication is initiated by the receiver node which transmits beacons indicating its availability to receive data. In the case of multiple senders having traffic for a given receiver, such beacons form In this paper, we present altruistic backoff AB , a novel collision avoidance mechanism that aims to avoid collisions before the transmission of a beacon.

      As a result of an early backoff, senders spend less time in idle listening waiting for a beacon, thus We present an implementation of AB for Texas Instruments' eZrf sensor nodes and we evaluate its performance with simulations and experiments A hybrid MAC protocol design for energy-efficient very-high-throughput millimeter wave, wireless sensor communication networks. An energy-efficient Superframe for wireless sensor communication network employing directional mm-wave wireless access technologies is proposed for systems that require very high throughput, such as high definition video signals, for sensing, processing, transmitting, and actuating functions.

      Energy consumption modeling for each network element and comparisons among various multi-access technologies in term of power and MAC layer operations are investigated for evaluating the energy-efficient improvement of proposed MAC protocol. Full Text Available Radio frequency signals are commonly used in the development of indoor localization systems. The infrastructure of these systems includes some beacons placed at known positions that exchange radio packets with users to be located.

      When the system is implemented using wireless sensor networks, the wireless transceivers integrated in the network motes are usually based on the IEEE But, the CSMA-CA, which is the basis for the medium access protocols in this category of communication systems, is not suitable when several users want to exchange bursts of radio packets with the same beacon to acquire the radio signal strength indicator RSSI values needed in the location process. Therefore, new protocols are necessary to avoid the packet collisions that appear when multiple users try to communicate with the same beacons.

      On the other hand, the RSSI sampling process should be carried out very quickly because some systems cannot tolerate a large delay in the location process. This is even more important when the RSSI sampling process includes measures with different signal power levels or frequency channels. The principal objective of this work is to speed up the RSSI sampling process in indoor localization systems.

      To achieve this objective, the main contribution is the proposal of a new MAC protocol that eliminates the medium access contention periods and decreases the number of packet collisions to accelerate the RSSI collection process. Moreover, the protocol increases the overall network throughput taking advantage of the frequency channel diversity. The presented results show the suitability of this protocol for reducing the RSSI gathering delay and increasing the network throughput in simulated and real environments.

      Radio frequency signals are commonly used in the development of indoor localization systems. A new energy-efficient MAC protocol with noise-based transmitted-reference modulation for wireless sensor network. Morshed, S. Energy-constrained behavior of sensor nodes is one of the most important criteria for successful deployment of wireless sensor networks. The medium access control MAC protocol determines to a large extent the time a sensor node transceiver spends listening or transmitting, and hence the energy.

      It is based on small, low cost and intelligent base stations running a medium access control MAC protocol using adaptive packet reservation multiple access APRMA. Full Text Available Collection of rare but delay-critical messages from a group of sensor nodes is a key process in many wireless sensor network applications. This is particularly important for security-related applications like intrusion detection and fire alarm systems. An event sensed by multiple sensor nodes in the network can trigger many messages to be sent simultaneously. We present Alert, a MAC protocol for collecting event-triggered urgent messages from a group of sensor nodes with minimum latency and without requiring any cooperation or prescheduling among the senders or between senders and receiver during protocol execution.

      Alert is designed to handle multiple simultaneous messages from different nodes efficiently and reliably, minimizing the overall delay to collect all messages along with the delay to get the first message. Moreover, the ability of the network to handle a large number of simultaneous messages does not come at the cost of excessive delays when only a few messages need to be handled. We analyze Alert and evaluate its feasibility and performance with an implementation on commodity hardware.

      We further compare Alert with existing approaches through simulations and show the performance improvement possible through Alert. Full Text Available Considering the energy constraint for fixed sensor nodes and the unacceptable long propagation delay, especially for latency sensitive applications of underwater acoustic sensor networks, we propose a MAC protocol that is latency-optimized and energy-efficient scheme and combines the physical layer and the MAC layer to shorten transmission delay. On physical layer, we apply convolution coding and interleaver for transmitted information.

      Moreover, dynamic code rate is exploited at the receiver side to accelerate data reception rate. On MAC layer, unfixed frame length scheme is applied to reduce transmission delay, and to ensure the data successful transmission rate at the same time. Furthermore, we propose a network topology: an underwater acoustic sensor network with mobile agent.

      Through fully utilizing the supper capabilities on computation and mobility of autonomous underwater vehicles, the energy consumption for fixed sensor nodes can be extremely reduced, so that the lifetime of networks is extended.

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      Full Text Available The nonnegligible propagation delay of acoustic signals causes spatiotemporal uncertainty that occasionally enables simultaneous, collision-free packet transmission among underwater nodes UNs. These transmissions can be handled by efficiently managing the channel access of the UNs in the data-link layer.

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      The scheduling strategy increases the number of UNs that send packets coincidentally via two subscheduling configurations i. Full Text Available In recent years, wireless technologies and application received great attention. The Medium Access Control MAC protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel in wireless local area networks WLANs. Our adaptive scheme performed even better when data rate increases. We verify our proposed scheme both analytically and with extensive network simulation using ns Full Text Available The propagation delay in mobile underwater acoustic sensor network MUASN is asymmetric because of its low sound propagation speed, and this asymmetry grows with the increase in packet travel time, which damages the collision avoidance mechanism of the spatial reuse medium access control MAC protocols for MUASN.

      Collisions at the SN are avoided by deferring data packet transmission after reception of a beacon packet from the SN, and data packets are arrived at the SN in a packet-train manner. The time-offset, which is the time for a node to wait before the transmission of a data packet after reception of a beacon packet, is determined by estimating the propagation delay over two consecutive cycles such that the idle interval at the SN is minimized, and this time-offset is announced by the beacon packet.

      Full Text Available Establishing high-speed and reliable underwater acoustic networks among multiunmanned underwater vehicles UUVs is basic to realize cooperative and intelligent control among different UUVs. In accordance with multichannel MAC protocols , data packets and control packets are transferred through different channels, which lowers the adverse effect of acoustic network and gradually becomes the popular issues of underwater acoustic networks MAC protocol research.

      In this paper, we proposed a control packet collision avoidance algorithm utilizing time-frequency masking to deal with the control packets collision in the control channel. This algorithm is based on the scarcity of the noncoherent underwater acoustic communication signals, which regards collision avoiding as separation of the mixtures of communication signals from different nodes.

      We first measure the W-Disjoint Orthogonality of the MFSK signals and the simulation result demonstrates that there exists time-frequency mask which can separate the source signals from the mixture of the communication signals. Then we present a pairwise hydrophones separation system based on deep networks and the location information of the nodes.

      Consequently, the time-frequency mask can be estimated. Prevention of suicidal behaviour is a public health priority in the European Union. A previous suicide attempt is the best risk predictor for future attempts, as well as completed suicides. The primary aim of this article is to describe a controlled study protocol designed for prevention of recurrent suicidal behaviour that proposes case management, and includes a psychoeducation program, as compared with the standard intervention PSy MAC.

      Patients admitted from January to June to the emergency room of the Hospital Universitario Central de Asturias were evaluated using a protocol including sociodemographic, psychiatric, and psychosocial assessment. Patients were randomly assigned to either a group receiving continuous case management including participation in a psychoeducation program experimental group , or a control group receiving standard care. The primary objective is to examine whether or not the period of time until recurrent suicidal behaviour in the experimental group is significantly different from that of the control group.

      PSy MAC proposes low cost and easily adaptable interventions to the usual clinical setting that can help to compensate the shortcoming of specific action protocols and suicidal behaviour prevention programs in our country. The evaluation of PSy MAC results will determine their real effectivity as a case-magament program to reduce suicidal risk. All rights reserved. Full Text Available A Caucus-based medium access control protocol C- MAC is proposed to reduce the end to end delay and battery consumption of the sensor nodes deployed in the monitoring of various smart grid regions, such as substation, pole and wires, perimeter security, real time and non-real-time monitoring using wireless sensor networks.

      The objective is to prolong the network lifetime and to reduce the end to end delay by mitigating the energy-hole problem and by eliminating bottlenecks significantly by using caucus based efficient synchronization techniques in multi-hop square grid topology of the wireless sensor networks WSNs. It induces a low duty cycle for adjusting wake-up times of sensor nodes. The appropriate selection of active and sleep time slots and next hop relay nodes are proposed to minimize the data transmission latency and to reduce battery consumption to increase the network lifetime.

      The uniform and synchronized transmission of the data packets is of prime importance to improve the network performance. Simulation results justify that the proposed C- MAC protocol increases the network lifetime, successful data transmission ratio along-with the reduction in end to end delay. The objective of this paper is to envisage benefits and utilization of C- MAC protocol for WSNs deployed in smart grids and to draw the attention of researchers in this area. We use a Markov chain to capture the behavior of TCP sessions, particularly the impact on network throughput performance due to the effect of queue.

      Low-power low-latency MAC protocol for aeronautical applications. Sensor data is acquired and collected on request, by means of a mobile device, and later stored in a centralized database. In order to have the smallest power consumption the wireless sensor has to remain in deep sleep mode as long as possible and wake up and listen periodically for RF activity. If its unique ID is mentioned in the destination address field, the complete frame is received, processed and replied if necessary.

      If the detected packet is addressed to another sensor the reception will stop immediately and the wireless sensor will go into deep sleep mode again. Listening instead of sending actively does not 'pollute' the already crowded 2. The mobile data concentrator can not be synchronized with all the sensors installed in a distributed environment, therefore smart asynchronous data transmission strategies are needed to reduce latencies and increase throughput. For the considered application, sensors are independent of each other, simply share the medium and together with the data concentrator are organized in a star network topology.

      The centre of the star is the concentrator which is rarely in range. It coordinates and activates the wireless sensor nodes to collect the measured data. Wireless networking in cyber-physical systems CPSs is characteristically different from traditional wireless systems due to the harsh radio frequency environment and applications that impose high real-time and reliability constraints. admin