Standards For Wireless Communications Computer Science Essay

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The standard for wireless communications as IEEE802: 11 were designed from a high-speed ubiquitous access to data or information. The desire for greater data rate communications system has challenged researcher's worldwide wireless. Thus, the data rate offered by current wireless systems has improved dramatically. Current wireless local area networks (WLAN), IEEE as standard 802:11 / g provides the data rate physical (PHY) layer up to 54 Mbps. The introduction of new applications such as streaming video at high definition television (HDTV), video streaming, and video phones, etc, the demand for high data rates. The newest digital communication techniques can be used to enhance the data. The main ways to increase the data are greater channel bandwidth by increasing the number of data subcarriers, the constellation of larger, higher rate of coding and the use of various antennas.

Thus, the hunger for higher data rate and range are extinguished by the techniques used in the IEEE 802:11n.802:11n the PHY has multiple antennas at the transmitter with Orthogonal Frequency Division Multiplexing (OFDM) to achieve higher data rates and range make [IEEE802.11n]. Moreover, 802:11 s PHY offers a maximum data rate of up to 600 Mbps, short guard interval of 400 ns and 40 MHz bandwidth channel [IEEE802.11n] IEEE standard is supposed to be 802:11 n in 2008.

In actual scenarios, the wireless channel varies over time. Therefore, updated link(LA) can be used to address various channels in order to maintain a reliable communication and to increase system performance. The IEEE standard 802:11 n protocol, which allows the modulation and coding system being implemented according to the current condition of the channel to increase speed.

2.Overview of 802.11 a/g/n

2.1 IEEE 802.11a

802.11a was formed at the same time with 802.11b support capacity in the 5GHz bandwidth to 55Mbps. 802.11a is not very popular due to the slow availability of the 5 GHz mechanism necessary to implement the supplier's products, costly and not compatible with 802.11b.The higher frequency also allows 802.11a signal have more complexity penetrating walls and other obstacles.

But the benefit of 802.11a is that it operate at a frequency that is less obstructed by competing signals from other wireless users, cellular phones and microwave ovens. The maximum bandwidth and higher compared with 802.11b. 802.11a is usually found in enterprise networks, while most suitable for 802.11b home network.

2.2 IEEE 802.11g

Because 802.11b and 802.11a is not compatible with the need for greater bandwidth, 802.11g was ratified in June 2003 to provide high speed data and compatibility with 802.11b products.

802.11g supports up to 55Mbps with 2.4GHz bandwidth, 802.11g is compatible with 802.11b products, since both use the same frequency (2.4 GHz) to transmit data through the air, it means router 802.11g Wireless will be able to speak 80.11b wireless adapter. 802.11g offers greater security, including Wi-Fi Protected Access (WAP) and WPA2 with authentication pre-shared-key or a RADIUS server.

2.3 IEEE 802.11n

802.11n is the most recent wireless communication standard in the IEEE in October 2009, and be able to provide a bandwidth of 600 Mbps; it is 10 times faster than 802.11g. [1]

New Improvements in 802.11n

IEEE 802.11n is the major change in the wireless Local Area Network in the world since the approval of the original standard in 1997. 802.11n define engaged to both the MAC and PHY layers. The most impact of 802.11n technology used for the PHY. The possibility of low cost CMOS radios, today it is possible simultaneously with multiple radios and antennas on each client.Advanced signal 802.11n possible to add multiple radios a number of other improvements PHY burst actually increase transmission speed and overall system capability by a factor of ten, when all the new extensions are used. [2]

2.4 Benefits of 802.11n

A wider range - When two or more times greater robustness to fading. Such a wider range will be especially important for networks that use channels 5 GHz 5 GHz 802.11n is much more useful and therefore significantly increases the effective capacity of the system.

Enhanced Data Rate - up to ten times the speed burst of data from the legacy 802.11 a / b / g systems. For stations using advanced MIMO maximale to 4 spatial streams to provide a channel connection, IG, and short burst data speeds of up to 600 Mbps possible.

protocol Improving quality of service - in addition to 802.11n MAC modest improvements to improve efficiency, improvements in most implementations of the 802.11n 802.11e quality of service to further improve the performance of streaming media. [2]

2.5 MIMO(Multiple-input multiple-output)

MIMO is the heart of the 802.11n standard. This technical conversation of MIMO provides a base for considerate how 802.11n can arrive at speeds of 600 Mbps.

Basics of Radio Operation

To understand the improvements introduced by MIMO technology, it is important to understand some basic principles that determine how well a traditional radio does. In a traditional single input-output radio, the amount of information that can be carried by a radio signal received depends on the amount by which the received signal strength of the noise is higher than the receiver's call signal to noise ratio, or SNR. SNR is expressed in decibels (dB). The higher the SNR, the more information that can be applied to the signal and recovered by the receiver.

To understand this, imagine the analogy of the eye as a receiver. Is it the eye can perceive, or a table lamp on or off in the house next to the? In this analogy, the ambient light is the noise. At night, they detect that the lamp is switched off or is easy. However, in broad daylight, it is much more difficult than the same determination as the ambient light is much brighter, and the small amount of additional light from the lamp can be detected.

Light, like a radio wave, spreads evenly from the source. The more the recipient of the source, less power from the source. In fact, the amount of received power decreases more rapidly than the square of the distance from the source. The sound, unfortunately, often a constant in the environment due to both natural and human causes.

So, back to the table lamp, for example, when it is too bright to determine if the lamp by the door is on or off, it might be possible to make this assessment from outside the neighbor's window. Alternatively, it might be possible to determine if the neighbor changed the 40-watt bulb for a 150 watt bulb. In both cases, the SNR increases in the first case, because the distance from the source is reduced, and in the second case, because the transmitter power is higher.

Once the minimum SNR is achieved in exchange of information at the desired speed, no additional SNR is like money in the bank. This ratio S / R can spend extra on increasing the information rate, increasing the distance, or a little of both. You can not give the same dB more than once, like you can not spend the same amount of dollars more than once (at least not without a fight some unpleasant consequences.)

This is the substance of the improvements made MIMO 802.11 understood.

Beamforming

MIMO technology uses other techniques to improve SNR at the receiver. One technique is beam forming transmission. When more than one antenna is transmitting, it is possible to coordinate the signal from each antenna so that the signal at the receiver has improved dramatically. This technique is generally used when the recipient has only a single antenna and when there are few obstructions or radio reflective surfaces such as open storage yards.

To understand transmit beam forming, consider a radio signal as a waveform with a wavelength that is specific to the frequency of the signal. When two radio signals are transmitted from different antennas, these signals are added to the receiver antenna (see Figure 1). Depending on the distance that each radio signal, is likely to reach the receiver out of phase with each other.This phase difference at the receiver affects the strength of the signal from the received signal.By carefully adjusting the phase of radio signals from the transmitter, the received signal can be maximized in the receiver, the SNR increases. This is what transmit beamforming, focusing, in fact, the channels in a receiver, as shown in Figure2.

Figure 1. Destructive Interference

Figure 2. Transmit Beanforming (Constructive Interference)

Transmit beamforming is not something that can easily be done at the station without informing the receiver about the received signal. This information is only available through 802.11n devices, not the 802.11a, b or g devices. To maximize the signal at the receiver, the feedback from the receiver should be sent to the transmitter so the transmitter can send any song from the signal. This reaction is not immediate and is valid only for a short time. Any physical movement of the transmitter, receiver, or elements in the environment quickly invalidates the parameters used for beamforming. The wavelength of a 2.4-GHz radio is only 120 mm, 55 mm and only for the 5-GHz radio. Therefore, a normal pace of 1 meter per second faster step of the receiver when the transmitter beamforming efforts are most effective.

Transmit beamforming is only useful when sending a single receiver. It is possible to optimize the phase of the transmitted signal to send broadcast or multicast transmissions. For this reason, network applications in general, the usefulness of the transmission beam formation is somewhat limited and therefore an improved signal to noise ratio at the receiver only transmissions that are sent to one recipient . Transmit beamforming can increase the data rate available at greater distances from the AP. But it does not increase the coverage area of an access point, which is determined largely by the ability to receive beacons to access. Beacons are a broadcasting transmission services that do not benefit from the transmission beamforming.

Multipath or Spatial Diversity

In typical indoor WLAN deployments for example offices, hospitals, warehouses and the radio signal is often not the direct, the shortest route from sender to recipient. This is because there are rarely "line of sight" between transmitter and receiver. Often there is a wall of cubes, door or other structure that obscures the line of sight. All these barriers to reduce the strength of the radio signal as it passes through them. Fortunately, most of these environments are full of surfaces that a radio signal to display as a mirror reflects light.

Imagine that all metal surfaces, large and small, who are in an environment that mirrors reality.Nails and screws, frames, grates on the ceiling, and structural beams, all devices of radio signals. Could the same WLAN access point can be viewed simultaneously on many of these mirrors. Some images of the access point would be a direct reflection through a mirror. Some of the images were a reflection of a reflection. Others would be accompanied by an even larger number of reflections. This phenomenon is called multipath (see Figure 3).

Figure 3. Multipath

When a signal via different paths to a receiver, the time of the signal reaches the receiver depends on the length of the path traveled. The signal travels the shortest path will arrive first, followed by copies or echoes of the signal is slightly delayed by each of the roads and paths for copies. When traveling at the speed of light and radio signals to the delay between the first signal to arrive and the copies is very small, only nanoseconds. (A rule of thumb for the distance that the speed of light is about one meter by one nanosecond.) This delay is sufficient to be a significant degradation of the signal causing a single antenna, as all cases interfere with first signal to arrive.

A MIMO radio radio transmits multiple signals simultaneously and multiple uses. Each of these signals, a spatial stream. Each spatial stream is sent from your own antenna, using a private channel. Because there is some space between each of these antennas, each signal uses a slightly different route to the receiver. This is known as spatial diversity. Each radio can also be another stream of the other radios. The receiver has multiple antennas, thus, each with its own radio. Each of the radio to receive input signals independently of the decoding (see Figure 4).Then, each received radio signal is combined with signals from other radios to receive. With a lot of complex mathematics, the result is a much better signal to receive more than what can be achieved with a single antenna or even transmit beamforming. One of the two main advantages of MIMO is that it dramatically improves the SNR, greater flexibility for the wireless system designer.

MIMO systems are described by the number of transmitters and receivers in the system, for example, 2x1 is "two for one", which means two transmitters and a receiver. 802.11n defines a number of different combinations for the number of channels and the number of beneficiaries, 2x1, right to transmit beamforming, 4x4. Each additional transmitter or receiver in the system increases the S /. However, the incremental benefits of each additional receiver transmitter or rapid decline. The gain in SNR is great for every step of 2x1 to 2x2 and 3x2, but the improvement in the 3x3 and then is relatively small. The use of multiple transmitters, the second great advantage of MIMO, the possibility for each spatial stream using your own information, which carries a higher data rate.

3.Main differences between 802.11n when compared to 802.11a and 802.11g

3.1 Bandwidth

Bandwidth is the measure of both the amount of data and the number of users that the network can support at any time. Bandwidth decreases with increasing distance from the signal source.Data rate alone does not determine the bandwidth, because the number of available channels and access points are important variables. While 802.11a and g technologies have similar practical data rates, 802.11a technology is considered a higher bandwidth, as more channels and therefore more able to support dense populations of Access Point (802.11a, however 'sLimited has more access points are required for large deployments of field). 802.11n, operating at the same frequencies are compatible with 802.11a and 802.11b / g, the shortest route available, which is one reason which is the highest speed option.

3.2 Frequency

802.11a systems in a different frequency band (5 GHz) or 802.11b / g (2.4 GHz), impeding interoperability between 802.11a and 802.11b / g systems. The 802.11n standard provides separate 2.4 GHz and 5 GHz versions of the technology.

Table 1. Comparison of IEEE 802.11 a/g/n Protocols

Protocols

802.11a ( Released October 1999)

802.11g ( Released June 2003)

802.11n* (Released September 2009)

Operating frequency

5 GHz

2.4 GHz

2.4 or 5 GHz

Channels**

11chanels

3chanels

14chanels

Maximum data rate

54 Mbps

54 Mbps

600 Mbps

Operating range

30 m

100 m

70 m

Interoperable with:

802.11n

802.11b, n

802.11a, b, g***

Issues

Requires more access points (APs) since range is shorter

• Higher signal absorption by walls and other objects

Interference from other devices operating in the 2.4 GHz band

• Based on 802.11b, and subject to the same low throughput issues

Though some hardware suppliers have products that support this protocol on the market already, most are still working to catch up and cannot operate at full speeds until the release of new hardware and software

* The IEEE 802.11n standard is not ratified and therefore specifications are subject to change.pre-standard products are available in the market (especially for home users).

** The 802.11 standards are international, but the channel availability is subject to national legislation. All channels may not be available in all countries.

*** If you use the same frequency. [3]

3.3 Range

Wireless range is measured by the area in which a mobile device may be useful to maintain wireless LAN connection. The range varies depending on the available SNR can be found at different carrier frequencies and data rates. Different frequencies have different characteristics of range. The radio propagation characteristics at 5 GHz operation shows a loss of over 2.4 GHz as access points over 802.11a wireless LAN infrastructure requires an 802.11b network to cover the same area. The 802.11n standard specifies the use of multiple-input multiple-output (MIMO) technology that is not included in 802.11a/b/g. 802.11n MIMO technology is a major reason it is expected that a greater range and performance 802.11a/b/g systems.

3.4Interoperability

The 2.4 GHz version of 802.11n is backward compatible with 802.11b / g systems,

802.11b /g devices can communicate with 802.11n access points, and 802.11n devices can communicate with 802.11b / g AP media . In this kind of mixed-use environments, the data rate is limited by the slow protocol (eg, 802.11b / g devices do not communicate 802.11n speeds when using 802.11n access points). 802.11n 5GHz systems are also compatible with 802.11a technology.

4. The advantages and disadvantages of 802.11n when compared to 802.11a and 802.11g

4.1 Advantages of 802.11n

While 802.11g has a maximum speed of 54 Mbps 802.11n is expected to stabilize at around 320Mbps. 802.11n uses MIMO (Multiple Input Multiple Output). This means that the use of multiple transmitters and antennas to transmit and receive. While a sample can bounce off a metal object, not multiple transmissions will be successful. This helps a lot with the interference and dead spots and will result in a significant increase in range. The advantage is much faster and more reliable transportation for your MP3, videos and games consoles! [4]

The last amendment to be put up for consideration for the ratification of the 802.11n standard.The 802.11n standard has been in development since mid-2005. Theoretical current limit speed 802.11n fifty times faster than 802.11b, and ten faster than 802.11a and 802.11g, with an estimate of 540 megabits per second.

802.11a, 802.11b and 802.11g originally used an antenna. Recently, some manufacturers have begun to implement MIMO (Multiple In, Multiple Out) on some 802.11g devices. To the right is D-Link DI-634M Wireless 108G MIMO Router. Many vendors have begun to apply MIMO to improve the coverage and signal. The data for maximum performance with the 802.11g standard is 108mb.

802.11n is proud to be a theoretical 600 Mbps away. Actual performance will initially be closer to 200Mbps. This will take place on a line with more attractive 802.11n Fast Ethernet (100 Mbps Ethernet cable). A 200 Mbps will be possible to stream high quality video and voice over a wireless signal. Some manufacturers are already selling "Pre-N" products, including Belkin, D-Link, Netgear, Linksys and Asus. But since these "pre-n" not guaranteed to be compatible with the 802.11n standard when published. Most of these vendors are promising to support firmware upgrade to help support the final standard. [5]

[ Wireless Networking and the 802.11n Standard Roman White and Pratt Hinds] word file...

4.2 Disadvantages of 802.11n

The two main disadvantages of the Pre-N are the costs and compatibility in the future. Natural Pre-N gear is more expensive than 802.11g gear and not quite ready for prime time yet. Yes, you see many of MIMO products out there and do not use the Pre-N MIMO technology, but is still only "pre-n". The 802.11n standard is not yet certified. From Pre-N is not a standard, it is important to understand that an access point for foreign manufacturers usually work with an adapter anothers. Moreover, there is no way a manufacturer can ensure that the Pre-N equipment you buy today will work with the current 802.11n future.

At the time the current 802.11n products on the market, along with inevitable improvements and price reductions that come with the time you are "stabbing" and wish you had waited. The best advice from a financial standpoint, that stand out with its 802.11g equipment, as long as possible and wait for 802.11n around for a while and pick up when prices down a bit. If money is no object now in a hurry and pick up some cool gear Shiney new Pre-N to leave it on eBay when the 802.11n standard is real! [4]

5.0 Consumer Applications Demand 802.11n

Because the promise of much higher bandwidth, longer range and reliability, 802.11n is advantageous in a variety of network configurations. And if the new network applications to take home, a growing number of consumers will come to see 802.11n as not only an extension of your existing network, but as a necessity.With most Internet connection speeds below 5 Mbps, it is unlikely that consumers using wireless technology on a single computer with a web link to your existing network load, at least when used at short distance.

Also from this group of consumers may be pleasantly surprised by the increased range and reliability than a hardware upgrade of draft-n WLAN can offer. Some of the current and new applications driving the need for 802.11n are Voice over IP (VoIP), video and music, gaming and streaming, network attached storage. VoIP is mushrooming as consumers and companies realize they can save money on long distance calls over the Internet instead of traditional phone service. An increasingly popular way for Internet calling with a VoIP phone, which is battery-powered devices that are connected to the Internet with integrated 802.11b or 802.11g. Phone high bandwidth, but it is a reliable network to be usable. Both 802.11b and 802.11g 802.11n MIMO consume less power than in the case, but only the current.

802.11n could be mostly in VoIP phones. VoIP phones can now benefit from a greater range and reliability of a draft-n access point.As with voice, streaming music is an application that a reliable connection that can reach the house requires. Millions of consumers to create digital music libraries on their personal computers by ripping their CD collections and the purchase of digital recordings over the Internet. In addition, more and more streaming music directly from the Internet

Like their digital music collections grow, more consumers can find you want to listen through the stereo players room or in another room of the house. Despite a higher bandwidth is not essential, the additional coverage and reliability offered by the draft-n may be more suitable for streaming music over the last generation WLAN hardware older.

The game is an application that will increasingly use wireless at home, or users connect wirelessly to the Internet from their computers and portable entertainment devices or use the network to compete with others in the house. One application each time you take a lot to offer 802.11n high data rates and coverage and reliability of network-attached storage, or NAS. NAS has become popular in the company as a cheap easy to install alternative for data backup. More recently, NAS is taking hold in small offices and homes, including some, such as users want their digital photo albums growing hard disk is not protected and, when the price of self-contained NAS backup systems safety well below $ 1,000. Most interesting new applications are emerging for the SAN, and video storage centers, providing reliable connections for high bandwidth to stream pre-recorded television programs, music videos and movies of the total demand for televisions and computers throughout the house. [6]

6.0 Should all new wireless deployments be based on 802.11n instead of 802.11a and 802.11g

Network Backbone Impacts of 802.11n

Effects of backbone 802.11n Wireless LANs are usually served mainly to networks of convenience, so imagine if overlays are implemented in an existing wired network. WLAN have also suffered from the perception of a slow and / or unreliable, and often used for mission-critical data to play. In this regard, the WLAN had little effect on the main backbone of the company, nor has the design of WLAN traffic is a major concern.

This paradigm is changing with the advent of the 802.11n standard. If the yield, performance and improve reliability, the WLAN is a viable alternative and complement to the wired network bandwidth and business-critical applications. At this point, it is very important to the flow of traffic on the WLAN understand. There are two types of traffic to be examined, and can be intertwined - data, actual data sent and received by wireless clients and traffic control, how the access point is mobility, and RF control allows the user policy and roaming customers. This traffic will mainly depend on the architecture used for the wireless system and can result in a wide variety of real WLAN performance. Settings that were acceptable in a low performance network can operate with even greater performance requirements. And if the WLAN performance begins to be the first consideration of network performance, these settings have unforeseen effects on the wired network as well.

Are we ready for 802.11n?

In reflecting on the impact of 802.11n backbone of today, it is also necessary to carry out the reforms proposed in the thought horizon. We need only look back a few years to see that performance increases, as with 802.11g and took 11-54 Mbps 802.11g rates or when AP began to support simultaneous 802.11a and g, resulting in 2 x 54 Mbps rates . Today there are plans for additional energy chipsets spatial possibilities, that the performance of 802.11n 300 Mbps to 450 Mbps to improve, and finally, 600 Mbps per radio. To say that 802.11n will be the last word on improving performance would be unwise. But we have a very similar adoption curve with Wired clients have moved from 10 Mbps to 100 Mbps for Gigabit switching networks share necessary and 10Gb switching and routing infrastructure to keep pace. The key to this adoption curve is located traffic through switching and routing, and spine with multiple paths. The fact that the possibility that this growth is based on the platforms will facilitate the migration to high-speed wireless networks.

Aerohive cooperative control architecture is reminiscent of the past, the introduction of innovations in wired networks, including dynamic routing and Spanning Tree.

By eliminating the controller, Aerohive allows customers to take advantage similar wireless network design, including the bandwidth and resilience, our customers enjoy cable. For the IT manager, the effects of 802.11n and beyond are in the same light that a bandwidth upgrade from a wired client. Aerohive Cooperative control approach makes it easier to plan for innovation and its impact on the network as a whole rather predictable.We have seen that, while the disadvantages of a centralized approach based on drivers may be overlooked in the convenience 802.11a/b/g architectures will inevitably be faced with obstacles such as the substantial increase in bandwidth promised by the 802.11n offer . The domino impact on both the driver and network devices in the environment can be rotated by the driver or switch vendors, but the fact is that you will have very real consequences for the speed of top network design based on actual learned. The migration of "fat AP" there is no centralized coordination, administrative control was always a fully centralized model. Now, with Aerohive, this model is being developed for the benefit of cooperative control and central administration to capture without treatment or adverse effects on the data and control traffic. [7]

7.0 Conclusion

Real world have much to grow by advancement to 802.11n. 802.11n can use advanced techniques for signal processing, such as spatial multiplexing transmission beamforming and improving efficiency to significantly increase their WLAN range, throughput and reliability. On the other hand, the large number of potential 802.11n configurations and the many ways that could affect the heritage 802.11a / g requires commitment to the plan to maximize benefits and minimize disruptions and high costs. 802.11n version 2.0 is already here, ratified standard products are shipped very quickly. No time like the present to start receiving your network ready for this new generation of wireless products more robust and reliable.

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