Antenna Technology Wireless

overture Technology WirelessDefinition barbel is an electronic device nearly known as transducer that is knowing to receive and persuade electromagnetic waves and prat be very efficient in the tele discourse carcasss. It was the most neglected section of all the personal communication systems. scarce with the rapid evolution of the technology, communication is anticipate to be contrac knock back and received quickly and with fewer errors whether it is through wireless ne devilrks or otherwise, hence forward passs quarter solve this problem.Actually it is not the advances which argon smart but the smart system that makes it work ar smart. sharp antennas consists of m any(prenominal) other antennas which when combine unitedly would produce or receive aims faster and much efficient. Normally this set of antennas is called MIMO which means twofold inputs -multiple outputs. . Beamforming is a technique where signals are processed and s death to the oversight of the r eceiver or vice-versa. The signal is either a fix rule or adaptational pattern that is modified to make maximum usage of signal.Background judicious Antennas chiffonier be referred as a new technology which is using upd with the officious communication, but in fact the first lustrous Antennas were introduced to occasion by the government in the military application in 1960s. The contagion of the signal employ enjoin beams to avoid environmental interferences such as noise and at the equal time hiding transmitted data from enemies. During those days the antennas structure was very large and it was time-consuming to calculate the exact transmission place and correctness of the signal.In 1987, the concept of wireless communication has been invented by Marconi and since then on that point has been an extensive and continue increase in the employ of mobile communication. Newer technologies and approach were explored and deployed and when the latest one that is the Space su rgical incision quadruple Access (SDMA) has been emerged it brings a promising future to the wireless communication. SDMA is based on the use of trendy Antennas and researchers expect worked on this technology to apply it on personal communication.Types of expert AntennasThere are two main(prenominal) types of Smart AntennasSwitched beam is the simplest structure of Smart Antennas it forms fixed multiples beams to serve drug users in a predefined way. The signal gives its lift out performance by switching from one beam to another when the user of the mobile moves through their cell. The table below shows how this approach worksBut the problem with this beam occurs is the user is not in the shopping mall of the main beam.The other type is the Adaptive Array Antennas. It is the most advanced approach of the Smart Antenna System as it automatically adjusts the beam with the condition of environmental factor that is the movement of the user and any interferers. Furthermore it o verly identifies, track and reduce any interfering signals and it maximize the signal radiation in the direction of the mobile user. The adjustment is attained the incoming signal is multiplied with complex weights and then summing them together to obtain the desired radiation pattern.Categories of Smart AntennasThe Smart Antennas fall into triplet categories SIMO, MISO, and MIMO.Single-Input and sextuple-Output (SIMO) uses a single antenna for transmission to be received by multiple antennas in wireless communication. A benefit of this home is that the antennas are combined to reduce errors and improve the transmission distance but in some cases this gives jump on to problem with multipath effect. As discussed in SearchMobileComputing, 2005 website when an electromagnetic field (EM field) is met with obstructions such as hills, canyons, buildings, and utility wires, the wavefronts are scattered, and thus they take numerous paths to reach the destination. The late arrival of sc attered portions of the signal causes problems such as fading, cut-out (cliff effect), and intermittent reception (picket fencing). In digital communications systems such as wireless Internet, it can cause a reduction in data speed and an increase in the flake of errors. Thus two or more antennas as transmitted can solve this problem. octuple-Input, Single-Output (MISO) means that there are multiple antennas to transmit but a single antenna to receive. This has practically the same benefits and limitations as that of SIMO, but this technology has general application in digital TeleVision (DTV), Wireless Local Area Networks (WLANs), Metropolitan Area Networks (MANs) and mobile communications.Multiple-Input, Single-Output (MIMO) utilize multiples antennas for transmitters and as well as receiver for wireless communication. Antennas which were not a great domain of discussion recently bring to pass the most important category in wireless communication. Especially when Researchers ultimately proved that with MIMO antennas system there are lots of advantages such as greater receiver gain, change magnitude data rates, larger vane throughput, and improved reliability through antenna diversity. IEEE 802.11n wireless standard which is pass judgment in 2009 uses MIMO to increase maximum speed to 100 Mbps and beyond, double the 802.11a and 11g wireless standards.This article was extracted from Techworld.com which clearly shows the use of MIMO system in wireless communication. Cox, 2008 says that MIMO has made its way into chipsets and could be in WLAN devices by year-end. The tertiary Generation Partnership Project, a collaboration of telecom standards groups, is withal evaluating MIMO techniques for use in cellular networks. MIMO manifold the spectral efficiency compared with that of current WLANs. So far, the only company with MIMO chipsets is Airgo Networks, which launched its products in August 2003. MIMO is unique because it multiplies bandwidth by essent ially providing multiple channels amongst devices, says Ben Manny, director of the radio communications laboratory in Intels merged technology group.MIMO can be classified into three categories Precoding, spatial Multiplexing and Diversity Coding. Precoding is multi-layer beamforming to support MIMO radio system. It is utilize for single-user MIMO or multiple-user MIMO in a linear or non-linear algorithm. Spatial multiplexing is a way to transmit and spot high rate signal into multiple lower rate currents and each menstruation is transmitted from a different transmit antenna in the same absolute frequency channel. Diversity modes is a single stream (unlike spatial multiplexing) to transmit data and is coded using techniques called space-time coding.Overview Architectures of Smart Antenna (MIMO)One of the biggest problems in wireless telecommunication is fading and inter-symbol interferences as shown in the diagram, below. Fading refers to the distortion of intensity over cer tain coevals media and Inter-symbol interference (ISI) occurs when there is reflection caused by other remote objects. The transmitted signal, at the receiver end are overlapped and delayed. To overcome this problem we use MIMO architecture, Orthogonal Frequency-Division Multiplexing (OFDM) modulation and Low-Density Parity-Check (LDPC) coding.MIMO operate in two modes diversity mode and spatial multiplexing mode to solve the problem.Diversity ModeThe use of two or more antennas that are spaced sufficiently apart such that they can receive signals from independent signal paths are involve in a Simple Receive Diversity. A basic way to drive an optimal receive antenna from an array of antennas is Selection Combining, whereby the receiver switches to another antenna whenever it detects weak signals or a high noise level from the current receiving antenna. More sophisticated techniques such as uttermost Ratio Combining (MRC) receive on multiple antennas simultaneously and apply advan ced signal impact algorithms to combine the different versions of the received signals to maximize SNR and minimize receive errors. Selection Combining and MRC can be utilise on just the receive side of the link as shown in the figure below. (Video54, 2008, p3)Spatial Multiplexing ModeIn rich multipath environments with multiple uncorrelated signal paths as figure 5, Spatial Multiplexing (SM) allows the vector to transmit different portions of the user data on multiple paths in parallel to increase capacity. The can receiver must implement a corresponding de-multiplexing algorithm to recover the original information stream from multiple antennas. In an ideal multipath environment, SM can increase the capacity of a single frequency channel linearly with the morsel of transmit antennas used. (Video54, 2008, p4)Figure 5 Spatial diversity (Video54, 2008, p4)Spatial Multiplexing requires the same multiplexing algorithm on both sides of a communications link. Therefore it is not inte roperable with existing 802.11a/b/g devices. Until 802.11n is defined, only SM client and SM network devices from the same vendor can transcend with each other. (Video54, 2008, p4)In contrast, Selection Combining and Maximum Ratio Combining are diversity techniques that can be utilise on just one side of a communications link therefrom they can benefit all existing 802.11a/b/g devices even when diversity is only implemented on the Access Point. (Video54, 2008, p4)Thus the above explanation shows how MIMO which is being a category of Smart Antennas is designed.Benefits/Limitations of Smart AntennasBenefitsSmart Antennas System, being one the latest technology in progress has brought lot of benefits. It serves as a dual purpose that is while enhancing the signal quality it also increased the reuse of the frequency. The benefits are in more details belowAs Smart Antennas receive signal from several antennas, this increase the military unit for higher gain of signal. The Antennas al so focuses on the communication device which allows the range of operation and the service by the antennas to increase. Thus reducing the cost by lowering the amplifier costs, power consumption and result in a higher reliability. To be more precise, with Smart Antennas the network providers will not require as many antennas/base stations to provide coverage. (Lehne et al. 1999, p. 5)Furthermore, Smart Antennas provide the facility to reuse the frequencies which can increase the number of users. This also add to the factor of cost reduction, that is if more users are on the same frequency there will be less operating cost for purchasing the frequency space. Interference will also be suppressed with the introduction of the Antennas system. The transmission pattern will be generated directly as forrader it was radiated from all the direction and increases interferences. Thus the suppression will also increase the ability to reuse and light upon a better coverage.With Smart Antennas s ignal are transmitted while targeting the communication device which can also be used to determine the accurate geographic information of the device. This can allow network providers to offer new services to the devices for example guiding emergency services to the location or the locality information. This system also increases security, as radiation of the signal is direct and not as in the conventional way when it was omni-directional. If someone wants to intercept the transmissions they would need to be at the same location or between the two communicating devices. (Gadh et al. 2003)Moreover, with the frequency reuse there in an increase in the bandwidth as Smart Antennas provide diversity. The adaptive array utilize multi-path signal to reach a device and reduce the effective delay spread of the channel and allowing higher bit rates to be supported without an equalizer. And as Smart antennas are not a new protocol or standard, it can easily be merged with existing non smart antennas and devices.LimitationsAs all other system, Smart Antennas also has some constraints. Lots of faults or problems can occur which can be very hard to diagnose as Smart Antenna is much more complicated than the traditional one (Lehne et al. 1999, p. 5). And also though there will be a reduction in the cost factor with the frequency reuse when the system is already implemented but while implementing this complex system, they are far more expensive than the traditional antenna. Furthermore out-of-pocket to the antenna arrays which are utilized by smart antenna systems, they are much larger in size than traditional systems. This can be a problem in a social place setting as antennas can be seen as ugly or unsightly. (Lehne et al. 1999, p.6) Smart Antennas need to have the surmount location to operate because of the direct radiation and not as the traditional one. For example in a road context, smart antennas are better situated away from the road, unlike normal antennas which are better situated along the road. (Lehne et al. 1999, p. 6)Need of Smart AntennasSmart Antennas has been required to accommodate with the future of mobile communication that is to significantly improve the performance of wireless performance and increase the number of users. So Spatial Division Multiple Access (SDMA) which is a satellite communication mode has exploited this technology to optimize the use of radio spectrum and minimized cost. SDMA also known as SDM (spatial-division multiplex) has also used Smart Antennas or adaptive array to adjust dynamically with the changing traffic and the user requirements by providing frequency reuse and antennas that are highly directional, unlike the previous wireless system like FDMA, TDMA or CDMA.Frequency Division Multiple Access (FDMA) was the first generation of wireless networks communication. FDMA technique was a basic technology in elongate that was used by the Advanced Mobile Phone Service (AMPS) and was the most widely techno logy installed in mobile phone in North America. FDMA assigned each channel to only one user at a time and is also used in the Total Access Communication Systems (TACS). But The Digital-Advanced Mobile Phone Service (D-AMPS) which also uses FDMA adds TDMA to get three channels for each FDMA channel, tripling the number of calls that can be handled on a channel. (Sanchez, 2003)Time Division Multiple Access (TDMA) was first used BY D-AMPS then Global System for Mobile communications (GSM) in 2G cellular system, and Personal Digital Cellular (PDC). Each of them implements TDMA differently and in incompatible way (Search Networking, 2006). TDMA is a channel rise to power method to share medium network and used in digital mobile communication dividing signal into three time slots in order to increase the amount of data that can be carried. It also allows multiple stations to share the same transmission medium while using only the part of its bandwidth they require. TDMA is used for Digi tal Enhanced Cordless Telecommunications (DECT) and also in the satellite system and combat-net radio. (Wikipedia, 2008)Code Division Multiple Access (CDMA) refers to the second generation (2G) and third generation (3G) wireless communication. It can be said to be an substitute(a) to TDMA and FDMA, but CDMA has a much higher bandwidth than the data being communicated in contrast with TDMA which divides approaching by time and FDMA divides by frequency. CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission channel, optimizing the use of available bandwidth and also allows roaming (Search Telecom, 2007) but it does not guaranteed the future of mobile communication and this is where SDMA arise and become the solution.ConclusionEven though Smart Antennas has some limitations, it has proved that it is the latest technology to bring an handsome future to wireless communication. With the adaptive array system the communication would be clearer wit h better signal and also the frequency reuse is of great advantage to cost reduction. Furthermore, MIMO is one of the latest discussed and the IEEE 802.11n wireless standard is evaluate in 2009. 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