Local access networks can be described as a network connection that limits access to the network over a specific radius. There are wired and wireless local access networks. Wired local access networks are characterized by the use of cables and adapters for network connection whereas wireless networks are characterized by the use of receptors and nodes for network access. Wireless local access networks are used in institutions such as hospitals, schools factories, offices and homes. In the named institutions, wireless LAN is used by hospitals and offices to access records and work without the use of bulky material such as paperwork.
The wireless access network is considered superior to the use of wired local access networks. The advantages attributed to the use of wireless access networks are mobility, whereby the user can access the network at the comfort of the office or the workstation without having to move from one location in order to access work, documents or records. In addition, the user has low costs of installation compared to the wired local access network that has very many cables and adapters, which enable transmission in the network. The wireless local access network has low infrastructure in that no wire connections are necessary for the user to access the network. Moreover, the use of wireless networks enables the user to ease the change in the network topology into any that best works to the advantage of the network users. Wireless networks are catastrophe resistant in that they are manageable and scalable in size. Furthermore, wireless networks are easily maintained in that they do not require complex maintenance routines.
However, the wireless networks are not free from problems. They are faced by interference by other signals such other networks from around the area of operation and radio signals from devices such as mobile phones and media gadgets such as radios and television sets. In addition, they also are coupled by security threats from hackers and malicious software. The wireless networks are rarely interoperable because of lack of transferability from one vendor to another owing to the very many regulations in each vendor system. Wireless networks also accrue health and safety issues in that they pose health risks associated by the electromagnetic fields associated with wireless gadgets. Moreover, the use of wireless networks is associated with lower data charges
There are several technologies for wireless networking in a private local access network. They are mainly Bluetooth, HIPERLAN, Ultrawideband, cellular/Personal Computers infrastructure and custom /private protocols. The use of a standard wireless local access network is advantageous in that it serves as a guide for developing new and reliable hardware. In addition, the wireless network enables the network user to interoperate the network with other network vendors such that one network has multiple network vendors. It also reduces the risk associated with new products, which might corrupt the network and even wreck the whole system of the user. However, these advantages are countered by disadvantages whereby the use of a specific standard does not allow for innovation on the part of the users. It also may lead to dormancy in the development of technology in a fast-growing technology field. Standard sharing vendors cannot fully market and sell their products with the existence of rigid standards.
The IEEE 802.11 is a standard for implementing wireless networks. It release was by unlicensed use whereby the spectrum is free. The unlicensed bands for the wireless networks are essentially good for deploying relatively small private radio networks. Wireless networks are also forced to compete with other in-band users, which are erratic in number and interference. Unlicensed band usage is categorized into the 2.4GHZ-ISM band and the U-NII band. The 2.4GHZ ISM band is referred to an Industrial Scientific Medical band; it is specifically on the 2.4000-2.4835 GHz band. It has 83.5 MHz of free spectrum, and it has inexpensive hardware. The band is very useful to the users because of its easy compatibility with other users. The U-NII band is described as the Unlicensed National Information Infrastructure band. It lies on the bands of 5.15-5.35 GHz and on 5.725-5.825 GHz and comes with 300 MHz of free spectrum and fewer co-existing systems. It is relatively inexpensive to install and use but its radio hardware is the only expensive bit about the band.
The IEEE 802.11 has more extensions to it. They are mainly 802.11a, which is a standard, which adds more Orthogonal Frequency Division Multiplexing (OFDM) to the standard for high data rates in the U-NII band. Another extension is the 802.11b whereby there are additional 5.5mbps and 11 mbps capabilities to the IEEE 802.11standard.furthermore 802.11e is a future extension that is responsible for maintaining the quality of service capability for some applications by the user. It also has the 802.11g, a future extension for 2.4 GHz links for using the OFDM for 22 mbps data rates. For security purposes, the 802.11i was developed to counter threats to the network.
The IEEE 802.11 has two parts, which are PHY and MAC. The PHY correspond to the physical outlines and the operations of the standard to the OSI protocol stack. It also ahs many different specifications and its specific extensions only exist for the 802.11 standard. It entails of how the data in the network is specifically sent in and out of the network. Whereas the MAC consists of and correspond to data links and outline operations in the OSI protocol. In summary, it handles the data part of a network. The Mac is the same for all 802.11 standards regardless of which PHY is specified and its main aim is concerned with how data is framed into data packets for transmission via the network. The PHY is divided into two main parts namely the Physical Medium Dependent (PMD) and the Physical Layer Convergence Protocol (PLCP) The PMD is responsible for modulation, coding and decoding, and multiple access of the network. The PLCP is responsible for channel assessment, physical layer services that are independent of any physical medium. The Data Link layer is divided into two parts the Medium Access Control MAC and the Logical Link Control (LLC). The data link layer’s purpose is to transfer data within adjacent network nodes while the Medium access control is a protocol sub layer of the data link layer that provides channel access and addressing the control mechanisms between several terminals for them to communicate within a multiple access network.
The IEEE 802.11 standard for wireless networks has interoperability challenges. There existed difficulties in the cross vendor operations for the users such that it was impossible for the users to change network vendors. The network vendors did not follow the IEEE 802.11 standard to the latter, which brought rise to numerous problems to both the vendors and the users. However, some issues were addressed and some were not therefore some problems regarding the standards still exist and need address. The interoperability issues prevent the public from accepting new technology thus the industry loses a lot of money and its credibility. In addition, the lack of interoperability leads to little or no innovation as new technology is prevented from the development of new technology.
Interoperability issues were countered by the solution of formation of the Wireless Ethernet Compatibility Alliance. WECA is an industrial association formed on 23 August in the year1999.It sole purpose is to provide interoperability-testing services for vendors of the IEEE 802.11 wireless modem. The WECA is responsible certification of Wi-Fi enabled equipment, which gives any equipment tested by the organization a very high degree of reliability and interoperability. In the use of Wireless networks, multiple access issues also arise. For the wireless network to fully function simultaneous links must be coordinated in the same network. The interference in ISM bands and deep fading in the frequency of the bands is also another issue facing network users. The direct spread system consists of eleven overlapping channels with each channel having 22 MHz total bandwidth. The radio links can also use the overlapping channels simultaneously. Frequency hopped spread spectrum is characterized by the presence of over seventy nine channels with each channel having a total 1 MHz bandwidth. The unique hop sequence is characterized by a unique hop sequence for each length, which avoids simultaneous use.
Direct sequence spread spectrum is a modulation technique favored by modem designers. It is best for coexistence of networks where there are in-band wireless systems. In addition it also woks to the contribution of more gentle interference to other in-band systems thus for this reasons it is regarded highly among the information modem designers. The Direct sequence spread spectrum enables the links to be easily modified for IEEE 802.11b extensions. Japan has the largest number of channels with fourteen frequencies followed by Europe in overall and then by the United States and France and Spain respectively. Spreading a signal in the IEEE 802.11 standard uses the Barker sequence due to the low correlation properties of the method. The method implies change of phase of the waves at 180degrees.A barker’s spread signal is similar to that of a spread signal. When signal is interfered by noise it becomes blurred and is represented by an almost straight line whereas a realistic signal is almost similar to that of the spread signal. When noise is filtered in a despread signal, it becomes refined and it becomes easily transmittable through the network. Despreading is the art of spreading an interfered signal to come up a new signal that is ready for retransmission through the network. Spreading increases with bandwidth of the signal for increasing resistance to interference of the signal.