The 802.16 standard was developed by the Institute of Electrical and Electronics Engineers (IEEE), called WirelessMANTM, providing a new perspective in accessing the internet at high speed without depending on cable networks or modems. In 2002, the Worldwide Interoperability for Microwave Access (WiMAX) forum was formed, referring to the 802.16 standard and tasked with interconnecting various global technical standards into one unit. WiMAX technology is cheaper than other broadband technologies such as digital subscriber line (DSL) or cable modems. Connection speed or new technological advances are not only important aspects to evaluate, but both are facts of unsafe wireless transmission for communication. The security aspect is very important for broadband technology in accessing information from the internet.
Mesh networking is a way to route data, voice and instructions between nodes. It is a continuous connection and also "hopping" from node-to-node until the destination is reached. In a Mesh network, all nodes are connected to each other in a single network. Mesh differs from other networks, in the sense that all component parts can be connected to each other by multiple hops, and are generally not mobile. Mesh can be seen as one type of ad-hoc. Mobile ad-hoc networking (MANet), and then interconnected, but mobile ad-hoc networks also have to deal with the problem of node mobility.
This paper discusses the development of WiMAX, its differences with WiFi, existing features and security systems in WirelessMANTM technology based on the 802.16 standard specifications. It also discusses the development of WiMESH, as well as the working principles of WiMESH.
Understanding Wi-Max
1. Introduction
WiMAX (Worldwide Interoperability for Microwave Access) is a Broadband Wireless Access standard with the ability to provide high-speed data services. WiMAX technology is a development of WiFi technology (802.11x) which is designed to meet non-LOS (Line of Sight) conditions. Currently, WiMAX is used for wireless internet connections with speeds of up to 70 Mbps. Unlike WiFi which only covers around homes or offices, WiMAX has a wider coverage of up to 50 km. WiMAX technology can be used for various applications such as broadband access, backhaul and personal broadband. For broadband access, WiMAX can be used as a lastmile technology to serve the needs of broadband services for corporations, SoHo (Small Office Home Office) and residential customers. For backhaul applications, WiMAX can be used as WiMAX backhaul itself, hotspot backhaul or cellular technology backhaul.
Figure 11.1. Communication specification standards
2. History of Wi-Max
How did WiMAX technology and the name WiMAX itself originate? According to James A. Johnson (Vice President, Intel Communications Group/General Manager, Wireless Networking Group), the term WiMAX comes from the abbreviation wireless (abbreviated Wi) Microwave Access (abbreviated MAX). WiMAX resembles Wi-Fi in terms of using the same modulation technology.
This technology is called OFDM (Orthogonal Frequency Division Multiplexing). OFDM is a digital modulation system in which a signal is divided into several channels with narrow frequency bands that are close together, with each channel using a different frequency. The technology was developed in the 1960s - 1970s. This technology was developed during research to reduce frequency interference between channels that are close together.
On non-WiMAX frequencies, a radio wave will usually interfere with another radio wave, especially if the frequency has a close vibration cycle[2]. The most obvious thing is when we play two remote control cars on adjacent radio frequencies, for example car A (frequency 27.125MHz) and car B (frequency 27.5MHz). If both cars (including their radio controls) are turned on, the two frequencies will be able to interfere with each other. As a result, if we are going to move car A, car B can also move. Or if we turn car B, car A will move back a few meters.
Imagine what would happen if this were experienced by the frequency used to carry data (carrier) such as in wireless data communication. The interference could cause various losses, such as damage to data carried by the frequency, failure of data transmission, or errors in data transfer.
With the technology offered by WiMAX, all these obstacles will disappear by themselves. WiMAX technology allows us to transmit various signals in a very close distance, without having to worry that the various signals will interfere with each other. Thus, we can overlap high-density data traffic in various channels. With many channels that can be overlapped by abundant data at one time, ISPs or broadband service providers can present cable or DSL-based services to many customers as a replacement for copper cable media.
Although the basic technology is the same, Wi-Fi and WiMAX still have differences. According to James, the difference between the two lies in the division of the spectrum used, and in the use of licensed frequencies in WiMAX[2]. Although WiMAX and Wi-Fi use one unlicensed frequency (namely the 5.8GHz frequency), WiMAX is also directed to be able to utilize two other licensed frequencies, namely 2.5GHz and 3.5GHz. This allows us to increase the output power of WiMAX devices so that they can reach further distances.
Thus, if WiFi only operates in the range of meters, WiMAX can operate in the range of kilometers. In addition, WiMAX is designed in the carrier-grade technology level. This makes WiMAX have better reliability and quality of service than Wi-Fi. With a longer range, and the ability to pass through various obstacles such as buildings or trees, WiMAX is suitable for application in urban areas that have office buildings and housing.
3. Wi-Max and WiFi
Actually, WiMAX performance is almost the same as WiFi, namely, both use "hotspots" or the environment around the antenna where we can access information with a PDA, Laptop or other gadgets. The difference is in terms of radius coverage. For WiFi can reach 100 feet or around a radius of 30 meters, while WiMAX has a range of 25-30 miles or around 40-50 Km (maximum 50 Km) [3]. This means that WiMAX can be used as a replacement for traditional broadband that still uses telephone lines (such as ASDL, ISDN) and cables (Internet via Cable TV or PLN network for example). For starters, WiMAX is intended for fixed wireless use.
Currently, many IT businessmen are convinced that WiMAX will soon go global. In fact, the development of Wi-Fi alone took 10 years. This technology is actually a further development of the Wi-Fi concept. This technology has provided many conveniences for humans, but has the constraint of limited capacity and range. While many large companies in the world need wireless network access that has large data capacity, low cost and can be accessed from all places.
Wi-Fi technology has a limited range, at most about 100 meters. Compare that to WiMAX which has a range of about 7 to 10 km. It is not wrong if WiMAX is projected as a wireless network technology for urban areas.
With WiMAX wherever we go in the city, internet access can be done without too much cost. To find information, you don't need to go to the office or internet cafe, just sit in the car while waiting for the traffic jam, then open the notebook. While for Wi-Fi, once you leave the hotspot area, the data connection immediately dies.
WiMAX has the ability to transmit data at speeds of up to 75 megabits per second (Mbps), while Wi-Fi is only 11 Mbps. Another advantage is that WiMAX plays at a fairly low and wide frequency, namely 2 - 6 gigahertz (GHz). While Wi-Fi is regulated in the 802.11b protocol at 2.4 GHz and the 802.11a protocol at 5 GHz.
This WiMAX standard promises to provide long-distance broadband connectivity at DSL speeds. This wireless component is expected to be the first cost-effective system-on-a-chip design for Customer Premise Equipment (CPE) that supports IEEE 802.16-2004 (formerly known as IEEE 802.16REVd). The CPE itself is used for applications that send and receive a wireless broadband signal that provides Internet connectivity.
WiFi (Wireless Fidelity) as another wireless technology that is quite popular with the scope of local networks. Of course, with this WiFi technology has been widely used in restaurants and cafes that provide WiFi services for their customers by purchasing a prepaid WiFi card to be able to access wireless internet from notebooks or PDAs.
What distinguishes WiFi from WiMAX is that WiFi is installed primarily on one spectrum, namely 2.4 GHz, which generally does not require a license. Whereas when compared to WiMAX, it is based on frequencies between 2 -- 11 GHz.
Figure 11.2. WiMax and WiFi
4. WiMax and DSL
There are many varieties used by telecommunications operators to provide broadband access services to customers. In terms of the media used, it can be divided into two, namely wireline technology (cable) and wireless technology (without cables). From the wireline technology category, DSL (Digital Subscriber Line), cable modem, HFC, and optics can be used. While from the wireless category, you can utilize wireless LAN technology, BWA (Broadband Wireless Access) and the latest WiMAX (Worldwide Interoperability for Microwave Access) technology.
With the various solutions above, some operators utilize DSL (cable) and BWA (for wireless) technology. For incumbent telecommunications operators in a country, for example TELKOM for Indonesia which has deployed around 6 million cable lines, they will utilize DSL technology to enhance their physical network to distribute high-speed data to customers. While for new operators, it is certainly very difficult and expensive to deploy a broadband network with DSL. The alternative is to utilize wireless technology (BWA). With the birth of the latest wireless technology (WiMAX), it can be used as a replacement or alternative to distribute broadband services to customers.
When viewed from the market segment, WiMAX and DSL have similarities, namely that they are both intended for MAN (Metro Area Network) where the distance to the customer is around 10 km.
Figure 11.69. DSL configuration
DSL itself is high speed with cable broadband access only available to some computer users. So with WiMAX will allow high speed wireless connections with relatively cheaper and more effective costs for home and business users, both in urban and rural areas.
The problems in the broadband sector have been solved with the presence of WiMAX technology. It is very unfortunate for users/consumers who want to enjoy services such as telephone and local networks that are starting to move to wireless systems, broadband access for business or housing still tends to rely on cables for data distribution. As a result, it is detrimental to operators and consumers who are outside the reach of the cable.
Cable technologies such as Digital Subscriber Line (DSL), modem cable and leased line still have competitiveness in terms of cost, convenience and easy-to-find devices. And the solution falls on WiMAX which seeks to unify the wireless industry while lowering the price of wireless devices.
5. Advantages and Disadvantages of Wi-Max
There are several advantages to WiMAX, when compared to WiFi, including the following.
- Microelectronics manufacturers will have a new field to work on, by making more general chips that can be used by many wireless device manufacturers to make their BWA. Wireless device manufacturers will not need to develop end-to-end solutions for their users, because there is already a clear standard.
- Telecommunication operators can save on equipment investment, because WIMAX capabilities can serve their customers in a wider area and with higher compatibility.
- End users will get many choices in surfing the internet. WiMAX is one of the technologies that can make it easier for us to connect to the internet easily and with quality.
- Having many features that have not been available in WiFi technology with the IEEE 802.11 standard. The IEEE 802.16 standard is combined with ETSI HiperMAN, so it can serve a wider market share.
- In terms of coverage alone, reaching a maximum of 50 kilometers, WiMAX has made a huge contribution to the existence of wireless MAN. The ability to deliver data with a high transfer rate over long distances will close all broadband gaps that cannot be reached by cable and digital subscriber line (DSL) technology.
- Can serve subscribers, both those in line of sight (LOS) and those that are not in line of sight (NLOS).
Meanwhile, the disadvantages of WiMax are:
- Because it uses a high frequency spectrum band, the WiMAX service coverage is smaller than 3G, so a greater number of base stations are needed to cover the same area.
- WiMAX frequency spectrum allocation requires adjustments to existing frequency allocations in each country. The uneven frequency allocation causes expensive equipment prices.
- WiMAX's mobility capabilities will not be as good as cellular systems and battery consumption will be more wasteful.
6. Wi-Max Standardization
The IEEE 802.16 standard is an output from the IEEE organization, just like IEEE 802.11 is a standard created specifically to regulate communication via wireless media. What distinguishes it is that WiMAX has a higher data transfer rate with a longer distance, so that the quality of service using this communication can be classified into the broadband class. This standard is often called the air interface for fixed broadband wireless access system or air interface for broadband connections.
Actually, the IEEE 802.16 standardization is more about developing technical aspects of the physical layer and datalink layer (MAC) of the BWA communication system. The initial version of the 802.16 standard was issued by the IEEE in 2002. In this initial session, 802.16 devices operated in a frequency range of 10-66 GHz with a line of sight (LOS) communication path between devices. The bandwidth provided by this technology is 32-134 Mbps in a maximum coverage area of 5 kilometers. Its capacity is designed to accommodate hundreds of users per BTS. With this capability, device technology that uses the 802.16 standard is suitable for use as a provider of broadband connections via wireless media. The technical differences between IEEE 802.11 and IEEE 802.16 can be seen in the following table.
Table 11.4. Differences between IEEE 802.11 and IEEE 802.16 technologies
7. Wi-Max Technology
WiMAX (worldwide interoperability for microwave access, IEEE.802.16) is specifically developed from OFDM (orthogonal frequency division multiplexing) technology to achieve wide coverage area (several miles or around 50 km) with high speed (around 72 Mbps wireless) and additional multiple access (see IEEE.802.16e: OFDMA access method) that may be applied to future cellular communication systems. This additional multiple access with good performance could become a new competitor for existing cellular telephone networks.
Its predecessor technology, namely WiFi (IEEE.802.11) which we still use in laboratories, campuses, airports, conference rooms to coffee shops and supermarkets, can only reach 20-100 meters with a speed of several tens of Mbps. That is why WiMAX is more promising for expanding cheap networks in rural areas where infrastructure development such as DSL cables feels very expensive. Perhaps this is what underlies the comments of experts, that WiMAX technology is vital and very suitable (read: cheap) to be applied in developing countries such as Indonesia, where the cost of fixed communication investment is still considered heavy.
8. OFDM Wi-Max
OFDM is not a new thing because it has actually been widely studied since the 60s although it only boomed after being triggered by the discovery of FFT (Fast Fourier Transform) around the 70s, coupled with recent applications in DSL, cable modems, WiFi, Digital Television and WiMAX. OFDM is able to support high-speed data because of its efficiency, namely with overlapping frequencies but is guaranteed not to be damaged because it is orthogonal (unless there are other problems such as frequency offset due to the Doppler effect).
With the basic character of OFDM above, in the WiMAX Standard, OFDM will be able to reach 72Mbps (clean data) or up to 100Mbps (data plus coding) in the 20MHz spectrum. This means that OFDM in WiMAX is able to transmit 3.6 bps per Hz. For example, we have a bandwidth allocation of 100MHz, implemented at a frequency of 5.8GHz (i.e. for example 5.725-5.825GHz), obtained 5 band blocks (i.e. 5 x 20MHz = 100MHz), then we will get a capacity of 5x72Mbps = 360Mbps (assuming all channels are added and with 1x frequency reuse). Then with sectorization, the total capacity of a base station will reach more than 1Gbps, a very high speed for wireless access.
9. Wi-Max components
The main components of the WiMAX system are the Subscriber Station (SS) or known as CPE and Base Station (BS). BS and one or more SS can form a cell with a point-to-multipoint (P2MP) structure. In the air, the BS controls the activities of the cell, including access to the medium by the SS, allocation for quality of service (QoS) and managing the security of the network below it.
The 802.16 system uses antennas at the SS site. These antennas cover the coverage area. Equipment such as Adaptive Antenna System (AAS) and sub-channels are also supported by the standard for link budget planning for indoor installations. IEEE 802.16e works specifically for mobility standards and supports the power of SS terminals.
BS generally uses directional or omni-directional sector antennas. Fixed SS generally uses directional country while mobile or portable SS generally uses directional country.
Multiple BSs can be configured to form a wireless cellular network. When Orthogonal Frequency Division Multiplexing (OFDM) is used, the cell radius is 30 miles. In practice, the minimum cell radius is approximately 5 miles.
The 802.16 standard can also be used in point-to-point (P2P) or Mesh topologies, using a pair of directional states. This can be used to increase the effective range of a system relative to supporting P2MP mode.
WiMAX is an IEEE 802.16 standard that governs various derivative standards. This standard regulates the use of wireless devices for urban network purposes (Metropolitan Area Network/MAN). This standard is specifically designed to meet the network needs for high-speed wireless access or BWA (broadband wireless access). The presence of this technology is expected to enable access to various multimedia applications via wireless connections with greater distances between devices.
10. Wi-Max Characteristics
The 802.16 standard (and its derivatives) operates in the radio frequency band between 2GHz and 11GHz. This standard has a transfer rate of 75Mbit per second with low latency, and efficient use of frequency spectrum space.
To secure the connection that occurs, this standard also supports data encryption features, with Forward Error Correction (FEC) type error settings. The distance that can be reached by this standard can be extended to about 30 miles, or about 48 kilometers with a throughput level that is still adequate to transfer data.
WiMax is divided into two utilization models, each represented by two different IEEE standards. The first utilization model is the utilization of fixed access, or fixed connections that use the IEEE 802.16-2004 standard (as a revision of the IEEE 802.16a standard). This standard is included in the "fixed wireless" service category because it uses antennas installed at the customer's location. These antennas can be installed on roofs or high poles just like satellite dishes for TV. The technology of this standard is a substitute for technologies such as cable modems, all kinds of digital subscriber lines (xDSL), transmit/exchange circuits (Tx/Ex), and optical carrier circuits (Oc-x).
While the second utilization model, often called portable or mobile utilization, uses the IEEE 802.16e standard. This standard is specifically implemented for data communication on various handheld devices, or mobile devices such as PDAs or notebooks.
11. Wi-Max Configuration
In general, WiMAX configuration is divided into 3 parts, namely subscriber station, base station and transport site. For subscriber station is located in the customer environment (can be fixed or mobile/portable). While the base station is usually one location with the operator network (IP/internet network or TDM/PSTN network). To clarify the configuration in question, the following image (Figure 2) is a generic configuration of WiMAX.
Figure 11.70. Wi-MAX configuration
Figure 11.70. Another example of a Wi-MAX configuration.
Open standard, one of the advantages of WiMAX is open standard. So that vendors, customers and operators do not need to worry anymore because they can use any brand (not dependent on one brand).
Installation speed, another advantage of WiMAX is the installation speed. For customer installation with outdoor antennas it takes less than an hour. Compare that to having to roll out a cable network and a DSL modem.
Regulation issues, it seems that people have to be patient to be able to utilize WiMAX. This is because there is no regulation from the government, especially regarding frequency issues. For the current 3.5 GHz WiMAX frequency, it still clashes with satellite frequencies while 2.5 GHz interferes with Microwave and cable TV.
High speed, WiMAX is capable of transmitting data at speeds of up to 75 Mbps with a spacing width of 20 MHz.
Flexible, WiMAX is not only intended for fixed customers such as DSL customers, but can also serve nomadic and mobile customers.
Investment, along with the maturity of WiMAX products, many vendors promise a decrease in the investment price of WiMAX devices. Even the next stage of WiMAX will be produced embedded (united like WiFi on a centrino notebook) with notebook devices, PDAs and even mobile phones.
Not dependent on cables, unlike DSL which requires a cable network, WiMAX does not depend on the available cable infrastructure. Thus WiMAX is more flexible to use to provide broadband access services to rural areas or locations that have not or are difficult to use cable networks.
12. How Wi-Max Works
WiMAX technology can cover an area of about 50 kilometers, where hundreds of customers will be shared signals and channels to transmit data at speeds of up to 155 Mbps. The security aspect is a very important aspect and will be evaluated by internet users using ADSL facilities or cable modem technology or those who subscribe to WiMAX technology.
The data security system is carried out on the physical layer (PHY) and data link layer (MAC) in a network architecture, precisely at the base station (BS) to be distributed to the surrounding area and the subscriber station (SS) for point to multipoint communication. The base station (BS) is connected directly to the public network.
In general, WirelessMAN traffic is divided into three parts, as follows.
- Customers send data at speeds of 2 -- 155 Mbps from the subscriber station (SS) to the base station (BS).
- The base station will receive signals from various customers and send messages via wireless or cable to the switching center via the IEEE 802.16 protocol.
- The switching center will send a message to the internet service provider (ISP) or
- public switched telephone network (PSTN).
13. Wi-Max Application
WiMAX can be used for WiMAX backhaul itself, Hotspot backhaul and other technology backhaul. In the context of WiMAX as a backhaul of WiMAX, its application is similar to the function of BTS as a repeater to extend the range of WiMAX. While as a backhaul of other technologies, WiMAX can be used for cellular backhaul. Also, if hotspots usually use ADSL channels as their backhaul, but due to the limitations of the cable network, WiMAX can be used as a hotspot backhaul.
Figure 11.71. WiMAX as Cellular Backhaul
WiMAX can be used as a "Last Mile" technology to serve broadband needs for customers. From residential and business customers can be met by this WiMAX technology.
WiMAX as a personal broadband service provider can be utilized for two market segments, namely nomadic and mobile. For nomadic solutions, the level of movement of WiMAX users is usually not frequent and if they move, it is at a low speed. The devices are usually not as simple as for mobile applications. For mobile applications, WiMAX service users perform mobility like using WiFi terminals such as notebooks, PDAs or smartphones.
Understanding WiMesh
Mesh networking is a way to route data, voice, and instructions between nodes. It is a continuous connection and also "hopping" from node-to-node until the destination is reached. In a mesh network, all nodes are connected to each other in a single network. Mesh is different from other networks, in the sense that all component parts can be connected to each other by multiple hops, and are generally not mobile. Mesh can be seen as one type of ad-hoc. Mobile ad hoc networking (MANet), and then interconnected, but mobile ad hoc networks also have to deal with the problem of node mobility. Self-healing mesh networks where a network can still operate even if a node breaks down or there is no connection at all.
A Wi-Mesh network is designed to extend the range of a Wi-Fi network indoors and outdoors over long distances. It does this by allowing multiple access points to relay traffic to different access points. If a Wi-Fi hotspot requires a direct connection to the internet, the mesh network forwards the data request until a network connection is found.
2. Working Principle
Where the Internet is mostly wired, a cooperative electronic communications infrastructure similar to the agreements associated with international postal services, messages are sent to each other and broadcasted in separate areas for free (i.e. if you rebroadcast a message sent in your area it will be rebroadcast in your area), Mesh is a cooperative wireless communications infrastructure between a large number of individual wireless transceivers (i.e. a wireless mesh) that is Ethernet.
This type of infrastructure can be decentralized (with no central server) for immutable applications or centrally controlled for immutable applications (with a single server); both are relatively inexpensive, and are very reliable and resilient, as long as each node only needs to transmit as far as the next node. Nodes act as repeaters to transmit data from nearby nodes to peers that are too far away to reach, resulting in a network that can span large distances. Mesh networks are also very reliable, as each node is connected to several other nodes. If one node in the network goes down, due to hardware failure or other reasons, its neighbors simply find another route. Large capacity can be installed by many nodes. Mesh networks may use fixed or mobile equipment. Solutions are similar for communicating in difficult situations such as emergency situations, tunneling and oil rings, to high-speed motion video applications and mobile video applications on public transport.
The principle is the same as sending packets over an internet cable --- data will hop from one device to another until it reaches a given destination. Dynamic routing capabilities are included in each device. To implement such dynamic routing capabilities, each device needs to communicate its routing to every device connected to it. Each device then decides what to do with the received data --- pass it on to the next device or store it. The routing algorithms used always ensure that the data is retrieved quickly and reaches its destination.
The choice of radio technology for a wireless mesh network is complicated. In a wireless network where laptops are simply connected to a single access point, each laptop must share a fixed pool of bandwidth. With mesh technology and adaptive radio, devices in a mesh network are connected only to other devices within range. The advantage is that, like a load balancing system, the more devices there are, the more bandwidth is available, provided that the number of hops in the average communication path is kept low.
3. Creating WiMesh from WLan
Physically connecting wireless access points to a wired network infrastructure can be one of the most challenging and expensive tasks associated with a wireless LAN deployment. In organizations with flexible structured cabling, it is simply a complementary nuisance, but in a distributed campus, housing complex, or municipality, running cables to every access point is nearly impossible.
In a fragmented environment, mesh networking may be an option. Instead of backhauling Wi-Fi traffic over an Ethernet cable connected to a switch, we can backhaul it wirelessly. Mesh networking is not a new concept. The 802.11 standard includes provisions for WDS (wireless distribution system) that connects APs to each other via radio instead of cables. However, WDS offers limited capabilities compared to modern mesh systems.
(designed specifically to connect only two APs wirelessly), so the IEEE 802.11s working group developed a new mesh standard, aiming for completion in 2007.
In a wireless mesh, each wireless network node can be an active participant in a mesh. A dedicated mesh theoretically provides the widest coverage at the lowest cost. However, because nodes can appear and disappear at any time, this type of mesh is not suitable for many applications. A mesh infrastructure, in which the mesh forwards the delivery of wireless backhaul/backbone services, is typically more widespread.
In a wired network, alternative paths can be taken through the mesh. Mesh nodes optimize these paths. The wire mesh architecture is similar to the wired mesh used in the Internet, where routers make forwarding decisions using dynamic routing protocols. In both cases, the specific paths that packets pass through intermediate nodes are transparent to the client. Many factors, including traffic levels, link capacity, routing protocol efficiency, and overhead, can affect overall performance. Networks with small hop counts will generally have better throughput and latency characteristics than networks with large hop counts, which experience a performance hit for each intermediate hop. To overcome this, a fast, dedicated mesh backhaul connection may be desirable.
4. Design Options
Although some mesh systems limit themselves to providing wireless backbone services, most provide a combination of backbone/infrastructure and client access services. Thus, a Wi-Fi client can connect to a node that simultaneously acts as an infrastructure device for the mesh backbone. In these systems, the mesh node must handle Wi-Fi access standards (usually 802.11 b/g but sometimes 802.11 a is also acceptable), ingress traffic from other mesh nodes, egress traffic to other mesh nodes, and, in some cases, an Ethernet connection to the wired network.
The simplest wireless mesh design uses a single radio for access, ingress, and egress. Its distinguishing characteristics are simplicity and low cost. In a single-radio design, both client access and communication between mesh nodes take place over a single radio, which dynamically switches functions from AP-node to mesh-node (see the “Solo radio” chart below).
These systems, typically using 2.4 GHz 802.11b/g, are somewhat expensive to deploy, but they offer performance and capacity limitations. That is why the single-radio in each mesh node must time-slice between client access, ingress, and egress. To overcome this limitation, the network must be designed to minimize the hop count. So about one-third to one-half of all mesh nodes must also have a connection to the wired network, either directly via Ethernet or through a dedicated point-to-point, or point-to-multipoint, fixed wireless backhaul system. Larger, single-radio mesh networks are typically deployed in conjunction with 5 GHz multipoint wireless backhaul systems from Alvarion or Motorola. That can mean higher costs as well as network management complications.
More sophisticated wireless mesh networks use a multiradio design, separating access, ingress, and egress functions. In a two-radio design, client access traffic takes place on one radio channel (usually 2.4 GHz 802.11b/g) while ingress/egress mesh traffic uses a different channel (usually 5 GHz 802.11a). By separating access and mesh functions, dual-radio designs offer several performance and design advantages.
There is an increase in overall system capacity and more flexible allocation of RF channels. Trading stops, however, mean that dual-radio systems tend to cost more than single-radio systems, because the hardware for a dual-radio setup is more expensive and they generally rely on 5 GHz for mesh communications.
These signals are heavily attenuated by buildings and tree foliage, so more mesh points are required for such a system than for a single-radio, 2.4 GHz design. And their deployment requires more complex radio-link designs to ensure LOS between mesh points.
The last and arguably most sophisticated mesh network design uses three or more radios per node. These additional radios can be used for two purposes. First, they can create a multisector and/or multichannel access system with directional antennas to increase range and provide greater client access capacity. Second, they can optimize mesh traffic by separating ingress and egress traffic on different radio channels. This multiradio offers excellent performance, but is more expensive and complex to install.
It is important to remember that adding more radios to a mesh node does not necessarily guarantee superior performance. That is because other factors, including radio efficiency, routing protocols, and mesh diameter, also contribute to performance. In general, however, more radios translate to better performance and capacity, albeit at a higher cost.
5. Miz and Mash
Because there is no wireless mesh standard, interoperability between systems from different vendors is limited. It is theoretically possible to build a large mesh network using gear from multiple vendors, but most organizations opt for a single vendor. As the popularity of wireless mesh increases, the need for interoperability will only increase.
This is especially true for systems designed for the consumer market, where enjoyment of installation is a key requirement.
The IEEE 802.11 working group began considering proposals for a mesh extension to the 802.11 standard in July. The leading proposal, which received 83 percent of the vote, is known as SEEMesh (Simple, Efficient, and Extensible Mesh). SEEMesh is being spearheaded by a large group of high-profile vendors including Intel, Motorola, Nokia, NTT DoCoMo, and Texas Instruments. Further details of the proposal are not available at this time, but it is oriented toward making standardized mesh capabilities available to a potentially broad consumer market.
Close behind (with 76 percent of the vote) was a proposal submitted by the Wi-Mesh Alliance, which includes Accton, Nexthop, Nortel and Philips. The Wi-Mesh proposal addresses a broader range of needs, including both single- and multi-radio element designs, quality of service (QoS) and security enhancements. More details of the proposal are available at www.wi-mesh.org .
6. Mash Development
In the development of WLAN, there is a clear distinction between infrastructure equipment and those in the client to be able to join the WLAN. WLAN infrastructure equipment is developed based on the 802.11 AP standard that provides several services, especially support for equipment power savings, to save traffic, authentication services and use the AP network is usually directly connected to the wired network, and provides wireless connectivity services to client equipment beyond the connectivity of the wireless equipment itself. Client equipment, in other words, is implemented as 802.11 which must be combined with the AP in access gain to the network. STA depends on the connected AP to communicate. The WLAN development model and its equipment are illustrated in the following figure:
Figure 11.6. 802.11 Development Model and Equipment
There is no reason, however, that many devices used in WLANs cannot support flexible wireless connectivity. Infrastructure devices such as APs must be able to establish peer-to-peer wireless with adjacent APs to establish a mesh backhaul infrastructure, without the need for network cables to be connected to each AP. Typically, legacy devices that are categorized as clients must also establish peer-to-peer wireless with their clients and APs on the mesh network. In some cases, these mesh-enabled client devices provide the same services as APs to help establish STA access gain on the network.
The architectural goal here is to divide wireless equipment into two main classes: mesh class nodes are nodes that are capable of serving the mesh, while the non-mesh class includes STA clients. Mesh class nodes can optimally support AP services and can be configured or not.
Mesh service can be implemented as a MAC interface that is independent of 802.11 MAc. In principle, a single device can play from the function of both mesh points and AP or the function of both mesh points with STA. In short, how to realize multi-role devices.
7. Conclusion
WiMAX (Worldwide Interoperability for Microwave Access) is a Broadband Wireless Access standard with the ability to provide high-speed data services. WiMAX technology is a development of WiFi technology (802.11x) which is designed to meet non-LOS (Line of Sight) conditions. Currently, WiMAX is used for wireless internet connections with speeds of up to 70 Mbps. Unlike WiFi which only covers around homes or offices, WiMAX has a wider coverage of up to 50 km. WiMAX technology can be used for various applications such as broadband access, backhaul and personal broadband. Mesh networks are a way to direct data, voice and instructions between nodes. This is a continued connection and also "hopping" from node-to-node until its destination is reached. In Mesh networks, all nodes are connected to each other in one network. Mesh is different from other networks, in the sense that all component parts can be connected to each other with various hops, and are generally not mobile. Mesh can be seen as one type of ad-hoc.
8. QUESTIONS
- Explain what is meant by Wi MAX and briefly explain its working principle.
- Name the standards used in WiMAX and state the differences with WLAN standards.
- Explain what WiMESH is and briefly describe how it works.
- Describe the WiMAX configuration and give a brief explanation.
- How to create a WiMESH network from WLAN?