Motorola Dsl
CHALLENGES indoor coverage in WiMAX
CHALLENGES indoor coverage in WiMAX
Dr.Hari Ramakrishna
Professor, Dept. of CSE,
Chaitanya Bharathi Institute of Technology
Gandipet 500 075, Hyderabad,
dr.hariramakrishna @ rediffmail.com
K. Delighted
Asst. Professor
Department Computer
Institute of Management Sciences Allure
K. Anil Kumar
Assoc. Professor
Department Computer
Allure Institute of Management Sciences
ABSTRACT
Now using a mobile day is higher here than anywhere else in the world and mobile devices are used inside buildings, and mobile operators are to provide coverage inside with their service. To ensure the blanket inside without having too much extra cost, as many additional cell sites, optimal planning of the network to perform using the coverage area by using the network models.
In this article We provide the concepts of what is inside coverage, difficulties in the inside cover. How WiFi and WiMAX technologies are used to improve the ability to provide indoor coverage. This document also covers models and architecture to provide better coverage inside.
Keywords: Inside Cover, internal circulation, WiMAX, Wi-Fi Modem BTS, antenna,
1. INTRODUCTION
Mobile phone usage is higher here than anywhere else in the world and millions of customers demand a quality service wherever they go. Unfortunately for the operator, these subscribers usually go to the most difficult to cover with a cellular wireless macro, due to the unique topology, high-rise office buildings, Metro stations, dense urban streets, shopping areas and entertainment with irregular hours worked, hundreds of railway lines, and small apartments in large buildings.
Outside the Great coverage does not always mean perfect coverage inside. outer covering (the network macro) has steadily improved over time with better and more cell sites dropped call rates. But in capacities coverage – in offices, commercial buildings and residences, can often be affected by things outside your control operator. Our numbers cell phone and email are increasingly a way to stay connected wherever we are. But building materials like concrete, concrete block, steel, brick and stained glass, and location of buildings in the shadows, may limit the penetration of cellular signals and PCS in your location. Even changes in weather and environmental conditions outside, the foliage changes, or terrain may affect the signal indoors.
Many WiMAX operators are at a crucial stage in the planning or deployment WiMAX networks. Their expectation for spectrum licenses necessary to get the first delivery of mobile WiMAX products, or to select a vendor is over or about to end. Finally, they are ready to start rolling out their networks and test them in environments of real life, with subscribers Pay on busy networks.
As operators have increased with the planning or deployment of network major issues in the radio access network (RAN) became the outdoors and achieve indoor coverage. As customers start using their network, providing the density of large capacity as new devices and applications will require another key objective.
These are problems recurring for all new wireless data technologies, such as the underlying physical they must overcome to obtain good coverage and capacity are the same. WiMAX is no exception, despite the fact that techniques such as Orthogonal Frequency Division Multiple Access (OFDMA) and Multiple Input Multiple Output (MIMO) will improve coverage and capacity.
2. DIFFICULTIES IN indoor coverage
The combination the requirements of high capacity and extended network access from locations within it a challenge to build a wireless broadband network. This is not a unique challenge to WiMAX operators: Long Term Evolution (LTE) and Ultra Mobile Broadband (UMB) operators will face a very similar situation in a timely manner. WiMAX indoor coverage adds a significant burden on the existing network resources, such as loss penetration due to the first wall of a building is generally between 10 to 20 dB.
To extend the coverage area and improve indoor coverage, WiMAX changes its modulation scheme dynamically depending on the location of subscribers. But there is a stiff price to pay: increase the scope and results within reach at low speeds.
Devices installed outside near the base station (BTS) will use the system most efficient modulation, Quadrature Amplitude Modulation (QAM), which has a higher spectral efficiency. However, Most customers are likely to be in locations within or around the edge of the cell, where Quadrature Phase Shift Keying (QPSK) is used instead and has a lower spectral efficiency. The impact of modulation is significant. When using QPSK 1 / 2 the data rate can be as little that 20% of the maximum throughput available with QAM 5 / 6 as shown in Figure 1.
Figure 1: Impact of modulation flow of data in a WiMAX network
To make matters worse, customers inside are more likely to have longer sessions and run applications more bandwidth-hungry, simply because indoor premises are more welcoming to users data. Over time, the largest number of users and mobile devices, coupled with the wider use of broadband applications, will further increase the overall need for capacity in the network, such as mobile devices to use network resources more strongly, because of their antenna smaller and more limited power.
WiMAX networks provide capacity constraints and higher density capabilities will be necessary due to the combination of high levels of domestic use coupled with the growing adoption of mobile terminals, which generally can not use the most efficient modulation in locations inside and with the increase in user traffic levels.
Greater density of BTS will be needed to meet the requirements for both cover and inside capacity. The new cell sites added need to make efficient use of spectrum resources and network effectively and the ability of the pack have more traffic in the same area. To do this, new network architectures are necessary and BTS will move towards the interior of the premises where subscribers.
3. ARCHITECTURE HIERARCHICAL PLACEMENT
Assume that the handheld devices carried by mobile users are able to receive signals from heterogeneous wireless technologies such as WLAN and infrared. Figure 2 shows the architecture hierarchical positioning of the service offered within. For example, the mobile device is equipped with the appropriate network interfaces to receive the ID signal transmitted by the WLAN access points and infrared signal transmitters. The exact positions of access points WLAN and infrared signal emitters are given in advance. One program, called the client finds, is installed in each mobile host.
Figure 2: Service Architecture proposed hierarchical positioning within
The signals are received ID, the customer location of the mobile host delivers the signal strengths and IDs of all wireless access points detected, or simply the ID of the transmitter infrared signal to the location server. The location server will estimate the position of the mobile host, and then you provide the estimated position at customer location. Then the location-based services corresponding to the estimated position will be recovered for use in the mobile user. The estimated positions are stored in the database, so that the location server is able to retrace the historic route of travel each user Mobile. As a mobile host receives the identification signal of a transmitter of infrared signal, the distance error of the estimated position is only a few centimeters to several meters from the infrared signal transmitter. However, as the identification signal from an access point WLAN is received, the distance error of the estimated position is approximately 10 to 100 meters from the WLAN access point.
Figure functional structure of the client and the server where the site: 3
The position information provided by the issuer infrared signal is more accurate than that provided by the WLAN access points, because the transmission range of positioning devices is far infrared smaller than the WLAN access points. In general, the WLAN access points can be deployed to cover any indoor environment easily, but it is difficult for the infrared signal transmitters. Therefore, the positions estimated by the location server are almost on the basis of information signal of WLAN access points. Once the infrared signal is detected, the position of the mobile host will be adjusted immediately to the position the infrared signal transmitter, because the infrared technology is more precise.
The architecture proposed hierarchical positioning is based on client / server model.
The functional structure of the location server and the client location is shown in Figure 3. The customer is implemented in the portable module consists of a sensor signal module location, and location-based service module. The sensor module signal is responsible for detecting the positioning signals for heterogeneous wireless technologies. The localization module is responsible for providing the data collected signal information such as received signal indicator (RSSI) and infrared ID (IRID), the location server, and receiving the estimated position of location server.
After receipt of the estimated position, the service module provides location-based services immediately correspondents or actions for the mobile user. The location server comprises the positioning engine and database. The positioning motor is responsible for estimating the position of the mobile user according to the information signal supplied by the customer location. Basically, the position can be estimated RSSI values measured by at least three access points.
Then, the engine makes positioning and adjusting the overlap for the estimated position, according to information from other signal heterogeneous wireless technologies to improve precision. Another mission motor control is to transmit the estimated position back to the module location location of the customer. The database is responsible for registering estimated positions, so that the trajectory of movement of each mobile user can be tracked and monitored.
4. WIMAX AND indoor coverage
General WiMAX promises ubiquitous connectivity, access to fixed appliances mobile and supports bandwidth-intensive applications without sweat. However, similar to other broadband technologies wireless market, the question underlying remains for WiMAX offering coverage of high performance inside. Therein lies the challenge, as most users connect to the inside while WiMAX. In fact, according to Senza Fili Consulting, 75% of WiMAX operators estimate that more than 80% of their subscribers to connect WiMAX network indoors.
More often than not, users within the longer sessions and a more intensive use of bandwidth applications, hence the need for operators to provide high capacity in addition to coverage Within optimized. Therefore, for the user experience the best in its class, improved indoor coverage becomes a crucial task.
4.1 CHALLENGE IN WIMAX indoor coverage
The request for coverage within large and high density translates into the need for building in high-density BTS, with the number of BTS is increasing as users sign up for services, using multiple devices and additional applications. Deployment of other multi-sector macro BTS is often impossible or cost effective. For operators, it becomes increasingly difficult and costly to accommodate a greater number of macro cells.
The equipment cost, while important, is often not the main obstacle to macro dense deployments. the acquisition of the site, site preparation and installation can have an even greater impact on overall capital expenditures. This may make it impossible for operators operating in areas with high density of users to close their business case or it may unnecessarily delay the return.
As the number of BTS and traffic increases, operators must also closely monitor the rising cost of connection. If traffic from each BTS must be transported by a wire-line solution, costs can escalate quickly if opex each BTS has its own link. Depending on the location, the connection to the infrastructure Line wire (perhaps DSL or fiber) can be expensive and can not be easily accessible from certain locations (eg, streetlights).
Conversely, wireless links can reduce backhaul operating costs significantly, because it then allows the operator of the effective global circulation and avoid recurring backhaul costs associated with each BTS deployed, but may require additional spectrum and additional capital investment. In addition, relay stations with the support of integrated wireless backhaul to eliminate the need for lengthy and costly process of preparing several sites for backhaul.
4.2 BEYOND OF MACRO BTS
In the early stages of most WiMAX deployments, network architecture centered on multi-sector macro BTS prevails because it actually makes a good outdoor coverage with a limited number of BTS. However, a network architecture centered around the macro cells often do not scale well when the requirements for indoor coverage and capacity become more pressing. The cost of equipment, acquisition and site preparation, installation and recovers quickly earning opportunities, making it difficult to achieve a positive ROI.
To meet the requirements of the new coverage and capacity, operators need to deploy more compact, smaller than BTS backhaul cost-effective support solutions. They also come with less onerous requirements and costs of acquiring the site because they can be installed in locations more accessible (lampposts, building walls), closer to the street, and they consume less energy. Because of their size and reduced weight make it easier for operators access to the location of cell sites and to meet existing regulatory requirements.
The next IEEE 802.16j provide additional support for WiMAX wireless backhaul integrated. It demonstrates the commitment of industry to provide a solution based on the standard for several compact BTS backhaul based on Band Wireless.
Table 1: WiMAX options BTS
WiMAX operators have started to explore alternative network architectures that can be used to increase the initial infrastructure macro, and are also increasingly used by mobile operators to boost capacity and inside cover. These options are based on different types of BTS (Table 1) which form a sub-layer which is used to extend coverage within and strengthen the capacity available within subscribers. They are:
- Pico cells or microcells in areas outdoors near the buildings they cover. Outdoor microcells and Pico cells are smaller and less expensive than macro BTS Multi-sector but they generally have a more limited scope and, if they have a single sector, the more limited capacity. They are generally used in areas urban concentration of users and traffic. They are deployed in dense networks, where each cell covers a small area, ensuring good coverage and high capacity. They can be placed on lampposts, rooftops, or on the walls of the building. Pico cells and microcells use of wire line or wireless links. mesh topologies can be adopted when wireless link is fully integrated into the BTS.
- Pico cells in different indoor public places or in buildings of the company, ability to provide high density and extent of coverage capabilities. interior solutions are often the only way to provide in-depth coverage of construction. They are smaller than microcells and outside cells Pico, and their cost and ease of installation is even lower because they can be mounted on walls or ceilings. Picocell can use wireless or wired, depending on the reliability and cost of connectivity options available. Inexpensive links High-speed wired, if any, often prove to be the most viable solutions. In buildings where wired connectivity is not available to the operator or are too expensive, wireless link can be used instead.
- Extension the coverage and small businesses with femtocells. Auto-install, low-cost femtocells could be used to improve coverage in homes or small offices. They rely on existing DSL or broadband cable modem for backhaul. The operator is generally not directly involved with the installation of femtocells. Subscribers typically buy in a store and install them at home or office.
5. STRATEGIES WITHIN improved coverage WIMAX
In general, industry Broadband Wireless focuses on the backend system (Radio Access Network and Core Network) to optimize the network, particularly in improving the inside cover. Regarding WiMAX is concerned, WiMAX modems are often treated as an access device connectivity for end users, whose role is simply to transmit and receive. It is time that the unit is receiving more credit and trust with a larger role – improvement the inside cover.
There are 4 methods that can be used by WiMAX modems to play a role in improving Cover inside:
1) Improve the reception of uplink (through the next generation antenna technologies)
2) Use the appropriate type of antenna
3) optimal placement modem
4) Increase coverage Indoor WiFi
Figure 4: WiMAX role in improving coverage indoor
5.1 Improve RECEIVING UPLINK
There are many technologies introduced by base stations such as 4T4R MIMO, radio unit on top of the tower to reduce power loss and higher transmission power. Unfortunately, these technologies do little to improve reception of uplink which is often the bottleneck that limits coverage to inside. uplink is generally lower than the downlink, as uplink is activated by a transmitter modem inside which has less power (200mW) compared to that of a transmitter of the base station (10W). Therefore, the uplink coverage is always limited.
Figure 5 illustrates the downlink and uplink coverage using different antenna technologies. Loss uplink (point A) is at a distance much earlier than the loss of downlink (Points B, C & D) and at this stage, internal modems can longer connect to the base station. Although MIMO and beam forming can extend the receipt of downlink (B, C & D), these technologies do not contribute step in the strengthening of receiving uplink.
Figure 5: Uplink and coverage downlink antenna technologies different
There are several technologies that can improve uplink performance. One of the popular method is switched Tx diversity requires an antenna booster and includes an algorithm to determine the transmission path based on the better antenna. This method allows the modem to transmit radio signals from the best antenna to improve signal strength for transmission, with the difference light for an additional switch and a minimum loss of energy.
An improved method is available double emitter using cyclic delay diversity (CDD 2Tx) which requires two power amplifiers (PA) and two antennas. This method can further improve the transmission overall signal strength. Apart 2Tx CSD, another method of performance is Space Time Coding 2Tx added (TCC). However, WiMAX base stations must be R1.5 able to support TCC for users to enjoy a better uplink performance.
Figure 6 explains how the performance of uplink can be extended via Switched Tx diversity (Point E), dual transmitter using cyclic delay diversity (Item F) and spatial encoding 2Tx time (point G). It is important to note that only one of these technologies can be used at any time.
Figure 6: Uplink performance may be extended through the next generation antenna technology
5.2 USE OF TYPE suitable antenna
antenna design is often considered a black art. There are several factors that can affect the antenna performance. For example, factors such as material, length, type and design of antennas contribute to the antenna gain real.
The common type of antennas are patch antennas and omnidirectional antennas. patch antennas consist of a or more conductive plates which are spaced above and parallel to a ground plane. This design allows patch antennas have radiation patterns that are highly directional. On the other hand, omnidirectional antennas are made from a piece of conductive material generally orthogonal to the plane mass. This design allows omnidirectional antennas to transmit signals perpendicular to the antenna in a uniform manner.
Figure 7 below shows the 3D radiation pattern for the patch and omnidirectional antennas. The color red indicates the most sensitive spot or area with the largest increase compared to the antenna. From the diagram, it is obvious that the patch antenna has high directionality, so the modem should be placed correctly to ensure that the surface modem emits radiation patterns facing the base station for optimal performance.
Figure 7: Patch and the radiation pattern of omni antennas
However, omni antenna radiates signals uniformly in a plane and does not need to deal with the base station in a manner pre-designed. Therefore, it is ideal for indoor use where the exact location of the base station nearest is difficult to determine.
5.3 Place MODEM OPTIMAL
It is important to note that the WiMAX signals are transmitted by radio waves and careful placement inside can greatly enhance indoor coverage.
WiMAX operators must educate users on how and where to place their modem inside. First, by simple place the modem inside near the window that faces the base station closest as shown in Figure 8 can improve the performance of the antenna dramatically. This is because the loss of penetration of radio waves to the glass (-6 dB) is significantly less than the loss of penetration concrete walls (13dB or more).
Figure 8: An indoor WiMAX modem front of the station Basic
Second, by placing the modem near the window, as opposed to a certain distance from the window gives a better flow Following the improved indoor coverage. Observation and trial runs conducted.
5.4 PROCEDURE COVER BOOST WIFI
Some users can express it is not always convenient to restrict the use computers to a domain that is beside the window. In addition, they may want the convenience and flexibility in sharing wireless broadband WiFi.
Therefore, using WiFi to supplement WiMAX can provide benefits that improve indoor coverage. One ways to do this is to use a modem WiMAX-Wi-Fi combination also called WiMAX Integrated Access Device (IAD) that enables WiMAX-WiFi-to-Out. WiFi and WiMAX transmitters are placed in the same modem so that issuers are able to connect to WiFi enabled devices and respective WiMAX base stations simultaneously.
For example, as shown in Figure 9 below, users can place the WiMAX modem within a situation optimal (usually next to a window) and enjoy WiMAX with the flexibility of several WiFi-enabled devices in the perimeter the home or office.
Figure 9: Place of WiMAX for better indoor coverage
However, having both WiMAX and WiFi in one device comes with a price. In many countries, particularly in Asia and the U.S., WiMAX is offered on the 2.3 GHz and 2.5 GHz frequency band which coincides almost with the frequency of WiFi which is 2.4 GHz. When the share WiMAX and WiFi RF approximate interference may occur and jeopardize connectivity. To overcome the interference problem, a modem designed with care is needed to enable both wireless technologies to coexist in the same device.
The advantage of having the modem combination WiFi-WiMAX is that the antennas can be optimally designed to isolate radio interference in a very controlled. In addition, the antennas are fixed in the modem, there is a better control over WiFi and WiMAX radio signals to ensure that users gain the best connectivity at the same WiFi and WiMAX place.
6. MODEL FOR LTE indoor coverage
The challenges 3G/Universal Mobile Telecommunications System (UMTS) to the increasingly demanding requirements of LTE. The Third Generation Partnership Project (3GPP) has developed specifications specifications for LTE is an evolution of UMTS. It is to provide a number of benefits including increased capacity and reduced latency, better spectrum utilization and performance of the cell edge while offering both GSM / HSPA and CDMA / EVDO service providers a migration path to a 4G platform that addresses interoperability issues.
However, the benefits of LTE developments will only be felt if service providers are able to effectively reach their customers. In ABI Research's 2009 report, he predicts that by 2013 over 67% of all handsets shipped will be able 3G +. The volume of mobile traffic from inside the buildings is already over 60% for voice calls and is expected to grow by more 90% for data sessions. Taking the technical issues and the habits of users so we can see that the majority of the revenue opportunity data Mobile is located in buildings. It is therefore essential to have pervasive in building wireless coverage and an issue that must be addressed both for the service provider and subscribers as well.
Poor indoor wireless coverage is now recognized worldwide as one of the biggest obstacles facing today's mobile subscribers. This is particularly true with data services and LTE licenses issued in frequencies as high as 2.6 GHz with a promise to download 100 Mbps and 50 Mbps download speeds per cell. There are many issues to consider for building effective coverage of wireless with some key questions to be asked by those seeking deploy a solution for LTE.
6.1 DIFFERENT SOLUTIONS
Traditionally, networks cells were designed using an "outside" approach, the service provider uses the network of micro and macro to enter buildings. With most sessions from building coupled with modern, environmentally friendly and energy building techniques and saving materials, the penetration of network buildings macro is no longer viable. Therefore service providers, strengthening of homeowners and businesses must deploy effective systems to provide wireless coverage inside the building. It the only way to maintain the signal strength is good and achieve the level of service and data rate required by mobile broadband subscribers today while ensuring efficient use of network infrastructure for the service.
LTE comes with the option of diversity provided by multiple antenna-in-Multiple-Out (MIMO). MIMO was developed for outdoor deployments and a lot of debate about the need MIMO deployments in a building. There is also uncertainty as to whether it is profitable. However, there may be specific projects that could MIMO be an advantage, it is important that any solution should be deployed to cover this flexibility available. Careful planning of budgets places the antenna and the link to the solution of the coverage will be necessary to ensure the performance edge of the cell by the handset user issues the appropriate bandwidth.
6.2 Frequency and duplex
LTE allows both frequency division duplex (FDD) and Time Division Duplex (TDD) variants with licenses to the study through a wide range of frequencies, including 700MHz, 800MHz, 900MHz, 1800MHz, 2100MHz and 2600MHz. The ABI 2009 report on wireless in-building was found that the LTE deployments in China will almost certainly TDD. This provides a challenge in selection of appropriate technology in building wireless coverage that has the flexibility to support all these options and variants. In multi-carrier deployments, it is possible that several frequencies and two-sided systems are needed on the same system. In addition, such a deployment multi-operator may also need to support existing 2G and 3G services at the same time.
There are three main options available to improve coverage in wireless capabilities, including distributed repeaters, distributed radio solutions and distributed Antenna Systems (DAS). DAS is generally favored moderate to major infrastructure to be able to offer improved and unified within wireless coverage for multiple services to reduce capital and operating costs.
6.3 DISTRIBUTED ANTENNA SYSTEM
distributed antenna system (DAS) includes a network of antennas that are placed in a building to provide dedicated coverage to construction. Traditionally, there are two types of available DAS, passive and active. Hybrid solutions are also in use where the active units are distributed in a building at each feeding a small antenna network passive.
Passive DAS consists of a network of coaxial cables, couplers and power dividers to distribute wireless signals in buildings. ABI Research identifies in its 2009 report that passive DAS systems are known to suffer higher losses at higher frequencies
and are therefore not readily suitable for LTE. It also recognizes that buildings over 20,000 m2 will need an active deployment DAS.
Active DAS the service takes feeds from a base station or relay amplified and distributes wireless signals inside buildings over cable fiber optic and RF fiber that connect to several remote antenna units located in different areas of the building. In the past, it was an issue with Active DAS solutions for their ability to support TDD and multiple frequencies simultaneously on physical infrastructure unique. With the need for additional hardware overlays add services at a later date, there are repercussions on the hidden costs upgrade many active DAS solutions.
More recently, another cost effective option DAS was introduced which has made a real broadband active approach. This solution simultaneously supports DAS any number or combination of wireless services, protocols, plans or duplex frequencies on a system without needing specific services overlays. The system has the ability to handle any type of service, which provides also peace of mind for the future proofing of new investments in infrastructure wireless capabilities, enabling new services to be added without additional components or expensive upgrades.
7. ABSTRACT
Increasingly WiMAX operators have started to seek solutions that meet their stringent coverage and capacity requirements with scalable network architecture flexible and cost effective. The strategy that operators choose to enhance coverage and the ability will have a significant impact on their network plans from the very beginning. As the original plan of the network can facilitate or hinder the future expansion of infrastructure, it is crucial to begin to address issues of coverage inside and density of high capacity in the early stages of network planning.
There is no single solution. Operators need to take a critical look at their market, and understand what the market demands and challenges specific to their physical environment. Most likely, each operator is an alternative is to obtain the best coverage and capacity it needs in a cost-effective manner. There is no way yet been established and a selection limited product. But a large capacity and better coverage of issues whose importance is escalating rapidly, the demand for WiMAX services is growing and mobile devices are appearing on the market.
8. REFERENCES
[1]. L.-D. Chou, C.-C. Lee, M.-Y. Lee, and C.-Y. Chang, "Position-Aware Active Learning Based on
Connectionless positioning in indoor "Positioning, navigation and communication,
Series in Beiträge zur Nachrichtentechnik Hannoversche, P. 189-194, Shaker Verlag publishers,
Germany, ISBN: 3-8322-2553-6, March 2004.
[2]. L.-D. Chou, C.-H. Wu, S.-P. Ho, and C.-C. Lee, "Position-Aware Mobile Multimedia Learning
Systems in museums, "Proceedings of IASTED WBE 2004 – International Conference on Web-Based Education, Innsbruck, Austria February 2004.
[3]. L.-D. Chou, C.-C. Lee, M.-Y. Lee, G.-Y. Chang, C.-H. Liao, and K.-F. Jian, "Design and
Implementation systems based on multimedia localization Tour Guide ", Proceedings of 2003 Tanet
[4]. Taiwan Area Network Conference, Taipei, Taiwan, ROC, P. 957-962, October 2003.
[5]. Ojanpera T. and R. Prasad, "Overview of air interface multiple access for IMT-2000/UMTS" IEEE
[6]. L.-D. Chou, C.-C. Lee, M.-Y. Lee, C.-Y. Chang, "a tour guide system for mobile learning in
Museum ", Proceedings of IEEE 2004 WMTE The second IEEE International Workshop on
Wireless and Mobile Technologies in Education Chungli, Taoyuan, Taiwan, ROC, March 2004.
[7]. Antenna patterns and their significance in Cisco Systems
[8]. Manual DS230 by Green Packet
[9]. DV230 Service Manual by Green Packet
[10]. A Practical Guide to WiMAX Antennas: MIMO and Beamforming Technical Overview by Motorola Corporation
[11]. Inside, high-capacity coverage with WiMAX How managers address the challenge? Senza Fili by consulting
[12]. Sequans Communications: 4G WiMAX by Sequans Communications
[13]. Wireless Communications by Andrea Goldsmith, Cambridge University Press
About the Author
K.RAVI
Assist.Professor
Dept. of Informatics
Alluri Institute of Management Sciences
Hunter Road, Warangal, A.P., India.
e-Mail ID: kolipakaravi@yahoo.co.in
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